Bio-based polyamide resin as well as preparation method and application thereof

Abstract

The invention provides bio-based polyamide resin as well as a preparation method and application thereof. The molecular structure of the bio-based polyamide resin comprises a diamine structural unit and a binary acid structural unit, the diamine structural unit at least comprises a pentamethylene diamine structural unit; the molecular structure of the bio-based polyamide resin also comprises a structural unit containing an acyl piperidine group; the molar percentage content of a structural unit containing an acyl piperidine group in the bio-based polyamide resin relative to a diamine structural unit is less than or equal to 3.0 mol%. The bio-based polyamide resin is high in relative viscosity and good in crystallization property, and the pH value of filtrate obtained after water boiling is appropriate; after the bio-based polyamide resin is rapidly formed, the demolding capacity is high, the smoothness ratio of a workpiece is high, and decomposition or yellowing of the resin in the processing process can be avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering plastics, and specifically relates to a bio-based polyamide resin and a preparation method and application thereof. Background Art

[0002] All-bio-based polyamide is made from bio-based raw materials, usually obtained by condensation of dibasic acids and diamines. Compared with traditional petroleum-based polyamide, all-bio-based polyamide meets the requirements of carbon reduction and environmental protection, and is gradually replacing petroleum-based polyamide.

[0003] 1,5-pentanediamine is a bio-based platform compound, which is obtained from lysine through biological fermentation. It is a key monomer for synthesizing odd-even polyamides and has extremely high commercial application value. However, the polyamide resin prepared with 1,5-pentanediamine as raw material in the prior art has the problems of low relative viscosity, inability to obtain high molecular weight polyamide resin, poor crystallization performance, and low pH value of the filtrate after boiling. After the polyamide resin is rapidly molded, the obtained parts have poor demoulding ability, rough surface and poor quality. Especially when the content of 1,5-pentanediamine is high, it is more difficult to obtain a polyamide resin with high molecular weight, relatively good crystallization performance and high pH value of the filtrate after boiling.

[0004] For example, CN117209751A discloses a method for preparing a fully bio-based polyamide, which uses bio-based 2,5-furandicarboxylic acid and bio-based 1,5-pentanediamine as raw materials and adopts a salt-forming-step polycondensation method to prepare the fully bio-based polyamide. However, the obtained polyamide still has the problems of low relative viscosity, poor crystallization performance, and low proportion of smooth parts.

[0005] Therefore, it is an urgent problem to be solved in this field to develop a bio-based polyamide material using pentamethylenediamine as raw material, which has high relative viscosity, good crystallization performance, suitable pH value of the filtrate after boiling, and good quality of parts obtained by rapid molding. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a bio-based polyamide resin and a preparation method and application thereof. The bio-based polyamide resin has high relative viscosity, good crystallization performance, and a suitable pH value of the filtrate after boiling in water; the bio-based polyamide resin can be quickly molded, has good demoulding ability, and has a high proportion of smooth parts. It can also effectively reduce the problem of resin decomposition caused by excessive acidic substances or yellowing caused by excessive ammonia content during processing, thereby improving the performance of parts.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a bio-based polyamide resin, wherein the molecular structure of the bio-based polyamide resin comprises a diamine structural unit and a dibasic acid structural unit; the diamine structural unit comprises at least a pentamethylenediamine structural unit; the molecular structure of the bio-based polyamide resin further comprises a structural unit containing an acylpiperidine group; the molar percentage of the structural unit containing an acylpiperidine group in the bio-based polyamide resin relative to the diamine structural unit is ≤3.0 mol%.

[0009] In the present invention, the molar percentage of the structural unit containing an acyl piperidine group in the bio-based polyamide resin relative to the diamine structural unit is ≤3.0 mol%, for example, it can be 0 mol%, 0.01 mol%, 0.1 mol%, 0.2 mol%, 0.5 mol%, 0.7 mol%, 0.8 mol%, 0.9 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol%, 3.0 mol% or a range between any of the above values.

[0010] Preferably, the molar percentage of the structural units containing acyl piperidine groups in the bio-based polyamide resin relative to the diamine structural units is 0.01-2.0 mol%, and preferably the molar percentage of the structural units containing acyl piperidine groups relative to the diamine structural units is 0.5-1.0 mol%.

[0011] In the present invention, when pentamethylenediamine is used as a raw material to prepare a bio-based polyamide resin, pentamethylenediamine will undergo a side reaction to produce piperidine, and piperidine reacts with a carboxyl group to form an acylpiperidine group, and the formation of the acylpiperidine group is related to the content of pentamethylenediamine in the raw material diamine, the type of dibasic acid, the type of diamine, and the preparation process. When the content of the structural unit containing the acylpiperidine group is too much, the relative viscosity of the bio-based polyamide resin will be low. When the polymer chain of the structural unit containing the acylpiperidine group increases, the crystallinity of the bio-based polyamide resin will be poor, so that the bio-based polyamide resin will not have time to crystallize during the rapid molding process, resulting in poor demoulding ability, and thus a smaller proportion of smooth parts. In addition, the structural unit containing the acylpiperidine group If the unit content is too high, the amino-carboxyl ratio in the system will be unbalanced, resulting in more diacids being unable to participate in the reaction, which in turn leads to a lower pH value of the filtrate after the resin is boiled in water, causing the polyamide resin to decompose due to too much acidic substance during subsequent processing, thereby reducing product performance; if the pH value is too high, it indicates that the ammonia content in the system is high, which is easy to cause yellowing; therefore, by controlling the content of the structural unit containing the acyl piperidine group within a specific range, it is beneficial to improve the relative viscosity and crystallization performance of the polyamide resin prepared based on pentamethylenediamine and to make the pH value of the filtrate after boiling in water within an appropriate range; on the other hand, the inventors found that if the content of the structural unit containing the acyl piperidine group is too low, it will easily gel in the subsequent processing, which will also lead to a decrease in the proportion of smooth parts.

[0012] In the present invention, by controlling the content of the structural unit containing the acylpiperidine group within a specific range, a bio-based polyamide resin with high relative viscosity, fast crystallization rate, good crystallization performance and appropriate pH value of the filtrate after boiling can be obtained; after the bio-based polyamide resin is quickly molded, it has strong demoulding ability and high finish rate of the product, and can avoid the problem of decomposition of the resin due to excessive acidic substances or yellowing due to excessive ammonia content during processing.

[0013] Preferably, the molar percentage of the pentamethylenediamine structural unit in the diamine structural unit is ≤100 mol%, for example, it can be 4 mol%, 5 mol%, 8 mol%, 9 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 46 mol%, 48 mol%, 50 mol%, 52 mol%, 54 mol%, 56 mol%, 58 mol%, 60 mol%, 62 mol%, 64 mol%, 66 mol%, 68 mol%. %, 70 mol%, 72 mol%, 74 mol%, 76 mol%, 78 mol%, 80 mol%, 82 mol%, 84 mol%, 86 mol%, 88 mol%, 90 mol%, 92 mol%, 94 mol%, 96 mol%, 98 mol%, 100 mol% or any range therebetween; preferably, the molar percentage of the pentamethylenediamine structural unit is ≤90 mol%, more preferably, the molar percentage of the pentamethylenediamine structural unit is ≤75 mol%, and more preferably, the molar percentage of the pentamethylenediamine structural unit is 4-72 mol%.

[0014] In the present invention, the content of pentamethylenediamine structural units will affect the content of structural units containing acylpiperidine groups in the bio-based polyamide resin; a high content of pentamethylenediamine structural units will lead to an increase in the content of structural units containing acylpiperidine groups in the bio-based polyamide resin. By regulating the content of pentamethylenediamine structural units within a specific range, a polyamide resin with a high bio-based content can be obtained, and the content of structural units containing acylpiperidine groups can be avoided to be too high, which is conducive to obtaining a polyamide resin material prepared based on pentamethylenediamine with high relative viscosity, good crystallization performance and a pH value of the filtrate after boiling in a suitable range.

[0015] Preferably, the diamine structural unit further comprises at least one of a hexamethylenediamine structural unit, a heptamethylenediamine structural unit, an octanediamine structural unit, a nonamethylenediamine structural unit or a decanediamine structural unit, preferably a hexamethylenediamine structural unit and / or a decanediamine structural unit.

[0016] Preferably, the dibasic acid structural unit comprises an aliphatic dibasic acid structural unit and / or an aromatic dibasic acid structural unit.

[0017] Preferably, the aliphatic dibasic acid structural unit includes C4 to C12 aliphatic dibasic acid structural units, for example, it can be C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14 aliphatic dibasic acid structural units, illustratively, including but not limited to succinic acid structural units, adipic acid structural units, pimelic acid structural units, suberic acid structural units, azelaic acid structural units, sebacic acid structural units, undecanedioic acid structural units, tridecanedioic acid structural units, etc.

[0018] Preferably, the aliphatic dibasic acid structural unit includes at least one of an adipic acid structural unit, an azelaic acid structural unit or a sebacic acid structural unit.

[0019] Preferably, the aromatic dibasic acid structural unit comprises a furandicarboxylic acid structural unit and / or a terephthalic acid structural unit.

[0020] Preferably, the molar percentage of the aliphatic dibasic acid structural unit in the dibasic acid structural unit is ≤80mol%, and specific values ​​can be, for example, 0mol%, 5mol%, 10mol%, 15mol%, 20mol%, 25mol%, 30mol%, 35mol%, 40mol%, 45mol%, 50mol%, 55mol%, 60mol%, 65mol%, 70mol%, 75mol%, 80mol% or ranges between any of the above values; more preferably, the molar percentage of the aliphatic dibasic acid structural unit is 38-70mol%, and particularly preferably, the molar percentage of the aliphatic dibasic acid structural unit is 42-66mol%.

[0021] In the present invention, the type of dibasic acid structural unit selected will also affect the content of structural units containing acylpiperidine groups in the bio-based polyamide resin; preferably, the dibasic acid structural unit is selected from a compound of aliphatic dibasic acid structural units with a specific content and aromatic dibasic acid structural units, and even in the case of a high content of pentamethylenediamine, the content of structural units containing acylpiperidine groups in the bio-based polyamide resin can be controlled within a relatively low range, because the reaction activity of aromatic dibasic acids is higher than that of aliphatic dibasic acids. If only aromatic dibasic acids are used, the obtained resin has a high melting point, and the corresponding reaction temperature is relatively high, resulting in an increase in the content of structural units containing acylpiperidine groups; if only When using aliphatic dibasic acids, due to their low reaction activity, the reaction time needs to be extended to obtain the target product, and extending the reaction time will also lead to an increase in the content of structural units containing acylpiperidine groups; therefore, the content of aliphatic dibasic acids and aromatic dibasic acids needs to be controlled within a specific ratio range to obtain a bio-based polyamide resin with relatively high viscosity and good crystallization performance; and the dibasic acid structural units are selected from a specific content of aliphatic dibasic acid structural units and aromatic dibasic acid structural units, which can also regulate the effect of structural units containing acylpiperidine groups on the pH value of the resin, which is beneficial to control the pH value of the filtrate after the resin is boiled in water within an appropriate range.

[0022] Preferably, the molecular chain of the bio-based polyamide resin further comprises a diamine structural unit terminated by a monobasic acid.

[0023] Preferably, the molar percentage of the monoacid-terminated diamine structural unit is 0.5-5 mol% of the diacid structural unit, for example, it can be 0.5 mol%, 1 mol%, 1.5 mol%, 2 mol%, 2.5 mol%, 3 mol%, 3.5 mol%, 4 mol%, 4.5 mol%, 5 mol% or any range between the above values, more preferably 1-3 mol%.

[0024] Preferably, the monoacid includes at least one of stearic acid, benzoic acid, acetic acid, lauric acid or cyclohexanecarboxylic acid.

[0025] Preferably, after the powder of the bio-based polyamide resin is mixed with water in a mass ratio of 3:10, the pH value of the filtrate after boiling at 80°C for 24 hours is 5 to 7.5, for example, it can be 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 6, 6.1, 6.2, 6.3, 6.5, 6.6, 6.8, 7, 7.2, 7.4, 7.5 or a range between any of the above values, and the more preferred pH value is 5.8 to 6.5.

[0026] Preferably, the relative viscosity of the bio-based polyamide resin is ≥1.8, for example, it can be 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8 or any range between the above values; more preferably, the relative viscosity is 2.0-2.5.

[0027] In the present invention, the relative viscosity of the bio-based polyamide resin is measured in 96% concentrated sulfuric acid at 25±0.01° C. according to the standard GB / T 12006.1-2009, and the test concentration of the bio-based polyamide resin is 1 g / dL.

[0028] In a second aspect, the present invention provides a method for preparing the bio-based polyamide resin according to the first aspect, the preparation method comprising the following steps:

[0029] The bio-based polyamide resin is obtained by reacting a diamine with a dibasic acid; the diamine includes at least pentamethylenediamine; the reaction includes a step of draining water; and the reaction temperature of the material during the drainage is 170-220°C.

[0030] In the present invention, the content of the structural unit containing the acylpiperidine group in the bio-based polyamide resin can be reduced by controlling the drainage temperature within a specific range.

[0031] In the present invention, the temperature of the drainage is 170-220°C, for example, it can be 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C or a range between any of the above values.

[0032] Preferably, the drainage time is less than 120 min, for example, it can be 2 min, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 22 min, 25 min, 28 min, 30 min, 32 min, 35 min, 38 min, 40 min, 42 min, 45 min, 48 min, 50 min, 52 min, 55 min, 58 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, 95 min, 100 min, 105 min, 110 min, 115 min, 118 min or any range between the above values; more preferably, the drainage time is 10 to 60 min.

[0033] In the present invention, by controlling the drainage time within a specific range, it is also beneficial to reduce the content of the structural unit containing the acyl piperidine group in the bio-based polyamide resin.

[0034] Preferably, the raw materials for the reaction also include a monobasic acid.

[0035] Preferably, the reaction materials further include at least one of a catalyst, an antioxidant or a solvent.

[0036] Preferably, the addition amount of the catalyst and antioxidant is independently 0.05-0.2% of the total mass of the reaction raw materials, for example, it can be 0.05%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2% or any range between the above values.

[0037] In the present invention, the total mass of the reaction raw materials refers to the total mass of the diamine, the dibasic acid, the monobasic acid, the antioxidant and the catalyst.

[0038] Preferably, the ratio of the amount of the solvent added to the total mass of the reaction system is 1:9 to 4:6.

[0039] In the present invention, the total mass of the reaction system refers to the total mass of the diamine, the dibasic acid, the monobasic acid, the antioxidant, the catalyst and the solvent.

[0040] In the present invention, the antioxidant includes but is not limited to any one of N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine (antioxidant 1098), pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1010), tris[2.4-di-tert-butylphenyl]phosphite (antioxidant 168), and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076), or a composite antioxidant composed of at least two of them.

[0041] In the present invention, the catalyst includes but is not limited to hypophosphite, zinc isooctanoate, phosphoric acid, boric acid, organic sulfonic acid and the like.

[0042] In the present invention, the solvent includes water.

[0043] Preferably, the reaction is carried out in the presence of a protective atmosphere; the protective atmosphere includes but is not limited to nitrogen, argon, etc.

[0044] Preferably, the reaction method includes method A, method B or method C; the method A includes a polymerization method of prepolymerization and solid phase viscosity enhancement; the method B includes a polymerization method of prepolymerization and extrusion viscosity enhancement; the method C includes a melt polymerization method.

[0045] In the present invention, the melting point of the bio-based polyamide resin is greater than 270°C, and method A or method B is used, that is, a polymerization method of prepolymerization combined with solid phase viscosity enhancement; the specific steps include:

[0046] The diamine is mixed with a dibasic acid and a monobasic acid, an antioxidant, a catalyst and a solvent, and the mixture is heated to 170 to 220° C. within 1 to 4 hours in the presence of a protective atmosphere. The mixture is drained until the remaining water content in the system is 13 to 15%, and high-pressure discharge is performed to obtain a prepolymer. The prepolymer is then subjected to solid phase viscosity enhancement or extrusion viscosity enhancement to obtain the bio-based polyamide resin.

[0047] In the present invention, the solid phase viscosity increasing method comprises: heating the prepolymer to 5 to 40° C. below the melting point of the prepolymer under vacuum conditions or in the presence of a protective atmosphere, reacting for 1 to 24 hours to obtain the bio-based polyamide resin.

[0048] In the present invention, when solid phase thickening is used, during the solid phase thickening process, the material is taken and its relative viscosity is measured according to standard GB / T12006.1-1989 until the relative viscosity changes by ≤0.01, then the solid phase thickening is stopped. The time at this time is the solid phase thickening time, which is also the reaction endpoint.

[0049] In the present invention, the extrusion viscosity increasing method comprises: extruding the prepolymer through a twin-screw extruder, the extrusion temperature being 15° C. above the melting point of the prepolymer, to obtain the bio-based polyamide resin.

[0050] In the present invention, the melting point of the bio-based polyamide resin is ≤270°C, and method C, i.e., melt polymerization method, is adopted; the specific steps include:

[0051] The diamine is mixed with a dibasic acid and a monobasic acid, an antioxidant, a catalyst and a solvent, and the mixture is heated to 170-220° C. within 1-4 hours in the presence of a protective atmosphere, and the water is drained. Before the drainage is completed, the polymerization temperature must reach 20° C. higher than the melting point of the product and then remain unchanged. The mixture is vacuumed for reaction for 1-2 hours, and the molecular weight of the polymer is increased by removing the formed water. When the stirring power of the reaction device tends to be stable, the reaction is completed and the material is discharged to obtain the bio-based polyamide resin.

[0052] In a third aspect, the present invention provides a use of the bio-based polyamide resin according to the first aspect in a rapid prototyping process.

[0053] In the present invention, the products produced by the rapid prototyping process include but are not limited to LED lighting materials, electronic connectors, etc.

[0054] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] The bio-based polyamide resin provided by the present invention includes a structural unit containing an acyl piperidine group in its molecular structure, and the content of the structural unit containing the acyl piperidine group is controlled within a specific range, so that the bio-based polyamide resin has a high relative viscosity and good crystallization performance; the bio-based polyamide resin can be quickly molded, has good demoulding ability, and has a high proportion of smooth parts. DETAILED DESCRIPTION

[0057] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0058] The materials used in the present invention can be purchased from the market. Unless otherwise specified, the materials used in the present invention are as follows:

[0059] Bio-based pentamethylenediamine: purity 99.99%, Heilongjiang Yipin New Materials Co., Ltd., no piperidine detected;

[0060] Hexamethylenediamine: purity 99%, China Chemical Tianchen Qixiang New Materials Co., Ltd.;

[0061] Bio-based decanediamine: purity 99%, Wuxi Yinda Nylon Co., Ltd.

[0062] Bio-based sebacic acid: purity 99%, Wuxi Yinda Nylon Co., Ltd.

[0063] Azelaic acid: purity 99%, Hoda Xipu Chemical (Sichuan) Co., Ltd.;

[0064] Terephthalic acid: purity 99%, Hengli Petrochemical Co., Ltd.

[0065] Antioxidant 1098: Double Bond Chemical Company;

[0066] Sodium hypophosphite: analytical grade, purchased from Sigma-Aldrich.

[0067] In the present invention, the test method for the content of structural units containing acylpiperidine groups in the bio-based polyamide resin is as follows:

[0068] The bio-based polyamide resin sample was dried to constant weight, 0.3g of resin was taken into an ampoule, 6mL48wt% hydrobromic acid and 3mL trifluoroacetic acid were added, and the bottle was sealed and hydrolyzed in an oven at 140℃ for 24h. The hydrolyzate was placed in a 250mL beaker, and 50mL of water was added thereto to dilute the hydrolyzate. A stirrer was added, and the beaker was placed on a magnetic stirrer and stirred. 50wt% sodium hydroxide solution was slowly added to the diluted hydrolyzate, and the pH was adjusted to 10-12, and the solution became clear. Extracted with chloroform, 30mL of chloroform was used each time, extracted 3 times, and the organic phase (lower layer) was collected into a conical flask. Anhydrous sodium sulfate was added to the collected organic phase (the mass volume ratio of the anhydrous sodium sulfate to the organic phase was 2g / 10mL), and stirred for 5-10min. Then filtered, the filtrate was decompressed and distilled to 2-5mL in a rotary evaporator, and the amine substance concentrate was collected. The collected concentrated solution of amine substances was fixed to 10 mL with chloroform, and 1 mL was transferred to a chromatographic bottle for gas chromatography (GC) testing. Test method: the temperature was raised to 100 ° C at 5 ° C / min, and kept at 100 ° C for 2 minutes, and then the temperature was raised from 100 ° C to 260 ° C at a rate of 20 ° C / min for testing. The signal peak area of ​​acylpiperidine was integrated and recorded as A1, and the signal peak area of ​​diamine was integrated and recorded as A2. The molar percentage of the structural unit containing acylpiperidine group relative to the diamine structural unit = A1 / A2×100%. Instrument: Agilent (7890A) gas chromatograph; Chromatographic column: CP-Sil 8CB amine analysis special chromatographic column; Detector: FID (flame ionization detector); Among them, the peak position of the signal peak of diamine was obtained by testing the gas chromatography of diamine monomer.

[0069] In the present invention, the molar content of the diamine structural unit and the dibasic acid structural unit in the molecular structure of the bio-based polyamide resin can be tested by nuclear magnetic resonance carbon spectroscopy. The specific method includes: taking 60 mg of the bio-based polyamide resin sample and dissolving it in 0.5 mL of hexafluoroisopropanol, adding 0.2 mL of deuterated chloroform after dissolution, and then using Bruker AV 500 nuclear magnetic resonance spectrometer for quantitative determination. 13 C NMR, the molar ratio of the diamine structural unit to the dibasic acid structural unit and the respective composition were determined by the integrated area of ​​the characteristic peaks of the diamine and the dibasic acid.

[0070] For example, taking the diamines pentamethylenediamine and decamethylenediamine as examples, the characteristic peak positions of pentamethylenediamine and decamethylenediamine are known (which can be obtained by testing the diamine monomers or known from the literature), wherein the integral area of ​​the characteristic peak of pentamethylenediamine is denoted as A1, and the integral area of ​​the characteristic peak of decamethylenediamine is denoted as A2, then the molar percentage content of pentamethylenediamine in the diamine is A1 / (A1+A2)×100%.

[0071] Examples 1 to 14, Comparative Examples 1 to 4

[0072] Examples 1 to 14 and Comparative Examples 1 to 4 respectively provide a bio-based polyamide resin, wherein the molar percentage of the structural unit containing an acylpiperidine group relative to the diamine structural unit in the bio-based polyamide resin is as shown in Tables 1 to 3; the composition of the diamine in the bio-based polyamide resin is as shown in Tables 1 to 3, taking the total molar amount of the diamine structural unit as 100%; and the composition of the dibasic acid in the bio-based polyamide resin is as shown in Tables 1 to 3, taking the total molar amount of the dibasic acid structural unit as 100%. " / " indicates that the component is not included in the formula.

[0073] The preparation method of the bio-based polyamide resin comprises the following steps:

[0074] Add diamine, dibasic acid and stearic acid (accounting for 2 mol% of the molar content of dibasic acid), antioxidant 1098 (accounting for 0.1% of the total mass of reaction raw materials), sodium hypophosphite (accounting for 0.1% of the total mass of reaction raw materials) and water (accounting for 20% of the total mass of the system) into a pressure autoclave equipped with magnetic coupling stirring, condenser, gas phase port, feeding port and pressure explosion-proof port, mix and stir, and in the presence of nitrogen, heat to 170-220°C within 2 hours and drain.

[0075] Sampling is performed, and the melting point of the reactants is tested by a differential scanning calorimeter (DSC). When the melting point of the bio-based polyamide resin is greater than 270°C, a prepolymerization and solid phase viscosity enhancement polymerization method is adopted, and the water volume in the system is drained to 13-15% relative to the total mass of the reaction system. At the same time, the drainage time is controlled to be less than 120 min, and high-pressure discharge is performed to obtain a prepolymer. The prepolymer is heated to 20°C below the melting point of the prepolymer in the presence of nitrogen, and the reaction is carried out for 10 hours to obtain the bio-based polyamide resin (in all embodiments and comparative examples, the reaction endpoint is reached after 10 hours of reaction).

[0076] When the melting point of the bio-based polyamide resin is less than 270°C, a melt polymerization method is used. Before the drainage is completed, the polymerization temperature needs to be 20°C higher than the melting point of the product and then maintained unchanged. The reaction is carried out in a vacuum for 2 hours. The molecular weight of the polymer is increased by removing the formed water. After the reaction is completed, the material is discharged to obtain the bio-based polyamide resin.

[0077] In the preparation methods of bio-based polyamide resins provided in Examples 1 to 14 and Comparative Examples 1 to 4, specific drainage temperatures (i.e., the reaction temperature of the materials during drainage) and drainage times (i.e., the reaction time of the materials during drainage) are shown in Tables 1 to 3.

[0078] Table 1

[0079]

[0080] Table 2

[0081]

[0082] Table 3

[0083]

[0084] Performance Testing

[0085] (1) Relative viscosity ηr: Referring to the standard GB / T 12006.1-2009, the specific test method is: measuring the relative viscosity of the bio-based polyamide resin with a concentration of 1 g / dL in 96% concentrated sulfuric acid at 25±0.01°C; the larger the relative viscosity, the higher the molecular weight obtained.

[0086] (2) pH value of the filtrate after boiling: After 3 g of bio-based polyamide resin was crushed into powder, 10 g of pure water was added, extracted at 80 °C for 24 h, and then filtered. After the filtrate was cooled to 25 °C, the pH value of the filtrate was tested with an aqueous pH meter.

[0087] (3) Proportion of smooth parts: The bio-based polyamide resin was injection molded into a 0.3 mm thick square plate (5 cm × 5 cm) at a temperature 15°C higher than the melting point of the material, the mold temperature was room temperature, the cooling time was 3s, and the mold and baffle were polished; 100 square plates were injection molded for each sample, and the surface of the square plate was observed with the naked eye to see if there were rough surfaces caused by slow crystallization rate. The number of color plates with rough surfaces was calculated to account for B%, and the proportion of smooth parts was 100%-B%.

[0088] The specific test results are shown in Table 4.

[0089] Table 4

[0090] Relative viscosity pH Ratio of smooth parts (%) Example 1 2.23 6.5 92 Example 2 2.18 6.4 94 Example 3 2.15 6.3 99 Example 4 2.12 6.1 98 Example 5 2.01 5.5 94 Example 6 2.14 6.1 97 Example 7 2.13 6.2 99 Example 8 2.09 5.6 96 Example 9 1.98 5.1 91 Example 10 2.26 5.9 99 Embodiment 11 2.28 6.1 98 Example 12 2.31 6.2 96 Embodiment 13 2.21 6.0 95 Embodiment 14 2.27 6.2 97 Comparative Example 1 1.85 4.9 88 Comparative Example 2 1.80 4.8 85 Comparative Example 3 1.78 4.6 83 Comparative Example 4 1.73 4.4 80

[0091] As can be seen from Table 4, the bio-based polyamide resin provided by the present invention has a relatively high relative viscosity, which is ≥1.98; the pH value of the filtrate after boiling is ≥5.0, and the acidity is relatively low, which can effectively reduce the problem of decomposition of the resin due to excessive acidic substances in the subsequent processing; and the crystallization performance is good. After the bio-based polyamide resin is quickly molded, the proportion of smooth parts obtained is high, which is ≥91%, and can even reach 99%.

[0092] It can be seen from the comparative examples that when the content of the structural unit containing the acylpiperidine group is too high, the relative viscosity of the bio-based polyamide resin is low, the crystallization performance is poor, and the proportion of smooth and clean parts obtained is low.

[0093] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bio-based polyamide resin, characterized in that: The molecular structure of the bio-based polyamide resin comprises a diamine structural unit and a dibasic acid structural unit; the diamine structural unit comprises at least a pentamethylenediamine structural unit; The molecular structure of the bio-based polyamide resin also includes a structural unit containing an acylpiperidine group; The molar percentage of the structural unit containing the acylpiperidine group in the bio-based polyamide resin relative to the diamine structural unit is less than or equal to 3.0 mol%.

2. The bio-based polyamide resin according to claim 1, characterized in that The molar percentage of the structural unit containing acylpiperidine groups in the bio-based polyamide resin relative to the diamine structural unit is 0.01-2.0 mol %, and preferably the molar percentage of the structural unit containing acylpiperidine groups relative to the diamine structural unit is 0.5-1.0 mol %.

3. The bio-based polyamide resin according to claim 1 or 2, characterized in that: The molar percentage of the pentamethylenediamine structural unit in the diamine structural unit is ≤100 mol%, preferably the molar percentage of the pentamethylenediamine structural unit is ≤90 mol%, more preferably the molar percentage of the pentamethylenediamine structural unit is ≤75 mol%, and more preferably the molar percentage of the pentamethylenediamine structural unit is 4 to 72 mol%; Preferably, the diamine structural unit further comprises at least one of a hexamethylenediamine structural unit, a heptamethylenediamine structural unit, an octanediamine structural unit, a nonamethylenediamine structural unit or a decanediamine structural unit, preferably a hexamethylenediamine structural unit and / or a decanediamine structural unit.

4. The bio-based polyamide resin according to any one of claims 1 to 3, characterized in that: The dibasic acid structural unit includes an aliphatic dibasic acid structural unit and / or an aromatic dibasic acid structural unit; Preferably, the aliphatic dibasic acid structural unit comprises a C4-C12 aliphatic dibasic acid structural unit; Preferably, the aliphatic dibasic acid structural unit includes at least one of an adipic acid structural unit, an azelaic acid structural unit or a sebacic acid structural unit; Preferably, the aromatic dibasic acid structural unit comprises a furandicarboxylic acid structural unit and / or a terephthalic acid structural unit; Preferably, the molar percentage of the aliphatic dibasic acid structural unit in the dibasic acid structural unit is ≤80 mol%, more preferably the molar percentage of the aliphatic dibasic acid structural unit is 38-70 mol%, and particularly preferably the molar percentage of the aliphatic dibasic acid structural unit is 42-66 mol%; Preferably, the molecular chain of the bio-based polyamide resin further comprises a diamine structural unit terminated by a monobasic acid; Preferably, the molar percentage of the monoacid-terminated diamine structural unit is 0.5 to 5 mol% of the diacid structural unit; Preferably, the monoacid includes at least one of stearic acid, benzoic acid, acetic acid, lauric acid or cyclohexanecarboxylic acid.

5. The bio-based polyamide resin according to any one of claims 1 to 4, characterized in that: The powder of the bio-based polyamide resin is mixed with water at a mass ratio of 3:10, and the pH value of the filtrate is 5-7.5 after being boiled at 80° C. for 24 hours.

6. The bio-based polyamide resin according to any one of claims 1 to 5, characterized in that: The relative viscosity of the bio-based polyamide resin is ≥1.8, and more preferably the relative viscosity is 2.0-2.

5.

7. A method for preparing a bio-based polyamide resin according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: reacting a diamine with a dibasic acid to obtain the bio-based polyamide resin; The diamine at least includes pentamethylenediamine; the reaction includes a step of draining water; and the reaction temperature of the material during the drainage is 170-220°C.

8. The preparation method according to claim 7, characterized in that: The drainage time is less than 120 minutes, and more preferably the drainage time is 10 to 60 minutes; Preferably, the raw materials of the reaction also include a monoacid; Preferably, the reaction materials further include at least one of a catalyst, an antioxidant or a solvent; Preferably, the added amount of the catalyst and antioxidant is independently 0.05-0.2% of the total mass of the reaction raw materials.

9. The preparation method according to claim 7 or 8, characterized in that: The reaction is carried out in the presence of a protective atmosphere; Preferably, the reaction method includes method A, method B or method C; the method A includes a polymerization method of prepolymerization and solid phase viscosity enhancement; the method B includes a polymerization method of prepolymerization and extrusion viscosity enhancement; the method C includes a melt polymerization method.

10. Use of the bio-based polyamide resin according to any one of claims 1 to 6 in a rapid prototyping process.

Images