Antifreeze packaging film and preparation process thereof

Abstract

The present application relates to the field of food packaging, and in particular to an antifreeze packaging film and its preparation process. The antifreeze packaging film comprises an outer film, a middle film, and an antifreeze inner film. The outer film, the middle film, and the antifreeze inner film are bonded together using an adhesive. The antifreeze inner film comprises the following raw materials in parts by weight: 20-30 parts of polypropylene, 20-30 parts of propylene-ethylene copolymer, 20-30 parts of linear low-density polyethylene, and 6-10 parts of an antifreeze agent. The preparation process is as follows: take an outer film, a middle film, and an antifreeze inner film of specified sizes, apply adhesive to one side of the antifreeze inner film using a glue roller, then composite the side of the antifreeze inner film coated with adhesive with one side of the middle film, apply adhesive to one side of the outer film, and composite the side of the outer film coated with adhesive with the side of the middle film facing away from the antifreeze inner film; the three-layer composite film is cured at room temperature to obtain the product. The present application has the effect of improving the impact resistance of the packaging film in a freezing environment.

Description

Technical Field

[0001] The present application relates to the field of food packaging, and in particular to an antifreeze packaging film and a preparation process thereof. Background Art

[0002] Frozen products, such as meat products, seafood, steamed buns, dumplings, and cold drinks, have experienced rapid growth in recent years. These products, however, require transportation, loading, and unloading before being sold, necessitating packaging in bags to protect them. Products also need to be stored in freezers for extended periods of time before being sold, making packaging bags essential to prevent contamination. Frozen product bags are made from film formed through a specialized molding process, which then serves to protect the product.

[0003] Cold drink bags are one of the main packaging materials for frozen products. Most cold drink bags are made of polypropylene film. However, polypropylene film has insufficient antifreeze properties when exposed to temperatures below -20°C. It cannot maintain its original properties, resulting in a decrease in film toughness, poor impact resistance, and brittleness. Frozen products are hard, which can easily cause the bags to break during transportation, resulting in poor product protection. Summary of the Invention

[0004] In order to improve the impact resistance of packaging films in freezing environments, the present application provides antifreeze packaging films and a preparation process thereof.

[0005] In the first aspect, the present application provides an antibacterial and oil-repellent fabric, which adopts the following technical solution:

[0006] The antifreeze packaging film includes an outer film, a middle film and an antifreeze inner film. The outer film, the middle film and the antifreeze inner film are bonded together using an adhesive. The antifreeze inner film includes the following raw materials in parts by weight: 20-30 parts of polypropylene, 20-30 parts of propylene-ethylene binary copolymer, 20-30 parts of linear low-density polyethylene, and 6-10 parts of an anti-blocking agent.

[0007] By adopting the above technical solution, the single use of polypropylene is replaced by the addition of propylene-ethylene binary copolymer. Polyethylene has excellent low-temperature resistance, and the propylene-ethylene binary copolymer contains ethylene, which can greatly improve the low-temperature resistance of the antifreeze inner film and make the antifreeze inner film have better impact strength, making the packaging film have better impact resistance in a freezing environment; linear low-density polyethylene is an ethylene polymer, which has many advantages such as high strength, good toughness, heat resistance, and cold resistance. It can have good resistance to environmental stress cracking, impact resistance, tearing resistance, and good chemical stability. The addition of linear low-density polyethylene can make the antifreeze inner film have better impact resistance in a freezing environment, thereby improving the overall cold resistance and strength of the antifreeze inner film. The use of polypropylene, propylene-ethylene binary copolymer and linear low-density polyethylene as the main components of the antifreeze inner film has better compatibility and is easier to melt and mix with each other, so the prepared film has better performance and better processability.

[0008] Preferably, the mass ratio of the polypropylene, propylene-ethylene binary copolymer and linear low-density polyethylene is 4-6:5:4-6.

[0009] By adopting the above technical scheme, when the mass ratio of polypropylene, propylene-ethylene binary copolymer and linear low-density polyethylene is different, the barrier performance, impact strength, low-temperature resistance, etc. of the antifreeze inner film will also be different. Polypropylene, as the main body, ensures the barrier performance and chemical corrosion resistance of the antifreeze inner film. Propylene-ethylene binary copolymer can improve the barrier performance as well as the impact resistance and low-temperature resistance, while linear low-density polyethylene mainly plays the role of improving the impact resistance and low-temperature resistance. If there is too much polypropylene and too little linear low-density polyethylene, the barrier performance of the antifreeze inner film will be improved, but the impact resistance and low-temperature resistance will be insufficient. If there is too little polypropylene and too much linear low-density polyethylene, although the impact resistance and low-temperature resistance of the antifreeze inner film will be improved, the barrier performance will be insufficient, and it will be difficult to protect the product from environmental influences. Therefore, the present application proposes an optimal mass ratio of polypropylene, propylene-ethylene binary copolymer and linear low-density polyethylene, so that the overall performance of the antifreeze inner film is better.

[0010] Preferably, the opening agent is a polypropylene copolymer containing 5% highly dispersed glass microbeads.

[0011] By adopting the above technical solution, the polypropylene copolymer contains some highly dispersed glass microbeads, which can increase the unevenness of the film surface and prevent the film from sticking when it is rolled up. The smooth surface of the glass microbead particles can also avoid scratching the film surface. In addition, the polypropylene copolymer with 5% highly dispersed glass microbeads can also increase the printability of the antifreeze inner film and the adhesion when bonding with other films.

[0012] Preferably, the preparation of the antifreeze inner film comprises the following steps:

[0013] Step 1: After accurately measuring polypropylene, propylene-ethylene binary copolymer, linear low-density polyethylene and anti-blocking agent, the mixture is fed into a screw extruder for melt extrusion at a melting temperature of 190-220°C and an extrusion temperature of 200-220°C to obtain a slurry;

[0014] Step 2: After the slurry is extruded, it is first filtered with a filter mesh of 150-180 mesh, and then cast and cooled on a casting machine through a T-die at a temperature of 210-230°C to obtain a cast film;

[0015] Step 3: The prepared cast film is firstly subjected to thickness measurement, and the surface is subjected to corona treatment, and then subjected to swinging, traction cutting, winding and aging for 46-50 hours to obtain the antifreeze inner film.

[0016] Preferably, the weight of the antifreeze inner film is 30-40g / m 2 .

[0017] By adopting the above technical solution, the gram weight of the antifreeze inner film is different, and the thickness of the film is also different. The thickness of the film will affect the performance and uniformity of the film. If the film thickness is too low, the performance is poor. If the film thickness is too high, the film is unevenly distributed at different positions. When multiple films are compounded, it will affect the processing performance of the composite film, resulting in poor barrier performance of the packaging film. Therefore, this application proposes a gram weight of the antifreeze inner film, which makes the performance of the packaging film better.

[0018] Preferably, the outer film is a BOPP film, and the gram weight of the BOPP film is 20-30g / m 2 .

[0019] By adopting the above technical solution, BOPP film has high tensile strength, impact strength, rigidity, toughness, and is non-toxic and odorless. As the outer film of the packaging bag, it can greatly improve the overall performance of the packaging bag and protect the product well. The BOPP film has different weights and thicknesses. Appropriate thickness can make the BOPP film more tough.

[0020] Preferably, the middle film is kraft paper, and the gram weight of kraft paper is 35-45g / m 2 .

[0021] By adopting the above technical solution, kraft paper has excellent toughness and impact resistance. As the middle film, kraft paper is in direct contact with the antifreeze inner film. Kraft paper also has good low-temperature resistance and excellent shrinkage and deformation resistance at low temperatures. Kraft paper of different gram weights has different thicknesses. As the middle film, appropriate thickness can better bond the outer film and the antifreeze inner film.

[0022] Preferably, the adhesive is a one-component solvent-free polyurethane adhesive.

[0023] By adopting the above technical solution, the one-component solvent-free polyurethane adhesive has excellent bonding strength, good water resistance and aging resistance, and also meets the environmental protection requirements of being non-toxic and pollution-free. When used, it can be directly applied to bond between films.

[0024] In a second aspect, the present application provides a process for preparing an antifreeze packaging film, which adopts the following technical solution:

[0025] The preparation process of the antifreeze packaging film comprises the following steps:

[0026] Step 1: Take the outer film, middle film and antifreeze inner film of specified size, apply adhesive on one side of the antifreeze inner film with a glue roller, then laminate the side of the antifreeze inner film coated with adhesive with one side of the middle film, then apply adhesive on one side of the outer film, then laminate the side of the outer film coated with adhesive with the side of the middle film facing away from the antifreeze inner film;

[0027] Step 2: Curing the three-layer composite film at room temperature for 24-36 hours to obtain the product.

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

[0029] 1. Since the present application adopts polypropylene as the main component and adds propylene-ethylene binary copolymer and linear low-density polyethylene for modification, the low-temperature resistance of the antifreeze inner film can be greatly improved, and the antifreeze inner film can have better impact strength and good resistance to environmental stress cracking, so that the packaging film has better impact resistance in a freezing environment. The use of polypropylene, propylene-ethylene binary copolymer and linear low-density polyethylene as the main components of the antifreeze inner film has better compatibility, is easier to melt and mix with each other, and the prepared film has better performance and better processability. DETAILED DESCRIPTION

[0030] Preparation Example

[0031] Preparation Example 1

[0032] The preparation of the antifreeze inner film includes the following steps:

[0033] Step 1: 2 kg of polypropylene (6908), 2.5 kg of propylene-ethylene binary copolymer (BX3980), 3 kg of linear low-density polyethylene (3812) and an opening agent (AB6089CPP) are mixed uniformly by a feeder, and the mixture is put into a screw extruder for melt extrusion. The melting temperature of the first section is 190-195 ° C, the melting temperature of the second section is 195-200 ° C, the melting temperature of the third section is 195-200 ° C, the melting temperature of the fourth section is 200-205 ° C, the melting temperature of the fifth section is 205-210 ° C, the melting temperature of the sixth section is 210-215 ° C, the melting temperature of the seventh section is 215-220 ° C, the melting temperature of the eighth section is 215-220 ° C, and the extrusion temperature is 210-220 ° C to obtain a slurry;

[0034] Step 2: After the slurry is extruded, it is first filtered with a 180-mesh filter, and then cast and cooled on a casting machine through a T-die at a temperature of 215-225°C to obtain a cast film;

[0035] Step 3: The prepared cast film is first measured by a film thickness gauge, and the surface is corona treated. Then, it is subjected to swing, traction, trimming, and winding for 46 hours to obtain an antifreeze inner film. The weight of the antifreeze inner film is 30g / m 2 .

[0036] Preparation Example 2

[0037] The difference between Preparation Example 2 and Preparation Example 1 is that the preparation of the antifreeze inner film includes the following steps:

[0038] Step 1: 3 kg of polypropylene (6908), 2.5 kg of propylene-ethylene binary copolymer (BX3980), 2 kg of linear low-density polyethylene (3812) and an opening agent (AB6089CPP) are mixed uniformly by a feeder, and the mixture is put into a screw extruder for melt extrusion. The first section melt temperature is 190-195 ° C, the second section melt temperature is 195-200 ° C, the third section melt temperature is 195-200 ° C, the fourth section melt temperature is 200-205 ° C, the fifth section melt temperature is 205-210 ° C, the sixth section melt temperature is 210-215 ° C, the seventh section melt temperature is 215-220 ° C, the eighth section melt temperature is 215-220 ° C, and the extrusion temperature is 210-220 ° C to obtain a slurry;

[0039] Step 2: After the slurry is extruded, it is first filtered with a 180-mesh filter, and then cast and cooled on a casting machine through a T-die at a temperature of 215-225°C to obtain a cast film;

[0040] Step 3: The prepared cast film is first measured by a film thickness gauge, and the surface is corona treated. Then, it is subjected to swing, traction, trimming, and winding for 46 hours to obtain an antifreeze inner film. The weight of the antifreeze inner film is 30g / m 2 .

[0041] Preparation Example 3

[0042] Preparation Example 3 differs from Preparation Example 1 in that the preparation of the antifreeze inner film includes the following steps:

[0043] Step 1: 2.5 kg of polypropylene (6908), 2.5 kg of propylene-ethylene copolymer (BX3980), 2.5 kg of linear low-density polyethylene (3812) and an opening agent (AB6089CPP) are mixed uniformly by a feeder, and the mixture is put into a screw extruder for melt extrusion. The first section melt temperature is 190-195 ° C, the second section melt temperature is 195-200 ° C, the third section melt temperature is 195-200 ° C, the fourth section melt temperature is 200-205 ° C, the fifth section melt temperature is 205-210 ° C, the sixth section melt temperature is 210-215 ° C, the seventh section melt temperature is 215-220 ° C, the eighth section melt temperature is 215-220 ° C, and the extrusion temperature is 210-220 ° C to obtain a slurry;

[0044] Step 2: After the slurry is extruded, it is first filtered with a 180-mesh filter, and then cast and cooled on a casting machine through a T-die at a temperature of 215-225°C to obtain a cast film;

[0045] Step 3: The prepared cast film is first measured by a film thickness gauge, and the surface is corona treated. Then, it is subjected to swing, traction, trimming, and winding for 46 hours to obtain an antifreeze inner film. The weight of the antifreeze inner film is 30g / m 2 .

[0046] Preparation Example 4

[0047] Preparation Example 4 differs from Preparation Example 1 in that the preparation of the antifreeze inner film includes the following steps:

[0048] Step 1: 2.5 kg of polypropylene (6908), 2.5 kg of propylene-ethylene copolymer (BX3980), 2.5 kg of linear low-density polyethylene (3812) and an opening agent (AB6089CPP) are mixed uniformly by a feeder, and the mixture is put into a screw extruder for melt extrusion. The first section melt temperature is 190-195 ° C, the second section melt temperature is 195-200 ° C, the third section melt temperature is 195-200 ° C, the fourth section melt temperature is 200-205 ° C, the fifth section melt temperature is 205-210 ° C, the sixth section melt temperature is 210-215 ° C, the seventh section melt temperature is 215-220 ° C, the eighth section melt temperature is 215-220 ° C, and the extrusion temperature is 210-220 ° C to obtain a slurry;

[0049] Step 2: After the slurry is extruded, it is first filtered with a 180-mesh filter, and then cast and cooled on a casting machine through a T-die at a temperature of 215-225°C to obtain a cast film;

[0050] Step 3: The prepared cast film is first measured by a film thickness gauge, and the surface is corona treated. Then, it is subjected to swing, traction, trimming, and winding for 46 hours to obtain an antifreeze inner film. The weight of the antifreeze inner film is 40g / m 2 .

[0051] Preparation Example 5

[0052] Preparation Example 5 differs from Preparation Example 1 in that the preparation of the antifreeze inner film includes the following steps:

[0053] Step 1: 2.5 kg of polypropylene (6908), 2.5 kg of propylene-ethylene copolymer (BX3980), 2.5 kg of linear low-density polyethylene (3812) and an opening agent (AB6089CPP) are mixed uniformly by a feeder, and the mixture is put into a screw extruder for melt extrusion. The first section melt temperature is 190-195 ° C, the second section melt temperature is 195-200 ° C, the third section melt temperature is 195-200 ° C, the fourth section melt temperature is 200-205 ° C, the fifth section melt temperature is 205-210 ° C, the sixth section melt temperature is 210-215 ° C, the seventh section melt temperature is 215-220 ° C, the eighth section melt temperature is 215-220 ° C, and the extrusion temperature is 210-220 ° C to obtain a slurry;

[0054] Step 2: After the slurry is extruded, it is first filtered with a 180-mesh filter, and then cast and cooled on a casting machine through a T-die at a temperature of 215-225°C to obtain a cast film;

[0055] Step 3: The prepared cast film is first measured by a film thickness gauge, and the surface is corona treated. Then, it is subjected to swing, traction, trimming, and winding for 46 hours to obtain an antifreeze inner film. The weight of the antifreeze inner film is 35g / m 2 .

[0056] Preparation Example 6

[0057] The difference between Preparation Example 6 and Preparation Example 1 is that the preparation of the antifreeze inner film includes the following steps:

[0058] Step 1: 1.5 kg of polypropylene (6908), 2.5 kg of propylene-ethylene copolymer (BX3980), 3.5 kg of linear low-density polyethylene (3812) and an opening agent (AB6089CPP) are mixed uniformly by a feeder, and the mixture is put into a screw extruder for melt extrusion. The first section melt temperature is 190-195 ° C, the second section melt temperature is 195-200 ° C, the third section melt temperature is 195-200 ° C, the fourth section melt temperature is 200-205 ° C, the fifth section melt temperature is 205-210 ° C, the sixth section melt temperature is 210-215 ° C, the seventh section melt temperature is 215-220 ° C, the eighth section melt temperature is 215-220 ° C, and the extrusion temperature is 210-220 ° C to obtain a slurry;

[0059] Step 2: After the slurry is extruded, it is first filtered with a 180-mesh filter, and then cast and cooled on a casting machine through a T-die at a temperature of 215-225°C to obtain a cast film;

[0060] Step 3: The prepared cast film is first measured by a film thickness gauge, and the surface is corona treated. Then, it is subjected to swing, traction, trimming, and winding for 46 hours to obtain an antifreeze inner film. The weight of the antifreeze inner film is 35g / m 2 .

[0061] Preparation Example 7

[0062] Preparation Example 7 differs from Preparation Example 1 in that the preparation of the antifreeze inner film includes the following steps:

[0063] Step 1: 3.5 kg of polypropylene (6908), 2.5 kg of propylene-ethylene copolymer (BX3980), 1.5 kg of linear low-density polyethylene (3812) and an opening agent (AB6089CPP) are mixed uniformly by a feeder, and the mixture is put into a screw extruder for melt extrusion. The first section melt temperature is 190-195 ° C, the second section melt temperature is 195-200 ° C, the third section melt temperature is 195-200 ° C, the fourth section melt temperature is 200-205 ° C, the fifth section melt temperature is 205-210 ° C, the sixth section melt temperature is 210-215 ° C, the seventh section melt temperature is 215-220 ° C, the eighth section melt temperature is 215-220 ° C, and the extrusion temperature is 210-220 ° C to obtain a slurry;

[0064] Step 2: After the slurry is extruded, it is first filtered with a 180-mesh filter, and then cast and cooled on a casting machine through a T-die at a temperature of 215-225°C to obtain a cast film;

[0065] Step 3: The prepared cast film is first measured by a film thickness gauge, and the surface is corona treated. Then, it is subjected to swing, traction, trimming, and winding for 46 hours to obtain an antifreeze inner film. The weight of the antifreeze inner film is 35g / m 2 .

[0066] Preparation Example 8

[0067] The difference between Preparation Example 8 and Preparation Example 1 is that the preparation of the antifreeze inner film includes the following steps:

[0068] Step 1: 3.75 kg of polypropylene (6908), 3.75 kg of linear low-density polyethylene (3812) and an opening agent (AB6089CPP) are mixed uniformly by a feeder, and the mixture is put into a screw extruder for melt extrusion. The melting temperature of the first section is 190-195 ° C, the melting temperature of the second section is 195-200 ° C, the melting temperature of the third section is 195-200 ° C, the melting temperature of the fourth section is 200-205 ° C, the melting temperature of the fifth section is 205-210 ° C, the melting temperature of the sixth section is 210-215 ° C, the melting temperature of the seventh section is 215-220 ° C, the melting temperature of the eighth section is 215-220 ° C, and the extrusion temperature is 210-220 ° C to obtain a slurry;

[0069] Step 2: After the slurry is extruded, it is first filtered with a 180-mesh filter, and then cast and cooled on a casting machine through a T-die at a temperature of 215-225°C to obtain a cast film;

[0070] Step 3: The prepared cast film is first measured by a film thickness gauge, and the surface is corona treated. Then, it is subjected to swing, traction, trimming, and winding for 46 hours to obtain an antifreeze inner film. The weight of the antifreeze inner film is 35g / m 2 .

[0071] Preparation Example 9

[0072] Preparation Example 9 differs from Preparation Example 1 in that the preparation of the antifreeze inner film includes the following steps:

[0073] Step 1: 3.75 kg of polypropylene (6908), 3.75 kg of propylene-ethylene binary copolymer (BX3980) and an opening agent (AB6089CPP) are mixed uniformly by a feeder, and the mixture is put into a screw extruder for melt extrusion. The first section melt temperature is 190-195 ° C, the second section melt temperature is 195-200 ° C, the third section melt temperature is 195-200 ° C, the fourth section melt temperature is 200-205 ° C, the fifth section melt temperature is 205-210 ° C, the sixth section melt temperature is 210-215 ° C, the seventh section melt temperature is 215-220 ° C, the eighth section melt temperature is 215-220 ° C, and the extrusion temperature is 210-220 ° C to obtain a slurry;

[0074] Step 2: After the slurry is extruded, it is first filtered with a 180-mesh filter, and then cast and cooled on a casting machine through a T-die at a temperature of 215-225°C to obtain a cast film;

[0075] Step 3: The prepared cast film is first measured by a film thickness gauge, and the surface is corona treated. Then, it is subjected to swing, traction, trimming, and winding for 46 hours to obtain an antifreeze inner film. The weight of the antifreeze inner film is 35g / m 2 .

[0076] Example

[0077] Example 1

[0078] The preparation process of the antifreeze packaging film comprises the following steps:

[0079] Step 1: Take a weight of 20g / m 2 BOPP outer film, weight 35g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 1 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with one side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film;

[0080] Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain the product.

[0081] Example 2

[0082] The difference between Example 2 and Example 1 is that: Step 1: Take a weight of 20g / m 2 BOPP outer film, weight 35g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 2 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0083] Example 3

[0084] The difference between Example 3 and Example 1 is that: Step 1: Take a weight of 20g / m 2 BOPP outer film, weight 35g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 3 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0085] Example 4

[0086] The difference between Example 4 and Example 1 is that: Step 1: Take a weight of 20g / m 2 BOPP outer film, weight 35g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 4 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0087] Example 5

[0088] The difference between Example 5 and Example 1 is that: Step 1: Take a weight of 20g / m 2 BOPP outer film, weight 35g / m 2The kraft paper middle film and the antifreeze inner film in Preparation Example 5 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0089] Example 6

[0090] The difference between Example 6 and Example 1 is that: Step 1: Take a weight of 30g / m 2 BOPP outer film, weight 35g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 5 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0091] Example 7

[0092] The difference between Example 7 and Example 1 is that: Step 1: Take a weight of 25g / m 2 BOPP outer film, weight 35g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 5 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0093] Example 8

[0094] The difference between Example 8 and Example 1 is that: Step 1: Take a weight of 25g / m 2 BOPP outer film, weight 45g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 5 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0095] Example 9

[0096] The difference between Example 9 and Example 1 is that: Step 1: Take a weight of 25g / m 2 BOPP outer film, weight 40g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 5 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0097] Comparative Example

[0098] Comparative Example 1

[0099] The difference between Comparative Example 1 and Example 1 is that: Step 1: Take a gram weight of 20g / m 2 BOPP outer film, weight 35g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 6 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0100] Comparative Example 2

[0101] The difference between Comparative Example 2 and Example 1 is that: Step 1: Take a gram weight of 20g / m 2 BOPP outer film, weight 35g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 7 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0102] Comparative Example 3

[0103] The difference between Comparative Example 3 and Example 1 is that: Step 1: Take a gram weight of 20g / m 2 BOPP outer film, weight 35g / m 2The kraft paper middle film and the antifreeze inner film in Preparation Example 8 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0104] Comparative Example 4

[0105] The difference between Comparative Example 4 and Example 1 is that: Step 1: Take a gram weight of 20g / m 2 BOPP outer film, weight 35g / m 2 The kraft paper middle film and the antifreeze inner film in Preparation Example 9 are coated with a single-component solvent-free polyurethane adhesive (ZC-305) on one side of the antifreeze inner film by a glue roller, and then the side of the antifreeze inner film coated with the adhesive is compounded with the side of the middle film, and then the adhesive is coated on one side of the outer film, and then the side of the outer film coated with the adhesive is compounded with the side of the middle film away from the antifreeze inner film; Step 2: The three-layer composite film is cured at room temperature for 36 hours to obtain a product.

[0106] Performance testing

[0107] 1. Impact resistance: According to GB / T9639.1-2008 "Plastic film and sheeting. Test method for impact resistance. Free-fall dart method. Part 1: Step method", the samples of Examples 1-9 and Comparative Examples 1-4 and ordinary samples of Examples 1-9 and Comparative Examples 1-4, which had been refrigerated at -20°C for 24 hours, were tested for impact resistance under refrigerated conditions and under ordinary conditions using a drop weight impact tester.

[0108] 2. Barrier properties: According to GB / T1038-2000 “Plastic Film and Sheeting Gas Permeability Test Method - Pressure Differential Method”, the gas barrier properties of Examples 1-9 and Comparative Examples 1-4 were tested using a food packaging material permeability tester (TOYOSEIKO).

[0109] Table 1 Performance test of Examples 1-9 and Comparative Examples 1-4

[0110]

[0111] From Examples 1-5 and Comparative Examples 1-4 and Table 1, it can be seen that when the ratio of polypropylene to linear low-density polyethylene is different, the barrier properties, impact resistance and frost resistance of the packaging film are different. Polypropylene can effectively improve the barrier properties of the packaging film, and linear low-density polyethylene can also effectively improve the impact resistance and frost resistance of the packaging film. When polypropylene is excessive, the impact resistance and frost resistance of the packaging film are poor, and when linear low-density polyethylene is excessive, the barrier properties of the packaging film are poor. In addition, the thickness of the prepared antifreeze inner film also directly affects the performance of the packaging film. Taking all factors into consideration, the ratio of polypropylene to linear low-density polyethylene and the gram weight of the antifreeze inner film in Example 5 are optimal, and the barrier properties, impact resistance and frost resistance of the packaging film are good.

[0112] Combining Examples 6-9 and Table 1, it can be seen that different thicknesses of the outer film and the middle film will affect the overall processability of the packaging film, as well as the barrier properties, impact resistance, and frost resistance of the packaging film. In contrast, when the thicknesses of the outer film, middle film, and antifreeze inner film are those in Example 9, the processability of the packaging film is better, and the barrier properties, impact resistance, and frost resistance of the prepared packaging film are the best.

[0113] 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 non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. Antifreeze packaging film, characterized by: The antifreeze film comprises an outer film, a middle film and an antifreeze inner film, wherein the outer film, the middle film and the antifreeze inner film are bonded together by an adhesive, and the antifreeze inner film comprises the following raw materials in parts by weight: 20-30 parts of polypropylene, 20-30 parts of propylene-ethylene binary copolymer, 20-30 parts of linear low-density polyethylene, and 6-10 parts of an antifreeze agent; The mass ratio of the polypropylene, propylene-ethylene binary copolymer and linear low-density polyethylene is 4-6:5:4-6; The opening agent is a polypropylene copolymer containing 5% highly dispersed glass beads; The weight of the antifreeze inner film is 35 g / m 2 The outer film is a BOPP film, and the weight of the BOPP film is 25 g / m 2 The middle film is kraft paper, the gram weight of kraft paper is 40 g / m 2 .

2. The antifreeze packaging film according to claim 1, characterized in that: The preparation of the antifreeze inner film comprises the following steps: Step 1: After accurately measuring polypropylene, propylene-ethylene binary copolymer, linear low-density polyethylene and anti-blocking agent, the mixture is fed into a screw extruder for melt extrusion at a melting temperature of 190-220°C and an extrusion temperature of 200-220°C to obtain a slurry; Step 2: After the slurry is extruded, it is first filtered with a filter mesh of 150-180 mesh, and then cast and cooled on a casting machine through a T-die at a temperature of 210-230°C to obtain a cast film; Step 3: The prepared cast film is firstly subjected to thickness measurement, and the surface is subjected to corona treatment, and then subjected to swinging, traction cutting, winding and aging for 46-50 hours to obtain the antifreeze inner film.

3. The antifreeze packaging film according to claim 1, characterized in that: The adhesive is a single-component solvent-free polyurethane adhesive.

4. The process for preparing the antifreeze packaging film according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Take the outer film, middle film and antifreeze inner film of specified size, apply adhesive on one side of the antifreeze inner film with a glue roller, then laminate the side of the antifreeze inner film coated with adhesive with one side of the middle film, then apply adhesive on one side of the outer film, then laminate the side of the outer film coated with adhesive with the side of the middle film facing away from the antifreeze inner film; Step 2: Curing the three-layer composite film at room temperature for 24-36 hours to obtain the product.

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