Oil-resistant and solvent-resistant food packaging film and preparation method thereof

Abstract

The invention relates to the technical field of packaging films, and discloses an oil-resistant and solvent-resistant food packaging film and a preparation method. Under the initiation of dicumyl peroxide or dibenzoyl peroxide, triallyl isocyanurate is used as a crosslinking agent to cause polyethylene, triallyl isocyanurate, and allyl isocyanurate structure modified on the surface of graphene to undergo melt co-crosslinking to obtain a graphene crosslinked polyethylene food packaging film. Graphene nanoparticles form chemical crosslinks in the polyethylene matrix to improve the barrier properties of the polyethylene food packaging film. The swelling degree and solubility of polyethylene in organic solvents are reduced, and the oil and solvent resistance of the food packaging film is improved. Graphene nanoparticles are chemically bonded in the polyethylene matrix, which improves the dispersibility of graphene, so that graphene has a better reinforcing effect on polyethylene, and improves the mechanical properties of the food packaging film, such as tensile properties and elastic modulus.

Description

Technical Field

[0001] The invention relates to the technical field of packaging films, in particular to an oil-resistant and solvent-resistant food packaging film and a preparation method thereof. Background Art

[0002] Polyethylene has the advantages of being odorless, non-toxic, and having good electrical insulation. It is widely used in food cling film, packaging film, etc. Improving the comprehensive properties of polyethylene film materials such as barrier properties, mechanical strength, and solvent resistance will help expand the practical application of polyethylene film in food cling film, packaging film, etc. Graphene is a nanomaterial with excellent performance and is widely used in the modification of polymer materials such as polyethylene. For example, the document "Migration of two antioxidants in graphene / low-density polyethylene composite packaging film to food simulant isooctane" reported that the adsorption of graphene and graphene microsheet nanoparticles inhibited the migration of two antioxidants in food packaging to the food simulant isooctane, thereby avoiding the diffusion and migration of food additives into food and causing food safety problems. Functionalization and surface modification of graphene can make graphene better applied in materials such as polyethylene. For example, the document "Preparation and Characterization of Functionalized Graphene / Polyethylene Composite Film" reports that graphene oxide is modified by isophorone diisocyanate and then reduced by hydrazine hydrate. The obtained functionalized graphene reduces the volume resistivity of polyethylene materials and improves the antistatic properties of the materials. The present invention aims to functionalize the surface of graphene oxide, cross-link and modify polyethylene, and improve the mechanical properties, barrier properties and solvent resistance of polyethylene food packaging films. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] The invention provides a high-strength, high-barrier, oil-resistant and solvent-resistant food packaging film and a preparation method thereof.

[0005] (II) Technical solution

[0006] An oil-resistant and solvent-resistant food packaging film comprises the following raw materials in proportion by mass: 95.7-98.2% polyethylene resin, 0.2-1% allyl isocyanurate-modified graphene, 1-2% triallyl isocyanurate, 0.4-0.7% initiator, and 0.2-0.6% antioxidant.

[0007] Preferably, the initiator is any one of dibenzoyl peroxide or dicumyl peroxide.

[0008] Preferably, the method for preparing the oil-resistant and solvent-resistant food packaging film is characterized in that: the preparation method is: adding polyethylene resin, allyl isocyanurate modified graphene, triallyl isocyanurate, initiator, and antioxidant to a double-roll mill, with a mixing temperature of 160-180°C and a time of 10-20 min; then the material is molded in a flat vulcanizer, with a molding temperature of 170-190°C, a pressure of 7-12 MPa, and a time of 8-15 min to obtain an oil-resistant and solvent-resistant food packaging film.

[0009] Preferably, the preparation method of the allyl isocyanurate modified graphene is:

[0010] (1) adding graphene oxide to thionyl chloride, heating under reflux for chlorination; dispersing the obtained chlorinated graphene in a reaction solvent, adding dithioerythritol and triethylamine in an ice bath, stirring to dissolve, heating to 20-35° C. and reacting for 24-48 hours, centrifuging after the reaction, washing with ethanol, and obtaining polythiolated graphene.

[0011] (2) Dispersing the polythiolated graphene in a reaction solvent, then adding triallyl isocyanurate and benzoin dimethyl ether, stirring and dissolving, irradiating the mixture under ultraviolet light for reaction for 1-2 hours, centrifuging, and washing with deionized water and ethanol to obtain allyl isocyanurate-modified graphene.

[0012] Preferably, the reaction solvent in (1) comprises one of tetrahydrofuran, dichloromethane, chloroform, acetone and ethyl acetate.

[0013] Preferably, the mass ratio of acylated graphene, dithioerythritol and triethylamine in (1) is 1:6-20:4-15.

[0014] Preferably, the reaction solvent in (2) comprises one of acetone, tetrahydrofuran, N,N-dimethylformamide or N,N-dimethylacetamide.

[0015] Preferably, the mass ratio of the polythiolated graphene dispersion, triallyl isocyanurate and benzoin dimethyl ether in (2) is 1:2-7:0.02-0.08.

[0016] (III) Beneficial technical effects

[0017] The hydroxyl group of dithioerythritol is used to undergo an esterification reaction with acylated graphene to modify the graphene surface with abundant thiol groups. The introduced thiol groups then undergo a thiol-ene click reaction with an olefinic group of triallyl isocyanurate to obtain allyl isocyanurate-modified graphene, thereby modifying the graphene surface with a large number of allyl isocyanurate structures.

[0018] Under the initiation of diisopropylbenzene peroxide or dibenzoyl peroxide, triallyl isocyanurate is used as a crosslinking agent to cause polyethylene, triallyl isocyanurate, and allyl isocyanurate structure modified on the surface of graphene to undergo melt co-crosslinking to obtain graphene crosslinked polyethylene food packaging film. Graphene nanoparticles form chemical crosslinks in the polyethylene matrix and are uniformly dispersed in the polyethylene matrix. The graphene with a sheet structure can hinder the permeability of oxygen gas molecules and water vapor, thereby improving the barrier properties of the polyethylene food packaging film. After graphene chemically crosslinks polyethylene, the swelling degree and solubility of polyethylene in organic solvents can be reduced, thereby improving the oil resistance and solvent resistance of the food packaging film. Graphene nanoparticles are chemically bonded in the polyethylene matrix, thereby improving the interface bonding force between graphene and polyethylene, improving the dispersibility of graphene, making graphene have a better reinforcing effect on polyethylene, and improving the tensile properties and elastic modulus of the food packaging film. A polyethylene food packaging film with excellent comprehensive properties is obtained. DETAILED DESCRIPTION

[0019] Example 1

[0020] (1) 0.2 g of graphene oxide is added to 10 mL of thionyl chloride and heated under reflux for chlorination; 0.2 g of the obtained chlorinated graphene is weighed and dispersed in 30 mL of tetrahydrofuran, 2.8 g of dithioerythritol and 2 g of triethylamine are added under ice bath, stirred and dissolved, and then heated to 20-35° C. for reaction for 48 h, centrifuged after reaction, and washed with ethanol to obtain polythiolated graphene.

[0021] (2) 0.2 g of polythiols graphene was dispersed in tetrahydrofuran, and then 1.4 g of triallyl isocyanurate and 16 mg of benzoin dimethyl ether were added. After stirring and dissolving, the mixture was irradiated under ultraviolet light for reaction for 1 h, centrifuged, and washed with deionized water and ethanol to obtain allyl isocyanurate-modified graphene.

[0022] (3) 97.9% by weight of polyethylene resin, 0.2% of allyl isocyanurate modified graphene, 1% of triallyl isocyanurate, 0.5% of initiator diisopropyl peroxide, and 0.4% of antioxidant 1010 were added to a double-roll mill at a mixing temperature of 180°C for 10 min; the material was then molded in a flat vulcanizer at a molding temperature of 180°C, a pressure of 12 MPa, and a time of 10 min to obtain an oil-resistant and solvent-resistant food packaging film.

[0023] Example 2

[0024] (1) 0.2 g of acylated graphene was dispersed in 20 mL of ethyl acetate, 1.2 g of dithioerythritol and 0.8 g of triethylamine were added under ice bath, stirred to dissolve, and then heated to 25° C. to react for 24-48 h. After the reaction, centrifugation was performed, and the mixture was washed with ethanol to obtain polythiolated graphene.

[0025] (2) 0.2 g of polythiols graphene was dispersed in N,N-dimethylformamide, and then 0.4 g of triallyl isocyanurate and 4 mg of benzoin dimethyl ether were added. After stirring and dissolving, the mixture was irradiated under ultraviolet light for 2 h, centrifuged, and washed with deionized water and ethanol to obtain allyl isocyanurate-modified graphene.

[0026] (3) 97.1% by weight of polyethylene resin, 0.5% of allyl isocyanurate modified graphene, 1.5% of triallyl isocyanurate, 0.7% of initiator dibenzoyl peroxide, and 0.2% of antioxidant 1076 are added to a double-roll mill at a mixing temperature of 180°C for 15 min; the material is then molded in a flat vulcanizer at a molding temperature of 190°C, a pressure of 7 MPa, and a time of 8-15 min to obtain an oil-resistant and solvent-resistant food packaging film.

[0027] Example 3

[0028] (1) 0.2 g of acyl chloride graphene was dispersed in 40 mL of dichloromethane, 4 g of dithioerythritol and 3 g of triethylamine were added under ice bath, stirred to dissolve, and then heated to 25° C. for reaction for 36 h. After the reaction, centrifugation was performed and the mixture was washed with ethanol to obtain polythiolated graphene.

[0029] (2) 0.2 g of polythiocarbyl graphene was dispersed in acetone, and then 1.4 g of triallyl isocyanurate and 16 mg of benzoin dimethyl ether were added. After stirring and dissolving, the mixture was irradiated under ultraviolet light for 2 h, centrifuged, and washed with deionized water and ethanol to obtain allyl isocyanurate-modified graphene.

[0030] (3) 96.6% by weight of polyethylene resin, 0.8% of allyl isocyanurate modified graphene, 1.5% of triallyl isocyanurate, 0.7% of initiator dibenzoyl peroxide, and 0.6% of antioxidant 1076 were added to a double-roll mill at a mixing temperature of 170°C for 10 min; the material was then molded in a flat vulcanizer at a molding temperature of 180°C, a pressure of 12 MPa, and a time of 15 min to obtain an oil-resistant and solvent-resistant food packaging film.

[0031] Example 4

[0032] (1) Disperse 0.2 g of acylated graphene in 20-40 mL of acetone, add 1.2-4 g of dithioerythritol and 0.8-3 g of triethylamine in an ice bath, stir to dissolve, then heat to 35° C. and react for 24-48 h. After the reaction, centrifuge and wash with ethanol to obtain polythiolated graphene.

[0033] (2) 0.2 g of polythiocarbyl graphene was dispersed in acetone, and then 0.8 g of triallyl isocyanurate and 10 mg of benzoin dimethyl ether were added. After stirring and dissolving, the mixture was irradiated under ultraviolet light for 2 h, centrifuged, and washed with deionized water and ethanol to obtain allyl isocyanurate-modified graphene.

[0034] (3) 95.9% by weight of polyethylene resin, 1% of allyl isocyanurate modified graphene, 2% of triallyl isocyanurate, 0.7% of initiator dibenzoyl peroxide, and 0.4% of antioxidant 1010 were added to a double-roll mill at a mixing temperature of 160°C for 20 min; the material was then molded in a flat vulcanizer at a molding temperature of 190°C, a pressure of 10 MPa, and a time of 15 min to obtain an oil-resistant and solvent-resistant food packaging film.

[0035] Comparative Example 1

[0036] (1) 0.2 g of acylated graphene was dispersed in 20 mL of tetrahydrofuran, and 2.5 g of dithioerythritol and 1.5 g of triethylamine were added under ice bath, stirred to dissolve, and then heated to 35° C. for reaction for 24-48 h. After the reaction, centrifugation was performed, and the mixture was washed with ethanol to obtain polythiolated graphene.

[0037] (2) 97.6% by weight of polyethylene resin, 0.2% of polythiographene, 1% of triallyl isocyanurate, 0.6% of initiator diisopropyl peroxide, and 0.6% of antioxidant 1010 are added to a double-roll mill at a mixing temperature of 180°C for 15 min; the material is then molded in a flat vulcanizer at a molding temperature of 190°C, a pressure of 10 MPa, and a time of 10 min to obtain a food packaging film.

[0038] Comparative Example 2

[0039] (1) 97.4% by weight of polyethylene resin, 0.2% of graphene oxide, 1.5% of triallyl isocyanurate, 0.4% of initiator diisopropylbenzene peroxide, and 0.5% of antioxidant 1010 are added to a double-roll mill at a mixing temperature of 180° C. for 10 min; the material is then molded in a flat vulcanizer at a molding temperature of 190° C., a pressure of 10 MPa, and a time of 8 min to obtain a food packaging film.

[0040] Referring to the method of ASTM F1249-90, a water vapor transmission rate tester was used to measure the water vapor transmission coefficient of food packaging films. Referring to the method of GB / T 19789-2005, an oxygen transmission tester was used to measure the oxygen transmission rate of food packaging films.

[0041] With reference to the method of GB / T 1040.1-2006, the tensile properties of food packaging films were measured using a tensile testing machine. The tensile rate was 100 mm / min, and the sample was a strip with a length of 120 mm, a width of 50 mm, and a height of 4 mm.

[0042]

[0043] Weigh 0.500 g of food packaging film and add it into N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone solvents respectively. After soaking for 24 hours, take out the food packaging film and observe the swelling and dissolution.

[0044]

[0045]

[0046] After cross-linking of allyl isocyanurate-modified graphene, the polyethylene food packaging film does not swell or dissolve in N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

Claims

1. An oil-resistant and solvent-resistant food packaging film, characterized in that: The food packaging film comprises the following raw materials in the following weight proportions: 95.7-98.2% polyethylene resin, 0.2-1% allyl isocyanurate modified graphene, 1-2% triallyl isocyanurate, 0.4-0.7% initiator, and 0.2-0.6% antioxidant; The initiator is any one of dibenzoyl peroxide or dicumyl peroxide; The preparation method comprises the following steps: adding polyethylene resin, allyl isocyanurate modified graphene, triallyl isocyanurate, an initiator and an antioxidant into a double-roll open mill, mixing at a temperature of 160-180°C for 10-20 min; then molding the materials in a flat vulcanizer at a temperature of 170-190°C, a pressure of 7-12 MPa and a time of 8-15 min to obtain an oil-resistant and solvent-resistant food packaging film; The preparation method of the allyl isocyanurate modified graphene is: (1) adding graphene oxide to thionyl chloride and heating under reflux for acyl chlorination; dispersing the obtained acyl chloride graphene in a reaction solvent, adding dithioerythritol and triethylamine under an ice bath, stirring and dissolving, heating to 20-35°C and reacting for 24-48 hours, centrifuging and washing after the reaction to obtain polythiolated graphene; (2) Dispersing the polythiolated graphene in a reaction solvent, then adding triallyl isocyanurate and benzoin dimethyl ether, stirring and dissolving, and then irradiating the mixture under ultraviolet light for 1-2 h, centrifuging and washing to obtain allyl isocyanurate-modified graphene.

2. The oil-resistant and solvent-resistant food packaging film according to claim 1, characterized in that: The reaction solvent in (1) comprises one of tetrahydrofuran, dichloromethane, chloroform, acetone and ethyl acetate.

3. The oil-resistant and solvent-resistant food packaging film according to claim 1, characterized in that: The mass ratio of acylated graphene, dithioerythritol and triethylamine in (1) is 1:6-20:4-15.

4. The oil-resistant and solvent-resistant food packaging film according to claim 1, characterized in that: The reaction solvent in (2) includes one of acetone, tetrahydrofuran, N,N-dimethylformamide or N,N-dimethylacetamide.

5. The oil-resistant and solvent-resistant food packaging film according to claim 1, characterized in that: The mass ratio of polythiographene, triallyl isocyanurate and benzoin dimethyl ether in (2) is 1:2-7:0.02-0.08.

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