Solid phase tackifying method of PEF

Abstract

The solid-phase tackifying method of the PEF is characterized by comprising the following steps: putting amorphous PEF slices with the initial viscosity of 0.4-0.6 dL / g and tackifying powder into a tackifying rotary drum together, and carrying out vacuum-pumping solid-phase tackifying for 20-36 hours at the temperature of 120-210 DEG C, so as to obtain PEF slices with the viscosity of more than 0.8. The solid-phase tackifying method provided by the invention has the advantages of high PEF slice crystallization rate, short tackifying period, simple whole process and easiness in operation.

Description

Technical Field

[0001] The invention relates to a processing method of polyethylene 2,5-furandicarboxylate, in particular to a solid phase viscosity increasing method of polyethylene 2,5-furandicarboxylate, belonging to the technical field of polymer materials. Background Art

[0002] Polyethylene 2,5-furandicarboxylate, abbreviated as PEF, is a bio-based thermoplastic polyester. As a bio-based material converted from biomass resources, PEF plays an important role in the field of fiber and food packaging due to its many advantages such as high gas barrier properties and chemical stability, as well as high operating temperature and low processing temperature. Although PEF has many advantages over PET, since the furandicarboxylate group is an asymmetric group with a large polarity and a large intermolecular force, extending the melt polycondensation time often leads to side reactions such as polymer degradation, which affects the color value of the product. Moreover, it is difficult to control the acetaldehyde content at a low level in melt polycondensed PEF, so that after the PEF slices are subsequently processed into bottles, acetaldehyde is released during the storage of beverages, affecting the flavor of the bottled beverages.

[0003] Solid phase thickening of low-viscosity PEF slices is an effective method to obtain PEF slices with better color value, high viscosity and low acetaldehyde content. PEF slices with a certain degree of crystallinity can reduce adhesion during the solid phase thickening process because the crystal region plays a role of physical cross-linking. However, the crystallization rate of PEF amorphous slices is slow, and PEF slices are easy to stick in the early stage of crystallization. Mechanical separation of agglomerated slices is required, which is a cumbersome process and a long thickening cycle. In order to realize the industrial production of PEF solid phase thickening, it is necessary to improve the crystallization rate of PEF amorphous slices and eliminate the adhesion problem during the PEF crystallization process.

[0004] See the Chinese invention patent application with application number 202310943517.3, "A method for preparing polyethylene 2,5-furandicarboxylate" (application publication number CN 117209740 A); raw materials containing 2,5-furandicarboxylic acid, ethylene glycol, catalyst, and phosphate are placed in a closed container, and subjected to esterification reaction, prepolymerization reaction, and polycondensation reaction to obtain the polyethylene 2,5-furandicarboxylate; the catalyst includes pentavalent antimony salt and tin salt. The technical solution of this application uses pentavalent antimony salt and tin salt of double anion as the main catalyst for esterification and polycondensation, and phosphorus-containing compounds as stabilizers. The preparation method has the characteristics of fast esterification rate, short time, high polyester polymerization viscosity, and less polyester degradation and yellowing. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a solid phase adhesion method for PEF in response to the above technical status, which can improve the crystallization and solid phase adhesion rate and effectively reduce the risk of slice adhesion.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a solid phase viscosity increasing method of PEF, characterized by comprising the following steps:

[0007] Amorphous PEF slices with an initial viscosity of 0.4-0.6 dL / g and thickening powder are placed in a thickening drum and vacuum solid phase thickening is performed at a temperature of 120-210° C. for 20-36 hours to obtain PEF slices with a viscosity of more than 0.8 dL / g.

[0008] The yield was calculated by the mass fraction of the slices obtained by sieving the powder and agglomerating the slices after thickening to the mass fraction of the initial slices. The melting enthalpy (ΔH) of the slices was measured by differential scanning calorimetry (DSC) to compare the crystallization rates of the slices. The experimental results show that the addition of powder can not only reduce the adhesion of PEF slices, but also accelerate the crystallization rate of PEF slices and shorten the solid phase thickening cycle, providing a new way for the large-scale production of high-viscosity PEF slices and expanding the scope of application of PEF.

[0009] Preferably, the viscosity-enhancing powder is at least one of talc, titanium dioxide, fused silica, boron nitride, mica, calcium carbonate, stearate, fatty acid salt, disodium 2,5-furandicarboxylate, aromatic phosphate, crystalline PET, and PEF.

[0010] Preferably, the particle size of the viscosity-enhancing powder is 400-800 meshes.

[0011] Preferably, the added amount of the viscosity-increasing powder is 0.05-1% of the mass fraction of the PEF slices.

[0012] Compared with the prior art, the advantages of the present invention are: the solid phase thickening of PEF amorphous slices is performed by the method provided by the present invention, and characterization by DSC and the like shows that the slices with added PEF crystalline powder have a fast crystallization rate, a short thickening cycle, and a simple and easy overall process. The thickening powder can play a role in physical isolation of anti-adhesion and heterogeneous nucleation, thereby increasing the crystallization temperature of the PEF slices, accelerating the crystallization rate, and shortening the thickening cycle, specifically based on the following analysis:

[0013] First, heterogeneous nucleation: As a nucleating agent, the viscosity-enhancing powder can provide a crystallization core, thereby accelerating the crystallization process. The smaller the particle size, the more obvious the nucleation effect.

[0014] Second, grain growth: The presence of viscosity-enhancing powder can guide the growth direction of the grains and form a more regular and uniform crystal structure.

[0015] Third, thermal resistance is reduced: the viscosity-enhancing powder can reduce the thermal resistance of the polyester material, allowing heat to be transferred to the interior faster and accelerating crystallization.

[0016] Fourth, interfacial effect: the interfacial effect between the viscosity-enhancing powder and the polyester material can change the microstructure of the material, thereby affecting the crystallization behavior. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the DSC test curve of the PEF sample in Example 1 during the heating process of 10°C / min after the PEF slice was heated at 140°C for 30 minutes.

[0018] Figure 2 This is the DSC test curve of the PEF sample in the comparative example after the PEF slice was heated at 140°C for 30 minutes during the heating process of 10°C / min. DETAILED DESCRIPTION

[0019] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments. Other changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention are also included in the protection scope of the present invention.

[0020] Example 1

[0021] 0.5 g of 800-mesh talc and 50 g of PEF amorphous slices with a viscosity of 0.45 were placed in a 500 ml flask, vacuumed, heated at 140°C for 3 hours, heated at 210°C for 21 hours, then cooled to 100°C, discharged, and the powder and agglomerated slices were sieved to obtain high-viscosity PEF crystalline slices.

[0022] Figure 1 This is the DSC test curve of the PEF sample in Example 1 during the heating process of 10°C / min after the PEF slice was heated at 140°C for 30 minutes.

[0023] Example 2

[0024] 100 g of 800-mesh FDCA and 20 kg of PEF amorphous slices with a viscosity of 0.57 were placed in a 50-liter rotary drum viscosifier and vacuumed, heated at 140°C for 3 hours, heated at 195°C for 21 hours, and then cooled to 100°C for discharge. The powder and agglomerated slices were sieved to obtain high-viscosity PEF crystalline slices.

[0025] Example 3

[0026] 50 g of 400-mesh PET powder and 20 kg of PEF amorphous slices with a viscosity of 0.59 were placed in a 50-liter rotary drum viscosifier and vacuumed, heated at 140°C for 3 hours and at 190°C for 21 hours, then cooled to 100°C and discharged. The powder and agglomerated slices were sieved to obtain high-viscosity PEF crystalline slices.

[0027] Example 4

[0028] 20 g of 400-mesh talc and 20 kg of PEF amorphous slices with a viscosity of 0.59 were placed in a 50-liter rotary drum viscosifier and vacuumed, heated at 120°C for 4 hours, heated at 195°C for 20 hours, and then cooled to 100°C for discharge. The powder and agglomerated slices were sieved to obtain high-viscosity PEF crystalline slices.

[0029] Comparative Example

[0030] 50 g of PEF amorphous slices with a viscosity of 0.45 were placed in a 500 ml flask and vacuumed, and heated at 140°C for 3 hours and at 210°C for 21 hours, then cooled to 100°C and discharged, and the powder and agglomerated slices were sieved to obtain PEF slices as a reference.

[0031] Figure 2 This is the DSC test curve of the PEF sample in the comparative example after the PEF slice was heated at 140°C for 30 minutes during the heating process of 10°C / min.

[0032] The solid phase adhesion enhancement effect of the adhesion enhancement powder assisted PEF amorphous slices is as follows:

[0033] Through observation, it was found that powder adhered to the surface of the slices 5 minutes after the slices were stirred. When the temperature was raised to 90°C, the PEF slices without powder began to stick to each other and stick to the inner wall of the flask; while the PEF slices with powder did not stick. When the temperature continued to rise to 130°C, the PEF slices without powder all stuck together and could not be stirred; the PEF slices with powder did not stick. After heating at 140°C for 30 minutes, the PEF slices with powder added became opaque, while the PEF slices without powder added only had slight changes.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and simple improvements made to the essential contents of the present invention should be included in the protection scope of the present invention.

[0035] Table 1 Data related to viscosity and discharge rate of PEF slices before and after solid phase thickening in Examples 1 to 4

[0036]

[0037] The results in Table 1 show that the viscosity of the PEF slices with added powder rises to above 0.8, and the viscosity of the PEF slices without added powder can also be greatly improved after thickening, but the discharge rate is very low, less than 25%, while the discharge rate of the slices with added powder is above 98%.

[0038] Table 2 Viscosity and DSC test data of the PEF slices in the early crystallization process in Example 1

[0039] Heating time Viscosity (dL / g) Melting peak temperature(℃) ΔHm(J / g) 30min 0.45 205 9.4 60min 0.45 148，205 27.4 90min 0.45 150，205 39.7

[0040] Table 3 Viscosity and DSC test data of PEF slices in the early crystallization process of the comparative example

[0041] Heating time Viscosity (dL / g) Melting peak temperature(℃) ΔHm(J / g) 30min 0.45 205 3.8 60min 0.45 148，205 16.7 90min 0.45 150，205 25.7

[0042] The data in Table 2 and Table 3 show that under the same heating conditions, the melting enthalpy increase rate of the PEF slices with added powder is faster, indicating that it has a faster crystallization rate.

[0043] The principle of powder-based crystallization accelerators promoting polyester crystallization is mainly based on the following aspects: (1) Heterogeneous nucleation: Powder, as a nucleating agent, can provide a crystallization core, thereby accelerating the crystallization process. The smaller the particle size, the more obvious the nucleation effect. (2) Grain growth: The presence of powder can guide the growth direction of the grains to form a more regular and uniform crystal structure. (3) Reduction of thermal resistance: Powder can reduce the thermal resistance of polyester materials, allowing heat to be transferred to the interior faster and accelerating crystallization. (4) Interface effect: The interface effect between powder and polyester materials can change the microstructure of the material, thereby affecting the crystallization behavior.

[0044] Comparison of the data shows that the 800-mesh talc in Example 1 significantly promotes the crystallization of PEF, and the rate of increase in melting enthalpy is faster (Table 2 and Table 3). The discharge rate after viscosity increase is significantly improved in PEF with 800-mesh talc compared to pure PEF.

Claims

1. A solid phase viscosity increasing method for PEF, characterized in that The steps include: Amorphous PEF slices with an initial viscosity of 0.4-0.6 dL / g and thickening powder are placed in a thickening drum and vacuum solid phase thickening is performed at a temperature of 120-210° C. for 20-36 hours to obtain PEF slices with a viscosity of more than 0.86 dL / g.

2. The solid phase viscosity increasing method of PEF according to claim 1, characterized in that The viscosity-enhancing powder is at least one of talc, titanium dioxide, fused silica, boron nitride, mica, calcium carbonate, stearate, fatty acid salt, disodium 2,5-furandicarboxylate, aromatic phosphate, crystalline PET, and PEF.

3. The solid phase viscosity increasing method of PEF according to claim 2, characterized in that The particle size of the tackifying powder is 400-800 meshes.

4. The solid phase viscosity increasing method of PEF according to claim 1, characterized in that The added amount of the viscosity-increasing powder is 0.05-1% of the mass fraction of the PEF slices.

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