Extraction process and purification of polybutylene succinate

Abstract

The application relates to the technical field of polybutylene succinate processing, and discloses an extraction method of polybutylene succinate and purified polybutylene succinate, wherein the polybutylene succinate is contacted with a supercritical fluid containing an entraining agent; the entraining agent is a compound shown in formula (1); wherein R1 is H, C1-C4 alkyl or -R4OH, R2 is C2-C6 alkylene, R3 is H, C1-C4 alkyl or -R5OH, and R4 and R5 are each independently C1-C4 alkylene; the extraction method and the purified polybutylene succinate have high extraction efficiency.

Description

Technical Field

[0001] This invention relates to the field of polybutylene succinate processing technology, specifically to an extraction method and purification method for polybutylene succinate. Background Technology

[0002] In existing technologies, when supercritical fluid is used to extract polybutylene succinate (PBS), the extraction efficiency is low due to the low extraction temperature. At the same time, PBS contains some high molecular weight oligomers, which have low solubility in supercritical carbon dioxide, further resulting in low extraction efficiency. Summary of the Invention

[0003] The purpose of this invention is to overcome the problem of low efficiency in the extraction of polybutylene succinate using supercritical fluid, and to provide an extraction method and purification method for polybutylene succinate, wherein the extraction method for polybutylene succinate has high extraction efficiency.

[0004] To achieve the above objectives, the first aspect of the present invention provides a method for extracting polybutylene succinate, wherein the polybutylene succinate is in contact with a supercritical fluid containing an entrainer.

[0005] Wherein, the entrainer is the compound represented by formula (1);

[0006]

[0007] Wherein, R1 is H, a C1-C4 alkyl group or -R4OH, R2 is a C2-C6 alkylene group, R3 is H, a C1-C4 alkyl group or -R5OH, and R4 and R5 are each independently a C2-C4 alkylene group, wherein R1 and R3 are not both H.

[0008] A second aspect of the present invention provides a purified polybutylene succinate obtained by the above-described extraction method.

[0009] Through the above technical solutions, the extraction method and purification method of polybutylene succinate of the present invention have the following beneficial effects.

[0010] The supercritical fluid of the present invention contains a specific type of entrainer to improve the solubility of oligomers in polybutylene succinate in the supercritical fluid, thereby improving the extraction efficiency of polybutylene succinate.

[0011] Furthermore, when the amount of entrainer meets a specific range, it can further improve the solubility of oligomers in polybutylene succinate in supercritical fluid, thereby improving the extraction efficiency of polybutylene succinate and obtaining polybutylene succinate with low migration. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the extraction process of the present invention. Detailed Implementation

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0014] The first aspect of the present invention provides a method for extracting polybutylene succinate, wherein the polybutylene succinate is contacted with a supercritical fluid containing an entrainer.

[0015] Wherein, the entrainer is the compound represented by formula (1);

[0016]

[0017] Wherein, R1 is H, a C1-C4 alkyl group or -R4OH, R2 is a C2-C6 alkylene group, R3 is H, a C1-C4 alkyl group or -R5OH, and R4 and R5 are each independently a C2-C4 alkylene group, wherein R1 and R3 are not both H.

[0018] In this invention, the supercritical fluid contains a specific type of entrainer, which can improve the solubility of oligomers in polybutylene succinate in the supercritical fluid, thereby improving the extraction efficiency of polybutylene succinate.

[0019] Further, in formula (1), R1 is H, a C1-C3 alkyl group or -R4OH, R2 is a C2-C4 alkylene group, R3 is H, a C1-C3 alkyl group or -R5OH, and R4 and R5 are each independently a C2-C4 alkylene group, wherein R1 and R3 are not both H.

[0020] Furthermore, the entrainer is selected from at least one of dimethyl succinate (R1, R3 are methyl, R2 is ethylidene), diethyl succinate (R1, R3 are ethyl, R2 is ethylidene), dibutyl succinate (R1 is -R4OH, R4 is butylidene, R2 is ethylidene, R3 is -R5OH, R5 is butylidene), and dibutyl adipate (R1 is -R4OH, R4 is butylidene, R2 is butylidene, R3 is -R5OH, R5 is butylidene).

[0021] According to a preferred embodiment of the present invention, the entrainer is dibutyl succinate and dibutyl adipate. When a special entrainer combination is used, the solubility of oligomers in polybutylene succinate in supercritical fluids can be further improved, thereby increasing the extraction efficiency of polybutylene succinate.

[0022] Furthermore, the mass ratio of dibutyl succinate to dibutyl adipic acid is 0.5-1.5:1, more preferably 0.8-1.3:1.

[0023] According to the present invention, the content of the entrainer is 0.1-5 wt%, based on the total mass of the entrainer and the supercritical fluid.

[0024] In this invention, when the amount of entrainer meets the above-mentioned range, it is beneficial to improve the solubility of oligomers in polybutylene succinate in supercritical fluid, thereby improving the extraction efficiency of polybutylene succinate and obtaining polybutylene succinate with low migration.

[0025] Furthermore, based on the total mass of the entrainer and the supercritical fluid, the content of the entrainer is 1-2 wt%.

[0026] According to the present invention, the supercritical fluid is selected from at least one of carbon dioxide, nitrous oxide, nitrogen, methane, ethane, and ethylene.

[0027] In this invention, when the type of supercritical fluid meets the above-mentioned range, a supercritical fluid can be formed at a lower temperature, thereby meeting the requirements of the extraction process.

[0028] Furthermore, the supercritical fluid is selected from carbon dioxide and / or nitrogen.

[0029] According to the present invention, the flow rate of the supercritical fluid is 20-200 L / (h·kg polybutylene succinate).

[0030] In this invention, when the flow rate of the supercritical fluid meets the above-mentioned range, the supercritical fluid can promptly remove the target extract from polybutylene succinate, thereby improving the extraction efficiency and avoiding increased energy consumption.

[0031] Furthermore, the flow rate of the supercritical fluid is 60-150 L / (h·kg polybutylene succinate).

[0032] According to the present invention, the pressure of the supercritical fluid is 10-50 MPa.

[0033] In this invention, when the pressure of the supercritical fluid meets the above-mentioned range, on the one hand, the gas can form a supercritical state, and on the other hand, the wetting ability of the supercritical fluid on polybutylene succinate can be improved, and the solubility of the target extract in the supercritical fluid can be improved, thereby improving the extraction efficiency and obtaining polybutylene succinate with lower migration.

[0034] Furthermore, the pressure of the supercritical fluid is 20-35 MPa.

[0035] According to the present invention, the contact temperature is 35-100°C, and the contact time is 1-5 hours.

[0036] In this invention, when the conditions for contact between polybutylene succinate and supercritical fluid meet the above-mentioned range, on the one hand, the supercritical conditions of gas are met, and on the other hand, the wetting ability of supercritical fluid in polybutylene succinate is improved, and the solubility of the target extract in supercritical fluid is improved, thereby improving the extraction efficiency and obtaining polybutylene succinate with lower migration.

[0037] Furthermore, the contact temperature is 70-90℃, and the contact time is 1.5-4h.

[0038] According to the present invention, the number average molecular weight of the polybutylene succinate is 20,000-200,000 g / mol.

[0039] In this invention, when the number-average molecular weight of polybutylene succinate meets the above-mentioned range, the supercritical fluid has a high extraction efficiency for polybutylene succinate, and the purified polybutylene succinate obtained has a low migration amount, which can meet the needs of practical applications.

[0040] Furthermore, the number-average molecular weight of the polybutylene succinate is 30,000-100,000 g / mol.

[0041] According to the present invention, the total weight of 100 polybutylene succinate particles is 1.5-2.5g.

[0042] According to the present invention, the density of the polybutylene succinate is 0.85-1.6 kg / m³. 3 .

[0043] In this invention, by limiting the density of polybutylene succinate and the total weight of 100 polybutylene succinate particles, polybutylene succinate has a specific particle size range. Supercritical fluid containing a specific type of entrainer can have better wetting ability on polybutylene succinate, higher extraction efficiency, and high removal uniformity of products in the same batch.

[0044] Furthermore, the density of the polybutylene succinate is 1.15-1.55 kg / m³. 3 .

[0045] Furthermore, the total weight of 100 polybutylene succinate particles is 1.8-2.2g.

[0046] In this invention, there are no special requirements for the morphology of polybutylene succinate; preferably, the polybutylene succinate is selected from at least one of spherical, near-spherical, ellipsoidal, and cylindrical shapes. In this invention, there are no special limitations on the height and base radius of the cylindrical polyester resin.

[0047] In this invention, the extraction is carried out in a fixed-bed reactor.

[0048] The invention will be further described below with reference to the accompanying drawings, such as... Figure 1 As shown, the extraction method for polybutylene succinate includes: storing gas from a gas cylinder or a separation tank in a gas storage tank; injecting an entrainer into the gas and then pressurizing it to a specific pressure using a booster pump to create a supercritical state; passing the supercritical fluid through heat exchange system I to regulate its temperature; contacting the temperature-regulated supercritical fluid with the polybutylene succinate in the extraction system to extract impurities from the polybutylene succinate, thereby purifying it; the supercritical fluid flowing out of the extraction system entering heat exchange system II to cool it down, causing the impurities in the supercritical fluid to transform into a liquid or solid state; and the supercritical fluid containing impurities entering the separation tank and being depressurized to transform into a gas, thus separating the gas from the impurities.

[0049] In this invention, there are no special requirements for the type of extraction system; for example, the extraction system can be an extraction tank.

[0050] A second aspect of the present invention provides a purified polybutylene succinate obtained by the above-described extraction method.

[0051] According to the present invention, the migration amount of the purified polybutylene succinate is less than or equal to 10 mg / dm³. 2 .

[0052] According to a particularly preferred embodiment of the present invention, the extraction method of polybutylene succinate includes: contacting polybutylene succinate with a supercritical fluid containing an entrainer;

[0053] Wherein, the entrainer is the compound represented by formula (1);

[0054]

[0055] In formula (1), R1 is H, a C1-C3 alkyl group or -R4OH, R2 is a C2-C4 alkylene group, R3 is H, a C1-C3 alkyl group or -R5OH, and R4 and R5 are each independently a C2-C4 alkylene group, wherein R1 and R3 are not simultaneously H;

[0056] The content of the entrainer is 1-2 wt%, based on the total mass of the entrainer and the supercritical fluid; the flow rate of the supercritical fluid is 60-150 L / (h·kg polybutylene succinate); the pressure of the supercritical fluid is 20-35 MPa; and the contact temperature is 70-90℃.

[0057] The present invention will be described in detail below through embodiments.

[0058] Migration of polybutylene succinate: Purified polybutylene succinate was injection molded into small square specimens. The size of the specimens conformed to type D1 of GB / T17037.3-2003 "Preparation of Injection Molded Specimens for Thermoplastic Plastics - Part 3: Small Square Specimens". Migration was tested according to GB31604.8-2016. The test conditions were: 50 vol% ethanol aqueous solution as the simulated solution, temperature 70℃, 2 hours, per 6 dm². 2 The small square sample was immersed in 1L of simulated solution, and the migration amount Q was calculated according to Formula 1 in 6.1, in mg / dm³. 2 .

[0059] Resin 1: Polybutylene succinate (PBS resin) is a commercially available product from Yizheng Chemical Fiber Co., Ltd., brand name AS009; the PBS is spherical with a density of 1.26 kg / m³. 3 The number average molecular weight is 100,000 g / mol, and the total weight of 100 polybutylene succinate particles is 2.0 g.

[0060] Resin 2: Polybutylene succinate (Polybutylene succinate) was prepared via a two-step melt polymerization method, namely, esterification followed by polycondensation. The specific reaction conditions were as follows: In a 20L reactor, 5.4 kg of butanediol, 3.54 kg of succinic acid, and 4.4 g of tetrabutyl titanate catalyst were added. Esterification was carried out at atmospheric pressure and a temperature of 220℃. After esterification, polycondensation was performed at a temperature of 245℃ and a pressure of 80 Pa. The reactor was discharged after the stirring power reached the target value. The particle weight per 100 particles was adjusted by controlling the discharge pressure and regulating the melt strip thickness. The specific parameters of the obtained Polybutylene succinate were as follows: the total weight of 100 Polybutylene succinate particles was 2.5 g; the Polybutylene succinate was cylindrical; and the density was 1.26 kg / m³. 3 The number-average molecular weight is 30,000 g / mol.

[0061] Example 1

[0062] PBS resin (resin 1) was filled into an extraction vessel. The supercritical carbon dioxide flow rate was set to 100 L / (h·kg) for polybutylene succinate. The entrainers were dibutylene succinate and dibutylene adipate, added at 2 wt% (mass ratio of dibutylene succinate to dibutylene adipate was 1:1). The mixture was contacted for 2 hours at 80℃ and 30 MPa to obtain purified polybutylene succinate. The test results for purified polybutylene succinate are shown in Table 1.

[0063] Example 2-11

[0064] Polybutylene succinate was extracted according to the method in Example 1. The extraction conditions are shown in Table 1. The test results of the purified polybutylene succinate are shown in Table 1.

[0065] Example 12

[0066] Polybutylene succinate was extracted according to the method in Example 1, except that resin 2 was used for extraction. Other extraction conditions are shown in Table 1, and the test results for the purification of polybutylene succinate are shown in Table 1.

[0067] Comparative Example 1

[0068] The extraction process conditions and methods of Example 1 were followed, except that no entrainer was added. The test results are shown in Table 1.

[0069] Comparative Examples 2-3

[0070] Polybutylene succinate was extracted according to the method in Example 1. The specific extraction conditions are shown in Table 1. The test results of the purified polybutylene succinate are shown in Table 1.

[0071] Table 1

[0072]

[0073] As can be seen from the results in Table 1, the embodiments of the present invention, by introducing specific types of entrainers, shorten the extraction time and significantly improve the extraction efficiency; the preferred embodiments of the present invention can further improve the extraction efficiency. By combining dibutyl succinate and dibutyl adipic acid, not only is the extraction time shortened, but the migration amount of the final product is also lower.

[0074] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for extracting polybutylene succinate, characterized in that, The polybutylene succinate is in contact with a supercritical fluid containing an entrainer; Wherein, the entrainer is the compound represented by formula (1); Wherein, R1 is H, a C1-C4 alkyl group or -R4OH, R2 is a C2-C6 alkylene group, R3 is H, a C1-C4 alkyl group or -R5OH, and R4 and R5 are each independently a C2-C4 alkylene group, wherein R1 and R3 are not both H.

2. The extraction method according to claim 1, wherein, In formula (1), R1 is H, a C1-C3 alkyl group or -R4OH, R2 is a C2-C4 alkylene group, R3 is H, a C1-C3 alkyl group or -R5OH, and R4 and R5 are each independently a C2-C4 alkylene group, wherein R1 and R3 are not both H; Preferably, the entrainer is selected from at least one of dimethyl succinate, diethyl succinate, dibutyl succinate, and dibutyl adipate.

3. The extraction method according to claim 1 or 2, wherein, Based on the total mass of the entrainer and the supercritical fluid, the content of the entrainer is 0.1-5 wt%, preferably 1-2 wt%.

4. The extraction method according to any one of claims 1-3, wherein, The supercritical fluid is selected from at least one of carbon dioxide, nitrous oxide, nitrogen, methane, ethane, and ethylene; Preferably, the supercritical fluid is selected from carbon dioxide and / or nitrogen.

5. The extraction method according to any one of claims 1-4, wherein, The flow rate of the supercritical fluid is 20-200 L / (h·kg polybutylene succinate), preferably 60-150 L / (h·kg polybutylene succinate).

6. The extraction method according to any one of claims 1-5, wherein, The pressure of the supercritical fluid is 10-50 MPa, preferably 20-35 MPa.

7. The extraction method according to any one of claims 1-6, wherein, The contact temperature is 35-100℃, preferably 70-90℃.

8. The extraction method according to any one of claims 1-7, wherein, The contact time is 1-5 hours, preferably 1.5-4 hours.

9. The extraction method according to any one of claims 1-8, wherein, The polybutylene succinate has a number-average molecular weight of 20,000-200,000 g / mol, preferably 30,000-100,000 g / mol; Preferably, the total weight of 100 polybutylene succinate particles is 1.5-2.5g, more preferably 1.8-2.2g; Preferably, the density of the polybutylene succinate is 0.85-1.6 kg / m³. 3 The preferred value is 1.15-1.55 kg / m³. 3 .

10. A purified polybutylene succinate obtained by the extraction method according to any one of claims 1-9; Preferably, the migration amount of the purified polybutylene succinate is less than or equal to 10 mg / dm³. 2 .

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