Anti-fog high-transparency BOPP heat-seal film and preparation method thereof

Abstract

The application provides a kind of anti-fog high-transmittance BOPP heat-seal film and its preparation method, anti-fog high-transmittance BOPP heat-seal film includes heat-seal anti-fog layer, core layer and surface layer in turn, the heat-seal anti-fog layer includes copolymerized polypropylene and composite anti-fog system, the proportion of the composite anti-fog system is 3-5 wt% of the mass of copolymerized polypropylene in the heat-seal anti-fog layer, the material of the core layer and the surface layer is all copolymerized polypropylene.The anti-fog high-transmittance BOPP heat-seal film of the application can significantly improve the anti-fog performance and durability of BOPP film through the synergistic effect of small molecules + nanomaterials and reactive monomers (HEMA + GMS) in the composite anti-fog agent system, combined with nano-dispersion and process optimization, reduce the migration of anti-fog agent through physical anchoring and chemical bonding, while maintaining the long-term stability of surface hydrophilicity.

Description

Technical Field

[0001] This invention belongs to the field of heat-sealing film, and in particular relates to an anti-fog high-transparency BOPP heat-sealing film and its preparation method. Background Technology

[0002] Anti-fog high-transparency BOPP (biaxially oriented polypropylene) heat-sealable film, as a high-end functional packaging material, has become the preferred material for packaging fresh food, flowers, mushrooms, and other commodities. Through formula upgrades and process innovations, it not only meets basic packaging requirements but also solves the visual obstruction problem caused by moisture condensation in traditional packaging. Currently, anti-fog high-transparency BOPP heat-sealable film generally adopts a multi-layer co-extrusion structure, typically consisting of a heat-sealing anti-fog layer, an intermediate support layer, and a functional surface layer. This layered design allows each layer to independently perform different functions, optimizing functionality while ensuring overall performance.

[0003] Heat-sealed anti-fogging layers typically incorporate anti-fogging agents to condense water vapor into a uniform water film rather than mist-like droplets. Traditional single anti-fogging agents have limited effectiveness in high or low temperature environments, while compound anti-fogging systems broaden their applicable temperature range through synergistic effects. For example, the combination of nonionic surfactants and zwitterionic compounds allows the film to maintain the E-grade anti-fogging standard (fog dissipates within 5 seconds) under both refrigerated (4°C) and room temperature (25°C) conditions. Furthermore, patent CN116141790A discloses the introduction of reactive groups (such as acid anhydride modifiers) into the anti-fogging layer, which improves the compatibility of the anti-fogging agent with the polypropylene substrate and reduces performance degradation caused by additive precipitation.

[0004] Currently, most mainstream antifogging agents are small-molecule surfactants (such as polyol fatty acid esters). These surfactants exert their antifogging effect by migrating from the polypropylene matrix to the surface. However, this migration process is difficult to control stably, and the antifogging effect of the film decreases significantly after a period of time. How to achieve both high transparency and antifogging performance while ensuring service life is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention aims to overcome the defects in the prior art and proposes an anti-fog high-transparency BOPP heat-sealing film and its preparation method.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] In a first aspect, the present invention provides an anti-fog high-transparency BOPP heat-sealable film, comprising a heat-sealable anti-fog layer, a core layer, and a surface layer, wherein the heat-sealable anti-fog layer comprises copolymer polypropylene and a composite anti-fog system, wherein the proportion of the composite anti-fog system is 3-5 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer, and the core layer and the surface layer are both made of copolymer polypropylene.

[0008] Preferably, the composite anti-fogging system comprises a first composite anti-fogging agent and a second composite anti-fogging agent in a mass ratio of (3-10):1.

[0009] Preferably, the first composite antifogging agent comprises polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles in a mass ratio of (50-100):(0.01-0.05):(0.1-1).

[0010] Preferably, the second composite antifogging agent comprises hydroxyethyl methacrylate (HEMA) and glyceryl monostearate (GMS) in a mass ratio of (3-8):(5-15).

[0011] Preferably, the preparation method of the first composite antifogging agent is as follows: after mixing polyvinyl alcohol solution with α-ZrP nanosheets, aminated nano-SiO2 particles are added and stirred until uniformly mixed to obtain the first composite antifogging agent.

[0012] Preferably, the second composite antifogging agent is prepared by heating and melting glyceryl monostearate, adding hydroxyethyl methacrylate, an initiator and an antioxidant, and then extruding and granulating the mixture using a twin-screw extruder.

[0013] Preferably, the initiator is selected from at least one of benzoyl peroxide, dicumyl peroxide, and tert-butyl peroxide.

[0014] Preferably, the antioxidant is selected from at least one of antioxidant 1010, antioxidant 168, antioxidant 1330, and antioxidant 3113.

[0015] Secondly, the present invention also provides a method for preparing the aforementioned anti-fog high-transparency BOPP heat-sealing film, comprising the following steps:

[0016] Copolymer polypropylene is added to the main extruder and heated to a molten state to serve as the main extrusion melt for the core layer. The raw materials for the heat-sealing anti-fog layer and the surface layer are added to the extruder and melted to obtain the melts for the heat-sealing anti-fog layer and the surface layer, respectively. The above melts are combined and extruded into a film in a three-layer structure die at a combined extrusion temperature of 190-220℃. After cooling, a sheet is formed. The sheet is then stretched longitudinally and laterally to obtain an anti-fog high-transparency BOPP heat-sealing film.

[0017] Preferably, the longitudinal stretching ratio is 4.5-5.0 times, and the transverse stretching ratio is 4.0-5.5 times.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The anti-fogging high-transparency BOPP heat-sealing film of the present invention can significantly improve the anti-fogging performance and durability of BOPP film by combining the synergistic effect of small molecules + nanomaterials and reactive monomers (HEMA + GMS) in the composite anti-fogging agent system with nano-dispersion and process optimization. It can also reduce the migration of anti-fogging agent through physical anchoring and chemical bonding, while maintaining the long-term stability of surface hydrophilicity.

[0020] (2) In the anti-fog high-transparency BOPP heat-sealing film of the present invention, the α-ZrP nanosheets and nano-SiO2 particles of the first composite anti-fog agent are anchored by phosphate group hydrogen bonds and cooperate with the physical confinement between layers to construct a relatively closed "molecular cage", which hinders the migration path of PVA and slows down the migration speed of PVA to the surface. This is significantly better than other layered materials or nanomaterials, and provides an innovative solution for BOPP film that combines long-term anti-fog and mechanical reinforcement.

[0021] (3) In the anti-fogging high-transparency BOPP heat-sealing film of the present invention, the second composite anti-fogging agent HEMA and GMS work together to achieve ultra-long-lasting transparency of the BOPP heat-sealing film. Due to its small molecular weight and low migration activation energy, GMS quickly diffuses to the film surface and quickly establishes a hydrophilic surface, solving the anti-fogging requirement in the early stage of film use. After polymerization, HEMA forms a network embedded in the PP matrix. It has a high migration activation energy and provides long-lasting water-locking ability through high-density hydroxyl groups and three-dimensional structure, and its anti-migration properties are significantly improved. Detailed Implementation

[0022] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] In this document, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0024] In this document, when values ​​are described as ranges, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as the specific numerical values ​​falling within that range, regardless of whether the specific numerical value or specific subrange is explicitly specified.

[0025] In this article, the terms "multiple" or "more than" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0026] In this document, the terms "preferred" and "more preferred" are used only to describe implementation methods or embodiments with better effects, and should be understood as not constituting a limitation on the scope of protection of this invention.

[0027] In this document, terms such as "further" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0028] In this article, the term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0029] In this document, the term "about" means + / - 10% of a specified value, preferably + / - 5%, and more preferably + / - 1%.

[0030] In this article, the terms “include,” “including,” “have,” “contain,” etc., are all open-ended terms, meaning that they include but are not limited to.

[0031] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0032] The present invention will be described in detail below with reference to the embodiments.

[0033] The preparation method of BOPP heat-sealing film in the following examples and comparative examples includes the following steps: Copolymer polypropylene (with a melt index of 5 g / 10 min measured at 230°C and 2.16 kg) is added to the main extruder and heated to a molten state as the main extrusion melt for the core layer; the raw materials of heat-sealing anti-fog layer and surface layer, copolymer polypropylene, are added to the extruder and melted to obtain the melts for heat-sealing anti-fog layer and surface layer, respectively; the above melts are combined and extruded into a film in a three-layer structure die at an extrusion temperature of 220°C, cooled to form a sheet, and the sheet is stretched longitudinally by 4.5 times and transversely by 5.0 times to obtain BOPP heat-sealing film, wherein the total thickness of BOPP heat-sealing film is 25 µm, the thickness of the surface layer is 5 µm, the thickness of the core layer is 18 µm, and the thickness of the heat-sealing anti-fog layer is 2 µm.

[0034] Example 1

[0035] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 3 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 3:1.

[0036] The preparation method of the first composite antifogging agent is as follows: 20 wt% polyvinyl alcohol solution is mixed with α-ZrP nanosheets, and then aminated nano-SiO2 particles are added and stirred until uniformly mixed to obtain the first composite antifogging agent. The mass ratio of polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles is 80:0.03:0.5.

[0037] The second composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 1010, and extruding and granulating the mixture using a twin-screw extruder. The mass ratio of HEMA to GMS is 1:2. The amounts of BPO and antioxidant 1010 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0038] Example 2

[0039] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 3 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 5:1.

[0040] The preparation method of the first composite antifogging agent is as follows: 20 wt% polyvinyl alcohol solution is mixed with α-ZrP nanosheets, and then aminated nano-SiO2 particles are added and stirred until uniformly mixed to obtain the first composite antifogging agent. The mass ratio of polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles is 50:0.01:0.1.

[0041] The second composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 1010, and extruding and granulating the mixture using a twin-screw extruder. The mass ratio of HEMA to GMS is 3:5. The amounts of BPO and antioxidant 1010 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0042] Example 3

[0043] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 5 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 8:1.

[0044] The preparation method of the first composite antifogging agent is as follows: 20 wt% polyvinyl alcohol solution is mixed with α-ZrP nanosheets, and then aminated nano-SiO2 particles are added and stirred until homogeneous to obtain the first composite antifogging agent. The mass ratio of polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles is 100:0.05:1.

[0045] The second composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 1330, and extruding and granulating the mixture using a twin-screw extruder. The mass ratio of HEMA to GMS is 8:15. The amounts of BPO and antioxidant 1330 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0046] Example 4

[0047] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 5 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 10:1.

[0048] The preparation method of the first composite antifogging agent is as follows: 20 wt% polyvinyl alcohol solution is mixed with α-ZrP nanosheets, and then aminated nano-SiO2 particles are added and stirred until homogeneous to obtain the first composite antifogging agent. The mass ratio of polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles is 60:0.02:0.5.

[0049] The second composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 3113, and extruding and granulating the mixture using a twin-screw extruder. The mass ratio of HEMA to GMS is 5:12. The amounts of BPO and antioxidant 3113 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0050] Comparative Example 1

[0051] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 3 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 3:1.

[0052] The preparation method of the first composite antifogging agent is as follows: 20 wt% polyvinyl alcohol solution is mixed with α-ZrP nanosheets, and then aminated nano-SiO2 particles are added and stirred until homogeneous to obtain the first composite antifogging agent. The mass ratio of polyvinyl alcohol to nano-SiO2 particles is 80:0.5.

[0053] The second composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 1010, and extruding and granulating the mixture using a twin-screw extruder. The mass ratio of HEMA to GMS is 1:2. The amounts of BPO and antioxidant 1010 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0054] Comparative Example 2

[0055] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 3 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 3:1.

[0056] The first composite antifogging agent is prepared by uniformly mixing a 20wt% polyvinyl alcohol solution with α-ZrP nanosheets. The mass ratio of polyvinyl alcohol to α-ZrP nanosheets is 80:0.03.

[0057] The second composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 1010, and extruding and granulating the mixture using a twin-screw extruder. The mass ratio of HEMA to GMS is 1:2. The amounts of BPO and antioxidant 1010 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0058] Comparative Example 3

[0059] A high-transparency anti-fog BOPP heat-sealable film comprises a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system. The composite anti-fog agent accounts for 3 wt% of the mass of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene.

[0060] The composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 1010, followed by extrusion granulation using a twin-screw extruder. The mass ratio of HEMA to GMS is 1:2. The amounts of BPO and antioxidant 1010 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0061] Comparative Example 4

[0062] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 3 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 3:1.

[0063] The preparation method of the first composite antifogging agent is as follows: 20 wt% polyvinyl alcohol solution is mixed with α-ZrP nanosheets, and then aminated nano-SiO2 particles are added and stirred until uniformly mixed to obtain the first composite antifogging agent. The mass ratio of polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles is 80:0.03:0.5.

[0064] The second composite antifogging agent is prepared by heating and melting GMS, then adding BPO and antioxidant 1010, and extruding and granulating the mixture using a twin-screw extruder. The amount of BPO and antioxidant 1010 added is 0.1 wt% of the mass of GMS.

[0065] Comparative Example 5

[0066] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 3 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 3:1.

[0067] The preparation method of the first composite antifogging agent is as follows: 20 wt% polyvinyl alcohol solution is mixed with α-ZrP nanosheets, and then aminated nano-SiO2 particles are added and stirred until uniformly mixed to obtain the first composite antifogging agent. The mass ratio of polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles is 80:0.03:0.5.

[0068] The second composite antifogging agent is prepared by extruding and granulating HEMA, BPO, and antioxidant 1010 using a twin-screw extruder. The amount of BPO and antioxidant 1010 added is 0.1 wt% of the total mass of HEMA.

[0069] Comparative Example 6

[0070] A high-transparency anti-fog BOPP heat-sealable film comprises a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system. The composite anti-fog system accounts for 3 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene.

[0071] The composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 1010, followed by extrusion granulation using a twin-screw extruder. The mass ratio of HEMA to GMS is 1:2. The amounts of BPO and antioxidant 1010 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0072] Comparative Example 7

[0073] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 7 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 3:1.

[0074] The preparation method of the first composite antifogging agent is as follows: 20 wt% polyvinyl alcohol solution is mixed with α-ZrP nanosheets, and then aminated nano-SiO2 particles are added and stirred until uniformly mixed to obtain the first composite antifogging agent. The mass ratio of polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles is 80:0.03:0.5.

[0075] The second composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 1010, and extruding and granulating the mixture using a twin-screw extruder. The mass ratio of HEMA to GMS is 1:2. The amounts of BPO and antioxidant 1010 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0076] Comparative Example 8

[0077] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 3 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 3:1.

[0078] The preparation method of the first composite antifogging agent is as follows: 20 wt% polyvinyl alcohol solution is mixed with α-ZrP nanosheets, and then aminated nano-SiO2 particles are added and stirred until uniformly mixed to obtain the first composite antifogging agent. The mass ratio of polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles is 80:0.1:0.5.

[0079] The second composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 1010, and extruding and granulating the mixture using a twin-screw extruder. The mass ratio of HEMA to GMS is 1:2. The amounts of BPO and antioxidant 1010 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0080] Comparative Example 9

[0081] A high-transparency anti-fog BOPP heat-sealable film comprises, in sequence, a heat-sealable anti-fog layer, a core layer, and a surface layer. The heat-sealable anti-fog layer is prepared from copolymer polypropylene and a composite anti-fog system, wherein the composite anti-fog system accounts for 3 wt% of the copolymer polypropylene in the heat-sealable anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system consists of a first composite anti-fog agent and a second composite anti-fog agent with a mass ratio of 3:1.

[0082] The preparation method of the first composite antifogging agent is as follows: 20 wt% polyvinyl alcohol solution is mixed with α-ZrP nanosheets, and then aminated nano-SiO2 particles are added and stirred until uniformly mixed to obtain the first composite antifogging agent. The mass ratio of polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles is 80:0.03:0.5.

[0083] The second composite antifogging agent is prepared by heating and melting GMS, then adding HEMA, BPO, and antioxidant 1010, and extruding and granulating the mixture using a twin-screw extruder. The mass ratio of HEMA to GMS is 2:1. The amounts of BPO and antioxidant 1010 added are both 0.1 wt% of the total mass of GMS and HEMA.

[0084] The BOPP heat-sealable films prepared in Examples 1-4 and Comparative Examples 1-6 were subjected to the following tests:

[0085] (1) Haze: The haze of BOPP heat-sealing film was tested according to the haze meter method in GB / T 2410-2008;

[0086] (2) Contact angle: The BOPP heat-sealing film was tested according to GB / T 10003-2008, and the 45° angle method was used for measurement;

[0087] To test the anti-fog life of the BOPP heat-sealable film, the BOPP heat-sealable films prepared in Examples 1-4 and Comparative Examples 1-6 were placed in a constant temperature and humidity test chamber for damp heat aging tests. After being kept at 85°C and 85% humidity for 1000 hours, they were removed. After removal, the haze and contact angle were measured respectively.

[0088] The test results are shown in the table below:

[0089]

[0090] As shown in the table above, the heat-sealing anti-fogging layer of the BOPP heat-sealing films in Comparative Examples 1-3 does not contain α-ZrP nanosheets, nano-SiO2 particles, or the first composite anti-fogging agent. This prevents the formation of physical confinement within the PP matrix, leading to excessively rapid migration of PVA to the surface and poor haze after hygrothermal aging. Combined with the data from Comparative Examples 4-6, it can be seen that the synergistic effect of HEMA and GMS in the second composite anti-fogging agent extends the hydrophilicity of the BOPP heat-sealing film both in the initial use phase and after prolonged use. Comparative Examples 3 and 6 demonstrate that both the first composite anti-fogging agent and the second anti-fogging agent are indispensable. Physical anchoring and chemical bonding reduce anti-fogging agent migration and improve anti-fogging lifespan.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-transparency, anti-fog BOPP heat-sealing film, characterized in that: The product comprises, in sequence, a heat-sealed anti-fog layer, a core layer, and a surface layer. The heat-sealed anti-fog layer includes copolymer polypropylene and a composite anti-fog system. The composite anti-fog system accounts for 3-5 wt% of the copolymer polypropylene in the heat-sealed anti-fog layer. The core layer and the surface layer are both made of copolymer polypropylene. The composite anti-fog system includes a first composite anti-fog agent and a second composite anti-fog agent in a mass ratio of (3-10):

1. The first composite anti-fog agent includes polyvinyl alcohol, α-ZrP nanosheets, and nano-SiO2 particles in a mass ratio of (50-100):(0.01-0.05):(0.1-1). The second composite anti-fog agent includes hydroxyethyl methacrylate and glyceryl monostearate in a mass ratio of (3-8):(5-15).

2. The anti-fog high-transparency BOPP heat-sealing film according to claim 1, characterized in that: The preparation method of the first composite antifogging agent is as follows: after mixing polyvinyl alcohol solution with α-ZrP nanosheets, aminated nano-SiO2 particles are added and stirred until uniformly mixed to obtain the first composite antifogging agent.

3. The anti-fog high-transparency BOPP heat-sealing film according to claim 1, characterized in that: The second composite antifogging agent is prepared by heating and melting glyceryl monostearate, adding hydroxyethyl methacrylate, an initiator and an antioxidant, and then extruding and granulating it using a twin-screw extruder.

4. The anti-fog high-transparency BOPP heat-sealing film according to claim 3, characterized in that: The initiator is selected from at least one of benzoyl peroxide, dicumyl peroxide, and tert-butyl peroxide.

5. The anti-fog high-transparency BOPP heat-sealing film according to claim 3, characterized in that: The antioxidant is selected from at least one of antioxidant 1010, antioxidant 168, antioxidant 1330, and antioxidant 3113.

6. The method for preparing the anti-fog high-transparency BOPP heat-sealing film according to any one of claims 1-5, characterized in that: Includes the following steps: Copolymer polypropylene is added to the main extruder and heated to a molten state to serve as the main extrusion melt for the core layer; the raw materials for the heat-sealing anti-fog layer and the surface layer are added to the extruder and melted to obtain the melts for the heat-sealing anti-fog layer and the surface layer, respectively. The above melt is extruded into a film in a three-layer die head. The extrusion temperature is 190-220℃. After cooling, a sheet is formed. The sheet is then stretched longitudinally and laterally to obtain an anti-fog high-transparency BOPP heat-sealing film.

7. The method for preparing the anti-fog high-transparency BOPP heat-sealing film according to claim 6, characterized in that: The longitudinal stretching ratio is 4.5-5.0 times, and the transverse stretching ratio is 4.0-5.5 times.

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