Nylon powder for hydrogen storage bottle inner container, preparation method of nylon powder, hydrogen storage bottle inner container and forming process of hydrogen storage bottle inner container

Abstract

The invention relates to the technical field of chemical engineering, and discloses nylon powder for a hydrogen storage bottle inner container and a preparation method thereof, the hydrogen storage bottle inner container and a forming process thereof.The method comprises the following steps that S1, nylon resin, an antioxidant and an organic solvent are mixed, heat preservation is conducted for 15 min to 120 min at the temperature of 140 DEG C to 160 DEG C, and a mixed solution A is formed; s2, the mixed solution A is cooled to 25-60 DEG C, nylon resin is separated out, and slurry B is formed; and S3, removing the organic solvent in the slurry B, and drying to obtain the product. According to the preparation method, the nylon resin and the antioxidant are jointly dissolved in the organic solvent at the specific temperature, the cooling and precipitation conditions are controlled, reconstruction and optimization of the particle size and morphology of the powder are effectively achieved, the obtained powder has the high sphericity degree, uniform particle size distribution and good fluidity, and the preparation method is suitable for industrial production. The melt consistency and the spreading performance in the rotational molding process are improved, the integrity and the air tightness of the hydrogen storage bottle liner structure are improved, and the problems that existing nylon powder is poor in particle size control, insufficient in fluidity and the like are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, and in particular to a nylon powder for a hydrogen storage bottle liner and a preparation method thereof, a hydrogen storage bottle liner and a molding process thereof. Background Art

[0002] Hydrogen is considered an ideal future automotive energy source due to its abundant resources, high energy density, environmental friendliness, and renewable nature. However, hydrogen is a colorless, odorless, flammable, and explosive gas at room temperature, posing significant safety risks in its storage and transportation. High-pressure gaseous hydrogen storage, by contrast, is currently the most common and convenient method, avoiding the cryogenic conditions required for liquid hydrogen storage and the approximately 1% daily volatility loss.

[0003] In hydrogen fuel cell vehicles, high-pressure hydrogen storage cylinders are core components used to store high-pressure hydrogen. These cylinders are primarily categorized as Type III with a fiber-wound aluminum liner and Type IV with a fiber-wound plastic liner. Type IV cylinders offer advantages over Type III in terms of operating pressure, weight, hydrogen storage density, and service life, and are a key development direction for the future.

[0004] High-pressure hydrogen storage cylinders are key components in hydrogen fuel cell vehicles, primarily used for the safe storage of high-pressure hydrogen. Currently, automotive high-pressure hydrogen storage cylinders are primarily divided into Type III, with a fiber-wound aluminum liner, and Type IV, with a fiber-wound plastic liner. Type IV cylinders offer superior performance in operating pressure, lightweight, hydrogen storage density, and service life, and are a key area of ​​future development.

[0005] In Type IV hydrogen storage bottles, the liner structure plays a crucial role in airtightness. Currently, hydrogen storage bottle liners are mostly injection molded, often requiring subsequent welding. This welded interface can compromise airtightness and structural strength, leading to a decrease in product yield. Furthermore, the metal inserts and plastic liner are sealed with adhesive, which is prone to failure under extreme operating conditions and has limited durability. Therefore, existing injection molding processes still have significant deficiencies in terms of airtightness and long-term reliability.

[0006] In contrast, rotational molding technology can achieve seamless structural molding, which helps improve the airtightness and stability of the hydrogen storage bottle liner and has greater development potential. Rotomolding usually uses nylon powder as the raw material. Currently, the commonly used powder production processes include solvent precipitation and cryogenic pulverization. Although they have certain process adaptability, the powder particle size is difficult to control and the particle size distribution is uneven. The powder particle morphology is poorly consistent, affecting the fluidity and density during the molding process. When adding additives such as plasticizers and nucleating agents, the powder's ability to control performance is insufficient, which can easily lead to a decrease in the stability of the rotational molding process, thereby affecting the structure and performance of the final product. Summary of the Invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the nylon powder particles used for the molding of hydrogen storage bottle liners in the prior art, such as poor morphology consistency, insufficient fluidity, and poor compatibility with additives such as plasticizers and nucleating agents, thereby providing a nylon powder for hydrogen storage bottle liners and a preparation method thereof, a hydrogen storage bottle liners and a molding process thereof.

[0008] According to an embodiment of the present invention, in a first aspect, a method for preparing nylon powder for a hydrogen storage bottle liner is provided, comprising the following steps:

[0009] S1. Mixing nylon resin, antioxidant and organic solvent, and keeping the mixture at 140°C to 160°C for 15 to 120 minutes to form a mixed solution A;

[0010] S2, the mixed solution A is cooled to 25°C to 60°C to precipitate nylon resin to form slurry B;

[0011] S3, removing the organic solvent from the slurry B, and drying to obtain.

[0012] In some optional embodiments, in step S2, after the insulation is completed, the temperature is lowered to 25°C to 60°C at a rate of 0.5°C / min to 3°C / min.

[0013] In some optional embodiments, in step S1, the nylon resin, antioxidant and organic solvent are mixed and stirred at a stirring speed of 50 rpm to 100 rpm, preferably 60 rpm to 80 rpm; for example, the stirring speed can be set to 50 rpm, 60 rpm, 70 rpm, 80 rpm or 100 rpm.

[0014] The present invention employs stirring, heating, and dissolving at 140°C to 160°C to ensure full and uniform dispersion of the nylon resin and antioxidant, improving the consistency and thermal stability of the powder composition. Controlling the stirring speed to 50-100 rpm, preferably 60-80 rpm, facilitates rapid dissolution of the nylon resin and antioxidant, prevents local overheating or uneven precipitation, and further optimizes the structural uniformity of the powder and the blending effect of the additives, thereby improving molding fluidity and product consistency in the subsequent rotational molding process and enhancing the density and airtightness of the liner.

[0015] By dissolving nylon resin and antioxidants in an organic solvent and precipitating a reconstructed powder under controlled temperature conditions, the present invention significantly improves the powder's particle morphology and particle size distribution, imparting greater sphericity and fluidity. This also enhances the powder's compatibility and dispersion uniformity with other functional additives, improving its spreadability and melt consistency during rotational molding. This effectively overcomes the problems of conventional nylon powders, such as uneven particle size, poor fluidity, and insufficient blending stability, significantly improving the molding quality and airtightness of hydrogen storage bottle liners.

[0016] In some optional embodiments, in step S1, the mass ratio of nylon resin to antioxidant is 99-99.9:0.1-1;

[0017] In some optional embodiments, the nylon resin includes one or more of nylon 612, nylon 1010, nylon 1012, nylon 11, and nylon 12;

[0018] In some optional embodiments, the antioxidant includes one or more of hindered amine antioxidants, cuprous iodide antioxidants, potassium iodide antioxidants, hindered phenol antioxidants, phosphite antioxidants, and inorganic phosphate antioxidants;

[0019] The hindered amine antioxidant includes one or both of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate and bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate;

[0020] The hindered phenol antioxidant includes one or both of butylated hydroxytoluene and antioxidant 1010;

[0021] The phosphite antioxidant includes one or two of tris(2,4-di-tert-butylphenyl)phosphite and bis(2,4-dicumylphenyl)pentaerythritol diphosphite;

[0022] The inorganic phosphate antioxidant includes one or more of calcium hypophosphite, sodium phosphite and calcium phosphite.

[0023] In some optional embodiments, the organic solvent includes one or more of ethanol, N,N-dimethylformamide, and acetonitrile. The amount of organic solvent used is determined to fully dissolve the nylon resin, and is generally used in an appropriate excess to ensure optimal dissolution. Preferably, the amount of organic solvent used is 4 to 6 liters per kilogram of nylon resin.

[0024] In some optional embodiments, in step S3, the dried material is mixed with other additives, wherein the other additives include one or more of a catalyst, a fluorescent whitening agent, a plasticizer, a nucleating agent, and a toughening agent.

[0025] The present invention introduces catalysts and fluorescent brighteners, which can not only increase the compatibility of nylon powder with other additives, but also improve the color stability and appearance purity of the finished powder, thereby further improving the molding quality and appearance consistency of the hydrogen storage bottle liner, and meeting the application requirements of high strength and high sealing.

[0026] The present invention introduces plasticizers, nucleating agents and toughening agents, which not only effectively improves the fluidity and molding stability of the powder during the rotational molding process, but also further improves the mechanical properties, dimensional stability and appearance quality of the liner product.

[0027] In some optional embodiments, the mass fraction of the catalyst is less than or equal to 1% based on the total mass of the nylon resin and the antioxidant;

[0028] In some optional embodiments, based on the total mass of the nylon resin and the antioxidant, the mass fraction of the fluorescent whitening agent is less than or equal to 0.1%;

[0029] In some optional embodiments, based on the total mass of the nylon resin and the antioxidant, the mass fraction of the plasticizer is less than or equal to 10%;

[0030] In some optional embodiments, based on the total mass of the nylon resin and the antioxidant, the mass fraction of the nucleating agent is less than or equal to 1%;

[0031] In some optional embodiments, based on the total mass of the nylon resin and the antioxidant, the mass fraction of the toughening agent is less than or equal to 5%.

[0032] In some optional embodiments, the catalyst includes one or more of phosphoric acid, phosphorous acid, hypophosphorous acid, sodium hypophosphite, and triphenyl phosphate.

[0033] In some optional embodiments, the fluorescent whitening agent includes one or more of stilbene-type, coumarin-type, pyrazoline-type, benzoxazine-type, and phthalimide-type fluorescent whitening agents.

[0034] Among them, the distyrene type fluorescent whitening agents include 4,4'-bis(2-sulfonatostyrene)biphenyl; the coumarin type fluorescent whitening agents include 7-diethylamino-4-methylcoumarin; the pyrazoline type fluorescent whitening agents include 3-(4-chlorophenyl)-1-(4-aminosulfonylphenyl)-2-pyrazoline; the benzoxazine type fluorescent whitening agents include 2,2-(4,4-distyrene)bisbenzoxazole; and the phthalimide type fluorescent whitening agents include N-methyl-4-methoxy-1,8-naphthalimide.

[0035] In some optional embodiments, the plasticizer includes one or more of a benzenesulfonamide derivative, an ester of hydroxybenzoic acid, an ester or ether of tetrahydrofurfuryl alcohol, an ester of citric acid or a hydroxymalonic acid.

[0036] Preferably, the plasticizer includes one or more of N-butylbenzenesulfonamide, propyl parahydroxybenzoate, tetrahydrofurfuryl acrylate, and acetyl tributyl citrate.

[0037] Plasticizers have good compatibility, thermal stability and flow control properties. The addition of plasticizers not only improves the fluidity and molding quality of nylon powder during the rotational molding process, but also improves the toughness, appearance and structural stability of the product, ensuring the safety and reliability of the hydrogen storage bottle liner under high-pressure conditions.

[0038] In some optional embodiments, the nucleating agent includes one or more of carboxylate, phosphate, and amide nucleating agents.

[0039] Preferably, the nucleating agent includes one or more of sodium benzoate, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, and N,N'-ethylenebisstearamide.

[0040] Nucleating agents can effectively increase the crystallization rate and crystallinity of the powder, thereby optimizing the molding efficiency and dimensional stability of the rotationally molded liner.

[0041] In some optional embodiments, the toughening agent includes one or more of maleic anhydride grafted elastomer, polyolefin elastomer, and acrylic core-shell particles;

[0042] Among them, maleic anhydride grafted elastomers include maleic anhydride grafted POE; acrylic core-shell particles refer to a type of toughened particles composed of a rigid shell (such as polymethyl methacrylate, PMMA) and a flexible core (such as polybutyl acrylate, PBA). When the material is impacted, the core-shell structured particles absorb energy by inducing silver streaks 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 particles has both good rigidity and toughness.

[0043] Introducing toughening agents into the nylon powder system not only effectively improves the impact toughness and crack resistance of the rotomolded hydrogen storage bottle liner, but also improves the material's stability in use under complex environments and enhances its overall structural safety and durability.

[0044] In some optional embodiments, in step S3, the mixture is dried to a moisture content of less than 1%, broken up and sieved, and then mixed with other additives through a mixer, wherein the other additives include one or more of a catalyst, a fluorescent whitening agent, a plasticizer, a nucleating agent, and a toughening agent.

[0045] Preferably, the mixing speed of the mixer is 800 rpm-1200 rpm, and the mixing time is 3 min-6 min; for example, the mixer mixes at a mixing speed of 800 rpm for 6 min, at a mixing speed of 1000 rpm for 5 min, or at a mixing speed of 1200 rpm for 6 min.

[0046] According to an embodiment of the present invention, in a second aspect, there is provided a nylon powder for a hydrogen storage bottle liner, which is prepared by any of the preparation methods described in the above technical solutions;

[0047] Preferably, the nylon powder satisfies at least one of the following characteristics:

[0048] The median particle size range is 53μm-302μm, which makes the powder particles evenly distributed in the mold, heats and melts quickly, and has high molding efficiency;

[0049] The bulk density is 401g / L-433.2g / L, which helps improve powder filling efficiency and cavity coverage density, ensuring the compact structure and high strength of the molded liner.

[0050] The nylon powder is generally spherical, with a yellowness index of less than 0 and a pure color, which effectively improves the thermal stability and appearance quality of the material and avoids discoloration, coking and other appearance defects during the molding process.

[0051] According to an embodiment of the present invention, in a third aspect, a molding process for a hydrogen storage bottle liner is provided, wherein the nylon powder as described in any of the above technical solutions is used as a raw material, and the hydrogen storage bottle liner is prepared by rotational molding.

[0052] In some optional embodiments, rotational molding comprises the following steps:

[0053] S1. Mold loading and closing

[0054] The nylon powder of the present invention is put into a rotational molding mold, and the feeding amount is controlled according to the designed wall thickness of the inner liner of the hydrogen storage bottle to ensure uniform charging, and then the mold is closed to ensure a firm seal.

[0055] S2, heating, melting and rotational molding

[0056] The loaded mold is placed in a rotational molding machine and heated until the nylon powder melts and reaches the optimal flow temperature. The heat is then maintained and the mold is controlled to rotate and revolve simultaneously along two axes in different directions, so that the nylon powder melts in the mold cavity and is evenly coated on the mold cavity wall, gradually forming a seamless hollow structure.

[0057] S3, cooling and solidification

[0058] After heating and insulation, the mold begins to cool down. Specifically, it first cools freely to below the cooling point of the nylon powder, and then performs air cooling to reduce the overall temperature of the mold to below 60°C, effectively controlling internal stress and preventing uneven wall thickness or deformation. During the cooling stage, the mold still keeps rotating to ensure uniform thickness and smooth surface of the liner.

[0059] S4, demoulding and taking out parts

[0060] After cooling is completed, stop the mold rotation, remove the heads and inserts at both ends of the mold in turn, and use water spray to assist in rapid cooling if necessary. Open the mold and take out the molded hydrogen storage bottle liner.

[0061] According to an embodiment of the present invention, in a fourth aspect, a hydrogen storage bottle liner is provided, which is prepared by a molding process as described in any of the above technical solutions.

[0062] The technical solution of the present invention has the following advantages:

[0063] The present invention effectively achieves the reconstruction and optimization of powder particle size and morphology by dissolving nylon resin and antioxidant in an organic solvent at a specific temperature and controlling the cooling and precipitation conditions. The obtained powder has high sphericity, uniform particle size distribution and good fluidity, which helps to improve the melt consistency and spreading performance during the rotational molding process, further improve the structural integrity and air tightness of the molded liner, and overcome the technical bottlenecks of existing nylon powder such as poor particle size control and insufficient fluidity.

[0064] Additional aspects and advantages of embodiments of the present invention will be described and shown in part in the following description, or will be explained through the practice of embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0066] Figure 1 1 is a comparison chart of the antioxidant results of the nylon powders of Example 1, Comparative Example 4, and Comparative Example 5 of the present invention (in the figure: the left figure (a) is the sample of Comparative Example 5, the middle figure (b) is the sample of Comparative Example 4, and the right figure (c) is the sample of Example 1);

[0067] Figure 2 2 are electron microscope images of nylon powders of Example 1 and Comparative Example 1 of the present invention (the left image (a) is the sample of Example 1, and the right image (b) is the sample of Comparative Example 1);

[0068] Figure 3 This is an electron microscope image of the nylon powder after mixing with the plasticizer in Example 5 of the present invention;

[0069] Figure 4 This is an image of the inner liner of a hydrogen storage bottle prepared in Example 5 of the present invention;

[0070] Figure 5 This is an image of the inner liner of the hydrogen storage bottle prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0071] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0072] In the following examples and comparative examples, if specific experimental steps or conditions are not specified, the conventional experimental steps or conditions described in the literature in the field can be used. The reagents or instruments used, if the manufacturer is not specified, are all commercially available conventional reagents.

[0073] The present invention is further described in detail below with reference to specific examples. These examples should not be construed as limiting the scope of protection claimed in the present invention.

[0074] The nylon resin used in the following examples and comparative examples was purchased from Wanhua Chemical Group Co., Ltd.; the plasticizer, antioxidant, catalyst, fluorescent brightener, nucleating agent, and toughening agent were purchased from Shandong Yinuokai Chemical Co., Ltd.

[0075] Example 1

[0076] This embodiment provides a method for preparing nylon powder for a hydrogen storage bottle liner, comprising the following steps:

[0077] S100, 10 kg of nylon 12, 30 g of antioxidant 168 and 30 g of antioxidant 1098 were added to the nylon crystallization kettle in sequence; then 50 L of ethanol was added as a solvent, the stirring device was turned on for stirring at a stirring speed of 60 rpm, and the temperature was started to rise.

[0078] S101. When the system temperature rises to 140°C, maintain the temperature at this temperature for 30 minutes to fully dissolve nylon 12 to form a mixed solution A.

[0079] S200. After the insulation is completed, the temperature is gradually lowered at a rate of 0.5°C / min until it drops to 50°C. During this process, the nylon resin gradually precipitates to form slurry B, which is then discharged.

[0080] S300, the discharged material is filtered to remove a large amount of ethanol in slurry B to obtain a powder filter cake with a moisture content of 45%, the filter cake is dried in a dryer to obtain a nylon powder with a moisture content of less than 1%, and the powder is broken up and sieved to obtain nylon powder;

[0081] The median particle size of the nylon powder is 58 μm, the particle morphology is regular spherical, the yellowness index is -1.7, and the color is pure; the nylon powder can be compounded with other additives such as catalysts, fluorescent brighteners, plasticizers, nucleating agents, toughening agents, etc., and used for rotational molding to obtain the inner liner of the hydrogen storage bottle.

[0082] Example 2

[0083] This embodiment provides a method for preparing nylon powder for a hydrogen storage bottle liner, comprising the following steps:

[0084] S100, 10 kg of nylon 1012, 30 g of antioxidant 168 and 30 g of antioxidant 1098 were added to the nylon crystallization kettle in sequence; then 50 L of ethanol was added as a solvent, the stirring device was turned on for stirring at a stirring speed of 60 rpm, and the temperature was started to rise.

[0085] S101. When the system temperature rises to 160°C, maintain the temperature at this temperature for 30 minutes to allow the nylon 1012 resin to fully dissolve to form a mixed solution A.

[0086] S200, after the insulation is completed, the temperature is gradually lowered at a rate of 0.5°C / min until it drops to 50°C, nylon resin is precipitated to form slurry B, and then the discharging operation is carried out.

[0087] S300, the discharged material is filtered to remove a large amount of ethanol in slurry B to obtain a powder filter cake with a moisture content of 40%, the filter cake is dried in a dryer to obtain a nylon powder with a moisture content of less than 1%, and the powder is broken up and sieved to obtain nylon powder;

[0088] The median particle size of the nylon powder is 54 μm, the particle morphology is regular spherical, the yellowness index is -1.8, and the color is pure; the nylon powder can be compounded with other additives such as catalysts, fluorescent brighteners, plasticizers, nucleating agents, toughening agents, etc., and used for rotational molding to obtain the inner liner of the hydrogen storage bottle.

[0089] Example 3

[0090] This embodiment provides a method for preparing nylon powder for a hydrogen storage bottle liner, comprising the following steps:

[0091] S100, 10 kg of nylon 11 resin, 30 g of antioxidant 168 and 30 g of antioxidant 1098 are added to the nylon crystallization kettle in sequence; then 50 L of ethanol is added as a solvent; the stirring device is turned on for stirring at a stirring speed of 60 rpm, and the temperature is started to rise.

[0092] S101. When the system temperature rises to 160° C., the temperature is maintained constant for 30 minutes to ensure that the nylon 11 resin is completely dissolved to form a mixed solution A.

[0093] S200, after the insulation is completed, the temperature is gradually lowered at a rate of 0.5°C / min until it drops to 50°C, nylon resin is precipitated to form slurry B, and then the discharging operation is carried out.

[0094] S300, the discharged material is filtered to remove a large amount of ethanol in slurry B to obtain a powder filter cake with a moisture content of 60%, and the filter cake is dried in a dryer to obtain a nylon powder with a moisture content of less than 1%. The powder is broken up and sieved to obtain nylon powder.

[0095] The median particle size of the nylon powder is 59 μm, the particle morphology is regular spherical, the yellowness index is -1.7, and the color is pure; the nylon powder can be compounded with other additives such as catalysts, fluorescent brighteners, plasticizers, nucleating agents, toughening agents, etc., and used for rotational molding to obtain the inner liner of the hydrogen storage bottle.

[0096] Example 4

[0097] This embodiment provides a nylon powder for a hydrogen storage bottle liner and a method for preparing the hydrogen storage bottle liner, comprising the following steps:

[0098] S100, add 10 kg of nylon 12 resin and 30 g of antioxidant H10 to a nylon crystallization kettle; then add 50 L of ethanol as a solvent, turn on the stirring device for stirring at a stirring speed of 60 rpm, and start heating.

[0099] S101. When the system temperature rises to 140° C., maintain the temperature at this temperature for 30 minutes to ensure that the nylon 12 resin is fully dissolved to form a mixed solution A.

[0100] S200, after the insulation is completed, the temperature is gradually lowered at a rate of 0.5°C / min until it drops to 50°C, the nylon resin is precipitated to form slurry B, and then the material is discharged.

[0101] S300, the discharged material is filtered to remove a large amount of ethanol in slurry B to obtain a powder filter cake with a moisture content of 45%, the filter cake is dried in a dryer to obtain a nylon powder with a moisture content of less than 1%, and the powder is broken up and sieved to obtain nylon powder A;

[0102] The median particle size of the nylon powder is 53 μm, the particle morphology is regular spherical, the yellowness index is -2, and the color is pure.

[0103] S400, on the basis of the above nylon powder A, further adding 100 g of phosphoric acid as a catalyst by physical mixing in a mixer, wherein the mixing speed of the mixer is 1000 rpm and the mixing time is 4 minutes to obtain nylon powder B;

[0104] S500, using nylon powder B in a rotational molding process to prepare a hydrogen storage bottle liner at a molding temperature of 246°C; specifically, putting nylon powder B into the mold cavity, after the mold is closed, heating to 246°C and then starting to keep warm, and molding along two mutually perpendicular axes of revolution and rotation. After molding is completed, cooling and solidification are carried out, and demolding is carried out to obtain the hydrogen storage bottle liner.

[0105] Example 5

[0106] This embodiment provides a nylon powder for a hydrogen storage bottle liner and a method for preparing the hydrogen storage bottle liner, comprising the following steps:

[0107] S100, 10 kg of nylon 12 resin, 30 g of antioxidant 168 and 30 g of antioxidant 1098 were added to the nylon crystallization kettle in sequence; then 50 L of ethanol was added as a solvent, the stirring device was turned on, the stirring speed was set to 60 rpm, and the temperature was started.

[0108] S101. When the system temperature rises to 140° C., maintain the temperature at this temperature for 30 minutes to ensure that the nylon 12 resin is fully dissolved to form a mixed solution A.

[0109] S200, after the heat preservation is completed, the temperature is gradually lowered at a rate of 0.5°C / min until it drops to 50°C, the nylon resin is precipitated to form slurry B, and then the material is discharged.

[0110] S300, the discharged material is filtered to remove a large amount of ethanol in slurry B to obtain a powder filter cake with a moisture content of 45%, the filter cake is dried in a dryer to obtain a nylon powder with a moisture content of less than 1%, and the powder is broken up and sieved to obtain nylon powder A;

[0111] The median particle size of the nylon powder is about 58 μm, the particles are regular spherical, the yellowness index is 1.7, and the color is pure.

[0112] S400, on the basis of the above nylon powder A, further adding 804.8 g of plasticizer N-butylbenzenesulfonamide and 100.6 g of nucleating agent bis(2,4-dicumylphenyl)pentaerythritol-diphosphite by physical mixing in a mixer, wherein the mixing speed of the mixer is 1000 rpm and the mixing time is 4 min to obtain nylon powder B;

[0113] S500, using nylon powder B in a rotational molding process to prepare a hydrogen storage bottle liner at a molding temperature of 235°C; specifically, putting nylon powder B into the mold cavity, after the mold is closed, heating to 235°C and then starting to keep warm, and molding along two mutually perpendicular axes of revolution and rotation. After molding is completed, cooling and solidification are carried out, and demolding is carried out to obtain the hydrogen storage bottle liner.

[0114] Example 6

[0115] The only difference between this embodiment and embodiment 5 is that in step S400, a fluorescent whitening agent is further added, as follows:

[0116] S400. On the basis of nylon powder A, 804.8 g of plasticizer N-butylbenzenesulfonamide, 100.6 g of nucleating agent bis(2,4-dicumylphenyl)pentaerythritol diphosphite, and 100.6 g of 2-(4,4-distyryl)bisbenzoxazole fluorescent whitening agent were further added by physical mixing in a mixer, wherein the mixing speed of the mixer was 1000 rpm and the mixing time was 4 min to obtain nylon powder B.

[0117] S500, using nylon powder B in a rotational molding process to prepare a hydrogen storage bottle liner at a molding temperature of 238°C; specifically, putting nylon powder B into the mold cavity, after the mold is closed, heating to 238°C and then starting to keep warm, and molding along two mutually perpendicular axes of revolution and rotation. After molding is completed, cooling and solidification are carried out, and demolding is carried out to obtain the hydrogen storage bottle liner.

[0118] Example 7

[0119] The only difference between this embodiment and embodiment 5 is that in step S400, a toughening agent is further added, as follows:

[0120] S400. On the basis of nylon powder A, 804.8 g of plasticizer N-butylbenzenesulfonamide, 100.6 g of nucleating agent bis(2,4-dicumylphenyl)pentaerythritol-diphosphite, and 301.8 g of toughening agent were added by physical mixing in a mixer, wherein the toughening agent was a core-shell structured polymer particle, the shell inside the core-shell structure particle was formed by polymethyl methacrylate (PMMA), and the shell layer inside the particle was formed by polybutyl acrylate (PBA), so as to improve the toughness of the liner, and obtain nylon powder B.

[0121] S500, using nylon powder B in a rotational molding process to prepare a hydrogen storage bottle liner at a molding temperature of 240°C; specifically, putting nylon powder B into the mold cavity, after the mold is closed, heating to 240°C and then starting to keep warm, and molding along two mutually perpendicular axes of revolution and rotation. After molding is completed, cooling and solidification are carried out, and demolding is carried out to obtain the hydrogen storage bottle liner.

[0122] Example 8

[0123] The difference between this embodiment and embodiment 1 is that the cooling speed is different. That is, in step S200 of this embodiment, the temperature is gradually cooled at a rate of 2° C. / min until it drops to 50° C.

[0124] Example 9

[0125] The difference between this embodiment and embodiment 1 is that the cooling speed is different. That is, in step S200 of this embodiment, the temperature is gradually cooled at a rate of 3° C. / min until it drops to 50° C.

[0126] Example 10

[0127] This embodiment provides a method for preparing a hydrogen storage bottle liner, comprising the following steps:

[0128] S100, 9.99 kg of nylon 612, 5 g of antioxidant 168 and 5 g of antioxidant 1098 were added to the nylon crystallization kettle in sequence; then 39.96 L of N,N-dimethylformamide was added as a solvent, the stirring device was turned on, the stirring speed was set to 50 rpm, and the temperature was started.

[0129] S101. When the system temperature rises to 150° C., maintain the temperature at this temperature for 120 minutes to ensure that the nylon 612 resin is fully dissolved to form a mixed solution A.

[0130] S200, after the heat preservation is completed, the temperature is gradually lowered at a rate of 0.5°C / min until it drops to 25°C, the nylon resin is precipitated to form slurry B, and then the material is discharged.

[0131] S300, the discharged material is filtered to remove a large amount of ethanol in slurry B to obtain a powder filter cake with a moisture content of 45%, and the filter cake is dried in a dryer to obtain a nylon powder with a moisture content of <1%. The powder is broken up and sieved to obtain a nylon powder with a pure color.

[0132] S400, using nylon powder in a rotational molding process, specifically, putting the nylon powder into a rotational molding mold, placing the loaded rotational molding mold in a rotational molding machine, heating it to 235° C. to mold and prepare the hydrogen storage bottle liner.

[0133] Example 11

[0134] This embodiment provides a nylon powder for a hydrogen storage bottle liner and a method for preparing the hydrogen storage bottle liner, comprising the following steps:

[0135] S100, adding 9.9 kg of nylon 12, 50 g of antioxidant 168, and 50 g of antioxidant 1098 to a nylon crystallization kettle; then adding 59.4 L of acetonitrile as a solvent, turning on the stirring device, setting the stirring speed to 100 rpm, and starting to heat;

[0136] S101. When the system temperature rises to 160°C, maintain the temperature at this temperature for 15 minutes to ensure that the nylon 12 resin is fully dissolved to form a mixed solution A.

[0137] S200, after the heat preservation is completed, the temperature is gradually lowered at a rate of 0.5°C / min until it drops to 60°C, the nylon resin is precipitated to form slurry B, and then the material is discharged.

[0138] S300, the discharged material is filtered to remove a large amount of ethanol in slurry B to obtain a powder filter cake with a moisture content of 45%, and the filter cake is dried in a dryer to obtain a nylon powder with a moisture content of less than 1%. The powder is broken up and sieved to obtain nylon powder A, which has a pure color.

[0139] S400. On the basis of the above-mentioned nylon powder A, 1000 g of N-butylbenzenesulfonamide as a plasticizer, 100 g of bis(2,4-dicumylphenyl)pentaerythritol-diphosphite as a nucleating agent, and 500 g of a toughening agent (the toughening agent is a core-shell polymer particle, the shell inside the particle is composed of polymethyl methacrylate (PMMA), and the core layer outside the particle is composed of polybutyl acrylate (PBA)) are further added by physical mixing in a mixer, based on the total mass of nylon powder A, wherein the mixing speed of the mixer is 800 rpm and the mixing time is 6 min to obtain nylon powder B;

[0140] S500, using nylon powder B in a rotational molding process. Specifically, the nylon powder B is put into a rotational molding mold, the loaded rotational molding mold is placed in a rotational molding machine, and heated to 235° C. to form a hydrogen storage bottle liner.

[0141] Comparative Example 1

[0142] This comparative example provides a method for preparing nylon powder and a hydrogen storage bottle liner, which specifically includes the following steps:

[0143] S100, 10 kg of nylon 12, 30 g of antioxidant 168, 30 g of antioxidant 1098, and 300 g of plasticizer N-butylbenzenesulfonamide are sequentially added into a screw extruder, and melt-mixed and granulated at 190° C. to obtain nylon pellets.

[0144] S200, placing the obtained pellets in a liquid nitrogen environment for cryogenic treatment, the temperature of which drops to -170°C, and then performing a crushing operation to obtain primary nylon powder.

[0145] S300, filtering the obtained primary nylon powder through multiple layers of sieves in sequence, and further grinding it to ensure uniform particle size.

[0146] S400, placing the ground primary nylon powder in an oven at 100° C. and drying it for 2 hours to obtain a nylon powder suitable for rotational molding.

[0147] S500: Use the above nylon powder in a rotational molding process to prepare a hydrogen storage bottle liner at a molding temperature of 235°C.

[0148] Comparative Example 2

[0149] This comparative example provides a method for preparing a hydrogen storage bottle liner, comprising the following steps:

[0150] S100, taking 10 kg of nylon 12, placing it in a liquid nitrogen environment for cryogenic treatment, the temperature dropped to -170 ° C, and then performing a crushing operation to obtain primary nylon powder.

[0151] S200, placing the obtained primary nylon powder in an oven at 100° C. and drying for 2 hours to obtain nylon powder.

[0152] S300, using the dried nylon powder in a rotational molding process at a molding temperature of 240° C. to prepare a hydrogen storage bottle liner.

[0153] Comparative Example 3

[0154] This comparative example provides a method for preparing nylon powder and a hydrogen storage bottle liner, which specifically includes the following steps:

[0155] S100, 10 kg of nylon 12, 30 g of antioxidant 168, and 30 g of antioxidant 1098 are sequentially added into a screw extruder, and melt-mixed and granulated at 190° C. to obtain nylon pellets.

[0156] S200, placing the obtained pellets in a liquid nitrogen environment for cryogenic treatment, the temperature of which drops to -170°C, and then performing a crushing operation to obtain primary nylon powder.

[0157] S300, filtering the obtained primary nylon powder through multiple layers of sieves in sequence, and further grinding it to ensure uniform particle size.

[0158] S400, placing the ground primary nylon powder in an oven at 100° C. and drying it for 2 hours to obtain a nylon powder suitable for rotational molding.

[0159] S500: Use the above nylon powder in a rotational molding process to prepare a hydrogen storage bottle liner at a molding temperature of 235°C.

[0160] Comparative Example 4

[0161] The only difference between this comparative example and Example 1 is that the timing of adding the antioxidant is different, that is, in this comparative example, the antioxidant is added to the slurry B in step S200.

[0162] Comparative Example 5

[0163] The only difference between this comparative example and Example 1 is that no antioxidant is added.

[0164] Test Example 1

[0165] This test example tested the median particle size, bulk density, melt index and yellowness index of the nylon powders of Examples 1 to 11 and Comparative Examples 1 to 3;

[0166] Among them, the median particle size of nylon powder was tested by laser particle size analyzer;

[0167] The bulk density is calculated by pouring the powder to be tested into a 100 mL measuring cylinder in a natural stacking state without vibration, recording the mass of powder required to fill the container, and then calculating the bulk density of the powder per unit volume (unit: g / cm 3 );

[0168] Melt index: The mass of a polymer in a molten state extruded from a standard die within 10 minutes is measured under the test parameters of a temperature of 190°C and a load of 2160 g. The unit is g / 10min (grams per 10 minutes).

[0169] The yellowness index is tested according to the standard ASTM E3132015.

[0170] The test results are shown in Table 1 below:

[0171] Table 1:

[0172] Group Median particle size (μm) Bulk density (g / L) Melt index (g / 10min) Yellowness Index Example 1 58 422.3 18.632 -1.7 Example 2 54 417.8 5.632 -1.8 Example 3 59 423.6 6.012 -1.7 Example 4 53 411.2 18.326 -2 Example 5 58 419.6 18.411 -1.7 Example 6 58 422.1 17.988 -2.2 Example 7 59 433.2 18.645 -1.6 Example 8 126 411.2 19.865 -1.7 Example 9 302 401 17.655 -1.6 Example 10 57 420.1 1.332 -1.5 Example 11 58 422.2 17.665 -1.6 Comparative Example 1 546 401.2 18.961 -2.0 Comparative Example 2 568 403.2 17.031 -1.9 Comparative Example 3 693 406.5 17.102 -1.9

[0173] Examples 1 to 11 of the present invention all employ an organic solvent as the dispersion medium, using a dissolution-precipitation process involving nylon resin and an antioxidant to prepare nylon powder. This method effectively controls powder particle size, morphology, and bulk properties under mild process conditions. Measured results indicate that the resulting nylon powders have a median particle size ranging from 53 to 302 μm and a bulk density of 401 to 433.2 g / L. The powders exhibit excellent overall performance and are suitable for subsequent molding processes or modified applications.

[0174] Among them, the melt index of Example 2, Example 3 and Example 10 is relatively low because the selected matrices are nylon 1012, nylon 11 and nylon 612, respectively. However, their particle size and bulk density are still within the appropriate range, indicating that the method of the present invention has good adaptability to different types of nylon systems.

[0175] In contrast, Comparative Examples 1 to 3 did not use the dissolution-precipitation powder making technology, but instead used screw extrusion granulation, cryogenic crushing and simple screening processes, resulting in poor performance of the obtained powders in terms of particle size, bulk density and morphology control. Specifically, the median particle size of the nylon powder in Comparative Example 1 was 546 μm, and the bulk density was only 401.2 g / L. The particle size was large and the morphology was irregular. Problems such as uneven melting and insufficient product density were prone to occur during rotational molding. The median particle size of the nylon powder in Comparative Example 2 was further increased to 568 μm, and the bulk density was only 403.2 g / L, with poor processing stability. The median particle size of the nylon powder in Comparative Example 3 was as high as 693 μm, the bulk density was low and the powder distribution was extremely uneven, seriously affecting the rotational molding effect.

[0176] By comparing Example 1, Example 8 and Example 9, it can be found that the rapid cooling treatment significantly affects the structural properties of the powder:

[0177] On the one hand, rapid cooling leads to uneven distribution of powder particle size, which easily causes agglomeration between particles, thereby causing a decrease in the bulk density of the powder; this indicates that the powder structure is relatively loose and lacks density. In practical applications, such as the manufacturing process of the liner, internal defects may occur, reducing the structural integrity and performance stability of the product.

[0178] On the other hand, rapid cooling can also lead to incomplete formation of the particle crystal structure. If not optimized and controlled, this can easily lead to a decrease in the thermal stability of the powder and deterioration in the uniformity of the particle morphology, further affecting the material's processability and reliability. Rapid cooling can also cause incomplete formation of the particle crystal structure. If not optimized and controlled, this can lead to problems such as decreased thermal stability or morphological uniformity of the powder.

[0179] In contrast, the slow-descent process employed in Example 1 provides ample time and energy for crystal growth during particle precipitation, helping the particles form a regular crystal structure and yielding a spherical powder with uniform particle size and regular morphology. This type of powder exhibits stable melting behavior and good adaptability during subsequent processing, making it particularly suitable for applications such as rotational molding, which require high powder morphology consistency and melt uniformity.

[0180] Test Example 2

[0181] This test example evaluated the antioxidant properties of the nylon powders prepared in Example 1, Comparative Example 4, and Comparative Example 5. The specific method was as follows: Each nylon powder prepared in Example 1, Comparative Example 4, and Comparative Example 5 was heated to melt in an oven at 235°C, then removed and allowed to cool naturally to solidify. The surface color change of the sample was observed and recorded as a visual indicator of the degree of oxidation.

[0182] The results are as follows Figure 1As shown, the left picture (a) is the sample of comparative example 5, the middle picture (b) is the sample of comparative example 4, and the right picture (c) is the sample of embodiment 1. Figure 1 It can be clearly observed that the color of the sample in Example 1 is well maintained after melting and solidification, with no obvious discoloration, indicating that it has excellent antioxidant stability; in contrast, the samples in Comparative Examples 4 and 5 all show varying degrees of yellowing or browning under high temperature conditions, exhibiting poor thermal oxidation stability.

[0183] The main reason for the above differences is the different ways of introducing the antioxidant. Example 1 adopts the method of dissolving and precipitating the antioxidant from the nylon resin, so that the antioxidant can be more evenly and fully dispersed inside the powder, thereby effectively improving the antioxidant ability of the material during the melt processing process.

[0184] Comparative Example 4, however, adds an antioxidant to slurry B in step S200, a high-temperature physical blending method. This can easily lead to thermal degradation of the antioxidant at high temperatures and uneven distribution, thereby reducing antioxidant stability. Comparative Example 5, in which no antioxidant is added at all, lacks the necessary antioxidant protection during high-temperature processing and exhibits the worst thermal-oxidative stability.

[0185] The present invention introduces an antioxidant during the dissolution-precipitation process, thereby achieving deep dispersion of the antioxidant within the powder and maintaining thermal stability, thereby effectively improving the antioxidant capacity of the material during melt processing and use.

[0186] Test Example 3

[0187] In this test example, the morphology of nylon powder samples was characterized using an optical microscope to analyze the effects of different preparation processes on the powder particle morphology. The optical microscope used was a Zeiss polarizing microscope Axio Imager 2 from Beijing Presai Instrument Co., Ltd.

[0188] Specific as Figure 2 As shown, the left figure (a) corresponds to the nylon powder prepared in Example 1, and the right figure (b) corresponds to the nylon powder prepared in Example 1. Figure 2 It can be seen that the nylon powder particles of Example 1 are regular spherical, with a smooth particle surface, clear boundaries, and uniform particle size distribution, showing excellent morphological consistency; while the powder particles prepared in Comparative Example 1 are obviously irregular, mainly polygonal or irregular fragments, with rough particle edges, discrete distribution, and easy agglomeration, indicating that the traditional low-temperature pulverization process is difficult to ensure the controllability of the powder morphology.

[0189] Furthermore, if Figure 3The following is an electron microscope image of the nylon powder in Example 5 after physical mixing with a plasticizer. As can be seen, the powder particles retain a relatively regular spherical structure, with clear particle boundaries and a uniform particle size distribution. No significant agglomeration is observed. This indicates that the introduction of the plasticizer did not disrupt the original particle morphology, and the powder maintains good structural stability.

[0190] In addition, in order to evaluate the effect of powder morphology on the quality of rotational molding, the present invention further compares the actual molding effects of the hydrogen storage bottle liner prepared in Example 5 and Comparative Example 1, and the results are as follows: Figure 4 and Figure 5 As shown, Figure 4 This is a photo of the inner liner of the hydrogen storage bottle prepared in Example 5. The overall structure is regular, the color is uniform, and the surface is smooth, showing good molding consistency; Figure 5 This is a photo of the inner liner made in Comparative Example 1. Although the structure of the molded part is basically complete, there are obvious uneven areas on its outer surface, indicating that the irregular particle morphology is not conducive to melt flow, which in turn affects the molding quality and appearance uniformity.

[0191] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing nylon powder for hydrogen storage bottle liner, characterized in that: The following steps are involved: S1. Mixing nylon resin, antioxidant and organic solvent, and keeping the mixture at 140°C to 160°C for 15 to 120 minutes to form a mixed solution A; S2. Cooling the mixed solution A to 25°C to 60°C to precipitate the nylon resin to form slurry B; S3, removing the organic solvent from the slurry B, and drying to obtain.

2. The method for preparing nylon powder for hydrogen storage bottle liner according to claim 1, characterized in that: In step S2, after the insulation is completed, the temperature is lowered to 25°C to 60°C at a rate of 0.5°C / min to 3°C / min.

3. The method for preparing nylon powder for hydrogen storage bottle liner according to claim 1 or 2, characterized in that: In the step S1, the nylon resin, the antioxidant and the organic solvent are mixed and stirred at a stirring speed of 50 rpm to 100 rpm, preferably 60 rpm to 80 rpm.

4. A method for preparing nylon powder for a hydrogen storage bottle liner according to any one of claims 1 to 3, characterized in that: In step S1, the mass ratio of nylon resin to antioxidant is 99-99.9:0.1-1; Preferably, the nylon resin includes one or more of nylon 612, nylon 1010, nylon 1012, nylon 11, and nylon 12; And / or, the antioxidant includes one or more of hindered amine antioxidants, cuprous iodide antioxidants, potassium iodide antioxidants, hindered phenol antioxidants, phosphite antioxidants, and inorganic phosphate antioxidants; And / or, the organic solvent includes one or more of ethanol, N,N-dimethylformamide, and acetonitrile.

5. A method for preparing nylon powder for a hydrogen storage bottle liner according to any one of claims 1 to 4, characterized in that: In step S3, the dried material is mixed with other additives, wherein the other additives include one or more of a catalyst, a fluorescent whitening agent, a plasticizer, a nucleating agent, and a toughening agent.

6. The method for preparing nylon powder for hydrogen storage bottle liner according to claim 5, characterized in that: The mass fraction of the catalyst is less than or equal to 1% based on the total mass of the nylon resin and the antioxidant; And / or, based on the total mass of the nylon resin and the antioxidant, the mass fraction of the fluorescent whitening agent is less than or equal to 0.1%; And / or, based on the total mass of the nylon resin and the antioxidant, the mass fraction of the plasticizer is less than or equal to 10%; And / or, based on the total mass of the nylon resin and the antioxidant, the mass fraction of the nucleating agent is less than or equal to 1%; And / or, based on the total mass of the nylon resin and the antioxidant, the mass fraction of the toughening agent is less than or equal to 5%.

7. The method for preparing nylon powder for hydrogen storage bottle liner according to claim 5 or 6, characterized in that: The catalyst includes one or more of phosphoric acid, phosphorous acid, hypophosphorous acid, sodium hypophosphite, and triphenyl phosphate; And / or, the fluorescent whitening agent includes one or more of stilbene type, coumarin type, pyrazoline type, benzoxazine type, and phthalimide type fluorescent whitening agents; and / or, the plasticizer comprises one or more esters of diacids; and / or, the nucleating agent comprises one or more of carboxylate, phosphate, and amide nucleating agents; And / or, the toughening agent includes one or more of maleic anhydride grafted elastomer, polyolefin elastomer, and acrylic core-shell particles.

8. A nylon powder for hydrogen storage bottle liner, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7 above; Preferably, the nylon powder satisfies at least one of the following characteristics: The median particle size ranges from 53 μm to 302 μm; Bulk density is 401g / L~433.2g / L; The yellowness index is less than 0.

9. A forming process for a hydrogen storage bottle liner, characterized in that: The nylon powder as claimed in claim 8 is used as a raw material to prepare the inner liner of the hydrogen storage bottle by rotational molding.

10. A hydrogen storage bottle liner, characterized in that: The molding process as claimed in claim 9 is used for preparation.

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