Nano-scale polyamide particles and preparation method thereof

Abstract

The present invention relates to nano-scale polyamide particles and a preparation method thereof, belonging to the technical field of polyamide particle preparation. The method comprises: (1) mixing a diacyl chloride monomer substituted with furandicarboxylic acid or its derivatives, an aromatic diamine monomer, and a diamine monomer with a sulfonic acid group in a first polymerization solvent to carry out a polymerization reaction; (2) adding an alkali to the semi-aromatic polyamide; (3) spraying the polyamide for drying, then soaking it in water, and then filtering, washing, and drying the soaked polyamide; (4) mixing the polyamide particles with a second polymerization solvent, and then adding an unstable solvent; (5) mixing the mixed solution with a salt solution, then emulsifying it, and then removing the second polymerization solvent to obtain nano-scale polyamide particles. The nano-scale polyamide particles prepared by the present invention can have a particle size of less than 10 nm, and can also expand the preparation range of the polyamide particle size, thereby expanding the application scenarios.

Description

Technical Field

[0001] The invention belongs to the technical field of polyamide particle preparation, and particularly relates to nanometer-scale polyamide particles and a preparation method thereof. Background Art

[0002] Lithium batteries primarily consist of a positive electrode, a negative electrode, an electrolyte, and a separator between them. Aside from the electrolyte, the other components are typically coated onto a substrate using specialized materials to enhance performance. Positive electrodes are typically coated with oil, negative electrodes with water, and separators with either water or oil. Oil coatings produce more uniform coatings, while water coatings are more environmentally friendly. Water-based separator coatings typically use inorganic materials like alumina, while those for negative electrodes are primarily hard carbon materials. Both utilize water-soluble polymers as additives to adhere the materials to the substrate.

[0003] Polyamide particles are a common material used in water-based coatings. For example, Publication (Announcement) No. CN116315425A discloses a method for preparing a highly wettable water-based coated diaphragm with electrolytes. The addition of modified bio-based polyamide particles reduces the contact angle with the electrolyte, significantly improving electrolyte wettability. Another example is Publication (Announcement) No. CN116162266A, which discloses a method for preparing nano-scale bio-based semi-aromatic polyamide particles. This can be used in any coating system using water as a solvent, effectively improving the heat resistance and membrane rupture temperature of the coated product.

[0004] However, the polyamide particles produced by the existing polyamide preparation method cannot reach below 10 nanometers, and there are still certain limitations when applied to water-based coatings. In addition, the existing polyamide preparation scheme generates a large amount of waste liquid and cannot effectively control the particle size of the polyamide. Summary of the Invention

[0005] The purpose of the present invention is to provide a nano-scale polyamide particle and a preparation method thereof in order to solve the above problems.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] A method for preparing nanoscale polyamide particles comprises the following steps:

[0008] (1) mixing a diacyl chloride monomer substituted with furandicarboxylic acid or its derivatives, an aromatic diamine monomer, and a diamine monomer having a sulfonic acid group in a first polymerization solvent to carry out a polymerization reaction to obtain a semi-aromatic polyamide;

[0009] (2) adding a base to the semi-aromatic polyamide for neutralization to obtain a polyamide;

[0010] (3) drying and spraying the polyamide, then soaking it in water, and then filtering, washing, and drying the soaked polyamide to obtain polyamide particles;

[0011] (4) mixing the polyamide particles with a second polymerization solvent to form a diluted solution having a solid content of 1 wt% to 15 wt%, and then adding an unstable solvent to obtain a mixed solution;

[0012] (5) mixing the mixed solution with a salt solution, and then emulsifying the mixture to obtain a suspension containing nano-polyamide particles, and then removing the second polymerization solvent to obtain nano-scale polyamide particles.

[0013] As a further optimized solution of the present invention, the first polymerization solvent and the second polymerization solvent independently include at least one of N-methylpyrrolidone, N,N-dimethylacetamide and N,N-dimethylformamide.

[0014] As a further optimization scheme of the present invention, in step (1), the diacyl chloride monomer substituted with furandicarboxylic acid or its derivatives accounts for 3%-10% in the first polymerization solvent, the diamine monomer with a sulfonic acid group accounts for 3%-10% in the first polymerization solvent, and the aromatic diamine monomer accounts for 3%-10% in the first polymerization solvent, calculated by mass percentage.

[0015] As a further optimized solution of the present invention, in step (1), the diacyl chloride monomer substituted from furandicarboxylic acid is 2,5-furandicarboxylic acid chloride; the diacyl chloride monomer substituted from furandicarboxylic acid derivatives includes one or more of terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, 1,9-naphthalene dicarboxylic acid chloride, adipoyl chloride, azelayl chloride, and dodecanedioyl chloride.

[0016] As a further optimized solution of the present invention, in step (1), the aromatic diamine monomer includes at least one of 4,4-diaminodiphenyl ether, 4,4-diaminodiphenylmethane, 4,4-diphenylenediamine, 2,5-furandimethylamine, p-phenylenediamine, and m-phenylenediamine.

[0017] As a further optimized solution of the present invention, in step (1), the diamine monomer with a sulfonic acid group includes at least one of 2,5-diaminobenzenesulfonic acid, 2,5-diamino-1,4-benzenedisulfonic acid, and benzidine disulfonic acid.

[0018] As a further optimized solution of the present invention, in step (2), the base includes at least one of calcium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, liquid ammonia, sodium carbonate, calcium carbonate, potassium carbonate and lithium carbonate, and the added amount of the base is 2wt%-7wt% of the semi-aromatic polyamide.

[0019] As a further optimized solution of the present invention, in step (4), the unstable solvent includes at least one of water, ethanol, ethylene glycol, propanol and isopropanol.

[0020] As a further optimized solution of the present invention, in step (5), the salt in the salt solution includes at least one of calcium chloride, sodium chloride, potassium chloride and lithium chloride, the solvent includes at least one of water, ethanol, ethylene glycol, propanol and isopropanol, the mass concentration of the salt solution is 0%-2%, and the volume ratio of the salt solution to the mixed solution is not less than 1.

[0021] Nano-scale polyamide particles are prepared by the above preparation method. The particle size D90 is below 500 nm when detected by a laser particle size analyzer, and the particle size is below 10 nm when detected by a scanning electron microscope (SEM).

[0022] The beneficial effects of the present invention are:

[0023] (1) The nanoscale polyamide particles prepared by the present invention have a small particle size. Using a laser particle size analyzer, the particle size can reach a D90 of less than 500 nm, and scanning electron microscopy (SEM) reveals that the particle size can be less than 10 nm. The nanoscale polyamide particles are insoluble in water and can be used as a material for water-based coatings.

[0024] (2) The nano-scale polyamide particles prepared by the present invention are in the form of agglomerated particles and have excellent dispersibility in water. They can be dispersed in water for a long time and have a slow sedimentation rate.

[0025] (3) The present invention can reduce the amount of waste liquid after the reaction. At the same time, due to the introduction of sulfonic acid groups, which have good hydrophilicity, the solid content of polyamide can be increased, so that large particles of polyamide can be diluted into a solution with a solid content of 1wt% to 15wt%. In the prior art, the solid content of polyamide in the diluted solution is generally around 1wt%. This can expand the particle size range of the prepared polyamide, expand its application range, and be more conducive to marketization. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic flow chart of a method for preparing nano-scale polyamide particles according to one embodiment of the present invention;

[0027] Figure 2 This is a SEM image of the nanoscale polyamide particles prepared in Example 1;

[0028] Figure 3 This is a SEM image of the nanoscale polyamide particles prepared in Example 3;

[0029] Figure 4This is a TEM image of the nanoscale polyamide particles prepared in Example 3. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are described in detail below, which are intended to explain the present invention but are not to be construed as limiting the present invention.

[0031] In one aspect of the present invention, the present invention provides a method for preparing nano-scale polyamide particles. Figure 1 , the method comprising:

[0032] S1: mixing a diacyl chloride monomer substituted with furandicarboxylic acid or a derivative thereof, an aromatic diamine monomer, and a diamine monomer having a sulfonic acid group in a first polymerization solvent to carry out a polymerization reaction.

[0033] In this step, a diacyl chloride monomer substituted with furandicarboxylic acid or its derivatives, an aromatic diamine monomer and a diamine monomer with a sulfonic acid group are mixed in a first polymerization solvent to carry out a polymerization reaction to obtain a semi-aromatic polyamide.

[0034] Furthermore, the diacyl chloride monomer substituted with furandicarboxylic acid or its derivatives accounts for 3%-10% by mass in the first polymerization solvent, the diamine monomer having a sulfonic acid group accounts for 3%-10% by mass in the first polymerization solvent, and the aromatic diamine monomer accounts for 3%-10% by mass in the first polymerization solvent. The inventors have discovered that if the amount of the diamine monomer having a sulfonic acid group added is too small, the particle size of the subsequently prepared polyamide particles increases, while if the amount of the diamine monomer having a sulfonic acid group added is too large, the molecular weight of the semi-aromatic polyamide may be too low. It should be noted that the diacyl chloride monomer substituted from furandicarboxylic acid is 2,5-furandicarboxylic acid chloride, and the diacyl chloride monomer substituted from furandicarboxylic acid derivatives includes one or more of terephthaloyl chloride, isophthaloyl chloride, o-phthaloyl chloride, 1,9-naphthalenedicarboxylic acid chloride, adipoyl chloride, azelayl chloride, and dodecanedicarboxylic acid chloride. The first polymerization solvent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide. The aromatic diamine monomer includes at least one of 4,4-diaminodiphenyl ether, 4,4-diaminodiphenylmethane, p-phenylenediamine, and m-phenylenediamine. The diamine monomer with a sulfonic acid group includes at least one of 2,5-diaminobenzenesulfonic acid and 2,5-diamino-1,4-benzenedisulfonic acid.

[0035] S2: adding a base to the semi-aromatic polyamide for neutralization.

[0036] In this step, a base is added to the semi-aromatic polyamide to obtain the polyamide. The added base is used to neutralize the acidic substances such as hydrogen chloride generated in step S1 to prevent corrosion of the reaction equipment.

[0037] Furthermore, the amount of base added is 2-7 wt% of the semi-aromatic polyamide. The inventors have found that if the amount of base added is too small, the generated hydrogen chloride cannot be completely neutralized, causing corrosion to the reaction equipment. It should be noted that the base includes at least one of calcium hydroxide, sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0038] S3: Dry spray the polyamide, soak it in water, and then filter, wash and dry the soaked polyamide.

[0039] In this step, the polyamide obtained in step S2 is spray-dried to form smaller particles. The particles are then soaked in water to remove the salts produced by the neutralization reaction and the excess alkali. The soaked polyamide is then filtered, washed, and dried to obtain polyamide particles.

[0040] S4: mixing the polyamide particles with a second polymerization solvent to form a diluted solution with a solid content of 1 wt% to 15 wt%, and then adding an unstable solvent.

[0041] In this step, the polyamide particles are mixed with a second polymerization solvent to form a diluted solution with a solid content of 1wt%-15wt%. The solid content of polyamide in the diluted solution is 1wt%-15wt%, which is significantly higher than the solid content of polyamide in the prior art, and the range of solid content is wider, which is conducive to the subsequent regulation of the particle size of the polyamide particles according to demand. Then, an unstable solvent is added to make the diluted solution reach an unstable state to obtain a mixed solution. It should be noted that the second polymerization solvent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide and N,N-dimethylformamide, and the unstable solvent includes at least one of water, ethanol, ethylene glycol, propanol and isopropanol.

[0042] S5: mixing the mixed solution with the salt solution, and then emulsifying to obtain a suspension containing nano-polyamide particles, and then removing the second polymerization solvent.

[0043] In this step, the mixed solution obtained in step S4 is mixed with a salt solution, which can make the particle size of the prepared polyamide particles smaller, and then emulsified to obtain a suspension containing nano-polyamide particles. The second polymerization solvent can then be removed by filtration, centrifugation or using a ceramic membrane device to finally obtain nano-scale polyamide particles.

[0044] Furthermore, the mass concentration of the salt solution is 0%-2%. The inventors have found that adding too much salt solution can result in excessively large polyamide particles. Furthermore, the volume ratio of the salt solution to the mixed solution is not less than 1. It should be noted that the salt in the salt solution includes at least one of calcium chloride, sodium chloride, potassium chloride, and lithium chloride, and the solvent includes at least one of water, ethanol, ethylene glycol, propanol, and isopropanol.

[0045] In a second aspect, the present invention provides nanoscale polyamide particles. According to embodiments of the present invention, the nanoscale polyamide particles are prepared using the aforementioned method. As a result, the nanoscale polyamide particles have a wide range of particle sizes, meeting a wider range of market demands, and can reach particle sizes below 10 nm.

[0046] Unless otherwise specified, the methods used in the present invention are conventional methods known to those skilled in the art, and the reagents and other materials used are commercially available products unless otherwise specified.

[0047] Example 1

[0048] The nano-scale polyamide particles in this embodiment are prepared as follows:

[0049] 8.4 kg of N,N-dimethylacetamide, 0.4 kg of 4,4-diaminodiphenyl ether and 0.4 kg of 2,5-diaminobenzenesulfonic acid were added to the reactor; after both amines were dissolved, 0.8 kg of 2,5-furandicarbonyl chloride was added in three portions, and the mixture was allowed to react for 5 hours; after the reaction was completed, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to obtain polyamide.

[0050] The resulting polyamide was dried into smaller particles using a drying spray device, then soaked in water for 24 hours, filtered, washed, and dried to obtain granular polyamide. The resulting granular polyamide was dissolved in 158.4 kg of N,N-dimethylacetamide to obtain a polyamide diluted solution with a solid content of 1%, and 33.6 kg of isopropyl alcohol was added and stirred for half an hour to obtain a mixed solution.

[0051] The mixed solution and water are then introduced into an emulsification pump in a volume ratio of 1:1 for emulsification. After emulsification, a suspension containing nano-polyamide particles is obtained. The suspension is then filtered, washed, centrifuged, or filtered through a ceramic membrane to remove N,N-dimethylacetamide to obtain nano-scale polyamide particles.

[0052] Example 2

[0053] The nano-scale polyamide particles in this embodiment are prepared as follows:

[0054] 8.4 kg of N,N-dimethylacetamide was added to the reactor, followed by 0.4 kg of 4,4-diaminodiphenylmethane and 0.4 kg of 2,5-diamino-1,4-benzenedisulfonic acid; after both amines were dissolved, 0.8 kg of 2,5-furandicarbonyl chloride was added in three portions, and the mixture was allowed to react for 5 hours; after the reaction was completed, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to obtain polyamide.

[0055] The resulting polyamide was dried into smaller particles using a drying spray device, then soaked in water for 24 hours, filtered, washed, and dried to obtain granular polyamide. The resulting granular polyamide was dissolved in 78.4 kg of N,N-dimethylacetamide to obtain a polyamide diluted solution with a solid content of 2%, and then 16.8 kg of isopropyl alcohol was added and stirred for half an hour to obtain a mixed solution.

[0056] The mixed solution and water are then introduced into an emulsification pump in a ratio of 1:1 for emulsification. After emulsification, a suspension containing nano-polyamide particles is obtained. The suspension is then filtered, washed, centrifuged, or filtered through a ceramic membrane to remove N,N-dimethylacetamide to obtain nano-scale polyamide particles.

[0057] Example 3

[0058] The nano-scale polyamide particles in this embodiment are prepared as follows:

[0059] 8.4 kg of N,N-dimethylacetamide was added to the reactor, followed by 0.4 kg of 4,4-diphenylenediamine and 0.4 kg of benzidine disulfonic acid; after both amines were dissolved, 0.8 kg of 2,5-furandicarbonyl chloride was added in three portions, and the mixture was allowed to react for 5 hours; after the reaction was completed, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to obtain polyamide.

[0060] The resulting polyamide was dried into smaller particles using a drying spray device, then soaked in water for 24 hours, filtered, washed, and dried to obtain granular polyamide. The resulting granular polyamide was dissolved in 51.7 kg of N,N-dimethylacetamide to obtain a polyamide diluted solution with a solid content of 3%, and then 11.2 kg of isopropyl alcohol was added and stirred for half an hour to obtain a mixed solution.

[0061] The mixed solution and water are then introduced into an emulsification pump in a ratio of 1:1 for emulsification. After emulsification, a suspension containing nano-polyamide particles is obtained. The suspension is then filtered, washed, centrifuged, or filtered through a ceramic membrane to remove N,N-dimethylacetamide to obtain nano-scale polyamide particles.

[0062] Example 4

[0063] The nano-scale polyamide particles in this embodiment are prepared as follows:

[0064] 8.4 kg of N,N-dimethylacetamide was added to the reactor, followed by 0.4 kg of 2,5-furandimethylamine and 0.4 kg of 2,5-diaminobenzenesulfonic acid; after both amines were dissolved, 0.8 kg of 2,5-furandicarbonyl chloride was added in three portions, and the mixture was allowed to react for 5 hours; after the reaction was completed, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to obtain polyamide.

[0065] The resulting polyamide was dried into smaller particles using a drying spray device, then soaked in water for 24 hours, filtered, washed, and dried to obtain granular polyamide. The resulting granular polyamide was dissolved in 38.4 kg of N,N-dimethylacetamide to obtain a polyamide diluted solution with a solid content of 4%, and then 8 kg of isopropyl alcohol was added and stirred for half an hour to obtain a mixed solution.

[0066] The mixed solution and water are then introduced into an emulsification pump in a ratio of 1:1 for emulsification. After emulsification, a suspension containing nano-polyamide particles is obtained. The suspension is then filtered, washed, centrifuged, or filtered through a ceramic membrane to remove N,N-dimethylacetamide to obtain nano-scale polyamide particles.

[0067] Example 5

[0068] The nano-scale polyamide particles in this embodiment are prepared as follows:

[0069] 8.4 kg of N,N-dimethylacetamide was added to the reactor, followed by 0.4 kg of p-phenylenediamine and 0.4 kg of 2,5-diamino-1,4-benzenedisulfonic acid. After both amines were dissolved, 0.8 kg of 2,5-furandicarbonyl chloride was added in three portions, and the mixture was allowed to react for 5 hours. After the reaction was completed, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to obtain polyamide.

[0070] The resulting polyamide was dried into smaller particles using a drying spray device, then soaked in water for 24 hours, filtered, washed, and dried to obtain granular polyamide. The resulting granular polyamide was dissolved in 30.4 kg of N,N-dimethylacetamide to obtain a polyamide diluted solution with a solid content of 5%, and then 5.6 kg of isopropyl alcohol was added and stirred for half an hour to obtain a mixed solution.

[0071] The mixed solution and water are then introduced into an emulsification pump in a ratio of 1:1 for emulsification. After emulsification, a suspension containing nano-polyamide particles is obtained. The suspension is then filtered, washed, centrifuged, or filtered through a ceramic membrane to remove N,N-dimethylacetamide to obtain nano-scale polyamide particles.

[0072] Example 6

[0073] The nano-scale polyamide particles in this embodiment are prepared as follows:

[0074] 8.4 kg of N,N-dimethylacetamide, 0.4 kg of 4,4-diaminodiphenylmethane (MDA) and 0.4 kg of 2,5-diaminobenzenesulfonic acid were added to the reactor; after both amines were dissolved, 0.8 kg of 2,5-furandicarbonyl chloride was added in three portions, and the mixture was allowed to react for 5 hours; after the reaction was completed, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to obtain polyamide.

[0075] The resulting polyamide was dried into smaller particles using a drying spray device, then soaked in water for 24 hours, filtered, washed, and dried to obtain granular polyamide. The resulting granular polyamide was dissolved in 38.4 kg of N,N-dimethylacetamide to obtain a polyamide diluted solution with a solid content of 4%, and then 8 kg of isopropyl alcohol was added and stirred for half an hour to obtain a mixed solution.

[0076] The mixed solution and a 0.1wt% calcium chloride aqueous solution are then introduced into an emulsification pump in a volume ratio of 1:1 for emulsification. After emulsification, a suspension containing nano-polyamide particles is obtained. The suspension is then filtered, washed, centrifuged, or filtered through a ceramic membrane to remove N,N-dimethylacetamide to obtain nano-scale polyamide particles.

[0077] Example 7

[0078] The nano-scale polyamide particles in this embodiment are prepared as follows:

[0079] 8.4 kg of N,N-dimethylacetamide, 0.4 kg of 4,4-diaminodiphenylmethane (MDA) and 0.4 kg of 2,5-diaminobenzenesulfonic acid were added to the reactor; after both amines were dissolved, 0.8 kg of isophthaloyl chloride was added in three portions, and the mixture was allowed to react for 5 hours; after the reaction was completed, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to obtain polyamide.

[0080] The resulting polyamide was dried into smaller particles using a drying spray device, then soaked in water for 24 hours, filtered, washed, and dried to obtain granular polyamide. The resulting granular polyamide was dissolved in 14.4 kg of N,N-dimethylacetamide to obtain a polyamide diluted solution with a solid content of 10%. 2.3 kg of isopropyl alcohol was then added and stirred for half an hour to obtain a mixed solution.

[0081] The mixed solution and water are then introduced into an emulsification pump in a ratio of 1:1 for emulsification. After emulsification, a suspension containing nano-polyamide particles is obtained. The suspension is then filtered, washed, centrifuged, or filtered through a ceramic membrane to remove N,N-dimethylacetamide to obtain nano-scale polyamide particles.

[0082] Example 8

[0083] The nano-scale polyamide particles in this embodiment are prepared as follows:

[0084] 8.4 kg of N,N-dimethylacetamide, 0.4 kg of 4,4-diaminodiphenylmethane (MDA) and 0.4 kg of 2,5-diaminobenzenesulfonic acid were added to the reactor; after both amines were dissolved, 0.8 kg of terephthaloyl chloride was added in three portions, and the mixture was allowed to react for 5 hours; after the reaction was completed, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to obtain polyamide.

[0085] The resulting polyamide was dried into smaller particles using a drying spray device, then soaked in water for 24 hours, filtered, washed, and dried to obtain granular polyamide. The resulting granular polyamide was dissolved in 9.06 kg of N,N-dimethylacetamide to obtain a polyamide diluted solution with a solid content of 15%, and 1.3 kg of isopropyl alcohol was added and stirred for half an hour to obtain a mixed solution.

[0086] The mixed solution and water are then introduced into an emulsification pump in a ratio of 1:1 for emulsification. After emulsification, a suspension containing nano-polyamide particles is obtained. The suspension is then filtered, washed, centrifuged, or filtered through a ceramic membrane to remove N,N-dimethylacetamide to obtain nano-scale polyamide particles.

[0087] Comparative Example 1

[0088] 8.4 kg of N,N-dimethylacetamide and 0.8 kg of 4,4-diaminodiphenyl ether (ODA) were added to a reactor. After the amines were dissolved, 0.8 kg of 2,5-furandicarbonyl chloride was added in three portions and allowed to react for 5 hours. After the reaction, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to produce polyamide. The resulting polyamide was dried into small particles using a drying spray device, then soaked in water for 24 hours, filtered, washed, and dried to produce granular polyamide. The resulting granular polyamide was dissolved in 78.4 kg of N,N-dimethylacetamide and 16.8 kg of isopropyl alcohol was added and stirred for half an hour to produce a diluted polyamide solution. The diluted solution was then emulsified by passing it into an emulsifier pump at a 1:1 ratio with water. This produced a suspension containing nano-polyamide particles. The suspension was then filtered, washed, centrifuged, or passed through a ceramic membrane to remove the N,N-dimethylacetamide, resulting in nano-sized polyamide particles.

[0089] Comparative Example 2

[0090] 8.4 kg of N,N-dimethylacetamide and 0.8 kg of 4,4-diaminodiphenylmethane (MDA) were added to a reactor. After the amines were dissolved, 0.8 kg of 2,5-furandicarboxylic acid chloride was added in three portions and allowed to react for 5 hours. After the reaction, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to produce polyamide. The resulting polyamide was dried into small particles using a drying spray device, then soaked in water for 24 hours, filtered, washed, and dried to produce granular polyamide. The resulting granular polyamide was dissolved in 48.7 kg of N,N-dimethylacetamide, and 11.2 kg of isopropyl alcohol was added and stirred for half an hour to produce a diluted polyamide solution. The diluted solution was then emulsified by passing it into an emulsifier pump at a 1:1 ratio with water. This produced a suspension containing nano-polyamide particles. The suspension was then filtered, washed, centrifuged, or passed through a ceramic membrane to remove the N,N-dimethylacetamide, resulting in nano-sized polyamide particles.

[0091] Comparative Example 3

[0092] Add 8.4 kg of N,N-dimethylacetamide to a reactor, followed by 0.4 kg of 4,4-diaminodiphenyl ether (ODA) and 0.4 kg of 2,5-diaminobenzenesulfonic acid. Once both amines have dissolved, add 0.8 kg of 2,5-furandicarbonyl chloride in three portions, allowing the mixture to react for 5 hours. After the reaction is complete, add 0.4 kg of calcium hydroxide and stir for 1 hour to produce polyamide. Then, add 70 kg of N,N-dimethylacetamide and 16.8 kg of isopropyl alcohol and stir for half an hour to produce a diluted polyamide solution. This diluted solution is then emulsified with water in a 1:1 ratio through an emulsifier pump to produce a suspension containing nano-polyamide particles. This suspension is then filtered, washed, centrifuged, or passed through a ceramic membrane to remove the N,N-dimethylacetamide, resulting in nano-scale polyamide particles.

[0093] Comparative Example 4

[0094] 8.4 kg of N,N-dimethylacetamide, 0.4 kg of 4,4-diaminodiphenylmethane (MDA), and 0.4 kg of 2,5-diamino-1,4-benzenedisulfonic acid were added to a reactor. Once both amines were dissolved, 0.8 kg of 2,5-furandicarboxylic acid chloride was added in three portions and allowed to react for 5 hours. After the reaction, 0.4 kg of calcium hydroxide was added and stirred for 1 hour to produce polyamide. 49.3 kg of N,N-dimethylacetamide and 11.2 kg of isopropyl alcohol were then added and stirred for half an hour to produce a diluted polyamide solution. The diluted solution was then emulsified with water in a 1:1 ratio through an emulsifier pump to produce a suspension containing nano-polyamide particles. The suspension was then filtered, washed, centrifuged, or passed through a ceramic membrane to remove the N,N-dimethylacetamide, resulting in nano-scale polyamide particles.

[0095] Effect verification:

[0096] The nano-scale polyamide particles obtained in Examples 1-8 and Comparative Examples 1-4 were prepared into a 2% suspension, dispersed using a high shear homogenizer for 25 minutes, and then diluted to obtain 50 g of a 0.5% solid content dilution solution. 0.2 g of a 1 wt% sodium lauryl sulfate solution was added, and ultrasonication was performed at 720 W for 20 minutes. The particle size was then measured using a laser particle size analyzer. The results are shown in Table 1 below:

[0097] Table 1 Particle size

[0098]

[0099]

[0100] From the detection data of the laser particle size analyzer in Table 1, it can be found that as the concentration of the diluted solution increases, the particle size also increases. At the same time, the laser particle size analyzer may not be very accurate in detecting small nano-sized particles. The nano-sized polyamide particles prepared in Examples 1 and 3 were subjected to SEM scanning electron microscopy and TEM transmission electron microscopy. The SEM image of the polyamide particles obtained in Example 1 is as follows: Figure 2 The SEM images of the polyamide particles obtained in Example 3 are as follows: Figure 3 As shown in the TEM image Figure 4 As shown in the figure, the scale and annotations indicate that the actual polyamide particle size is smaller than the data measured by the laser particle size analyzer. The above data show that the particle size D10 of the polyamide particles obtained in Examples 1 to 8 ranges from 0.081 μm to 0.744 μm, indicating that the polyamide prepared by this method has a wide range of particle sizes. Therefore, polyamide particles of different sizes can be prepared according to actual needs, and the particle size of the polyamide particles can be controlled to better meet market demand.

[0101] Comparing Comparative Example 1 with Example 2, and Comparative Example 2 with Example 3, the polyamides obtained in Comparative Examples 1 and 2 have larger particle sizes, indicating that the absence of a diamine monomer containing a sulfonic acid group leads to larger particle sizes. Comparing Comparative Example 3 with Example 2, and Comparative Example 4 with Example 3, the polyamides obtained in Comparative Examples 3 and 4 have larger particle sizes, indicating that the polyamides obtained without the spray drying step have larger particle sizes.

[0102] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A method for preparing nano-scale polyamide particles, characterized in that: The following steps are involved: (1) 2,5-furandicarboxylic acid chloride, an aromatic diamine monomer, and a diamine monomer with a sulfonic acid group are mixed in a first polymerization solvent for polymerization reaction to obtain a semi-aromatic polyamide; in terms of mass percentage, the 2,5-furandicarboxylic acid chloride accounts for 3% to 10% of the first polymerization solvent, the diamine monomer with a sulfonic acid group accounts for 3% to 10% of the first polymerization solvent, and the aromatic diamine monomer accounts for 3% to 10% of the first polymerization solvent; (2) adding a base to the semi-aromatic polyamide for neutralization to obtain polyamide; (3) Drying and spraying the polyamide, then soaking it in water, and then filtering, washing, and drying the soaked polyamide to obtain polyamide particles; (4) mixing the polyamide particles with a second polymerization solvent to form a diluted solution having a solid content of 1 wt% to 15 wt%, and then adding an unstable solvent to obtain a mixed solution; the unstable solvent comprises at least one of water, ethanol, ethylene glycol, propanol, and isopropanol; (5) mixing the mixed solution with a salt solution, and then emulsifying to obtain a suspension containing nano-polyamide particles, and then removing the second polymerization solvent to obtain nano-scale polyamide particles; The first polymerization solvent and the second polymerization solvent independently include at least one of N-methylpyrrolidone, N,N-dimethylacetamide and N,N-dimethylformamide; The salt in the salt solution includes at least one of calcium chloride, sodium chloride, potassium chloride and lithium chloride, and the mass concentration of the salt solution is 0%-2%.

2. The method for preparing nano-scale polyamide particles according to claim 1, wherein: In step (1), the aromatic diamine monomer includes at least one of 4,4-diaminodiphenyl ether, 4,4-diaminodiphenylmethane, 4,4-diphenylenediamine, 2,5-furandimethylamine, p-phenylenediamine, and m-phenylenediamine.

3. The method for preparing nano-scale polyamide particles according to claim 1, wherein: In step (1), the diamine monomer having a sulfonic acid group includes at least one of 2,5-diaminobenzenesulfonic acid, 2,5-diamino-1,4-benzenedisulfonic acid, and benzidine disulfonic acid.

4. The method for preparing nano-scale polyamide particles according to claim 1, wherein: In step (2), the alkali includes at least one of calcium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, liquid ammonia, sodium carbonate, potassium carbonate and lithium carbonate, and the added amount of the alkali is 2wt%-7wt% of the semi-aromatic polyamide.

5. A nanoscale polyamide particle, characterized in that: The invention is prepared by the preparation method described in any one of claims 1 to 4.

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