A low-melting packaging bag and its preparation method

Abstract

The present application belongs to the technical field of packaging bags, and specifically discloses a low-melting-point packaging bag and a preparation method thereof. The low-melting-point packaging bag comprises an inner layer and an outer layer, wherein an adhesive is bonded between the inner layer and the outer layer, and the raw material components of the inner layer, in parts by weight, comprise the following raw materials: 60-70 parts of ethylene-vinyl acetate copolymer, 15-25 parts of linear low-density polyethylene, 20-30 parts of nano-silicon dioxide, 5-10 parts of epoxy soybean oil, 18-28 parts of polyvinyl alcohol fiber, 12-20 parts of modified graphene, and 1-3 parts of sodium carboxymethyl starch; the outer layer comprises the following raw materials: polybutylene terephthalate-adipate-butylene glycol ester, carrageenan, modified starch, citrate, nano-carbon fiber, plasticizer, dispersant, silane coupling agent. The packaging bag prepared in the present application has good mechanical properties, and can resist the impact or extrusion of carbon black during the loading process of carbon black, and will not cause the valve bag to break or leak.

Description

Technical Field

[0001] The present application relates to the technical field of packaging bags, and in particular to a low melting point packaging bag and a preparation method thereof. Background Art

[0002] Valve bags are used to package powdered or granular solid materials such as edible powder, chemical powder, and synthetic materials. They are fed from the top or bottom valve port and are filled with special filling equipment. After filling, they are packed into cubes for easy transportation.

[0003] Carbon black is a black fine powder made from carbonaceous raw materials such as bituminous coal and petroleum coke. It has a wide range of applications, mainly in plastic products, rubber products, inks, ceramics, coatings, electronics and other industries. However, carbon black is not environmentally friendly and harmful to human health, so special attention should be paid during use and transportation. Valve bags for packaging carbon black have the advantages of good moisture resistance, good sealing, strong load-bearing capacity and good wear resistance.

[0004] However, during the loading process of carbon black, the valve bag is very likely to be deformed due to the collision or extrusion of the carbon black, which may easily cause the valve bag to break and leak, thereby affecting the production of carbon black. Summary of the invention

[0005] In order to improve the problem that valve bags are prone to breakage and leakage, the present application provides a low-melting-point packaging bag and a preparation method thereof.

[0006] The present application provides a low melting point packaging bag, which adopts the following technical solution:

[0007] A low melting point packaging bag, comprising an inner layer and an outer layer, wherein an adhesive is bonded between the inner layer and the outer layer, and the raw material components of the inner layer, in parts by weight, comprise the following raw materials: 60-70 parts of ethylene-vinyl acetate copolymer, 15-25 parts of linear low-density polyethylene, 20-30 parts of nano silicon dioxide, 5-10 parts of epoxy soybean oil, 18-28 parts of polyvinyl alcohol fiber, 12-20 parts of modified graphene, and 1-3 parts of sodium carboxymethyl starch;

[0008] The outer layer comprises the following raw materials: poly(butylene terephthalate-adipate-butylene glycol) ester, carrageenan, modified starch, citrate, nano-carbon fiber, plasticizer, dispersant and silane coupling agent.

[0009] By adopting the above technical solutions, ethylene-vinyl acetate copolymer has good transparency, low-temperature resistance, impact resistance, and crack resistance. Linear low-density polyethylene has high tensile strength, puncture resistance, tear resistance, and elongation at break. The combination of ethylene-vinyl acetate copolymer and linear low-density polyethylene has excellent low water permeability, low-temperature flexibility, ductility, and good processability. Nano-silica has advantages such as light transmittance and small particle size distribution. When applied to packaging bags, it can improve the transparency, strength, toughness, and waterproof performance of the packaging bags. Epoxidized soybean oil, as a lubricant and viscosity reducer, can greatly extend the service life of packaging bags when applied to packaging bags. Polyvinyl alcohol fiber has unique strong adhesion, film flexibility, smoothness, oil resistance, and wear resistance. Nano-silica can be loaded on the outer surface of polyvinyl alcohol fiber, increasing the specific surface area of polyvinyl alcohol fiber and further improving the mechanical properties such as tensile properties and tear resistance of the packaging bag. Modified graphene has high mechanical strength and toughness and can coat the surface of polyvinyl alcohol fiber. The mixture of nano-silica, modified graphene, and polyvinyl alcohol fiber forms a network structure, thereby improving the corresponding mechanical properties of the packaging bag. Sodium carboxymethyl starch has thickening and film-forming properties, can adjust the viscosity between the raw material components of the inner layer, is beneficial to improving the shaping of the inner layer, and is conducive to the processing of the inner layer film.

[0010] Polybutylene adipate terephthalate is a completely biodegradable natural polymer with good ductility and elongation at break. As the outer layer, it has good mechanical properties. Carrageenan has good elasticity and toughness and can improve the adhesion between the components of the outer layer. Modified starch has certain film-forming properties, can make the prepared outer layer soft and have a certain tensile strength. Citric acid ester has certain wetting properties and can improve the wear resistance of the outer layer surface, making the outer layer easier to coat and bond, thereby improving the processing performance of the outer layer and the inner layer. Nano-carbon fiber has good affinity, is relatively easy to mix with other components, and at the same time has good mechanical properties such as flexural strength, flexural modulus, and compressive strength, thereby improving the corresponding mechanical properties of the outer layer. The plasticizer can increase the plasticity of the outer layer, reduce elasticity, improve the flexibility of the outer layer, and at the same time can increase its impact resistance strength and prevent the outer layer from cracking. The dispersant acts as a lubricant, reducing the friction between the component mixtures, thereby improving the fluidity and processing efficiency of the outer layer components. The silane coupling agent can improve the weather resistance of the outer layer, enhance the strength and hardness of the outer layer, and improve the wear resistance and chemical corrosion resistance of the outer layer.

[0011] Preferably, the preparation method of the modified graphene includes the following steps:

[0012] (1) Disperse graphene in absolute ethanol, ultrasonically stir for 20 - 30 min to obtain a graphene suspension, then add betaine, ultrasonically stir for 10 - 20 min at a temperature of 60 - 80 °C, and filter to obtain a treated product;

[0013] (2) Disperse the carbon nanotubes in a sodium hydroxide solution, stir at a temperature of 80 - 90 °C for 1 - 2 h, wash with water, filter, and then disperse in citric acid, add chitosan to obtain a mixed solution;

[0014] (3) Disperse the treated product obtained in step (1) in an aqueous rutin solution, then add the mixed solution obtained in step (2), stir at a temperature of 75 - 80 °C for 2 - 3 h, wash with water, filter to obtain modified graphene.

[0015] By adopting the above technical solution, graphene has good mechanical properties, and at the same time has good toughness and can be bent. Betaine has strong surface activity and contains amino and carboxyl groups in its structure. When graphene and betaine are mixed, the amino and carboxyl groups in betaine can react with the amino and carboxyl groups in graphene to form a macromolecular structure. The graphene obtained after modification not only retains a large amount of the lamellar structure of graphene oxide, but also improves the surface activity, which helps the loading of subsequent components.

[0016] Carbon nanotubes have strong tensile strength and flexibility. When carbon nanotubes are dispersed in a sodium hydroxide solution, carbon nanotubes are modified with sodium hydroxide to obtain hydroxylated carbon nanotubes, which have good dispersibility and water solubility. Adding chitosan increases the viscosity of the solution, which helps the mixing of subsequent components.

[0017] The treated product obtained in step (1) is dispersed in an aqueous rutin solution. The aqueous rutin solution is a strong antioxidant for scavenging free radicals, which can terminate the chain reaction of free radicals and inhibit the peroxidation of polyunsaturated fatty acids in the packaging film, and has good antioxidant properties. At the same time, rutin can adsorb graphene, improve the surface properties of graphene, enable graphene to mix better with carbon nanotubes, and carbon nanotubes can be loaded on the surface of graphene, thereby increasing the mechanical properties of graphene. In addition, chitosan can coat graphene, thereby increasing the adhesion between graphene and carbon nanotubes, which is beneficial to further improving the mechanical properties of graphene.

[0018] Preferably, the mass ratio of the graphene, carbon nanotubes and chitosan is 1 mg : 0.5 - 0.8 g : 0.1 - 0.3 g.

[0019] By adopting the above technical solution, further limiting the mass ratio of graphene, carbon nanotubes and chitosan within a certain range, modified graphene with better mechanical properties is obtained. Carbon nanotubes can be loaded on the surface of graphene, increasing the mechanical properties of graphene. Chitosan can coat graphene, thereby increasing the adhesion between graphene and carbon nanotubes, which is beneficial to further improving the mechanical properties of graphene.

[0020] Preferably, the concentration of rutin in the rutin aqueous solution is 0.005-0.008 μg / mL.

[0021] By adopting the above technical solution, rutin has strong antioxidant properties, and a reasonable concentration of the rutin aqueous solution is set, so that the subsequent rutin can better modify the surface properties of graphene, which in turn helps to change the mechanical properties of graphene.

[0022] Preferably, the adhesive is water-based polyurethane.

[0023] By adopting the above technical solution, water-based polyurethane is used as an adhesive for the coating adhesive of the outer layer and the inner memory, which has sufficient viscosity, increases the softness of the outer layer, is more conducive to the combination of the inner layer and the outer layer, and thus helps the molding of the packaging bag.

[0024] Preferably, the raw material components of the outer layer include the following raw materials in parts by weight: 45-60 parts of polybutylene terephthalate-adipate, 10-20 parts of carrageenan, 30-40 parts of modified starch, 5-15 parts of citrate, 15-20 parts of nano-carbon fibers, 0.5-1 parts of plasticizer, 0.2-0.6 parts of dispersant, and 0.3-0.5 parts of silane coupling agent.

[0025] By adopting the above technical solution, the weight of each raw material component of the outer layer is further limited to obtain an outer layer with better performance. The combination of each raw material component makes the outer layer have better ductility and elongation at break, and the combination of each component has better mechanical properties.

[0026] Preferably, the method for preparing the modified starch comprises the following steps:

[0027] (1) dispersing corn starch in deionized water, stirring at a temperature of 50-60° C. for 20-30 minutes, then adding acetic acid solution, continuing to stir, filtering, and drying to obtain powder;

[0028] (2) dispersing white carbon black in anhydrous ethanol, adding the powder obtained in step (1), continuing to stir at a temperature of 55-65° C. for 1-2 hours, then adding nanocellulose, continuing to stir, filtering, and drying to obtain modified starch.

[0029] By adopting the above technical solution, acetic acid is used to modify corn starch to denature the corn starch, resulting in corn starch with increased viscosity; silica has good adsorption properties, strong adhesion, tear resistance, heat resistance, and anti-aging properties. When added to the powder obtained in step (1), the polyhydroxy structure of corn starch can undergo physicochemical interactions with silica molecules to form a coating layer. The coating of these starch macromolecular chains improves the compatibility and mechanical properties of part of the silica; nanocellulose has a high porosity. When nanocellulose is added, nanocellulose can adsorb with silica, thereby increasing the specific surface area of silica, further improving the specific surface area of corn starch, and simultaneously improving the mechanical properties of corn starch.

[0030] Preferably, the mass ratio of the corn starch, silica, and nanocellulose is 1:0.6 - 0.9:0.05 - 0.08.

[0031] By adopting the above technical solution, further limiting the mass ratio of corn starch, silica, and nanocellulose within a certain range, modified starch with better mechanical properties is obtained. The corn starch and silica form a coating layer, improving the compatibility and mechanical properties of silica. Nanocellulose can adsorb with silica, thereby increasing the specific surface area of silica and simultaneously improving the mechanical properties of corn starch.

[0032] Preferably, the plasticizer is one or more of glycerol, polyethylene glycol, dioctyl phthalate, and urea.

[0033] By adopting the above technical solution, the plasticizer has the functions of reducing the viscosity of the composition, increasing the flexibility of the composition, and simultaneously increasing the elongation at break of the composition, thereby reducing the molding processing temperature of the composition and facilitating the processing of the packaging bag.

[0034] In a second aspect, the present application also provides a method for preparing a low-melting-point packaging bag, including the following steps:

[0035] Mix ethylene-vinyl acetate copolymer, linear low-density polyethylene, nano-silica, epoxy soybean oil, polyethylene fiber, modified graphene, and sodium carboxymethyl starch evenly to obtain an inner layer mixture. Heat and melt the inner layer mixture, extrude and blow it into a film, and cool and shape it to obtain an inner layer film;

[0036] Mix polybutylene terephthalate adipate, carrageenan, modified starch, citrate, nanofiber, plasticizer, dispersant, and silane coupling agent to obtain an outer layer mixture. Heat and melt the outer layer mixture and make it into a paper. Coat one side of the paper with an adhesive, then adhere the inner layer film to the adhesive, dry, and cool to obtain a low-melting-point packaging film. After cutting, a low-melting-point packaging bag is obtained.

[0037] By adopting the above technical solution and the above step-by-step preparation method, the raw materials are evenly mixed, the operation is simple, and it is easy to process. The prepared low-melting packaging bag has good mechanical properties, which is helpful for subsequent industrial production.

[0038] In summary, the present application has the following beneficial effects:

[0039] 1. In the present application, the combination of ethylene-vinyl acetate copolymer and linear low-density polyethylene has excellent low water permeability, low-temperature flexibility, ductility and good processability; the application of nano-silica in the packaging bag can improve the transparency, strength, toughness and waterproof performance of the packaging bag; nano-silica can be loaded on the outer surface of polyvinyl alcohol fiber, increasing the specific surface area of polyvinyl alcohol fiber, further improving the mechanical properties such as the tensile performance and tear resistance of the packaging bag. Modified graphene has high mechanical strength and toughness and can coat the surface of polyvinyl alcohol fiber. The mixture of nano-silica, modified graphene and polyvinyl alcohol fiber forms a network structure, thereby improving the corresponding mechanical properties of the packaging bag.

[0040] 2. In the present application, poly(butylene adipate terephthalate) has good ductility and elongation at break and has good mechanical properties as the outer layer. Modified starch has certain film-forming properties, which can make the prepared outer layer soft and have certain tensile strength. Nano-carbon fiber has good affinity and is relatively easy to mix with other components. At the same time, it has good mechanical properties such as bending strength, bending modulus and compressive strength, thereby improving the corresponding mechanical properties of the outer layer.

[0041] 3. In the present application, the amino group and carboxyl group in betaine can react with the amino group and carboxyl group in graphene to form a macromolecular structure. The graphene obtained after modification not only retains a large amount of the lamellar structure of graphene oxide, but also improves the surface activity, which is helpful for the loading of carbon nanotubes, thereby improving the performance of graphene. Detailed Embodiments

[0042] The following further elaborates on the present application with reference to embodiments.

[0043] The raw materials used in the examples and comparative examples can all be obtained commercially. Among them, the adhesive is waterborne polyurethane and the plasticizer is glycerol.

[0044] Preparation Example of Modified Graphene

[0045] Preparation Example 1-1

[0046] The preparation method of modified graphene includes the following steps:

[0047] (1) Disperse 0.5 g of graphene into 2 L of absolute ethanol, ultrasonically stir for 25 min to obtain a graphene suspension, then add 0.1 kg of betaine, ultrasonically treat for 15 min at 70 °C, and filter to obtain a treated product;

[0048] (2) Disperse carbon nanotubes in 0.5 L of sodium hydroxide solution, stir at 85 °C for 2 h, wash with water, filter, and then disperse in 1 L of citric acid with a mass concentration of 12%, and add chitosan to obtain a mixed solution;

[0049] (3) Disperse the treated product obtained in step (1) in 1 L of rutin aqueous solution, then add the mixed solution obtained in step (2), stir at 80 °C for 3 h, wash with water, and filter to obtain modified graphene; wherein, the mass ratio of graphene, carbon nanotubes, and chitosan is 1 mg: 0.8 g: 0.3 g; the concentration of rutin in the rutin aqueous solution is 0.008 μg / mL.

[0050] Preparation Example 1-2

[0051] The difference from Preparation Example 1-1 is that in step (1), betaine is not added.

[0052] Preparation Example 1-3

[0053] The difference from Preparation Example 1-1 is that in step (2), carbon nanotubes are not added.

[0054] Preparation Example 1-4

[0055] The difference from Preparation Example 1-1 is that in step (2), chitosan is not added.

[0056] Preparation Example 1-5

[0057] The difference from Preparation Example 1-1 is that in step (3), the rutin aqueous solution is not added.

[0058] Preparation Example 1-6

[0059] The difference from Preparation Example 1-1 is that the mass ratio of graphene, carbon nanotubes, and chitosan is 1 mg: 0.5 g: 0.1 g.

[0060] Preparation Example 1-7

[0061] The difference from Preparation Example 1-1 is that the mass ratio of graphene, carbon nanotubes, and chitosan is 1 mg: 1.1 g: 0.5 g.

[0062] Preparation Example 1-8

[0063] The difference from Preparation Example 1-1 is that the concentration of rutin in the rutin aqueous solution is 0.005 μg / mL.

[0064] Preparation Examples of Modified Starch

[0065] Preparation Example 2-1

[0066] The preparation method of the modified starch comprises the following steps:

[0067] (1) Disperse 1 kg of corn starch in 2 L of deionized water, stir at 55 °C for 25 min, then add 0.5 L of acetic acid solution with a mass concentration of 10%, continue to stir for 1 h, filter, and dry to obtain a powder;

[0068] (2) Disperse silica white in 2 L of absolute ethanol, add the powder obtained in step (1), continue to stir at 60 °C for 2 h, then add nanocellulose and continue to stir for 2 h, filter, and dry to obtain the modified starch; wherein, the mass ratio of corn starch, silica white, and nanocellulose is 1:0.6:0.08.

[0069] Preparation Example 2-2

[0070] The difference from Preparation Example 2-1 is that in step (1), no acetic acid solution is added.

[0071] Preparation Example 2-3

[0072] The difference from Preparation Example 2-1 is that in step (2), no silica white is added.

[0073] Preparation Example 2-4

[0074] The difference from Preparation Example 2-1 is that in step (2), no nanocellulose is added.

[0075] Preparation Example 2-5

[0076] The difference from Preparation Example 2-1 is that the mass ratio of corn starch, silica white, and nanocellulose is 1:0.9:0.05.

[0077] Preparation Example 2-6

[0078] The difference from Preparation Example 2-1 is that the mass ratio of corn starch, silica white, and nanocellulose is 1:0.3:0.1.

[0079] Examples

[0080] Example 1

[0081] A low-melting packaging bag comprises an inner layer and an outer layer, and an adhesive is bonded between the inner layer and the outer layer. The raw material components of the inner layer, by weight, include the following raw materials: 60 kg of ethylene-vinyl acetate copolymer, 15 kg of linear low-density polyethylene, 20 kg of nano-silica, 10 kg of epoxy soybean oil, 18 kg of polyvinyl alcohol fiber, 20 kg of modified graphene, and 3 kg of sodium carboxymethyl starch.

[0082] The raw material components of the outer layer, by weight, include the following raw materials: 45 kg of poly(butylene terephthalate-co-adipate), 20 kg of carrageenan, 40 kg of modified starch, 5 kg of citrate ester, 20 kg of nanofiber carbon, 1 kg of plasticizer, 0.6 kg of dispersant, and 0.5 kg of silane coupling agent; the dispersant is sodium dodecyl sulfate.

[0083] The preparation method of the above-mentioned low-melting-point packaging bag includes the following steps: Mix ethylene-vinyl acetate copolymer, linear low-density polyethylene, nano-silica, epoxy soybean oil, polyethylene fiber, modified graphene, and sodium carboxymethyl starch evenly to obtain an inner layer mixture. Heat and melt the inner layer mixture, extrude and blow it into a film, and cool and shape it to obtain an inner layer film; Mix poly(butylene terephthalate-co-adipate), carrageenan, modified starch, citrate ester, nanofiber carbon, plasticizer, dispersant, and silane coupling agent to obtain an outer layer mixture. Heat and melt the outer layer mixture and make it into a paper. Coat an adhesive on one side of the paper, then adhere the inner layer film to the adhesive, dry, and cool to obtain a low-melting-point packaging film. After cutting, a low-melting-point packaging bag is obtained.

[0084] The modified graphene is prepared by Preparation Example 1-1; the modified starch is prepared by Preparation Example 2-1.

[0085] Example 2

[0086] A low-melting-point packaging bag, different from Example 1 in that the modified graphene is prepared by Preparation Example 1-2.

[0087] Example 3

[0088] A low-melting-point packaging bag, different from Example 1 in that the modified graphene is prepared by Preparation Example 1-3.

[0089] Example 4

[0090] A low-melting-point packaging bag, different from Example 1 in that the modified graphene is prepared by Preparation Example 1-4.

[0091] Example 5

[0092] A low-melting-point packaging bag, different from Example 1 in that the modified graphene is prepared by Preparation Example 1-5.

[0093] Example 6

[0094] A low-melting-point packaging bag, different from Example 1 in that the modified graphene is prepared by Preparation Example 1-6.

[0095] Example 7

[0096] A low-melting-point packaging bag, which is different from Example 1 in that the modified graphene is prepared by Preparation Examples 1-7.

[0097] Example 8

[0098] A low-melting-point packaging bag, which is different from Example 1 in that the modified graphene is prepared by Preparation Examples 1-8.

[0099] Example 9

[0100] A low-melting-point packaging bag, which is different from Example 1 in that the modified starch is prepared by Preparation Example 2-2.

[0101] Example 10

[0102] A low-melting-point packaging bag, which is different from Example 1 in that the modified starch is prepared by Preparation Example 2-3.

[0103] Example 11

[0104] A low-melting-point packaging bag, which is different from Example 1 in that the modified starch is prepared by Preparation Example 2-4.

[0105] Example 12

[0106] A low-melting-point packaging bag, which is different from Example 1 in that the modified starch is prepared by Preparation Example 2-5.

[0107] Example 13

[0108] A low-melting-point packaging bag, which is different from Example 1 in that the modified starch is prepared by Preparation Example 2-6.

[0109] Example 14

[0110] A low-melting-point packaging bag, which is different from Example 1 in that the raw material components of the inner layer, by weight, include the following raw materials: 70 kg of ethylene-vinyl acetate copolymer, 25 kg of linear low-density polyethylene, 30 kg of nano-silica, 5 kg of epoxy soybean oil, 18 kg of polyvinyl alcohol fiber, 12 kg of modified graphene, and 1 kg of sodium carboxymethyl starch.

[0111] Example 15

[0112] A low-melting-point packaging bag, which is different from Example 1 in that the raw material components of the outer layer, by weight, include the following raw materials: 60 kg of poly(butylene adipate terephthalate), 10 kg of carrageenan, 30 kg of modified starch, 15 kg of citrate ester, 15 kg of nano-carbon fiber, 0.5 kg of plasticizer, 0.2 kg of dispersant, and 0.3 kg of silane coupling agent.

[0113] Example 16

[0114] A low-melting-point packaging bag, which is different from that of Example 1. The raw material components of the outer layer, by weight, include the following raw materials: 70 kg of poly(butylene terephthalate-co-adipate), 5 kg of carrageenan, 45 kg of modified starch, 20 kg of citrate, 12 kg of nanofiber carbon, 2 kg of plasticizer, 0.1 kg of dispersant, and 0.7 kg of silane coupling agent.

[0115] Comparative example

[0116] Comparative example 1

[0117] A low-melting-point packaging bag, which is different from that of Example 1. The raw material components of the inner layer, by weight, include the following raw materials: 55 kg of ethylene-vinyl acetate copolymer, 10 kg of linear low-density polyethylene, 35 kg of nano-silica, 12 kg of epoxidized soybean oil, 15 kg of polyvinyl alcohol fiber, 25 kg of modified graphene, and 5 kg of sodium carboxymethyl starch.

[0118] Comparative example 2

[0119] A low-melting-point packaging bag, which is different from that of Example 1. It does not add nano-silica.

[0120] Comparative example 3

[0121] A low-melting-point packaging bag, which is different from that of Example 1. It does not add polyvinyl alcohol fiber.

[0122] Comparative example 4

[0123] A low-melting-point packaging bag, which is different from that of Example 1. It does not add modified graphene.

[0124] Comparative example 5

[0125] A low-melting-point packaging bag, which is different from that of Example 1. It uses an equal amount of graphene to replace modified graphene.

[0126] Comparative example 6

[0127] A low-melting-point packaging bag, which is different from that of Example 1. It does not add modified starch.

[0128] Comparative example 7

[0129] A low-melting-point packaging bag, which is different from that of Example 1. It uses an equal amount of starch to replace modified starch.

[0130] Performance detection test

[0131] The low-melting-point packaging bags prepared in Examples 1-16 and Comparative Examples 1-7 were tested for tensile strength and fracture properties according to GB / T 1040.3-2006. The specimen width was 15 mm and the test speed (no load) was 500 mm / min. An electronic tensile testing machine model GBL-L was used for detection; the results are shown in Table 1.

[0132] Table 1 Test data of Examples and Comparative Examples

[0133]

[0134]

[0135] As can be seen from Table 1, the low-melting-point packaging bags prepared in Examples 1, 6, 8, 12 and 14-16 of this application have good mechanical properties. Among them, the data of Example 1 are the best, with a transverse tensile strength of 26.9 MPa, a longitudinal tensile strength of 29.4 MPa; a transverse elongation at break of 890%, a longitudinal elongation at break of 850%; the heat seal strength of upper and lower heat seals is 49.9 N / 15 mm, and the heat seal strength of four-corner heat seals is 48.6 N / 15 mm, indicating that the packaging bags prepared in this application have high tensile strength, elongation at break and heat seal strength. During the loading process of carbon black, they can resist the impact or extrusion of carbon black, making the valve bags not easily deformed and not causing leakage of the valve bags; in addition, the greater the heat seal strength, the more firmly sealed, and the less likely to be damaged during transportation and storage, and the better the storage effect.

[0136] In Example 2, betaine was not added in the preparation method of modified graphene. As can be seen from Table 1, the transverse tensile strength is 24.1 MPa, the longitudinal tensile strength is 27.3 MPa; the transverse elongation at break is 870%, the longitudinal elongation at break is 830%; the heat seal strength of upper and lower heat seals is 47.1 N / 15 mm, and the heat seal strength of four-corner heat seals is 46.2 N / 15 mm. The mechanical properties and heat seal strength decreased slightly, indicating that betaine can change the surface strength of graphene, improve the surface activity, and contribute to the loading of subsequent components.

[0137] In Example 3, carbon nanotubes were not added in the preparation method of modified graphene. As can be seen from Table 1, the transverse tensile strength is 20.4 MPa, the longitudinal tensile strength is 23.1 MPa; the transverse elongation at break is 810%, the longitudinal elongation at break is 780%; the heat seal strength of upper and lower heat seals is 41.2 N / 15 mm, and the heat seal strength of four-corner heat seals is 40.6 N / 15 mm. The mechanical properties and heat seal strength decreased significantly, indicating that carbon nanotubes can be loaded on the surface of graphene, thereby increasing the mechanical properties of graphene.

[0138] Example 4: Chitosan was not added in the preparation method of modified graphene. As can be seen from Table 1, the transverse tensile strength was 22.2 MPa, and the longitudinal tensile strength was 25.4 MPa; the transverse elongation at break was 830%, and the longitudinal elongation at break was 800%; the heat-sealing strength for top-bottom heat-sealing was 43.1 N / 15 mm, and the heat-sealing strength for four-corner heat-sealing was 42.9 N / 15 mm. The mechanical properties and heat-sealing strength decreased significantly, indicating that chitosan can coat graphene, thereby increasing the adhesion between graphene and carbon nanotubes, which is beneficial to further improving the mechanical properties of graphene.

[0139] Example 5: Rutin aqueous solution was not added in the preparation method of modified graphene. As can be seen from Table 1, the transverse tensile strength was 23.1 MPa, and the longitudinal tensile strength was 26.2 MPa; the transverse elongation at break was 860%, and the longitudinal elongation at break was 820%; the heat-sealing strength for top-bottom heat-sealing was 46.3 N / 15 mm, and the heat-sealing strength for four-corner heat-sealing was 45.1 N / 15 mm. The mechanical properties and heat-sealing strength decreased significantly, indicating that rutin can adsorb graphene, improve the surface properties of graphene, and enable graphene to mix better with carbon nanotubes.

[0140] Example 7: The mass ratios of graphene, carbon nanotubes, and chitosan were changed. As can be seen from Table 1, the mechanical properties and heat-sealing strength were significantly worse than those of Example 1 and Example 6, but better than those of Example 3 - 4, indicating that the combination of graphene, carbon nanotubes, and chitosan has a better effect. Chitosan can coat graphene, thereby increasing the adhesion between graphene and carbon nanotubes, which is beneficial to further improving the mechanical properties of graphene.

[0141] Example 9: Acetic acid solution was not added in the preparation method of modified starch. As can be seen from Table 1, the transverse tensile strength was 25.1 MPa, and the longitudinal tensile strength was 28.2 MPa; the transverse elongation at break was 875%, and the longitudinal elongation at break was 840%; the heat-sealing strength for top-bottom heat-sealing was 48.1 N / 15 mm, and the heat-sealing strength for four-corner heat-sealing was 47.3 N / 15 mm. The mechanical properties and heat-sealing strength decreased significantly, indicating that acetic acid was used to modify corn starch, making the corn starch denatured to obtain corn starch with increased viscosity, which is helpful for subsequent improvement of the starch properties.

[0142] Example 10: White carbon black was not added in the preparation method of modified starch. As can be seen from Table 1, the transverse tensile strength was 22.9 MPa, and the longitudinal tensile strength was 25.9 MPa; the transverse elongation at break was 840%, and the longitudinal elongation at break was 810%; the heat-sealing strength for top-bottom heat-sealing was 43.6 N / 15 mm, and the heat-sealing strength for four-corner heat-sealing was 43.1 N / 15 mm. The mechanical properties and heat-sealing strength decreased significantly, indicating that white carbon black has strong adhesion, tear resistance, heat resistance, and anti-aging properties, which is helpful for improving the corresponding properties of starch.

[0143] Example 11 Without adding nanocellulose in the preparation method of the modified starch, it can be seen from Table 1 that the transverse tensile strength is 23.2 MPa, and the longitudinal tensile strength is 26.3 MPa; the transverse elongation at break is 845%, and the longitudinal elongation at break is 820%; the heat-sealing strength of the upper and lower heat seals is 44.1 N / 15 mm, and the heat-sealing strength of the four-corner heat seals is 44.2 N / 15 mm. The mechanical properties and heat-sealing strength have decreased significantly, indicating that nanocellulose can adsorb with silica, thereby increasing the specific surface area of silica and further improving the mechanical properties of corn starch.

[0144] Example 13 Change the mass ratio of corn starch, silica, and nanocellulose. It can be seen from Table 1 that the mechanical properties and heat-sealing strength are significantly worse than those of Example 1 and Example 12, but better than those of Examples 10-11, indicating that the combination of corn starch, silica, and nanocellulose has a better effect. Corn starch and silica form a coating layer, and nanocellulose can adsorb with silica, thereby increasing the specific surface area of silica and improving the mechanical properties of corn starch at the same time.

[0145] Comparative Example 1 Change the raw material dosage of the low-melting packaging bag. It can be seen from Table 1 that compared with Example 1, the mechanical properties such as the tensile strength and elongation at break of the packaging bag and the heat-sealing strength have decreased significantly, indicating that each raw material component has better mechanical properties according to a certain content ratio, and the change of each raw material dosage affects the mechanical properties of the packaging bag.

[0146] Comparative Example 2 Do not add nano-silica in the raw material components of the inner layer. It can be seen from Table 1 that the transverse tensile strength is 18.4 MPa, and the longitudinal tensile strength is 22.1 MPa; the transverse elongation at break is 800%, and the longitudinal elongation at break is 770%; the heat-sealing strength of the upper and lower heat seals is 40.1 N / 15 mm, and the heat-sealing strength of the four-corner heat seals is 39.1 N / 15 mm. The mechanical properties and heat-sealing strength have decreased significantly, indicating that nano-silica can be loaded on the outer surface of the polyvinyl alcohol fiber, increasing the specific surface area of the polyvinyl alcohol fiber and further improving the mechanical properties such as the tensile performance and tear resistance of the packaging bag.

[0147] Comparative Example 3 Do not add polyvinyl alcohol fiber in the raw material components of the inner layer. It can be seen from Table 1 that the transverse tensile strength is 17.2 MPa, and the longitudinal tensile strength is 21.3 MPa; the transverse elongation at break is 790%, and the longitudinal elongation at break is 760%; the heat-sealing strength of the upper and lower heat seals is 39.1 N / 15 mm, and the heat-sealing strength of the four-corner heat seals is 38.2 N / 15 mm. The mechanical properties and heat-sealing strength have decreased significantly, indicating that polyvinyl alcohol fiber has unique strong adhesion, film flexibility, smoothness, oil resistance, and wear resistance, and can improve the corresponding properties of the packaging bag.

[0148] In Comparative Example 4, modified graphene is not added to the raw material components of the inner layer. As can be seen from Table 1, the transverse tensile strength is 16.4 MPa, and the longitudinal tensile strength is 20.1 MPa; the transverse elongation at break is 780%, and the longitudinal elongation at break is 750%; the heat-sealing strength of top-bottom heat-sealing is 38.2 N / 15 mm, and the heat-sealing strength of four-corner heat-sealing is 37.1 N / 15 mm. The mechanical properties and heat-sealing strength decrease significantly, indicating that modified graphene has high mechanical strength and toughness, can coat the surface of polyvinyl alcohol fibers, and thus improve the corresponding mechanical properties of the packaging bag.

[0149] In Comparative Example 5, graphene in an equal amount is used to replace modified graphene in the raw material components of the inner layer. As can be seen from Table 1, the transverse tensile strength is 19.1 MPa, and the longitudinal tensile strength is 22.3 MPa; the transverse elongation at break is 800%, and the longitudinal elongation at break is 765%; the heat-sealing strength of top-bottom heat-sealing is 40.0 N / 15 mm, and the heat-sealing strength of four-corner heat-sealing is 39.0 N / 15 mm. The mechanical properties and heat-sealing strength decrease significantly, indicating that the modified graphene of the present application has strong comprehensive properties and is more conducive to improving the corresponding properties of the packaging bag subsequently.

[0150] In Comparative Example 6, modified starch is not added to the raw material components of the outer layer. As can be seen from Table 1, the transverse tensile strength is 16.8 MPa, and the longitudinal tensile strength is 20.3 MPa; the transverse elongation at break is 785%, and the longitudinal elongation at break is 755%; the heat-sealing strength of top-bottom heat-sealing is 38.5 N / 15 mm, and the heat-sealing strength of four-corner heat-sealing is 37.6 N / 15 mm. The mechanical properties and heat-sealing strength decrease significantly, indicating that modified starch has certain film-forming properties, can make the prepared outer layer soft and have certain tensile strength, and can improve the structural properties of the outer layer.

[0151] In Comparative Example 7, starch in an equal amount is used to replace modified starch in the raw material components of the outer layer. As can be seen from Table 1, the transverse tensile strength is 19.8 MPa, and the longitudinal tensile strength is 22.9 MPa; the transverse elongation at break is 795%, and the longitudinal elongation at break is 766%; the heat-sealing strength of top-bottom heat-sealing is 41.1 N / 15 mm, and the heat-sealing strength of four-corner heat-sealing is 40.1 N / 15 mm. The mechanical properties and heat-sealing strength decrease significantly, indicating that the modified starch of the present application has strong comprehensive properties and is more conducive to improving the corresponding properties of the outer layer structure of the packaging bag subsequently.

[0152] This specific embodiment is only an explanation of the present application and does not limit the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A low-melting packaging bag, characterized in that, It comprises an inner layer and an outer layer, wherein the inner layer and the outer layer are bonded with an adhesive, and the raw material components of the inner layer, in parts by weight, comprise the following raw materials: 60-70 parts of ethylene-vinyl acetate copolymer, 15-25 parts of linear low-density polyethylene, 20-30 parts of nano-silicon dioxide, 5-10 parts of epoxy soybean oil, 18-28 parts of polyvinyl alcohol fiber, 12-20 parts of modified graphene, and 1-3 parts of sodium carboxymethyl starch; The outer layer comprises the following raw materials: in parts by weight, 45-60 parts of polybutylene terephthalate-adipate, 10-20 parts of carrageenan, 30-40 parts of modified starch, 5-15 parts of citrate, 15-20 parts of nano-carbon fiber, 0.5-1 parts of plasticizer, 0.2-0.6 parts of dispersant, and 0.3-0.5 parts of silane coupling agent; The preparation method of the modified graphene comprises the following steps: (1) dispersing graphene in anhydrous ethanol, stirring with ultrasound for 20-30 min to obtain a graphene suspension, then adding betaine, stirring with ultrasound at a temperature of 60-80° C. for 10-20 min, filtering, and obtaining a treated product; (2) dispersing the carbon nanotubes in a sodium hydroxide solution, stirring at a temperature of 80-90° C. for 1-2 hours, washing with water, filtering, and then dispersing the carbon nanotubes in citric acid, adding chitosan, and obtaining a mixed solution; (3) dispersing the treated product obtained in step (1) in a rutin aqueous solution, then adding the mixed solution obtained in step (2), stirring at a temperature of 75-80° C. for 2-3 hours, washing with water, and filtering to obtain modified graphene; The preparation method of the modified starch comprises the following steps: (1) Disperse corn starch in deionized water, stir at 50-60°C for 20-30 minutes, then add acetic acid solution, continue stirring, filter, and dry to obtain powder; (2) Dispersing white carbon black in anhydrous ethanol, adding the powder obtained in step (1), continuing to stir at a temperature of 55-65° C. for 1-2 hours, then adding nanocellulose, continuing to stir, filtering, and drying to obtain modified starch.

2. The low-melting-point packaging bag according to claim 1, wherein The mass ratio of the graphene, carbon nanotubes and chitosan is 1 mg: 0.5-0.8 g: 0.1-0.3 g.

3. A low-melting-point packaging bag according to claim 1, characterized in that, The concentration of rutin in the rutin aqueous solution is 0.005-0.008 μg / mL.

4. A low-melting-point packaging bag according to claim 1, characterized in that, The adhesive is water-based polyurethane.

5. A low-melting-point packaging bag according to claim 1, characterized in that, The mass ratio of the corn starch, white carbon black and nanocellulose is 1:0.6-0.9:0.05-0.

08.

6. The low-melting-point packaging bag according to claim 1, wherein, The plasticizer is one or more of glycerol, polyethylene glycol, dioctyl phthalate and urea.

7. A method for preparing a low-melting packaging bag according to any one of claims 1-6, characterized in that, The method comprises the following steps: uniformly mixing ethylene-vinyl acetate copolymer, linear low-density polyethylene, nano-silicon dioxide, epoxy soybean oil, polyvinyl alcohol fiber, modified graphene and sodium carboxymethyl starch to obtain an inner layer mixture, heating and melting the inner layer mixture, extruding and blowing it into a film, cooling and shaping it to obtain an inner layer film; Mix poly(butylene adipate terephthalate), carrageenan, modified starch, citrate ester, nanofiber carbon, plasticizer, dispersant and silane coupling agent to obtain an outer layer mixture. Heat and melt the outer layer mixture to make paper. Coat one side of the paper with an adhesive, then adhere the inner layer film to the adhesive, dry and cool to obtain a low melting point packaging film. After cutting, a low melting point packaging bag is obtained.

Images