Polyethylene rotational molding resin special for high-pressure hydrogen storage cylinder lining and preparation method of polyethylene rotational molding resin

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to special polyethylene rotational molding resin for a high-pressure hydrogen storage cylinder lining and a preparation method thereof. The material comprises the following raw material components: polyethylene resin, polyethylene powder, an ethylene-vinyl acetate copolymer, an antioxidant, an acid acceptor, a lubricant and modified aluminum nitride, according to the preparation method, the polyethylene rotational molding resin special for the high-pressure hydrogen storage cylinder lining is prepared through the processes of auxiliary agent activation, material mixing, granulation, grinding and the like, and the resin has good thermal stability and can keep the stability and reliability of physical and chemical properties of the resin for a long time under the high-temperature condition of the rotational molding process. The high-pressure hydrogen storage tank liner prepared by rotational molding of the resin has excellent hydrogen permeation barrier performance, sufficient mechanical strength and environmental stress resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a polyethylene roto-molding resin specially used for the lining of a high-pressure hydrogen storage cylinder and a preparation method thereof. Background Art

[0002] With the rapid development of the world economy and the sharp increase in the global population, human energy demand is increasing day by day. The use of traditional fossil fuels has led to serious environmental pollution and greenhouse effect problems, so countries are seeking more environmentally friendly and more accessible efficient green energy. Hydrogen energy is a renewable energy with significant advantages. Hydrogen has a wide range of sources, is environmentally friendly, has high mass energy density, and is easy to match with other renewable energy sources. It has the potential to replace fossil fuels in the future.

[0003] In the hydrogen energy system, hydrogen production is the foundation, and hydrogen storage and transportation are the prerequisites for large-scale application. Due to the small size of hydrogen molecules, it is very easy to penetrate or dissolve in common tank materials, resulting in a stable loss of hydrogen during storage and transportation. At the same time, hydrogen is flammable and explosive (especially when in contact with air). Safety issues during storage and transportation also bring huge challenges to hydrogen storage technology and restrict the application scenarios of hydrogen energy. Therefore, seeking safe, efficient, economical and more energy-saving hydrogen storage technology is the main direction of hydrogen energy utilization and development. At present, the main hydrogen storage methods include high-pressure gaseous hydrogen storage, low-temperature hydraulic hydrogen storage, solid hydrogen storage and organic liquid hydrogen storage, which store hydrogen by compression, liquefaction, physical or chemical combination. In comparison, high-pressure gaseous hydrogen storage has the advantages of simple equipment structure, low energy consumption for compressed hydrogen preparation, fast filling and discharge speed, and wide temperature adaptability. It is the most mature and most commonly used hydrogen storage technology. It is expected to continue to dominate hydrogen energy storage technology for a long time in the future.

[0004] High-pressure hydrogen storage cylinders are the key technology for the widespread use of compressed hydrogen, and are widely used in hydrogen refueling stations and on-board hydrogen storage. With the continuous increase in application demand (especially on-board hydrogen storage), lightweight and high pressure are the unremitting pursuit of the development of high-pressure hydrogen storage cylinders. At present, high-pressure hydrogen storage containers have gradually developed from all-metal cylinders (Type I bottles) to non-metallic liner fiber-wrapped cylinders (Type IV bottles). The liner materials of high-pressure hydrogen storage cylinders can be selected from polyethylene and polyamide, and the molding methods can be injection molding, blow molding and rotational molding. Considering the material cost and process feasibility, the production of Type IV cylinders by polyethylene rotational molding process has certain advantages. However, the polyethylene rotational molding resin used for the lining of hydrogen storage cylinders currently still has problems such as poor impact strength, poor cracking resistance and high hydrogen permeability. Patent CN113881150A discloses a polymer material inner liner hydrogen storage bottle material and its preparation method. The material is composed of polyvinyl chloride, polyethylene, EPDM rubber, and chlorinated polyvinyl chloride, and can be used as an insulating layer in the inner liner of a hydrogen storage pressure vessel. However, maleic anhydride grafted chlorinated polyvinyl chloride is added to its raw material components, which reduces the impact strength to a certain extent. Summary of the invention

[0005] In view of the deficiencies of the prior art, the object of the present invention is to provide a polyethylene roto-molding resin for the lining of a high-pressure hydrogen storage cylinder, which has a good barrier effect on hydrogen and can reduce the hydrogen permeability; at the same time, it can provide sufficient mechanical strength and environmental stress resistance to maintain its integrity and stability under high pressure conditions; and has good thermal stability, and can maintain the reliability of its physical and chemical properties for a long time under high temperature conditions of the roto-molding process;

[0006] Another object of the present invention is to provide a method for preparing a polyethylene rotational molding resin specially used for the lining of a high-pressure hydrogen storage cylinder, which method has simple process and is scientific and reasonable.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The polyethylene rotomolding resin specially used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0009]

[0010] The polyethylene resin adopts a metallocene catalyst system and 1-hexene as a comonomer. Its melt mass flow rate is 3 to 10 g / 10 min, preferably 5.5 to 8.0 g / 10 min; its density is 0.932 to 0.952 g / cm 3 .

[0011] The polyethylene powder adopts a chromium catalyst system and 1-hexene as a comonomer, and its melt mass flow rate is 0.01 to 0.5 g / 10 min, preferably 0.05 to 0.2 g / 10 min; the relative molecular mass is (80 to 150)×10 4 , density is 0.95~0.966g / cm 3 , particle size is 100-200 mesh; dosage is 1-8 parts, preferably 2-6 parts.

[0012] The mass ratio of the ethylene-vinyl acetate copolymer to the polyethylene powder is 1:(1-4).

[0013] The antioxidant is a composite antioxidant of a hindered phenol antioxidant and a phosphite antioxidant, and the mass ratio thereof is 1:(1-2); preferably, the hindered phenol antioxidant is antioxidant 1010: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; and the phosphite antioxidant is tris(2,4-di-tert-butylphenyl)phosphite.

[0014] The acid absorber is one of calcium stearate or zinc stearate, and the dosage is 0.05 to 0.1 parts, preferably 0.05 parts.

[0015] The lubricant is a cyclic polyester oligomer, preferably CBT100; the amount used is 0.01 to 0.1 parts, preferably 0.01 to 0.05 parts.

[0016] The preparation method of the modified aluminum nitride is as follows: drying the aluminum nitride in an oven at 80 degrees for 3 to 4 hours, mixing the dried aluminum nitride and a coupling agent in a mass ratio of 1:10, placing the mixture in anhydrous ethanol for ultrasonic stirring, and obtaining an ethanol dispersion system of the modified aluminum nitride; the coupling agent is a silane coupling agent, preferably γ-glycidyloxypropyltrimethoxysilane; the anhydrous ethanol is used for dilution and is completely volatilized during high-speed stirring.

[0017] The preparation method of the polyethylene rotomolding resin for the lining of the high-pressure hydrogen storage cylinder comprises the following steps:

[0018] (1) mixing polyethylene resin, polyethylene powder, ethylene-vinyl acetate copolymer, antioxidant, acid absorbent, lubricant and ethanol dispersion system of modified aluminum nitride, stirring at high speed to obtain a mixed material;

[0019] (2) adding the mixture obtained in step (1) into a co-rotating twin-screw extruder for melt mixing, extruding and granulating to obtain a rotomolding polyethylene composition;

[0020] (3) Grinding the roto-molded polyethylene composition obtained in step (2) into fine powder to obtain a polyethylene roto-molded resin for the lining of a high-pressure hydrogen storage cylinder.

[0021] The specific steps of high-speed stirring in the step (1) are: stirring for 1 to 2 minutes at room temperature and a rotation speed of 1000 to 1500 r / min, heating to 60°C and stirring for 3 to 4 minutes; the extrusion granulation temperature in the step (2) is 190 to 230°C, the main speed of the extruder is 150 to 230 r / min, and the feeding speed is 30 to 50 r / min; in the powder of the polyethylene rotational molding resin for the lining of the high-pressure hydrogen storage cylinder obtained in the step (3), the powder with a particle size of 80 to 100 mesh accounts for 20% to 50% of the total mass of the powder, and the powder with a particle size of 40 to 80 mesh accounts for 30% to 65% of the total mass of the powder.

[0022] The polyethylene roto-molding resin for high-pressure hydrogen storage cylinder linings prepared by the method for preparing the polyethylene roto-molding resin for high-pressure hydrogen storage cylinder linings can be used for 35MPa high-pressure hydrogen storage cylinder linings.

[0023] The polyethylene resin used in the present invention will not produce adverse chemical reactions or adsorption effects on hydrogen, and can effectively avoid hydrogen embrittlement.

[0024] The lining material of the high-pressure hydrogen storage cylinder requires that the resin used should have excellent hydrogen permeation barrier properties, that is, it can effectively prevent hydrogen from penetrating from the container. This helps to maintain the stability and safe storage of hydrogen in the hydrogen storage bottle. The ethylene-vinyl acetate copolymer used in the present invention has a certain degree of gas barrier properties. At the same time, the ethylene-vinyl acetate copolymer and the polyethylene powder and polyethylene resin have certain similarities in chemical properties and structures. There is a certain interaction force between them, and a uniform mixture can be formed without phase separation or obvious mutual incompatibility, that is, the ethylene-vinyl acetate copolymer can be well mixed with the polyethylene powder and polyethylene resin. In addition, the ethylene-vinyl acetate copolymer and the polyethylene powder and polyethylene resin can form a "ternary composite" structure, which has a good barrier function for hydrogen, but the compounding ratio of the ethylene-vinyl acetate copolymer and the polyethylene powder must be controlled within a suitable range, otherwise the ethylene-vinyl acetate copolymer cannot be evenly dispersed in the polyethylene powder and the polyethylene resin, thereby reducing the barrier effect on hydrogen.

[0025] The lining material of the high-pressure hydrogen storage cylinder requires that the resin used can provide sufficient mechanical strength and environmental stress resistance to withstand the pressure applied inside the high-pressure hydrogen storage cylinder and maintain integrity and stability under high pressure conditions. The polyethylene powder used in the present invention is a resin with a relatively high molecular weight, which can effectively improve the mechanical strength and environmental stress cracking time of the material.

[0026] The lining material of the high-pressure hydrogen storage cylinder requires that the resin used has good thermal stability and can maintain the stability and reliability of its physical and chemical properties for a long time under high temperature conditions. The antioxidant, special lubricant and modified aluminum nitride used in the present invention can effectively improve the thermal stability of the material.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The polyethylene rotomolding resin specially used for the lining of the high-pressure hydrogen storage cylinder prepared by the present invention has a hydrogen permeability of 0.5 to 1.0 x 10 -3 mol / (m 2 ·s·Pa), can be used for the lining of 35MPa high-pressure hydrogen storage cylinders; its simply supported beam impact strength reaches 30-38MPa, its modulus reaches 590-670MPa, and its environmental stress cracking resistance time is significantly improved;

[0029] (2) The method for preparing the polyethylene rotational molding resin for the lining of the high-pressure hydrogen storage cylinder is simple in process, scientific and reasonable, and easy to implement in industry. DETAILED DESCRIPTION

[0030] The present invention is further described below with reference to the embodiments, but they do not limit the implementation of the present invention.

[0031] Unless otherwise specified, the raw materials used in the examples and comparative examples are conventional commercially available products.

[0032] Example 1

[0033] The polyethylene rotomolding resin specially used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0034]

[0035] in:

[0036] The polyethylene resin adopts a metallocene catalyst system and 1-hexene as a comonomer. The melt mass flow rate is 10 g / 10 min at a temperature of 190 ° C and a weight of 2.16 kg. The density is 0.938 g / cm 3 ;

[0037] The polyethylene powder adopts a chromium catalyst system and 1-hexene as a comonomer. Its melt mass flow rate is 0.05g / 10min and its relative molecular mass is 104×10 4 , density is 0.965g / cm 3 , particle size is 120 mesh.

[0038] The mass ratio of ethylene-vinyl acetate copolymer to polyethylene powder is 1:2;

[0039] The antioxidant is a composite antioxidant of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and tris(2,4-di-tert-butylphenyl) phosphite, and the mass ratio thereof is 1:1.

[0040] The acid absorbent is calcium stearate;

[0041] The lubricant is CBT100;

[0042] The preparation method of modified aluminum nitride is as follows: aluminum nitride with a particle size of 800 mesh is dried in an oven at 80 degrees for 3 hours, the dried aluminum nitride and a coupling agent are mixed in a mass ratio of 1:10, and the mixture is placed in anhydrous ethanol and ultrasonically stirred for 10 minutes to obtain an ethanol dispersion system of modified aluminum nitride; the coupling agent is γ-glycidyloxypropyltrimethoxysilane.

[0043] The preparation method of the polyethylene rotomolding resin for the lining of the high-pressure hydrogen storage cylinder comprises the following steps:

[0044] (1) mixing polyethylene resin, polyethylene powder, ethylene-vinyl acetate copolymer, compound antioxidant, calcium stearate, CBT100 and an ethanol dispersion system of modified aluminum nitride, placing in a high-speed stirrer, stirring at room temperature and a speed of 1000 / min for 2 minutes, raising the temperature of the high-speed stirrer to 60° C. and stirring for another 3 minutes to obtain a mixed material;

[0045] (2) adding the mixture obtained in step (1) into a co-rotating twin-screw extruder for melt kneading, and the extrusion granulation temperatures are 190° C., 200° C., 210° C., 220° C., 230° C., and 230° C. in sequence, extruding and granulating to obtain a rotomolding polyethylene composition, the main extruder speed is 180 r / min, and the feed speed is 40 r / min;

[0046] (3) Grinding the roto-molded polyethylene composition obtained in step (2) into fine powder on a grinder to obtain a polyethylene roto-molded resin for high-pressure hydrogen storage cylinder lining, wherein the powder with a particle size of 80 to 100 mesh accounts for 50% of the total mass of the powder, and the powder with a particle size of 40 to 80 mesh accounts for 30% of the total mass of the powder.

[0047] Example 2

[0048] The polyethylene rotomolding resin specially used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0049]

[0050] in:

[0051] The polyethylene resin adopts a metallocene catalyst system and 1-hexene as a comonomer. The melt mass flow rate is 10 g / 10 min at a temperature of 190 ° C and a weight of 2.16 kg. The density is 0.938 g / cm 3 ;

[0052] The polyethylene powder adopts a chromium catalyst system and 1-hexene as a comonomer. Its melt mass flow rate is 0.05g / 10min and its relative molecular mass is 104×10 4 , density is 0.965g / cm 3 , particle size is 120 mesh.

[0053] The mass ratio of ethylene-vinyl acetate copolymer to polyethylene powder is 1:1;

[0054] The antioxidant is a composite antioxidant of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and tris(2,4-di-tert-butylphenyl) phosphite, and the mass ratio thereof is 1:1.

[0055] The acid absorbent is calcium stearate;

[0056] The lubricant is CBT100;

[0057] The preparation method of modified aluminum nitride is as follows: aluminum nitride with a particle size of 800 mesh is dried in an oven at 80 degrees for 3 hours, the dried aluminum nitride and a coupling agent are mixed in a mass ratio of 1:10, and the mixture is placed in anhydrous ethanol and ultrasonically stirred for 10 minutes to obtain an ethanol dispersion system of modified aluminum nitride; the coupling agent is γ-glycidyloxypropyltrimethoxysilane.

[0058] The preparation method of the polyethylene rotomolding resin for the lining of the high-pressure hydrogen storage cylinder comprises the following steps:

[0059] (1) mixing polyethylene resin, polyethylene powder, ethylene-vinyl acetate copolymer, compound antioxidant, calcium stearate, CBT100 and an ethanol dispersion system of modified aluminum nitride, placing in a high-speed stirrer, stirring at room temperature and a speed of 1000 / min for 2 minutes, raising the temperature of the high-speed stirrer to 60° C. and stirring for another 3 minutes to obtain a mixed material;

[0060] (2) adding the mixture obtained in step (1) into a co-rotating twin-screw extruder for melt kneading, and the extrusion granulation temperatures are 190° C., 200° C., 210° C., 220° C., 230° C., and 230° C. in sequence, extruding and granulating to obtain a rotomolding polyethylene composition, the main extruder speed is 180 r / min, and the feed speed is 40 r / min;

[0061] (3) Grinding the roto-molded polyethylene composition obtained in step (2) into fine powder on a grinder to obtain a polyethylene roto-molded resin for high-pressure hydrogen storage cylinder lining, wherein the powder with a particle size of 80 to 100 mesh accounts for 40% of the total mass of the powder, and the powder with a particle size of 40 to 80 mesh accounts for 40% of the total mass of the powder.

[0062] Example 3

[0063] The polyethylene rotomolding resin specially used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0064]

[0065] in:

[0066] The polyethylene resin adopts a metallocene catalyst system and 1-hexene as a comonomer. The melt mass flow rate is 10 g / 10 min at a temperature of 190 ° C and a weight of 2.16 kg. The density is 0.938 g / cm 3 ;

[0067] The polyethylene powder adopts a chromium catalyst system and 1-hexene as a comonomer. Its melt mass flow rate is 0.05g / 10min and its relative molecular mass is 104×10 4 , density is 0.965g / cm 3 , particle size is 120 mesh.

[0068] The mass ratio of ethylene-vinyl acetate copolymer to polyethylene powder is 1:3;

[0069] The antioxidant is a composite antioxidant of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and tris(2,4-di-tert-butylphenyl) phosphite, and the mass ratio thereof is 1:1.

[0070] The acid absorbent is calcium stearate;

[0071] The lubricant is CBT100;

[0072] The preparation method of modified aluminum nitride is as follows: aluminum nitride with a particle size of 800 mesh is dried in an oven at 80 degrees for 3 hours, the dried aluminum nitride and a coupling agent are mixed in a mass ratio of 1:10, and the mixture is placed in anhydrous ethanol and ultrasonically stirred for 10 minutes to obtain an ethanol dispersion system of modified aluminum nitride; the coupling agent is γ-glycidyloxypropyltrimethoxysilane.

[0073] The preparation method of the polyethylene rotomolding resin for the lining of the high-pressure hydrogen storage cylinder comprises the following steps:

[0074] (1) mixing polyethylene resin, polyethylene powder, ethylene-vinyl acetate copolymer, compound antioxidant, calcium stearate, CBT100 and an ethanol dispersion system of modified aluminum nitride, placing in a high-speed stirrer, stirring at room temperature and a speed of 1000 / min for 2 minutes, raising the temperature of the high-speed stirrer to 60° C. and stirring for another 3 minutes to obtain a mixed material;

[0075] (2) adding the mixture obtained in step (1) into a co-rotating twin-screw extruder for melt kneading, and the extrusion granulation temperatures are 190° C., 200° C., 210° C., 220° C., 230° C., and 230° C. in sequence, extruding and granulating to obtain a rotomolding polyethylene composition, the main extruder speed is 180 r / min, and the feed speed is 40 r / min;

[0076] (3) Grinding the roto-molded polyethylene composition obtained in step (2) into fine powder on a grinder to obtain a polyethylene roto-molded resin for high-pressure hydrogen storage cylinder lining, wherein the powder with a particle size of 80 to 100 mesh accounts for 35% of the total mass of the powder, and the powder with a particle size of 40 to 80 mesh accounts for 45% of the total mass of the powder.

[0077] Example 4

[0078] The polyethylene rotomolding resin specially used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0079]

[0080] in:

[0081] The polyethylene resin adopts a metallocene catalyst system and 1-hexene as a comonomer. The melt mass flow rate is 10 g / 10 min at a temperature of 190 ° C and a weight of 2.16 kg. The density is 0.938 g / cm 3 ;

[0082] The polyethylene powder adopts a chromium catalyst system and 1-hexene as a comonomer. Its melt mass flow rate is 0.05g / 10min and its relative molecular mass is 104×10 4 , density is 0.965g / cm 3 , particle size is 120 mesh.

[0083] The mass ratio of ethylene-vinyl acetate copolymer to polyethylene powder is 1:2;

[0084] The antioxidant is a composite antioxidant of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and tris(2,4-di-tert-butylphenyl) phosphite, and the mass ratio thereof is 1:1.

[0085] The acid absorbent is calcium stearate;

[0086] The lubricant is CBT100;

[0087] The preparation method of modified aluminum nitride is as follows: aluminum nitride with a particle size of 800 mesh is dried in an oven at 80 degrees for 3 hours, the dried aluminum nitride and a coupling agent are mixed in a mass ratio of 1:10, and the mixture is placed in anhydrous ethanol and ultrasonically stirred for 10 minutes to obtain an ethanol dispersion system of modified aluminum nitride; the coupling agent is γ-glycidyloxypropyltrimethoxysilane.

[0088] The preparation method of the polyethylene rotomolding resin for the lining of the high-pressure hydrogen storage cylinder comprises the following steps:

[0089] (1) mixing polyethylene resin, polyethylene powder, ethylene-vinyl acetate copolymer, compound antioxidant, calcium stearate, CBT100 and an ethanol dispersion system of modified aluminum nitride, placing in a high-speed stirrer, stirring at room temperature and a speed of 1000 / min for 2 minutes, raising the temperature of the high-speed stirrer to 60° C. and stirring for another 3 minutes to obtain a mixed material;

[0090] (2) adding the mixture obtained in step (1) into a co-rotating twin-screw extruder for melt kneading, and the extrusion granulation temperatures are 190° C., 200° C., 210° C., 220° C., 230° C., and 230° C. in sequence, extruding and granulating to obtain a rotomolding polyethylene composition, the main extruder speed is 180 r / min, and the feed speed is 40 r / min;

[0091] (3) Grinding the roto-molded polyethylene composition obtained in step (2) into fine powder on a grinder to obtain a polyethylene roto-molded resin for high-pressure hydrogen storage cylinder lining, wherein the powder with a particle size of 80 to 100 mesh accounts for 30% of the total mass of the powder, and the powder with a particle size of 40 to 80 mesh accounts for 55% of the total mass of the powder.

[0092] Example 5

[0093] The polyethylene rotomolding resin specially used for the lining of the high-pressure hydrogen storage cylinder is composed of the following raw materials in parts by weight:

[0094]

[0095] in:

[0096] The polyethylene resin adopts a metallocene catalyst system and 1-hexene as a comonomer. The melt mass flow rate is 10 g / 10 min at a temperature of 190 ° C and a weight of 2.16 kg. The density is 0.938 g / cm 3 ;

[0097] The polyethylene powder adopts a chromium catalyst system and 1-hexene as a comonomer. Its melt mass flow rate is 0.05g / 10min and its relative molecular mass is 104×10 4, density is 0.965g / cm 3 , particle size is 120 mesh.

[0098] The mass ratio of ethylene-vinyl acetate copolymer to polyethylene powder is 1:2;

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

[0100] The acid absorbent is calcium stearate;

[0101] The lubricant is CBT100;

[0102] The preparation method of modified aluminum nitride is as follows: aluminum nitride with a particle size of 800 mesh is dried in an oven at 80 degrees for 3 hours, the dried aluminum nitride and a coupling agent are mixed in a mass ratio of 1:10, and the mixture is placed in anhydrous ethanol and ultrasonically stirred for 10 minutes to obtain an ethanol dispersion system of modified aluminum nitride; the coupling agent is γ-glycidyloxypropyltrimethoxysilane.

[0103] The preparation method of the polyethylene rotomolding resin for the lining of the high-pressure hydrogen storage cylinder comprises the following steps:

[0104] (1) mixing polyethylene resin, polyethylene powder, ethylene-vinyl acetate copolymer, compound antioxidant, calcium stearate, CBT100 and an ethanol dispersion system of modified aluminum nitride, placing in a high-speed stirrer, stirring at room temperature and a speed of 1000 / min for 2 minutes, raising the temperature of the high-speed stirrer to 60° C. and stirring for another 3 minutes to obtain a mixed material;

[0105] (2) adding the mixture obtained in step (1) into a co-rotating twin-screw extruder for melt kneading, and the extrusion granulation temperatures are 190° C., 200° C., 210° C., 220° C., 230° C., and 230° C. in sequence, extruding and granulating to obtain a rotomolding polyethylene composition, the main extruder speed is 180 r / min, and the feed speed is 40 r / min;

[0106] (3) Grinding the roto-molded polyethylene composition obtained in step (2) into fine powder on a grinder to obtain a polyethylene roto-molded resin for high-pressure hydrogen storage cylinder lining, wherein the powder with a particle size of 80 to 100 mesh accounts for 20% of the total mass of the powder, and the powder with a particle size of 40 to 80 mesh accounts for 65% of the total mass of the powder.

[0107] Comparative Example 1

[0108] The polyethylene rotomolding resin is composed of the following raw materials in parts by weight:

[0109]

[0110] in:

[0111] The polyethylene resin adopts a metallocene catalyst system and 1-hexene as a comonomer. The melt mass flow rate is 10 g / 10 min at a temperature of 190 ° C and a weight of 2.16 kg. The density is 0.938 g / cm 3 ;

[0112] The antioxidant is a composite antioxidant of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and tris(2,4-di-tert-butylphenyl) phosphite, and the mass ratio thereof is 1:1.

[0113] The acid absorbent is calcium stearate;

[0114] The lubricant is CBT100;

[0115] The preparation method of modified aluminum nitride is as follows: aluminum nitride with a particle size of 800 mesh is dried in an oven at 80 degrees for 3 hours, the dried aluminum nitride and a coupling agent are mixed in a mass ratio of 1:10, and the mixture is placed in anhydrous ethanol and ultrasonically stirred for 10 minutes to obtain an ethanol dispersion system of modified aluminum nitride; the coupling agent is γ-glycidyloxypropyltrimethoxysilane.

[0116] The preparation method of the polyethylene rotomolding resin is the same as that of Example 1.

[0117] Comparative Example 2

[0118] The polyethylene rotomolding resin is composed of the following raw materials in parts by weight:

[0119]

[0120] in:

[0121] The polyethylene resin adopts a metallocene catalyst system and 1-hexene as a comonomer. The melt mass flow rate is 10 g / 10 min at a temperature of 190 ° C and a weight of 2.16 kg. The density is 0.938 g / cm 3 ;

[0122] The polyethylene powder adopts a chromium catalyst system and 1-hexene as a comonomer. Its melt mass flow rate is 0.05g / 10min and its relative molecular mass is 104×10 4 , density is 0.965g / cm 3 , particle size is 120 mesh.

[0123] The antioxidant is a composite antioxidant of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and tris(2,4-di-tert-butylphenyl) phosphite, and the mass ratio thereof is 1:1.

[0124] The acid absorbent is calcium stearate;

[0125] The lubricant is CBT100;

[0126] The preparation method of modified aluminum nitride is as follows: aluminum nitride with a particle size of 800 mesh is dried in an oven at 80 degrees for 3 hours, the dried aluminum nitride and a coupling agent are mixed in a mass ratio of 1:10, and the mixture is placed in anhydrous ethanol and ultrasonically stirred for 10 minutes to obtain an ethanol dispersion system of modified aluminum nitride; the coupling agent is γ-glycidyloxypropyltrimethoxysilane.

[0127] The preparation method of the polyethylene rotomolding resin has the same steps as Example 1.

[0128] Comparative Example 3

[0129] Polyethylene rotomolding resin specially used for lining hydrogen storage cylinders available on the market.

[0130] Detection method:

[0131] (1) Melt flow rate (MFR): tested according to GB / T 3682-2000, temperature is 190 °C, load is 2.16 kg;

[0132] (2) Density: Tested in accordance with GB / T 1033.1-2008;

[0133] (3) Simply supported beam notched impact strength: tested in accordance with GB / T 1043.1-2008;

[0134] (4) Tensile strength: tested in accordance with GB / T1040.2-2006;

[0135] (5) Nominal strain at break: tested in accordance with GB / T1040.2-2006;

[0136] (6) Flexural modulus: tested in accordance with GB / T 9341-2008;

[0137] (7) Environmental stress cracking performance: tested in accordance with GB / T 1842-2008;

[0138] (8) Hydrogen permeability: tested in accordance with GB / T 1038.1-2022.

[0139] The test results of the embodiments and comparative examples are shown in Table 1.

[0140] Table 1

[0141]

[0142] Examples 1 to 5 are samples prepared according to the preparation method of the present invention, all of which have good rigidity-toughness balance performance, good environmental stress cracking resistance, and the hydrogen permeability of 1 mm pressed sheets is less than 1.0x10 -3 mol / (m 2 ·s·Pa). In Comparative Example 1, ethylene-vinyl acetate was not added, and the density, tensile strength and flexural modulus of the material were improved, but the impact strength and environmental stress cracking time were significantly reduced; in Comparative Example 2, polyethylene powder was not added, and the impact strength and environmental stress cracking time of the material were significantly improved, but the tensile strength and flexural modulus were reduced. The hydrogen permeability of the 1mm pressed sheets of Comparative Examples 1 and 2 was higher than that of the embodiment. The mechanical properties of Comparative Example 3 were inferior to those of the embodiment, and the hydrogen permeability of the 1mm pressed sheet was much higher than that of the embodiment, so it was not suitable for hydrogen storage cylinders.

Claims

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

2. The polyethylene rotomolding resin for high-pressure hydrogen storage cylinder lining according to claim 1 is characterized in that: The polyethylene resin adopts a metallocene catalyst system and 1-hexene as a comonomer, and its melt mass flow rate is 3-10 g / 10 min and its density is 0.932-0.952 g / cm 3 .

3. The polyethylene rotomolding resin for high-pressure hydrogen storage cylinder lining according to claim 1, characterized in that: The polyethylene powder adopts a chromium catalyst system and 1-hexene as a comonomer, and its melt mass flow rate is 0.01-0.5 g / 10 min, and its relative molecular mass is (80-150)×10 4 , density is 0.95~0.966g / cm 3 , particle size is 100-200 mesh.

4. The polyethylene rotomolding resin for high-pressure hydrogen storage cylinder lining according to claim 1, characterized in that: The mass ratio of the ethylene-vinyl acetate copolymer to the polyethylene powder is 1:(1-4).

5. The polyethylene rotomolding resin for high-pressure hydrogen storage cylinder lining according to claim 1, characterized in that: The antioxidant is a compound antioxidant of a hindered phenol antioxidant and a phosphite antioxidant, and the mass ratio thereof is 1:(1-2).

6. The polyethylene rotomolding resin for high-pressure hydrogen storage cylinder lining according to claim 1, characterized in that: The acid absorber is one of calcium stearate or zinc stearate.

7. The polyethylene rotomolding resin for high-pressure hydrogen storage cylinder lining according to claim 1, characterized in that: The lubricant is a cyclic polyester oligomer.

8. The polyethylene rotomolding resin for high-pressure hydrogen storage cylinder lining according to claim 1, characterized in that: The preparation method of the modified aluminum nitride is as follows: the dried aluminum nitride and the coupling agent are mixed in a mass ratio of 1: (5-10), and ultrasonically stirred in anhydrous ethanol to obtain an ethanol dispersion system of the modified aluminum nitride; the coupling agent is a silane coupling agent.

9. A method for preparing a polyethylene rotomolding resin for high-pressure hydrogen storage cylinder lining according to any one of claims 1 to 8, characterized in that: Here are the steps: (1) mixing polyethylene resin, polyethylene powder, ethylene-vinyl acetate copolymer, antioxidant, acid absorbent, lubricant and ethanol dispersion system of modified aluminum nitride, stirring at high speed to obtain a mixed material; (2) adding the mixture obtained in step (1) into a co-rotating twin-screw extruder for melt mixing, extruding and granulating to obtain a rotomolding polyethylene composition; (3) Grinding the roto-molded polyethylene composition obtained in step (2) into fine powder to obtain a polyethylene roto-molded resin for the lining of a high-pressure hydrogen storage cylinder.

10. The method for preparing the polyethylene rotational molding resin for the lining of the high-pressure hydrogen storage cylinder according to claim 9, characterized in that: The extrusion granulation temperature in the step (2) is 190-230° C.; in the powder of the polyethylene rotational molding resin for the lining of the high-pressure hydrogen storage cylinder obtained in the step (3), the powder with a particle size of 80-100 mesh accounts for 20%-50% of the total mass of the powder, and the powder with a particle size of 40-80 mesh accounts for 30%-65% of the total mass of the powder.

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