阅读说明：本技术 一种可降解发泡共聚酯及其制备方法 (Degradable foamed copolyester and preparation method thereof ) 是由 朱楷 冉启迪 王松林 李金隆 于 2021-08-31 设计创作，主要内容包括：本发明涉及聚酯领域,本发明公开了一种可降解发泡共聚酯及其制备方法,该可降解发泡共聚酯包括：对苯二甲酸100份,乙二醇30-60份,除乙二醇外的二醇共聚单体10-40份,可降解醇酸组分0.1-10份,催化剂0.01-1份,稳定剂0.01-1份。其制备方法包括：(1)将对苯二甲酸、乙二醇、二醇共聚单体和催化剂混合进行酯化反应；加入稳定剂和可降解醇酸组分；(2)先后进行预缩聚、终缩聚反应,制得无规改性聚酯切片；(3)进行超临界流体发泡,制得成品。本发明通过在聚酯单体中添加二醇共聚单体,以及可降解醇酸组分,使得共聚所得的共聚酯具备低温可发泡性以及可降解性,并且抗冲性能优异。(The invention relates to the field of polyester, and discloses degradable foamed copolyester and a preparation method thereof, wherein the degradable foamed copolyester comprises the following components in parts by weight: 100 parts of terephthalic acid, 30-60 parts of ethylene glycol, 10-40 parts of glycol comonomer except the ethylene glycol, 0.1-10 parts of degradable alkyd component, 0.01-1 part of catalyst and 0.01-1 part of stabilizer. The preparation method comprises the following steps: (1) mixing terephthalic acid, ethylene glycol, glycol comonomer and a catalyst for esterification reaction; adding a stabilizer and a degradable alkyd component; (2) carrying out pre-polycondensation and final polycondensation reaction in sequence to obtain a random modified polyester chip; (3) foaming with supercritical fluid to obtain the final product. According to the invention, the diol comonomer and the degradable alkyd component are added into the polyester monomer, so that the copolyester obtained by copolymerization has low-temperature foamability and degradability, and the impact resistance is excellent.)

1. A degradable foamed copolyester is characterized in that: the feed comprises the following raw materials in parts by weight:

100 parts of terephthalic acid, namely terephthalic acid,

30-60 parts of ethylene glycol,

10-40 parts of glycol comonomer except ethylene glycol,

0.1 to 10 portions of degradable alkyd component,

0.01-1 part of catalyst,

0.01-1 part of stabilizer.

2. The degradable foamed copolyester of claim 1, wherein:

the diol comonomer is selected from one or more of propylene glycol, butanediol, 1, 4-cyclohexanedimethanol and 2-butyl-2-ethyl-1, 3-propanediol;

the degradable alkyd component is selected from one or more of lactic acid oligomer with molecular weight of 2000-8000 and lactic acid monomer.

3. The degradable foamed copolyester of claim 2, wherein:

the diol comonomer is one or more of 2 butyl-2 ethyl-1, 3 propanediol and 1, 4-cyclohexanedimethanol;

the degradable alkyd component is a lactic acid oligomer with molecular weight of 2000-8000.

4. The degradable foamed copolyester of claim 1, wherein: the catalyst is one or more of a two-dimensional composite titanium heterogeneous polyester catalyst, ethylene glycol antimony, antimony trioxide, antimony acetate, tetrabutyl titanate, tetraisopropyl titanate and zinc acetate.

5. The degradable foamed copolyester of claim 1, wherein: the stabilizer is triphenyl phosphite.

6. A method for preparing the degradable foamed copolyester according to any one of claims 1 to 5, wherein the method comprises the following steps: the method comprises the following steps:

(1) adding terephthalic acid, ethylene glycol, glycol comonomer and a catalyst into a polymerization reactor to carry out esterification reaction; adding a stabilizer and a degradable alkyd component after the esterification reaction, and uniformly stirring;

(2) heating and vacuumizing, and carrying out pre-polycondensation and final polycondensation reaction in sequence to obtain a random modified polyester chip;

(3) and (3) placing the random modified polyester slices into a foaming device, and filling a foaming agent medium to perform supercritical fluid foaming to prepare the degradable foamed copolyester.

7. The method of claim 6, wherein: in the step (1), the preheating temperature of the polymerization reactor is 50-160 ℃, the esterification reaction temperature is 190-250 ℃, and the pressure is 0.1-0.35 MPa.

8. The method of claim 6, wherein: in the step (2), the condition of the pre-polycondensation reaction is that the vacuum pumping is carried out for 60-120min until the absolute pressure is below 1000Pa, and the pre-polycondensation temperature is 240-280 ℃; the final polycondensation temperature is 245-285 ℃, the pressure is 0-500Pa, and the final polycondensation reaction time is 60-120 min.

9. The method of claim 6, wherein: in the step (3), the foaming agent is one or two of carbon dioxide and nitrogen.

10. The production method according to claim 6 or 9, characterized in that: in the step (3), the foaming temperature is 80-200 ℃, the foaming pressure is 10-30MPa, the pressure maintaining time is 20-120min, the pressure relief time is controlled at 0-10s, and the cooling time is controlled at 0-30 min.

Technical Field

The invention relates to the field of polyester, in particular to degradable foamed copolyester and a preparation method thereof.

Background

The foamed plastic is a plastic product which is formed by adding a foaming agent and other auxiliary materials into synthetic resin and contains a large number of micropore structures inside, and is widely applied to the fields of military manufacturing, rail transit, ship transportation, building heat preservation, automobile interior trim parts and the like due to light weight, heat insulation, sound insulation and noise reduction and other properties. In 2020, the yield of the foam plastic industry in China is 256.6 million tons, the foam plastic mainly takes polyurethane, polystyrene, polyvinyl chloride and polyolefin elastomer as main materials, and most of the materials are non-degradable materials, so the recovery is difficult and the problem of white pollution is easily caused. At present, related policies such as plastic limit and the like are also put out in China to limit white pollution. In recent years, degradable foam materials have become a great focus of attention, some biodegradable plastics such as polylactic acid, polybutylene succinate (PBS) and the like are sequentially used for foaming materials, for example, patent CN201310606455.3 discloses a preparation method of polylactic acid foam, which uses polylactic acid as a base material, water as a foaming agent, and a series of additives such as a carrier material, a plasticizer, a nucleating agent, a chain extender and the like are added, and finally, polylactic acid foams with different foaming ratios are obtained, and the foams have biodegradability, but are limited by poor toughness of the polylactic acid material, insufficient heat resistance and weather resistance, and limited by wide use of the material.

Polyester is also gaining increasing attention in the foaming field as one of the largest amounts of plastics used. The conventional PET has high crystallinity, excellent mechanical property, higher melting point (245-. For example, patent CN105778066A proposes a method for preparing low-melting-point polyester, in which diol and diacid are respectively used as a tri-monomer and a tetra-monomer to be subjected to two-degree copolymerization modification with a polyester PET finished product, the melting point of the obtained product is 90-250 ℃, and the glass transition temperature is 35-43 ℃. Modified polyester materials are widely used in the fields of core filling and soft and hard packaging and transportation due to excellent toughness and impact strength after foaming, and are generally treated in a recycling mode after being used. However, in practice, there are still many polyester foams flowing into the natural world, and due to the good corrosion resistance, these polyester foams flowing into the natural world will exist in rivers and soils for a long time, and will have serious influence on the ecological environment. Therefore, it has important ecological significance to further modify the polyester to make the polyester degradable.

Disclosure of Invention

In order to solve the technical problems, the invention provides degradable foamed copolyester and a preparation method thereof. According to the invention, the glycol comonomer except ethylene glycol and the degradable alkyd component are added into the polyester monomer, so that the copolyester obtained by copolymerization has low-temperature foamability and degradability, has excellent impact resistance, and is suitable for being used as packaging, buffering, heat-insulating materials and the like.

The specific technical scheme of the invention is as follows:

in a first aspect, the invention discloses degradable foamed copolyester, which comprises the following raw materials in parts by weight:

100 parts of terephthalic acid, namely terephthalic acid,

30-60 parts of ethylene glycol,

10-40 parts of glycol comonomer except ethylene glycol,

0.1 to 10 portions of degradable alkyd component,

0.01-1 part of catalyst,

0.01-1 part of stabilizer.

On one hand, the invention destroys the crystallization by adding the diol comonomer except the ethylene glycol to form the random copolyester without melting point, and reduces the processing temperature; on the other hand, the addition of the alkyd degradable component in the invention endows the copolyester material with degradability. The finally obtained copolyester has good low-temperature foaming effect and is degradable. It is noted that the amounts of glycol comonomer and degradable alkyd component added are controlled within appropriate ranges. Wherein, the degradable alkyd component can enter into the copolyester chain segment, the impact resistance of the polyester is greatly influenced by the content of the degradable alkyd component, and meanwhile, the foam can be slowly degraded under natural conditions. Therefore, the addition amount of the degradable alkyd component needs to be in the range, if the addition amount is too small, the degradation effect is not obvious, and if the addition amount is too large, the impact resistance of the material is not good. Too little diol comonomer addition results in a higher polyester melting point, with crystallization affecting foaming, and too much with severe sticking and increased cost.

Through the improvement of the two aspects, compared with the conventional polyester foam material, the degradable foaming copolyester can be slowly degraded under natural conditions, and the influence on an ecological system is minimized. Compared with the conventional polylactic acid foaming material, the degradable foaming copolyester has the advantages of high foaming ratio, good toughness, sufficient tensile strength, excellent heat and cold resistance, low processing cost and contribution to industrial production, and can be used in packaging and transportation industries.

Preferably, the diol comonomer is selected from one or more of propylene glycol, butylene glycol, 1, 4-cyclohexanedimethanol, and 2-butyl-2-ethyl-1, 3-propanediol; further preferred is one or more of 2-butyl-2 ethyl-1, 3-propanediol and 1, 4-cyclohexanedimethanol.

The 2-butyl-2-ethyl-1, 3-propanediol and 1, 4-cyclohexanedimethanol are further preferred because the difference between the structure of the ethylene glycol and the ethylene glycol is large, the original crystals can be destroyed by adding a small amount of ethylene glycol, and meanwhile, the ethylene glycol shows high polymerization activity in the polymerization process, the product has high viscosity, shows good melt strength and is beneficial to the growth of cells in the foaming process.

Preferably, the degradable alkyd component is selected from one or more of lactic acid oligomer with molecular weight of 2000-8000 and lactic acid monomer. Further preferred is a lactic acid oligomer having a molecular weight of 2000-.

During the research process, the inventor finds that the polyester degradability of the added lactic acid oligomer is better than that of the added lactic acid monomer, because the molecules of the lactic acid oligomer can enter into the polyester chain segment in a small block mode and are easier to degrade in the natural environment than the randomly arranged single lactic acid unit. The molecular weight of the selected lactic acid oligomer is 2000-8000, the degradation effect is not obvious when the molecular weight is too low, the lactic acid molecular chain is degraded in advance when the molecular weight is too high, the degradation effect generated after copolymerization is consistent with the lower molecular weight, and the polymerization effect is influenced.

Preferably, the catalyst is one or more selected from two-dimensional composite titanium heterogeneous polyester catalyst, ethylene glycol antimony, antimony trioxide, antimony acetate, tetrabutyl titanate, tetraisopropyl titanate and zinc acetate. Further preferably a two-dimensional composite titanium heterogeneous polyester catalyst, ethylene glycol antimony or tetrabutyl titanate.

Preferably, the stabilizer is triphenyl phosphite.

Triphenyl phosphite can effectively prevent degradation caused by high temperature in the synthesis process.

In a second aspect, the invention provides a preparation method of degradable foamed copolyester, which comprises the following steps:

(1) adding terephthalic acid, ethylene glycol, glycol comonomer and a catalyst into a polymerization reactor to carry out esterification reaction; after the esterification reaction, adding the stabilizer and the degradable alcohol acid component and uniformly stirring.

All raw materials except the stabilizer and the degradable alkyd component are added into a polymerization reactor at one time before polymerization is started, the stabilizer and the degradable alkyd component are added after the esterification process is finished, and premature addition of the stabilizer and the degradable alkyd component can cause hydrolysis at high temperature for a long time and also has certain influence on esterification.

(2) Heating and vacuumizing, and carrying out pre-polycondensation and final polycondensation reaction in sequence to obtain the random modified polyester chip.

(3) And (3) placing the random modified polyester slices into a foaming device, and filling a foaming agent medium to perform supercritical fluid foaming to prepare the degradable foamed copolyester. The density range of the obtained degradable expanded copolyester beads is 15-150kg/m³The diameter of the cells is 80-300 μm.

Preferably, in the step (1), the preheating temperature of the polymerization reactor is 50-160 ℃, the esterification reaction temperature is 190-250 ℃ and the pressure is 0.1-0.35 MPa.

Preferably, in the step (2), the conditions of the pre-polycondensation reaction are that the vacuum pumping is carried out for 60-120min to the absolute pressure of below 1000Pa, and the pre-polycondensation temperature is 240-280 ℃; the final polycondensation temperature is 245-285 ℃, the pressure is 0-500Pa, and the final polycondensation reaction time is 60-120 min.

Preferably, in the step (2), the obtained randomly modified polyester chip has an intrinsic viscosity of 0.50 to 0.95dl/g and a glass transition temperature of 60 to 80 ℃.

Preferably, in the step (3), the foaming agent is one or both of carbon dioxide and nitrogen.

Preferably, in the step (3), the foaming temperature is 80-200 ℃, the foaming pressure is 10-30MPa, the pressure maintaining time is 20-120min, the pressure relief time is controlled at 0-10s, and the cooling time is controlled at 0-30 min.

In the foaming process, the key steps are the control of pressure maintaining time and a pressure relief mode, and unreasonable pressure maintaining time can cause material bonding collapse and foaming failure; the pressure relief is not uniform, too fast can cause the foam cells to be too small and have low multiplying power, too slow can cause the foam cells to be too large, and the foam rebound rate is low.

Compared with the prior art, the invention has the following technical effects:

(1) on one hand, the invention destroys the crystallization by adding the diol comonomer except the ethylene glycol to form the random copolyester without melting point, and reduces the processing temperature; on the other hand, the addition of the alkyd degradable component in the invention endows the copolyester material with degradability. The finally obtained copolyester has good low-temperature foaming effect and is degradable.

(2) Compared with the conventional polyester foam material, the degradable foamed copolyester foam can be slowly degraded under natural conditions, and the influence on an ecological system is minimized. Compared with the conventional polylactic acid foaming material, the material obtained by foaming has high foaming ratio, good toughness, sufficient tensile strength and excellent heat and cold resistance, can be used for packaging and transportation industries, has lower processing cost and is beneficial to industrial production.

(3) The invention adopts an in-situ copolymerization method, directly synthesizes the final polymer from the monomer, and has simple preparation process.

Detailed Description

The present invention will be further described with reference to the following examples.

General examples

The degradable foamed copolyester comprises the following raw materials in parts by weight: 100 parts of terephthalic acid, 30-60 parts of ethylene glycol, 10-40 parts of glycol comonomer except the ethylene glycol, 0.1-10 parts of degradable alkyd component, 0.01-1 part of catalyst and 0.01-1 part of stabilizer.

Preferably, the diol comonomer is selected from one or more of propylene glycol, butylene glycol, 1, 4-cyclohexanedimethanol, and 2-butyl-2-ethyl-1, 3-propanediol; further preferred is one or more of 2-butyl-2 ethyl-1, 3-propanediol and 1, 4-cyclohexanedimethanol.

Preferably, the degradable alkyd component is selected from one or more of lactic acid oligomer with molecular weight of 2000-8000 and lactic acid monomer. Further preferred is a lactic acid oligomer having a molecular weight of 2000-.

Preferably, the stabilizer is triphenyl phosphite.

Preferably, the catalyst is one or more selected from two-dimensional composite titanium heterogeneous polyester catalyst, ethylene glycol antimony, antimony trioxide, antimony acetate, tetrabutyl titanate, tetraisopropyl titanate and zinc acetate. Further preferably a two-dimensional composite titanium heterogeneous polyester catalyst, ethylene glycol antimony and tetrabutyl titanate.

The preparation method of the two-dimensional composite titanium heterogeneous polyester catalyst comprises the following steps:

(a) mixing titanium carbide material MXene (Ti)₃C₂T_x、Ti₂CT_x、(Ti_0.5，Nb_0.5)₂CT_x、Zr₃C₂T_x、Ti₃CNT_x、Mo₂TiC₂T_xOr Mo₂Ti₂C₃T_x(ii) a T represents MXene surface group (-OH, -F, ═ O, etc.), x is positive integer, adding into corrosive agent (mixed solution of hydrochloric acid and fluorine salt, hydrochloric acid concentration is 6-9mol/L), molar ratio of fluorine salt and titanium carbide material MXene is 1: 7.5-9. Stirring sequentially (30-45 deg.C, 24-48h) under protective atmosphere, washing, drying, ultrasonic stripping, and alkali solution (4-10 wt% NaOH, KOH or Mg (OH))₂Solution) treatment (20-45 ℃ for 1-3h), centrifugation, washing and drying to obtain the alkalized two-dimensional MXene.

(b) Dissolving a guanidine modifier (guanidine, guanidine hydrochloride or guanidine-naphthalenesulfonic acid) in ethylene glycol to obtain a 10-30 wt% guanidine solution; dispersing the alkalized two-dimensional MXene in ethylene glycol to obtain 10-20 wt% of alkalized two-dimensional MXene dispersion liquid; and uniformly mixing the guanidine solution and the MXene dispersion liquid, wherein the mass ratio of the guanidine modifier to the alkalized two-dimensional MXene is 1: 5-10. Adjusting pH to 7-11 with pH regulator (triethanolamine, 2-aminomethyl propanol), and grinding (25-45 deg.C, 1-3h, grinding medium is mixed zirconium bead with diameter of 0.3-0.7mm, and filling ratio is 60-75%) to obtain grinding dispersion.

(c) Performing first-step centrifugation (1000-; storing at 5-10 deg.C in the absence of oxygen.

A preparation method of degradable foamed copolyester comprises the following steps:

(1) adding terephthalic acid, ethylene glycol, glycol comonomer and a catalyst into a polymerization reactor with the preheating temperature of 50-160 ℃ for esterification reaction; the esterification reaction temperature is 190 ℃ and 250 ℃ and the pressure is 0.1-0.35 MPa. After the esterification reaction, adding the stabilizer and the degradable alcohol acid component and uniformly stirring.

(2) Heating to 240-280 ℃, vacuumizing for 60-120min to the absolute pressure below 1000Pa, performing pre-polycondensation, and performing final polycondensation reaction at 245-285 ℃ and 0-500Pa for 60-120min to obtain the random modified polyester slice with the intrinsic viscosity of 0.50-0.95d1/g and the glass transition temperature of 60-80 ℃.

(3) Placing the random modified polyester chip in a foaming device, charging foaming agent medium (carbon dioxide and/or nitrogen) to perform supercritical fluid foaming, heating to 80-200 deg.C, maintaining the temperature and pressure at 10-30MPa for 2-120min, then relieving pressure for 0-10s, cooling for 0-30min to obtain the final product with density range of 15-150kg/m³And the diameter of the cells is 80-300 mu m.

Example 1

830g of terephthalic acid, 240g of ethylene glycol, 300g of 2-butyl-2-ethyl-1, 3-propanediol and 0.334g of ethylene glycol antimony were put into a 2.5L reactor, stirred at 150 ℃ for 10min and then N was introduced₂The esterification reaction is started under the conditions of 225 ℃ and 0.3MPaShould be used. After the end of the effluent, 0.48g of triphenyl phosphite, and 100g of lactic acid oligomer (molecular weight 2000-. The vacuum was pulled down for 90min while the kettle temperature was set to 270 ℃. After the vacuum meter reached-102 kPa, the vacuum was pulled high, and the torque reading was recorded, starting from the torque rise, and the reaction was carried out for 70 min. Stopping the reaction, discharging and pelletizing. Placing the prepared slices in a foaming kettle, charging foaming agent carbon dioxide, and preheating to 130 ℃ and 10MPa until the supercritical state is achieved. And (3) after keeping the constant temperature and the constant pressure for 20min, quickly decompressing for 4s to the normal pressure through a manual valve, cooling in ice water for 30min, opening the kettle body and drying to obtain the foaming beads.

Collecting foamed samples, carrying out density test, appearance observation and degradation test on the materials, preparing sample bars by using unfoamed raw materials, and carrying out impact resistance test, wherein the experimental formula and the test results are shown in table 1.

Comparative example 1: the difference from example 1 is that no lactic acid oligomer was added.

Comparative example 2: the difference from example 1 is that lactic acid monomer is added during the first step of adding raw materials, and no lactic acid oligomer is added.

Comparative example 3: the difference from example 1 is that an excess polylactic acid oligomer (30 parts or more) was added.

Comparative example 4: the difference from example 1 is that a small amount of lactic acid oligomer (0.01 part) was added.

Comparative example 5: the difference from example 1 is that no diol comonomer is added.

Comparative example 6: the difference from example 1 is that no diol comonomer and no lactic acid oligomer are added.

Example 2

830g of terephthalic acid, 240g of ethylene glycol, 300g of 2-butyl-2-ethyl-1, 3-propanediol and 0.334g of ethylene glycol antimony were put into a 2.5L reactor, stirred at 150 ℃ for 10min and then N was introduced₂The esterification reaction was started at 225 ℃ and 0.3 MPa. After the end of the effluent, 0.48g of triphenyl phosphite, and 180g of lactic acid oligomer (molecular weight 5000-. The vacuum was pulled down for 90min while the kettle temperature was set to 270 ℃. After the vacuum instrument reaches-102 kPa, high vacuum is pumped, torque reading is recorded, and torque reading is carried outThe moment rises and the reaction is started for 70 min. Stopping the reaction, discharging and pelletizing. Placing the prepared slices in a foaming kettle, charging foaming agent carbon dioxide, and preheating to 130 ℃ and 10MPa until the supercritical state is achieved. And (3) after keeping the constant temperature and the constant pressure for 20min, quickly decompressing for 4s to the normal pressure through a manual valve, cooling in ice water for 30min, opening the kettle body and drying to obtain the foaming beads.

Collecting foamed samples, carrying out density test, appearance observation and degradation test on the materials, preparing sample bars by using unfoamed raw materials, and carrying out impact resistance test, wherein the experimental formula and the test results are shown in table 1.

Example 3

830g of terephthalic acid, 240g of ethylene glycol, 280g of 1, 4-cyclohexanedimethanol and 0.334g of ethylene glycol antimony were put into a 2.5L reactor, stirred at 150 ℃ for 10min and then N was introduced₂The esterification reaction was started at 225 ℃ and 0.3 MPa. After the end of the effluent, 0.48g of triphenyl phosphite, and 100g of lactic acid oligomer (molecular weight 2000-. The vacuum was pulled down for 90min while the kettle temperature was set to 270 ℃. After the vacuum meter reached-102 kPa, the vacuum was pulled high, and the torque reading was recorded, starting from the torque rise, and the reaction was carried out for 70 min. Stopping the reaction, discharging and pelletizing. Placing the prepared slices in a foaming kettle, charging foaming agent carbon dioxide, and preheating to 130 ℃ and 10MPa until the supercritical state is achieved. And (3) after keeping the constant temperature and the constant pressure for 20min, quickly decompressing for 4s to the normal pressure through a manual valve, cooling in ice water for 30min, opening the kettle body and drying to obtain the foaming beads.

Collecting foamed samples, carrying out density test, appearance observation and degradation test on the materials, preparing sample bars by using unfoamed raw materials, and carrying out impact resistance test, wherein the experimental formula and the test results are shown in table 1.

Example 4

830g of terephthalic acid, 240g of ethylene glycol, 280g of 1, 4-cyclohexanedimethanol and 0.334g of ethylene glycol antimony were put into a 2.5L reactor, stirred at 150 ℃ for 10min and then N was introduced₂The esterification reaction was started at 225 ℃ and 0.3 MPa. After the end of the effluent, 0.48g of triphenyl phosphite, and 180g of lactic acid oligomer (molecular weight 5000-. Vacuumizing for 90min, and setting the temperature of the kettleTo 270 ℃. After the vacuum meter reached-102 kPa, the vacuum was pulled high, and the torque reading was recorded, starting from the torque rise, and the reaction was carried out for 70 min. Stopping the reaction, discharging and pelletizing. Placing the prepared slices in a foaming kettle, charging foaming agent carbon dioxide, and preheating to 130 ℃ and 10MPa until the supercritical state is achieved. And (3) after keeping the constant temperature and the constant pressure for 20min, quickly decompressing for 4s to the normal pressure through a manual valve, cooling in ice water for 30min, opening the kettle body and drying to obtain the foaming beads.

Collecting foamed samples, carrying out density test, appearance observation and degradation test on the materials, preparing sample bars by using unfoamed raw materials, and carrying out impact resistance test, wherein the experimental formula and the test results are shown in table 1.

Example 5 (different from example 4 in that 0.334g of ethylene glycol antimony was replaced with a ethylene glycol solution (catalyst content: 0.083g) of a two-dimensional composite titanium-based heterogeneous polyester catalyst)

The preparation method of the two-dimensional composite titanium heterogeneous polyester catalyst comprises the following steps:

(1) preparing 1L of 9mol/L hydrochloric acid solution, adding LiF with the total molar weight of 1.93mol, stirring to dissolve, adding 50g of raw material Ti₃AlC₂. Then, the atmosphere was replaced with argon gas, the mixture was sealed, and the mixture was stirred continuously at 40 ℃ for 48 hours and then washed with pure water until the pH was 7. After centrifugal separation, vacuum drying at 60 ℃ for 12h, adding the obtained powder into oxygen-free water according to the mass ratio of 1: 300, performing ultrasonic treatment for 1h, centrifuging at 3500rpm for 1h, adding KOH into the obtained suspension to enable the KOH mass concentration to be 6 wt%, continuously stirring at 25 ℃ for 2h, centrifuging and washing the sediment to pH 7, and finally centrifuging and vacuum drying for 12h to obtain the alkalized two-dimensional MXene.

(2) Dissolving 3g of guanidine in 12g of ethylene glycol to prepare a solution with the mass concentration of 20 wt%; 30g of the above-mentioned alkalized two-dimensional MXene was dispersed in 270g of ethylene glycol at a mass concentration of 10% by weight, and the guanidine solution was added to the MXene dispersion with stirring. Adjusting the pH value of the MXene dispersion liquid to 8 by using triethanolamine, and adjusting the temperature to 25 ℃; and fully grinding for 3 hours by using a grinder.

(3) The ground dispersion was centrifuged at 1500rpm for 30min in a centrifuge, the resulting sediment was removed and the suspension was centrifuged in the next step. And centrifuging at 8000rpm for 20min to obtain precipitate, and adjusting mass concentration of the obtained suspension to 8 wt% with ethylene glycol.

The catalyst is a catalyst self-developed by the applicant, and the preparation principle and the advantages thereof are as follows: firstly, corroding by using a corrosion reagent to remove an Al layer on MXene, simultaneously intercalating MXene by using metal ions in the corrosion reagent, stripping in an ultrasonic mode to obtain a large number of fragmented two-dimensional MXene, and then replacing Ti-F sites on the surface of MXene by using alkali to obtain the alkalified two-dimensional MXene with a large number of Ti-OH functional groups. Because the Ti-OH sites on the surface of the alkalized two-dimensional MXene are electronegative and are easy to react with amino compounds to form hydrogen bonds, the guanidine modifier is adopted to grind and modify the surface of the MXene, so that the grafting modification purpose can be achieved, and in the grinding process of the MXene, the solvent and the small guanidine molecules can be inserted into the MXene layers, the interlayer acting force is further weakened, so that the two-dimensional MXene can be further stripped, part of the MXene can be broken into small pieces of MXene in collision, and more terminal titanium sites are exposed. The two effects can improve the dispersibility of the MXeen catalyst, so that the polycondensation time is short, and the reaction speed is faster and more uniform. After modification, not only can guanidine be introduced to improve catalytic activity, but also a synergistic effect can be generated between the Ti-based site and the guanidine, so that the reaction process is balanced while the electron transfer is promoted to accelerate the reaction rate, the surface electrical property is favorably changed, the contact reaction between the Ti-based site and a hydroxylated substance in the polymerization process is blocked, the generation of a colored organic titanium compound is inhibited, and the hue deviation of polyester is avoided. In addition, the doping of a small amount of two-dimensional material is also beneficial to enhancing the strength of the polyester. Compared with an antimony catalyst, the catalyst is green and nontoxic, and can realize similar catalytic effect with a very small addition amount.

Performance testing

The foamed modified polyesters obtained in the examples and the comparative examples were subjected to performance tests, wherein:

1) intrinsic viscosity: polyester samples were dissolved in phenol: in a mixed solvent of tetrachloroethane at a mass ratio of 3: 2, the intrinsic viscosity of the sample was measured at room temperature using an Ubbelohde viscometer.

2) Melting point and glass transition temperature: and (3) adopting a differential scanning calorimeter to scan a sample for heating and cooling cycles between 30 and 280 ℃, and determining the melting point and the glass transition temperature of the polymer.

3) Foam density: the actual density of the foam beads was determined by draining and the average of 3 samples was taken.

4) Degradation period: the remaining weight was measured 45 days after burying in soil and 90 days after burying in soil.

5) Impact resistance: the unfoamed bars were tested using the Izod impact strength test method of ASTM D256.

The formulations and the test data of the samples obtained in the examples and comparative examples are shown in Table 1.

TABLE 1 comparison of sample parameters for each example and comparative example

It can be seen from the comparison of example 1, comparative example 1 and comparative example 2 that the addition of lactic acid oligomer can impart the degradable property to the copolyester material, and the polyester degradability of the addition of lactic acid oligomer as a preferred group is better than that of the lactic acid monomer as a non-preferred group, because the molecules of the preferred lactic acid oligomer can enter the polyester segment in a small block manner and are more easily degraded in the natural environment than the randomly arranged single lactic acid units. After the lactic acid oligomer molecules enter, the foaming performance of the material is slightly deteriorated, and the impact strength is also reduced. It can be seen from comparative examples 1, 3 and 4 that the amount of the lactic acid oligomer needs to be within a proper range, and the impact strength is obviously reduced when the amount is too high, because the proportion of lactic acid segments in the molecule is large, the characteristics of the lactic acid segments are close to those of polylactic acid, but the degradation performance of the lactic acid segments is not greatly increased, probably because the synthesis and degradation of the lactic acid molecule chain reach equilibrium at higher temperature in the reaction process, and the proportion of the lactic acid oligomer capable of entering the polyester molecular chain is limited. While the excessively low addition amount of comparative example 4 has a limited effect on the copolyester itself, and its characteristics are close to those of the normal copolyester. In addition, the foaming effect of the material also decreases with increasing lactic acid oligomer content. It can be seen from comparison of examples 1 and 2 that the molecular weight of the lactic acid oligomer has less influence on the degradation effect, the impact resistance of the material and the foaming effect, because at high temperature under the reaction conditions, the long chain may be degraded before entering into the copolyester chain, and then changed into the lactic acid oligomer with smaller molecular weight. Compared with the embodiment 4 and the embodiment 5, the self-developed two-dimensional composite titanium heterogeneous polyester catalyst can be used for obtaining a better copolyester foaming material, the foaming effect is not obviously different from that of an antimony system, the impact resistance of the foaming material is improved to a certain extent due to the doping of a small amount of two-dimensional material, and the degradability of the foaming material is slightly better than that of a foaming material of a common antimony system, so that the environment friendliness of the degradable copolyester is further improved. Comparative example 1, example 3, comparative example 5 and comparative example 6 show that the addition of the diol comonomer can enable the material to be foamed at a lower processing temperature, because the addition of the diol monomer destroys the original regularity of the polyester and changes the polyester into an amorphous material, which is beneficial to avoiding degradation of the material added with the degradable chain segment in the processing process, and the type of the added diol comonomer has little influence on the degradability and mainly influences the foaming characteristic and the mechanical property of the material. In addition, neither the glass transition temperature nor the intrinsic viscosity is greatly affected by the lactic acid oligomer.

As can be seen from the data of examples 1 to 5 and comparative examples 1 to 6, the above requirements can be satisfied in all aspects only by the scheme within the preferred range of the present invention, and the optimized random modified polyester for degradable foaming can be obtained. The change of the mixture ratio and the replacement/addition/subtraction of the raw materials can bring corresponding negative effects.

The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.