Polyethylene powder for high-pressure hydrogen storage cylinder lining and preparation method thereof

Abstract

This invention belongs to the field of polymer materials technology, specifically relating to polyethylene rotational molding resin powder for high-pressure hydrogen storage cylinder linings and its preparation method. The polyethylene rotational molding resin powder for high-pressure hydrogen storage cylinder linings of this invention is composed of the following raw materials: polyethylene, POE, polyvinylidene chloride, antioxidant, acid scavenger, lubricant, and modified boron nitride; the polyethylene rotational molding resin powder has a melt flow rate of 4.8–5.7 g / 10 min and a density of 0.932–0.938 g / cm³. 3 The bulk density is 0.39–0.45 g / cm³. 3 The flow time is 18–23 s / 100g, the particle size distribution is 40–60 mesh with 50%–65% of the particles, and the hydrogen permeability coefficient is 0.65–0.85 mol·m / (m 2 ·s·Pa)×10 ‑15 It has high bulk density, short dry flow time, reasonable particle size distribution, and low hydrogen permeability coefficient.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to polyethylene rotational molding resin powder for high-pressure hydrogen storage cylinder linings and its preparation method. Background Technology

[0002] When exploring the widespread application of hydrogen energy, a future energy star, the importance of rotational molding—a particularly crucial technological step—is becoming increasingly apparent. Given the critical role of hydrogen storage in the commercialization of hydrogen energy systems, how to efficiently and safely store this high-energy-density clean energy has become a focus of attention for both research and industry. Among these efforts, rotational molding technology, with its unique advantages, plays a central role in the manufacture of high-pressure hydrogen storage cylinders.

[0003] The reason rotational molding is an indispensable step lies in its stringent requirements for raw material processing: ensuring that resin particles are uniformly heated and reach a molten state in a very short time. Precise execution of this step is the cornerstone for manufacturing high-quality hydrogen storage containers. To achieve this, the raw resin particles are typically finely ground into powder to better promote uniform heat transfer and absorption. This fine powder is then placed into a mold and gradually shaped into the inner liner of the hydrogen storage container according to the design requirements through the rotational molding process.

[0004] Of particular note is the decisive role played by the powder quality in this process. It directly affects not only the uniformity of the final product's wall thickness but also the container's porosity control, aesthetic appearance, and, crucially, hydrogen permeability. Hydrogen permeability is a key indicator for evaluating the sealing performance and long-term safety of hydrogen storage containers; excessively high or low permeability can threaten the overall efficiency and safety of the hydrogen energy system. Therefore, optimizing powder quality to ensure perfect integration during rotational molding, forming a robust and dense inner liner structure, is of immeasurable value in improving the overall performance of hydrogen storage containers.

[0005] Chinese patent application number 2023113915347 discloses a polyethylene rotational molding resin for high-pressure hydrogen storage cylinder linings and its preparation method. The raw material components include: polyethylene resin, polyethylene powder, ethylene-vinyl acetate copolymer, antioxidant, acid scavenger, lubricant, and modified aluminum nitride. The preparation method involves processes such as additive activation, mixing, granulation, and grinding to produce the polyethylene rotational molding resin for high-pressure hydrogen storage cylinder linings. High-pressure hydrogen storage tank liners prepared using this resin exhibit excellent hydrogen permeation barrier properties, sufficient mechanical strength, and environmental stress resistance. This patented formula is relatively complex and costly. Although it has a low hydrogen permeability coefficient, its thermal stability is slightly lacking, and it requires a high-precision rotational molding process.

[0006] In conclusion, the rapid and uniform heating and melting of raw materials during rotational molding, along with the stringent control of powder quality, presents not only technical challenges but also represents a crucial step in advancing the hydrogen energy industry. It directly impacts the safety, efficiency, and economic viability of hydrogen storage technology and is an indispensable component for realizing the large-scale application of hydrogen energy. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a polyethylene rotational molding resin powder for high-pressure hydrogen storage cylinder liners, which has high bulk density, short dry time, and reasonable particle size distribution, making it suitable for rotational molding processes to prepare hydrogen storage cylinder liners, and the product has a low hydrogen permeability coefficient.

[0008] The present invention also provides a preparation method that is simple, easy to implement, and suitable for large-scale production.

[0009] The polyethylene rotational molding resin powder for the lining of the high-pressure hydrogen storage cylinder described in this invention is composed of the following raw materials in parts by weight:

[0010]

[0011] The polyethylene rotational molding resin powder has a melt flow rate of 4.8–5.7 g / 10 min and a density of 0.932–0.938 g / cm³. 3 The bulk density is 0.39–0.45 g / cm³. 3 The flow time is 18–23 s / 100g, the particle size distribution is 40–60 mesh with 50%–65% of the particles, and the hydrogen permeability coefficient is 0.65–0.85 mol·m / (m 2 ·s·Pa)×10 -15 .

[0012] The polyethylene used employs a metallocene catalyst system, with 1-hexene as the comonomer. The melt flow rate is 3–10 g / 10 min, preferably 5.5–8.0 g / 10 min, and the density is 0.932–0.952 g / cm³. 3 .

[0013] The amount of POE added is 1 to 5 parts, preferably 2 to 4 parts.

[0014] The mass ratio of polyvinylidene chloride to POE is (3-0.5):1.

[0015] The antioxidant is a compound antioxidant of hindered phenolic antioxidant and phosphite antioxidant, with a mass ratio of 1:(1-2).

[0016] The hindered phenolic antioxidant is 1010: pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid].

[0017] The phosphite antioxidant is 168: tris(2,4-di-tert-butylphenyl) phosphite.

[0018] The acid absorbent is either calcium stearate or zinc stearate, and the amount added is 0.05 to 0.1 parts, preferably 0.05 parts.

[0019] The lubricant is a cyclic polyester oligomer, preferably CBT100, which has good lubricating properties.

[0020] The modified boron nitride is prepared by mixing dried boron nitride and coupling agent in a mass ratio of 1:(8-10), and then ultrasonically stirring in anhydrous ethanol to obtain an ethanol dispersion system of modified boron nitride. The coupling agent is a silane coupling agent. The amount of anhydrous ethanol is not specifically limited, but is used for dilution and will evaporate during high-speed stirring and mixing later.

[0021] The preparation method of the polyethylene rotational molding resin powder for the lining of the high-pressure hydrogen storage cylinder according to the present invention comprises the following steps:

[0022] (1) Mix the ethanol dispersion system of polyethylene, POE, polyvinylidene chloride, antioxidant, acid absorbent, lubricant and modified boron nitride.

[0023] (2) Add the uniformly mixed material to a co-rotating twin-screw extruder for melt mixing and extrusion granulation;

[0024] (3) Grind the granulated resin into powder to obtain polyethylene rotational molding resin powder for high-pressure hydrogen storage cylinder lining.

[0025] The specific steps of stirring and mixing in step (1) are as follows: stir for 1 to 2 minutes at room temperature and a speed of 1000 to 1200 r / min, then heat to 60℃ and stir for another 3 to 4 minutes.

[0026] The extrusion granulation temperature in step (2) is 190-230℃, the main extruder speed is 150-230r / min, and the feeding speed is 30-50r / min; in step (3), the polyethylene rotational molding resin powder used for the lining of the high-pressure hydrogen storage cylinder contains 65-90% powder between 40-100 mesh and 50-65% powder between 40-60 mesh.

[0027] Polyethylene resin does not produce adverse chemical reactions or adsorption effects on hydrogen, and can avoid possible hydrogen embrittlement.

[0028] The lining material of high-pressure hydrogen storage cylinders requires resins with excellent hydrogen permeation barrier properties, effectively preventing hydrogen from seeping out of the container. This helps maintain the stability and safe storage of hydrogen in the cylinder. The polyvinylidene chloride (PVDC) described in this invention possesses a certain degree of gas barrier properties. Furthermore, PVDC, POE, and polyethylene matrix resins share certain similarities in chemical properties and structure, exhibiting certain interactions. They can form a homogeneous mixture without phase separation or significant incompatibility, meaning that PVDC can be well mixed with POE and polyethylene matrix resins. In addition, PVDC, POE, and polyethylene matrix resins can form a "ternary composite" structure, which provides good hydrogen barrier properties. However, the mixing ratio of PVDC to POE must be controlled within a suitable range; otherwise, PVDC cannot be uniformly dispersed in POE and polyethylene matrix resins, thus reducing the hydrogen barrier effect.

[0029] The lining material of high-pressure hydrogen storage cylinders requires the resin used to provide sufficient mechanical strength and environmental stress resistance to withstand the pressure applied inside the cylinder, maintaining integrity and stability under high pressure conditions. The POE described in this invention can effectively improve the mechanical strength and environmental stress cracking resistance time of the polyethylene matrix resin.

[0030] The lining material for high-pressure hydrogen storage cylinders requires resins with good thermal stability, capable of maintaining the stability and reliability of their physical and chemical properties over long periods at high temperatures. The antioxidants, special lubricants, and modified boron nitride described in this invention can effectively improve the thermal stability of the polyethylene matrix resin.

[0031] In step (3), the powder quality needs to be strictly controlled. Generally, the powder quality is evaluated by its bulk density, dry time, and particle size distribution. Bulk density and dry time are important indicators for judging powder quality. The higher the bulk density of the powder, the less air is trapped inside the powder, the lower the bubble content in the rotational molding product, and the higher the strength of the product accordingly. The shorter the dry time of the powder, the more uniform the heating in the mold, the better the uniformity of the wall thickness of the product, and the smoother the appearance. Uniform spherical particles theoretically have the best dryness, but the small contact area between spherical particles is not conducive to heat conduction, resulting in a longer heating and melting time. The tightly packed angular structure can obtain the maximum bulk density and the minimum porosity, but the interlocking of powder particles causes poor dryness. Powder particles with stringy and curled shapes will cause an increase in pores in the melt and make it difficult to discharge, and at the same time cause poor dryness of the powder, which should be avoided as much as possible.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The polyvinylidene chloride and POE and polyethylene matrix resin used in this invention have certain similarities in chemical properties and structure, and can be mixed well. In addition, polyvinylidene chloride, POE and polyethylene matrix resin can form a "ternary composite" structure, which has a good barrier function against hydrogen.

[0034] (2) The resin obtained by this invention is in powder form, with a melt flow rate of 4.8–5.7 g / 10 min and a density of 0.932–0.938 g / cm³. 3 The bulk density is 0.39–0.45 g / cm³. 3 The drying time is 18–23 s / 100g, and the particle size distribution is 40–60 mesh, accounting for 50%–65%. The resin powder obtained by this invention has high quality, less air entrainment inside the powder, low bubble content in rotational molding products, and correspondingly higher product strength. The shorter the drying time of the powder, the more uniform the heating in the mold, resulting in products with good wall thickness uniformity, smooth appearance, and excellent application performance.

[0035] (3) The hydrogen permeability coefficient of the polyethylene rotomolded resin used for the inner lining of the hydrogen storage cylinder is 0.65–0.85 mol·m / (m 2 ·s·Pa)×10 -15 .

[0036] (4) The resin preparation process is simple and easy to implement in industry. Detailed Implementation

[0037] The present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0038] Unless otherwise specified, all raw materials used in the examples were commercially available.

[0039] Example 1

[0040] The polyethylene rotational molding resin powder used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0041]

[0042] The polyethylene used employs a metallocene catalyst system, with 1-hexene as the comonomer, a melt flow rate of 8 g / 10 min (190℃, 2.16 kg), and a density of 0.936 g / cm³. 3 ;

[0043] Antioxidant A is pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant B is tris(2,4-di-tert-butylphenyl)phosphite. The mass ratio of A to B in the compound is 1:1.

[0044] The method for preparing the modified boron nitride is as follows:

[0045] Boron nitride of 800 mesh was dried in an oven at 80°C for 3 hours, then mixed with a coupling agent and anhydrous ethanol. The mixture was then stirred in an ultrasonic mixer for 10 minutes. The mass of the coupling agent added was 8 times that of the boron nitride. The amount of anhydrous ethanol was not specifically limited; it was only used for dilution and would evaporate during subsequent high-speed stirring. The coupling agent was γ-glycidoxypropyltrimethoxysilane.

[0046] The preparation method of the polyethylene rotational molding resin powder for hydrogen storage cylinder lining includes the following steps:

[0047] (1) Place polyethylene, POE, polyvinylidene chloride, antioxidant, acid absorber, lubricant and treated boron nitride in a high-speed mixer and stir at 1000 r / min for 2 min. Then heat the high-speed mixer to 60℃ and stir for another 4 min.

[0048] (2) The uniformly mixed material is added to a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest temperature of the extruder is 210℃, the main speed of the extruder is 180r / min, and the feeding speed is 40r / min.

[0049] (3) Grind the granulated composition into fine powder on a grinder.

[0050] Example 2

[0051] The polyethylene rotational molding resin powder used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0052]

[0053] The polyethylene used employs a metallocene catalyst system, with 1-hexene as the comonomer, a melt flow rate of 8 g / 10 min (190℃, 2.16 kg), and a density of 0.936 g / cm³. 3 ;

[0054] Antioxidant A is pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant B is tris(2,4-di-tert-butylphenyl)phosphite. The mass ratio of A to B is 1:1.5.

[0055] The method for preparing the modified boron nitride is as follows:

[0056] Boron nitride of 800 mesh was dried in an oven at 80°C for 3 hours, then mixed with a coupling agent and anhydrous ethanol. The mixture was then stirred in an ultrasonic mixer for 10 minutes. The mass of the coupling agent added was 8.5 times that of the boron nitride. The amount of anhydrous ethanol was not specifically limited; it was only used for dilution and would evaporate during subsequent high-speed stirring. The coupling agent was γ-glycidoxypropyltrimethoxysilane.

[0057] The preparation method of the polyethylene rotational molding resin powder for hydrogen storage cylinder lining includes the following steps:

[0058] (1) Place polyethylene, POE, polyvinylidene chloride, antioxidant, acid absorber, lubricant and treated boron nitride in a high-speed mixer and stir at 1000 r / min for 2 min. Then heat the high-speed mixer to 60℃ and stir for another 4 min.

[0059] (2) The uniformly mixed material is added to a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest temperature of the extruder is 210℃, the main speed of the extruder is 180r / min, and the feeding speed is 40r / min.

[0060] (3) Grind the granulated composition into fine powder on a grinder.

[0061] Example 3

[0062] The polyethylene rotational molding resin powder used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0063]

[0064] The polyethylene used employs a metallocene catalyst system, with 1-hexene as the comonomer, a melt flow rate of 8 g / 10 min (190℃, 2.16 kg), and a density of 0.936 g / cm³. 3 ;

[0065] Antioxidant A is pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant B is tris(2,4-di-tert-butylphenyl)phosphite. The mass ratio of A to B is 1:1.5.

[0066] The method for preparing the modified boron nitride is as follows:

[0067] Boron nitride of 800 mesh was dried in an oven at 80°C for 3 hours, then mixed with a coupling agent and anhydrous ethanol. The mixture was then stirred in an ultrasonic mixer for 10 minutes. The mass of the coupling agent added was 9 times that of the boron nitride. The amount of anhydrous ethanol was not specifically limited; it was only used for dilution and would evaporate during subsequent high-speed stirring. The coupling agent was γ-glycidoxypropyltrimethoxysilane.

[0068] The preparation method of the polyethylene rotational molding resin powder for hydrogen storage cylinder lining includes the following steps:

[0069] (1) Place polyethylene, POE, polyvinylidene chloride, antioxidant, acid absorber, lubricant and treated boron nitride in a high-speed mixer and stir at 1000 r / min for 2 min. Then heat the high-speed mixer to 60℃ and stir for another 4 min.

[0070] (2) The uniformly mixed material is added to a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest temperature of the extruder is 210℃, the main speed of the extruder is 180r / min, and the feeding speed is 40r / min.

[0071] (3) Grind the granulated composition into fine powder on a grinder.

[0072] Example 4

[0073] The polyethylene rotational molding resin powder used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0074]

[0075]

[0076] The polyethylene used employs a metallocene catalyst system, with 1-hexene as the comonomer, a melt flow rate of 8 g / 10 min (190℃, 2.16 kg), and a density of 0.936 g / cm³. 3 ;

[0077] Antioxidant A is pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant B is tris(2,4-di-tert-butylphenyl)phosphite. The mass ratio of A to B is 1:1.5.

[0078] The method for preparing the modified boron nitride is as follows:

[0079] Boron nitride of 800 mesh was dried in an oven at 80°C for 3 hours, then mixed with a coupling agent and anhydrous ethanol. The mixture was then stirred in an ultrasonic mixer for 10 minutes. The mass of the coupling agent added was 9.5 times that of the boron nitride. The amount of anhydrous ethanol was not specifically limited; it was only used for dilution and would evaporate during subsequent high-speed stirring. The coupling agent was γ-glycidoxypropyltrimethoxysilane.

[0080] The preparation method of the polyethylene rotational molding resin powder for hydrogen storage cylinder lining includes the following steps:

[0081] (1) Place polyethylene, POE, polyvinylidene chloride, antioxidant, acid absorber, lubricant and treated boron nitride in a high-speed mixer and stir at 1000 r / min for 2 min. Then heat the high-speed mixer to 60℃ and stir for another 4 min.

[0082] (2) The uniformly mixed material is added to a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest temperature of the extruder is 210℃, the main speed of the extruder is 180r / min, and the feeding speed is 40r / min.

[0083] (3) Grind the granulated composition into fine powder on a grinder.

[0084] Example 5

[0085] The polyethylene rotational molding resin powder used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0086]

[0087] The polyethylene used employs a metallocene catalyst system, with 1-hexene as the comonomer, a melt flow rate of 8 g / 10 min (190℃, 2.16 kg), and a density of 0.936 g / cm³. 3 ;

[0088] Antioxidant A is pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant B is tris(2,4-di-tert-butylphenyl)phosphite. The mass ratio of A to B is 1:2.

[0089] The method for preparing the modified boron nitride is as follows:

[0090] Boron nitride of 800 mesh was dried in an oven at 80°C for 3 hours, then mixed with a coupling agent and anhydrous ethanol. The mixture was then stirred in an ultrasonic mixer for 10 minutes. The mass of the coupling agent added was 10 times that of the boron nitride. The amount of anhydrous ethanol was not specifically limited; it was only used for dilution and would evaporate during subsequent high-speed stirring. The coupling agent was γ-glycidoxypropyltrimethoxysilane.

[0091] The preparation method of the polyethylene rotational molding resin powder for hydrogen storage cylinder lining includes the following steps:

[0092] (1) Place polyethylene, POE, polyvinylidene chloride, antioxidant, acid absorber, lubricant and treated boron nitride in a high-speed mixer and stir at 1000 r / min for 2 min. Then heat the high-speed mixer to 60℃ and stir for another 4 min.

[0093] (2) The uniformly mixed material is added to a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest temperature of the extruder is 210℃, the main speed of the extruder is 180r / min, and the feeding speed is 40r / min.

[0094] (3) Grind the granulated composition into fine powder on a grinder.

[0095] Comparative Example 1

[0096] The polyethylene rotational molding resin powder used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0097]

[0098] The polyethylene used employs a metallocene catalyst system, with 1-hexene as the comonomer, a melt flow rate of 8 g / 10 min (190℃, 2.16 kg), and a density of 0.936 g / cm³. 3 ;

[0099] Antioxidant A is pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant B is tris(2,4-di-tert-butylphenyl)phosphite. The mass ratio of A to B is 1:2.

[0100] The method for preparing the modified boron nitride is as follows:

[0101] Boron nitride of 800 mesh was dried in an oven at 80°C for 3 hours, then mixed with a coupling agent and anhydrous ethanol. The mixture was then stirred in an ultrasonic mixer for 10 minutes. The amount of coupling agent added was 8 times that of the boron nitride. The amount of anhydrous ethanol was not specifically limited; it was only used for dilution and would evaporate during subsequent high-speed stirring. The coupling agent was γ-glycidoxypropyltrimethoxysilane.

[0102] The preparation method of the polyethylene rotational molding resin powder for hydrogen storage cylinder lining includes the following steps:

[0103] (1) Place polyethylene, POE, antioxidant, acid absorber, lubricant and treated boron nitride in a high-speed mixer and stir at 1000 r / min for 2 min. Then heat the high-speed mixer to 60℃ and stir for another 4 min.

[0104] (2) The uniformly mixed material is added to a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest temperature of the extruder is 210℃, the main speed of the extruder is 180r / min, and the feeding speed is 40r / min.

[0105] (3) Grind the granulated composition into fine powder on a grinder.

[0106] Comparative Example 2

[0107] The polyethylene rotational molding resin powder used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0108]

[0109] The polyethylene used employs a metallocene catalyst system, with 1-hexene as the comonomer, a melt flow rate of 8 g / 10 min (190℃, 2.16 kg), and a density of 0.936 g / cm³. 3 ;

[0110] Antioxidant A is pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and antioxidant B is tris(2,4-di-tert-butylphenyl)phosphite. The mass ratio of A to B is 1:2.

[0111] The method for preparing the modified boron nitride is as follows:

[0112] Boron nitride of 800 mesh was dried in an oven at 80°C for 3 hours, then mixed with a coupling agent and anhydrous ethanol. The mixture was then stirred in an ultrasonic mixer for 10 minutes. The amount of coupling agent added was 8 times that of the boron nitride. The amount of anhydrous ethanol was not specifically limited; it was only used for dilution and would evaporate during subsequent high-speed stirring. The coupling agent was γ-glycidoxypropyltrimethoxysilane.

[0113] The preparation method of the polyethylene rotational molding resin powder for hydrogen storage cylinder lining includes the following steps:

[0114] (1) Place polyethylene, polyvinylidene chloride, antioxidant, acid absorber, lubricant and treated boron nitride in a high-speed mixer and stir at 1000 r / min for 2 min. Then heat the high-speed mixer to 60℃ and stir for another 4 min.

[0115] (2) The uniformly mixed material is added to a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest temperature of the extruder is 210℃, the main speed of the extruder is 180r / min, and the feeding speed is 40r / min.

[0116] (3) Grind the granulated composition into fine powder on a grinder.

[0117] Comparative Example 3

[0118] Commercially available polyethylene rotational molding resin for lining hydrogen storage cylinders.

[0119] The polyethylene rotational molding resin used for hydrogen storage cylinder liners in the examples and comparative examples was tested using the following methods:

[0120] (1) Melt mass flow rate (MFR): Tested according to GB / T 3682-2000, at a temperature of 190℃ and a load of 2.16kg.

[0121] (2) Density: Tested according to GB / T 1033-2008.

[0122] (3) Hydrogen permeability coefficient: tested according to GB / T 1038.1-2022;

[0123] (4) Mainstream time: Tested according to GB / T 40934-2021.

[0124] (5) Tensile properties: Tested according to GB / T 1040.2-2022, using type I specimens, with a tensile speed of 50 mm·min. -1 (6) Environmental stress cracking time (ESCR): Tested according to GB / T 1842-2008, using condition B. The performance test results are shown in Table 1, and the particle size distribution test results are shown in Table 2.

[0125] Table 1. Performance test results of the resins in the examples and comparative examples.

[0126]

[0127] Table 2 Comparison of particle size distribution of rotational molding powder

[0128]

Claims

1. A polyethylene rotational molding resin powder for the lining of a high-pressure hydrogen storage cylinder, characterized in that, It consists of the following parts by weight of raw materials:

2. The polyethylene rotational molding resin powder for the lining of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The polyethylene used employs a metallocene catalyst system, with 1-hexene as the comonomer, a melt flow rate of 3–10 g / 10 min, and a density of 0.932–0.952 g / cm³. 3 .

3. The polyethylene rotational molding resin powder for the lining of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The mass ratio of polyvinylidene chloride to POE is (0.5–3):

1.

4. The polyethylene rotational molding resin powder for the lining of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The antioxidant is a compound antioxidant of hindered phenolic antioxidant and phosphite antioxidant, with a mass ratio of 1:(1-2).

5. The polyethylene rotational molding resin powder for the lining of a high-pressure hydrogen storage cylinder according to claim 4, characterized in that, The hindered phenolic antioxidant is 1010: pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; the phosphite antioxidant is 168: tris(2,4-di-tert-butylphenyl)phosphite.

6. The polyethylene rotational molding resin powder for the lining of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The acid absorbent is either calcium stearate or zinc stearate.

7. The polyethylene rotational molding resin powder for the lining of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The lubricant is a cyclic polyester oligomer.

8. The polyethylene rotational molding resin powder for the lining of a high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The modified boron nitride is prepared by mixing dried boron nitride and a coupling agent at a mass ratio of 1:(8-10), and then ultrasonically stirring it in anhydrous ethanol to obtain an ethanol dispersion system of modified boron nitride; the coupling agent is a silane coupling agent.

9. A method for preparing polyethylene rotational molding resin powder for the lining of a high-pressure hydrogen storage cylinder according to any one of claims 1-8, characterized in that, The steps are as follows: (1) Mix the ethanol dispersion system of polyethylene, POE, polyvinylidene chloride, antioxidant, acid absorbent, lubricant and modified boron nitride. (2) Add the uniformly mixed material to a co-rotating twin-screw extruder for melt mixing and extrusion granulation; (3) Grind the granulated resin into powder to obtain polyethylene rotational molding resin powder for high-pressure hydrogen storage cylinder lining.

10. The method for preparing polyethylene rotational molding resin powder for high-pressure hydrogen storage cylinder lining according to claim 9, characterized in that, The extrusion granulation temperature in step (2) is 190-230℃, the main extruder speed is 150-230r / min, and the feeding speed is 30-50r / min; in step (3), the polyethylene rotational molding resin powder used for the lining of the high-pressure hydrogen storage cylinder contains 65-90% powder between 40-100 mesh and 50-65% powder between 40-60 mesh.

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