A high heat-sealing strength linear easy-tear polyester film and preparation method thereof

Abstract

The invention discloses a high heat-sealing strength linear tearable polyester film, which comprises an anti-sticking layer, a core layer and a heat-sealing layer in sequence; wherein the raw material of the heat-sealing layer is a copolymer modified masterbatch, which is made by esterification and polycondensation with terephthalic acid, ethylene glycol, phthalic acid, isosorbide and neopentyl glycol as comonomers; and the core layer comprises polyester chips and inorganic fillers. The BOPET film of the invention has both high heat-sealing strength and linear tearability, and does not need to be composited with PE and other films on its surface to meet the requirements of high heat-sealing strength. It can not only realize single packaging, easy recycling, environmental protection and high efficiency, but also in the field of food and medicine packaging, the unpacking process is more convenient and quick, easy to use and safer.

Description

Technical Field

[0001] The invention relates to the technical field of BOPET films, and in particular to a linear easy-tear polyester film with high heat-sealing strength and a preparation method thereof. Background Art

[0002] With the development of social economy, people are increasingly pursuing convenience in life, especially in the field of packaging. Existing products used for packaging of food, medicine, etc. usually adopt composite film structure, which takes advantage of the high heat sealing strength of materials such as PE and PP, adopts PE, PP and other materials as heat sealing layer, and adopts PA, PET and other materials as outer layer. Bags of this structure have the characteristics of high heat sealing strength, good sealing and excellent barrier properties. However, due to its composite film structure, there are problems such as a large number of packaging material layers, difficulty in recycling and high environmental pressure. Therefore, it is of certain research significance to develop a film packaging material with a single structure that can meet the requirements of high heat sealing performance. In addition, the existing packaging film materials also have the problem of large tearing resistance and cannot be torn straight along the scratch when used. When torn, the contents are easy to fall out, which affects its convenience of use. Therefore, the demand for single film packaging materials with both high-strength heat sealing performance and linear tearability has been increasing in recent years, and has a good market prospect. Summary of the invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a linear easy-tear polyester film with high heat-sealing strength and a preparation method thereof.

[0004] The invention provides a high heat-sealing strength linear tearable polyester film, which comprises an anti-sticking layer, a core layer and a heat-sealing layer in sequence;

[0005] The raw material of the heat sealing layer is a copolymer modified masterbatch, which is made by esterification and polycondensation with terephthalic acid, ethylene glycol, phthalic acid, isosorbide and neopentyl glycol as comonomers, and includes the following raw materials in parts by weight: 250-350 parts of terephthalic acid, 50-100 parts of ethylene glycol, 80-120 parts of phthalic acid, 15-30 parts of isosorbide, 10-20 parts of neopentyl glycol, 0.1-0.3 parts of catalyst and 0.02-0.04 parts of stabilizer;

[0006] The core layer comprises the following raw materials in parts by mass: 90-95 parts of polyester chips and 5-10 parts of inorganic filler masterbatch. The inorganic filler masterbatch comprises the following raw materials in parts by mass: 10-20 parts of calcium carbonate with a particle size of 1.0-1.5 μm, 10-20 parts of silicon dioxide with a particle size of 2.0-3.0 μm, 10-20 parts of montmorillonite with a particle size of 0.5-1.0 μm, 2-3 parts of dispersant and 40-60 parts of polyester chips.

[0007] Preferably, the copolymer modified masterbatch has an intrinsic viscosity of 0.70-0.72 dl / g, a number average molecular weight of 18000-20000, a melting temperature of 160-180° C., and a terminal carboxyl content of 16-20 mmol / kg.

[0008] Preferably, the preparation method of the copolymer modified masterbatch is as follows: terephthalic acid, ethylene glycol, phthalic acid, isosorbide, neopentyl glycol, a catalyst and a stabilizer are added to a reactor, the air in the reactor is replaced with nitrogen three times, the nitrogen pressure in the reactor is maintained at 340-380KPa, and the esterification reaction is started. The conditions of the esterification reaction are as follows: the reactor temperature is 260-270°C, the esterification tower temperature is 125-135°C, the esterification time is 2-3h, the reaction process is continuously stirred, the stirring frequency is 50Hz, and the esterification rate is ≥96%; then a polycondensation reaction is carried out, and the conditions of the polycondensation reaction are as follows: vacuumizing the reactor to maintain the pressure at -100±5KPa, the reactor temperature is 275-285°C, the polycondensation time is 1.5-2.5h, and the reaction process is continuously stirred, and the stirring frequency is 50-25Hz.

[0009] Preferably, the inorganic filler masterbatch is prepared by uniformly mixing calcium carbonate, silicon dioxide, montmorillonite, a dispersant and polyester chips, and then melting, extruding and granulating the mixture.

[0010] Preferably, the catalyst is antimony glycolate.

[0011] Preferably, the stabilizer is triethyl phosphate.

[0012] Preferably, the dispersant is vinyl bisstearamide.

[0013] Preferably, the anti-sticking layer comprises the following raw materials in parts by mass: 40-60 parts of polyester chips and 60-40 parts of anti-sticking masterbatch; preferably, the anti-sticking masterbatch comprises the following raw materials in parts by mass: 5-15 parts of silicon dioxide and 85-95 parts of polyester chips.

[0014] Preferably, the anti-sticking masterbatch is prepared by blending, extruding and pelletizing silica and polyester chips, and the silica particle size is 2.0-2.5 μm.

[0015] Preferably, the total thickness of the film is 15-30 μm, the thickness of the heat-sealing layer is 2.5-3.5 μm, and the thickness of the anti-sticking layer is 1.5-2.0 μm.

[0016] A method for preparing the high heat-sealing strength linear easy-tear polyester film comprises: feeding the raw materials of the core layer, the raw materials of the heat-sealing layer and the raw materials of the anti-sticking layer into three twin-screw extruders for melting respectively, conveying them to the die head for mixed extrusion, and then casting, longitudinal stretching, transverse stretching, shaping, pulling and winding to obtain the film.

[0017] Preferably, the melting temperature of the raw material of the core layer is 275℃-280℃, the melting temperature of the raw material of the anti-sticking layer is 275℃-280℃, the melting temperature of the raw material of the heat sealing layer is 220℃-230℃, the stretching ratio of the longitudinal stretching is 3.0-4.0, the stretching ratio of the transverse stretching is 3.0-4.0, and the setting temperature is 210-230℃.

[0018] The beneficial effects of the present invention are as follows:

[0019] The present invention proposes a high heat-sealing strength linear tearable polyester film, comprising an anti-sticking layer, a core layer and a heat-sealing layer; wherein the raw material of the heat-sealing layer is made of terephthalic acid, ethylene glycol, phthalic acid, isosorbide and neopentyl glycol in a specific ratio as comonomers, and is made through esterification and polycondensation. Compared with the existing polyester materials, its heat-sealing strength is significantly improved, and a high heat-sealing strength of 8N / 15mm can be achieved; inorganic fillers of different particle sizes are proportioned in the raw material of the core layer, giving the film the characteristic of being easy to tear, and the maximum tear deviation of the film is less than 20%, which improves the convenience and safety of the film as a packaging material. The BOPET film of the present invention has both high heat-sealing strength and linear tearability, and does not need to be composited with PE and other films on its surface to meet the requirements of high heat-sealing strength. It can not only achieve single packaging, easy recycling, environmental protection and high efficiency, but also in the field of food and drug packaging, the unpacking process is more convenient and quick, easy to use and safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the calculation method for the maximum tearing deviation of the film. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is described in detail below through specific embodiments.

[0022] Example 1

[0023] A linear tearable polyester film with high heat-sealing strength, comprising an anti-sticking layer, a core layer and a heat-sealing layer in sequence;

[0024] The raw material of the heat sealing layer is a copolymer modified masterbatch, wherein the copolymer modified masterbatch includes the following raw materials in parts by weight: 300 parts of terephthalic acid, 75 parts of ethylene glycol, 100 parts of phthalic acid, 20 parts of isosorbide, 15 parts of neopentyl glycol, 0.175 parts of ethylene glycol antimony, and 0.03 parts of triethyl phosphate. The preparation method is as follows: terephthalic acid, ethylene glycol, phthalic acid, isosorbide, neopentyl glycol, ethylene glycol antimony and triethyl phosphate are added to a reactor, and the air in the reactor is replaced with nitrogen three times, and the nitrogen pressure in the reactor is maintained at 340-380KPa, and the esterification reaction is started. The reaction kettle temperature is 265°C, the esterification tower temperature is 130°C, the esterification time is 2.5h, stirring is continued during the reaction, the stirring frequency is 50Hz, and the esterification rate is ≥96%; then the polycondensation reaction is carried out: the pressure in the vacuum kettle is maintained at -100±5KPa, the reaction kettle temperature is 280°C, the polycondensation time is 2h, stirring is continued during the reaction, and the stirring frequency is 50-25Hz; the intrinsic viscosity of the obtained copolymer modified masterbatch is 0.70dl / g, the number average molecular weight is 18500, the melting temperature is 165°C, and the terminal carboxyl content is 16mmol / kg.

[0025] The core layer includes the following raw materials in parts by mass: 92 parts of polyester chips and 8 parts of inorganic filler masterbatch. The inorganic filler masterbatch includes the following raw materials in parts by mass: 15 parts of calcium carbonate with a particle size of 1.0-1.5 μm, 15 parts of silica with a particle size of 2.0-3.0 μm, 15 parts of montmorillonite with a particle size of 0.5-1.0 μm, 2 parts of vinyl bisstearamide, and 55 parts of polyester chips.

[0026] The anti-sticking layer comprises the following raw materials in parts by weight: 50 parts of polyester chips and 50 parts of anti-sticking masterbatch, wherein the anti-sticking masterbatch comprises the following raw materials in parts by weight: 10 parts of silicon dioxide with a particle size of 2.0-2.5 μm and 90 parts of polyester chips.

[0027] The total thickness of the film is 15 μm, the thickness of the heat-sealing layer is 2.5 μm, and the thickness of the anti-sticking layer is 1.5 μm.

[0028] The preparation method of the above-mentioned high heat-sealing strength linear easy-tear polyester film includes: sending the raw materials of the core layer, the raw materials of the heat-sealing layer and the raw materials of the anti-sticking layer into three twin-screw extruders for melting respectively, conveying them to the die head for mixed extrusion, and then casting, longitudinal stretching, transverse stretching, shaping, pulling, and winding to obtain; wherein the melting temperature of the raw materials of the core layer is 275°C, the melting temperature of the raw materials of the anti-sticking layer is 275°C, the melting temperature of the raw materials of the heat-sealing layer is 220°C, the stretching ratio of the longitudinal stretching is 3.0, the stretching ratio of the transverse stretching is 3.5, and the shaping temperature is 210°C.

[0029] Example 2

[0030] A linear tearable polyester film with high heat-sealing strength, comprising an anti-sticking layer, a core layer and a heat-sealing layer in sequence;

[0031] The raw material of the heat sealing layer is a copolymer modified masterbatch, wherein the copolymer modified masterbatch is the same as that in Example 1;

[0032] The core layer includes the following raw materials in parts by mass: 90 parts of polyester chips and 10 parts of inorganic filler masterbatch. The inorganic filler masterbatch includes the following raw materials in parts by mass: 20 parts of calcium carbonate with a particle size of 1.0-1.5 μm, 20 parts of silica with a particle size of 2.0-3.0 μm, 20 parts of montmorillonite with a particle size of 0.5-1.0 μm, 3 parts of vinyl bisstearamide, and 60 parts of polyester chips.

[0033] The anti-sticking layer comprises the following raw materials in parts by weight: 60 parts of polyester chips and 40 parts of anti-sticking masterbatch, wherein the anti-sticking masterbatch comprises the following raw materials in parts by weight: 15 parts of silicon dioxide with a particle size of 2.0-2.5 μm and 85 parts of polyester chips.

[0034] The total thickness of the film is 15 μm, the thickness of the heat-sealing layer is 2.5 μm, and the thickness of the anti-sticking layer is 1.5 μm.

[0035] The preparation method of the film is the same as that of Example 1.

[0036] Example 3

[0037] A linear tearable polyester film with high heat-sealing strength, comprising an anti-sticking layer, a core layer and a heat-sealing layer in sequence;

[0038] The raw material of the heat sealing layer is a copolymer modified masterbatch, wherein the copolymer modified masterbatch is the same as that in Example 1;

[0039] The core layer includes the following raw materials in parts by mass: 95 parts of polyester chips and 5 parts of inorganic filler masterbatch. The inorganic filler masterbatch includes the following raw materials in parts by mass: 10 parts of calcium carbonate with a particle size of 1.0-1.5 μm, 10 parts of silica with a particle size of 2.0-3.0 μm, 10 parts of montmorillonite with a particle size of 0.5-1.0 μm, 2.5 parts of vinyl bisstearamide, and 40 parts of polyester chips.

[0040] The anti-sticking layer comprises the following raw materials in parts by weight: 40 parts of polyester chips and 60 parts of anti-sticking masterbatch, wherein the anti-sticking masterbatch comprises the following raw materials in parts by weight: 5 parts of silicon dioxide with a particle size of 2.0-2.5 μm and 95 parts of polyester chips.

[0041] The total thickness of the film is 15 μm, the thickness of the heat-sealing layer is 2.5 μm, and the thickness of the anti-sticking layer is 1.5 μm.

[0042] The preparation method of the film is the same as that of Example 1.

[0043] Comparative Example 1

[0044] The only difference between Comparative Example 1 and Example 1 is that the raw materials of the copolymer modified masterbatch are different. The copolymer modified masterbatch in Comparative Example 1 includes the following raw materials in parts by mass: 400 parts of terephthalic acid, 75 parts of ethylene glycol, 20 parts of isosorbide, 15 parts of neopentyl glycol, 0.175 parts of ethylene glycol antimony, and 0.03 parts of triethyl phosphate.

[0045] Comparative Example 2

[0046] The only difference between Comparative Example 2 and Example 1 is that the raw materials of the copolymer modified masterbatch are different. The copolymer modified masterbatch in Comparative Example 2 includes the following raw materials in parts by mass: 300 parts of terephthalic acid, 95 parts of ethylene glycol, 100 parts of phthalic acid, 15 parts of neopentyl glycol, 0.175 parts of ethylene glycol antimony, and 0.03 parts of triethyl phosphate.

[0047] Comparative Example 3

[0048] The only difference between Comparative Example 3 and Example 1 is that the raw materials of the copolymer modified masterbatch are different. The copolymer modified masterbatch in Comparative Example 3 includes the following raw materials in parts by mass: 300 parts of terephthalic acid, 90 parts of ethylene glycol, 100 parts of phthalic acid, 20 parts of isosorbide, 0.175 parts of ethylene glycol antimony, and 0.03 parts of triethyl phosphate.

[0049] Comparative Example 4

[0050] The only difference between Comparative Example 4 and Example 1 is that the copolymer modified masterbatch in Example 1 is replaced by a commercially available conventional terephthalic acid, ethylene glycol, and isophthalic acid copolymer masterbatch.

[0051] Comparative Example 5

[0052] The difference between Comparative Example 5 and Example 1 is that the inorganic filler masterbatch comprises the following raw materials in parts by weight: 45 parts of silica with a particle size of 2.0-3.0 μm, 2 parts of vinyl bisstearamide, and 53 parts of polyester chips.

[0053] Test example

[0054] Performance tests were performed on Example 1, Comparative Examples 1-5, and commercially available common heat-sealable BOPET films;

[0055] The maximum tearing deviation of the film is calculated as follows: dx = (d1-d0) / d0×100%, dx is the maximum tearing deviation, the unit is %; Figure 1 , d1 is the maximum deviation, the unit is mm, d0 is the vertical length of the crack, the unit is mm.

[0056] The test results are shown in Table 1:

[0057] Table 1 Performance test data of the film

[0058] Test items Heat seal strength (N / 15mm) Maximum tearing deviation (%) Example 1 8.0 16 Comparative Example 1 3.8 15 Comparative Example 2 3.7 16 Comparative Example 3 3.8 15 Comparative Example 4 4.0 15 Comparative Example 5 8.0 44 Commercially available heat-sealable BOPET film 3.5 46 Testing standards QB / T5076 /

[0059] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A linear tearable polyester film with high heat-sealing strength, characterized in that: It comprises an anti-sticking layer, a core layer and a heat-sealing layer in sequence; The raw material of the heat sealing layer is a copolymer modified masterbatch, which is made by esterification and polycondensation with terephthalic acid, ethylene glycol, phthalic acid, isosorbide and neopentyl glycol as copolymer monomers, and comprises the following raw materials in parts by weight: 250-350 parts of terephthalic acid, 50-100 parts of ethylene glycol, 80-120 parts of phthalic acid, 15-30 parts of isosorbide, 10-20 parts of neopentyl glycol, 0.1-0.3 parts of catalyst and 0.02-0.04 parts of stabilizer; the intrinsic viscosity of the copolymer modified masterbatch is 0.70-0.72dl / g, the number average molecular weight is 18000-20000, the melting temperature is 160-180°C, and the terminal carboxyl content is 16-20mmol / kg; The core layer comprises the following raw materials in parts by mass: 90-95 parts of polyester chips and 5-10 parts of inorganic filler masterbatch. The inorganic filler masterbatch comprises the following raw materials in parts by mass: 10-20 parts of calcium carbonate with a particle size of 1.0-1.5 μm, 10-20 parts of silicon dioxide with a particle size of 2.0-3.0 μm, 10-20 parts of montmorillonite with a particle size of 0.5-1.0 μm, 2-3 parts of dispersant and 40-60 parts of polyester chips.

2. The high heat-seal strength straight-line tearable polyester film according to claim 1, characterized in that: The preparation method of the copolymer modified masterbatch is as follows: terephthalic acid, ethylene glycol, phthalic acid, isosorbide, neopentyl glycol, a catalyst and a stabilizer are added into a reactor, the air in the reactor is replaced by nitrogen three times, the nitrogen pressure in the reactor is maintained at 340-380 KPa, and an esterification reaction is started, and the conditions of the esterification reaction are as follows: the reactor temperature is 260-270° C., the esterification tower temperature is 125-135° C., the esterification time is 2-3 hours, the reaction process is continuously stirred, the stirring frequency is 50 Hz, and the esterification rate is ≥96%; and then a polycondensation reaction is carried out, and the conditions of the polycondensation reaction are as follows: vacuuming the reactor to maintain the pressure at -100±5 KPa, the reactor temperature is 275-285° C., the polycondensation time is 1.5-2.5 hours, the reaction process is continuously stirred, and the stirring frequency is 50-25 Hz.

3. The high heat-seal strength straight-line tearable polyester film according to claim 1, characterized in that: The anti-sticking layer comprises the following raw materials in parts by weight: 40-60 parts of polyester chips and 60-40 parts of anti-sticking masterbatch; the anti-sticking masterbatch comprises the following raw materials in parts by weight: 5-15 parts of silicon dioxide with a particle size of 2.0-2.5 μm and 85-95 parts of polyester chips.

4. The high heat-seal strength straight-line tearable polyester film according to claim 1, characterized in that: The total thickness of the film is 15-30 μm, the thickness of the heat-sealing layer is 2.5-3.5 μm, and the thickness of the anti-sticking layer is 1.5-2.0 μm.

5. A method for preparing a linear tearable polyester film with high heat-sealing strength according to any one of claims 1 to 4, characterized in that: include: The raw materials of the core layer, the heat-sealing layer and the anti-sticking layer are respectively sent to three twin-screw extruders for melting, transported to the die head for mixed extrusion, and then subjected to sheet casting, longitudinal stretching, transverse stretching, shaping, pulling and winding to obtain the product.

6. The method for preparing a linear tearable polyester film with high heat-sealing strength according to claim 5, characterized in that: The melting temperature of the raw material of the core layer is 275℃-280℃, the melting temperature of the raw material of the anti-sticking layer is 275℃-280℃, the melting temperature of the raw material of the heat sealing layer is 220℃-230℃, the stretching ratio of the longitudinal stretching is 3.0-4.0, the stretching ratio of the transverse stretching is 3.0-4.0, and the setting temperature is 210-230℃.

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