A furanyl polyamide and its preparation method

Abstract

This invention belongs to the field of polymer synthetic chemistry and discloses a furanyl polyamide and its preparation method. The method involves reacting an aliphatic diamine monomer containing an oxalic acid amide group (as shown in Formula II) with a furanyl dicarboxylic acid derivative monomer to prepare the furanyl polyamide (as shown in Formula I). ​​The furanyl polyamide of this invention has a unique trans-arranged carbonyl structure on its molecular chain, resulting in a significantly increased hydrogen bond density. This endows it with properties such as low water absorption, high modulus, and high melting point, solving the problem of poor thermal properties of furanyl polyamide and providing a new approach for its industrial application. The method of this invention is green, non-toxic, and simple to operate, and can yield high molecular weight furanyl polyamide.

Description

Technical Field

[0001] This invention relates to the field of polymer synthetic chemistry, and in particular to a novel furanyl polyamide and its preparation method. Background Technology

[0002] This section provides only background information relevant to this disclosure and is not necessarily prior art.

[0003] Polyamide, commonly known as nylon, is a general term for polymers whose macromolecular chains contain amide groups (-NHCO-). It is mainly obtained through the self-polymerization of amino acid lactams or the condensation polymerization of diacids and diamines. There are many types of polyamides, which can be classified into aliphatic polyamides, aromatic polyamides, and copolyamides based on their composition and structure. Due to the presence of amide groups in the nylon molecular chain, stable hydrogen bonds can form between the molecular chains, promoting nylon's easy crystallization and thus endowing it with strong mechanical properties and good thermal properties. At the same time, nylon has a higher specific strength than metals and a low coefficient of friction, exhibiting excellent fatigue resistance, chemical resistance, and self-lubricating properties, making it a high-performance polymer material. Since DuPont developed PA6 in the 1930s, nylon has rapidly developed as a general-purpose engineering plastic, resulting in a wide variety of commercial products.

[0004] 2,5-Furfurandicarboxylic acid (FDCA) is a bio-based dicarboxylic acid monomer obtained from sugars. It is a substitute for PTA, exhibiting good biodegradability. It has fewer carbon atoms than benzene rings, weaker aromaticity, and even better thermodynamic and mechanical properties than terephthalic acid polymers. The use of furan-based aliphatic polyamides to replace traditional aromatic polyamides as high-performance materials has attracted considerable attention. This not only breaks the dependence of the traditional polyamide synthesis industry on petroleum resources but also reduces the generation and emission of hazardous waste. However, currently reported furan-based polyamides have poor thermal stability and are prone to decomposition during high-temperature reactions, limiting the development of their applications. Therefore, we need to enhance the thermal properties of furan-based polyamides by modifying their structure to provide performance assurance for expanding the industrial applications of polyamides. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a high heat-resistant furan-based semi-aromatic polyamide and its preparation method, which addresses the shortcomings of the prior art.

[0006] To solve the above-mentioned technical problems, the present invention discloses the following technical solution:

[0007] In a first aspect, the present invention provides an aliphatic diamine monomer with a designed structure as shown in Formula II;

[0008]

[0009] in,

[0010] R is selected from C4-C 12 Alkyl groups, including C4-C 12 Straight-chain alkyl groups, and branched alkylene groups.

[0011] Secondly, the method for preparing the aliphatic diamine monomer with the designed structure shown in Formula II provided by the present invention includes reacting an oxalate diester with a C4-C4 bond. 12 Aliphatic diamine reaction.

[0012] The oxalic acid diester includes dimethyl oxalate, diethyl oxalate, dibutyl oxalate, or any combination thereof, with diethyl oxalate being preferred.

[0013] The C4-C12 aliphatic diamine includes 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,8-octanediamine, 1,10-decanediamine, 1,11-diaminoundecane, 1,12-diaminododecane, or any combination thereof.

[0014] The molar ratio of the oxalic acid diester to the C4-C12 aliphatic diamine is 0.1-0.3:1, such as 0.15:1, 0.2:1, or 0.25:1.

[0015] The solvent used in the method is methanol or ethanol, preferably ethanol; the volume ratio of the solvent to the C4-C12 aliphatic diamine is 1:0.8-1.2, preferably 1:1.

[0016] The specific process steps and conditions for this preparation method are as follows:

[0017] First, an excess of diamine is dissolved in a solvent, and then a dioxate solution is added dropwise under an inert gas atmosphere and with stirring. Further, after the reaction is complete, the mixture is filtered, washed with ethanol, and the solid is dried to obtain a white crude aliphatic diamine monomer. This crude product is then recrystallized with butyl acetate, the insoluble solid is filtered off, the solution is allowed to stand at low temperature, the precipitated product is washed with ethanol, and the solid is dried to obtain a white monomer containing aliphatic diamine.

[0018] The stirring speed is 50-500 rpm, such as 350-500 rpm.

[0019] The oxalic acid diester solution is added dropwise at a flow rate of 200-400 μL / min.

[0020] During the reaction, stirring is continued for 1-3 hours after the addition is completed. During esterification, the excess diamine will cap the oxalate ester, yielding the desired product.

[0021] Thirdly, the present invention uses aliphatic diamines and furan dicarboxylic acids with designed structures as raw materials to design a furan-based polyamide with alternating structures as shown in Formula I;

[0022]

[0023] in,

[0024] R is selected from C4-C 12 Alkyl groups, including C4-C 12 Straight-chain alkyl groups, and branched alkylene groups;

[0025] n is any integer from 10 to 500.

[0026] The furanyl polyamide of this invention features a unique trans-arranged carbonyl structure on its molecular chain, significantly increasing the hydrogen bond density. This results in properties such as low water absorption, high modulus, and high melting point, solving the problem of poor thermal properties in furanyl polyamides and providing a new approach for their industrial application. The method of this invention is green, non-toxic, and simple to operate, and can yield high molecular weight furanyl polyamides.

[0027] Fourthly, the present invention discloses a method for preparing furanyl polyamide as shown in Formula I in the third aspect above.

[0028] The method comprises reacting an aliphatic diamine monomer containing an oxalamide group as shown in Formula II with a furan dicarboxylic acid derivative monomer.

[0029] The furan dicarboxylic acid derivative monomer includes 2,5-furandicarboxylic acid, dimethyl 2,5-furandicarboxylate, diethyl 2,5-furandicarboxylate, dibutyl 2,5-furandicarboxylate, 2,5-furandicarboxyl chloride, or any combination thereof.

[0030] In Formula II, the molar ratio of the aliphatic diamine monomer containing an oxalic acid amide group to the furan dicarboxylic acid derivative monomer is 1-3:1, such as 1.1:1, 1.5:1, 2:1, etc.

[0031] Further, the method includes adding an aliphatic diamine monomer containing an oxalamide group (as shown in Formula II) and a furan dicarboxylic acid derivative monomer to a reaction vessel under an inert atmosphere, heating to a first temperature, then gradually heating to a second temperature and holding for 1-4 hours to carry out an ester exchange reaction, then heating to a third temperature and adjusting the pressure to negative pressure and vacuuming for 1-9 hours to carry out a polycondensation reaction, and finally cooling in water after the reaction to obtain the furan-based polyamide.

[0032] Wherein, the first temperature is selected from 110-170℃, preferably 120-160℃; the second temperature is selected from 170-230℃, preferably 180-220℃; the third temperature is selected from 190-260℃, preferably 200-250℃; and the first temperature < the second temperature < the third temperature; in some embodiments, the second temperature is 40-80℃ higher than the first temperature, such as 50℃, 60℃, or 70℃; in some embodiments, the third temperature is 20-50℃ higher than the second temperature, such as 30℃ or 40℃.

[0033] The gradient temperature increase is 3-6°C every ten minutes.

[0034] The pressure during the vacuuming stage is 30-300 Pa.

[0035] During the transesterification and polycondensation stages, stirring can be carried out at a speed of 50-500 rpm, such as 350-500 rpm.

[0036] Fifthly, the present invention discloses the application of the furanyl polyamide shown in Formula I above in the reprocessing of chemically recyclable materials.

[0037] The novel furanyl polyamide prepared by this invention degrades to monomers under certain conditions, achieving closed-loop chemical recycling of the polyamide; the monomers include 2,5-furandicarboxylic acid and diamines, such as 1,5-pentanediamine.

[0038] The degradation conditions are as follows: 120-200℃, with sodium hydroxide aqueous solution as solvent, and furanyl polyamide is reacted under these conditions for 5-12 hours.

[0039] Furthermore, after the reaction is complete, the pH of the degradation solution is adjusted to 2-3 with hydrochloric acid. During this process, furanyl dicarboxylic acid gradually precipitates out. The precipitate is collected, washed with ethanol, and dried to obtain pure furanyl dicarboxylic acid. The recovery rate of furanyl dicarboxylic acid is 80%-85%. Therefore, the novel furanyl polyamide prepared by this invention can be completely degraded to monomers without further purification, further expanding the application of the bio-based raw material furanyl dicarboxylic acid and opening up new avenues for polyamide recovery research.

[0040] In this invention, the inert gas includes helium, neon, argon, krypton, xenon, carbon dioxide, or nitrogen, preferably argon.

[0041] The relative viscosity of the furanyl polyamide represented by Formula I in this invention is 1.3-1.65, such as 1.37-1.58; the glass transition temperature of the furanyl polyamide represented by Formula I is 57-142℃, such as 69-130℃; the melting point Tm of the furanyl polyamide represented by Formula I is 171-250℃, such as 180-241℃; the initial decomposition temperature Td5% of the furanyl polyamide represented by Formula I is 338-412℃, such as 380-412℃; the maximum decomposition temperature Tmax of the furanyl polyamide represented by Formula I is 446-486℃, such as 459-473℃; and the tensile strength of the furanyl polyamide represented by Formula I is 50-124MPa, such as 59-115MPa.

[0042] Beneficial effects:

[0043] (1) The furanyl polyamide provided by this invention introduces more amide bonds into the repeating units, providing more intermolecular hydrogen bonds. The resulting internal network needs to be disrupted at higher temperatures. Compared with previously reported furanyl semi-aromatic polyamides (initial decomposition temperature 367℃), the thermal stability is significantly improved. In addition, the furanyl polyamide provided by this invention is crystallizable, with a melting point of 180-250℃, and is a semi-crystalline polymer, providing excellent thermal stability and excellent solvent resistance.

[0044] (2) The preparation method of furanyl polyamide provided by the present invention is bulk polymerization, which does not require solvents and catalysts, saves energy and reduces emissions, and the preparation process is simple and green and environmentally friendly, reducing environmental pollution.

[0045] (3) The furanyl polyamide provided by this invention can recover the initial monomer from the degradation solution through a simple, efficient, and high-recovery-rate acidification and filtration method, thereby achieving closed-loop chemical recovery of polyamide. This work will further expand the application of the bio-based raw material furanyl dicarboxylic acid and open up new avenues for polyamide recovery research. Attached Figure Description

[0046] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0047] Figure 1 Aliphatic diamine monomers with the designed structures of Examples 1-4 1 H NMR spectrum.

[0048] Figure 2 The polyamide products of Examples 1-4 1 H NMR spectrum.

[0049] Figure 3 The polyamide product of Example 4 13 C NMR spectrum.

[0050] Figure 4 The image shows the TGA diagram of the polyamide product from Example 4.

[0051] Figure 5 The image shows the DSC chromatogram of the polyamide product in Example 4 (a second heating curve scanned from 30°C to 300°C at a heating rate of 10°C / min under N2 atmosphere).

[0052] Figure 6 The image shows the X-ray diffraction pattern of the polyamide product from Example 4.

[0053] Figure 7 The polyamide depolymerization product 1,5-pentanediamine and furanyl dicarboxylic acid of Example 5 1 H NMR spectrum. Detailed Implementation

[0054] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the invention as detailed in the claims.

[0055] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0056] In the following embodiments, the products were analyzed using a 400MHz Bruker nuclear magnetic resonance instrument. 1 1H NMR measurement: Take 6 mg of polyamide sample into an NMR tube, add deuterated trifluoroacetic acid, shake until completely dissolved, and then measure the sample.

[0057] The products were analyzed using a 400MHz Bruker nuclear magnetic resonance instrument. 13 C NMR measurement: Take 20 mg of polyamide sample into an NMR tube, add deuterated sulfuric acid, shake until completely dissolved, and then measure the sample.

[0058] The sample decomposition temperature was determined using a TGA 550 instrument and was the temperature at which a 5% mass loss occurred. 5-10 mg of sample was weighed onto a platinum pan, and under nitrogen atmosphere (inert gas), the temperature was increased at a rate of 20 °C / min, with the measured temperature range being 30-800 °C.

[0059] The sample melting temperature was determined using a DSC 250 instrument through a second temperature-scanning curve. 5-10 mg of sample was weighed onto a platinum pan. Under inert nitrogen protection, the program was set to first heat, then cool, and finally heat again. The initial heating temperature was 30°C, and the final temperature was the temperature at which the sample degraded by 5% under thermogravimetric analysis. Cooling involved reducing the sample temperature from the highest point back to 30°C. The melting point was measured at 10°C / min.-1 It proceeds at a certain rate.

[0060] The relative viscosity of the furanyl polyamide described in this invention was measured using an Ubbelohde viscometer with an inner diameter of 1.07 mm, with 96% concentrated sulfuric acid as the solvent and a sample concentration of 10 mg / mL.

[0061] Example 1

[0062] At room temperature, 1 mol of 1,4-butanediamine was dissolved in an equal volume of ethanol. Then, under nitrogen protection and stirring at 400 rpm, 0.2 mol of dibutyl oxalate solution was added dropwise at a flow rate of 300 μL / min. After the addition was complete, stirring continued for 2 hours. During esterification, excess 1,4-butanediamine capped the oxalate ester, yielding the desired product. After the reaction was complete, the white solid obtained by filtration was washed with ethanol, and the solid was dried to obtain the crude product. The crude product was recrystallized from butyl acetate, and the insoluble matter was filtered off. The solution was allowed to stand at low temperature, and the precipitated product was washed with ethanol. The solid was dried to obtain the white aliphatic diamine monomer.

[0063] 1.02 mmol of the aliphatic diamine monomer and 1 mmol of dimethyl 2,5-furandicarboxylate were added to the reaction vessel. Argon gas was purged at room temperature for 10 minutes. The reaction vessel was then heated to 120 °C, and the temperature was gradually increased to 180 °C at a rate of 3 °C / 10 min, and held at this temperature for 3 hours. The temperature was then increased to 200 °C, and a vacuum of 50 Pa was maintained for 4 hours.

[0064] After polycondensation is complete, stirring is stopped, the polymer is drained into cooling water, and then placed in an oven at 60°C for 12 hours to obtain furanyl polyamide with a relative viscosity of 1.47. g The temperature is 120℃, T m The temperature was 241℃, T d5％ The temperature is 380℃, T max The temperature is 459℃, and the tensile strength is 62MPa.

[0065] Example 2

[0066] At room temperature, 1 mol of 1,5-pentanediamine was dissolved in an equal volume of ethanol. Then, under nitrogen protection and stirring at 500 rpm, 0.25 mol of diethyl oxalate solution was added dropwise at a flow rate of 200 μL / min. After the addition was complete, stirring continued for 2 hours. During esterification, excess 1,5-pentanediamine capped the oxalate ester, yielding the desired product. After the reaction was complete, the white solid obtained by filtration was washed with ethanol, and the solid was dried to obtain the crude product. The crude product was recrystallized from butyl acetate, and the insoluble matter was filtered off. The solution was allowed to stand at low temperature, and the precipitated product was washed with ethanol. The solid was dried to obtain the white aliphatic diamine monomer.

[0067] 1.04 mmol of the designed aliphatic diamine monomer and 1 mmol of 2,5-furandicarboxylic acid chloride were added to the reaction vessel. Argon gas was purged at room temperature for 10 minutes. The reaction vessel was then heated to 140 °C, and the temperature was gradually increased to 200 °C at a rate of 5 °C / 10 min, and held at this temperature for 3 hours. The temperature was then increased to 220 °C, and a vacuum of 80 Pa was maintained for 4 hours.

[0068] After polycondensation is complete, stirring is stopped, the polymer is drained into cooling water, and then placed in an oven at 60°C for 12 hours to obtain furanyl polyamide with a relative viscosity of 1.58. g The temperature is 130℃, T d5％ The temperature is 390℃, T max The temperature is 462℃, and the tensile strength is 39MPa.

[0069] Example 3

[0070] At room temperature, 1.2 mol of 1,6-hexanediamine was dissolved in an equal volume of ethanol. Then, under nitrogen protection and stirring at 350 rpm, 0.2 mol of diethyl oxalate solution was added dropwise at a flow rate of 400 μL / min. After the addition was complete, stirring continued for 2 hours. During esterification, excess 1,6-hexanediamine capped the oxalate ester, yielding the desired product. After the reaction was complete, the white solid obtained by filtration was washed with ethanol, and the solid was dried to obtain the crude product. The crude product was recrystallized from butyl acetate, and the insoluble matter was filtered off. The solution was allowed to stand at low temperature, and the precipitated product was washed with ethanol. The solid was dried to obtain the white aliphatic diamine monomer with the designed structure.

[0071] 1.01 mmol of the aliphatic diamine monomer and 1 mmol of dibutyl 2,5-furandicarboxylate were added to the reaction vessel. Argon gas was purged at room temperature for 10 minutes. The reaction vessel was then heated to 160 °C, and the temperature was gradually increased to 200 °C at a rate of 6 °C / 10 min, and held at this temperature for 3 hours. The temperature was then increased to 250 °C, and a vacuum of 120 Pa was maintained for 5 hours.

[0072] After polycondensation is complete, stirring is stopped, the polymer is drained into cooling water, and then placed in an oven at 60°C for 12 hours to obtain furanyl polyamide with a relative viscosity of 1.49. g The temperature is 120℃, T m The temperature was 217℃, T d5％ The temperature was 393℃, T max The temperature is 471℃, and the tensile strength is 55MPa.

[0073] Example 4

[0074] At room temperature, 1 mol of 1,10-decanediamine was dissolved in an equal volume of ethanol. Then, under nitrogen protection and stirring at 450 rpm, 0.2 mol of diethyl oxalate solution was added dropwise at a flow rate of 250 μL / min. After the addition was complete, stirring continued for 2 hours to carry out esterification. During this process, excess 1,10-decanediamine capped the oxalate ester, yielding the desired product. After the reaction was complete, the white solid obtained by filtration was washed with ethanol, and the solid was dried to obtain the crude product. The crude product was recrystallized from butyl acetate, and the insoluble matter was filtered off. The solution was allowed to stand at low temperature, and the precipitated product was washed with ethanol. The solid was dried to obtain the white aliphatic diamine monomer with the designed structure.

[0075] 1.03 mmol of the aliphatic diamine monomer and 1 mmol of diethyl 2,5-furandicarboxylate were added to the reaction vessel. Argon gas was purged at room temperature for 10 minutes. The reaction vessel was then heated to 140 °C, and the temperature was gradually increased to 220 °C at a rate of 4 °C / 10 min, and maintained at this temperature for 3 hours. The temperature was then increased to 250 °C, and a vacuum of 300 Pa was applied for 5 hours.

[0076] After polycondensation is complete, stirring is stopped, the polymer is drained into cooling water, and then placed in an oven at 60°C for 12 hours to obtain furanyl polyamide with a relative viscosity of 1.37. g The temperature was 69℃, T m For 180℃, T d5％ The temperature was 412℃, T max The temperature is 473℃, and the tensile strength is 49MPa.

[0077] Example 5

[0078] 200 mg of the furanyl polyamide prepared in Example 2 and 5 mL of 1 M sodium hydroxide aqueous solution were added to a pressure-resistant tube. The reaction vessel was heated to 180 °C and maintained at this temperature for 10 h. After cooling to room temperature, the filtrate was collected and 1,5-pentanediamine was obtained by vacuum distillation in a yield of approximately 55%. The pH of the remaining salt solution after vacuum distillation was adjusted to 2–3 by adding hydrochloric acid aqueous solution. Furandicarboxylic acid precipitated out, was washed with ethanol, and dried under vacuum overnight to obtain pure furandicarboxylic acid in a yield of 81%.

[0079] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. 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 modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A furanyl polyamide as shown in Formula I; in, R is selected from C4-C 12 alkyl; n is any integer from 10 to 500.

2. The method for preparing the furanyl polyamide according to claim 1, characterized in that, The process includes reacting an aliphatic diamine monomer containing an oxalamide group, as shown in Formula II, with a furan dicarboxylic acid derivative monomer to prepare a furan-based polyamide, as shown in Formula I. in, R is selected from C4-C 12 alkyl.

3. The preparation method according to claim 2, characterized in that, The method for preparing the aliphatic diamine monomer containing an oxalamide group as shown in Formula II includes: reacting an oxalate diester with a C4-C... 12 Aliphatic diamine reaction.

4. The preparation method according to claim 3, characterized in that, The oxalic acid diester includes dimethyl oxalate, diethyl oxalate, dibutyl oxalate, or any combination thereof; the molar ratio of the oxalic acid diester to the C4-C12 aliphatic diamine is 0.1-0.3:

1.

5. The preparation method according to claim 2, characterized in that, The furan dicarboxylic acid derivative monomers include 2,5-furandicarboxylic acid, dimethyl 2,5-furandicarboxylate, diethyl 2,5-furandicarboxylate, dibutyl 2,5-furandicarboxylate, 2,5-furandicarboxyl chloride, or any combination thereof.

6. The preparation method according to claim 2, characterized in that, Under an inert atmosphere, the aliphatic diamine monomer containing oxalamide groups as shown in Formula II and the furan dicarboxylic acid derivative monomer are heated to a first temperature, then heated to a second temperature to carry out an ester exchange reaction, and then heated to a third temperature to carry out a polycondensation reaction to obtain the furan-based polyamide.

7. The preparation method according to claim 6, characterized in that, The first temperature is selected from 110-170℃; the second temperature is selected from 170-230℃; the third temperature is selected from 190-260℃; and the first temperature < the second temperature < the third temperature.

8. The preparation method according to claim 6, characterized in that, The first temperature is selected from 120-160℃; the second temperature is selected from 180-220℃; and the third temperature is selected from 200-250℃.

9. The preparation method according to claim 6, characterized in that, The temperature is raised to the second temperature and maintained for 1-4 hours to carry out the transesterification reaction.

10. The preparation method according to claim 6, characterized in that, The temperature is raised to the third temperature and a vacuum is applied for 1-9 hours to carry out the polycondensation reaction.

11. The use of the furanyl polyamide of claim 1 in the preparation of chemically recyclable materials.

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