What is the PUR

PUR is a macromolecular compound with ammonia ester bond (nh-co-o), and the end of its molecular chain is isocyanate base. The basic composition of PUR is the addition of polyol (polyester, polyether, etc.) with active hydrogen and the addition of low molecular weight diethyl alcohol (chain extender) and isocyanate. The reaction of diglycol and isocyanate forms the rigid molecular chain segment, while the polyols and isocyanates react to form the flexible molecular chain segment, so PUR is a kind of rigid and hot melt adhesive. In addition, the isocyanate base meets the water in the air and produces an irreversible crosslinking reaction, forming a strong bond layer. This is the characteristic of PUR hot melt adhesive.

The background of PUR.

With the diversification of printing products, printing industry use different gram of printing paper, plastic film, glazing oil and printing ink, etc., the latest applied to the material sticking PUR adhesives, will there is a big difficulty. The hot-melt adhesive of PUR is able to bond the coated paper firmly, and its bonding strength is 40-60% higher than that of traditional adhesive. In the ordinary wireless adhesive binding, the printing ink on the paper will be transferred to the spine, and the PUR hot-melt adhesive will not appear at all.

The uniqueness of PUR is that it can adhere to a variety of materials, including varnish coating, UV curing layer, plastic film and coating paper.

The development of PUR.

Although the first generation of PUR hot-melt adhesive can realize the linkage production, it takes 24 hours to reach the maximum bonding strength after the binding of the books and magazines, which can withstand the external forces in transportation.

The second generation PUR hot melt adhesive was introduced in 1994 and realized the linkage cutting. If there is a certain amount of moisture in the paper, the binding area maintains a high air humidity, and after four hours of brushing, the adhesive strength can be large enough. In spite of this, the second generation of PUR has some disadvantages: in the cold winter, the air relative humidity drops to 20%, and the cross-linking of PUR glue is a difficult problem.

The third generation of PUR can be completely dry in one hour, and only the moisture in the paper can complete the wet curing crosslinking reaction, and the book can be removed directly from the machine for plastic sealing. , however, the third generation of PUR hot melt adhesive of modified also brought negative impact, because the PUR in a relatively short period of time can realize initial bonding strength, so some factories in use process found PUR soon in the pot becomes sticky glue, especially in the moist areas and the main binding thin book manufacturer is more apparent, because the binding thin book PUR to remain in the coating machine for a long time.

The fourth generation of PUR is already in the market. It is better than the third generation of PUR hot-melt adhesive, which can achieve the expected initial adhesion strength, while extending the stay time of PUR in the glue pot. Fourth-generation PUR has replaced most second-generation and third-generation PUR products, especially in the new nozzle system. At the same time, the fourth generation of PUR hot-melt adhesive binding book, the day can be shipped to all places. Due to the fast drying, the productivity of books and periodicals has been improved, and the production flexibility has also been improved.