Nylon reinforced high-barrier packaging film and preparation method thereof

Abstract

The invention discloses a nylon-reinforced high-barrier packaging film and a preparation method thereof, belongs to the technical field of packaging film processing, and aims to solve the technical problem that the barrier property and the mechanical property of a packaging film in the prior art need to be further improved. The hydrophobic modified PA6 material specifically comprises the following raw materials in parts by weight: 60-80 parts of hydrophobic modified PA6, 10-15 parts of a toughening elastomer, 1-2 parts of a modified nucleating agent and 5-8 parts of an auxiliary additive. The hydrophobic modified PA6, the toughening elastomer, the modified nucleating agent and the auxiliary additive are subjected to melt casting to form a film, so that the high-barrier packaging film is obtained, the barrier property of the packaging film to water vapor and oxygen is improved, and the toughness of the packaging film is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging film processing, and in particular to a nylon-reinforced high-barrier packaging film and a preparation method thereof. Background Art

[0002] In recent years, as the packaging industry's requirements for material performance continue to increase, nylon has become a key substrate in the field of high-barrier packaging due to its excellent mechanical strength, puncture resistance, heat resistance and chemical stability. Through blending modification, copolymerization technology or nano-composite methods, the performance of nylon-based packaging films has been significantly expanded.

[0003] Currently, polyamide 6 (PA6) and polyamide 66 (PA66) are widely used in the field of functional packaging films due to their low cost and good film-forming properties. By compounding with materials such as polyethylene, polypropylene, and ethylene-vinyl alcohol copolymer, they can achieve comprehensive performance requirements such as light and thin structure, strong barrier properties, and good heat sealing performance, meeting the needs of packaging in multiple scenarios such as food preservation, drug stability, and protection of high-end electronic components.

[0004] Nowadays, despite the excellent performance of nylon-based packaging films, there are still some problems in practical applications. The amide groups in the nylon molecular chain are highly hydrophilic, which causes the film material to easily absorb moisture and expand in a humid environment, resulting in reduced dimensional stability. The barrier layer may fail due to hydrolysis, and is especially unsuitable for cold chain transportation or packaging in high humidity areas. At the same time, the crystallization rate of nylon during the film formation process is slow, and the cooling and setting time is long. The low crystallinity easily forms microporous paths, which weakens the barrier effect of the nylon packaging film on water vapor and oxygen. The addition of inorganic nucleating agents to improve the crystallinity of the nylon packaging film, because the inorganic nucleating agents themselves are rigid particles, form a rigid-flexible interface in the polymer matrix. When stress is concentrated around the particles, they easily become the starting point of microcracks, reducing the toughness of the packaging film. Summary of the Invention

[0005] The object of the present invention is to provide a nylon reinforced high barrier packaging film and a preparation method thereof, so as to solve the technical problem in the prior art that the barrier properties and mechanical properties of the packaging film need to be further improved.

[0006] The object of the present invention can be achieved by the following technical solution: A nylon reinforced high barrier packaging film comprises the following raw materials, measured in parts: 60-80 parts of hydrophobically modified PA6, 10-15 parts of toughening elastomer, 1-2 parts of modified nucleating agent and 5-8 parts of auxiliary additives;

[0007] The hydrophobically modified PA6 is prepared by the following method:

[0008] A1. Place 1,12-diaminododecane, sebacic acid, and ethanol in a reactor, heat to 65-75°C, and react for 4-6 hours. Post-treat to obtain a hydrophobically modified PA6 precursor.

[0009] A2. Place caprolactam, m-xylenediamine and hydrophobically modified PA6 precursor in a reactor, introduce nitrogen, raise the temperature to 240-250°C, and keep the temperature for reaction for 6-8 hours to obtain hydrophobically modified PA6.

[0010] The preparation reaction formula of hydrophobically modified PA6 is:

[0011]

[0012] The preparation reaction principle of hydrophobically modified PA6 is:

[0013] During the reaction, the carboxyl group of sebacic acid and the amino group of 1,12-diaminododecane form an ion-pair structured nylon salt in ethanol to obtain a hydrophobically modified PA6 precursor. Under high temperature conditions, caprolactam undergoes ring-opening polymerization and copolymerizes with the hydrophobically modified PA6 precursor, with m-xylenediamine as a molecular weight regulator, to obtain a hydrophobically modified PA6.

[0014] Furthermore, in step A1, the amount ratio of the 1,12-diaminododecane, sebacic acid and ethanol is 2-4 g: 2-4 g: 150-200 mL, and the post-treatment step includes: after the reaction is completed, the reaction temperature is cooled to room temperature, filtered, and the filter cake is transferred to an oven at a temperature of 50-60°C and dried to constant weight to obtain a hydrophobically modified PA6 precursor; in step A2, the amount ratio of the caprolactam, m-xylenediamine and hydrophobically modified PA6 precursor is 10-20 g: 0.1-0.3 g: 8-10 g.

[0015] Furthermore, the toughened elastomer is prepared by the following steps:

[0016] B1. Place 1-heptene, methylaluminoxane solution, 5-vinylbicyclo[2.2.1]hept-2-ene, toluene, and a catalyst in a reactor protected by a nitrogen atmosphere, heat to 100-105° C., keep the temperature for reaction for 0.5-1 hour, and perform post-treatment to obtain a modified polyolefin;

[0017] The preparation reaction formula of modified polyolefin is:

[0018]

[0019] The preparation reaction principle of modified polyolefin is:

[0020] During the reaction, methylaluminoxane activates the dimethylsilyl-tert-butylamine tetramethylcyclopentadiene titanium dichloride through an alkylation reaction, generating a cationic active center whose vacant orbital can coordinate with the olefin monomer, initiating polymerization. The monomer π bonds of 1-heptene and 5-vinylbicyclo[2.2.1]hept-2-ene coordinate with the vacant orbital of the Ti⁺ center to form a π-complex. The olefin double bond opens and inserts between the Ti-C bonds, initiating chain growth. The catalytic activity of dimethylsilyl-tert-butylamine tetramethylcyclopentadiene titanium dichloride is highly selective. The bridging double bond in 5-vinylbicyclo[2.2.1]hept-2-ene has concentrated electron density and high spatial tension, making it more easily captured by the Ti center and preferentially undergoing coordination insertion. The vinyl group in the molecule is located in the side chain and has low steric hindrance. However, in this catalytic system, it is not as affinity with the metal center as the endocyclic double bond and does not participate in the polymerization reaction, ultimately yielding a modified polyolefin.

[0021] B2. Place the modified polyolefin, 3-mercapto-1,2-propanediol, azobiscyclohexylcarbonitrile and toluene in a reactor protected by a nitrogen atmosphere, heat to 85-95° C., keep the temperature for reaction for 4-6 hours, and post-treat to obtain a hydroxyl-modified polyolefin;

[0022] The preparation reaction formula of hydroxyl-modified polyolefin is:

[0023]

[0024] The preparation reaction principle of hydroxyl-modified polyolefins is:

[0025] During the reaction, azobiscyclohexylcarbonitrile decomposes under high temperature to generate free radicals, which trigger an ene-thiol click reaction between the unsaturated double bond of the side chain olefin in the modified polyolefin and 3-mercapto-1,2-propanediol to obtain a hydroxyl-modified polyolefin.

[0026] B3. Place hydroxy-modified polyolefin, N-benzo-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)phenyl)aniline and acetone in a reaction kettle, stir for 15-30 minutes, heat to 170-180°C, remove acetone, keep warm for reaction for 5-10 minutes, and post-treat to obtain a toughened elastomer.

[0027] The preparation reaction formula of toughened elastomer is:

[0028]

[0029] Where: .

[0030] The preparation reaction principle of toughened elastomer is:

[0031] During the reaction process, under high temperature conditions, the pinacol borate group in N-benzo-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)phenyl)aniline undergoes an ester exchange reaction with the hydroxyl-modified polyolefin to form a dynamic borate ester bond to obtain a toughened elastomer.

[0032] Furthermore, in step B1, the amount ratio of the 1-heptene, methylaluminoxane solution, 5-vinylbicyclo[2.2.1]hept-2-ene, toluene and catalyst is 4-6g:1-2mL:6-8g:150-200mL:0.01-0.02g, the methylaluminoxane solution is composed of methylaluminoxane and toluene in a ratio of 1g:10mL, and the catalyst is dimethylsilyl tert-butylamine tetramethylcyclopentadiene titanium dichloride. The post-treatment step includes: after the reaction is completed, the reaction temperature is cooled to room temperature, the reaction solution is added to 500-600mL of 0.5vol% hydrochloric acid ethanol solution, stirred for 4-6h, filtered, the filter cake is washed with ethanol 3-5 times, transferred to an oven at a temperature of 40-50°C, and dried to constant weight to obtain a modified polyolefin;

[0033] In step B2, the modified polyolefin, 3-mercapto-1,2-propanediol, azobiscyclohexylcarbonitrile and toluene are used in a ratio of 2-4 g: 5-7 g: 0.5-1 g: 100-150 mL. The post-treatment step includes: after the reaction is completed, the reaction temperature is cooled to room temperature, the reaction solution is added to 300-400 mL of ethanol, filtered, and the filter cake is transferred to an oven at a temperature of 50-60° C. and dried to constant weight to obtain a hydroxyl-modified polyolefin;

[0034] In step B3, the amount ratio of the hydroxy-modified polyolefin, N-benzo-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)phenyl)aniline and acetone is 4-6g:3-5g:150-200mL, and the post-treatment step includes: after the reaction is completed, the reaction solution is cooled to room temperature, filtered, the filter cake is washed with acetone 2-3 times, transferred to an oven at a temperature of 50-60°C, and dried to constant weight to obtain a toughened elastomer.

[0035] Furthermore, the modified nucleating agent is prepared by the following steps:

[0036] C1. Add expanded vermiculite into a double planetary ball mill and mill for 15-20 minutes to obtain layered vermiculite;

[0037] The preparation reaction principle of layered vermiculite is:

[0038] During the ball milling process, the expanded vermiculite is subjected to high-frequency impact, shear and centrifugal force, which promotes slip and separation between crystal layers. The original tight layered structure is decomposed into multiple layers of flaky vermiculite to obtain layered vermiculite.

[0039] C2. Place layered vermiculite, sodium chloride and deionized water in a reactor, stir at room temperature for 0.5-1 hour, and post-treat to obtain a modified nucleating agent precursor;

[0040] The preparation reaction principle of the modified nucleating agent precursor is:

[0041] During the reaction, sodium chloride dissolves and dissociates into Na⁺ and Cl⁻. Na⁺ diffuses into the interlayer of vermiculite and undergoes ion exchange reaction with the original cations K⁺, Ca²⁺, etc. in the interlayer of the layered vermiculite, replacing the original ions to obtain a modified nucleating agent precursor.

[0042] C3. Place the modified nucleating agent precursor, hexadecyltrimethylammonium bromide and deionized water in a reaction kettle, heat to 50-60° C., keep the temperature for reaction for 4-6 hours, and perform post-treatment to obtain the modified nucleating agent.

[0043] The preparation reaction principle of the modified nucleating agent is:

[0044] During the reaction, hexadecyltrimethylammonium bromide is hydrolyzed to CTAB + and Br - , further undergoes cation exchange reaction with the sodium ions in the modified nucleating agent precursor, and the long-chain alkyl part is directionally arranged between the layers to obtain a modified nucleating agent.

[0045] Furthermore, in step C1, the ball mill speed is 600 r / min, the ball-to-material ratio is 10:1, and the grinding balls are zirconia with a diameter of 5-20 mm; in step C2, the amount ratio of the layered vermiculite, sodium chloride and deionized water is 1-2 g:1-3 g:30-50 mL, and the post-processing step includes: after the reaction is completed, filtering, washing the filter cake with deionized water 2-3 times, transferring it to an oven at a temperature of 40-50°C, and drying it to constant weight to obtain a modified nucleating agent precursor; in step C3, the amount ratio of the modified nucleating agent precursor, hexadecyltrimethylammonium bromide and deionized water is 2-4 g:1-3 g:35-45 mL, and the post-processing step includes: after the reaction is completed, filtering, washing the filter cake with deionized water 2-3 times, transferring it to an oven at a temperature of 60-70°C, and drying it to constant weight to obtain a modified nucleating agent.

[0046] The present invention also provides a method for preparing a nylon-reinforced high-barrier packaging film, comprising uniformly mixing hydrophobically modified PA6, a toughening elastomer, a modified nucleating agent, and auxiliary additives, adding the mixture to a casting machine, and casting the mixture into a film to obtain a high-barrier packaging film.

[0047] Furthermore, the auxiliary additives are composed of an antioxidant, a light stabilizer, and an antistatic agent in a mass ratio of 2:1:1, the antioxidant is one or more of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, or 4,4'-thiobis(6-tert-butyl-3-methylphenol), the light stabilizer is one or more of 2-hydroxy-4-n-octyloxybenzophenone, 2-(2-hydroxy-5-methylphenyl)benzotriazole, or 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, and the antistatic agent is one or more of polyvinyl alcohol, alkylphenol polyoxyethylene ether, or amide phosphate;

[0048] The temperatures of each section of the casting machine from the feed port to the discharge port are 220°C, 240°C, 260°C, 280°C, 280°C, 260°C, 240°C, and 220°C, the screw speed is 50-70r / min, and the casting roller speed is 3-5mm / s.

[0049] The present invention has the following beneficial effects:

[0050] 1. The present invention introduces a long carbon chain structure into PA6 to obtain hydrophobically modified PA6, prepares a linear polyolefin using a metallocene catalyst, further prepares a toughened elastomer containing borate dynamic bonds through an ene-thiol click reaction and an ester exchange reaction, obtains a modified nucleating agent by ball milling and intercalation modification of expanded vermiculite, and forms a high-barrier packaging film by melt casting using the hydrophobically modified PA6, the toughened elastomer, the modified nucleating agent, and auxiliary additives. The present invention introduces a long carbon chain structure into the PA6 molecular chain to dilute the proportion of amide groups in the molecular chain, reduce the overall polarity of the PA6 molecule, and weaken the interaction between the amide group and water molecules, thereby reducing the surface energy of the packaging film and increasing the water contact angle, thereby improving the hydrophobic properties of PA6 and making the prepared packaging film have good water vapor barrier properties. At the same time, the flexibility of the long carbon chain increases the mobility of the molecular chain, thereby improving the toughness and tear resistance of the packaging film, and enhancing the tear strength of the packaging film, making it less likely to break when dropped or squeezed.

[0051] 2. When preparing the toughened elastomer, the present invention uses a metallocene catalyst to prepare a modified polyolefin containing an olefin double bond in the side chain. This structure not only improves the processing fluidity of the polymer, but also provides active sites for subsequent chemical modification, so that the packaging film has good ductility and film uniformity during the molding process. Further, a toughened elastomer with borate dynamic bonds is prepared through ene-thiol click reaction and ester exchange reaction. The reversible properties of the borate dynamic bonds give the packaging film self-healing ability and toughness. The borate dynamic bonds dissipate energy through bond breaking and recombination under the action of external force, thereby improving the tear strength and impact resistance of the packaging film. When microcracks are generated on the surface of the packaging film, the borate bonds can spontaneously recombine at room temperature or under slight heating conditions, realizing autonomous healing of micron-level damage and improving the barrier properties of the packaging film.

[0052] 3. The present invention ball-mills expanded vermiculite to significantly refine the particle size of the expanded vermiculite powder. The fine particle size enables the modified nucleating agent to be more evenly dispersed in the packaging film matrix. The sodium chloride treatment replaces the original cations between the vermiculite layers with Na⁺ through ion exchange, expands the interlayer spacing, and provides more heterogeneous nucleation sites for the hydrophobically modified PA6 molecular chains. In the molten state, the nylon molecular chains preferentially adsorb on the active sites on the vermiculite surface, achieving a transition from homogeneous nucleation to heterogeneous nucleation, thereby increasing the crystallization rate of the modified PA6. The hexadecyltrimethylammonium bromide intercalation modification further inserts hydrophobic long-chain alkyl groups to form an organic-inorganic composite interface. It promotes the crystallization of the polymer in the packaging film on the vermiculite surface, thereby improving the mechanical strength and barrier properties of the packaging film. At the same time, the hydrophobic long-chain alkyl portion of hexadecyltrimethylammonium bromide is directionally arranged between the layers, changing the water contact angle of the modified nucleating agent from hydrophilic to hydrophobic. The barrier properties of the vermiculite layered structure and the dense organic layer formed by the intercalation of hexadecyltrimethylammonium bromide work synergistically to significantly improve the barrier properties of the packaging film against water vapor and oxygen. At the same time, the hydroxyl groups of the toughened elastomer and the carboxyl groups of the hydrophobically modified PA6 undergo an esterification reaction under high-temperature melt film-forming conditions, thereby improving the interfacial bonding performance between the packaging film matrix and further enhancing its mechanical properties. DETAILED DESCRIPTION

[0053] 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.

[0054] The expanded vermiculite used in the present invention is purchased from Lingshou County Dekai Mineral Products Processing Plant, with a specification of 2-4 mm, a product name of mineral silicate, a product name of vermiculite, and a product density of 2.56 g / cm3 g / cm³;

[0055] The dimethylsilyl tert-butylamine tetramethylcyclopentadiene titanium dichloride used in the present invention is purchased from Pushan Industrial (Shaanxi) Co., Ltd., with the brand name Pushan and the product category being metal catalyst.

[0056] Example 1

[0057] This embodiment provides a method for preparing hydrophobically modified PA6 for nylon-reinforced high-barrier packaging film, comprising the following steps:

[0058] Step I: Preparation of hydrophobically modified PA6 precursor

[0059] Weigh: 20 g of 1,12-diaminododecane, 20 g of sebacic acid and 1500 mL of ethanol, place them in a reactor, heat to 65°C, and keep warm for 4 hours. After the reaction is completed, wait for the reaction temperature to cool to room temperature, filter, and transfer the filter cake to an oven at 50°C and dry to constant weight to obtain a hydrophobically modified PA6 precursor.

[0060] Step II: Preparation of hydrophobically modified PA6

[0061] Weigh: 100 g of caprolactam, 80 g of m-xylenediamine and 1 g of hydrophobically modified PA6 precursor and place them in a reactor. Pass nitrogen into the reactor, heat it to 240° C., and keep the temperature to react for 6 h to obtain hydrophobically modified PA6.

[0062] Example 2

[0063] This embodiment provides a method for preparing hydrophobically modified PA6 for nylon-reinforced high-barrier packaging film, comprising the following steps:

[0064] Step I: Preparation of hydrophobically modified PA6 precursor

[0065] Weigh: 30 g of 1,12-diaminododecane, 30 g of sebacic acid and 1700 mL of ethanol, place them in a reactor, heat to 70°C, and keep warm for 5 hours. After the reaction is completed, wait for the reaction temperature to cool to room temperature, filter, and transfer the filter cake to an oven at 55°C and dry to constant weight to obtain a hydrophobically modified PA6 precursor.

[0066] Step II: Preparation of hydrophobically modified PA6

[0067] Weigh: 150 g of caprolactam, 90 g of m-xylenediamine and 2 g of hydrophobically modified PA6 precursor, place them in a reactor, introduce nitrogen, raise the temperature to 245° C., and keep the temperature for 7 hours to obtain hydrophobically modified PA6.

[0068] Example 3

[0069] This embodiment provides a method for preparing hydrophobically modified PA6 for nylon-reinforced high-barrier packaging film, comprising the following steps:

[0070] Step I: Preparation of hydrophobically modified PA6 precursor

[0071] Weigh: 40 g of 1,12-diaminododecane, 40 g of sebacic acid and 2000 mL of ethanol, place them in a reactor, heat to 75°C, and keep warm for 6 hours. After the reaction is completed, wait for the reaction temperature to cool to room temperature, filter, and transfer the filter cake to an oven at 60°C and dry to constant weight to obtain a hydrophobically modified PA6 precursor.

[0072] Step II: Preparation of hydrophobically modified PA6

[0073] Weigh 200 g of caprolactam, 100 g of m-xylenediamine and 3 g of hydrophobically modified PA6 precursor and place them in a reactor. Pass nitrogen into the reactor, heat the reactor to 250° C., and keep the temperature to react for 8 h to obtain hydrophobically modified PA6.

[0074] Example 4

[0075] This embodiment provides a method for preparing a toughened elastomer for a nylon-reinforced high-barrier packaging film, comprising the following steps:

[0076] Step ①: Preparation of modified polyolefin

[0077] Mix methylaluminoxane and toluene in a ratio of 1 g:10 mL to obtain a methylaluminoxane solution for later use.

[0078] Weigh: 40 g of 1-heptene, 10 mL of methylaluminoxane solution, 60 g of 5-vinylbicyclo[2.2.1]hept-2-ene, 1500 mL of toluene and 0.1 g of dimethylsilyl tert-butylamine tetramethylcyclopentadiene titanium dichloride, place them in a reactor protected by a nitrogen atmosphere, heat to 100° C., and keep the temperature for 0.5 h. After the reaction is completed, wait for the reaction to cool to room temperature, add the reaction solution into 5000 mL of 0.5 vol% hydrochloric acid ethanol solution, stir for 4 h, filter, wash the filter cake with ethanol three times, transfer it to an oven at 40° C., and dry it to constant weight to obtain a modified polyolefin.

[0079] Step ②, preparation of hydroxyl-modified polyolefin

[0080] Weigh 20 g of modified polyolefin, 50 g of 3-mercapto-1,2-propylene glycol, 5 g of azobiscyclohexylcarbonitrile and 1000 mL of toluene, place them in a reactor protected by a nitrogen atmosphere, heat to 85° C., keep the temperature for 4 h, and post-treat to obtain hydroxyl-modified polyolefin.

[0081] Step ③: Preparation of toughened elastomer

[0082] Weigh: 40 g of hydroxy-modified polyolefin, 30 g of N-benzo-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)phenyl)aniline and 1500 mL of acetone, place them in a reactor, stir for 15 minutes, heat to 170°C, remove acetone, and keep warm for 5 minutes. After the reaction is completed, the reaction liquid is cooled to room temperature and filtered. The filter cake is washed twice with acetone, transferred to an oven at 50°C, and dried to constant weight to obtain a toughened elastomer.

[0083] Example 5

[0084] This embodiment provides a method for preparing a toughened elastomer for a nylon-reinforced high-barrier packaging film, comprising the following steps:

[0085] Step ①: Preparation of modified polyolefin

[0086] Mix methylaluminoxane and toluene in a ratio of 1 g:10 mL to obtain a methylaluminoxane solution for later use.

[0087] Weigh: 50 g of 1-heptene, 15 mL of methylaluminoxane solution, 70 g of 5-vinylbicyclo[2.2.1]hept-2-ene, 1700 mL of toluene and 0.15 g of dimethylsilyl tert-butylamine tetramethylcyclopentadiene titanium dichloride, place them in a reactor protected by a nitrogen atmosphere, heat to 102° C., and keep the reaction for 0.5 h. After the reaction is completed, wait for the reaction to cool to room temperature, add 5500 mL of 0.5 vol% hydrochloric acid ethanol solution, stir for 5 h, filter, wash the filter cake with ethanol four times, transfer it to an oven at 45° C., and dry it to constant weight to obtain a modified polyolefin.

[0088] Step ②, preparation of hydroxyl-modified polyolefin

[0089] Weigh: 30 g of modified polyolefin, 60 g of 3-mercapto-1,2-propanediol, 7 g of azobiscyclohexylcarbonitrile and 1250 mL of toluene, place them in a reactor protected by a nitrogen atmosphere, heat to 90° C., keep the temperature for reaction for 5 h, and post-treat to obtain hydroxyl-modified polyolefin.

[0090] Step ③: Preparation of toughened elastomer

[0091] Weigh: 50 g of hydroxy-modified polyolefin, 40 g of N-benzo-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)phenyl)aniline and 1700 mL of acetone, place them in a reactor, stir for 20 minutes, heat to 175°C, remove acetone, and keep warm for 7 minutes. After the reaction is completed, the reaction liquid is cooled to room temperature and filtered. The filter cake is washed twice with acetone, transferred to an oven at 55°C, and dried to constant weight to obtain a toughened elastomer.

[0092] Example 6

[0093] This embodiment provides a method for preparing a toughened elastomer for a nylon-reinforced high-barrier packaging film, comprising the following steps:

[0094] Step ①: Preparation of modified polyolefin

[0095] Mix methylaluminoxane and toluene in a ratio of 1 g:10 mL to obtain a methylaluminoxane solution for later use.

[0096] Weigh 60 g of 1-heptene, 20 mL of methylaluminoxane solution, 80 g of 5-vinylbicyclo[2.2.1]hept-2-ene, 2000 mL of toluene, and 0.2 g of dimethylsilyltert-butylaminetetramethylcyclopentadienetitanium dichloride in a reactor protected by a nitrogen atmosphere, heat to 105° C., and keep warm for 1 hour. After the reaction is completed, wait for the reaction to cool to room temperature, add 6000 mL of 0.5 vol% hydrochloric acid ethanol solution, stir for 6 hours, filter, wash the filter cake with ethanol 5 times, transfer to an oven at 50° C., and dry to constant weight to obtain a modified polyolefin.

[0097] Step ②, preparation of hydroxyl-modified polyolefin

[0098] Weigh: 40 g of modified polyolefin, 70 g of 3-mercapto-1,2-propanediol, 10 g of azobiscyclohexylcarbonitrile and 1500 mL of toluene, place them in a reactor protected by a nitrogen atmosphere, heat to 95° C., keep the temperature for 6 h, and post-treat to obtain hydroxyl-modified polyolefin.

[0099] Step ③: Preparation of toughened elastomer

[0100] Weigh: 60 g of hydroxy-modified polyolefin, 50 g of N-benzo-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)phenyl)aniline and 2000 mL of acetone, place them in a reactor, stir for 30 minutes, heat to 180°C, remove acetone, and keep warm for 10 minutes. After the reaction is completed, the reaction liquid is cooled to room temperature and filtered. The filter cake is washed with acetone three times, transferred to an oven at 60°C, and dried to constant weight to obtain a toughened elastomer.

[0101] Example 7

[0102] This embodiment provides a method for preparing a modified nucleating agent for a nylon-reinforced high-barrier packaging film, comprising the following steps:

[0103] Step ⒜, preparation of layered vermiculite

[0104] The expanded vermiculite was added into a double planetary ball mill with a ball milling speed of 600 r / min, a ball-to-material ratio of 10:1, and zirconia balls with a diameter of 5 mm. After ball milling for 15 minutes, layered vermiculite was obtained.

[0105] Step ⒝: Preparation of modified nucleating agent precursor

[0106] Weigh: 10 g of layered vermiculite, 10 g of sodium chloride and 300 mL of deionized water were placed in a reactor and stirred at room temperature for 0.5 h. After the reaction was completed, the filter cake was filtered and washed twice with deionized water, transferred to an oven at a temperature of 40° C., and dried to constant weight to obtain a modified nucleating agent precursor.

[0107] Step 7: Preparation of modified nucleating agent

[0108] Weigh: 20 g of modified nucleating agent precursor, 10 g of hexadecyltrimethylammonium bromide and 350 mL of deionized water, place them in a reactor, heat to 50 ° C, and keep warm for 4 hours. After the reaction is completed, filter, wash the filter cake twice with deionized water, transfer it to an oven at a temperature of 60 ° C, and dry it to constant weight to obtain a modified nucleating agent.

[0109] Example 8

[0110] This embodiment provides a method for preparing a modified nucleating agent for a nylon-reinforced high-barrier packaging film, comprising the following steps:

[0111] Step ⒜, preparation of layered vermiculite

[0112] The expanded vermiculite was added into a double planetary ball mill with a ball milling speed of 600 r / min, a ball-to-material ratio of 10:1, and zirconia balls with a diameter of 10 mm. After ball milling for 17 minutes, layered vermiculite was obtained.

[0113] Step ⒝: Preparation of modified nucleating agent precursor

[0114] Weigh: 15 g of layered vermiculite, 20 g of sodium chloride and 400 mL of deionized water were placed in a reactor and stirred at room temperature for 0.5 h. After the reaction was completed, the filter cake was filtered and washed twice with deionized water, transferred to an oven at a temperature of 40° C., and dried to constant weight to obtain a modified nucleating agent precursor.

[0115] Step 7: Preparation of modified nucleating agent

[0116] Weigh: 30 g of modified nucleating agent precursor, 20 g of hexadecyltrimethylammonium bromide and 400 mL of deionized water, place them in a reactor, heat to 55 ° C, and keep warm for 5 hours. After the reaction is completed, filter, wash the filter cake twice with deionized water, transfer it to an oven at a temperature of 65 ° C, and dry it to constant weight to obtain a modified nucleating agent.

[0117] Example 9

[0118] This embodiment provides a method for preparing a modified nucleating agent for a nylon-reinforced high-barrier packaging film, comprising the following steps:

[0119] Step ⒜, preparation of layered vermiculite

[0120] The expanded vermiculite was added into a double planetary ball mill with a ball milling speed of 600 r / min, a ball-to-material ratio of 10:1, and a grinding ball of zirconia with a diameter of 20 mm. After ball milling for 20 minutes, layered vermiculite was obtained.

[0121] Step ⒝: Preparation of modified nucleating agent precursor

[0122] Weigh: 20 g of layered vermiculite, 30 g of sodium chloride and 500 mL of deionized water were placed in a reactor and stirred at room temperature for 1 hour. After the reaction was completed, the filter cake was filtered and washed three times with deionized water. The filter cake was transferred to an oven at 50° C. and dried to constant weight to obtain a modified nucleating agent precursor.

[0123] Step 7: Preparation of modified nucleating agent

[0124] Weigh: 40 g of modified nucleating agent precursor, 30 g of hexadecyltrimethylammonium bromide and 450 mL of deionized water, place them in a reactor, heat to 60 ° C, and keep warm for 6 hours. After the reaction is completed, filter, wash the filter cake with deionized water 3 times, transfer it to an oven at a temperature of 70 ° C, and dry it to constant weight to obtain a modified nucleating agent.

[0125] Example 10

[0126] This embodiment provides a method for preparing a nylon-reinforced high-barrier packaging film, comprising the following steps:

[0127] 2,6-di-tert-butyl-4-methylphenol, 2-(2-hydroxy-5-methylphenyl)benzotriazole and alkylphenol polyoxyethylene ether are uniformly mixed in a mass ratio of 2:1:1 to obtain an auxiliary additive, which is set aside;

[0128] 60 parts of the hydrophobically modified PA6 prepared in Example 1, 10 parts of the toughened elastomer prepared in Example 4, 1 part of the modified nucleating agent prepared in Example 7, and 5 parts of auxiliary additives were mixed evenly, added to a casting machine, and cast into a film to obtain a high barrier packaging film;

[0129] The temperatures of each section of the casting machine from the feed port to the discharge port are 220°C, 240°C, 260°C, 280°C, 280°C, 260°C, 240°C, and 220°C, the screw speed is 50r / min, and the casting roller speed is 3mm / s.

[0130] Example 11

[0131] This embodiment provides a method for preparing a nylon-reinforced high-barrier packaging film, comprising the following steps:

[0132] 2,6-di-tert-butyl-4-methylphenol, 2-(2-hydroxy-5-methylphenyl)benzotriazole and alkylphenol polyoxyethylene ether are uniformly mixed in a mass ratio of 2:1:1 to obtain an auxiliary additive, which is set aside;

[0133] 70 parts of the hydrophobically modified PA6 prepared in Example 2, 13 parts of the toughened elastomer prepared in Example 5, 1.5 parts of the modified nucleating agent prepared in Example 8, and 6.5 parts of auxiliary additives were mixed evenly, added to a casting machine, and cast into a film to obtain a high barrier packaging film;

[0134] The temperatures of each section of the casting machine from the feed port to the discharge port are 220°C, 240°C, 260°C, 280°C, 280°C, 260°C, 240°C, and 220°C, the screw speed is 60r / min, and the casting roller speed is 4mm / s.

[0135] Example 12

[0136] This embodiment provides a method for preparing a nylon-reinforced high-barrier packaging film, comprising the following steps:

[0137] 2,6-di-tert-butyl-4-methylphenol, 2-(2-hydroxy-5-methylphenyl)benzotriazole and alkylphenol polyoxyethylene ether are uniformly mixed in a mass ratio of 2:1:1 to obtain an auxiliary additive, which is set aside;

[0138] 80 parts of the hydrophobically modified PA6 prepared in Example 3, 15 parts of the toughened elastomer prepared in Example 6, 2 parts of the modified nucleating agent prepared in Example 9, and 8 parts of auxiliary additives were mixed evenly, added to a casting machine, and cast into a film to obtain a high barrier packaging film;

[0139] The temperatures of each section of the casting machine from the feed port to the discharge port are 220°C, 240°C, 260°C, 280°C, 280°C, 260°C, 240°C, and 220°C, the screw speed is 70r / min, and the casting roller speed is 5mm / s.

[0140] Comparative Example 1

[0141] The difference between this comparative example and Example 12 is that, in step II, when preparing the hydrophobically modified PA6, the addition of the hydrophobically modified PA6 precursor is omitted.

[0142] Comparative Example 2

[0143] The difference between this comparative example and Example 12 is that the addition of the toughening elastomer is omitted when preparing the high barrier packaging film.

[0144] Comparative Example 3

[0145] The difference between this comparative example and Example 12 is that the addition of the modified nucleating agent is omitted when preparing the high barrier packaging film.

[0146] Performance testing:

[0147] The tensile strength and elongation at break of the high barrier packaging films prepared in Examples 10-12 and Comparative Examples 1-3 were measured with reference to the standard GB / T 1040.3-2006 “Determination of tensile properties of plastics Part 3: Test conditions for films and sheets”;

[0148] The tear strength of the high barrier packaging films prepared in Examples 10-12 and Comparative Examples 1-3 was measured with reference to the standard GB / T 16578.1-2008 “Plastic Film and Sheeting - Determination of Tear Resistance - Part 1: Trouser Tear Method”;

[0149] The oxygen and water vapor permeability of the samples were measured with reference to the standard GB / T 40266-2021 “General rules for quality of oxide barrier transparent plastic composite films and bags for food packaging”. Specific data are shown in Table 1.

[0150] Table 1 - Performance test data of each sample

[0151] Project Group Example 10 Example 11 Example 12 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength / MPa 63.6 64.7 64.0 45.3 36.7 41.2 Elongation at break / % 322.4 323.6 321.9 287.5 154.8 245.3 <![CDATA[Tear strength / kN·m -1 > 55.4 56.2 55.3 41.7 36.2 34.6 <![CDATA[Oxygen permeability / cm 3 ·(m 2 ·24h·0.1MPa) -1 > 0.12 0.13 0.13 0.15 0.18 0.17 <![CDATA[Water vapor transmission rate / g·(m 2 ·24h) -1 > 0.09 0.10 0.08 0.16 0.17 0.16

[0152] Data Analysis:

[0153] By comparing and analyzing the data in the above table, it can be seen that the tensile strength of the high barrier packaging film prepared by the present invention is 64.7MPa, the elongation at break is 323.6%, and the tear strength is 56.2kN·m -1 , oxygen permeability is 0.13cm 3 ·(m 2·24h·0.1MPa) -1 And the water vapor transmission rate is 0.10g·(m 2 24h) -1 ;

[0154] A comparative analysis of the tabular data from Example 12 and Comparative Example 1 reveals that the tensile strength, elongation at break, tear strength, and water vapor permeability of the high-barrier packaging film prepared in Comparative Example 1 were significantly reduced. This demonstrates that the present invention, by introducing long carbon chains into the PA6 molecular chain, dilutes the proportion of amide groups in the molecular chain, reduces the overall polarity of the PA6 molecules, and weakens their interaction with water molecules. This reduces the surface energy of the packaging film, increases the water contact angle, and improves the hydrophobicity of PA6, resulting in excellent water vapor barrier properties for the prepared packaging film. Furthermore, the flexibility of the long carbon chains increases the mobility of the molecular chains, improving the toughness and tear resistance of the packaging film, making it less susceptible to rupture when dropped or squeezed.

[0155] A comparative analysis of the tabular data of Example 12 and Comparative Example 2 reveals that the tensile strength, elongation at break, tear strength, oxygen permeability, and water vapor permeability of the high-barrier packaging film prepared in Comparative Example 2 were significantly reduced. This demonstrates that, in preparing the toughened elastomer, the present invention uses a metallocene catalyst to prepare a modified polyolefin containing olefin double bonds in the side chain. This structure not only improves the processing fluidity of the polymer but also provides active sites for subsequent chemical modification, resulting in good ductility and film uniformity during the molding process of the packaging film. Furthermore, a toughened elastomer containing borate dynamic bonds was prepared through an ene-thiol click reaction and an ester exchange reaction. The reversible nature of the borate dynamic bonds imparts self-healing ability and toughness to the packaging film. The borate dynamic bonds dissipate energy through bond breakage and recombination under external force, thereby improving the tear strength and impact resistance of the packaging film. When microcracks form on the packaging film surface, the borate bonds spontaneously recombine at room temperature or under mild heating conditions, enabling autonomous healing of micron-level damage and improving the barrier properties of the packaging film.

[0156] Comparative analysis of the tabular data of Example 12 and Comparative Example 3 shows that the tensile strength, elongation at break, tear strength, oxygen permeability and water vapor permeability of the high barrier packaging film prepared in Comparative Example 3 are significantly reduced, indicating that the present invention greatly refines the particle size of the expanded vermiculite powder by ball milling the expanded vermiculite. The fine particle size enables the modified nucleating agent to be more evenly dispersed in the packaging film matrix. The sodium chloride treatment replaces the original cations between the vermiculite layers with Na⁺ through ion exchange, expands the interlayer spacing, and provides more heterogeneous nucleation sites for the hydrophobically modified PA6 molecular chains. In the molten state, the nylon molecular chains are preferentially adsorbed on the active sites on the vermiculite surface, realizing the transition from homogeneous nucleation to heterogeneous nucleation, thereby improving the crystallization rate of the modified PA6. The methylammonium bromide intercalation modification further inserts hydrophobic long-chain alkyl groups to form an organic-inorganic composite interface, promotes the crystallization of the polymer in the packaging film on the vermiculite surface, and improves the mechanical strength and barrier properties of the packaging film. At the same time, the hydrophobic long-chain alkyl parts of hexadecyltrimethylammonium bromide are directionally arranged between the layers, so that the water contact angle of the modified nucleating agent changes from hydrophilic to hydrophobic. The barrier properties of the vermiculite layered structure and the dense organic layer formed by the hexadecyltrimethylammonium bromide intercalation work synergistically, significantly improving the barrier properties of the packaging film to water vapor and oxygen. At the same time, the hydroxyl groups of the toughened elastomer and the carboxyl groups of the hydrophobically modified PA6 undergo esterification reaction under high-temperature melt film-forming conditions, which improves the interfacial bonding performance between the packaging film matrix and further improves its mechanical properties.

[0157] 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 nylon reinforced high barrier packaging film, characterized in that: The invention comprises the following raw materials in parts: 60-80 parts of hydrophobically modified PA6, 10-15 parts of toughening elastomer, 1-2 parts of modified nucleating agent and 5-8 parts of auxiliary additives; The hydrophobically modified PA6 is prepared by the following method: A1. Place 1,12-diaminododecane, sebacic acid, and ethanol in a reactor, heat to 65-75°C, and react for 4-6 hours. Post-treat to obtain a hydrophobically modified PA6 precursor. A2. Place caprolactam, m-xylenediamine and hydrophobically modified PA6 precursor in a reactor, introduce nitrogen, raise the temperature to 240-250°C, and keep the temperature for reaction for 6-8 hours to obtain hydrophobically modified PA6.

2. The nylon reinforced high barrier packaging film according to claim 1, characterized in that: In step A1, the usage ratio of 1,12-diaminododecane, sebacic acid and ethanol is 2-4 g:2-4 g:150-200 mL; in step A2, the usage ratio of caprolactam, m-phenylenediamine and hydrophobically modified PA6 precursor is 10-20 g:0.1-0.3 g:8-10 g.

3. The nylon reinforced high barrier packaging film according to claim 1, characterized in that: The toughened elastomer is prepared by the following steps: B1. Place 1-heptene, methylaluminoxane solution, 5-vinylbicyclo[2.2.1]hept-2-ene, toluene, and a catalyst in a reactor protected by a nitrogen atmosphere, heat to 100-105° C., keep the temperature for reaction for 0.5-1 hour, and perform post-treatment to obtain a modified polyolefin; B2. Place the modified polyolefin, 3-mercapto-1,2-propanediol, azobiscyclohexylcarbonitrile and toluene in a reactor protected by a nitrogen atmosphere, heat to 85-95° C., keep the temperature for reaction for 4-6 hours, and post-treat to obtain a hydroxyl-modified polyolefin; B3. Place hydroxy-modified polyolefin, N-benzo-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)phenyl)aniline and acetone in a reaction kettle, stir for 15-30 minutes, heat to 170-180°C, remove acetone, keep warm for reaction for 5-10 minutes, and post-treat to obtain a toughened elastomer.

4. The nylon reinforced high barrier packaging film according to claim 3, characterized in that: In step B1, the amount ratio of 1-heptene, methylaluminoxane solution, 5-vinylbicyclo[2.2.1]hept-2-ene, toluene and catalyst is 4-6g:1-2mL:6-8g:150-200mL:0.01-0.02g, the methylaluminoxane solution is composed of methylaluminoxane and toluene in an amount ratio of 1g:10mL, and the catalyst is dimethylsilyl tert-butylamine tetramethylcyclopentadiene titanium dichloride; in step B2, the modified polyolefin, 3-mercapto-1 , the amount ratio of 2-propylene glycol, azobiscyclohexylcarbonitrile and toluene is 2-4g:5-7g:0.5-1g:100-150mL; in step B3, the amount ratio of the hydroxy-modified polyolefin, N-benzo-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl)phenyl)aniline and acetone is 4-6g:3-5g:150-200mL.

5. The nylon reinforced high barrier packaging film according to claim 1, characterized in that: The modified nucleating agent is prepared by the following steps: C1. Add expanded vermiculite into a double planetary ball mill and mill for 15-20 minutes to obtain layered vermiculite; C2. Place layered vermiculite, sodium chloride and deionized water in a reactor, stir at room temperature for 0.5-1 hour, and post-treat to obtain a modified nucleating agent precursor; C3. Place the modified nucleating agent precursor, hexadecyltrimethylammonium bromide and deionized water in a reaction kettle, heat to 50-60° C., keep the temperature for reaction for 4-6 hours, and perform post-treatment to obtain the modified nucleating agent.

6. The nylon reinforced high barrier packaging film according to claim 5, characterized in that: In step C1, the ball mill speed is 600 r / min, the ball-to-material ratio is 10:1, and the grinding balls are zirconia with a diameter of 5-20 mm; in step C2, the amount ratio of the layered vermiculite, sodium chloride and deionized water is 1-2 g:1-3 g:30-50 mL; in step C3, the amount ratio of the modified nucleating agent precursor, hexadecyltrimethylammonium bromide and deionized water is 2-4 g:1-3 g:35-45 mL.

7. The method for preparing a nylon reinforced high barrier packaging film according to any one of claims 1 to 6, characterized in that: The hydrophobically modified PA6, toughening elastomer, modified nucleating agent and auxiliary additives are mixed evenly, added into a casting machine, cast into film, and a high barrier packaging film is obtained.

8. The method for preparing a nylon reinforced high barrier packaging film according to claim 7, characterized in that: The auxiliary additives are composed of an antioxidant, a light stabilizer, and an antistatic agent in a mass ratio of 2:1:1, wherein the antioxidant is one or more of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, or 4,4'-thiobis(6-tert-butyl-3-methylphenol); the light stabilizer is one or more of 2-hydroxy-4-n-octyloxybenzophenone, 2-(2-hydroxy-5-methylphenyl)benzotriazole, or 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole; and the antistatic agent is one or more of polyvinyl alcohol, alkylphenol polyoxyethylene ether, or amide phosphate.

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