Features of PUR Hot Melt Coating Head EP48V

The main advantages of PUR hot melt adhesives are good heat and cold resistance, chemical resistance (ink) corrosion resistance, high bond strength, and good leveling properties. At present, mainstream EVA hot melt adhesives are not as good as PUR hot melt adhesives in these properties, and in particular, it is required to maintain a high adhesive strength of the paper while also having a good leveling property, which is a difficult requirement. In fact, EVA hot-melt adhesives are generally powerless.

In general, PUR hot melt adhesive has strong adhesion to paper and metal, and it is also very flexible after hardening. In addition, the PUR hot melt adhesive can be completely separated in the waste paper remanufacturing project, which is also favorable for improving the recovery quality of waste paper. In particular, after its complete curing, its flux resistance is very strong, and it is particularly suitable for the bonding of photobooks and high-grade books using coated paper.

PUR hot melt adhesive is characterized by its heat resistance, which is not possessed by thermoplastic hot melt adhesives. Although the PUR hot melt adhesive is heated and melted and applied to the spine and then cooled and solidified like the ordinary hot melt adhesive, the PUR then absorbs the moisture in the air to generate a secondary reaction, forming a cross-network structure. . The strength of such a network structure is very high.

In addition, there is also a characteristic that the amount of hot melt adhesive can be reduced due to high adhesive strength. EVA hot-melt adhesives must be thick (<1mm) in order to increase their bond strength, while PUR hot-melt adhesives can achieve high bond strength when the adhesive layer thickness is more than 0.4mm. The layer thickness is about 0.3mm and the bond strength is high and the flatness is good). Even considering the unit price and running cost of hot-melt adhesives, there are many cases that deserve serious study.

PUR hot melt adhesives that were first introduced in Europe have been used not only in the bookbinding industry, but also in building materials, auto parts, and other areas.

Although PUR hot melt adhesives entered Japan in the 1980s, they have not yet been widely used. The reason for this can be the kind of the binder, the price factor, the operating factor, and the like. Unlike ordinary hot-melt adhesives, it is difficult to use due to the reaction after coating. In addition, in terms of production, high technology is also needed. In the bookbinding field, roller coating methods for PUR hot melt adhesives have been used in many applications in Japan, but daily cleaning operations are necessary.

The EP48V nozzle applicator developed by a Japanese company is a dedicated hot melt applicator designed based on the experience of PUR hot melt adhesives used in the market.

A typical roll coating method has a plastic tank for melting the hot melt glue, and the glue is applied to the back of the Book by rotating the glue wheel placed in the tank.

In contrast, the EP48V coating head uses a method of transferring the melted hot melt glue in the barrel glue pan to the coating head through a hose. The features of the coating head are as follows:

1) Non-contact coating method;

2) The portion of hot melt adhesive exposed to air is very small;

3) Excellent high-speed adaptability (can be matched with 12,000/hour binding speed);

4) Less maintenance hours;

5) Easy to change the format, etc.

Points 2 and 4 above are the main advantages.

In the case of roll coating, if hot melt adhesives such as EVA are used, it is only necessary to cut off the power supply at the end of the daily work; when using PUR hot melt adhesives, the cleaning work must be increased, but the EP48V device only has The tip portion of the nozzle is in contact with the atmosphere. Cleaning after the end of the daily operation is limited to the cleaning of the nozzle portion, which can greatly reduce the amount of cleaning work. In other words, there is almost no place for cleaning.

The EP48V system produced by this Japanese company has increased its export volume to Germany, which has stringent requirements in terms of recycling, and this trend has been shown in North America, South America, and Japan. This coating method has established the position of an alternative roll coating.

Source: Print World