Microwave heating exhaust bag and preparation method thereof

Abstract

The present invention relates to the technical field of packaging materials, and specifically to a microwave heated exhaust bag and a preparation method thereof. The microwave heated exhaust bag comprises a bag body, and the bag body is formed by side sealing of overlapping composite films, and the composite film comprises a base film and an outer film. The base film is made of raw materials including the following parts by weight: 80-100 parts of modified polyvinyl alcohol, 6-8 parts of modified nano silicon dioxide, and 10-12 parts of polylactic acid. The outer film is made of raw materials including the following parts by weight: 60-90 parts of polyethylene terephthalate and 10-15 parts of hydrophobic aluminum oxide @ polyurethane. The prepared microwave heated exhaust bag has good heat resistance, strong insulation, and automatically exhausts after heating and expansion.

Description

Technical Field

[0001] The invention relates to the technical field of packaging materials, and in particular to a microwave heating exhaust bag and a preparation method thereof. Background Art

[0002] In recent years, microwave heating of food has been increasingly widely used for its convenience and hygiene. With the promotion of microwave oven applications, it is becoming more and more common to use microwave ovens to directly heat packaged food. Food packaging bags refer to containers that are in direct contact with food and are used to hold and protect food. Food packaging bags are usually made of heat-sealed plastic films. Plastic films used for food packaging must meet various requirements for packaging materials, such as good stability, safety, aesthetics, and economy. In the process of using a microwave oven to heat packaged food, a large amount of hot steam will accumulate in the packaging bag, which poses a risk of explosion. In addition, commonly used plastic films have poor heat resistance and may deform or even decompose when heated in a microwave oven, affecting the aesthetics of the packaging bag and the safety of the food. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a microwave heating exhaust bag and a preparation method thereof.

[0004] The present invention is achieved through the following technical solutions:

[0005] A microwave heating exhaust bag comprises a bag body, wherein the bag body is formed by side sealing of overlapping composite films, wherein the composite films comprise a base film and an outer film; and the base film is located inside the outer film.

[0006] Furthermore, the raw materials for preparing the base film include the following components in parts by weight: 80-100 parts of modified polyvinyl alcohol, 6-8 parts of modified nano-silicon dioxide, and 10-12 parts of polylactic acid.

[0007] Furthermore, the preparation method of the modified polyvinyl alcohol comprises the following steps:

[0008] (1) adding polyvinyl alcohol to deionized water, stirring at 180-200 rpm for 2 h at 80-85° C. to obtain a polyvinyl alcohol solution, adding folic acid to anhydrous dimethyl sulfoxide and mixing well to obtain a folic acid solution;

[0009] (2) adding 1-hydroxybenzotriazole and N-N'-dicyclohexylcarbodiimide to the folic acid solution obtained in step (1), stirring at 25° C. and 100-150 rpm for 3-4 h to obtain an activated folic acid solution; mixing the activated folic acid solution with the polyvinyl alcohol solution obtained in step (1), and reacting at 70-80° C. for 24 h under nitrogen protection;

[0010] (3) After the reaction in step (2) is completed, the mixture is placed at 4°C for 5-6 hours, centrifuged at 5000 rpm for 30 minutes, and the precipitate is washed three times with 0.1 mol / L sodium carbonate solution, washed three times with anhydrous ethanol, and dried under vacuum at 50°C to constant weight to obtain modified polyvinyl alcohol.

[0011] Furthermore, in step (1), the mass ratio of the polyvinyl alcohol to deionized water is 1:20-25.

[0012] Furthermore, in step (1), the ratio of folic acid to anhydrous dimethyl sulfoxide is 1 g:10-15 mL.

[0013] Furthermore, in step (2), the mass ratio of folic acid, 1-hydroxybenzotriazole and N-N'-dicyclohexylcarbodiimide is 15:4:7.

[0014] Furthermore, in step (2), the volume ratio of the polyvinyl alcohol solution to the activated folic acid solution is 1:1-1.2.

[0015] Furthermore, the preparation method of the modified nano-silicon dioxide comprises the following steps:

[0016] (a) adding nano-silica with a particle size of 80-100 nm into tetrahydrofuran, dispersing with 300 W ultrasonic wave for 20-30 min to obtain a nano-silica dispersion, and dissolving 3-aminopropyltriethoxysilane (APTES) in tetrahydrofuran to obtain an APTES solution;

[0017] (b) adding the APTES solution of step (a) to the nano-silica dispersion of step (a), heating and reflux at 70-80° C. for 6-8 h, stopping the reaction, cooling to room temperature, centrifuging at 8000 rpm for 30 min, and drying the precipitate at 90° C. for 2-3 h to obtain amino nano-silica;

[0018] (c) tetrahydrofuran and carboxymethyl chitosan are mixed to obtain a carboxymethyl chitosan solution, N,N'-carbonyldiimidazole (CDI) is dissolved in tetrahydrofuran to obtain a CDI solution, the CDI solution is added dropwise to the carboxymethyl chitosan solution under nitrogen protection at a dropping speed of 0.8-1.2 mL / min, and after the dropwise addition is completed, the mixture is stirred at 60-80 rpm for 4-5 h at room temperature, and then the amino nano-silica obtained in step (b) is added, and the stirring is continued for 5-6 h to obtain a reaction suspension;

[0019] (d) The reaction suspension obtained in step (c) was centrifuged at 8000 rpm for 30 min, the precipitate was washed with distilled water for 4-6 times, and dried at 100° C. to obtain modified nano-silica.

[0020] Furthermore, in step (a), the mass ratio of nano-silicon dioxide to tetrahydrofuran in the nano-silicon dioxide dispersion is 1:20-30.

[0021] Furthermore, in step (a), the mass ratio of APTES to tetrahydrofuran in the APTES solution is 1:1.

[0022] Furthermore, in step (b), the mass ratio of the nano-silicon dioxide to APTES is 1:2-3.

[0023] Furthermore, in step (c), the mass ratio of carboxymethyl chitosan to tetrahydrofuran in the carboxymethyl chitosan solution is 1:2.

[0024] Furthermore, in step (c), the mass ratio of CDI to tetrahydrofuran in the CDI solution is 1:5-8.

[0025] Furthermore, in step (c), the mass ratio of the carboxymethyl chitosan to CDI is 1:0.6-0.8.

[0026] Furthermore, in step (c), the mass ratio of the amino nano-silica to carboxymethyl chitosan is 1:2-3.

[0027] Furthermore, the raw materials for preparing the outer layer film include the following components in parts by weight: 60-90 parts of polyethylene terephthalate and 10-15 parts of hydrophobic aluminum oxide@polyurethane.

[0028] Furthermore, the preparation method of the hydrophobic aluminum oxide@polyurethane comprises the following steps:

[0029] (i) 1-dodecylphosphonic acid is added to tetrahydrofuran, heated to reflux at 80°C for 1-2 h, nano-alumina with a particle size of 40-50 nm is added, stirred at 100 rpm for 10-12 h at room temperature, centrifuged at 10000 rpm for 15 min, the precipitate is dried at 120°C for 5-6 h, washed with deionized water, and centrifuged again to obtain hydrophobic nano-alumina;

[0030] (ii) drying polyethylene glycol under vacuum at 100° C. for 2-3 h, mixing the mixture with isophorone diisocyanate, adding dibutyltin dilaurate, and reacting the mixture at 75-80° C. and 800 rpm for 1.5-2 h to obtain a polyurethane prepolymer;

[0031] (iii) The polyurethane prepolymer obtained in step (ii) and the hydrophobic nano-alumina and butyl acetate obtained in step (i) are stirred and mixed uniformly, and then added into a polyvinyl alcohol aqueous solution. After stirring uniformly, the mixture is homogenized at 10,000 rpm for 5 min, kept at a constant temperature of 50° C. for 4 min, and a 40 wt % aqueous solution of diethylenetriamine is slowly added dropwise. After the addition is completed, the mixture is kept warm for 2 h, allowed to stand at 4° C. for 2 h, filtered, and the filter cake is washed with deionized water and dried at 80° C. to obtain a hydrophobic alumina@polyurethane.

[0032] Furthermore, in step (i), the mass ratio of 1-dodecylphosphonic acid to tetrahydrofuran is 1:150-200.

[0033] Furthermore, in step (i), the mass ratio of 1-dodecylphosphonic acid to nano-alumina is 1:3-4.

[0034] Furthermore, in step (ii), the mass ratio of the polyethylene glycol to isophorone diisocyanate is 2:3.

[0035] Furthermore, in step (ii), the mass ratio of the polyethylene glycol to dibutyltin dilaurate is 1 g:1 mg.

[0036] Furthermore, in step (iii), the mass ratio of the polyurethane prepolymer to the hydrophobic nano-aluminum oxide and butyl acetate is 2:1:1.

[0037] Furthermore, in step (iii), the polyvinyl alcohol aqueous solution is prepared by the following method: polyvinyl alcohol and distilled water are mixed in a mass ratio of 1:20, and stirred at 90° C. and 400 rpm for 1-2 h to obtain a polyvinyl alcohol aqueous solution.

[0038] Furthermore, in step (iii), the mass ratio of the polyvinyl alcohol aqueous solution to the polyurethane prepolymer is 5:1.

[0039] Furthermore, in step (iii), the mass ratio of the polyvinyl alcohol aqueous solution to the diethylenetriamine aqueous solution is 5:1.

[0040] Furthermore, the method for preparing the microwave heated exhaust bag comprises the following steps:

[0041] S1: Take the base film raw material and the outer film raw material, stir and mix them respectively, add them into a twin-screw extruder, perform melt processing, send them into a casting machine for co-extrusion into a film, cool them, and obtain a composite film;

[0042] S2: The composite film obtained in step S1 is used as the bag material, and one side of the base film in the composite film is stacked as the inner side, and a three-stage segmented horizontal seal is used to form a bag body (1). The first-level horizontal seal adopts an integrated sealing and is heat-sealed with a first-level hot knife. The first-level hot knife has a flat blade, a temperature of 165°C, and a pressure of 0.5-0.55 MPa; the second-level and third-level horizontal seals adopt a slotted hot knife, the slotting position corresponds to the stretched area, the heat sealing temperature is 175°C, the pressure is 0.4-0.5 MPa, and the stretched area (2) is formed by processing. The sealing strength at the stretched area is 15-18 N, and the sealing strength of the remaining parts is ≥50 N. The length of the stretched area is 8-10 mm, and an exhaust hole (3) is punched at the center of the corresponding stretched area (2) with a perforating needle. The diameter of the needle hole is 0.05 mm and the hole spacing is 1 mm; an easy-tear opening (4) is provided on the heat-sealed edge.

[0043] Furthermore, in step S1, the mass ratio of the base layer membrane raw material to the outer layer membrane raw material is 5:3.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention provides a microwave-heated exhaust bag and a preparation method thereof. The present invention improves the structure of the exhaust bag and adopts a double-layer film structure. The base film is modified with a degradable material to improve the heat resistance of the base film of the exhaust bag. The outer film is made of polyethylene terephthalate and polyurethane as the base material. After modification, the heat resistance and barrier property of the outer film can be increased, and the performance of the exhaust bag is comprehensively improved. In the material of the base film of the present invention, the modified polyvinyl alcohol introduces folic acid on the molecular chain. The folic acid not only contains polar groups but also contains benzene rings, which has a large steric hindrance and can hinder the relative movement of molecular chain segments during heating, thereby improving the heat resistance of the microwave-heated exhaust bag. The folic acid contains phenyl and amide groups with strong rigidity, and has good heat resistance, thermal stability and good mechanical properties. The present invention modifies nano silicon dioxide and introduces chitosan. The modified nano silicon dioxide can be better connected with the molecular chain, improves heat resistance, improves dispersibility in modified polyvinyl alcohol and polylactic acid, and improves antibacterial performance; increases crosslinking density, and increases the tensile properties of the polymer film; the modified nano silicon dioxide contains polar groups, and can be crosslinked with the modified polyvinyl alcohol through hydrogen bonding, resulting in a decrease in the mobility of the polymer molecular chain segments, improving the crosslinking degree of the base film structure, and improving the heat resistance of the microwave heating exhaust bag; the introduction of modified nano silicon dioxide can improve the mechanical strength of the base film material; at the same time, nano silicon dioxide is an inorganic high temperature resistant material, which can effectively improve the heat resistance of the finished film material, and no component seepage occurs under high temperature environment, and it is safe and reliable to use. The present invention adds polylactic acid to the raw material of the base film, and there is a hydrogen bond interaction between the modified polyvinyl alcohol and the polylactic acid to form a three-dimensional network crosslinking structure, which can improve heat resistance, and the polylactic acid can be crosslinked with the modified polyvinyl alcohol and the modified nano silicon dioxide through hydrogen bonding, further improving the crosslinking degree of the base film structure, and improving the heat resistance of the microwave heating exhaust bag. Alumina is a commonly used material for vapor deposition layer and has good barrier properties. The present invention hydrophobically modifies alumina, which can effectively enhance water resistance, heat resistance and barrier properties. The present invention uses polyurethane, which has good heat resistance and chemical stability. It is used as the capsule wall material, and hydrophobically modified alumina is used as the core material to obtain hydrophobically modified alumina @ polyurethane, which can significantly improve the heat resistance and barrier properties of microwave heating exhaust bags. At the same time, it can be cross-linked with polyethylene terephthalate through hydrogen bonds to further improve the barrier properties and heat resistance. The present invention adopts a three-stage segmented horizontal sealing method for heat sealing, so that the heat sealing strength at the exhaust port is lower than that of the rest of the parts. The steam generated by heating causes the bag body to swell, and the air pressure in the bag body gradually increases. The expanded area will be expanded and discharged from the bag through the exhaust hole. When high-temperature expansion is reached, it can be automatically exhausted, and has the effect of high-temperature explosion-proof. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 This is a schematic diagram of the structure of the microwave heating exhaust bag of the present invention;

[0048] Among them, 1. bag body, 2. opening area, 3. exhaust hole, 4. easy tearing edge;

[0049] Figure 2 A schematic diagram of the layer structure of the microwave heated exhaust bag of the present invention;

[0050] Among them, 5, base membrane, 6, outer membrane;

[0051] Figure 3 This is a test of the heat resistance of the microwave heating exhaust bag of the present invention;

[0052] Figure 4 This is a tensile property test of the microwave heated exhaust bag of the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. It should be noted that, unless otherwise specified, the chemical reagents involved in the present invention are purchased through commercial channels.

[0054] Example 1: This example provides a microwave heated exhaust bag, including a bag body, wherein the bag body is formed by side edge sealing of overlapping composite films, wherein the composite film includes a base film and an outer film; the base film is located inside the outer film.

[0055] The raw materials for preparing the base film include the following components in parts by weight: 100 parts of modified polyvinyl alcohol, 8 parts of modified nano silicon dioxide, and 12 parts of polylactic acid.

[0056] The preparation method of modified polyvinyl alcohol comprises the following steps:

[0057] (1) Add 10 g of polyvinyl alcohol to 250 g of deionized water, stir at 200 rpm at 85 °C for 2 h to obtain a polyvinyl alcohol solution, add 3 g of folic acid to 45 mL of anhydrous dimethyl sulfoxide and mix well to obtain a folic acid solution;

[0058] (2) adding 0.8 g of 1-hydroxybenzotriazole and 1.4 g of N-N'-dicyclohexylcarbodiimide to the folic acid solution obtained in step (1), stirring at 25°C and 150 rpm for 4 h to obtain an activated folic acid solution; mixing 12 mL of the activated folic acid solution with 10 mL of the polyvinyl alcohol solution obtained in step (1), and reacting at 80°C for 24 h under nitrogen protection;

[0059] (3) After the reaction in step (2) is completed, the mixture is placed at 4°C for 6 h, centrifuged at 5000 rpm for 30 min, and the precipitate is washed three times with 0.1 mol / L sodium carbonate solution, washed three times with anhydrous ethanol, and dried at 50°C in a vacuum until constant weight is obtained to obtain modified polyvinyl alcohol.

[0060] The preparation method of modified nano silicon dioxide comprises the following steps:

[0061] (a) 10 g of nano-silica with a particle size of 100 nm was added to 300 g of tetrahydrofuran and subjected to 300 W ultrasonic dispersion treatment for 30 min to obtain a nano-silica dispersion. 30 g of 3-aminopropyltriethoxysilane (APTES) was dissolved in 30 g of tetrahydrofuran to obtain an APTES solution.

[0062] (b) adding the APTES solution of step (a) to the nano-silica dispersion of step (a), heating and reflux at 80° C. for 8 h, stopping the reaction, cooling to room temperature, centrifuging at 8000 rpm for 30 min, and drying the precipitate at 90° C. for 3 h to obtain amino nano-silica;

[0063] (c) 30 g of tetrahydrofuran and 15 g of carboxymethyl chitosan were mixed to obtain a carboxymethyl chitosan solution, 12 g of N, N'-carbonyldiimidazole (CDI) was dissolved in 60 g of tetrahydrofuran to obtain a CDI solution, and the CDI solution was added dropwise to the carboxymethyl chitosan solution under nitrogen protection at a dropping speed of 1.2 mL / min. After the dropwise addition was completed, the mixture was stirred at 80 rpm for 5 h at room temperature, and then 7.5 g of the amino nano-silica obtained in step (b) was added, and the mixture was stirred for 6 h to obtain a reaction suspension;

[0064] (d) The reaction suspension obtained in step (c) was centrifuged at 8000 rpm for 30 min, the precipitate was washed with distilled water for 6 times, and dried at 100° C. to obtain modified nano-silica.

[0065] The raw materials for preparing the outer layer film include the following components in parts by weight: 90 parts of polyethylene terephthalate and 15 parts of hydrophobic aluminum oxide@polyurethane.

[0066] The preparation method of hydrophobic aluminum oxide@polyurethane comprises the following steps:

[0067] (i) 1 g of 1-dodecylphosphonic acid was added to 200 g of tetrahydrofuran, heated under reflux at 80°C for 2 h, 4 g of nano-alumina with a particle size of 50 nm was added, stirred at 100 rpm for 12 h at room temperature, centrifuged at 10,000 rpm for 15 min, the precipitate was dried at 120°C for 6 h, washed with deionized water, and centrifuged again to obtain hydrophobic nano-alumina;

[0068] (ii) 20 g of polyethylene glycol was dried under vacuum at 100 °C for 3 h, mixed with 30 g of isophorone diisocyanate, 20 mg of dibutyltin dilaurate was added, and the mixture was stirred at 80 °C and 800 rpm for 2 h to obtain a polyurethane prepolymer;

[0069] (iii) 10 g of polyvinyl alcohol was mixed with 200 g of distilled water, and stirred at 90° C. and 400 rpm for 2 h to obtain a polyvinyl alcohol aqueous solution. 20 g of the polyurethane prepolymer obtained in step (ii) was mixed with 10 g of the hydrophobic nano-alumina obtained in step (i) and 10 g of butyl acetate, and added to 100 g of the polyvinyl alcohol aqueous solution. After stirring, the mixture was homogenized at 10,000 rpm for 5 min, kept at 50° C. for 4 min, and 20 g of a 40 wt% diethylenetriamine aqueous solution was slowly added dropwise. After the addition was completed, the mixture was kept warm for 2 h, allowed to stand at 4° C. for 2 h, filtered, the filter cake was washed with deionized water, and dried at 80° C. to obtain hydrophobic alumina@polyurethane.

[0070] This embodiment also provides a method for preparing a microwave heated exhaust bag, comprising the following steps:

[0071] S1: 500 g of the base film raw material and 300 g of the outer film raw material are stirred and mixed respectively, added into a twin-screw extruder for melt processing, sent into a casting machine for co-extrusion into a film, cooled, and obtained a composite film;

[0072] S2: The composite film obtained in step S1 is used as the bag material, and one side of the base film in the composite film is overlapped as the inner side, and a three-stage segmented horizontal seal is adopted to form a bag body 1. The first-level horizontal seal adopts an integrated sealing, and is heat-sealed with a first-level hot knife. The shape of the first-level hot knife is a flat blade, the temperature is 165°C, and the pressure is 0.55 MPa; the second and third-level horizontal seals adopt a slotted hot knife, and the slot position corresponds to the stretched area. The heat sealing temperature is 175°C and the pressure is 0.5 MPa. The stretched area 2 is formed by processing. The sealing strength at the stretched area is 18 N, and the sealing strength of the remaining parts is 60 N. The length of the stretched area is 10 mm, and a vent 3 is punched at the center position corresponding to the stretched area 2 with a perforating needle. The diameter of the needle hole is 0.05 mm, and the hole spacing is 1 mm; an easy-tear opening 4 is provided on the heat-sealed edge; the schematic diagram of the structure of the microwave heated exhaust bag is as shown in Figure 1 As shown, the schematic diagram of the bag layer structure is as follows Figure 2 shown.

[0073] Example 2: This example provides a microwave heated exhaust bag, including a bag body, wherein the bag body is formed by side edge sealing of overlapping composite films, wherein the composite films include a base film and an outer film; the base film is located inside the outer film.

[0074] The raw materials for preparing the base film include the following components in parts by weight: 80 parts of modified polyvinyl alcohol, 6 parts of modified nano silicon dioxide, and 10 parts of polylactic acid.

[0075] The preparation method of modified polyvinyl alcohol comprises the following steps:

[0076] (1) Add 10 g of polyvinyl alcohol to 200 g of deionized water, stir at 180 rpm at 80 °C for 2 h to obtain a polyvinyl alcohol solution, add 3 g of folic acid to 30 mL of anhydrous dimethyl sulfoxide and mix well to obtain a folic acid solution;

[0077] (2) adding 0.8 g of 1-hydroxybenzotriazole and 1.4 g of N-N'-dicyclohexylcarbodiimide to the folic acid solution obtained in step (1), stirring at 25°C and 100 rpm for 3 h to obtain an activated folic acid solution; mixing 10 mL of the activated folic acid solution with 10 mL of the polyvinyl alcohol solution obtained in step (1), and reacting at 70°C for 24 h under nitrogen protection;

[0078] (3) After the reaction in step (2) is completed, the mixture is placed at 4°C for 5 h, centrifuged at 5000 rpm for 30 min, and the precipitate is washed three times with 0.1 mol / L sodium carbonate solution, washed three times with anhydrous ethanol, and dried at 50°C in a vacuum oven until constant weight is obtained to obtain modified polyvinyl alcohol.

[0079] The preparation method of modified nano silicon dioxide comprises the following steps:

[0080] (a) 10 g of nano-silica with a particle size of 80 nm was added to 200 g of tetrahydrofuran and subjected to 300 W ultrasonic dispersion treatment for 20 min to obtain a nano-silica dispersion. 20 g of 3-aminopropyltriethoxysilane (APTES) was dissolved in 20 g of tetrahydrofuran to obtain an APTES solution.

[0081] (b) adding the APTES solution of step (a) to the nano-silica dispersion of step (a), heating and reflux at 70° C. for 6 h, stopping the reaction, cooling to room temperature, centrifuging at 8000 rpm for 30 min, and drying the precipitate at 90° C. for 2 h to obtain amino nano-silica;

[0082] (c) 30 g of tetrahydrofuran and 15 g of carboxymethyl chitosan were mixed to obtain a carboxymethyl chitosan solution, 9 g of N,N'-carbonyldiimidazole (CDI) was dissolved in 72 g of tetrahydrofuran to obtain a CDI solution, and the CDI solution was added dropwise to the carboxymethyl chitosan solution under nitrogen protection at a dropping speed of 0.8 mL / min. After the dropwise addition was completed, the mixture was stirred at 60 rpm for 4 h at room temperature, and then 5 g of amino nano-silica obtained in step (b) was added, and the mixture was stirred for 5 h to obtain a reaction suspension;

[0083] (d) The reaction suspension obtained in step (c) was centrifuged at 8000 rpm for 30 min, the precipitate was washed four times with distilled water, and dried at 100° C. to obtain modified nano-silica.

[0084] The raw materials for preparing the outer layer film include the following components in parts by weight: 60 parts of polyethylene terephthalate and 10 parts of hydrophobic aluminum oxide@polyurethane.

[0085] The preparation method of hydrophobic aluminum oxide@polyurethane comprises the following steps:

[0086] (i) 1 g of 1-dodecylphosphonic acid was added to 150 g of tetrahydrofuran, heated to reflux at 80°C for 1 h, 3 g of nano-alumina with a particle size of 40 nm was added, stirred at 100 rpm for 10 h at room temperature, centrifuged at 10,000 rpm for 15 min, the precipitate was dried at 120°C for 5 h, washed with deionized water, and centrifuged again to obtain hydrophobic nano-alumina;

[0087] (ii) 20 g of polyethylene glycol was dried under vacuum at 100 °C for 2 h, mixed with 30 g of isophorone diisocyanate, 20 mg of dibutyltin dilaurate was added, and the mixture was stirred at 75 °C and 800 rpm for 1.5 h to obtain a polyurethane prepolymer;

[0088] (iii) 10 g of polyvinyl alcohol was mixed with 200 g of distilled water, and stirred at 90° C. and 400 rpm for 1 h to obtain a polyvinyl alcohol aqueous solution. 20 g of the polyurethane prepolymer obtained in step (ii) was mixed with 10 g of the hydrophobic nano-alumina obtained in step (i) and 10 g of butyl acetate, and added to 100 g of the polyvinyl alcohol aqueous solution. After stirring, the mixture was homogenized at 10,000 rpm for 5 min, kept at 50° C. for 4 min, and 20 g of a 40 wt% aqueous solution of diethylenetriamine was slowly added dropwise. After the addition was completed, the mixture was kept warm for 2 h, allowed to stand at 4° C. for 2 h, filtered, the filter cake was washed with deionized water, and dried at 80° C. to obtain hydrophobic alumina@polyurethane.

[0089] This embodiment also provides a method for preparing a microwave heated exhaust bag, comprising the following steps:

[0090] S1: 500 g of the base film raw material and 300 g of the outer film raw material are stirred and mixed respectively, added into a twin-screw extruder for melt processing, sent into a casting machine for co-extrusion into a film, cooled, and obtained a composite film;

[0091] S2: The composite film obtained in step S1 is used as the bag material, and one side of the base film in the composite film is overlapped as the inner side, and a three-stage segmented horizontal seal is adopted to form a bag body 1. The first-level horizontal seal adopts an integrated sealing, and is heat-sealed with a first-level hot knife. The shape of the first-level hot knife is a flat blade, the temperature is 165°C, and the pressure is 0.5 MPa; the second and third-level horizontal seals adopt a slotted hot knife, the slotting position corresponds to the stretched area, the heat sealing temperature is 175°C, the pressure is 0.4 MPa, and the stretched area 2 is formed by processing. The sealing strength at the stretched area is 15 N, and the sealing strength of the remaining parts is 60 N. The length of the stretched area is 8 mm, and an exhaust hole 3 is punched at the center position corresponding to the stretched area 2 with a perforating needle. The diameter of the needle hole is 0.05 mm, and the hole spacing is 1 mm; an easy-tear opening 4 is provided on the heat-sealed edge.

[0092] Example 3: This example provides a microwave heated exhaust bag, including a bag body, wherein the bag body is formed by side edge sealing of overlapping composite films, wherein the composite films include a base film and an outer film; the base film is located inside the outer film.

[0093] The raw materials for preparing the base film include the following components in parts by weight: 90 parts of modified polyvinyl alcohol, 7 parts of modified nano silicon dioxide, and 11 parts of polylactic acid.

[0094] The preparation method of modified polyvinyl alcohol comprises the following steps:

[0095] (1) Add 10 g of polyvinyl alcohol to 220 g of deionized water, stir at 190 rpm at 82 °C for 2 h to obtain a polyvinyl alcohol solution, add 3 g of folic acid to 40 mL of anhydrous dimethyl sulfoxide and mix well to obtain a folic acid solution;

[0096] (2) adding 0.8 g of 1-hydroxybenzotriazole and 1.4 g of N-N'-dicyclohexylcarbodiimide to the folic acid solution obtained in step (1), stirring at 25°C and 120 rpm for 3.5 h to obtain an activated folic acid solution; mixing 11 mL of the activated folic acid solution with 10 mL of the polyvinyl alcohol solution obtained in step (1), and reacting at 75°C for 24 h under nitrogen protection;

[0097] (3) After the reaction in step (2) is completed, the mixture is placed at 4°C for 5.5 h, centrifuged at 5000 rpm for 30 min, and the precipitate is washed three times with 0.1 mol / L sodium carbonate solution, washed three times with anhydrous ethanol, and dried at 50°C in a vacuum until constant weight is obtained to obtain modified polyvinyl alcohol.

[0098] The preparation method of modified nano silicon dioxide comprises the following steps:

[0099] (a) 10 g of nano-silica with a particle size of 90 nm was added to 250 g of tetrahydrofuran and subjected to 300 W ultrasonic dispersion treatment for 25 min to obtain a nano-silica dispersion. 25 g of 3-aminopropyltriethoxysilane (APTES) was dissolved in 25 g of tetrahydrofuran to obtain an APTES solution.

[0100] (b) adding the APTES solution of step (a) to the nano-silica dispersion of step (a), heating and reflux at 75° C. for 7 h, stopping the reaction, cooling to room temperature, centrifuging at 8000 rpm for 30 min, and drying the precipitate at 90° C. for 2.5 h to obtain amino nano-silica;

[0101] (c) 30 g of tetrahydrofuran and 15 g of carboxymethyl chitosan were mixed to obtain a carboxymethyl chitosan solution, 10 g of N, N'-carbonyldiimidazole (CDI) was dissolved in 70 g of tetrahydrofuran to obtain a CDI solution, and the CDI solution was added dropwise to the carboxymethyl chitosan solution under nitrogen protection at a dropping rate of 1 mL / min. After the addition was completed, the mixture was stirred at 70 rpm at room temperature for 4.5 h, and then 6 g of the amino nano-silica obtained in step (b) was added, and the stirring was continued for 5.5 h to obtain a reaction suspension;

[0102] (d) The reaction suspension obtained in step (c) was centrifuged at 8000 rpm for 30 min, the precipitate was washed with distilled water for 5 times, and dried at 100° C. to obtain modified nano-silica.

[0103] The raw materials for preparing the outer layer film include the following components in parts by weight: 80 parts of polyethylene terephthalate and 12 parts of hydrophobic aluminum oxide@polyurethane.

[0104] The preparation method of hydrophobic aluminum oxide@polyurethane comprises the following steps:

[0105] (i) 1 g of 1-dodecylphosphonic acid was added to 180 g of tetrahydrofuran, heated under reflux at 80°C for 1.5 h, 3.5 g of nano-alumina with a particle size of 45 nm was added, stirred at 100 rpm for 11 h at room temperature, centrifuged at 10,000 rpm for 15 min, the precipitate was dried at 120°C for 5.5 h, washed with deionized water, and centrifuged again to obtain hydrophobic nano-alumina;

[0106] (ii) 20 g of polyethylene glycol was dried under vacuum at 100 °C for 2.5 h, mixed with 30 g of isophorone diisocyanate, 20 mg of dibutyltin dilaurate was added, and the mixture was stirred at 78 °C and 800 rpm for 1.8 h to obtain a polyurethane prepolymer;

[0107] (iii) 10 g of polyvinyl alcohol was mixed with 200 g of distilled water, and stirred at 90° C. and 400 rpm for 1.5 h to obtain a polyvinyl alcohol aqueous solution. 20 g of the polyurethane prepolymer obtained in step (ii) was mixed with 10 g of the hydrophobic nano-alumina obtained in step (i) and 10 g of butyl acetate, and added to 100 g of the polyvinyl alcohol aqueous solution. After stirring, the mixture was homogenized at 10,000 rpm for 5 min, kept at 50° C. for 4 min, and 20 g of a 40 wt% diethylenetriamine aqueous solution was slowly added dropwise. After the addition was completed, the mixture was kept warm for 2 h, allowed to stand at 4° C. for 2 h, filtered, the filter cake was washed with deionized water, and dried at 80° C. to obtain hydrophobic alumina@polyurethane.

[0108] This embodiment also provides a method for preparing a microwave heated exhaust bag, comprising the following steps:

[0109] S1: 500 g of the base film raw material and 300 g of the outer film raw material are stirred and mixed respectively, added into a twin-screw extruder for melt processing, sent into a casting machine for co-extrusion into a film, cooled, and obtained a composite film;

[0110] S2: The composite film obtained in step S1 is used as the bag material, and one side of the base film in the composite film is overlapped as the inner side, and a three-stage segmented horizontal seal is adopted to form a bag body 1. The first-level horizontal seal adopts an integrated sealing, and is heat-sealed with a first-level hot knife. The shape of the first-level hot knife is a flat blade, the temperature is 165°C, and the pressure is 0.52 MPa; the second and third-level horizontal seals adopt a slotted hot knife, the slotting position corresponds to the stretched area, the heat sealing temperature is 175°C, the pressure is 0.45 MPa, and the stretched area 2 is formed by processing. The sealing strength at the stretched area is 16 N, and the sealing strength of the remaining parts is 60 N. The length of the stretched area is 9 mm, and an exhaust hole 3 is punched at the center position corresponding to the stretched area 2 with a perforating needle. The diameter of the needle hole is 0.05 mm, and the hole spacing is 1 mm; an easy-tear opening 4 is provided on the heat-sealed edge.

[0111] The only difference between Comparative Example 1 and Example 1 is that polyvinyl alcohol is used instead of modified polyvinyl alcohol.

[0112] The only difference between Comparative Example 2 and Example 1 is that nano silicon dioxide is used instead of modified nano silicon dioxide.

[0113] The only difference between Comparative Example 3 and Example 1 is that hydrophobic aluminum oxide@polyurethane is replaced by aluminum oxide.

[0114] Experimental Example 1: Take the composite film samples prepared in Examples 1-3 and Comparative Examples 1-3, cut them into 15 cm × 15 cm, and stick them on a stainless steel plate with a thickness of 1 mm. Use an alcohol lamp to bake the other side of the stainless steel until the composite film curls up, and test the temperature of the stainless steel surface to characterize the heat resistance of the composite film. The results are as follows: Figure 3 shown.

[0115] Figure 3 The results show that the temperature at which curling just appears on the composite films prepared in Examples 1-3 is >200°C, which shows that the microwave heated exhaust bags prepared in the present application have good heat resistance. The temperature at which curling just appears on the composite films prepared in Examples 1-3 is higher than that in Comparative Examples 1-3, indicating that modified polyvinyl alcohol and modified nano-silica can increase the degree of cross-linking of the base film structure. At the same time, the introduction of groups such as benzene rings into modified polyvinyl alcohol can improve the heat resistance of microwave heated exhaust bags.

[0116] Experimental Example 2: Take the composite film samples prepared in Examples 1-3 and Comparative Examples 1-3, cut them into 15 cm × 15 cm, and test the tensile strength of the composite film samples according to the method in GB / T1040.1-2006 to characterize the mechanical properties of the composite film. Figure 4 shown.

[0117] Figure 4 The results show that the tensile strength of the composite films prepared in Examples 1-3 is >40 MPa, which is better than that in Comparative Examples 1-3, indicating that the microwave heated exhaust bag of the present invention has high tensile strength and good mechanical properties.

[0118] Experimental Example 3: The composite films prepared in Examples 1-3 and Comparative Examples 1-3 were placed at a relative humidity of 85% and a temperature of 25°C for 72 hours to test the oxygen permeability and water vapor permeability of the composite films. The results are shown in Table 1.

[0119] Table 1: Oxygen and water vapor barrier performance test

[0120]

[0121] The results in Table 1 show that the oxygen permeability and water vapor permeability of Examples 1-3 are lower than those of Comparative Examples 1-3, indicating that the microwave heating exhaust bag of the present invention has good barrier properties, and the hydrophobically modified alumina@polyurethane can further enhance the barrier effect against oxygen and water vapor.

[0122] Experimental Example 4: Referring to the standard QB / T2591-2003 "Test method for antibacterial performance and antibacterial effect of antibacterial plastics", Escherichia coli (ATCC8099) and Staphylococcus aureus (ATCC6538) were inoculated on the surface of the base film of the composite film obtained in Example 1-3 and Comparative Example 1-3, covered with a polyethylene film, and cultured at (37±1)°C and relative humidity>90% for 24 h. The antibacterial rate was calculated based on the actual number of live bacteria recovered. The measurement results are shown in Table 2.

[0123] Table 2: Antibacterial performance test

[0124]

[0125] The results in Table 2 show that the composite film of Comparative Example 2 has the lowest antibacterial rate and poor antibacterial performance, indicating that modified nano-silica can improve the antibacterial performance. The microwave heating exhaust bag of the present invention has good antibacterial performance.

[0126] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A microwave heating exhaust bag, characterized in that: The bag comprises a bag body, wherein the bag body is formed by side sealing of overlapping composite films, wherein the composite films comprise a base film and an outer film; the base film is located inside the outer film; The raw materials for preparing the base film include the following components in parts by weight: 80-100 parts of modified polyvinyl alcohol, 6-8 parts of modified nano silicon dioxide, and 10-12 parts of polylactic acid; The preparation method of the modified polyvinyl alcohol comprises the following steps: (1) adding polyvinyl alcohol to deionized water and stirring to obtain a polyvinyl alcohol solution, and adding folic acid to anhydrous dimethyl sulfoxide and mixing to obtain a folic acid solution; (2) adding 1-hydroxybenzotriazole and N-N'-dicyclohexylcarbodiimide to the folic acid solution obtained in step (1), stirring to obtain an activated folic acid solution; mixing the activated folic acid solution with the polyvinyl alcohol solution obtained in step (1), and reacting under nitrogen protection; (3) After the reaction in step (2) is completed, the mixture is allowed to stand, centrifuged, and the precipitate is washed with a sodium carbonate solution and anhydrous ethanol, and dried to obtain a modified polyvinyl alcohol; The preparation method of the modified nano silicon dioxide comprises the following steps: (a) adding nano-silica to tetrahydrofuran, subjecting to ultrasonic dispersion treatment to obtain a nano-silica dispersion, and dissolving APTES in tetrahydrofuran to obtain an APTES solution; (b) adding the APTES solution of step (a) to the nano-silica dispersion of step (a), heating to reflux, stopping the reaction, cooling to room temperature, centrifuging, and drying to obtain amino nano-silica; (c) mixing tetrahydrofuran and carboxymethyl chitosan to obtain a carboxymethyl chitosan solution, dissolving CDI in tetrahydrofuran to obtain a CDI solution, adding the CDI solution dropwise to the carboxymethyl chitosan solution under nitrogen protection, stirring after the dropwise addition is completed, then adding the amino nano-silica obtained in step (b), and continuing to stir to obtain a reaction suspension; (d) centrifuging the reaction suspension obtained in step (c), washing the precipitate, and drying to obtain modified nano-silica; The raw materials for preparing the outer layer film include the following components in parts by weight: 60-90 parts of polyethylene terephthalate and 10-15 parts of hydrophobic aluminum oxide@polyurethane; The preparation method of the hydrophobic aluminum oxide@polyurethane comprises the following steps: (i) adding 1-dodecylphosphonic acid to tetrahydrofuran, heating to reflux, adding nano-alumina, stirring, centrifuging, drying, and washing to obtain hydrophobic nano-alumina; (ii) vacuum drying polyethylene glycol, mixing it with isophorone diisocyanate, adding dibutyltin dilaurate, stirring and reacting to obtain a polyurethane prepolymer; (iii) The polyurethane prepolymer obtained in step (ii) is stirred and mixed with the hydrophobic nano-alumina and butyl acetate obtained in step (i), and then added to a polyvinyl alcohol aqueous solution. After stirring, the mixture is homogenized and kept at a constant temperature, and a 40 wt % aqueous solution of diethylenetriamine is slowly added dropwise. After the addition is completed, the mixture is kept warm, allowed to stand, filtered, the filter cake is washed, and dried to obtain a hydrophobic alumina@polyurethane.

2. A microwave heating exhaust bag according to claim 1, characterized in that: In step (1), the mass ratio of polyvinyl alcohol to deionized water is 1:20-25; the amount ratio of folic acid to anhydrous dimethyl sulfoxide is 1 g:10-15 mL.

3. A microwave heating exhaust bag according to claim 2, characterized in that: In step (2), the mass ratio of folic acid, 1-hydroxybenzotriazole and N-N'-dicyclohexylcarbodiimide is 15:4:7; and the volume ratio of polyvinyl alcohol solution to activated folic acid solution is 1:1-1.

2.

4. A microwave heating exhaust bag according to claim 3, characterized in that: In step (a), the mass ratio of nano-silicon dioxide to tetrahydrofuran in the nano-silicon dioxide dispersion is 1:20-30; the mass ratio of APTES to tetrahydrofuran in the APTES solution is 1:

1.

5. A microwave heating exhaust bag according to claim 4, characterized in that: In step (b), the mass ratio of the nano-silicon dioxide to APTES is 1:2-3.

6. A microwave heating exhaust bag according to claim 5, characterized in that: In step (c), the mass ratio of carboxymethyl chitosan to tetrahydrofuran in the carboxymethyl chitosan solution is 1:2; the mass ratio of CDI to tetrahydrofuran in the CDI solution is 1:5-8; the mass ratio of carboxymethyl chitosan to CDI is 1:0.6-0.8; and the mass ratio of amino nano-silica to carboxymethyl chitosan is 1:2-3.

7. A microwave heating exhaust bag according to claim 6, characterized in that: In step (i), the mass ratio of 1-dodecylphosphonic acid to tetrahydrofuran is 1:150-200; the mass ratio of 1-dodecylphosphonic acid to nano-alumina is 1:3-4.

8. The microwave heating exhaust bag according to claim 7, characterized in that: In step (ii), the mass ratio of polyethylene glycol to isophorone diisocyanate is 2:3; the mass ratio of polyethylene glycol to dibutyltin dilaurate is 1 g:1 mg.

9. The microwave heating exhaust bag according to claim 8, characterized in that: In step (iii), the mass ratio of the polyurethane prepolymer to the hydrophobic nano-alumina and butyl acetate is 2:1:1; the polyvinyl alcohol aqueous solution is prepared by the following method: polyvinyl alcohol and distilled water are mixed in a mass ratio of 1:20, and stirred at 90°C and 400 rpm for 1-2 h to obtain a polyvinyl alcohol aqueous solution; the mass ratio of the polyvinyl alcohol aqueous solution to the polyurethane prepolymer is 5:1; the mass ratio of the polyvinyl alcohol aqueous solution to the diethylenetriamine aqueous solution is 5:

1.

10. The method for preparing a microwave heated exhaust bag according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: Take the base film raw material and the outer film raw material, stir and mix them respectively, add them into a twin-screw extruder, perform melt processing, send them into a casting machine for co-extrusion into a film, cool them, and obtain a composite film; S2: The composite film obtained in step S1 is used as the bag material, and one side of the base film in the composite film is stacked as the inner side, and a three-stage segmented horizontal seal is used to make a bag body (1). The first-level horizontal seal adopts an integrated sealing and is heat-sealed with a first-level hot knife. The first-level hot knife has a flat blade, a temperature of 165°C, and a pressure of 0.5-0.55 MPa; the second-level and third-level horizontal seals adopt a slotted hot knife, the slot position corresponds to the stretched area, the heat sealing temperature is 175°C, the pressure is 0.4-0.5 MPa, and the stretched area (2) is formed by processing. The sealing strength at the stretched area is 15-18 N, and the sealing strength of the remaining parts is ≥50 N. The length of the stretched area is 8-10 mm, and an exhaust hole (3) is punched at the center of the corresponding stretched area (2) with a perforating needle. The diameter of the needle hole is 0.05 mm and the hole spacing is 1 mm; an easy-tear opening (4) is provided on the heat-sealed edge; In step S1, the mass ratio of the base layer film raw material to the outer layer film raw material is 5:3.

Images