Polyethylene terephthalate-2,5-furandicarboxylate glycol copolyester foam and method of making

Abstract

The present application relates to a kind of polyethylene terephthalate-2,5-furandicarboxylic acid glycol copolyester foamed material and its preparation method, the preparation method includes the following steps: polyethylene terephthalate-2,5-furandicarboxylic acid glycol copolyester material is heat pressed, and the preform of molten state is obtained;The preform of molten state is treated with melt isothermal crystallization and quenching, and sheet material is obtained;Sheet material is treated with foaming, and polyethylene terephthalate-2,5-furandicarboxylic acid glycol copolyester foamed material is obtained.The present application uses melt isothermal crystallization treatment, can improve the melt strength in the foaming process of polyethylene terephthalate-2,5-furandicarboxylic acid glycol copolyester, strengthens its foaming performance, simultaneously can also be realized by strengthening bubble nucleation and controlling bubble growth to adjust the bubble morphology of foamed material, so polyethylene terephthalate-2,5-furandicarboxylic acid glycol copolyester foamed material with uniform bubble size and controllable foaming ratio can be obtained.

Description

Technical Field

[0001] This invention relates to the field of foaming materials technology, and in particular to polyethylene terephthalate-2,5-furandicarboxylate copolyester foaming materials and their preparation methods. Background Technology

[0002] The molding of foamed materials is generally divided into three stages: bubble nucleus formation, bubble growth, and bubble stabilization. In the bubble growth stage, the gas expands due to heat and diffuses into the bubble nucleus, thereby promoting the continuous growth of the bubble. At this time, the melt strength of the matrix is ​​the key factor affecting the growth of the bubble.

[0003] Polyethylene terephthalate-2,5-furandicarboxylate copolyester (PEFT) is a semi-crystalline polymer with a slow crystallization rate and relatively low crystallinity. Its melting point is generally above 200℃, exhibiting insufficient melt strength at higher foaming temperatures, leading to cell rupture and aggregation during foaming. Furthermore, the higher the content of the 2,5-furandicarboxylic acid copolymer unit, the lower the melting point of the copolyester, and the more pronounced the cell rupture and aggregation during foaming. Therefore, improving melt strength and suppressing cell rupture is crucial for preparing high-performance polyethylene terephthalate-2,5-furandicarboxylate copolyester foam materials. Summary of the Invention

[0004] Therefore, it is necessary to address the above problems by providing a polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material and its preparation method. The preparation method improves the melt strength during the foaming process of polyethylene terephthalate-2,5-furandicarboxylate copolyester, and also controls the cell morphology of the foam material by strengthening cell nucleation and controlling cell growth, thereby obtaining a polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material with uniform cell size and controllable foaming ratio.

[0005] A method for preparing a polyethylene terephthalate-2,5-furandicarboxylic acid copolyester foam material includes the following steps:

[0006] Poly(2,5-furandicarboxylic acid)-ethylene glycol copolyester material is hot-pressed to obtain a molten preform.

[0007] The molten preform is subjected to melt isothermal crystallization and quenching to obtain sheet material; and

[0008] The sheet material is foamed to obtain polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material.

[0009] In one embodiment, in the melt isothermal crystallization treatment step, the temperature is (T+15)℃-(T+30)℃ and the time is 3min-40min, where T is the melt crystallization initiation temperature of the polyethylene terephthalate-2,5-furandicarboxylate copolyester.

[0010] In one embodiment, the polyethylene terephthalate-2,5-furandicarboxylate copolyester is a random copolyester, wherein the comonomer 2,5-furandicarboxylic acid accounts for less than 15% of the total molar amount of dicarboxylic acid comonomers in the polyethylene terephthalate-2,5-furandicarboxylate copolyester.

[0011] In one embodiment, the quenching medium in the quenching process is selected from ice water or liquid nitrogen.

[0012] In one embodiment, the thickness of the sheet material is 0.5 mm to 2 mm.

[0013] In one embodiment, the step of foaming the sheet material is as follows: the sheet material is saturated by adsorption in a foaming gas to obtain saturated sheet material, and then the saturated sheet material is foamed in a foaming medium.

[0014] In one embodiment, the step of saturating the sheet material with adsorption in a foaming gas is performed at a pressure of 2 MPa-6 MPa for a time of 24-120 hours.

[0015] In one embodiment, the foaming gas is selected from carbon dioxide, nitrogen, or air.

[0016] In one embodiment, the step of foaming the saturated sheet material in a foaming medium is carried out at a temperature of 100°C-200°C for a time of 10s-30s.

[0017] A polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material obtained by the preparation method described above, wherein the foam material has a cell size of 10μm-150μm and an expansion ratio of 2-20 times.

[0018] In the preparation method of this invention, the molten polyethylene terephthalate-2,5-furandicarboxylate copolyester preform is subjected to melt isothermal crystallization treatment. This melt crystallization method induces the polyethylene terephthalate-2,5-furandicarboxylate copolyester to crystallize isothermally at a suitable temperature, resulting in the formation of tiny crystalline regions within the obtained sheet material. This improves the melt strength during the foaming process of the polyethylene terephthalate-2,5-furandicarboxylate copolyester, enhances its foaming performance, and prevents phenomena such as cell rupture and aggregation. Simultaneously, the interface between the crystalline and amorphous regions can serve as heterogeneous nucleation sites, lowering the cell nucleation energy barrier and increasing the cell nucleation density. Therefore, the morphology of the foamed material can be controlled by enhancing cell nucleation and regulating cell growth.

[0019] Therefore, the preparation method of the present invention can obtain polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material with uniform cell size and controllable foaming ratio, which can be widely used in building decoration materials, thermal insulation materials, packaging materials, cushioning materials, transportation and separation membranes and other fields. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 Differential scanning calorimetry cooling curves of polyethylene terephthalate and polyethylene terephthalate-2,5-furandicarboxylate copolyester used in the embodiments of the present invention.

[0022] Figure 2 This is a cross-sectional cell morphology diagram of the polyethylene terephthalate-2,5-furandicarboxylic acid copolyester foam material obtained in Example 1 of the present invention.

[0023] Figure 3 This is a cross-sectional cell morphology diagram of the polyethylene terephthalate-2,5-furandicarboxylic acid copolyester foam material obtained in Example 2 of the present invention.

[0024] Figure 4 This is a cross-sectional cell morphology diagram of the polyethylene terephthalate-2,5-furandicarboxylic acid copolyester foam material obtained in Example 3 of the present invention.

[0025] Figure 5 This is a cross-sectional cell morphology diagram of the polyethylene terephthalate-2,5-furandicarboxylic acid copolyester foam material obtained in Example 5 of the present invention.

[0026] Figure 6 The cross-sectional cell morphology of the polyethylene terephthalate-2,5-furandicarboxylate copolyester sample obtained in Comparative Example 1 of this invention is shown in the figure.

[0027] Figure 7 This is a cross-sectional cell morphology image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester sample obtained in Comparative Example 2 of the present invention.

[0028] Figure 8 This is a cross-sectional cell morphology image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester sample obtained in Comparative Example 3 of the present invention.

[0029] Figure 9 This is a cross-sectional cell morphology image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester sample obtained in Comparative Example 4 of the present invention. Detailed Implementation

[0030] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments or examples only and is not intended to be limiting of the invention.

[0032] The present invention provides a method for preparing a polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material, comprising the following steps:

[0033] S1, hot-press the polyethylene terephthalate-2,5-furandicarboxylate copolyester material to obtain a molten pre-product;

[0034] S2, the molten pre-product is subjected to melt isothermal crystallization treatment and quenching treatment to obtain sheet material;

[0035] S3, the sheet material is foamed to obtain polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material.

[0036] The crystallization process of polymers includes two stages: nucleus formation and grain growth. Crystallization by heating the polymer above its melting point and then rapidly cooling it from the molten state to a constant temperature is called isothermal melt crystallization. In the molten state, molecular chain segments form ordered bundles that act as nuclei through thermal motion. The orderly arrangement and regular stacking of these molecular chain segments towards the nuclei under constant temperature conditions allows for continuous grain growth.

[0037] Specifically, polyethylene terephthalate (PET) exhibits good symmetry and regularity in its molecular chain, which is conducive to crystallization. However, the main chain of PET-2,5-furandicarboxylate contains rigid furan ring structures, restricting molecular chain movement. Therefore, its unique molecular chain structure allows for the control of the degree of crystallization perfection of PET-2,5-furandicarboxylate through melt isothermal crystallization.

[0038] Therefore, in this application, the polyethylene terephthalate-2,5-furandicarboxylate copolyester material is first made into a molten preform, and then the molten preform is subjected to melt isothermal crystallization treatment. The melt crystallization method is used to induce the polyethylene terephthalate-2,5-furandicarboxylate copolyester to crystallize isothermally at a suitable temperature, so that tiny crystalline regions are formed inside the obtained sheet material.

[0039] First, this crystalline region can act as a heterogeneous nucleation site for bubbles, lowering the nucleation energy barrier and increasing the nucleation density. This is beneficial for obtaining polyethylene terephthalate-2,5-furandicarboxylate copolyester foamed materials with smaller cell size and higher cell density, and it can also control the cell morphology and size. Second, this crystalline region can improve melt strength, enhance its foaming performance, and prevent cell rupture and aggregation, which is beneficial for obtaining polyethylene terephthalate-2,5-furandicarboxylate copolyester foamed materials with a larger expansion ratio. Third, by increasing melt strength, this crystalline region can effectively widen the foaming temperature window of polyethylene terephthalate-2,5-furandicarboxylate copolyester.

[0040] Therefore, the preparation method of the present invention can obtain polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material with uniform cell size and controllable foaming ratio, which can be widely used in building decoration materials, thermal insulation materials, packaging materials, cushioning materials, transportation and separation membranes and other fields.

[0041] Specifically, in polyethylene terephthalate-2,5-furandicarboxylate copolyester, the content of the comonomer 2,5-furandicarboxylic acid has a significant impact on the onset temperature of melt isothermal crystallization. As the content of 2,5-furandicarboxylic acid increases, the onset temperature of melt isothermal crystallization gradually shifts towards a lower temperature, making crystallization more difficult and inhibiting the crystallization behavior.

[0042] To better ensure the crystallization ability of polyethylene terephthalate-2,5-furandicarboxylate copolyester, and thus to better control the crystallization process through melt isothermal crystallization to impart different degrees of crystallinity to the sheet material, in step S1, the polyethylene terephthalate-2,5-furandicarboxylate copolyester is a random copolyester, wherein the comonomer 2,5-furandicarboxylic acid accounts for less than 15% of the total molar amount of dicarboxylic acid comonomers in the polyethylene terephthalate-2,5-furandicarboxylate copolyester.

[0043] During isothermal crystallization of a melt, the crystallization rate, including the nucleation rate and the crystal growth rate, is highly temperature-dependent. At excessively high temperatures, the thermal motion of the molecular chains becomes too vigorous, making it difficult for crystal nuclei to form or resulting in unstable nuclei. As the temperature decreases, the nucleation rate increases, but the viscosity of the melt increases, reducing chain segment mobility and decreasing the crystal growth rate. Therefore, controlling the temperature during isothermal crystallization of a melt is crucial for controlling the crystallization process.

[0044] During isothermal crystallization of the melt, the nucleation process significantly affects the crystallization rate within a range of tens of degrees below the melting point. Lowering the crystallization temperature increases the crystallization rate and shortens the time required for complete crystallization. Therefore, within a suitable crystallization temperature range, the degree of crystallization perfection of polyethylene terephthalate-2,5-furandicarboxylate copolyester can be controlled by either lowering the crystallization temperature while reducing the crystallization time, or by increasing the crystallization temperature while extending the annealing time.

[0045] The crystallinity of polyethylene terephthalate-2,5-furandicarboxylate copolyester has a significant impact on cell morphology. On the one hand, when the crystallinity is too low, it has little effect on melt strength, making it difficult for the cell walls to trap gas, resulting in cell rupture. On the other hand, excessive crystallinity reduces the solubility of gas in the polymer, increases matrix strength, leads to a decrease in cell density and cell size, and may even result in a large number of unfoamed areas.

[0046] Taking into account the above factors, in the melt isothermal crystallization treatment step S2, the temperature is (T+15)℃-(T+30)℃ and the time is 3min-40min, where T is the melt crystallization initiation temperature of polyethylene terephthalate-2,5-furandicarboxylate copolyester.

[0047] Furthermore, during the isothermal crystallization of the melt, pressure can be applied to prevent the melt from flowing freely, ensuring that the sheet material after isothermal crystallization has a good morphology. It should be noted that pressure has almost no effect on the isothermal crystallization process. Furthermore, in the step of quenching the melt after isothermal crystallization, the quenching medium is selected from ice water or liquid nitrogen to prevent the room temperature cooling process from affecting the crystallinity of the sheet material.

[0048] Furthermore, the thickness of the sheet material is preferably 0.5mm-2mm, so that when the sheet material is foamed, the foaming gas can diffuse better within the sheet material, shorten the saturation adsorption time, and at the same time, the escape rate of the foaming gas during the foaming process can be better controlled, ensuring that the cell size distribution of the foam material is uniform.

[0049] In actual operation, the specific process of steps S1 and S2 of the present invention can be as follows: a mold for preparing sheet material is provided, and granular polyethylene terephthalate-2,5-furandicarboxylic acid copolyester material is placed in the mold. Then, the mold is placed in a molding press and hot-pressed into a sheet-like pre-product. At this time, the pre-product is in a molten state. Then, the mold carrying the pre-product is placed in another molding press for melt isothermal crystallization treatment. After isothermal crystallization treatment, quenching treatment is performed.

[0050] In step S3, the step of foaming the sheet material is as follows: the sheet material is saturated by adsorption in a foaming gas to obtain saturated sheet material, and then the saturated sheet material is foamed in a foaming medium.

[0051] Specifically, the foaming gas is selected from carbon dioxide, nitrogen, or air. Carbon dioxide can also play a plasticizing role in sheet materials, increasing the mobility of molecular chains, lowering the crystallization energy barrier, and helping to increase the crystallization density to obtain uniformly distributed cells. Therefore, the foaming gas is preferably carbon dioxide.

[0052] During the adsorption saturation process, the plasticizing effect is too strong when the foaming gas reaches a certain concentration, which will induce the crystallization of polyethylene terephthalate-2,5-furandicarboxylate copolyester, forming a crystalline skin on the surface of the foaming material and affecting the uniform distribution of the cells. Therefore, in the step of adsorbing the sheet material in the foaming gas to saturate, the pressure is 2MPa-6MPa and the time is 24h-120h.

[0053] In the step of foaming the saturated system in a foaming medium, the foaming medium is selected from dimethyl silicone oil, glycerin, vegetable oil, machine oil or lubricating oil. The foaming medium, as a heat transfer medium, can transfer heat to the saturated sheet material to cause it to foam.

[0054] During the heating and foaming process, if the foaming temperature is too high, the strength of the sheet material will decrease, and it may even melt completely. Conversely, if the foaming temperature is too low, the strength of the sheet material will increase, which is not conducive to foaming, and may even result in unfoamed areas. Therefore, in the step of foaming the saturated sheet material in the foaming medium, the preferred temperature is 100℃-200℃, and the preferred time is 10s-30s.

[0055] The present invention also provides a polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material obtained by the preparation method described above, wherein the foam material has a cell size of 10μm-150μm and an expansion ratio of 2-20 times.

[0056] Therefore, the apparatus and equipment used in the preparation method of this invention are all common equipment, such as molding machines and high-pressure autoclaves. The processing is easy to control, simple to operate, and has a short process flow. The foaming gas is used as a physical foaming agent, which has high solubility and diffusion coefficient compared with traditional chemical foaming agents. Moreover, it is a very environmentally friendly and green foaming system. This invention can adjust the cell morphology simply by changing the processing parameters. The production process is simple and has no impact on the performance and safety of the foamed material. It can be widely used in building decoration materials, thermal insulation materials, packaging materials, cushioning materials, transportation and separation membranes and other fields.

[0057] The following specific embodiments will further illustrate the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material and its preparation method.

[0058] In the following examples and comparative examples, the copolymer monomer 2,5-furandicarboxylic acid accounts for X% of the total molar amount of the dicarboxylic acid in the polyethylene terephthalate-2,5-furandicarboxylic acid copolyester, named PEFTX%. The intrinsic viscosity of the polyethylene terephthalate-2,5-furandicarboxylic acid copolyester is approximately 0.8.

[0059] Figure 1 In the diagram, a represents the differential scanning calorimetry (DSC) cooling curve for PET, b represents the DSC cooling curve for PEFT 5%, and c represents the DSC cooling curve for PEFT 10%. Figure 1 It can be seen that as the content of 2,5-furandicarboxylic acid increases, the melt crystallization initiation temperature gradually shifts towards a lower temperature and the crystallization enthalpy decreases, indicating that crystallization becomes more difficult and therefore a lower isothermal crystallization treatment temperature is required.

[0060] Example 1:

[0061] PEFT 5% (melt crystallization initiation temperature of 200.3℃) plastic granules were placed in a vacuum oven and dried at 80℃ for 12 hours to remove the moisture inside the plastic granules.

[0062] PEFT 5% plastic granules were placed in a mold with a thickness of 1 mm and molded for 5 minutes at a temperature of 280℃ and a pressure of 10 MPa to obtain a molten preform. The molten preform, along with the mold, was then quickly placed on another mold with a temperature of 218℃ for isothermal crystallization at a pressure of 10 MPa for 10 minutes. After isothermal crystallization, the melt, along with the mold, was quickly placed in an ice-water bath for quenching to obtain a sheet material with a thickness of 1 mm.

[0063] The obtained sheet material was placed in an autoclave and saturated with carbon dioxide gas. The pressure inside the autoclave was maintained at 4 MPa for 72 hours. Then, the pressure was rapidly released within 15 seconds, and the saturated sheet material was placed in dimethyl silicone oil at 150°C for 20 seconds to foam. Finally, the foamed sample was placed in ice water to fix the cell morphology, resulting in a polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material.

[0064] The cross-sectional scanning electron microscope image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material obtained in this embodiment is shown below. Figure 2 As shown, from Figure 2 It can be seen that the sample is fully foamed and the cell size is uniform, with a cell size of 36.5 μm and an expansion ratio of 3.2 times.

[0065] Example 2:

[0066] The difference between Example 2 and Example 1 is that after obtaining the molten preform, the molten preform along with the mold is quickly placed on another molding press at a temperature of 220°C for isothermal crystallization of the melt, with a pressure of 10 MPa and an isothermal crystallization time of 10 min.

[0067] The cross-sectional scanning electron microscope image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material obtained in this embodiment is shown below. Figure 3 As shown, from Figure 3 It can be seen that the sample is fully foamed and the cell size is uniform, with a cell size of 41.2 μm and an expansion ratio of 4.2 times.

[0068] Example 3:

[0069] The difference between Example 3 and Example 1 is that after obtaining the molten preform, the molten preform along with the mold is quickly placed on another molding press at a temperature of 225°C for isothermal crystallization of the melt, with a pressure of 10 MPa and an isothermal crystallization time of 10 min.

[0070] The cross-sectional scanning electron microscope image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material obtained in this embodiment is shown below. Figure 4 As shown, from Figure 4 It can be seen that the sample is fully foamed and the cell size is uniform, with a cell size of 56.7 μm and an expansion ratio of 7.5 times.

[0071] Example 4:

[0072] The only difference between Example 4 and Example 1 is that after obtaining the molten preform, the molten preform along with the mold is quickly placed on another molding press at a temperature of 225°C for isothermal crystallization of the melt, with a pressure of 10 MPa and an isothermal crystallization time of 15 min.

[0073] The polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material obtained in this embodiment is fully foamed with uniform cell size of 38.2 μm and an expansion ratio of 4.2 times.

[0074] Example 5:

[0075] PEFT 10% (melt crystallization initiation temperature is 185.2℃) plastic granules were placed in a vacuum oven and dried at 80℃ for 12 hours to remove the moisture inside the plastic granules.

[0076] PEFT 10% plastic granules were placed in a mold with a thickness of 1 mm and molded for 5 minutes at a temperature of 280℃ and a pressure of 10 MPa to obtain a molten preform. The molten preform, along with the mold, was then quickly placed on another mold with a temperature of 205℃ for isothermal crystallization at a pressure of 10 MPa for 10 minutes. After isothermal crystallization, the melt, along with the mold, was quickly placed in an ice-water bath for quenching to obtain a sheet material with a thickness of 1 mm.

[0077] The obtained sheet material was placed in an autoclave and saturated with carbon dioxide gas. The pressure inside the autoclave was maintained at 4 MPa for 72 hours. Then, the pressure was rapidly released within 15 seconds, and the saturated sheet material was placed in dimethyl silicone oil at 150°C for 20 seconds to foam. Finally, the foamed sample was placed in ice water to fix the cell morphology, resulting in a polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material.

[0078] The cross-sectional scanning electron microscope image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material obtained in this embodiment is shown below. Figure 5 As shown, from Figure 5It can be seen that the sample is fully foamed and the cell size is uniform, with a cell size of 58.6 μm and an expansion ratio of 4.8 times.

[0079] Example 6:

[0080] The only difference between Example 6 and Example 5 is that the saturated sheet material was foamed in dimethyl silicone oil at 180°C for 20 seconds.

[0081] The polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material obtained in this embodiment is fully foamed with uniform cell size of 68.6 μm and an expansion ratio of 6.3 times.

[0082] Example 7:

[0083] The only difference between Example 7 and Example 5 is that after obtaining the molten preform, the molten preform along with the mold is quickly placed on another molding press at a temperature of 207°C for isothermal crystallization of the melt, with a pressure of 10 MPa and an isothermal crystallization time of 10 min.

[0084] The polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material obtained in this embodiment is fully foamed with uniform cell size of 65.2 μm and an expansion ratio of 5.5 times.

[0085] Comparative Example 1:

[0086] The only difference between Comparative Example 1 and Example 1 is that the molten preform, along with the mold, was quickly placed in an ice-water bath for quenching.

[0087] The cross-sectional scanning electron microscope image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam obtained in the comparative example is shown below. Figure 6 As shown, from Figure 6 It can be seen that the sample exhibits severe cell aggregation and cell wall rupture.

[0088] Comparative Example 2:

[0089] The only difference between Comparative Example 2 and Example 1 is that after obtaining the molten preform, the molten preform along with the mold is quickly placed on another molding press at a temperature of 210°C for isothermal crystallization of the melt, with a pressure of 10 MPa and an isothermal crystallization time of 10 min.

[0090] The cross-sectional scanning electron microscope image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam obtained in the comparative example is shown below. Figure 7 As shown, from Figure 7 It can be seen that the sample cannot foam at all.

[0091] Comparative Example 3:

[0092] The only difference between Comparative Example 3 and Example 1 is that after obtaining the molten preform, the molten preform along with the mold is quickly placed on another molding press at a temperature of 235°C for isothermal crystallization of the melt, with a pressure of 10 MPa and an isothermal crystallization time of 10 min.

[0093] The cross-sectional scanning electron microscope image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam obtained in the comparative example is shown below. Figure 8 As shown, from Figure 8 It can be seen that the sample exhibits severe cell aggregation and cell wall rupture.

[0094] Comparative Example 4:

[0095] The only difference between Comparative Example 4 and Example 5 is that after obtaining the molten preform, the molten preform along with the mold is quickly placed on another molding press at a temperature of 198°C for isothermal crystallization of the melt, with a pressure of 10 MPa and an isothermal crystallization time of 10 min.

[0096] The cross-sectional scanning electron microscope image of the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam obtained in the comparative example is shown below. Figure 9 As shown, from Figure 9 It can be seen that the sample contains a large number of unfoamed areas and the cell size distribution is uneven.

[0097] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a polyethylene terephthalate-2,5-furandicarboxylic acid copolyester foam material, characterized in that, Includes the following steps: Poly(2,5-furandicarboxylic acid) ethylene glycol copolyester material is hot-pressed to obtain a molten preform, wherein the poly(2,5-furandicarboxylic acid) ethylene glycol copolyester is a random copolyester, and the comonomer 2,5-furandicarboxylic acid accounts for less than 15% of the total molar amount of dicarboxylic acid comonomers in the poly(2,5-furandicarboxylic acid) ethylene glycol copolyester. The molten preform is subjected to melt isothermal crystallization and quenching to obtain sheet material. In the melt isothermal crystallization step, the temperature is (T+15)℃-(T+30)℃, and the time is 3min-40min, where T is the melt crystallization initiation temperature of the polyethylene terephthalate-2,5-furandicarboxylate copolyester. The sheet material is foamed to obtain polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material.

2. The method for preparing the polyethylene terephthalate-2,5-furandicarboxylic acid copolyester foam material according to claim 1, characterized in that, In the quenching process, the quenching medium is selected from ice water or liquid nitrogen.

3. The method for preparing the polyethylene terephthalate-2,5-furandicarboxylic acid copolyester foam material according to claim 1, characterized in that, The thickness of the sheet material is 0.5mm-2mm.

4. The method for preparing the polyethylene terephthalate-2,5-furandicarboxylic acid copolyester foam material according to claim 1, characterized in that, The steps for foaming the sheet material are as follows: the sheet material is saturated by adsorption in a foaming gas to obtain saturated sheet material, and then the saturated sheet material is foamed in a foaming medium.

5. The method for preparing the polyethylene terephthalate-2,5-furandicarboxylic acid copolyester foam material according to claim 4, characterized in that, In the step of saturating the sheet material with adsorption in a foaming gas, the pressure is 2MPa-6MPa and the time is 24h-120h.

6. The method for preparing the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material according to claim 4, characterized in that, The foaming gas is selected from carbon dioxide, nitrogen, or air.

7. The method for preparing the polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material according to claim 4, characterized in that, In the step of foaming the saturated sheet material in a foaming medium, the temperature is 100℃-200℃ and the time is 10s-30s.

8. A polyethylene terephthalate-2,5-furandicarboxylate copolyester foam material obtained by the preparation method according to any one of claims 1-7, characterized in that, The poly(ethylene glycol terephthalate) copolyester foam material has a cell size of 10μm-150μm and an expansion ratio of 2-20 times.

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