CN102329421A - A method for preparing lactide-propylene oxide-CO2 terpolymer with rare earth ternary catalyst - Google Patents

Abstract

The invention discloses a preparation method of a lactide-propylene oxide-CO ₂ terpolymer, comprising the following steps: adding a rare earth three-way catalyst, lactide, propylene oxide and CO ₂ into a reaction kettle, and Described lactide, propylene oxide and _CO Carry out polymerization reaction under the effect of rare earth three-way catalyst, obtain lactide-propylene oxide- _CO Terpolymer, and described rare earth three-way catalyst consists of trichloroacetic acid Yttrium, diethylzinc, glycerol and 1,3-dioxane, the molar ratio of said yttrium trichloroacetate, diethylzinc and glycerol is 1:20:10, said diethyl The concentration of zinc in the 1,3-dioxane is 0.5×10 ^-3 mol/ml. Compared with the prior art, since the present invention uses a rare earth three-way catalyst to catalyze the polymerization of lactide, propylene oxide and _CO , the polymerization reaction time is shorter, and the ether segment content in the prepared terpolymer is <2% , is conducive to industrial production.

Description

A method for preparing lactide-propylene oxide-CO2 terpolymer with rare earth ternary catalyst

technical field

The invention relates to the technical field of polymers, more specifically, to a method for preparing a lactide-propylene oxide- _CO terpolymer with a rare earth ternary catalyst.

Background technique

Polypropylene carbonate (PPC) is an alternating copolymer of carbon dioxide and propylene oxide. It is an environmentally friendly polymer material with excellent gas barrier properties, good biocompatibility and biodegradability. However, polypropylene carbonate has a low glass transition temperature (T _g = 35-41°C), poor thermal stability, and a narrow thermal processing window (130-140°C), which seriously affects its processing performance and application range. .

At present, adopting physical blending modification to modify the self local defects of PPC is a common method to improve the performance of PPC. The Chinese patent literature with publication number CN1058408 has reported a modification method of aliphatic polycarbonate nitrile rubber, In this method, PPC and butyl rubber are physically blended to improve the mechanical properties and thermal stability of PPC, but the biodegradability of the physical blend prepared by this method is poor. In addition, the Chinese patent literature with the publication number CN1371942 has reported a method of blending PPC with biodegradable polyester to obtain a physical blend, although this method can guarantee the biodegradation of the prepared physical blend to a certain extent However, the blending compatibility between PPC and biodegradable polyester is poor, so that phase separation occurs easily at the two-phase interface of the physical blend (Chinese patent CN1371942; Ma, X.F.et al.J .Polym.Sci.: Polym.Phys.44, 94, 2006; Pang, M.Z.et al.J.Appl.Polym.Sci.107, 2854, 2008; Peng, S.W.et al.J.Appl.Polym.Sci. 90, 4054, 2003).

Compared with physical blending modification, chemical modification essentially improves the mechanical properties and thermal stability of PPC by changing the chain structure of PPC, so it has been extensively studied. Relevant researchers have found that the overall performance of PPC can be improved by adding a third monomer, lactide, to the copolymerization of propylene oxide and carbon dioxide for terpolymerization. For example, Huang Kelong et al. used polymer-supported bimetallic catalysts to catalyze the ternary copolymerization of propylene oxide, carbon dioxide and DL-lactide (Polym.Bull.66, 327, 2011), and the polymerization reaction time was 24 hours. The resulting ternary copolymerization The content of ether segments in the molecular structure of the product exceeds 20%; US Patent No. 6,713,593B2 uses a zinc glutarate catalyst to catalyze the ternary copolymerization of propylene oxide, carbon dioxide, and lactide, and the polymerization reaction time is 40 hours. However, the polymerization reaction time of the method reported above is long, which is unfavorable for industrial production.

Contents of the invention

In view of this, the technical problem to be solved in the present invention is to provide a kind of method for preparing lactide-propylene oxide-CO terpolymer with rare earth three- _way catalyst, the polymerization reaction time of this method is shorter, and the prepared The content of ether segment in lactide-propylene oxide-CO ₂ terpolymer is low.

The invention provides a method for preparing lactide-propylene oxide- _CO terpolymer with a rare earth ternary catalyst, comprising the following steps:

Add a rare earth three-way catalyst, lactide, propylene oxide and _CO2 into the reaction kettle, and polymerize the lactide, propylene oxide and _CO2 under the action of the rare earth three-way catalyst to obtain lactide - Propylene oxide-CO _terpolymer , the rare earth ternary catalyst is composed of yttrium trichloroacetate, diethyl zinc, glycerol and 1,3-dioxane, the yttrium trichloroacetate, di The molar ratio of ethyl zinc to glycerol is 1:20:10, and the concentration of diethyl zinc in the 1,3-dioxane is 0.5×10 ^-3 mol/mL.

Preferably, the molar ratio of the lactide to the propylene oxide is (1-10):100.

Preferably, the molar ratio of the diethylzinc to the propylene oxide is 1:143.1.

Preferably, the pressure of the CO ₂ is 3.0-4.5 MPa.

Preferably, the temperature of the polymerization reaction is 60-90°C.

Preferably, the temperature of the polymerization reaction is 65-75°C.

Preferably, the time for the polymerization reaction is 6-15 hours.

Preferably, the rare earth three-way catalyst is prepared as follows:

mixing yttrium trichloroacetate, 1,3-dioxane and glycerin to obtain a first solution;

Diethyl zinc is added dropwise to the first solution, and after aging, a rare earth three-way catalyst is obtained, and the molar ratio of yttrium trichloroacetate, diethyl zinc and glycerol is 1:20:10, and the The concentration of diethylzinc in the 1,3-dioxane is 0.5×10 ^-3 mol/mL.

Preferably, after the polymerization reaction, it also includes: cooling the reactor to room temperature in a water bath, removing residual carbon dioxide in the reactor, and adding ethanol into the reactor.

Preferably, it also includes:

Add the lactide- _propylene oxide-CO terpolymer into dichloromethane to obtain a mixed solution, the mass concentration of the terpolymer in the mixed solution is 15%;

Add a mixed solution of hydrochloric acid and ethanol with a mass ratio of 1:100 to the mixed solution until the copolymer is completely precipitated, and then wash with ethanol after stirring for 1 to 5 hours, and wash with ethanol until neutral. Vacuum dry.

The invention provides a method for preparing lactide-propylene oxide-CO terpolymer with a rare earth three _- way catalyst, comprising the following steps: adding a rare earth three-way catalyst, lactide, propylene oxide and CO ₂ , the lactide, propylene oxide and CO ₂ are polymerized under the action of a rare earth three-way catalyst to obtain a lactide-propylene oxide-CO ₂ terpolymer, and the rare earth three-way catalyst It consists of yttrium trichloroacetate, diethyl zinc, glycerol and 1,3-dioxane, the molar ratio of said yttrium trichloroacetate, diethyl zinc and glycerol is 1:20:10, so The concentration of diethylzinc in the 1,3-dioxane is 0.5×10 ^-3 mol/mL. . Compared with the prior art, because the present invention catalyzes the polymerization of lactide, propylene oxide and _CO with rare earth three-way catalyst, therefore, the polymerization reaction time is shorter, and the lactide-propylene oxide- The ether segment content in the CO ₂ terpolymer is less than 2%, which is beneficial to industrial production. Experimental results show that the yield of the polymerization reaction of the present invention is 4.77×10 ³ to 7.26×10 ³ g polymer/molZn, the thermal decomposition temperature of the terpolymer is 229.7°C, and the elongation at break can be determined by the amount of starting lactide Regulation, up to 40.5%.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is the lactide-propylene oxide-carbon dioxide terpolymer PPCLA prepared by the embodiment of the present invention 6 and the blend of polylactic acid (PLA) and polypropylene carbonate (PPC) solution prepared by comparative example 2 DSC spectrum;

Fig. 2 is the ¹ H NMR chart of the lactide-propylene oxide-CO ₂ terpolymer prepared in Example 2 of the present invention.

Detailed ways

The following clearly and completely describes the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

The invention discloses a method for preparing a lactide-propylene oxide- _CO terpolymer with a rare earth three-way catalyst, comprising the following steps:

Add a rare earth three-way catalyst, lactide, propylene oxide and _CO2 into the reaction kettle, and polymerize the lactide, propylene oxide and _CO2 under the action of the rare earth three-way catalyst to obtain lactide - Propylene oxide-CO _terpolymer , the rare earth ternary catalyst is composed of yttrium trichloroacetate, diethyl zinc, glycerol and 1,3-dioxane, the yttrium trichloroacetate, di The molar ratio of ethyl zinc to glycerol is 1:20:10, and the concentration of diethyl zinc in the 1,3-dioxane is 0.5×10 ^-3 mol/mL.

According to the present invention, the molar ratio of the lactide to the propylene oxide is preferably (1-10):100, more preferably (2-5):100, most preferably (3-5):100; The molar ratio of the diethylzinc to the propylene oxide is preferably 1:143.1. In the preparation process of the terpolymer, the pressure of the _CO2 is preferably 3.0-4.5MPa, more preferably 3.5-4.0MPa; the temperature of the polymerization reaction is preferably 60-90°C, more preferably 65-85 °C, most preferably 65-75 °C; the polymerization reaction time is preferably 6-15 hours, more preferably 8-14 hours, most preferably 8-10 hours.

In the present invention, the polymerization reaction of lactide, propylene oxide and _CO2 under the action of a rare earth three-way catalyst is as follows: the reactor is evacuated to 20-40Pa at 80°C, filled with _CO2 for 2 hours, and then filled CO ₂ was injected 6 times, and then cooled to room temperature; the aged rare earth three-way catalyst and lactide-dissolved propylene oxide were respectively injected into the reactor for polymerization to obtain lactide-propylene oxide-CO ₂ terpolymers, the molar ratio of the yttrium trichloroacetate, diethylzinc and glycerin is 1:20:10, the diethylzinc in the 1,3-dioxane The concentration is 0.5×10 ^-3 mol/mL.

In addition, after the polymerization reaction, it also preferably includes: cooling the reactor to room temperature in a water bath, removing residual carbon dioxide in the reactor, and adding ethanol into the reactor, the addition of ethanol is beneficial to the precipitation of the copolymer. After obtaining the lactide-propylene oxide-CO terpolymer, it also preferably includes: adding the lactide-propylene oxide- _CO terpolymer into methylene chloride to obtain _a mixed solution, the The mass concentration of the terpolymer in the mixed solution is 15%; the mixed solution of hydrochloric acid and ethanol with a mass ratio of 1: 100 is added to the mixed solution until the copolymer is completely precipitated from the dichloromethane solution, After stirring for 1-5 hours, wash with ethanol, and vacuum-dry at 35-45° C.; the stirring time is preferably 2-3 hours, and the stirring speed is preferably 150 rpm. The precipitated copolymer is preferably washed with ethanol (100 mL each time) in batches under stirring, and stirred and washed for 30 minutes each time until the washing liquid is neutral, and the precipitate is vacuum-dried in a vacuum oven at 35 to 45 ° C until constant Weight, a white lactide-propylene oxide-carbon dioxide terpolymer was obtained.

The present invention catalyzes the polymerization reaction of lactide, propylene oxide and CO with rare earth three-way catalyst, and described rare earth three _- way catalyst can be prepared according to the method in the Chinese patent literature of CN1257753, CN1257885 and CN1306021 and U.S. Patent US6815529B2 , preferably prepared according to the following method: mixing yttrium trichloroacetate (Y(CCl ₃ COO) ₃ ), 1,3-dioxane and glycerol to obtain a first solution; adding dropwise to the first solution Diethylzinc (ZnEt ₂ ), after aging, the rare earth three-way catalyst is obtained, and the molar ratio of the yttrium trichloroacetate, diethylzinc and glycerol is 1:20:10, and the diethylzinc is in The concentration in the 1,3-dioxane is 0.5×10 ^-3 mol/mL. In the preparation process of the rare earth three-way catalyst, the aging conditions are preferably: the temperature of the constant temperature water bath is 60°C; the frequency of mechanical oscillation is 150 times/min; the amplitude is 40mm; and the oscillation time is 2-2.5 hours.

More specifically, the rare earth three-way catalyst can be prepared according to the following method: the two-necked bottle used to configure the rare earth three-way catalyst is decompressed and evacuated (20-40Pa) at 80°C, and replaced with high-purity argon every 20 minutes Once, a total of 5 replacements, and finally cooled to room temperature under the protection of high-purity argon; under the protection of high-purity argon, add a certain amount of Y(CCl ₃ COO) ₃ to the rare earth three-way catalyst bottle, and then sequentially Add the calculated amount of 1,3-dioxane and glycerin, and after Y(CCl ₃ COO) ₃ is completely dissolved, add the calculated amount of diethyl zinc dropwise into the bottle, and then add the calculated amount of diethyl zinc dropwise. During the process, the reaction temperature in the bottle is controlled at 20-25°C. After diethyl zinc is added dropwise, after no reaction gas is released, the bottle is sealed and placed in a constant temperature water bath oscillator for aging. The aging conditions are: The temperature of the constant temperature water bath is 60°C; the frequency of mechanical oscillation is 150 times/min; the amplitude is 40mm; the mechanical oscillation is carried out for 2 to 2.5 hours in total, and the white suspension liquid is obtained as the rare earth three-way catalyst.

Compared with _the prior art, because the present invention catalyzes lactide, propylene oxide and CO with rare earth three-way catalyst Polymerization, rare earth _three -way catalyst can effectively catalyze lactide, propylene oxide and CO Polymerization, therefore , the polymerization reaction time is short, and the ether content in the prepared lactide-propylene oxide-CO ₂ terpolymer is relatively low (<2%), which is beneficial to industrial production.

In order to further illustrate the technical solution of the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

Example 1

Preparation of Rare Earth Three-way Catalyst

Evacuate a 50mL two-neck bottle under reduced pressure at 80°C to 20-40Pa, replace it with high-purity argon every 20 minutes, and replace it 5 times in total, and then cool it to room temperature under the protection of high-purity argon;

Under the protection of high-purity argon, add 0.0005mol Y(CCl ₃ COO) ₃ into the two-necked flask, then add 20mL 1,3-dioxane and 0.005mol glycerol in sequence, and wait until the Y(CCl 3 COO) 3 in the two-necked flask After (CCl ₃ COO) ₃ is completely dissolved, add 0.01 mol of diethyl zinc dropwise into the bottle. During the process of adding diethyl zinc, the reaction temperature in the bottle is controlled at 20-25°C. After the reaction gas is no longer released, the two-necked bottle is sealed and placed in a constant temperature water bath oscillator for aging to obtain a white suspension liquid, that is, a rare earth three-way catalyst. The aging conditions are: the temperature of the constant temperature water bath is 60 ° C, and mechanical vibration The frequency is 150 times/min, the amplitude is 40mm, and the mechanical oscillation is carried out for 2.5 hours.

Example 2

The reactor was evacuated to 20-40Pa at 80°C, filled with CO ₂ treatment for 2 hours, filled with CO ₆ times, then cooled to room temperature; the rare earth three-way catalyst (0.0005mol yttrium trichloroacetate , 20mL1, 3-dioxane, 0.005mol glycerol, 0.01mol ZnEt ₂ ) were added into the reaction kettle under the protection of CO ₂ , and 100mL of propylene oxide was dissolved with 2.06g recrystallized lactide Injected into the reactor, the molar ratio of lactide to propylene oxide is 0.01431:1.431;

Put the reaction kettle into an adjustable constant temperature heating bath, quickly pass the carbon dioxide pressure regulator to make the carbon dioxide pressure in the kettle reach 4.0MPa under the condition of a stirring rate of 500rpm, the polymerization reaction temperature is 70°C, and the reaction time is 10 hours;

After the polymerization reaction is over, cool the reactor to room temperature with a cold water bath at a temperature of 12-15°C, slowly remove the residual carbon dioxide in the reactor, and add 200mL of ethanol to the reactor to precipitate all the polymers; Dissolve with dichloromethane to form a 15wt% solution, and slowly add 1wt% ethanol solution of HCl dropwise at a stirring rate of 150rpm until the copolymer is completely precipitated from the dichloromethane solution, and continue to stir for 2.5 hours, and the precipitated The copolymer was washed with ethanol under stirring, and the stirring and washing time was 30 minutes until the washing liquid was neutral, and then placed in a vacuum oven at 35-45°C to vacuum-dry to constant weight to obtain 47.7g of lactide-propylene oxide-CO ₂ Terpolymers.

The yield of the polymerization reaction in this example is 4.77×10 ³ g polymer/mol Zn, the number average molecular weight of the polymer is 15.4×10 ⁴ g/mol, the glass transition temperature is 39.3°C, and the initial decomposition temperature is 216.6 °C, the tensile strength is 39.9MPa, and the elongation at break is 27.6%. Fig. 2 is the ¹ HNMR figure of the lactide-propylene oxide-CO terpolymer prepared in this embodiment _{, calculates} from the integrated area of figure, the ether of lactide-propylene oxide-CO terpolymer Segment content <2%.

Example 3

The reactor was evacuated to 20-40Pa at 80°C, filled with CO ₂ treatment for 2 hours, filled with CO ₆ times, then cooled to room temperature; the rare earth three-way catalyst (0.0005mol yttrium trichloroacetate , 20mL 1,3-dioxane, 0.005mol glycerol, 0.01mol ZnEt ₂ ) were added into the reaction kettle under the protection of CO ₂ , and 100mL was dissolved with 4.12g recrystallized lactide epoxy Propane is injected into the reactor, and the molar ratio of lactide to propylene oxide is 0.02862:1.431;

Put the reaction kettle into an adjustable constant temperature heating bath, quickly pass the carbon dioxide pressure regulator to make the carbon dioxide pressure in the kettle reach 4.0MPa under the condition of a stirring rate of 500rpm, the polymerization reaction temperature is 70°C, and the reaction time is 10 hours;

After the polymerization reaction is over, cool the reactor to room temperature with a cold water bath at a temperature of 12-15°C, slowly remove the residual carbon dioxide in the reactor, and add 200mL of ethanol to the reactor to precipitate all the polymers; Dissolve with dichloromethane to form a 15wt% solution, and slowly add 1wt% ethanol solution of HCl dropwise at a stirring rate of 150rpm until the copolymer is completely precipitated from the dichloromethane solution, and continue to stir for 2.5 hours, and the precipitated The copolymer was washed with ethanol under stirring, and the stirring and washing time was 30 minutes until the washing liquid was neutral, and then placed in a vacuum oven at 35-45°C to vacuum-dry to constant weight to obtain 50.7g of lactide-propylene oxide-CO ₂ Terpolymers.

In this example, the polymerization yield is 5.07×10 ³ g polymer/mol Zn, the number average molecular weight of the polymer is 11.0×10 ⁴ g/mol, the glass transition temperature is 38.9°C, and the initial decomposition temperature is 229.7°C. The tensile strength is 40.6MPa, the elongation at break is 40.5%, and the ether segment content of the copolymer is the same as in Example 2.

Example 4

The reactor was evacuated to 20-40Pa at 80°C, filled with CO ₂ treatment for 2 hours, filled with CO ₆ times, then cooled to room temperature; the rare earth three-way catalyst (0.0005mol yttrium trichloroacetate , 20mL1, 3-dioxane, 0.005mol glycerol, 0.01mol ZnEt ₂ ) were added into the reaction kettle under the protection of CO ₂ , and 100mL of propylene oxide was dissolved with 6.87g recrystallized lactide Injected into the reactor, the molar ratio of lactide to propylene oxide is 0.0477:1.431;

Put the reaction kettle into an adjustable constant temperature heating bath, quickly pass the carbon dioxide pressure regulator to make the carbon dioxide pressure in the kettle reach 4.0MPa under the condition of a stirring rate of 500rpm, the polymerization reaction temperature is 70°C, and the reaction time is 10 hours;

After the polymerization reaction is over, cool the reactor to room temperature with a cold water bath at a temperature of 12-15°C, slowly remove the residual carbon dioxide in the reactor, and add 200mL of ethanol to the reactor to precipitate all the polymers; Dissolve with dichloromethane to form a 15wt% solution, and slowly add 1wt% ethanol solution of HCl dropwise at a stirring rate of 150rpm until the copolymer is completely precipitated from the dichloromethane solution, and continue to stir for 2.5 hours, and the precipitated The copolymer was washed with ethanol under stirring, and the stirring and washing time was 30 minutes until the washing liquid was neutral, and then placed in a vacuum oven at 35-45°C to vacuum-dry to constant weight to obtain 59.3g of lactide-propylene oxide-CO ₂ Terpolymers.

In this example, the polymerization yield is 5.93×10 ³ g polymer/mol Zn, the number average molecular weight of the polymer is 11.5×10 ⁴ g/mol, the glass transition temperature is 39.6°C, and the initial decomposition temperature is 231.9°C. The tensile strength is 39.9MPa, the elongation at break is 13.4%, and the ether segment content of the copolymer is the same as in Example 2.

Example 5

The reactor was evacuated to 20-40Pa at 80°C, filled with CO ₂ treatment for 2 hours, filled with CO ₆ times, then cooled to room temperature; the rare earth three-way catalyst (0.0005mol yttrium trichloroacetate , 20mL1, 3-dioxane, 0.005mol glycerol, 0.01mol ZnEt ₂ ) were added into the reaction kettle under the protection of CO ₂ , and 100mL of propylene oxide was dissolved with 10.3g recrystallized lactide Injected into the reactor, the molar ratio of lactide to propylene oxide is 0.07155:1.431;

Put the reaction kettle into an adjustable constant temperature heating bath, quickly pass the carbon dioxide pressure regulator to make the carbon dioxide pressure in the kettle reach 4.0MPa under the condition of a stirring rate of 500rpm, the polymerization reaction temperature is 70°C, and the reaction time is 10 hours;

After the polymerization reaction is over, cool the reactor to room temperature with a cold water bath at a temperature of 12-15°C, slowly remove the residual carbon dioxide in the reactor, and add 200mL of ethanol to the reactor to precipitate all the polymers; Dissolve with dichloromethane to form a 15wt% solution, and slowly add 1wt% ethanol solution of HCl dropwise at a stirring rate of 150rpm until the copolymer is completely precipitated from the dichloromethane solution, and continue to stir for 2.5 hours, and the precipitated The copolymer was washed with ethanol under stirring, and the stirring and washing time was 30 minutes until the washing liquid was neutral, and then placed in a vacuum oven at 35-45°C to vacuum-dry to constant weight to obtain 65.5g of lactide-propylene oxide-CO ₂ Terpolymers.

In this example, the polymerization yield is 6.55×10 ³ g polymer/mol Zn, the number average molecular weight of the polymer is 5.5×10 ⁴ g/mol, the glass transition temperature is 39.5°C, and the initial decomposition temperature is 242.9°C. The tensile strength is 45.0MPa, the elongation at break is 5.97%, and the ether segment content of the copolymer is the same as in Example 2.

Example 6

The reactor was evacuated to 20-40Pa at 80°C, filled with CO ₂ treatment for 2 hours, filled with CO ₆ times, then cooled to room temperature; the rare earth three-way catalyst (0.0005mol yttrium trichloroacetate , 20mL1, 3-dioxane, 0.005mol glycerol, 0.01mol ZnEt ₂ ) were added into the reaction kettle under the protection of CO ₂ , and 100mL of propylene oxide dissolved in 20.6g recrystallized lactide Injected into the reactor, the molar ratio of lactide to propylene oxide is 0.1431:1.431;

Put the reaction kettle into an adjustable constant temperature heating bath, quickly pass the carbon dioxide pressure regulator to make the carbon dioxide pressure in the kettle reach 3.5MPa under the condition of a stirring rate of 500rpm, the polymerization temperature is 75°C, and the reaction time is 8 hours;

After the polymerization reaction is over, cool the reactor to room temperature with a cold water bath at a temperature of 12-15°C, slowly remove the residual carbon dioxide in the reactor, and add 200mL of ethanol to the reactor to precipitate all the polymers; Dissolve with dichloromethane to form a 15wt% solution, and slowly add 1wt% ethanol solution of HCl dropwise at a stirring rate of 150rpm until the copolymer is completely precipitated from the dichloromethane solution, and continue to stir for 2.5 hours, and the precipitated The copolymer was washed with ethanol under stirring, and the stirring and washing time was 30 minutes until the washing liquid was neutral, and then placed in a vacuum oven at 35-45°C to vacuum-dry to constant weight to obtain 72.6g of lactide-propylene oxide-CO ₂ Terpolymers.

In this example, the polymerization yield is 7.26×10 ³ g polymer/mol Zn, the number average molecular weight of the polymer is 7.2×10 ⁴ g/mol, the glass transition temperature is 39.6°C, and the initial decomposition temperature is 227.8°C. The elongation at break was 5.25%, and the ether segment content of the copolymer was the same as in Example 2.

Comparative example 1

The reactor was evacuated to 20-40Pa at 80°C, filled with CO ₂ treatment for 2 hours, filled with CO ₆ times, then cooled to room temperature; the rare earth three-way catalyst (0.0005mol yttrium trichloroacetate , 20mL1, 3-dioxane, 0.005mol glycerol, 0.01mol ZnEt ₂ ) were added into the reaction kettle under the protection of CO ₂ , and 100mL propylene oxide (1.431mol) was injected into the autoclave;

Put the reaction kettle into an adjustable constant temperature heating bath, quickly pass the carbon dioxide pressure regulator to make the carbon dioxide pressure in the kettle reach 4.0MPa under the condition of a stirring rate of 500rpm, the polymerization reaction temperature is 70°C, and the reaction time is 10 hours;

After the polymerization reaction is over, cool the reactor to room temperature with a cold water bath at a temperature of 12-15°C, slowly remove the residual carbon dioxide in the reactor, and add 200mL of ethanol to the reactor to precipitate all the polymers; Dissolve with dichloromethane to form a 15wt% solution, and slowly add 1wt% ethanol solution of HCl dropwise at a stirring rate of 150rpm until the copolymer is completely precipitated from the dichloromethane solution, and continue to stir for 2.5 hours, and the precipitated The copolymer was washed with ethanol under stirring, and the stirring and washing time was 30 minutes until the washing liquid was neutral, and then placed in a vacuum oven at 35 to 45°C and vacuum-dried to constant weight to obtain 45.3g of propylene oxide-CO ₂ copolymer.

In this comparative example, the yield of the polymerization reaction was 4.53×10 ³ g polymer/mol Zn, the number average molecular weight of the polymer was 11.9×10 ⁴ g/mol, the glass transition temperature was 38.5°C, and the initial decomposition temperature was 197 °C, the tensile strength is 50.4MPa, the elongation at break is 12.9%, and the ether segment content of the copolymer is 3.5%.

Comparative example 2

Polylactic acid (PLA) and polypropylene carbonate (PPC) solutions with a mass ratio of 70:30 were blended to obtain a blend. Lactide-propylene oxide- _CO terpolymer PPCLA prepared in Example 6 and the blend prepared in this Comparative Example were analyzed by differential scanning calorimetry, as shown in Figure 1, which is Example 6 The prepared lactide-propylene oxide-carbon dioxide terpolymer PPCLA and the DSC spectrum of the blend of this comparative example polylactic acid (PLA) and polypropylene carbonate (PPC) solution blending, wherein, curve a is Lactide-propylene oxide-carbon dioxide terpolymer, wherein the lactide unit content is 25.8%; b is a blend of polypropylene carbonate (PPC) and polylactic acid (PLA), wherein the mass of PPC and PLA The ratio is 70:30. It can be seen from the DSC spectrum that the lactide-propylene oxide-CO terpolymer obtained under the rare earth three- _way catalyst has only one Tg, while the blend of polylactic acid and PPC has two Tgs, which is generally considered to be random. Copolymers have only one Tg, and incompatible or partially compatible blends have two Tgs (Ion Exchange and Adsorption, 23, 1, 2007).

It can be seen from the above examples and comparative examples that under the action of the rare earth three-way catalyst, the present invention realizes the three-way copolymerization of lactide-propylene oxide-carbon dioxide, and the polymerization yield is 4.77×10 ³ to 7.26× 10 ³ g polymer/mol Zn, the thermal decomposition temperature of the terpolymer is 229.7 ℃, which is greatly increased compared with the thermal decomposition temperature of pure PPC; and the elongation at break can reach up to 40.5%.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. one kind prepares rac-Lactide-propylene oxide-CO with rare-earth ternary catalyst ₂The method of terpolymer may further comprise the steps:

In reaction kettle, add rare-earth ternary catalyst, rac-Lactide, propylene oxide and CO ₂, with said rac-Lactide, propylene oxide and CO ₂Under the effect of rare-earth ternary catalyst, carry out polyreaction, obtain rac-Lactide-propylene oxide-CO ₂Terpolymer; Said rare-earth ternary catalyst is by trichoroacetic acid(TCA) yttrium, zinc ethyl, USP Kosher and 1, and the 3-dioxolane is formed, and the mol ratio of said trichoroacetic acid(TCA) yttrium, zinc ethyl and USP Kosher is 1: 20: 10; Said zinc ethyl is said 1, and the concentration in the 3-dioxolane is 0.5 * 10 ^-3Mol/mL.

2. according to the said preparation method of claim 1, it is characterized in that the mol ratio of said rac-Lactide and said propylene oxide is (1～10): 100.

3. according to the said preparation method of claim 1, it is characterized in that the mol ratio of said zinc ethyl and said propylene oxide is 1: 143.1.

4. according to the said preparation method of claim 1, it is characterized in that said CO ₂Pressure be 3.0～4.5MPa.

5. according to the said preparation method of claim 1, it is characterized in that the temperature of said polyreaction is 60～90 ℃.

6. according to the said preparation method of claim 5, it is characterized in that the temperature of said polyreaction is 65～75 ℃.

7. according to the said preparation method of claim 1, it is characterized in that the time of said polyreaction is 6～15 hours.

8. according to the said preparation method of claim 1, it is characterized in that said rare-earth ternary catalyst prepares by following method:

With trichoroacetic acid(TCA) yttrium, 1,3-dioxolane and USP Kosher mix, and obtain first solution;

In said first solution, drip zinc ethyl, obtain rare-earth ternary catalyst after the ageing, the mol ratio of said trichoroacetic acid(TCA) yttrium, zinc ethyl and USP Kosher is 1: 20: 10, and said zinc ethyl is said 1, and the concentration in the 3-dioxolane is 0.5 * 10 ^-3Mol/mL.

9. according to the said preparation method of claim 1, it is characterized in that, also comprise after the polyreaction: the reaction kettle water-bath is cooled to room temperature, gets rid of the residual carbon dioxide in the reaction kettle, and in reaction kettle, add ethanol.

10. according to the said preparation method of claim 1, it is characterized in that, also comprise:

With said rac-Lactide-propylene oxide-CO ₂Terpolymer adds in the methylene dichloride, obtains mixing solutions, and the mass concentration of this terpolymer in said mixing solutions is 15%;

The hydrochloric acid and alcoholic acid mixing solutions to the multipolymer that in said mixing solutions, added mass ratio and be 1: 100 all settle out, and stir and use washing with alcohol after 1～5 hour, and be washed till neutrality with ethanol, 35～45 ℃ of following vacuum-dryings.

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