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Saturated Polyester Resin Industry Calls For High-purity

Jun 03, 2020

In recent years, in order to cope with the rising prices of raw materials such as phthalic anhydride and maleic anhydride, the unsaturated polyester resin (UPR) industry has put forward the slogan "fight against raw material price increases" and has turned its attention to dicyclopentane in ethylene by-product C5 resources. Ene (DCPD).

 DCPD UPR production status

The history of using DCPD to prepare UPR in my country can be traced back to the early stage of UPR industrialization in China. In the mid-1960s, Tianjin Synthetic Materials Research Institute, Beijing Chemical Industry Research Institute and Tianjin Synthetic Materials Factory started research work on the preparation of UPR with DCPD, and realized industrial production in Tianjin Synthetic Materials Factory in the late 1960s. The large-scale industrialization of DCPD for UPR began in the 1980s, when Jiangsu Changzhou Yabang Chemical Co., Ltd. used a large amount of DCPD in the production of UPR, thereby reducing the cost of resin production and improving the company's position in the market competition . In 2006, Changzhou Yabang Chemical Co., Ltd. produced 50,000 tons of DCPD modified UPR, plus the output of several other companies in Changzhou, the output of DCPD modified UPR resin in Changzhou has reached 100,000 tons, accounting for about 1/3 of the total UPR output of Jiangsu Province In 2006, the output of such resins in the country was about 150,000 tons, accounting for 13.6% of the total output of UPR, and a total of about 45,000 tons of DCPD was required.

Factors restricting the application of DCPD

 Although the performance of UPR has been significantly improved and improved after the introduction of DCPD, the output of modified UPR only accounts for about 13.6% of the total output of UPR. The reasons are roughly as follows:

(1) Serious environmental pollution Currently, the purity of DCPD used in domestic UPR is only 82% to 89%. The low molecular weight impurities contained in the UPR production process are continuously separated from the reaction system with the water generated by the esterification reaction. There are also a lot of low-molecular compounds extracted in vacuum, and the stench emitted by these impurities is unbearable. As the country pays more and more attention to environmental protection work, DCPD's pollution to the environment is bound to be interfered by environmental protection departments. In 2006, all UPR production enterprises in Jiangyin City signed a guarantee letter to the environmental protection department to stop using DCPD. This is a signal that deserves attention: the exhaust gas and waste liquid generated by DCPD in the process of UPR production have reached the point of no control. Time, otherwise its application will be completely rejected due to environmental issues.

(2) DCPD accelerates the corrosion of UPR production equipment and shortens the service life of the equipment.

(3) The price of DCPD climbs all the way. The price of DCPD has risen from 3100 yuan/t in 2003 to 10300~10500 yuan/t in 2006, which has almost no price advantage compared with the production of UPR using phthalic anhydride.

(4) Insufficient DCPD production, large market gap my country's total ethylene production capacity reached 11.86 million t/a in 2005, and by-product C5 should account for 15%, of which DCPD and CPD fractions should reach 200,000 t. In fact, in 2005, my country's DCPD output was only 40,000 tons, while in the same year UPR consumed more than 45,000 tons and imported 5,000 tons. In 2006, the situation was even more severe. Most companies using DCPD to produce UPR had operating rates of less than 50%. DCPD is in short supply, which has severely restricted its application in UPR production.

(5) DCPD modified UPR has some quality defects, such as darker color and poor mechanical strength, especially impact resistance, which limits its application in many fields.

DCPD quality needs to be improved

Although DCPD with lower purity can be used to produce UPR, the lower the purity, the greater the pollution to the environment and the darker the product. The Japanese and British Shell companies have good DCPD product holdings, and their technical indicators are shown in Table 1 and Table 2. Foreign DCPD indicators are not unattainable. Domestic DCPD manufacturers can use this as a goal to strive to improve product quality and reach or exceed the international advanced level as soon as possible.

Development proposals

At present, my country's UPR output has ranked first in the world, and it is expected that it will enter a stage of stable development in the future, with an annual growth rate of about 10%, of which DCPD modified UPR will account for 10% to 30% of the total UPR. It is estimated that the output of UPR will reach 1.2 million tons in 2007 and the demand for DCPD will be about 70,000 tons; the output of UPR in 2010 will be about 1.5 million tons and the consumption of modified UPR will be about 100,000 tons of DCPD; the output of URR in 2015 will be about 1.9 million tons and the modified UPR It consumes about 130,000 t of DCPD.

In order to promote the large-scale application of DCPD in the UPR industry, we should start from the following five aspects.

(2) Improving quality While increasing the output of DCPD, we should use the technical indicators of foreign manufacturers as the overtaking goal and strive to reach the international advanced level as soon as possible.

(3) The price reduction of DCPD was originally a part of the C5 by-product of petroleum cracking, and its price should not be too high. It is recommended to refer to the gasoline price in the same period to fluctuate upwards or downwards, otherwise it will restrict its application in UPR.

(4) Environmental protection The exhaust gas and waste water produced by using DCPD to manufacture UPR will cause serious environmental pollution. Therefore, the UPR industry, the petrochemical industry and relevant scientific research institutes should put pollution control issues on the agenda, and work together to find practical ways to eliminate the pollution caused by the use of DCPD, so that the technology will embark on a healthy development path.

(5) Innovation fully mobilizes the scientific and technological strength of UPR industry and outside, and strives to develop new varieties of UPR manufactured by DCPD, such as: ①The use of its high solid content, fast curing, and good air drying characteristics, the development of special coating resin and structural adhesive Varieties; ② Development of low styrene volatile resins with its low viscosity characteristics; ③ Development and improvement of new chlorobridge acid (HET) series UPR products; ④ Development of new DCPD corrosion-resistant UPR varieties.

DCPD UPR preparation method

1.Diels-Alder reaction

 At 160~170℃, DCPD decomposes into cyclopentadiene (CPD). CPD will undergo diene addition reaction with maleic anhydride above 170℃, and then carry out esterification reaction with glycol and dibasic acid. It is also called "anhydride method"; maleic anhydride and diol can be esterified first to form monoester, then DCPD is added dropwise at 170-175°C for Diels-Alder reaction, and then the esterification reaction is completed at 200°C.

2. DCPD direct addition reaction

Under acid catalysis, alcohol or acid can be directly added to the double bond of DCPD to form ether or ester. There are four ways for this direct addition reaction:

①Initial method: Put maleic anhydride, phthalic anhydride, diol and DCPD into the reaction kettle, heat to 150℃, reflux for 30~60min, then change to condensation and raise the temperature to 200℃ to complete the esterification.

②Hydrolysis method: maleic anhydride is heated to 80℃~100℃ with equimolar water to maleic acid, then DCPD is added dropwise to complete the reaction quickly, and then glycol and modified acid are added to complete the ester at 200℃ Change.

③ "Half ester" method: First, maleic anhydride and diol are reacted at 150 ℃ to make the ring opening of maleic anhydride to form a "half ester", and then dropwise add DCPD at 150 ℃ to add hydroxyl to the double bond of DCPD The etherification reaction, or the esterification reaction where the carboxyl group is added to the double bond of DCPD, and finally the temperature is raised to 200°C to complete the esterification.

④ End-capping method: first make maleic anhydride, phthalic anhydride and glycol complete esterification at 200 ℃, when the acid value drops to a lower value, lower the temperature to 160 ℃ and add DCPD to react, so that it will carry out the terminal hydroxyl and carboxyl Closed.

DCPD UPR performance characteristics

Due to the introduction of DCPD structure, the performance of UPR products has been significantly improved and improved, mainly in the following aspects:

1. Improve the air-drying performance of UPR. Since DCPD has a molecular structure similar to allyl ether, it is easily oxidized in the air to generate tertiary carbon hydrogen peroxide and secondary carbon hydrogen peroxide, and the generated hydrogen peroxide can generate a highly active free radical, allowing the reaction to continue , Thereby overcoming the deficiencies of the universal UPR anaerobic, so that it has good surface curing properties.

2. The DCPD modified UPR molecule contains double bonds, so that after curing after heat, the heat resistance and some mechanical properties are improved.

3. Due to the existence of five-membered ring and six-membered ring in the molecular structure of DCPD modified UPR, its compatibility with the cross-linked monomer styrene is significantly improved.

4. Due to the addition of DCPD, the chain termination reaction of UPR occurs, so the molecular weight of UPR is reduced. At the same time, the effect of DCPD on UPR

The end group blocking effect greatly reduces the polar groups such as hydroxyl and carboxyl groups at the end of the UPR chain, and reduces the hydrogen bonding between macromolecules, which effectively reduces the viscosity of the UPR. Due to the reduced viscosity, the amount of styrene added can be reduced. Therefore, on the one hand, it can reduce the volatilization of styrene and reduce environmental pollution. At the same time, it can also improve the wettability of UPR to reinforcing materials or fillers, and reduce the curing shrinkage of the resin. The end group sealing increases the steric hindrance, protects the ester group at the UPR chain end, and effectively improves the chemical resistance and atmospheric aging resistance of the UPR.

5. After the introduction of DCPD, because the viscosity of UPR is reduced, the amount of expensive styrene monomer can be reduced; less expensive phthalic anhydride can be used or less; less expensive propylene glycol and other raw materials are used, thereby It can reduce the production cost of UPR.

 DCPD modified UPR is not only widely used in the field of FRP production, but also suitable for putty, man-made due to its low shrinkage, low viscosity, good air drying, corrosion resistance, high solid content, fast curing, good wettability, etc. Stone, anchoring agent, coating, RTM molding process, anti-corrosion engineering and many other fields have very broad prospects.