阅读说明：本技术 一种生物可降解共聚酯的制备系统、制备方法及其共聚酯 (Preparation system and preparation method of biodegradable copolyester and copolyester thereof ) 是由 邱志成 李鑫 王颖 金剑 钟淑芳 武术芳 梁颖 于 2020-12-29 设计创作，主要内容包括：本发明公开了一种生物可降解共聚酯的制备系统、制备方法及其共聚酯,所述制备系统包括：依次连接的酯化系统和缩聚系统,所述酯化系统和缩聚系统之间还设有鼓泡式反应器,从酯化系统流出的物料经所述鼓泡式反应器进行深度酯化和预缩聚反应后送入缩聚系统。本发明提供的生物可降解共聚酯的制备系统,实现了脂肪族-芳香族共聚酯酯化物的高效深度酯化与熔融缩聚的同时发生,大幅缩短脂肪族-芳香族二元酸浆料的酯化时间,制备出满足后续终缩聚反应要求的脂肪族-芳香族共聚酯预聚物；利用该系统连续生产的脂肪族-芳香族共聚酯具有良好的生物可降解性能以及低端羧基含量和色相佳的特点。(The invention discloses a preparation system, a preparation method and copolyester of biodegradable copolyester, wherein the preparation system comprises the following components: the esterification system and the polycondensation system are connected in sequence, a bubbling reactor is further arranged between the esterification system and the polycondensation system, and materials flowing out of the esterification system are sent into the polycondensation system after being subjected to deep esterification and pre-polycondensation reaction through the bubbling reactor. The preparation system of the biodegradable copolyester provided by the invention realizes the simultaneous occurrence of efficient deep esterification and melt polycondensation of aliphatic-aromatic copolyester ester, greatly shortens the esterification time of aliphatic-aromatic dibasic acid slurry, and prepares the aliphatic-aromatic copolyester prepolymer meeting the requirements of subsequent final polycondensation reaction; the aliphatic-aromatic copolyester continuously produced by the system has the characteristics of good biodegradability, low-end carboxyl content and good hue.)

1. A system for preparing biodegradable copolyester, comprising: the esterification system and the polycondensation system are connected in sequence, and the device is characterized in that a bubbling reactor is also arranged between the esterification system and the polycondensation system, and materials flowing out of the esterification system are sent into the polycondensation system after being subjected to deep esterification and pre-polycondensation reaction through the bubbling reactor.

2. The system for preparing biodegradable copolyester according to claim 1, wherein the bubbling reactor comprises a preheater, a reactor body and a gas-liquid separator which are sequentially arranged along the material flow direction, the bottom of the preheater is provided with a material inlet, the top of the reactor body is provided with a material outlet, and the top of the gas-liquid separator is provided with a steam outlet;

preferably, the bubble reactor is a column reactor.

3. The system for preparing biodegradable copolyester according to claim 2,

a plurality of layers of tower plates are arranged in the reactor body at intervals along the material flowing direction, a plurality of liquid lifting pipes are arranged on each layer of tower plate, baffles are arranged at the bottoms of the liquid lifting pipes, and gaps are formed between the baffles and the bottoms of the liquid lifting pipes.

4. The system for preparing biodegradable copolyester according to claim 1,

the esterification system comprises an esterification reaction kettle, two independent cavities are formed in the esterification reaction kettle and are separated by a partition plate, and a flow guide hole for flowing of materials and steam is formed in the partition plate and is controlled by an opening adjusting valve;

preferably, an agitator, a guide cylinder and a heating coil are arranged inside each chamber.

5. A method for preparing biodegradable copolyester using the system for preparing biodegradable copolyester according to any one of claims 1 to 4, comprising the steps of:

s1, preparing aliphatic dibasic acid, aromatic dibasic acid, aliphatic dihydric alcohol and a catalyst into aliphatic-aromatic dibasic acid slurry;

s2, carrying out esterification reaction on the aliphatic-aromatic dibasic acid slurry to obtain aliphatic-aromatic copolyester ester;

s3, carrying out deep esterification and pre-polycondensation reaction on the aliphatic-aromatic copolyester ester and the aliphatic dihydric alcohol for bubbling to obtain an aliphatic-aromatic copolyester prepolymer;

s4, sequentially carrying out final polycondensation reaction and liquid phase tackifying reaction on the aliphatic-aromatic copolyester prepolymer to obtain biodegradable copolyester;

in step S1, the catalyst is a ternary mixture of titanium, aluminum and phosphorus in a molar ratio of 1: 0.1-1: 0.05-0.5.

6. The method for preparing biodegradable copolyester according to claim 5,

in step S2, the reaction temperature of the first chamber is 150-220 ℃, and the reaction pressure is 50-130 kPa; the reaction temperature of the second chamber is 220-260 ℃, the reaction pressure is 30-100 kPa, and the acid value of the prepared aliphatic-aromatic copolyester ester is 30-60 mgKOH/g.

7. The method for preparing biodegradable copolyester according to claim 5,

in the step S3, the mass ratio of the aliphatic-aromatic copolyester ester to the aliphatic diol for bubbling is 100: 5-20; the reaction temperature of the bubbling reactor is 230-270 ℃, and the reaction pressure is 3-20 kPa.

8. The method for preparing biodegradable copolyester according to claim 5,

in the step S1, the molar ratio of the alkyd in the aliphatic-aromatic dibasic acid slurry is 1.1-2.0: 1, and the molar ratio of the aliphatic dibasic acid to the aromatic dibasic acid is 33-67: 67-33;

the catalyst is prepared by mixing an organic titanium compound, an organic aluminum compound and an organic phosphorus compound according to the molar ratio of titanium element to aluminum element to phosphorus element of 1: 0.1-1: 0.05-0.5 and reacting for 0.5-12 h at the temperature of 150-250 ℃.

9. The method for preparing biodegradable copolyester according to claim 5,

the intrinsic viscosity of the aliphatic-aromatic copolyester prepolymer prepared in the step S3 is 0.2-0.5 dL/g; the intrinsic viscosity of the aliphatic-aromatic copolyester final polymer prepared in the step S4 is 0.6-0.8 dL/g.

10. A biodegradable copolyester, characterized by being prepared by the preparation system of biodegradable copolyester according to any one of claims 1 to 4 and the preparation method of biodegradable copolyester according to any one of claims 5 to 9;

the intrinsic viscosity of the biodegradable copolyester is 0.8-1.5 dL/g, the chroma b value is not higher than 8, and the carboxyl end group content is not higher than 20 mol/t.

Technical Field

The invention belongs to the technical field of preparation of biodegradable materials, and particularly relates to a preparation system and a preparation method of biodegradable copolyester, and the copolyester.

Background

The biodegradable copolyester is a copolyester of aliphatic dibasic acid, aromatic dibasic acid and aliphatic dihydric alcohol, has good biodegradability and flexibility of the aliphatic polyester and good heat resistance and mechanical property of the aromatic polyester, and is widely applied to manufacturing shopping bags, agricultural mulching films, express packaging bags, garbage bags, disposable lunch boxes, paper cups and the like.

The continuous polymerization production process of the biodegradable copolyester mainly comprises a parallel esterification method and a co-esterification method at present. The parallel esterification process means that aliphatic dibasic acid and aromatic dibasic acid are respectively esterified in two esterification reaction kettles, and the obtained polyester esterification products enter a polycondensation system together to carry out pre-polycondensation reaction and final polycondensation reaction in sequence to prepare the biodegradable copolyester. Because the aliphatic dibasic acid and the aromatic dibasic acid ester are easy to generate homopolymers with a plurality of polymerization degrees in the parallel independent esterification process, the randomness of the finally prepared biodegradable copolyester is reduced, and the content of the aromatic dibasic acid ester chain segment with the sequence length higher than 2, which is not degradable by microorganisms, is increased; the co-esterification process means that aliphatic dibasic acid and aromatic dibasic acid are subjected to esterification reaction in the same reaction kettle at the same esterification temperature, and then pre-polycondensation reaction and final polycondensation reaction are sequentially carried out to prepare the biodegradable copolyester. Due to the fact that a proper matching temperature is difficult to find in the co-esterification process so as to enable the aliphatic dibasic acid and the aromatic dibasic acid to be esterified efficiently at the same time, sublimation or decarboxylation of the aliphatic dibasic acid due to a high esterification temperature or insufficient esterification of the aromatic dibasic acid due to a low esterification temperature is easy to cause pipeline blockage accidents in the continuous polymerization production process of the biodegradable copolyester, and a slice product produced by the co-esterification process is low in intrinsic viscosity and high in terminal carboxyl content, so that the processing and use of the biodegradable copolyester are limited.

The present invention has been made in view of this situation.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a preparation system and a preparation method of biodegradable copolyester and the copolyester thereof.

In order to solve the technical problems, the invention adopts the technical scheme that:

the first object of the present invention provides a system for preparing biodegradable copolyester, comprising: the esterification system and the polycondensation system are connected in sequence, a bubbling reactor 10 is further arranged between the esterification system and the polycondensation system, and materials flowing out of the esterification system are sent into the polycondensation system after being subjected to deep esterification and pre-polycondensation reaction through the bubbling reactor.

The further scheme of the invention is as follows: the bubbling reactor 10 comprises a preheater 11, a reactor body 12 and a gas-liquid separator 13 which are sequentially arranged along the material flowing direction, wherein the bottom of the preheater 11 is provided with a material inlet 111, the top of the reactor body 12 is provided with a material outlet 121, and the top of the gas-liquid separator 13 is provided with a steam outlet 131;

preferably, the bubble reactor 10 is a column reactor.

Preferably, the top of the reactor body 12 is extended toward the gas-liquid separator for collecting the liquid melt of the aliphatic-aromatic copolyester prepolymer.

In the scheme, the bubbling reactor is added between the existing esterification system and the existing polycondensation system, so that the efficient deep esterification and melt polycondensation of the aliphatic-aromatic copolyester ester are realized simultaneously, the esterification time of the aliphatic-aromatic dibasic acid slurry can be greatly shortened, and the occurrence of thermal degradation side reaction in the continuous production process is reduced; in addition, the top of the reactor body extends towards the direction close to the gas-liquid separator, so that the reactor body is beneficial to receiving the liquid melt of the aliphatic-aromatic copolyester prepolymer settled from the gas-liquid separator.

The further scheme of the invention is as follows: a plurality of layers of tower plates 122 are arranged in the reactor body 12 at intervals along the material flowing direction, a plurality of lift tubes 123 are arranged on each layer of tower plate 122, baffles 124 are arranged at the bottoms of the lift tubes 123, and a gap is formed between each baffle 124 and the bottom of each lift tube 123.

Specifically, 10-30 tower plates 122 are arranged in the reactor body 12, each tower plate is provided with a lift pipe 123, and the bottom of each lift pipe is provided with a baffle 124. The material is pressed into a slit between a liquid lifting pipe and a baffle plate thereof by aliphatic diol steam under the action of pressure difference between an upper layer of tower plate and a lower layer of tower plate, and enters the upper layer of tower plate through bubbling of the liquid lifting pipe. In the bubbling process, the high-efficiency removal of water generated by esterification of terminal carboxyl in aliphatic diol and aliphatic-aromatic copolyester ester and the high-efficiency removal of aliphatic diol steam generated by condensation between the aliphatic-aromatic copolyester ester can be realized through the multilayer tower plates arranged in the reactor body, so that the high-efficiency esterification and high-efficiency melt polycondensation of the aliphatic-aromatic copolyester ester are realized, and finally the aliphatic-aromatic copolyester prepolymer is generated. In order to prevent the materials from splashing into the polycondensation steam pipe, a bubble cap 125 is provided at the upper part of the riser tube of the topmost tray, and a gas rectifying plate 132 is provided at the upper part of the gas-liquid separator to rectify the polycondensation steam, thereby further preventing the entrainment of the materials by the polycondensation steam.

As an embodiment of the present invention, the esterification system includes an esterification reaction kettle 20, two independent chambers are separated by a partition plate 21 in the esterification reaction kettle 20, and a diversion hole 23 for flowing material and steam is provided on the partition plate 21 and controlled by an opening degree adjusting valve 22;

preferably, an agitator 24, a guide cylinder 25 and a heating coil 26 are provided inside each chamber.

Preferably, the agitator 24 includes, but is not limited to, an axial flow type agitator.

In the scheme, the bottoms of the two cavities are in an oval structure, the two cavities are connected in series to form a kettle body of the esterification reaction kettle, a stirrer 24, a guide cylinder 25 and a heating coil 26 are arranged in each cavity, and the stirrer and the guide cylinder which are arranged in each cavity can enable materials to axially and circularly flow in a large flow rate in the cavity of the reaction kettle, so that a detention area is avoided, short circuit of the materials is reduced, and the uniformity of the esterification reaction is favorably ensured; the temperature of each chamber can be independently controlled by the heating coil; the partition plate of the esterification reaction kettle is provided with a flow guide hole for flowing materials and steam, which is controlled by an opening regulating valve, and the pressure of each chamber in the esterification reaction kettle can be regulated and controlled by regulating the opening of the regulating valve; a reaction kettle material inlet 201 of the esterification reaction kettle is arranged at the bottom of the first cavity, a reaction kettle material outlet 202 is arranged at the bottom of the second cavity, and an esterification steam outlet 203 is arranged at the top of the second cavity. The temperature of the first chamber and the second chamber in the esterification reaction kettle can be independently regulated and controlled to ensure that the aliphatic-aromatic dibasic acid slurry is sequentially esterified in the two reaction chambers; the reaction pressure may be controlled in a gradient decreasing manner from the first chamber to the second chamber. The selective low-temperature esterification of the aliphatic dibasic acid in the aliphatic-aromatic dibasic acid slurry entering the cavity can be realized by regulating and controlling the temperature and the pressure of the first cavity, so as to generate a heat-resistant mixture of the aliphatic dibasic acid glycol ester and the aromatic dibasic acid; the mixture prepared in the first chamber overflows into the second chamber through the flow guide holes in the partition plate, and the high-temperature esterification of the aromatic dibasic acid and the terminal hydroxyl of the aliphatic dibasic acid glycol ester in the mixture can be realized by adjusting the temperature and the pressure of the second chamber, so that the aliphatic-aromatic copolyester ester is prepared.

Preferably, the polycondensation system includes a final polycondensation reaction unit and a liquid phase tackifying reaction unit.

The second purpose of the invention is to provide a preparation method applying the biodegradable copolyester preparation system, which comprises the following steps:

s1, preparing aliphatic dibasic acid, aromatic dibasic acid, aliphatic dihydric alcohol and a catalyst into aliphatic-aromatic dibasic acid slurry;

s2, carrying out esterification reaction on the aliphatic-aromatic dibasic acid slurry to obtain aliphatic-aromatic copolyester ester;

s3, carrying out deep esterification and pre-polycondensation reaction on the aliphatic-aromatic copolyester ester and the aliphatic dihydric alcohol for bubbling to obtain an aliphatic-aromatic copolyester prepolymer;

s4, sequentially carrying out final polycondensation reaction and liquid phase tackifying reaction on the aliphatic-aromatic copolyester prepolymer to obtain biodegradable copolyester;

in step S1, the catalyst is a ternary mixture of titanium, aluminum and phosphorus in a molar ratio of 1: 0.1-1: 0.05-0.5.

In one embodiment of the present invention, the reaction temperature of the first chamber is 150 to 220 ℃, and the reaction pressure is 50 to 130 kPa; the reaction temperature of the second chamber is 220-260 ℃, the reaction pressure is 30-100 kPa, and the acid value of the prepared aliphatic-aromatic copolyester ester is 30-60 mgKOH/g.

The reaction conditions in the two cavities of the esterification reaction kettle are controlled within the range, and the aliphatic-aromatic copolyester ester with the acid value of 30-60 mgKOH/g, which meets the requirements of a subsequent bubbling reactor, can be prepared.

As an embodiment of the invention, the step S3 is carried out in the bubbling reactor, the pressure of each layer of tower plate in the bubbling reactor is different, the aliphatic-aromatic copolyester ester and the aliphatic diol for bubbling firstly enter a preheater, the aliphatic diol is heated to generate steam, the aliphatic-aromatic copolyester ester is sequentially pressed into a riser on a plurality of layers of tower plates to complete deep esterification and pre-polycondensation reaction, the gas-liquid mixture of the aliphatic-aromatic copolyester prepolymer is obtained by bubbling from the tower plate at the topmost layer of the reactor body and then enters a gas-liquid separator, the separated polycondensation steam flows regularly through a gas rectifying plate and then flows to the top of the gas-liquid separator, the polycondensation steam is pumped out by a vacuum system through a polycondensation steam pipeline, the liquid melt of the aliphatic-aromatic copolyester is settled on the top of the reactor body from the gas-liquid separator under the action of gravity, then overflows into a material outlet arranged at the top of the reactor body and finally is taken out of the bubbling reactor.

In one embodiment of the present invention, in step S3, the mass ratio of the aliphatic-aromatic copolyester ester to the aliphatic diol for bubbling is 100: 5-20; the reaction temperature of the bubbling reactor is 230-270 ℃, and the reaction pressure is 3-20 kPa.

The mass ratio of the aliphatic-aromatic copolyester ester and the aliphatic diol for bubbling, which are conveyed to the bubbling reactor, is controlled within the range, so that the requirements of deep esterification and efficient polycondensation of the aliphatic-aromatic copolyester ester with the acid value of 30-60 mgKOH/g can be met; the reaction conditions of the bubbling reactor are controlled within the range, and the aliphatic-aromatic copolyester prepolymer with the intrinsic viscosity of 0.2-0.5 dL/g can be prepared to meet the subsequent final polycondensation reaction requirement.

As an embodiment of the present invention, the polycondensation system comprises a final polycondensation reaction unit for carrying out step 4 and a liquid-phase tackifying reaction unit which are connected in series.

The aliphatic-aromatic copolyester prepolymer from the bubbling reactor sequentially passes through a final polycondensation reaction unit and a liquid-phase tackifying reaction unit of a polycondensation system to prepare the biodegradable copolyester.

Preferably, the temperature of the final polycondensation reaction unit is 240-270 ℃, and the reaction pressure is 100-200 Pa; the temperature of the liquid phase tackifying reaction unit is 250-270 ℃, and the reaction pressure is 50-100 Pa.

Controlling the reaction conditions of the final polycondensation reaction unit within the range, and preparing an aliphatic-aromatic copolyester final polymer with the intrinsic viscosity of 0.6-0.8 dL/g; the reaction conditions of the liquid-phase tackifying reaction unit are controlled within the range, and the high-viscosity aliphatic-aromatic copolyester with the intrinsic viscosity of 0.8-1.5 dL/g can be prepared.

In one embodiment of the present invention, in step S1, the molar ratio of the alkyd in the aliphatic-aromatic dibasic acid slurry is 1.1 to 2.0:1, and the molar ratio of the aliphatic dibasic acid to the aromatic dibasic acid is 33 to 67:67 to 33.

The molar ratio of the mole number of the aliphatic dibasic alcohol to the total mole number of the aliphatic dibasic acid and the aromatic dibasic acid in the aliphatic-aromatic dibasic acid slurry is controlled within the range, so that the aliphatic-aromatic dibasic acid slurry has good slurry forming stability and esterification reaction activity. The molar ratio of the aromatic dibasic acid to the aliphatic dibasic acid in the aliphatic-aromatic dibasic acid slurry is controlled within the range, and the sequence length of the prepared aromatic dibasic acid ester chain segment can be effectively controlled to be not higher than 2, so that the continuously produced aliphatic-aromatic copolyester has good biodegradability.

Preferably, the aliphatic dibasic acid is at least one of succinic acid, adipic acid and sebacic acid, the aromatic dibasic acid is at least one of terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid, and the aliphatic diol is at least one of ethylene glycol, propylene glycol and butanediol.

The aliphatic dibasic acids include but are not limited to succinic acid, adipic acid and sebacic acid, the aromatic dibasic acids include but are not limited to terephthalic acid, isophthalic acid and naphthalene dicarboxylic acid, and the aliphatic dihydric alcohols include but are not limited to ethylene glycol, propylene glycol and butylene glycol.

The microorganism has good degradation capability on the aliphatic dibasic acid glycol ester chain segment, and the existence of the aliphatic dibasic acid glycol ester chain segment can endow the copolyester with good biodegradability. The existence of the aromatic dibasic acid aliphatic diol ester chain segment can endow the copolyester with good heat resistance and mechanical property, and the microorganism also has good degradation capability on the aromatic dibasic acid aliphatic diol ester chain segment with the sequence length not more than 2.

Preferably, the catalyst is prepared by mixing an organic titanium compound, an organic aluminum compound and an organic phosphorus compound according to the molar ratio of titanium element to aluminum element to phosphorus element of 1: 0.1-1: 0.05-0.5 and reacting at the temperature of 150-250 ℃ for 0.5-12 h.

Titanium ions in the organic titanium compound and aluminum ions in the organic aluminum compound have high catalytic activity on the condensation polymerization reaction of aliphatic-aromatic copolyester, titanium ions in the organic titanium compound also have high-efficiency catalytic effect on the esterification reaction of aliphatic dibasic acid and aromatic dibasic acid, and aluminum ions in the organic aluminum compound can form a complex with terminal carboxyl of a macromolecular chain of the aliphatic-aromatic copolyester to block the complex. The molar ratio of the titanium element, the aluminum element and the phosphorus element in the catalyst is controlled within the range, the phosphorus atom in the organic phosphorus compound can be coordinated and complexed with the titanium ion in the organic titanium compound and the aluminum ion in the organic aluminum compound to the maximum extent, the hydrolysis resistance of the organic titanium compound and the organic aluminum compound serving as catalyst components is improved, and the phosphorus element can efficiently capture residual catalyst metal ions and inhibit the occurrence of thermal degradation side reaction at the later stage of the high-temperature melting pre-polycondensation reaction of the aliphatic-aromatic copolyester.

The catalyst is prepared by mixing an organic titanium compound, an organic aluminum compound and an organic phosphorus compound according to the molar ratio of titanium element to aluminum element to phosphorus element of 1: 0.1-1: 0.05-0.5 and reacting for 0.5-12 h at the temperature of 150-250 ℃. The organic titanium compound is titanium alkoxide selected from at least one of tetrabutyl titanate, tetraisopropyl titanate, tetra (2-ethylhexyl) titanate, tetraisooctyl titanate and tetraoctyl orthotitanate; the organic aluminum compound is at least one selected from aluminum acetylacetonate, aluminum ethylene glycol, aluminum ethoxide, aluminum isopropoxide and aluminum tert-butoxide, and the organic phosphorus compound is phosphite ester and is at least one selected from triphenyl phosphite, tris (nonylphenyl) phosphite, tris (2, 4-di-tert-butylphenyl) phosphite, bis (2, 4-di-tert-butylphenyl) pentaerythritol diphosphite, dioctadecyl pentaerythritol diphosphite and bis (2,4, 6-tri-tert-butylphenyl) pentaerythritol diphosphite.

The titanium alkoxide, the organic aluminum compound and the phosphite ester compound are mixed according to the molar ratio of the titanium element to the aluminum element to the phosphorus element of 1: 0.1-1: 0.05-0.5, and react for 0.5-12 hours at the temperature of 150-250 ℃, so that the phosphite ester compound can fully coordinate and complex titanium ions and aluminum ions of catalyst ions, and the ternary composite catalyst with good hydrolysis resistance of the titanium element, the aluminum element and the phosphorus element is prepared. In addition, the high steric hindrance phosphite ester has double functions of decomposing hydroperoxyl radical and terminating radical chain, can obviously improve the thermal stability of copolyester molecular chains, especially aliphatic polyester chain segments, and avoids the occurrence of thermal degradation side reaction.

As an embodiment of the present invention, the intrinsic viscosity of the aliphatic-aromatic copolyester prepolymer prepared in step S3 is 0.2 to 0.5 dL/g; the intrinsic viscosity of the aliphatic-aromatic copolyester final polymer prepared in the step S4 is 0.6-0.8 dL/g.

The third purpose of the invention is to provide a biodegradable copolyester, which is prepared by the preparation system and the preparation method of the biodegradable copolyester;

the intrinsic viscosity of the biodegradable copolyester is 0.8-1.5 dL/g, the chroma b value is not higher than 8, and the carboxyl end group content is not higher than 20 mol/t.

After adopting the technical scheme, compared with the prior art, the invention has the following beneficial effects:

according to the preparation system of the biodegradable copolyester, the bubbling reactor is added between the existing esterification system and the existing polycondensation system, so that the efficient deep esterification and melt polycondensation of the aliphatic-aromatic copolyester ester are realized simultaneously, the esterification time of the aliphatic-aromatic dibasic acid slurry is greatly shortened, and the aliphatic-aromatic copolyester prepolymer meeting the requirements of the subsequent final polycondensation reaction is prepared.

The preparation system of the biodegradable copolyester provided by the invention can realize the sequential esterification of the aliphatic dibasic acid and the aromatic dibasic acid, effectively solves the problem of large temperature gradient of esterification reaction of the aliphatic dibasic acid and the aromatic dibasic acid, avoids the occurrence of decarboxylation side reaction caused by thermolabile aliphatic dibasic acid in the esterification process, effectively controls the sequence length of the chain segment of the aromatic dibasic acid ester to be not higher than 2, and ensures that the continuously produced aliphatic-aromatic copolyester has good biodegradability and has the characteristics of good low-end carboxyl content and good hue.

The preparation method of the biodegradable copolyester provided by the invention adopts a ternary composite catalyst of titanium element, aluminum element and phosphorus element as a catalyst for synthesizing the biodegradable copolyester. The catalyst has high-efficiency catalytic activity on esterification reaction and polycondensation reaction, and the prepared biodegradable copolyester has high intrinsic viscosity, good hue and low carboxyl end group content, is suitable for producing high-quality film products, and the products processed by the catalyst have longer shelf life.

The preparation method of the biodegradable copolyester provided by the invention is easy for industrial implementation and can realize large-scale industrial continuous production of the biodegradable copolyester.

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention, are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention without limiting the invention to the right. It is obvious that the drawings in the following description are only some embodiments, and that for a person skilled in the art, other drawings can be derived from them without inventive effort. In the drawings:

FIG. 1 is a schematic structural diagram of a bubble reactor in a biodegradable copolyester preparation system according to the present invention;

FIG. 2 is a schematic structural diagram of an esterification reaction kettle in the biodegradable copolyester preparation system according to the present invention;

FIG. 3 is a process flow diagram of the preparation method of biodegradable copolyester according to the present invention;

fig. 4 is a process flow diagram of the biodegradable copolyester preparation system of the present invention.

In the figure: 10. a bubble reactor; 11. a preheater; 111. a material inlet; 12. a reactor body, 121 and a material outlet; 122. a column plate; 123. a riser tube; 124. a baffle plate; 125. a blister; 13. a gas-liquid separator; 131. a steam outlet; 132. a gas rectifying plate; 20. an esterification reaction kettle; 201. a material inlet of the reaction kettle; 202. a material outlet of the reaction kettle; 203. an esterification steam outlet; 21. a partition plate; 22. an opening degree regulating valve; 23. a flow guide hole; 24. a stirrer; 25. a draft tube; 26. a heating coil.

It should be noted that the drawings and the description are not intended to limit the scope of the inventive concept in any way, but to illustrate it by a person skilled in the art with reference to specific embodiments.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and the following embodiments are used for illustrating the present invention and are not intended to limit the scope of the present invention.

Experimental example:

a system for preparing biodegradable copolyester, comprising: an esterification reaction kettle 20, a bubbling reactor 10, a final polycondensation reaction kettle and a liquid phase tackifying reaction kettle which are connected in sequence.

The esterification reaction kettle 20 is internally provided with two independent chambers separated by a partition plate 21, a reaction kettle material inlet 201 of the esterification reaction kettle 20 is arranged at the bottom of the first chamber, a reaction kettle material outlet 202 is arranged at the bottom of the second chamber, and an esterification steam outlet 203 is arranged at the top of the second chamber; an axial flow type stirrer, a guide cylinder 25 and a heating coil 26 are arranged in each chamber, and a guide hole 23 for the flow of materials and steam controlled by an opening adjusting valve 22 is arranged on the partition plate 21.

The bubbling reactor 10 comprises a preheater 11, a reactor body 12 and a gas-liquid separator 13 which are sequentially arranged along the material flowing direction, wherein the bottom of the preheater 11 is provided with a material inlet 111, the top of the reactor body 12 is provided with a material outlet 121, and the top of the gas-liquid separator 13 is provided with a steam outlet 131; a plurality of layers of tower plates 122 are arranged in the reactor body 12 at intervals along the material flowing direction, a plurality of lift tubes 123 are arranged on each layer of tower plate 122, baffles 124 are arranged at the bottoms of the lift tubes 123, and a gap is formed between each baffle 124 and the bottom of each lift tube 123.

The materials are sequentially esterified through a first cavity and a second cavity of the esterification reaction kettle, then are subjected to deep esterification and pre-polycondensation reaction through the bubbling reactor, and then are sequentially sent to the final polycondensation reaction kettle and the liquid phase tackifying reaction kettle, and finally the biodegradable copolyester is prepared.

Example 1

In this embodiment, the preparation method of the biodegradable copolyester preparation system in the application experimental example includes the following steps:

s1, mixing succinic acid, terephthalic acid, butanediol and succinic acid-terephthalic acid slurry which is prepared by taking a ternary compound with the molar ratio of titanium element, aluminum element and phosphorus element of 1:0.5:0.2 as a catalyst and has the molar ratio of alkyd of 1.3: 1. Wherein the molar ratio of terephthalic acid to succinic acid is 50: 50; the catalyst is prepared by mixing tetrabutyl titanate, aluminum ethylene glycol and bis (2, 4-di-tert-butylphenyl) pentaerythritol diphosphite according to the molar ratio of titanium element, aluminum element and phosphorus element of 1:0.5:0.2, and reacting for 5 hours at 200 ℃.

S2, delivering the succinic acid-terephthalic acid slurry to an esterification reaction kettle to prepare succinic acid-terephthalic acid-butanediol copolyester esterified substance with an acid value of 50 mgKOH/g. Wherein the reaction temperature of the first cavity chamber is 180 ℃, the reaction pressure is 100kPa, the reaction temperature of the second cavity chamber is 235 ℃, and the reaction pressure is 50 kPa.

S3, delivering the esterified succinic acid-terephthalic acid-butanediol copolyester and the butanediol for bubbling to a bubbling reactor according to the mass ratio of 100:10 to prepare the succinic acid-terephthalic acid-butanediol copolyester prepolymer with the intrinsic viscosity of 0.40 dL/g. Wherein 20 layers of tower plates are arranged in the reactor body of the bubbling reactor, the reaction temperature of the bubbling reactor is 260 ℃, and the reaction pressure is 10 kPa.

S4, conveying the succinic acid-terephthalic acid-butanediol copolyester prepolymer to a subsequent polycondensation system for a final polycondensation reaction and a liquid phase tackifying reaction in sequence, wherein the final polycondensation reaction temperature is 255 ℃, the reaction pressure is 150Pa, and the intrinsic viscosity of the prepared succinic acid-terephthalic acid-butanediol copolyester final polymer is 0.75 dL/g; the liquid phase tackifying reaction temperature is 260 ℃, the reaction pressure is 80Pa, and the high-viscosity succinic acid-terephthalic acid-butanediol copolyester with the intrinsic viscosity of 1.2dL/g is prepared.

Example 2

In this embodiment, the preparation method of the biodegradable copolyester preparation system in the application experimental example includes the following steps:

s1, mixing adipic acid, terephthalic acid, butanediol and adipic acid-terephthalic acid slurry which is prepared by taking a ternary compound of titanium element, aluminum element and phosphorus element with the molar ratio of 1:0.3:0.1 as a catalyst and has the molar ratio of 1.4:1 to prepare the alkyd. Wherein the molar ratio of terephthalic acid to adipic acid is 50: 50; the catalyst is prepared by mixing tetrabutyl titanate, aluminum ethoxide and tris (2, 4-di-tert-butylphenyl) phosphite according to the molar ratio of titanium element to aluminum element to phosphorus element of 1:0.3:0.1, and reacting at 180 ℃ for 3 hours.

S2, conveying the adipic acid-terephthalic acid slurry to an esterification reaction kettle to prepare the adipic acid-terephthalic acid-butanediol copolyester esterified substance with the acid value of 30 mgKOH/g. Wherein the reaction temperature of the first chamber is 220 ℃ and the reaction pressure is 50kPa, and the reaction temperature of the second chamber is 260 ℃ and the reaction pressure is 30 kPa.

S3, conveying the adipic acid-terephthalic acid-butanediol copolyester esterified substance and the butanediol for bubbling to a bubbling reactor according to the mass ratio of 100:5 to prepare the adipic acid-terephthalic acid-butanediol copolyester prepolymer with the intrinsic viscosity of 0.45 dL/g. Wherein 20 layers of tower plates are arranged in the reactor body of the bubbling reactor, the reaction temperature of the bubbling reactor is 270 ℃, and the reaction pressure is 6 kPa.

S4, conveying the adipic acid-terephthalic acid-butanediol copolyester prepolymer to a subsequent polycondensation system for a final polycondensation reaction and a liquid phase tackifying reaction in sequence, wherein the final polycondensation reaction temperature is 260 ℃, the reaction pressure is 100Pa, and the intrinsic viscosity of the prepared adipic acid-terephthalic acid-butanediol copolyester final polymer is 0.80 dL/g; the liquid phase tackifying reaction temperature is 260 ℃, the reaction pressure is 50Pa, and the high-viscosity adipic acid-terephthalic acid-butanediol copolyester with the intrinsic viscosity of 1.5dL/g is prepared.

Example 3

In this embodiment, the preparation method of the biodegradable copolyester preparation system in the application experimental example includes the following steps:

s1, preparing succinic acid-naphthalenedicarboxylic acid slurry with the molar ratio of 1.1:1 of alkyd by using a ternary compound with the molar ratio of titanium element, aluminum element and phosphorus element being 1:0.1:0.05 as a catalyst, wherein the molar ratio of the naphthalenedicarboxylic acid to the succinic acid is 67: 33; the catalyst is prepared by mixing tetraisopropyl titanate, aluminum acetylacetonate and triphenyl phosphite according to the molar ratio of titanium element to aluminum element to phosphorus element of 1:0.1:0.05 and reacting for 3h at 210 ℃.

S2, delivering the succinic acid-naphthalenedicarboxylic acid slurry to an esterification reaction kettle to prepare succinic acid-naphthalenedicarboxylic acid-ethylene glycol copolyester esterified substance with an acid value of 60 mgKOH/g. Wherein the reaction temperature of the first chamber is 200 ℃, the reaction pressure is 130kPa, the reaction temperature of the second chamber is 250 ℃, and the reaction pressure is 100 kPa.

S3, delivering the succinic acid-naphthalenedicarboxylic acid-ethylene glycol copolyester esterified substance and the ethylene glycol for bubbling to a bubbling reactor according to the mass ratio of 100:20 to prepare the succinic acid-naphthalenedicarboxylic acid-ethylene glycol copolyester prepolymer with the intrinsic viscosity of 0.20 dL/g. Wherein the reactor body of the bubbling reactor is internally provided with 8 layers of tower plates, the reaction temperature of the bubbling reactor is 250 ℃, and the reaction pressure is 5 kPa.

S4, conveying the succinic acid-naphthalenedicarboxylic acid-ethylene glycol copolyester prepolymer to a subsequent polycondensation system for final polycondensation reaction and liquid phase tackifying reaction in sequence, wherein the final polycondensation reaction temperature is 260 ℃, the reaction pressure is 200Pa, and the intrinsic viscosity of the prepared succinic acid-naphthalenedicarboxylic acid-ethylene glycol copolyester final polymer is 0.60 dL/g; the liquid phase tackifying reaction temperature is 260 ℃, the reaction pressure is 100Pa, and the high-viscosity succinic acid-naphthalic acid-ethylene glycol copolyester with the intrinsic viscosity of 0.80dL/g is prepared.

Example 4

In this embodiment, the preparation method of the biodegradable copolyester preparation system in the application experimental example includes the following steps:

s1, mixing adipic acid, terephthalic acid, ethylene glycol and adipic acid-terephthalic acid slurry which is prepared by taking a ternary compound with a molar ratio of titanium element, aluminum element and phosphorus element of 1:0.2:0.05 as a catalyst and has an alkyd molar ratio of 1.5:1, wherein the molar ratio of the terephthalic acid to the adipic acid is 60: 40; the catalyst is prepared by mixing tetraisopropyl titanate, aluminum isopropoxide and tris (nonylphenyl) phosphite according to the molar ratio of titanium element to aluminum element to phosphorus element of 1:0.2:0.05 and reacting for 12 hours at 150 ℃.

S2, conveying the adipic acid-terephthalic acid slurry to an esterification reaction kettle to prepare the adipic acid-terephthalic acid-ethylene glycol copolyester esterified substance with the acid value of 40 mgKOH/g. Wherein the reaction temperature of the first chamber is 200 ℃, the reaction pressure is 130kPa, the reaction temperature of the second chamber is 260 ℃, and the reaction pressure is 100 kPa.

S3, conveying the adipic acid-terephthalic acid-ethylene glycol copolyester esterified substance and ethylene glycol for bubbling to a bubbling reactor according to the mass ratio of 100:8 to obtain the adipic acid-terephthalic acid-ethylene glycol copolyester prepolymer with the intrinsic viscosity of 0.35 dL/g. Wherein the reactor body of the bubbling reactor is internally provided with 15 layers of tower plates, the reaction temperature of the bubbling reactor is 260 ℃, and the reaction pressure is 3 kPa.

S4, conveying the adipic acid-terephthalic acid-ethylene glycol copolyester prepolymer to a subsequent polycondensation system for final polycondensation reaction and liquid phase tackifying reaction in sequence, wherein the final polycondensation reaction temperature is 270 ℃, the reaction pressure is 200Pa, and the intrinsic viscosity of the prepared adipic acid-terephthalic acid-ethylene glycol copolyester final polymer is 0.65 dL/g; the liquid phase tackifying reaction temperature is 270 ℃, the reaction pressure is 100Pa, and the high-viscosity adipic acid-terephthalic acid-ethylene glycol copolyester with the intrinsic viscosity of 0.90dL/g is prepared.

Example 5

In this embodiment, the preparation method of the biodegradable copolyester preparation system in the application experimental example includes the following steps:

s1, mixing adipic acid, terephthalic acid, propylene glycol and adipic acid-terephthalic acid slurry which is prepared by taking a ternary compound with a molar ratio of titanium element, aluminum element and phosphorus element of 1:1:0.5 as a catalyst and has an alkyd molar ratio of 1.4:1, wherein the molar ratio of the terephthalic acid to the adipic acid is 50: 50; the catalyst is prepared by mixing tetraisopropyl titanate, tert-butyl aluminum and triphenyl phosphite according to the molar ratio of titanium element, aluminum element and phosphorus element of 1:1:0.5, and reacting for 8h at 180 ℃.

S2, conveying the adipic acid-terephthalic acid slurry to an esterification reaction kettle to prepare the adipic acid-terephthalic acid-propylene glycol copolyester esterified substance with the acid value of 40 mgKOH/g. Wherein the reaction temperature of the first chamber is 200 ℃, the reaction pressure is 80kPa, the reaction temperature of the second chamber is 240 ℃, and the reaction pressure is 60 kPa.

S3, conveying the adipic acid-terephthalic acid-propanediol copolyester ester and the propylene glycol for bubbling to a bubbling reactor together according to the mass ratio of 100:12 to obtain the adipic acid-terephthalic acid-propanediol copolyester prepolymer with the intrinsic viscosity of 0.50 dL/g. Wherein the reactor body of the bubbling reactor is internally provided with 30 layers of tower plates; the bubbling reactor had a reaction temperature of 260 ℃ and a reaction pressure of 3 kPa.

S4, conveying the adipic acid-terephthalic acid-propanediol copolyester prepolymer to a subsequent polycondensation system for final polycondensation reaction and liquid phase tackifying reaction in sequence, wherein the final polycondensation reaction temperature is 270 ℃, the reaction pressure is 150Pa, and the intrinsic viscosity of the prepared adipic acid-terephthalic acid-propanediol copolyester final polymer is 0.80 dL/g; the liquid phase tackifying reaction temperature is 270 ℃, the reaction pressure is 50Pa, and the high-viscosity adipic acid-terephthalic acid-propylene glycol copolyester with the intrinsic viscosity of 1.5dL/g is prepared.

Example 6

In this embodiment, the preparation method of the biodegradable copolyester preparation system in the application experimental example includes the following steps:

s1, preparing sebacic acid, terephthalic acid, isophthalic acid and ethylene glycol and sebacic acid-terephthalic acid-isophthalic acid slurry with molar ratio of 1.8:1 by using a ternary compound of titanium element, aluminum element and phosphorus element in a molar ratio of 1:0.5:0.1 as a catalyst, wherein the ratio of the total mole number of the terephthalic acid and the isophthalic acid to the mole number of the sebacic acid is 40:60, and the molar ratio of the terephthalic acid to the isophthalic acid is 90:10, and the catalyst is prepared by mixing tetra (2-ethylhexyl) titanate, aluminum glycol and bis (2,4, 6-tri-tert-butylphenyl) pentaerythritol diphosphite according to the molar ratio of the titanium element, the aluminum element and the phosphorus element in a ratio of 1:0.1:0.05 and reacting at 220 ℃ for 0.5 h.

S2, conveying the sebacic acid-terephthalic acid-isophthalic acid slurry to an esterification reaction kettle to prepare sebacic acid-terephthalic acid-isophthalic acid-ethylene glycol copolyester esterified substance with an acid value of 50 mgKOH/g. Wherein the reaction temperature of the first cavity chamber is 180 ℃, the reaction pressure is 100kPa, the reaction temperature of the second cavity chamber is 250 ℃, and the reaction pressure is 100 kPa.

S3, conveying the sebacic acid-terephthalic acid-isophthalic acid-ethylene glycol copolyester ester and the ethylene glycol for bubbling together to a bubbling reactor according to the mass ratio of 100:6 to obtain the sebacic acid-terephthalic acid-isophthalic acid-ethylene glycol copolyester prepolymer with the intrinsic viscosity of 0.30 dL/g. Wherein, 15 layers of tower plates are arranged in the reactor body of the bubbling reactor; the bubbling reactor had a reaction temperature of 260 ℃ and a reaction pressure of 6 kPa.

S4, conveying the sebacic acid-terephthalic acid-isophthalic acid-ethylene glycol copolyester prepolymer to a subsequent polycondensation system for final polycondensation reaction and liquid phase tackifying reaction in sequence, wherein the final polycondensation reaction temperature is 270 ℃, the reaction pressure is 150Pa, and the intrinsic viscosity of the prepared sebacic acid-terephthalic acid-isophthalic acid-ethylene glycol copolyester final polymer is 0.80 dL/g; the liquid phase tackifying reaction temperature is 270 ℃, the reaction pressure is 80Pa, and the high-viscosity sebacic acid-terephthalic acid-isophthalic acid-ethylene glycol copolyester with the intrinsic viscosity of 1.0dL/g is prepared.

Example 7

In this embodiment, the preparation method of the biodegradable copolyester preparation system in the application experimental example includes the following steps:

s1, preparing succinic acid-terephthalic acid slurry with the molar ratio of 2.0:1 of alkyd by taking a ternary compound with the molar ratio of titanium element, aluminum element and phosphorus element being 1:0.8:0.2 as a catalyst, wherein the molar ratio of terephthalic acid to succinic acid is 50: 50; the catalyst is prepared by mixing tetraisooctyl titanate, aluminum glycol and pentaerythritol dioctadecyl diphosphite according to the molar ratio of titanium element, aluminum element and phosphorus element of 1:0.8:0.2 and then reacting for 5 hours at 200 ℃.

S2, delivering the succinic acid-terephthalic acid slurry to an esterification reaction kettle to prepare succinic acid-terephthalic acid-ethylene glycol copolyester esterified substance with an acid value of 60 mgKOH/g. Wherein the reaction temperature of the first cavity chamber is 150 ℃, the reaction pressure is 100kPa, the reaction temperature of the second cavity chamber is 250 ℃, and the reaction pressure is 100 kPa.

S3, delivering the succinic acid-terephthalic acid-ethylene glycol copolyester esterified substance and the bubbling ethylene glycol to a bubbling reactor according to the mass ratio of 100:5 to prepare the succinic acid-terephthalic acid-ethylene glycol copolyester prepolymer with the intrinsic viscosity of 0.50 dL/g. Wherein the reactor body of the bubbling reactor is internally provided with 30 layers of tower plates; the bubbling reactor had a reaction temperature of 260 ℃ and a reaction pressure of 3 kPa.

S4, conveying the succinic acid-terephthalic acid-ethylene glycol copolyester prepolymer to a subsequent polycondensation system for final polycondensation reaction and liquid phase tackifying reaction in sequence, wherein the final polycondensation reaction temperature is 260 ℃, the reaction pressure is 150Pa, and the intrinsic viscosity of the prepared succinic acid-terephthalic acid-ethylene glycol copolyester final polymer is 0.75 dL/g; the liquid phase tackifying reaction temperature is 260 ℃, the reaction pressure is 50Pa, and the high-viscosity succinic acid-terephthalic acid-ethylene glycol copolyester with the intrinsic viscosity of 1.2dL/g is prepared.

Example 8

In this embodiment, the preparation method of the biodegradable copolyester preparation system in the application experimental example includes the following steps:

s1, mixing adipic acid, terephthalic acid, butanediol and adipic acid-terephthalic acid slurry with the molar ratio of 1.3:1 of alkyd, which is prepared by taking a ternary compound with the molar ratio of titanium element, aluminum element and phosphorus element being 1:1:0.3 as a catalyst, wherein the molar ratio of the terephthalic acid to the succinic acid is 33: 67; the catalyst is prepared by mixing tetraoctyl titanate, aluminum acetylacetonate and bis (2, 4-di-tert-butylphenyl) pentaerythritol diphosphite according to the molar ratio of titanium element, aluminum element and phosphorus element of 1:1:0.3, and reacting for 1h at 250 ℃.

S2, conveying the adipic acid-terephthalic acid slurry to an esterification reaction kettle to prepare the adipic acid-terephthalic acid-butanediol copolyester esterified substance with the acid value of 50 mgKOH/g. Wherein the reaction temperature of the first chamber is 220 ℃ and the reaction pressure is 80kPa, and the reaction temperature of the second chamber is 220 ℃ and the reaction pressure is 30 kPa.

S3, conveying the adipic acid-terephthalic acid-butanediol copolyester esterified substance and the butanediol for bubbling to a bubbling reactor according to the mass ratio of 100:20 to prepare an adipic acid-terephthalic acid-butanediol copolyester prepolymer with the intrinsic viscosity of 0.25 dL/g. Wherein 20 layers of tower plates are arranged in the reactor body of the bubbling reactor; the bubbling reactor had a reaction temperature of 230 ℃ and a reaction pressure of 20 kPa.

S4, conveying the adipic acid-terephthalic acid-butanediol copolyester prepolymer to a subsequent polycondensation system for final polycondensation reaction and liquid phase tackifying reaction in sequence, wherein the final polycondensation reaction temperature is 240 ℃, the reaction pressure is 100Pa, and the intrinsic viscosity of the prepared adipic acid-terephthalic acid-butanediol copolyester final polymer is 0.60 dL/g; the liquid phase tackifying reaction temperature is 250 ℃, the reaction pressure is 50Pa, and the high-viscosity adipic acid-terephthalic acid-butanediol copolyester with the intrinsic viscosity of 1.2dL/g is prepared.

Comparative example 1

In this comparative example, the process steps for preparing the biodegradable copolyester were as follows:

s1, preparing succinic acid slurry with the molar ratio of alkyd being 1.3:1 from succinic acid, butanediol and tetrabutyl titanate serving as a catalyst. And (3) conveying the succinic acid slurry to an esterification reaction kettle, and preparing a succinic acid butanediol ester esterified substance of 20mgKOH/g under the conditions of reaction temperature of 180 ℃, reaction pressure of 100kPa and reaction time of 3 h.

S2, preparing terephthalic acid, butanediol and tetrabutyl titanate serving as a catalyst into terephthalic acid slurry with the molar ratio of the alkyd being 1.3: 1. And (3) conveying the terephthalic acid slurry to an esterification reaction kettle, and preparing 15mgKOH/g butylene terephthalate esterified substance under the conditions of reaction temperature of 240 ℃, reaction pressure of 40kPa and reaction time of 3 h.

S3, conveying the butylene terephthalate ester and the butylene succinate ester together to a polycondensation system according to the molar ratio of 50:50 of the terephthalic acid to the succinic acid, and sequentially carrying out a pre-polycondensation reaction, a final polycondensation reaction and a liquid-phase tackifying reaction to obtain the biodegradable terephthalic acid-succinic acid-butanediol copolyester. Wherein the pre-polycondensation reaction temperature is 250 ℃, the reaction time is 1h, and the reaction pressure is 10kPa, so as to prepare a terephthalic acid-succinic acid-butanediol copolyester prepolymer with the intrinsic viscosity of 0.4 dL/g; the final polycondensation reaction temperature is 255 ℃, the reaction time is 3h, and the reaction pressure is 150Pa, so that the terephthalic acid-succinic acid-butanediol copolyester final polymer with the intrinsic viscosity of 0.75dL/g is prepared; the liquid phase tackifying reaction temperature is 260 ℃, the reaction time is 1h, and the reaction pressure is 80Pa, so that the high-viscosity terephthalic acid-succinic acid-butanediol copolyester with the intrinsic viscosity of 1.2dL/g can be prepared.

Comparative example 2

In this comparative example, the process steps for preparing the biodegradable copolyester were as follows:

s1, blending terephthalic acid, succinic acid, butanediol and tetrabutyl titanate serving as a catalyst into terephthalic acid-succinic acid slurry with the molar ratio of alkyd being 1.3:1, wherein the molar ratio of terephthalic acid to succinic acid is 50: 50. And (2) conveying the terephthalic acid-succinic acid slurry to a first esterification reaction kettle, and preparing the terephthalic acid-succinic acid-butylene glycol ester esterified substance with the acid value of 40mgKOH/g under the conditions of the reaction temperature of 220 ℃, the reaction pressure of 100kPa and the reaction time of 4 h.

S2, conveying the terephthalic acid-succinic acid-butylene glycol ester from the first esterification reaction kettle to a second esterification reaction kettle, and preparing the terephthalic acid-succinic acid-butylene glycol ester with the acid value of 15mgKOH/g under the conditions of the reaction temperature of 240 ℃, the reaction pressure of 100kPa and the reaction time of 2 h.

S3, conveying the terephthalic acid-succinic acid-butanediol ester esterified substance from the second esterification reaction kettle to a polycondensation system, and sequentially carrying out pre-polycondensation reaction, final polycondensation reaction and liquid phase tackifying reaction to obtain the biodegradable terephthalic acid-succinic acid-butanediol copolyester. Wherein the pre-polycondensation reaction temperature is 250 ℃, the reaction time is 1h, and the reaction pressure is 10kPa, so as to prepare a terephthalic acid-succinic acid-butanediol copolyester prepolymer with the intrinsic viscosity of 0.4 dL/g; the final polycondensation reaction temperature is 255 ℃, the reaction time is 3h, and the reaction pressure is 150Pa, so that the terephthalic acid-succinic acid-butanediol copolyester final polymer with the intrinsic viscosity of 0.75dL/g is prepared; the liquid phase tackifying reaction temperature is 260 ℃, the reaction time is 1h, and the reaction pressure is 80Pa, so that the high-viscosity terephthalic acid-succinic acid-butanediol copolyester with the intrinsic viscosity of 1.2dL/g can be prepared.

Comparative example 3

In this comparative example, the process steps for preparing the biodegradable copolyester were as follows:

s1, preparing the succinic acid-terephthalic acid slurry with the molar ratio of 1.3:1 by using terephthalic acid, succinic acid, butanediol and a ternary compound with the molar ratio of titanium element, aluminum element and phosphorus element being 1:0.5:0.2 as a catalyst. Wherein the molar ratio of terephthalic acid to succinic acid is 50: 50; the catalyst is prepared by mixing tetrabutyl titanate, aluminum ethylene glycol and bis (2, 4-di-tert-butylphenyl) pentaerythritol diphosphite according to the molar ratio of titanium element, aluminum element and phosphorus element of 1:0.5:0.2, and reacting for 5 hours at 200 ℃.

S2, conveying the adipic acid-terephthalic acid slurry to an esterification reaction kettle, and preparing 18mgKOH/g butanediol terephthalate esterified substance under the conditions of the reaction temperature of 240 ℃, the reaction pressure of 40kPa and the reaction time of 3 h.

S3, conveying the terephthalic acid-succinic acid-butanediol ester esterified substance from the esterification reaction kettle to a polycondensation system, and sequentially carrying out pre-polycondensation reaction, final polycondensation reaction and liquid phase tackifying reaction to obtain the biodegradable terephthalic acid-succinic acid-butanediol copolyester. Wherein the pre-polycondensation reaction temperature is 250 ℃, the reaction time is 1h, and the reaction pressure is 10kPa, so as to prepare a terephthalic acid-succinic acid-butanediol copolyester prepolymer with the intrinsic viscosity of 0.2 dL/g; the final polycondensation reaction temperature is 255 ℃, the reaction time is 3h, and the reaction pressure is 150Pa, so that the terephthalic acid-succinic acid-butanediol copolyester final polymer with the intrinsic viscosity of 0.55dL/g is prepared; the liquid phase tackifying reaction temperature is 260 ℃, the reaction time is 1h, and the reaction pressure is 80Pa, so that the high-viscosity terephthalic acid-succinic acid-butanediol copolyester with the intrinsic viscosity of 1.1dL/g can be prepared.

Comparative example 4

In the comparative example, the preparation method of the biodegradable copolyester preparation system applied in the experimental example comprises the following steps:

s1, blending terephthalic acid, succinic acid, butanediol and tetrabutyl titanate serving as a catalyst into terephthalic acid-succinic acid slurry with the molar ratio of alkyd being 1.3:1, wherein the molar ratio of terephthalic acid to succinic acid is 50: 50.

S2, delivering the succinic acid-terephthalic acid slurry to an esterification reaction kettle to prepare succinic acid-terephthalic acid-butanediol copolyester esterified substance with an acid value of 35 mgKOH/g. Wherein the reaction temperature of the first cavity chamber is 180 ℃, the reaction pressure is 100kPa, the reaction temperature of the second cavity chamber is 235 ℃, and the reaction pressure is 50 kPa.

S3, conveying the esterified succinic acid-terephthalic acid-butanediol copolyester and the butanediol for bubbling to a bubbling reactor according to the mass ratio of 100:10 to prepare the succinic acid-terephthalic acid-butanediol copolyester prepolymer with the intrinsic viscosity of 0.38 dL/g. Wherein 20 layers of tower plates are arranged in the reactor body of the bubbling reactor, the reaction temperature of the bubbling reactor is 260 ℃, and the reaction pressure is 10 kPa.

S4, conveying the succinic acid-terephthalic acid-butanediol copolyester prepolymer to a subsequent polycondensation system for a final polycondensation reaction and a liquid phase tackifying reaction in sequence, wherein the final polycondensation reaction temperature is 255 ℃, the reaction pressure is 150Pa, and the intrinsic viscosity of the prepared succinic acid-terephthalic acid-butanediol copolyester final polymer is 0.68 dL/g; the liquid phase tackifying reaction temperature is 260 ℃, the reaction pressure is 80Pa, and the high-viscosity succinic acid-terephthalic acid-butanediol copolyester with the intrinsic viscosity of 1.2dL/g is prepared.

Experimental example 1

The molecular structures of the biodegradable semi-aromatic polyesters (aliphatic-aromatic copolyesters) prepared in examples 1 to 8 and comparative examples 1 to 4 were subjected to the correlation performance test, and the correlation performance test was as follows:

(1) intrinsic viscosity η (dL/g), test method: reference GB/T14190-;

(2) carboxyl end group content (mol/t), test method: reference GB/T14190-;

(3) sequence length of aromatic dibasic acid ester chain segment, test method: in Bruker AVANCE III 600M NMR spectrometer (¹HNMR:600MHz), deuterated chloroform CDCl₃As a solvent, tetramethylsilane TMS is used as an internal standard;

the results of the above tests for each property are shown in Table 1.

TABLE 1

As can be seen from Table 1, the biodegradable copolyesters prepared in examples 1-8 have no more than 20mol/t of carboxyl end group content, no more than 8 of chroma b value, and no more than 2 of sequence length of aromatic dibasic acid ester chain segment, which indicates that the aliphatic-aromatic copolyester prepared by the continuous preparation method of the invention has good biodegradability, low carboxyl end group content and good hue.

The biodegradable copolyesters continuously prepared in example 1, comparative example 1 and comparative example 2 are all terephthalic acid-succinic acid-butanediol copolyester with a succinic acid to terephthalic acid molar ratio of 50: 50. As can be seen from table 1, the sequence length of the aromatic dibasic acid ester segment in the macromolecular chain of the terephthalic acid-succinic acid-butanediol copolyester prepared in comparative example 1 and comparative example 2 was more than 2, while the sequence length of the aromatic dibasic acid ester segment in the macromolecular chain of the terephthalic acid-succinic acid-butanediol copolyester prepared in example 1 was 1.86. The continuous preparation method can effectively control the aromatic dibasic acid ester chain segment in the copolyester not to exceed 2 so as to ensure the microbial degradability of the copolyester. As can be seen from Table 1, the terephthalic acid-succinic acid-butanediol copolyester prepared in comparative example 1 has a chroma b value of 9.3 and a carboxyl end group content of 29mol/t, the terephthalic acid-succinic acid-butanediol copolyester prepared in comparative example 2 has a chroma b value of 11.6 and a carboxyl end group content of 38mol/t, and the terephthalic acid-succinic acid-butanediol copolyester prepared in example 1 has a chroma b value of 5.9 and a carboxyl end group content of 16 mol/t. The continuous preparation method and the ternary composite catalyst of the titanium element, the aluminum element and the phosphorus element can effectively inhibit the thermal degradation of succinic acid and copolyester in the continuous polymerization process, and block part of terminal carboxyl groups of the copolyester to prepare the terephthalic acid-succinic acid-butanediol copolyester with good hue and low content of the terminal carboxyl groups, thereby being beneficial to improving the humidity and heat aging resistance of the terephthalic acid-succinic acid-butanediol copolyester and prolonging the shelf life of products thereof.

The biodegradable copolyesters continuously prepared in example 1, comparative example 3 and comparative example 4 are all terephthalic acid-succinic acid-butanediol copolyester with a succinic acid to terephthalic acid molar ratio of 50: 50. In contrast, comparative example 3 used only the ternary complex of titanium element, aluminum element and phosphorus element of the present invention as a catalyst and did not use the preparation system having an esterification reaction vessel and a bubble reactor of the present invention; comparative example 4 only employs the preparation system having the esterification reaction vessel and the bubble reactor of the present invention, and does not employ the ternary complex of titanium element, aluminum element and phosphorus element of the present invention as a catalyst. As can be seen from table 1, the sequence lengths of the aromatic dibasic acid ester segments in the macromolecular chains of the terephthalic acid-succinic acid-butanediol copolyesters prepared in comparative examples 3 and 4 are both greater than 2, while the sequence length of the aromatic dibasic acid ester segments in the macromolecular chains of the terephthalic acid-succinic acid-butanediol copolyester prepared in example 1 is 1.86; and the chrominance b value of the terephthalic acid-succinic acid-butanediol copolyester prepared in the comparative example 3 is 10.8, and the terminal carboxyl group content is 35mol/t, the chrominance b value of the terephthalic acid-succinic acid-butanediol copolyester prepared in the comparative example 4 is 11.2, and the terminal carboxyl group content is 27mol/t, and the chrominance b value of the terephthalic acid-succinic acid-butanediol copolyester prepared in the example 1 is 5.9, and the terminal carboxyl group content is 16 mol/t. The aliphatic-aromatic copolyester prepared by the preparation system with the esterification reaction kettle and the bubble reactor, which is disclosed by the invention, not only is the catalyst adopted, but also the aromatic dibasic acid ester chain segment in the copolyester can be effectively controlled to be not more than 2, so that the microbial degradability of the copolyester is ensured, the thermal degradation of succinic acid and the copolyester in the continuous polymerization process can be effectively inhibited, and part of terminal carboxyl groups of the copolyester are sealed, the terephthalic acid-succinic acid-butanediol copolyester with good hue and low terminal carboxyl group content is prepared, the wet-heat aging resistance of the terephthalic acid-succinic acid-butanediol copolyester is favorably improved, and the shelf life of the product is prolonged.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.