Environment-friendly inflatable puffed food packaging film
Technical Field
The invention belongs to the technical field of food packaging, and particularly relates to an environment-friendly inflatable puffed food packaging film.
Background
At present, puffed food on the market is liked by people as a snacks, and the mode that this kind of food was used fried more is cooked, and it is crisp delicious to eat, because the characteristic of this kind of food itself can't preserve for a long time under normal environment, for preventing that this kind of food is at the packing at the in-process of storing, transporting cracked, influence product quality, mostly use gas packaging or boxed mode to preserve, and the puffed food packaging material on the market is formed by BOPP film and CPP film complex more.
The Chinese invention patent with the patent number of CN201810779277.7 discloses an inflatable packaging composite film for puffed food suitable for plateau environment and a preparation method thereof, the composite film consists of a printing layer, a barrier layer and a heat sealing layer, a solvent-free adhesive process is adopted between the layers to form the composite film, wherein the heat sealing layer is formed by three layers of polymeric film layers through co-extrusion blow molding composite molding, and the inner layer is a low-density polyethylene blend of bimodal terpolymer polyethylene; the middle layer is linear low density polyethylene; the outer layer is a composite layer of ethylene and acrylic acid copolymer, the composite packaging film can meet the pressure resistance of 80KPa, and has the advantages of flexible material and simple and easy process. However, the polyethylene resin is adopted as the main raw material, so that the polyethylene resin is still deficient in biodegradability and not in accordance with environmental protection requirements, and in addition, the barrier property cannot meet the requirements, and the original crisp mouthfeel of the puffed food is lost after the puffed food is stored for a long time, so that the shelf life of the food is usually only a few months.
Disclosure of Invention
The invention aims to provide an environment-friendly inflatable puffed food packaging film, which adopts non-woven fabrics as a middle framework layer of the packaging film, adopts polyurethane as main film forming substances for both a wear-resistant TPU layer and a heat sealing layer, and meets the requirement of environmental protection; the heat-sealing layer adopts the modified graphene oxide and the waterborne polyurethane as main raw materials, so that the heat-sealing layer has strong barrier property, can prevent moisture and gas from entering a packaging bag, ensures the hardness and crisp taste of the puffed food, has good antibacterial property, can prevent the growth of microorganisms, and prolongs the shelf life of the puffed food; through adopting wear-resisting TPU layer as the outmost of packaging film, wear resistance is good for puffed food is difficult for being ground out the aperture in the transportation in the surface, avoids the circumstances such as gas leakage intaking that arouses, and then can further protect the puffed food in the packaging film, guarantees the quality of puffed food.
The purpose of the invention can be realized by the following technical scheme:
an environment-friendly inflatable puffed food packaging film comprises a wear-resistant TPU layer, a non-woven fabric layer and a heat sealing layer which are sequentially compounded, wherein the wear-resistant TPU layer is positioned on the outermost side, and the heat sealing layer is positioned on the innermost side and is in direct contact with puffed food;
the packaging film is prepared by the following steps:
firstly, adding waterborne polyurethane into deionized water, stirring until the waterborne polyurethane is dissolved, adding modified graphene oxide, stirring at normal temperature for 20-30min, and then performing ultrasonic treatment for 10min to obtain a heat-sealing layer coating;
secondly, placing the non-woven fabric into an ethanol water solution for soaking for 180min, then transferring the non-woven fabric into an oscillator for oscillation for 60min, then repeatedly washing the non-woven fabric for 3-4 times by using deionized water, and finally drying the non-woven fabric in a blast drying oven at 60 ℃ for later use;
thirdly, coating the heat-sealing layer coating on the surface of the non-woven fabric by using a film coater, drying for 8min at normal temperature, then coating for the second time, and finally drying at 70 ℃;
fourthly, drying and dehydrating polycarbonate diol and hydroxyl silicone oil at 110 ℃ in vacuum for 1h, dissolving the polycarbonate diol and the hydroxyl silicone oil in DMF, adding ethylene glycol, stirring uniformly, adding isophorone diisocyanate under stirring at 150r/min, keeping the temperature at 70-80 ℃, reacting for 4-5h, and adding methanol to terminate the reaction to obtain wear-resistant polyurethane emulsion;
and fifthly, coating the wear-resistant polyurethane emulsion on the other surface of the non-woven fabric, keeping the temperature of 90 ℃ for 3 hours in an electric heating air blast drying oven, then heating to 120 ℃ and keeping the temperature for 2 hours to form a wear-resistant TPU layer, and naturally cooling to room temperature to obtain the packaging film.
Further, the heat-seal layer coating is prepared from 30-40 parts of waterborne polyurethane, 2-3 parts of modified graphene oxide and 20-30 parts of deionized water.
Further, the mass ratio of polycarbonate diol, hydroxyl silicone oil, ethylene glycol, isophorone diisocyanate and DMF in the preparation process of the wear-resistant polyurethane emulsion is 10:0.8-1:0.5-0.6:11-13: 30-32.
Further, the modified graphene oxide is prepared by the following method:
(1) ultrasonically dispersing 0.3g of graphene oxide in 300mL of DMF (dimethyl formamide), adding 112g of potassium fluoride and 15g of potassium iodide, uniformly stirring, heating to 100 ℃, continuously dropwise adding 40mL of epoxy chloropropane, carrying out reflux reaction for 15h, centrifuging, and repeatedly washing a product for 5-7 times by using ethanol and deionized water to obtain a slurry;
(2) 4.5g polyvinylpyrrolidone was weighed into 22mL of the slurry, magnetically stirred for 6h, and then 7.2mL of AgNO was added3And (3) quickly adding the aqueous solution into the mixed solution, stirring for 6min, heating the mixed solution to 60 ℃, preserving heat for 2d, centrifugally separating a reaction product at 8000r/min, washing with deionized water for 6-7 times, and drying in vacuum to obtain the modified graphene oxide.
Further, AgNO in step (2)3The mass concentration of the aqueous solution was 31.93/L.
The invention has the beneficial effects that:
according to the invention, the heat-sealing layer is used as the innermost layer of the packaging film and is in direct contact with puffed food, the heat-sealing layer is made of waterborne polyurethane and modified graphene oxide, epichlorohydrin reacts with-COOH on the graphene oxide, an epoxy functional group is introduced into the graphene, and the introduced epoxy group is dispersed on the surface of the graphene oxide, so that the interlayer spacing of the modified graphene oxide is increased, and the loading of nano-silver particles in subsequent treatment is facilitated; the modified graphene oxide is uniformly dispersed in the waterborne polyurethane, in the process of drying and film forming, epoxy groups enter a hydrophilic micro area of the waterborne polyurethane, and generate ring-opening reaction with-NH-, -COOH and other groups in the micro area, the modified graphene oxide generates crosslinking in the hydrophilic micro area of polyurethane molecules, hydrogen bond combination can be formed between-C ═ O and-OH on the molecules and-NH-in the polyurethane molecules, several polyurethane molecules are welded together through the modified graphene oxide, so that the molecules present a three-dimensional network structure, the compactness of the film is increased, and meanwhile, the lamellar graphene oxide can more effectively prolong the bending and winding diffusion path of gas and water molecules in the film, thereby increasing the barrier property of the film layer; the porous structure of the puffed food enables the puffed food to easily absorb water in the environment, and as the waterborne polyurethane and graphene oxide molecules in the heat sealing layer contain hydrophilic groups, the water molecules permeating inside and outside the package can be absorbed, so that the water molecules are prevented from entering the chips, and the heat sealing layer has strong barrier property, so that the outside water molecules and gas molecules are prevented from entering, so that the puffed food keeps better hardness, maintains crisp taste and can prolong the shelf life of the puffed food;
in the aspect of bacteriostasis, the graphene oxide can wrap bacteria, so that the bacteria can neither consume nutrient substances nor breed and finally die, the nano silver promotes the bacteria to die by releasing the permeability of the silver ion reinforced membrane, the graphene oxide is used as a carrier, oxygen-containing groups (such as hydroxyl, carboxyl, oxygen-containing groups and the like) rich in the surface of the graphene oxide fixedly carry easily aggregated nano silver particles on a lamellar structure, and the nano silver is dispersed and fixedly carried, so that the nano silver particles have more excellent antibacterial performance, and the graphene oxide and the nano silver have synergistic effect, so that the membrane layer has excellent bacteriostasis performance; can inhibit the growth of microorganisms, ensure the quality of the puffed food in the packaging film and prolong the shelf life;
the invention adopts the wear-resistant TPU layer as the outermost layer of the packaging film, the hydroxyl silicone oil is used for modifying polyurethane through the hydroxyl silicone oil, the hydroxyl silicone oil participates in the copolymerization reaction of the polyurethane and enters the molecular chain segment of the polyurethane, the polysiloxane chain segment is introduced, the regularity of the original soft segment is damaged, the crystallinity is reduced, meanwhile, the surface energy of the polysiloxane chain segment is obviously lower than that of the molecular chain segment of the polyurethane, therefore, the organic silicon chain segment is enriched to the surface in the film forming process, the bond energy of the Si-O bond is up to 422.5kJ/mol and is far higher than that of the C-C bond by 344.4kJ/mol, the chain segment structure is stable, and the molecular chain segment of the polyurethane at the main pole makes up the defect of weak molecular acting force among the polysiloxane chain segments through the block copolymerization mode, therefore, the surface of the wear-resistant TPU layer is not easy to be damaged by external force, the wear-resistant performance is excellent, the, the quality of food in the packaging film is affected by air leakage, water inflow and the like caused by the air leakage;
according to the invention, the non-woven fabric is used as the middle framework layer of the packaging film, and the wear-resistant TPU layer and the heat sealing layer both adopt polyurethane as main film forming substances, so that the environment-friendly requirement is met; the heat-sealing layer adopts the modified graphene oxide and the waterborne polyurethane as main raw materials, so that the heat-sealing layer has strong barrier property, can prevent moisture and gas from entering a packaging bag, ensures the hardness and crisp taste of the puffed food, has good antibacterial property, can prevent the growth of microorganisms, and prolongs the shelf life of the puffed food; through adopting wear-resisting TPU layer as the outmost of packaging film, wear resistance is good for puffed food is difficult for being ground out the aperture in the transportation in the surface, avoids the circumstances such as gas leakage intaking that arouses, and then can further protect the puffed food in the packaging film, guarantees the quality of puffed food.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
An environment-friendly inflatable puffed food packaging film comprises a wear-resistant TPU layer, a non-woven fabric layer and a heat sealing layer which are sequentially compounded, wherein the wear-resistant TPU layer is positioned on the outermost side, and the heat sealing layer is positioned on the innermost side and is in direct contact with puffed food;
wherein the heat sealing layer is prepared from 30-40 parts of waterborne polyurethane, 2-3 parts of modified graphene oxide and 20-30 parts of deionized water;
the modified graphene oxide is prepared by the following method:
(1) ultrasonically dispersing 0.3g of graphene oxide in 300mL of DMF (N, N-dimethylformamide), adding 112g of potassium fluoride and 15g of potassium iodide, uniformly stirring, heating to 100 ℃, continuously dropwise adding 40mL of epoxy chloropropane, carrying out reflux reaction for 15h, centrifuging, and repeatedly washing a product for 5-7 times by using ethanol and deionized water to obtain a slurry;
(2) 4.5g polyvinylpyrrolidone was weighed into 22mL of the slurry, magnetically stirred for 6h, and then 7.2mL of AgNO was added3Quickly adding an aqueous solution (with the mass concentration of 31.93/L) into the solution, stirring for 6min, heating the mixed solution to 60 ℃, preserving heat for 2d, centrifugally separating a reaction product at 8000r/min, washing with deionized water for 6-7 times, and drying in vacuum to obtain modified graphene oxide;
epoxy chloropropane reacts with-COOH on the graphene oxide, an epoxy functional group is introduced into the graphene, and the introduced epoxy group is dispersed on the surface of the graphene oxide, so that the interlayer spacing of the modified graphene oxide is increased, and the loading of nano silver particles in subsequent treatment is facilitated; the modified graphene oxide is uniformly dispersed in the waterborne polyurethane, in the process of drying and film forming, epoxy groups enter a hydrophilic micro area of the waterborne polyurethane, and generate ring-opening reaction with-NH-, -COOH and other groups in the micro area, the modified graphene oxide generates crosslinking in the hydrophilic micro area of polyurethane molecules, hydrogen bond combination can be formed between-C ═ O and-OH on the molecules and-NH-in the polyurethane molecules, several polyurethane molecules are welded together through the modified graphene oxide, so that the molecules present a three-dimensional network structure, the compactness of the film is increased, and meanwhile, the lamellar graphene oxide can more effectively prolong the bending and winding diffusion path of gas and water molecules in the film, thereby increasing the barrier property of the film layer; the porous structure of the puffed food enables the puffed food to easily absorb water in the environment, and as the waterborne polyurethane and graphene oxide molecules in the heat sealing layer contain hydrophilic groups, the water molecules permeating inside and outside the package can be absorbed, so that the water molecules are prevented from entering the chips, and the heat sealing layer has strong barrier property, so that the outside water molecules and gas molecules are prevented from entering, so that the puffed food keeps better hardness, maintains crisp taste and can prolong the shelf life of the puffed food;
in the aspect of bacteriostasis, the graphene oxide can wrap bacteria, so that the bacteria can neither consume nutrient substances nor breed and finally die, the nano silver promotes the bacteria to die by releasing the permeability of the silver ion reinforced membrane, the graphene oxide is used as a carrier, oxygen-containing groups (such as hydroxyl, carboxyl, oxygen-containing groups and the like) rich in the surface of the graphene oxide fixedly carry easily aggregated nano silver particles on a lamellar structure, and the nano silver is dispersed and fixedly carried, so that the nano silver particles have more excellent antibacterial performance, and the graphene oxide and the nano silver have synergistic effect, so that the membrane layer has excellent bacteriostasis performance; can inhibit the growth of microorganisms, ensure the quality of the puffed food in the packaging film and prolong the shelf life;
the packaging film is prepared by the following steps:
firstly, adding waterborne polyurethane into deionized water, stirring until the waterborne polyurethane is dissolved, adding modified graphene oxide, stirring at normal temperature for 20-30min, and then performing ultrasonic treatment for 10min to obtain a heat-sealing layer coating;
secondly, placing the non-woven fabric into an ethanol water solution (the mass fraction is 60%) to be soaked for 180min, then transferring the non-woven fabric into an oscillator to be oscillated for 60min to remove residual impurities on the surface of the non-woven fabric, then repeatedly washing the non-woven fabric for 3-4 times by using deionized water to remove residual ethanol, and finally drying the non-woven fabric in a blast drying oven at 60 ℃ for later use;
thirdly, coating the heat-sealing layer coating on the surface of the non-woven fabric by using a film coater, drying for 8min at normal temperature, then coating for the second time, and finally drying at 70 ℃;
fourthly, drying and dehydrating polycarbonate diol and hydroxyl silicone oil at 110 ℃ in vacuum for 1h, dissolving the polycarbonate diol and the hydroxyl silicone oil in DMF, adding ethylene glycol, stirring uniformly, adding isophorone diisocyanate under stirring at 150r/min, keeping the temperature at 70-80 ℃, reacting for 4-5h, and adding methanol (a reaction terminator) to terminate the reaction to obtain wear-resistant polyurethane emulsion;
the mass ratio of polycarbonate diol, hydroxyl silicone oil, glycol, isophorone diisocyanate and DMF is 10:0.8-1:0.5-0.6:11-13: 30-32;
fifthly, coating the wear-resistant polyurethane emulsion on the other surface of the non-woven fabric, keeping the temperature of 90 ℃ for 3 hours in an electric heating air blast drying oven, then heating to 120 ℃ and keeping the temperature for 2 hours to form a wear-resistant TPU layer, and naturally cooling to room temperature to obtain a packaging film;
hydroxyl silicone oil participates in the copolymerization reaction of polyurethane, enters a polyurethane molecular chain segment, and leads the regularity of the original soft segment to be damaged and the crystallinity to be reduced by introducing a polysiloxane chain segment, meanwhile, the surface energy of the polysiloxane chain segment is obviously lower than that of the polyurethane molecular chain segment, so that the organosilicon chain segment is enriched to the surface in the film forming process, the bond energy of Si-O bond is up to 422.5kJ/mol and is much higher than that of C-C bond 344.4kJ/mol, the chain segment structure is stable, and the main polar polyurethane molecular chain segment makes up the defect of weak molecular acting force between polysiloxane chain segments through a block copolymerization mode, therefore, the surface of the wear-resistant TPU layer is not easy to be damaged by external force, the wear-resistant performance is excellent, the wear-resistant performance of the surface layer of the packaging film is good, the surface of the puffed food is not easy to be ground into small holes in the transportation process, air leakage, water inflow and the like are caused, and the quality of the food in the packaging film is influenced.
Example 1
The modified graphene oxide is prepared by the following method:
(1) ultrasonically dispersing 0.3g of graphene oxide in 300mL of DMF (N, N-dimethylformamide), adding 112g of potassium fluoride and 15g of potassium iodide, uniformly stirring, heating to 100 ℃, continuously dropwise adding 40mL of epoxy chloropropane, carrying out reflux reaction for 15h, centrifuging, and repeatedly washing a product for 5-7 times by using ethanol and deionized water to obtain a slurry;
(2) 4.5g polyvinylpyrrolidone was weighed into 22mL of the slurry, magnetically stirred for 6h, and then 7.2mL of AgNO was added3Quickly adding water solution (mass concentration of 31.93/L) into the above solution, stirring for 6min, and mixingHeating the mixed solution to 60 ℃, preserving heat for 2d, centrifugally separating the reaction product at 8000r/min, washing with deionized water for 6-7 times, and drying in vacuum to obtain the modified graphene oxide.
Comparative example 1
The slurry obtained in step (1) of example 1 was freeze-dried to obtain graphene oxide.
Comparative example 2
Graphene oxide without any treatment was subjected to the procedure of step (2) in example 1 to obtain silver-supported graphene oxide.
Example 2
An environment-friendly inflatable puffed food packaging film comprises a wear-resistant TPU layer, a non-woven fabric layer and a heat sealing layer which are sequentially compounded;
the packaging film is prepared by the following steps:
firstly, adding waterborne polyurethane into deionized water, stirring until the waterborne polyurethane is dissolved, adding modified graphene oxide, stirring at normal temperature for 20min, and then performing ultrasonic treatment for 10min to obtain a heat-sealing layer coating;
the heat-sealing layer coating is prepared from 30 parts of waterborne polyurethane, 2 parts of modified graphene oxide and 20 parts of deionized water;
secondly, placing the non-woven fabric into an ethanol water solution (the mass fraction is 60%) to be soaked for 180min, then transferring the non-woven fabric into an oscillator to be oscillated for 60min to remove residual impurities on the surface of the non-woven fabric, then repeatedly washing the non-woven fabric for 3 times by using deionized water to remove residual ethanol, and finally drying the non-woven fabric in a blast drying oven at 60 ℃ for later use;
thirdly, coating the heat-sealing layer coating on the surface of the non-woven fabric by using a film coater, drying for 8min at normal temperature, then coating for the second time, and finally drying at 70 ℃;
fourthly, drying and dehydrating polycarbonate diol and hydroxyl silicone oil at 110 ℃ in vacuum for 1h, dissolving the polycarbonate diol and the hydroxyl silicone oil in DMF, adding ethylene glycol, stirring uniformly, adding isophorone diisocyanate under stirring at 150r/min, keeping the temperature at 70 ℃, reacting for 4h, and adding methanol to terminate the reaction to obtain wear-resistant polyurethane emulsion;
the mass ratio of polycarbonate diol to hydroxyl silicone oil to glycol to isophorone diisocyanate to DMF is 10:0.8:0.5:11: 30;
and fifthly, coating the wear-resistant polyurethane emulsion on the other surface of the non-woven fabric, keeping the temperature of 90 ℃ for 3 hours in an electric heating air blast drying oven, then heating to 120 ℃ and keeping the temperature for 2 hours to form a wear-resistant TPU layer, and naturally cooling to room temperature to obtain the packaging film.
Example 3
An environment-friendly inflatable puffed food packaging film comprises a wear-resistant TPU layer, a non-woven fabric layer and a heat sealing layer which are sequentially compounded;
the packaging film is prepared by the following steps:
firstly, adding waterborne polyurethane into deionized water, stirring until the waterborne polyurethane is dissolved, adding modified graphene oxide, stirring at normal temperature for 25min, and then performing ultrasonic treatment for 10min to obtain a heat-sealing layer coating;
the heat-sealing layer coating is prepared from 35 parts of waterborne polyurethane, 2.5 parts of modified graphene oxide and 25 parts of deionized water;
secondly, placing the non-woven fabric into an ethanol water solution (the mass fraction is 60%) to be soaked for 180min, then transferring the non-woven fabric into an oscillator to be oscillated for 60min to remove residual impurities on the surface of the non-woven fabric, then repeatedly washing the non-woven fabric for 3-4 times by using deionized water to remove residual ethanol, and finally drying the non-woven fabric in a blast drying oven at 60 ℃ for later use;
thirdly, coating the heat-sealing layer coating on the surface of the non-woven fabric by using a film coater, drying for 8min at normal temperature, then coating for the second time, and finally drying at 70 ℃;
fourthly, drying and dehydrating polycarbonate diol and hydroxyl silicone oil at 110 ℃ in vacuum for 1h, dissolving the polycarbonate diol and the hydroxyl silicone oil in DMF (dimethyl formamide), adding ethylene glycol, stirring uniformly, adding isophorone diisocyanate under stirring at 150r/min, keeping the temperature at 75 ℃, reacting for 4.5h, and adding methanol to terminate the reaction to obtain wear-resistant polyurethane emulsion;
the mass ratio of polycarbonate diol to hydroxyl silicone oil to glycol to isophorone diisocyanate to DMF is 10:0.9:0.55:12: 31;
and fifthly, coating the wear-resistant polyurethane emulsion on the other surface of the non-woven fabric, keeping the temperature of 90 ℃ for 3 hours in an electric heating air blast drying oven, then heating to 120 ℃ and keeping the temperature for 2 hours to form a wear-resistant TPU layer, and naturally cooling to room temperature to obtain the packaging film.
Example 4
An environment-friendly inflatable puffed food packaging film comprises a wear-resistant TPU layer, a non-woven fabric layer and a heat sealing layer which are sequentially compounded;
the packaging film is prepared by the following steps:
firstly, adding waterborne polyurethane into deionized water, stirring until the waterborne polyurethane is dissolved, adding modified graphene oxide, stirring at normal temperature for 30min, and then performing ultrasonic treatment for 10min to obtain a heat-sealing layer coating;
the heat-sealing layer coating is prepared from 40 parts of waterborne polyurethane, 3 parts of modified graphene oxide and 30 parts of deionized water;
secondly, placing the non-woven fabric into an ethanol water solution (the mass fraction is 60%) to be soaked for 180min, then transferring the non-woven fabric into an oscillator to be oscillated for 60min to remove residual impurities on the surface of the non-woven fabric, then repeatedly washing the non-woven fabric for 4 times by using deionized water to remove residual ethanol, and finally drying the non-woven fabric in a blast drying oven at the temperature of 60 ℃ for later use;
thirdly, coating the heat-sealing layer coating on the surface of the non-woven fabric by using a film coater, drying for 8min at normal temperature, then coating for the second time, and finally drying at 70 ℃;
fourthly, drying and dehydrating polycarbonate diol and hydroxyl silicone oil at 110 ℃ in vacuum for 1h, dissolving the polycarbonate diol and the hydroxyl silicone oil in DMF, adding ethylene glycol, stirring uniformly, adding isophorone diisocyanate under stirring at 150r/min, keeping the temperature at 80 ℃, reacting for 5h, and adding methanol to terminate the reaction to obtain wear-resistant polyurethane emulsion;
the mass ratio of polycarbonate diol to hydroxyl silicone oil to glycol to isophorone diisocyanate to DMF is 10:1:0.6:13: 32;
and fifthly, coating the wear-resistant polyurethane emulsion on the other surface of the non-woven fabric, keeping the temperature of 90 ℃ for 3 hours in an electric heating air blast drying oven, then heating to 120 ℃ and keeping the temperature for 2 hours to form a wear-resistant TPU layer, and naturally cooling to room temperature to obtain the packaging film.
Comparative example 3
The graphene oxide prepared in comparative example 1 was used, and the rest was the same as in example 2.
Comparative example 4
The graphene oxide prepared in comparative example 2 was used, and the rest was the same as in example 2.
Comparative example 5
The remainder of the example 2 was the same as in example 2 except that modified graphene oxide was not added to the heat seal layer.
Comparative example 6
The wear resistant TPU layer was coated with a conventional TPU, as in example 2.
The following performance tests were performed on the packaging films obtained in examples 2 to 4 and comparative examples 3 to 6:
testing the oxygen transmission rate according to the national standard GBT 1038-2000; the moisture permeability is tested according to GB 1037-1988; testing the friction coefficient of the wear-resistant TPU layer by GB 10006-88; taking 10g of freshly puffed potato chips which are just fried, packaging the fresh puffed potato chips by using the packaging films prepared in the examples 2-4 and the comparative examples 3-6 respectively in a three-edge sealing mode, storing the fresh puffed potato chips in the same environment, and measuring the weight loss and sensory evaluation conditions of the fresh puffed potato chips after 4d and 8d respectively, wherein 10 of the sensory evaluation is full, and the taste, hardness and color of the potato chips are optimal, and the test results are as follows:
it can be seen that the packaging films obtained in examples 2 to 4 had oxygen transmittances of 250.6 to 250.9cm3/(m2d.Pa) and the moisture permeability of 0.69 to 0.70 g/(m)2D) shows that the packaging film prepared by the invention has lower oxygen transmission rate and moisture transmission rate, and shows that the packaging film has high barrier property; compared with comparative example 4, the graphene oxide which is not pre-modified in the step (1) is weak in combination with the membrane substrate, cannot form more cross-linked or hydrogen bond structures, and affects the compactness of the membrane layer, and further affects the oxygen transmission rate and the moisture permeability; the packaging films obtained in examples 2-4 were used to package potato chips with a hardness of 2.83-2.84 x 10 after 4 days5Pa, 8d post-hardness of 2.80-2.81 x 105Pa, little change in hardness, indicating good barrier properties, and a total number of colonies after 4 days of 2.0-2.1 x 104CFU·g-1And the total number of colonies after 8 days is 9.1-9.2 x 104CFU·g-1Bacteria ofThe number of the drops is also small, which indicates that the packaging film prepared by the invention has good antibacterial performance, and compared with comparative example 4, indicates that the pre-modified graphene oxide not subjected to the step (1) is not beneficial to the subsequent deposition of nano silver, so that the antibacterial effect is influenced; compared with the comparative example 5, the film layer without the graphene oxide is poor in barrier property, and the quality of the puffed food is affected; the friction coefficient of the wear-resistant TPU of the outer layer of the packaging film prepared in the examples 2-4 is 0.168-0.170, and compared with the friction coefficient of the wear-resistant TPU of the outer layer of the packaging film prepared in the comparative example 6, the wear-resistant TPU of the outermost layer can be effectively improved through the modified polyurethane, and the wear in the transportation process can be effectively reduced.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.