Preparation method of bio-based semi-crystalline semi-aromatic furan polyamide

Abstract

The invention discloses a preparation method of bio-based semi-crystalline semi-aromatic furan polyamide, which comprises the following steps: (1) dissolving dicarboxylic acid, diamine, a piperazine analogue and a catalyst in a solvent to obtain a mixed solution; (2) heating the mixed solution obtained in the step (1) to carry out polymerization reaction, and obtaining a reaction solution after the reaction is finished; and (3) adding the reaction solution obtained in the step (2) into ethyl acetate for precipitation, collecting the precipitate, washing and drying to obtain the product. The selected piperazine analogue effectively inhibits formation of intramolecular hydrogen bonds of polyamide, so that semi-crystalline polyamide is obtained, and a foundation is laid for further synthesis of bio-based polyamide suitable for high-performance application.

Description

Technical Field

[0001] The present invention relates to the technical field of polyamide material synthesis, and particularly relates to a preparation method of a bio-based semi-crystalline semi-aromatic furan polyamide. Background Art

[0002] Polyamide (PA for short), commonly known as Nylon, is a general term for a class of polymers containing several amide group —(NHCO)— repeating units in the molecular main chain. It has excellent comprehensive properties such as good mechanical properties, high mechanical strength, heat resistance, wear resistance and easy processing, and is thus widely used in multiple fields such as textiles, electronic appliances, automobiles, medical and pharmaceutical industries, and thus ranks first among the five major engineering plastics. Polyamide can be obtained by polycondensation reaction of diamine and dicarboxylic acid or through related cyclic amides. According to the different structural compositions of its molecular main chain, it can be divided into three categories: aliphatic nylon, aromatic nylon and semi-aromatic nylon. Due to the different monomers and contents constituting their main chains, these three types of nylons have large differences in physical and chemical properties, and are thus applied in different industrial fields.

[0003] Bio-based polyamide usually refers to obtaining the precursors of polyamide by completely or partially using renewable biomass raw materials, and then synthesizing these monomers into environmentally friendly and renewable polyamide through polymerization reaction. At present, the main applications of nylon in the world are PA6 and PA66. However, the raw materials of PA6 and PA66 mainly come from fossil fuels, which have the disadvantages of non-renewability and environmental unfriendliness. Therefore, it is of great significance to develop environmentally friendly renewable bio-based nylon to replace traditional nylon produced from fossil fuels. Currently, the common polyamide polymerization methods in industry mainly include: melt polymerization, interfacial polymerization, solution polymerization and solid-phase polymerization. Melt polymerization refers to a method of directly carrying out condensation polymerization of reaction monomers in a solvent-free molten state under certain conditions to obtain a nylon polymer. However, the melt polymerization method has high requirements for the airtightness of the reaction kettle and the polymerization process. The obtained product has high viscosity, is not easy to separate and is prone to carbonization. The polymerization temperature is also relatively high, and decomposition cross-linking is likely to occur between reactants. Solution polycondensation can effectively reduce monomer volatilization and by-product generation, and obtain a polymerization product with a relatively high molecular weight.

[0004] In recent years, 2,5-furandicarboxylic acid (FDCA) has received considerable attention as a main raw material for bio-based polyamides and is considered a bio-based alternative to non-renewable terephthalic acid. Compared with polyamides with similar structures, the thermal and mechanical properties of polyamides derived from 2,5-furandicarboxylic acid are improved because the intermolecular hydrogen bonds increase the interaction between polymer chains. However, these polymers are usually amorphous or show very low crystallinity, and most cannot crystallize from the molten state, which limits the further high-performance applications of bio-based polyamides due to the formation of intramolecular hydrogen bonds between the oxygen heteroatom in the furan ring and the hydrogen of the amide bond. By reducing the formation of intramolecular hydrogen bonds between the oxygen heteroatom in the furan ring and the hydrogen of the amide bond, the thermal and mechanical properties of these materials can be changed. Therefore, there is an urgent need to develop a method in the synthesis of bio-based polyamides using 2,5-furandicarboxylic acid as a raw material to reduce the formation of intramolecular hydrogen bonds between the oxygen heteroatom in the furan ring and the hydrogen of the amide bond, laying a foundation for the further synthesis of bio-based polyamides suitable for high-performance applications. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing bio-based semi-crystalline semi-aromatic furan polyamides based on solution polymerization for the problem that polymers with 2,5-furandicarboxylic acid as the amide part in the polyamide main chain are usually amorphous or show very low crystallinity and most cannot crystallize from the molten state. Adding a piperazine structural analog as a polymerization monomer during the synthesis of semi-aromatic furan polyamides can effectively inhibit the formation of intramolecular hydrogen bonds in the polyamide. This synthesis strategy can obtain semi-crystalline polyamides that show rapid crystallization in the molten state and an increase in crystallinity with an increase in the concentration of the amide part in the polyamide main chain.

[0006] To achieve the above object, the technical solutions provided by the present invention are as follows:

[0007] A bio-based semi-crystalline semi-aromatic furan polyamide, whose structural formula is shown in Formula I:

[0008]

[0009] Wherein, m and n are the degrees of polymerization of the corresponding structural units; ran represents random copolymerization;

[0010] Wherein, m:n = (1 - 10):3;

[0011] X is any one of ;

[0012] Y is any one of ;

[0013] Z is Any one of the following.

[0014] In the process of randomly alternating copolymerizing the X, Y, and Z structural units to form a polymer, the Y structural unit or the Z structural unit randomly couples with the X structural unit to form a ternary random copolymer.

[0015] The present invention also provides a method for preparing the bio-based semi-crystalline semi-aromatic furan polyamide, which is obtained by dissolving a dicarboxylic acid, a diamine, a piperazine structural analog, and a catalyst in a solvent and performing a polymerization reaction.

[0016] Among them, the dicarboxylic acid is a furan-based dicarboxylic acid monomer or a furan-based dicarboxylic acid ester derivative, preferably a furan-based dicarboxylic acid ester derivative.

[0017] Among them, the furan-based dicarboxylic acid monomer is any one or several combinations of 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 3,4-furandicarboxylic acid, and 2,5-furandiacetic acid; the furan-based dicarboxylic acid ester derivative is any one or several combinations of dimethyl 2,5-furandicarboxylate, dimethyl 2,4-furandicarboxylate, and dimethyl 3,4-furandicarboxylate, preferably dimethyl 2,5-furandicarboxylate.

[0018] Among them, the diamine is any one or several combinations of 1,5-pentanediamine, 1,8-octanediamine, 1,10-decanediamine, 4,4′-diaminodicyclohexylmethane, 2,5-furandimethanamine, and 2,5-furandietheramine, preferably 1,5-pentanediamine or 1,10-decanediamine.

[0019] Among them, the piperazine structural analog is any one or several combinations of piperazine, 2,6-dimethylpiperazine, 4-aminopiperidine, and piperazine-2,5-dione, preferably piperazine or piperazine-2,5-dione.

[0020] Among them, the catalyst is 1,5,7-triazabicyclo[4.4.0]dec-5-ene or 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0021] Among them, the solvent is any one or several combinations of N-methylpyrrolidone, N,N-dimethylformamide, N,N-diethylformamide, dimethyl sulfoxide, diphenyl ether, 2-methylnaphthalene, and 1,2-dichlorobenzene, preferably N-methylpyrrolidone or N,N-diethylformamide.

[0022] Among them, the ratio of the amount of substance of the dicarboxylic acid to the sum of the amounts of substance of the diamine and the piperazine structural analog is 1:1 to 1.3; the molar ratio of the diamine to the piperazine structural analog is 3:1 to 10; the concentration of the catalyst in the solvent is 4 to 13 mol / L.

[0023] Among them, the temperature of the polymerization reaction is 80 - 140 °C, and the time is 0.5 - 2 h.

[0024] Among them, after the polymerization reaction is completed, the obtained reaction solution is dropped into ethyl acetate for precipitation, and the precipitate is washed and dried to obtain the bio-based semi-crystalline semi-aromatic furan polyamide.

[0025] Among them, the washing is carried out with ethyl acetate; the drying is carried out at a temperature of 60 - 70 °C until the ethyl acetate in the precipitate is completely removed.

[0026] The number-average molecular weight of the bio-based semi-crystalline semi-aromatic furan polyamide prepared by the method of the present invention is 46128 - 58932 Da, preferably 46128 - 47710 Da.

[0027] Beneficial effects:

[0028] (1) The present invention uses solution polymerization to achieve the preparation of semi-aromatic furan polyamide. Compared with melt polymerization, solution polymerization can achieve rapid polymerization of monomers at a lower reaction temperature, effectively reduce monomer volatilization and the generation of oligomers, the reaction time is precisely controllable, the reaction efficiency is improved, the degree of incomplete reaction is effectively reduced, and side reactions such as thermal cleavage decarboxylation of carboxylic acid (>190 °C), N-methylation of polyamide (the main factor affecting polymer performance), self-condensation of diamine, and cyclization of diamine are effectively avoided. The reaction does not need to be carried out in a vacuum environment, and the solution polymerization method requires a small reactor volume, high degree of automation control, good safety, and is convenient for industrial operation and implementation.

[0029] (2) The polymer product prepared by the method of the present invention is a semi-aromatic furan polyamide, whose molecular main chain contains both aromatic rings and aliphatic chains, combining the excellent thermal properties of aromatic polyamide and the good molding processability of aliphatic polyamide.

[0030] (3) In the preparation method of the semi-aromatic furan polyamide of the present invention, by adding a piperazine structure analog as a polymerization monomer, the formation of intramolecular hydrogen bonds in the semi-aromatic furan polyamide is effectively inhibited, making it in a semi-crystalline state, showing the phenomenon of rapid crystallization from the molten state and the increase of crystallinity with the increase of the amide part concentration in the polymer main chain, laying a foundation for further synthesizing bio-based polyamides suitable for high-performance applications. Brief description of the drawings

[0031] The following further specifically describes the present invention in conjunction with the drawings and specific embodiments, and the above and / or other advantages of the present invention will become clearer.

[0032] Figure 11H NMR spectrum of the bio-based semi-crystalline semi-aromatic furan polyamide prepared in Example 1.

[0033] Figure 2 IR spectrum of the bio-based semi-crystalline semi-aromatic furan polyamide prepared in Example 1.

[0034] Figure 3 XRD pattern of the bio-based semi-crystalline semi-aromatic furan polyamide prepared in Example 1.

[0035] Figure 4 TG curve of the bio-based semi-crystalline semi-aromatic furan polyamide prepared in Example 1.

[0036] Figure 5 DSC curve of the bio-based semi-crystalline semi-aromatic furan polyamide prepared in Example 1. Detailed implementation manners

[0037] The present invention will be further described below according to the following examples. It should be understood that the following embodiments are only used to illustrate the present invention and not to limit the present invention.

[0038] For specific technologies or conditions not specified in the examples, they shall be in accordance with the technologies or conditions described in the literature in this field or in accordance with the product specifications. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through regular channels.

[0039] Example 1

[0040] (1) Weigh accurately 0.007 mol of dimethyl 2,5-furandicarboxylate, 0.00525 mol of 1,5-pentanediamine, 0.00175 mol of piperazine and 0.00182 mol of 1,5,7-triazabicyclo[4.4.0]dec-5-ene using an analytical balance accurate to one ten-thousandth, transfer them to a 25 mL glass bottle, and use a syringe to extract 6 mL of N,N-diethylformamide and transfer it to the above 25 mL glass bottle.

[0041] (2) Place the above 25 mL glass bottle in an oil bath at 140 °C and react for 2 h, and record the reaction phenomenon.

[0042] (3) After the reaction, a pale yellow viscous reaction solution is obtained. Slowly drop the reaction solution containing the polymer into an excess of ethyl acetate (to ensure that all the polymers in the reaction solution can precipitate out) for precipitation, perform solid-liquid separation, collect the solid part, wash it thoroughly with ethyl acetate to remove the solvent and unreacted monomers, and then dry it under vacuum at 60 °C for 12 h to obtain the bio-based semi-crystalline semi-aromatic furan polyamide of the present invention, and its yield is 88%.

[0043] The proton nuclear magnetic resonance spectrum, infrared spectrum and XRD pattern of the bio-based semi-crystalline semi-aromatic furan polyamide prepared in this example are respectively as follows Figure 1 、 Figure 2 and Figure 3 shown. From Figure 2 it can be seen that the stretching vibration peak attributed to the intermolecular hydrogen bond is at 3290 cm -1 , the stretching vibration peak attributed to the =C-H of furan is at 3115 cm -1 , the stretching vibration peak attributed to -C=O is at 1622 cm -1 , the stretching vibration peak belonging to -C=C is at 1570 cm -1 , the stretching vibration peak attributed to the -C-N- of piperazine is at 1260 cm -1 , and the stretching vibration peak attributed to piperazine is at 1034 cm -1 . From Figure 3 it can be seen that the polymer shows obvious diffraction peaks at 2θ = 19.6°, 20.7° and 23.6°, indicating that the polymer is semi-crystalline with a crystallinity of 35%. For the bio-based semi-crystalline semi-aromatic furan polyamide prepared by the method of the present invention, similar diffraction peaks appear at the same position of the polymer. The bio-based semi-crystalline semi-aromatic furan polyamide prepared in this example was subjected to thermogravimetric analysis and differential scanning calorimetry (DSC) tests. The experimental results are as follows Figure 4 and Figure 5 shown. The results show that the glass transition temperature is 105 °C, and T d5％ (5% thermal weight loss temperature) is 292 °C, indicating its excellent thermal stability.

[0044] Example 2

[0045] (1) Accurately weigh 0.007 mol of dimethyl 2,5-furandicarboxylate, 0.00525 mol of 1,5-pentanediamine, 0.00175 mol of piperazine-2,5-dione and 0.00182 mol of 1,5,7-triazabicyclo[4.4.0]dec-5-ene using an analytical balance accurate to one ten-thousandth, transfer them to a 25 mL glass bottle, and use a syringe to extract 6 mL of N,N-diethylformamide and transfer it to the above 25 mL glass bottle.

[0046] (2) Place the above 25 mL glass bottle in an oil bath at 140 °C and react for 2 h, and record the reaction phenomenon.

[0047] (3) After the reaction, a light yellow viscous reaction solution is obtained. Slowly drop the reaction solution containing the polymer into ethyl acetate for precipitation, separate the solid and liquid, collect the solid part, wash it thoroughly with ethyl acetate to remove the solvent and unreacted monomers, and then dry it in vacuo at 60 °C for 12 h to obtain the bio-based semi-crystalline semi-aromatic furan polyamide of the present invention, and its yield is 85%.

[0048] The crystallinity of the bio-based semi-crystalline semi-aromatic furan polyamide prepared in this example is 20%, the glass transition temperature is 100 °C, and T d5％ is 237 °C, indicating its excellent thermal stability.

[0049] Example 3

[0050] (1) Accurately weigh 0.007 mol of dimethyl 2,5-furandicarboxylate, 0.00525 mol of 4,4′-diaminodicyclohexylmethane, 0.00175 mol of piperazine, and 0.00182 mol of 1,5,7-triazabicyclo[4.4.0]dec-5-ene using a ten-thousandth balance, transfer them to a 25 mL glass bottle, and use a syringe to draw 6 mL of N,N-diethylformamide and transfer it to the above 25 mL glass bottle.

[0051] (2) Place the above 25 mL glass bottle in an oil bath at 140 °C and react for 2 h, and record the reaction phenomenon.

[0052] (3) After the reaction, a light yellow viscous reaction solution is obtained. Slowly drop the reaction solution containing the polymer into an excess of ethyl acetate (to ensure that all the polymer in the reaction solution can precipitate), perform solid-liquid separation, collect the solid part, wash it thoroughly with ethyl acetate to remove the solvent and unreacted monomers, and then dry it under vacuum at 60 °C for 12 h to obtain the bio-based semi-crystalline semi-aromatic furan polyamide of the present invention, and its yield is 86%.

[0053] The crystallinity of the bio-based semi-crystalline semi-aromatic furan polyamide prepared in this example is 25%, the glass transition temperature is 91 °C, and T d5％ is 241 °C, indicating its excellent thermal stability.

[0054] Comparative Example 1

[0055] Prepare bio-based semi-aromatic furan polyamide using a conventional method:

[0056] Accurately weigh 0.007 mol of dimethyl 2,5-furandicarboxylate, 0.007 mol of 1,5-pentanediamine, and 0.00182 mol of 1,5,7-triazabicyclo[4.4.0]dec-5-ene using a ten-thousandth balance, transfer them to a 25 mL glass bottle, and use a syringe to draw 6 mL of N,N-diethylformamide and transfer it to the above 25 mL glass bottle. Place the above 25 mL glass bottle in an oil bath at 140 °C and react for 2 h, and record the reaction phenomenon.

[0057] After the reaction ended, a light yellow viscous reaction solution was obtained. The reaction solution containing the polymer was slowly dropped into an excessive amount of ethyl acetate (to ensure that all the polymers in the reaction solution could precipitate out) for precipitation. The solid and liquid were separated, and the solid part was collected. It was thoroughly washed with ethyl acetate to remove the solvent and unreacted monomers, and then vacuum dried at 60 °C for 12 h. Finally, a bio-based semi-aromatic furan polyamide was obtained with a yield of 85%.

[0058] The crystallinity of the bio-based semi-aromatic furan polyamide prepared in this comparative example was 0, and the glass transition temperature was 92 °C. T d5％ was 233 °C. It shows that the bio-based semi-aromatic furan polyamide prepared by the conventional method is completely amorphous.

[0059] The present invention provides an idea and method for preparing a bio-based semi-crystalline semi-aromatic furan polyamide. There are many specific methods and ways to implement this technical solution. The above description is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention. Each component not clearly defined in this embodiment can be realized by the prior art.

Claims

1. A bio-based semi-crystalline semi-aromatic furan polyamide, the structural formula of which is shown in Formula I: in, m and n are the degrees of polymerization of the corresponding structural units; ran represents random copolymerization; Wherein, m:n=(1-10):3; X is Any of the following: Y is Any of the following: Z is Any one of .

2. The method for preparing the bio-based semi-crystalline semi-aromatic furan polyamide according to claim 1, characterized in that: The dicarboxylic acid, diamine, piperazine structural analog and catalyst are dissolved in a solvent to carry out polymerization reaction to obtain the product.

3. The preparation method according to claim 2, characterized in that: The dicarboxylic acid is a furanyl dicarboxylic acid monomer or a furanyl dicarboxylic acid ester derivative; the furanyl dicarboxylic acid monomer is any one or a combination of 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 3,4-furandicarboxylic acid and 2,5-furandiacetic acid; the furanyl dicarboxylic acid ester derivative is any one or a combination of 2,5-furandicarboxylic acid dimethyl ester, 2,4-furandicarboxylic acid dimethyl ester and 3,4-furandicarboxylic acid dimethyl ester.

4. The preparation method according to claim 2, characterized in that: The diamine is any one or a combination of 1,5-pentanediamine, 1,8-octanediamine, 1,10-decanediamine, 4,4′-diaminodicyclohexylmethane, 2,5-furandimethylamine and 2,5-furandiethylamine.

5. The preparation method according to claim 2, characterized in that: The piperazine structural analogue is any one or a combination of piperazine, 2,6-dimethylpiperazine, 4-aminopiperidine and piperazine-2,5-dione.

6. The preparation method according to claim 2, characterized in that: The catalyst is 1,5,7-triazabicyclo[4.4.0]decene-5-ene or 1,8-diazabicyclo[5.4.0]undecene-7-ene.

7. The preparation method according to claim 2, characterized in that: The solvent is any one or a combination of N-methylpyrrolidone, N,N-dimethylformamide, N,N-diethylformamide, dimethyl sulfoxide, diphenyl ether, 2-methylnaphthalene and 1,2-dichlorobenzene.

8. The method according to claim 2, characterized in that: The ratio of the amount of the dicarboxylic acid to the sum of the amounts of the diamine and the piperazine structural analog is 1:1-1.3; the molar ratio of the diamine to the piperazine structural analog is 3:1-10; and the amount of the catalyst added is 7-13% of the total amount of the dicarboxylic acid, diamine and piperazine structural analog.

9. The method according to claim 2, characterized in that: The reaction temperature of the polymerization reaction is 80-140° C., and the reaction time is 0.5-2 h.

10. The method according to claim 2, characterized in that After the polymerization reaction is completed, the obtained reaction solution is added dropwise into ethyl acetate for precipitation, and the precipitate is washed with ethyl acetate and dried to obtain the bio-based semi-crystalline semi-aromatic furan polyamide.

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