Preparation method of high-barrier engineering plastic applied to processing of grease storage barrel of grease gun

Abstract

The invention discloses a preparation method of high-barrier engineering plastic applied to processing of grease storage barrels of grease guns, belongs to the technical field of plastic processing, and aims to solve the technical problem that the barrier property and the oil resistance of the engineering plastic need to be further improved in the prior art. The preparation method specifically comprises the following steps: adding the modified polyimide, the modified fiber and the auxiliary additive into a double-screw extruder, and carrying out melt extrusion to obtain the high-barrier-property engineering plastic. The high-barrier engineering plastic is prepared by preparing the modified fiber and performing melt extrusion on the modified fiber, the modified polyimide and the auxiliary additive, so that the barrier property and the oil resistance of the engineering plastic are improved, and the mechanical property of the engineering plastic is also improved.

Description

Technical Field

[0001] The invention relates to the technical field of plastic processing, in particular to a method for preparing high-barrier engineering plastics used in processing grease gun oil storage cylinders. Background Art

[0002] With the widespread application of engineering plastics in the fields of automobiles, machinery, lubrication equipment, etc., they play an increasingly important role in replacing metal materials, reducing structural weight, improving corrosion resistance and processing efficiency. Common engineering plastics such as polyamide, polycarbonate, polyimide, polyester plastics, polyetheretherketone, etc. have been widely used in the preparation of structural components, seals and storage containers.

[0003] In order to improve their comprehensive performance, performance optimization is often carried out through means such as blending modification, filler reinforcement and surface treatment. However, when used in the processing of grease gun oil storage cylinders, these conventional engineering plastics still have obvious deficiencies in barrier properties and oil resistance. Specifically, the material has a high penetration rate of oil in grease, and is prone to oil seepage, swelling and softening, and reduced sealing performance under high pressure or high temperature environments, which seriously affects the service life and sealing safety of the oil storage cylinder.

[0004] In the prior art, the barrier properties and oil resistance of engineering plastics used in grease contact environments are insufficient due to the limitations of their molecular structure and interface configuration. On the one hand, most traditional engineering plastics lack spatial shielding groups in their molecular chains, and the chain segments are loosely arranged and have large free volumes, which cannot effectively prevent the diffusion and penetration of small molecule oils in grease, resulting in poor air tightness and oil tightness of the material. On the other hand, under high temperature or long-term load conditions, some plastics will experience structural relaxation or molecular chain swelling due to oil absorption, resulting in a decrease in material strength, poor surface adhesion, and even cracks. In addition, the interfacial bonding force between inorganic fillers and the polymer matrix is ​​limited, and microscopic debonding or penetration channels are prone to occur, further reducing the barrier effect. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing high-barrier engineering plastics used in the processing of grease gun oil storage cylinders, so as to solve the technical problem in the prior art that the barrier properties and oil resistance of engineering plastics need to be further improved.

[0006] The object of the present invention can be achieved by the following technical solution: A method for preparing a high-barrier engineering plastic used in the processing of a grease gun oil storage cylinder comprises the following steps: S1. Place aminopropyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl and N-methylpyrrolidone in a reaction kettle and stir. Cool the reaction kettle to 0-5°C, slowly add pyromellitic dianhydride, and stir at this temperature for 10-15 minutes. Heat the reaction kettle to 50-60°C, add triethylamine, and stir at this temperature for 8-10 hours to obtain a mixed solution. S2, placing the mixed solution and N-methylpyrrolidone in a reaction kettle and stirring, heating the reaction kettle to 60-65° C., slowly adding acetic anhydride and triethylamine, keeping the temperature to react for 10-12 hours, and post-treating to obtain modified polyimide; The preparation reaction formula of modified polyimide is:

[0007] The preparation reaction principle of modified polyimide is: During the reaction, under low temperature conditions, acid anhydride undergoes a nucleophilic addition-elimination reaction with the terminal amine groups of aminopropyl ether and 2,2'-bis(trifluoromethyl)diaminobiphenyl to form an amide structure and release hydrochloric acid. Triethylamine is added to neutralize the generated hydrochloric acid to avoid the occurrence of side reactions. Acetic anhydride is used as a dehydration reagent, and triethylamine assists in acid absorption. Under the action of acetic anhydride and triethylamine, the amide acid structure that has not yet closed the ring in the mixed solution is dehydrated and condensed to form an imide ring, thereby obtaining a modified polyimide.

[0008] S3. Adding the modified polyimide, modified fiber and auxiliary additives into a twin-screw extruder, and melt-extruded to obtain high-barrier engineering plastics.

[0009] Further, in step S1, the amount ratio of aminopropyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl, N-methylpyrrolidone, pyromellitic dianhydride and triethylamine is 2-4g:3-5g:150-200mL:2-4g:6-8g; in step S2, the amount ratio of the mixed solution, N-methylpyrrolidone, acetic anhydride and triethylamine is 50-80mL:80-100mL:6-9g:8- 10g, the post-treatment step includes: after the reaction is completed, the reaction system is cooled to room temperature, the reaction solution is added to 250-300mL of deionized water for precipitation, filtered, the filter cake is washed with deionized water 2-3 times, transferred to an oven at a temperature of 60-80°C, and dried to constant weight to obtain a modified polyimide; in step S3, the mass ratio of the modified polyimide, modified fiber and auxiliary additive is 6-8:1.5-2:0.5-1; Furthermore, the auxiliary additives are composed of an antioxidant, a lubricant, and a plasticizer in a mass ratio of 1:2:4, wherein the antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-diphenyl-p-phenylenediamine, and distearyl thiodipropionate; the lubricant is one or more of fatty acid amide, oleic acid amide, and paraffin; and the plasticizer is one or more of 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole and bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate; Furthermore, the temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 290°C, 290°C, 300°C, 300°C, 310°C, 310°C, 330°C, and 330°C, respectively. The main engine speed of the twin-screw extruder is 100-120rpm, and the pressure is 100-150bar.

[0010] Furthermore, the modified fiber is prepared by the following steps: A1. Ball milling silica to obtain pretreated silica; A2. Pretreated silica, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, deionized water, and ethanol were placed in a reactor and stirred. The reactor was heated to 45-55° C. and kept warm for 2-4 hours. Modified silica was obtained by post-treatment. The preparation reaction principle of modified silica is: During the reaction, under heating conditions, the silicon-oxygen bond of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is hydrolyzed into silanol, which further undergoes a condensation reaction with the hydroxyl groups on the surface of the pretreated silica to obtain modified silica.

[0011] A3. Place modified polyurethane, N,N-dimethylformamide and modified silica in a reactor, stir at room temperature for 20-30 minutes, add glass fiber, ultrasonically disperse for 2-4 hours, and post-treat to obtain modified fiber.

[0012] The reaction principle for preparing modified fiber is: During the reaction process, the modified polyurethane is dissolved in deionized water, and the modified silica modified with a silane coupling agent is dispersed in the modified polyurethane solution. After glass fiber is added for ultrasonic dispersion, the epoxy resin in the modified polyurethane is further chemically bonded with the modified silica and glass fiber by heating, and then cured to obtain modified fibers.

[0013] Furthermore, in step A1, the ball milling operation step includes: adding silica to a planetary ball mill, adding zirconia grinding balls with a diameter of 5-10 mm, a ball-to-material ratio of 10:1, and ball milling for 1-2 hours to obtain pretreated silica; in step A2, the amount ratio of the pretreated silica, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, deionized water and ethanol is 2-4g:0.5-1g:5-10mL:50-80mL, and the post-processing step includes: after the reaction is completed, the reaction mixture is heated to 100°C. The system is cooled to room temperature, filtered, and the filter cake is washed 2-3 times with deionized water and ethanol, transferred to an oven at a temperature of 50-60° C., and dried to constant weight to obtain modified silica; in step A3, the amount ratio of the modified polyurethane, N,N-dimethylformamide, modified silica and glass fiber is 2-4 g:100-200 mL:1-2 g:3-5 g, and the post-processing step includes: after the reaction is completed, transferring the product to an oven at a temperature of 90-100° C. and drying to constant weight to obtain modified fiber.

[0014] Furthermore, the modified polyurethane is prepared by the following steps: B1. Place polycarbonate diol, 2,2-dimethylolpropionic acid, stannous octoate, and acetone in a reactor protected by a nitrogen atmosphere and stir. Add a calculated amount of 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane. Heat the reactor to 80-90° C. and keep the temperature for 2-4 hours to obtain a prepolymer solution. B2. Place the prepolymer liquid, epoxy resin and modified polysiloxane in a reactor protected by nitrogen atmosphere and stir. Heat the reactor to 55-65° C., add triethylamine, keep the temperature and react for 20-30 minutes, and post-treat to obtain modified polyurethane.

[0015] The preparation reaction principle of modified polyurethane is: During the reaction, under the action of high temperature and catalyst, the terminal hydroxyl structures of polycarbonate diol and 2,2-dimethylolpropionic acid undergo nucleophilic reaction with the isocyanate group of 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane to obtain a prepolymer liquid. The prepolymer in the prepolymer liquid further undergoes nucleophilic reaction with the amino group of the modified polysiloxane to obtain an interpenetrating cross-linked emulsion-like modified polyurethane.

[0016] Furthermore, in step B1, the amount ratio of the polycarbonate diol, 2,2-dimethylolpropionic acid, stannous octoate and acetone is 3-5g:0.5-1g:0.2-0.4g:30-60mL, and the amount of 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane added is 0.55 times the total molar amount of hydroxyl groups of the polycarbonate diol and 2,2-dimethylolpropionic acid; in step B2, the amount ratio of the prepolymer liquid, epoxy resin, modified polysiloxane and triethylamine is 20-25mL:2-4g:1-2g:1-3g, and the post-treatment step includes: after the reaction is completed, the reaction liquid is cooled to room temperature, the reaction liquid is transferred to a rotary evaporator at a temperature of 50-60°C, and vacuum rotary evaporation is performed until no liquid is recovered to obtain a modified polyurethane.

[0017] Furthermore, the preparation method of the modified polysiloxane is as follows: hexamethylcyclotrisiloxane, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane and N,N-dimethylformamide are added to a reactor, the temperature of the reactor is increased to 100-120°C, sulfuric acid solution is added to the reactor, the reaction is kept warm for 4-5 hours, and then post-processed to obtain the modified polysiloxane.

[0018] The preparation reaction formula of modified polysiloxane is:

[0019] The preparation reaction principle of modified polysiloxane is: During the reaction, under the action of an alkaline catalyst, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane undergo a ring-opening condensation reaction to obtain an amino-terminated modified polysiloxane.

[0020] Furthermore, the amount ratio of hexamethylcyclotrisiloxane, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, N,N-dimethylformamide and sulfuric acid solution is 2.5-3.5 g:2-4 g:3-5 g:80-120 mL:2-4 mL, the sulfuric acid solution is a 40-50 wt% aqueous sulfuric acid solution, and the post-treatment step includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction solution is transferred to a rotary evaporator at a temperature of 80-100 ° C, and distilled under reduced pressure until no liquid is produced to obtain modified polysiloxane.

[0021] The present invention has the following beneficial effects: The present invention prepares a modified polysiloxane having a fluorine atom and an amino end capping in a side chain by telomerization, and uses the modified polysiloxane and an epoxy resin as a polyurethane chain extender to prepare the modified polyurethane. The amino end capping polysiloxane can react with an isocyanate group in a prepolymer solution or an epoxy group of the epoxy resin to form a block structure. The Si-O bond is flexible and has a high bond energy, so that the modified polyurethane chain segment has a strong deformation energy absorption capacity. When the engineering plastic is subjected to an impact load, the modified polyurethane chain segment can undergo reversible curling and slippage, buffering stress concentration, delaying crack propagation, and improving the impact resistance of the engineering plastic. The trifluoropropyl side chain has the characteristics of being hydrophobic and having low surface energy. When the trifluoropropyl side chain is used as a block structure, the waterproof and oil resistance of the surface of the modified polyurethane is improved, and the waterproof and oil resistance of the engineering plastic is further improved. Moreover, under the action of the modified polyurethane, the bonding between white carbon black and glass fiber is enhanced, and the modified polyurethane is not easy to fall off or become hollow during friction, thereby improving the wear resistance of the engineering plastic.

[0022] The present invention combines white carbon black and glass fiber by physical and covalent bonding through modified polyurethane to obtain modified fibers, and melt-extrudes the modified fibers, modified polyimide, and auxiliary additives to prepare high-barrier engineering plastics. White carbon black and glass fiber can form a micro-scale inorganic barrier phase, which is arranged in a staggered and overlapping manner in the high-barrier engineering plastic matrix to extend the penetration path. The modified polyurethane coating interface forms a hermetic sealing layer, reduces micropore permeability, and avoids problems such as debonding of the filler and matrix interface, hole formation, and microcrack propagation caused by grease penetration. The modified polyimide has natural low permeability and high polarity chain segments, which combine to form a synergistic barrier structure, thereby improving the waterproof and oil-resistant properties of the engineering plastics. The white carbon black and glass fiber work together to improve the wear resistance and impact resistance of the engineering plastics. The modified polyurethane serves as an intermediate bonding layer, and enhances the interfacial bonding force between the inorganic reinforcing phase and the modified polyimide matrix through covalent bonding, thereby avoiding stress concentration and substrate peeling caused by grease, and further improving the mechanical properties and oil resistance of the engineering plastics.

[0023] The present invention uses a diamine monomer containing a trifluoromethyl group and a diamine monomer containing an ether bond to react with anhydride, and further obtains a modified polyimide through dehydration condensation. The modified polyimide contains an ether bond and a fluorine group, and has strong compatibility with the silicon oxygen chain and the fluorocarbon chain in the modified polyurethane, thereby enhancing the wetting and coating ability of the modified fiber surface, promoting the penetration of the molecular chain, improving the interface bonding strength, and further enhancing the mechanical properties of the engineering plastic. The modified polyimide has a coexistence structure of medium rigidity and flexible segments, and the modified fiber has a rigid core and a flexible coating layer. After the two are melt-blended, a soft and hard combined layered or network structure is formed, which can have It effectively dissipates impact energy. The ether bonds and flexible chain segments in the flexible polyimide have the ability to absorb stress and adjust volume. The coating layer of the modified polyurethane surrounds the rigid filler core to form a buffer zone at the interface. When oil enters the surface of the material, it can delay and alleviate the oil-induced swelling reaction of the polymer chain, significantly improving the impact resistance and oil resistance of engineering plastics. The fluorine element and ether bond in the modified polyimide main chain give it natural low permeability and polar screening properties, forming a micro-scale inorganic barrier with the white carbon black and glass fiber in the modified fiber, forming a multi-phase and multi-level barrier channel, and greatly improving the barrier ability of engineering plastics to water vapor, gas and oil. DETAILED DESCRIPTION

[0024] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] The density of the white carbon black used in the present invention is 2.6 g / cm 3 , particle size is 325 mesh, water content is 0.01%; The glass fiber used in the present invention has a specification of 3-20 mm and a diameter of 11-13 μm; The polycarbonate diol used in the present invention has a molecular weight of 1000, a melting point of 33°C, and a water content of less than 0.1; The specific name of the epoxy resin used in the present invention is epoxy resin E-44, with a viscosity of 0.041 and a solid content of 99%.

[0026] Example 1 This embodiment provides a method for preparing a modified polyurethane used in a modified fiber for high-barrier engineering plastics used in the processing of grease gun oil storage cylinders, comprising the following steps: Step I: Preparation of modified polysiloxane Weigh: 25 g of hexamethylcyclotrisiloxane, 20 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 30 g of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane and 800 mL of N,N-dimethylformamide and add them to the reactor. After the temperature of the reactor is raised to 100 ° C, 20 mL of 40 wt% sulfuric acid aqueous solution is added to the reactor. After the reaction is kept warm for 4 hours, after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is transferred to a rotary evaporator at a temperature of 80 ° C, and distilled under reduced pressure until no liquid is produced to obtain modified polysiloxane.

[0027] Step II: Preparation of prepolymer solution Weigh: 30 g of polycarbonate diol, 5 g of 2,2-dihydroxymethylpropionic acid, 2 g of stannous octoate and 300 mL of acetone, place them in a reactor protected by a nitrogen atmosphere and stir, add 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane at a rate of 0.55 times the total molar amount of hydroxyl groups of polycarbonate diol and 2,2-dihydroxymethylpropionic acid, heat the reactor to 80°C, and keep the reaction warm for 2 hours to obtain a prepolymer solution.

[0028] Step III: Preparation of modified polyurethane Weigh: 200 mL of prepolymer liquid, 20 g of epoxy resin and 10 g of modified polysiloxane are placed in a reactor protected by a nitrogen atmosphere and stirred. The reactor is heated to 55°C, 10 g of triethylamine is added, and the reaction is kept warm for 20 minutes. After the reaction is completed, the reaction liquid is cooled to room temperature and transferred to a rotary evaporator at a temperature of 50°C. Reduced pressure rotary evaporation is carried out until no liquid is recovered to obtain a modified polyurethane.

[0029] Example 2 This embodiment provides a method for preparing a modified polyurethane used in a modified fiber for high-barrier engineering plastics used in the processing of grease gun oil storage cylinders, comprising the following steps: Step I: Preparation of modified polysiloxane Weigh: 30 g of hexamethylcyclotrisiloxane, 30 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 40 g of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane and 1000 mL of N,N-dimethylformamide and add them to the reactor. After the temperature of the reactor is raised to 110°C, 30 mL of 45 wt% aqueous sulfuric acid solution is added to the reactor. After the reaction is kept warm for 4.5 hours, after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is transferred to a rotary evaporator at a temperature of 90°C, and distilled under reduced pressure until no liquid is produced to obtain modified polysiloxane.

[0030] Step II: Preparation of prepolymer solution Weigh: 40 g of polycarbonate diol, 7 g of 2,2-dihydroxymethylpropionic acid, 3 g of stannous octoate and 450 mL of acetone, place them in a reactor protected by a nitrogen atmosphere and stir, add 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane at a rate of 0.55 times the total molar amount of hydroxyl groups of polycarbonate diol and 2,2-dihydroxymethylpropionic acid, heat the reactor to 85°C, and keep the reaction warm for 3 hours to obtain a prepolymer solution.

[0031] Step III: Preparation of modified polyurethane Weigh: 225 mL of prepolymer liquid, 30 g of epoxy resin and 15 g of modified polysiloxane are placed in a reactor protected by a nitrogen atmosphere and stirred. The reactor is heated to 60°C, 20 g of triethylamine is added, and the reaction is kept warm for 25 minutes. After the reaction is completed, the reaction liquid is cooled to room temperature and transferred to a rotary evaporator at a temperature of 55°C. Reduced pressure rotary evaporation is carried out until no liquid is recovered to obtain a modified polyurethane.

[0032] Example 3 This embodiment provides a method for preparing a modified polyurethane used in a modified fiber for high-barrier engineering plastics used in the processing of grease gun oil storage cylinders, comprising the following steps: Step I: Preparation of modified polysiloxane Weigh: 35 g of hexamethylcyclotrisiloxane, 40 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 50 g of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane and 1200 mL of N,N-dimethylformamide and add them to the reactor. After the temperature of the reactor is raised to 120°C, 40 mL of a 50 wt% aqueous sulfuric acid solution is added to the reactor. After the reaction is kept warm for 5 hours, after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction solution is transferred to a rotary evaporator at a temperature of 100°C, and distilled under reduced pressure until no liquid is produced to obtain a modified polysiloxane.

[0033] Step II: Preparation of prepolymer solution Weigh: 50 g of polycarbonate diol, 10 g of 2,2-dihydroxymethylpropionic acid, 4 g of stannous octoate and 600 mL of acetone, place them in a reactor protected by a nitrogen atmosphere and stir, add 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane at a rate of 0.55 times the total molar amount of hydroxyl groups of polycarbonate diol and 2,2-dihydroxymethylpropionic acid, heat the reactor to 90°C, and keep the reaction for 4 hours to obtain a prepolymer solution.

[0034] Step III: Preparation of modified polyurethane Weigh: 250 mL of prepolymer liquid, 40 g of epoxy resin and 20 g of modified polysiloxane are placed in a reactor protected by a nitrogen atmosphere and stirred. The reactor is heated to 65°C, 30 g of triethylamine is added, and the reaction is kept warm for 30 minutes. After the reaction is completed, the reaction liquid is cooled to room temperature and transferred to a rotary evaporator at a temperature of 60°C. Reduced pressure rotary evaporation is carried out until no liquid is recovered to obtain a modified polyurethane.

[0035] Example 4 This embodiment provides a method for preparing a modified fiber for high-barrier engineering plastics used in the processing of grease gun oil storage cylinders, comprising the following steps: Step ①: Preparation of pretreated white carbon black Add silica into a planetary ball mill, add zirconia grinding balls with a diameter of 5 mm, and the ball-to-material ratio is 10:1. Ball milling is carried out for 1 hour to obtain pretreated silica.

[0036] Step ②, preparation of modified silica Weigh: 20 g of pretreated silica, 5 g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 50 mL of deionized water and 500 mL of ethanol, place them in a reactor and stir, heat the reactor to 45°C, and keep the reaction for 2 hours. After the reaction is completed, cool the reaction system to room temperature, filter, wash the filter cake twice with deionized water and ethanol, transfer it to an oven at 50°C, and dry it to constant weight to obtain modified silica.

[0037] Step 3: Preparation of modified fiber Weigh: 20 g of the modified polyurethane prepared in Example 1, 1000 mL of N,N-dimethylformamide and 10 g of modified silica were placed in a reactor, stirred at room temperature for 20 min, 30 g of glass fiber was added, and ultrasonic dispersion was performed for 2 h. After the reaction was completed, the product was transferred to an oven at a temperature of 90°C and dried to constant weight to obtain modified fiber.

[0038] Example 5 This embodiment provides a method for preparing a modified fiber for high-barrier engineering plastics used in the processing of grease gun oil storage cylinders, comprising the following steps: Step ①: Preparation of pretreated white carbon black Add silica into a planetary ball mill, add zirconia grinding balls with a diameter of 10 mm, and the ball-to-material ratio is 10:1. Ball milling is carried out for 1.5 hours to obtain pretreated silica.

[0039] Step ②, preparation of modified silica Weigh: 30 g of pretreated silica, 7 g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 70 mL of deionized water and 600 mL of ethanol, place them in a reactor and stir, heat the reactor to 50°C, and keep the reaction for 3 hours. After the reaction is completed, cool the reaction system to room temperature, filter, and wash the filter cake three times with deionized water and ethanol, transfer it to an oven at 55°C, and dry it to constant weight to obtain modified silica.

[0040] Step 3: Preparation of modified fiber Weigh: 30 g of the modified polyurethane prepared in Example 2, 1500 mL of N,N-dimethylformamide and 15 g of modified silica were placed in a reactor, stirred at room temperature for 25 min, 40 g of glass fiber was added, and ultrasonic dispersion was performed for 3 h. After the reaction was completed, the product was transferred to an oven at a temperature of 95°C and dried to constant weight to obtain modified fiber.

[0041] Example 6 This embodiment provides a method for preparing a modified fiber for high-barrier engineering plastics used in the processing of grease gun oil storage cylinders, comprising the following steps: Step ①: Preparation of pretreated white carbon black Add silica into a planetary ball mill, add zirconia grinding balls with a diameter of 10 mm, and the ball-to-material ratio is 10:1. Ball milling is carried out for 2 hours to obtain pretreated silica.

[0042] Step ②, preparation of modified silica Weigh: 40 g of pretreated silica, 10 g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 100 mL of deionized water and 800 mL of ethanol, place them in a reactor and stir, heat the reactor to 55 ° C, and keep the reaction for 4 hours. After the reaction is completed, the reaction system is cooled to room temperature, filtered, and the filter cake is washed 3 times with deionized water and ethanol, transferred to an oven at a temperature of 60 ° C, and dried to constant weight to obtain modified silica.

[0043] Step 3: Preparation of modified fiber Weigh: 40 g of the modified polyurethane prepared in Example 3, 2000 mL of N,N-dimethylformamide and 20 g of modified silica were placed in a reactor, stirred at room temperature for 30 min, 50 g of glass fiber was added, and ultrasonic dispersion was performed for 4 h. After the reaction was completed, the product was transferred to an oven at a temperature of 100°C and dried to constant weight to obtain modified fiber.

[0044] Example 7 This embodiment provides a method for preparing a high-barrier engineering plastic used in the processing of a grease gun oil storage cylinder, comprising the following steps: Step (1): preparing a mixed solution Weigh 20 g of aminopropyl ether, 30 g of 2,2'-bis(trifluoromethyl)diaminobiphenyl and 1500 mL of N-methylpyrrolidone and place them in a reactor and stir. Cool the reactor to 0°C, slowly add 20 g of pyromellitic dianhydride, and stir at this temperature for 10 minutes. Heat the reactor to 50°C, add 60 g of triethylamine, and stir at this temperature for 8 hours. Post-treat to obtain a mixed solution.

[0045] Step (2): Preparation of modified polyimide Weigh: 500 mL of the mixed solution and 800 mL of N-methylpyrrolidone are placed in a reactor and stirred. The reactor is heated to 60°C, 60 g of acetic anhydride and 80 g of triethylamine are slowly added, and the reaction is kept warm for 10 hours. After the reaction is completed, the reaction system is cooled to room temperature, and the reaction liquid is added to 2500 mL of deionized water for precipitation. The filter cake is washed twice with deionized water, transferred to an oven at 60°C, and dried to constant weight to obtain a modified polyimide.

[0046] Step (3): Preparation of high barrier engineering plastics N,N'-diphenyl-p-phenylenediamine, paraffin wax and bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate are uniformly mixed in a mass ratio of 1:2:4 to obtain an auxiliary additive for later use; The modified polyimide, the modified fiber prepared in Example 4, and the auxiliary additives were added into a twin-screw extruder in a mass ratio of 6:1.5:0.5, melt-extruded, and pelletized to obtain a high-barrier engineering plastic; The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 290°C, 290°C, 300°C, 300°C, 310°C, 310°C, 330°C, and 330°C, respectively. The main engine speed of the twin-screw extruder is 100 rpm and the pressure is 100 bar.

[0047] Example 8 This embodiment provides a method for preparing a high-barrier engineering plastic used in the processing of a grease gun oil storage cylinder, comprising the following steps: Step (1): preparing a mixed solution Weigh: 30 g of aminopropyl ether, 40 g of 2,2'-bis(trifluoromethyl)diaminobiphenyl and 1700 mL of N-methylpyrrolidone, place them in a reactor and stir, cool the reactor to 3°C, slowly add 30 g of pyromellitic dianhydride, keep warm and stir for 12 minutes, heat the reactor to 55°C, add 70 g of triethylamine, keep warm and stir for 9 hours, and post-treat to obtain a mixed solution.

[0048] Step (2): Preparation of modified polyimide Weigh: 650 mL of the mixed solution and 900 mL of N-methylpyrrolidone were placed in a reactor and stirred. The reactor was heated to 63°C, 80 g of acetic anhydride and 90 g of triethylamine were slowly added, and the reaction was kept warm for 11 hours. After the reaction was completed, the reaction system was cooled to room temperature, and the reaction solution was added to 2700 mL of deionized water for precipitation. The filter cake was washed three times with deionized water, transferred to an oven at 70°C, and dried to constant weight to obtain a modified polyimide.

[0049] Step (3): Preparation of high barrier engineering plastics N,N'-diphenyl-p-phenylenediamine, paraffin wax and bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate are uniformly mixed in a mass ratio of 1:2:4 to obtain an auxiliary additive for later use; The modified polyimide, the modified fiber prepared in Example 5, and the auxiliary additives were added into a twin-screw extruder in a mass ratio of 6.5:1.7:0.7, melt-extruded, and pelletized to obtain a high-barrier engineering plastic; The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 290°C, 290°C, 300°C, 300°C, 310°C, 310°C, 330°C, and 330°C, respectively. The main engine speed of the twin-screw extruder is 110rpm and the pressure is 125bar.

[0050] Example 9 This embodiment provides a method for preparing a high-barrier engineering plastic used in the processing of a grease gun oil storage cylinder, comprising the following steps: Step (1): preparing a mixed solution Weigh: 40 g of aminopropyl ether, 50 g of 2,2'-bis(trifluoromethyl)diaminobiphenyl and 2000 mL of N-methylpyrrolidone, place them in a reactor and stir, cool the reactor to 5°C, slowly add 40 g of pyromellitic dianhydride, keep warm and stir for 15 minutes, heat the reactor to 60°C, add 80 g of triethylamine, keep warm and stir for 10 hours, and post-treat to obtain a mixed solution.

[0051] Step (2): Preparation of modified polyimide Weigh: 800 mL of the mixed solution and 1000 mL of N-methylpyrrolidone were placed in a reactor and stirred. The reactor was heated to 65°C, 90 g of acetic anhydride and 100 g of triethylamine were slowly added, and the reaction was kept warm for 12 hours. After the reaction was completed, the reaction system was cooled to room temperature, and the reaction solution was added to 3000 mL of deionized water for precipitation. The filter cake was washed three times with deionized water, transferred to an oven at 80°C, and dried to constant weight to obtain a modified polyimide.

[0052] Step (3): Preparation of high barrier engineering plastics N,N'-diphenyl-p-phenylenediamine, paraffin wax and bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate are uniformly mixed in a mass ratio of 1:2:4 to obtain an auxiliary additive for later use; The modified polyimide, the modified fiber prepared in Example 6, and the auxiliary additives were added into a twin-screw extruder at a mass ratio of 8:2:1, melt-extruded, and pelletized to obtain a high-barrier engineering plastic; The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 290°C, 290°C, 300°C, 300°C, 310°C, 310°C, 330°C, and 330°C, respectively. The main engine speed of the twin-screw extruder is 120rpm and the pressure is 150bar.

[0053] Comparative Example 1 The difference between this comparative example and Example 9 is that, when preparing the modified polyurethane in step III, the use of modified polysiloxane is omitted.

[0054] Comparative Example 2 The difference between this comparative example and Example 9 is that, in step (3), when preparing the high barrier engineering plastic, an equal amount of glass fiber is used instead of the modified fiber.

[0055] Comparative Example 3 The difference between this comparative example and Example 9 is that, in step (1) of preparing the mixed solution, the use of 2,2'-bis(trifluoromethyl)diaminobiphenyl is omitted.

[0056] Performance testing: The volumetric wear of the engineering plastics prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 9867-2008 "Determination of wear resistance of vulcanized or thermoplastic rubber (rotating roller abrader method)". The Izod impact strength of the engineering plastics prepared in Examples 7-9 and Comparative Examples 1-3 was tested with reference to the standard GB / T 1843-2008 “Determination of Izod Impact Strength of Plastics”; The engineering plastics prepared in Examples 7-9 and Comparative Examples 1-3 were subjected to grease penetration tests with reference to the standard GB 18296-2019 “Safety performance requirements and test methods for automobile fuel tanks and their installation”. The volume wear and Izod impact strength of the test samples were tested with reference to the standards GB / T 9867-2008 and GB / T 1843-2008, and the volume wear retention rate and Izod impact strength retention rate were calculated. The oil resistance of the test samples was tested. The specific data are shown in Table 1.

[0057] Table 1 - Performance test data of each sample

[0058] Data Analysis: Comparing and analyzing the data in Table 1, it can be found that the volume wear of the engineering plastic prepared by the present invention is 3.6mm 3 , Izod impact strength is 84.3kJ·m -2 , grease permeability is 0.05%, volume wear retention rate is 98.7%, and cantilever beam impact strength retention rate is 99.1%. All data are better than the comparative example. The present invention prepares modified polysiloxane with fluorine atoms and amino end-capping in the side chain through polymerization reaction, and uses modified polysiloxane and epoxy resin as polyurethane chain extenders to prepare modified polyurethane. Through the modified polyurethane, white carbon black and glass fiber are combined together through physical and covalent bonds to obtain modified fibers. The modified fibers are melt-extruded with modified polyimide and auxiliary additives to prepare high-barrier engineering plastics, which not only improves the barrier properties and oil resistance of the engineering plastics, but also improves its mechanical properties.

[0059] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing high-barrier engineering plastics for use in grease gun oil storage cylinders, characterized in that: The following steps are involved: S1. Place aminopropyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl and N-methylpyrrolidone in a reaction kettle and stir. Cool the reaction kettle to 0-5°C, slowly add pyromellitic dianhydride, and stir at this temperature for 10-15 minutes. Heat the reaction kettle to 50-60°C, add triethylamine, and stir at this temperature for 8-10 hours to obtain a mixed solution. S2, placing the mixed solution and N-methylpyrrolidone in a reaction kettle and stirring, heating the reaction kettle to 60-65° C., slowly adding acetic anhydride and triethylamine, keeping the temperature to react for 10-12 hours, and post-treating to obtain modified polyimide; S3. Adding the modified polyimide, modified fiber and auxiliary additives into a twin-screw extruder, and melt-extruded to obtain high-barrier engineering plastics.

2. The method for preparing high-barrier engineering plastics for grease gun oil storage cylinder processing according to claim 1, characterized in that: In step S1, the amount ratio of the aminopropyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl, N-methylpyrrolidone, pyromellitic dianhydride and triethylamine is 2-4g:3-5g:150-200mL:2-4g:6-8g; in step S2, the amount ratio of the mixed solution, N-methylpyrrolidone, acetic anhydride and triethylamine is 50-80mL:80-100mL:6-9g:8-10g; in step S3, the mass ratio of the modified polyimide, modified fiber and auxiliary additives is 6-8:1.5-2:0.5-1.

3. The method for preparing high-barrier engineering plastics for grease gun oil storage cylinder processing according to claim 1, characterized in that: The modified fiber is prepared by the following steps: A1. Ball milling silica to obtain pretreated silica; A2. Pretreated silica, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, deionized water, and ethanol were placed in a reactor and stirred. The reactor was heated to 45-55° C. and kept warm for 2-4 hours. Modified silica was obtained by post-treatment. A3. Place modified polyurethane, N,N-dimethylformamide and modified silica in a reactor, stir at room temperature for 20-30 minutes, add glass fiber, ultrasonically disperse for 2-4 hours, and post-treat to obtain modified fiber.

4. The method for preparing high-barrier engineering plastics for use in grease gun oil storage cylinder processing according to claim 3, characterized in that: In step A2, the amount ratio of the pretreated silica, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, deionized water and ethanol is 2-4g:0.5-1g:5-10mL:50-80mL; in step A3, the amount ratio of the modified polyurethane, N,N-dimethylformamide, modified silica and glass fiber is 2-4g:100-200mL:1-2g:3-5g.

5. The method for preparing high-barrier engineering plastics for use in grease gun oil storage cylinder processing according to claim 3, characterized in that: The modified polyurethane is prepared by the following steps: B1. Place polycarbonate diol, 2,2-dimethylolpropionic acid, stannous octoate, and acetone in a reactor protected by a nitrogen atmosphere and stir. Add a calculated amount of 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane. Heat the reactor to 80-90° C. and keep the temperature for 2-4 hours to obtain a prepolymer solution. B2. Place the prepolymer liquid, epoxy resin and modified polysiloxane in a reactor protected by nitrogen atmosphere and stir. Heat the reactor to 55-65° C., add triethylamine, keep the temperature and react for 20-30 minutes, and post-treat to obtain modified polyurethane.

6. The method for preparing high-barrier engineering plastics for use in grease gun oil storage cylinder processing according to claim 5, characterized in that: In step B1, the amount ratio of the polycarbonate diol, 2,2-dimethylolpropionic acid, stannous octoate and acetone is 3-5g:0.5-1g:0.2-0.4g:30-60mL, and the amount of 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane added is 0.55 times the total molar amount of hydroxyl groups of the polycarbonate diol and 2,2-dimethylolpropionic acid; in step B2, the amount ratio of the prepolymer liquid, epoxy resin, modified polysiloxane and triethylamine is 20-25mL:2-4g:1-2g:1-3g.

7. The method for preparing high-barrier engineering plastics for use in grease gun oil storage cylinder processing according to claim 5, characterized in that: The modified polysiloxane preparation method comprises the following steps: adding hexamethylcyclotrisiloxane, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane and N,N-dimethylformamide into a reaction kettle; raising the temperature of the reaction kettle to 100-120° C.; adding potassium hydroxide into the reaction kettle; carrying out heat preservation reaction for 4-5 hours; and performing post-treatment to obtain the modified polysiloxane.

8. The method for preparing high-barrier engineering plastics for use in grease gun oil storage cylinder processing according to claim 7, characterized in that: The amount ratio of the hexamethylcyclotrisiloxane, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, N,N-dimethylformamide and sulfuric acid solution is 2.5-3.5 g:2-4 g:3-5 g:80-120 mL:2-4 mL, and the sulfuric acid solution is a 40-50 wt% sulfuric acid aqueous solution.

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