Research On Novel Compound Preservative For Natural Rubber Latex

Nowadays, ammonia（NH₃） is widely used in saving natural rubber latex（NRL） as a preservative in producing, while the ammonia and tetramethyl thiuram disulfide（TT）/zinc oxide（Zn O） compound preservation system are used for saving concentrated natural rubber latex（CNRL）. But annomia is volatile and pungent, which pollutes the environment seriously. TT produces nitrosamine impacts the safety of products and Zn O affects the stability of latex and vulcanization. Therefore, the research and development of environment friendly, safe and high efficient low ammonia even non-ammonia preservatives without TT and Zn O are becoming the key points in the field of natural rubber processing.BCT-2, a water-soluble effective preservative, was used by this research to compound with ammonia to preserve NRL and CNRL. The influence of BCT-2/NH₃ compound preservatives on preservative effects of NRL, properties of raw natural rubber, preserved effects of CNRL and properties of CNRL were reasearched.The results indicated that BCT-2/NH₃ had good preservative effects on NRL. Particularly when NRL was preserved by formula B5, B6, B8, B9 respectively, the preserved effects were better than NH₃ and NH₃+TT/Zn O. After preserving 144 hours, the volatile fatty acid number（VFA NO.） were about 0.05, the viscosities were about 10 m Pa·s, the p H were above 9.0.BCT-2/NH₃ did not affect the structure of raw natural rubber. The six indexes test of natural raw rubber of sample B5, B6, B8, B9 all met the standard of TSR SCR5 and the mooney viscosity were lower than NH₃ preserved one. The vulcanization rate of these rubber compounds were high and the viscoelasticity were also good. The physical and mechanical properties were better than NH₃ preserved one. The tensile strength of B8 and B9 were 26.23 MPa and 26.48 MPa, respectively. The tear strength of sample B9 was 31.26 k N/m which was higher than others. BCT-2/NH₃ promoted the cross-linking density of vulcanized rubber.When CNRL were preserved by BN-6 and BN-9, the preservative effects were good. After preserving 180 days, the VFA NO. were below 0.03, which were far below 0.08 GB/T 8289-2008 required. The mechanical stability test results kept above 650 s steady after 60 days, the viscositis were about 20 m Pa·s, and the p H were more than 9.7. Compared with HA, the total numbers of colony were little, the mean diameters were higher and the surface areas were smaller.BCT-2/NH₃ did not affect the change of viscosity and residue content of pre-vulcanized CNRL. The film forming characteristic was fine and the thickness dipped products were larger than sample HA. When CNRL was saving by BN-6, the structure of vulcanized film was normal. The drying rate of vulcanized film was higher compared with HA, the drying rate constant was 9.04×10-3 /min-1. The physical and mechanical properties were good, the tear strength was 53.72 k N/m particularly which was 9.55 k N/m higher than HA. The thermal degradation performance of vulcanized film was not be affected, and there was non-stimulation on skin, the cytotoxicity was lower than HA which signified the film was more secure.