Studies On Preparation And Properties Of Cationic Waterborne Polyurethane Adhesives

Cationic waterborne polyurethane (CWPU) emulsion was prepared from the materials of toluene diisocyanate (TDI-80), isophorone diisocyanate (IPDI), poly(butyl adipate)glyol(PBA) and N-methyl diethanol amine (N-MDEA) by the acetone method. In order to improve the drying rate of CWPU emulsion, high solid content CWPU emulsion was prepared. In order to further improve the water-resistance of cast film, high solid content CWPU adhesives with good water-resistance were prepared form the cross-linked modifier of epoxy(662). Properties of the products we prepared were characterized, and T peel strength was studied.In order to prepared high solid content CWPU adhesive with good properties, the factors which impact the properties of CWPU emulsion were studied, such as content of N-MDEA, kind of soft segments, R value of polyurethane prepolymer, content of latent solvent acetone, degree of neutralization, neutralization order and emulsion time etc. The results showed that it was the best when content of N-MDEA was 7.0%～9.5%,R value was 1.3～1.5,the polyester glyol (Mn= 2000) was used as soft segment, degree of neutralization was 80%-100%, and the best technics were that neutralization was taken before emulsification, and emulsifying for 60min.The stable high solid content (50%) CWPU emulsion was prepared when content of N-MDEA was 5.5%-7.0%, and content of latent solvent acetone was 8.7%. Besides, the properties of cast film of CWPU emulsion and crystallization were studied.In order to prepared CWPU adhesive with good water-resistance,662 was used as the cross-linked modifier, and studied the factors which impact the properties of CWPU emulsion, such as content of 662 and the stages to add 662.The results showed that the stable high solid content(50%) CWPU emulsion modified by epoxy was obtained when content of 662 was 0.5%～1.5%,662 was added at the same stage with 1,4-butanediol (BDO). Besides, the properties of CWPU emulsion modified by epoxy were studied.The adhesive properties of CWPU adhesive modified by epoxy with low solid content CWPU adhesive and high solid content CWPU adhesive were compared. The results showed that the CWPU adhesive modified by epoxy had best adhesive properties while high solid content CWPU adhesive had 41.8N/25mm initial peel strength and 74.8N/25mm 24hT peel strength, but the CWPU adhesive modified by epoxy had 45.5N/25mm initial peel strength and 80.3N/25mm 24hT peel strength.