PA4 or PA5 and a process for their preparation

Abstract

The application belongs to the technical field of polymer materials, and relates to PA4 or PA5 and a preparation method thereof. The preparation method comprises the following steps: firstly, preparing PA4 prepolymer or PA5 prepolymer by melt polycondensation on reaction raw materials; and secondly, performing solid-phase polymerization on the PA4 prepolymer or the PA5 prepolymer to obtain the PA4 or the PA5. The reaction raw materials comprise a binary amine and a reaction monomer. The reaction monomer is amino butyric acid, or butyrolactam, or a mixture of amino butyric acid and butyrolactam, or amino valeric acid, or valerolactam, or a mixture of amino valeric acid and valerolactam. When the reaction raw materials contain butyrolactam or valerolactam, the reaction raw materials also contain water. The reaction temperature of the melt polycondensation is 180-200 DEG C. By means of targeted regulation on the reaction system and the process, the application inhibits the generation of end-lactam groups, improves the monomer conversion rate, the polymer molecular weight and the thermal stability, the process does not need harmful solvents, is mild, controllable and easy to scale up.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to PA4 or PA5 and their preparation methods. Background Technology

[0002] PA4 (polyamide 4, also known as polybutyrolactam PBL) and PA5 (polyamide 5) are novel green polymer materials with unique properties. Their hygroscopicity is close to that of natural fibers, and they have excellent antistatic properties. PA4 can be chemically recycled and biodegraded, and its monomer sources are widely available, giving it broad application prospects. However, current problems such as immature polymerization processes, poor thermal stability of products, and difficulty in large-scale preparation greatly limit their application.

[0003] The traditional preparation process is melt polycondensation, which is the classic preparation process for traditional polyamides such as PA6 and PA66. It is generally believed in the industry that melt polycondensation requires increasing the temperature to promote the polymerization reaction. For example, the melt polycondensation method of PA4 with aminobutyric acid as monomer disclosed in patent CN101974151B and the melt polycondensation methods of PA4 and PA6 disclosed in literature 1 (Preparation and Structure of Nylon4 / 6 Random-Copolymer Nanofibers [J]. Macromolecular Research, 2012, 20(8):817-823.) both follow the traditional idea of ​​"increasing the temperature to promote polymerization". However, the inventors discovered that if PA4 or PA5 is prepared using this method, the monomer of PA4, aminobutyric acid, readily cyclizes to form a small molecule butyrolactam with high thermal stability, and the monomer of PA5, aminovaleric acid, readily cyclizes to form a small molecule valeric acid with high thermal stability. When using conventional melt polymerization processes for PA66 and PA6, a large amount of small molecule butyrolactam and valeric acid accumulate in the system, and they easily form terminal lactam groups on the polymer chain. This not only inhibits linear polymerization but also results in extremely low monomer conversion, polymer yield, and molecular weight, making conventional melt polycondensation processes unsuitable for industrial application. Patent CN101974151B and Document 1 did not consider the negative impact of terminal lactam / valeric acid groups on product performance and did not take any measures to inhibit the formation of these groups. The products disclosed in these documents do not specify key performance indicators such as thermal stability, and the resulting products actually suffer from low monomer conversion, polymer yield, and molecular weight, as well as insufficient thermal stability, failing to overcome the industry's technical bottleneck.

[0004] At present, the preparation of PA4 mainly relies on anionic ring-opening polymerization. For example, Reference 2 (Synthesis and properties of bio-based butyrolactam and polybutyrolactam[J]. Journal of Functional Polymers, 2019, 32 (01):110-116.) reported that PA4 was synthesized by using NaOH as an initiator and butyrolactam as a raw material. However, the product has a low molecular weight, a melting point below 212.4℃, and poor thermal stability. Reference 3 (Suspension polymerization of 2-pyrrolidone in the presence of CO2 and organic promoters [J]. Journal of Applied Polymer Science, 2021, 138:e49736.) and patents CN111154097B and CN109851778B optimized the anionic ring-opening polymerization process by introducing alkane inert solvents, organic promoters and CO2. Although this improved the yield and intrinsic viscosity of PA4 and the thermal stability to some extent, the use of solvents brings both safety and environmental risks. Moreover, the solvent recovery cost is high and the monomer consumption is large, resulting in high production costs and making it difficult to apply on a large scale.

[0005] In addition, references 4 (Research progress on biodegradable polybutyrolactam [J]. Synthetic Fibers, 2023, 52 (04):7-11.) and 5 (Crystallization properties of polybutyrolactam modified by eutectic solvent [J]. Journal of Functional Polymers, 2024, 37 (05):388-398.) both point out that the melting point (260-268℃) of PA4 is close to its thermal decomposition temperature (270-285℃), and thermal decomposition easily occurs during the melting and heating process. Therefore, it is difficult to achieve melt processing under conventional conditions, which greatly limits its application fields. In order to solve this problem, patent application CN118879063A introduced anionic ring-opening polymerization by adding long-chain hyperbranched polymers to the butyrolactam / alkali catalyst mixture, which reduced the melting point of PA4 to a certain extent and increased the thermal decomposition temperature. However, this improvement is due to the additive effect of long-chain hyperbranched polymers and does not fundamentally change the chain structure of PA4, so the improvement is limited. Summary of the Invention

[0006] The purpose of this invention is to solve the problems existing in the prior art and to provide a PA4 or PA5 and its preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The preparation method of PA4 or PA5 involves first performing melt polycondensation on the reactants to obtain PA4 prepolymer or PA5 prepolymer, and then performing solid-state polymerization on the PA4 prepolymer or PA5 prepolymer to obtain PA4 or PA5.

[0009] The reaction raw materials include diamine and reaction monomers. The reaction monomers are aminobutyric acid, butyrolactam, or a mixture of aminobutyric acid and butyrolactam, or aminovaleric acid, or valeric acid, or a mixture of aminovaleric acid and valeric acid.

[0010] When the reaction raw materials contain butyrolactam or valproic acid, the reaction raw materials also contain water;

[0011] The reaction temperature for melt polycondensation is 180-200℃.

[0012] Unlike existing technologies, this invention incorporates a diamine during the preparation of PA4 or PA5, which significantly reduces the content of terminal lactam groups. This effectively enhances the polymerization activity of the terminal groups in PA4 or PA5, increasing monomer conversion and molecular weight. Furthermore, it significantly improves the thermal stability of PA4 or PA5. The principle behind this significant reduction in the content of terminal lactam groups is explained below, using GABA as an example:

[0013] Without the addition of a diamine, the terminal group (carboxyl-COOH) of the oligomer reacts with aminobutyric acid, which then re-engages a terminal lactam group. The reaction equation is as follows:

[0014] -(HN-(CH2)3-CO-) n -HN-(CH2)3-COOH+H2N-(CH2)3-COOH→-(HN-(CH2)3-CO-) n -HN-(CH2)3-CONCO(CH2)3 (terminal lactam group)

[0015] When a diamine is added, the terminal group of the oligomer is a terminal amino group. The terminal amino group reacts with the new gamma-aminobutyric acid, and the resulting product also has a terminal amino group, which cannot be reversed. The reaction equation is as follows:

[0016] -(HN-(CH2)3-CO-) n -HN-(CH2) X -NH2+H2N-(CH2)3-COOH→-(HN-(CH2)3-CO-) n -HN-(CH2) X -NHCO-(CH2)3-NH2

[0017] When a diamine is added, the diamine and aminobutyric acid undergo a dehydration reaction to generate diamide diamine (structure: H2N-(CH2)3-CO-HN-(CH2)x-NH-CO-(CH2)3-NH2). The formation of diamide diamine can inhibit the formation of terminal lactam groups and improve the thermal stability and molecular weight of the polymer.

[0018] Unlike existing technologies, this invention controls the reaction temperature of melt polycondensation to be lower during the preparation of PA4 or PA5, which can promote the transformation of reactant monomers into polymers PA4 and PA5, inhibit the cyclization of aminobutyric acid or aminovaleric acid to form butyrolactam or valeractam, and improve the conversion rate of reactant monomers and the molecular weight of polymers.

[0019] This invention controls the presence of water in the reaction raw materials when butyrolactam or valeramide is present. This is because butyrolactam and valeramide themselves lack functional groups that can participate in the polymerization reaction; without water, the ring-opening reaction cannot occur, and thus PA4 or PA5 cannot be formed. However, aminobutyric acid can provide the water required for the reaction through its own dehydration, allowing it to participate in polymerization without the need for additional water. Taking butyrolactam as an example, the reaction equation is as follows:

[0020] n-Butyrolactam + H2O → nH2N-(CH2)3-COOH + H2O → -(HN-(CH2)3-CO-) n -+H2O

[0021] As a preferred technical solution:

[0022] In the preparation method of PA4 or PA5 as described above, the molar ratio of diamine to reactant monomer is 1-5:100.

[0023] In the preparation method of PA4 or PA5 as described above, the diamine is one or more selected from ethylenediamine, propylenediamine, butanediamine, hexanediamine, 2-methyl-1,5-pentanediamine, octanediamine, nonanediamine, decanediamine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 1,4-cyclohexanediamine, isophorone diamine, 4,4'-diaminodicyclohexylmethane (PACM), 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane (MACM), polyether diamine, fluorinated diamine, and diamide diamine. The structural formula of the diamide diamine is as follows:

[0024] ;

[0025] In the formula, R1 represents -(CH2)3- or -(CH2)4-, and R2 represents one or more combinations of -CH2-, phenyl, and cyclohexyl.

[0026] In the preparation method of PA4 or PA5 as described above, when the reaction raw materials contain butyrolactam or valproic acid, the mass ratio of water to the reaction monomer is 2-5:100.

[0027] The preparation method of PA4 or PA5 as described above also includes a monofunctional molecular weight regulator as a reactant; the monofunctional molecular weight regulator is acetic acid, benzoic acid, lauric acid, stearic acid or cyclohexanecarboxylic acid; the molar ratio of the monofunctional molecular weight regulator to the reactant monomer is 0.1-3:100.

[0028] Unlike existing technologies, this invention introduces a monofunctional molecular weight regulator when preparing PA4 or PA5. This regulator can react with terminal amino groups, reduce the content of active terminal amino groups, and form medium and long chain end groups. It is not easy to cyclize and form terminal lactam groups, thereby further improving the thermal stability of PA4 or PA5.

[0029] As described above, the reaction time for melt polycondensation of PA4 or PA5 is 1-6 hours, and the melt polycondensation is carried out in a closed reactor under the protection of nitrogen or an inert atmosphere.

[0030] In the preparation method of PA4 or PA5 as described above, the reaction time for melt polycondensation is 6 hours.

[0031] As described above, the preparation method of PA4 or PA5 involves further purification of the reaction product after melt polycondensation (because the reaction product contains unreacted monomers). The purification method is as follows: water is added to the reaction product, and the mixture is stirred (the purpose is to fully dissolve the unreacted monomers in the water). Then, solid-liquid separation is performed, and the separated solid is the PA4 prepolymer or PA5 prepolymer. The mass ratio of water to the reaction product is 1-10:1.

[0032] As described above, the solid-state polymerization reaction temperature is 175-190℃, the reaction time is 3-5h, and the reaction pressure is 200-1000Pa.

[0033] The solid-phase polymerization of the present invention is carried out at a lower temperature, which can effectively suppress side reactions such as thermal decomposition, and is beneficial to improving the yield and molecular weight of PA4 or PA5.

[0034] The present invention also provides PA4 or PA5, which are prepared by the preparation method of PA4 or PA5 as described in any of the preceding claims;

[0035] The terminal amino group content of PA4 or PA5 is 76.8-505.2 mmol / kg, the terminal lactam group content is ≤96 mmol / kg, the relative viscosity is 1.42-1.94, and the 5% thermal weight loss temperature T0 is... d5 ≥301.5℃ (5% thermogravimetric temperature T of PA4 prepared by anionic ring-opening polymerization in the prior art) d5 The temperature is approximately 260℃, which is significantly higher than that of the prior art. The melting point is 193-247.6℃, and the enthalpy of fusion is 17.6-28.5 J / g.

[0036] Beneficial effects:

[0037] (1) By adding diamine to the reaction raw materials, controlling the melt polycondensation reaction temperature, and adding water when the reaction raw materials contain butyrolactam or valerolactam, and then performing solid-phase polymerization, the present invention effectively reduces the content of terminal lactam groups in PA4 or PA5, improves the polymerization activity of terminal groups, thereby improving monomer conversion rate and polymer molecular weight, and significantly enhances the thermal stability of PA4 or PA5.

[0038] (2) The preparation process of the present invention is mild and precisely controllable, without the need to use alkane inert solvents, thus avoiding safety and environmental hazards and high recycling costs. It breaks through the bottleneck of large-scale preparation of PA4 or PA5, making it easy to achieve large-scale production and with low production costs.

[0039] (3) The PA4 or PA5 prepared by this invention has improved thermal stability, and the difference between its melting point and thermal decomposition temperature is increased. It has good melt processing performance, which fully utilizes the unique characteristics of PA4 or PA5 and expands its application prospects in the fields of fiber, film and plastic products. Attached Figure Description

[0040] Figure 1 A photograph of PA4 prepared in Example 1;

[0041] Figure 2 The FT-IR (Fourier transform infrared) curves of PA4 prepared in Examples 1 and 2 and diamide diamine prepared in Example 6 are shown.

[0042] Figure 3 The 5% thermogravimetric temperature T of PA4 prepared in Example 1 d5 curve;

[0043] Figure 4 DSC curves of PA4 prepared in Example 1 and PA5 prepared in Example 5;

[0044] Figure 5 The ¹H NMR spectra of PA4 prepared in Example 1 and diamide diamine prepared in Example 6 are shown.

[0045] Figure 6 for Figure 5 A schematic diagram showing the chemical shift assignments of the corresponding proton NMR spectra. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0047] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0048] Terminal amino group content: Accurately weigh 0.5000g of sample and place it in a 250mL reflux flask. Add 45mL of phenol and reflux in an oil bath at 130℃ for 1-2 hours until the sample is completely dissolved. Stop heating and allow it to cool naturally to room temperature. Add 5mL of 0.1mol / L NaOH in methanol and stir thoroughly. Titrate the endpoint using a potentiometric titrator. The test standard is based on ISO 9712:1990. Perform the test in parallel three times and take the average value as the final result.

[0049] Terminal lactam group content: The test was performed using nuclear magnetic resonance spectroscopy with deuterated trifluoroacetic acid as the solvent. 5-10 mg of sample was weighed and dissolved in deuterated trifluoroacetic acid. The characteristic proton peak of the terminal lactam group at a chemical shift of 2.53 ppm and the reference proton peak at a chemical shift of 2.41 ppm were integrated, and the terminal lactam group content (unit converted to mmol / kg) was calculated by combining the ratio of the integrated areas of the two with the corresponding proton number correction.

[0050] Relative viscosity: The sample was dissolved in 96% (mass fraction) sulfuric acid aqueous solution to prepare a sample solution of 0.01 g / mL. The solution was then tested using an Ubbelohde viscometer in a constant temperature water bath at 25.00℃. The test standard was based on ISO 307:2019 (determination of viscosity of polyamide).

[0051] 5% thermogravimetric temperature T d5 Thermogravimetric analysis (TGA) was used. 10 mg of sample was accurately weighed and placed in an alumina sample crucible. The test atmosphere was nitrogen protection (nitrogen flow rate 50 mL / min). The test range was from 30℃ to 600℃, with a heating rate of 10℃ / min. The temperature at which the sample mass loss reached 5% was recorded; this temperature is the 5% thermogravimetric temperature T. d5 The testing standard is based on ISO 11358-1:2014 (Thermogravimetric analysis of plastics (TGA) - Part 1: General principles).

[0052] Melting point and enthalpy of fusion: Differential scanning calorimetry (DSC) was used for testing. 5-8 mg of sample was weighed and placed in an aluminum sample cell. The test atmosphere was nitrogen protection (nitrogen flow rate 50 mL / min). The test procedure was as follows: the temperature was first raised from room temperature to 300 °C and held for 2 min to eliminate thermal history. Then, the temperature was lowered to 50 °C at a rate of 10 °C / min, and then raised to 300 °C at a rate of 10 °C / min. The melting peak temperature during the second heating process was recorded as the melting point. The enthalpy of fusion of the sample was obtained by integrating the melting peak area. The test standard was based on ISO 11357-3:2018 (Thermal analysis of plastics - Part 3: Determination of melting point and crystallization temperature).

[0053] In the following individual embodiments, water A and water B are both essentially water. The two are distinguished by labels to clarify that they belong to different process systems: water A belongs to the reaction raw material system, and water B is used in the process of preparing PA4 or PA5 prepolymers (added after the reaction product is obtained by melt polycondensation).

[0054] Example 1

[0055] The preparation method of PA4 is as follows:

[0056] (1) Preparation of materials;

[0057] The reaction raw materials consist of a diamine (hexamethylenediamine), a reactive monomer (aminobutyric acid), and a monofunctional molecular weight regulator (acetic acid). The molar ratio of the diamine to the reactive monomer is 1:100, and the molar ratio of the monofunctional molecular weight regulator to the reactive monomer is 0.1:100.

[0058] water;

[0059] (2) Preparation of PA4 prepolymer;

[0060] The reactants are subjected to melt polycondensation to obtain the reaction product. Water is added to the reaction product, and after stirring and mixing, solid-liquid separation is performed. The separated solid is the PA4 prepolymer. The melt polycondensation reaction temperature is 180℃ and the reaction time is 6h. The mass ratio of water to reaction product is 1:1.

[0061] (3) Preparation of PA4;

[0062] PA4 prepolymer is subjected to solid-state polymerization to obtain PA4; wherein the reaction temperature of solid-state polymerization is 190℃, the reaction time is 5h, and the reaction pressure is 200Pa.

[0063] The final PA4 (actual product as shown) Figure 1 As shown, the FT-IR curve is as follows Figure 2 As shown, the NMR 1H spectrum and chemical shift assignments are as follows: Figure 5 and Figure 6The yield (yield = (actual mass of product / theoretical mass of product) × 100%) was 10.9%, the terminal amino group content was 110.9 mmol / kg, the terminal lactam group content was 70 mmol / kg, the relative viscosity was 1.91, and the 5% thermal decomposition temperature T0 was [not specified]. d5 The temperature is 329.4℃ (5% thermogravimetric temperature T). d5 Curves Figure 3 As shown), the melting point is 246.5℃ (DSC curve as shown). Figure 4 As shown in the figure, the enthalpy of fusion is 27.1 J / g.

[0064] Comparative Example 1

[0065] The preparation method of PA4 differs from that in Example 1 in that no diamine is present in the reaction raw materials.

[0066] The final PA4 had a terminal amino group content of 332 mmol / kg, a terminal lactam group content of 153 mmol / kg, a relative viscosity of 1.2, and a 5% thermal weight loss temperature T0. d5 Its temperature is 294.5℃, its melting point is 241.5℃, and its enthalpy of fusion is 21.2 J / g.

[0067] Compared with Example 1, Comparative Example 1 showed that the final PA4 had increased content of terminal lactam groups, increased content of terminal amino groups, decreased relative viscosity, and a 5% thermal weight loss temperature T. d5 The melting point and enthalpy of fusion are reduced because the reaction raw materials in Comparative Example 1 do not contain a diamine. The terminal groups (carboxyl groups) of the oligomer react with GABA, and GABA easily bites back to form terminal lactam groups. At the same time, the absence of a diamine cannot improve the polymerization activity of the terminal groups, monomer conversion rate and molecular weight, nor can it improve thermal stability.

[0068] Example 2

[0069] The preparation method of PA4 is as follows:

[0070] (1) Preparation of materials;

[0071] The reaction raw materials consist of a diamine (butanediamine), a reaction monomer (butanelactam), a monofunctional molecular weight regulator (benzoic acid), and water A. The molar ratio of the diamine to the reaction monomer is 5:100, the molar ratio of the monofunctional molecular weight regulator to the reaction monomer is 3:100, and the mass ratio of water A to the reaction monomer is 5:100.

[0072] Water B;

[0073] (2) Preparation of PA4 prepolymer;

[0074] The reactants are subjected to melt polycondensation to obtain the reaction product. Water B is added to the reaction product, and after stirring and mixing, solid-liquid separation is performed. The separated solid is the PA4 prepolymer. The melt polycondensation reaction temperature is 180℃ and the reaction time is 6h. The mass ratio of water B to the reaction product is 5:1.

[0075] (3) Preparation of PA4;

[0076] PA4 prepolymer is subjected to solid-state polymerization to obtain PA4; wherein the reaction temperature of solid-state polymerization is 190℃, the reaction time is 5h, and the reaction pressure is 1000Pa.

[0077] The final PA4 (FT-IR curve as shown) Figure 2 The yield of the product (shown) was 11.2%, the terminal amine content was 505.2 mmol / kg, the terminal lactam content was 59 mmol / kg, the relative viscosity was 1.42, and the 5% thermal weight loss temperature was T. d5 Its temperature is 322.5℃, its melting point is 247.6℃, and its enthalpy of fusion is 17.6 J / g.

[0078] Example 3

[0079] The preparation method of PA4 is as follows:

[0080] (1) Preparation of materials;

[0081] The reaction raw materials consist of a diamine (decanediamine), a reaction monomer (a mixture of aminobutyric acid and butyrolactam), a monofunctional molecular weight regulator (acetic acid), and water A. The molar ratio of the diamine, aminobutyric acid, and butyrolactam is 1:50:50, the molar ratio of the monofunctional molecular weight regulator, aminobutyric acid, and butyrolactam is 0.5:50:50, and the mass ratio of water A to the reaction monomer is 3:100.

[0082] Water B;

[0083] (2) Preparation of PA4 prepolymer;

[0084] The reactants are subjected to melt polycondensation to obtain the reaction product. Water B is added to the reaction product, and after stirring and mixing, solid-liquid separation is performed. The separated solid is the PA4 prepolymer. The melt polycondensation reaction temperature is 200℃ and the reaction time is 6h. The mass ratio of water B to the reaction product is 1:1.

[0085] (3) Preparation of PA4;

[0086] PA4 prepolymer is subjected to solid-state polymerization to obtain PA4; wherein the reaction temperature of solid-state polymerization is 190℃, the reaction time is 5h, and the reaction pressure is 1000Pa.

[0087] The final PA4 yield was 8.9%, with a terminal amine content of 135.6 mmol / kg, a terminal lactam content of 74 mmol / kg, a relative viscosity of 1.78, and a 5% thermal decomposition temperature T0. d5 Its temperature is 329.5℃, its melting point is 245.3℃, and its enthalpy of fusion is 24.2 J / g.

[0088] Example 4

[0089] The preparation method of PA4 is as follows:

[0090] (1) Preparation of materials;

[0091] The reaction raw materials consist of a diamine (p-phenylenediamine), a reaction monomer (aminobutyric acid), and a monofunctional molecular weight regulator (lauric acid). The molar ratio of the diamine to the reaction monomer is 1:100, and the molar ratio of the monofunctional molecular weight regulator to the reaction monomer is 0.1:100.

[0092] water;

[0093] (2) Preparation of PA4 prepolymer;

[0094] The reactants are subjected to melt polycondensation to obtain the reaction product. Water is added to the reaction product, and after stirring and mixing, solid-liquid separation is performed. The separated solid is the PA4 prepolymer. The melt polycondensation reaction temperature is 180℃, and the reaction time is 6h. The mass ratio of water to reaction product is 10:1.

[0095] (3) Preparation of PA4;

[0096] PA4 prepolymer is subjected to solid-state polymerization to obtain PA4; wherein the reaction temperature of solid-state polymerization is 175℃, the reaction time is 5h, and the reaction pressure is 200Pa.

[0097] The final PA4 yield was 7.5%, with a terminal amine content of 195.3 mmol / kg, a terminal lactam group content of 76 mmol / kg, a relative viscosity of 1.66, and a 5% thermal decomposition temperature T0. d5 Its temperature is 325.6℃, its melting point is 244.8℃, and its enthalpy of fusion is 20.5 J / g.

[0098] Example 5

[0099] The preparation method of PA5 is as follows:

[0100] (1) Preparation of materials;

[0101] The reaction raw materials consist of diamine (ethylenediamine), reactant monomer (valeronamide), monofunctional molecular weight regulator (acetic acid) and water A. The molar ratio of diamine to reactant monomer is 1:100, the molar ratio of monofunctional molecular weight regulator to reactant monomer is 0.1:100, and the mass ratio of water A to reactant monomer is 2:100.

[0102] Water B;

[0103] (2) Preparation of PA5 prepolymer;

[0104] The reaction raw materials are subjected to melt polycondensation to obtain the reaction product. Water B is added to the reaction product, and after stirring and mixing, solid-liquid separation is performed. The separated solid is the PA5 prepolymer. The reaction temperature of melt polycondensation is 180℃, and the reaction time is 6h. The mass ratio of water B to the reaction product is 2:1.

[0105] (3) Preparation of PA5;

[0106] PA5 is obtained by solid-state polymerization of PA5 prepolymer; wherein the reaction temperature of solid-state polymerization is 175℃, the reaction time is 5h, and the reaction pressure is 200Pa.

[0107] The final PA5 yield was 10.5%, with a terminal amine content of 335.6 mmol / kg, a terminal lactam content of 96 mmol / kg, a relative viscosity of 1.5, and a 5% thermal decomposition temperature T5. d5 The temperature is 301.5℃, and the melting point is 193℃ (DSC curve as shown). Figure 4 As shown in the figure, the enthalpy of fusion is 20.2 J / g.

[0108] In particular, this invention has found that when the diamine is a diamide diamine, the molecular weight increases rapidly during the solid-state thickening process; on the other hand, using a diamide diamine as a reaction anchor results in a higher product yield. This is because the diamide diamine has a larger molecular weight and a longer molecular chain, and the terminal group of the product is a terminal amino group, which cannot be bitten back to form a terminal lactam group. At the same time, the diamide diamine structural unit has a larger molecular weight, making it easier to react and obtain a product with the target viscosity. To support this view, this invention has also designed Examples 6 to 9. The only difference between these examples and Example 1 is that the diamine used is a diamide diamine, and a lower reaction temperature and a shorter reaction time are used in the solid-state polymerization process in step (3). The specific diamide diamine used is shown in Table 1.

[0109] Table 1: Diamide diamines and their structural formulas used in Examples 6-9

[0110]

[0111] Hexamethylenediamine bis(4-aminobutyramide) is a diamide diamine synthesized from hexamethylenediamine and aminobutyric acid in a molar ratio of 1:2. The reaction temperature is 180℃ and the reaction time is 2h. The FT-IR curve of hexamethylenediamine bis(4-aminobutyramide) is shown below. Figure 2 As shown, the NMR 1H spectrum and chemical shift assignments are as follows: Figure 5 and Figure 6 As shown; m-phenylenediamine bis(4-aminobutyramide) is a diamide diamine synthesized from m-phenylenediamine and aminobutyric acid in a molar ratio of 1:2, with a reaction temperature of 200℃ and a reaction time of 2h; ethylenediamine bis(5-aminopentanamide) is a diamide diamine synthesized from ethylenediamine and aminopentanamide in a molar ratio of 1:2, with a reaction temperature of 160℃ and a reaction time of 2h; 4,4'-diaminodicyclohexylmethane bis(4-aminobutyramide) is a diamide diamine synthesized from 4,4'-diaminodicyclohexylmethane and aminobutyric acid in a molar ratio of 1:2, with a reaction temperature of 180℃ and a reaction time of 2h.

[0112] The reaction temperature, reaction time, and relevant performance indicators of the final PA4 obtained in step (3) of Examples 6-9 are shown in Table 2.

[0113] Table 2: Reaction temperature, reaction time, and relevant performance indicators of the final PA4 obtained in step (3) of Examples 6-9 for solid-state polymerization.

[0114] Example 6 Example 7 Example 8 Example 9 Reaction temperature of solid-phase polymerization (°C) 180 180 180 180 Reaction time (h) of solid-phase polymerization 3 3 3 3 Yield (%) 20.5 21.6 22.4 19.6 Terminal amino group content (mmol / kg) 76.8 135.2 87.4 105.7 Terminal lactam group content (mmol / kg) 59 61 43 58 relative viscosity 1.85 1.94 1.88 1.89 <![CDATA[5% Thermogravimetric Temperature T d5 (°C)]]> 329.2 332.7 328.5 328.7 Melting point (°C) 244.5 246.3 245.7 247.0 Enthalpy of fusion (J / g) 27.1 28.5 26.8 27.5

[0115] The comparison shows that the performance indicators of PA4 obtained in Examples 6-9 are basically the same as those in Example 1. During the solid-phase thickening process, the reaction rate is significantly accelerated; at a lower reaction temperature, the target viscosity can be reached in just 3 hours, improving the efficiency of PA4 industrial production. Furthermore, the yield is better than in Example 1, indicating that the use of diamide diamine can accelerate product formation and improve the selectivity of polymer formation.

[0116] In the above embodiments and comparative examples, unless the pressure value is explicitly specified, the pressure is assumed to be atmospheric pressure.

Claims

1. A method for preparing PA4 or PA5, characterized in that, First, the reactants are melt-polymerized to obtain the reaction product. Then, the reaction product is purified to obtain PA4 prepolymer or PA5 prepolymer. Then, the PA4 prepolymer or PA5 prepolymer is solid-state polymerized to obtain PA4 or PA5. The reaction raw materials include diamine and reaction monomer, and the molar ratio of diamine to reaction monomer is 1-5:

100. The diamine is one or more of the following: ethylenediamine, propylenediamine, butanediamine, hexamethylenediamine, 2-methyl-1,5-pentanediamine, octanediamine, nonanediamine, decanediamine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 1,4-cyclohexanediamine, isophorone diamine, 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, polyether diamine, and diamide diamine. The structural formula of diamide diamine is as follows: ； In the formula, R1 represents -(CH2)3- or -(CH2)4-, and R2 represents one or more combinations of -CH2-, phenylene, and cyclohexylene. The reaction monomer is aminobutyric acid, or butyrolactam, or a mixture of aminobutyric acid and butyrolactam, or aminovaleric acid, or valeric acid, or a mixture of aminovaleric acid and valeric acid; When the reaction raw materials contain butyrolactam or valproic acid, the reaction raw materials also contain water; The reaction temperature for melt polycondensation is 180-200℃; The purification method is as follows: water is added to the reaction product, and after stirring and mixing, solid-liquid separation is carried out. The separated solid is PA4 prepolymer or PA5 prepolymer. The mass ratio of water to reaction product is 1-10:

1.

2. The method for preparing PA4 or PA5 according to claim 1, characterized in that, When the reaction raw materials contain butyrolactam or valproic acid, the mass ratio of water to the reaction monomer is 2-5:

100.

3. The method for preparing PA4 or PA5 according to claim 1, characterized in that, The reaction raw materials also include a monofunctional molecular weight regulator; the monofunctional molecular weight regulator is acetic acid, benzoic acid, lauric acid, stearic acid or cyclohexanecarboxylic acid; the molar ratio of the monofunctional molecular weight regulator to the reaction monomer is 0.1-3:

100.

4. The method for preparing PA4 or PA5 according to claim 1, characterized in that, The reaction time for melt polycondensation is 1-6 hours.

5. The method for preparing PA4 or PA5 according to claim 1, characterized in that, The reaction temperature for solid-phase polymerization is 175-190℃, the reaction time is 3-5h, and the reaction pressure is 200-1000Pa.

6. PA4 or PA5, characterized in that, It is prepared by the preparation method of PA4 or PA5 as described in any one of claims 1 to 5; The terminal amino group content of PA4 or PA5 is 76.8-505.2 mmol / kg, the terminal lactam group content is ≤96 mmol / kg, the relative viscosity is 1.42-1.94, and the 5% thermal weight loss temperature T0 is... d5 ≥301.5℃, melting point is 193-247.6℃, enthalpy of fusion is 17.6-28.5J / g.

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