High-temperature-cooking-resistant packaging bag and preparation process thereof

Abstract

The invention relates to the technical field of packaging materials, and discloses a packaging bag resistant to high-temperature cooking and a preparation technology thereof.The base material of the packaging bag is prepared from, by weight, 30-40 parts of polyamide, 20-35 parts of high-density polyethylene, 15-25 parts of polyethylene glycol terephthalate, 5-12 parts of a modified material, 2-5 parts of a plasticizer and 0.5-2 parts of an antioxidant; the modified material is prepared by the following steps: step 1, taking nano silicon dioxide, adding a silane coupling agent KH-550 accounting for 3-8% of the mass of the nano silicon dioxide, then adding an ethanol water solution (the volume ratio of ethanol to water is 3: 1), and stirring and reacting at 60-80 DEG C for 1.5-2.5 hours to obtain silane modified nano silicon dioxide; through the improved processes of silane coupling agent KH-550 modification, montmorillonite compounding and 600 DEG C nitrogen calcination, under the condition of the same dosage, no fracture layering is achieved, and the antibacterial rate and tensile strength are improved, so that the preparation process of the modified material is the key for solving the problems of insufficient compatibility, poor high-temperature resistance and weak antibacterial effect of the base material, and the comprehensive performance of the material is improved.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, specifically to a high-temperature resistant retort packaging bag and its preparation process. Background Technology

[0002] High-temperature retort pouches are widely used in food packaging for meat, grains, and prepared meals. They need to withstand high-temperature sterilization at temperatures above 121°C while possessing good mechanical properties and hygienic safety. Existing technologies have the following shortcomings: Insufficient high-temperature resistance: Traditional packaging bags use a single polyamide or polyethylene substrate, which is prone to cracking and delamination after 30 minutes of retort at 121°C, failing to meet sterilization requirements; Antibacterial dependence on additives: To achieve antibacterial effects, antibacterial agents such as nano-silver and zinc oxide need to be added, which not only increases costs but also may pose a risk of heavy metal migration. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a high-temperature resistant retort packaging bag and its preparation process. By using biaxial stretching parameters and heat-sealing pretreatment, it achieves a synergistic improvement in properties such as high temperature resistance, high antibacterial properties, and tensile strength without adding antibacterial agents.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a high-temperature resistant retort packaging bag, wherein the base material of the packaging bag is composed of the following components in parts by weight: 30-40 parts of polyamide, 20-35 parts of high-density polyethylene, 15-25 parts of polyethylene terephthalate, 5-12 parts of modified material, 2-5 parts of plasticizer, and 0.5-2 parts of antioxidant; The modified material is prepared through the following steps: Step 1: Take nano-silica, add 3-8% of its mass of silane coupling agent KH-550, then add an aqueous ethanol solution (ethanol to water volume ratio 3:1), stir and react at 60-80℃ for 1.5-2.5 hours to obtain silane-modified nano-silica; Step 2: Mix silane-modified nano-silica and montmorillonite at a weight ratio of 1:(0.3-0.6), add maleic anhydride-grafted polyethylene (20-40% of the total mass of silane-modified nano-silica and montmorillonite), and then add deionized water (solid-liquid ratio 1:5). Disperse the mixture ultrasonically at 300-500W for 20-40 minutes to obtain a mixed slurry. Step 3: Dry the mixed slurry at 80-100℃ until the moisture content is ≤0.5%, then place it in a muffle furnace and heat it to 550-650℃ at a heating rate of 1-2℃ / min. Calcine for 2-3 hours, cool to room temperature, and then pulverize to a particle size of 5-10μm to obtain the modified material. In the modified material, the weight ratio of nano-silica, montmorillonite, and maleic anhydride-grafted polyethylene is 1:0.4-0.5:0.25-0.35.

[0005] Preferably, in step 1, the amount of silane coupling agent KH-550 is 5-7% of the mass of nano-silica, the amount of ethanol aqueous solution added is 8-12 times the mass of nano-silica, and the stirring speed is 500-700 r / min.

[0006] Preferably, in step 2, the temperature is controlled at 40-50℃ during ultrasonic dispersion, and after ultrasonication, the mixture is stirred at a constant temperature of 50-60℃ for 10-15 minutes before proceeding to step 3, which involves drying.

[0007] Preferably, in step 3, nitrogen gas is introduced for protection during calcination, with a nitrogen flow rate of 100-150 mL / min. After calcination, the furnace is cooled to 100-120°C, and then the furnace is removed and placed in a desiccator to cool to room temperature.

[0008] A process for preparing a high-temperature resistant retort pouch, comprising the following steps: Step A: Mix polyamide, high-density polyethylene, polyethylene terephthalate, modifier, plasticizer, and antioxidant according to the weight parts, and stir at 800-1200 r / min for 15-25 minutes to obtain a mixed substrate; Step B: Add the mixed substrate to a twin-screw extruder, control the temperature of the first zone of the extruder to 160-180℃, the temperature of the second zone to 200-220℃, the temperature of the third zone to 210-230℃, the screw speed to 30-50 r / min, and the vacuum degree to -0.08 to -0.09 MPa. After extrusion, the substrate is formed into a film preform through the die. Step C: The film preform is biaxially stretched, with the longitudinal stretching temperature at 80-95℃ and the stretching ratio at 2.5-3.2 times; the transverse stretching temperature at 95-110℃ and the stretching ratio at 3.0-3.5 times; after stretching, it is heat-set at 120-140℃ for 5-10 seconds to obtain the substrate film. Step D: The substrate film is heat-sealed at a temperature of 180-200℃, a pressure of 0.3-0.5MPa, and a time of 1-2 seconds. After cooling to 25-35℃, it is cut to obtain the high-temperature resistant retort packaging bag. This packaging bag has an antibacterial rate of ≥90% against Escherichia coli without the addition of any antibacterial materials, and can withstand boiling at 121℃ for 30 minutes without cracking or delamination.

[0009] Preferably, in step B, the temperature of the four zones of the twin-screw extruder is controlled at 220-235℃, the die temperature is controlled at 230-240℃, and the thickness of the extruded film preform is controlled at 0.8-1.2mm.

[0010] Preferably, in step C, the film preform is preheated at 60-70°C for 5-8 minutes before biaxial stretching, and then cooled to 50-60°C by air cooling after heat setting, before the heat sealing process in step D is performed.

[0011] Preferably, in step D, the heat-sealing area of ​​the substrate film is subjected to plasma treatment before heat sealing. The plasma treatment power is 200-300W, the treatment time is 3-5 seconds, and the treatment distance is 2-3mm.

[0012] Preferably, in step A, the polyamide, high-density polyethylene, and polyethylene terephthalate are preheated at 100-110°C for 10-15 minutes before the modified material, plasticizer, and antioxidant are added and stirred.

[0013] Preferably, in step D, the cooling adopts a segmented cooling method: first, cooling at 50-60℃ for 1-2 minutes, then cooling at 30-40℃ for 1-2 minutes, and finally cooling to 25-35℃. The edges of the cut packaging bag are trimmed with hot air at a temperature of 150-180℃ for 0.5-1 seconds.

[0014] Compared with the prior art, the present invention provides a high-temperature resistant retort packaging bag and its preparation process, which has the following beneficial effects: The present invention achieves no cracking and delamination under the same dosage through the improved process of modification with silane coupling agent KH-550, composite with montmorillonite and nitrogen calcination at 600℃, and improves the antibacterial rate and tensile strength. It can be seen that the modified material preparation process is the key to solving the problems of insufficient compatibility of the substrate, poor high-temperature resistance and weak antibacterial effect, thereby improving the overall performance of the material.

[0015] By improving the process of raw material preheating at 100-110℃, precise extrusion at 160-235℃, biaxial stretching at 2.5-3.5 times, and plasma treatment at 200-300W, not only can 121℃ cooking be achieved without damage, but tensile strength and antibacterial rate are also significantly improved, solving the problems of poor heat sealing reliability, insufficient mechanical properties, and reliance on antibacterial additives in the existing process. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] The equipment, instruments, and corresponding models required for the preparation and testing of high-temperature resistant retort packaging bags in this application are as follows: For the modified material preparation stage, a constant-temperature magnetic stirrer (model DF-101S, meeting the requirements of 60-80℃ temperature control and 500-700r / min stirring), an ultrasonic cleaner (model KQ-500DE, power 300-500W, capable of 40-50℃ temperature-controlled ultrasonic dispersion), a forced-air drying oven (model DHG-9070A, used for drying at 80-100℃ to a moisture content ≤0.5%), a muffle furnace with nitrogen protection (model SX2-4-10N, supporting a heating rate of 1-2℃ / min and calcination at 550-650℃), and a planetary ball mill (model XQM-4, capable of pulverizing to 5-10μm) are required. Particle size); The packaging bag preparation stage requires a twin-screw extruder (model SHJ-35, capable of precise control of multi-zone temperature 160-235℃ and rotation speed 30-50r / min), a biaxially oriented film forming machine (model KL-300, meeting longitudinal stretching of 80-95℃ / 2.5-3.2 times and transverse stretching of 95-110℃ / 3.0-3.5 times), a plasma surface treatment machine (model PT-2000, power 200-300W, processing distance 2-3mm), and a heat sealer (model DLS-300, temperature control 180-200℃ and pressure 0.3-0.5MPa); the performance testing stage requires an electronic universal tensile testing machine (model WDW-5, for testing tensile strength and elongation at break), and a high-temperature retort (model LS-120, maintaining 121℃ / 0.12MPa). (Steaming / boiling), sterile ultra-clean workbench (model SW-CJ-2FD, used for aseptic operation of antibacterial testing), constant temperature and humidity incubator (model LRH-250, 37℃ / 90% humidity incubation), pipette (model Gilson P1000, used for bacterial inoculation and elution transfer).

[0018] It should be noted that the equipment, instruments and models are not specifically limited, and those skilled in the art can use them to achieve the desired purpose, without further details.

[0019] Example 1: A process for preparing a high-temperature resistant retort packaging bag specifically includes the following steps: Preparation of modified materials: Step 1: Take 10g of nano silica, add 0.5g (5%) KH-550, add 80g of ethanol aqueous solution (3:1), stir at 70℃ and 600r / min for 2 hours to obtain silane modified nano silica; Step 2: Mix silane-modified nano-silica and montmorillonite at a ratio of 1:0.4, add 25% of the total mass of MAH-g-PE, add deionized water (solid-liquid ratio 1:5), sonicate at 45℃ and 400W for 30 minutes, and stir at 55℃ for 12 minutes. Step 3: Dry at 80℃ to a moisture content of 0.4%, heat to 600℃ in a muffle furnace at 1.5℃ / min, calcine with nitrogen at 120mL / min for 2.5 hours, cool and then pulverize to 8μm.

[0020] Packaging bag preparation: Step A: Mix 30 parts PA, 35 parts HDPE, and 25 parts PET, preheat at 105℃ for 12 minutes, add 5 parts modified material, 2 parts DOP, and 0.5 parts antioxidant, and stir at 1000r / min for 20 minutes. Step B: Twin-screw extruder, zone 1 170℃, zone 2 210℃, zone 3 220℃, zone 4 225℃, speed 40r / min, vacuum -0.085MPa, die head 235℃, extruding 1.0mm preform; Step C: Preheat at 65℃ for 6 minutes, stretch longitudinally at 85℃ and 2.8 times, stretch laterally at 100℃ and 3.2 times, heat set at 130℃ for 8 seconds, and air cool to 55℃; Step D: 250W plasma treatment for 4 seconds (distance 2.5mm), 190℃, 0.4MPa heat sealing for 1.5 seconds, segmented cooling (55℃ for 1.5 minutes → 35℃ for 1.5 minutes → 30℃), 160℃ hot air trimming for 0.8 seconds.

[0021] Example 2 A process for preparing a high-temperature resistant retort packaging bag specifically includes the following steps: Preparation of modified materials: Step 1: 10g nano silica + 0.6g (6%) KH-550 + 100g ethanol aqueous solution, stir at 75℃ and 650r / min for 2 hours to obtain silane modified nano silica; Step 2: Mix silane-modified nano-silica and montmorillonite in a 1:0.45 ratio, add 30% MAH-g-PE, sonicate at 45℃ and 450W for 25 minutes, and stir at 55℃ for 12 minutes; Step 3: Dry at 90℃ to a moisture content of 0.3%, heat to 600℃ at 1.5℃ / min, calcine with nitrogen at 120mL / min for 2.5 hours, and pulverize to 8μm.

[0022] Packaging bag preparation: Step A: Add 35 parts PA, 28 parts HDPE, and 20 parts PET, preheat at 105℃ for 12 minutes, then add 8.5 parts modified material, 3.5 parts DOP, and 1.2 parts antioxidant, and stir at 1000r / min for 20 minutes. The parameters for step BD are the same as in Example 1.

[0023] Example 3 A process for preparing a high-temperature resistant retort packaging bag specifically includes the following steps: Preparation of modified materials: Step 1: 10g nano silica + 0.7g (7%) KH-550 + 120g ethanol aqueous solution, stir at 80℃ and 700r / min for 2 hours to obtain silane modified nano silica; Step 2: Mix silane-modified nano-silica and montmorillonite in a 1:0.5 ratio, add 35% MAH-g-PE, sonicate at 45℃ and 500W for 20 minutes, and stir at 55℃ for 12 minutes. Step 3: Dry at 100℃ to a moisture content of 0.2%, heat to 600℃ at 1.5℃ / min, calcine with nitrogen at 120mL / min for 2.5 hours, and pulverize to 8μm.

[0024] Packaging bag preparation: Step A: 40 parts PA, 20 parts HDPE, and 15 parts PET are preheated at 105℃ for 12 minutes. Then, 12 parts of modified material, 5 parts DOP, and 2 parts antioxidant are added, and the mixture is stirred at 1000r / min for 20 minutes. The parameters for step BD are the same as in Example 1.

[0025] Example 4 A process for preparing a high-temperature resistant retort packaging bag specifically includes the following steps: Preparation of modified materials: Same as in Example 2 (1:0.45:0.3 ratio); Packaging bag preparation: Step B: Twin-screw extruder, zone 1 180℃, zone 2 220℃, zone 3 230℃, zone 4 235℃, speed 50r / min; Step C: Preheat at 70℃ for 8 minutes, stretch longitudinally at 95℃ and 3.2 times, stretch laterally at 110℃ and 3.5 times, and heat set at 140℃ for 10 seconds; Step D: 300W plasma treatment for 5 seconds, heat sealing at 200℃ and 0.5MPa for 2 seconds; the remaining steps are the same as in Example 2.

[0026] Comparative Example 1 The replacement material was 5 parts of unmodified nano-silica, and the remaining steps were the same as in Example 1.

[0027] Comparative Example 2 In step 1 of the modified material preparation, KH-550 is not added, and the remaining steps are the same as in Example 1.

[0028] Comparative Example 3 The calcination temperature in step 3 of the modified material preparation is 400℃, and the remaining steps are the same as in Example 1.

[0029] Comparative Example 4 The temperature in zone B of the packaging bag preparation step is 150℃, and the remaining steps are the same as in Example 1.

[0030] Comparative Example 5 In step C of the packaging bag preparation, the longitudinal stretching ratio is 2.0 times, and the remaining steps are the same as in Example 1.

[0031] Comparative Example 6 In step D of the packaging bag preparation, plasma treatment is not performed; the remaining steps are the same as in Example 1.

[0032] Comparative Example 7 In step 2 of the modified material preparation, the ratio of silane-modified nano-silica to montmorillonite is 1:0.2, and the remaining steps are the same as in Example 1.

[0033] Comparative Example 8 In step A of packaging bag preparation, PA / HDPE / PET are mixed directly without preheating, and the remaining steps are the same as in Example 1.

[0034] Reference standard for high temperature retort resistance test: GB / T10004-2008 "Packaging Plastic Composite Films and Bags - Dry Lamination and Extrusion Lamination".

[0035] Detailed testing steps: Sample preparation: Randomly cut 3 samples with a size of 100mm×100mm from the packaging bags prepared in the examples / comparative examples (ensure that the samples are free of wrinkles and scratches and the heat-sealed edges are intact); inject 50mL of distilled water into each sample (simulating the actual contents of the packaging), and seal the opening end of the sample with the same heat-sealing parameters as the packaging bag preparation (e.g., 190℃, 0.4MPa, 1.5 seconds in Example 1) to ensure no leakage. (2) Equipment preparation: Use a high-temperature cooking pot with pressure control, add water to the specified scale in the pot, preheat to 121℃±1℃, and maintain the pressure in the pot at 0.12MPa±0.01MPa (corresponding to the saturated steam pressure at 121℃). (3) Cooking operation: Completely immerse the sealed sample in the water in the cooking pot, ensuring that the sample does not directly contact the pot wall, start the timer, and continue cooking for 30 minutes±1 minute at 121℃±1℃ and 0.12MPa±0.01MPa. (4) Cooling and observation: After the cooking is completed, turn off the heat source. After the pressure in the pot drops to atmospheric pressure and the temperature drops to below 50℃, take out the sample, wipe the surface moisture with clean gauze, and place it at room temperature (25℃±2℃) for 30 minutes. Then observe whether the sample shows cracking, delamination, deformation, leakage, etc., and record the state of each sample. (5) Result judgment: If there is no cracking, delamination, or leakage in 3 samples, it is considered "qualified for high temperature cooking"; if one or more samples show the above phenomena, it is considered "unqualified".

[0036] Reference standard for Escherichia coli inhibition rate test: GB / T31402-2015 "Test method for antibacterial properties of plastic surfaces".

[0037] Detailed testing steps: (1) Preparation of test strains and bacterial suspension: Escherichia coli (ATCC25922, standard strain) was used. Single colonies were picked from the slant culture medium and inoculated into nutrient broth medium. The culture was shaken at 37℃±1℃ and 180r / min for 18 hours±2 hours to obtain a bacterial suspension. The bacterial suspension was diluted with sterile physiological saline to a concentration of 1×10. 5 CFU / mL ~ 1×10 6 CFU / mL (concentration calibrated by plate count).

[0038] (2) Preparation of test samples and control samples: Cut three test samples (test group) with a size of 50mm×50mm from the packaging bag, and take three blank substrate films of the same size (prepared by mixing polyamide, HDPE and PET in the proportion of Example 1, without modification materials, control group); wipe the surface of the test samples and control samples with 75% ethanol, air dry in a sterile ultra-clean workbench, and sterilize with ultraviolet light for 30 minutes (surface sterilization only, to avoid affecting the substrate itself).

[0039] (3) Inoculation and culture: Under aseptic conditions, 0.1 mL of diluted Escherichia coli suspension was evenly dropped onto the surface of each sample (experimental group) and control sample (control group). The bacterial suspension was covered with a sterile polyethylene film (60 mm × 60 mm, sterilized) to ensure that the bacterial suspension was in full contact with the sample surface (without air bubbles). The sample and control sample were placed in a sterile petri dish and cultured in an incubator at 37℃ ± 1℃ and relative humidity above 90% for 24 hours ± 1 hour.

[0040] (4) Colony counting: After the culture is completed, the sample / control sample is transferred to an Erlenmeyer flask containing 10 mL of sterile physiological saline and shaken for 10 minutes (200 r / min) to fully wash away the bacteria attached to the surface and obtain the eluent; take 0.1 mL of the eluent and inoculate it onto nutrient agar medium using the "plate spread method" and incubate in an incubator at 37℃±1℃ for 24 hours±1 hour. Count the number of colonies (CFU) on each plate. Each sample / control sample is tested in parallel 3 times and the average value is taken.

[0041] Antibacterial rate (%) = [(average colony count of control group - average colony count of experimental group) ÷ average colony count of control group] × 100% (Note: If the colony count of the experimental group is 0, the antibacterial rate is calculated as 100%; if the colony count of the experimental group is greater than that of the control group, the antibacterial rate is calculated as 0%. The antibacterial rate of all embodiments in this application is ≥90%).

[0042] The reference standard for testing tensile strength and elongation at break is GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets".

[0043] Detailed testing steps: (1) Sample preparation: Cut samples from the film of the packaging bag substrate along the "longitudinal direction (stretching direction during packaging bag preparation)" and "transverse direction (perpendicular to the longitudinal direction)" respectively. Use "Type 1A dumbbell type" sample (standard size: total length 115mm, gauge length 50mm, gauge width 10mm, end width 25mm, thickness is the actual thickness of the film), and prepare 5 samples in each direction. Use vernier calipers (accuracy 0.01mm) to measure the width and thickness of the gauge segment of each sample. Measure each parameter 3 times, take the average value, and calculate the original cross-sectional area of ​​the sample (width × thickness).

[0044] (2) Equipment preparation: An electronic universal tensile testing machine is used, with the range selected to be 20%-80% of the maximum test force (the tensile strength of the specimen in this application is approximately 20-35 MPa, and the cross-sectional area is approximately 0.01-0.02 mm²). 2The maximum tensile force is approximately 0.2-0.7N; select the 0-1N range. calibrate the force and displacement accuracy of the tensile testing machine, set the tensile speed to 50mm / min ± 5mm / min, and the gauge length to 50mm (consistent with the gauge length of the sample).

[0045] (3) Test operation: Clamp both ends of the specimen in the upper and lower clamps of the tensile testing machine, respectively, to ensure that the specimen axis is aligned with the center line of the clamp (without skew) to avoid the specimen being subjected to additional tension or relaxation; start the tensile testing machine and begin the tensile test, and record the tensile force and displacement values ​​in real time until the specimen breaks (if the specimen breaks at the clamp, the data is invalid and the test needs to be repeated); record the "maximum tensile force" (maximum force before breakage) and the "gauge length at breakage" (actual length of the gauge length after breakage) of each specimen.

[0046] (4) Data processing: For each direction, the maximum and minimum values ​​of the 5 valid sample data are removed, and the average value of the remaining 3 data is taken as the tensile strength and elongation at break in that direction (in this application, "tensile strength" and "elongation at break" refer to the average value of the longitudinal and transverse directions).

[0047] Tensile strength (MPa) = Maximum tensile force (N) ÷ Original cross-sectional area of ​​specimen (mm²) 2 (Note: 1MPa = 1N / mm) 2 When performing calculations, it is essential to ensure that the units are consistent, such as a maximum tensile force of 1N and a cross-sectional area of ​​0.04mm². 2 , Tensile strength = 1 ÷ 0.04 = 25 MPa). (2) Elongation at break (%) = [(gauge length at break - original gauge length) ÷ original gauge length] × 100% (Note: the original gauge length is 50 mm. If the gauge length at break is 200 mm, the elongation at break = (200 - 50) ÷ 50 × 100% = 300%).

[0048] The packaging bags obtained from the examples and comparative examples were subjected to performance tests, including 121°C cooking for 30 minutes, Escherichia coli inhibition rate (%), tensile strength (MPa), and elongation at break (%). The specific test results are shown in the table below.

[0049] Comparative Example 1, using unmodified nano-silica, showed slight stratification after cooking at 121℃, with an E. coli inhibition rate of only 60% and a tensile strength of 18 MPa. In contrast, Example 1, through an improved process involving modification with silane coupling agent KH-550, composite with 1:0.4 montmorillonite, and nitrogen calcination at 600℃, achieved no stratification under the same dosage, increasing the antibacterial rate to 92% and the tensile strength to 26 MPa. Comparative Example 2, omitting the silane coupling agent, resulted in direct rupture of the packaging bag. Comparative Example 3, by lowering the calcination temperature to 400℃, showed severe stratification. Comparative Example 7, deviating from the 1:0.3-0.6 montmorillonite ratio, resulted in slight stratification. This demonstrates that the modified material preparation process is key to solving the problems of insufficient substrate compatibility, poor high-temperature resistance, and weak antibacterial effect, thereby improving the overall performance of the material.

[0050] Comparative Example 4, with the extrusion temperature reduced to 150℃, resulted in direct rupture of the packaging bag and a tensile strength of only 19MPa. Comparative Example 5, with the longitudinal stretching ratio reduced to 2.0 times, showed slight wrinkles and a tensile strength of 23MPa. Comparative Example 6, with the omission of plasma treatment, resulted in rupture at the heat seal. Comparative Example 8, with the lack of raw material preheating, caused uneven mechanical properties. In contrast, Examples 1 to 4, through an improved process involving raw material preheating at 100-110℃, precise extrusion at 160-235℃, 2.5-3.5 times biaxial stretching, and 200-300W plasma treatment, not only achieved no damage during 121℃ cooking but also maintained a stable antibacterial rate of over 92%. Example 4, with optimized parameters, further increased the tensile strength to 32MPa and achieved an antibacterial rate of 96%, all without the addition of any antibacterial materials, completely solving the problems of poor heat seal reliability, insufficient mechanical properties, and reliance on antibacterial additives in existing processes.

[0051] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A high-temperature resistant retort packaging bag, characterized in that, The base material of this packaging bag is composed of the following components in parts by weight: 30-40 parts polyamide, 20-35 parts high-density polyethylene, 15-25 parts polyethylene terephthalate, 5-12 parts modified material, 2-5 parts plasticizer, and 0.5-2 parts antioxidant. The modified material is prepared through the following steps: Step 1: Take nano-silica, add 3-8% of its mass of silane coupling agent KH-550, then add an aqueous ethanol solution with a volume ratio of ethanol to water of 3:1, stir and react at 60-80℃ for 1.5-2.5 hours to obtain silane-modified nano-silica; Step 2: Mix silane-modified nano-silica and montmorillonite at a weight ratio of 1:0.3-0.6, add maleic anhydride-grafted polyethylene, the amount of which is 20-40% of the total mass of silane-modified nano-silica and montmorillonite, and then add deionized water with a solid-liquid ratio of 1:

5. Ultrasonically disperse the mixture at a power of 300-500W for 20-40 minutes to obtain a mixed slurry. Step 3: Dry the mixed slurry at 80-100℃ until the moisture content is ≤0.5%, then place it in a muffle furnace and heat it to 550-650℃ at a heating rate of 1-2℃ / min. Calcine for 2-3 hours, cool to room temperature, and then pulverize to a particle size of 5-10μm to obtain the modified material. In the modified material, the weight ratio of nano-silica, montmorillonite, and maleic anhydride-grafted polyethylene is 1:0.4-0.5:0.25-0.

35.

2. The high-temperature resistant retort packaging bag according to claim 1, characterized in that: In step 1, the amount of silane coupling agent KH-550 is 5-7% of the mass of nano-silica, the amount of ethanol aqueous solution added is 8-12 times the mass of nano-silica, and the stirring speed is 500-700 r / min.

3. The high-temperature resistant retort packaging bag according to claim 1, characterized in that: In step 2, the temperature is controlled at 40-50℃ during ultrasonic dispersion. After ultrasonication, the mixture is stirred at a constant temperature of 50-60℃ for 10-15 minutes before proceeding to step 3, which involves drying.

4. The preparation process of a high-temperature resistant retort packaging bag according to claim 1, characterized in that: In step 3, nitrogen gas is introduced for protection during calcination, with a flow rate of 100-150 mL / min. After calcination, the furnace is cooled to 100-120°C, and then the furnace is removed and placed in a desiccator to cool to room temperature.

5. A process for preparing a high-temperature resistant retort pouch as described in any one of claims 1-4, characterized in that: The preparation process of high-temperature resistant retort pouches includes the following steps: Step A: Mix polyamide, high-density polyethylene, polyethylene terephthalate, modifier, plasticizer, and antioxidant according to the weight parts, and stir at 800-1200 r / min for 15-25 minutes to obtain a mixed substrate; Step B: Add the mixed substrate to a twin-screw extruder, control the temperature of the first zone of the extruder to 160-180℃, the temperature of the second zone to 200-220℃, the temperature of the third zone to 210-230℃, the screw speed to 30-50 r / min, and the vacuum degree to -0.08 to -0.09 MPa. After extrusion, the substrate is formed into a film preform through the die. Step C: The film preform is biaxially stretched, with the longitudinal stretching temperature at 80-95℃ and the stretching ratio at 2.5-3.2 times; the transverse stretching temperature at 95-110℃ and the stretching ratio at 3.0-3.5 times; after stretching, it is heat-set at 120-140℃ for 5-10 seconds to obtain the substrate film. Step D: Heat seal the substrate film at a temperature of 180-200℃, a pressure of 0.3-0.5MPa, and a time of 1-2 seconds. After cooling to 25-35℃, cut the film to obtain the high-temperature resistant retort packaging bag.

6. The preparation process of a high-temperature resistant retort packaging bag according to claim 5, characterized in that: In step B, the temperature of the four zones of the twin-screw extruder is controlled at 220-235℃, the die temperature is controlled at 230-240℃, and the thickness of the extruded film preform is controlled at 0.8-1.2mm.

7. The preparation process of a high-temperature resistant retort packaging bag according to claim 5, characterized in that: In step C, the film preform is preheated at 60-70℃ for 5-8 minutes before biaxial stretching. After heat setting, it is cooled to 50-60℃ by air cooling before the heat sealing process in step D is performed.

8. The preparation process of a high-temperature resistant retort packaging bag according to claim 5, characterized in that: In step D, the heat-sealing area of ​​the substrate film is first subjected to plasma treatment before heat sealing. The plasma treatment power is 200-300W, the treatment time is 3-5 seconds, and the treatment distance is 2-3mm.

9. The preparation process of a high-temperature resistant retort packaging bag according to claim 5, characterized in that: In step A, the polyamide, high-density polyethylene, and polyethylene terephthalate are preheated at 100-110°C for 10-15 minutes before mixing. Then, the modifier, plasticizer, and antioxidant are added and stirred.

10. The preparation process of a high-temperature resistant retort packaging bag according to claim 5, characterized in that: In step D, the cooling is carried out in stages: first, it is cooled at 50-60℃ for 1-2 minutes, then at 30-40℃ for 1-2 minutes, and finally cooled to 25-35℃. The edges of the cut packaging bags are trimmed with hot air at a temperature of 150-180℃ for 0.5-1 seconds.

Images