A continuous process for the synthesis of a polyadipate

Abstract

The application discloses a continuous synthesis method of polybutanedioate, and belongs to the field of high polymer material preparation. The method uses succinic anhydride and polyhydric alcohol as monomer raw materials, and obtains corresponding polybutanedioate products through five-step continuous reactions of normal-pressure ring opening, pressurized esterification, reduced-pressure esterification, negative-pressure pre-polymerization and vacuum final polymerization. The polyhydric alcohol used in the application can be various, and a series of polyester materials with different structures and properties can be prepared by combination; the polyester products synthesized by the application have good quality, stable quality, low acid value and high melt strength; in addition, the raw materials and energy consumption of the application are low, the product yield is high, the production cost is low, and the process is clean and environmentally-friendly.

Description

Technical Field

[0001] This invention belongs to the field of polymer material synthesis technology, specifically relating to a continuous synthesis method for polysuccinate. Background Technology

[0002] Polyesters are an extremely important class of polymer materials with wide applications in aerospace, biomedicine, agriculture, and daily life, and have become an indispensable basic material for the national economy and modern life. Polysuccinates, such as polyethylene succinate (PES) and polybutylene succinate (PBS), are a large class of polyester materials with special properties and applications, and have become the focus of public attention. my country's future demand is enormous, therefore, there is an urgent need to develop advanced, low-cost, large-scale continuous production technologies for polysuccinates.

[0003] Existing methods for synthesizing polysuccinate mainly include direct esterification and transesterification. Direct esterification uses succinic acid and a polyol as monomers. First, esterification generates oligomers and twice the molar amount of water as succinic acid monomers. Then, the oligomers undergo prepolymerization and final polycondensation under high temperature and high vacuum conditions to produce high molecular weight polyester. Transesterification uses succinate diester (methyl or ethyl) and a polyol as monomers. First, transesterification generates oligomers and twice the molar amount of alcohol as succinate diester monomers. Then, the oligomers undergo prepolymerization and final polycondensation to obtain polysuccinate. However, both methods produce a large amount of small molecules as byproducts, resulting in low raw material utilization and low polyester product yield. Furthermore, the generation of a large number of small molecules is detrimental to increasing the polymer molecular weight, leading to poor polyester product quality and performance. Finally, the recovery and treatment of these small molecules increases environmental treatment costs, indirectly increasing production costs.

[0004] Using succinic anhydride instead of succinic acid or succinate diester in ring-opening polycondensation with polyols can effectively avoid the above-mentioned problems. Since the reaction process only produces an equimolar amount of water from the monomeric succinic anhydride, it can significantly reduce raw material consumption and increase product yield. The polyester yield, calculated based on succinic anhydride, reaches over 90 wt% (compared to no more than 72 wt% for the succinic acid route and no more than 65% for the succinate diester route). Furthermore, the ring-opening process does not involve chemical equilibrium, which greatly improves reaction efficiency and increases the molecular weight of the product, resulting in significantly enhanced mechanical and thermal properties. However, there are few reports on the preparation of polysuccinates from succinic anhydride and polyols. For example, patent CN102964581A discloses a method for preparing polyester polyols by a two-step esterification reaction of succinic anhydride with aliphatic diols such as 1,4-butanediol, ethylene glycol, and diethylene glycol via a gradient temperature increase. The polyester polyols obtained by this method are used as monomers or intermediates for polymerization, and typically have low molecular weights, making them unsuitable for direct use as materials. Patents CN101880377A, CN104130381B, and CN104130382B report the preparation of aliphatic polyesters using a three-step reaction of succinic anhydride with aliphatic diols via ring-opening esterification, negative pressure prepolymerization, and vacuum polycondensation. The weight-average molecular weights of the obtained polyesters are all above 100,000, with some reaching 300,000. However, this method only uses a one-step ring-opening esterification process, resulting in incomplete esterification, particularly with a high acid value in the esterified product. This leads to increased side reactions, ultimately resulting in a high acid value (generally above 50 mol / t) and poor color in the product, sometimes even causing yellowing. Furthermore, increased side reactions can also reduce the molecular weight and increase the molecular weight distribution of polyester, affecting the final use of the product. For example, the PBS product disclosed in the aforementioned patent has poor melt strength, with a melt index generally between 30 and 50 g / 10 min, resulting in poor blow molding processing capability. Numerous studies have shown that polyesters formed from polyols (3 or more) or rigid-structured diols typically have higher melt strength and can be used as blow-molded products; however, the aforementioned patent does not address this. Currently, the ring-opening polymerization of succinic anhydride and polyols to form polysuccinate is mostly carried out in batch operations. The disadvantage of this method is that it leads to inconsistent product quality, poor batch-to-batch controllability, and also affects product quality.

[0005] Our team previously disclosed in patents CN114920916A, CN114015026B, and CN113980252B a technique for preparing high molecular weight, high-performance polybutylene succinate (PBS) or modified PBS using succinic anhydride, tetrahydrofuran, and a modifier as monomer raw materials through three reaction steps: ring-opening esterification, negative pressure prepolymerization, and vacuum final polymerization. Recently, we unexpectedly discovered that adding reaction steps, such as ring-opening or pressurized esterification, can significantly reduce the acid value and melt index of the product. Therefore, comparative analysis of the polymerization of succinic anhydride and polyols revealed that using only one-step ring-opening esterification results in incomplete esterification due to low ring-opening efficiency and low alcohol utilization, thus affecting the quality of the final product. Therefore, adding a ring-opening step alone can improve the ring-opening efficiency of polyols and succinic anhydride, and directionally obtain ring-opening products. Subsequent pressure esterification can effectively avoid the volatilization or decomposition of residual alcohol, improving its utilization rate. After the esterification rate reaches a certain level, vacuum esterification can further increase the esterification rate, making the esterification nearly complete. These steps effectively solve the problem of incomplete esterification, thereby resolving the resulting technical issues. Furthermore, by using polyols (3 or more members) or rigid-structured diols, the melt strength of the product can be significantly improved, expanding its application range. In view of this, this invention develops an advanced continuous polymerization technology for preparing polysuccinate using succinic anhydride and polyols as polymerization raw materials, involving five steps: pressure ring-opening, pressure esterification, vacuum esterification, negative pressure prepolymerization, and vacuum final polymerization, specifically addressing the aforementioned technical problems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a continuous synthesis method for polysuccinate, using succinic anhydride and polyol as polymerizing monomers. Through five steps—normal pressure ring opening, pressure esterification, reduced pressure esterification, negative pressure prepolymerization, and vacuum final polymerization—it continuously and cost-effectively produces high-quality polysuccinate materials with uniform quality. This method mainly overcomes the problems of high acid value, poor color, poor melt strength, high production cost, and intermittent operation in existing technologies.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A continuous synthesis method for polysuccinate uses succinic anhydride and polyol as monomer raw materials, and continuously synthesizes polysuccinate through five steps including atmospheric pressure ring opening, pressure esterification, vacuum esterification, negative pressure prepolymerization, and vacuum final polymerization. The specific steps are as follows:

[0009] (1) The monomer raw material succinic anhydride and a portion of polyol are continuously fed into the ring-opening reaction device and the ring-opening reaction is carried out at a temperature of 60-120℃, at atmospheric pressure, and at a residence time of 5-120min to obtain the atmospheric pressure ring-opening product.

[0010] (2) The ring-opening product obtained in step (1) is continuously fed into the pressurized esterification reaction device, and the remaining polyol and esterification catalyst are continuously added. The pressurized esterification reaction is carried out at a temperature of 100-220℃, a pressure of 0.10-1.0MPa(A), and a residence time of 30-300min to obtain the pressurized esterification product.

[0011] (3) The pressurized esterification product obtained in step (2) is continuously fed into the vacuum esterification reaction device, and the small molecules are removed under reduced pressure at a temperature of 140-240℃, a pressure of 10-80kPa(A) and a residence time of 30-180min to obtain the vacuum esterification product.

[0012] (4) The reduced pressure esterification product obtained in step (3) is continuously fed into the prepolymerization reactor and mixed with the polymerization catalyst. The prepolymerization reaction is carried out at a temperature of 180-240℃, a pressure of 1-60kPa(A), and a residence time of 20-180min to obtain the negative pressure prepolymerization product.

[0013] (5) The prepolymer obtained in step (4) is continuously fed into a final polymerization reactor and subjected to a vacuum final polymerization reaction at a temperature of 200-280°C, a pressure of 5-200 Pa(A), and a residence time of 30-240 min to obtain polysuccinate. The obtained polysuccinate is continuously discharged and granulated and dried underwater to obtain polyester granules.

[0014] Further, in step (1), the ring-opening reaction conditions are a temperature of 70-100°C, a pressure of atmospheric pressure, and a residence time of 20-90 min.

[0015] Furthermore, in step (1), the conditions for the ring-opening reaction are a temperature of 70–90°C, a pressure of atmospheric pressure, and a residence time of 30–60 min.

[0016] Further, in step (2), the pressure esterification reaction conditions are a temperature of 150-200℃, a pressure of 0.2-0.7MPa, and a residence time of 60-240min.

[0017] Further, in step (2), the pressure esterification reaction conditions are a temperature of 170–190°C, a pressure of 0.3–0.5 MPa, and a residence time of 90–180 min.

[0018] Further, in step (3), the reduced pressure esterification reaction conditions are a temperature of 160–210 °C, a pressure of 20–60 kPa, and a residence time of 60–150 min.

[0019] Furthermore, in step (3), the reduced pressure esterification reaction conditions are a temperature of 180–200 °C, a pressure of 30–50 kPa, and a residence time of 90–120 min.

[0020] Furthermore, in step (4), the negative pressure prepolymerization reaction conditions are a temperature of 190–230°C, a pressure of 2–30 kPa, and a residence time of 45–150 min.

[0021] Furthermore, in step (4), the pre-condensation reaction conditions are a temperature of 200–220 °C, a pressure of 3–15 kPa, and a residence time of 60–120 min.

[0022] Further, in step (5), the vacuum final polymerization reaction conditions are a temperature of 210–260°C, a pressure of 10–150 Pa, and a residence time of 60–210 min.

[0023] Furthermore, in step (5), the vacuum final polymerization reaction conditions are a temperature of 230–250°C, a pressure of 30–80 Pa, and a residence time of 90–180 min.

[0024] Further, the molar ratio of the monomer raw materials is succinic anhydride:polyol = 1.00:(1.00~2.00), preferably 1.00:(1.10~1.45).

[0025] Further, in step (1), the molar ratio of succinic anhydride to polyol is 1.00:(1.00~1.10), preferably 1.00:(1.00~1.05), and the remaining polyol is continuously added in the pressurized esterification reaction in step (2).

[0026] Further, the amount of the esterification catalyst is 0.01 to 2.00% of the molar amount of succinic anhydride, preferably 0.05 to 0.20%.

[0027] Further, the amount of the polymerization catalyst is 0.01 to 1.00% of the molar amount of succinic anhydride, preferably 0.05 to 0.20%.

[0028] Furthermore, the esterification catalyst is selected from one or more of methanesulfonic acid, p-toluenesulfonic acid, p-toluenesulfonic acid hydrate, trifluoromethanesulfonic acid, trifluoroacetic acid, and trichloroacetic acid; the polymerization catalyst is selected from one or more of titanium, tin, antimony, and germanium compounds.

[0029] Further, the polymerization catalyst is one or more of the following: titanium dioxide, titanium-silicon composite, titanium trichloride, titanium tetrachloride, tributoxytitanium chloride, tetraethyl titanate, tetraisopropyl titanate, tetrabutyl titanate, tetraisooctyl titanate, tetrahydroxyethyl titanate, diethylene glycol titanate, tetrahydroxypropyl titanate, dipropylene glycol titanate, tetrahydroxybutyl titanate, or dibutyl titanate; or tin dichloride, tin tetrachloride, stannous succinate, stannous octoate, stannous benzoate, dioctyltin oxide, tetrabutyltin, dibutyltin acetate; or antimony pentoxide, antimony trioxide, antimony trichloride, antimony pentachloride, antimony ethylene glycol or antimony butanediol; or germanium dioxide, germanium tetrachloride, tetrabutoxygermanium, tetramethylgermanium or tetraethylgermanium.

[0030] Furthermore, the polymerization catalyst is at least one selected from tetrabutyl titanate, diethylene glycol titanate, tetrahydroxybutyl titanate, dibutyl titanate, and antimony glycol ethylene glycol.

[0031] Furthermore, the polyol is one or more of the following: fatty polyol, aromatic polyol, heterocyclic polyol, polyfatty alcohol ether polyol, polyaromatic alcohol ether polyol, polyaromatic phenol ether polyol, polyheterocyclic alcohol ether polyol, polyfatty acid ester polyol, polyaromatic acid ester polyol, and polyheterocyclic acid ester polyol.

[0032] Furthermore, the molecular weight Mn of the polyfatty alcohol ether polyol is 300-10000 g / mol, the molecular weight Mn of the polyaromatic alcohol ether polyol is 500-5000 g / mol, the molecular weight Mn of the polyaromatic phenol ether polyol is 500-5000 g / mol, the molecular weight Mn of the polyheterocyclic alcohol ether polyol is 500-5000 g / mol, the molecular weight Mn of the polyfatty acid ester polyol is 400-10000 g / mol, the molecular weight Mn of the polyaromatic acid ester polyol is 300-10000 g / mol, and the molecular weight Mn of the polyheterocyclic acid ester polyol is 300-10000 g / mol.

[0033] Further, the fatty polyols include 1,2-ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,2-propanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,2,4,4 One or more of the following: tetramethyl-1,3-cyclobutanediol, glycerol, trimethylolethane, trimethylolpropane, pentaerythritol, erythritol, xylitol, sorbitol, lactitol, glucose, fructose, chitosan, and starch; wherein the aromatic polyol comprises one or more of phenylethylene glycol, terephthalic acid, o-phenylenediethanol, iso-phenylenediethanol, terephthalic acid diethanol, o-phenylenediethanol, iso-phenylenediethanol, o-chlorophenylethylene glycol, and 4,4'-dimethylolbiphenyl; and wherein the heterocyclic polyol comprises one or more of 2,5-furandiethanol, tetrahydro-2-methyl-2H-pyran-3,4-diol, hydroxypropyltetrahydropyrantriol, 2,6-pyridinidinediethanol, and 2,3-thiophene. The polyfatty alcohol ether polyol comprises one or more of diethanol, 3,4-thiophene diol, and 3,4-tetrahydrothiophene diol, wherein the polyfatty alcohol ether polyol includes ethylene glycol or ethylene oxide, 1,2-propanediol or propylene oxide, 1,4-butanediol or tetrahydrofuran, 1,2-butanediol or 1,2-epoxybutane, 2,3-butanediol or 2,3-epoxybutane, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol or cyclohexene oxide, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, glycerol or glycidyl ether or epichlorohydrin, and polyols thereof. The copolymer comprises one or more of the following: the polyaromatic alcohol ether polyol includes one or more of the following: polyethers of terephthalic acid, isophthalic acid, orophthalic acid, styrene oxide, or phenyl glycol, and their copolymers with polyols; the polyaromatic phenol ether polyol includes one or more of the following: hydroquinone, resorcinol, and / or catechol, and their copolymers with polyols; the polyheterocyclic alcohol ether polyol includes one or more of the following: polyethers of 2,5-furandiethanol, 2,6-pyridinyldiethanol, 2,3-thiophenediethanol, 3,4-thiophene diol, and 3,4-tetrahydrothiophene diol, and their copolymers with polyols; and the polyfatty acid ester polyol includes poly(C1-C2)... 10The polyol comprises one or more of fatty acid polyester polyols, polyhydroxy acid esters, and polyhydroxy acid ester polyols, wherein the polyaromatic acid ester polyol comprises one or more of polyphthalic acid polyols, polytrimethylphthalic acid polyols, and polynaphthalic acid polyols, and the polyheterocyclic acid ester polyol comprises one or more of poly2,5-furan dicarboxylate polyols, poly2,6-pyridine dicarboxylate polyols, and poly2,3-thiophene dicarboxylate polyols.

[0034] Further, the fatty polyols include one or more of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 1,2-propanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, 2,2,4-trimethyl-1,3-pentanediol, glycerol, trimethylolethane, trimethylolpropane, pentaerythritol, erythritol, xylitol, sorbitol, and lactitol; and the aromatic polyols include terephthalic acid, isophthalic acid, and 4... One or more of 4'-dihydroxymethylbiphenyl, wherein the heterocyclic polyol includes one or more of 2,5-furandiethanol, 2,6-pyridinediethanol, 2,3-thiophenedimethanol, and 3,4-thiophenedimethanol, wherein the polyfatty alcohol ether polyol includes one or more of ethylene glycol, 1,2-propanediol, poly-1,4-butanediol, poly-1,4-cyclohexanediol, poly-1,4-cyclohexanediethanol, polyethylene glycol glycerol ether, polypropylene glycol glycidyl ether, poly-1,2-cyclohexanediol ethylene glycol ether, and poly-1,4-butanediol pentaerythritol ether, wherein the polyaromatic alcohol ether polyol includes poly(terephthalamide), poly(isophthalamide), and poly(oxyethylene glycol). The polyol comprises one or more of styrene, poly(terephthalamide) glycol ether, and polystyrene glycerol ether; the polyaromatic phenol ether polyol comprises one or more of poly(hydroquinone) glycol ether and poly(hydroquinone) glycidyl ether; the polyheterocyclic alcohol ether polyol comprises one or more of poly(2,5-furandiethanol), poly(2,6-pyridinyldiethanol), poly(3,4-thiophene diol), and poly(2,5-furandiethanol) glycol ether; and the polyfatty acid ester polyol comprises polyethylene glycol diol, polybutylene succinate diol, polyhexyl adipate diol, polyhexyl sebacate diol, polycyclohexanedicarboxylate diol, and poly(ethylene glycol diol). The polyol comprises one or more of the following: lactide diol, poly(glycolic acid-lactide) diol, polylactide diol, polyglycolic acid glyceride, polyhydroxybutyric acid, polycaprolactone diol, and polyhydroxyhexanoate glyceride; the polyaromatic ester polyol comprises one or more of the following: polyethylene terephthalate diol, polyethylene isophthalate diol, polyethylene pyromellitic acid triol, and polyethylene naphthalate diol; and the polyheterocyclic ester polyol comprises one or more of the following: polyethylene 2,5-furandicarboxylate diol, polyethylene 2,5-furandicarboxylate-2,5-furandimethyl ester diol, and polyethylene 2,6-pyridinedicarboxylate diol.

[0035] Further, the fatty polyol includes one or more of ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanediol, glycerol, trimethylolpropane, pentaerythritol, erythritol, or sorbitol; the aromatic polyol is terephthalic acid; the heterocyclic polyol is 2,5-furandiethanol; the polyfatty alcohol ether polyol is one of polyethylene glycol, poly1,2-propanediol, poly1,4-butanediol, polyethylene glycol glycerol ether, polypropylene glycol glycidyl ether, and poly1,4-butanediol pentaerythritol ether; the polyaromatic alcohol ether polyol is polyoxystyrene glycerol ether; and the polyaromatic phenol ether polyol is polyhydroquinone glycol ether or polyhydroquinone glycol ether. The polyhexanediol ether is poly(2,5-furandimethylethanol) ether or poly(2,5-furandimethylethanol) glycol ether; the polyfatty acid ester polyol is polyethylene glycol diol, polybutylene succinate diol, polyhexanediol adipate diol, polyethylene adipate diol, polyglycolic acid diol, poly(glycolic acid-lactide) diol, poly(glycolic acid-lactide) diol, poly(hydroxybutyric acid) diol, or polycaprolactone diol; the polyaromatic ester polyol is polyethylene terephthalate diol, polyethylene isophthalate diol, or polyethylene pyromellitic acid triol; and the polyhexanediol is polyethylene 2,5-furandimethyl ether diol or poly(2,5-furandimethylethanol) diol.

[0036] Further, the polyol is a combination of at least one of ethylene glycol, 1,3-propanediol, pentaerythritol, aromatic diols, polyethylene glycol, and 1,4-butanediol.

[0037] Further, the polyol is a composition of one of 1,3-propanediol, pentaerythritol, aromatic diol, polyethylene glycol and 1,4-butanediol, wherein the molar amount of 1,4-butanediol in the composition is not less than the molar amount of the other alcohols; preferably, the molar ratio of 1,4-butanediol and any other alcohol in the composition is (50-95):(50-5).

[0038] The present invention also provides a polysuccinate prepared by the continuous synthesis method of the polysuccinate described above.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The ring-opening polycondensation of succinic anhydride and polyol can improve reaction efficiency, increase raw material utilization, and improve product molecular weight and quality, while significantly reducing raw material costs. This is because the ring-opening reaction between succinic anhydride and polyol is highly efficient, and the amount of small molecules generated by esterification is small, which is easy to remove under vacuum, thereby increasing the polymer molecular weight. At the same time, the energy consumption for vacuum removal of small molecules is greatly reduced, and the emission of environmental pollutants is also greatly reduced, making the production process cleaner and reducing subsequent treatment costs.

[0041] (2) The five-step operation, especially the ring-opening and two-step esterification units, can significantly improve the esterification rate, make the esterification reaction close to complete, and the acid value of the esterified product is low. This reduces the acid-catalyzed side reactions during polymerization, resulting in a low acid value of the product, which is conducive to storage and transportation. The product also has good color, excellent performance, and high quality.

[0042] (3) The continuous polymerization process ensures uniform material concentration and temperature, and a shorter residence time, avoiding the thermal depolymerization of polyester at high temperatures. This results in a high degree of polymerization and good quality of the synthesized product, enabling large-scale continuous production of polysuccinate products with uniform quality. In addition, the continuous polymerization process helps reduce production costs.

[0043] (4) The raw materials and processes of this invention are flexible. By flexibly changing the types and proportions of polyols and the process conditions, a variety of products with different properties and grades can be produced. In particular, the use of polyols (terhydric and above) or rigid diols has yielded polyester products with high melt strength to meet the needs of specific downstream users. Detailed Implementation

[0044] To further understand the present invention, preferred embodiments are described below with reference to examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0045] Examples 1-9

[0046] Polybutylene succinate (PBS) was prepared using succinic anhydride (SAA) and 1,4-butanediol (BDO) as monomer raw materials through a five-step continuous reaction process: atmospheric pressure ring-opening, pressure esterification, vacuum esterification, negative pressure prepolymerization, and vacuum final polymerization. The preparation process is as follows:

[0047] (1) Succinic anhydride and 1,4-butanediol are continuously fed into a ring-opening reactor at a molar ratio of anhydride:alcohol = 1.00:(1.00~1.10) and subjected to an atmospheric pressure ring-opening reaction at a temperature of 60~120℃, a pressure of atmospheric pressure and a residence time of 5~120min to obtain an atmospheric pressure ring-opening product.

[0048] (2) The ring-opening product under normal pressure is then continuously fed into a pressurized esterification reactor, and the remaining polyol (0.01 to 0.90 times the molar amount of succinic anhydride) and esterification catalyst (0.01 to 2.0% of the molar amount of succinic anhydride) are continuously added through the raw material tank. The pressurized esterification reaction is carried out at a temperature of 100 to 220°C, a pressure of 0.11 to 1.0 MPa and a residence time of 30 to 300 min to obtain the pressurized esterification product.

[0049] (3) The pressurized esterification product is continuously fed into the vacuum esterification kettle, and the small molecules are removed under reduced pressure at a temperature of 140-240℃, a pressure of 10-80kPa and a residence time of 30-180min to further improve the esterification rate and obtain the vacuum esterification product.

[0050] (4) The reduced pressure esterification product is continuously fed into the negative pressure prepolymerization reactor and mixed with the polymerization catalyst (0.01-1.00% of the molar amount of succinic anhydride). The prepolymerization reaction is carried out at a temperature of 180-240℃, a pressure of 1-60kPa and a residence time of 20-180min to obtain the negative pressure prepolymerization product.

[0051] (5) The prepolymer under negative pressure is continuously fed into the final polymerization reactor, and a vacuum final polymerization reaction is carried out at a temperature of 200-280℃, a pressure of 5-200Pa, and a residence time of 30-240min to obtain polybutylene succinate. The product is continuously discharged and granulated and dried underwater to obtain PBS granules. The specific formulations and process conditions of Examples 1-9 are shown in Tables 1 and 2. Table 1 shows the total ratio of succinic anhydride to 1,4-butanediol monomers, the feed ratio in the open-ring reactor, and the type and amount of catalyst. Table 2 shows the process conditions for each stage of each example. Table 3 shows the molecular weight and performance indicators of the polymers prepared in the specific examples.

[0052] Table 1. Raw material ratios, catalyst types, and dosage conditions for the ring-opening polymerization of SAA and BDO to synthesize PBS.

[0053]

[0054] Table 2. Process conditions for the ring-opening polymerization of succinic anhydride and 1,4-butanediol to synthesize PBS

[0055]

[0056] Table 3 shows the molecular weight and main performance indicators of the obtained polymers.

[0057]

[0058]

[0059] As can be seen from the results of the various embodiments given in Table 3, the proportions, catalysts and dosages, and process conditions described in this invention can all yield PBS products with higher molecular weights. Under more optimized conditions (Examples 1-7), the molecular weight of the obtained PBS is even higher, ranging from 210,000 to 310,000, which is higher than the molecular weight of PBS obtained by esterification and transesterification under optimized conditions. Moreover, the molecular weight distribution Mw / Mn is 1.39-1.87, which is relatively narrow. In addition, the PBS has a low acid value of 19-29 mol / t, excellent color quality, and an L value above 88. Its melt index can reach 8.5-15.7 g / 10 min, generally below 20 g / 10 min, which significantly improves its melt strength and processing performance.

[0060] The above results demonstrate that the five-step continuous operation can significantly increase the polymer molecular weight and reduce the molecular weight distribution by improving the esterification rate, thereby improving its performance. In particular, it greatly reduces the acid value and improves the melt index, thus significantly improving the quality of PBS products and expanding their application areas.

[0061] Comparative Example 1

[0062] Compared to Example 1, the difference lies in the use of succinic acid and 1,4-butanediol as monomer raw materials to prepare PBS products via esterification. Following similar procedures to ring-opening polycondensation: succinic acid and 1,4-butanediol were continuously fed into a pressurized reactor at a molar ratio of succinic acid:alcohol = 1.00:1.35, along with an esterification catalyst (0.05% of the molar amount of succinic acid). The pressurized esterification reaction was carried out at 170°C, 0.3 MPa, and a residence time of 100 min. Subsequently, the mixture was continuously fed into a reduced-pressure esterification reactor, where it was subjected to a reaction at 190°C and 45 kJ / min. Small molecules were removed under reduced pressure at Pa and a residence time of 110 min to further improve the esterification rate. Then, the product was continuously fed into a prepolymer reactor and mixed with a polymerization catalyst (0.05% of the molar amount of succinic acid). The prepolymerization reaction was carried out at a temperature of 200℃, a pressure of 4 kPa, and a residence time of 80 min to obtain a negative pressure prepolymer product. Finally, the product was continuously fed into a final polymerization reactor and subjected to a vacuum final polymerization reaction at a temperature of 235℃, a pressure of 50 Pa, and a residence time of 120 min to obtain polybutylene succinate. The product was continuously discharged and granulated and dried underwater to obtain PBS granules.

[0063] Testing revealed that the obtained polymer had a molecular weight of 144,000, a molecular weight distribution of 2.13, a relatively high acid value of 58.7 mol / t, an L value of approximately 74, and a melt index of 36 g / 10 min. It is evident that compared to ring-opening polycondensation, the esterification method yields a product with a lower molecular weight, a larger molecular weight distribution, a higher acid value, and poorer quality, while exhibiting a higher melt index.

[0064] Comparative Example 2

[0065] Compared to Example 1, the difference lies in the use of dimethyl succinate and 1,4-butanediol as monomer raw materials to prepare PBS products via transesterification. Following similar procedures to ring-opening polycondensation: dimethyl succinate and 1,4-butanediol were continuously fed into a pressurized reactor at a molar ratio of dimethyl succinate: alcohol = 1.00:1.35, along with an esterification catalyst (0.05% of the molar amount of dimethyl succinate). A pressurized esterification reaction was carried out at 170°C, 0.3 MPa, and a residence time of 100 min. Subsequently, the mixture was continuously fed into a reduced-pressure esterification reactor, where a reaction was carried out at 190°C and a pressure of 0.3 MPa. Small molecules were removed under reduced pressure (45 kPa, 110 min) to further improve the esterification rate. The product was then continuously fed into a prepolymer reactor and mixed with a polymerization catalyst (0.05% of the molar amount of dimethyl succinate). The product was then subjected to a negative pressure prepolymerization reaction at 200 °C, 4 kPa, and 80 min to obtain a negative pressure prepolymer. Finally, the product was continuously fed into a final polymerization reactor and subjected to a vacuum final polymerization reaction at 235 °C, 50 Pa, and 120 min to obtain polybutylene succinate. The product was then continuously discharged and granulated and dried underwater to obtain PBS granules.

[0066] The obtained polymer had a molecular weight of 183,000, a molecular weight distribution of 1.98, a relatively high acid value of 33.4 mol / t, an L value of around 89, and a melt index of 30 g / 10 min. Although the molecular weight and product quality were improved compared to the esterification method, they were still lower than those of the ring-opening polycondensation method, especially the melt index, which was significantly higher.

[0067] Comparative Example 3

[0068] Compared with Example 1, the difference lies in the fact that the PBS product is prepared by a three-step reaction of SAA and BDO through ring-opening esterification, negative pressure prepolymerization, and vacuum polycondensation. The specific steps are as follows:

[0069] Succinic anhydride and 1,4-butanediol were added to a ring-opening esterification reactor at a molar ratio of anhydride:alcohol = 1.00:1.35, and mixed with p-toluenesulfonic acid (0.05% of the molar amount of succinic anhydride). The ring-opening esterification reaction was carried out at a temperature of 190℃, a pressure of 45 kPa, and a residence time of 110 min. Then, the mixture was continuously fed into a prepolymerization reactor and mixed with the polymerization catalyst tetrabutyl titanate (0.05% of the molar amount of succinic anhydride). The mixture was then subjected to a prepolymerization reaction at a temperature of 200℃, a pressure of 4 kPa, and a residence time of 80 min to obtain a negative pressure prepolymer product. Finally, the mixture was continuously fed into a final polymerization reactor and subjected to a vacuum final polymerization reaction at a temperature of 235℃, a pressure of 50 Pa, and a residence time of 120 min to obtain polybutylene succinate. The product was continuously discharged and granulated and dried underwater to obtain polyester granules.

[0070] Testing revealed that the obtained polymer had a molecular weight of 178,000, a molecular weight distribution of 1.94, a relatively high acid value of 41 mol / t, an L value of approximately 83, and a melt index of 37 g / 10 min. This indicates that the three-step method, due to incomplete esterification, resulted in a product with a high acid value, poor quality, and a high melt index.

[0071] Comparative Example 4

[0072] Compared to Example 1, the difference lies in the fact that the PBS product was prepared by a four-step reaction of SAA and BDO, involving ring-opening under normal pressure, esterification under pressure, prepolymerization under negative pressure, and final polymerization under vacuum. Comparative Example 4 removed the reduced-pressure esterification process from Example 1, while maintaining the same four-step operation. Testing revealed that the resulting polymer had a molecular weight of 143,000, a molecular weight distribution of 2.04, an acid value of 46 mol / t, an L value of approximately 80, and a melt index of 44 g / 10 min. It is evident that due to the reduction of the reduced-pressure esterification process, the esterification was incomplete, resulting in lower polymer molecular weight and product quality, significantly lower than the results of Example 1, and even lower than the three-step method of Comparative Example 3.

[0073] Comparative Example 5

[0074] Compared with Example 1, the difference is that PBS is prepared by reacting SAA and BDO in four steps: normal pressure ring opening, reduced pressure esterification, negative pressure prepolymerization, and vacuum final polymerization.

[0075] Comparative Example 5 removed the pressurized esterification process from Example 1, while maintaining the same other operations as Example 1, resulting in a four-step process. Testing revealed that the obtained polymer had a molecular weight of 203,000, a molecular weight distribution of 1.68, an acid value of 42 mol / t, an L value of approximately 82, and a melt index of 18 g / 10 min. It is evident that reducing the pressurized esterification process lowers monomer utilization, resulting in an actual alcohol-acid ratio significantly lower than the feed ratio. Consequently, the product acid value increases significantly, and the color is also poor. However, the presence of reduced-pressure esterification improves the esterification rate, ultimately having a smaller impact on the polymer molecular weight and melt index. In conclusion, Comparative Example 5 demonstrates that the presence of pressurized esterification is highly beneficial to the product's acid value and color.

[0076] Comparative Example 6

[0077] Compared with Example 1, the difference is that SAA and BDO are reacted in four steps to prepare PBS: reduced pressure esterification, pressurized esterification, negative pressure prepolymerization, and vacuum final polymerization.

[0078] Comparative Example 6 removed the atmospheric pressure ring-opening process from Example 1, while maintaining the same other operations as Example 1, resulting in a four-step process. Testing revealed that the obtained polymer had a molecular weight of 213,000, a molecular weight distribution of 1.79, an acid value of 38 mol / t, an L value of approximately 90, and a melt index of 17 g / 10 min. It is evident that reducing the ring-opening process, without directional ring-opening product formation, leads to simultaneous ring-opening and esterification, resulting in a wider molecular weight distribution and a slightly increased acid value. However, the presence of both pressurized and depressurized esterification steps improves the esterification rate, ultimately having a minimal impact on the polymer's molecular weight, color, and melt index. Therefore, Comparative Example 6 demonstrates the beneficial nature of the atmospheric pressure ring-opening step.

[0079] Comparative Example 7

[0080] Compared to Example 1, Comparative Example 7 is an intermittent operation. In order to compare the quality of 5 batches of products obtained by intermittent operation and continuous operation, the advantages of continuous operation are verified.

[0081] The batch operation is as follows: Succinic anhydride and 1,4-butanediol are added separately to the reaction vessel at a molar ratio of succinic anhydride:alcohol = 1.00:1.01. The mixture is then heated to 70°C and reacted at atmospheric pressure for 30 minutes. Next, p-toluenesulfonic acid (0.05% of the molar amount of succinic anhydride) and the remaining 1,4-butanediol (0.34 times the molar amount of succinic anhydride) are added. The mixture is then heated to 170°C and reacted at a pressure of 0.3 MPa for 10 minutes. The pressure was lowered to 45 kPa and the temperature increased to 190 °C for 110 min. After the reaction, nitrogen gas was introduced, and tetrabutyl titanate (0.05% of the molar amount of succinic anhydride) was added through the top of the reactor. A negative pressure prepolymerization reaction was carried out at 200 °C and 4 kPa. After 80 min, the temperature was increased to 235 °C and the pressure decreased to 50 Pa for a further vacuum final polymerization reaction of 120 min. After the final polymerization reaction, the material in the reactor was kept warm and pressurized and released through the bottom valve. It was then water-cooled into strips and granulated. The granules were collected for performance testing. This process was repeated 5 times. The experimental results are shown in Table 4.

[0082] Table 4 Comparison of product quality obtained from intermittent and continuous operations

[0083]

[0084] As shown in Table 4, the product quality obtained by continuous operation in Example 1 was more stable (5 sampling evaluations), with excellent controllability in molecular weight, molecular weight distribution, melt index, and acid value. Furthermore, the product color and performance were better. In contrast, the product quality obtained by intermittent operation in Comparative Example 7 was unstable, with significant fluctuations in the 5 evaluations, mainly due to the instability of intermittent operation and thermal decomposition.

[0085] Examples 10-29

[0086] The preparation of polysuccinate was investigated using succinic anhydride and other diols or polyols as monomer raw materials through a five-step continuous reaction process involving atmospheric pressure ring opening, pressure esterification, vacuum esterification, negative pressure prepolymerization, and vacuum final polymerization. The alcohols selected in Examples 10–29 are shown in Table 5, and the preparation steps are as follows:

[0087] Succinic anhydride and alcohol were continuously fed into a ring-opening reactor at a molar ratio of 1.00:1.05. The ring-opening reaction was carried out at 80±20℃, atmospheric pressure, and a residence time of 60±10 min to obtain an atmospheric pressure ring-opening product. This product was then continuously fed into a pressurized esterification reactor, where the remaining polyol (0.25–0.45 times the molar amount of succinic anhydride) and the esterification catalyst p-toluenesulfonic acid (0.1% of the molar amount of succinic anhydride) were continuously added through a feed tank. The reaction was carried out at 170±20℃, 0.5±0.1 MPa, and a residence time of 120±30 min to obtain a pressurized esterification product. This product was then continuously fed into a vacuum esterification reactor. In the process, small molecules were removed under reduced pressure at 190±10℃, 30±10kPa, and 90±20min to further improve the esterification rate. The product was then continuously fed into a prepolymerization reactor and mixed with the polymerization catalyst tetrabutyl titanate (0.12% of the molar amount of succinic anhydride). A prepolymerization reaction was then carried out at 210±20℃, 5±2kPa, and 90±20min to obtain a negative pressure prepolymer. Finally, the product was continuously fed into a final polymerization reactor and subjected to a vacuum final polymerization reaction at 240±15℃, 70±20Pa, and 120±30min to obtain polysuccinate. The product was continuously discharged and underwater pelletized and dried to obtain polyester granules. The molecular weight and color information of the obtained product are shown in Table 5.

[0088] Table 5. Polysuccinate prepared by polymerization of succinic anhydride with diols and polyols

[0089]

[0090]

[0091] As can be seen from the experimental results in Table 5, the polysuccinate products obtained in Examples 10-29 have high molecular weights, with Mw ranging from 150,000 to 310,000, and a relatively narrow molecular weight distribution (Mw / Mn) between 1.4 and 2.0. Furthermore, they exhibit excellent color quality, with L generally above 88, and generally low acid values, typically below 30 mol / t. This also demonstrates that the five-step continuous operation described above can yield polysuccinate products with higher molecular weights and better performance.

[0092] Of particular note is that the use of ternary or higher polyols (Examples 17-19) and rigid-structure diols (Examples 20-25) significantly reduced the melt index of the products (typically <10g / 10min), allowing them to be used in blow molding to produce various blow-molded products. Therefore, by flexibly adjusting the types of monomers, polyester products with different properties, applications, and grades can be developed.

[0093] Example 30

[0094] Polysuccinate was prepared by polymerizing succinic anhydride with 1,3-propanediol and 1,4-butanediol. The preparation steps are as follows: The raw materials, succinic anhydride:alcohol, were continuously fed into a ring-opening reactor at a molar ratio of 1.00:1.15 (and the molar ratio of 1,3-propanediol to 1,4-butanediol was 0.3:0.7). The ring-opening reaction was carried out at 90℃, atmospheric pressure, and a residence time of 45 min to obtain the atmospheric pressure ring-opening product. Subsequently, the product was continuously fed into a pressurized esterification reactor, and the remaining polyol (0.35 times the molar amount of succinic anhydride) and the esterification catalyst trichloroacetic acid (0.05% of the molar amount of succinic anhydride) were continuously added through a raw material tank. The reaction was carried out at 180℃, 0.3 MPa, and a residence time of 90 min. The product undergoes a pressurized esterification reaction at 180°C, 55 kPa, and 100 min to remove small molecules, further improving the esterification rate. It is then continuously fed into a vacuum esterification reactor and mixed with a polymerization catalyst, diethylene glycol titanate (0.15% of the molar amount of succinic anhydride), followed by a pre-polymerization reaction at 200°C, 8 kPa, and 100 min to obtain a negative pressure prepolymer. Finally, it is continuously fed into a final polycondensation reactor and subjected to a vacuum final polymerization reaction at 245°C, 90 Pa, and 100 min to obtain polysuccinate. The product is then continuously discharged and underwater pelletized and dried to obtain polyester granules.

[0095] The molecular weight M of the resulting polysuccinate (similar to modified polybutylene succinate) product w The molecular weight is 198,000, the molecular weight distribution is 1.71, the melt index is 22 g / 10 min, the acid value is 24 mol / t, and the elongation at break is as high as 760%, while the elongation at break of polybutylene succinate products is usually between 200 and 300%. It is evident that adding a small amount of aliphatic diol to modify polybutylene succinate can significantly improve its tensile properties.

[0096] Example 31

[0097] Polysuccinate was prepared by polymerizing succinic anhydride with 1,4-butanediol and terephthalic acid. The preparation steps are as follows: The raw materials, succinic anhydride:alcohol, were continuously fed into a ring-opening reactor at a molar ratio of 1.00:1.10 (molar ratio of 1,4-butanediol to terephthalic acid was 0.75:0.25). The ring-opening reaction was carried out at 120℃, atmospheric pressure, and a residence time of 80 min to obtain the atmospheric pressure ring-opening product. Subsequently, the product was continuously fed into a pressurized esterification reactor, and the remaining polyol (0.5 times the molar amount of succinic anhydride) and the esterification catalyst p-toluenesulfonic acid (0.15% of the molar amount of succinic anhydride) were continuously added through a raw material tank. The reaction was carried out at 190℃, 0.2 MPa, and a residence time of 90 min. The product undergoes a pressurized esterification reaction at 200°C, 25 kPa, and 120 min to remove small molecules, further increasing the esterification rate. It is then continuously fed into a prepolymerization reactor and mixed with a polymerization catalyst, tetraisopropyl titanate (0.10% of the molar amount of succinic anhydride). A prepolymerization reaction is then carried out at 230°C, 2 kPa, and 110 min to obtain a negative pressure prepolymer. Finally, the product is continuously fed into a final polymerization reactor and subjected to a vacuum final polymerization reaction at 245°C, 40 Pa, and 160 min to obtain polysuccinate. The product is then continuously discharged and underwater pelletized and dried to obtain polyester granules.

[0098] The molecular weight M of the resulting polysuccinate (similar to rigid glycol-modified polybutylene succinate) product w It has a molecular weight of 168,000, a molecular weight distribution of 1.39, an acid value of 18 mol / t, an elongation at break of up to 560%, and a melt index of less than 10 (7.9 g / 10 min). Compared with polybutylene succinate, it has a significantly increased elongation at break. In addition, it also significantly improves its melt strength and blow molding processability.

[0099] Example 32

[0100] Polysuccinate was prepared by polymerizing succinic anhydride with 1,4-butanediol and pentaerythritol. The preparation steps are as follows: The raw materials, succinic anhydride:alcohol, were continuously fed into a ring-opening reactor at a molar ratio of 1.00:1.06 (molar ratio of 1,4-butanediol to pentaerythritol was 0.95:0.05). The ring-opening reaction was carried out at 90℃, atmospheric pressure, and a residence time of 30 min to obtain the atmospheric pressure ring-opening product. Subsequently, the product was continuously fed into a pressurized esterification reactor, and the remaining polyol (0.5 times the molar amount of succinic anhydride) and the esterification catalyst p-toluenesulfonic acid monohydrate (0.08% of the molar amount of succinic anhydride) were continuously added through a raw material tank. The reaction was carried out at 160℃, 0.1 MPa, and a residence time of 9 min. The product was subjected to a pressurized esterification reaction at 0 min to obtain an esterified product. It was then continuously fed into a vacuum esterification reactor, where small molecules were removed under reduced pressure at 180℃, 55 kPa, and a residence time of 120 min to further improve the esterification rate. The product was then continuously fed into a prepolymerization reactor and mixed with a polymerization catalyst, tetrabutyl titanate (0.08% of the molar amount of succinic anhydride). The product was then subjected to a prepolymerization reaction at 210℃, 9 kPa, and a residence time of 60 min to obtain a negative pressure prepolymer. Finally, the product was continuously fed into a final polymerization reactor, where a vacuum final polymerization reaction was carried out at 245℃, 100 Pa, and a residence time of 70 min to obtain polysuccinate. The product was then continuously discharged and granulated and dried underwater to obtain polyester granules.

[0101] The molecular weight M of the resulting polysuccinate (similar to polyol-modified polybutylene succinate) product is... w The molecular weight is 298,000, and the molecular weight distribution is 2.29. This means that the addition of a small amount of polyol can significantly increase the molecular weight of polyester. In addition, the product has an acid value of 19 mol / t and a melt index of less than 10 (3.9 g / 10 min), which significantly improves the polymer melt strength and blow molding processing capability.

[0102] Example 33

[0103] Polysuccinate was prepared by polymerizing succinic anhydride with 1,4-butanediol and polyethylene glycol (Mn = 2000 g / mol). The preparation steps are as follows: The raw materials were continuously fed into a ring-opening reactor at a molar ratio of succinic anhydride:alcohol = 1.00:1.10 (the molar ratio of 1,4-butanediol to polyethylene glycol was 0.7:0.3). The ring-opening reaction was carried out at a temperature of 110℃, a pressure of atmospheric pressure, and a residence time of 60 min to obtain the ring-opening product under atmospheric pressure. Subsequently, the product was continuously fed into a pressurized esterification reactor, and the remaining polyol (0.30 times the molar amount of succinic anhydride) and the esterification catalyst p-toluenesulfonic acid (0.10% of the molar amount of succinic anhydride) were continuously added through a raw material tank. The reaction was carried out at a temperature of 180℃, a pressure of 0.2 MPa, and a residence time of 60 min. The product was subjected to a pressurized esterification reaction for 100 min to obtain an esterified product. It was then continuously fed into a vacuum esterification reactor, where small molecules were removed under reduced pressure at 190℃, 40 kPa, and a residence time of 120 min to further improve the esterification rate. Next, it was continuously fed into a prepolymerization reactor and mixed with a polymerization catalyst, tin tetrachloride (0.20% of the molar amount of succinic anhydride). A prepolymerization reaction was then carried out at 220℃, 5 kPa, and a residence time of 75 min to obtain a negative pressure prepolymerized product. Finally, it was continuously fed into a final polymerization reactor, where a vacuum final polymerization reaction was carried out at 245℃, 70 Pa, and a residence time of 180 min to obtain polysuccinate. The product was continuously discharged and underwater pelletized and dried to obtain polyester granules.

[0104] The molecular weight M of the obtained polysuccinate product w The molecular weight is 243,000, the molecular weight distribution is 1.65, the melt index is 31 g / 10 min, the product acid value is 21 mol / t, the color is good, the L value is 91, the a value is 3.7, and the b value is 1.9.

[0105] Example 34

[0106] Polysuccinate was prepared by polymerizing succinic anhydride with ethylene glycol, 1,3-propanediol, and 1,4-butanediol. The preparation steps are as follows: The raw materials were continuously fed into a ring-opening reactor at a molar ratio of succinic anhydride:alcohol = 1.00:1.02 (molar amounts of ethylene glycol, 1,3-propanediol, and 1,4-butanediol were 0.25:0.25:0.50). The ring-opening reaction was carried out at 70℃, atmospheric pressure, and a residence time of 45 min to obtain the atmospheric pressure ring-opening product. Subsequently, the product was continuously fed into a pressurized esterification reactor, and the remaining polyol (0.33 times the molar amount of succinic anhydride) and the esterification catalyst p-toluenesulfonic acid monohydrate (0.10% of the molar amount of succinic anhydride) were continuously added through a raw material tank. The reaction was carried out at 180℃ and a pressure of 0.25 Mn. The product was subjected to a pressurized esterification reaction at 100 min and a pressure of 200 °C, 70 kPa, and a residence time of 120 min to remove small molecules and further improve the esterification rate. The product was then continuously fed into a prepolymerization reactor and mixed with a polymerization catalyst, diethylene glycol titanate (0.06% of the molar amount of succinic anhydride). A prepolymerization reaction was then carried out at 210 °C, 6 kPa, and a residence time of 60 min to obtain a negative pressure prepolymer. Finally, the product was continuously fed into a final polymerization reactor and subjected to a vacuum final polymerization reaction at 240 °C, 110 Pa, and a residence time of 150 min to obtain polysuccinate. The product was then continuously discharged and underwater pelletized and dried to obtain polyester granules.

[0107] The molecular weight M of the obtained polysuccinate product w The molecular weight is 257,000, the molecular weight distribution is 1.58, the melt index is 18 g / 10 min, the acid value of the product is 27 mol / t, the color is good, the L value is 89, the a value is 1.7, the b value is 3.9, and the elongation at break of the product is 640%.

[0108] As can be seen from Examples 30-34, by flexibly adjusting and applying the types and ratios of monomers, polyester products with different properties and grades can be developed to meet different downstream application scenarios.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the continuous synthesis of polydialkyl succinates, characterized in that, is a succinic anhydride and a polyol as monomer raw material, and is continuously synthesized by five steps including normal pressure ring opening, pressurized esterification, reduced pressure esterification, negative pressure pre-polymerization and vacuum final polymerization, and specifically includes the following steps: (1) continuously conveying the monomer raw material succinic anhydride and part of the polyol into a ring opening reaction device to perform ring opening reaction at a temperature of 70-90℃, a pressure of normal pressure and a residence time of 30-60 min, to obtain a normal pressure ring opening product; (2) continuously feeding the ring opening product obtained in step (1) into a pressurized esterification reaction device, and continuously adding the remaining polyol and an esterification catalyst, to perform pressurized esterification reaction at a temperature of 150-200℃, a pressure of 0.2-0.7 MPa and a residence time of 60-240 min, to obtain a pressurized esterification product; (3) continuously feeding the pressurized esterification product obtained in step (2) into a reduced pressure esterification reaction device, to remove small molecules at a temperature of 160-210℃, a pressure of 20-60 kPa and a residence time of 60-150 min, to obtain a reduced pressure esterification product; (4) continuously feeding the reduced pressure esterification product obtained in step (3) into a pre-polymerization reaction device, and uniformly mixing with a polymerization catalyst, to perform pre-polymerization reaction at a temperature of 200-220℃, a pressure of 3-15 kPa and a residence time of 60-120 min, to obtain a negative pressure pre-polymerization product; (5) continuously feeding the pre-polymerization product obtained in step (4) into a final polymerization reaction device, to perform vacuum final polymerization reaction at a temperature of 230-250℃, a pressure of 30-80 Pa and a residence time of 90-180 min, to obtain a polybutylene succinate; The molar ratio of the monomer raw material is succinic anhydride:polyol = 1.00:(1.10-1.45); wherein in step (1), the molar ratio of succinic anhydride:polyol = 1.00:(1.00-1.10), and the remaining part of the polyol is continuously added in the pressurized esterification reaction in step (2).

2. A continuous synthesis process of a polyadipate according to claim 1, characterized in that, In step (2), the pressurized esterification reaction conditions are a temperature of 170-190℃, a pressure of 0.3-0.5 MPa and a residence time of 90-180 min.

3. A continuous process for the synthesis of a polydialkyl succinate according to claim 1, wherein, In step (3), the reduced pressure esterification reaction conditions are a temperature of 180-200℃, a pressure of 30-50 kPa and a residence time of 90-120 min.

4. The process for continuous synthesis of poly succinates as claimed in claim 1 wherein, The esterification catalyst is selected from one or more of methyl sulfonic acid, p-toluene sulfonic acid, p-toluene sulfonic acid hydrate, trifluoromethanesulfonic acid, trifluoroacetic acid and trichloroacetic acid, and the amount of the esterification catalyst is 0.01-2.00% of the molar amount of succinic anhydride; the polymerization catalyst is selected from one or more of titanium, tin, antimony and germanium compounds, and the amount of the polymerization catalyst is 0.01-1.00% of the molar amount of succinic anhydride.

5. The process for continuous synthesis of a polyadipate according to claim 4, characterized in that, The amount of the esterification catalyst is 0.05-0.20% of the molar amount of succinic anhydride.

6. The process for continuous synthesis of a polyadipate according to claim 4, characterized in that, The amount of the polymerization catalyst is 0.05-0.20% of the molar amount of succinic anhydride.

7. The process for continuous synthesis of a polyadipate according to claim 4, characterized in that, The polymerization catalyst is one or more of titanium dioxide, titanium silicon composite, titanium trichloride, titanium tetrachloride, titanium tributoxide chloride, tetraethyl titanate, tetraisopropyl titanate, tetrabutyl titanate, tetraisooctyl titanate, tetrahydroxyethyl titanate, diethylene glycol titanate, tetrahydroxypropyl titanate, dipropylene glycol titanate, tetrahydroxybutyl titanate, or dibutylene glycol titanate, or tin dichloride, tin tetrachloride, stannous succinate, stannous octoate, stannous benzoate, dioctyl tin oxide, tetrabutyl tin, dibutyl tin acetate, or diantimony pentoxide, diantimony trioxide, antimony trichloride, antimony pentachloride, ethylene glycol antimony, or butylene glycol antimony, or germanium dioxide, germanium tetrachloride, germanium tetrabutoxide, germanium tetramethyl, or germanium tetraethyl.

8. The process for continuous synthesis of poly succinates as claimed in claim 1 wherein, The polyol is one or more of a fatty polyol, an aromatic polyol, a heterocyclic polyol, a polyfatty alcohol ether polyol, a polyaromatic alcohol ether polyol, a polyaromatic phenol ether polyol, a polyheterocyclic alcohol ether polyol, a polyfatty acid ester polyol, a polyaromatic acid ester polyol, and a polyheterocyclic acid ester polyol.

9. The process for continuous synthesis of a polyadipate according to claim 8, characterized in that, The fatty polyols include one or more of 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,2-propanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4-trimethyl-1,3-pentanediol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, glycerol, trimethylolethane, trimethylolpropane, pentaerythritol, erythritol, xylitol, sorbitol, lactitol, glucose, fructose, chitosan, starch; the aromatic polyols include one or more of phenylethanediol, p-xylylenediol, o-xylylenediol, m-xylylenediol, p-phenylenediol, o-phenylenediol, m-phenylenediol, o-chlorophenylethanediol, 4,4'-dihydroxymethylbiphenyl; the heterocyclic polyols include one or more of 2,5-furandiol, tetrahydro-2-methyl-2H-pyran-3,4-diol, hydroxypropyltetrahydropyranyltriose, 2,6-pyridinediol, 2,3-thiophenediol, 3,4-thiophenediol, and 3,4-tetrahydrothiophenediol; the polyfatty alcohol ether polyols include one or more of polyethers of ethylene oxide or oxirane, 1,2-propanediol or oxetane, 1,4-butanediol or tetrahydrofuran, 1,2-butanediol or 1,2-epoxybutane, 2,3-butanediol or 2,3-epoxybutane, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediol or oxycyclohexene, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, glycerol or glycidol or epichlorohydrin, and copolymers thereof with polyols; the polyaromatic alcohol ether polyols include one or more of polyethers of p-xylylenediol, m-xylylenediol, o-xylylenediol, styrene oxide or phenylethanediol, and copolymers thereof with polyols; the polyaromatic phenol ether polyols include one or more of p-dihydroxybenzene, m-dihydroxybenzene, and / or o-dihydroxybenzene, and polyethers thereof with polyols; the polyheterocyclic alcohol ether polyols include one or more of polyethers of 2,5-furandiol, 2,6-pyridinediol, 2,3-thiophenediol, 3,4-thiophenediol, and 3,4-tetrahydrothiophenediol, and copolymers thereof with polyols; the polyfatty acid ester polyols include one or more of poly-C1-C10fatty polyacid ester polyols, polyhydroxy acid esters, polyhydroxy acid ester polyols; the polyaromatic acid ester polyols include one or more of polybenzene diacid polyols, polybenzene triacid polyols, polynaphthalene diacid polyols.The polyheterocyclic diacid ester polyols include one or more of poly-2,5-furandicarboxylate polyols, poly-2,6-pyridinedicarboxylate polyols, and poly-2,3-thiophenedicarboxylate polyols.

10. The process for continuous synthesis of a polyadipate according to claim 9, characterized in that, The fatty polyols include one or more of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 1,2-propanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2,2,4-trimethyl-1,3-pentanediol, glycerol, trimethylol ethane, trimethylol propane, pentaerythritol, erythritol, xylitol, sorbitol, lactitol; the aromatic polyols include one or more of p-xylyl glycol, m-xylyl glycol, 4,4'-dihydroxymethyl biphenyl; the heterocyclic polyols include one or more of 2,5-furandimethanol, 2,6-pyridinedimethanol, 2,3-thiophenedimethanol, and 3,4-thiophenediol; the polyfatty alcohol ether polyols include one or more of polyethylene glycol, poly-1,2-propanediol, poly-1,4-butanediol, poly-1,4-cyclohexanediol, poly-1,4-cyclohexanedimethanol, polyethylene glycol glyceryl ether, polypropylene glycol glyceryl ether, poly-1,2-cyclohexanediol ethylene glycol ether, and poly-1,4-butanediol pentaerythritol ether; the polyaromatic alcohol ether polyols include one or more of poly-p-xylyl glycol, poly-m-xylyl glycol, polystyrene oxide, poly-p-xylyl glycol ethylene glycol ether, polystyrene oxide glyceryl ether; the polyaromatic phenol ether polyols include one or more of poly-p-quinol ethylene glycol ether and poly-p-quinol glycidyl ether; the polyheterocyclic alcohol ether polyols include one or more of poly-2,5-furandimethanol, poly-2,6-pyridinedimethanol, poly-3,4-thiophenediol, and poly-2,5-furandimethanol ethylene glycol ether; the polyfatty acid ester polyols include one or more of polyethylene adipate glycol, polyhexanedioate glycol, polybutanedioate glycol, polyhexanedioate hexyleneglycol, polysebacate hexyleneglycol, polycyclohexanedicarboxylate glycol, polyglycolide glycol, poly(glycolide-lactide) glycol, polylactide glycol, polyglyceryl hydroxybutyrate, polycaprolactone glycol, polyglyceryl hydroxyhexanoate; the polyaromatic acid ester polyols include one or more of poly-p-xylyl adipate glycol, poly-m-xylyl adipate glycol, poly-1,3,5-benzenetricarboxylic acid glycol, poly-1,4-naphthalenedicarboxylic acid glycol; the polyheterocyclic acid ester polyols include one or more of poly-2,5-furandicarboxylic acid-ethylene glycol ester diol, poly-2,5-furandicarboxylic acid-2,5-furandimethanol ester diol, poly-2,6-pyridinedicarboxylic acid ethylene glycol ester diol.

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