A PBT copolyester with high glass transition temperature and preparation method thereof

Abstract

The invention discloses a PBT copolyester with a high glass transition temperature and a preparation method thereof. The PBT copolyester is a linear copolyester containing a butylene terephthalate block and a 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methyl terephthalate block. The 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methyl terephthalate block is provided by a monomer obtained by acetalization reaction of 5-hydroxymethylfurfural and trimethylolpropane. Since the main acetal structure and furan structure of the monomer have good rigidity, introducing the monomer into the PBT polyester can effectively improve the glass transition temperature of the PBT, thereby broadening the application range of the PBT. In addition, the preparation method of the PBT copolyester of the invention has mild reaction conditions, a simple synthesis process, easy operation, high synthesis yield, and has the prospect of large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, the utilization of renewable resources and the technical field of green synthesis, and in particular to a PBT copolyester with a high glass transition temperature and a preparation method thereof. Background Art

[0002] Polybutylene terephthalate (PBT) is a biodegradable aliphatic polyester with numerous advantages, including excellent mechanical properties and good biodegradability. It is one of the most promising environmentally friendly materials to replace traditional polymers, primarily used in packaging, tableware, and biomedical devices. However, its low glass transition temperature of 30°C makes it unsuitable for high-temperature applications.

[0003] Under normal circumstances, a variety of methods can be used to increase the glass transition temperature of PBT: 1) Blending modification, such as improving the performance of PBT by adding inorganic fillers, organic small molecule additives or macromolecular modifiers to the PBT melt; 2) Copolymerization modification, such as introducing copolymer components such as flexible structural monomers and rigid structural monomers into the PBT main chain to improve the performance of PBT; 3) Copolymerization / blending modification, such as copolymerizing PBT and then further melt blending it with unmodified PBT for modification.

[0004] However, the above methods have many problems, such as the high cost of modified raw materials, complex modification steps, cumbersome operations, and the modified raw materials still come from non-renewable petrochemical by-products. Summary of the Invention

[0005] In view of this, the present invention provides a PBT copolyester with a glass transition temperature and a preparation method thereof, which solves the problems of various existing methods for increasing the glass transition temperature of PBT, such as complex modification steps, cumbersome operations, and the modified raw materials coming from non-renewable petrochemical by-products.

[0006] In a first aspect, the PBT copolyester having a high glass transition temperature is a linear copolyester containing a butylene terephthalate block and a 5-ethyl-2-(5-hydroxymethyl-2-furyl)-1,3-dioxane-5-methyl terephthalate block, and has a number average molecular weight of not less than 10,000 g / mol.

[0007] In the present disclosure and possible embodiments, based on the total molar sum of each block being 100%, the 5-ethyl-2-(5-hydroxymethyl-2-furyl)-1,3-dioxane-5-methyl terephthalate block accounts for 5%-50%, and the remainder is the butylene terephthalate block.

[0008] In the present disclosure and possible embodiments, the 5-ethyl-2-(5-hydroxymethyl-2-furyl)-1,3-dioxane-5-methyl terephthalate block accounts for 20% to 50%.

[0009] In a second aspect, the preparation method of the PBT copolyester described in the first aspect is to obtain it by bulk polymerization of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, dimethyl terephthalate and 1,4-butanediol.

[0010] In the present disclosure and possible embodiments, the bulk polymerization method includes:

[0011] The 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, dimethyl terephthalate, and 1,4-butanediol are placed in a closed reactor, a catalyst is added, and the mixed system in the reactor sequentially undergoes an ester exchange reaction, a pre-condensation reaction, and a polycondensation reaction to obtain the PBT copolyester.

[0012] In the present disclosure and possible embodiments, the ratio of the molar amount of dimethyl terephthalate to the sum of the molar amounts of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol and 1,4-butanediol is 1:1.2-3.

[0013] In the present disclosure and possible embodiments, the ratio of the molar amount of dimethyl terephthalate to the sum of the molar amounts of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol and 1,4-butanediol is 1:1.5; and / or,

[0014] The catalyst is dibutyltin oxide, and the added amount thereof is 0.05% to 0.4% of the sum of the molar amounts of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol and 1,4-butanediol.

[0015] In the present disclosure and possible embodiments, the catalyst is added in an amount of 0.1% to 0.3% of the sum of the molar amounts of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol and 1,4-butanediol; and / or,

[0016] The transesterification reaction is carried out under nitrogen protection, with a reaction temperature of 180-230° C. and a reaction time of 8-10 hours.

[0017] In the present disclosure and possible embodiments, the transesterification reaction temperature is 220° C.; and / or,

[0018] The vacuum degree of the pre-polycondensation reaction is 5kPa-20kPa, the reaction temperature is 220-240°C, and the reaction time is 0.5-1h.

[0019] In the present disclosure and possible embodiments, the vacuum degree of the pre-polycondensation reaction is 12 kPa; and / or,

[0020] The polycondensation reaction is carried out under a vacuum degree of less than or equal to 60 Pa, the polycondensation reaction temperature is 240° C., and the polycondensation reaction time is 2 to 5 hours.

[0021] In the present disclosure and possible embodiments, the method for preparing 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol comprises:

[0022] 5-Hydroxymethylfurfural and trimethylolpropane are dissolved in a solvent, and under acidic conditions and stirring, the 5-Hydroxymethylfurfural and the trimethylolpropane undergo an acetalization reaction, and the reaction product is post-treated to obtain the 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol.

[0023] In the present disclosure and possible embodiments, the molar ratio of the 5-hydroxymethylfurfural to the trimethylolpropane is 1:1.05-1.50; and / or,

[0024] The solvent is isopropyl alcohol; and / or,

[0025] The acetalization reaction temperature is 20-35° C., and the reaction time is 12-24 hours; and / or,

[0026] generating the acidic conditions by p-toluenesulfonic acid; and / or,

[0027] The post-processing method comprises:

[0028] After the acetalization reaction is completed, the solvent in the reaction product is removed by evaporation.

[0029] The present invention has the following beneficial effects:

[0030] The PBT copolyester disclosed herein is obtained by copolymerizing 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol monomer. This monomer is synthesized based on 5-hydroxymethylfurfural, a green, renewable resource with a wide range of sources. The PBT copolyester synthesized using 5-hydroxymethylfurfural as a raw material can reduce dependence on petrochemical resources. In addition, because the main acetal structure and furan structure of this monomer have good rigidity, introducing them into PBT polyester can effectively increase its glass transition temperature, thereby broadening the scope of use of PBT. At the same time, the method for preparing the PBT copolyester of the present invention has mild reaction conditions, a simple and easy-to-operate synthesis process, a high synthesis yield, and has the prospect of large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0032] Figure 1 PHT of Example 2 20 BT 80 DSC melting curve of copolyester;

[0033] Figure 2 PHT of Example 3 50 BT 50 H NMR spectrum of copolyester;

[0034] Figure 3 PHT of Example 3 50 BT 50 DSC melting curve of copolyester. DETAILED DESCRIPTION

[0035] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts not described in detail, those skilled in the art can also fully understand the present disclosure.

[0036] The PBT copolyester with a high glass transition temperature of the present invention comprises a butylene terephthalate block represented by formula (I) and a 5-ethyl-2-(5-hydroxymethyl-2-furyl)-1,3-dioxane-5-methyl terephthalate block represented by formula (II) in its molecular structure;

[0037]

[0038] The PBT copolyester is named polybutylene terephthalate-co-5-ethyl-2-(5-hydroxymethyl-2-furyl)-1,3-dioxane-5-methyl terephthalate, and its number average molecular weight is not less than 10,000 g / mol.

[0039] In the molecular structure of the PBT copolyester, based on the total molar sum of all blocks being 100%, the 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methyl terephthalate block preferably accounts for 5% to 50%, with the remainder being butylene terephthalate blocks. More preferably, the 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methyl terephthalate block accounts for 20% to 50%.

[0040] In the embodiment of the present disclosure, the PBT copolyester is obtained by bulk polymerization of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, dimethyl terephthalate, and 1,4-butanediol. Specifically, 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, dimethyl terephthalate, and 1,4-butanediol are put into a closed reactor, a catalyst is added, and an ester exchange reaction, a pre-condensation reaction, and a final polycondensation reaction are carried out in sequence to obtain the PBT copolyester. Among them, the ratio of the molar amount of dimethyl terephthalate to the sum of the molar amounts of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol and 1,4-butanediol is 1:1.2-3, and preferably the ratio is 1:1.5.

[0041] The catalyst is dibutyltin oxide, and the amount of the catalyst added is 0.05% to 0.4% of the total molar amount of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol and 1,4-butanediol, preferably 0.1% to 0.3%.

[0042] The temperature of the transesterification reaction is 180-230° C., and the time of the transesterification reaction is 8-10 h. The transesterification reaction is preferably carried out under the protection of nitrogen, and the temperature of the transesterification reaction is preferably 220° C.

[0043] The vacuum degree of the pre-polycondensation reaction is 5kPa-20kPa, the reaction temperature is 220-240°C, and the reaction time is 0.5-1h. Preferably, the vacuum degree of the pre-polycondensation reaction is 12kPa.

[0044] The polycondensation reaction is carried out under a vacuum degree of less than or equal to 60 Pa, the polycondensation reaction temperature is 240° C., and the polycondensation reaction time is 2 to 5 hours. Preferably, the polycondensation reaction is carried out under a vacuum degree of 60 Pa for the final polycondensation reaction.

[0045] In the present disclosure, when preparing the PBT copolyester, the 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol used has the structural formula:

[0046]

[0047] In the present disclosure, the 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol is derived from 5-hydroxymethylfurfural, which is obtained by acetalization of 5-hydroxymethylfurfural and trimethylolpropane; preferably, the molar ratio of 5-hydroxymethylfurfural to trimethylolpropane is 1:1.05-1.50; and the specific steps of its preparation method are:

[0048] 5-Hydroxymethylfurfural and trimethylolpropane are dissolved in a solvent, and an acetalization reaction is carried out between 5-Hydroxymethylfurfural and trimethylolpropane under acidic and stirring conditions. The reaction product is post-treated to obtain the 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol monomer.

[0049] The solvent is isopropanol; the acidic condition can be provided by p-toluenesulfonic acid; the reaction temperature of the acetalization reaction is 20-35° C., and the reaction time is 12-24 hours; and the post-treatment is to evaporate excess solvent in the reaction product after the reaction is completed to obtain a 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol monomer containing an acetal structure.

[0050] In the following embodiments of the present disclosure, nuclear magnetic resonance spectroscopy 1 H-NMR was performed using Bruker Ascend TM Thermal transition analysis was performed using a TA Instruments Q2000 Differential Scanning Calorimeter at room temperature, at a heating rate of 10°C / min, in a nitrogen atmosphere, over a temperature range of -50 to 250°C.

[0051] In the following embodiments, the polybutylene terephthalate-co-terephthalic acid 5-ethyl-2-(5-hydroxymethyl-2-furyl)-1,3-dioxane-5-methyl ester, referred to as PHT x BT y, wherein H, T and B represent 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, dimethyl terephthalate and 1,4-butanediol, respectively; the value range of x is greater than 5 and less than 50, and the value range of y is greater than 50 and less than 90, which are the molar proportions of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methyl terephthalate block and butylene terephthalate block in PBT copolyester * 100%.

[0052] Example 1

[0053] 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol is prepared from 5-hydroxymethylfurfural and trimethylolpropane. The specific process is as follows:

[0054] 10.09 g of 5-hydroxymethylfurfural (0.080 mol), 12.88 g of trimethylolpropane (0.096 mol), and 0.34 g of p-toluenesulfonic acid (0.18 mmol) were weighed and dissolved in 50 mL of isopropanol solution. The mixture was then stirred at 25° C. for 15 h to allow the mixture to undergo an acetalization reaction. After the reaction was completed, the reaction product was evaporated until all the isopropanol solvent was evaporated to obtain the 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol monomer of Example 1 as a yellow powder.

[0055] Example 2

[0056] 1. PHT 20 BT 80 Preparation of copolyester:

[0057] In this embodiment 2, the PHT 20 BT 80 It means that the molar proportion of the PHT block in the PBT copolyester is 20%.

[0058] 1) Preparation of PHT by melt polycondensation of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, dimethyl terephthalate and 1,4-butanediol 20 BT 80 Copolyester:alkyd molar ratio is 1.5:1;

[0059] 2) Weigh 3.63 g of 5-ethyl-2-(5-hydroxymethyl-2-furyl)-1,3-dioxane-5-methanol, 9.71 g of dimethyl terephthalate, and 5.41 g of 1,4-butanediol according to the above molar ratio of alcohol to acid, place the above monomers in an airtight round-bottom flask, add 0.025 g of dibutyltin oxide catalyst, and under a nitrogen atmosphere, incubate the mixture in the round-bottom flask at a reaction temperature of 220° C. for 8 hours for transesterification;

[0060] 3) The temperature was raised to 240° C., and the nitrogen protection was removed. At this temperature and a vacuum of 12 kPa, the reaction system in the round-bottom flask continued to undergo pre-polycondensation for 0.5 h.

[0061] 4) The vacuum degree was adjusted to 60 Pa, the temperature was kept constant at 240 ° C, and the reaction system continued to undergo polycondensation for 2 hours to obtain the PHT 20 BT 80 Copolyester.

[0062] 2. PHT of Example 2 20 BT 80 Copolyester DSC test:

[0063] 1) Weigh 5-10 mg of PHT prepared in Example 1 20 BT 80 The copolyester was placed in a differential scanning calorimeter to test the melting curve;

[0064] 2) Set the "heating-isothermal-cooling-isothermal-heating" program with a temperature test range of -50 to 250°C and a heating and cooling rate of 10°C / min to obtain a melting curve.

[0065] Figure 1 PHT of Example 2 20 BT 80 Copolyester DSC melting curve, from Figure 1 The PHT was observed 20 BT 80 The glass transition temperature (T g ) is 40°C, which is 30°C higher than the glass transition temperature of PBT.

[0066] Example 3

[0067] 1. PHT 50 BT 50 Preparation of copolyester:

[0068] 1) Preparation of PHT by melt polycondensation of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, dimethyl terephthalate and 1,4-butanediol 50 BT50 Copolyester:alkyd molar ratio is 1.5:1;

[0069] 2) Weighing 9.08 g of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, 9.71 g of dimethyl terephthalate, and 3.38 g of 1,4-butanediol according to the above alcohol-acid molar ratio, the monomers were placed in an airtight round-bottom flask, 0.025 g of dibutyltin oxide catalyst was added, and the mixed system in the round-bottom flask was subjected to an ester exchange reaction at a reaction temperature of 220° C. for 9.5 hours under a nitrogen atmosphere;

[0070] 3) The temperature of the mixed system was raised to 240° C., and the nitrogen protection was removed. At this temperature and a vacuum of 12 kPa, the reaction system in the round-bottom flask continued to undergo pre-polycondensation for 0.5 h;

[0071] 4) After the pre-polycondensation reaction is completed, the vacuum degree is adjusted to 60 Pa, the system temperature is kept constant at 240 ° C, and the reaction system in the round-bottom flask continues the polycondensation reaction for 2 hours. After the polycondensation reaction is completed, the PHT 50 BT 50 Copolyester.

[0072] 2. Determination of PHT by NMR 50 BT 50 Chemical structure of copolyester:

[0073] Figure 2 PHT is prepared by melt polycondensation of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, dimethyl terephthalate and 1,4-butanediol. 50 BT 50 Copolyester 1 H-NMR, such as Figure 2 As shown in Figure 2, the peaks at δ2.05-1.87ppm (l) and δ4.54-4.33ppm (k) are attributed to the -CH2- protons in 1,4-butanediol; the peaks at δ6.49ppm (b) and δ6.35ppm (c) are attributed to the protons on the furan ring; the peak at δ5.59-5.28ppm (d) is attributed to the -CH- protons in the acetal ring; the peak at δ4.70ppm (a) is attributed to the -CH2- protons connected to the ester group and the furan ring. The peak at δ3.93ppm(g) is attributed to the -CH2- proton connected to the ester group and the acetal ring; the peaks at δ4.18ppm(e) and δ3.75ppm(f) are attributed to the -CH2- proton in the acetal ring; the peaks at δ1.42-1.20ppm(h) and δ1.02-0.85ppm(i) are attributed to the -CH2CH3 proton close to the acetal ring; the peak at δ8.08ppm(j) is attributed to the proton in the benzene ring of terephthalic acid.

[0074] Combined with the above 1 H-NMR analysis can prove that PHT 50 BT 50 The synthesis of copolyester was successful.

[0075] 3. PHT of Example 3 50 BT 50 Copolyester DSC test:

[0076] 1) Weigh 5-10 mg of PHT prepared in Example 1 50 BT 50 The copolyester was placed in a differential scanning calorimeter to test the melting curve;

[0077] 2) Set the "heating-isothermal-cooling-isothermal-heating" program with a temperature test range of -50 to 250°C and a heating and cooling rate of 10°C / min to obtain a melting curve.

[0078] Figure 3 PHT of Example 3 50 BT 50 Copolyester DSC melting curve, from Figure 3 The PHT was observed 50 BT 50 The glass transition temperature (T g ) is 60°C, which is 30°C higher than the glass transition temperature of PBT.

[0079] The above-described embodiments are merely examples of implementation methods of the present disclosure, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art may make various modifications, equivalent substitutions, and improvements without departing from the scope of the present disclosure, and these modifications are all within the scope of protection of the present disclosure. Therefore, the scope of protection of the present invention shall be based on the appended claims.

Claims

1. A PBT copolyester with a high glass transition temperature, characterized in that: The PBT copolyester is a linear copolyester containing butylene terephthalate blocks and 5-ethyl-2-(5-hydroxymethyl-2-furyl)-1,3-dioxane-5-methyl terephthalate blocks, and has a number average molecular weight of not less than 10,000 g / mol.

2. The PBT copolyester with a high glass transition temperature according to claim 1, wherein: Based on the total molar amount of each block being 100%, the 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methyl terephthalate block accounts for 5%-50%, and the remainder is the butylene terephthalate block.

3. The PBT copolyester with a high glass transition temperature according to claim 2, wherein: The 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methyl terephthalate block accounts for 20% to 50%.

4. The method for preparing the PBT copolyester according to any one of claims 1 to 3, wherein: The PBT copolyester is obtained by bulk polymerization of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, dimethyl terephthalate and 1,4-butanediol.

5. The method for preparing PBT copolyester according to claim 4, wherein: The bulk polymerization method comprises: The 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol, dimethyl terephthalate, and 1,4-butanediol are placed in a closed reactor, a catalyst is added, and the mixed system in the reactor sequentially undergoes an ester exchange reaction, a pre-condensation reaction, and a polycondensation reaction to obtain the PBT copolyester.

6. The method for preparing PBT copolyester according to claim 5, wherein: The ratio of the molar amount of dimethyl terephthalate to the sum of the molar amounts of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol and 1,4-butanediol is 1:1.2-3.

7. The method for preparing PBT copolyester according to claim 6, wherein: The ratio of the molar amount of dimethyl terephthalate to the sum of the molar amounts of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol and 1,4-butanediol is 1:1.5; and / or, The catalyst is dibutyltin oxide, and the added amount thereof is 0.05% to 0.4% of the sum of the molar amounts of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol and 1,4-butanediol.

8. The method for preparing PBT copolyester according to claim 7, wherein: The amount of the catalyst added is 0.1% to 0.3% of the sum of the molar amounts of 5-ethyl-2-(5-hydroxymethyl-2-furan)-1,3-dioxane-5-methanol and 1,4-butanediol; and / or, The transesterification reaction is carried out under nitrogen protection, with a reaction temperature of 180-230° C. and a reaction time of 8-10 hours.

9. The method for preparing PBT copolyester according to claim 8, wherein: The transesterification reaction temperature is 220°C; and / or, The vacuum degree of the pre-polycondensation reaction is 5 kPa-20 kPa, the reaction temperature is 220-240° C., and the reaction time is 0.5-1 h.

10. The preparation method according to claim 5, characterized in that: The vacuum degree of the pre-polycondensation reaction is 12 kPa; and / or, The polycondensation reaction is carried out under a vacuum degree of less than or equal to 60 Pa, the polycondensation reaction temperature is 240° C., and the polycondensation reaction time is 2 to 5 hours.

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