PETG (Polyethylene Terephthalate Glycol) heat shrink film for sealing and preparation method thereof

Abstract

The invention relates to a PETG heat shrink film for sealing and a preparation method thereof, the PETG heat shrink film for sealing comprises a core layer, a functional layer and two surface layers, the raw materials of the core layer comprise a PETG reclaimed material, an epsilon-caprolactone homopolymer and nano-silica, the functional layer is located between the core layer and the surface layers, and the raw materials comprise PETG and a photoinitiator TPO; and the surface layer is prepared from the following raw materials: PETG, a bio-based plasticizer TBC and an ultraviolet light absorber UV-326. According to the PETG thermal shrinkage film for sealing, the plasticizing efficiency of a reclaimed material is improved through the surface layer raw materials, ultraviolet damage is reduced, and the service life of a product is prolonged; the core layer raw material can still improve the mechanical property of the product when the ratio of the reclaimed material is increased, and the product has better toughness, tear resistance and higher light transmittance; the functional layer raw material can improve the tightness of the seal; the preparation method effectively improves the overall tensile strength and flexibility of the film, so that the product has both toughness and strength in the use process.

Description

Technical Field

[0001] This invention belongs to the field of heat shrink film, specifically relating to a PETG heat shrink film for sealing and its preparation method. Background Technology

[0002] PETG (polyethylene terephthalate-neopentyl glycol) heat shrink film is an environmentally friendly polyester film with non-toxic properties. It also has good mechanical strength, barrier properties, chemical stability and environmental affinity, and is widely used in beverage packaging, daily chemical packaging and battery packaging.

[0003] Currently, most PETG heat shrink films on the market suffer from reduced mechanical strength due to impurities and molecular chain breakage when using recycled PETG as a raw material. The tensile strength of the product decreases by 30%-40%, and high proportions of recycled PETG can easily lead to problems such as reduced light transmittance and surface defects. Due to wear and tear during transportation and use, some products on the market are prone to brittle fracture and tearing during sealing, which seriously affects the sealing effect and leads to resource waste. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a PETG heat-shrinkable film for sealing and its preparation method.

[0005] The technical solution adopted in this invention is as follows: A PETG heat shrink film for sealing includes a core layer, a functional layer, and a surface layer.

[0006] The core layer raw materials, by weight, include: 80-88 parts recycled PETG, 10-15 parts ε-caprolactone homopolymer, and 2-5 parts nano-silica; the functional layer is located between the core layer and the surface layer, and its raw materials, by weight, include: 98.5-99.5 parts PETG and 0.5-1.5 parts photoinitiator TPO; the surface layer raw materials, by weight, include: 69.7-79.9 parts PETG, 20-30 parts bio-based plasticizer TBC, and 0.1-0.3 parts ultraviolet absorber UV-326.

[0007] The number-average molecular weight of the ε-caprolactone homopolymer is 50,000-70,000 g / mol. Preferably, the molecular weight distribution index of the recycled PETG material in the core layer is ≤1.8; the surface of the nano-silica is modified with silane coupling agent KH-570, and the particle size is 20-50nm.

[0008] Preferably, the core layer raw materials, by weight, comprise: 84.3 parts of recycled PETG, 12.4 parts of ε-caprolactone homopolymer, and 3.3 parts of nano-silica; the functional layer raw materials, by weight, comprise: 99.0 parts of PETG and 1.0 part of photoinitiator TPO; and the surface layer raw materials, by weight, comprise: 74.8 parts of PETG, 25 parts of bio-based plasticizer TBC, and 0.2 parts of ultraviolet absorber UV-326.

[0009] Preferably, the thickness of the PETG heat shrink film is 60-80 μm.

[0010] Preferably, the thickness ratio of the core layer, functional layer, and surface layer is 60:10:30.

[0011] To achieve the above technical objectives, this application also provides a method for preparing the aforementioned PETG heat-shrinkable film for sealing, comprising the following steps: S1, the core layer, functional layer and surface layer raw materials are respectively fed into different high-speed mixing equipment and dried in a vacuum dryer to obtain the materials of each layer; S2, the dried core layer, functional layer and surface layer materials are mixed in a mixer, and then the materials of each layer are fed into a twin-screw extruder for melt plasticization according to the mixing of the core layer, functional layer and surface layer. S3, the molten and plasticized raw materials of each layer are extruded through a T-die, then cooled and cast by a rapid cooling roller, biaxially stretched and then wound up to obtain a PETG heat shrink film roll for sealing.

[0012] Preferably, in step S1, the raw material is dried to a moisture content of ≤50ppm.

[0013] Preferably, in step S2, the mixing parameters are: mixing time 1-2h, mixing temperature 70-80℃; the extruder melt plasticizing parameters are: screw diameter 80mm, screw length-to-diameter ratio 32, temperature 260℃-265℃.

[0014] Preferably, the temperature of the T-shaped die head in step S3 is 285-290℃.

[0015] Preferably, in step S3, the water temperature of the cooling drum in the casting sheet cooling step is 27-30℃.

[0016] Preferably, the stretching ratio of the transverse stretching step is 1:4.5-5.5, and the stretching ratio of the longitudinal stretching step is 1:1.5-2.5. The biaxial stretching step includes four steps: preheating, stretching, setting and cooling. The preheating temperature is 90-110℃, the stretching temperature is 85-95℃, the setting temperature is 60-80℃, and the cooling temperature is 40-45℃.

[0017] The technical solution provided by this invention has the following beneficial effects and advantages: 1. The PETG heat shrink film for sealing provided by this invention uses recycled PETG material and bio-based plasticizer TBC as the surface material, which improves the plasticizing efficiency of the recycled material; the ultraviolet absorber UV-326 can effectively reduce the damage of ultraviolet rays to the film and extend the product's service life.

[0018] 2. The PETG heat shrink film for sealing provided by the present invention uses recycled PETG material with a molecular weight distribution index ≤1.8 as the core layer, combined with added ε-caprolactone homopolymer and silane-modified nano-silica. When the proportion of recycled material is increased, the mechanical properties of the PETG heat shrink film product are improved, with better toughness and tear resistance, while maintaining high light transmittance.

[0019] 3. The PETG heat shrink film for sealing provided by the present invention contains a photoinitiator TPO in the functional layer, which can achieve efficient heat shrinkage under certain light conditions, thereby improving the tightness of the seal.

[0020] 4. The method for preparing PETG heat shrink film for sealing provided by the present invention effectively improves the overall tensile strength and flexibility of the film, increases the longitudinal and transverse tensile strength of the product, reduces the elongation at break, and provides both toughness and strength during use. Detailed Implementation

[0021] The technical solution of the invention will be further described below with reference to specific embodiments. It should also be understood that the following embodiments are only for further illustration of the invention and should not be construed as limiting the scope of protection of the invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the invention are within the scope of protection of the invention.

[0022] The raw materials used in the examples are all commercially available.

[0023] Example 1 A PETG heat shrink film for sealing includes a core layer, a functional layer, and a surface layer.

[0024] The core layer raw materials, by weight, include: 80 parts recycled PETG, 15 parts ε-caprolactone homopolymer, and 5 parts nano-silica; the functional layer is located between the core layer and the surface layer, and its raw materials, by weight, include: 98.5 parts PETG and 1.5 parts TPO; the surface layer raw materials, by weight, include: 69.7 parts PETG, 30 parts TBC, and 0.3 parts UV-326.

[0025] The molecular weight distribution index of the recycled PETG material in the core layer is 1.5; the surface of the nano-silica is modified with silane coupling agent KH-570, and the particle size is 20nm.

[0026] The PETG heat shrink film has a thickness of 60μm, and the thickness ratio of the core layer, functional layer and surface layer is 60:10:30.

[0027] To achieve the above technical objectives, a method for preparing the aforementioned PETG heat-shrinkable film for sealing is provided, comprising the following steps: S1, the core layer, functional layer and surface layer raw materials are respectively put into different high-speed mixing equipment and dried in a vacuum dryer until the moisture content is 40ppm to obtain the materials of each layer; S2, the dried core layer, functional layer and surface layer materials are mixed in a mixer for 1 hour at a temperature of 70°C. Then, the materials of each layer are separated according to the mixing of the core layer, functional layer and surface layer and fed into a twin-screw extruder for melt plasticization. The screw diameter of the extruder is 80 mm, the length-to-diameter ratio of the screw is 32, and the temperature is 260°C. S3, the molten and plasticized raw materials are extruded through a T-die at a temperature of 285°C. After extrusion, the material enters a rapid cooling roller to cool the casting. The water temperature of the casting cooling drum is 27°C. After casting, the material is biaxially stretched. The stretching ratio for the transverse stretching is 1:4.5, and the stretching ratio for the longitudinal stretching is 1:1.5. The biaxial stretching process includes four steps: preheating, stretching, setting, and cooling. The preheating temperature is 90°C, the stretching temperature is 85°C, the setting temperature is 60°C, and the cooling temperature is 40°C.

[0028] Finally, the PETG heat shrink film rolls for sealing are obtained.

[0029] Example 2 A PETG heat shrink film for sealing includes a core layer, a functional layer, and a surface layer.

[0030] The core layer materials, by weight, consist of: 84.3 parts recycled PETG, 12.4 parts ε-caprolactone homopolymer, and 3.3 parts nano-silica. The functional layer, located between the core layer and the top layer, consists of: 99.0 parts PETG and 1.0 parts TPO. The top layer materials, by weight, consist of: 74.8 parts PETG, 25 parts TBC, and 0.2 parts UV-326.

[0031] The molecular weight distribution index of the recycled PETG material in the core layer is 1.7; the surface of the nano-silica is modified with silane coupling agent KH-570, and the particle size is 34nm.

[0032] The PETG heat shrink film has a thickness of 70μm, and the thickness ratio of the core layer, functional layer and surface layer is 60:10:30.

[0033] To achieve the above technical objectives, a method for preparing the aforementioned PETG heat-shrinkable film for sealing is provided, comprising the following steps: S1, the core layer, functional layer and surface layer raw materials are respectively put into different high-speed mixing equipment and dried in a vacuum dryer until the moisture content is 45ppm to obtain the materials of each layer; S2, the dried core layer, functional layer and surface layer materials are mixed in a mixer for 1.5 hours at a temperature of 75°C. Then, the materials of each layer are separated according to the mixing of the core layer, functional layer and surface layer and fed into a twin-screw extruder for melt plasticization. The screw diameter of the extruder is 80 mm, the length-to-diameter ratio of the screw is 32, and the temperature is 263°C. S3. The molten and plasticized raw materials are extruded through a T-die at a temperature of 287°C. After extrusion, the material enters a quenching roller to cool and cast the sheet. The water temperature of the casting cooling drum is 29°C. The sheet is then biaxially stretched. The stretching ratio for the transverse stretching is 1:5.0, and the stretching ratio for the longitudinal stretching is 1:2.0. The biaxial stretching process includes four steps: preheating, stretching, setting, and cooling. The preheating temperature is 100°C, the stretching temperature is 90°C, the setting temperature is 70°C, and the cooling temperature is 43°C.

[0034] Finally, the PETG heat shrink film rolls for sealing are obtained.

[0035] Example 3 A PETG heat shrink film for sealing includes a core layer, a functional layer, and a surface layer.

[0036] The core layer raw materials, by weight, include: 88 parts recycled PETG, 10 parts ε-caprolactone homopolymer, and 2 parts nano-silica; the functional layer is located between the core layer and the surface layer, and its raw materials, by weight, include: 99.5 parts PETG and 0.5 parts TPO; the surface layer raw materials, by weight, include: 79.9 parts PETG, 20 parts TBC, and 0.1 parts UV-326.

[0037] The molecular weight distribution index of the recycled PETG material in the core layer is 1.8; the surface of the nano-silica is modified with silane coupling agent KH-570, and the particle size is 50nm.

[0038] The PETG heat shrink film has a thickness of 80μm, and the thickness ratio of the core layer, functional layer and surface layer is 60:10:30.

[0039] To achieve the above technical objectives, a method for preparing the aforementioned PETG heat-shrinkable film for sealing is provided, comprising the following steps: S1, the core layer, functional layer and surface layer raw materials are respectively put into different high-speed mixing equipment and dried in a vacuum dryer until the moisture content is 50ppm to obtain the materials of each layer; S2, the dried core layer, functional layer and surface layer materials are mixed in a mixer for 2 hours at a temperature of 80°C. Then, the materials of each layer are separated according to the mixing of the core layer, functional layer and surface layer and fed into a twin-screw extruder for melt plasticization. The screw diameter of the extruder is 80 mm, the length-to-diameter ratio of the screw is 32, and the temperature is 265°C. S3, the molten and plasticized raw materials are extruded through a T-die at a temperature of 290°C. After extrusion, the material enters a rapid cooling roller to cool the casting sheet. The water temperature of the casting sheet cooling drum is 30°C. After casting, the material is biaxially stretched. The stretching ratio for the transverse stretching is 1:5.5, and the stretching ratio for the longitudinal stretching is 1:2.5. The biaxial stretching process includes four steps: preheating, stretching, setting, and cooling. The preheating temperature is 110°C, the stretching temperature is 95°C, the setting temperature is 80°C, and the cooling temperature is 45°C.

[0040] Finally, the PETG heat shrink film rolls for sealing are obtained.

[0041] Comparative Example A PETG heat shrink film for sealing includes a core layer, a functional layer, and two surface layers.

[0042] The core layer is made of recycled PETG; the functional layer is located between the core layer and the surface layer and is made of PETG; the surface layer is made of PETG.

[0043] The molecular weight distribution index of the recycled PETG in the core layer is 1.7.

[0044] The preparation method of PETG heat shrink film includes the following steps: S1, the core layer, functional layer and surface layer raw materials are respectively put into different high-speed mixing equipment and dried in a vacuum dryer until the moisture content is 45ppm to obtain the materials of each layer; S2, the dried core layer, functional layer and surface layer materials are mixed in a mixer for 1.5 hours at a temperature of 75°C. Then, the materials of each layer are separated according to the mixing of the core layer, functional layer and surface layer and fed into a twin-screw extruder for melt plasticization. The screw diameter of the extruder is 80 mm, the length-to-diameter ratio of the screw is 32, and the temperature is 263°C. S3. The molten and plasticized raw materials are extruded through a T-die at a temperature of 287°C. After extrusion, the material enters a quenching roller to cool and cast the sheet. The water temperature of the casting cooling drum is 29°C. The sheet is then biaxially stretched. The stretching ratio for the transverse stretching is 1:5.0, and the stretching ratio for the longitudinal stretching is 1:2.0. The biaxial stretching process includes four steps: preheating, stretching, setting, and cooling. The preheating temperature is 100°C, the stretching temperature is 90°C, the setting temperature is 70°C, and the cooling temperature is 43°C.

[0045] Finally, the PETG heat shrink film rolls for sealing are obtained.

[0046] The performance of the PETG heat shrink films for sealing obtained in Examples 1-3 and the comparative example was tested, and the test results are shown in Table 1: Table 1. Standard data for PETG heat shrink film for sealing.

[0047] As shown in Table 1, Examples 1-3 have better light transmittance than the comparative examples, and have higher tensile strength in both the transverse and longitudinal directions, and lower elongation at break.

[0048] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a PETG heat-shrinkable film for sealing, characterized by, The method comprises the following steps: S1, the core layer, the functional layer and the surface layer raw materials are respectively put into different high-speed mixing devices and dried in a vacuum dryer to obtain materials of each layer; S2, the dried materials of the core layer, the functional layer and the surface layer are respectively mixed in a mixer, and then each layer of the mixed materials is respectively put into a double screw extruder for melting and plasticizing according to the core layer, the functional layer and the surface layer; S3, the materials of each layer after melting and plasticizing are extruded through a T-shaped die, then cooled into a casting sheet through a quenching roller, stretched in two directions and wound to obtain a PETG heat shrinkable film roll for sealing; The core layer raw material contains, by mass fraction: PETG regenerated material 80-88 parts, ε-caprolactone homopolymer 10-15 parts, and nano-silicon dioxide 2-5 parts; The functional layer is located between the core layer and the surface layer, and the raw material contains, by mass fraction: PETG 98.5-99.5 parts, and photoinitiator TPO 0.5-1.5 parts; The surface layer raw material contains, by mass fraction: PETG 69.7-79.9 parts, bio-based plasticizer TBC 20-30 parts, and ultraviolet absorber UV-326 0.1-0.3 parts.

2. The method for preparing PETG heat-shrinkable film for sealing according to claim 1, characterized in that, The raw materials in step S1 are dried to a water content of ≤50ppm; and the number average molecular weight of the ε-caprolactone homopolymer is 50000-70000g / mol.

3. The method for preparing PETG heat-shrinkable film for sealing according to claim 1, characterized in that, In step S2, the mixing parameters are: mixing time 1-2h, and mixing temperature 70-80℃; and the extruder melting and plasticizing parameters are: screw diameter 80mm, screw length-diameter ratio 32, and temperature 260℃-265℃.

4. The method for preparing PETG heat-shrinkable film for sealing according to claim 1, characterized in that, The temperature of the T-shaped die in step S3 is 285-290℃.

5. The method for preparing PETG heat-shrinkable film for sealing according to claim 1, characterized in that, In the step of cooling the casting sheet in step S3, the water temperature for the casting sheet cooling drum is 27-30℃; In the step of two-way stretching, the stretching ratio of the transverse stretching is 1:4.5-5.5, and the stretching ratio of the longitudinal stretching is 1:1.5-2.5; The two-way stretching comprises four steps of preheating, stretching, setting and cooling, and the preheating temperature is 90-110℃, the stretching temperature is 85-95℃, the setting temperature is 60-80℃, and the cooling temperature is 40-45℃.

6. The PETG heat shrinkable film for sealing prepared by the method according to any one of claims 1-5.

7. The PETG heat-shrinkable film for sealing according to claim 6, characterized by, The molecular weight distribution index of the PETG regenerated material in the core layer is ≤1.8; The surface of the nano-silicon dioxide is modified by silane coupling agent KH-570, and the particle size is 20-50nm.

8. The PETG heat-shrinkable film for sealing according to claim 6, characterized by, The core layer raw material contains, by mass fraction: PETG regenerated material 84.3 parts, ε-caprolactone homopolymer 12.4 parts, and nano-silicon dioxide 3.3 parts; The functional layer raw material contains, by mass fraction: PETG 99.0 parts, and photoinitiator TPO 1.0 part; The surface layer raw material contains, by mass fraction: PETG 74.8 parts, bio-based plasticizer TBC 25 parts, and ultraviolet absorber UV-326 0.2 parts.

9. The PETG heat-shrinkable film for sealing according to claim 6, characterized by, The thickness of the PETG heat shrinkable film is 60-80μm.

10. The PETG heat-shrinkable film for sealing according to claim 6, characterized by, The thickness ratio of the core layer, the functional layer and the surface layer is 60:10:30.

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