Abstract: This article mainly introduces the preparation and properties of new fast curing polyurethane adhesives for composite films. The adhesive has low viscosity, strong initial adhesion and high peel strength, and is suitable for high-speed composite film production lines.
Keywords: Food Packaging, Polyurethane, Adhesives, Dry-Compound Composite films prepared by compounding various films with different properties because of their good barrier properties, heat resistance, cold resistance, oil resistance, acid resistance, chemical resistance, abrasion resistance , transparent, opaque, impervious, impermeable to gas, and puncture-resistant, etc., in food, medicine, daily necessities, chemicals, medical devices, instruments, weapons, ammunition, radiation protection, antibacterial, anti-gas, etc. Widely used. Due to the fierce competition in the domestic flexible packaging industry, both large and small customers face the same problem in the huge market of adhesives for ordinary composite films: that is, the customer's own inventory is becoming less and less, and at the same time it requires a delivery period. Shorter and shorter. The general adhesive must be cured for at least 24 to 48 hours, which can not meet the customer's time requirements, low production efficiency, waste of energy, and high cost. In order to solve this problem, adhesives for fast curing (cured) composite films have been introduced abroad. Afterwards, similar products were launched in China, and their performances are shown in Table 1. It can be seen from the table that the viscosity of the main adhesives and curing agents at home and abroad is very high, which is not suitable for the production of high-speed coating machines, and the price of the adhesive is high.
Adhering to the principle of “comforting with diversified needs, providing professional services, and providing customers with a full range of flexible packaging solutionsâ€, Gaomeng has made painstaking research and redesigned the molecular structure based on anatomical analysis of domestic and foreign products, in June 2002. YH2800, YH2800A, and YH2800B series fast curing adhesives for composite films were introduced. This series of adhesives has the advantages of short curing time, high initial tack, and high peel strength, which can meet the different requirements of different manufacturers.
First, the test part 1, the main raw material YH2800, batch number: 0204116;
YH2800A, lot number: 0205096;
YH2800B, lot number: 0205113;
YH15 curing agent, lot number: 0204113;
NY25, Unikka; Transparent PE60, provided by Hebei manufacturers; Transparent PE105, provided by Beijing manufacturers; Milky white PE90, provided by Beijing manufacturers; OPP, Shenda; CPP, Wuxi Huanya; PET, Zhongshan Puji.
2, equipment, equipment HIROSHIMA laminating machine (Japan), composite speed of 60 ~ 120m/mIN;
BLD200S electronic peel tester.
3, performance test According to GB279081, measuring T-type (90 °) peel strength.
Second, the results and discussion 1, rapid curing adhesive design principle Two-component polyurethane adhesive, the main agent and curing agent need to be mixed before use. The principle is that after the two components are mixed, a chemical reaction takes place under certain conditions, and an appropriate cross-linked network macromolecule is formed before it has a good cohesive strength. The chemical reaction proceeds as follows: for example, -NCO and -OH react, the reacting group first collides, and the colliding group must have sufficient energy. If the colliding group does not have the minimum energy, it can not reach the alternating state of the old and the new chemical bond, so the chemical reaction can not occur. The energy that an ordinary molecule or group needs to absorb when it becomes an activated molecule or group is the activation energy (EA). As shown in Figure 1.
Therefore, any chemical reaction can take place and must be carried out under certain conditions and after absorbing a certain amount of energy EA. The reaction between different substances and different groups is very different. The design principle of fast curing adhesives is how to reduce the activation energy (EA) of the reaction. There are two main ways to reduce EA: 1 Select EA low reactants or groups under the same conditions; 2 Change the reaction process.
Fig.1 Sketch of chemical reaction energy change 2. Basic properties of YH2800 series adhesives 1Physical andchemical properties The basic physicochemical properties of YH2800 series adhesives are shown in Table 2. (To be continued)