Preparation And Application Of Functional Isocyanate Crosslinking Agent

Isocyanates are often used as crosslinking agent to modified waterborne polymer adhesives,which can enhance water resistance and bonding strength of the composite adhesive significantly,there is a drawback of short probation in the using process because of its high reactivity.In this paper,functional crosslinking agents were synthesized to improve the above shortcomings which were prepared by isocyanates modified montmorillonite and isocyanate blocked by sodium bisulfite.In this paper,the functional isocyanate crosslinking agent was prepared with two kinds of modification methods,after this used the functional isocyanate crosslinking agent modifying the PVA solution to synthesize composite adhesive.And then the functional isocyanate crosslinking agent were synthesized with isocyanates modified by two kinds of montmorillonite(K-10 and TCN).The results show that the composite adhesive obtained by the PVA solution intercalated with montmorillonite modified by isocyanate crosslinking agent has a uniform particle size distribution,thermal stability was enhanced significantly.The initial decomposition temperature of the composite adhesive is increased by 14.4 ?When the addition amount of montmorillonite is 3%.However,in this system,the application period of the isocyanate crosslinking agent is shortened.And the composite adhesive obtained by the PVA solution modified by isocyanate crosslinking agent intercalated with montmorillonite also has a uniform particle size distribution.The initial decomposition temperature of the composite adhesive modified by different content of montmorillonite was between 274.5 and 278.8 ?.Thermal stability has increased slightly,at the same time,extends the presence time of isocyanate groups in composite adhesives and extends their pot life significantly.The particle size distribution of composite adhesive obtained by the PVA solution modified by isocyanate crosslinking agent intercalated with K-10 montmorillonite was widest when the content of K-10 montmorillonite was 2%,the rest distribution is uniform.The thermal stability of the crosslinked products was improved.When the content of K-10 montmorillonite was 1%,the initial temperature was the highest,about 13.7 ?.The addition of K-10 montmorillonite content in addition to 3%,the other addition content of montmorillonite increased the application period.The application period increased by 109.5%when K-10 montmorillonite content was 1%.The wet strength of the plywood was enhanced by K-10 montmorillonite.The composite adhesive obtained by the PVA solution modified by isocyanate crosslinking agent which was intercalated with montmorillonite has a uniform particle size distribution.With the increase of the addition of montmorillonite,the thermal stability of the crosslinked product decreased first and then increased.When TCN montmorillonite content was 2%,working time increased by 127%.TCN montmorillonite enhances the dry strength of the plywood.A blocked isocyanate crosslinking agent was prepared by using sodium bisulfite as a blocking agent.The effects of different R values,DMPA content.and neutralization degree on the properties of blocked isocyanate crosslinking agents were discussed systematically.The results show that the average particle sizes of the blocked isocyanate crosslinking agents with different DMPA content were uniform relatively.With the increase of DMPA content,the average particle size of the blocked isocyanate crosslinking agents decreases,the viscosity increases and the thermal stability increases gradually.The viscosity of the blocked isocyanate crosslinking agent increases with the increase of neutralization degree.When the degree of neutralization is less than 100%,the average particle size of the blocked isocyanate crosslinking agent decreases with the increase of neutralization degree.When the degree is higher than 100%,the change of the particle size of the blocked isocyanate crosslinking agent tends to be gentle and the thermal stability is improved gradually.The average particle size of the blocked isocyanate crosslinking agent decreases first and then increases with the increase of the R value.And the viscosity decreases gradually.