Oxidation-resistant monomer casting nylon material and preparation method thereof

Abstract

The invention discloses an oxidation-resistant monomer casting nylon material and a preparation method thereof, and relates to the field of material preparation, and the monomer casting nylon material is applied to a high-temperature and oxygen-enriched environment and comprises the following components in parts by mass: 100 parts of caprolactam; 0.1-0.3 part of a catalyst which is one of sodium hydroxide, potassium hydroxide or lithium hydroxide; 0.5 to 1.5 parts of an activating agent, wherein the activating agent is N-acetyl caprolactam; 0.7 to 3 parts of a main antioxidant, wherein the main antioxidant comprises a hindered phenol antioxidant and a thioester antioxidant; 0.1-0.5 part of an auxiliary antioxidant, which is a metal deactivator; 1-3 parts of an inorganic filler which is modified montmorillonite; and 0.5-2 parts of a hydrophobic agent which is a silane coupling agent. By constructing a composite anti-oxidation system, multi-level synergistic protection can be formed for three key oxidation stages of free radical initiation, peroxide accumulation and metal catalysis, and a full path of an oxidation chain reaction is covered from a molecular level, so that the aging process of the material is remarkably delayed, and the service life of the material is prolonged. And high oxygen resistance and relatively long service life are provided for nylon application under severe working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation, in particular to a composition of polymer compounds, specifically an oxidation-resistant monomer cast nylon material and a preparation method thereof. Background Art

[0002] Monomer Cast Nylon (MC Nylon) is an engineering plastic directly molded through anionic ring-opening polymerization. Due to its high molecular weight (>100,000), high crystallinity, good wear resistance and low water absorption, it is widely used in mechanical transmission components (such as gears, bearings, guide rails, etc.) and key structural parts of industrial equipment.

[0003] However, with increasingly stringent material performance requirements for industrial equipment, especially in applications subject to long-term service in high-temperature, oxygen-rich environments (such as automotive engine compartment components and aerospace oxidation-resistant structural parts), the limitations of traditional MC nylon are becoming increasingly apparent. Under prolonged high-temperature, oxidative conditions, the amide bonds (—CONH—) in the MC nylon molecular chain are susceptible to free radical attack and breakage, leading to yellowing of the material and a significant decrease in mechanical properties (such as tensile strength and impact toughness), severely shortening its service life.

[0004] Therefore, it is necessary to improve the deficiencies in the prior art to solve the above problems. Summary of the Invention

[0005] The present invention overcomes the shortcomings of the existing technology, provides an oxidation-resistant monomer cast nylon material and a preparation method thereof, breaks through the performance limitations of traditional MC nylon, constructs a composite antioxidant system, uses hindered phenol antioxidants to capture free radicals generated during the oxidation process, uses thioester antioxidants to decompose generated hydroperoxides, and uses metal passivators to inhibit metal ion-catalyzed oxidation reactions, forming a multi-level synergistic protection mechanism to meet the urgent demand for high-performance engineering plastics in the field of high-end equipment manufacturing.

[0006] To achieve the above object, the technical solution adopted by the present invention is: an oxidation-resistant monomer cast nylon material, suitable for use in high-temperature, oxygen-rich environments, comprising the following components in parts by mass:

[0007] 100 parts of caprolactam;

[0008] 0.1-0.3 parts of catalyst, which is one of sodium hydroxide, potassium hydroxide or lithium hydroxide;

[0009] 0.5-1.5 parts of activator, which is N-acetyl caprolactam;

[0010] 0.7-3 parts of primary antioxidant, including hindered phenol antioxidant and thioester antioxidant;

[0011] 0.1-0.5 parts of auxiliary antioxidant, which is a metal passivator;

[0012] 1-3 parts of inorganic filler, which is modified montmorillonite;

[0013] 0.5-2 parts of hydrophobic agent, which is a silane coupling agent;

[0014] Wherein, the mass ratio of the hindered phenol antioxidant to the thioester antioxidant is 1:0.2-0.5.

[0015] In a preferred embodiment of the present invention, the hindered phenol antioxidant is one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] or octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; and the thioester antioxidant is one of dilauryl thiodipropionate or distearyl thiodipropionate.

[0016] In a preferred embodiment of the present invention, the metal deactivator is one of oxalic acid anilide, N,N'-diphenyloxamide or N-salicylidene-N'-salicylic acid hydrazide.

[0017] In a preferred embodiment of the present invention, the modified montmorillonite is a montmorillonite having a larger interlayer distance and active epoxy groups obtained by ion exchange modification of natural montmorillonite with epoxy quaternary ammonium salt.

[0018] In a preferred embodiment of the present invention, the silane coupling agent is one of γ-aminopropyltriethoxysilane or vinyltrimethoxysilane.

[0019] The present invention provides a method for preparing an oxidation-resistant monomer cast nylon material, comprising the following steps:

[0020] S1. Heating caprolactam to 110-130° C. to melt and vacuum dehydrating, adding a catalyst and an activator to the dehydrated caprolactam in sequence, and stirring for 5-15 minutes to form a catalytic system;

[0021] S2. Adding a primary antioxidant, a secondary antioxidant, an inorganic filler and a hydrophobic agent to the catalytic system, and forming a uniform mixed liquid through high-speed shearing;

[0022] S3, injecting the mixed solution into a preheated mold, performing gradient temperature-controlled polymerization, and then naturally cooling to 60-80°C for demoulding to obtain a primary material;

[0023] S4. The demoulded raw material is subjected to a first-stage annealing at 100-120° C. and then to a second-stage annealing at 130-150° C. to obtain a monomer cast nylon material.

[0024] In a preferred embodiment of the present invention, in step S1, the dehydration conditions are: vacuum degree>99.5kPa, at a temperature of 130-140°C, and maintained for 10-20 minutes.

[0025] In a preferred embodiment of the present invention, in step S2, the high-speed shearing is: dispersing at a rotation speed of 2000-4000 rpm for 10-30 minutes.

[0026] In a preferred embodiment of the present invention, in step S3, the conditions of the gradient temperature control polymerization are: the first stage is at a temperature of 150-160°C and is kept warm for 10-20 minutes, and the second stage is at a temperature of 165-180°C and is kept warm for 10-30 minutes.

[0027] In a preferred embodiment of the present invention, in step S4, the processing time of the first stage annealing is 1-2 hours, and the processing time of the second stage annealing is 0.5-1.5 hours.

[0028] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0029] (1) The present invention provides an oxidation-resistant monomer cast nylon material and a preparation method thereof. By constructing a composite antioxidant system, in an oxygen-rich environment, the main antioxidant uses the phenolic hydroxyl group of hindered phenols to capture free radicals generated during the oxidation process, blocking the propagation of the chain reaction, and the thioester decomposes the generated hydroperoxides to prevent them from further decomposing into new free radicals. At the same time, the metal passivator in the auxiliary antioxidant cooperates to chelate metal ions and inhibit the metal ion-catalyzed oxidation reaction, thereby forming a multi-level synergistic protection for the three key oxidation stages of free radical initiation, peroxide accumulation and metal catalysis, covering the entire path of the oxidation chain reaction at the molecular level, thereby significantly delaying the aging process of the material and providing high oxygen resistance and a long service life for nylon applications under harsh working conditions.

[0030] (2) In the present invention, by combining modified montmorillonite with a large interlayer spacing and active epoxy groups in the catalytic system, a dense physical barrier can be formed, which significantly delays the diffusion and penetration of oxygen molecules and reduces the contact probability between the nylon matrix and oxygen. The metal ions between the layers and at the edges will preferentially combine with the metal passivator in the auxiliary antioxidant to catalyze the oxidation active sites. At the same time, the surface active epoxy groups can combine with the hindered phenol in the main antioxidant through covalent bonds or strong hydrogen bonds to anchor the antioxidant on the surface and between the layers of the montmorillonite layer, inhibiting the migration loss of the antioxidant at high temperature and ensuring the uniform distribution and long-term stable release of the antioxidant components inside the material, thereby achieving synergistic enhancement of the stability of the high-temperature resistant structure and the dynamic protection of the antioxidant system.

[0031] (3) In the present invention, the hydrophobic alkyl chain of the silane coupling agent is covered on the surface of the filler and in the pores of the matrix, thereby reducing the surface polarity of the material, hindering the penetration of water molecules, and thus reducing the swelling stress and hydrolysis side reactions caused by moisture absorption. At the same time, the active functional groups of the silane coupling agent can form chemical bonds with the hydroxyl groups on the surface of montmorillonite or the terminal groups of the nylon molecular chain, thereby enhancing the filler-matrix interface bonding force, avoiding the preferential oxygen permeation path caused by interface microcracks, and indirectly improving the stability of the antioxidant system.

[0032] (4) In the present invention, by adopting gradient temperature-controlled polymerization, the anionic ring-opening polymerization reaction can be fully carried out to form longer and more regular nylon molecular chains, reduce chain end defects, and reduce the number of oxidation-sensitive sites. At the same time, high temperature conditions help to uniformly disperse the montmorillonite flakes in the melt and promote the chemical bonding of the silane coupling agent with the matrix to form a dense filler-matrix interface, thereby further limiting the migration and diffusion channels of oxygen and water molecules.

[0033] (5) In the present invention, by controlling the temperature in stages during gradient annealing, stress can be eliminated at low temperature first, and then crystallization can be promoted at high temperature, thereby guiding the nylon molecular chains to gradually rearrange from a disordered amorphous state to an ordered crystalline state. The hydrogen bond network density in the crystalline region is increased, the molecular chains are stacked tightly, and the oxidation attack sites of the loose chain segments in the amorphous region are reduced, thereby being able to exhibit a more stable size and lasting antioxidant ability. DETAILED DESCRIPTION

[0034] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0036] It should be noted that the raw materials, equipment, reagents, etc. used in the present invention can be purchased from the market or obtained through existing preparation methods.

[0037] An oxidation-resistant monomer cast nylon material for use in high-temperature, oxygen-rich environments, comprising the following components in parts by mass:

[0038] 100 parts of caprolactam;

[0039] 0.1-0.3 parts of catalyst, which is one of sodium hydroxide (NaOH), potassium hydroxide (KOH) or lithium hydroxide (LiOH);

[0040] 0.5-1.5 parts of activator, which is N-acetyl caprolactam;

[0041] 0.7-3 parts of primary antioxidant, including hindered phenol antioxidant and thioester antioxidant;

[0042] 0.1-0.5 parts of auxiliary antioxidant, which is a metal passivator;

[0043] 1-3 parts of inorganic filler, which is modified montmorillonite;

[0044] 0.5-2 parts of hydrophobic agent, which is a silane coupling agent;

[0045] The mass ratio of the hindered phenol antioxidant to the thioester antioxidant is 1:0.2-0.5.

[0046] In some specific embodiments, the hindered phenol antioxidant is one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010) or octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1076); and the thioester antioxidant is one of dilauryl thiodipropionate (DSTDP) or distearyl thiodipropionate (DLTDP).

[0047] In some specific embodiments, the metal deactivator is one of oxalic acid anilide, N,N'-diphenyloxamide or N-salicylidene-N'-salicylic acid hydrazide.

[0048] In some specific embodiments, the modified montmorillonite is a montmorillonite having a larger interlayer distance and active epoxy groups obtained by ion-exchange modification of natural montmorillonite with epoxy quaternary ammonium salt.

[0049] In some specific embodiments, the silane coupling agent is one of γ-aminopropyltriethoxysilane (KH-550) or vinyltrimethoxysilane (A-171).

[0050] The present invention provides a method for preparing an oxidation-resistant monomer cast nylon material, comprising the following steps:

[0051] S1. Heating caprolactam to 110-130° C. to melt and vacuum dehydrating, adding a catalyst and an activator to the dehydrated caprolactam in sequence, and stirring for 5-15 minutes to form a catalytic system;

[0052] S2. Adding a primary antioxidant, a secondary antioxidant, an inorganic filler and a hydrophobic agent to the catalytic system, and forming a uniform mixed liquid through high-speed shearing;

[0053] S3, injecting the mixed solution into a preheated mold, performing gradient temperature-controlled polymerization, and then naturally cooling to 60-80°C for demoulding to obtain a primary material;

[0054] S4. The demoulded raw material is subjected to a first-stage annealing at 100-120° C. and then to a second-stage annealing at 130-150° C. to obtain a monomer cast nylon material.

[0055] In some specific embodiments, in step S1, the dehydration conditions are: vacuum degree>99.5kPa, at a temperature of 130-140°C, and maintained for 10-20 minutes.

[0056] In some specific embodiments, in step S2, the high-speed shearing is: dispersing at a rotation speed of 2000-4000 rpm for 10-30 min.

[0057] In some specific embodiments, in step S3, the conditions of gradient temperature control polymerization are: the first stage is at a temperature of 150-160° C. and is kept warm for 10-20 minutes, and the second stage is at a temperature of 165-180° C. and is kept warm for 10-30 minutes.

[0058] In some specific embodiments, in step S4, the processing time of the first stage annealing is 1-2 hours, and the processing time of the second stage annealing is 0.5-1.5 hours.

[0059] In order to further make the purpose and effect of the present invention simple and easy to understand, the present invention is further described in conjunction with examples and comparative examples.

[0060] It should be noted that, in the Examples and Comparative Examples, the description of the preparation of raw materials is as follows:

[0061] Caprolactam: CAS No. 105-60-2, moisture content ≤50ppm, melting point 68-70℃, density 1.02g / cm 3 , purchased from Jinan Chuangshi Chemical; NaOH: CAS No. 1310-73-2, purity ≥98%, density 2.13 g / cm 3 , purchased from Jinan Jiewei Chemical; KOH: CAS No. 1310-58-3, purity ≥ 85%, density 2.04 g / cm 3 , purchased from Changzhou Guangcheng Chemical; LiOH: CAS No. 1310-65-2, purity ≥98%, density 1.46 g / cm 3 , purchased from Shanghai Oujin Industry; N-acetylcaprolactam: CAS No. 1883-83-4, purity ≥99%, molecular weight 155.20, density 1.08 g / cm 3, purchased from Jinan Zi'an Chemical; Irganox 1010: CAS No. 6683-19-8, molecular weight 1177.65, melting point 110-125℃, purchased from Jinan Shenghe Chemical; Irganox 1076: CAS No. 2082-79-3, molecular weight 530.87, melting point 50-55℃, purchased from Shandong Xuchen Chemical; DSTDP: CAS No. 123-28-4, molecular weight 514.86, melting point 40-45℃, purchased from Suzhou Senfida Chemical; DLTDP: CAS No. 693-36-7, molecular weight 683.18, melting point 64-67℃, purchased from Suzhou Senfida Chemical; oxalic acid anilide: CAS No. 495-54-5, molecular weight 2 68.27, purity ≥98%, melting point 280-285℃, purchased from Hubei Jinte Biological; N,N'-diphenyloxamide: CAS No. 1027-15-6, molecular weight 240.25, melting point 280℃, purchased from Jinde Chemical; N-salicylidene-N'-salicylic hydrazide: CAS No. 94-91-7, molecular weight 270.28, melting point 250℃, purchased from Jingmen Meiruian Chemical; KH-550: CAS No. 919-30-2, density 1.05g / cm 3 , purity ≥98%, purchased from Shandong Rongsheng New Materials; A-171: CAS No. 2768-02-7, molecular weight 148.23, density 0.968 g / cm 3 , purchased from Shandong Rongsheng New Materials;

[0062] The preparation of modified montmorillonite specifically includes the following steps: taking 2g of sodium montmorillonite with a cation exchange capacity of 100meq / 100g (meq / 100g is the unit of cation exchange capacity, 1meq / 100g means that each gram of sodium montmorillonite contains 1mmol of exchangeable Na + ions), added 250 mL of water, and ultrasonically dispersed to obtain a montmorillonite suspension. Dissolve 2.5 g of epoxy quaternary ammonium salt in 50 mL of water and slowly add dropwise to the montmorillonite suspension. Heat to 65°C and mechanically stir at 500 rpm for 6 hours. The yellow montmorillonite suspension gradually turns white. Centrifuge the mixture at 7000 rpm, detect with silver nitrate, wash until chloride ion-free, dry in vacuo at 80°C for 24 hours, grind, and pass through a 500-mesh sieve to obtain a modified montmorillonite with an interlayer spacing of 4.41 nm and an epoxy group content of 3.5 mol / 100 g.

[0063] The raw materials and raw material ratios of the monomer cast nylon materials in Examples 1-6 are different, as shown in Table 1, and the raw materials are measured in parts by mass.

[0064] Table 1: Raw materials and proportions for preparing the monomer cast nylon materials of Examples 1-6

[0065]

[0066] Example 1

[0067] A method for preparing an oxidation-resistant monomer cast nylon material comprises the following steps:

[0068] S1. Heating caprolactam to 130° C. to melt, dehydrating for 15 min under vacuum at 99.8 kPa and 130° C. to reduce the water content to ≤100 ppm, sequentially adding NaOH and N-acetyl caprolactam to the dehydrated caprolactam, and stirring at 500 rpm for 10 min to form a catalytic system;

[0069] S2. Irganox 1010 and DSTDP in a mass ratio of 1:0.4, as well as oxalic acid anilide, modified montmorillonite, and KH-550 were added to the catalytic system, and dispersed in a high-speed shearing machine at 3000 rpm for 20 minutes to form a uniform mixed solution;

[0070] S3, injecting the mixed liquid into a metal mold preheated to 160°C, keeping the temperature at 160°C for 15 minutes in the first stage, keeping the temperature at 180°C for 20 minutes in the second stage, and demoulding after naturally cooling to 70°C to obtain the primary material;

[0071] S4. The demolded raw material is subjected to a first-stage annealing at 110° C. for 1 hour, and then to a second-stage annealing at 140° C. for 1.5 hours to obtain a monomer cast nylon material.

[0072] Example 2

[0073] This embodiment is substantially the same as embodiment 1, except that the raw materials and their ratios are different, as shown in Table 1. Step S2 specifically comprises adding Irganox 1010 and DSTDP at a mass ratio of 1:0.2, as well as N,N'-diphenyloxamide, modified montmorillonite, and KH-550 to the catalyst system, and dispersing the mixture in a high-speed shearing machine at 3000 rpm for 20 minutes to form a uniform mixed solution.

[0074] Example 3

[0075] This embodiment is substantially the same as Example 1, except that the raw materials and their ratios are different, as shown in Table 1. Step S2 specifically comprises adding Irganox 1076 and DSTDP at a mass ratio of 1:0.5, as well as N,N'-diphenyloxamide, modified montmorillonite, and KH-550 to the catalyst system, and dispersing the mixture in a high-speed shearing machine at 3000 rpm for 20 minutes to form a uniform mixed solution.

[0076] Example 4

[0077] This embodiment is basically the same as Example 1, except that the raw materials and their ratios are different, as shown in Table 1. Step S3 specifically comprises injecting the mixed solution into a metal mold preheated to 160°C, keeping the temperature at 150°C for 15 minutes in the first stage, keeping the temperature at 165°C for 20 minutes in the second stage, and naturally cooling to 70°C before demolding to obtain a primary material.

[0078] Example 5

[0079] This embodiment is basically the same as embodiment 1, except that the raw materials and their ratios are different, as shown in Table 1. Step S4 specifically comprises: subjecting the demolded raw material to a first-stage annealing at 100° C. for 1 hour, and then to a second-stage annealing at 130° C. for 1.5 hours, to obtain a monomer cast nylon material.

[0080] Example 6

[0081] This embodiment is basically the same as embodiment 1, except that the raw materials and their ratios are different, as shown in Table 1. Step S4 specifically comprises: subjecting the demolded raw material to a first-stage annealing at 120° C. for 1 hour, and then to a second-stage annealing at 150° C. for 1.5 hours, to obtain a monomer cast nylon material.

[0082] Performance testing: The monomer cast nylon materials obtained in Examples 1-6 above were prepared into 50 mm × 10 mm × 4 mm strips, and the oxidation resistance, high temperature resistance and dimensional stability performance tests were carried out in sequence. The results are shown in Table 2.

[0083] Oxidation resistance: Monomer cast nylon strips were tested for 48 hours at an oxygen concentration of 70% O2 (simulating an extreme oxygen-rich environment, 21% higher than the normal atmosphere), a temperature of 150°C and a pressure of 2 MPa.

[0084] Oxidation resistance test (1): The oxidation induction time (OIT) of the material under oxygen-rich conditions was measured by DSC (differential scanning calorimetry).

[0085] Oxidation resistance test (2): Refer to GB / T1040.2-2022 standard, the change rate of tensile strength before and after the test, the calculation formula is:

[0086]

[0087] Oxidation resistance test (3): ΔE value (yellowing degree) was measured using a colorimeter.

[0088] High temperature resistance: Refer to GB / T1634.2-2019 "Determination of deflection temperature of plastics under load Part 2: Plastics and hard rubber".

[0089] Dimensional stability: Refer to GB / T1034-2008 "Determination of water absorption of plastics", 24h immersion water absorption rate.

[0090] Table 2: Performance test results of the monomer cast nylon materials obtained in Examples 1-6

[0091]

[0092]

[0093] As shown in Table 2:

[0094] Comparison of Examples 1-6 reveals that the resulting monomer-cast nylon material exhibits excellent oxidation resistance in extremely oxygen-rich environments, while also demonstrating excellent high-temperature resistance and dimensional stability. Example 1 exhibits an OIT of 72 minutes, a tensile strength retention of 93.53%, and a water absorption rate of only 0.52% at 197°C. The composite antioxidant system works synergistically with the inorganic filler: the hindered phenolic antioxidant captures free radicals via its phenolic hydroxyl groups, the thioester antioxidant decomposes hydroperoxides, and the metal passivator chelates metal ions, forming a multi-layered protective network covering the entire oxidation chain reaction pathway. The epoxy groups introduced by the modified montmorillonite through ion exchange form covalent bonds with the antioxidant, inhibiting its migration at high temperatures. Furthermore, its enlarged interlayer spacing (4.41 nm) significantly extends the oxygen diffusion path and reduces permeability. The silane coupling agent caps the matrix pores with hydrophobic alkyl chains, reducing water penetration, and strengthens the filler-matrix interface through chemical bonding, preventing interfacial microcracks from becoming preferential oxygen permeation pathways. The gradient temperature-controlled polymerization and annealing process further optimizes the molecular chain arrangement, improves crystallinity, and reduces the oxidation-sensitive sites of loose chain segments in the amorphous region, thereby achieving a comprehensive improvement in material performance.

[0095] Comparative Example 1

[0096] This comparative example is basically the same as Example 1, except that there is no S2 step, and specifically includes the following steps:

[0097] S1. Heating caprolactam to 130° C. to melt, dehydrating for 15 min under vacuum at 99.8 kPa and 130° C. to reduce the water content to ≤100 ppm, sequentially adding NaOH and N-acetyl caprolactam to the dehydrated caprolactam, and stirring at 500 rpm for 10 min to form a catalytic system;

[0098] S2, injecting the mixed liquid into a metal mold preheated to 160°C, keeping the temperature at 160°C for 15 minutes in the first stage, keeping the temperature at 180°C for 20 minutes in the second stage, and demoulding after naturally cooling to 70°C to obtain the primary material;

[0099] S3. The demoulded raw material is subjected to a first-stage annealing at 110° C. for 1 hour, and then to a second-stage annealing at 140° C. for 1.5 hours to obtain a monomer cast nylon material.

[0100] Comparative Example 2

[0101] This comparative example is basically the same as Example 1, except that no secondary antioxidant is added. The specific step of S2 is: adding Irganox 1010 and DSTDP in a mass ratio of 1:0.4, as well as modified montmorillonite and KH-550 to the catalytic system, and dispersing them in a high-speed shearing machine at 3000 rpm for 20 minutes to form a uniform mixed solution.

[0102] Comparative Example 3

[0103] This comparative example is basically the same as Example 1, except that the amount of the auxiliary antioxidant is different, and the amount of oxalanilide is 0.6 parts.

[0104] Comparative Example 4

[0105] This comparative example is basically the same as Example 1, except that the amounts of the hindered phenol oxidant and the thioester oxidant are different. Step S2 specifically comprises adding Irganox 1010 and DSTDP in a mass ratio of 1:0.1, as well as oxalic acid anilide, modified montmorillonite, and KH-550 to the catalyst system, and dispersing the mixture in a high-speed shearing machine at 3000 rpm for 20 minutes to form a uniform mixed solution.

[0106] Comparative Example 5

[0107] This comparative example is basically the same as Example 1, except that the amounts of the hindered phenol oxidant and the thioester oxidant are different. Step S2 specifically comprises the following steps: adding Irganox 1010 and DSTDP in a mass ratio of 1:0.6, as well as oxalic acid anilide, modified montmorillonite, and KH-550 to the catalyst system, and dispersing the mixture in a high-speed shearing machine at 3000 rpm for 20 minutes to form a uniform mixed solution.

[0108] Comparative Example 6

[0109] This comparative example is basically the same as Example 1, except that no inorganic filler is added. The specific step of S2 is: Irganox 1010 and DSTDP in a mass ratio of 1:0.4, as well as oxalic acid anilide and KH-550 are added to the catalytic system, and dispersed in a high-speed shearing machine at 3000 rpm for 20 minutes to form a uniform mixed solution.

[0110] Comparative Example 7

[0111] This comparative example is basically the same as Example 1, except that the types of inorganic fillers are different. Step S2 is as follows: Irganox 1010 and DSTDP in a mass ratio of 1:0.4, as well as oxalic acid anilide and montmorillonite (CAS No. 1318-93-0, surface area 220-270m 2 / g, interlayer spacing of 1.25nm), KH-550, and dispersed in a high-speed shearing machine at 3000rpm for 20min to form a uniform mixed liquid.

[0112] Comparative Example 8

[0113] This comparative example is basically the same as Example 1, except that the amount of inorganic filler used is different, and the amount of modified montmorillonite used is 0.5 parts.

[0114] Comparative Example 9

[0115] This comparative example is basically the same as Example 1, except that the amount of inorganic filler used is different, and the amount of modified montmorillonite used is 4 parts.

[0116] Comparative Example 10

[0117] This comparative example is basically the same as Example 1, except that no hydrophobic agent is added, and the specific step of S2 is: adding Irganox1010 and DSTDP in a mass ratio of 1:0.4, as well as oxalic acid anilide and modified montmorillonite to the catalytic system, and dispersing them in a high-speed shearing machine at 3000 rpm for 20 minutes to form a uniform mixed solution.

[0118] Performance testing: The monomer cast nylon materials obtained in Comparative Examples 1-10 were prepared into 50 mm × 10 mm × 4 mm strips. The same performance testing methods as those used for the monomer cast nylon materials obtained in Examples 1-6 were used to perform performance tests on oxidation resistance, high temperature resistance, and dimensional stability. The results are shown in Table 3.

[0119] Table 3: Comparative performance test results of the monomer cast nylon materials obtained in Comparative Examples 1-10 and Example 1

[0120]

[0121]

[0122] As shown in Table 3:

[0123] Comparison of Examples 1-6 with Comparative Example 1 shows that conventional MC nylon lacks antioxidants and physical barrier structures, leading to accelerated chain breakage caused by free radical attacks on amide bonds (—CONH—) and intensified amide bond hydrolysis, resulting in a collapse of mechanical properties and direct penetration of oxygen into the matrix. The OIT is only 18 minutes, the tensile retention rate is as low as 45.22%, the HDT is 85°C, the water absorption rate is 2.43%, and yellowing is significant.

[0124] By comparing Example 1 with Comparative Example 2, it can be seen that after the metal passivator is missing, the metal ions (Al 3+ Mg 2+ ) are not chelated, the catalytic oxidation reaction is intensified, and the synergistic effect of the antioxidant and the filler is weakened, resulting in an accelerated free radical generation rate and accelerated antioxidant consumption.

[0125] Comparison of Example 1 with Comparative Example 3 shows that excessive oxalic acid anilide may interfere with the dispersion of the antioxidant, forming local agglomerates, and excessively high local concentration may trigger side reactions, thereby weakening the passivation effect. The OIT is only 55 minutes, and the retention rate is 78.69%.

[0126] By comparing Examples 1-3 with Comparative Examples 4-5, it can be seen that when the thioester content is too low, the decomposition efficiency of the hydroperoxide is reduced, the free radical regeneration is not blocked, and the oxidation chain reaction is prolonged; when the thioester is excessive, it may interfere with the free radical capture efficiency of the hindered phenol, triggering side reactions such as antioxidant migration or thermal decomposition, and weakening the protective effect of the hindered phenol.

[0127] By comparing Examples 1-6 with Comparative Example 6, it can be seen that when the physical barrier of modified montmorillonite is missing, the oxygen diffusion path is shortened, the antioxidant lacks physical barrier protection, is difficult to anchor through the filler, and the migration loss is aggravated, thereby causing the oxidation resistance and high temperature resistance to decrease simultaneously.

[0128] By comparing Examples 1-6 with Comparative Example 7, it can be seen that the interlayer spacing of the unmodified montmorillonite is only 1.25 nm, the oxygen diffusion path is short, the barrier effect is poor, and there is a lack of epoxy groups on the surface to anchor the antioxidant. Oxygen penetrates along the interface defects, resulting in a sharp drop in antioxidant efficiency.

[0129] By comparing Example 1 with Comparative Examples 8-9, it can be seen that when the filler content is too low, the physical barrier network is incomplete, the oxygen permeability increases, the OIT drops to 62 min, and the HDT is only 166°C; and excessive filler easily causes agglomeration, reduces the interfacial bonding strength, forms stress concentration points, accelerates the propagation of oxidation cracks, and limits the oxidation resistance.

[0130] By comparing Examples 1-6 with Comparative Example 10, it can be seen that the absence of silane coupling agent leads to increased water absorption of the material (2.17%), water penetration triggers hydrolysis side reactions, releases active free radicals, and at the same time weakens the interfacial bonding force, and oxygen diffuses preferentially along the interface.

[0131] The above description is based on the ideal embodiment of the present invention. From the above description, it will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all perspectives, the embodiments should be regarded as illustrative and non-restrictive. The scope of the present invention is defined by the appended claims rather than the foregoing description, and it is intended that all changes that come within the meaning and range of equivalents of the claims be included within the present invention.

[0132] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. An oxidation-resistant monomer cast nylon material, used in high-temperature, oxygen-rich environments, characterized by: The composition includes the following parts by mass: 100 parts of caprolactam; 0.1-0.3 parts of catalyst, which is one of sodium hydroxide, potassium hydroxide or lithium hydroxide; 0.5-1.5 parts of activator, which is N-acetyl caprolactam; 0.7-3 parts of primary antioxidant, including hindered phenol antioxidant and thioester antioxidant; 0.1-0.5 parts of auxiliary antioxidant, which is a metal passivator; 1-3 parts of inorganic filler, which is modified montmorillonite; 0.5-2 parts of hydrophobic agent, which is a silane coupling agent; Wherein, the mass ratio of the hindered phenol antioxidant to the thioester antioxidant is 1:0.2-0.

5.

2. The oxidation-resistant monomer cast nylon material according to claim 1, characterized in that: The hindered phenol antioxidant is one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] or octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; and the thioester antioxidant is one of dilauryl thiodipropionate or distearyl thiodipropionate.

3. The oxidation-resistant monomer cast nylon material according to claim 1, characterized in that: The metal passivator is one of oxalylanilide, N,N'-diphenyloxamide or N-salicylidene-N'-salicylic acid hydrazide.

4. The oxidation-resistant monomer cast nylon material according to claim 1, characterized in that: The modified montmorillonite is a montmorillonite with a larger interlayer distance and active epoxy groups obtained by modifying natural montmorillonite through ion exchange with epoxy quaternary ammonium salt.

5. The oxidation-resistant monomer cast nylon material according to claim 1, characterized in that: The silane coupling agent is one of γ-aminopropyltriethoxysilane and vinyltrimethoxysilane.

6. A method for preparing an oxidation-resistant monomer cast nylon material according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Heating caprolactam to 110-130° C. to melt and vacuum dehydrating, adding a catalyst and an activator to the dehydrated caprolactam in sequence, and stirring for 5-15 minutes to form a catalytic system; S2. Adding a primary antioxidant, a secondary antioxidant, an inorganic filler and a hydrophobic agent to the catalytic system, and forming a uniform mixed liquid through high-speed shearing; S3, injecting the mixed solution into a preheated mold, performing gradient temperature-controlled polymerization, and then naturally cooling to 60-80°C for demoulding to obtain a primary material; S4. The demoulded raw material is subjected to a first-stage annealing at 100-120° C. and then to a second-stage annealing at 130-150° C. to obtain a monomer cast nylon material.

7. The method for preparing an oxidation-resistant monomer cast nylon material according to claim 6, characterized in that: In the step S1, the dehydration conditions are: vacuum degree>99.5kPa, at a temperature of 130-140°C, and maintained for 10-20 minutes.

8. The method for preparing an oxidation-resistant monomer cast nylon material according to claim 6, characterized in that: In the step S2, the high-speed shearing is: dispersing at a rotation speed of 2000-4000 rpm for 10-30 minutes.

9. The method for preparing an oxidation-resistant monomer cast nylon material according to claim 6, characterized in that: In the step S3, the conditions of the gradient temperature control polymerization are: the first stage is at a temperature of 150-160° C. and is kept warm for 10-20 minutes, and the second stage is at a temperature of 165-180° C. and is kept warm for 10-30 minutes.

10. The method for preparing an oxidation-resistant monomer cast nylon material according to claim 6, characterized in that: In the step S4, the processing time of the first stage annealing is 1-2 hours, and the processing time of the second stage annealing is 0.5-1.5 hours.

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