阅读说明：本技术 一种高强度高韧性高阻隔性的无规共聚酯及其制备方法 (High-strength high-toughness high-barrier random copolyester and preparation method thereof ) 是由 吴林波 孟洪旭 李志松 李伯耿 于 2021-07-28 设计创作，主要内容包括：本发明涉及高分子材料领域,公开一种高强度高韧性高阻隔性的无规共聚酯及其制备方法。包括65-95mol％的式(I)所示的呋喃二甲酸二元醇酯重复单元和5-35mol％的式(II)所示的间苯二甲酸二元醇酯重复单元；其制备方法是将二元酸或其二酯和二元醇混合得到混合物；再加入催化剂和稳定剂酯化得到中间产物,缩聚反应得到无规共聚酯；本发明以间苯二甲酸或其二酯作为共聚单体,与呋喃二甲酸或其二酯共聚,能够显著改善PEF、PTF等脆性的呋喃二甲酸聚酯的拉伸韧性的同时,实现了高效地保持其优异的力学强度和模量、气体阻隔性以及玻璃化温度的效果,克服了现有技术中多项良好性能不可兼得的问题。(The invention relates to the field of high polymer materials, and discloses high-strength, high-toughness and high-barrier random copolyester and a preparation method thereof. Comprises 65 to 95mol percent of furan dicarboxylic acid diol ester repeating units shown in a formula (I) and 5 to 35mol percent of isophthalic acid diol ester repeating units shown in a formula (II); the preparation method comprises mixing dibasic acid or diester thereof and dihydric alcohol to obtain a mixture; then adding a catalyst and a stabilizer for esterification to obtain an intermediate product, and carrying out polycondensation reaction to obtain random copolyester; the invention takes the isophthalic acid or diester thereof as a comonomer, and the isophthalic acid or diester thereof is copolymerized with the furandicarboxylic acid or diester thereof, so that the tensile toughness of brittle furandicarboxylic acid polyesters such as PEF and PTF can be obviously improved, and simultaneously, the effects of efficiently keeping excellent mechanical strength, modulus, gas barrier property and glass transition temperature are realized, and the problem that a plurality of good performances cannot be obtained simultaneously in the prior art is solved.)

1. A random copolyester with high strength, high toughness and high barrier property is characterized by comprising 65-95 mol% of furan dicarboxylic acid diol ester repeating units shown as a formula (I) and 5-35 mol% of isophthalic acid diol ester repeating units shown as a formula (II),

wherein R is an alkylene or substituted alkylene group having not more than 3 carbon atoms in the main chain; the intrinsic viscosity of the random copolyester is not less than 0.7 dL/g.

2. The high strength, high toughness and high barrier random copolyester of claim 1, wherein said random copolyester comprises 70 to 90 mole% of the repeating units of furandicarboxylic acid diol ester represented by formula (I) and 10 to 30 mole% of the repeating units of isophthalic acid diol ester represented by formula (II).

3. The high strength, high toughness and high barrier random copolyester of claim 1, wherein said repeating units of furan dicarboxylic acid diol ester are repeating units of 2, 5-furan dicarboxylic acid diol ester; r is selected from any one of ethylene, 1, 3-propylene or 2-methyl-1, 3-propylene.

4. A high strength, high toughness and high barrier random copolyester according to claim 1, wherein said random copolyester has an intrinsic viscosity of not less than 1.0 dL/g; young modulus is not less than 2.0GPa, tensile breaking strength is not less than 60MPa, breaking elongation is not less than 10%, and oxygen permeability coefficient is not more than 0.02 barrer.

5. A high strength, high toughness and high barrier property random copolyester according to claim 1, wherein the Young modulus of the random copolyester is not less than 3.0GPa, the tensile breaking strength is not less than 60MPa, the elongation at break is not less than 100%, and the oxygen permeability coefficient is not more than 0.015 barrer.

6. A process for preparing a high strength, high toughness, high barrier random copolyester according to any one of claims 1 to 5, which comprises the steps of:

(1) mixing dibasic acid or diester thereof and dihydric alcohol to obtain a mixture;

(2) adding a catalyst into the mixture to perform esterification reaction to obtain an intermediate product;

(3) carrying out polycondensation reaction on the intermediate product to obtain the random copolyester;

wherein the dibasic acid or diester thereof comprises 65 to 95 mol% of furan dicarboxylic acid or diester thereof and 5 to 35 mol% of isophthalic acid or diester thereof, based on 100 mol% of the total amount.

7. The method for preparing high-strength high-toughness high-barrier random copolyester according to claim 6, wherein in the step (1), the molar ratio of the dibasic acid or the diester thereof to the glycol is 1: 1.05-2.5; in the step (2), the mass of the catalyst is 0.01-0.5 wt% of that of the dibasic acid or the diester thereof.

8. The method for preparing high-strength high-toughness high-barrier random copolyester as claimed in claim 6, wherein in the step (2), the temperature of the esterification reaction is 170-210 ℃; the temperature of the polycondensation reaction is 230-280 ℃, and the absolute pressure is 5-200 Pa.

9. A method of preparing a high strength, high toughness, high barrier property random copolyester according to claim 6, wherein the catalyst comprises at least one of zinc acetate, cobalt acetate, antimony acetate, manganese acetate, tetrabutyl titanate, antimony trioxide, isopropyl titanate, ethylene glycol antimony, ethylene glycol titanium, dibutyl tin oxide.

10. The method for preparing high-strength high-toughness high-barrier random copolyester according to claim 6, wherein a stabilizer is added in step (2) or (3), and the stabilizer comprises at least one of phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, trimethyl phosphate, dimethyl phosphate, triphenyl phosphate, diphenyl phosphate, triphenyl phosphite, diphenyl phosphite, ammonium phosphite and ammonium dihydrogen phosphate; the mass of the stabilizer is 0-0.5 wt% of that of the dibasic acid or diester thereof.

Technical Field

The invention relates to the field of high polymer materials, in particular to high-strength high-toughness high-barrier random copolyester and a preparation method thereof.

Background

Furan dicarboxylic acid (FDCA) is an important biobased diacid monomer, has similar aromaticity and physical and chemical properties with terephthalic acid (TPA), and is considered to be an excellent substitute of TPA. Polyesters of furandicarboxylic acid and short-chain diols such as polyethylene furandicarboxylate (PEF) and 1, 3-propanediol Polyfurandicarboxylate (PTF) have higher glass transition temperatures (T.sub.t) than polyesters of terephthalic acid and short-chain diols such as polyethylene terephthalate (PET) and 1, 3-propanediol terephthalate (PTT)_g) Mechanical strength and modulus, and gas barrier properties, provide new opportunities for selection of high barrier packaging materials. However, compared with PET and PTT, PEF and PTF have obvious defects in performance, such as insufficient tensile toughness and impact toughness, the elongation at break is generally only 2-5%, the processing and application of the PEF and PTF are affected, and modification is urgently needed while the original performance advantages are maintained.

Copolymerization is a common means of improving polymer properties. For PEF and PTF, the tensile toughness of random copolyesters can be improved to a large extent by incorporating flexible aliphatic dibasic acids or diols and other monomers, but this often results in a significant reduction in glass transition temperature, tensile strength and modulus, and gas barrier properties. For example, document 1(Journal of Applied Polymer Science, volume 2018,135, 46076) reports that a series of PEDoF copolyesters were synthesized using dodecanedioic acid as a comonomer, and their elongations at break reached 380% while maintaining a certain tensile modulus (1.2GPa) and strength (45MPa), but their Telongations at break reached_gThe drop is significant. Chinese patent CN 108264634A discloses 2, 5-furandicarboxylic acid copolyester and a preparation method thereof, wherein cyclohexanedicarboxylic acid or dimethyl isoidide is used as a comonomer to carry out copolymerization modification on PEF and PTF, the copolyester with the comonomer content of 30-50 mol% has better modulus, strength and elongation at break, and the elongation at break is improved to the extent that the modulus, the strength and the elongation at break are better>30 percent, tensile modulus of 0.84-1.7GPa, tensile strength of 36-54MPa, obviously reduced tensile modulus and strength compared with PEF and PPF, and T_gAlso drops significantly to 48-53 ℃.

Because the high gas barrier property of the PEF is benefited by furan rings, the copolymerization of the PEF and aliphatic dibasic acid causes the reduction of the FDCA content, which inevitably causes the reduction of the gas barrier property; in contrast, copolymerization with a diol is advantageous in maintaining a high FDCA content, and thus, in maintaining gas barrier properties. Document 2(Polymer, volume 26 of 2016,103, 1-8) synthesizes a series of PECF copolyesters by using 1, 4-Cyclohexanedimethanol (CHDM) as a comonomer, when the content of cyclohexanedimethanol furandicarboxylate repeating units is 32-76 mol%, the toughness of the copolyesters is greatly improved (elongation at break is 50-186%), and good gas barrier property (O) is maintained₂And CO₂Barrier 4 times higher than PET). The Chinese invention patent CN 108129644A adopts CHDM to modify PEF, PPF and PBF through copolymerization, after CHDM accounting for 45 mol% of the total amount of dihydric alcohol is introduced, the copolyester improves the elongation at break (up to 130-_gBut the tensile modulus and strength are significantly reduced (20-32% and 9-38% respectively) compared to PEF. Chinese patent CN 108409949A discloses a 2, 5-furan dicarboxylic acid based copolyester material and a preparation method thereof, 1, 4-Cyclohexanedimethanol (CHDM) is adopted to copolymerize and modify PTF to synthesize PTCF copolyester, when the CHDM molar percentage is more than 30 mol%, the toughness of the copolyester is greatly improved (the elongation at break is 100-170%), and simultaneously, higher glass transition temperature (65-75 ℃) and better gas barrier property (O) are kept₂Barrier properties higher than PET). These systems using CHDM as a diol comonomer achieve better copolymerization toughening modification effect at higher CHDM content, but the high CHDM content increases the cost of the copolymer undoubtedly. Document 3(Biomacromolecules,2019, volume 20, 353-.

Lactones may also be used as comonomers.Document 3(European Polymer Journal,2018,109 vol., 191-197) reports that copolymerization of PEF and epsilon-caprolactone yields a series of samples P (EF-co-CL), in which the elongation at break is significantly increased (to 30-40%) when epsilon-caprolactone is added in an amount of 20-30 mol%; at 40 mol%, the elongation at break of the copolymer is up to 980%, while the modulus (1.2GPa) and strength (51MPa) are maintained at a high value, but the T is_gThe gas barrier property is not reported when the temperature is remarkably reduced to 34 ℃. Chinese patent CN 108467479A discloses toughened 2, 5-furandicarboxylic acid copolyester and a preparation method thereof, wherein a series of copolyesters synthesized by taking 2, 5-furandicarboxylic acid monomer, dihydric alcohol and lactone as raw materials have higher elongation at break and Young modulus, but T is T_gThe gas barrier property is not reported even if the temperature is remarkably reduced to 50 ℃.

In contrast to the flexible diacid, diol and lactone comonomers, rigid aromatic diacids are generally considered to be difficult to copolymerize as comonomers to toughen them, although rigid aromatic diacids have also been reported as comonomers for furan dicarboxylic acid polyesters. Chinese patent CN 102432847A discloses furandicarboxylic acid and C₂-C₈Copolyesters of linear diols with terephthalic acid have glass transition temperatures close to those of the corresponding polyethylene terephthalate, but do not relate to barrier properties and mechanical properties. Document 4 (journal of Polymer science, 2013, volume 8, 1092-. Compared with PEF homopolyester, the obtained copolyester can obviously improve the elongation at break only when the content of terephthalic acid is as high as 70-90 mol%, and has limited improvement on the elongation at break when the content of terephthalic acid is not 70-90 mol%, and lower strength and modulus. Therefore, the terephthalic acid modified PEF can well keep high glass transition temperature, but cannot obtain obvious toughening modification effect.

In summary, for furandicarboxylic acid polyesters PEF and PTF with excellent mechanical strength, modulus and gas barrier property, high glass transition temperature and brittleness, a small amount of comonomer is introduced to perform random copolymerization to significantly improve the tensile toughness of the furandicarboxylic acid polyesters PEF and PTF, and simultaneously maintain the mechanical strength, modulus, gas barrier property, glass transition temperature and other advantageous properties of the furandicarboxylic acid polyesters at high efficiency, which is still a technical problem to be solved for PEF and PTF modification.

Disclosure of Invention

The invention aims to solve the technical problems that the mechanical strength, the tensile modulus, the glass transition temperature and the gas barrier property of polyesters such as PEF and PTF are obviously reduced and multiple properties cannot be obtained simultaneously during copolymerization toughening in the prior art, and provides a random copolyester with high strength, high toughness and high barrier property.

In order to achieve the purpose, the invention adopts the technical scheme that:

a high-strength high-toughness high-barrier random copolyester comprises 65 to 95mol percent of furan dicarboxylic acid diol ester repeating units shown as a formula (I) and 5 to 35mol percent of isophthalic acid diol ester repeating units shown as a formula (II):

wherein R is an alkylene or substituted alkylene group having not more than 3 carbon atoms in the main chain; the intrinsic viscosity of the random copolyester is not less than 0.7 dL/g.

The invention takes specific rigid aromatic dibasic acid or diester thereof, namely isophthalic acid or diester thereof as comonomer, and copolymerizes the specific rigid aromatic dibasic acid or diester thereof with furandicarboxylic acid or diester thereof to prepare random copolyester, thereby surprisingly toughening the brittle furandicarboxylic acid polyesters such as PEF and PTF, and effectively maintaining the effects of excellent mechanical strength, modulus, gas barrier property and glass transition temperature while obviously enhancing the tensile toughness, obtaining the copolyester with excellent comprehensive performance, and overcoming the problem that a plurality of performances in the prior art cannot be obtained at the same time.

Preferably, the random copolyester comprises 70 to 90 mol% of furan dicarboxylic acid diol ester repeating units shown in the formula (I) and 10 to 30 mol% of isophthalic acid diol ester repeating units shown in the formula (II). In the preferred groupInsofar as the random copolyesters both retain a high T_gThe high-strength high-toughness polyethylene composite material has excellent tensile strength, modulus and gas barrier property, and simultaneously has a more remarkable tensile toughening effect, and the elongation at break is remarkably increased to more than 10 percent, even more than 100 percent.

Preferably, the furan dicarboxylic acid diol ester repeating unit is a 2, 5-furan dicarboxylic acid diol ester repeating unit; r is selected from any one of ethylene, 1, 3-propylene or 2-methyl-1, 3-propylene. Compared with 3, 4-furandicarboxylic acid, 2, 5-furandicarboxylic acid is easier to obtain and lower in cost; compared with 1, 2-propylene, the preferable dihydric alcohol corresponding to R is primary alcohol, which is beneficial to preparing high molecular weight polymer.

The random copolyester obtained by the invention has the intrinsic viscosity higher than 0.7dL/g, even higher than 1.0dL/g, the high intrinsic viscosity is beneficial to improving the tensile toughness and maintaining or improving the tensile strength, the Young modulus is not lower than 2.0GPa, the tensile breaking strength is not lower than 60MPa, the breaking elongation is not lower than 10 percent, and the oxygen permeability coefficient is not higher than 0.02 barrer.

Preferably, the Young modulus of the regular copolyester is not less than 3.0GPa, the tensile breaking strength is not less than 60MPa, the breaking elongation is not less than 100 percent, and the oxygen permeability coefficient is not more than 0.015 barrer.

The invention also provides a preparation method of the random copolyester with high strength, high toughness and high barrier property, which comprises the following steps:

(1) mixing dibasic acid or diester thereof and dihydric alcohol to obtain a mixture;

(2) adding a catalyst into the mixture to perform esterification reaction to obtain an intermediate product;

(3) carrying out polycondensation reaction on the intermediate product to obtain the random copolyester;

wherein the dibasic acid or diester thereof comprises 65 to 95 mol% of furan dicarboxylic acid or diester thereof and 5 to 35 mol% of isophthalic acid or diester thereof, based on 100 mol% of the total amount.

In the step (1), the molar ratio of the dibasic acid or the diester thereof to the dihydric alcohol is 1: 1.05-2.5; in the step (2), the mass of the catalyst is 0.01-0.5 wt% of that of the dibasic acid or the diester thereof.

In the step (2), the temperature of the esterification reaction is 170-210 ℃; the temperature of the polycondensation reaction is 230-280 ℃, and the absolute pressure is 5-200 Pa.

Preferably, the dibasic acid or diester thereof comprises 70 to 90 mol% of furan dicarboxylic acid or diester thereof, 10 to 30 mol% of isophthalic acid or diester thereof, based on 100 mol% of the total amount.

Preferably, the furan dicarboxylic acid diester is furan dicarboxylic acid dimethyl ester; the isophthalic acid diester is dimethyl isophthalate.

The catalyst is a compound or mixture based on at least one element of Ti, Sn, Sb, Pb, Ge, Zn, Fe, Mn, Co, Zr, Mg, V, Al or rare earth elements.

Preferably, the catalyst comprises at least one of zinc acetate, cobalt acetate, antimony acetate, manganese acetate, tetrabutyl titanate, antimony trioxide, isopropyl titanate, antimony glycol, titanium glycol and dibutyltin oxide. The catalyst can improve the reaction rate, accelerate the reaction progress and improve the yield.

Preferably, a stabilizer can be further added in step (2) or (3), wherein the stabilizer comprises at least one of phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, trimethyl phosphate, dimethyl phosphate, triphenyl phosphate, diphenyl phosphate, triphenyl phosphite, diphenyl phosphite, ammonium phosphite and ammonium dihydrogen phosphate. The dosage of the stabilizer is 0-0.5 wt% of the mass of the dibasic acid or the diester thereof.

In general, copolymerization with comonomers having a flexible structure can significantly improve the tensile toughness of rigid/brittle polymers, but also tends to result in significant decreases in tensile modulus, strength, glass transition temperature, and other physical properties such as gas barrier properties. If rigid comonomer is adopted for copolymerization, the physical and mechanical properties such as tensile modulus, strength, glass transition temperature, gas barrier property and the like are favorably maintained, but the effect of improving or remarkably improving the tensile toughness is difficult to achieve. The invention surprisingly discovers that when a rigid/brittle polyester such as PEF, PTF and the like is subjected to copolymerization modification by using a specific rigid aromatic dibasic acid monomer, i.e. isophthalic acid or diester thereof as a comonomer, the tensile toughness can be remarkably improved within a specific composition range, so that the rigid/brittle polyester is changed from brittle fracture to tough fracture, the elongation at break is increased from 2-4% to 10% or even more than 100%, the original excellent physical and mechanical properties such as tensile modulus, strength, glass transition temperature and gas barrier property can be well maintained, and the same modification effect cannot be achieved by using phthalic acid and terephthalic acid with similar structures as comonomers.

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

(1) in the invention, isophthalic acid or diester thereof is used as a modified monomer to be copolymerized with furan dicarboxylic acid or diester thereof, so that the toughening effect of furan dicarboxylic acid polyester is unexpectedly realized, and the copolyester can keep high glass transition temperature, excellent mechanical strength and modulus and excellent gas barrier property.

(2) The isophthalic acid or diester thereof is introduced in an amount of only 10-20 mol% to realize a good modification effect, the cost is low, the effect is good, the intrinsic viscosity of the obtained copolyester is higher than 0.7dL/g, even higher than 1.0dL/g, the preparation of the copolyester with high molecular weight is realized, and the preparation method is one of the reasons that the product can keep excellent mechanical properties.

(3) The preparation method of the random copolyester is efficient, economic and environment-friendly, consumes less comonomer and has low cost, thereby being beneficial to realizing large-scale production.

Drawings

FIG. 1 is a nuclear magnetic hydrogen spectrum of PEFI random copolyesters of different compositions.

FIG. 2 is a DSC second temperature rise curve for PEFI random copolyesters of different compositions.

FIG. 3 is a tensile stress-strain curve for PEFI random copolyesters of different compositions.

Fig. 4 is a tensile stress-strain curve for PEF-based random copolyesters of different comonomers.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Those skilled in the art should understand that they can make modifications and equivalents without departing from the spirit and scope of the present invention, and all such modifications and equivalents are intended to be included within the scope of the present invention.

The raw materials used in the following embodiments are all commercially available and used as they are without treatment. The test analysis method used therein is illustrated below:

characteristic viscosity number: the intrinsic viscosity of the sample was measured using a Hangzhou Zhongwang semi-automatic viscometer at 25 deg.C using phenol/tetrachloroethane (w/w: 3/2 mass ratio) as the solvent for PEI, PEF, and their copolyesters.

Nuclear magnetic hydrogen spectrum (¹H NMR): approximately 10mg of sample was dissolved in 0.5mL of deuterated trifluoroacetic acid (TFA-d) with TMS as an internal standard₁) The measurements were carried out using an AC-80 nuclear magnetic resonance apparatus (400MHz) from Bruker, Germany.

Thermal transition (DSC): DSC measurement is carried out on the sample by adopting a TA-Q200 thermal analyzer, and a standard temperature rising-reducing-temperature rising program is adopted. Firstly, heating from 30 ℃ to 280 ℃ at a heating rate of 10 ℃/min, and keeping for 5 min; then cooling to 30 ℃ at a cooling rate of 10 ℃/min, and preserving heat for 5 min; finally, the temperature is increased to 280 ℃ at the heating rate of 10 ℃/min.

Tensile strength: 6 groups of dumbbell-shaped sample bars with the thickness of 2mm and the width of 4mm are prepared by a Haake MiniJet II micro injection molding machine. Tensile tests were carried out according to ASTM D638 using a Roell Z020 model universal material testing machine, Zwick, Germany, at 25 ℃ and a tensile rate of 10mm/min, and the average value was taken as the test result.

Gas permeability: the polyester samples were hot-pressed into film samples having a film thickness of about 300. mu.m. The oxygen permeability coefficient of the sample was measured using a BSG-33E gas permeability tester of the electromechanical technology ltd, west down, guangzhou, china under the conditions of 1atm, 23 ℃ and high purity oxygen (99.9%). Each sample was tested for 3 sheets of the hot-press formed film sample gas permeability coefficient, and the average value was taken as the test result.

Example 1 copolyester PEFI₁₂Synthesis of (2)

2, 5-furandicarboxylic acid (70.0 g, 0.45mol), isophthalic acid (8.3 g, 0.05mol), and ethylene glycol (62.6 g, 1.01mol) were added to a 250mL flask and mixed well to give a monomer mixture; adding titanium glycol in an amount which is 0.3 percent of the total mass of the dibasic acid into the monomer mixture, carrying out normal pressure esterification reaction at the temperature of 180-200 ℃ under the protection of nitrogen, and obtaining an intermediate product after the reaction is carried out for 5 hours;

after the esterification reaction is finished, heating the intermediate product to 240 ℃ within 45min, reducing the pressure to 50Pa, reacting for 1.3h at constant temperature, then heating to 250 ℃, reacting for 3.5h at 250 ℃, and then stopping the reaction to obtain brown yellow poly (2, 5-furandicarboxylic acid-co-ethylene isophthalate).

Testing the nuclear magnetic spectrum, DSC and tensile strength of the product, wherein the nuclear magnetic spectrum is shown in figure 1, and the spectral peaks at 8.92ppm, 9.46ppm and 7.71ppm correspond to the chemical shifts of H atoms (g, H and i) on the benzene ring of the isophthalic acid residue; the peak at 7.53ppm corresponds to the chemical shift of the H atom (f) on the furan ring of the 2, 5-furandicarboxylic acid residue; the peak at 4.98ppm corresponds to the chemical shift of the H atom (a) of the ethylene group attached to the ester group in the ethylene of the ethylene-2, 5-furandicarboxylate (EF) mer (note: the mer is also called repeat unit), the Ethylene Isophthalate (EI) mer. In addition, very small peaks appear at δ -4.84 ppm (b) and δ -4.36 ppm (c), corresponding to the methylene groups in the diethylene glycol residues in the diethylene glycol 2, 5-furandicarboxylate (DF) and isophthalic acid (DI) segments. This is because, in the polycondensation or copolycondensation reaction involving ethylene glycol, the terminal hydroxyethyl ester group of ethylene glycol or an intermediate inevitably causes an etherification side reaction, and therefore, it is known that a small amount of diethylene glycol diester units of dibasic acid is formed in addition to the ethylene glycol ester units of dibasic acid. The diacid diglycol ester is generally not distinguished from the diacid glycol ester linkages because of its low content. In the present invention, such a treatment is also employed that the ethylene furandicarboxylate segment and the diethylene furandicarboxylate segment are not distinguished and collectively referred to as the ethylene furandicarboxylate segment; indiscriminate isophthalic acid ethylene glycolAlcohol ester units and diethylene glycol isophthalate units, which are collectively referred to as ethylene isophthalate units. According to the above description, the copolymer composition can be defined and calculated by the corresponding nuclear magnetic peak area, see formula (3), wherein I_hAnd I_fPeak areas at chemical shifts h and f, respectively.

According to¹The calculated H NMR spectrum gives an EI chain link content of 12 mol%, so that the copolyester is designated as PEFI₁₂(ii) a The DSC curve is shown in figure 2, and the tensile curve is shown in figure 3.

Example 2 copolyester PEFI₂₀Synthesis of (2)

2, 5-furandicarboxylic acid (60.1 g, 0.39mol), isophthalic acid (16.0 g, 0.09mol), and ethylene glycol (61.8 g, 1.00mol) were added to a 250mL flask and mixed well to give a monomer mixture;

adding titanium glycol in an amount which is 0.3 percent of the total mass of the dibasic acid into the monomer mixture, carrying out normal pressure esterification reaction at the temperature of 180-200 ℃ under the protection of nitrogen, and reacting for 4.5h to obtain an intermediate product;

after the esterification reaction is finished, heating the intermediate product to 240 ℃ within 60min, reducing the pressure to 50Pa, reacting for 1.0h at constant temperature, heating to 10 ℃ every 1h until the temperature is 270 ℃, reacting for 1h until obvious rod climbing effect appears, and stopping the reaction to obtain brown yellow poly (2, 5-furandicarboxylic acid-co-ethylene isophthalate), wherein the method comprises the steps of¹The H NMR spectrum calculated gives a content of EI chain units of 20 mol%, so that the copolyester is designated as PEFI₂₀(ii) a The DSC curve is shown in figure 2, and the tensile curve is shown in figure 3.

Example 3 copolyester PEFI₃₀Synthesis of (2)

2, 5-furandicarboxylic acid (56.0 g, 0.36mol), isophthalic acid (25.8 g, 0.16mol), and ethylene glycol (62.0 g, 1.00mol) were added to a 250mL flask and mixed well to give a monomer mixture;

adding titanium glycol in an amount which is 0.3 percent of the total mass of the dibasic acid into the monomer mixture, carrying out normal pressure esterification reaction at the temperature of 180-200 ℃ under the protection of nitrogen, and reacting for 5.5h to obtain an intermediate product;

after the esterification reaction is finished, heating the intermediate product to 240 ℃ within 55min, reducing the pressure to 50Pa, reacting for 0.8h at constant temperature, then heating to 10 ℃ every 1h until the temperature is lower than 270 ℃, reacting for 1h until obvious rod climbing effect appears, and then stopping the reaction to obtain brown yellow poly (2, 5-furandicarboxylic acid-co-ethylene isophthalate), wherein the poly (ethylene isophthalate) is brown yellow¹The H NMR spectrum is shown in FIG. 1, according to¹The calculated H NMR spectrum gave an EI chain unit content of 30 mol%, so that the copolyester was designated as PEFI₃₀(ii) a The DSC curve is shown in figure 2, and the tensile curve is shown in figure 3.

Example 4 copolyester PTFI₃₀Synthesis of (2)

Adding dimethyl 2, 5-furandicarboxylate (67.6 g, 0.37mol), dimethyl isophthalate (31.3 g, 0.17mol) and 1, 3-propanediol (101.1 g, 1.33mol) into a 250mL flask, and uniformly mixing to obtain a monomer mixture;

tetrabutyl titanate accounting for 0.5 percent of the total mass of the dibasic acid is added into the monomer mixture, and the normal pressure esterification reaction is carried out under the protection of nitrogen and at the temperature of 170-210 ℃, and after the reaction is carried out for 3 hours, an intermediate product is obtained;

after the esterification reaction is finished, 0.1% triphenyl phosphite is added into the intermediate product, the temperature is raised to 240 ℃ within 40min, the pressure is reduced to 50Pa, the reaction is carried out for 0.5h at constant temperature, then the temperature is raised to 10 ℃ every 0.5h until the temperature is lower than 280 ℃, the reaction is continued for 1h until obvious rod climbing effect appears, and then the reaction is stopped, so that the brown yellow poly (2, 5-furandicarboxylic acid-co-isophthalic acid trimethylene glycol ester) is obtained. The copolyester is denoted PTFI₃₀。

Example 5 copolyester PMFI₃₀Synthesis of (2)

Adding dimethyl 2, 5-furandicarboxylate (67.0 g, 0.36mol), dimethyl isophthalate (30.3 g, 0.16mol) and 2-methyl-1, 3 propanediol (90.0 g, 1.00mol) into a 250mL flask, and mixing uniformly to obtain a monomer mixture;

antimony trioxide and triphenyl phosphate accounting for 0.2 percent of the total mass of the dibasic acid and accounting for 0.3 percent of the total mass of the dibasic acid are added into the monomer mixture, and under the protection of nitrogen, normal pressure esterification reaction is carried out at the temperature of 170-210 ℃, and after the reaction is carried out for 5.5 hours, an intermediate product is obtained;

after the esterification reaction is finished, heating the intermediate product to 240 ℃ within 40min, reducing the pressure to 50Pa, reacting for 1h at constant temperature, heating for 10 ℃ every 1h until the temperature is 270 ℃, reacting for 1.2h until obvious rod climbing effect appears, and stopping the reaction to obtain brown yellow poly (2, 5-furandicarboxylic acid-co-isophthalic acid 2-methyl 1, 3-propylene glycol ester), wherein the copolyester is marked as PMFI₃₀。

COMPARATIVE EXAMPLE 1 Synthesis of homopolyester PEF (without isophthalic acid monomer)

Uniformly mixing the 2, 5-furandicarboxylic acid (70.1 g, 0.45mol) and ethylene glycol (57.8 g, 0.93mol), adding titanium glycol with the mass being 0.3% of that of the 2, 5-furandicarboxylic acid, carrying out esterification reaction under the conditions of the temperature being 180 DEG and the pressure being 0.1MPa under the protection of nitrogen, and obtaining an intermediate product after the reaction is carried out for 3.5 h;

after the esterification reaction is finished, the temperature is increased to 240 ℃, the pressure is reduced to 50Pa within 40min for reaction, and after the reaction is carried out for 4.5h, light tan poly (ethylene 2, 5-furandicarboxylate) is obtained, and the light tan poly (ethylene 2, 5-furandicarboxylate) is obtained¹The H NMR spectrum is shown in FIG. 1, the DSC curve is shown in FIG. 2, and the tensile curve is shown in FIG. 3.

Comparative example 2 Synthesis of homopolyester PEI

Uniformly mixing isophthalic acid (76.0 g, 0.48mol) and ethylene glycol (61.8 g, 1.00mol), adding titanium glycol with the mass being 0.3% of that of the isophthalic acid, carrying out esterification reaction under the conditions of the temperature of 180-;

after the esterification reaction is finished, heating to 240 ℃, reducing the pressure to 50Pa within 40min for reaction, then heating to 10 ℃ every 1h until the temperature is lower than 270 ℃, continuing the reaction for 1.5h until a rod climbing effect appears, and stopping the reaction to obtain pale yellow polyethylene isophthalate, wherein the pale yellow polyethylene isophthalate is obtained¹The H NMR spectrum is shown in FIG. 1, the DSC curve is shown in FIG. 2, and the tensile curve is shown in FIG. 3.

Comparative example 3 copolyester PEFI₄₀Synthesis of (2)

2, 5-furandicarboxylic acid (48.5 g, 0.31mol), isophthalic acid (34.6 g, 0.21mol), and ethylene glycol (61.8 g, 1.00mol) were added to a 250mL flask and mixed well to give a monomer mixture;

adding titanium glycol in an amount which is 0.3 percent of the total mass of the dibasic acid into the monomer mixture, carrying out normal pressure esterification reaction at the temperature of 180-200 ℃ under the protection of nitrogen, and obtaining an intermediate product after the reaction is carried out for 5 hours;

after the esterification reaction is finished, heating the intermediate product to 240 ℃ within 40min, reducing the pressure to 50Pa, reacting for 1h at constant temperature, heating to 10 ℃ every 1h until the temperature is 270 ℃, reacting for 1h until obvious rod climbing effect appears, and stopping the reaction to obtain brown yellow poly (2, 5-furandicarboxylic acid-co-isophthalic acid glycol ester) which is¹The H NMR spectrum is shown in FIG. 1, according to¹The H NMR spectrum calculated gives a content of EI chain units of 40 mol%, so that the copolyester is designated as PEFI₄₀(ii) a The DSC curve is shown in figure 2, and the tensile curve is shown in figure 3.

Comparative example 4 copolyester PEFI₅₀Synthesis of (2)

2, 5-furandicarboxylic acid (42.4 g, 0.27mol), isophthalic acid (45.2 g, 0.27mol), and ethylene glycol (67.4 g, 1.09mol) were added to a 250mL flask and mixed well to give a monomer mixture;

adding titanium glycol in an amount which is 0.3 percent of the total mass of the dibasic acid into the monomer mixture, carrying out normal pressure esterification reaction at the temperature of 180-200 ℃ under the protection of nitrogen, and reacting for 5.5h to obtain an intermediate product;

after the esterification reaction is finished, heating the intermediate product to 240 ℃ within 40min, reducing the pressure to 50Pa, reacting for 0.8h at constant temperature, then heating to 10 ℃ every 1h until the temperature is lower than 270 ℃, reacting for 1h until obvious rod climbing effect appears, and then stopping the reaction to obtain brown yellow poly (2, 5-furandicarboxylic acid-co-ethylene isophthalate), wherein the poly (2, 5-furandicarboxylic acid-co-ethylene isophthalate) is prepared¹The H NMR spectrum is shown in FIG. 1, according to¹The H NMR spectrum calculated gives a content of EI chain units of 50 mol%, so that the copolyester is designated as PEFI₅₀Which is¹The H NMR spectrum is shown in FIG. 1, and the DSC curve is shown in FIG. 2.

Comparative example 5 copolyester PEPE₁₈Synthesis of F

Adding 2, 5-furandicarboxylic acid (70.0 g, 0.45mol), ethylene glycol (50.2 g, 0.81mol) and 1, 5-pentanediol (9.4 g, 0.09mol) into a 250mL flask, and uniformly mixing to obtain a monomer mixture;

adding tetrabutyl titanate accounting for 0.3 percent of the mass of 2, 5-furandicarboxylic acid into the monomer mixture, carrying out normal pressure esterification reaction for 1h at the temperature of 190 ℃ under the protection of nitrogen, and then heating to 200 ℃ for reaction for 3h to obtain an intermediate product;

after the esterification reaction is finished, heating the intermediate product to 230 ℃ within 40min, reducing the pressure to 50Pa, reacting for 1h at constant temperature, then heating to 240 ℃ and reacting for 3h at 240 ℃, and then stopping the reaction to obtain grayish yellow poly (ethylene-co-pentanediol 2, 5-furandicarboxylate), wherein the grayish yellow poly (ethylene-co-pentanediol 2, 5-furandicarboxylate) is obtained according to the formula¹The H NMR spectrum calculated gives a content of PeF mer of 18 mol%, so that the copolyester is designated PEPE₁₈F。

Comparative example 6 copolyester PEFT₂₀Synthesis of (2)

Adding 2, 5-furandicarboxylic acid (69.6 g, 0.45mol), terephthalic acid (18.7 g, 0.18mol) and ethylene glycol (70.1 g, 1.13mol) into a 250mL flask, and uniformly mixing to obtain a monomer mixture;

adding titanium glycol in an amount which is 0.3 percent of the total mass of the dibasic acid into the monomer mixture, carrying out normal pressure esterification reaction at the temperature of 180-200 ℃ under the protection of nitrogen, and obtaining an intermediate product after the reaction is carried out for 5 hours;

after the esterification reaction is finished, heating the intermediate product to 240 ℃ within 40min, reducing the pressure to 50Pa, reacting for 1h at constant temperature, heating 10 ℃ every 1h until the temperature is lower than 280 ℃, reacting for 1h until obvious rod climbing effect appears, and stopping the reaction to obtain brown yellow poly (2, 5-furandicarboxylic acid-co-ethylene terephthalate), wherein the copolyester is marked as PEFT₂₀The tensile curve is shown in FIG. 4.

Comparative example 7 copolyester PEFO₂₀Synthesis of (2)

Adding 2, 5-furandicarboxylic acid (61.1 g, 0.40mol), phthalic acid (16.7 g, 0.10mol) and ethylene glycol (62.1 g, 1.00mol) into a 250mL flask, and uniformly mixing to obtain a monomer mixture;

adding titanium glycol in an amount which is 0.3 percent of the total mass of the dibasic acid into the monomer mixture, carrying out normal pressure esterification reaction at the temperature of 180-200 ℃ under the protection of nitrogen, and obtaining an intermediate product after the reaction is carried out for 5 hours;

after the esterification reaction is finished, heating the intermediate product to 240 ℃ within 40min, reducing the pressure to 50Pa, reacting for 0.8h at constant temperature, heating to 10 ℃ every 1h until the temperature is lower than 280 ℃, reacting for 1h until obvious rod climbing effect appears, and stopping the reaction to obtain brown yellow poly (2, 5-furandicarboxylic acid-co-ethylene phthalate), wherein the copolyester is marked as PEFO₂₀The tensile curve is shown in FIG. 4.

The copolymer compositions, intrinsic viscosities, glass transition temperatures, tensile mechanical properties and oxygen barrier properties of the polyesters and copolyesters synthesized in the examples and comparative examples are summarized in table 1.

TABLE 1 results of various property tests of homo-and copolyesters prepared in examples and comparative examples

^a: the glass transition temperature is obtained by a DSC second heating curve;

^b: the intrinsic viscosity is measured at 25.0 ℃ and the solvent is a mixed solvent of phenol and tetrachloroethane (the mass ratio w/w is 3/2);

^c-g: respectively testing the Young modulus, the yield strength, the breaking strength, the yield elongation and the breaking elongation at 25 ℃ and 10mm/min of tensile rate;

^h: oxygen permeability coefficient, the sample was hot-pressed into a film having a thickness of about 0.3mm, measured at 23 ℃ under 1atm of high purity oxygen, and the unit was barrer, 1barrer ═ 7.50E^-18m³.m.m^-2.s^-1.Pa^-1。

From the results of comparative examples 1 and 2, it is seen that unmodified PEF and PEI homopolyester are high strength, high modulus, brittle polymers with elongation at break of less than 5% and high gas barrier and glass transition temperature.

From the results of examples 1-3, it can be seen that by adding 10-30 mol% of isophthalic acid as a comonomer to modify the PEF by copolymerization, a copolyester with high intrinsic viscosity can be obtained, the tensile toughness of the obtained copolyester is significantly improved, the elongation at break is increased to 19-112%, and the tensile modulus, yield strength, breaking strength, glass transition temperature and oxygen barrier property of the copolyester are well maintained compared with PEF homopolyester.

Comparing example 2 with comparative example 5, it can be seen that PEFI is a copolyester of PEF₂₀And PEPE₁₈F have similar copolymer composition (PEFI)₂₀:20mol％EI；PEPe₁₈18 mol% PeF) and both have significantly improved tensile toughness while maintaining high tensile strength, modulus, glass transition temperature, and gas barrier properties, but in comparison, PEFI₂₀The yield strength, the breaking strength, the glass transition temperature and the oxygen barrier property of the composite material are comprehensively superior to those of PEPE₁₈F, especially PEFI₂₀Has breaking strength and glass transition temperature which are obviously higher than PEPE₁₈F。

Comparing examples 1-3 and comparative examples 3-4, it can be seen that the PEFI copolyester loses ductile fracture property and changes into brittle fracture again when the EI chain link content is more than or equal to 40 mol%, which shows that the effect of stretching and toughening can be achieved only within a proper copolymer composition range.

Comparing example 2 with comparative examples 6-7, it can be seen that the copolyester PEFO obtained using phthalic acid or terephthalic acid of similar structure as comonomer, at the same composition₂₀And PEFT₂₀Although the tensile modulus and the breaking strength are higher, the breaking elongation is only about 4 percent and is equivalent to PEF, and the phthalic acid or the terephthalic acid serving as the comonomer cannot play an effective toughening effect.

In summary, although polyethylene isophthalate (PEI) is a hard and brittle polyester material, a proper amount of isophthalic acid as a comonomer has unexpected special tensile toughening modification effect on brittle furandicarboxylic acid polyesters such as PEF and PTF, and the obtained random copolyester has the characteristics of high intrinsic viscosity, high glass transition temperature, high modulus, high strength, high tensile toughness and high barrier property in a specific composition range, and can be used as high-performance materials such as engineering plastics and high-barrier packages.