A multilayer co-extruded linear easy-tear heat-sealable BOPA film and its preparation method

Abstract

This invention relates to the field of film packaging, and particularly to a multi-layer co-extruded, straight-line easy-tear, heat-sealable BOPA film and its preparation method. The multi-layer co-extruded, straight-line easy-tear, heat-sealable BOPA film provided by this invention has a film structure comprising a toughening anti-stick layer, a straight-line easy-tear layer, a barrier core layer, an adhesive layer, and a heat-sealable layer. The toughening anti-stick layer enhances the film's toughness and improves its mechanical properties. The straight-line easy-tear layer not only provides the film with straight-line easy-tear properties, but the aromatic polyamide resin or long-chain aliphatic polyamide resin in its raw materials also synergistically improves the barrier properties with the barrier core layer. The adhesive layer uses maleic anhydride-grafted polyolefin to bond the barrier core layer and the heat-sealable layer, resulting in high material compatibility. This invention also provides a method for preparing the multi-layer co-extruded, straight-line easy-tear, heat-sealable BOPA film, employing multi-layer co-extrusion and biaxial stretching technology to produce a packaging film with good barrier properties, straight-line easy-tear properties, heat-sealable properties, and mechanical properties in one step.

Description

Technical Field

[0001] This invention relates to the field of film packaging, and in particular to a multilayer co-extruded linear easy-tear heat-sealable BOPA film and its preparation method. Background Technology

[0002] BOPA film is widely used in flexible packaging due to its excellent mechanical strength, puncture resistance, transparency, oil and chemical solvent resistance, and non-toxicity. However, because nylon has a high melting point, it lacks heat-sealing properties. Current technology typically involves laminating nylon with heat-sealable polyolefin materials such as polypropylene and polyethylene using solvent-based adhesives for packaging applications. However, this method usually produces a thicker heat-sealable layer, and the added adhesive lamination process increases production costs and, to some extent, limits the full realization of the inherent advantages of nylon film.

[0003] Furthermore, as packaging materials, they also need to possess good barrier properties and tear resistance to extend the shelf life of the contents, protect their quality, and optimize the customer's user experience. However, in actual production, integrating these functions requires additional processes such as coating and lamination, which increases production costs and impacts productivity.

[0004] Chinese patent CN213108563U disclosed a composite film for packaging on May 4, 2021. The film structure includes a polyester layer, an ink layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, a toughened nylon layer, a third adhesive layer, a polyethylene layer, a fourth adhesive layer, and a heat-sealable nylon layer. It exhibits excellent barrier properties, mechanical strength, and toughness. The total film thickness is 68-148 μm. Specifically, the polyethylene layer has a thickness of 12-30 μm, the fourth adhesive layer is a water-based acrylic adhesive or a two-component polyurethane adhesive with an independent thickness of 2-5 μm, and the heat-sealable nylon layer has a thickness of 15-30 μm, comprising a heat-sealable nylon surface layer, a nylon core layer, and a nylon outer layer. It is evident that in existing technologies, achieving the heat-sealability of nylon requires a sacrifice in film thickness.

[0005] Therefore, how to achieve good barrier properties, easy tearing, heat sealing and mechanical properties of film through one-step processing is still an urgent problem to be solved to further broaden the application fields of film. Summary of the Invention

[0006] To address the technical challenge of achieving excellent barrier properties, easy tearing, heat sealing, and mechanical properties in a single-step processing method, this invention provides a multi-layer co-extruded, easy-tear, heat-sealable BOPA film. The film structure comprises, from top to bottom, a toughening anti-stick layer, an easy-tear layer, a barrier core layer, an adhesive layer, and a heat-sealable layer.

[0007] By weight percentage, the toughened anti-blocking layer comprises 0.01% to 1% anti-blocking agent, 0.01% to 1% slip agent, and 98% to 99.98% toughened nylon resin;

[0008] The straight tear-off layer comprises 10% to 30% special nylon resin and 70% to 90% nylon 6 resin.

[0009] The barrier core layer comprises 100% EVOH resin;

[0010] The adhesive layer comprises 100% maleic anhydride grafts;

[0011] The heat-sealing layer comprises 0.5% to 2% anti-blocking agent, 0.5% to 2% slip agent, and 96% to 99% heat-sealing resin.

[0012] In one embodiment, the anti-blocking agent is composed of any one or more of silica, talc, and calcium carbonate.

[0013] In one embodiment, the slip agent is composed of any one or more of PE wax, erucamide, and oleamide.

[0014] In one embodiment, the toughened nylon resin is any one or more of PA6-b-12 copolymer, PA6-b-1010 copolymer, and PA6-b-PEG copolymer.

[0015] In one embodiment, the special nylon resin is an aromatic polyamide resin or a long-chain aliphatic polyamide resin, or a mixture of the two in a weight percentage ratio of (5~7):(3~5).

[0016] Furthermore, the aromatic polyamide resin is formed by the condensation polymerization of an aliphatic dicarboxylic acid with 6 to 12 carbon atoms and an aromatic diamine, or by the condensation polymerization of an aromatic diacid and an aliphatic diamine with 6 to 12 carbon atoms; the long-chain aliphatic polyamide resin is formed by the condensation polymerization of an aliphatic dicarboxylic acid with 4 to 18 carbon atoms and an aliphatic diamine with 4 to 18 carbon atoms.

[0017] In one embodiment, the maleic anhydride graft is either PE-g-MHA or PP-g-MHA.

[0018] In one embodiment, the heat-sealing resin is composed of any one or more of PE, modified PE, ternary copolymer PP, and modified PP.

[0019] In one embodiment, the total thickness of the multilayer co-extruded linear easy-tear heat-sealable BOPA film is 30~60μm; wherein, the thickness ratio of the toughening anti-stick layer, linear easy-tear layer, barrier core layer, adhesive layer and heat-sealable layer is (1~2):(2~3):(4~5):(1~2):(2~3).

[0020] The present invention also provides a method for preparing the multilayer co-extruded linear easy-tear heat-sealable BOPA film as described above, comprising the following steps:

[0021] The raw materials for the toughening anti-stick layer, the straight easy-tear layer, the barrier core layer, the adhesive layer and the heat-sealing layer are fed into extruder 1, extruder 2, extruder 3, extruder 4 and extruder 5 respectively according to the weight percentage, melted, plasticized and extruded, and flowed out through the T-die to form a molten sheet;

[0022] The film is cooled and solidified into a thick sheet by the action of a chilling roller and a high-pressure air knife.

[0023] The cast sheet is water-treated and then subjected to synchronous biaxial stretching.

[0024] The stretched film is heat-set, then cooled and corona-treated, and then wound up to obtain the multilayer co-extruded straight easy-tear heat-sealable BOPA film.

[0025] The extruder melting temperature is 220~250℃, the quench roll temperature is 30~60℃, the biaxial synchronous stretching temperature is 150~205℃, the stretching ratio is (3.0~3.6)×(3.0~3.6), and the heat setting temperature is 160~210℃.

[0026] The present invention provides a multi-layer co-extruded, straight-line easy-tear, heat-sealable BOPA film, the film structure of which includes a toughening anti-stick layer, a straight-line easy-tear layer, a barrier core layer, an adhesive layer, and a heat-sealable layer. The toughening anti-stick layer enhances the toughness of the film and improves its mechanical properties. The straight-line easy-tear layer not only provides the film with straight-line easy tearing, enhancing the user experience, but the aromatic polyamide resin or long-chain aliphatic polyamide resin in its raw materials can also improve the barrier properties to a certain extent. Working synergistically with the barrier core layer, the film obtains excellent oxygen barrier properties, which is beneficial for food packaging preservation. The adhesive layer uses maleic anhydride-grafted polyolefin as the adhesive resin to bond the barrier core layer and the heat-sealable layer, increasing material compatibility, avoiding film delamination, and improving film quality and appearance.

[0027] The present invention provides a method for preparing a multi-layer co-extruded, straight-line easy-tear, heat-sealable BOPA film, which adopts multi-layer co-extrusion and biaxial stretching technology, and can be formed in one step without glue lamination, thus producing a packaging film with good barrier properties, straight-line easy tearing, heat-sealable properties and mechanical properties.

[0028] In summary, compared with the prior art, the multi-layer co-extruded linear easy-tear heat-sealable BOPA film and its preparation method provided by the present invention can be prepared in one step without glue lamination, producing a packaging film that combines barrier properties, linear easy tearing, heat sealing and mechanical properties. It has good material compatibility and high film quality, and has full practical value. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the multilayer co-extruded linear easy-tear heat-sealable BOPA film structure provided in Embodiment 1 of the present invention.

[0031] Figure label:

[0032] Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] In the description of this invention, it should be noted that the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] Example 1

[0036] This embodiment provides a multilayer co-extruded, straight, easy-tear, heat-sealable BOPA film, such as... Figure 1As shown, its film structure includes, from top to bottom, a toughening anti-stick layer 10, a straight easy-tear layer 20, a barrier core layer 30, an adhesive layer 40, and a heat-sealing layer 50; the total thickness of the film is 33 μm, wherein the thickness ratio of the toughening anti-stick layer, the straight easy-tear layer, the barrier core layer, the adhesive layer, and the heat-sealing layer is 1:2:4:1:3.

[0037] The multilayer co-extruded linear easy-tear heat-sealable BOPA film is prepared according to the following steps:

[0038] The raw materials for the toughening anti-stick layer, the straight easy-tear layer, the barrier core layer, the adhesive layer and the heat-sealing layer are fed into extruder 1, extruder 2, extruder 3, extruder 4 and extruder 5 respectively according to the weight percentage. They are melted, plasticized and extruded at 220~250℃ and flow out through the T-die to form a molten sheet.

[0039] It is cooled and solidified into a thick sheet by the action of a 45°C chiller roller and a high-pressure air knife;

[0040] The cast sheet was water-treated and then subjected to synchronous biaxial stretching at a temperature of 180°C and a stretching ratio of 3.2 × 3.2.

[0041] The stretched film is heat-set at 200°C, then cooled and corona-treated before being wound up to obtain the multilayer co-extruded straight easy-tear heat-sealable BOPA film.

[0042] In this embodiment, preferably, the raw materials of the toughening and anti-sticking layer are: 0.5% anti-blocking agent, 0.5% slip agent and 99% toughening nylon resin by weight percentage; wherein, the anti-blocking agent is silica, the slip agent is a mixture of erucamide and oleamide in a weight percentage ratio of 4:1, and the toughening nylon resin is PA6-b-12 copolymer.

[0043] In this embodiment, preferably, the raw materials of the straight tear-off layer are: 10% special nylon resin and 90% nylon 6 resin by weight percentage; wherein, the special nylon resin is an aromatic polyamide resin, which is formed by the condensation polymerization of aliphatic dicarboxylic acid with 6 carbon atoms and m-phenylenediamine.

[0044] In this embodiment, preferably, the raw material of the barrier core layer is 100% EVOH resin by weight.

[0045] In this embodiment, preferably, the raw material of the adhesive layer is 100% maleic anhydride graft by weight; wherein, the maleic anhydride graft is a PE-g-MHA copolymer.

[0046] In this embodiment, preferably, the raw materials of the heat-sealing layer are 1% by weight of an anti-blocking agent, 1% of a slip agent, and 98% of a heat-sealing resin; wherein the anti-blocking agent is talc, the slip agent is PE wax, and the heat-sealing resin is LLDPE resin.

[0047] Example 2

[0048] This embodiment provides a multilayer co-extruded, straight-line, easy-tear, heat-sealable BOPA film; wherein the toughening anti-stick layer contains a PA6-b-1010 copolymer as the toughening nylon resin; the raw materials of the straight-line easy-tear layer are 15% by weight of a special nylon resin and 85% by weight of nylon 6 resin, and the special nylon resin is an aromatic polyamide resin. The remaining raw materials, proportions, and preparation steps are the same as in Example 1.

[0049] Example 3

[0050] This embodiment provides a multilayer co-extruded, linear, easy-tear, heat-sealable BOPA film; wherein the toughening anti-stick layer contains a PA6-b-PEG copolymer as the toughening nylon resin; the linear easy-tear layer is composed of 20% by weight of a special nylon resin and 80% by weight of nylon 6 resin, and the special nylon resin is a long-chain aliphatic polyamide resin, formed by the condensation polymerization of sebacic acid and pentanediamine. The remaining raw materials, proportions, and preparation steps are the same as in Example 1.

[0051] Comparative Example 1

[0052] This comparative example is a commercially available EHA film product. The EHA film is prepared by co-extrusion biaxial stretching of five layers of PA6, PA6, EVOH, PA6 and PA6, and does not have heat-sealing and straight tear-resistant properties.

[0053] Comparative Example 2

[0054] The difference between this comparative example and Example 1 of the present invention is that the toughening anti-stick layer is replaced with an anti-stick layer, and the raw materials of the anti-stick layer are 0.5% by weight of an anti-blocking agent, 0.5% by weight of a slip agent, and 99% by weight of PA6 resin, wherein the anti-blocking agent is silica, and the slip agent is a mixture of erucamide and oleamide in a weight ratio of 4:1; the raw materials of the straight easy-tear layer are 15% by weight of a special nylon resin and 85% by weight of nylon 6 resin, and the special nylon resin is an aromatic polyamide resin. The remaining raw materials, proportions, and preparation steps are the same as in Example 1.

[0055] Comparative Example 3

[0056] The difference between this comparative example and Example 1 of the present invention is that the straight tear-resistant layer is replaced with a nylon resin layer, and the raw material of the nylon resin layer is 100% nylon 6 resin by weight. The remaining raw materials, proportions, and preparation steps are the same as in Example 1.

[0057] Comparative Example 4

[0058] The difference between this comparative example and Example 1 of the present invention is that the adhesive layer is replaced with a nylon resin layer, and the raw material of the nylon resin layer is 100% nylon 6 resin by weight. The remaining raw materials, proportions, and preparation steps are the same as in Example 1.

[0059] Comparative Example 5

[0060] The difference between this comparative example and Example 1 of the present invention is that the heat-sealing layer is replaced with a nylon resin layer, and the raw materials of the nylon resin layer are 1% by weight of anti-blocking agent, 1% of slip agent and 98% of nylon 6 resin, wherein the anti-blocking agent is talc and the slip agent is PE wax. The remaining raw materials, proportions and preparation steps are the same as in Example 1.

[0061] The performance of the multilayer co-extruded linear easy-tear heat-sealable BOPA film prepared in Examples 1-3, the EHA film provided in Comparative Example 1, and the BOPA film prepared in Comparative Examples 2-5 were tested.

[0062] Tensile strength and elongation at break were tested in accordance with GB / T 20218-2021 Biaxially oriented polyamide (nylon) films;

[0063] Oxygen permeability was tested according to ASTM F1927;

[0064] Straight-line tear performance evaluation: 25 film samples were tested separately. A film with a length (MD direction) and width (TD direction) of 220 mm × 40 mm was cut. A 20 mm tear was cut in the middle of the film. The film was then torn 200 mm at a constant speed along the tear direction. The maximum distance of the tear from the center line of the tear opening during the tearing process was measured, i.e., the deviation displacement S. β If the tear displacement S0 is 200 mm, the average deviation displacement S β If the thickness is ≤6 mm, the film has good straight tear resistance, marked as ▲; otherwise, the film has poor straight tear resistance or no straight tear resistance, marked as ×.

[0065] Heat sealability evaluation: The heat sealability is tested according to QB / T 2358-1998 Test method for heat seal strength of plastic film packaging bags. Good heat sealability is marked as ▲, and poor heat sealability or no heat sealability is marked as ×.

[0066] The thin film performance test results provided in Examples 1-3 and Comparative Examples 1-5 are listed in Table 1:

[0067] Table 1. Performance test results of the thin films provided in Examples 1-3 and Comparative Examples 1-5

[0068]

[0069] As shown in Table 1, the tensile strength, elongation at break, and oxygen permeability of the multilayer co-extruded, straight-line easy-tear, heat-sealable BOPA films prepared in Examples 1-3 of this invention are significantly better than those of the commercially available EHA film provided in Comparative Example 1. Furthermore, the BOPA film provided by this invention, in addition to meeting the requirements for film packaging toughness and barrier properties, also possesses straight-line easy-tear and heat-sealable properties, and can be manufactured in one step without adhesive bonding, effectively solving the technical problem of how to achieve good barrier properties, straight-line easy-tear properties, heat-sealability, and mechanical properties in a one-step process.

[0070] Furthermore, according to the data in Table 1, replacing any one of the toughening anti-stick layer, straight easy-tear layer, adhesive layer, and heat-sealing layer in the film structure with a nylon resin layer will have a negative impact on the film performance, including but not limited to the impact on the film's mechanical properties, heat-sealing properties, or film quality.

[0071] Although this document frequently uses terms such as toughening and non-sticking, straight tear, adhesion, heat sealing, barrier properties, heat-sealing properties, multilayer co-extrusion, and biaxial stretching, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of this invention; interpreting them as any additional limitation would contradict the spirit of this invention.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-layer co-extruded, straight, easy-tear, heat-sealable BOPA film, characterized in that: Its membrane structure includes, from top to bottom, a toughening anti-stick layer, a straight easy-tear layer, a barrier core layer, an adhesive layer, and a heat-sealing layer; By weight percentage, the toughened anti-blocking layer comprises 0.01% to 1% anti-blocking agent, 0.01% to 1% slip agent, and 98% to 99.98% toughened nylon resin; The straight tear-off layer comprises 10% to 30% special nylon resin and 70% to 90% nylon 6 resin. The barrier core layer comprises 100% EVOH resin; The adhesive layer comprises 100% maleic anhydride grafts; The heat-sealing layer comprises 0.5% to 2% anti-blocking agent, 0.5% to 2% slip agent, and 96% to 99% heat-sealing resin; The toughened nylon resin is any one or any combination of PA6-b-12 copolymer, PA6-b-1010 copolymer and PA6-b-PEG copolymer; The special nylon resin is an aromatic polyamide resin or a long carbon chain aliphatic polyamide resin, or a mixture of the two in a weight percentage ratio of (5~7):(3~5); The maleic anhydride graft is either PE-g-MHA or PP-g-MHA; The heat-sealing resin is composed of any one or more of PE, modified PE, ternary copolymer PP, and modified PP.

2. The multilayer co-extruded linear easy-tear heat-sealable BOPA film according to claim 1, characterized in that: The anti-blocking agent is composed of any one or more of silicon dioxide, talc, and calcium carbonate.

3. The multilayer co-extruded linear easy-tear heat-sealable BOPA film according to claim 1, characterized in that: The slip agent is composed of any one or more of PE wax, erucamide, and oleamide.

4. The multilayer co-extruded linear easy-tear heat-sealable BOPA film according to claim 1, characterized in that: The aromatic polyamide resin is formed by the condensation polymerization of an aliphatic dicarboxylic acid with 6 to 12 carbon atoms and an aromatic diamine, or by the condensation polymerization of an aromatic dicarboxylic acid and an aliphatic diamine with 6 to 12 carbon atoms. The long-chain aliphatic polyamide resin is formed by the condensation polymerization of aliphatic dicarboxylic acids with 4 to 18 carbon atoms and aliphatic diamines with 4 to 18 carbon atoms.

5. The multilayer co-extruded linear easy-tear heat-sealable BOPA film according to claim 1, characterized in that: The total thickness of the multilayer co-extruded linear easy-tear heat-sealable BOPA film is 30~60 μm; The thickness ratio of the toughening anti-stick layer, the straight easy-tear layer, the barrier core layer, the adhesive layer and the heat-sealing layer is (1~2):(2~3):(4~5):(1~2):(2~3).

6. A method for preparing a multilayer co-extruded linear easy-tear heat-sealable BOPA film according to any one of claims 1 to 5, characterized in that, Includes the following steps: The raw materials for the toughening anti-stick layer, the straight easy-tear layer, the barrier core layer, the adhesive layer and the heat-sealing layer are fed into extruder 1, extruder 2, extruder 3, extruder 4 and extruder 5 respectively according to the weight percentage, melted, plasticized and extruded, and flowed out through the T-die to form a molten sheet; The film is cooled and solidified into a thick sheet by the action of a chilling roller and a high-pressure air knife. The cast sheet is water-treated and then subjected to synchronous biaxial stretching. The stretched film is heat-set, then cooled and corona-treated, and then wound up to obtain the multilayer co-extruded straight easy-tear heat-sealable BOPA film. The extruder melting temperature is 220~250℃, the quench roll temperature is 30~60℃, the biaxial synchronous stretching temperature is 150~205℃, the stretching ratio is (3.0~3.6)×(3.0~3.6), and the heat setting temperature is 160~210℃.

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