Polyterephthalic acid-1, 3-propylene glycol ester and preparation method thereof

Abstract

According to the poly (1, 3-propylene terephthalate) and the preparation method thereof, the stabilizer is added into the reaction liquid, so that the 1, 3-propylene glycol waste liquid can be directly utilized without additional treatment, the use amount of the 1, 3-propylene glycol is effectively reduced, the yield of the poly (1, 3-propylene terephthalate) is increased, and the yield of the poly (1, 3-propylene terephthalate) is increased. The production cost of the 1, 3-propylene glycol ester is reduced. The poly terephthalic acid-1, 3-propylene glycol ester prepared by the preparation method disclosed by the invention is good in product quality, and has no obvious influence on the intrinsic viscosity of slices. Meanwhile, the preparation method provided by the invention also can effectively reduce the problems of reduced reaction rate and side reaction in the reaction process caused by addition of a recovery solution in a reaction system in a conventional method, and effectively solves the problem that 1, 3-propylene glycol terephthalate produced in the preparation of the poly (1, 3-propylene glycol terephthalate) in the prior art is easily separated from the product. The problems of complex recovery process, high energy consumption, secondary pollution to the environment and the like of the 1, 3-propylene glycol waste liquid in the prior art are solved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer synthesis, and in particular to poly(1,3-trimethylene terephthalate) and a preparation method thereof. Background Art

[0002] In the preparation process of poly(1,3-propylene terephthalate) (PTT), there are two main steps: esterification reaction and polycondensation reaction. In the esterification stage, 1,3-propylene glycol reacts with terephthalic acid (PTA) to form a prepolymer; then in the polycondensation stage, the prepolymer further reacts under high temperature and vacuum conditions to form high molecular weight PTT. In this process, in order to ensure the completeness of the reaction and the performance of the product, 1,3-propylene glycol is often added in excess, resulting in the generation of waste liquid containing unreacted 1,3-propylene glycol, by-products and catalyst residues in the polycondensation stage. According to the GII report, the global market size of 1,3-propylene glycol reached US$402 million in 2020 and is expected to reach US$691 million in 2025, with a compound annual growth rate of 11.4%. Therefore, as a key monomer, the excessive use and recycling of 1,3-propylene glycol in the production process has always been the focus of industry attention.

[0003] Traditional treatment and recovery methods for these waste liquids often involve complex purification steps, such as distillation, extraction, filtration, etc., which aim to remove water, low molecular weight by-products and other impurities in the waste liquid to recover high-purity 1,3-propylene glycol. However, these purification processes are not only energy-intensive and complex to operate, increasing production costs, but also may cause secondary pollution during the waste liquid treatment process, causing adverse effects on the environment. For example, the high energy consumption and kettle residue treatment generated during the distillation process, as well as the wastewater generated during the rotary evaporation process, have increased the environmental burden of the production process. In addition, when 1,3-propylene glycol recovered by traditional methods is put back into use, there are also problems with the purity of 1,3-propylene glycol or residual impurities, which affect the efficiency of subsequent reactions and the performance of the final product.

[0004] Based on the above background, it has become an urgent need to develop a method that can directly use 1,3-propylene glycol waste liquid in the PTT synthesis process without an additional purification step, which can not only simplify the production process, reduce energy consumption and production costs, but also reduce the burden of waste liquid treatment on the environment, and also conform to the concept of green chemistry and circular economy. In order to solve the above problems, the present invention is specially proposed. Summary of the invention

[0005] The main purpose of the present invention is to provide a poly (1,3-propylene terephthalate) and a preparation method thereof, so as to solve the problems in the prior art of complex recovery process of 1,3-propylene glycol waste liquid generated in the preparation of poly (1,3-propylene terephthalate), high energy consumption and secondary pollution, thereby reducing the production cost of poly (1,3-propylene terephthalate).

[0006] In order to solve the above problems, the present invention provides a method for preparing poly(1,3-propylene terephthalate), which comprises the following steps: batching: mixing terephthalic acid, a catalyst, a stabilizer, 1,3-propylene glycol and a recovered liquid to obtain a mixed solution; esterification: subjecting the mixed solution to a first heating to perform an esterification reaction to obtain a prepolymer mixed solution; polymerization: subjecting the prepolymer mixed solution to a second heating to perform a condensation reaction to obtain poly(1,3-propylene terephthalate); meanwhile, 1,3-propylene glycol waste liquid is generated in the condensation reaction, and the 1,3-propylene glycol waste liquid is reused as a recovered liquid to the batching stage.

[0007] Further, the stabilizer is one or more of phosphoric acid, triphenyl phosphate, trimethyl phosphate, 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)sebacate and 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane; preferably, the stabilizer comprises a first component and a second component, the first component is phosphoric acid, phosphoric acid, The first component is at least one of triphenyl phosphate and trimethyl phosphate, and the second component is at least one of 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)sebacate and 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane; preferably, the weight ratio of the first component to the second component is (1-10):(1-20).

[0008] Furthermore, the amount of the stabilizer added is 5 to 2000 ppm by weight of the terephthalic acid; preferably, the amount of the stabilizer added is 30 to 1000 ppm by weight of the terephthalic acid.

[0009] Furthermore, the weight of 1,3-propylene glycol in the recovered liquid is 5 to 30% of the total weight of 1,3-propylene glycol in the mixed solution; preferably, the weight of 1,3-propylene glycol in the recovered liquid is 10 to 20% of the total weight of 1,3-propylene glycol in the mixed solution; preferably, the weight content of 1,3-propylene glycol in the recovered liquid is greater than 90%, and the weight content of water is less than 0.5%.

[0010] Furthermore, the amount of the catalyst added to the mixed solution is 100 to 800 ppm by weight of terephthalic acid; preferably, the molar amount of 1,3-propylene glycol in the mixed solution is 1.1 to 1.8 times the molar amount of terephthalic acid.

[0011] Furthermore, the amount of the catalyst added to the mixed solution is 200 to 600 ppm based on the weight of terephthalic acid.

[0012] Furthermore, the catalyst is a titanium compound; preferably, the catalyst is a titanate compound, more preferably one or more of tetraethyl titanate, tetraisopropyl titanate, and tetra-n-butyl titanate.

[0013] Furthermore, the esterification reaction is carried out under an inert atmosphere, the first heating temperature is 200-250° C., the pressure is 0.1-0.5 MPa, and the time is 3-6 hours.

[0014] Furthermore, the second heating temperature is 240-270° C., the pressure is below 100 Pa, and the time is 2-4 hours.

[0015] According to another aspect of the present invention, there is also provided poly(1,3-trimethylene terephthalate), which is prepared by the above preparation method. The intrinsic viscosity of the poly(1,3-trimethylene terephthalate) is 0.80-1.05 dL / g.

[0016] The present invention provides a poly(1,3-propylene terephthalate) and a preparation method thereof, the preparation method comprising: first mixing terephthalic acid, a catalyst, a stabilizer, 1,3-propylene glycol and 1,3-propylene glycol recovery liquid, then subjecting the mixed solution to an esterification reaction to obtain a prepolymer mixed solution, and then subjecting the obtained prepolymer mixed solution to a polycondensation reaction to obtain poly(1,3-propylene terephthalate); at the same time, the 1,3-propylene glycol waste liquid generated during the polycondensation reaction is continuously reused as a recovery liquid to the batching stage. The preparation method can directly utilize the 1,3-propylene glycol waste liquid without additional treatment by adding a stabilizer to the reaction liquid, and can also effectively reduce the amount of 1,3-propylene glycol used in the preparation process. Moreover, the poly(1,3-propylene terephthalate) prepared by the preparation method of the present invention has good product quality and has no significant effect on the characteristic viscosity of the slices. At the same time, in addition to the direct resource utilization of waste liquid, the preparation method provided by the present invention can also effectively reduce the problem of reduced reaction rate and side reactions during the reaction process caused by adding recycled liquid to the reaction system in conventional methods.

[0017] In summary, the preparation method effectively solves the problems of complicated recovery process, high energy consumption and secondary pollution to the environment of 1,3-propylene glycol waste liquid generated in the preparation of poly(1,3-propylene terephthalate) in the prior art. At the same time, it can further reduce the production cost of poly(1,3-propylene terephthalate), which has significant progress significance for actual production. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0019] As described in the background technology section, in the preparation and production of poly (trimethylene terephthalate), 1,3-propylene glycol (1,3-PDO) is a key monomer, and its excessive use and recycling treatment has always been the focus of industry attention. The existing treatment and recycling methods often use complex purification steps, such as distillation, extraction, filtration, etc., to remove moisture, low molecular weight by-products and other impurities in the waste liquid to recover high-purity 1,3-propylene glycol for further preparation reactions. This method not only has high energy consumption and complex operation, which increases production costs, but also may cause secondary pollution during the waste liquid treatment process, causing adverse effects on the environment.

[0020] In order to solve the above problems, the present invention provides a method for preparing poly(1,3-propylene terephthalate), which comprises the following steps: batching: mixing terephthalic acid, a catalyst, a stabilizer, 1,3-propylene glycol and a recovered liquid to obtain a mixed solution; esterification: subjecting the mixed solution to a first heating to perform an esterification reaction to obtain a prepolymer mixed solution; polymerization: subjecting the prepolymer mixed solution to a second heating to perform a condensation reaction to obtain poly(1,3-propylene terephthalate); meanwhile, 1,3-propylene glycol waste liquid is generated in the condensation reaction, and the 1,3-propylene glycol waste liquid is reused as a recovered liquid to the batching stage.

[0021] The present invention adds a stabilizer to the esterification reaction system when preparing poly(1,3-propylene terephthalate), thereby achieving direct participation in the reaction and recycling of the 1,3-propylene glycol waste liquid produced by the preparation of poly(1,3-propylene terephthalate) without additional treatment. This process can effectively reduce the use of 1,3-propylene glycol. The stabilizer plays an important role in the system, and it is speculated that it can be analyzed from the following aspects: First, preventing the deactivation of the catalyst due to high temperature: In the synthesis process of PTT, especially in the esterification and polycondensation reaction stages, high temperature is a necessary reaction condition. However, high temperature conditions often lead to the deactivation of the catalyst. The present invention proposes that the deactivation of the catalyst caused by high temperature can be effectively avoided by adding a stabilizer to the reaction system, thereby improving the phenomena of incomplete reaction of raw materials in the reaction system, complex system components, and reduced quality of PTT products. Second, prevent the raw material 1,3-propylene glycol (PDO) from etherifying to form 1,3-propylene glycol dimer (DPG): 1,3-propylene glycol (1,3-PDO) may undergo etherification reaction under high temperature conditions to form dimers such as 1,3-propylene glycol dimer (DPG) and other impurities. These by-products will not only reduce the purity and performance of the product, but also increase the difficulty and cost of subsequent separation and purification. The present application can effectively inhibit the etherification reaction of 1,3-PDO to form 1,3-propylene glycol dimer (DPG) by adding a stabilizer to the reaction system, promote the formation of poly (1,3-propylene terephthalate), and improve the quality of the generated poly (1,3-propylene terephthalate). Under the synergistic effect of the above-mentioned multiple effects, the poly(1,3-trimethylene terephthalate) prepared by the preparation method of the present invention has good product quality, and its intrinsic viscosity, terminal carboxyl content and other indicators are all good. It also has the characteristics of good color and good heat resistance stability, which can ensure that the requirements of practical applications in different aspects such as fiber and injection molding are met. At the same time, the above-mentioned effects can also effectively reduce the problems of reduced reaction rate and increased side reactions during the reaction process caused by adding recycled liquid to the reaction system.

[0022] In addition, the strategy of direct reuse of recycled liquid not only reduces the consumption of raw materials, but also reduces energy consumption in the production process. This preparation method is particularly suitable for resource-saving and environmentally friendly production models, especially in the current global context of advocating green manufacturing. It has important practical significance and application value.

[0023] In summary, the method for preparing poly(1,3-propylene terephthalate) proposed in the present invention can not only ensure product quality, but also achieve the purpose of directly utilizing the generated 1,3-propylene glycol waste liquid as a resource. The preparation method effectively solves the problems of the prior art in the complex recovery process, high energy consumption and secondary pollution of the 1,3-propylene glycol waste liquid generated in the preparation of poly(1,3-propylene terephthalate), and also further reduces the production cost of poly(1,3-propylene terephthalate).

[0024] In a preferred embodiment, the stabilizer is one or more of phosphoric acid, triphenyl phosphate, trimethyl phosphate, 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)sebacate and 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane. When preparing poly(1,3-propylene glycol) terephthalate using 1,3-propylene glycol waste liquid, adding the above-mentioned type of stabilizer to the reaction system is beneficial to further inhibit the occurrence of side reactions in the system, thereby being able to better improve the viscosity characteristics and quality of the product. Among them, phosphoric acid and phosphate compounds in the stabilizer have antioxidant properties, which can remove free radicals in the reaction system and prevent the titanium compound catalyst from being deactivated due to oxidation. The phosphorus spirocyclic compounds and phosphine ester compounds in the stabilizer can form stable complexes with titanium ions to protect the titanium catalyst from possible decomposition or oxidation under high temperature conditions, thereby extending the activity period of the catalyst and promoting the polymerization reaction to proceed faster and better. In addition, the above stabilizer can also compete with 1,3-PDO for the active sites of the reaction catalyst through specific interactions with 1,3-PDO molecules or reaction intermediates, reduce the probability of 1,3-PDO undergoing etherification reaction at the above active sites, block the occurrence of etherification side reactions, reduce the generation of DPG, and thus maintain the reaction activity of the raw materials. In addition, the above compounds also have the characteristics of heat aging resistance or free radical absorption, which inhibits the free radical reaction caused by heat aging and the like during the reaction process, which is conducive to further inhibiting the generation of by-products and improving product quality. Under the synergistic effect of the above-mentioned multiple aspects, the stabilizer in the reaction system can give full play to the role of stabilizing the occurrence of side reactions in the reaction system, effectively improve the quality of the product, and improve production efficiency.

[0025] Preferably, the stabilizer includes a first component and a second component, the first component is at least one of phosphoric acid, triphenyl phosphate and trimethyl phosphate, and the second component is at least one of 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate and 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane. The first component and the second component are mixed and used, and the two stabilizers act synergistically, which can further reduce the influence of impurities in the recovered liquid on the polymerization reaction, play a role in further inhibiting the side reactions in the system, and are conducive to further making the poly(1,3-propylene terephthalate) preparation process less susceptible to the influence of impurities in the 1,3-propylene glycol waste liquid, thereby improving product quality. More preferably, the first component of the stabilizer is trimethyl phosphate, and the second component is 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane; or, the first component of the stabilizer is triphenyl phosphate, and the second component is bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate; or, the first component of the stabilizer is phosphoric acid, and the second component is 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane. The stabilizer is compounded and used in the above manner, and the quality of the obtained poly(1,3-propylene terephthalate) is better. Preferably, the weight ratio of the first component to the second component is (1-10):(1-20), specifically, 1:1, 1:5, 1:8, 1:10, 1:15, 1:20, 2:5, 2:10, 3:15, 3:20, 5:20, 8:5, 8:15, 9:20, 10:1, 10:3, 10:5, 10:20, or any ratio between any two of the above ratios. The above effect is better when the addition amount of the above two components is controlled within the above range.

[0026] In a preferred embodiment, the amount of stabilizer added is 5 to 2000 ppm of the weight of terephthalic acid, specifically, 5 ppm, 20 ppm, 100 ppm, 300 ppm, 500 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, or any amount between any two of the above values. When preparing poly-1,3-trimethylene terephthalate, controlling the amount of stabilizer added within the above range can better play the role of the stabilizer, achieve the purpose of inhibiting the generation of side reactions, and thus enable the prepared poly-1,3-trimethylene terephthalate to increase the intrinsic viscosity and transparency of the product and improve the overall quality. Preferably, the amount of the stabilizer added is 30 to 1000 ppm of the weight of terephthalic acid, for example, 30 ppm, 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, or any amount between any two of the above values. When the amount of the stabilizer added is controlled within the above preferred range, the above preparation effect is better.

[0027] In a preferred embodiment, in the mixed solution after batching, the weight of 1,3-propylene glycol in the recovered liquid is 5-30% of the total weight of 1,3-propylene glycol in the mixed solution, specifically, for example, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 27%, 30%, or any ratio between any two of the above ratios. Controlling the amount of recovered liquid used within the above range can not only make poly(1,3-propylene terephthalate) have good quality, but also further reduce its reaction time and improve its production efficiency. Preferably, the weight of 1,3-propylene glycol in the recovered liquid in the mixed solution is 10-20% of the total weight of 1,3-propylene glycol in the mixed solution, specifically, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any ratio between any two of the above ratios. By controlling the amount of recovered liquid used within the above-mentioned preferred range, it is possible to effectively treat 1,3-propylene glycol waste liquid while making the obtained poly(1,3-propylene glycol terephthalate) of better quality and making the entire production process more efficient. Preferably, the weight content of 1,3-propylene glycol in the recovered liquid is greater than 90%, and the weight content of water is less than 0.5%. When the quality of the recovered liquid used is within the preferred range, the overall preparation reaction process is more effective. In particular, when the water content in the system is within the above-mentioned range, it is possible to further avoid the deactivation of the catalyst caused by excessive water content in the system, the extension of the esterification time, and the resulting effects on the color of the final poly(1,3-propylene glycol terephthalate) product.

[0028] In a preferred embodiment, the amount of catalyst added to the mixed solution is 100 to 800 ppm by weight of terephthalic acid; preferably, the molar amount of 1,3-propylene glycol in the mixed solution is 1.1 to 1.8 times the molar amount of terephthalic acid. Controlling the addition ratio of the catalyst and 1,3-propylene glycol within the above range is more conducive to the reaction. Preferably, the amount of catalyst added to the mixed solution is 200 to 600 ppm by weight of terephthalic acid. By optimizing and controlling the amount of catalyst added to the reaction system within the preferred range, the reaction process can be further accelerated, the production cycle can be shortened, and the production efficiency can be improved.

[0029] In a preferred embodiment, the catalyst is a titanium compound, and the use of such a catalyst to catalyze the reaction has the characteristics of high catalytic activity, good selectivity, and strong stability. Preferably, the catalyst is a titanate compound, and by way of example but not limitation, the catalyst is one or more of tetraethyl titanate, tetraisopropyl titanate, and tetra-n-butyl titanate. The specific catalysts in the above examples are relatively common and have good effects on catalyzing the esterification reaction and polycondensation reaction described in the present invention.

[0030] In a preferred embodiment, the esterification reaction is carried out under an inert atmosphere, the first heating temperature is 200-250°C, the pressure is 0.1-0.5 MPa, and the time is 3-6 hours. Carrying out the esterification reaction under an inert atmosphere can effectively prevent the oxidation of raw materials and intermediates, and improve the purity and stability of the product; using the preparation method of the present invention, the reaction temperature and reaction time of the esterification reaction are controlled within the above range, so that the esterification reaction can be carried out more completely.

[0031] In a preferred embodiment, the second heating temperature is 240-270°C, the pressure is below 100 Pa, and the time is 2-4 hours. By using the preparation method of the present invention, the reaction temperature and reaction time of the polycondensation reaction are controlled within the above ranges, so that the esterification reaction can be carried out better and more completely, and at the same time, the intrinsic viscosity and molecular weight distribution of the product can be within a suitable range.

[0032] According to another aspect of the present invention, there is also provided poly(1,3-trimethylene terephthalate), which is prepared by the above-mentioned preparation method, and its intrinsic viscosity, terminal carboxyl content and other indicators are consistent with those of poly(1,3-trimethylene terephthalate) prepared by conventional methods, and meets the application requirements of fiber, injection molding, etc., wherein its intrinsic viscosity is 0.80-1.05 dL / g.

[0033] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0034] It should be noted that the recovered liquid used in the examples of the present invention and the comparative examples is from the same batch, wherein the weight content of 1,3-propylene glycol (1,3-PDO) is 92%, and the weight content of water is 0.42%.

[0035] Example 1

[0036] Terephthalic acid, tetraethyl titanate, stabilizer phosphoric acid and 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane), 1,3-propylene glycol and recovered liquid are placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetraethyl titanate added is 550ppm of the weight of terephthalic acid, the amount of stabilizer phosphoric acid added is 50ppm of terephthalic acid, the amount of stabilizer 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane added is 50ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 5% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 240°C and 0.1MPa for 3.3 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 2.5 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0037] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0038] Example 2

[0039] Terephthalic acid, tetraisopropyl titanate, stabilizer triphenyl phosphate and bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, 1,3-propylene glycol and recovered liquid were placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetraisopropyl titanate added is 550ppm of the weight of terephthalic acid, the amount of stabilizer triphenyl phosphate added is 10ppm of terephthalic acid, the amount of stabilizer bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate added is 30ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 10% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 240°C and 0.1MPa for 3.5 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 3 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0040] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0041] Example 3

[0042] Terephthalic acid, tetra-n-butyl titanate, stabilizer trimethyl phosphate, 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, 1,3-propylene glycol and recovered liquid were placed in a 25L reactor. Among them, terephthalic acid is 6666g, the added amount of tetra-n-butyl titanate is 550ppm of the weight of terephthalic acid, the added amount of stabilizer trimethyl phosphate is 2ppm of terephthalic acid, the added amount of stabilizer 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane is 3ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 10% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 250°C and 0.2MPa for 3.5 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 250°C and below 100Pa for 3 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0043] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0044] Example 4

[0045] Terephthalic acid, tetraethyl titanate, stabilizer triphenyl phosphate and bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, 1,3-propylene glycol and recovered liquid were placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetraethyl titanate added is 550ppm of the weight of terephthalic acid, the amount of stabilizer triphenyl phosphate added is 5ppm of terephthalic acid, the amount of stabilizer bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate added is 5ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 20% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 240°C and 0.1MPa for 4 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 3 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0046] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0047] Example 5

[0048] Terephthalic acid, tetraisopropyl titanate, stabilizer trimethyl phosphate, 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, 1,3-propylene glycol and recovered liquid were placed in a 25L reactor. Among them, terephthalic acid is 6666g, the added amount of tetraisopropyl titanate is 550ppm of the weight of terephthalic acid, the added amount of stabilizer trimethyl phosphate is 10ppm of terephthalic acid, the added amount of stabilizer 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane is 20ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 20% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 240°C and 0.1MPa for 4 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 3 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0049] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0050] Example 6

[0051] Terephthalic acid, tetra-n-butyl titanate, stabilizer phosphoric acid, 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 1,3-propylene glycol and recovered liquid are placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetra-n-butyl titanate added is 550ppm of the weight of terephthalic acid, the amount of stabilizer phosphoric acid added is 10ppm of terephthalic acid, the amount of stabilizer 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane added is 190ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 20% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 250°C and 0.3MPa for 4 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 3.5 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0052] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0053] Example 7

[0054] Terephthalic acid, tetraethyl titanate, stabilizer trimethyl phosphate and 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, 1,3-propylene glycol and recovered liquid were placed in a 25L reactor. Among them, terephthalic acid is 6666g, the added amount of tetraethyl titanate is 550ppm of the weight of terephthalic acid, the added amount of stabilizer trimethyl phosphate is 5ppm of terephthalic acid, the added amount of stabilizer 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane is 20ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 30% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 240°C and 0.1MPa for 4.5 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 3 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0055] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0056] Example 8

[0057] Terephthalic acid, tetraisopropyl titanate, stabilizer phosphoric acid, 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, 1,3-propylene glycol and recovered liquid are placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetraisopropyl titanate added is 550ppm of the weight of terephthalic acid, the amount of stabilizer phosphoric acid added is 50ppm of terephthalic acid, the amount of stabilizer 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane added is 10ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 30% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 240°C and 0.1MPa for 4.5 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 3 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0058] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0059] Example 9

[0060] Terephthalic acid, tetra-n-butyl titanate, stabilizer triphenyl phosphate and bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, 1,3-propylene glycol and recovered liquid were placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetra-n-butyl titanate added is 550ppm of the weight of terephthalic acid, the amount of stabilizer triphenyl phosphate added is 50ppm of terephthalic acid, the amount of stabilizer bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate added is 5ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 30% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 250°C and 0.3MPa for 5.5 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 3 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0061] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0062] Example 10

[0063] Terephthalic acid, tetraethyl titanate, stabilizer phosphoric acid and 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane), 1,3-propylene glycol and recovered liquid are placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetraethyl titanate added is 110ppm of the weight of terephthalic acid, the amount of stabilizer phosphoric acid added is 2.5ppm of terephthalic acid, the amount of stabilizer 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane added is 2.5ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 5% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 200°C and 0.5MPa for 6 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 240°C and below 100Pa for 4 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0064] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0065] Embodiment 11

[0066] Terephthalic acid, tetraethyl titanate, stabilizer phosphoric acid and 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane), 1,3-propylene glycol and recovered liquid are placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetraethyl titanate added is 800ppm of the weight of terephthalic acid, the amount of stabilizer phosphoric acid added is 1000ppm of terephthalic acid, the amount of stabilizer 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane added is 1000ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.8 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 5% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 250°C and 0.1MPa for 3 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 270°C and below 100Pa for 2 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0067] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0068] Example 12

[0069] Terephthalic acid, tetraethyl titanate, stabilizer phosphoric acid and 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane), 1,3-propylene glycol and recovered liquid are placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetraethyl titanate added is 600ppm of the weight of terephthalic acid, the amount of stabilizer phosphoric acid added is 20ppm of terephthalic acid, the amount of stabilizer 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane added is 10ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 10% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 240°C and 0.1MPa for 3.3 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 2.5 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0070] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0071] Example 13

[0072] Terephthalic acid, tetraethyl titanate, stabilizer phosphoric acid and 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane), 1,3-propylene glycol and recovered liquid are placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetraethyl titanate added is 200ppm of the weight of terephthalic acid, the amount of stabilizer phosphoric acid added is 950ppm of terephthalic acid, the amount of stabilizer 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane added is 50ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 10% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 240°C and 0.1MPa for 3.3 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 2.5 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0073] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0074] Embodiment 14

[0075] The difference between Example 14 and Example 1 is that only phosphoric acid is added as a stabilizer, and the amount of phosphoric acid added as the stabilizer is 100 ppm of terephthalic acid.

[0076] Embodiment 15

[0077] The difference between Example 15 and Example 1 is that only 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane) is added as the stabilizer, and the added amount is 100 ppm of terephthalic acid.

[0078] Example 16

[0079] Terephthalic acid, tetraethyl titanate, stabilizer phosphoric acid and 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane), 1,3-propylene glycol and recovered liquid are placed in a 25L reactor. Among them, terephthalic acid is 6666g, the amount of tetraethyl titanate added is 50ppm of the weight of terephthalic acid, the amount of stabilizer phosphoric acid added is 50ppm of terephthalic acid, the amount of stabilizer 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane added is 50ppm of terephthalic acid, the molar amount of 1,3-propylene glycol is 1.5 times that of terephthalic acid, and the 1,3-propylene glycol in the recovered liquid accounts for 40% of the total weight of 1,3-propylene glycol. First, the mixed system is replaced three times under a nitrogen atmosphere, and then the obtained mixed solution is reacted at 240°C and 0.1MPa for 3.3 hours for esterification reaction to obtain a prepolymer mixed solution; the obtained prepolymer mixed solution is subjected to a condensation reaction at 260°C and below 100Pa for 2.5 hours to obtain poly(1,3-propylene terephthalate), and the 1,3-propylene glycol waste liquid generated in the process is recovered, and the 1,3-propylene glycol waste liquid is further reused as a recovered liquid in the esterification reaction.

[0080] After separation, the obtained poly(1,3-trimethylene terephthalate) was tested for its relevant properties. The results are shown in Table 2.

[0081] Comparative Example 1

[0082] The difference between Comparative Example 1 and Example 1 is that no 1,3-propylene glycol waste liquid is added, and only 1,3-propylene glycol is used.

[0083] Comparative Example 2

[0084] The difference between Comparative Example 2 and Example 1 is that no stabilizer is added to the reaction system.

[0085] In order to further compare the reaction conditions in the embodiment and the comparative example, some data in the embodiment are listed in a table, and the results are shown in Table 1.

[0086] Table 1

[0087]

[0088]

[0089]

[0090]

[0091] The poly(trimethylene terephthalate) prepared in the above examples and comparative examples was tested for relevant properties, and the results are shown in Table 2.

[0092] It should be further explained here that the intrinsic viscosity of poly(1,3-propylene terephthalate) will directly affect its physical and chemical properties, such as melting point, hardness, toughness, etc. Under normal circumstances, when the intrinsic viscosity of poly(1,3-propylene terephthalate) is in the range of 0.8 to 1.0, the viscosity of poly(1,3-propylene terephthalate) is considered to be within the qualified range. Within this range, the larger the intrinsic viscosity value, the better the quality. The terminal carboxyl content can reflect the degree of polymerization of poly(1,3-propylene terephthalate). When the terminal carboxyl content is <35 mol / t, its degree of polymerization is considered to be within the qualified range. Chroma can reflect the appearance of poly(1,3-propylene terephthalate), which includes two parameters, L value and b value. Under normal circumstances, when the L value is >60 and the b value is <8, the appearance of poly(1,3-propylene terephthalate) is considered to be qualified, and the larger the L value within this range, the better the appearance. The above parameters can reflect the comprehensive properties of poly(trimethylene terephthalate). Poly(trimethylene terephthalate) with the above qualities can be applied to the spinning field and other related fields with high quality requirements.

[0093] Table 2

[0094]

[0095]

[0096] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0097] Embodiments 1 to 16 are methods for preparing poly(1,3-propylene terephthalate) proposed by the present invention. When preparing poly(1,3-propylene terephthalate), by adding a stabilizer to the esterification reaction system, the 1,3-propylene glycol waste liquid produced by preparing poly(1,3-propylene terephthalate) is directly involved in the reaction cycle without additional treatment. It can be seen from the data in Table 2 that the intrinsic viscosity, degree of polymerization, chromaticity and melting point of the prepared poly(1,3-propylene terephthalate) are all within a good range. In addition, the parameters of the control preparation process are within the preferred range, and the prepared poly(1,3-propylene terephthalate) has better comprehensive properties. In particular, the quality of poly(1,3-propylene terephthalate) prepared by the preparation method described in the present application is comparable to the quality of poly(1,3-propylene terephthalate) prepared in Comparative Example 1 without adding 1,3-propylene glycol waste liquid in the process of preparing poly(1,3-propylene terephthalate). Moreover, although 1,3-propylene glycol waste liquid was added in Example 1, the reaction effect and reaction rate were not much different from those in Comparative Example 1. In contrast, in Comparative Example 2, 1,3-propylene glycol waste liquid was added in the process of preparing poly(1,3-propylene terephthalate) but no stabilizer was added, and the quality of the poly(1,3-propylene terephthalate) product prepared was even worse.

[0098] In summary, the method for preparing poly(1,3-propylene terephthalate) proposed in the present invention can not only ensure product quality, but also achieve the purpose of directly utilizing the generated 1,3-propylene glycol waste liquid as a resource. The preparation method effectively solves the problems of complex recovery process, high energy consumption and secondary pollution of 1,3-propylene glycol waste liquid generated in the preparation of poly(1,3-propylene terephthalate) in the prior art, and at the same time, further reduces the production cost of poly(1,3-propylene terephthalate), and can also effectively reduce the reaction rate reduction and side reaction problems during the reaction process caused by adding recovery liquid to the reaction system in the conventional method.

[0099] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing poly(1,3-trimethylene terephthalate), characterized in that: The preparation method comprises the following steps: Ingredients: terephthalic acid, a catalyst, a stabilizer, 1,3-propylene glycol and a recovery liquid are mixed to obtain a mixed solution; Esterification: heating the mixed solution for a first time to perform an esterification reaction to obtain a prepolymer mixed solution; Polymerization: The prepolymer mixed solution is subjected to a second heating to perform a polycondensation reaction to obtain the poly(trimethylene terephthalate); at the same time, 1,3-propylene glycol waste liquid is generated in the polycondensation reaction, and the 1,3-propylene glycol waste liquid is reused as the recovered liquid in the batching stage.

2. The method for preparing poly(trimethylene terephthalate) according to claim 1, characterized in that: The stabilizer is one or more of phosphoric acid, triphenyl phosphate, trimethyl phosphate, 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)sebacate and 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane; Preferably, the stabilizer comprises a first component and a second component, the first component is at least one of the phosphoric acid, the triphenyl phosphate and the trimethyl phosphate, and the second component is at least one of the 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, the bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)sebacate and the 3,9-bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane; Preferably, the weight ratio of the first component to the second component is (1-10):(1-20).

3. The method for preparing poly(trimethylene terephthalate) according to claim 1, characterized in that: The amount of the stabilizer added is 5 to 2000 ppm by weight of the terephthalic acid; preferably, the amount of the stabilizer added is 30 to 1000 ppm by weight of the terephthalic acid.

4. The method for preparing poly(trimethylene terephthalate) according to any one of claims 1 to 3, characterized in that: The weight of 1,3-propylene glycol in the recovered solution is 5 to 30% of the total weight of 1,3-propylene glycol in the mixed solution; Preferably, the weight of the 1,3-propylene glycol in the recovered solution is 10 to 20% of the total weight of the 1,3-propylene glycol in the mixed solution; Preferably, the weight content of the 1,3-propylene glycol in the recovered liquid is greater than 90%, and the weight content of water is less than 0.5%.

5. The method for preparing poly(trimethylene terephthalate) according to any one of claims 1 to 3, characterized in that: The amount of the catalyst added to the mixed solution is 100 to 800 ppm based on the weight of the terephthalic acid; Preferably, the molar amount of the 1,3-propylene glycol in the mixed solution is 1.1 to 1.8 times the molar amount of the terephthalic acid.

6. The method for preparing poly(trimethylene terephthalate) according to claim 5, characterized in that: The amount of the catalyst added to the mixed solution is 200 to 600 ppm based on the weight of the terephthalic acid.

7. The method for preparing poly(trimethylene terephthalate) according to any one of claims 1 to 5, characterized in that: The catalyst is a titanium compound; Preferably, the catalyst is a titanate compound, more preferably one or more of tetraethyl titanate, tetraisopropyl titanate, and tetra-n-butyl titanate.

8. The method for preparing poly(trimethylene terephthalate) according to any one of claims 1 to 5, characterized in that: The esterification reaction is carried out under an inert atmosphere, the first heating temperature is 200-250° C., the pressure is 0.1-0.5 MPa, and the time is 3-6 hours.

9. The method for preparing poly(trimethylene terephthalate) according to any one of claims 1 to 5, characterized in that: The second heating temperature is 240-270° C., the pressure is below 100 Pa, and the time is 2-4 hours.

10. A poly(trimethylene terephthalate), characterized in that: The poly(1,3-trimethylene terephthalate) is prepared by the preparation method according to any one of claims 1 to 9, and has an intrinsic viscosity of 0.80 to 1.05 dL / g.

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