BOPP (biaxially-oriented polypropylene) ultralow-temperature high-speed heat-sealing film and preparation method thereof

Abstract

The invention relates to the technical field of film preparation, and particularly discloses a BOPP (biaxially-oriented polypropylene) ultralow-temperature high-speed heat-sealing film and a preparation method thereof. The BOPP ultralow-temperature high-speed heat sealing film comprises a surface layer I, a core layer and a surface layer II, wherein the thickness of the surface layer I accounts for 20-30% of the thickness of the whole film; the thickness of the core layer accounts for 40-60% of the thickness of the whole film; the thickness of the surface layer II accounts for 20-30% of the thickness of the whole film; the surface layer I and the core layer are prepared from homo-polypropylene; and the surface layer II is prepared from metallocene polypropylene and a slipping agent. The research shows that the BOPP ultralow-temperature high-speed heat-sealing film prepared from the material has the heat-sealing strength of greater than or equal to 2.0 N / 15mm at the ultralow temperature of 80 DEG C and the like; good heat sealing strength is shown; in addition, the haze is smaller than or equal to 2.0%, and the low haze is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of thin film preparation, and particularly relates to a BOPP ultra-low temperature and high-speed heat-sealing film and a preparation method thereof. Background Art

[0002] Biaxially oriented polypropylene film (BOPP) is widely used in the packaging of food, medicine, daily chemicals and other fields due to its excellent mechanical properties, optical properties and barrier properties. In recent years, with the continuous improvement of the requirements of the packaging industry for high-speed production, energy conservation and environmental protection, and packaging aesthetics, ultra-low temperature and high-speed heat-sealing BOPP film has become a research hotspot.

[0003] At present, ultra-low temperature and high-speed heat-sealing BOPP film is mainly achieved through the following two methods: Coextrusion method: A heat-sealing layer is coextruded on the surface of the BOPP base film. The heat-sealing layer material is usually an elastomer such as ethylene-propylene copolymer (EPC), ethylene-vinyl acetate copolymer (EVA), EMA, EAA, etc. This method has mature technology, but there are problems such as insufficient adhesion between the heat-sealing layer and the base film, and a narrow heat-sealing temperature range. Coating method: A heat-sealing coating is coated on the surface of the BOPP base film. The heat-sealing coating is usually polyurethane (PU), polyacrylate (PA), etc. This method can effectively reduce the heat-sealing temperature, but there are problems such as poor coating uniformity, low heat-sealing strength, and high cost.

[0004] Although the above methods have achieved ultra-low temperature and high-speed heat-sealing of BOPP film to a certain extent, there is still the problem of low heat-sealing strength at ultra-low temperature (80°C); therefore, it is of important application value to provide a BOPP ultra-low temperature and high-speed heat-sealing film with good heat-sealing strength at ultra-low temperatures such as 80°C. Summary of the Invention

[0005] In order to overcome at least one of the technical problems existing in the prior art, the present invention provides a BOPP ultra-low temperature and high-speed heat-sealing film and a preparation method thereof.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a BOPP ultra-low temperature and high-speed heat-sealing film, which includes a first surface layer, a core layer, and a second surface layer; wherein, the thickness of the first surface layer accounts for 20% - 30% of the total thickness of the film; the thickness of the core layer accounts for 40% - 60% of the total thickness of the film; the thickness of the second surface layer accounts for 20% - 30% of the total thickness of the film;

[0008] The raw materials for preparing the first surface layer and the core layer are homopolypropylene;

[0009] The raw materials for preparing the second surface layer include metallocene polypropylene and a slip agent.

[0010] The inventor has shown in the research that the BOPP ultra-low temperature and high-speed heat-sealing

[0011] film made of the above materials of the present invention has a heat-sealing strength ≥ 2.0 N / 15 mm at ultra-low temperatures such as 80 °C; it shows good heat-sealing strength.

[0012] Preferably, the weight ratio of metallocene polypropylene and slip agent in the raw materials for preparing the second layer is 98.5 - 99.5:0.5 - 1.5.

[0013] Most preferably, the weight ratio of metallocene polypropylene and slip agent in the raw materials for preparing the second layer is 99:1.

[0014] Preferably, the slip agent is composed of talcum powder and silica.

[0015] Preferably, the weight ratio of talcum powder and silica is 1:1 - 3.

[0016] Most preferably, the weight ratio of talcum powder and silica is 1:2.

[0017] Preferably, the slip agent is a modified slip agent;

[0018] The modified slip agent is prepared by the following method:

[0019] (1) Add talcum powder and silica into a high-speed mixer and conduct preliminary mixing for 3 - 10 min;

[0020] (2) Then add the modification liquid and continue mixing for 30 - 60 min to obtain a modified mixture;

[0021] (3) Dry the modified mixture to obtain the modified slip agent.

[0022] The inventor has found in a large number of experiments that in the BOPP ultra-low temperature and high-speed heat-sealing film, adding the modified slip agent prepared by the above method can significantly improve the heat-sealing strength of the BOPP ultra-low temperature and high-speed heat-sealing film at ultra-low temperatures compared to adding an unmodified slip agent.

[0023] In addition, the inventor has found that in the BOPP ultra-low temperature and high-speed heat-sealing film, adding the modified slip agent prepared by the above method can also significantly reduce the haze of the BOPP ultra-low temperature and high-speed heat-sealing film at ultra-low temperatures compared to adding an unmodified slip agent.

[0024] Preferably, the weight ratio of talcum powder and silica in step (1) is 1:1 - 3.

[0025] Most preferably, the weight ratio of talcum powder and silica is 1:2.

[0026] Preferably, the weight of the modification liquid added in step (2) is 20-40% of the total weight of talcum powder and silica.

[0027] Most preferably, the weight of the modification liquid added in step (2) is 30% of the total weight of talcum powder and silica.

[0028] Preferably, the modification liquid described in step (2) is specifically prepared by the following method:

[0029] Add the modifier to the ethanol solution, and stir to dissolve to obtain the modification liquid; the dosage ratio of the modifier to the ethanol solution is 150-200 g: 1 L.

[0030] Most preferably, the dosage ratio of the modifier to the ethanol solution is 175 g: 1 L.

[0031] Preferably, the ethanol solution is an aqueous ethanol solution with a volume fraction of 70-95%.

[0032] Most preferably, the ethanol solution is an aqueous ethanol solution with a volume fraction of 95%.

[0033] Preferably, the modifier is composed of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide, and coconut oil amide propyl hydroxysulfobetaine.

[0034] Preferably, the weight ratio of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide, and coconut oil amide propyl hydroxysulfobetaine in the modifier is 1-3: 1-3: 1-3.

[0035] Most preferably, the weight ratio of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide, and coconut oil amide propyl hydroxysulfobetaine in the modifier is 2: 1: 1.

[0036] The inventors found in the research that in the preparation process of the modified slip agent, the selection of the modifier is very crucial; in the BOPP ultra-low temperature high-speed heat-sealing film, it is necessary to add a modified slip agent modified by a modifier composed of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide, and coconut oil amide propyl hydroxysulfobetaine to significantly improve the heat-sealing strength of the BOPP ultra-low temperature high-speed heat-sealing film at ultra-low temperature; however, simply adding a modified slip agent modified by one or any two of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide, and coconut oil amide propyl hydroxysulfobetaine cannot significantly improve the heat-sealing strength of the BOPP ultra-low temperature high-speed heat-sealing film at ultra-low temperature.

[0037] Similarly, in the BOPP ultra-low temperature and high-speed heat-sealing film, a modified slip agent modified by a modifier composed of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide, and cocamidopropyl hydroxysulfobetaine must be added to significantly reduce the haze of the BOPP ultra-low temperature and high-speed heat-sealing film at ultra-low temperatures; however, simply adding a modified slip agent modified by a modifier composed of only one or any two of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide, and cocamidopropyl hydroxysulfobetaine cannot significantly reduce the haze of the BOPP ultra-low temperature and high-speed heat-sealing film at ultra-low temperatures.

[0038] Preferably, the rotation speed of the high-speed mixer is 1000 - 1500 revolutions per minute.

[0039] The present invention also provides a preparation method of the above-mentioned BOPP ultra-low temperature and high-speed heat-sealing film, which comprises the following steps:

[0040] Put the preparation raw materials of the first surface layer, the core layer, and the second surface layer into three extruders respectively, melt them and extrude them through a die head, and then obtain the BOPP ultra-low temperature and high-speed heat-sealing film after inflation cooling, film forming, corona treatment, and winding.

[0041] Beneficial effects: The present invention provides a brand-new BOPP ultra-low temperature and high-speed heat-sealing film; research shows that the BOPP ultra-low temperature and high-speed heat-sealing film made of the materials of the present invention has a heat-sealing strength ≥ 2.0 N / 15 mm at ultra-low temperatures such as 80°C, showing good heat-sealing strength; in addition, its haze is all ≤ 2.0%, having a low haze. Detailed implementation mode

[0042] The following specific examples are used to further explain the present invention, but the examples do not limit the present invention in any form.

[0043] The homopolypropylene used in the following examples is the homopolypropylene with the brand name H4540 from Hyundai of South Korea; the metallocene polypropylene used is the metallocene polypropylene with the brand name MPP4912 from Yanshan Petrochemical; the remaining raw materials without specified sources are all conventional raw materials that those skilled in the art can obtain through regular purchase channels.

[0044] Example 1 Preparation of BOPP ultra-low temperature and high-speed heat-sealing film

[0045] The ultra-low temperature and high-speed heat-sealing film includes a first surface layer, a core layer, and a second surface layer; wherein, the thickness of the first surface layer accounts for 25% of the total thickness of the film; the thickness of the core layer accounts for 50% of the total thickness of the film; the thickness of the second surface layer accounts for 25% of the total thickness of the film;

[0046] The raw materials for preparing the first surface layer and the core layer are homopolypropylene;

[0047] The raw materials for preparing the second surface layer consist of metallocene polypropylene and a slip agent; among them, the metallocene

[0048] polypropylene

[0049] and the slip agent are in a weight ratio of 99:1;

[0050] The slip agent in the second surface layer consists of talcum powder and silica in a weight ratio of 1:2.

[0051] Preparation method: The raw materials for preparing the first surface layer, the core layer and the second surface layer are respectively put into three extruders, melted and then extruded through a die head, and then obtained the BOPP ultra-low temperature and high-speed heat-sealing film after inflation cooling, film forming, corona treatment and winding.

[0052] Example 2 Preparation of BOPP ultra-low temperature and high-speed heat-sealing film

[0053] The ultra-low temperature and high-speed heat-sealing film includes a first surface layer, a core layer and a second surface layer; among them, the thickness of the first surface layer accounts for 25% of the total thickness of the film; the thickness of the core layer accounts for 50% of the total thickness of the film; the thickness of the second surface layer accounts for 25% of the total thickness of the film;

[0054] The raw materials for preparing the first surface layer and the core layer are homopolypropylene;

[0055] The raw materials for preparing the second surface layer consist of metallocene polypropylene and a slip agent; among them, the metallocene

[0056] polypropylene

[0057] and the slip agent are in a weight ratio of 99:1;

[0058] The slip agent in the second surface layer is a modified slip agent;

[0059] The preparation method of the modified slip agent is as follows:

[0060] (1) Add talcum powder and silica into a high-speed mixer and mix preliminarily at a speed of 1200 revolutions per minute for 5 minutes; among them, the weight ratio of talcum powder and silica is 1:2;

[0061] (2) Then add the modification liquid and continue to mix for 40 minutes to obtain a modified mixture; among them, the added weight of the modification liquid is 30% of the total weight of talcum powder and silica;

[0062] (3) Dry the modified mixture to obtain the modified slip agent;

[0063] The modified liquid described in step (2) is specifically prepared by the following method: adding a modifier to an ethanol solution, and stirring and dissolving to obtain the modified liquid; the dosage ratio of the modifier to the ethanol solution is 175 g: 1 L; the ethanol solution is an ethanol aqueous solution with a volume fraction of 95%; the modifier is composed of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide, and cocamidopropyl hydroxysultaine with a weight ratio of 2:1:1.

[0064] Preparation of Comparative Example 1 BOPP Ultra-Low Temperature and High-Speed Heat-Sealing Film

[0065] The ultra-low temperature and high-speed heat-sealing film described includes a first surface layer, a core layer, and a second surface layer; among them, the thickness of the first surface layer accounts for 25% of the total thickness of the film; the thickness of the core layer accounts for 50% of the total thickness of the film; the thickness of the second surface layer accounts for 25% of the total thickness of the film;

[0066] The raw materials for preparing the first surface layer and the core layer are homopolypropylene;

[0067] The raw materials for preparing the second surface layer are composed of metallocene polypropylene and a slip agent; among them, metallocene

[0068] polypropylene

[0069] and the slip agent have a weight ratio of 99:1;

[0070] The slip agent in the second surface layer is a modified slip agent;

[0071] The preparation method of the modified slip agent is as follows:

[0072] (1) Add talcum powder and silica to a high-speed mixer, and perform preliminary mixing at a speed of 1200 revolutions per minute for 5 minutes; among them, the weight ratio of talcum powder to silica is 1:2;

[0073] (2) Then add the modified liquid and continue mixing for 40 minutes to obtain a modified mixture; among them, the added weight of the modified liquid is 30% of the total weight of talcum powder and silica;

[0074] (3) Dry the modified mixture to obtain the modified slip agent;

[0075] The modified liquid described in step (2) is specifically prepared by the following method: adding a modifier to an ethanol solution, and stirring and dissolving to obtain the modified liquid; the dosage ratio of the modifier to the ethanol solution is 175 g: 1 L; the ethanol solution is an ethanol aqueous solution with a volume fraction of 95%; the modifier is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0076] Preparation of Comparative Example 2 BOPP Ultra-Low Temperature and High-Speed Heat-Sealing Film

[0077] The ultra-low temperature and high-speed heat-sealing film described above includes surface layer 1, core layer, and surface layer 2. Among them, the thickness of surface layer 1 accounts for 25% of the total thickness of the film; the thickness of the core layer accounts for 50% of the total thickness of the film; the thickness of surface layer 2 accounts for 25% of the total thickness of the film.

[0078] The raw materials for preparing surface layer 1 and the core layer are homopolypropylene.

[0079] The raw materials for preparing surface layer 2 consist of metallocene polypropylene and a slip agent. Among them, metallocene

[0080] polypropylene

[0081] and the slip agent have a weight ratio of 99:1.

[0082] The slip agent in surface layer 2 is a modified slip agent.

[0083] The preparation method of the modified slip agent is as follows:

[0084] (1) Add talcum powder and silicon dioxide to a high-speed mixer and conduct preliminary mixing at a rotation speed of 1200 revolutions per minute for 5 minutes. Among them, the weight ratio of talcum powder to silicon dioxide is 1:2.

[0085] (2) Then add the modification liquid and continue mixing for 40 minutes to obtain a modified mixture. Among them, the added weight of the modification liquid is 30% of the total weight of talcum powder and silicon dioxide.

[0086] (3) Dry the modified mixture to obtain the modified slip agent.

[0087] The modification liquid described in step (2) is specifically prepared by the following method: Add the modifier to the ethanol solution, stir and dissolve to obtain the modification liquid. The dosage ratio of the modifier to the ethanol solution is 175 g:1 L. The ethanol solution is an ethanol aqueous solution with a volume fraction of 95%. The modifier is dodecyldimethylamine oxide.

[0088] Preparation of the comparative example 3 BOPP ultra-low temperature and high-speed heat-sealing film

[0089] The ultra-low temperature and high-speed heat-sealing film described above includes surface layer 1, core layer, and surface layer 2. Among them, the thickness of surface layer 1 accounts for 25% of the total thickness of the film; the thickness of the core layer accounts for 50% of the total thickness of the film; the thickness of surface layer 2 accounts for 25% of the total thickness of the film.

[0090] The raw materials for preparing surface layer 1 and the core layer are homopolypropylene.

[0091] The raw materials for preparing surface layer 2 consist of metallocene polypropylene and a slip agent. Among them, metallocene

[0092] polypropylene

[0093] and the weight ratio of the slip agent is 99:1;

[0094] The slip agent described in the second surface layer is a modified slip agent;

[0095] The preparation method of the described modified slip agent is as follows:

[0096] (1) Add talcum powder and silicon dioxide into a high-speed mixer, and conduct preliminary mixing at a rotation speed of 1200 revolutions per minute for 5 minutes; among them, the weight ratio of talcum powder and silicon dioxide is 1:2;

[0097] (2) Then add the modification liquid and continue mixing for 40 minutes to obtain a modified mixture; among them, the added weight of the modification liquid is 30% of the total weight of talcum powder and silicon dioxide;

[0098] (3) Dry the modified mixture to obtain the modified slip agent;

[0099] The modification liquid described in step (2) is specifically prepared by the following method: Add the modifier into the ethanol solution, stir and dissolve to obtain the modification liquid; the dosage ratio of the modifier to the ethanol solution is 175 g:1 L; the ethanol solution is an ethanol aqueous solution with a volume fraction of 95%; the modifier is cocamidopropyl hydroxysultaine.

[0100] Preparation of Comparative Example 4 BOPP Ultra-Low Temperature High-Speed Heat-Sealing Film

[0101] The described ultra-low temperature high-speed heat-sealing film includes a first surface layer, a core layer, and a second surface layer; among them, the thickness of the first surface layer accounts for 25% of the total thickness of the film; the thickness of the core layer accounts for 50% of the total thickness of the film; the thickness of the second surface layer accounts for 25% of the total thickness of the film;

[0102] The preparation raw materials of the described first surface layer and the core layer are homopolypropylene;

[0103] The preparation raw materials of the described second surface layer are composed of metallocene polypropylene and a slip agent; among them, metallocene

[0104] polypropylene

[0105] and the weight ratio of the slip agent is 99:1;

[0106] The slip agent described in the second surface layer is a modified slip agent;

[0107] The preparation method of the described modified slip agent is as follows:

[0108] (1) Add talcum powder and silicon dioxide into a high-speed mixer, and conduct preliminary mixing at a rotation speed of 1200 revolutions per minute for 5 minutes; among them, the weight ratio of talcum powder and silicon dioxide is 1:2;

[0109] (2) Then add the modified liquid and continue mixing for 40 min to obtain a modified mixture; wherein, the added weight of the modified liquid is 30% of the total weight of talcum powder and silica.

[0110] (3) Dry the modified mixture to obtain a modified slip agent.

[0111] The modified liquid described in step (2) is specifically prepared by the following method: Add the modifier to the ethanol solution, stir and dissolve to obtain the modified liquid; the dosage ratio of the modifier to the ethanol solution is 175 g: 1 L; the ethanol solution is an ethanol aqueous solution with a volume fraction of 95%; the modifier is composed of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and dodecyldimethylamine oxide with a weight ratio of 2:1.

[0112] Preparation of Comparative Example 5 BOPP Ultra-Low Temperature and High-Speed Heat-Sealing Film

[0113] The ultra-low temperature and high-speed heat-sealing film described above includes surface layer 1, core layer, and surface layer 2; wherein, the thickness of surface layer 1 accounts for 25% of the total thickness of the film; the thickness of the core layer accounts for 50% of the total thickness of the film; the thickness of surface layer 2 accounts for 25% of the total thickness of the film.

[0114] The raw materials for preparing surface layer 1 and the core layer are homopolypropylene.

[0115] The raw materials for preparing surface layer 2 are composed of metallocene polypropylene and a slip agent; wherein, metallocene

[0116] polypropylene

[0117] and the slip agent have a weight ratio of 99:1.

[0118] The slip agent in surface layer 2 is a modified slip agent.

[0119] The preparation method of the modified slip agent is as follows:

[0120] (1) Add talcum powder and silica to a high-speed mixer and conduct preliminary mixing at a rotation speed of 1200 revolutions per minute for 5 min; wherein, the weight ratio of talcum powder and silica is 1:2.

[0121] (2) Then add the modified liquid and continue mixing for 40 min to obtain a modified mixture; wherein, the added weight of the modified liquid is 30% of the total weight of talcum powder and silica.

[0122] (3) Dry the modified mixture to obtain a modified slip agent.

[0123] The modified liquid described in step (2) is specifically prepared by the following method: adding a modifier to an ethanol solution, and stirring and dissolving to obtain the modified liquid; the dosage ratio of the modifier to the ethanol solution is 175 g: 1 L; the ethanol solution is an ethanol aqueous solution with a volume fraction of 95%; the modifier is composed of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and cocamidopropyl hydroxysultaine with a weight ratio of 2:1.

[0124] Preparation of Comparative Example 6 BOPP Ultra-Low Temperature and High-Speed Heat-Sealing Film

[0125] The ultra-low temperature and high-speed heat-sealing film described above includes a first surface layer, a core layer, and a second surface layer; among them, the thickness of the first surface layer accounts for 25% of the total thickness of the film; the thickness of the core layer accounts for 50% of the total thickness of the film; the thickness of the second surface layer accounts for 25% of the total thickness of the film;

[0126] The raw materials for preparing the first surface layer and the core layer are homopolypropylene;

[0127] The raw materials for preparing the second surface layer are composed of metallocene polypropylene and a slip agent; among them, metallocene

[0128] polypropylene

[0129] and the slip agent have a weight ratio of 99:1;

[0130] The slip agent in the second surface layer is a modified slip agent;

[0131] The preparation method of the modified slip agent is as follows:

[0132] (1) Add talcum powder and silica to a high-speed mixer, and perform preliminary mixing at a speed of 1200 revolutions per minute for 5 minutes; among them, the weight ratio of talcum powder to silica is 1:2;

[0133] (2) Then add the modified liquid and continue mixing for 40 minutes to obtain a modified mixture; among them, the added weight of the modified liquid is 30% of the total weight of talcum powder and silica;

[0134] (3) Dry the modified mixture to obtain the modified slip agent;

[0135] The modified liquid described in step (2) is specifically prepared by the following method: adding a modifier to an ethanol solution, and stirring and dissolving to obtain the modified liquid; the dosage ratio of the modifier to the ethanol solution is 175 g: 1 L; the ethanol solution is an ethanol aqueous solution with a volume fraction of 95%; the modifier is composed of dodecyldimethylamine oxide and cocamidopropyl hydroxysultaine with a weight ratio of 1:1.

[0136] Refer to the standard of GB / T 10003-2008 to test the heat-sealing strength at 80°C of the BOPP ultra-low temperature and high-speed heat-sealing films prepared in Examples 1-2 and Comparative Examples 1-6; and refer to the standard of GB / T 2410-2008 to test the haze of the BOPP ultra-low temperature and high-speed heat-sealing films prepared in Examples 1-2 and Comparative Examples 1-6.

[0137]

[0138]

[0139] As can be seen from the experimental results in Table 1, for the BOPP ultra-low temperature and high-speed heat-sealing film prepared in Example 1, its heat-sealing strength (80°C) is 2.1 N / 15 mm and the haze is 1.9%; this shows that: for the BOPP ultra-low temperature and high-speed heat-sealing film made of the materials described in the present invention, its heat-sealing strength at ultra-low temperatures such as 80°C ≥ 2.0 N / 15 mm; it shows good heat-sealing strength; in addition, its haze is all ≤ 2.0%, having a low haze.

[0140] As can be seen from the experimental results in Table 1, for the BOPP ultra-low temperature and high-speed heat-sealing film prepared in Example 2, its heat-sealing strength (80°C) is much higher than that of Example 1; this shows that: in the BOPP ultra-low temperature and high-speed heat-sealing film, adding the modified slip agent prepared by the method described in the present invention can greatly improve the heat-sealing strength of the BOPP ultra-low temperature and high-speed heat-sealing film at ultra-low temperatures compared with adding an unmodified slip agent.

[0141] As can be seen from the experimental results in Table 1, for the BOPP ultra-low temperature and high-speed heat-sealing films prepared in Comparative Examples 1-6, although their heat-sealing strength (80°C) is improved compared with that of Example 1, the improvement amplitude is not large and far less than that of Example 2; this shows that: in the preparation process of the modified slip agent, the selection of the modifier is very crucial; in the BOPP ultra-low temperature and high-speed heat-sealing film, it is necessary to add the modified slip agent modified by the modifier composed of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide and cocamidopropyl hydroxysulfobetaine to greatly improve the heat-sealing strength of the BOPP ultra-low temperature and high-speed heat-sealing film at ultra-low temperatures; however, simply adding the modified slip agent modified by one or any two of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide and cocamidopropyl hydroxysulfobetaine cannot greatly improve the heat-sealing strength of the BOPP ultra-low temperature and high-speed heat-sealing film at ultra-low temperatures.

[0142] As can be seen from the experimental results in Table 1, the haze of the BOPP ultra-low temperature and high-speed heat-sealing film prepared in Example 2 is much smaller than that in Example 1; this shows that: in the BOPP ultra-low temperature and high-speed heat-sealing film, adding the modified slip agent prepared by the above method can significantly reduce the haze of the BOPP ultra-low temperature and high-speed heat-sealing film at ultra-low temperature compared with adding the unmodified slip agent.

[0143] As can be seen from the experimental results in Table 1, for the BOPP ultra-low temperature and high-speed heat-sealing films prepared in Comparative Examples 1-6, although their haze is lower than that in Example 1, the reduction amplitude is not large, far less than that in Example 2; this shows that: in the BOPP ultra-low temperature and high-speed heat-sealing film, it is necessary to add the modified slip agent modified by the modifier composed of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide and cocamidopropyl hydroxysultaine to significantly reduce the haze of the BOPP ultra-low temperature and high-speed heat-sealing film at ultra-low temperature; however, just adding the modified slip agent modified by one or any two of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide and cocamidopropyl hydroxysultaine cannot significantly reduce the haze of the BOPP ultra-low temperature and high-speed heat-sealing film at ultra-low temperature.

Claims

1. A BOPP ultra-low temperature and high-speed heat-sealing film, characterized in that, It includes surface layer 1, core layer and surface layer 2; among them, the thickness of surface layer 1 accounts for 20% - 30% of the total thickness of the film; the thickness of the core layer accounts for 40% - 60% of the total thickness of the film; the thickness of surface layer 2 accounts for 20% - 30% of the total thickness of the film; The raw materials for preparing the surface layer 1 and the core layer are homopolypropylene; The raw materials for preparing the surface layer 2 include metallocene polypropylene and a slip agent.

2. The BOPP ultra-low temperature and high-speed heat-sealing film according to claim 1, wherein The weight ratio of metallocene polypropylene to the slip agent in the raw materials for preparing the surface layer 2 is 98.5 - 99.5:0.5 - 1.5; Most preferably, the weight ratio of metallocene polypropylene to the slip agent in the raw materials for preparing the surface layer 2 is 99:

1.

3. The BOPP ultra-low temperature and high-speed heat-sealing film according to claim 2, characterized in that, The slip agent consists of talcum powder and silica.

4. The BOPP ultra-low temperature and high-speed heat-sealing film according to claim 3, characterized in that, The weight ratio of talcum powder to silica is 1:1 - 3; Most preferably, the weight ratio of talcum powder to silica is 1:

2.

5. The BOPP ultra-low temperature and high-speed heat-sealing film according to claim 1, wherein The slip agent is a modified slip agent; The modified slip agent is prepared by the following method: (1) Add talcum powder and silica into a high-speed mixer and conduct preliminary mixing for 3 - 10 min; (2) Then add the modification liquid and continue mixing for 30 - 60 min to obtain a modified mixture; (3) Dry the modified mixture to obtain the modified slip agent.

6. The BOPP ultra-low temperature and high-speed heat-sealing film according to claim 5, wherein In step (1), the weight ratio of talcum powder to silica is 1:1 - 3; Most preferably, the weight ratio of talcum powder to silica is 1:

2.

7. The BOPP ultra-low temperature and high-speed heat-sealing film according to claim 5, characterized in that, In step (2), the added weight of the modification liquid is 20 - 40% of the total weight of talcum powder and silica; Most preferably, in step (2), the added weight of the modification liquid is 30% of the total weight of talcum powder and silica.

8. The BOPP ultra-low temperature and high-speed heat-sealing film according to claim 5, characterized in that The modification liquid in step (2) is specifically prepared by the following method: Add the modifier into an ethanol solution, stir and dissolve to obtain the modification liquid; the dosage ratio of the modifier to the ethanol solution is 150 - 200 g:1 L.

9. The BOPP ultra-low temperature and high-speed heat-sealing film according to claim 8, characterized in that, The modifier consists of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, dodecyldimethylamine oxide and coconut oil amide propyl hydroxysulfobetaine.

10. The preparation method of the BOPP ultra-low temperature and high-speed heat-sealing film according to any one of claims 1 to 9, characterized in that, It includes the following steps: Put the raw materials for preparing surface layer 1, core layer and surface layer 2 into three extruders respectively, melt them, extrude them through a die head, then through inflation cooling, film forming, corona treatment and winding treatment to obtain the BOPP ultra-low temperature high-speed heat-sealing film.

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