Synthesis Of Disodium Bicyclo[2.2.1]-heptane-2,3-dicarbo Xylate And Its Application As The Nucleating Agent For Polypropylene

Polypropylene is an important product in the five general plastics and its demand is growing increasingly. The developments and application of polypropylene were recently limited due to its poor mechanical properties and transparency. In order to improve the performance of polypropylene, people usually adopt the method of adding nucleating agents. Carboxylate was one of the most widely used types of nucleating agents in recent years and disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate is a typical representative of this kind of nucleating agent.In this paper, disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate is synthesized from cyclopentadiene and maleic anhydride through the Diels-Alder addition reaction, hydrolysis-neutralization and catalytic hydrogenation. To obtain the optimal synthetic conditions, the processes of important steps are studied, and the important applying properties of the nucleating agent to the polypropylene are also studied.In this paper, norbornene dicarboxylic anhydride is synthesized through the Diels-Alder addition reaction. The optimum process condition is determined by investigating the kind of solvents and solvent dosage. The yield of norbornene dicarboxylic anhydride is 97.5%, which is 10.0% higher than that reported in the previous literatures.On this basis, disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate is synthesized from norbornene dicarboxylic anhydride by hydrolysis-neutralization and catalytic hydrogenation. By studying the effects of catalyst type, the amount of catalyst, reaction temperature and hydrogen pressure on the yield and purity of disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate, the suitable reaction conditions are obtained. The results show that the expensive catalyst of Pd/C can be replaced by inexpensive Renay Ni. The suitable reaction temperature is 60℃ and the suitable reaction pressure is 5MPa. The results of infrared spectrum analysis and nuclear magnetic resonance analysis are identical with the structural features of disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate.Applying properties of the nucleating agent to the polypropylene were also studied. The results showed that disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate can increase the mechanical properties and crystallization peak temperature(Tc). When the addition concentration of disodium bicyclo [2.2.1]-heptane-2,3-dicarboxylate is 0.4%(wt.), compared to the blank control sample, Tc increases 18.0% and crystallinity increases 23.0%; When the addition concentration of disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate is 0.2%(wt.), bending modulus and bending strength of polypropylene reaches the maximum value, which increases 26.4% and 19.8%, respectively. Along with the dosage increasing of disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate, elongation at break and tensile strength is reduced after the first increase trend. When the addition concentration of disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylateis 0.1%(wt.), elongation at break and tensile strength of polypropylene reaches the highest. At this time, tensile strength increases 9.0% and elongation at break increases 11.6%, disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate can make the modified polypropylene with the trend of the isotropic contraction, and the more additive amount the better.Compounding disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate with commercial nucleating agent NA-11 as the composite nucleating agent and the applying properties to the polypropyleneare also studied. The analysis result of PLM indicates that the composite nucleating agenthave the effect of refining crystal grain. DSC indicates that this nucleating agent is better than NA-11 in improving the crystallization temperature. After compositing, the extent of improvment is higher than using NA-11 alone but is not better than using disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate alone. TG indicates that composite nucleating agent can not improve the thermal stability of polypropylene. Mechanical properties analysis shows that this nucleating agentis not a patch on NA-11. The nucleation results of composite nucleating agent between disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate and NA-11 and the best ratio is disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate:NA-11=7:3. When using NA-11 alone, modification of Polypropylene gets the high anisotropic shrinkage.When disodium bicyclo[2.2.1]-heptane-2,3-dicarboxylate is used together with NA-11 as a composite nucleating agent, the anisotropic shrinkage of polypropylene can be improved observably.