Synthesis of dicyclopentadiene modified unsaturate

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Synthesis of dicyclopentadiene modified unsaturated polyester resin by low temperature catalysis (Part 2)

3 Experimental part

3.1 process flow

3.2 determination of reaction conditions

we used "industrial grade" and "polyester grade" dicyclopentadiene for synthesis reaction according to the methods in relevant literature. The results are as follows:

from the above table, we can see that using "industrial grade" dicyclopentadiene as raw material, we must first solve the defects of deep appearance color and poor storage stability of the finished resin. In order to overcome the above defects, some resin manufacturers have adopted the method of rectifying raw material dicyclopentadiene to remove some impurities in dicyclopentadiene in advance. However, this method adds a process, produces new three wastes, and also increases the cost. At the same time, the performance indexes of the resin still can not reach the ideal level. After repeated tests, we changed the traditional processing technology and adopted the low-temperature catalytic reaction method. The final product obtained satisfactory results. The principle is as follows:

(1) maleic anhydride reacts with water to form maleic acid, which reacts with DCPD to form monoester. This process is an exothermic reaction, and heat makes this reaction more intense. It is observed that the impurities in dicyclopentadiene often have decomposition side reactions in this step, and these side reaction products have Diels alder addition reaction with the double bond of maleic anhydride in the reactant, which makes the product discolored or even gelled. If the reaction temperature is reduced, the side reaction can be inhibited, but the esterification of dicyclopentadiene with CIS acid is difficult. This is because the melting point of maleic anhydride is 52.8 ℃ and that of CIS acid is ℃. During the hydrolysis reaction, maleic anhydride gradually changes to CIS acid, and the reaction system changes from liquid to solid, while dicyclopentadiene is liquid. If the reaction temperature is reduced, the liquid-solid reaction is difficult. In this process, we add a phase transfer catalyst a, and the hydrolysis and esterification reaction temperature is maintained below 100 ℃, The reaction of this step can be carried out smoothly under relatively warm conditions, and the occurrence of side reactions can be avoided. It was observed that there was no discoloration and gelation of the intermediate products in this step

(2) in the second step of the synthesis reaction, namely the polycondensation reaction stage, other diols and dibasic acids are added, which determines the reaction activity and other physicochemical properties of the final resin product. In order to reduce the cost, a large amount of dicyclopentadiene was added in the first step of the reaction (the content of dicyclopentadiene in the resin is more than 25%). At the same time, in order to improve the toughness of the resin, the feed ratio of maleic anhydride was reduced, which also reduced the content of double bonds in the resin, reducing the reaction activity and various strength indexes of the final product. Therefore, it is necessary to improve the reactivity of the resin in order to make the overall performance index of the final resin product reach a satisfactory result. According to relevant literature reports, in the polycondensation reaction stage, part of the CIS structure of CIS acid will be isomerized into trans (fumarate) structure with the progress of the reaction:

polyester fenluowen said that the higher the content of trans structure in the sub chain, the reactive activity of the resin will focus on the development of the third generation wide band gap semiconductor crystal The higher the optoelectronic materials such as high-power semiconductor laser epitaxial materials and nano lithium niobate single crystal film materials for intelligent manufacturing, the faster the curing speed in resin construction, and the better the physical and chemical properties of the final products. Generally, the conversion rate of CIS acid isomerization is improved by increasing the reaction temperature. However, increasing the reaction temperature will cause the impurities in dicyclopentadiene to react with soft PVC, causing the color to darken, and may cause gelation in the polycondensation kettle to scrap the product. After repeated experiments, we have adopted the method of continuously adding a composite catalyst B in the polycondensation reaction stage. This catalyst is composed of isomerization catalyst and side reaction inhibitor. This composite catalyst can not only promote the CIS acid isomerization conversion, but also inhibit the side reaction in cyclopentadiene, so that the resin will always maintain a low color number in the synthesis process. The performance of the final resin product proves this

with the method of maleic anhydride isomerization catalysis, the resin can increase the feeding amount of dicyclopentadiene, reduce the feeding amount of maleic anhydride and reduce the cost more under the premise of the same reaction activity; Or under the same feeding amount of maleic anhydride and dicyclopentadiene, the resin with higher reaction activity can be obtained

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