A packaging film and its preparation process and a composite packaging bag using the packaging film

Abstract

The present application relates to the technical field of packaging films and packaging bags, and in particular to a packaging film and its preparation process and a composite packaging bag using the packaging film. Among them, a packaging film is composed of an inner layer, a middle layer and an outer layer which are closely fitted in sequence with a thickness ratio of 1: (1-2): 1; in the inner and outer layers of the packaging film, metallocene linear polyethylene, low-density polyethylene and a slippery additive are used in combination, and in the middle layer of the packaging film, metallocene linear polyethylene, ultra-low-density polyethylene and a toughening agent are used in combination, which enhances the interaction between the middle layer and the inner and outer layers, as well as between the raw materials in the packaging film, so that the prepared packaging film is thinner and has higher tensile strength, elongation at break and tear strength; further, the thinner packaging film is softer, which is conducive to reducing the friction between the packaging films, thereby reducing the breakage of the composite packaging bag during use.

Description

Technical Field

[0001] The present application relates to the technical field of packaging films and packaging bags, and in particular to a packaging film and a preparation process thereof, and a composite packaging bag using the packaging film. Background Art

[0002] Existing liquid packaging mainly uses plastic bottles, plastic barrels or other containers for filling or barreling, but plastic barrels or bottles take up a large space when stacked and have relatively high transportation costs. Currently, there are many liquid packaging bags for foods such as beverages, alcohol, cooking oil and condiments on the market.

[0003] Compared with traditional filling or barrel packaging, liquid packaging bags are lightweight, occupy a small area and are easy to store and transport; however, during transportation, liquid packaging bags are difficult to fix, and under the action of friction or impact during transportation, leakage points or ruptures are prone to occur, causing the contents in the packaging bag to leak. Summary of the invention

[0004] In order to solve the problem that the existing liquid packaging bags use thick packaging films with poor tensile strength, tear elongation, softness and wear resistance, which makes the packaging bags easily broken under the action of friction or impact force, the present application provides a packaging film and its preparation process and a composite packaging bag using the packaging film.

[0005] In a first aspect, the present application provides a packaging film.

[0006] A packaging film comprises an inner layer, a middle layer and an outer layer which are closely fitted in sequence and have a thickness ratio of 1:(1-2):1, wherein the inner layer and the outer layer each comprise 50-70 parts by weight of metallocene linear polyethylene, 20-40 parts by weight of low-density polyethylene and 2-8 parts by weight of a slip additive; and the middle layer comprises 20-40 parts by weight of metallocene linear polyethylene, 40-60 parts by weight of ultra-low-density polyethylene and 10-30 parts by weight of a toughening agent.

[0007] By adopting the above technical scheme, metallocene linear polyethylene, low-density polyethylene and a slippery additive are used in the inner and outer layers of the packaging film, and metallocene linear polyethylene, ultra-low-density polyethylene and a toughening agent are used in the middle layer of the packaging film. This improves the interaction between the middle layer and the inner and outer layers, as well as between the raw materials in the packaging film, so that the prepared packaging film is thinner and has higher tensile strength, elongation at break and tear strength; further, a thinner packaging film is softer, which is conducive to reducing the friction between the packaging films, thereby reducing the breakage of the composite packaging bag during use.

[0008] Preferably, the packaging film has a thickness of 25-45 μm.

[0009] By adopting the above technical solution, a packaging film with a thinner thickness is prepared, and the packaging film is softer, which is beneficial to reduce the friction between the packaging films, thereby reducing the breakage of the composite packaging bag during use.

[0010] Preferably, the inner layer and the outer layer both further include 10-15 parts by weight of a modifier I, and the preparation process of the modifier I is as follows: 30-40 parts by weight of divinyl-1,4-butanediol ether and 30-70 parts by weight of a diene ether are mixed at high speed for 5-10 minutes to prepare a mixed material; then 0.01-0.07 parts by weight of an initiator and acetone are taken to prepare a mixed liquid; the mixed liquid is added to the mixed material, and stirring is continued for 10-20 minutes at 70-100° C. to prepare a preform, and the preform is placed in a sealed container for 3-7 hours to prepare the modifier I; the initiator is one of di-tert-butyl hydroperoxide, 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane, diisopropylbenzene peroxide, and benzoyl peroxide.

[0011] By adopting the above technical scheme, modifier I is prepared by polymerization of divinyl-1,4-butanediol ether and diene ether. Modifier I is a straight-chain polymer with a large molecular weight and a carbon-oxygen bond. The use of modifier I in the inner and outer layers not only increases the flexibility of the inner and outer layers, but also enhances the interaction between the raw materials in the inner and outer layers and the bonding force between the middle layer and the inner and outer layers, so that the packaging film has higher tensile strength, elongation at break, tear strength and lower friction coefficient.

[0012] Preferably, the middle layer further comprises 6-12 parts by mass of a modifier II; the preparation process of the modifier II is as follows: 30-40 parts by mass of divinyl-1,4-butanediol ether, 15-45 parts by mass of N-(hydroxymethyl)acrylamide and 30-70 parts by mass of a diene ether are mixed at high speed for 5-10 minutes to prepare a mixed material; then 0.01-0.07 parts by mass of an initiator and acetone are prepared into a mixed liquid; the mixed liquid is added to the mixed material, and stirring is continued for 10-20 minutes at 70-100° C. to prepare a preform, and the preform is placed in a sealed container for 3-7 hours to prepare the modifier II; the initiator is one of di-tert-butyl hydroperoxide, 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane, diisopropylbenzene peroxide, and benzoyl peroxide.

[0013] By adopting the above technical scheme, modifier II is obtained by polymerization of divinyl-1,4-butanediol ether, N-(hydroxymethyl)acrylamide and diene ether. Modifier II is a polymer with a large molecular weight and contains carbon-oxygen bonds and hydroxyl groups. Adding modifier II to the middle layer not only increases the flexibility of the middle layer and the interaction between the raw materials, but also enhances the bonding force between the middle layer and the inner layer and the outer layer, so that the packaging film has higher tensile strength, elongation at break, tear strength and lower friction coefficient.

[0014] Preferably, the amount of N-(hydroxymethyl)acrylamide used is 20-30 parts by mass.

[0015] By adopting the above technical solution, the dosage of N-(hydroxymethyl)acrylamide is optimized, so that the packaging film has higher tensile strength, elongation at break, tear strength and lower friction coefficient, thereby reducing the breakage of the composite packaging bag during use.

[0016] The use of N-(hydroxymethyl)acrylamide in modifier II is beneficial to enhancing the interaction between the middle layer and the inner layer and the outer layer, so that the packaging film has higher tensile strength, elongation at break, and tear strength. However, if the content of N-(hydroxymethyl)acrylamide is too high, the flexibility of the packaging film decreases, and the friction between the packaging films increases, which may lead to an increase in the breakage of composite packaging bags using the packaging film.

[0017] Preferably, the lubricating additive is at least one of oleamide, erucic acid amide, modified silica powder, paraffin, zinc stearate, calcium stearate, lead stearate, and lauric acid; the modified silica powder is prepared by surface-modifying silica powder with a silane coupling agent; and the toughening agent is one of toughening agent POE, toughening agent POP, and ethylene-propylene rubber.

[0018] By adopting the above technical solution and using a lubricating additive, not only the mixing effect of the raw materials in the packaging film is improved, thereby increasing the tensile strength, elongation at break and tear strength of the packaging film, but also the friction coefficient of the packaging film surface is reduced.

[0019] Preferably, the lubricating additive is a composition of modified silicon powder and erucic acid amide in a mass ratio of (1-3):1.

[0020] By adopting the above technical solution, the type and weight of the slip additive are optimized, the tensile strength, elongation at break and tear strength of the packaging film are further improved, and the friction coefficient of the packaging film surface is further reduced.

[0021] Preferably, the modified silicon powder is prepared by surface-modifying silicon powder with a vinyl silane coupling agent, and the mass ratio of the silicon powder to the vinyl silane coupling agent is 1:(0.2-0.4).

[0022] By adopting the above technical scheme, the modified silicon powder prepared by modifying the silicon powder with a vinyl silane coupling agent surface has better compatibility of the vinyl on the surface of the modified silicon powder with low-density polyethylene and metallocene linear polyethylene, thereby improving the dispersibility of the modified silicon powder in the inner layer and the outer layer, thereby better promoting the modified silicon powder to exert the effects of lubrication, toughening and strengthening; when the content of the silane coupling agent in the modified silicon powder is too much, the silane coupling agent wraps more of the silicon powder, which is not conducive to the dispersion of the silicon powder in the plastic film and the exertion of the effects of lubrication, toughening and strengthening.

[0023] In a second aspect, the present application provides a process for preparing a packaging film.

[0024] The preparation process of the packaging film of the present application adopts three-layer co-extrusion blow molding; the host temperature of the inner layer and the outer layer is set to 180-200°C; the host temperature of the middle layer is set to 190-200°C; and the die head temperature is set to 185-195°C.

[0025] By adopting the above technical solution, the raw materials in the packaging film are evenly mixed, and the middle layer has a high bonding force with the inner layer and the outer layer, so that the prepared packaging film has high tensile strength, elongation at break, tear strength and low friction coefficient.

[0026] In a third aspect, the present application provides a composite packaging bag.

[0027] A composite packaging bag is formed by sequentially stacking an aluminized barrier layer VMPET, two or more layers of packaging film of the present application, and heat-sealing the periphery of the aluminized barrier layer VMPET. The packaging bag is connected to a bag opening; the bag opening is connected to an inner cavity formed by the packaging film. By adopting the above technical scheme, the composite packaging bag prepared is relatively thin, has good mechanical properties, and has strong impact resistance. It can adapt to friction and liquid impact during long-distance transportation and is not prone to leakage or rupture.

[0028] In summary, this application has the following beneficial effects:

[0029] 1. A packaging film, the packaging film comprising an inner layer, a middle layer and an outer layer which are closely fitted in sequence at a thickness ratio of 1:(1-2):1; the inner layer and the outer layer of the packaging film are made of a combination of metallocene linear polyethylene, low-density polyethylene and a slip additive, and the middle layer is made of a combination of metallocene linear polyethylene, ultra-low-density polyethylene and a toughening agent, thereby enhancing the interaction between the middle layer and the inner layer and the outer layer, and between the raw materials in the packaging film, so that the prepared packaging film is thinner and has higher tensile strength, elongation at break and tear strength; further, the thinner packaging film is softer, which is conducive to reducing the friction between the packaging films, thereby reducing the breakage of the composite packaging bag during use.

[0030] 2. By using modifier I in the inner layer / outer layer and modifier II in the middle layer, modifier I is prepared by polymerizing divinyl-1,4-butanediol ether and diene ether, and modifier II is prepared by polymerizing divinyl-1,4-butanediol ether, N-(hydroxymethyl)acrylamide and diene ether, and by using the inner layer / outer layer of modifier I and the middle layer of modifier II, the tensile strength, elongation at break and tear strength of the packaging film are further improved, and the friction coefficient of the packaging film is reduced.

[0031] 3. A composition of modified silica powder and erucic acid amide in a mass ratio of (1-3):1 is used as a lubricating additive. The modified silica powder is prepared by surface-modifying silica powder with a vinyl silane coupling agent, which further improves the tensile strength, elongation at break and tear strength of the packaging film and reduces the friction coefficient of the packaging film. DETAILED DESCRIPTION

[0032] raw material

[0033] MDPE (density is 0.940g / cm3, melt index (190℃ / 2.16kg) is 0.90g / 10min), HDPE (density is 0.958g / cm3, melt index is 0.28g / 10min), ultra-low density polyethylene (density is 0.898g / cm3, melt index is 3.5g / 10min), metallocene linear polyethylene (density is 0.916g / cm3, melt index is 0.5g / 10min), low density polyethylene (density is 0.923g / cm3, melt index is 0.75g / 10min), paraffin (molecular weight is 360-540).

[0034] Preparation example of intermediate

[0035] Preparation Example 1-1, a method for preparing a modifier I, the preparation process is as follows:

[0036] 40 kg of divinyl-1,4-butanediol ether and 70 kg of divinyl ether were added into a reactor, mixed at 1800 r / min for 5 min, and a mixed material was prepared; then 0.07 kg of an initiator (benzoyl peroxide) and 1 kg of acetone were prepared into a mixed liquid; the mixed liquid was added into a reactor, and stirred for 10 min at 100° C. in a nitrogen atmosphere to prepare a preform, and the preform was placed in a sealed container for 7 h to prepare a modifier I.

[0037] Preparation Example 1-2, a method for preparing a modifier I, the preparation process is as follows:

[0038] 35 kg of divinyl-1,4-butanediol ether and 50 kg of divinyl ether were added into a reactor, mixed at 1600 r / min for 8 min to prepare a mixed material; then 0.05 kg of an initiator (using diisopropylbenzene peroxide) and 0.05 kg of acetone were prepared into a mixed liquid; the mixed liquid was added into a reactor, and stirred for 15 min at 80° C. in a nitrogen atmosphere to prepare a preform, and the preform was placed in a sealed container for 5 h to prepare a modifier I.

[0039] Preparation Example 1-3, a method for preparing a modifier I, the preparation process is as follows:

[0040] 30 kg of divinyl-1,4-butanediol ether and 30 g of diallyl ether were added to a reactor, and mixed for 10 min at 1500 r / min in a nitrogen atmosphere to prepare a mixed material; then 0.01 kg of an initiator (using di-tert-butyl hydroperoxide) and 0.1 kg of acetone were prepared into a mixed liquid; the mixed liquid was added to a reactor, and continued to stir for 20 min at 70° C. in a nitrogen atmosphere to prepare a preform, and the preform was placed in a sealed container for 3 hours to prepare a modifier I.

[0041] Preparation Example 1-4, a method for preparing modifier I, differs from Preparation Example 1-1 in that 60 kg of diene ether and 0.05 kg of initiator (benzoyl peroxide) are used.

[0042] Preparation Example 1-5, a method for preparing modifier I, is different from Preparation Example 1-1 in that 50 kg of diene ether and 0.01 kg of initiator (benzoyl peroxide) are used and placed in a sealed container for 5 hours.

[0043] Preparation Example 1-6, a method for preparing a modifier I, differs from Preparation Example 1-1 in that 35 kg of diene ether is used, an equal amount of diethylene glycol monovinyl ether is used to replace divinyl-1,4-butanediol ether, and 0.07 kg of initiator (benzoyl peroxide) is used, and the mixture is placed in a sealed container for 3 hours.

[0044] Preparation Example 2-1, a preparation method of modifier II, is different from the preparation method of modifier I in Preparation Example 1-1 in that 45 kg of N-(hydroxymethyl)acrylamide is also added to the mixed material.

[0045] Preparation Example 2-2, a preparation method of modifier II, is different from the preparation method of modifier I in Preparation Example 1-2 in that 30 kg of N-(hydroxymethyl)acrylamide is also added to the mixed material.

[0046] Preparation Example 2-3, a preparation method of modifier II, is different from the preparation method of modifier I in Preparation Example 1-3 in that 15 kg of N-(hydroxymethyl)acrylamide is also added to the mixed material.

[0047] Preparation Example 2-4, a preparation method of modifier II, is different from the preparation method of modifier I in Preparation Example 1-4 in that 45 kg of N-(hydroxymethyl)acrylamide is also added to the mixed material.

[0048] Preparation Example 2-5, a preparation method of modifier II, is different from the preparation method of modifier I in Preparation Example 1-5 in that 45 kg of N-(hydroxymethyl)acrylamide is also added to the mixed material.

[0049] Preparation Example 2-6, a preparation method of modifier II, is different from the preparation method of modifier I in Preparation Example 1-6 in that 45 kg of N-(hydroxymethyl)acrylamide is also added to the mixed material.

[0050] Preparation Example 2-7, a preparation method of modifier II, is different from the preparation method of modifier I in Preparation Example 1-4 in that 30 kg of N-(hydroxymethyl)acrylamide is also added to the mixed material.

[0051] Preparation Example 2-8, a preparation method of modifier II, is different from the preparation method of modifier I in Preparation Example 1-5 in that 20 kg of N-(hydroxymethyl)acrylamide is also added to the mixed material.

[0052] Preparation Example 2-9, a preparation method of modifier II, is different from the preparation method of modifier I in Preparation Example 1-6 in that 30 kg of N-(hydroxymethyl)acrylamide is also added to the mixed material.

[0053] Preparation Example 3-1, a modified silicon powder, the preparation process is as follows:

[0054] 0.2 kg of vinyltrimethoxysilane was added to 5 L of aqueous solution at pH 3, stirred for 10 min, and then 1 kg of silicon powder (particle size of 1 μm) was added for surface modification. The mixture was filtered and washed with water until neutral, and dried to obtain a modified thermal conductive filler.

[0055] Preparation Example 3-2, a modified silicon powder, the preparation process is as follows:

[0056] Surface modification: Add 0.3 kg of vinyltrimethoxysilane to 5 L of aqueous solution at pH 4, stir for 5 min, then add 1 kg of silicon powder (particle size 5 μm) for surface modification, filter and wash with water until neutral, and prepare modified thermal conductive filler after drying.

[0057] Preparation Example 3-3, a modified silicon powder, the preparation process of which is as follows:

[0058] Surface modification: Add 0.4 kg of vinyl triethoxysilane to 5 L of aqueous solution at pH 5, stir for 10 min, then add 1 kg of silicon powder (particle size 10 μm) for surface modification, filter and wash with water to neutrality, and prepare a modified thermal conductive filler after drying.

[0059] Preparation Example 3-4, a modified silicon powder, differs from Preparation Example 3-1 in that 0.6 kg of vinyltrimethoxysilane is used.

[0060] Preparation Example 3-5, a modified silicon powder, differs from Preparation Example 3-1 in that γ-aminopropyltriethoxysilane is used in equal amounts to replace vinyltrimethoxysilane.

[0061] Preparation Example 3-6, a modified silicon powder, differs from Preparation Example 3-1 in that γ-glycidyl ether propyl trimethoxy silane is used to replace vinyl trimethoxy silane in equal amounts.

[0062] Example

[0063] Example 1, a packaging film, using raw materials as shown in Table 1, and its preparation process is as follows:

[0064] S1. Ingredients: Prepare the inner layer raw materials, the middle layer raw materials and the outer layer raw materials according to the proportions for later use.

[0065] S2. Heating: Place the inner layer raw materials, middle layer raw materials and outer layer raw materials in a three-layer co-extrusion film blowing unit, and continuously heat up the temperature of the three-layer co-extrusion film blowing unit in different zones; the temperatures of the main machines of the inner and outer layers are: Zone 1 180°C, Zone 2 185°C, Zone 3 185°C, Zone 4 190°C, Zone 5 200°C, Zone 6 190°C, and the die opening temperature of the die head is 185°C.

[0066] The temperatures of each zone of the middle-layer main machine are: zone one 190°C, zone two 190°C, zone three 195°C, zone four 200°C, zone five 195°C, zone six 195°C, and the die opening temperature of the die head is 190°C.

[0067] The speed of the main engine of the inner and outer layers is 55r / min, and the speed of the main engine of the middle layer is 75r / min.

[0068] S3, Blow molding: The internal cooling air inlet frequency of the air cooler is 20Hz, and the internal cooling air exhaust frequency is 25Hz. Compressed air is injected into the air inlet of the die head, the blowing ratio is controlled to 1.8, and the film bubble is pulled up at a uniform speed with a traction rope.

[0069] S4, winding and slitting: the film bubble is passed through the deviation-correcting clip and enters the winding roller machine to prepare a packaging film with a thickness of 30 μm. The thickness ratio of the inner layer, middle layer and outer layer of the packaging film is 1:1.3:1.

[0070] Example 2, a packaging film, using raw materials as shown in Table 1, and its preparation process is as follows:

[0071] S1. Ingredients: Prepare the inner layer raw materials, the middle layer raw materials and the outer layer raw materials according to the proportions for later use.

[0072] S2. Heating: Place the inner layer raw materials, middle layer raw materials and outer layer raw materials in a three-layer co-extrusion film blowing unit, and continuously heat up the three-layer co-extrusion film blowing unit in different zones; the temperatures of the main machines of the inner and outer layers are: Zone 1 185°C, Zone 2 185°C, Zone 3 190°C, Zone 4 195°C, Zone 5 200°C, Zone 6 190°C, and the die mouth temperature of the die head is 190°C.

[0073] The temperatures of each zone of the middle-layer main machine are: zone one 195°C, zone two 195°C, zone three 198°C, zone four 200°C, zone five 195°C, zone six 195°C, and the die opening temperature of the die head is 195°C.

[0074] The speed of the main engine of the inner and outer layers is 50r / min, and the speed of the main engine of the middle layer is 70r / min.

[0075] S3, Blow molding: The internal cooling air inlet frequency of the air cooler is 20Hz, and the internal cooling air exhaust frequency is 25Hz. Compressed air is injected into the air inlet of the die head, the blowing ratio is controlled to 1.6, and the film bubble is pulled up at a uniform speed with a traction rope.

[0076] S4, winding and slitting: the film bubble passes through the deviation-correcting clip and enters the winding roller machine to prepare a packaging film with a thickness of 45 μm. The thickness ratio of the inner layer, middle layer and outer layer of the packaging film is 1:1:1.

[0077] Example 3, a packaging film, using raw materials as shown in Table 1, and its preparation process is as follows:

[0078] S1. Ingredients: Prepare the inner layer raw materials, the middle layer raw materials and the outer layer raw materials according to the proportions for later use.

[0079] S2. Heating: Place the inner layer raw materials, middle layer raw materials and outer layer raw materials in a three-layer co-extrusion film blowing unit, and continuously heat up the temperature of the three-layer co-extrusion film blowing unit in different zones; the temperatures of the main machines of the inner and outer layers are: Zone 1 180°C, Zone 2 185°C, Zone 3 190°C, Zone 4 195°C, Zone 5 200°C, Zone 6 190°C, and the die mouth temperature of the die head is 195°C.

[0080] The temperatures of each zone of the middle-layer main machine are: zone one 190°C, zone two 195°C, zone three 198°C, zone four 200°C, zone five 195°C, zone six 195°C, and the die opening temperature of the die head is 190°C.

[0081] The speed of the main engine of the inner and outer layers is 45r / min, and the speed of the main engine of the middle layer is 65r / min.

[0082] S3, Blow molding: The internal cooling air inlet frequency of the air cooler is 22Hz, the internal cooling air exhaust frequency is 27Hz, and compressed air is injected into the air inlet of the die head, the blowing ratio is controlled to 2.0, and the film bubble is pulled up at a uniform speed with a traction rope.

[0083] S4, winding and slitting: the film bubble passes through the deviation-correcting clip and enters the winding roller machine to prepare a packaging film with a thickness of 25 μm. The thickness ratio of the inner layer, middle layer and outer layer of the packaging film is 1:2:1.

[0084] Table 1. List of types and weights of raw materials used in the inner layer, middle layer, and outer layer in Examples 1 to 3

[0085]

[0086]

[0087] Examples 4 to 9 are packaging films, which differ from Example 1 in that different modifiers I and II are used, as shown in Table 2.

[0088] Table 2. List of settings of modifier I used in the inner layer and outer layer and modifier II used in the middle layer in Examples 4 to 9

[0089] distinguish Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Modifier Ⅰ Preparation Example 1-4 Preparation Example 1-5 Preparation Example 1-6 Preparation Example 1-4 Preparation Example 1-5 Preparation Example 1-5 Modifier Ⅱ Preparation Example 2-4 Preparation Example 2-5 Preparation Example 2-6 Preparation Example 2-7 Preparation Example 2-8 Preparation Example 2-9

[0090] Example 10 is a packaging film, which is different from Example 1 in that the slip additive is a composition of modified silicon powder (preparation example 3-1) and erucamide in a mass ratio of 3:1.

[0091] Example 11 is a packaging film, which is different from Example 1 in that the slip additive is a composition of modified silicon powder (preparation example 3-2) and erucamide in a mass ratio of 2:1.

[0092] Example 12, a packaging film, differs from Example 1 in that the slip additive is a composition of modified silicon powder (preparation example 3-3) and erucamide in a mass ratio of 1:1.

[0093] Example 13, a packaging film, differs from Example 1 in that the slip additive is a composition of modified silicon powder (preparation example 3-1) and erucamide in a mass ratio of 1:0.5.

[0094] Example 14, a packaging film, differs from Example 1 in that the slip additive is a composition of modified silicon powder (preparation example 3-1) and erucamide in a mass ratio of 3:1.

[0095] Example 15, a packaging film, is different from Example 1 in that the slip additive is modified silicon powder (using Preparation Example 3-1).

[0096] Example 16, a packaging film, is different from Example 1 in that erucamide is used as a slip additive.

[0097] Examples 17 to 19 are packaging films, which differ from Example 10 in that the modified silicon powders are the modified silicon powders of Preparation Examples 3-4 to 3-6, respectively.

[0098] Example 20, a packaging film, differs from Example 10 in that silicon powder (with a particle size of 1 μm) is used in equal amounts to replace the modified silicon powder.

[0099] Example 21, a packaging film, differs from Example 1 in that modifier I is not used in the inner layer / outer layer.

[0100] Example 22, a packaging film, differs from Example 1 in that modifier II is not used in the middle layer.

[0101] Example 23, a packaging film, is different from Example 1 in that modifier I is not used in the inner layer / outer layer; and modifier II is not used in the middle layer.

[0102] Comparative Example

[0103] Comparative Example 1 is a packaging film, which differs from Example 23 in that MDPE (density: 0.940 g / cm3, melt index (190°C / 2.16 kg): 0.90 g / 10 min) is used in equal amounts to replace the metallocene linear polyethylene in the inner and outer layers; in the middle layer, 21 kg of the metallocene linear polyethylene is used to prepare a packaging film with a thickness of 50 μm.

[0104] Comparative Example 2, a packaging film, is different from Example 23 in that a composition of MDPE and HDPE in a ratio of 4:1 is used in the inner layer; a composition of metallocene linear polyethylene, ultra-low density polyethylene and MDPE in a mass ratio of 3:4:3 is used in the middle layer; and a composition of low-density polyethylene, ultra-low density polyethylene and MDPE in a mass ratio of 3:5:12 is used in the outer layer, to prepare a packaging film with a thickness of 50 μm.

[0105] Comparative Example 3, a packaging film, differs from Example 23 in that 80 kg of metallocene linear polyethylene and 10 kg of low-density polyethylene are used in the inner layer and the outer layer; 50 kg of metallocene linear polyethylene and 30 kg of ultra-low-density polyethylene are used in the middle layer; the thickness ratio of the inner layer, the middle layer and the outer layer is 2:1:2.

[0106] Comparative Example 4 is a packaging film, which is different from Example 23 in that 40 kg of metallocene linear polyethylene is used in the inner layer and the outer layer; and 10 kg of low-density polyethylene is used in the middle layer.

[0107] Application Examples

[0108] Application Example 1: A composite packaging bag, the preparation process of which is as follows:

[0109] The aluminum-plated barrier layer VMPET and the packaging film (using Example 1) are cut into rectangles of the same shape on a bag making machine, and the first layer of the aluminum-plated barrier layer VMPET (thickness 60 μm), the second layer of the packaging film, the third layer of the packaging film, the fourth layer of the packaging film, the fifth layer of the packaging film and the sixth layer of the aluminum-plated barrier layer VMPET (thickness 60 μm) are stacked together in sequence from top to bottom, and then the periphery of the stacked aluminum-plated barrier layer VMPET and the packaging film are heat-sealed at a heat-sealing temperature of 155°C.

[0110] The first layer of aluminum-plated barrier layer VMPET, the second layer of packaging film, and the third layer of packaging film are connected with a bag opening, and the bag opening is connected to the inner cavity formed by the third layer of packaging film and the fourth layer of packaging film. The aluminum-plated barrier layer VMPET and the packaging film at the connection between the bag openings are adhered as a whole. After the bag opening is closed, the third layer of packaging film and the fourth layer of packaging film form a closed cavity, which can be used for filling and storage. After filling, the composite packaging bag is not easily damaged during long-term transportation.

[0111] Application Example 2: A composite packaging bag, the preparation process of which is as follows:

[0112] The aluminum-plated barrier layer VMPET and the packaging film (using Example 2) are cut into rectangles of the same shape on a bag making machine, and the first layer of the aluminum-plated barrier layer VMPET (thickness 60 μm), the second layer of the packaging film, the third layer of the packaging film and the fourth layer of the aluminum-plated barrier layer VMPET (thickness 60 μm) are stacked together in sequence from top to bottom, and then the edges of the stacked aluminum-plated barrier layer VMPET and the packaging film are heat-sealed at a heat-sealing temperature of 160°C.

[0113] The first layer of the aluminum-plated barrier layer VMPET and the second layer of the packaging film of Example 1 are connected with a bag opening, and the bag opening is connected to the inner cavity formed by the second layer of the packaging film and the third layer of the packaging film. The aluminum-plated barrier layer VMPET and the packaging film at the connection between the bag opening and the bag opening are adhered as a whole. After the bag opening is closed, the second layer of the packaging film and the third layer of the packaging film form a closed cavity, which can be used for filling and storage. After filling, the composite packaging bag is not easily damaged during long-term transportation.

[0114] Application Examples 3 to 23 are composite packaging bags, which differ from Application Example 1 in that the packaging films are the packaging films of Examples 3 to 23, respectively.

[0115] Comparative Application Examples 1 to 4 are composite packaging bags, which differ from Application Example 1 in that the packaging films are the packaging films of Comparative Examples 1 to 4, respectively.

[0116] Performance testing

[0117] Test 1: Tensile strength and elongation at break test method: Test in accordance with GB / T 1040.3-2006 "Determination of tensile properties of plastics Part 3: Test conditions for films and sheets"; use a strip sample with a length of 150 mm, a width of 15 mm, and a gauge length of (100 ± 1) mm. The sample tensile speed (no load) is (200 ± 20) mm / min.

[0118] Test 2: Tear Strength

[0119] The test was carried out in accordance with GB / T16578.1-2008 “Determination of tear resistance of plastic film and sheeting Part 1: Trouser tear method”.

[0120] Test 3: Friction coefficient

[0121] The test is carried out in accordance with GB / T10006-2021 "Friction coefficient of plastic films and sheets".

[0122] Test samples: The packaging films of Examples 1 to 23 are taken as example samples; the packaging films of Comparative Examples 1 to 4 are taken as comparative example samples.

[0123] Test results: The test results of tensile strength, elongation at break, tear strength and friction coefficient of the packaging films of Examples 1 to 23 and Comparative Examples 1 to 4 are shown in Table 3.

[0124] Test 4: Bag breaking evaluation results

[0125] Put 2L of water and 6.6g of agar powder into a glass container, immerse the container in hot water at 95°C, and heat for more than 1 hour to completely dissolve the agar. Use a 50-mesh metal mesh to filter the solution to remove gelled foreign matter. Add 0.14g of methylene blue to the solution. In a glove box that has been circulated with nitrogen for more than 15 minutes, add 1.25g of sodium dithionite to the solution and mix evenly to obtain a color developing solution (no color development); in a glove box that has been circulated with nitrogen for more than 15 minutes, add about half of the volume of the cavity of the color developing solution to the composite packaging bag, and seal the bag mouth of the composite packaging bag after filling with nitrogen.

[0126] After arranging the composite packaging bags with the color developing solution and nitrogen in a row in the height direction, they were dropped from a height of 1m onto the steel floor. This was considered one treatment, and after repeating the treatment 5 times, the amount of packaging bag damage was counted. Then, the damage was determined according to the following criteria A, B, C, and D.

[0127] A: No broken bags;

[0128] B: Bag breakage rate is above 0 and less than 10%;

[0129] C: The bag breakage rate is more than 10% and less than 20%;

[0130] D: The bag breakage rate is more than 20%.

[0131] Test samples: The composite packaging bags of Application Examples 1 to 23 are used as application example samples; the composite packaging bags of Comparative Application Examples 1 to 4 are used as comparative application example samples.

[0132] Test results: The bag breakage evaluation results of the composite packaging bags of Application Examples 1 to Application Examples 23 and Comparative Application Examples 1 to Comparative Application Examples 4 are shown in Table 3.

[0133] Table 3. Test results of tensile strength, elongation at break, tear strength and friction coefficient of packaging films of Examples 1 to 23 and Comparative Examples 1 to 4, and evaluation results of bag breakage of composite packaging bags of Application Examples 1 to 23 and Comparative Application Examples 1 to 4

[0134]

[0135]

[0136] Combining Examples 1 to 23 and Comparative Examples 1 to 4, and combining Table 3, it can be seen that:

[0137] The tensile strength, elongation at break and tear strength of the packaging films of Examples 1 to 23 are higher than those of Comparative Examples 1 to 4; the friction coefficient of the packaging films of Examples 1 to 23 is lower than those of Comparative Examples 1 to 4; the bag breaking evaluation of the composite packaging bags using the packaging films of Examples 1 to 23 is better than that of Comparative Examples 1 to 4, indicating that the packaging films are composed of an inner layer, a middle layer and an outer layer which are tightly fitted in a thickness ratio of 1:(1-2):1 in sequence; the raw materials of the inner layer and the outer layer are both composed of 50-70 parts by mass of metallocene linear polyethylene, 20-40 parts by mass of low-density polyethylene and 2-8 parts by mass of a slip additive; the raw materials of the middle layer are composed of 30-50 parts by mass of metallocene linear polyethylene, 40-60 parts by mass of ultra-low-density polyethylene and 10-30 parts by mass of a toughening agent, and the prepared packaging film is not only thin in thickness, but also has higher tensile strength, elongation at break and tear strength and lower friction coefficient.

[0138] The reason may be that: in the inner and outer layers of the packaging film, metallocene linear polyethylene, low-density polyethylene and a slippery additive are used, and the middle layer is made of metallocene linear polyethylene, ultra-low-density polyethylene and a toughening agent. This enhances the interaction between the middle layer and the inner and outer layers, as well as between the raw materials in the packaging film, so that the prepared packaging film is thinner and has higher tensile strength, elongation at break and tear strength. Furthermore, a thinner packaging film is softer, which is conducive to reducing the friction between the packaging films, thereby reducing the breakage of the composite packaging bags during use.

[0139] The tensile strength, elongation at break and tear strength of the packaging films of Examples 4 to 5 are better than those of Examples 1 to 3 and 6, indicating that 30-40 parts by mass of divinyl-1,4-butanediol ether and 50-60 parts by mass of diene ether are used in modifier I and modifier II, the initiator is 0.01-0.05, and the preform is placed in a closed container for 5-7 hours, so that the prepared packaging film has higher tensile strength, elongation at break and tear strength.

[0140] The reason may be that the increased content of diene ether in modifier Ⅰ and modifier Ⅱ makes modifier Ⅰ and modifier Ⅱ have more carbon-oxygen bonds, which improves the flexibility of modifier Ⅰ and modifier Ⅱ and reduces the friction coefficient of the packaging film; when the content of divinyl-1,4-butanediol ether is high, there are more carbon-carbon bonds in modifier Ⅰ and modifier Ⅱ, which is beneficial to improve the compatibility between modifier Ⅰ and modifier Ⅱ and polyethylene polymer; the better ratio of diene ether and divinyl-1,4-butanediol ether, and the optimized amount of initiator and polymerization time, make the packaging film have higher tensile strength, elongation at break, tear strength and lower friction coefficient at the same time.

[0141] The friction coefficient of the packaging film of Example 7 to Example 8 is lower than that of Example 4 to Example 5, while the tensile strength, elongation at break and tear strength do not change much, indicating that reducing N-(hydroxymethyl)acrylamide in Example 7 to Example 8 is beneficial to reducing the friction coefficient of the packaging film; this may be because the content of N-(hydroxymethyl)acrylamide in modifier II is relatively reduced, the stiffness of the packaging film is reduced, and thus the friction coefficient of the packaging film is reduced.

[0142] Compared with Examples 4 to 8, Example 4 and Example 5, although the friction coefficient of the packaging film of Example 9 is reduced, the tensile strength, elongation at break and tear strength are significantly reduced. This may be because as the content of N-(hydroxymethyl)acrylamide decreases, the flexibility of the packaging film improves, but the interaction between the middle layer and the inner layer and the outer layer of the packaging film decreases, and the synergistic effect between the layers decreases, resulting in a decrease in the tensile strength, elongation at break and tear strength of the packaging film.

[0143] The tensile strength, elongation at break and tear strength of the packaging films of Examples 10 to 12 are higher than those of Examples 1 to 3 and Examples 13 to 16; the friction coefficient of the packaging films of Examples 10 to 12 is lower than that of Examples 1 to 3 and Examples 13 to 16; this indicates that in the inner layer and the outer layer, the slip additive uses a composition of modified silica powder and erucic acid amide in a mass ratio of (1-3):1, so that the packaging film has higher tensile strength, elongation at break and tear strength, and lower friction coefficient.

[0144] The reasons may be that: compared with oleamide, erucamide precipitates slowly, has more stable processability and higher heat-sealing strength; erucamide is used in combination with modified silica powder to improve the dispersion effect of raw materials in the inner and outer layers of the packaging film, thereby improving the tensile strength, elongation at break and tear strength of the packaging film; after the packaging film is formed, small molecules of erucamide can migrate to the surface of the packaging film to reduce the friction coefficient of the packaging film surface; modified silica powder is dispersed in the inner and outer layers of the packaging film, and the tiny and smooth spheres of the modified silica powder can act as a lubricant, reduce the friction between material particles, improve the flexibility of the packaging film and reduce the surface friction coefficient; the polar groups on the surface of the modified silica powder enhance the interaction between the raw materials, further improving the tensile strength, crack resistance and impact resistance of the packaging film.

[0145] The tensile strength, elongation at break and tear strength of the packaging films of Examples 10 to 12 are higher than those of Examples 17 to 20; the friction coefficient of the packaging films of Examples 10 to 12 is lower than that of Examples 17 to 20, indicating that the silicon powder is modified by a silane coupling agent, and the type and amount of the silane coupling agent are preferred, which can further improve the tensile strength, elongation at break and tear strength of the packaging film and reduce the friction coefficient of the packaging film.

[0146] The reason may be that the vinyl on the surface of the modified silica powder has better compatibility with low-density polyethylene and metallocene linear polyethylene, thereby improving the dispersibility of the modified silica powder in the inner and outer layers, and thus better promoting the modified silica powder to exert its lubrication, toughening and strengthening effects; and when the content of silane coupling agent in the modified silica powder is too much, the silane coupling agent wraps more of the silica powder, which is not conducive to the dispersion of the silica powder in the plastic film and the exertion of its lubrication, toughening and strengthening effects.

[0147] The tensile strength, elongation at break and tear strength of the packaging films of Examples 21 to 23 are higher than those of Examples 1 to 3, and the friction coefficients of Examples 21 to 23 are lower than those of Examples 1 to 3, indicating that the use of modifier I in the inner / outer layer and modifier II in the middle layer improves the tensile strength, elongation at break and tear strength of the packaging film, and reduces the friction coefficient of the packaging film.

[0148] The reasons may be that: Modifier I is prepared by polymerization of divinyl-1,4-butanediol ether and diene ether, and Modifier I is a straight-chain polymer with a large molecular weight and containing a carbon-oxygen bond; Modifier II is obtained by polymerization of divinyl-1,4-butanediol ether, N-(hydroxymethyl)acrylamide and diene ether, and Modifier II is a polymer with a large molecular weight and containing a carbon-oxygen bond and a hydroxyl group; Modifier I is used in the inner and outer layers, and Modifier II is added to the middle layer, which not only increases the flexibility of the inner, outer and middle layers, but also enhances the interaction between the raw materials in the packaging film, enhances the bonding force and synergistic effect between the middle layer and the inner and outer layers, so that the packaging film has higher tensile strength, elongation at break, tear strength and lower friction coefficient.

[0149] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A packaging film, characterized in that: The invention is composed of an inner layer, a middle layer and an outer layer which are closely fitted in sequence with a thickness ratio of 1: (1-2): 1, wherein the inner layer and the outer layer each comprise 50-70 parts by weight of metallocene linear polyethylene, 20-40 parts by weight of low-density polyethylene and 2-8 parts by weight of a slip additive; the middle layer comprises 20-40 parts by weight of metallocene linear polyethylene, 40-60 parts by weight of ultra-low-density polyethylene and 10-30 parts by weight of a toughening agent; the inner layer and the outer layer each further comprise 10-15 parts by weight of a modifier I, and the preparation process of the modifier I is as follows : 30-40 parts by mass of divinyl-1,4-butanediol ether and 30-70 parts by mass of diene ether are mixed at high speed for 5-10 minutes to prepare a mixed material; then 0.01-0.07 parts by mass of initiator and acetone are prepared into a mixed solution; the mixed solution is added to the mixed material, and the mixture is stirred for 10-20 minutes at 70-100° C. to prepare a preform, and the preform is placed in a sealed container for 3-7 hours to prepare a modifier I; the initiator is di-tert-butyl hydroperoxide, 2,5-dimethyl -2,5-di-tert-butyl peroxide hexane, diisopropylbenzene peroxide, benzoyl peroxide; the middle layer also includes 6-12 parts by weight of modifier II; the preparation process of modifier II is as follows: 30-40 parts by weight of divinyl-1,4-butanediol ether, 15-45 parts by weight of N-(hydroxymethyl)acrylamide and 30-70 parts by weight of diene ether are mixed at high speed for 5-10 minutes to prepare a mixed material; then 0.01-0.07 parts by weight of initiator and acetone are taken to prepare a mixed solution; the mixed solution is added to the mixed solution The preform is placed in a sealed container for 3-7 hours to prepare a modifier II; the initiator is one of di-tert-butyl hydroperoxide, 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane, diisopropylbenzene peroxide and benzoyl peroxide; the slip additive is a composition of modified silicon powder and erucic acid amide in a mass ratio of (1-3):1; the modified silicon powder is prepared by surface-modifying the silicon powder with a silane coupling agent.

2. A packaging film according to claim 1, characterized in that: The thickness of the packaging film is 25-45 mm.

3. The packaging film according to claim 1, characterized in that: The amount of N-(hydroxymethyl)acrylamide used is 20-30 parts by weight.

4. The packaging film according to claim 1, characterized in that: The toughening agent is one of toughening agent POE, toughening agent POP and ethylene propylene rubber.

5. The packaging film according to claim 1, characterized in that: The modified silicon powder is prepared by surface-modifying silicon powder with a vinyl silane coupling agent, and the mass ratio of the silicon powder to the vinyl silane coupling agent is 1:(0.2-0.4).

6. The process for preparing the packaging film according to any one of claims 1 to 5, characterized in that: The packaging film is prepared by three-layer co-extrusion blow molding; the host temperature of the inner layer and the outer layer is set to 180-200°C; the host temperature of the middle layer is set to 190-200°C; and the die head temperature is set to 185-195°C.

7. A composite packaging bag, characterized in that: The aluminum-plated barrier layer VMPET, two or more layers of packaging film according to any one of claims 1 to 5, and the aluminum-plated barrier layer VMPET are sequentially stacked and heat-sealed around the periphery to form a packaging bag, wherein the packaging bag is connected to a bag opening; the bag opening is connected to an inner cavity formed by the packaging film.

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