A method for preparing a composite nylon material

Abstract

The application discloses a composite nylon material preparation method, which is prepared by blending modified polytrifluoropropyl methyl siloxane containing hydrophobic trifluoropropyl side chains with nylon 6, realizing nanoscale dispersion in a melt extrusion process, adding an epoxy functionalized silane coupling agent and an organic tin catalyst, forming a three-dimensional crosslinked network under the hydrophobic effect of the trifluoropropyl side chains and the water blocking effect of the three-dimensional crosslinked network in the extrusion process, effectively blocking the diffusion channel of water molecules, improving the moisture resistance of the material, maintaining the tensile property of the raw material at 92-95%, and enhancing the wear resistance and thermal stability of the material by modified nanosilica; the equilibrium water absorption rate is only 0.7-0.9%, the low-temperature resistance is improved by more than 25%, and the low-temperature resistance is far superior to the embrittlement temperature of traditional PA6, so that the nylon material modification method has the advantages of maintaining mechanical properties, water resistance and low-temperature brittleness.

Description

Technical Field

[0001] This invention belongs to the field of nylon materials, and specifically relates to a method for preparing composite nylon materials. Background Technology

[0002] Nylon materials are widely used in electronics, packaging, transportation, and other fields due to their excellent mechanical properties, heat resistance, and abrasion resistance. However, traditional nylon materials have some limitations. First, due to the large number of amide groups in its molecular structure, it has high water absorption, leading to decreased dimensional stability and affecting the precision and performance of the products. Second, at low temperatures, the molecular chain mobility of nylon materials decreases, making the material brittle and prone to brittle fracture. Furthermore, many nylon modification methods cannot simultaneously achieve all the desired properties; some sacrifice mechanical properties, while others only provide water resistance but lack sufficient low-temperature resistance.

[0003] In the prior art, patent CN115558287A discloses a wear-resistant, low-moisture-absorbing nylon material and its preparation method. This patent modifies nylon 66 resin by controlling the amount of polydimethylsiloxane added, thereby giving the prepared nylon material low moisture absorption and wear resistance. The prepared modified molybdenum disulfide is a ternary composite material composed of molybdenum disulfide, Cu-MOFs, and magnetic iron oxide. Introducing it into the nylon material improves its wear resistance and oxidation resistance, thereby improving the dimensional stability of the nylon material. However, the low-temperature performance of this patented material is poor and it still does not have good low-temperature performance. Similarly, patent CN120649179A discloses a method for preparing waterproof nylon fabric. A dicarboxylic acid mixture and a modified diamine mixture are mixed and dispersed at a weight ratio of 1:1 to 2, and the pH is adjusted to 7.0 to 7.5. The mixture is then heated to 80 to 90°C and reacted for 90 to 110 minutes to obtain a nylon salt solution. The nylon salt solution and an antioxidant are mixed at a weight ratio of 1:0.008 to 0. After mixing, the mixture is heated to 200-220℃ under nitrogen atmosphere protection and reacted for 2-3 hours to obtain nylon prepolymer; the nylon prepolymer is dried at 70-80℃ for 6-10 hours and then vacuumed to 8-10 Pa, followed by heating to 230-240℃ and reacting for 18-20 hours to obtain modified nylon; the modified nylon and double-bond-terminated polyurethane prepolymer are mixed in an extruder at a weight ratio of 5-8:2-3 to obtain waterproof nylon fabric. This material focuses more on water resistance, but its low-temperature performance, such as poor brittleness, cannot adapt to low-temperature environments.

[0004] How to effectively improve the water absorption and low-temperature resistance of nylon materials while maintaining their excellent mechanical properties remains a technical challenge that urgently needs to be solved. Summary of the Invention

[0005] To overcome the above shortcomings, this application provides a method for chemically modifying the molecular structure of nylon 6 using siloxane-epoxy crosslinking network technology, specifically including the following steps:

[0006] S1, Nylon 6 and modified polytrifluoropropylmethylsiloxane are mixed in a set ratio and melt-extruded in a twin-screw extruder to obtain the modified Nylon 6 material;

[0007] S2, add epoxy-functionalized silane coupling agent and organotin catalyst to the modified nylon 6 material obtained in step S1, and rotate and extrude to make the epoxy groups and the terminal groups of nylon 6 undergo ring-opening reaction to form a three-dimensional cross-linked network structure, thus obtaining cross-linked nylon.

[0008] S3. Add nano-silica to the material obtained in step S2 and disperse it evenly through a stirring process to obtain the final product.

[0009] Furthermore, in step S1, the mass ratio of modified polytrifluoropropylmethylsiloxane to nylon 6 is 8-12:100.

[0010] Furthermore, the melt extrusion temperature in step S1 is 260-270℃.

[0011] Furthermore, in step S2, the mass ratio of silane coupling agent to modified nylon is 3-5:100, and the mass ratio of organotin catalyst to modified nylon is 0.5-1:100.

[0012] Further, in step S2, the epoxy value of the epoxy-functionalized silane coupling agent is 2.0-2.4 equivalents / 100g, and the organotin catalyst is selected from one or a mixture of two of octyl tin oxide and butyl tin oxide.

[0013] Furthermore, in step S2, the rotary extrusion temperature is 240-260℃ and the rotation speed is 200-220rpm.

[0014] Furthermore, in step S3, the particle size of the nano-silica is 15-25 nm, and the mass ratio of the amount added to the crosslinked nylon is 1-2:100.

[0015] Furthermore, in step S3, the nano-silica is prepared by precipitation and then subjected to carboxylation treatment.

[0016] The specific method involves dispersing nano-silica in anhydrous ethanol, adding a 2-6% (v / v) solution of 3-aminopropyltriethoxysilane to obtain aminated nano-silica, then adding it to a succinic anhydride dimethyl sulfoxide (DMSO) solution, reacting, washing, and drying to finally obtain carboxylated nano-silica.

[0017] The method for obtaining the above-mentioned modified polytrifluoropropylmethylsiloxane is as follows:

[0018] Trifluoropropylmethylcyclotrisiloxane, 3-aminopropyltriethoxysilane, and deionized water were mixed in a molar ratio of 100:(5-15):(0.5-2). The mixture was heated to 60-70℃ under nitrogen protection and stirred at a constant temperature for 8-12 hours. The mixture was then heated to 120℃ and evacuated for 1 hour to remove small molecule byproducts, yielding modified polytrifluoropropylmethylsiloxane with a molecular weight of 2000-25000.

[0019] Technical effect

[0020] This composite material is produced by blending modified polytrifluoropropylmethylsiloxane containing hydrophobic trifluoropropyl side chains with nylon 6 and achieving nanoscale dispersion during melt extrusion. This significantly improves the water absorption of nylon materials and reduces the equilibrium water absorption rate. The addition of epoxy-functionalized silane coupling agents and organotin catalysts forms a three-dimensional cross-linked network during extrusion, effectively blocking water molecule diffusion channels and further improving the material's moisture resistance while maintaining excellent mechanical properties, with tensile strength remaining at 92-95% of the raw material. Furthermore, the introduction of nano-silica as a heterogeneous nucleating agent forms a good interfacial bond with nylon 6, significantly improving the molecular crystallinity of the cross-linked nylon 6. This enhances the material's wear resistance and thermal stability while maintaining toughness, effectively solving the problem of brittle fracture in traditional nylon materials at low temperatures. Based on the hydrophobic effect of the trifluoropropyl side chain and the water-blocking effect of the three-dimensional cross-linked network, the equilibrium water absorption rate of this composite material is 0.7-0.9% at 23℃ and 50% relative humidity, which is significantly lower than that of traditional nylon materials (2-3.5%). At the same time, based on the synergistic effect of high cross-linking degree and high crystallinity, it has a stable structure, strong toughness and is not easy to become brittle in low temperature environment. Its low temperature resistance is far superior to that of traditional PA6 (-40℃), reaching -52℃, which is more than 25% better. It can meet the application requirements in harsh environments. Attached Figure Description

[0021] Figure 1 This is the DSC spectrum of the nylon product obtained in Example 2;

[0022] Figure 2 This is the FTIR spectrum of the nylon product obtained in Example 2. Detailed Implementation

[0023] The preparation methods of the relevant components in the embodiments are as follows:

[0024] An epoxy-functionalized silane coupling agent (KH-560) and an organotin catalyst were added. The epoxy value of the epoxy-functionalized silane coupling agent was 2.0-2.4 equivalents / 100g. The added nano-silica was prepared by precipitation and then carboxylated. The specific carboxylation method was as follows: nano-silica was dispersed in anhydrous ethanol, and a 4% (v / v) solution of 3-aminopropyltriethoxysilane was added. The mixture was shaken at 37°C for 4 hours. After washing with anhydrous ethanol, aminated nano-silica was obtained. A 12 mg / mL solution of succinic anhydride dimethyl sulfoxide (DMSO) was prepared, and the above aminated product was added. The mixture was shaken at 37°C for 8 hours. The amino group (-NH2) reacted with the succinic anhydride to generate a carboxyl group (-COOH) through an acylation reaction. After washing with DMSO, centrifugation, and drying, carboxylated nano-silica was obtained.

[0025] Preparation of modified polytrifluoropropylmethylsiloxane

[0026] 43 kg of trifluoropropylmethylcyclotrisiloxane, 2.7 kg of 3-aminopropyltriethoxysilane, and 200 g of deionized water were mixed and heated to 65 °C under nitrogen protection, stirred at a constant temperature for 10 h, and then heated to 120 °C and vacuumed for 1 h to remove small molecule byproducts, yielding modified polytrifluoropropylmethylsiloxane with a molecular weight of 23000.

[0027] Example 1

[0028] A method for preparing a composite nylon material includes the following steps:

[0029] S1, the modified polytrifluoropropylmethylsiloxane obtained in Example 1 and nylon 6 were mixed at a mass ratio of 9:100 and melt-extruded at 268°C in a twin-screw extruder (L / D=40:1) to obtain the modified nylon 6 material;

[0030] S2, 2.5 wt% of epoxy-functionalized silane coupling agent KH-560 and 0.8 wt% of octyl tin oxide catalyst are added to the modified nylon 6 material obtained in step S1. During the extrusion process, the temperature is controlled at 250℃ and the rotation speed is 200 rpm, so that the epoxy groups and the terminal groups of nylon 6 undergo a ring-opening reaction to form a three-dimensional cross-linked network structure.

[0031] S3, add 1.5wt% of nano-silica (particle size 20nm, surface carboxylated) to the material obtained in step S2, stir to disperse evenly, and obtain the final product.

[0032] The tensile strength of the product obtained by this method remains at 92-95% of that of the raw material. Figure 1 It is known that cross-linked networks lead to non-uniform nylon crystal sizes. The half-width of the melting peak in the DSC curve will broaden from 5-8℃ (uncross-linked) to 15-20℃, and the peak shape will be flatter. Figure 2 The absorption peak is 1–3300 cm⁻¹ -1 Corresponding amide NH, 2—1640cm -1 Corresponding amide C=O, 3—1540cm -1 Corresponding amide CN, 4-1260cm -1 Corresponding amide CNH / Si-CH3 (polysiloxane), 5-1040 cm -1 Corresponding to trifluoropropyl CF, 6-466cm -1 Corresponding to Si-O (nano-silica).

[0033] Example 2

[0034] A method for preparing a composite nylon material includes the following steps:

[0035] S1, the modified polytrifluoropropylmethylsiloxane obtained in Example 1 and nylon 6 were mixed at a mass ratio of 10:100 and melt-extruded at 270°C in a twin-screw extruder (L / D=40:1) to obtain the modified nylon 6 material;

[0036] S2, 4 wt% of epoxy-functionalized silane coupling agent KH-560 and 0.7 wt% of butyl tin oxide catalyst are added to the modified nylon 6 material obtained in step S1. During the extrusion process, the temperature is controlled at 255℃ and the rotation speed is 210 rpm, so that the epoxy groups and the terminal groups of nylon 6 undergo a ring-opening reaction to form a three-dimensional cross-linked network structure.

[0037] S3, add 2wt% nano-silica (particle size 18nm, surface carboxylated) to the material obtained in step S2, stir to disperse evenly, and obtain the final product.

[0038] Example 3

[0039] A method for preparing a composite nylon material includes the following steps:

[0040] S1, the modified polytrifluoropropylmethylsiloxane obtained in Example 1 and nylon 6 were mixed at a mass ratio of 8:100 and melt-extruded at 260°C in a twin-screw extruder (L / D=40:1) to obtain the modified nylon 6 material;

[0041] S2, 3.5 wt% of epoxy-functionalized silane coupling agent KH-560 and 0.9 wt% of butyl tin oxide catalyst are added to the modified nylon 6 material obtained in step S1. During the extrusion process, the temperature is controlled at 245℃ and the rotation speed is 190 rpm, so that the epoxy groups and the terminal groups of nylon 6 undergo a ring-opening reaction to form a three-dimensional cross-linked network structure.

[0042] S3, add 1.8 wt% of nano-silica (particle size 22 nm, surface carboxylated) to the material obtained in step S2, stir to disperse evenly, and obtain the final product.

[0043] Test case

[0044] The samples obtained in Examples 2-4 were compared with commercially available ordinary nylon materials, and their water absorption was tested according to GB / T 1034-2008 standard. The samples were injection molded at 70℃ and 110MPa, and then their low-temperature resistance was tested according to GB / T 5470-2008 standard. The results are listed in the table below:

[0045] Water absorption rate / % <![CDATA[Brittleness temperature T 50 / ℃]]> Example 1 0.74 -52 Example 2 0.76 -51 Example 3 0.83 -50 ordinary nylon 3.11 -40

[0046] As can be seen from the data in the table, the product obtained by this method has an equilibrium water absorption rate of 0.7-0.9% under the conditions of 23℃ and 50% relative humidity, and an embrittlement temperature below -50℃. Compared with ordinary nylon on the market, the nylon prepared according to the technical solution of this application has a significantly lower water absorption rate and significantly enhanced low-temperature resistance, with a low-temperature resistance improvement of more than 25%.

Claims

1. A method for preparing a composite nylon material, characterized in that, Includes the following steps: S1, Nylon 6 and modified polytrifluoropropylmethylsiloxane are mixed in a set ratio and melt-extruded in a twin-screw extruder to obtain the modified Nylon 6 material; S2, add epoxy-functionalized silane coupling agent and organotin catalyst to the modified nylon 6 material obtained in step S1, and rotate and extrude to make the epoxy groups and the terminal groups of nylon 6 undergo ring-opening reaction to form a three-dimensional cross-linked network structure, thus obtaining cross-linked nylon. S3. Add nano-silica to the material obtained in step S2 and disperse it evenly through a stirring process to obtain the final product.

2. The method according to claim 1, characterized in that, In step S1, the mass ratio of modified polytrifluoropropylmethylsiloxane to nylon 6 is 8-12:

100.

3. The method according to claim 1, characterized in that, The melt extrusion temperature in step S1 is 260-270℃.

4. The method according to claim 1, characterized in that, The organotin catalyst in step S2 is selected from one or a mixture of two of octyl tin oxide and butyl tin oxide.

5. The method according to claim 1 or 4, characterized in that, In step S2, the mass ratio of silane coupling agent to modified nylon is 3-5:100, and the mass ratio of organotin catalyst to modified nylon is 0.5-1:

100.

6. The method according to claim 1, characterized in that, In step S2, the rotary extrusion temperature is 240-260℃ and the rotation speed is 200-220rpm.

7. The method according to claim 1, characterized in that, In step S3, the particle size of the nano-silica is 15-25 nm, and the mass ratio of the amount added to the cross-linked nylon is 1-2:

100.

8. The method according to claim 7, characterized in that, In step S3, the nano-silica is obtained by precipitation and then carboxylated. Specifically, the nano-silica is dispersed in anhydrous ethanol, and a 2-6% (v / v) solution of 3-aminopropyltriethoxysilane is added to obtain aminated nano-silica. Then, it is added to a succinic anhydride dimethyl sulfoxide (DMSO) solution. After the reaction, the nano-silica is washed and dried to finally obtain carboxylated nano-silica.

9. The method according to claim 1, characterized in that, The modified polytrifluoropropylmethylsiloxane is prepared by mixing trifluoropropylmethylcyclotrisiloxane, 3-aminopropyltriethoxysilane and deionized water in a molar ratio of 100:(5-15):(0.5-2), heating to 60-70℃ under nitrogen protection, stirring at a constant temperature for 8-12 hours, heating to 120℃ and evacuating under vacuum for 1 hour to remove small molecule byproducts.

10. A composite nylon material, characterized in that, Prepared by the method according to any one of claims 1-9.

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