Plastics Industry and Engineering Research on the Synthesis of Unsaturated Polyesters from DCPD and PET Liu Zhengping, Zhang Weimin, Dong Bingxiang (Department of Chemistry, Beijing Normal University, Beijing 100875, China) Discusses the synthesis of unsaturated polyglycols from dicyclopentadiene and polyethylene terephthalate wastes Ester resin method: PET alcohol solution with glycol, maleic anhydride and DCPD, 80-120 °C under the conditions of dropping and DCPD equivalent amount of water for reaction, about 2.5h reaction to join other components, Esterification is performed until the reaction is complete. In PET, the content of DCPD affects the mutual solubility and the curing process of unsaturated polyester with styrene. Compared with standard resins, unsaturated polyester resins synthesized by DCPD and PET have good mechanical properties, good air dryness, and solve environmental pollution, and have good economic benefits.
Polyethylene terephthalate (PET) is widely used in the production of polyester fibers, packaging containers, tapes and films. However, a large amount of waste will be generated during the production process. Taking a medium-sized polyester fiber plant as an example, there will be more than 100 tons of waste wire every year. If glycols are used instead of glycols to replace unsaturated polyesters with polyester wastes, not only wastes are recovered, but also the cost and performance of unsaturated polyester resins (UPR) can be improved, with good economic and social benefits. .
Zhelev et al. from Romania applied for the UPR patent for rice synthesis in 1976. Rebeizf1, Castano, Vaidya, Xiang Fengqi, Wang Desheng 5, and Wang Yuantong et al. used PET synthesis of UPR. However, according to our experience, the preparation of UPR by PET has a common defect. Polyester and styrene have poor mutual solubility and are easy to separate. To solve this problem, UPD was modified with dicyclopentadiene (DCPD) to investigate the effect of DCPD content and the process route on the properties of synthetic polyesters.
1 Experimental section 1.1 Raw material maleic anhydride (MA): industrial grade, Tianjin Zhonghe Chemical Plant; transparent polyethylene terephthalate (PET): industrial grade, Yanshan resin plant; diethylene glycol (DEG): Industrial Grade, Yanshan Petrochemical Company; Dicyclopentadiene (DCPD): Industrial Grade, Anshan Chemical No. 1 Plant; Ethylene Glycol (EG): Industrial Grade, Yanshan Petrochemical Company; Hydroquinone: Analytical Pure, Beijing Beijiao Farm Chemical Plant; Styrene: Industrial Grade, Yanshan Petrochemical Company; Zinc Acetate: Analytical Pure, Beijing Organic Chemical Plant; Accelerator: 2% Cobalt Liquid Made in the Laboratory; Curing Agent: 50% Methyl Ethyl Ketone Peroxide (MEPO) ), Industrial Grade, Beijing 251 Factory.
1.2 instrument electronic automatic balance recorder: XQC? 100 type, Beijing Automation Instrumentation Factory; super constant temperature sink: Shanghai Laboratory Instrument Factory; gel time analyzer: imported from the United Kingdom. 1.3 Determination of Gelation Time and Exothermic Peaks 0 g of cobalt solution was placed in a 25 C constant temperature water bath. Gel time was measured using a gel time meter, and the temperature of the exothermic peak was recorded with an electronic automatic balancer.
1.4 Performance test Air dryness is characterized by the curing speed (dry and dry time), measured according to GB1728?79; the bending strength and tensile strength of the resin casting are determined according to GB2570*81 and GB2568*81, respectively.
The synthesis principle of 2UPR resin is carried out in three steps. Firstly, the alcoholysis PET of PET undergoes the transesterification reaction under the action of hot glycol and catalyst, and the PET gradually degrades to generate the glycol with the lower molar mass, followed by the alcoholysis product. Addition reaction of maleic acid and DCPD, and finally alkyd through condensation reaction, generate modified UPR. 3 Results and discussion 3.1 Selection of DCPD addition process route Synthesis of DCPD modified UPR can be roughly divided into initial method and half Ester method, capping method and hydrolysis addition method. For the hydrolysis addition method, both the hydrolysis of maleic anhydride and the addition reaction of maleic acid and DCPD are strongly exothermic. If maleic anhydride, DCPD and water are fed into the reactor at the same ratio and reacted, two strong exothermic reactions occur at the same time, making it difficult to control the temperature of the system. Some DCPD may be decomposed into cyclopentadiene, while cyclopentadiene Diene, in turn, can undergo diene addition with maleic acid, consuming double bonds, and degrading the final resin activity. To solve this problem, we adopted the method of first putting PET pellets, a catalyst (zinc acetate), diethylene glycol, and a part of ethylene glycol into a reactor equipped with a thermometer, an electric stirrer, a reflux condenser, and a vent hole. In the heating, heating, high temperature reflux alcoholysis, when the PET is completely dissolved, continue to react 1h. Cooling to 120C will maleic acid *: Liu Zhengping, male, born in 1965, Ph.D., Professor, has been engaged in polymer chemistry for many years Work with physics teaching, as well as research on the direction of environmental friendly macromolecules and features 19 polymer 1 work has been published in more than articles. PublishingHouse.Allrightsreserved. Anhydride and DCPD were added to the reactor. The same amount of water as DCPD was added dropwise at 80~120C for about 2.5 h. Then the remaining ethylene glycol was added gradually to carry out the polycondensation reaction, and the maximum temperature was controlled at 210*. Within C, the column temperature does not exceed 103 *C. When the effluent reaches 2/3 of the theoretical effluent, vacuum is used to force a small amount of water to evaporate and the acid value falls below 40mgKOH/g, and the vacuum is stopped. Cool down to 180 to join hydroquinone, stirring 0.5h, continue to cool to 120 * C or less and styrene blending, mixing temperature control in 70 ~ 90 * C, and finally cooling, filtration, that is, products.
The effect of DCPD on the mutual solubility of polyester and styrene PET is a structurally symmetric linear polymer. The unsaturated polyester produced with it tends to have a high tendency to crystallize, has poor mutual solubility with styrene, and is easy to mix the resin with the resin, resulting in delamination. . The use of DCPD for endblocking, on the one hand, destroys the symmetry of the polyester molecular structure and reduces the crystallization ability of the polyester; on the other hand, the structure of DCPD is similar to that of styrene. Both factors contribute to the miscibility of PET-synthesized unsaturated polyesters with styrene. The effect of DCPD on the mutual solubility of polyester with styrene is shown in Table 1. From Table 1, it can be seen that when the mole fraction of DCPD is greater than 5.4%, the polyester can be completely miscible with styrene, and the layering problem is solved.
Table 1 Effect of DCPD on the mutual solubility of unsaturated polyesters and styrene! A 4 Appearance stratification slightly stratified miscible, transparent miscible, transparent DCPD dosage on the resin curing effect of DCPD dosage on the unsaturated polyester gel time and curing exothermic peak. It can be seen that when the mole fraction of DCPD is greater than 15%, the amount of DCPD has influenced the gelation time and the exothermic peak of the resin. This is obviously due to the excessive amount of DCPD, and the excess DCPD is decomposed into cyclopentadiene during the later temperature increase process. Contaminants such as cyclopentadiene and DCPD, such as olefins, can be added to unsaturated double bonds in the polyester chain. As a result of the reaction, the unsaturated double bonds of the polyester decrease, the activity decreases, and the curing slows down.
Performance Comparison of 5 and 191 UPR Performances of UP*5 and 191 UPR are shown in Tables 2 to 3. From Table 2, it can be seen that UP*5 has many excellent properties compared with general-purpose UPR, such as good mechanical properties and air-dryness. These excellent properties are related to the structure of the polyester. Under the conditions of this experiment, the introduction of DCPD adds the number of double bonds per unit of the molecular chain such that the end groups of most of the polyester molecular chains contain double bonds and polymerize, forming a rapid on the surface. Layer film, so that UPR is not inhibited by oxygen. The introduction of DCPD increases the density of the rigid ring and improves the physical properties of the polyester. When DCPD is used to cap the polyester, the carboxyl and hydroxyl groups of the terminal hydrophilic group are greatly reduced. After the terminal group is introduced into DCPD, the steric hindrance is large, so that the ester group on the terminal group is protected; the performance of the benzene-type UPR is better than that of the benzene-type UPR. The UPR has excellent properties, and thus polyesters prepared using DCPD and PET have improved chemical stability.
Dry time 1 dry time / h 1) UP? 5 without wax, 191UPR plus paraffin wax.
Table 3 Comparison of Mechanical Properties of UPR Castings Flexural Strength/MPa Tensile Strength/MPa Barbarian Hardness 1) Conclusions (1) Reasonable route for the preparation of unsaturated polyesters with DCPD and PET is: PET first in the reactor The same dihydric alcohol is subjected to high-temperature alcoholysis and then maleic anhydride and DCPD are added to the reactor, and the same amount of water as DCPD is added dropwise at 80 to 120° C. to carry out the reaction. Thus, due to the alcoholysis product to the system, The dilution is conducive to the absorption of the maleic anhydride hydrolysis reaction and the heat released by the two reactions of maleic acid and DCPD addition reaction; then the remaining glycol is added, and the esterified temperature is increased until the reaction is complete.
(2) DCPD content directly affects the mutual solubility and curing properties of unsaturated polyesters with styrene. When the molar fraction of DCPD is greater than 5.4%, the polyester is completely miscible with styrene, and the layering problem is solved. When the molar fraction of DCPD is greater than 15%, the process of curing the unsaturated polyester is affected.
(Continued on page 12) Becomes active point 1 Under the action of the initiator, a double bond with 3 points is struck with an Ashing skeleton vibration peak. There are 2 996cmCH3 stretching vibration peaks in the infrared spectrum of PDLLA, and there are no absorption peaks in 2 spots, which proves that the lactide ring structure disappears and the conversion rate is high.
3 Conclusions This experiment uses gradual warming, stage decompression dehydration to dimerize lactic acid into DL-LA.SnCk.2 out 0 catalytic vacuum is 0.66kPa, distilled DL-LA. Methanol as solvent, recrystallization three times, melting point It can achieve a 126% yield of DL-LA ring-opening polymerization with a yield of 126. The effect of Sn (Oct) catalyst is better than that of SnCV2H2, and different molar masses of PDLLA can be synthesized by different processes. The weight average molar mass can reach 100,000 or more.
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