Co-extrusion ultralow-temperature packaging film for cigar wood box cigarettes

Abstract

The invention discloses a co-extrusion ultralow-temperature packaging film for cigar wood box cigarettes, and belongs to the technical field of packaging materials. The packaging film comprises a base material layer, a barrier layer and a heat sealing layer which are co-extruded and compounded in sequence, the base material layer is a biaxially oriented polypropylene film, and the thickness of the base material layer is 15-25 microns; the barrier layer is made of polyamide or ethylene-vinyl alcohol copolymer, and the thickness of the barrier layer is 3-8 microns; the heat sealing layer is a propylene alpha-olefin copolymer, the number of carbon atoms of alpha-olefin is 5-8, the propylene alpha-olefin copolymer is prepared through a metallocene catalytic system, and the thickness of the propylene alpha-olefin copolymer is 10-20 microns. The ultralow-temperature heat sealing performance with the initial sealing temperature ranging from 85 DEG C to 100 DEG C is achieved, the temperature is reduced by 20-30 DEG C compared with a traditional BOPP cigarette film, the problem that varnish on the surface of a wooden box is damaged due to high-temperature heat sealing is effectively solved, and meanwhile the quality of cigars is prevented from being affected. The packaging film is formed at a time through a co-extrusion technology, glue coating is not needed, and the packaging film is more environmentally friendly and has excellent mechanical performance, optical performance and barrier performance.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, and more particularly to a co-extruded ultra-low temperature cigar box packaging film. Background Technology

[0002] High-end cigar boxes are typically coated with a layer of varnish or covered with a BOPP film to enhance their appearance and protect the surface. During the cigar box packaging process, a heat-sealing film is used to seal the wooden box. Existing BOPP films require heat-sealing temperatures above 115 degrees Celsius to achieve effective sealing. However, experiments have shown that when the soldering iron temperature exceeds 100 degrees Celsius, the outer packaging film can peel off the varnish from the wooden box surface during heat sealing, causing damage and affecting the product's appearance. Furthermore, excessively high heat-sealing temperatures can negatively impact the quality of the cigars, potentially leading to aroma loss and changes in moisture content, thus reducing product quality.

[0003] Existing technologies also include packaging film products prepared using coating processes; however, these products require the use of adhesives for coating, posing environmental concerns, and solvent residues in the adhesives may affect the safety of food contact materials. Traditional heat-sealing materials include binary and terpolymers, each with different Vicat softening and melting points, but none can meet the technical requirements for ultra-low temperature heat sealing in cigar box packaging. Therefore, there is an urgent need to develop a new type of packaging film product that can achieve heat sealing below 100 degrees Celsius, without damaging the varnish on the wooden box surface, and is more environmentally friendly, to meet the actual needs of high-end cigar packaging. Summary of the Invention

[0004] The purpose of this invention is to provide a co-extruded ultra-low temperature cigar box packaging film to solve the problems existing in the prior art.

[0005] The present invention provides a co-extruded ultra-low temperature cigar box packaging film, comprising a substrate layer, a barrier layer and a heat-sealing layer co-extruded sequentially; The substrate layer is a biaxially oriented polypropylene film with a thickness of 15 to 25 micrometers; The barrier layer is a polyamide or ethylene-vinyl alcohol copolymer with a thickness of 3 to 8 micrometers; The heat-sealing layer is a propylene α-olefin copolymer, wherein the α-olefin has 5 to 8 carbon atoms. The propylene α-olefin copolymer is prepared by a metallocene catalytic system, and the thickness of the heat-sealing layer is 10 to 20 micrometers.

[0006] This invention provides a co-extruded ultra-low temperature cigar box packaging film, comprising a substrate layer, a barrier layer, and a heat-sealing layer co-extruded sequentially. The substrate layer is a biaxially oriented polypropylene film with a thickness of 15 to 25 micrometers, providing good mechanical strength and optical properties. The barrier layer is a polyamide or ethylene-vinyl alcohol copolymer with a thickness of 3 to 8 micrometers, providing necessary oxygen and moisture barrier properties. The heat-sealing layer is a propylene α-olefin copolymer, wherein the α-olefin has 5 to 8 carbon atoms, and the propylene α-olefin copolymer is prepared using a metallocene catalytic system; the heat-sealing layer has a thickness of 10 to 20 micrometers.

[0007] Through the above technical solution, using a propylene α-olefin copolymer prepared by a metallocene catalytic system as the heat-sealing layer material, the sealing initiation temperature of the packaging film was successfully reduced to 85-100 degrees Celsius, achieving ultra-low temperature heat-sealing performance. This packaging film can complete heat sealing within a temperature range of 95-100 degrees Celsius, effectively avoiding damage to the varnish on the surface of the cigar box from high temperatures, while protecting the quality of the cigars. The packaging film is formed in one step through a co-extrusion process, eliminating the need for adhesive coating, making it more environmentally friendly and safer. The packaging film possesses excellent heat-sealing strength, mechanical properties, optical properties, and barrier properties, meeting the various technical requirements of high-end cigar packaging.

[0008] Furthermore, α-olefins have 6 to 7 carbon atoms.

[0009] Furthermore, the molar content of α-olefin in the copolymer is 8% to 15%.

[0010] Furthermore, the Vicat softening point of the propylene α-olefin copolymer is 90 to 105 degrees Celsius, the melting point is 110 to 125 degrees Celsius, and the sealing initiation temperature is 85 to 100 degrees Celsius.

[0011] Furthermore, the metallocene catalytic system includes a metallocene compound and a cocatalyst, wherein the metallocene compound is a derivative of zirconium diacene or titanium diacene, and the cocatalyst is methylaluminoxane or modified methylaluminoxane.

[0012] Furthermore, the heat-sealing layer also contains an anti-blocking agent, a slip agent, and an antioxidant; the amount of anti-blocking agent added is 0.3% to 0.8%, and it is diatomaceous earth or synthetic silica; the amount of slip agent added is 0.2% to 0.6%, and it is erucamide or oleamide; the amount of antioxidant added is 0.1% to 0.3%, and it is a hindered phenolic antioxidant.

[0013] Furthermore, the thickness of the substrate layer is 18 to 22 micrometers, the thickness of the barrier layer is 4 to 6 micrometers, the thickness of the heat-sealing layer is 12 to 16 micrometers, and the total thickness of the packaging film is 35 to 45 micrometers.

[0014] Furthermore, the α-olefin is 1-hexene, 1-heptene, or 1-octene.

[0015] The beneficial effects of this invention are: 1. This invention uses propylene α-olefin copolymer prepared by a metallocene catalytic system as a heat-sealing layer material, achieving ultra-low temperature heat-sealing performance with a sealing start temperature of 85 to 100 degrees Celsius. Compared with the heat-sealing temperature of traditional BOPP cigarette film above 115 degrees Celsius, it reduces the temperature by 20 to 30 degrees Celsius, effectively solving the technical problem of varnish sticking and damage to the surface of cigar wooden boxes caused by high-temperature heat sealing, ensuring the surface of the wooden box remains intact, and improving the appearance quality of the product.

[0016] 2. This invention uses a three-layer co-extrusion process to prepare the packaging film in a single molding process, eliminating the need for adhesive coating and removing the potential impact of residual solvents in adhesives on product safety, thus aligning with the development trend of green and environmentally friendly packaging. The packaging film has a heat-sealing strength of 35 to 38 Newtons per 15 millimeters, high mechanical strength, and excellent oxygen and moisture barrier properties. It can maintain the stable moisture content and aroma of cigars after 6 to 8 months of storage, fully protecting the quality of the cigars.

[0017] 3. The packaging film of this invention possesses excellent optical and processing properties, with a haze value as low as 2.5% to 2.8%, a gloss level of 95 to 96 degrees, and a light transmittance of 92% to 93%, exhibiting a transparent and aesthetically pleasing appearance. The packaging film demonstrates good processing stability, achieving a packaging efficiency of 60 boxes per minute on automated packaging lines, with a packaging qualification rate exceeding 99.2%. It is suitable for large-scale production applications and possesses promising market prospects and economic value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the packaging film structure of the present invention; Figure 2 This is a flow chart of the co-extrusion process of the present invention; Figure 3 This is a comparison chart of the heat sealing temperatures of the present invention. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0021] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0022] Generally, terms can be understood at least partly from their use in context. For example, depending at least partly on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least partly on the context, to allow for the presence of other factors that are not necessarily explicitly described.

[0023] See Figures 1 to 3 As shown This invention provides a co-extruded ultra-low temperature cigar box packaging film. The packaging film is prepared by co-extrusion process and uses propylene α-olefin copolymer as the heat-sealing layer 103 material, which achieves ultra-low temperature heat-sealing performance below 100 degrees Celsius. This effectively solves the technical problem that traditional BOPP cigarette film damages the varnish on the surface of the cigar box due to excessive temperature during the heat sealing process.

[0024] The packaging film has a multi-layer co-extruded composite structure, comprising, from the outside to the inside, a substrate layer 101, a barrier layer 102, and a heat-sealing layer 103. The substrate layer 101 is made of biaxially oriented polypropylene film with a thickness of 15 to 25 micrometers, providing good mechanical strength and optical properties. The barrier layer 102 is made of polyamide or ethylene-vinyl alcohol copolymer with a thickness of 3 to 8 micrometers, providing necessary oxygen and moisture barrier properties to protect the quality of the cigars. The heat-sealing layer 103 is made of propylene α-olefin copolymer, wherein the α-olefin has 5 to 8 carbon atoms, preferably 6 to 7 carbon atoms, and a thickness of 10 to 20 micrometers.

[0025] The propylene α-olefin copolymer was prepared using a metallocene catalytic system. The metallocene catalyst is a combination of a metallocene compound and a cocatalyst; the metallocene compound is selected as a derivative of zirconium diacene or titanium diacene, and the cocatalyst is selected as methylaluminoxane or modified methylaluminoxane. In the polymerization reactor, propylene monomer and α-olefin monomer undergo copolymerization under the action of the metallocene catalyst. The reaction temperature is controlled at 60 to 80 degrees Celsius, the reaction pressure at 2.0 to 3.5 MPa, and the reaction time at 2 to 4 hours. By adjusting the molar content of α-olefin in the copolymer, the melting point and sealing initiation temperature of the heat-sealing layer 103 can be precisely controlled. When the molar content of α-olefin is 8% to 15%, the obtained copolymer has a Vicat softening point of 90 to 105 degrees Celsius, a melting point of 110 to 125 degrees Celsius, and a sealing initiation temperature of 85 to 100 degrees Celsius.

[0026] The packaging film is prepared using a three-layer co-extrusion blow molding process. The raw materials for the substrate layer 101, barrier layer 102, and heat-sealing layer 103 are respectively fed into three independent extruders. The first extruder is used for the substrate layer 101, with a screw diameter of 65 mm, an aspect ratio of 30:1, and a set temperature range of 190 to 230 degrees Celsius, with heating sequentially from the hopper to the die. The second extruder is used for the barrier layer 102, with a screw diameter of 45 mm, an aspect ratio of 28:1, and a set temperature range of 200 to 240 degrees Celsius. The third extruder is used for the heat-sealing layer 103, with a screw diameter of 55 mm, an aspect ratio of 30:1, and a set temperature range of 170 to 210 degrees Celsius. Due to the low melting point of the propylene α-olefin copolymer, strict control of the processing temperature is necessary to avoid overheating and degradation.

[0027] The melt from the three extruders is precisely metered by its respective metering pump and then converges into the co-extrusion die. The die temperature is set to 200 to 220 degrees Celsius, and the die lip clearance is 1.2 to 1.8 millimeters. The tubular film extruded from the die is rapidly cooled by a cooling air ring at a temperature of 15 to 25 degrees Celsius and a velocity of 8 to 12 meters per second. The cooled tubular film is then pulled by a traction roller assembly at a speed of 35 to 55 meters per minute and then wound into a roll by a winding device. Throughout the production process, the thickness of each layer needs to be monitored in real time to ensure that the thickness of the substrate layer 101 is 18 to 22 micrometers, the thickness of the barrier layer 102 is 4 to 6 micrometers, the thickness of the heat-sealing layer 103 is 12 to 16 micrometers, and the total thickness is controlled within 35 to 45 micrometers.

[0028] To further improve the performance of the heat-sealing layer 103, appropriate functional additives can be added to the propylene α-olefin copolymer. An anti-blocking agent, at a concentration of 0.3% to 0.8%, preferably diatomaceous earth or synthetic silica, can prevent film sticking during winding and storage. A slip agent, at a concentration of 0.2% to 0.6%, preferably erucamide or oleamide, can improve the film's opening properties and processing performance. An antioxidant, at a concentration of 0.1% to 0.3%, preferably a hindered phenolic antioxidant, can improve the film's thermal stability and service life. These additives are thoroughly mixed with the propylene α-olefin copolymer resin before extrusion, pre-mixed and granulated using a twin-screw extruder, and then used in co-extrusion production.

[0029] The prepared packaging film needs to undergo a curing treatment, which involves storing the film roll in an environment with a temperature of 35 to 45 degrees Celsius and a relative humidity of 50% to 60% for 48 to 72 hours to fully release the internal stress of the film and stabilize its crystalline structure, thereby obtaining the best heat-sealing performance and mechanical properties.

[0030] Example 1 A copolymer of propylene and 1-hexene was selected as the heat-sealing layer material 103, wherein the molar content of 1-hexene was 10%. This copolymer was prepared using a metallocene catalytic system, employing zirconium dichloride as the main catalyst and methylaluminoxane as the co-catalyst. The polymerization temperature was 70°C, the polymerization pressure was 2.8 MPa, and the polymerization time was 3 hours. The resulting propylene-1-hexene copolymer had a melt flow rate of 3.5 g / 10 min, a density of 0.900 g / cm³, a Vicat softening point of 96°C, and a melting point of 118°C.

[0031] The packaging film is prepared using a three-layer co-extrusion blow molding process. The substrate layer 101 is made of biaxially oriented polypropylene with a density of 0.905 g / cm³ and a melt flow rate of 2.0 g / 10 min. The barrier layer 102 is made of polyamide 6 with a relative viscosity of 2.5. The heat-sealing layer 103 is made of the aforementioned propylene-1-hexene copolymer, with the addition of 0.5% diatomaceous earth as an anti-blocking agent, 0.4% erucamide as a slip agent, and 0.2% hindered phenolic antioxidant.

[0032] The first extruder processes the substrate layer 101 at a temperature set between 195°C and 225°C, with a screw speed of 90 rpm and an extrusion rate of 45 kg / h. The second extruder processes the barrier layer 102 at a temperature set between 210°C and 235°C, with a screw speed of 60 rpm and an extrusion rate of 8 kg / h. The third extruder processes the heat-sealing layer 103 at a temperature set between 175°C and 205°C, with a screw speed of 75 rpm and an extrusion rate of 25 kg / h. The co-extrusion die temperature is set at 210°C, and the die lip clearance is 1.5 mm. The cooling air temperature is 20°C, and the air velocity is 10 m / s. The traction speed is 45 m / min.

[0033] The resulting packaging film has a total thickness of 40 micrometers, with the substrate layer 101 having a thickness of 20 micrometers, the barrier layer 102 having a thickness of 5 micrometers, and the heat-sealing layer 103 having a thickness of 15 micrometers. The packaging film was then subjected to performance testing after being cured in an environment of 50 degrees Celsius and 55% relative humidity for 60 hours.

[0034] Performance test results show that the sealing initiation temperature of this packaging film is 90 degrees Celsius, and it can achieve complete heat sealing within a temperature range of 95 to 100 degrees Celsius, with a heat seal strength of 35 Newtons per 15 millimeters. The longitudinal tensile strength is 120 MPa, the transverse tensile strength is 110 MPa, the longitudinal elongation at break is 180%, and the transverse elongation at break is 200%. The haze value is 2.8%, the gloss is 95 degrees, and the light transmittance reaches 92%. The oxygen transmission rate is 50 cubic centimeters per square meter per day per 0.1 MPa, and the water vapor transmission rate is 4 grams per square meter per day.

[0035] The packaging film was applied to cigar boxes. The surface of the cigar box was coated with varnish, with a gloss level of 80 degrees. Packaging was performed using process parameters of 98 degrees Celsius heat sealing temperature, 0.4 MPa heat sealing pressure, and 0.8 seconds heat sealing time. After packaging, the varnish on the wooden box surface was found to be intact, with no peeling or adhesion. The packaging film adhered tightly to the wooden box, and the seal was secure. After 6 months of storage, the moisture content of the cigars remained stable, the aroma showed no significant change, and the quality was good.

[0036] Example 2 A copolymer of propylene and 1-octene was selected as the heat-sealing layer material 103, wherein the molar content of 1-octene was 12%. This copolymer was prepared using a metallocene catalytic system, employing titanium dioxide dichloride as the main catalyst and modified methylaluminoxane as the co-catalyst. The polymerization temperature was 65°C, the polymerization pressure was 3.0 MPa, and the polymerization time was 3.5 hours. The resulting propylene-1-octene copolymer had a melt flow rate of 4.0 g / 10 min, a density of 0.895 g / cm³, a Vicat softening point of 92°C, and a melting point of 115°C.

[0037] The packaging film is prepared using a three-layer co-extrusion blow molding process. The substrate layer 101 is made of biaxially oriented polypropylene with a density of 0.905 g / cm³ and a melt flow rate of 2.2 g / 10 min. The barrier layer 102 is made of ethylene-vinyl alcohol copolymer with an ethylene content of 32 mol%. The heat-sealing layer 103 is made of the aforementioned propylene-1-octene copolymer, with the addition of 0.6% synthetic silica as an anti-blocking agent, 0.5% oleamide as a slip agent, and 0.25% hindered phenolic antioxidant.

[0038] The first extruder processes the substrate layer 101 at a temperature set between 200°C and 230°C, with a screw speed of 95 rpm and an extrusion rate of 42 kg / h. The second extruder processes the barrier layer 102 at a temperature set between 205°C and 240°C, with a screw speed of 55 rpm and an extrusion rate of 10 kg / h. The third extruder processes the heat-sealing layer 103 at a temperature set between 170°C and 200°C, with a screw speed of 80 rpm and an extrusion rate of 28 kg / h. The co-extrusion die temperature is set at 215°C, and the die lip clearance is 1.6 mm. The cooling air temperature is 18°C, and the air velocity is 11 m / s. The traction speed is 50 m / min.

[0039] The resulting packaging film has a total thickness of 42 micrometers, with the substrate layer 101 having a thickness of 19 micrometers, the barrier layer 102 having a thickness of 6 micrometers, and the heat-sealing layer 103 having a thickness of 17 micrometers. The packaging film was then subjected to performance testing after being cured for 55 hours at 40 degrees Celsius and 60% relative humidity.

[0040] Performance test results show that the sealing initiation temperature of this packaging film is 87 degrees Celsius, and it can achieve complete heat sealing within a temperature range of 92 to 98 degrees Celsius, with a heat seal strength of 38 Newtons per 15 millimeters. The longitudinal tensile strength is 125 MPa, the transverse tensile strength is 115 MPa, the longitudinal elongation at break is 190%, and the transverse elongation at break is 210%. The haze value is 2.5%, the gloss is 96 degrees, and the light transmittance reaches 93%. The oxygen transmission rate is 45 cubic centimeters per square meter per day per 0.1 MPa, and the water vapor transmission rate is 3.5 grams per square meter per day.

[0041] This packaging film was applied to high-end cigar wooden boxes. The surface of the wooden box was covered with BOPP film and coated with varnish, achieving a surface gloss of 85 degrees. Packaging was performed using process parameters of 95 degrees Celsius heat sealing temperature, 0.35 MPa heat sealing pressure, and 0.7 seconds heat sealing time. After packaging, the BOPP film and varnish on the wooden box surface were inspected and found to be intact, with no peeling, adhesion, or damage. The packaging film adhered well to the wooden box, and the seal strength was high. After storage for 8 months at 25 degrees Celsius and 65% relative humidity, the moisture content, aroma, and taste of the cigars remained in good condition, and the product quality remained stable.

[0042] Example 3 A copolymer of propylene and 1-heptene was selected as the heat-sealing layer material 103, wherein the molar content of 1-heptene was 11%. This copolymer was prepared using a metallocene catalytic system, employing a mixture of zirconium dichloride and titanium dichloride as the main catalyst and methylaluminoxane as the co-catalyst. The polymerization temperature was 68°C, the polymerization pressure was 2.6 MPa, and the polymerization time was 3.2 hours. The resulting propylene-1-heptene copolymer had a melt flow rate of 3.8 g / 10 min, a density of 0.898 g / cm³, a Vicat softening point of 94°C, and a melting point of 116°C.

[0043] The packaging film is prepared using a three-layer co-extrusion blow molding process. The substrate layer 101 is made of biaxially oriented polypropylene with a density of 0.905 g / cm³ and a melt flow rate of 2.1 g / 10 min. The barrier layer 102 is a blend of polyamide 6 and ethylene-vinyl alcohol copolymer at a mass ratio of 3:2. The heat-sealing layer 103 is made of the aforementioned propylene-1-heptene copolymer, with the addition of 0.7% diatomaceous earth as an anti-blocking agent, 0.45% erucamide as a slip agent, and 0.18% hindered phenolic antioxidant.

[0044] The first extruder processes the substrate layer 101 at a temperature set between 198°C and 228°C, with a screw speed of 92 rpm and an extrusion rate of 44 kg / h. The second extruder processes the barrier layer 102 at a temperature set between 208°C and 238°C, with a screw speed of 58 rpm and an extrusion rate of 9 kg / h. The third extruder processes the heat-sealing layer 103 at a temperature set between 172°C and 202°C, with a screw speed of 78 rpm and an extrusion rate of 27 kg / h. The co-extrusion die temperature is set at 212°C, and the die lip clearance is 1.55 mm. The cooling air temperature is 19°C, and the air velocity is 10.5 m / s. The traction speed is 48 m / min.

[0045] The resulting packaging film has a total thickness of 41 micrometers, with the substrate layer 101 having a thickness of 20 micrometers, the barrier layer 102 having a thickness of 5 micrometers, and the heat-sealing layer 103 having a thickness of 16 micrometers. The packaging film was then subjected to performance testing after being cured for 58 hours at 42 degrees Celsius and 58% relative humidity.

[0046] Performance test results show that the packaging film has a sealing initiation temperature of 88 degrees Celsius and can achieve complete heat sealing within a temperature range of 93 to 99 degrees Celsius, with a heat seal strength of 36 Newtons per 15 millimeters. The longitudinal tensile strength is 122 MPa, the transverse tensile strength is 112 MPa, the longitudinal elongation at break is 185%, and the transverse elongation at break is 205%. The haze value is 2.6%, the gloss is 95.5 degrees, and the light transmittance reaches 92.5%. The oxygen transmission rate is 48 cubic centimeters per square meter per day per 0.1 MPa, and the water vapor transmission rate is 3.8 grams per square meter per day.

[0047] This packaging film was applied to a cigar wooden box packaging production line. The wooden box surface is coated with varnish, with a surface hardness of 2H. Automated packaging is performed using process parameters of 96 degrees Celsius heat sealing temperature, 0.38 MPa heat sealing pressure, and 0.75 seconds heat sealing time. The packaging efficiency reaches 60 boxes per minute, with a packaging qualification rate of 99.2%. The varnish on the packaged wooden box surface remains intact, without any heat damage, and the packaging film has a smooth and flat appearance with a firm and aesthetically pleasing seal. After 7 months of storage at room temperature, random sampling inspections showed that all physicochemical and sensory indicators of the cigars met product quality standards, resulting in high consumer satisfaction.

[0048] As can be seen from the above three embodiments, the co-extruded ultra-low temperature cigar box packaging film of the present invention successfully achieves ultra-low temperature heat sealing below 100 degrees Celsius, effectively solving the problem of damage to the varnish on the surface of the wooden box caused by excessively high heat sealing temperatures of traditional cigarette films. This packaging film possesses excellent heat-sealing performance, mechanical properties, and optical properties, while also exhibiting good barrier properties, effectively protecting the quality of the cigars. This product does not use adhesives, making it more environmentally friendly and in line with the development trend of green packaging, thus possessing good application prospects and market value.

[0049] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A co-extruded ultra-low temperature cigar box cigarette packaging film, characterized in that: The packaging film comprises a substrate layer, a barrier layer and a heat-seal layer which are sequentially co-extruded and compounded; The substrate layer is a biaxially stretched polypropylene film with a thickness of 15-25 microns; The barrier layer is polyamide or ethylene-vinyl alcohol copolymer with a thickness of 3-8 microns; The heat-seal layer is propylene alpha-olefin copolymer with 5-8 carbon atoms in the alpha-olefin, which is prepared by a metallocene catalytic system, and has a thickness of 10-20 microns.

2. A co-extruded ultra-low temperature cigar box packaging film according to claim 1, characterized in that: The alpha-olefin has 6-7 carbon atoms.

3. A co-extruded ultra-low temperature cigar box cigarette packaging film according to claim 1, characterized in that: The molar content of the alpha-olefin in the copolymer is 8%-15%.

4. A co-extruded ultra-low temperature cigar box cigarette packaging film according to claim 1, characterized by: The propylene alpha-olefin copolymer has a Vicat softening point of 90-105℃, a melting point of 110-125℃, and a seal initiation temperature of 85-100℃.

5. A co-extruded ultra-low temperature cigar box cigarette packaging film according to claim 1, characterized in that: The metallocene catalytic system comprises a metallocene compound which is a derivative of zirconocene or titanocene, and a co-catalyst which is methylaluminoxane or modified methylaluminoxane.

6. A co-extruded ultra-low temperature cigar box cigarette packaging film according to claim 1, characterized by: The heat-seal layer further comprises an anti-blocking agent, a slip agent and an antioxidant; the anti-blocking agent is diatomite or synthetic silicon dioxide with an addition amount of 0.3%-0.8%; the slip agent is erucic acid amide or oleic acid amide with an addition amount of 0.2%-0.6%; and the antioxidant is a hindered phenolic antioxidant with an addition amount of 0.1%-0.3%.

7. A co-extruded ultra-low temperature cigar box packaging film according to claim 1, characterized in that: The thickness of the substrate layer is 18-22 microns, the thickness of the barrier layer is 4-6 microns, the thickness of the heat-seal layer is 12-16 microns, and the total thickness of the packaging film is 35-45 microns.

8. A co-extruded ultra-low temperature cigar box packaging film according to claim 1, characterized in that: The alpha-olefin is 1-hexene, 1-heptene or 1-octene.

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