Anti-puncture skin film and production process thereof

Abstract

The invention belongs to the field of skin membranes, and particularly relates to an anti-puncture skin membrane and a production process thereof. Comprising a heat sealing layer, a blocking layer and an anti-puncture outer layer which are sequentially stacked, the heat sealing layer is prepared by blending 70wt% of linear low-density polyethylene and 25wt% of an ethylene-octylene copolymer plastomer; the thickness is 30 microns; the barrier layer is an ethylene-vinyl alcohol copolymer layer or a polyamide layer; the puncture-resistant outer layer is prepared by blending 50wt% of high-density polyethylene, 30wt% of metallocene polyethylene and 20wt% of modified polyolefin elastomer; the total thickness of the puncture-resistant skin membrane is 50-150 microns, and the thickness of the puncture-resistant outer layer accounts for 40%-60% of the total thickness; according to the invention, a novel skin film with ultrahigh puncture resistance, excellent low-temperature toughness and self-repairing potential is prepared by introducing a'rigid aromatic ring-dynamic carbamate bond 'synergistically modified polyolefin elastomer.

Description

Technical Field

[0001] This invention belongs to the field of patch films, specifically a puncture-resistant patch film and its manufacturing process. Background Technology

[0002] Skin packaging film, an advanced packaging material that can tightly wrap a product's outline through heating and vacuuming, is widely used in food (such as chilled meat, poultry, seafood, and high-end fruits and vegetables), medical devices, and precision instrument components. Its core value lies in significantly extending the product's shelf life and freshness by isolating it from oxygen, preventing juice loss, and preventing cross-contamination by microorganisms, while also providing excellent display effects.

[0003] To achieve the above functions, commercially available skin films typically employ a multi-layer co-extruded composite structure, generally including at least an inner heat-sealing layer, a middle barrier layer, and an outer protective layer. The heat-sealing layer often uses linear low-density polyethylene (LLDPE) or blends thereof with plasticizers (such as polyolefin elastomer POE or ethylene-vinyl acetate copolymer EVA) to ensure low-temperature heat sealing and skin flexibility. The barrier layer commonly uses ethylene-vinyl alcohol copolymer (EVOH) or polyamide (PA) to provide excellent oxygen barrier properties. The outer protective layer must possess sufficient mechanical strength to protect the inner layer from scratches or punctures during transportation and storage.

[0004] However, with the diversification of packaged goods and the increasing demands for packaging reliability, existing skin film technology has revealed several bottlenecks that urgently need to be addressed, especially in terms of puncture resistance: To improve the puncture resistance of the outer layer, the industry typically adds elastomers (such as POE) or inorganic rigid fillers (such as calcium carbonate and talc). However, this method faces a dilemma: toughening weakens the material, while strengthening makes it brittle. Adding a large amount of elastomer can improve toughness, but it significantly sacrifices the material's rigidity, stiffness, and heat resistance, causing the film to easily deform when stacked or heated. On the other hand, adding rigid fillers can increase hardness and modulus, but it severely impairs the material's flexibility, transparency, and impact resistance. Especially at low temperatures, the material's brittleness increases sharply, and its puncture and tear resistance decreases significantly, failing to meet the packaging requirements for sharp items such as bone and meat products, frozen seafood, or cold chain logistics. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0006] The technical solution adopted by the present invention to solve its technical problem is: the puncture-resistant patch film of the present invention comprises a heat-sealing layer, a barrier layer and an puncture-resistant outer layer stacked in sequence; The heat-sealing layer is made of a blend of 70 wt% linear low-density polyethylene and 25 wt% ethylene-octene copolymer plasmid; with a thickness of 30 μm. The barrier layer is an ethylene-vinyl alcohol copolymer layer or a polyamide layer; The puncture-resistant outer layer is made of a blend of 50 wt% high-density polyethylene, 30 wt% metallocene polyethylene, and 20 wt% modified polyolefin elastomer; the total thickness of the puncture-resistant patch film is 50-150 micrometers, and the thickness of the puncture-resistant outer layer accounts for 40%-60% of the total thickness; The preparation process of modified polyolefin elastomers includes the following steps: Step A: Dehydration of reactants: Place 4,4'-diaminodiphenylmethane and bis(2-oxo-1,3-dioxolane-4-yl)methyl ether in a dry reaction flask, and add anhydrous N,N-dimethylformamide; Under nitrogen protection, stir at room temperature to completely dissolve the solid; heat to 60-70℃ and continuously bubble with nitrogen for 30 minutes to remove trace amounts of moisture; Step B: Polymerization reaction: Heat the system to the preset reaction temperature of 80-90℃; add the catalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and stir magnetically in a nitrogen atmosphere at 80-90℃ for 6-12 hours. The system may become sticky in the early stage of the reaction.

[0007] As a further technical solution of the present invention: the ratio of 4,4'-diaminodiphenylmethane, bis(2-oxo-1,3-dioxolane-4-yl)methyl ether, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and anhydrous N,N-dimethylformamide is 1.98g:2.62g:50-70mL:2-3mg.

[0008] As a further technical solution of the present invention, the preparation process of the modified polyolefin elastomer further includes the following steps: Step C: Termination and Post-treatment: Cool the reaction solution to room temperature, and under vigorous stirring, drop the reaction solution into a large amount of deionized water or a methanol / water mixture (about 10 times the volume) to precipitate the polymer; filter and collect the precipitate, and wash it with a large amount of water 2-3 times; place the product in a vacuum drying oven at 50-60℃ and dry it for more than 24 hours until constant weight is obtained to obtain the modified polyolefin elastomer.

[0009] A manufacturing process for a puncture-resistant patch includes the following steps: S1. Raw material preparation and drying: Weigh the raw material particles for the heat-sealing layer, barrier layer and puncture-resistant outer layer respectively, and perform vacuum drying on the barrier layer raw material; S2. Co-extrusion casting: The dried raw materials of each layer are added to different extruders of the multi-layer co-extrusion casting equipment. After being melted and plasticized, they are extruded through a multi-layer composite die and cast onto a cooling roller to form a multi-layer composite casting sheet. S3. Biaxial stretching: The multilayer composite casting is subjected to biaxial stretching simultaneously or in stages to obtain a preliminary film; S4. Heat setting and post-treatment: The biaxially stretched film is heat-set and then wound up to obtain the finished puncture-resistant patch film.

[0010] As a further technical solution of the present invention: in step S2, the processing temperature of each extruder is controlled between 180℃ and 230℃.

[0011] As a further technical solution of the present invention: the temperature of the cooling roller is 20℃-40℃.

[0012] As a further technical solution of the present invention: in step S3, the longitudinal stretching ratio of the bidirectional stretching is 3-5, and the transverse stretching ratio is 3-5.

[0013] As a further technical solution of the present invention, the stretching temperature is between 90℃ and 120℃.

[0014] As a further technical solution of the present invention: in step S4, the temperature of the heat setting treatment is 10℃-30℃ higher than the stretching temperature.

[0015] As a further technical solution of the present invention: in step S4, the heat setting time is 2-10 seconds.

[0016] The beneficial effects of this invention are as follows: This invention introduces a modified polyolefin elastomer containing dynamic cyclic urethane bonds as a key toughening component into the puncture-resistant outer layer, and combines it with a specific multilayer co-extrusion casting and biaxial stretching process to prepare a puncture-resistant patch film. This invention, by introducing a polyolefin elastomer synergistically modified with "rigid aromatic rings-dynamic urethane bonds," prepares a novel patch film that combines ultra-high puncture resistance, excellent low-temperature toughness, and self-healing potential. The modified polyolefin elastomer prepared by this invention uses rigid aromatic rings (derived from 4,4'-diaminodiphenylmethane) in its molecular chain as physical crosslinking points and reinforcing phases, effectively dispersing and resisting puncture stress. Simultaneously, the dynamic cyclic urethane bonds dissipate a large amount of energy through reversible bond exchange upon impact, endowing the material with excellent toughness. Compared with films toughened using ordinary POE, the puncture resistance of the film of this invention can be increased by more than 40%. These dynamic bonds endow the material with potential self-healing properties. Micro-cracks generated during use or processing can be healed at the crack interface during subsequent heat treatment (such as heat sealing or pasteurization), thereby restoring some mechanical properties, extending service life, and reducing packaging failures caused by micro-damage.

[0017] The dynamic bonds in the modified polyolefin elastomer retain a certain degree of mobility at low temperatures, which helps maintain the flexibility of the matrix. Compared to systems toughened only with rigid fillers, the film of this invention retains more than 80% of its puncture and tear strength at -40°C, making it particularly suitable for packaging in harsh environments such as frozen foods and cold chain logistics.

[0018] The introduction of rigid aromatic rings increases the glass transition temperature and heat distortion temperature of modified POE, enabling the puncture-resistant outer layer to remain stable during subsequent high-temperature processing and use, resisting thermal creep. During the biaxial stretching and heat setting of the film, the dynamic network can release internal stress through topological adjustment, thereby obtaining a finished film with lower thermal shrinkage and higher dimensional stability. Detailed Implementation

[0019] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments. Example 1

[0020] An anti-puncture patch film according to an embodiment of the present invention includes: a heat-sealing layer, a barrier layer, and an anti-puncture outer layer stacked sequentially; The heat-sealing layer is made of a blend of 70 wt% linear low-density polyethylene and 25 wt% ethylene-octene copolymer plasmid; with a thickness of 30 μm. The barrier layer is an ethylene-vinyl alcohol copolymer layer or a polyamide layer; The puncture-resistant outer layer is made of a blend of 50 wt% high-density polyethylene, 30 wt% metallocene polyethylene, and 20 wt% modified polyolefin elastomer; the total thickness of the puncture-resistant patch film is 50 micrometers, and the thickness of the puncture-resistant outer layer accounts for 40% of the total thickness; The preparation process of modified polyolefin elastomers includes the following steps: Step A: Dehydration of reactants: Place 4,4'-diaminodiphenylmethane and bis(2-oxo-1,3-dioxolane-4-yl)methyl ether in a dry reaction flask, and add anhydrous N,N-dimethylformamide; Under nitrogen protection, stir at room temperature to completely dissolve the solid; heat to 60°C and continuously bubble with nitrogen for 30 minutes to remove trace amounts of moisture; Step B: Polymerization reaction: Heat the system to the preset reaction temperature of 80℃; add the catalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and stir magnetically in a nitrogen atmosphere at 80℃ for 6-12 hours. The system may become sticky in the early stage of the reaction. Step C: Termination and Post-treatment: Cool the reaction solution to room temperature, and under vigorous stirring, drop the reaction solution into a large amount of deionized water or a methanol / water mixture (about 10 times the volume) to precipitate the polymer; filter and collect the precipitate, and wash it twice with a large amount of water; place the product in a vacuum drying oven at 50°C and dry for more than 24 hours until constant weight, thus modifying the polyolefin elastomer. The ratio of 4,4'-diaminodiphenylmethane, bis(2-oxo-1,3-dioxolane-4-yl)methyl ether, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and anhydrous N,N-dimethylformamide was 1.98 g: 2.62 g: 50 mL: 2 mg. The manufacturing process of an anti-puncture patch membrane according to an embodiment of the present invention includes the following steps: S1. Raw material preparation and drying: Weigh the raw material particles for the heat-sealing layer, barrier layer and puncture-resistant outer layer respectively, and perform vacuum drying on the barrier layer raw material; S2. Co-extrusion casting: The dried raw materials of each layer are added to different extruders of the multi-layer co-extrusion casting equipment. After being melted and plasticized, they are extruded through a multi-layer composite die and cast onto a cooling roller to form a multi-layer composite casting sheet. S3. Biaxial stretching: The multilayer composite casting is subjected to biaxial stretching simultaneously or in stages to obtain a preliminary film; S4. Heat setting and post-treatment: The biaxially stretched film is heat-set and then wound up to obtain the finished puncture-resistant patch film.

[0021] In step S2, the processing temperature of each extruder is controlled between 180°C; the temperature of the cooling roller is 20°C.

[0022] In step S3, the longitudinal stretch ratio of the biaxial stretching is 3, the transverse stretch ratio is 3, and the stretching temperature is between 90℃.

[0023] In step S4, the heat setting temperature is 10°C higher than the stretching temperature, and the time is 2 seconds. Example 2

[0024] An anti-puncture patch film according to an embodiment of the present invention includes: a heat-sealing layer, a barrier layer, and an anti-puncture outer layer stacked sequentially; The heat-sealing layer is made of a blend of 70 wt% linear low-density polyethylene and 25 wt% ethylene-octene copolymer plasmid; with a thickness of 30 μm. The barrier layer is an ethylene-vinyl alcohol copolymer layer or a polyamide layer; The puncture-resistant outer layer is made of a blend of 50 wt% high-density polyethylene, 30 wt% metallocene polyethylene, and 20 wt% modified polyolefin elastomer; the total thickness of the puncture-resistant patch film is 100 micrometers, and the thickness of the puncture-resistant outer layer accounts for 50% of the total thickness. The preparation process of modified polyolefin elastomers includes the following steps: Step A: Dehydration of reactants: Place 4,4'-diaminodiphenylmethane and bis(2-oxo-1,3-dioxolane-4-yl)methyl ether in a dry reaction flask, and add anhydrous N,N-dimethylformamide; Under nitrogen protection, stir at room temperature to completely dissolve the solid; heat to 65°C and continuously bubble with nitrogen for 30 minutes to remove trace amounts of moisture; Step B: Polymerization reaction: Heat the system to the preset reaction temperature of 85℃; add the catalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and stir magnetically in a nitrogen atmosphere at 85℃ for 6-12 hours. The system may become sticky in the early stage of the reaction. Step C: Termination and Post-treatment: Cool the reaction solution to room temperature, and under vigorous stirring, drop the reaction solution into a large amount of deionized water or a methanol / water mixture (about 10 times the volume) to precipitate the polymer; filter and collect the precipitate, and wash it twice with a large amount of water; place the product in a vacuum drying oven at 55°C and dry for more than 24 hours until constant weight, thus modifying the polyolefin elastomer. The ratio of 4,4'-diaminodiphenylmethane, bis(2-oxo-1,3-dioxolane-4-yl)methyl ether, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and anhydrous N,N-dimethylformamide was 1.98 g: 2.62 g: 60 mL: 2.5 mg. The manufacturing process of an anti-puncture patch membrane according to an embodiment of the present invention includes the following steps: S1. Raw material preparation and drying: Weigh the raw material particles for the heat-sealing layer, barrier layer and puncture-resistant outer layer respectively, and perform vacuum drying on the barrier layer raw material; S2. Co-extrusion casting: The dried raw materials of each layer are added to different extruders of the multi-layer co-extrusion casting equipment. After being melted and plasticized, they are extruded through a multi-layer composite die and cast onto a cooling roller to form a multi-layer composite casting sheet. S3. Biaxial stretching: The multilayer composite casting is subjected to biaxial stretching simultaneously or in stages to obtain a preliminary film; S4. Heat setting and post-treatment: The biaxially stretched film is heat-set and then wound up to obtain the finished puncture-resistant patch film.

[0025] In step S2, the processing temperature of each extruder is controlled between 200°C; the temperature of the cooling roller is 30°C.

[0026] In step S3, the longitudinal stretch ratio of the biaxial stretching is 4, the transverse stretch ratio is 4, and the stretching temperature is between 105℃.

[0027] In step S4, the heat setting temperature is 20°C higher than the stretching temperature, and the time is 6 seconds. Example 3

[0028] An anti-puncture patch film according to an embodiment of the present invention includes: a heat-sealing layer, a barrier layer, and an anti-puncture outer layer stacked sequentially; The heat-sealing layer is made of a blend of 70 wt% linear low-density polyethylene and 25 wt% ethylene-octene copolymer plasmid; with a thickness of 30 μm. The barrier layer is an ethylene-vinyl alcohol copolymer layer or a polyamide layer; The puncture-resistant outer layer is made of a blend of 50 wt% high-density polyethylene, 30 wt% metallocene polyethylene, and 20 wt% modified polyolefin elastomer; the total thickness of the puncture-resistant patch film is 150 micrometers, and the thickness of the puncture-resistant outer layer accounts for 60% of the total thickness. The preparation process of modified polyolefin elastomers includes the following steps: Step A: Dehydration of reactants: Place 4,4'-diaminodiphenylmethane and bis(2-oxo-1,3-dioxolane-4-yl)methyl ether in a dry reaction flask, and add anhydrous N,N-dimethylformamide; Under nitrogen protection, stir at room temperature to completely dissolve the solid; heat to 70°C and continuously bubble with nitrogen for 30 minutes to remove trace amounts of moisture; Step B: Polymerization reaction: Heat the system to the preset reaction temperature of 90℃; add the catalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and stir magnetically in a nitrogen atmosphere at 80-90℃ for 12 hours. The system may become sticky in the early stage of the reaction. Step C: Termination and Post-treatment: Cool the reaction solution to room temperature, and under vigorous stirring, drop the reaction solution into a large amount of deionized water or a methanol / water mixture (about 10 times the volume) to precipitate the polymer; filter and collect the precipitate, and wash it three times with a large amount of water; place the product in a vacuum drying oven at 60°C and dry for more than 24 hours until constant weight is achieved, thus modifying the polyolefin elastomer. The ratio of 4,4'-diaminodiphenylmethane, bis(2-oxo-1,3-dioxolane-4-yl)methyl ether, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and anhydrous N,N-dimethylformamide was 1.98 g: 2.62 g: 70 mL: 3 mg. The manufacturing process of an anti-puncture patch membrane according to an embodiment of the present invention includes the following steps: S1. Raw material preparation and drying: Weigh the raw material particles for the heat-sealing layer, barrier layer and puncture-resistant outer layer respectively, and perform vacuum drying on the barrier layer raw material; S2. Co-extrusion casting: The dried raw materials of each layer are added to different extruders of the multi-layer co-extrusion casting equipment. After being melted and plasticized, they are extruded through a multi-layer composite die and cast onto a cooling roller to form a multi-layer composite casting sheet. S3. Biaxial stretching: The multilayer composite casting is subjected to biaxial stretching simultaneously or in stages to obtain a preliminary film; S4. Heat setting and post-treatment: The biaxially stretched film is heat-set and then wound up to obtain the finished puncture-resistant patch film.

[0029] In step S2, the processing temperature of each extruder is controlled between 230°C; the temperature of the cooling roller is 40°C.

[0030] In step S3, the longitudinal stretch ratio of the biaxial stretching is 5, the transverse stretch ratio is 5, and the stretching temperature is between 120℃.

[0031] In step S4, the heat setting temperature is 30°C higher than the stretching temperature, and the time is 10 seconds.

[0032] Comparative Example 1 Except for replacing 20 wt% of modified polyolefin elastomer in the puncture-resistant outer layer with an equal amount of ordinary ethylene-octene copolymer (POE, such as Engage 8150), the other raw materials, proportions and production processes are the same as in Example 2.

[0033] Performance testing The patch films of Examples 1-3 and Comparative Example 1 were subjected to puncture resistance test, low temperature performance test, and self-healing potential verification test. The standard for puncture resistance test was ASTM F1306, the standard for low temperature performance test was ASTM F1306, and the self-healing potential verification test involved creating standard microscopic scratches on the film surface with a blade, placing it in a 120°C oven for 30 minutes, and observing the changes in scratch morphology using an optical microscope or scanning electron microscope. The standard for heat shrinkage performance test was ASTM D2732.

[0034] This invention significantly improves puncture resistance and rigidity while maintaining extremely high elongation at break and low-temperature toughness; it also exhibits excellent performance retention under conditions of deep freezing at -40℃ and high temperature at 120℃.

[0035] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A puncture-resistant patch, characterized in that: include: A heat-sealing layer, a barrier layer, and a puncture-resistant outer layer are stacked in sequence; The heat-sealing layer is made of a blend of 70 wt% linear low-density polyethylene and 25 wt% ethylene-octene copolymer plasmid; with a thickness of 30 μm. The barrier layer is an ethylene-vinyl alcohol copolymer layer or a polyamide layer; The puncture-resistant outer layer is made of a blend of 50 wt% high-density polyethylene, 30 wt% metallocene polyethylene, and 20 wt% modified polyolefin elastomer; the total thickness of the puncture-resistant patch film is 50-150 micrometers, and the thickness of the puncture-resistant outer layer accounts for 40%-60% of the total thickness; The preparation process of modified polyolefin elastomers includes the following steps: Step A: Dehydration of reactants: Place 4,4'-diaminodiphenylmethane and bis(2-oxo-1,3-dioxolane-4-yl)methyl ether in a dry reaction flask, and add anhydrous N,N-dimethylformamide; Under nitrogen protection, stir at room temperature to completely dissolve the solid; heat to 60-70℃ and continuously bubble with nitrogen for 30 minutes to remove trace amounts of moisture; Step B: Polymerization reaction: Heat the system to the preset reaction temperature of 80-90℃; add the catalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and stir magnetically in a nitrogen atmosphere at 80-90℃ for 6-12 hours. The system may become sticky in the early stage of the reaction.

2. The puncture-resistant patch membrane according to claim 1, characterized in that: The ratio of 4,4'-diaminodiphenylmethane, bis(2-oxo-1,3-dioxolane-4-yl)methyl ether, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and anhydrous N,N-dimethylformamide is 1.98 g: 2.62 g: 50-70 mL: 2-3 mg.

3. The puncture-resistant patch membrane according to claim 2, characterized in that: The preparation process of modified polyolefin elastomers also includes the following steps: Step C: Termination and Post-treatment: Cool the reaction solution to room temperature, and under vigorous stirring, drop the reaction solution into a large amount of deionized water or a methanol / water mixture to precipitate the polymer; filter and collect the precipitate, and wash it with a large amount of water 2-3 times; place the product in a vacuum drying oven at 50-60℃ and dry it for more than 24 hours until constant weight is obtained to obtain the modified polyolefin elastomer.

4. A manufacturing process for a puncture-resistant patch, characterized in that: Includes the following steps: S1. Raw material preparation and drying: Weigh the raw material particles for the heat-sealing layer, barrier layer and puncture-resistant outer layer respectively, and perform vacuum drying on the barrier layer raw material; S2. Co-extrusion casting: The dried raw materials of each layer are added to different extruders of the multi-layer co-extrusion casting equipment. After being melted and plasticized, they are extruded through a multi-layer composite die and cast onto a cooling roller to form a multi-layer composite casting sheet. S3. Biaxial stretching: The multilayer composite casting is subjected to biaxial stretching simultaneously or in stages to obtain a preliminary film; S4. Heat setting and post-treatment: The biaxially stretched film is heat-set and then wound up to obtain the finished puncture-resistant patch film.

5. The manufacturing process of an anti-puncture patch film according to claim 4, characterized in that: In step S2, the processing temperature of each extruder is controlled between 180℃ and 230℃.

6. The manufacturing process of an anti-puncture patch film according to claim 4, characterized in that: The temperature of the cooling roller is 20℃-40℃.

7. The manufacturing process of an anti-puncture patch film according to claim 4, characterized in that: In step S3, the longitudinal stretching ratio of the biaxial stretching is 3-5, and the transverse stretching ratio is 3-5.

8. The manufacturing process of an anti-puncture patch film according to claim 4, characterized in that: The stretching temperature is between 90℃ and 120℃.

9. The manufacturing process of an anti-puncture patch film according to claim 4, characterized in that: In step S4, the temperature of the heat setting treatment is 10℃-30℃ higher than the stretching temperature.

10. The manufacturing process of an anti-puncture patch film according to claim 4, characterized in that: In step S4, the heat setting process takes 2-10 seconds.

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