Nylon powder, its preparation method and use

Abstract

The application belongs to the technical field of polymer materials, and particularly relates to a nylon powder and a preparation method and application thereof. The nylon powder comprises high-viscosity nylon resin, low-viscosity nylon resin and an additive, wherein the relative viscosity of the high-viscosity nylon resin is 1.75-1.85, the relative viscosity of the low-viscosity nylon resin is 1.55-1.65, the mass ratio of the high-viscosity nylon resin to the low-viscosity nylon resin is 10:1-3, and the additive comprises an antioxidant. The high-viscosity nylon resin and the low-viscosity nylon resin with specific viscosities are compounded and used in proportion, the high-viscosity nylon resin serves as a skeleton of a hydrogen storage bottle inner container and provides mechanical property support, and the low-viscosity nylon resin provides fluidity and ensures few defects in bottle forming. The use of the nylon powder of the application improves the mechanical property of the hydrogen storage bottle inner container and the integrity of the inner container structure, and a stable and defect-free type IV nylon hydrogen storage bottle inner container is prepared.

Description

Technical Field

[0001] This application belongs to the field of polymer materials technology, specifically relating to a nylon powder, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, due to its abundant resources, high energy density, and environmentally friendly and renewable characteristics, is widely considered an ideal choice for future automotive energy. However, hydrogen is a colorless and odorless flammable gas at room temperature and pressure, posing a significant safety challenge to its storage and transportation. Among various hydrogen storage methods, high-pressure gaseous hydrogen storage technology is the most mature and convenient. It not only avoids the extreme low-temperature conditions required for liquid hydrogen storage but also effectively prevents the approximately 1% daily evaporation loss of liquid hydrogen. Among various high-pressure hydrogen storage containers, Type IV hydrogen storage cylinders outperform in terms of operating pressure, lightweight design, hydrogen storage density, and fatigue life, and have become a key development direction for future high-pressure gaseous hydrogen storage.

[0003] The plastic liner is a crucial component of Type IV hydrogen storage cylinders. Currently, rotational molding is showing great promise in the manufacture of Type IV hydrogen storage cylinder liners due to its advantages such as low residual stress, absence of weld lines, and low cost for large parts. Rotational molding is characterized by its ability to mold complex hollow structures in a single process; however, poor powder flowability or melting behavior can lead to defects such as uneven wall thickness, bubbles, and unfused areas. Furthermore, hydrogen storage cylinders operate under high pressure, typically reaching 35 MPa or even 70 MPa. Under such conditions, any structural defect becomes a stress concentration point, thus placing higher demands on the mechanical properties of the liner material. Insufficient impact resistance or toughness can cause the cylinder to fail under pressure cycling, potentially leading to safety accidents.

[0004] Therefore, how to simultaneously improve the processability and mechanical reliability of materials to achieve the preparation of Type IV hydrogen storage cylinder liners with intact inner walls, excellent stability, and superior mechanical properties has become a technical problem that urgently needs to be solved in the field. Summary of the Invention

[0005] This application provides a nylon powder, its preparation method, and its application to solve the above-mentioned problems in the prior art.

[0006] In a first aspect, this application provides a nylon powder comprising: a high-viscosity nylon resin, a low-viscosity nylon resin, and additives.

[0007] The high-viscosity nylon resin has a relative viscosity of 1.75-1.85, and the low-viscosity nylon resin has a relative viscosity of 1.55-1.65.

[0008] The mass ratio of the high-viscosity nylon resin to the low-viscosity nylon resin is 10:1-3;

[0009] The additives include antioxidants.

[0010] As an example, the relative viscosity of the high-viscosity nylon resin can be 1.75, 1.78, 1.80, 1.82, 1.84, 1.85, or within any range of the above values; the relative viscosity of the low-viscosity nylon resin can be 1.55, 1.57, 1.59, 1.60, 1.63, 1.65, or within any range of the above values; the mass ratio of the high-viscosity nylon resin to the low-viscosity nylon resin is 10:1, 10:1.5, 10:2, 10:2.5, 10:3, or within any range of the above values.

[0011] In one optional embodiment, the additives include at least one of antioxidants, catalysts, fluorescent whitening agents, plasticizers, nucleating agents, toughening agents, and pigments;

[0012] And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the mass of the additives accounts for 0.01% to 10% of the total mass of the resin. As an example, the mass of the additives may be 0.01%, 1%, 3%, 5%, 7%, 9%, 10% of the resin mass, or within any range of the above values.

[0013] In one optional embodiment, the antioxidant accounts for less than or equal to 1% of the total mass of the high-viscosity nylon resin and the low-viscosity nylon resin.

[0014] And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the mass percentage of the catalyst is less than or equal to 1%;

[0015] And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the mass percentage of the fluorescent whitening agent is less than or equal to 0.1%;

[0016] And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the mass percentage of the plasticizer is less than or equal to 10%;

[0017] And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the mass percentage of the nucleating agent is less than or equal to 1%;

[0018] And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the toughening agent accounts for less than or equal to 5% by mass;

[0019] And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the pigment accounts for less than or equal to 3% of the total mass.

[0020] In one optional embodiment, the antioxidant accounts for 0.01%-1% of the total mass of the high-viscosity nylon resin and the low-viscosity nylon resin.

[0021] And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the plasticizer accounts for 0.01%-9.99% by mass.

[0022] In one optional embodiment, the high-viscosity nylon resin and the low-viscosity nylon resin independently include at least one of nylon 612, nylon 1010, nylon 1012, nylon 11, and nylon 12;

[0023] And / or, the antioxidant includes at least one of hindered amine antioxidants, cuprous iodide, potassium iodide, hindered phenolic antioxidants, phosphite antioxidants, and inorganic phosphate antioxidants;

[0024] And / or, the catalyst comprises at least one of phosphoric acid, phosphorous acid, hypophosphite, sodium hypophosphite, and triphenyl phosphate;

[0025] And / or, the fluorescent whitening agent includes at least one of stilbene-type fluorescent whitening agents, coumarin-type fluorescent whitening agents, pyrazoline-type fluorescent whitening agents, benzo[a]oxo[b]nitrile-type fluorescent whitening agents, and phthalimide-type fluorescent whitening agents;

[0026] And / or, the plasticizer comprises an ester of a diacid;

[0027] And / or, the nucleating agent includes at least one of carboxylate nucleating agents, phosphate nucleating agents, and amide nucleating agents;

[0028] And / or, the toughening agent includes at least one of maleic anhydride grafted elastomer, polyolefin elastomer, and acrylate core-shell particles;

[0029] And / or, the pigment includes at least one of organic dyes, inorganic pigments, or pearlescent pigments.

[0030] Secondly, this application provides a method for preparing the above-mentioned nylon powder, comprising the following steps:

[0031] S1, high-viscosity nylon resin is mixed with some additives, extruded and granulated, and then frozen and crushed to obtain a high-viscosity component;

[0032] S2, Dissolve the low-viscosity nylon resin and the antioxidant in the remaining additives in an organic solvent at 140-160℃, cool down, precipitate the resin component, mix with the remaining additives to obtain the low-viscosity component;

[0033] S3, the high-viscosity component and the low-viscosity component are mixed to obtain the nylon powder.

[0034] As an example, in S2, the temperature at which the solid components of the low-viscosity nylon resin and additives dissolve in the organic solvent can be 140°C, 145°C, 150°C, 155°C, 160°C, or within any range of the above values.

[0035] In one optional embodiment, in S1, the extrusion granulation temperature is 180-210°C; as an example, the extrusion granulation temperature can be 180°C, 190°C, 200°C, 210°C, or within any range of the above values.

[0036] And / or, the freezing and crushing temperature is -140℃ to -190℃, and the particle size Dv50 of the high-viscosity component is 200-300μm; as an example, the freezing and crushing temperature can be -140℃, -150℃, -160℃, -170℃, -180℃, -190℃, or within any range of the above values.

[0037] And / or, the mass ratio of the additive used in S1 to the additive used in S2 is 10:(1-3).

[0038] In one alternative embodiment, in S2, the amount of organic solvent used is 2-6 L of organic solvent per 1 kg of resin, based on the total mass of the high-viscosity nylon resin and the low-viscosity nylon resin; as an example, the amount of organic solvent used per 1 kg of resin is 2 L, 3 L, 4 L, 5 L, 6 L, or within any of the above values.

[0039] And / or, cool to 20-45°C; as an example, cool to 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, or within any range of the above values;

[0040] And / or, the organic solvent includes at least one of ethanol, N,N-dimethylformamide, and acetonitrile.

[0041] In one alternative embodiment, the nylon powder satisfies at least one of the following characteristics:

[0042] (1) The particle size range is 30 mesh to 120 mesh;

[0043] (2) The relative viscosity η ranges from 1.65 to 1.85;

[0044] (3) Yellowness index is less than 0.

[0045] Thirdly, this application provides a hydrogen storage cylinder liner as described above, which is prepared by rotational molding using the nylon powder described above or the nylon powder prepared by the above preparation method as raw material.

[0046] In this application, the hindered amine antioxidant includes one or both of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate and bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate.

[0047] The hindered phenolic antioxidants include one or more of butylated hydroxytoluene, antioxidant 1010, and antioxidant 1098;

[0048] The phosphite antioxidants include one or both of tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168) and bis(2,4-dicumylphenyl) pentaerythritol diphosphite.

[0049] The inorganic phosphate antioxidants include one or more of calcium hypophosphite, sodium phosphite, and calcium phosphite.

[0050] In this application, stilbene-type fluorescent whitening agents include 4,4'-bis(2-sulfonylstyryl)biphenyl; coumarin-type fluorescent whitening agents include 7-diethylamino-4-methylcoumarin; pyrazoline-type fluorescent whitening agents include 3-(4-chlorophenyl)-1-(4-aminosulfonylphenyl)-2-pyrazoline; benzo[a]oxazol-type fluorescent whitening agents include 2,2-(4,4-stilbeneyl)bisbenzoxazole; and phthalimide-type fluorescent whitening agents include N-methyl-4-methoxy-1,8-naphthalenediamide.

[0051] Among them, organic dyes include phthalocyanine blue, aniline black, and oriental black, inorganic pigments include titanium dioxide, carbon black, titanium yellow, and iron oxide red, and pearlescent pigments include pearlescent 119, pearlescent 113, and pearlescent 6117.

[0052] In this application, by introducing a catalyst, fluorescent whitening agent, and pigment, not only is the compatibility between the resin and other additives enhanced, but the color stability and appearance purity of the finished powder are also effectively improved. This improvement helps optimize the molding quality and appearance consistency of the hydrogen storage cylinder liner, thereby better meeting its performance requirements in high-strength, high-airtightness applications.

[0053] The plasticizer includes one or more of the following: benzenesulfonamide derivatives, esters of hydroxybenzoic acid, esters or ethers of tetrahydrofurfuryl alcohol, esters of citric acid or hydroxymalonic acid.

[0054] Preferably, the plasticizer includes one or more of N-butylbenzenesulfonamide, propylparaben, tetrahydrofurfuryl acrylate, and tributyl acetylacetonate.

[0055] In this application, the plasticizer plays a role in the rotational molding process of nylon powder due to its excellent compatibility, thermal stability, and flow control capabilities. Its addition not only effectively improves the flowability and molding quality of the powder melt, but also enhances the toughness, appearance, and structural stability of the product, thereby ensuring higher safety and operational reliability of the hydrogen storage cylinder liner under high-pressure operating conditions.

[0056] The nucleating agent includes one or more of sodium benzoate, bis(2,4-dicumylphenyl)pentaerythritol-diphosphite, and N,N'-ethylenebisstearamide.

[0057] In this application, the nucleating agent can improve the crystallization rate and crystallinity of the powder, thereby optimizing the molding efficiency and dimensional stability of the rotational molding liner.

[0058] Among them, maleic anhydride-grafted elastomers include maleic anhydride-grafted POE; acrylate core-shell particles refer to a type of toughening particles composed of a rigid shell (e.g., polymethyl methacrylate, PMMA) and a flexible core (e.g., polybutyl acrylate, PBA). When the material is subjected to impact, the core-shell structure particles absorb energy by inducing crazes and shear bands. The elastic part of the core can deform, while the shell part may have better compatibility with the matrix, promoting stress transfer. This type of particle has both good rigidity and toughness.

[0059] Introducing toughening agents into nylon powder systems can improve the impact toughness and crack resistance of rotationally molded hydrogen storage cylinder liners, while also enhancing the material's stability under complex working conditions, thereby further improving the overall structural safety and long-term durability.

[0060] In this application, by introducing plasticizers, nucleating agents and toughening agents, not only is the flow behavior and molding stability of powder in the rotational molding process effectively optimized, but the mechanical strength, dimensional accuracy and appearance quality of the inner liner product are also comprehensively improved, providing a reliable material basis for the manufacture of high-performance hydrogen storage cylinders.

[0061] This application uses different powdering methods to pulverize nylon resins of different viscosities. High-viscosity nylon resin is pre-mixed uniformly with additives, and then granulated by screw extrusion. This not only achieves excellent mechanical properties but also ensures good dispersion of the additives and nylon resin due to the screw's stirring action. This avoids the additives simply being dispersed on the resin surface, which could lead to poor additive performance. Furthermore, this process is unaffected by the physical state of the additives, overcoming the limitation of solvent powders not being able to use large-particle additives. Cryogenic crushing of high-viscosity nylon resin is employed because its toughness and heat sensitivity at room temperature present an irreconcilable contradiction with conventional pulverization processes. Cryogenic crushing physically alters the macroscopic phase of the material, transforming the tough nylon into a brittle, glass-like state. When mechanical shear force is applied at this point, the material undergoes brittle fracture rather than ductile tearing, thus enabling efficient and fine pulverization. Low-viscosity nylon resin is powdered through dissolution and crystallization, ensuring the sphericity of the powder and improving its flowability. The powder obtained through crystallization, due to its relatively small particle size, fills the gaps in the large-particle-size powder during the preheating stage of processing, and fills the gaps in the high-viscosity component during rotational molding, making the surface denser. At the same time, the low-viscosity component in the gap has higher melt flowability due to its low viscosity properties. During the high-temperature melting stage, it spreads in four directions in the form of melt to fill the defects, ensuring that the inner liner with fewer defects is produced from both the powder and melt aspects.

[0062] Furthermore, this application uses a compounding method to combine the obtained modified nylon powder (i.e., high-viscosity nylon resin and low-viscosity nylon resin). The high-viscosity component serves as the skeleton of the hydrogen storage cylinder liner, providing mechanical support, while the low-viscosity component provides flowability, ensuring fewer defects in the cylinder assembly. Compared with a single medium-viscosity powder, this compounding method results in high local melt flowability of the low-viscosity powder, which fills in defects and ensures leveling. In contrast, the medium-viscosity powder has uniform melt flow and lacks high-flowability melt, resulting in poor leveling in the cylinder assembly. At the same time, the mechanical properties of the high-viscosity powder are also higher than those of the medium-viscosity powder due to the skeleton support.

[0063] Preferably, the nylon powder satisfies at least one of the following characteristics:

[0064] The particle size range is 30-120 mesh, preferably 30-100 mesh, which makes the powder particles evenly distributed in the mold, heat and melt rapidly, and has high molding efficiency;

[0065] The relative viscosity η ranges from 1.65 to 1.85, ensuring the compatibility of high-viscosity and low-viscosity powders.

[0066] With a yellowness index of less than 0, the color is a pure color, which effectively improves the thermal stability and appearance quality of the material and avoids discoloration, yellowing and other appearance defects during the molding process.

[0067] According to an embodiment of this application, the inner liner of the hydrogen storage cylinder is prepared by rotational molding.

[0068] In one alternative implementation, rotational molding may include the following steps:

[0069] (1) Mold assembly and mold closing

[0070] The nylon powder of this application is put into a rotational molding mold. The amount of material added is controlled according to the wall thickness of the inner liner of the hydrogen storage cylinder to ensure uniform filling. Then the mold is closed to ensure a firm seal.

[0071] (2) Heating, melting and rotational molding

[0072] After the mold is filled with material, it is placed in a rotational molding machine and heated until the nylon powder melts and reaches the optimal flow temperature. Then, the mold is kept warm and controlled to rotate and revolve simultaneously along two axes in different directions. This causes the nylon powder to melt in the mold cavity and be evenly coated on the mold cavity wall, gradually forming a seamless hollow structure.

[0073] (3) Cooling and curing

[0074] After heating and heat preservation are completed, the mold begins to cool down. Specifically, it is first allowed to cool freely to below the cooling point of the nylon powder, and then air-cooled to reduce the overall temperature of the mold to below 60°C. This effectively controls internal stress and prevents uneven wall thickness or deformation. During the cooling stage, the mold continues to rotate to ensure that the inner liner has a uniform thickness and a smooth surface.

[0075] (4) Demolding and removing parts

[0076] After cooling is complete, stop the mold rotation, remove the end caps and inserts at both ends of the mold in sequence, and if necessary, use water spray to assist in rapid cooling. Open the mold and take out the molded hydrogen storage cylinder liner.

[0077] The technical solution of this application has the following advantages:

[0078] The nylon powder provided in this application comprises: high-viscosity nylon resin, low-viscosity nylon resin, and additives, wherein the relative viscosity of the high-viscosity nylon resin is 1.75-1.85, and the relative viscosity of the low-viscosity nylon resin is 1.55-1.65; the mass ratio of the high-viscosity nylon resin to the low-viscosity nylon resin is 10:1-3. This application utilizes a compounding of nylon resins with different viscosities, wherein the high-viscosity nylon resin serves as the skeleton of the rotationally molded hydrogen storage cylinder liner, improving the mechanical properties of the liner, while the low-viscosity nylon resin has better flowability, helping to reduce uneven wall thickness caused by leveling differences during the rotational molding process; this application improves the mechanical properties and structural integrity of the hydrogen storage cylinder liner, producing a nylon type IV hydrogen storage cylinder liner with high stability and few defects.

[0079] The method for preparing nylon powder provided in this application involves pre-mixing high-viscosity nylon resin with additives, then granulating by screw extrusion and cryogenic crushing to obtain a high-viscosity component that serves as the skeleton of the inner liner, providing excellent mechanical properties. Simultaneously, low-viscosity nylon resin and antioxidants are dissolved and crystallized, and then physically mixed with the remaining additives to obtain a powder with extremely high sphericity and excellent flowability, thus compensating for the defects in the inner liner caused by the insufficient flowability of the high-viscosity component. Finally, a nylon type IV hydrogen storage cylinder inner liner with good mechanical properties, high stability, and few defects is prepared.

[0080] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0081] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0082] Figure 1 These are electron micrographs of the high-viscosity component a in Preparation Example 1 and the low-viscosity component d in Preparation Example 4 of this application;

[0083] Figure 2 This is an image of the inner liner of the hydrogen storage bottle prepared according to Example 1 of this application;

[0084] Figure 3 This is an image of the inner liner of the hydrogen storage bottle prepared in Comparative Example 1 of this application;

[0085] Figure 4 This is an image of the inner liner of the hydrogen storage bottle prepared in Comparative Example 2 of this application;

[0086] Figure 5 This is an image of the inner liner of the hydrogen storage bottle prepared in Comparative Example 3 of this application;

[0087] Figure 6 This is an image of the inner liner of the hydrogen storage bottle prepared in Comparative Example 4 of this application. Detailed Implementation

[0088] The following embodiments are provided to better understand this application. However, the following embodiments do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining the features of this application with other prior art, falls within the scope of protection of this application.

[0089] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having” and any variations thereof in the text of this application are intended to cover non-exclusive inclusion.

[0090] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0091] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0092] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0093] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0094] In the description of the embodiments of this application, the term "at least one" refers to one or more (including two).

[0095] Unless otherwise specified, the method described in this application may include steps S1 and S2 performed sequentially, or steps S2 and S1 performed sequentially.

[0096] Unless otherwise specified, the experimental steps or conditions in the examples were performed in accordance with conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0097] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0098] The nylon resin used in the following examples and comparative examples was purchased from Wanhua Chemical Group Co., Ltd.; the plasticizer, antioxidant, catalyst, fluorescent whitening agent, nucleating agent, toughening agent and pigment were all purchased from Shandong Inokai Chemical Co., Ltd.

[0099] Preparation Example 1

[0100] This preparation example provides a method for preparing a high-viscosity component, comprising the following steps:

[0101] 20 kg of high-viscosity nylon 12 resin with a relative viscosity of 1.82, 100 g of antioxidant 168, 100 g of antioxidant 1098, 100 g of phosphoric acid as a catalyst, and 400 g of plasticizer N-butylbenzene sulfonamide were added to a screw extruder and mixed and granulated at 190°C. The granulated material was then cryogenically cooled to -170°C with liquid nitrogen and pulverized into powder with a Dv50 of 241 μm. The powder was dried in an oven at 100°C for 2 hours to obtain high-viscosity component a.

[0102] The high-viscosity component a obtained in this preparation example and the low-viscosity component d provided in preparation example 4 were characterized by optical microscopy to analyze the influence of different preparation processes on the morphology of powder particles. The optical microscope used was a Zeiss Axio Imager 2 polarizing microscope from Beijing Presys Instruments Co., Ltd.

[0103] Specifically, such as Figure 1 As shown, the left figure corresponds to the high-viscosity component a prepared in Preparation Example 1, and the right figure corresponds to the low-viscosity component d prepared in Preparation Example 4. Figure 1 As can be seen, the sample particles prepared in Preparation Example 4 are regular spherical with smooth surfaces, clear boundaries, and uniform particle size distribution, exhibiting excellent morphological consistency, stronger flowability, and more complete bottle structure, thus ensuring the overall leveling effect; while the sample particles prepared in Preparation Example 1 are obviously irregular, mainly polygonal or irregular fragments, with rough particle edges.

[0104] Preparation Example 2

[0105] This preparation example provides a method for preparing a high-viscosity component, comprising the following steps:

[0106] 20 kg of high-viscosity nylon 12 resin with a relative viscosity of 1.78, 100 g of antioxidant 168 and 100 g of antioxidant 1098, 400 g of plasticizer N-butylbenzenesulfonamide, 2 g of 2-(4,4-stilbene)bisbenzoxazole fluorescent whitening agent, 100 g of titanium dioxide, and 20 g of nucleating agent bis(2,4-dicumylphenyl)pentaerythritol-diphosphite were added to a screw extruder and mixed and granulated at 190°C. The granulated material was cryogenically cooled to -170°C with liquid nitrogen and then pulverized into powder with a Dv50 of 265 μm. The powder was dried in an oven at 100°C for 2 hours to obtain high-viscosity component b.

[0107] Preparation Example 3

[0108] This preparation example provides a method for preparing a high-viscosity component, comprising the following steps:

[0109] 20 kg of high-viscosity nylon 12 resin with a relative viscosity of 1.85, 100 g of antioxidant 168 and 100 g of antioxidant 1098, 400 g of plasticizer N-butylbenzenesulfonamide, and 301.8 g of toughening agent were added to a screw and mixed and granulated at 190°C. The toughening agent consisted of core-shell polymer particles, with the shell of the particles formed by polymethyl methacrylate (PMMA) and the core inside the particles formed by polybutyl acrylate (PBA), which was used to improve the toughness of the inner liner. The granulated material was cryogenically cooled to 170°C with liquid nitrogen and then pulverized into powder with a Dv50 of 255 μm. The powder was dried in an oven at 100°C for 2 hours to obtain the high-viscosity component c.

[0110] Preparation Example 4

[0111] This preparation example provides a method for preparing a low-viscosity component, comprising the following steps:

[0112] 20 kg of low-viscosity nylon 12 resin with a relative viscosity of 1.61, 100 g of antioxidant 168, and 100 g of antioxidant 1098 were dissolved in 50 L of ethanol at 150 °C. The solution was then cooled to 30 °C to precipitate the nylon resin and form a slurry. The slurry was dried to obtain nylon powder. Based on the nylon powder, 400 g of plasticizer N-butylbenzene sulfonamide and 100 g of phosphoric acid were added by physical mixing in a mixer at a speed of 1000 rpm for 4 min to obtain the low-viscosity component d with a Dv50 of 101 μm.

[0113] Preparation Example 5

[0114] This preparation example provides a method for preparing a low-viscosity component, comprising the following steps:

[0115] 20 kg of low-viscosity nylon 12 resin with a relative viscosity of 1.55, 100 g of antioxidant 168, and 100 g of antioxidant 1098 were dissolved in 50 L of ethanol at 150 °C. The solution was then cooled to 30 °C to precipitate the nylon resin and form a slurry. The slurry was dried to obtain nylon powder. Based on the nylon powder, 400 g of plasticizer N-butylbenzenesulfonamide, 2 g of 2-(4,4-stilbeneyl)bisbenzoxazole fluorescent whitening agent, 100 g of titanium dioxide, and 20 g of nucleating agent bis(2,4-dicumylphenyl)pentaerythritol-diphosphite were added by physical mixing in a mixer. The mixing speed of the mixer was 1000 rpm and the mixing time was 4 min to obtain the low-viscosity component e with a Dv50 of 100 μm.

[0116] Preparation Example 6

[0117] This preparation example provides a method for preparing a low-viscosity component, comprising the following steps:

[0118] 20 kg of low-viscosity nylon 12 resin with a relative viscosity of 1.57, 100 g of antioxidant 168, and 100 g of antioxidant 1098 were dissolved in 50 L of ethanol at 150 °C. The solution was then cooled to 30 °C to precipitate the nylon resin, forming a slurry. The slurry was dried to obtain nylon powder. Based on this nylon powder, 400 g of plasticizer N-butylbenzenesulfonamide and 301.8 g of toughening agent were added via physical mixing in a mixer. The toughening agent is a core-shell structured polymer powder, with the shell of the particles formed by polymethyl methacrylate (PMMA) and the core formed by polybutyl acrylate (PBA) to improve the toughness of the inner liner. The mixing speed of the mixer was 1000 rpm, the mixing time was 4 min, and the D50 was 98 μm. The low-viscosity component f was obtained.

[0119] Preparation Example 7

[0120] This preparation example provides a method for preparing a medium-viscosity component, comprising the following steps:

[0121] 20 kg of medium-viscosity nylon 12 resin with a relative viscosity of 1.69, 100 g of antioxidant 168, 100 g of antioxidant 1098, 100 g of phosphoric acid as a catalyst, and 400 g of plasticizer N-butylbenzene sulfonamide were added to a screw extruder and mixed and granulated at 190°C. The granulated resin was cryogenically cooled to -170°C with liquid nitrogen and then pulverized into powder with a Dv50 of 298 μm. The powder was dried in an oven at 100°C for 2 hours to obtain g of medium-viscosity component.

[0122] Preparation Example 8

[0123] This preparation example provides a method for preparing a high-viscosity component, which differs from Preparation Example 1 in that: nylon 11 resin of the same viscosity is used instead of nylon 12 resin to obtain the high-viscosity component h.

[0124] Preparation Example 9

[0125] This preparation example provides a method for preparing a low-viscosity component, which differs from preparation example 4 in that: nylon 11 resin of the same viscosity is used instead of nylon 12 resin to obtain low-viscosity component i.

[0126] Preparation Example 10

[0127] This preparation example provides a method for preparing a high-viscosity component, which differs from Preparation Example 1 in that: nylon 1012 resin of the same viscosity is used instead of nylon 12 resin to obtain high-viscosity component j.

[0128] Preparation Example 11

[0129] This preparation example provides a method for preparing a low-viscosity component. The difference from preparation example 4 is that nylon 1012 resin of the same viscosity is used instead of nylon 12 resin to obtain low-viscosity component k.

[0130] Example 1

[0131] This embodiment provides a nylon powder and a hydrogen storage cylinder liner, the specific composition and preparation method of which are as follows:

[0132] S100. The above 20kg high viscosity component a and 2kg low viscosity component d are physically mixed by a high-speed mixer, wherein the mixing speed of the mixer is 1000rpm and the mixing time is 6min, to obtain nylon powder A for rotational molding.

[0133] S200. Nylon powder A is used in the rotational molding process to prepare the hydrogen storage bottle liner at a molding temperature of 246°C. Specifically, the nylon powder is put into the mold cavity. After the mold is closed, it is heated to 246°C and kept at that temperature for 2 minutes. The liner is formed by rotating and revolving along two mutually perpendicular axes. After the molding is completed, it is cooled and solidified. The liner is then demolded and removed to obtain the hydrogen storage bottle liner.

[0134] Example 2

[0135] This embodiment provides a nylon powder and a hydrogen storage cylinder liner, the specific composition and preparation method of which are as follows:

[0136] S100. The above 20kg high viscosity component b and 2kg low viscosity component e are physically mixed by a high-speed mixer, wherein the mixing speed of the mixer is 1000rpm and the mixing time is 6min, to obtain nylon powder B for rotational molding.

[0137] S200. Nylon powder B is used in the rotational molding process to prepare the hydrogen storage bottle liner at a molding temperature of 253°C. Specifically, the nylon powder is put into the mold cavity. After the mold is closed, it is heated to 253°C and kept at that temperature for 2 minutes. The liner is formed by rotating and revolving along two mutually perpendicular axes. After the molding is completed, it is cooled and solidified. The liner is then demolded and removed to obtain the hydrogen storage bottle liner.

[0138] Example 3

[0139] This embodiment provides a nylon powder and a hydrogen storage cylinder liner, the specific composition and preparation method of which are as follows:

[0140] S100. The above 20kg high viscosity component c and 2kg low viscosity component f are physically mixed by a high-speed mixer, wherein the mixing speed of the mixer is 1000rpm and the mixing time is 6min, to obtain nylon powder C for rotational molding.

[0141] S200. Nylon powder C is used in rotational molding process to prepare hydrogen storage bottle liner at a molding temperature of 248℃. Specifically, nylon powder is put into the mold cavity. After the mold is closed, it is heated to 248℃ and kept at that temperature for 2 minutes. The liner is formed by rotating and revolving along two mutually perpendicular axes. After the molding is completed, it is cooled and solidified. The liner is then demolded and removed to obtain the hydrogen storage bottle liner.

[0142] Example 4

[0143] This embodiment provides a nylon powder and a hydrogen storage cylinder liner, which differs from Embodiment 1 in that the amount of low-viscosity component d is 4 kg.

[0144] Example 5

[0145] This embodiment provides a nylon powder and a hydrogen storage cylinder liner, which differs from Embodiment 1 in that the amount of low-viscosity component d is 6 kg.

[0146] Example 6

[0147] This embodiment provides a nylon powder and a hydrogen storage cylinder liner, which differs from Embodiment 1 in that: high viscosity component h replaces high viscosity component a, and low viscosity component i replaces low viscosity component d.

[0148] Example 7

[0149] This embodiment provides a nylon powder and a hydrogen storage cylinder liner, which differs from Embodiment 1 in that: high viscosity component j replaces high viscosity component a, and low viscosity component k replaces low viscosity component d.

[0150] Comparative Example 1

[0151] This comparative example provides a nylon powder and a hydrogen storage cylinder liner, the specific composition and preparation method of which are as follows:

[0152] S100. The above 20kg high viscosity component a and 10kg low viscosity component d are physically mixed by a high-speed mixer, wherein the mixing speed of the mixer is 1000rpm and the mixing time is 6min, to obtain nylon powder D for rotational molding.

[0153] S200. Nylon powder D is used in rotational molding process to prepare hydrogen storage bottle liner at a molding temperature of 246℃. Specifically, nylon powder is put into the mold cavity. After the mold is closed, it is heated to 246℃ and kept at that temperature for 2 minutes. The liner is formed by rotating and revolving along two mutually perpendicular axes. After the molding is completed, it is cooled and solidified. The liner is then demolded and removed to obtain hydrogen storage bottle liner.

[0154] Comparative Example 2

[0155] This comparative example provides a nylon powder and a hydrogen storage cylinder liner, the specific composition and preparation method of which are as follows:

[0156] The medium viscosity component g was directly used in the rotational molding process to prepare the hydrogen storage bottle liner at a molding temperature of 239℃. Specifically, nylon powder was put into the mold cavity. After the mold was closed, it was heated to 239℃ and kept at that temperature for 2 minutes. The liner was then formed by rotating and revolving along two mutually perpendicular axes. After the molding was completed, it was cooled and solidified. The liner was then demolded and removed to obtain the hydrogen storage bottle liner.

[0157] Comparative Example 3

[0158] This comparative example provides a nylon powder and a hydrogen storage cylinder liner, the specific composition and preparation method of which are as follows:

[0159] S100. The above 20kg high viscosity component a and 0.5kg low viscosity component d are physically mixed by a high-speed mixer, wherein the mixing speed of the mixer is 1000rpm and the mixing time is 6min, to obtain nylon powder F for rotational molding.

[0160] S200. Nylon powder F is used in rotational molding process to prepare hydrogen storage bottle liner at a molding temperature of 253°C. Specifically, nylon powder is put into the mold cavity. After the mold is closed, it is heated to 253°C and kept at that temperature for 2 minutes. The liner is formed by rotating and revolving along two mutually perpendicular axes. After the molding is completed, it is cooled, solidified, demolded, and the part is obtained as hydrogen storage bottle liner.

[0161] Comparative Example 4

[0162] This comparative example provides a nylon powder and a hydrogen storage cylinder liner, the specific composition and preparation method of which are as follows:

[0163] The high-viscosity component was prepared according to the method of Preparation Example 1, except that the relative viscosity of the nylon 12 resin was 2.5; the low-viscosity component was prepared according to the method of Preparation Example 4, except that the relative viscosity of the nylon 12 resin was 1.4.

[0164] The high-viscosity component prepared in this comparative example was used to replace the high-viscosity component a in Example 1, and the low-viscosity component prepared in this comparative example was used to replace the low-viscosity component d in Example 1. The hydrogen storage bottle liner was prepared according to the method of Example 1.

[0165] Experimental Example 1

[0166] The performance of the nylon powder and hydrogen storage cylinder liner provided in each embodiment was tested. The specific test items and methods are as follows:

[0167] Relative viscosity: Tested according to standard ASTM D789, with m-cresol as solvent.

[0168] Tensile properties: tested according to standard ISO 527-2:2012.

[0169] Impact mechanical properties: tested according to standard ISO 180:2023.

[0170] Yellowness index: Tested according to standard ASTM E313-2015.

[0171] The specific test results are shown in the table below:

[0172] Table 1

[0173]

[0174] The test results in the table above show that Comparative Example 2, made of medium-viscosity nylon powder, exhibits mechanical properties lower than those of the examples and other comparative examples in this application. This demonstrates that the compounded nylon powder can possess excellent mechanical properties, providing a guarantee for the mechanical performance of the hydrogen storage cylinder liner. Specifically, Example 2 demonstrates that the addition of fluorescent whitening agents and pigments can improve the yellowness of the powder, ultimately improving the color of the hydrogen storage cylinder liner. Example 3 shows that the toughening agent can improve the toughness of the liner material. Comparative Example 4 shows that when the high-viscosity component reaches a certain value, the improvement in mechanical properties is not significant, but as the relative viscosity increases, processing becomes increasingly difficult, and the high fluidity of the low-viscosity resin cannot compensate for the defects caused by the high-viscosity resin. In Comparative Example 1, the mechanical properties continuously decrease as the low-viscosity component increases. Furthermore, when a certain compounding ratio is reached, the low-viscosity component increases the overall fine powder content of the compounded powder, and excess fine powder can easily generate bubbles on the inner wall of the cylinder. Therefore, by compounding nylon powders of different viscosities and formulations, different properties can be selectively enhanced while ensuring mechanical properties, broadening the versatility of rotational molding liner applications.

[0175] To evaluate the impact of different compounding ratios and medium-viscosity components (without high-flow-rate melt) on rotational molding quality, this application further compares the actual molding effects of the nylon powder provided in the examples and comparative examples used for hydrogen storage cylinder liners. Figure 2 It can be seen that Example 1 has a regular overall structure, uniform color, and smooth surface, showing good molding consistency; the molding effects of other examples are similar to those of Example 1, and will not be shown one by one; while Comparative Example 1 ( Figure 3 Although the molded part has a basically intact structure, there are obvious perforations due to excessive melt flow, requiring strict control of the cooling rate and a narrow process range; Comparative Example 2 ( Figure 4 Its inner surface has obvious defects, mainly manifested as small pit defects on the inner wall; Comparative Example 3 ( Figure 5 Because of the high content of high-viscosity components, low-viscosity components cannot escape the constraints of high viscosity, resulting in poor melt flowability and significant uneven wall thickness due to melt accumulation. Comparative Example 4 ( Figure 6 Because the high-viscosity component used has a very high viscosity, it plays a dominant role in the entire processing. The low-viscosity component cannot overcome the influence of the high-viscosity component, resulting in very poor fluidity and obvious sagging on the inner wall. At the same time, there are significant differences in wall thickness at different locations.

[0176] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A nylon powder, characterized in that, It is composed of the following raw materials: high viscosity nylon resin, low viscosity nylon resin, and additives. The high-viscosity nylon resin has a relative viscosity of 1.75-1.85, and the low-viscosity nylon resin has a relative viscosity of 1.55-1.

65. The mass ratio of the high-viscosity nylon resin to the low-viscosity nylon resin is 10:1-3; The additives contain antioxidants; The additives also contain at least one of the following: catalyst, fluorescent whitening agent, plasticizer, nucleating agent, toughening agent, and pigment; The method for preparing the nylon powder includes the following steps: S1, high-viscosity nylon resin is mixed with some additives, extruded and granulated, and then frozen and crushed to obtain a high-viscosity component; S2, Dissolve the low-viscosity nylon resin and the antioxidant in the remaining additives in an organic solvent at 140-160℃, cool down, precipitate the resin component, mix with the remaining additives to obtain the low-viscosity component; S3, the high-viscosity component and the low-viscosity component are mixed to obtain the nylon powder; The relative viscosity was tested according to standard ASTM D789, with m-cresol as the solvent.

2. The nylon powder according to claim 1, characterized in that, The additives account for 0.01%-10% of the total mass of high-viscosity nylon resin and low-viscosity nylon resin.

3. The nylon powder according to claim 2, characterized in that, The antioxidant accounts for less than or equal to 1% of the total mass of high-viscosity nylon resin and low-viscosity nylon resin. And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the mass percentage of the catalyst is less than or equal to 1%; And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the mass percentage of the fluorescent whitening agent is less than or equal to 0.1%; And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the mass percentage of the plasticizer is less than or equal to 10%; And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the mass percentage of the nucleating agent is less than or equal to 1%; And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the toughening agent accounts for less than or equal to 5% by mass; And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the pigment accounts for less than or equal to 3% of the total mass.

4. The nylon powder according to claim 3, characterized in that, The antioxidant accounts for 0.01%-1% of the total mass of high-viscosity nylon resin and low-viscosity nylon resin. And / or, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the plasticizer accounts for 0.01%-9.99% by mass.

5. The nylon powder according to any one of claims 2-4, characterized in that, The high-viscosity nylon resin and the low-viscosity nylon resin independently include at least one of nylon 612, nylon 1010, nylon 1012, nylon 11, and nylon 12; And / or, the antioxidant includes at least one of hindered amine antioxidants, cuprous iodide, potassium iodide, hindered phenolic antioxidants, phosphite antioxidants, and inorganic phosphate antioxidants; And / or, the catalyst comprises at least one of phosphoric acid, phosphorous acid, hypophosphite, sodium hypophosphite, and triphenyl phosphate; And / or, the fluorescent whitening agent includes at least one of stilbene-type fluorescent whitening agents, coumarin-type fluorescent whitening agents, pyrazoline-type fluorescent whitening agents, benzo[a]oxo[b]nitrile-type fluorescent whitening agents, and phthalimide-type fluorescent whitening agents; And / or, the plasticizer comprises an ester of a diacid; And / or, the nucleating agent includes at least one of carboxylate nucleating agents, phosphate nucleating agents, and amide nucleating agents; And / or, the toughening agent includes at least one of maleic anhydride grafted elastomer, polyolefin elastomer, and acrylate core-shell particles; And / or, the pigment includes at least one of organic dyes, inorganic pigments, or pearlescent pigments.

6. A method for preparing nylon powder according to any one of claims 1-5, characterized in that, Includes the following steps: S1, high-viscosity nylon resin is mixed with some additives, extruded and granulated, and then frozen and crushed to obtain a high-viscosity component; S2, Dissolve the low-viscosity nylon resin and the antioxidant in the remaining additives in an organic solvent at 140-160℃, cool down, precipitate the resin component, mix with the remaining additives to obtain the low-viscosity component; S3, the high-viscosity component and the low-viscosity component are mixed to obtain the nylon powder.

7. The method for preparing nylon powder according to claim 6, characterized in that, In S1, the extrusion granulation temperature is 180-210℃; And / or, the freezing and crushing temperature is -140℃ to -190℃, and the particle size Dv50 of the high-viscosity component is 200-300μm; And / or, the mass ratio of the additive used in S1 to the additive used in S2 is 10:(1-3).

8. The method for preparing nylon powder according to claim 6, characterized in that, In S2, based on the total mass of high-viscosity nylon resin and low-viscosity nylon resin, the amount of organic solvent used is 2-6L of organic solvent per 1kg of resin. And / or, cool to 20-45℃; And / or, the organic solvent includes at least one of ethanol, N,N-dimethylformamide, and acetonitrile.

9. The method for preparing nylon powder according to any one of claims 6-8, characterized in that, The nylon powder satisfies at least one of the following characteristics: (1) The particle size range is 30 mesh to 120 mesh; (2) The relative viscosity η ranges from 1.65 to 1.85; (3) Yellowness index is less than 0.

10. A hydrogen storage cylinder liner, characterized in that, The nylon powder is prepared by rotational molding using nylon powder as described in any one of claims 1-5 or nylon powder prepared by the preparation method described in any one of claims 6-9 as raw material.

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