Separation method and application of CBDO isomer

Abstract

The invention discloses a separation method and application of CBDO cis-trans isomers, and relates to the technical field of compound isomer separation. The separation method comprises the following steps: respectively modifying hydroxyl groups of cis-CBDO and trans-CBDO to generate polarity difference, then separating the two isomers by a solvent dissolution-crystallization method, and finally removing protection to respectively obtain the cis-CBDO isomer and the trans-CBDO isomer. Through a modification protection-separation-deprotection method, the method has the advantages that the method is simple, the separation cost is reduced, and CBDO products with different cis-trans ratios and all-trans CBDO isomers can be obtained; the cis-trans ratio of the CBDO product can be up to 39.5 / 1, and compared with the commercially available CBDO, the copolyester prepared by using the CBDO product under the same condition has higher intrinsic viscosity and glass transition temperature, and the copolyester product with a full cis form can be obtained, so that the application range of the polymer can be expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of compound isomer separation, and in particular to a method for separating CBDO isomers, and more particularly to a method for separating cis-isomers and trans-isomers of CBDO and application thereof. Background Art

[0002] 2,2,4,4-Tetramethyl-1,3-cyclobutanediol (CBDO) is mainly used to produce high-performance copolyesters that replace traditional polycarbonate (PC). The copolyesters synthesized with CBDO as raw material have improved hydrolysis stability and chemical resistance, will not release bisphenol A during use, and are easy to process, making them suitable for the manufacture of medical bottles, baby bottles, personal care bottles, carbonated beverage bottles, hot-fill bottles, food containers and other products. The Tritan series products produced by Eastman Chemical Company in the United States use CBDO copolyesters as raw materials and are commercially produced on a large scale; the product is copolymerized by CBDO, terephthalic acid and 1,4-cyclohexanedimethanol. It not only has good temperature resistance, high flexibility and transparency, but also has no bisphenol A structure, is green and environmentally friendly, and has broad application prospects.

[0003] CBDO has two isomers, cis and trans, with symmetrical structures. Cis-CBDO is a non-planar structure of the C4 ring (dihedral angle is 17.5°), and trans-CBDO is a planar structure of the C4 ring. The cis-trans ratio of CBDO (mass ratio of cis-CBDO to trans-CBDO) has an important impact on the subsequent copolyester process and even product performance. The effect of cis-CBDO on improving the glass transition temperature of copolyester is about twice that of trans-CBDO. However, the reaction activity of CBDO is lower than that of ethylene glycol, resulting in that CBDO cannot effectively enter the copolyester molecular chain, and generally, the activity of cis-CBDO is higher than that of trans-CBDO; the cis-trans ratio of CBDO in the prior art is generally 1:1~1.6:1, and in the copolymerization process, trans-CBDO cannot enter the copolyester molecular chain, so the low cis-trans ratio (higher trans-CBDO content) leads to extremely low utilization rate of synthetic raw materials, and cannot effectively increase the CBDO content in the polycarbonate molecular chain, and also increases the actual production manufacturing cost; therefore, how to increase the cis-trans ratio of CBDO to increase the utilization rate of CBDO in the copolymerization process of generating polycarbonate is one of the problems that need to be solved urgently.

[0004] At present, the production process of CBDO mainly uses isobutyric anhydride as raw material, which is thermally cracked to generate dimethyl ketone (DMK), and DMK dimerizes to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanedione (CBDK), and then CBDO is obtained through CBDK hydrogenation process. For example, the US invention patent US3190928A uses nickel-based or ruthenium-based catalysts to obtain CBDO products with a maximum mass ratio of cis-CBDO to trans-CBDO of 1.2; the US invention patent US20080132738A1 uses Ni-based catalysts to obtain products with a maximum cis-trans ratio of 1.2; the US invention patent US20080132742A1 uses Cu-based catalysts to obtain products with a maximum cis-trans ratio of 1.68; the Chinese invention patent CN110124674A provides a CBDO product obtained by using Fe, Co or Ni-based catalysts, and its maximum cis-trans ratio is 1.5. It can be seen that the cis-trans ratio of the product directly obtained in the CBDO production process is usually low (<2), which cannot meet the requirements of the downstream polyester industry for the CBDO cis-trans ratio.

[0005] Based on the technical problem, the present invention provides a method for separating cis-CBDO isomers and trans-CBDO isomers to obtain a technology for obtaining a high cis-trans ratio CBDO, providing a basis for obtaining a copolyester product with a high molecular weight and a high CBDO content, thereby making the polymer have higher heat resistance and application range. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for separating cis-CBDO and trans-CBDO isomers to solve the problem of low cis-trans ratio of CBDO in the prior art.

[0007] In order to achieve the above-mentioned object, the present invention provides a method for separating cis-isomers and trans-isomers of CBDO, comprising respectively modifying the terminal hydroxyl groups of the cis-CBDO isomer and the trans-CBDO isomer to protect the hydroxyl groups, and at the same time making the modified cis-CBDO isomer and the trans-CBDO isomer have a polarity difference, then separating the two by a solvent dissolution-crystallization method, and finally removing the protection respectively to obtain CBDO isomers with a high cis-trans ratio.

[0008] Specifically, the separation method comprises the following steps: S1. using a modifying agent to modify the hydroxyl groups of the cis and trans isomers of CBDO respectively to obtain a mixture containing CBDO structural units; S2. adding the mixture containing the CBDO structural unit to a separation solvent, and obtaining the modified cis-CBDO isomer and the modified trans-CBDO isomer by filtering and / or rotary evaporation, respectively; S3. The product is demodified by a decomposition reaction, and finally physically separated to obtain cis-CBDO isomers and trans-CBDO isomers with different cis-trans ratios.

[0009] Preferably, in S1, the modifier is an ester, an acid (anhydride), an acyl chloride and an aldehyde, and the number of its functional groups is an integer not less than 1.

[0010] Furthermore, in S1, the modifier is any one of phenyl-substituted esters, phenyl-substituted monocarboxylic acids, phenyl-substituted acid chlorides, phenyl-substituted aldehydes, C2~C6 alkyl-substituted monocarboxylic acids, C2~C6 alkyl-substituted aldehydes; or any one of acid chlorides, acid anhydrides or polycarboxylic acids.

[0011] Preferably, in S2, the separation solvent may be a low-toxic solvent, such as one or a combination of water, methanol, ethanol, DMSO, DMF, acetone, ether, ethyl acetate; more preferably, acetone.

[0012] Preferably, in S3, the decomposition reaction includes any one of alcoholysis reaction, alkaline hydrolysis reaction or acid hydrolysis reaction.

[0013] Preferably, the modifier comprises any one of acetic acid, propionic acid, oxalic acid, malonic acid, dimethyl oxalate, dimethyl malonate, benzoic acid, terephthalic acid, isophthalic acid, phthalic acid, trimellitic acid, dimethyl terephthalate, dimethyl isophthalate, dimethyl phthalate, trimethyl trimellitate, acetic anhydride, propionic anhydride, phthalic anhydride, benzoic anhydride, phthalic anhydride, acetyl chloride, propionyl chloride, oxalyl chloride, monomethyl oxalyl chloride, malonic chloride, benzoyl chloride, terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, acetaldehyde, propionaldehyde, benzaldehyde, and hydroxybenzaldehyde.

[0014] Preferably, the decomposition reaction comprises adding alcohol to the product to carry out alcoholysis reaction, and the alcohol may be a monoalcohol or a polyol.

[0015] Preferably, the alcoholysis reaction includes a catalyst; the catalyst is selected from at least one of MXene, phosphoric acid, sulfuric acid, organic sulfonic acids, metal salts, and metal oxides; wherein the metal element in the metal salt and / or the metal oxide is selected from metal elements of groups IIA, IIIA, IVA, and IVB; introducing an appropriate amount of catalyst can accelerate the rate of the alcoholysis reaction.

[0016] Preferably, the catalyst is added in an amount of 50 to 2000 ppm.

[0017] Preferably, the decomposition reaction comprises adding alkali solution to the product to carry out alkaline hydrolysis reaction; the alkali solution is an aqueous solution of sodium hydroxide or potassium hydroxide.

[0018] More preferably, the concentration of the alkali solution is 5-15 wt %.

[0019] Preferably, the decomposition reaction comprises adding acid solution to the product for acidolysis reaction; the acid solution is an aqueous solution of hydrochloric acid, sulfuric acid, phosphoric acid or p-toluenesulfonic acid.

[0020] More preferably, the concentration of the acid solution is 1-5 mol / L.

[0021] Preferably, the physical separation method comprises extraction, (reduced pressure) distillation, sublimation, crystallization and filtration.

[0022] Preferably, the CBDO product obtained by separation includes cis-CBDO isomers and trans-CBDO isomers in a cis-to-trans ratio of 7 / 3 to 39.5 / 1.

[0023] In particular, the all-trans CBDO isomer can also be obtained by adopting the above technical solution.

[0024] The CBDO product with a high cis-trans ratio provided by the technical solution is used as a monomer, and a copolyester containing CBDO is prepared by a melt polycondensation method with ethylene glycol and dimethyl terephthalate. Compared with the commercially available CBDO with a cis-trans ratio of 1 / 1 as a monomer, the copolyester obtained by the present invention has a higher intrinsic viscosity and glass transition temperature, which is conducive to expanding the application range of the polymer.

[0025] Theoretically, compared with trans-CBDO, cis-CBDO has a much higher polarity (1.987 vs 0.1706 Debye), but the presence of hydroxyl groups results in similar solubility of the two in common solvents such as water, acetone, ether, and ethyl acetate, so the two cannot be effectively separated by simple extraction, crystallization, etc. Based on this, the present invention modifies the hydroxyl groups of CBDO to change the solubility of the two cis- and trans-isomers of CBDO in common solvents, so that the two can be separated by simple filtration and rotary evaporation operations, thereby obtaining CBDOX and CBDOX products with a high cis- and trans-ratio, and then removing the protecting group X, and finally regulating the cis- and trans-ratio of cis-CBDO and trans-CBDO isomers in the product.

[0026] Furthermore, the reaction mechanism of CBDO for hydroxyl protection is: .

[0027] Beneficial technical effects obtained by the present invention: (1) The present invention not only protects the hydroxyl group by reacting the modifier with the terminal hydroxyl group of CBDO, but also causes the overall polarity of the modified cis-trans isomers of CBDO to differ through the modified group, so that the cis-trans isomers of CBDO can be separated by dissolving, crystallizing and deprotecting with a common solvent. This method is simple and greatly reduces the separation cost. At the same time, CBDO with different cis-trans ratios can be obtained to meet different needs.

[0028] (2) By adopting the technical solution of the present invention, a CBDO product with a cis-conformation content of up to 70-97.5% can be obtained, which is beneficial to the subsequent copolyester polymerization process and improves product performance and reduces product prices. In addition, an all-trans CBDO product can be obtained.

[0029] (3) By adopting the technical solution of the present invention, the modifying agent can be recycled and reused, which greatly reduces the process cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the H-NMR spectrum of the CBDO product commercially available in the prior art.

[0031] Figure 2 This is the H NMR spectrum of the all-trans CBDO product prepared in Example 1 of the present invention.

[0032] Figure 3 This is the H NMR spectrum of the cis-CBDO product prepared in Example 1 of the present invention.

[0033] Figure 4 This is the H NMR spectrum of the cis-CBDO product prepared in Example 2 of the present invention.

[0034] Figure 5 is the precipitated product obtained in Comparative Example 1 of the present invention 1 H NMR spectrum.

[0035] Figure 6 The CBDO phthalate precipitate obtained in Example 1 of the present invention 1 H NMR spectrum.

[0036] Figure 7 is the phthalate CBDO in the acetone solution obtained in Example 1 of the present invention 1 H NMR spectrum.

[0037] Figure 8 The copolyester product obtained by using commercially available CBDO as a monomer of the present invention is 1 H NMR spectrum.

[0038] Fig. 9The copolyester product obtained by Example 1 of the present invention containing 97.5% cis-CBDO as a monomer is 1 H NMR spectrum.

[0039] Fig.10 It is a comparison diagram of the DSC curves of the copolyester products obtained by polycondensing the CBDO provided in Example 1 of the present invention as a monomer and the commercially available CBDO as a monomer.

[0040] Fig.11a and Fig.11b They are respectively the structural formulas of cis-phthalate CBDO and trans-phthalate CBDO in Example 1 of the present invention.

[0041] Figure 12a-Figure 12c Respectively PETB3, PETB4 and PETB5 provided by the present invention 1 H NMR spectrum.

[0042] Fig.13 It is a comparison diagram of the DSC curves of PETB3, PETB4 and PETB5 provided by the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0044] The raw materials used in the following examples were analytically pure with a purity of 99%. Phthalic anhydride and CBDO with a cis-trans isomer ratio of 1 were purchased from MacLean Company.

[0045] The technical scheme of the present invention is further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention, and do not have any limiting effect on it. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present invention. The experimental methods for which specific conditions are not specified in the following embodiments are usually carried out under conventional conditions or under the conditions recommended by the manufacturer.

[0046] Example 1 This embodiment provides a method for separating cis and trans isomers of CBDO, and the specific steps include: 1. Preparation of phthalate CBDO and terminal modification of the hydroxyl groups of CBDO The reaction raw materials phthalic anhydride (148.0 g, 1.0 mol) and CBDO (72.0 g, 0.5 mol) were added into the reactor. Under nitrogen protection, the temperature of the materials was gradually raised to 130-150°C, and the reaction was continued for 1 h, and the reaction was completed.

[0047] The reaction product is fully dissolved in acetone, and then filtered to collect the filtered product; the acetone solution is rotary evaporated to remove the solvent acetone and then dried to obtain a dried product; The obtained filtered product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly trans-phthalate CBDO.

[0048] The obtained drying product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly cis-phthalate CBDO.

[0049] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were subjected to alkaline hydrolysis with a sodium hydroxide solution having a concentration of 15 wt%, and then the solution was concentrated and distilled under reduced pressure to obtain cis-CBDO (97.5 mol%) and trans-CBDO (100 mol%), respectively.

[0050] See also Figure 1 , is the H NMR spectrum of the commercially available CBDO product used in this example, Figure 2 This is the H NMR spectrum of all-trans CBDO (100 mol%) obtained in step 2 of this example. Figure 3 This is the H NMR spectrum of cis-CBDO (97.5 mol%) prepared in this example. As can be seen from the figure, the signal peak at the chemical shift of 1.0 ppm is the methyl hydrogen in the CBDO structure. The commercially available CBDO has a triplet peak, the all-trans CBDO has only one peak, and the 97.5 mol% cis CBDO has mainly two peaks. This shows that the separation method has a good separation effect on the cis and trans isomers of CBDO.

[0051] See also Figure 7 , is the H NMR spectrum of phthalate CBDO in acetone solution of this example. It can be seen that the signal peak at the chemical shift of 1.0 ppm is mainly a double peak, indicating that the substance is mainly cis-phthalate CBDO.

[0052] See also Figure 6, is the H NMR spectrum of phthalate CBDO in acetone solution in this example. It can be seen that the signal peak at the chemical shift of 1.0 ppm is mainly a single peak, indicating that the substance is mainly trans-phthalate CBDO. This result shows that due to the different polarities of cis- and trans-phthalate CBDO caused by the cis- and trans-isomers of CBDO, their solubility behaviors in acetone are significantly different, thereby achieving separation from each other.

[0053] See also Fig.11a and Fig.11b The structural formulas are cis-phthalate CBDO and trans-phthalate CBDO, respectively. The dipole moment of the former is 3.6555De, and the dipole moment of the latter is 0.0995De. After the isomers of CBDO are modified by the same modifier, the dipole moments of the cis and trans products obtained are very different, thus forming a polarity difference, and then showing different dissolution behaviors in the solvent, achieving separation.

[0054] Example 2 This embodiment provides a method for separating cis and trans isomers of CBDO, and the specific steps include: 1. Preparation of phthalate CBDO and terminal modification of the hydroxyl groups of CBDO The reaction raw materials phthalic anhydride (148.0 g, 1.0 mol) and CBDO (144.0 g, 1.0 mol) were added into the reactor. Under nitrogen protection, the temperature of the materials was gradually raised to 130-150°C, and the reaction was continued for 1 h, and the reaction was completed.

[0055] The product is fully dissolved in acetone, then filtered, and the filtered product is collected; the solvent acetone is removed by rotary evaporation and the product is dried to obtain a dried product.

[0056] The obtained filtered product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly trans-phthalate CBDO.

[0057] The obtained drying product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly cis-phthalate CBDO.

[0058] 2. Deprotection (regeneration of CBDO) All the dried products and filtered products were subjected to alkaline hydrolysis with a sodium hydroxide solution having a concentration of 15 wt%, and then the solution was concentrated and distilled under reduced pressure to obtain cis-CBDO (70 mol%) and trans-CBDO (100 mol%), respectively.

[0059] See also Figure 4, is the H NMR spectrum of cis-CBDO (70 mol%) prepared in this example. The results show that by increasing the ratio of commercially available CBDO to phthalic anhydride, a product with a lower cis-CBDO content can be obtained under the same conditions; the H NMR spectrum of trans-CBDO (100 mol%) is the same as that of all-trans-CBDO (100 mol%) obtained in Example 1.

[0060] Example 3 This embodiment provides a method for separating cis and trans isomers of CBDO, and the specific steps include: 1. Preparation of phthalate CBDO and terminal modification of the hydroxyl groups of CBDO The raw materials of phthalic anhydride (297.0 g, 4.0 mol) and CBDO (72.0 g, 1.0 mol) were added into the reactor. Under nitrogen protection, the temperature of the materials was gradually raised to 130-150 ℃ , and react for 1 h, and the reaction is completed.

[0061] The product is fully dissolved in acetone, then filtered, and the filtered product is collected; the solvent acetone is removed by rotary evaporation and the product is dried to obtain a dried product.

[0062] The obtained filtered product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly trans-phthalate CBDO.

[0063] The obtained drying product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly cis-phthalate CBDO.

[0064] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were subjected to alkaline hydrolysis with a sodium hydroxide solution having a concentration of 15 wt%, and then the solution was concentrated and distilled under reduced pressure to obtain cis-CBDO (97 mol%) and trans-CBDO (100 mol%), respectively.

[0065] The H-NMR spectra of the cis- and trans-CBDO obtained in this example are the same as those in Example 1.

[0066] Example 4 This embodiment provides a method for separating cis and trans isomers of CBDO, and the specific steps include: 1. Preparation of phthalate CBDO and terminal modification of the hydroxyl groups of CBDO The reaction raw materials phthalic anhydride (148.0 g, 1.0 mol) and CBDO (72.0 g, 0.5 mol) were added into the reactor. Under nitrogen protection, the temperature of the materials was gradually raised to 130-150°C, and the reaction was continued for 1 h, and the reaction was completed.

[0067] The product is fully dissolved in acetone, then filtered, and the filtered product is collected; the solvent acetone is removed by rotary evaporation and the product is dried to obtain a dried product.

[0068] The obtained filtered product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly trans-phthalate CBDO.

[0069] The obtained drying product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly cis-phthalate CBDO.

[0070] 2. Deprotection (regeneration of CBDO) After the dried product and the filtered product were hydrolyzed with n-octanol, 0.02 g of catalyst MXene was added respectively, and then distilled under reduced pressure to obtain cis-CBDO (97.5 mol%), trans-CBDO (100 mol%), and dioctyl phthalate (97~99wt%).

[0071] The H-NMR spectra of the cis- and trans-CBDO obtained in this example are the same as those in Example 1.

[0072] Example 5 This embodiment provides a method for separating cis and trans isomers of CBDO, and the specific steps include: 1. Preparation of phthalate CBDO and terminal modification of the hydroxyl groups of CBDO The reaction raw materials phthalic anhydride (148.0 g, 1.0 mol) and CBDO (144.0 g, 1.0 mol) were added into the reactor. Under nitrogen protection, the temperature of the materials was gradually raised to 130-150°C, and the reaction was continued for 1 h, and the reaction was completed.

[0073] The product is fully dissolved in acetone, then filtered, and the filtered product is collected; the solvent acetone is removed by rotary evaporation and the product is dried to obtain a dried product.

[0074] The obtained filtered product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly trans-phthalate CBDO.

[0075] The obtained drying product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly cis-phthalate CBDO.

[0076] 2. Deprotection (regeneration of CBDO) After the dried product and the filtered product were hydrolyzed with n-octanol, 0.02 g of catalyst MXene was added respectively, and then distilled under reduced pressure to obtain cis-CBDO (70 mol%), trans-CBDO (100 mol%), and dioctyl phthalate (97~99wt%).

[0077] Example 6 This embodiment provides a method for separating cis and trans isomers of CBDO, and the specific steps include: 1. Preparation of phthalate CBDO and terminal modification of the hydroxyl groups of CBDO The reaction raw materials phthalic anhydride (297.0 g, 4.0 mol) and CBDO (72.0 g, 0.5 mol) were added into the reactor. Under nitrogen protection, the temperature of the materials was gradually raised to 130-150°C, and the reaction was continued for 1 h, and the reaction was completed.

[0078] The product is fully dissolved in acetone, then filtered, and the filtered product is collected; the solvent acetone is removed by rotary evaporation and the product is dried to obtain a dried product.

[0079] The obtained filtered product is carboxyl-terminated phthalate CBDO, and the conformation of CBDO is mainly trans-phthalate CBDO.

[0080] The obtained drying product is carboxyl-terminated phthalate CBDO, and the conformation of CBDO is mainly cis-phthalate CBDO.

[0081] 2. Deprotection (regeneration of CBDO) After the dried product and the filtered product were hydrolyzed with hexanediol, 0.02 g of catalyst MXene was added respectively, and then distilled under reduced pressure to obtain cis-CBDO (97.5 mol%) and trans-CBDO (100 mol%).

[0082] The H-NMR spectra of the cis- and trans-CBDO obtained in this example are the same as those in Example 1.

[0083] Example 7 This embodiment provides a method for separating cis and trans isomers of CBDO, and the specific steps include: 1. Preparation of phthalate CBDO and terminal modification of the hydroxyl groups of CBDO The raw materials of phthalic anhydride (148.0 g, 1.0 mol) and CBDO (72.0 g, 0.5 mol), 500 mL of acetone and 1.0 g of zinc acetate were added into the reactor. Under nitrogen protection, the temperature of the materials was gradually raised to 60°C, and the reaction was continued for 8 hours, and the reaction was completed.

[0084] The product is fully dissolved in acetone, then filtered, and the filtered product is collected; the solvent acetone is removed by rotary evaporation and the product is dried to obtain a dried product.

[0085] The obtained filtered product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly trans-phthalate CBDO.

[0086] The obtained drying product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly cis-phthalate CBDO.

[0087] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were subjected to alkaline hydrolysis with a sodium hydroxide solution having a concentration of 15 wt%, the solution was concentrated, and then distilled under reduced pressure to obtain cis-CBDO (97.5 mol%) and trans-CBDO (100 mol%).

[0088] The H-NMR spectra of the cis- and trans-CBDO obtained in this example are the same as those in Example 1.

[0089] Example 8 This embodiment provides a method for separating cis and trans isomers of CBDO, and the specific steps include: 1. Preparation of phthalate CBDO and terminal modification of the hydroxyl groups of CBDO The raw materials of phthalic anhydride (148.0 g, 1.0 mol) and CBDO (72.0 g, 0.5 mol), 500 mL of acetone and 1.0 g of zinc acetate were added into the reactor. Under nitrogen protection, the temperature of the materials was gradually raised to 60°C, and the reaction was continued for 8 hours, and the reaction was completed.

[0090] The product is fully dissolved in acetone, then filtered, and the filtered product is collected; the solvent acetone is removed by rotary evaporation and the product is dried to obtain a dried product.

[0091] The obtained filtered product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly trans-phthalate CBDO.

[0092] The obtained drying product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly cis-phthalate CBDO.

[0093] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were respectively hydrolyzed with n-octanol, and 0.2 g of TBT as a catalyst was added, and then vacuum distillation was performed to obtain cis-CBDO (97.5 mol%), trans-CBDO (100 mol%) and dioctyl phthalate (97~99wt%).

[0094] The H-NMR spectra of the cis- and trans-CBDO obtained in this example are the same as those in Example 1.

[0095] Example 9 This embodiment provides a method for separating cis and trans isomers of CBDO, and the specific steps include: 1. Preparation of phthalate CBDO and terminal modification of the hydroxyl groups of CBDO The reaction raw materials phthalic anhydride (148.0 g, 1.0 mol) and CBDO (72.0 g, 0.5 mol), 500 mL of a mixed solvent of acetone and water (volume ratio of 15:1), and 1.0 g of zinc acetate were added to the reactor. Under nitrogen protection, the temperature of the material was gradually raised to 60°C, and the reaction was continued for 8 h, and the reaction was completed.

[0096] The product is fully dissolved in acetone, then filtered, and the filtered product is collected; the solvent acetone is removed by rotary evaporation and the product is dried to obtain a dried product.

[0097] The obtained filtered product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly trans-phthalate CBDO.

[0098] The obtained drying product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly cis-phthalate CBDO.

[0099] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were respectively hydrolyzed with n-octanol and TBT (added amount 0.2 g) as a catalyst, and then distilled under reduced pressure to obtain cis-CBDO (97.5 mol%), trans-CBDO (100 mol%) and dioctyl phthalate (97~99wt%).

[0100] Example 10 This embodiment provides a method for separating cis and trans isomers of CBDO, and the specific steps include: 1. Preparation of phthalate CBDO and terminal modification of the hydroxyl groups of CBDO The reaction raw materials phthalic anhydride (148.0 g, 1.0 mol) and CBDO (72.0 g, 0.5 mol), 500 mL of a mixed solvent of acetone and ethanol (volume ratio of 15:1), and 1.0 g of zinc acetate were added to the reactor. Under nitrogen protection, the temperature of the material was gradually raised to 60°C, and the reaction was continued for 8 h, and the reaction was completed.

[0101] The product is fully dissolved in acetone, then filtered, and the filtered product is collected; the solvent acetone is removed by rotary evaporation and the product is dried to obtain a dried product.

[0102] The obtained filtered product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly trans-phthalate CBDO.

[0103] The obtained drying product is carboxyl-terminated CBDO phthalate, and the conformation of CBDO is mainly cis-phthalate CBDO.

[0104] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were respectively hydrolyzed with n-octanol and TBT (added amount 0.2 g) as a catalyst, and then distilled under reduced pressure to obtain cis-CBDO (97.5 mol%), trans-CBDO (100 mol%) and dioctyl phthalate (97~99wt%).

[0105] The H-NMR spectra of the cis- and trans-CBDO obtained in this example are the same as those in Example 1.

[0106] Embodiment 11 This embodiment provides a method for separating cis and trans isomers of CBDO, using isophthaloyl chloride as a modifier, and the specific steps include: 1. Preparation of isophthaloyl chloride CBDO and terminal modification of the hydroxyl groups of CBDO The reaction raw materials of isophthaloyl chloride (50.8 g, 0.250 mol) and CBDO (18.0 g, 0.125 mol), 500 mL of chloroform and 1.0 g of zinc chloride were added into the reactor and refluxed for 48 h to terminate the reaction.

[0107] The product is fully dissolved in ethyl acetate, then filtered to collect the filtered product; the solvent ethyl acetate is removed by rotary evaporation and dried to obtain a dried product.

[0108] The obtained filtered product is acyl chloride-terminated CBDO isophthalate, and the conformation of CBDO is mainly trans-isophthalate CBDO.

[0109] The obtained drying product is acyl chloride-terminated CBDO isophthalate, and the conformation of CBDO is mainly cis-isophthalate CBDO.

[0110] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were subjected to alkaline hydrolysis with 15 wt% NaOH, filtered, and then distilled under reduced pressure to obtain cis-CBDO (97.5 mol%), trans-CBDO (100 mol%) and disodium isophthalate.

[0111] The H-NMR spectra of the cis- and trans-CBDO obtained in this example are the same as those in Example 1.

[0112] Example 12 This embodiment provides a method for separating cis and trans isomers of CBDO, using salicylic acid as a modifier, and the specific steps include: 1. Preparation of salicylic acid CBDO and terminal modification of the hydroxyl groups of CBDO The product was fully dissolved in ethyl acetate, and then the reaction raw materials salicylic acid (34.5 g, 0.250 mol) and CBDO (18.0 g, 0.125 mol), 500 mL acetone solution, and 2.0 g dilute sulfuric acid were added to the reactor. The reaction was refluxed for 48 h, and then 400 mL acetone was evaporated at 40 °C, and the reaction was completed.

[0113] The product is fully dissolved in ethyl acetate, then filtered to collect the filtered product; the solvent ethyl acetate is removed by rotary evaporation and dried to obtain a dried product.

[0114] The obtained filtered product is hydroxyl-terminated CBDO salicylate, and the conformation of CBDO is mainly trans-salicylate CBDO.

[0115] The obtained drying product is hydroxyl-terminated CBDO salicylate, and the conformation of CBDO is mainly cis-salicylate CBDO.

[0116] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were respectively subjected to alkaline hydrolysis with 15 wt% NaOH, filtered, and then distilled under reduced pressure to obtain cis-CBDO (97.5 mol%), trans-CBDO (100 mol%) and disodium salicylate.

[0117] The H-NMR spectra of the cis- and trans-CBDO obtained in this example are the same as those in Example 1.

[0118] Embodiment 13 This embodiment provides a method for separating cis and trans isomers of CBDO, using salicylaldehyde as a modifier, and the specific steps include: 1. Preparation of hemiacetal CBDO and terminal modification of the hydroxyl groups of CBDO The reaction raw materials salicylaldehyde (61.0 g, 0.500 mol) and CBDO (18.0 g, 0.125 mol), 500 mL acetone solution, and 2.0 g dilute sulfuric acid were added into the reactor and refluxed for 48 h. Then, 400 mL acetone was evaporated at 40 °C and the reaction was terminated.

[0119] The product is fully dissolved in ethyl acetate, then filtered to collect the filtered product; the solvent ethyl acetate is removed by rotary evaporation and dried to obtain a dried product.

[0120] The obtained filtered product is a hemiacetal-terminated CBDO salicylaldehyde compound, and the conformation of CBDO is mainly trans-salicylaldehyde CBDO.

[0121] The obtained drying product is a hemiacetal-terminated CBDO salicylaldehyde compound, and the conformation of CBDO is mainly cis-salicylaldehyde CBDO.

[0122] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were respectively subjected to alkaline hydrolysis with 15 wt% NaOH, filtered, and then distilled under reduced pressure to obtain cis-CBDO (97.5 mol%), trans-CBDO (100 mol%) and disodium salicylate.

[0123] The H NMR spectra of the cis- and trans-CBDO obtained in this example are the same as those in Example 12.

[0124] Embodiment 14 This embodiment provides a method for separating cis and trans isomers of CBDO, using salicylic acid as a modifier, and the specific steps include: 1. Preparation of oxalic acid CBDO and terminal modification of the hydroxyl groups of CBDO The product was fully dissolved in ethyl acetate, and then the reaction raw materials oxalic acid (0.250 mol) and CBDO (0.125 mol), 500 mL acetone solution, and 2.0 g dilute sulfuric acid were added to the reactor. The reaction was refluxed for 48 h, and then 400 mL acetone was evaporated at 40 °C, and the reaction was completed.

[0125] The product is fully dissolved in ethyl acetate, then filtered to collect the filtered product; the solvent ethyl acetate is removed by rotary evaporation and dried to obtain a dried product.

[0126] The obtained filtered product is hydroxyl-terminated CBDO oxalate, and the conformation of CBDO is mainly trans-oxalate CBDO.

[0127] The obtained drying product is hydroxyl-terminated CBDO oxalate, and the conformation of CBDO is mainly cis-oxalate CBDO.

[0128] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were respectively subjected to alkaline hydrolysis with 15 wt% NaOH, filtered, and then distilled under reduced pressure to obtain cis-CBDO (97.5 mol%), trans-CBDO (100 mol%) and disodium oxalate.

[0129] The cis-trans ratio of CBDO in the precipitation of this example is 10:1.

[0130] Embodiment 15 This embodiment provides a method for separating cis and trans isomers of CBDO, using acetic acid as a modifying agent, and the specific steps include: 1. Preparation of CBDO acetate and terminal modification of the hydroxyl groups of CBDO The product was fully dissolved in ethyl acetate, and then the reaction raw materials acetic acid (0.250 mol) and CBDO (0.125 mol), 500 mL acetone solution, and 2.0 g dilute sulfuric acid were added to the reactor. The reaction was refluxed for 48 h, and then 400 mL acetone was evaporated at 40 °C, and the reaction was completed.

[0131] The product is fully dissolved in ethyl acetate, then filtered to collect the filtered product; the solvent ethyl acetate is removed by rotary evaporation and dried to obtain a dried product.

[0132] The obtained filtered product is hydroxyl-terminated CBDO acetate, and the conformation of CBDO is mainly trans-acetate CBDO. The obtained dried product is hydroxyl-terminated CBDO acetate, and the conformation of CBDO is mainly cis-acetate CBDO.

[0133] 2. Deprotection (regeneration of CBDO) The dried product and the filtered product were respectively subjected to alkaline hydrolysis with 15 wt% NaOH, filtered, and then distilled under reduced pressure to obtain cis-CBDO (97.5 mol%), trans-CBDO (100 mol%) and sodium acetate.

[0134] The cis-trans ratio of CBDO in the precipitate of this example is 7:3.

[0135] Comparative Example 1 In this comparative example, commercially available CBDO (cis-trans ratio of 1:1) was dissolved in acetone, and a precipitate was produced after concentration; however, the cis- and trans-isomer contents of CBDO in the precipitate were similar.

[0136] See also Figure 5 This is the H NMR spectrum of the precipitate in this comparative example. It can be seen from the figure that the cis-trans ratio of CBDO in the precipitate is 1:1.3, indicating that the separation effect is poor.

[0137] Comparative Example 2 Commercially available CBDO (cis-trans ratio of 1:1) was dissolved in a mixed solution of acetone and water in a volume ratio of 10:1, and a precipitate was obtained after concentration.

[0138] Analysis of H-NMR spectrum showed that the CBDO cis- and trans-isomer contents in the precipitated product were similar, and the separation effect was poor.

[0139] Comparative Example 3 The only difference between this comparative example and Example 14 is that formic acid is used as the modifier; the other steps are the same.

[0140] Analysis of H-NMR spectrum showed that the cis- and trans-isomer contents of CBDO in the precipitated product were similar, and the separation effect was poor.

[0141] Examples 1 to 4 are experiments conducted by changing the feed ratio of phthalic anhydride to CBDO. Examples 5 to 7 are experiments conducted by alcoholysis to regenerate CBDO. Examples 8 to 11 are experiments conducted by solvent method to prepare CBDO phthalate, and Examples 12 to 14 are experiments conducted by using other modifiers to separate CBDO phthalate. Compared with Examples 8 and 9, the separation solvents used in Examples 10 and 11 are mixed solvents.

[0142] Further, in order to illustrate the technical effect produced by the technical solution, the present invention uses CBDO (cis-trans ratio is 1), ethylene glycol (EG) and dimethyl terephthalate (DMT) as monomers, and adopts a melt polycondensation method to prepare a copolyester PETB2 containing CBDO; The polycondensation process is as follows: Process 1: Weigh 50 g of dimethyl terephthalate (DMT), 27 g of ethylene glycol (EG), 11 g of CBDO, 0.05 g of triphenyl phosphate, 0.05 g of zinc acetate and 0.05 g of antimony trioxide, react at normal pressure and 176 ° C for 6 h, then heat to 220 ° C within 1 h and continue to react for 1 h, react at 245 ° C and a pressure of 1000 Pa for 0.5 h, and finally react at 255~275 ° C and a pressure of 60 Pa to the required viscosity (PETB1 only needs 2 h, while PETB2 did not reach the required viscosity within 4 h), stop stirring and protect the discharge with nitrogen.

[0143] And, process 2: weigh 50 g of dimethyl terephthalate (DMT), 27 g of ethylene glycol (EG), 22 g of CBDO, and 0.05 g of triphenyl phosphate, react at normal pressure and 176°C for 10 h, then heat to 220°C within 1 h and continue to react for 1 h, react at 245°C and a pressure of 1000 Pa for 0.5 h, and finally react at 255-275°C and a pressure of 60 Pa to the desired viscosity (PETB3 only takes 2 h, PETB4 takes 3 h, and PETB5 (commercially available CBDO) takes 3.5 h to reach the desired viscosity), stop stirring and protect the discharge with nitrogen, and the catalysts in the polymerization process are 0.05 g of zinc acetate and 0.05 g of antimony trioxide.

[0144] PETB1 and PETB2 were obtained by polycondensing the PETB with a cis-trans ratio provided in the above embodiment and the commercially available CBDO with a cis-trans ratio of 1 / 1 as monomers with ethylene glycol (EG) and dimethyl terephthalate (DMT) using process 1.

[0145] At the same time, CBDO with cis-trans ratios of 10 / 1 and 7 / 3 provided in the above embodiments and CBDO with a commercially available cis-trans ratio of 1 / 1 were used as monomers, and ethylene glycol (EG) and dimethyl terephthalate (DMT) were polycondensed using process 2 to obtain PETB3, PETB4 and PETB5.

[0146] Structural characterization: AvIII NMR spectrometer (400 MHz) was used to measure the H NMR spectrum of the sample with deuterated chloroform (CDCl3) as solvent and TMS as internal standard. 1 H NMR).

[0147] Determination of intrinsic viscosity: The intrinsic viscosity of the prepared PETB copolyester was measured using an Ubbelohde viscometer (ZVISCO). The copolyester concentration was 0.5 g / dL, the solvent was a mixed solution of phenol and tetrachloroethane (mass ratio of 1:1), and the test temperature was (25±0.1)°C.

[0148] Melting behavior characterization: The melting behavior of the prepared copolyester was characterized by a differential scanning calorimetry (DSC) instrument (Diamond DSC, Perkine-Elmer); the weight of the test sample was about 5 mg; the test method included: heating the copolyester from room temperature to 260 °C at a heating rate of 80 °C / min, then cooling to -50 °C at a cooling rate of 80 °C / min to eliminate the thermal history; then heating to 260 °C at a heating rate of 10 °C / min to obtain the temperature rise curve of the sample.

[0149] By characterizing the structures and melting behaviors of the obtained products PETB1, PETB2, PETB3, PETB4 and PETB5, the influence of the structures and properties of the above five PETB copolyesters was analyzed respectively.

[0150] Specifically, when process one is adopted, the copolyester product obtained, the copolyester prepared from the CBDO monomer with a high cis-trans ratio has a higher intrinsic viscosity than that prepared from the copolyester with a low cis-trans ratio, the CBDO content in the copolyester is also higher, and it also has a higher glass transition temperature. The feed amount of CBDO with different cis-trans ratios of PETB1 and PETB2 is 30%, while the content of CBDO in the products is significantly different, the CBDO content in PETB1 is 18.0%, and the lowest content of PETB2 is 8.1%; when process two is adopted, the feed amount of CBDO monomers of PETB3, PETB4 and PETB5 is 60%, and the content of CBDO in the products is basically the same, about 40%.

[0151] Further analysis of the effect of cis-trans ratio on CBDO content and structure in copolyesters was conducted by combining H NMR spectra. Figure 8, is the H NMR spectrum of the copolyester PETB2 obtained by using CBDO (commercially available) with a cis-trans ratio of 1 / 1 as the monomer, Fig. 9 This is the H-NMR spectrum of the copolyester PETB1 obtained with CBDO having a cis ratio of 39.5 / 1 as the monomer. Figure 12a-Figure 12c The following are the H-NMR spectra of PETB3, PETB4 and PETB5, which are copolyesters obtained by using CBDO as monomers with cis-trans ratios of 10 / 1, 7 / 3 and 1 / 1, respectively. Fig. 9 , Figure 8 and Figure 12a-Figure 12c The results shown can be used to calculate the CBDO content and the cis-trans isomer ratio in PETB1, PETB2, PETB3, PETB4 and PETB5 respectively. The results show that the CBDO in the long chain of PETB1 and PETB3 is all cis, without trans-CBDO; while the long chain of PETB2, PETB4 and PETB5 contains two isomer structures, cis and trans-CBDO. This shows that in the copolymerization reaction, the reaction performance of cis-CBDO as a monomer is much higher than that of trans-CBDO. At the same time, when the cis-trans ratio of cis-CBDO is greater than or equal to 10 / 1, during the condensation reaction, the long chain structure of the copolymer contains only cis-CBDO isomers but not trans-CBDO isomers. Therefore, increasing the content of cis isomers in the cis-trans isomers of CBDO is more conducive to the subsequent copolymerization reaction. In addition, for the same content of CBDO, the more cis conformation content, the higher the copolyester T g When the PET copolyester is modified by Quanshun CBDO, only about 40% of CBDO can be used to obtain a 110 o PETB products of C.

[0152] See also Fig.10 , which is a comparison of the DSC curves of copolyesters PETB1 and PETB2. The glass transition temperature of PETB1 is 90°C, while the glass transition temperature of PETB2 is 73°C. Fig.13 , which is a comparison of the DSC curves of copolyesters PETB3, PETB4 and PETB5. The glass transition temperature of PETB3 is 113°C, the glass transition temperature of PETB4 is 107°C, and the glass transition temperature of PETB5 is 102°C. This shows that increasing the content of cis isomers in CBDO cis-trans isomers is also beneficial to obtain higher T g copolyester products, expanding the application areas of copolyesters; it also shows that only when the cis-trans ratio is 10 / 1 or above can the all-cis-CBDO copolyester be obtained.

[0153] Table 1 Structure, properties and molecular weight of a series of PETB copolyesters

[0154] In addition, the present invention can also refer to the aforementioned embodiments, and test the other methods listed in this specification for protecting the terminal hydroxyl groups of CBDO, separating them and then deprotecting them, and successfully prepare CBDO cis and trans isomer products with various cis-trans ratios. Therefore, the technical solution of the present invention can achieve the regulation of the cis-trans ratio of commercially available CBDO, and adjust the original cis-trans ratio from 1 to a maximum of 39.5 / 1. Compared with commercially available CBDO, the copolyester prepared using a CBDO product with a high cis-trans ratio under the same conditions has a higher intrinsic viscosity and glass transition temperature, which is conducive to expanding the application range of the polymer.

[0155] In summary, the present invention adopts a method of protecting the terminal hydroxyl groups of CBDO by using a modifier, and the polarity difference between the modified cis-CBDO and the modified trans-CBDO obtained by the reaction is generated by the structural difference, and then the separation is performed by selecting a separation solvent for solvent dissolution-crystallization, and finally the protection is performed to regenerate DBDO with a high cis-trans ratio and pure trans-CBDO, and the modifier can also be recycled. This separation and regeneration method is not only simple in method, but also easy to control the process. In particular, the modifier used is low in price and can be recycled and reused. The obtained CBDO with a high cis-trans ratio is applied to the preparation of copolyester, which can significantly increase the content of CBDO in the chain segment. Obviously, the technical solution provided by the present invention is suitable for large-scale promotion and application.

[0156] The various aspects, embodiments, features and embodiments of the present invention should be considered as illustrative in all aspects and are not intended to limit the present invention, the scope of the present invention is defined only by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0157] The use of titles and descriptions in the present invention is not meant to limit the present invention; each section may apply to any aspect, embodiment or feature of the present invention.

[0158] Unless specifically stated otherwise, the use of the terms "including", "having" and "comprising" should generally be construed as open ended and non-limiting.

[0159] It should be understood that the order of the various steps or the order in which a particular action is performed is not very important, as long as the teachings of the present invention remain operable. In addition, two or more steps or actions may be performed simultaneously.

[0160] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0161] Although the present invention has been described with reference to illustrative embodiments, it will be appreciated by those skilled in the art that various other changes, omissions and / or additions may be made without departing from the spirit and scope of the present invention and that the elements of the embodiments may be replaced by substantial equivalents. In addition, many modifications may be made without departing from the scope of the present invention to adapt specific circumstances or materials to the teachings of the present invention. Therefore, it is not intended herein to limit the present invention to the disclosed specific embodiments for performing the present invention, but it is intended that the present invention will include all embodiments within the scope of the appended claims. In addition, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather uses the terms first, second, etc. to distinguish one element from another.

Claims

1. A method for separating cis and trans isomers of CBDO, characterized in that: The terminal hydroxyl groups of the cis-CBDO isomer and the trans-CBDO isomer are modified to protect the hydroxyl groups, and the polarity of the modified cis-CBDO isomer and the trans-CBDO isomer is made different. The two are then separated by a solvent dissolution-crystallization method, and finally the protection is removed respectively to obtain CBDO isomers with a high cis-trans ratio.

2. The method for separating cis and trans isomers of CBDO according to claim 1, characterized in that: The specific steps include: S1. using a modifying agent to modify the hydroxyl groups of the cis and trans isomers of CBDO respectively to obtain a mixture containing CBDO structural units; S2. adding the mixture containing the CBDO structural unit to a separation solvent, and obtaining products containing the modified cis-CBDO isomer and the modified trans-CBDO isomer by filtering and / or rotary evaporation; S3. The product is deprotected by a decomposition reaction, and finally physically separated to obtain cis-CBDO isomers and trans-CBDO isomers with different cis-trans ratios.

3. The method for separating cis and trans isomers of CBDO according to claim 2, characterized in that: In S1, the modifier is any one of phenyl-substituted esters, phenyl-substituted monocarboxylic acids, phenyl-substituted acid chlorides, phenyl-substituted aldehydes, C2-C6 alkyl-substituted monocarboxylic acids, C2-C6 alkyl-substituted aldehydes; or any one of acid chlorides, acid anhydrides or polycarboxylic acids; In S2, the separation solvent is one or a combination of water, methanol, ethanol, DMSO, DMF, acetone, ether, and ethyl acetate; In S3, the decomposition reaction includes any one of alcoholysis reaction, alkaline hydrolysis reaction or acid hydrolysis reaction.

4. The method for separating cis and trans isomers of CBDO according to claim 3, characterized in that: The modifier includes any one of acetic acid, propionic acid, oxalic acid, malonic acid, dimethyl oxalate, dimethyl malonate, benzoic acid, salicylic acid, benzene dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, trimellitic acid, dimethyl oxalate, dimethyl malonate, dimethyl terephthalate, dimethyl isophthalate, dimethyl phthalate, trimethyl trimellitate, acetic anhydride, propionic anhydride, phthalic anhydride, benzoic anhydride, phthalic anhydride, acetyl chloride, propionyl chloride, oxalyl chloride, monomethyl oxalyl chloride, malonic chloride, benzoyl chloride, terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, acetaldehyde, propionaldehyde, benzaldehyde, and hydroxybenzaldehyde.

5. The method for separating cis and trans isomers of CBDO according to claim 2, characterized in that: The decomposition reaction comprises adding alcohol to the product to carry out alcoholysis reaction, and the alcohol may be a monoalcohol or a polyol; Or, the decomposition reaction includes adding alkali solution to the product to carry out alkaline hydrolysis reaction; the alkali solution is an aqueous solution of sodium hydroxide or potassium hydroxide; and / or, the concentration of the alkali solution is 5 to 15 wt %; Or, the decomposition reaction includes adding acid solution to the product to carry out acidolysis reaction; the acid solution is an aqueous solution of hydrochloric acid, sulfuric acid, phosphoric acid or p-toluenesulfonic acid; And / or, the concentration of the acid solution is 1-5 mol / L.

6. The method for separating cis and trans isomers of CBDO according to claim 5, characterized in that: The alcoholysis reaction includes a catalyst; the catalyst is selected from at least one of MXene, phosphoric acid, sulfuric acid, organic sulfonic acids, metal salts, and metal oxides; wherein the metal element in the metal salt and / or the metal oxide is selected from metal elements of groups IIA, IIIA, IVA, and IVB; The added amount of the catalyst is 50-2000 ppm.

7. The method for separating cis and trans isomers of CBDO according to claim 2, characterized in that: In S3, the physical separation method includes extraction, vacuum distillation, sublimation, crystallization and filtration; The method of physical separation also includes recovering the modifying agent.

8. A CBDO product obtained by the separation method according to any one of claims 1 to 7, characterized in that: The cis-trans ratio of the CBDO product is 7 / 3 to 39.5 / 1.

9. A CBDO product obtained by the separation method according to any one of claims 1 to 7, characterized in that: The CBDO product is an all-trans CBDO isomer.

10. A copolyester containing CBDO, comprising the CBDO product as claimed in claim 8 as a monomer, prepared by melt polycondensation with ethylene glycol and dimethyl terephthalate; wherein the cis-trans ratio of the CBDO product is 10 / 1 to 39.5 / 1; and the copolyester contains only cis-CBDO.

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