Nylon elastomer as well as preparation method and application thereof

Abstract

The invention provides a nylon elastomer as well as a preparation method and application thereof. The method comprises the following steps: S1, preparing a polyamide prepolymer from binary acid and diamine or lactam and an end-capping reagent, and then reacting with polyether polyol to obtain a nylon elastomer; s2, removing residual monomers from the nylon elastomer through a devolatilization type screw extruder, and then removing crystal points and impurity points through a melt filter; and S3, extracting and plasticizing the nylon elastomer obtained in the step S2 by using a supercritical fluid, and further removing residual monomers and crystal points. The preparation method can be continuously operated and is green and environment-friendly, and the nylon elastomer prepared by the process is low in residual monomer content and few in crystal point impurity points, and is suitable for the fields of medical treatment, food and moisture permeable films.

Description

Technical Field

[0001] This invention relates to the field of nylon, and more particularly to nylon elastomers. Background Technology

[0002] Nylon elastomers are block copolymers composed of highly crystalline nylon as the hard segment and amorphous polyether polyols. Compared with other elastomers, they possess characteristics such as high tensile strength, good resilience, high impact strength, excellent low-temperature resistance, and ease of processing, making them widely used in sports footwear materials, medical catheters, and waterproof and breathable applications. The nylon hard segment is generally obtained through ring-opening of lactams or amidation reaction of diacids with diamines. However, due to the influence of the ring-opening equilibrium constant and conversion rate, some monomers may remain unreacted. These unreacted monomers can migrate out of the product during use, limiting its application in medical, food, and other fields. During the polymerization of nylon elastomers, some regions may exhibit excessively ordered molecular chains, forming oversized spherulites or crystal structures. Additionally, some high-molecular-weight segments with poor mobility are difficult to completely melt and uniformly disperse during processing, making them more likely to act as nuclei, rapidly and excessively crystallizing in localized areas to form crystal points. Meanwhile, the polymerization of nylon elastomers is mostly carried out in batch batch esterification reactions. Due to the effects of high-temperature carbonization and catalyst hydrolysis, gel points, black spots, and impurities are inevitably generated. These crystal points, gel points, black spots, and impurities will affect the processability of products such as pipe extrusion or film casting.

[0003] Currently, there are only patents addressing the issue of residual monomers in nylon elastomers, but no patents offering effective solutions to the problem of crystal point impurities. Specifically, CN117801267A proposes cleaning nylon 12 hard segments with organic solvents to obtain nylon 12 hard segments with low LL precipitates. However, using organic solvents raises safety and environmental concerns, and may also leave residues in the nylon elastomer or cause swelling, affecting performance. Supercritical fluids exhibit good solubility for low molecular weight monomers; literature reports that their solubility is comparable to that of ether solvents, and they are safe and environmentally friendly, without causing polymer swelling. US patent US5519097 uses 60 ppm hypophosphoric acid in a continuous tubular reactor to polymerize dodecyl lactam. Compared to an example without a catalyst, the molecular weight increased, but the residual monomer content was 0.3%, failing to further remove the residual monomer content. Summary of the Invention

[0004] This invention provides a nylon elastomer, its preparation method, and its applications. The preparation method is continuous and environmentally friendly, and the nylon elastomer has a low residual monomer content and a small number of crystal point impurities.

[0005] To achieve the objectives of this invention, the following technical solution is adopted:

[0006] A method for preparing a nylon elastomer with low residual monomer content and few crystal point impurities includes the following steps:

[0007] S1, a combination of dicarboxylic acid and diamine or lactam, reacts in the presence of a capping agent to prepare a dicarboxylated polyamide prepolymer. The polyamide prepolymer is then esterified with a polyether polyol under the action of a catalyst to obtain a nylon elastomer.

[0008] S2. Remove residual monomers from the nylon elastomer using a devolatilization screw extruder, and remove crystal points and impurities using a melt filter;

[0009] S3. The nylon elastomer obtained from S2 is extracted using supercritical fluid extraction.

[0010] The residual monomer content of the nylon elastomer prepared by the method of the present invention is limited to less than 5 ppm, the crystal point size is limited to less than 0.4 mm, and the number is limited to 20 per 1520 cm. 2 Within this range, the size of impurities is limited to below 200um and the number is limited to 10 per 200g.

[0011] In S1 of the present invention, the dicarboxylic acid includes one or more of C5-C18 dicarboxylic acids, preferably one or more of adipic acid, sebacic acid, and dodecanoic acid.

[0012] In S1 of the present invention, the diamine includes one or more of C5-C13 diamines, preferably one or more of hexamethylenediamine and dodecanediamine.

[0013] In S1 of this invention, the lactam includes one or more of caprolactam and dodecanolactam.

[0014] The capping agent described in this invention may be the same as or different from the dicarboxylic acid, but preferably the same.

[0015] The capping agent of the present invention includes C5-C 18 The dicarboxylic acid is preferably one or more of adipic acid, sebacic acid, and dodecanoic acid.

[0016] The polymerization temperature of the present invention is 220-280℃, the pressure is 2-4 MPaG, and the time is 2-10h.

[0017] The number-average molecular weight of the polyamide prepolymer described in this invention is 1000-20000 g / mol.

[0018] The polyether polyol described in this invention is selected from one or more of polyethylene glycol, polypropylene glycol, or polybutylene glycol, with a molecular weight of 500-2000 g / mol.

[0019] The catalyst described in this invention is selected from those with the general formula M(OR).n Metal alkoxides; wherein M is Sb, Ti, Zr or Ge, and R is C. 1～10 The alkyl group, n takes the value of 1 to 4, and suitable examples include, but are not limited to, one or more of tetrabutyl titanate, antimony glycolate, zirconium propoxide, and tetraethyl germanate.

[0020] As a preferred option, an auxiliary agent is added before the esterification reaction, preferably an antioxidant and / or a UV absorber.

[0021] The esterification reaction described in this invention is carried out at a temperature of 200-270℃, a vacuum degree of ≤500PaA, and a time of 2-8h.

[0022] The main devolatilization section of the devolatilization screw extruder of the present invention has a barrel vacuum degree of ≤50PaA, a devolatilization temperature controlled at 220-280℃, and a devolatilization speed of 100-600rpm.

[0023] The residual monomers mentioned in this invention are one or more of the dicarboxylic acid, diamine, lactam, and capping agent.

[0024] The mesh size of the melt filter described in this invention is below 200 μm, preferably 20-50 μm.

[0025] The impurity points described in this invention include gel points, black spots, and other impurities.

[0026] The supercritical fluid described in this invention includes supercritical carbon dioxide; the extraction temperature is 40-250℃, preferably above the melting point of polyamide elastomer, the pressure is 8-40MPa, and the extraction time is 0.5-3h.

[0027] The nylon elastomer described in this invention is used in fields such as medical catheters, breathable membranes, and food conveyor belts.

[0028] The present invention has the following beneficial effects:

[0029] (1) The method of combining devolatilization screw extraction with supercritical fluid extraction can effectively remove residual monomers from nylon elastomers, limiting the residual monomer content to less than 5 ppm. Compared with organic solvents, supercritical fluid extraction is safe and environmentally friendly, and will not cause nylon elastomers to swell and affect their structural properties;

[0030] (2) The method of plasticizing with melt filter and supercritical fluid can effectively reduce impurity points and crystal points in nylon elastomer. Melt filter can only remove impurities such as gel points and black points in nylon elastomer, while the plasticizing effect of supercritical fluid can increase the free volume between polymer chains, causing molecular chains to move and rearrange, homogenizing the crystalline regions with excessively high molecular weight and high order, thereby effectively reducing the number of crystal points.

[0031] (3) Using the above preparation method, a residual monosodium glutamate content of less than 5 ppm, a crystal point size limited to less than 0.4 mm, and a quantity limited to 20 crystals / 1520 cm² can be obtained. 2 Nylon elastomer products with impurity point sizes below 200um and quantities below 10 per 200g can be used in fields such as medical catheters, waterproof and breathable membranes, and food conveyor belts. Detailed Implementation

[0032] To better understand the technical solution of the present invention, the content of the present invention will be further described below with reference to the embodiments, but the content of the present invention is not limited to the following embodiments;

[0033] The following test methods are used in various embodiments of the present invention:

[0034] (1) Residual monomers: According to ASTM D6865-17 "Standard Test Method for Determination of Soluble Monomer and Oligomer Content in Polyamide Materials by Gas Chromatography", residual monomers in polyamide elastomers were tested;

[0035] (2) Impurity points: According to SH / T 1541.1-2019 "Appearance Test Methods for Plastic Particles - Part 1: Visual Inspection", the size and number of impurity points in polyamide elastomers are tested.

[0036] (3) Crystal points: According to ASTM D3351-93 "Standard Test Method for Gel Counting of Plastic Films", the size and number of crystal points in polyamide elastomers are tested. Impurity points are not included in the number of crystal points.

[0037] The equipment used in the various embodiments of the present invention includes: Jiangsu Chengmeng STSH-36 devolatilization type three-screw extruder with a length-to-diameter ratio of 68:1 and an ultimate vacuum of 0.06Pa; Weihai Xuri melt filter with a filter mesh size of 20µm; and Shianjia supercritical fluid extractor SFE-850A with a maximum pressure of 40MPa.

[0038] Unless otherwise specified, the raw materials used in the comparative examples and embodiments of this invention can be purchased through commercial channels.

[0039] Example 1

[0040] (1) 98.782 kg dodecyl lactam, 1.218 kg adipic acid and 10 kg water were added to the polymerization reactor. The reaction conditions were 280 °C and 4 MPa for 10 h to obtain nylon 12 hard segments with a number average molecular weight of 12000 g / mol and dicarboxyl end caps. Then, 8.33 kg polybutane glycol with a number average molecular weight of 1000 g / mol and 0.3 kg tetrabutyl titanate were added to the polymerization reactor and nitrogen was purged. The stirring was turned on and the temperature was raised to 240 °C. The reaction was carried out under vacuum of 400 PaA for 2 h to prepare nylon 12 elastomer.

[0041] (2) The nylon 12 elastomer prepared in step (1) was devolatilized using a devolatilization screw extruder with a devolatilization barrel vacuum of 20 PaA, a devolatilization temperature of 220°C, and a screw speed of 600 rpm. Then it was filtered through a melt filter with a mesh size of 20 μm.

[0042] (3) Place 500g of the nylon 12 elastomer prepared in step (2) into a supercritical extractor and extract it for 0.5h using supercritical carbon dioxide at 180℃ and 40MPa to obtain nylon elastomer resin 1 with low residual monosodium content and few crystal points.

[0043] Example 2

[0044] (1) 85.386 kg caprolactam, 14.614 kg adipic acid and 10 kg water were added to the polymerization reactor. The reaction conditions were 220 °C and 3.5 MPa for 2 h to obtain nylon 6 hard segments with a number average molecular weight of 1000 g / mol and dicarboxyl end caps. Then, 50 kg polypropylene glycol with a number average molecular weight of 500 g / mol and 0.6 kg zirconium n-propoxide were added to the polymerization reactor and nitrogen was purged. The stirring was turned on and the temperature was raised to 200 °C. The reaction was carried out under vacuum of 200 PaA for 8 h to obtain nylon 6 elastomer.

[0045] (2) The nylon 6 elastomer prepared in step (1) was devolatilized using a devolatilization screw extruder with a devolatilization barrel vacuum of 50 PaA, a devolatilization temperature of 250°C, and a screw speed of 100 rpm. Then it was filtered through a melt filter with a mesh size of 50 μm.

[0046] (3) Place 500g of the nylon 6 elastomer prepared in step (2) into a supercritical extractor and extract it for 3h at 40℃ and 8MPa using supercritical carbon dioxide to obtain nylon elastomer resin 2 with low residual monosodium content and few crystal points.

[0047] Example 3

[0048] (1) 97.989 kg of dodecyl lactam, 1.011 kg of sebacic acid and 10 kg of water were added to the polymerization reactor. The reaction conditions were 280 °C and 4 MPa for 5 h to obtain nylon 12 hard segments with a number average molecular weight of 20000 g / mol and dicarboxyl end caps. Then, 10 kg of polyethylene glycol with a number average molecular weight of 2000 g / mol and 0.36 kg of antimony glycol were added to the polymerization reactor for nitrogen purging. After purging, the reactor temperature was raised to 270 °C and the reaction was carried out under vacuum of 500 PaA for 3 h to obtain nylon 12 elastomer.

[0049] (2) The nylon 12 elastomer prepared in step (1) was devolatilized using a devolatilization screw extruder with a barrel vacuum of 40 PaA, a devolatilization temperature of 280°C, and a screw speed of 300 rpm. Then it was filtered through a melt filter with a mesh size of 40 μm.

[0050] (3) Place 500g of the nylon 12 elastomer prepared in step (2) into a supercritical extractor and extract it for 2h at 200℃ and 15MPa using supercritical carbon dioxide to obtain nylon elastomer resin 3 with low residual monosodium content and few crystal points.

[0051] Example 4

[0052] (1) 44.367 kg dodecanediamine, 55.633 kg dodecanoic acid and 50 kg water were added to the polymerization reactor. The reaction conditions were 260℃ and 3.2 MPa for 4 h to obtain nylon 1212 hard segments with a number average molecular weight of 5000 g / mol and dicarboxyl end caps. Then, 3 kg polyethylene glycol with a number average molecular weight of 1500 g / mol and 0.3 kg antimony glycol were added to the polymerization reactor for nitrogen purging. After purging, the reactor temperature was raised to 250℃ and the reaction was carried out under vacuum of 200 PaA for 8 h to prepare nylon 1212 elastomer.

[0053] (2) The nylon 1212 elastomer prepared in step (1) was devolatilized using a devolatilization screw extruder with a devolatilization barrel vacuum of 50 PaA, a devolatilization temperature of 260℃, and a screw speed of 400 rpm. After that, it was filtered through a melt filter with a mesh size of 30 μm.

[0054] (3) Place 500g of the nylon 1212 elastomer prepared in step (2) into a supercritical extractor and extract it for 1h at 180℃ and 30MPa using supercritical carbon dioxide to obtain nylon elastomer resin 4 with low residual monosodium content and few crystal points.

[0055] Example 5

[0056] (1) 42.161 kg hexamethylenediamine, 57.839 kg adipic acid, and 10 kg water were added to a polymerization reactor. The reaction conditions were 250 °C and 3 MPa for 6 h to obtain nylon 66 hard segments with a number average molecular weight of 3000 g / mol and dicarboxyl-terminated segments. Then, 50 kg of polybutanediol with a number average molecular weight of 1500 g / mol and 0.45 kg of tetraethyl germanate were added to the polymerization reactor for nitrogen purging. After purging, the reactor temperature was raised to 260 °C and the reaction was carried out under vacuum of 100 PaA for 4 h to prepare nylon 66 elastomer.

[0057] (2) The nylon 66 elastomer prepared in step (1) was devolatilized using a devolatilization screw extruder with a barrel vacuum of 40 PaA, a devolatilization temperature of 240°C, and a screw speed of 400 rpm. Then it was filtered through a melt filter with a mesh size of 20 μm.

[0058] (3) Place 500g of the nylon 66 elastomer prepared in step (2) into a supercritical extractor and extract it for 2h at 250℃ and 20MPa using supercritical carbon dioxide to obtain nylon elastomer resin 5 with low residual monosodium content and few crystal points.

[0059] Comparative Example 1-1

[0060] The product of step (1) of Example 1 is denoted as Nylon Elastomer Resin 1-1, without undergoing screw devouring, melt filtration and supercritical fluid extraction.

[0061] Comparative Examples 1-2

[0062] The nylon 12 elastomer prepared in step (1) of Example 1 was devolatilized using a devolatilization screw extruder with a barrel vacuum of 20 PaA, a devolatilization temperature of 220°C, and a screw speed of 600 rpm. This elastomer was denoted as nylon elastomer resin 1-2.

[0063] Comparative Examples 1-3

[0064] The nylon 12 elastomer prepared in step (1) of Example 1 was filtered through a melt filter with a mesh size of 20 μm and is referred to as nylon elastomer resin 1-3.

[0065] Comparative Examples 1-4

[0066] 500g of the nylon 12 elastomer prepared in step (1) of Example 1 was placed in a supercritical extraction apparatus and extracted for 0.5h using supercritical carbon dioxide at 180°C and 40MPa. This was denoted as nylon elastomer resin 1-4.

[0067] Comparative Examples 1-5

[0068] The nylon 12 elastomer prepared in step (1) of Example 1 was devolatilized using a devolatilization screw extruder with a barrel vacuum of 20 PaA, a devolatilization temperature of 220°C, and a screw speed of 600 rpm. After that, it was filtered through a melt filter with a mesh size of 20 μm and is referred to as nylon elastomer resin 1-5.

[0069] Comparative Examples 1-6

[0070] The nylon 12 elastomer prepared in step (1) of Example 1 was devolatilized using a devolatilization screw extruder with a barrel vacuum of 20 PaA, a devolatilization temperature of 220°C, and a screw speed of 600 rpm. Then, 500 g of the nylon 12 elastomer that had been devolatilized by the screw was placed in a supercritical extraction apparatus and extracted with supercritical carbon dioxide at 180°C and 40 MPa for 0.5 h. This was recorded as nylon elastomer resin 1-6.

[0071] Comparative Examples 1-7

[0072] The nylon 12 elastomer prepared in step (1) of Example 1 was filtered through a melt filter with a mesh size of 20 μm. Then, 500 g of the nylon 12 elastomer that had passed through the melt filter was placed in a supercritical extractor and extracted for 0.5 h using supercritical carbon dioxide at 180 °C and 40 MPa. This was recorded as nylon elastomer resin 1-7.

[0073] The nylon elastomer resin prepared above was tested for residual monomers and the number of crystal points. The results are shown in Table 1 below.

[0074] Table 1. Number of residual monomers and crystal points in the examples and comparative examples.

[0075]

[0076] As shown in Table 1, the nylon elastomer prepared using this method can significantly reduce the number of residual monomers, crystal points, and impurity points. The combination of screw devouring and supercritical fluid extraction effectively removes residual monomers from the nylon elastomer, limiting the residual monomer content to below 5 ppm. Furthermore, the use of melt filtration and supercritical fluid plasticization effectively reduces crystal points and impurity points in the nylon elastomer, limiting the crystal point size to below 0.4 mm and the number to 20 per 1520 cm². 2 Within a certain range, with impurity point size below 200um and quantity below 10 per 200g, it can be applied to fields such as medical catheters, waterproof and breathable membranes, and food conveyor belts.

Claims

1. A method for preparing a nylon elastomer, comprising the following steps: S1. reacting a combination of a dibasic acid and a dibasic amine or a lactam in the presence of an end-capping agent to produce a dicarboxyl end-capped polyamide prepolymer, and esterifying the polyamide prepolymer with a polyether polyol in the presence of a catalyst to obtain a nylon elastomer; S2. removing residual monomers from the nylon elastomer by a devolatilization screw extruder, and removing crystal points and impurity points from the nylon elastomer by a melt filter; S3. extracting the nylon elastomer obtained in S2 using a supercritical fluid.

2. The method of claim 1, wherein, In S1, the dibasic acid comprises one or more of C5-C18 dibasic acids, preferably one or more of adipic acid, sebacic acid, dodecanedioic acid; and / or, the dibasic amine comprises one or more of C5-C13 dibasic amine, preferably one or more of hexamethylene diamine, dodecanediamine; and / or, the lactam comprises one or more of caprolactam, lauryl lactam.

3. The method according to claim 1 or 2, characterized in that, The end-capping agent is the same or different from the diacid, preferably the same; more preferably comprises one or more of C5-C 18 diacids, preferably one or more of adipic acid, sebacic acid, dodecanedioic acid; and / or, the polyether polyol is selected from one or more of polyethylene glycol, polypropylene glycol or polybutylene glycol, having a molecular weight of 500-2000 g / mol.

4. The method according to any one of claims 1 to 3, characterized in that, The number average molecular weight of the polyamide prepolymer is 1000-20000 g / mol.

5. The method according to any one of claims 1 to 4, characterized in that, The catalyst is selected from metal alkoxides of the general formula M(OR)n, wherein M is Sb, Ti, Zr or Ge, R is a C1-10 alkyl group, and n is 1-4, preferably one or more of tetrabutyl titanate, ethylene glycol antimony, zirconium n-propyl alcohol, tetraethyl germanate.

6. The method according to any one of claims 1 to 5, characterized in that, The main devolatilization section of the devolatilization screw extruder has a barrel vacuum of ≤50 PaA, a devolatilization temperature of 220-280°C, and a devolatilization rotation speed of 100-600 rpm.

7. The method according to any one of claims 1 to 6, characterized in that, The mesh size of the melt filter is ≤200 um, preferably 20-50 um.

8. The method according to any one of claims 1 to 7, characterized in that, The supercritical fluid comprises supercritical carbon dioxide; the extraction temperature is 40-250°C, preferably above the melting point of the polyamide elastomer, the pressure is 8-40 MPa, and the extraction time is 0.5-3 h.

9. The nylon elastomer prepared according to the method of any one of claims 1-8, characterized by, Residual single content 5 ppm or less, the crystal point size is below 0.4 mm, the number is 20 / 1520 cm 2 Impurity point size below 200 um, number below 10 / 200 g.

10. The nylon elastomer prepared by the method of any one of claims 1-8 or the nylon elastomer of claim 9 for use in preparing a medical catheter, a moisture-permeable film, or a food conveying belt.

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