Preparation And Properties Of Non-ammonia Concentrated Natural Rubber Latex

The natural rubber latex contains some non-rubber substances,in which the bacteria can easily use sugar,protein to grow and then to make the latex spoilage.At present,ammonia（NH₃）and its compound preservation system ammonia（NH₃）+tetramethyl thiuram disulfide（TT）/zinc oxide（ZnO）,are regarded as the main preservative of natural rubberlatex.However,ammonia（NH₃）is volatile and pungent,corroding equipment and endangering workers’health.At the same time,TT and ZnO not only adversely affects the consistency of the production process,but also produces toxic nitrosamines at high temperatures.Therefore,the research and development of high-efficiency,environment friendly and economical non-ammonia preservatives without TT and ZnO are becoming the key points in the field of natural rubber processing.In the 1950s and 1960s,people began to research on the technology of non-ammonia preservation of natural rubber latex.However,due to the preservative effect,the toxicity and the cost of the preservative,the technology of non-ammonia preservation has not achieved a breakthrough.Since 2010,our research group began to research on the non-ammonia preservative of natural rubber latex.On the basis of previous research by the research group,this study used a relatively low-cost high-efficiency fungicide HY with inexpensive inorganics to preserve fresh natural rubber latex,and studied the preservation effect of HY composite preservative on fresh natural rubber latex.The environment friendly high-efficiency broad-spectrum fungicide BCT-2 with inexpensive inorganics was used to preserve the concentrated natural rubber latex,and studied the preservation effect of BCT-2composite preservative on concentrated natural rubber latex.And the effects of non-ammonia composite preservatives on the properties of concentrated natural rubber latex were also investigated.The results showed that with the content of 0.1%HY,0.3%sodiumcarbonate（Na₂CO₃）,0.1%sodium dodecyl sulfate（SDS）respectively,the preservative effect on fresh natural rubber latex was good.When the fresh natural rubber latex was stored on the 5th day,its VFA NO.was still lower than 0.06,and the viscosity was about 10mPa﹒s,the pH was still alkaline and the cost was the lowest.With the content of 0.1%BCT-2,0.1%potassium hydroxide（KOH）,0.03%lauric acid,0.07%potassium laurate respectively,it had a good preservation effect on concentrated natural rubber latex.When stored for 180 days,the VFA NO.was 0.041,which was much lower than the requirements of GB/T 8289-2016,the mechanical stability was 650s,and the viscosity and pH met the requirements of subsequent products.The non-ammonia preservative didn’taffect on the structure of the vulcanized film and the properties of the pre-vulcanized latex.The film forming performance was good,and the color of the product was lighter than that of the high ammonia sample.The drying time of the vulcanized film of the non-ammonia sample was short,and the drying rate constant was 5-6times of the high ammonia sample.Non-ammonia preservative could promote the formation of vulcanized film cross-linking network,and was more conducive to improve the physical and mechanical properties of vulcanized film.Non-ammonia preservative did not affect the thermal stability of vulcanized film.And the degradation rate of non-ammonia sample was lower.