Bio-based polyamide solution, powder, film and preparation method thereof

Abstract

The invention relates to the technical field of polyamide materials, in particular to a bio-based polyamide solution, powder, a film and a preparation method thereof, the bio-based polyamide solution contains bio-based polyamide and a solvent, and the concentration of the bio-based polyamide is 1-40%; the bio-based polyamide contains a diamine unit and a diacid unit, the diacid unit contains an aliphatic diacid unit and an aromatic diacid unit, and the diamine unit contains a pentamethylene diamine unit; the water content of the solvent is below 25%; and the viscosity of the bio-based polyamide solution is 100 to 10000 mPa. S. The invention provides huge potential for breaking through the limitation of the conventional polyamide material.

Description

Technical Field

[0001] The invention relates to the technical field of polyamide materials, and in particular to a bio-based polyamide solution, powder, film and a preparation method thereof. Background Art

[0002] As one of the five major engineering plastics, polyamide has good comprehensive properties, such as mechanical properties, wear resistance, chemical corrosion resistance, and self-lubrication. There are many varieties of polyamide. Polyamide can show different properties due to different monomer types and can be used in different scenarios. However, as a solid material, polyamide has certain limitations. It is very important to research and develop new forms of polyamide materials to meet the needs of different scenarios. Summary of the invention

[0003] In view of the shortcomings of the prior art, the present invention provides a bio-based polyamide solution and a preparation method thereof, which combines the advantages of liquid phase and solid phase, and provides great potential for breaking through the limitations of conventional polyamide materials. The present invention also prepares bio-based polyamide powder and bio-based polyamide film by using the above-mentioned bio-based polyamide solution, thereby providing micron-sized bio-based polyamide powder particles with excellent mechanical properties, greatly expanding downstream application scenarios.

[0004] The first aspect of the present invention provides a bio-based polyamide solution, which contains bio-based polyamide and a solvent, and the concentration of the bio-based polyamide is 1-40%;

[0005] The bio-based polyamide contains a diamine unit and a diacid unit, wherein the diacid unit contains an aliphatic diacid unit and an aromatic diacid unit, and the diamine unit contains a pentamethylenediamine unit;

[0006] The water content of the solvent is below 25%;

[0007] The bio-based polyamide solution has a viscosity of 100-10000 mPa.s.

[0008] The bio-based polyamide solution of the present invention can be used to manufacture bio-based polyamide powder with excellent performance. The bio-based polyamide powder is a thermoplastic powder with a wide processing temperature range and good mechanical properties, a small friction coefficient, excellent electrical insulation, wear resistance and weather resistance, etc. When the bio-based polyamide powder is melted, it has good leveling properties, especially low-melting-point bio-based polyamide powder has good leveling properties and good adhesion to various metals, so it has important use value in industry and is widely used in the fields of chemical industry, machinery, automobile, electrical appliances, ocean, etc., and is gradually developing into the fields of decoration, sound insulation and shock absorption, etc.

[0009] In some specific embodiments, the bio-based polyamide solution has a viscosity of 90-9000 mPa.s.

[0010] In some specific embodiments, the bio-based polyamide solution has a viscosity of 90-1500 mPa.s.

[0011] In some specific application fields, the viscosity of the bio-based polyamide solution is preferably 100-650 mPa.s, for example, 609 mPa.s, 98 mPa.s, 142 mPa.s, 403 mPa.s, 429 mPa.s, 434 mPa.s, 490 mPa.s, 540 mPa.s, 324 mPa.s, 207 mPa.s, 443 mPa.s, 521 mPa.s. The viscosity of the bio-based polyamide solution of the present invention is tested by a rotation method, for example, with reference to the method of GB / T 10247-2008.

[0012] In some specific embodiments, the concentration of the bio-based polyamide solution is 2%-35%. The concentration percentage of the bio-based polyamide in the present invention is the mass percentage of the bio-based polyamide in the bio-based polyamide solution.

[0013] In some specific embodiments, for example, when the bio-based polyamide solution is used to prepare the bio-based polyamide powder, the concentration of the bio-based polyamide solution is preferably 2-20%, for example, 5%, 8%, 9%, 10%, 12%, 13%, 14%, 15%, 17%, 19%, 20%.

[0014] The present invention does not particularly limit the preparation method or reaction conditions of the bio-based polyamide solution. The bio-based polyamide and the solvent may be stirred and mixed at a mixing temperature of -10°C to 100°C, and the mixing time is not particularly limited. Preferably, the mixing temperature is 30-60°C. The preferred temperature range can improve the mixing efficiency and obtain a solution with lower viscosity.

[0015] In some specific embodiments, the molar ratio of the diamine unit to the diacid unit may be (0.9-1.2):1, preferably (0.95-1.1):1, for example, 1.05:1.

[0016] In some specific embodiments, the diamine unit is derived from an aliphatic diamine, preferably butanediamine, pentanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine or a combination thereof. Among them, the pentamethylenediamine is preferably 1,5-pentanediamine.

[0017] In some specific embodiments, the molar percentage of the pentamethylenediamine units to the diamine units is 20%-100%.

[0018] In some specific embodiments, the pentamethylenediamine unit is derived from bio-based pentamethylenediamine, which refers to pentamethylenediamine synthesized from biomass-derived compounds such as glucose and lysine by enzyme reaction, yeast reaction or fermentation reaction in a monomer synthesis process. The biobased content of bio-based pentamethylenediamine can be determined by a method for measuring the radioactive C14 content, such as the American Society for Testing and Materials standard ASTM-D6866 method.

[0019] In some embodiments, the aliphatic diacid units are derived from aliphatic short-chain diacids and / or aliphatic long-chain diacids.

[0020] In some specific embodiments, the aliphatic short-chain diacid includes oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid or a combination thereof, preferably adipic acid, such as 1,6-hexanedioic acid.

[0021] In some specific embodiments, the aliphatic long-chain diacid includes azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedicarboxylic acid or a combination thereof, preferably sebacic acid, undecanedicarboxylic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid or a combination thereof.

[0022] In some specific embodiments, the aliphatic diacid unit is derived from a combination of an aliphatic short-chain diacid and an aliphatic long-chain diacid, wherein the aliphatic short-chain diacid is, for example, adipic acid, and the aliphatic long-chain diacid is, for example, selected from sebacic acid, undecanedicarboxylic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, or a combination thereof.

[0023] In some specific embodiments, the aromatic diacid unit may be derived from an aromatic diacid and / or an aromatic diacid derivative, preferably phthalic acid and / or phthalate.

[0024] In some specific embodiments, the phthalic acid may be one or more of terephthalic acid, isophthalic acid and orthophthalic acid, for example, terephthalic acid.

[0025] In some specific embodiments, the phthalate ester may be terephthalate ester, and preferably, the terephthalate ester is dimethyl terephthalate and / or diethyl terephthalate.

[0026] In some specific embodiments, the molar ratio of the aliphatic diacid unit to the aromatic diacid unit is 30-70:30-70, for example, 30:70, 35:65, 56:44, 67:33, 50:50, 55:45, 60:40, 70:30, etc.

[0027] In some specific embodiments, the diamine units are derived from 1,5-pentanediamine, the aliphatic diacid units are derived from 1,6-adipic acid, and the aromatic diacid units are derived from terephthalic acid.

[0028] In some specific embodiments, the bio-based polyamide can be expressed as bio-based polyamide 5X, or simply referred to as PA5X, wherein "5" represents a pentamethylenediamine unit, and "X" represents other diamine or diacid units.

[0029] In some specific embodiments, the bio-based polyamide 5X contains diamine units from bio-based pentamethylenediamine, which has the advantage of being renewable in source. Examples of bio-based polyamide 5X include commercially available polyamides provided by Cathay Biotech Inc. A series of materials, such as

[0030] or wait A range of bio-based polyamides.

[0031] In some specific embodiments, the relative viscosity of the bio-based polyamide may be 1.2-6.0, preferably 2.0-5.2, for example, 2.57, 2.73, 3.15, 3.20, 3.27, 3.34, 3.50, 4.20, 4.50, 5.00 or 5.20. The relative viscosity is measured by the Ubbelohde viscometer concentrated sulfuric acid (concentration 96%) method.

[0032] In some specific embodiments, the bio-based polyamide may be subjected to a viscosity enhancement treatment before use. The purpose of the viscosity enhancement treatment is to make the viscosity of the polyamide meet the above requirements. The specific method of resin viscosity enhancement is to put the polyamide resin into a drying oven and dry it under vacuum at 160-180°C for 100-180 hours, and the temperature and drying time are selected according to the target viscosity.

[0033] In some specific embodiments, the melting point of the bio-based polyamide is 250°C-320°C, preferably 260°C-310°C, for example 267°C, 279°C, 275°C, 287°C, 289°C, 298°C or 300°C.

[0034] In some specific embodiments, the bio-based polyamide may further include additives, and the content of the additives may be selected according to actual conditions.

[0035] The additives may include heat stabilizers, antioxidants, fluorescent brighteners, pigments, dyes, UV inhibitors, flame retardants, flow modifiers, organic fillers, inorganic fillers, silica powder, powder binders, carbon nanotubes or combinations thereof, such as heat stabilizers and / or antioxidants.

[0036] The heat stabilizer may be phosphoric acid, phosphorous acid, trimethyl phosphite, triphenyl phosphite, trimethyl phosphate, triphenyl phosphate, sodium hypophosphite, zinc hypophosphite, calcium hypophosphite, potassium hypophosphite or a combination thereof, such as sodium hypophosphite.

[0037] Wherein, the antioxidant is selected from one or more of hindered phenol antioxidants, hindered amine antioxidants and phosphite antioxidants;

[0038] The hindered phenol antioxidant can be purchased commercially. Preferably, the hindered phenol antioxidant is selected from antioxidant 1098 and / or antioxidant 1010, such as antioxidant 1098.

[0039] The phosphite antioxidant can be purchased commercially. Preferably, the phosphite antioxidant is selected from antioxidant 168 and / or antioxidant S9228.

[0040] Preferably, the antioxidant is selected from one or more of the commercially available antioxidant 168, antioxidant 1098, antioxidant 1010 and antioxidant S9228.

[0041] In some specific embodiments, the polyamide contains sodium hypophosphite and antioxidant 1098.

[0042] In the above specific implementation, the content of the heat stabilizer may be 0.01-0.05 wt%, such as 0.03 wt% sodium hypophosphite, where the percentage is the mass of the heat stabilizer to the sum of the masses of the various raw materials of the polyamide.

[0043] In the above specific implementation, the content of the antioxidant may be 0.01-0.05 wt%, such as 0.3 wt% of antioxidant 1098, where the percentage is the percentage of the mass of the antioxidant to the sum of the masses of the various raw materials of the polyamide.

[0044] In some preferred embodiments, the polyamide is prepared by the following method: after mixing monomers and water to obtain a polyamide salt solution, controlling the temperature and pressure to perform a polymerization reaction to obtain a melt, and then subjecting the melt to stranding and pelletizing to obtain the polyamide; wherein the monomers include at least one diamine and at least one diacid, the diacid contains at least one aliphatic diacid and at least one aromatic diacid, and the diamine contains pentamethylenediamine.

[0045] In some specific embodiments, the polyamide can be prepared by the following method:

[0046] S1, mixing monomers and water to prepare a polyamide salt aqueous solution with a concentration of 30-75wt%; wherein the monomers include at least one diamine and at least one diacid, the diacid contains at least one aliphatic diacid and at least one aromatic diacid, and the diamine contains at least pentamethylenediamine;

[0047] S2. In a nitrogen or inert gas atmosphere, heat the polyamide salt aqueous solution to a temperature of 230-310° C. and a reaction pressure of 0.7-2.5 MPa, and maintain for 60-180 min; then vent to normal pressure and raise the temperature to 260-340° C.; evacuate to reduce the pressure to -(0.02-0.08) MPa, and maintain for 0.1-120 minutes to obtain a melt, and then strand and pelletize to obtain the polyamide.

[0048] In some specific embodiments, the solvent is used to destroy the hydrogen bonds between the polyamide molecules, thereby promoting their dissolution in the solvent, preferably a polar solvent, such as dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), sodium thiocyanate aqueous solution, zinc chloride aqueous solution, nitric acid, sulfuric acid, formic acid, acetic acid, dichloromethane, benzene, toluene, xylene, methanol, ethanol, trifluoroacetic acid, hexafluoroisopropanol, phenol, chloroform, they can be used alone or in combination of two or more, and can also be mixed with water, that is, aqueous solutions of the above solvents.

[0049] In some specific embodiments, the solvent is preferably any one or a combination of formic acid, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, trifluoroacetic acid or hexafluoroisopropanol. Preferably, the solvent is conducive to improving the dissolution efficiency and the subsequent preparation of polyamide powder or film.

[0050] Preferably, the purity of the solvent is above 98%, for example, analytically pure.

[0051] In some specific embodiments, the water content of the solvent is 0-25 wt %, further 0.1-20 wt %, and further 0.01-15 wt %.

[0052] In some specific embodiments, when the solvent is mixed with water, the percentage of the solvent in the total mass of the solvent and water is 80-99.99wt%, further 75-99.99wt%. The percentage of the solvent in the total mass of the solvent and water can be adjusted by diluting with water or evaporating and concentrating.

[0053] The second aspect of the present invention provides a bio-based polyamide powder, which is obtained by spray-drying the above bio-based polyamide solution, wherein the concentration of the bio-based polyamide solution is 2-20%, preferably 2-10%.

[0054] The present invention also provides a method for preparing bio-based polyamide powder, which comprises spray-drying the bio-based polyamide solution to prepare the bio-based polyamide powder, wherein the concentration of the bio-based polyamide solution is 2-20%, preferably 2-10%.

[0055] The preparation method of the bio-based polyamide powder is simple to operate and can meet the requirements of continuous production. At the same time, the solution can be condensed and recovered to avoid the generation of a large amount of waste. It is environmentally friendly and low-cost.

[0056] In some embodiments, the inlet temperature of the spray drying is 100-200°C, and the outlet temperature is 100-150°C. Specifically, for example, the inlet temperature of the spray drying is 160-180°C, and the outlet temperature is 110-120°C. In some embodiments, the ratio of the flow rate of the polyamide solution to the flow rate of the gas during the spray drying is controlled to be 1:4-1000, and then 1:5-50, more preferably 1:5-20, for example 1:4-15. Too low a flow rate will result in failure to obtain qualified powder, and too high a flow rate will bring unnecessary waste.

[0057] In some specific embodiments, the particle size of the bio-based polyamide powder is in the range of 0.2-150 μm, preferably 5-40 μm.

[0058] In some embodiments, the gas is nitrogen or an inert gas, such as argon.

[0059] In some embodiments, the biobased polyamide powder is at least partially produced from renewable or bio-derived materials, which then contain 14C, the biochar content being determined according to standard ASTM D 6866.

[0060] Preferably, the bio-based polyamide powder may further comprise at least one additive selected from the group consisting of fluorescent brighteners, pigments, dyes, UV inhibitors, flame retardants, antioxidants, stabilizers, flow agents, organic or inorganic fillers, silica powder, powder binders, carbon nanotubes and mixtures thereof.

[0061] The third aspect of the present invention is to provide a bio-based polyamide film, which is obtained by coating the above bio-based polyamide solution on a clean glass substrate and drying it at 25-100° C. to remove the solvent.

[0062] The present invention also provides a method for preparing a bio-based polyamide film, which comprises coating the bio-based polyamide solution on a clean glass substrate, and drying and removing the solvent at 25-100° C. to prepare the bio-based polyamide film.

[0063] In some specific embodiments, the coating method can use common methods known in the art without limitation, for example, spin coating, dip coating, solvent casting, slot die coating, spray coating, etc.

[0064] In some specific embodiments, the thickness of the bio-based polyamide film is not particularly limited, and the polyamide solution can be coated more than once to adjust the thickness to a range of hundreds of nm to tens of μm, such as 50-200 μm.

[0065] In some specific embodiments, the light transmittance of the bio-based polyamide film is not less than 80%, and further is greater than 88%.

[0066] In some specific embodiments, the bio-based polyamide film has a chromaticity lower than 5, preferably a chromaticity of 2-4.

[0067] The bio-based polyamide film can be used in a variety of fields, for example, for preparing solvent-resistant diaphragms, fiber composite materials, etc.

[0068] The beneficial effects that can be achieved by adopting the technical solution of the present invention include: (1) The bio-based polyamide solution obtained by the solution method can be directly used in the field of powder preparation and coating process for preparing membrane materials, avoiding the degradation of bio-based polyamide during the melting process. Especially for bio-based polyamide with a higher melting point, the solution method provides a simple and efficient method. (2) Bio-based polyamide powder with a size of 0.2-150μm can be prepared by the spray drying method, providing micron-sized bio-based polyamide powder particles with excellent mechanical properties, which can be directly used in surface spraying or cosmetics, reducing further mechanical grinding or ball milling processes, and helping to reduce the cost of powder preparation. (3) Bio-based polyamide films with low chroma and high transmittance can also be obtained by the coating method. It provides great potential for breaking through the limitations of conventional polyamide materials. DETAILED DESCRIPTION

[0069] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions therein are essentially used as illustrations rather than to limit the present invention.

[0070] The test methods involved in the embodiments are as follows:

[0071] (1) Relative viscosity: The relative viscosity is measured by the concentrated sulfuric acid method using an Ubbelohde viscometer, and the steps are as follows: 0.5±0.0002 g of a polyamide resin sample is dissolved in 50 mL of concentrated sulfuric acid (96%), and the flow time t0 of the concentrated sulfuric acid and the flow time t of the polyamide resin sample concentrated sulfuric acid solution are measured and recorded in a 25°C constant temperature water bath. The relative viscosity calculation formula is: relative viscosity VN=t / t0; t-solution flow time; t0-solvent flow time.

[0072] (2) Melting point: measured by differential scanning calorimetry (DSC).

[0073] (3) Solution viscosity: measured at 25°C using a rotational viscometer.

[0074] (4) Powder: Use an optical microscope to observe and count the particle size range of the powder.

[0075] (5) Film: The thickness of the film was characterized by a thickness gauge. The film transmittance was characterized by cutting the film into 40 mm × 40 mm samples and using an ultraviolet spectrophotometer (wavelength range 200-800 nm). The transmittance in the range of 380-780 nm was taken as the transmittance of the film.

[0076] The raw materials used in the following examples and comparative examples are all commercially available unless otherwise specified.

[0077] Bio-based polyamide raw material 1: Bio-based polyamide resin PA5X, relative viscosity 2.6, melting point 298°C, containing repeating units from a1 bio-based 1,5-pentanediamine, a2 1,6-adipic acid and a3 terephthalic acid, and the molar ratio of a1 / [a2+a3] is 1.15:1, and the molar ratio of a2 / a3 is 56:44, and is self-made.

[0078] Bio-based polyamide raw material 2: Bio-based polyamide resin PA5X, relative viscosity 2.6, melting point 272°C, containing repeating units from a1 bio-based 1,5-pentanediamine, a2 1,6-adipic acid and a3 terephthalic acid, and the molar ratio of a1 / [a2+a3] is 1.15:1, and the molar ratio of a2 / a3 is 67:33, and is self-made.

[0079] Example 1-12 Preparation of Bio-based Polyamide Solution

[0080] The solvent concentration in Example 1 without water dilution was 99%, and the solvents in Examples 2-10 were diluted with water to a concentration of 75-85%. 15 wt% of bio-based polyamide raw materials were added to Examples 1-10, and mechanical stirring was performed at a mixing temperature of 25-70°C for 2.5-8h. The specific results are shown in Table 1 below.

[0081] Example 11 is the same as Example 2, except that the concentration of the bio-based polyamide raw material is 2 wt %.

[0082] Example 12 is the same as Example 2, except that the concentration of the bio-based polyamide raw material is 5 wt %.

[0083] Example 13 is the same as Example 2, except that the concentration of the bio-based polyamide raw material is 20 wt %.

[0084] The solvent formic acid in Comparative Example 1 was diluted with water to a concentration of 70%, and then 15 wt % of bio-based polyamide raw material was added, and mechanical stirring was performed at 25° C. for 4-8 hours. The specific results are shown in Table 1 below.

[0085] Table 1

[0086]

[0087]

[0088] As can be seen from Table 1, the bio-based polyamide defined in the present invention is mixed with a solvent, the water content of the solvent is below 25%, the bio-based polyamide concentration is 2-20wt%, and a clear bio-based polyamide solution with a viscosity of 98-609mPa.s is obtained. The larger viscosity range can be applied to different usage scenarios. Example 10 was stirred at 60°C for 6h before the polyamide dissolved, and the final solution viscosity was relatively high, reaching 8934mPa.s. In the comparative example, the solvent concentration was 70%, that is, the water content was 30%. Comparative Example 1 was stirred at 25°C for 4h, and the polyamide could not be dissolved. After stirring for 8h, the polyamide had swelled and the solution became a gel. .

[0089] Examples 14-26 Preparation of Bio-based Polyamide Powder

[0090] The bio-based polyamide solution prepared in the above embodiment was placed in a YC-015A spray dryer, the inlet temperature of the spray dryer was controlled to be 150-180°C, the outlet temperature was controlled to be 100-120°C, the flow rate of the bio-based polyamide solution and the flow rate of nitrogen were controlled to be 1:10 (referred to as flow rate ratio), and bio-based polyamide powder was obtained. The particle size range of the powder was detected and counted by electron microscopy, as shown in Table 2.

[0091] Table 2

[0092]

[0093]

[0094] As can be seen from Table 2, spray drying can be used to prepare bio-based polyamide powders with a particle size of less than 40μm, and then less than 20μm, and the color of the powder is white. When the inlet temperature is lowered, the powder particle size is larger and the distribution becomes wider; reducing the flow rate ratio is beneficial to reducing the powder particle size. The bio-based polyamide solutions obtained using different types of bio-based polyamide raw materials have similar powder particle size range results. When the concentration of bio-based polyamide raw materials in the bio-based polyamide solution reaches 20%, it is difficult to obtain a uniform powder, and more filamentous and blocky polyamides are produced. The polyamide concentration can be selected according to the needs of downstream application scenarios.

[0095] Comparative Example 2 Preparation of bio-based polyamide powder by mechanical pulverization

[0096] After the bio-based polyamide raw material 1 is cryogenically treated at -190°C by mechanical cryogenic pulverizing equipment, the particles become brittle. The particles are crushed into powder by mechanical pulverization to obtain a powder particle size of 80-150μm. The equipment consumes a large amount of liquid nitrogen, and the cost is higher than that of the method of the present invention. In addition, due to the strong mechanical force, this method causes the long chain of polyamide to break partially, resulting in a significant decrease in mechanical properties, and also has a great impact on crystallization properties. In addition, heat will be generated during the mechanical pulverization process, which requires high temperature control of the equipment, and the strong mechanical force will cause great wear on the equipment.

[0097] Examples 27-32 Preparation of Bio-based Polyamide Films

[0098] The bio-based polyamide solution prepared in Example 1 was spin-coated on a clean glass plate, and dried in a convection oven in a nitrogen atmosphere while slowly heating up the temperature in stages at 5°C / min. The drying temperature was controlled to be 80-100°C. After the solvent in the bio-based polyamide solution was completely evaporated, the film was peeled off from the glass plate to obtain a transparent bio-based polyamide film. The performance parameters of the bio-based polyamide film were tested, as shown in Table 3.

[0099] Comparative Example 3

[0100] The polyamide solution prepared in Comparative Example 1 was spin-coated on a clean glass plate, and dried in a convection oven in a nitrogen atmosphere while slowly heating the temperature in stages at 5°C / min. The drying temperature was controlled to be 100°C. After the solvent evaporated completely, it was found that no film could be formed and only block products were obtained.

[0101] Comparative Example 4

[0102] The bio-based polyamide solution prepared in Example 1 was spin-coated on a clean glass plate, and dried in a convection oven in a nitrogen atmosphere while slowly heating up the temperature in stages at 5°C / min. The drying temperature was controlled to be 25°C. After the solvent was completely evaporated, the film was peeled off from the glass plate to obtain a transparent bio-based polyamide film. The performance parameters of the bio-based polyamide film were tested, as shown in Table 3.

[0103] Table 3

[0104]

[0105] As can be seen from Table 3, after the bio-based polyamide solution is dried on the glass plate, a micron-sized film can be obtained. The film transmittance is as high as above 88%. As the solution concentration decreases, the film thickness decreases and the transparency increases. Using a swelling system such as the solution in Comparative Example 1, it is impossible to form a film. In addition, the low drying temperature is not conducive to obtaining a film with high transparency. Specifically, a suitable drying procedure can be selected according to the needs of the usage scenario. The film in Comparative Example 4 is not very transparent and is whitish. It is speculated that the evaporation rate of the solvent at a lower temperature is greater than the evaporation rate of water, so that the water content gradually increases, the solubility of polyamide decreases, and precipitation occurs.

Claims

1. A bio-based polyamide solution, characterized in that: It contains bio-based polyamide and solvent, and the concentration of bio-based polyamide is 1-40%; The bio-based polyamide contains a diamine unit and a diacid unit, wherein the diacid unit contains an aliphatic diacid unit and an aromatic diacid unit, and the diamine unit contains a pentamethylenediamine unit; The water content of the solvent is below 25%; The bio-based polyamide solution has a viscosity of 100-10000 mPa.s.

2. The bio-based polyamide solution according to claim 1, characterized in that The molar ratio of the diamine unit to the diacid unit may be (0.9-1.2):1, preferably (0.95-1.1):

1.

3. The bio-based polyamide solution according to claim 1, characterized in that: The diamine unit is derived from an aliphatic diamine, preferably butanediamine, pentanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine or a combination thereof; and / or, the aliphatic diacid unit is derived from an aliphatic short-chain diacid and / or an aliphatic long-chain diacid; and / or, the aromatic diacid unit may be derived from an aromatic diacid and / or an aromatic diacid derivative; and / or, the molar ratio of the aliphatic diacid unit to the aromatic diacid unit is 30-70:30-70.

4. The bio-based polyamide solution according to claim 1, characterized in that: The polyamide may have a relative viscosity of 1.2-6.0; and / or a melting point of 250°C-320°C.

5. The bio-based polyamide solution according to claim 1, characterized in that: The solvent is selected from any one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, sodium thiocyanate aqueous solution, zinc chloride aqueous solution, nitric acid, sulfuric acid, formic acid, acetic acid, dichloromethane, benzene, toluene, xylene, methanol, ethanol, trifluoroacetic acid, hexafluoroisopropanol, phenol, chloroform or a combination thereof, or an aqueous solution thereof.

6. The bio-based polyamide solution according to claim 1, characterized in that: The water content of the solvent is 0-25 wt %, further 0.01-15 wt %.

7. A bio-based polyamide powder, characterized in that: The method is obtained by spray-drying the bio-based polyamide solution according to any one of claims 1 to 6, wherein the concentration of the bio-based polyamide solution is 2-20%, preferably 2-10%.

8. The bio-based polyamide powder according to claim 7, characterized in that The inlet temperature of the spray drying is 100-200°C, and the outlet temperature is 100-150°C; and / or, during the spray drying, the ratio of the polyamide solution flow rate to the gas flow rate is controlled to be 1:4-1000; and / or, the gas is nitrogen or an inert gas.

9. The bio-based polyamide powder according to claim 7, characterized in that The particle size of the bio-based polyamide powder particles ranges from 0.2 to 150 μm.

10. A bio-based polyamide film, characterized in that: The bio-based polyamide solution according to any one of claims 1 to 6 is coated on a clean glass substrate, and then dried at 25-100° C. to remove the solvent.

11. The bio-based polyamide film according to claim 10, characterized in that: The light transmittance of the bio-based polyamide film is not less than 80%, and furthermore is above 88%; and / or the chromaticity of the bio-based polyamide film is less than 5, and preferably is 2-4.

Images