A BOPP functional film with high barrier properties

Abstract

The present invention relates to the technical field of BOPP films, and in particular to a BOPP functional film with high barrier properties, comprising a core layer and a first barrier layer and a second barrier layer attached to the upper and lower sides of the core layer; the barrier layer comprises elastic hydrophobic montmorillonite grafted modified polypropylene; a preparation process of the modified polypropylene comprises the following steps: adding dodecanediamine, a catalyst lithium hydroxide, and a solvent benzene into a reactor, and adding an epoxidized styrene-butadiene-styrene block copolymer, reacting to obtain a long-chain alkane-modified elastic material; adding the long-chain alkane-modified elastic material to an exfoliated montmorillonite suspension to obtain an elastic hydrophobic modified montmorillonite; and stirring the elastic hydrophobic montmorillonite and a coupling agent at a temperature of 70-120° C. for 2-4 hours, and then adding polypropylene to obtain the elastic hydrophobic montmorillonite grafted modified polypropylene. The present invention provides a BOPP film with high barrier properties, excellent mechanical properties, and environmental stability.

Description

Technical Field

[0001] The present invention relates to the technical field of BOPP films, and in particular to a BOPP functional film with high barrier properties. Background Art

[0002] Biaxially oriented polypropylene film has the advantages of light weight, high strength and high flatness, and is currently the most widely used film material.

[0003] Patent publication number CN113603965A discloses an environmentally friendly, long-lasting, high-wetting tension transparent BOPP masterbatch for transparent BOPP film. The masterbatch is composed of 60-80% polypropylene resin, 1-10% organically modified nano-montmorillonite, 3-10% polypropylene grafted with hydroxyethyl methacrylate, 2-10% polyamide-6, 5-15% ethylene-vinyl alcohol copolymer, 5-20% polyethylene methacrylic acid copolymer, and 0.2-1% thermal stabilizer. This invention addresses the issue of residual solvents by utilizing organically modified nano-montmorillonite to improve the polypropylene's structural refinement and act as a barrier agent to reduce the polypropylene's ability to bind to solvents.

[0004] Existing technologies improve barrier properties by adding materials such as montmorillonite. However, these methods present several technical challenges: Montmorillonite is a layered silicate, but unmodified montmorillonite exhibits a highly hydrophilic surface, poor compatibility with the hydrophobic polypropylene matrix, and tends to agglomerate into micron-sized particles. This not only reduces barrier efficiency but also causes interfacial defects, leading to film embrittlement and a significant decrease in tensile strength and impact resistance. Conventional montmorillonite is highly hygroscopic, and especially under high temperature and humidity conditions, moisture adsorbed between the montmorillonite layers can cause expansion, disrupting the film's microstructure and leading to a sharp decline in barrier properties. Summary of the Invention

[0005] The object of the present invention is to provide a BOPP film having high barrier properties, excellent mechanical properties and environmental stability.

[0006] The technical problems solved by the present invention are:

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A BOPP functional film with high barrier properties, comprising a core layer and a first barrier layer and a second barrier layer attached to the upper and lower sides of the core layer;

[0009] The barrier layer includes elastic hydrophobic montmorillonite grafted modified polypropylene and homopolymer polypropylene;

[0010] The preparation process of modified polypropylene comprises the following steps:

[0011] Step 1: Preparation of elastic hydrophobically modified montmorillonite

[0012] In a reactor, dodecanediamine, catalyst lithium hydroxide and solvent benzene are added, and epoxidized styrene-butadiene-styrene block copolymer is added at a temperature of 150°C. The reaction is carried out for 10-20 hours, and the reaction is cooled to room temperature to obtain a long-chain alkane-modified elastic material.

[0013] Adding a long-chain alkane-modified elastic material to the exfoliated montmorillonite suspension, stirring at 60-100° C. for 2-5 hours to obtain an elastic hydrophobically modified montmorillonite;

[0014] Step 2: Elastic hydrophobic montmorillonite grafted onto polypropylene

[0015] After stirring the elastic hydrophobic montmorillonite and the coupling agent at a temperature of 70-120° C. for 2-4 hours, polypropylene is added and stirred at a temperature of 50-90° C. for 2-4 hours to obtain the elastic hydrophobic montmorillonite graft-modified polypropylene.

[0016] As a further solution of the present invention: the barrier layer comprises the following raw materials in parts by weight: 20-30 parts of elastic hydrophobic montmorillonite grafted modified polypropylene, 70-80 parts of homopolypropylene; the core layer is homopolypropylene.

[0017] As a further solution of the present invention: the core layer is homopolymer polypropylene.

[0018] As a further solution of the present invention: the mass ratio of the elastic hydrophobic montmorillonite, the coupling agent and the polypropylene is 0.5-1:1-3:100.

[0019] As a further solution of the present invention, the mass ratio of dodecanediamine, epoxidized styrene-butadiene-styrene block copolymer, catalyst lithium hydroxide and solvent benzene is 34.8-40.6:100:0.5-1:800-1000.

[0020] As a further solution of the present invention: the mass ratio of montmorillonite to the elastic material modified by long-chain alkane is 100:50-160.

[0021] As a further solution of the present invention: Preparation of an exfoliated montmorillonite suspension: dissolving montmorillonite in deionized water to obtain an exfoliated montmorillonite suspension.

[0022] As a further solution of the present invention: the mass concentration of montmorillonite in the suspension is 0.1-2%.

[0023] As a further solution of the present invention: the montmorillonite is sodium montmorillonite.

[0024] As a further solution of the present invention: It is characterized in that the preparation process of the BOPP functional film comprises the following steps:

[0025] The raw materials of the first barrier layer, the core layer and the second barrier layer are melt-extruded separately to obtain the first barrier layer melt, the core layer melt and the second barrier layer melt, which are co-extruded through a three-layer structure die head and cooled and solidified at 30-35°C using a chilled roller to form a thick sheet;

[0026] The thick sheet is sequentially stretched longitudinally and transversely, then cooled and corona treated to obtain a high barrier BOPP film.

[0027] Beneficial effects of the present invention:

[0028] The present invention connects an epoxidized styrene-butadiene-styrene block copolymer to montmorillonite via dodecanediamine. Montmorillonite extends the permeation path through a "maze effect," thereby improving barrier properties. The hydrophobic modification of the montmorillonite by dodecanediamine effectively alleviates the hygroscopic expansion of the montmorillonite under high-temperature and high-humidity conditions, which can damage the BOPP film structure and reduce the long-term stability of its barrier properties. Furthermore, the styrene-butadiene-styrene block is a thermoplastic elastomer with excellent mechanical properties, elasticity, and compatibility, effectively improving the elastic tensile properties of the BOPP film during hot packaging. Furthermore, the styrene-butadiene-styrene block can compensate for the decrease in tensile properties of the BOPP film caused by the addition of montmorillonite.

[0029] And, long-chain alkane grafting and elastomer synergistic modification:

[0030] Montmorillonite is dually modified with dodecanediamine and epoxidized styrene-butadiene-styrene block copolymer (SBS), imparting both hydrophobicity and elasticity. The long-chain alkane (dodecanediamine) expands the interlayer spacing of the montmorillonite and reduces agglomeration; the SBS elastomer forms a flexible buffer network between the layers, enhancing interfacial toughness and avoiding the brittleness associated with traditional montmorillonite. This results in improved impact strength for the composite material.

[0031] Therefore, the BOPP film prepared by grafting elastic hydrophobic montmorillonite to modify polypropylene in the present invention effectively improves its barrier properties and overcomes the problems of reduced barrier properties and reduced tensile properties caused by high temperature and high humidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 This is a flow chart of a BOPP functional film with high barrier properties of the present invention;

[0034] In the figure, 1, first barrier layer; 2, core layer; 3, second barrier layer. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention. Example

[0036] like Figure 1 As shown, this embodiment provides a BOPP functional film with high barrier properties, including a core layer 2 and a first barrier layer 1 and a second barrier layer 3 attached to the upper and lower sides of the core layer 2;

[0037] The barrier layer comprises the following raw materials by weight: 200% elastic hydrophobic montmorillonite grafted modified polypropylene and 70% homopolymer polypropylene; the core layer 2 is homopolymer polypropylene;

[0038] The preparation process of modified polypropylene comprises the following steps:

[0039] Step 1: Preparation of elastic hydrophobically modified montmorillonite

[0040] Dodecanediamine, lithium hydroxide as a catalyst, and benzene as a solvent were added to a reactor, and the mixture was evacuated by nitrogen. The mixture was heated to 150°C at a heating rate of 2°C / min with stirring, and epoxidized styrene-butadiene-styrene block copolymer was added. The mixture was reacted for 10 hours, cooled to room temperature, washed with water, and the solvent was removed by rotary evaporation to obtain a long-chain alkane-modified elastic material.

[0041] Adding a long-chain alkane-modified elastic material to the exfoliated montmorillonite suspension, stirring at 60° C. for 2-5 hours, and after the reaction is completed, washing the product by centrifugation twice and drying to obtain an elastic hydrophobically modified montmorillonite;

[0042] Step 2: Elastic hydrophobic montmorillonite grafted onto polypropylene

[0043] After stirring the elastic hydrophobic montmorillonite and the coupling agent at 70°C for 2 hours, polypropylene was added and stirred at 50°C for 2 hours to obtain elastic hydrophobic montmorillonite grafted modified polypropylene;

[0044] The mass ratio of the elastic hydrophobic montmorillonite, the coupling agent and the polypropylene is 0.5:1:100; the coupling agent comprises a mixture of a silane coupling agent and a titanate coupling agent in a mass ratio of 3:7;

[0045] The mass ratio of dodecanediamine, epoxidized styrene-butadiene-styrene block copolymer, catalyst lithium hydroxide and solvent benzene is 34.8:100:0.5:800;

[0046] The mass ratio of montmorillonite to the long-chain alkane-modified elastic material is 100:50;

[0047] Preparation of an exfoliated montmorillonite suspension: dissolving montmorillonite in deionized water, and obtaining an exfoliated montmorillonite suspension under magnetic stirring, wherein the mass concentration of montmorillonite in the suspension is 0.1%; the montmorillonite is sodium montmorillonite;

[0048] This embodiment also provides a process for preparing a BOPP functional film with high barrier properties, comprising the following steps:

[0049] The raw materials of the first barrier layer 1, the core layer 2, and the second barrier layer 3 are melt-extruded separately to obtain the melt of the first barrier layer 1, the melt of the core layer 2, and the melt of the second barrier layer 3, which are co-extruded through a three-layer structure die and cooled and solidified at 30°C using a chilled roller to form a thick sheet;

[0050] The thick sheet is sequentially stretched longitudinally and transversely, then cooled and corona treated to obtain a high barrier BOPP film. Example

[0051] like Figure 1 As shown, this embodiment provides a BOPP functional film with high barrier properties, including a core layer 2 and a first barrier layer 1 and a second barrier layer 3 attached to the upper and lower sides of the core layer 2;

[0052] The barrier layer comprises the following raw materials by weight: 25% of elastic hydrophobic montmorillonite grafted modified polypropylene and 75% of homopolymer polypropylene; the core layer 2 is homopolymer polypropylene;

[0053] The preparation process of modified polypropylene comprises the following steps:

[0054] Step 1: Preparation of elastic hydrophobically modified montmorillonite

[0055] Dodecanediamine, lithium hydroxide as a catalyst, and benzene as a solvent were added to a reactor, and the mixture was evacuated by nitrogen. The mixture was heated to 150°C at a heating rate of 2°C / min with stirring, and epoxidized styrene-butadiene-styrene block copolymer was added. The mixture was reacted for 15 hours, cooled to room temperature, washed with water, and the solvent was removed by rotary evaporation to obtain a long-chain alkane-modified elastic material.

[0056] Adding a long-chain alkane-modified elastic material to the exfoliated montmorillonite suspension, stirring at 80° C. for 3 hours, and after the reaction is completed, washing the product by centrifugation 2-5 times and drying to obtain an elastic hydrophobically modified montmorillonite;

[0057] Step 2: Elastic hydrophobic montmorillonite grafted onto polypropylene

[0058] After stirring the elastic hydrophobic montmorillonite and the coupling agent at 90°C for 3 hours, polypropylene was added and stirred at 70°C for 3 hours to obtain elastic hydrophobic montmorillonite grafted modified polypropylene;

[0059] The mass ratio of the elastic hydrophobic montmorillonite, the coupling agent and the polypropylene is 0.8:2:100; the coupling agent comprises a mixture of a silane coupling agent and a titanate coupling agent in a mass ratio of 3:7;

[0060] The mass ratio of dodecanediamine, epoxidized styrene-butadiene-styrene block copolymer, catalyst lithium hydroxide and solvent benzene is 37.5:100:0.8:900;

[0061] The mass ratio of montmorillonite to the long-chain alkane-modified elastic material is 100:105;

[0062] Preparation of an exfoliated montmorillonite suspension: dissolving montmorillonite in deionized water, and obtaining an exfoliated montmorillonite suspension under magnetic stirring, wherein the montmorillonite mass concentration in the suspension is 1.2%; the montmorillonite is sodium montmorillonite;

[0063] This embodiment also provides a process for preparing a BOPP functional film with high barrier properties, comprising the following steps:

[0064] The raw materials of the first barrier layer 1, the core layer 2, and the second barrier layer 3 are melt-extruded separately to obtain the melt of the first barrier layer 1, the melt of the core layer 2, and the melt of the second barrier layer 3, which are co-extruded through a three-layer structure die and cooled and solidified at 33°C using a chilled roller to form a thick sheet;

[0065] The thick sheet is sequentially stretched longitudinally and transversely, then cooled and corona treated to obtain a high barrier BOPP film. Example

[0066] like Figure 1 As shown, this embodiment provides a BOPP functional film with high barrier properties, including a core layer 2 and a first barrier layer 1 and a second barrier layer 3 attached to the upper and lower sides of the core layer 2;

[0067] The barrier layer comprises the following raw materials by weight: 30% of elastic hydrophobic montmorillonite grafted modified polypropylene and 80% of homopolymer polypropylene; the core layer 2 is homopolymer polypropylene;

[0068] The preparation process of modified polypropylene comprises the following steps:

[0069] Step 1: Preparation of elastic hydrophobically modified montmorillonite

[0070] Dodecanediamine, lithium hydroxide as a catalyst, and benzene as a solvent were added to a reactor, and the mixture was evacuated by nitrogen. The mixture was heated to 150°C at a heating rate of 2°C / min with stirring, and epoxidized styrene-butadiene-styrene block copolymer was added. The mixture was reacted for 20 hours, cooled to room temperature, washed with water, and the solvent was removed by rotary evaporation to obtain a long-chain alkane-modified elastic material.

[0071] Adding a long-chain alkane-modified elastic material to the exfoliated montmorillonite suspension, stirring at 100°C for 5 hours, and after the reaction is completed, washing the product by centrifugation 5 times and drying to obtain an elastic hydrophobically modified montmorillonite;

[0072] Step 2: Elastic hydrophobic montmorillonite grafted onto polypropylene

[0073] Stirring the elastic hydrophobic montmorillonite and the coupling agent at 120°C for 2-4 hours, adding polypropylene, and stirring at 90°C for 4 hours to obtain elastic hydrophobic montmorillonite grafted modified polypropylene;

[0074] The mass ratio of the elastic hydrophobic montmorillonite, the coupling agent and the polypropylene is 1:3:100; the coupling agent comprises a mixture of a silane coupling agent and a titanate coupling agent in a mass ratio of 3:7;

[0075] The mass ratio of dodecanediamine, epoxidized styrene-butadiene-styrene block copolymer, catalyst lithium hydroxide and solvent benzene is 40.6:100:1:1000;

[0076] The mass ratio of montmorillonite to the long-chain alkane-modified elastic material is 100:160;

[0077] Preparation of an exfoliated montmorillonite suspension: dissolving montmorillonite in deionized water, and obtaining an exfoliated montmorillonite suspension under magnetic stirring, wherein the montmorillonite mass concentration in the suspension is 2%; the montmorillonite is sodium montmorillonite;

[0078] This embodiment also provides a process for preparing a BOPP functional film with high barrier properties, comprising the following steps:

[0079] The raw materials of the first barrier layer 1, the core layer 2, and the second barrier layer 3 are melt-extruded separately to obtain the melt of the first barrier layer 1, the melt of the core layer 2, and the melt of the second barrier layer 3, which are co-extruded through a three-layer structure die and cooled and solidified at 30°C using a chilled roller to form a thick sheet;

[0080] The thick sheet is sequentially stretched longitudinally and transversely, then cooled and corona treated to obtain a high barrier BOPP film.

[0081] Comparative Example 1

[0082] Comparative Example 1 uses the BOPP film disclosed in Example 1 of application publication number CN113603965A;

[0083] The BOPP films of Examples 1-3 and Comparative Example 1 were tested for barrier properties according to DB43 / T1168.5-2019. Mechanical properties were also tested. The test results are shown in Table 1.

[0084] <![CDATA[Water permeability (g / m 2 .24h)]]> <![CDATA[Oxygen permeability (cm 3 / m 2 .24h.atm)]]> Tensile strength (MPa) Example 1 1.16 35 137 Example 2 1.19 41 144 Example 3 1.23 43 148 Comparative Example 1 3.6 68 116

[0085] As can be seen from the above table, the BOPP films prepared by elastic hydrophobic montmorillonite grafted modified polypropylene in Examples 1-3 of the present invention have better high barrier properties and mechanical properties than the BOPP films of the prior art.

[0086] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A BOPP functional film with high barrier properties, characterized in that: It includes a core layer and a first barrier layer and a second barrier layer attached to the upper and lower sides of the core layer; The barrier layer includes homopolymer polypropylene and elastic hydrophobic montmorillonite grafted modified polypropylene; The preparation process of modified polypropylene comprises the following steps: Step 1: Preparation of elastic hydrophobically modified montmorillonite In a reactor, dodecanediamine, catalyst lithium hydroxide and solvent benzene are added, and epoxidized styrene-butadiene-styrene block copolymer is added at a temperature of 150°C. The reaction is carried out for 10-20 hours, and the reaction is cooled to room temperature to obtain a long-chain alkane-modified elastic material. Adding a long-chain alkane-modified elastic material to the exfoliated montmorillonite suspension, stirring at 60-100° C. for 2-5 hours to obtain an elastic hydrophobically modified montmorillonite; Step 2: Elastic hydrophobic montmorillonite grafted onto polypropylene After the elastic hydrophobic modified montmorillonite and the coupling agent are stirred at a temperature of 70-120° C. for 2-4 hours, polypropylene is added and stirred at a temperature of 50-90° C. for 2-4 hours to obtain the elastic hydrophobic montmorillonite grafted modified polypropylene.

2. The BOPP functional film with high barrier properties according to claim 1, characterized in that: The barrier layer comprises the following raw materials in parts by weight: 20-30 parts of elastic hydrophobic montmorillonite grafted modified polypropylene and 70-80 parts of homopolypropylene; the core layer is homopolypropylene.

3. The BOPP functional film with high barrier properties according to claim 1, characterized in that: The core layer is homopolymer polypropylene.

4. The BOPP functional film with high barrier properties according to claim 1, characterized in that: The mass ratio of the elastic hydrophobic montmorillonite, the coupling agent and the polypropylene is 0.5-1:1-3:

100.

5. The BOPP functional film with high barrier properties according to claim 1, characterized in that: The mass ratio of dodecanediamine, epoxidized styrene-butadiene-styrene block copolymer, catalyst lithium hydroxide and solvent benzene is 34.8-40.6:100:0.5-1:800-1000.

6. The BOPP functional film with high barrier properties according to claim 1, characterized in that: The mass ratio of montmorillonite to the long-chain alkane-modified elastic material is 100:50-160.

7. The BOPP functional film with high barrier properties according to claim 1, characterized in that: Preparation of exfoliated montmorillonite suspension: Montmorillonite was dissolved in deionized water to obtain an exfoliated montmorillonite suspension.

8. The BOPP functional film with high barrier properties according to claim 7, characterized in that: The mass concentration of montmorillonite in the suspension is 0.1-2%.

9. The BOPP functional film with high barrier properties according to claim 8, characterized in that: The montmorillonite is sodium montmorillonite.

10. The BOPP functional film with high barrier properties according to claim 1, characterized in that: The preparation process of BOPP functional film includes the following steps: The raw materials of the first barrier layer, the core layer and the second barrier layer are melt-extruded separately to obtain the first barrier layer melt, the core layer melt and the second barrier layer melt, which are co-extruded through a three-layer structure die head and cooled and solidified at 30-35°C using a chilled roller to form a thick sheet; The thick sheet is sequentially stretched longitudinally and transversely, then cooled and corona treated to obtain a high barrier BOPP film.

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