PETG (polyethylene terephthalate glycol) composite thermal shrinkage film with low shrinkage force

Abstract

The invention relates to the field of heat shrinkage films, in particular to a PETG composite heat shrinkage film with low shrinkage force. The PETG composite thermal shrinkage film comprises an upper surface layer, an inner core layer and a lower surface layer which are sequentially arranged from top to bottom, the upper surface layer and the lower surface layer are PETG films, and the inner core layer is a PETG / PBAT composite film. The PETG composite shrink film designed by the invention can maintain lower shrinkage stress and enhance the thermal stability while ensuring the strength, so that more uniform skin shrinkage can be realized during interface shrinkage, and the phenomenon of local deformation or poor arc-shaped shrinkage is avoided.

Description

Technical Field

[0001] The invention relates to the field of heat shrinkable films, in particular to a low-shrinkage-force PETG composite heat shrinkable film. Background Art

[0002] Heat shrink film refers to the label used to wrap around the outer circumference of the container, including plastic bottles, glass bottles, etc. Heat shrink film has good gloss, fit and shrinkage properties, and due to the gloss and shrinkage of heat shrink film, the packaging pattern on the container is more vivid, which can better highlight the image on the supermarket shelves, creating an unexpected container effect, and is widely used in container packaging.

[0003] The existing heat shrinkable film materials for labels mainly include polyvinyl chloride (PVC), polyethylene terephthalate-1,4-cyclohexanedimethanol (PETG), oriented polystyrene (OPS), etc. PVC heat shrinkable film has the characteristics of high tensile strength, large elongation, good self-adhesion, high transparency, etc., but it also has the defects of easy generation of highly toxic dioxins during recycling and poor environmental protection, and is gradually banned from use; OPS heat shrinkable film has the characteristics of high strength, high rigidity, stable shape, good gloss and transparency, and is easy to process, easy to color, good printing performance, and extremely high printing resolution, but it is expensive and requires special ink solvents; PETG heat shrinkable film has the characteristics of non-toxic, odorless, high strength, high heat shrinkage, good optical properties, mechanical extensibility, and beautiful packaging effect, which makes the use of OPS heat shrinkable film and PETG heat shrinkable film grow rapidly.

[0004] At present, the market requirements for PETG composite heat shrinkable film are usually reflected in how to balance the shrinkage stress and shrinkage force. The introduction of fillers such as nano-silicon dioxide or talcum powder can disperse the shrinkage stress, but excessive addition will cause a significant decrease in strength and heat shrinkage rate. In addition, due to the large amount of additives added, it is easy to cause local deformation or arc-shaped poor shrinkage when the interface shrinks. Summary of the invention

[0005] In view of the problems existing in the prior art, the object of the present invention is to provide a low-shrinkage-force PETG composite heat shrinkable film.

[0006] The purpose of the present invention is achieved by the following technical solutions: In a first aspect, the present invention provides a low shrinkage force PETG composite heat shrinkable film, comprising an upper surface layer, an inner core layer and a lower surface layer arranged in sequence from top to bottom; the upper surface layer and the lower surface layer are both PETG films, and the inner core layer is a PETG / PBAT composite film; Among them, the PETG / PBAT composite film is calculated by weight and includes the following components: 60-80 parts of PETG resin, 20-40 parts of PBAT resin, 1-3 parts of plasticizer and 0.2-0.6 parts of chain extender.

[0007] Among them, the PETG film is calculated by weight and includes the following components: 100 parts of PETG resin, 3-7 parts of anti-blocking agent, 2-6 parts of lubricant, 1-2 parts of antioxidant and 0.5-1 parts of light stabilizer.

[0008] Preferably, the thickness ratio of the upper surface layer, the inner core layer and the lower surface layer is 1-3:6:1-3.

[0009] Preferably, the density of the PETG resin is 1.22-1.31 g / cm 3 , more preferably 1.27 g / cm 3 ; Melt index is 8-12g / 10min (230℃, 2.16kg).

[0010] Preferably, the density of the PBAT resin is 1.18-1.22 g / cm 3 , the melt index is 2-5g / 10min (190℃, 2.16kg).

[0011] Preferably, the plasticizer is a mixture of one or more of epoxidized soybean oil, epoxidized linseed oil, tributyl citrate, and acetyl tributyl citrate.

[0012] Preferably, the chain extender is phthalic anhydride and 2,2'-bis(2-oxazoline) in a mass ratio of 1.1-1.5:1.

[0013] Preferably, the anti-adhesion agent is modified nano-silicon dioxide, and the preparation method comprises: S1. Surface treatment: Weigh nano-silica powder, coupling agent KH-550 and ethanol solution, mix them, heat them to 60-80°C, reflux them for 2-6 hours, filter and dry them to obtain amino-modified nano-silica; S2. Activation reaction: Weigh tris(2-carboxyethyl)isocyanurate and add it to dichloromethane. Stir evenly in an ice-water bath, then introduce nitrogen as a protective gas, add N,N'-dicyclohexylcarbodiimide (DCC), stir for 0.5-1h, then warm to room temperature, add N-hydroxysuccinimide (NHS), stir for 1-2h to obtain an activated reaction solution; S3, modification reaction: Add the amino-modified nano-silica into the activation reaction solution, stir for 5-10 hours at room temperature under the protection of nitrogen, and after the reaction is completed, remove the solvent under reduced pressure, wash with water 2-3 times, and dry to obtain modified nano-silica.

[0014] Preferably, during the preparation of the aminated nano-silica, the particle size of the nano-silica is 50±10 nm, the mass fraction of the ethanol solution is 30-60 wt%, and the mass ratio of the nano-silica powder, coupling agent KH-550 and the ethanol solution is 1:0.1-0.3:5-10.

[0015] Preferably, during the preparation of the modified nano-silica, the mass ratio of the aminated nano-silica, tris(2-carboxyethyl)isocyanurate, N,N'-dicyclohexylcarbodiimide, N-hydroxysuccinimide and dichloromethane is 1:0.25-0.45:0.5-0.8:0.76-0.98:5-10.

[0016] Preferably, the lubricant is one or a mixture of more of zinc stearate, calcium stearate, polyethylene wax, and paraffin wax.

[0017] Preferably, the antioxidant is obtained by mixing a primary antioxidant and a secondary antioxidant in a mass ratio of 1:1.2-3.6; wherein, the primary antioxidant is one of antioxidant 1010, antioxidant 1076, and antioxidant 1098; the secondary antioxidant is antioxidant 168. More preferably, the primary antioxidant is antioxidant 1010 and the secondary antioxidant is antioxidant 168.

[0018] Preferably, the light stabilizer is one or a mixture of more of UV-622, UV-770, UV-944, UV-326, UV-328, and UV-1577. More preferably, it is UV-622.

[0019] In a second aspect, the present invention provides a method for preparing a low shrinkage force PETG composite heat shrinkable film, comprising the following steps: Step 1, respectively weigh the raw materials of the upper surface layer, the lower surface layer and the inner core layer, and place them in an oven at 70-80 °C to dry to a constant weight; Step 2, after mixing the raw materials of each layer respectively, introduce them into different twin-screw extruders, and after melting and pelletizing in the temperature range of 250-290 °C, obtain the upper surface layer masterbatch, the lower surface layer masterbatch and the inner core layer masterbatch respectively; Step 3, add the three kinds of materials obtained in Step 2 into three extruders, and after compounding through a die head, cast and form a sheet, first carry out biaxial stretching treatment, and then quickly cool and shape to obtain a low shrinkage force PETG composite heat shrinkable film.

[0020] Preferably, in Step 3, the extrusion molding temperature is: 200-240 °C for the upper surface layer, 240-260 °C for the inner core layer, and 200-240 °C for the lower surface layer.

[0021] Preferably, in the step 3, the biaxial stretching treatment includes longitudinal stretching (MDO) and transverse stretching (TDO); wherein, the stretching temperature for longitudinal stretching is 85 - 90 °C, and the stretching ratio is 1.5 - 3 times; the stretching temperature for transverse stretching is 105 - 110 °C, and the stretching ratio is 3 - 4.5 times; the rapid cooling and shaping temperature is 35 - 50 °C.

[0022] Preferably, in the step 3, the thickness of the antistatic PETG heat - shrinkable film obtained is 40 - 60 μm.

[0023] The beneficial effects of the present invention are as follows: 1. The present invention prepares a PETG composite heat - shrinkable film, which includes upper and lower surface layers and an inner core layer in the middle. The compositions of the upper and lower surface layers are the same, both being PETG films, while the inner core layer is a PETG / PBAT composite film. The PETG composite shrinkable film designed by the present invention can maintain a low shrinkage stress while ensuring strength, and enhance its thermal stability, enabling more uniform shrinkage when performing interfacial shrinkage, thus avoiding phenomena such as local deformation or poor arc - shaped shrinkage.

[0024] 2. The present invention designs the compositions of the three - layer films of the PETG composite heat - shrinkable film. In the composition of the inner core layer, in addition to the PETG resin, PBAT resin, plasticizer, and chain extender are added to enhance the heat resistance and strength of the film layer; while in the upper and lower surface layers, an anti - blocking agent and additives are added on the basis of the PETG resin. The anti - blocking agent, on the one hand, enhances the melt fluidity, mechanical properties, and thermal stability of the film layer, and on the other hand, makes the heat conductivity of the shrinkable film more uniform, reducing uneven shrinkage caused by local overheating, and ultimately making the shrinkage of the composite film more uniform and balanced.

[0025] 3. The anti - blocking agent added to the upper and lower surface layer films of the present invention is modified nano - silica, which is obtained by surface modification treatment of nano - scale silica. Specifically, the surface of silica is first aminated, and then amidation reaction is carried out with tris(2 - carboxyethyl) isocyanurate through the DCC / NHS system to obtain a core - shell structure coated with an organic substance containing amide groups and isocyanurate. After the modification treatment, the compatibility of the nano - silica as an anti - blocking agent with the PETG resin is significantly enhanced, and the strength, thermal stability, and shrinkage balance of the PETG film all show good performance. Specific embodiments

[0026] The technical solution of the present invention is described below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to limit the scope of the present invention. The change or adjustment of the relative relationship thereof shall also be regarded as the scope of the present invention without substantially changing the technical content.

[0027] In order to better understand the above technical scheme, the exemplary embodiments of the present invention are described in more detail below. Although exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0028] The present invention will be further described below in conjunction with the following examples.

[0029] Example 1 A low shrinkage force PETG composite heat shrinkable film, comprising an upper surface layer, an inner core layer and a lower surface layer arranged in sequence from top to bottom; wherein the thickness ratio of the upper surface layer, the inner core layer and the lower surface layer is 2:6:2; The inner core layer is a PETG / PBAT composite film, which includes the following components calculated by weight: 70 parts of PETG resin, 30 parts of PBAT resin, 2 parts of plasticizer and 0.4 parts of chain extender.

[0030] Among them, the density of PETG resin is 1.27g / cm 3 , melt index is 10g / 10min (230℃, 2.16kg); density of PBAT resin is 1.2g / cm 3 , the melt index is 3.2g / 10min (300℃, 1.2kg); the plasticizer is epoxidized soybean oil; the chain extender is phthalic anhydride and 2,2'-bis(2-oxazoline) in a mass ratio of 1.3:1.

[0031] The upper and lower surfaces are both PETG films, and the PETG films are calculated by weight and include the following components: 100 parts of PETG resin, 5 parts of anti-blocking agent, 4 parts of lubricant, 1 part of antioxidant and 0.6 parts of light stabilizer.

[0032] Among them, the density of PETG resin is 1.27g / cm3 with a melt index of 10 g / 10 min (230 °C, 2.16 kg); the lubricant is zinc stearate; the antioxidant is obtained by mixing antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2.4; the light stabilizer is UV-622.

[0033] Among them, the anti-blocking agent is modified nano-silica, and the preparation method includes: S1. Weigh 1 g of nano-silica powder with a size of 50 ± 10 nm, 0.2 g of coupling agent KH-550, and 10 g of 40 wt% ethanol solution, mix them, heat up to 70 °C, carry out reflux treatment for 4 h, filter and dry to obtain amino-functionalized nano-silica; S2. Weigh 0.35 g of tris(2-carboxyethyl)isocyanurate and add it to 10 g of dichloromethane. After stirring evenly in an ice-water bath, introduce nitrogen as a protective gas, add 0.5 - 0.8 g of N,N'-dicyclohexylcarbodiimide (DCC), stir for 1 h, then heat up to room temperature, and then add 0.87 g of N-hydroxysuccinimide (NHS), stir for 1.5 h to obtain an activated reaction solution; S3. Add 1 g of amino-functionalized nano-silica to the activated reaction solution, stir for 8 h under the protection of room temperature and nitrogen. After the reaction is completed, remove the solvent under reduced pressure, wash with water 3 times, and dry to obtain modified nano-silica.

[0034] The preparation method of the above low-shrinkage PETG composite heat-shrinkable film includes the following steps: Step 1. Weigh the raw materials for the upper surface layer, the lower surface layer, and the inner core layer respectively, and place them in an oven at 75 °C to dry to a constant weight; Step 2. After mixing the raw materials of each layer respectively, introduce them into different twin-screw extruders, and carry out melt granulation in the temperature range of 250 - 290 °C to obtain the upper surface layer masterbatch, the lower surface layer masterbatch, and the inner core layer masterbatch respectively; Step 3. Pour the three masterbatches obtained in Step 2 into a three-layer co-extrusion blown film machine, press and extrude them in sequence. The extrusion temperature is: 220 °C for the upper surface layer, 250 °C for the inner core layer, and 220 °C for the lower surface layer; then carry out biaxial stretching treatment. The stretching temperature for longitudinal stretching is 90 °C, and the stretching ratio is 2.5 times. The stretching temperature for transverse stretching is 110 °C, and the stretching ratio is 4 times; then quickly cool to 45 °C for shaping to obtain a low-shrinkage PETG composite heat-shrinkable film with a thickness of 50 μm.

[0035] Example 2 A low-shrinkage PETG composite heat-shrinkable film, which includes an upper surface layer, an inner core layer, and a lower surface layer arranged in sequence from top to bottom; among them, the thickness ratio of the upper surface layer, the inner core layer, and the lower surface layer is 1:6:1; The inner core layer is a PETG / PBAT composite film, which includes the following components calculated by weight: 60 parts of PETG resin, 20 parts of PBAT resin, 1 part of plasticizer and 0.2 parts of chain extender.

[0036] Among them, the density of PETG resin is 1.27g / cm 3 , melt index is 10g / 10min (230℃, 2.16kg); density of PBAT resin is 1.2g / cm 3 , the melt index is 3.2g / 10min (300℃, 1.2kg); the plasticizer is epoxy linseed oil; the chain extender is phthalic anhydride and 2,2'-bis(2-oxazoline) in a mass ratio of 1.1:1.

[0037] The upper and lower surfaces are both PETG films, and the PETG films include the following components calculated by weight: 100 parts of PETG resin, 3 parts of anti-blocking agent, 2 parts of lubricant, 1 part of antioxidant and 0.5 parts of light stabilizer.

[0038] Among them, the density of PETG resin is 1.27g / cm 3 , the melt index is 10g / 10min (230°C, 2.16kg); the lubricant is calcium stearate; the antioxidant is a mixture of antioxidant 1076 and antioxidant 168 in a mass ratio of 1:1; the light stabilizer is UV-770.

[0039] Wherein, the anti-adhesion agent is modified nano-silicon dioxide, and the preparation method comprises: S1, weigh 1g of 50±10nm nano-silica powder, 0.1g of coupling agent KH-550 and 5g of 30wt% ethanol solution, mix them, heat to 60°C, reflux for 2h, filter and dry to obtain amino-modified nano-silica; S2. Weigh 0.25 g of tris(2-carboxyethyl)isocyanurate and add it to 5 g of dichloromethane. Stir evenly in an ice-water bath, introduce nitrogen as a protective gas, add 0.5 g of N,N'-dicyclohexylcarbodiimide (DCC), stir for 0.5 h, then warm to room temperature, add 0.76 g of N-hydroxysuccinimide (NHS), stir for 1 h, and obtain an activated reaction solution. S3. Add 1 g of amino-modified nano-silica to the activation reaction solution, stir for 5 hours at room temperature under the protection of nitrogen. After the reaction is completed, remove the solvent under reduced pressure, wash with water twice, and dry to obtain modified nano-silica.

[0040] The method for preparing the low shrinkage force PETG composite heat shrinkable film comprises the following steps: Step 1, weigh the raw materials of the upper surface layer, the lower surface layer and the inner core layer respectively, and place them in a 70° C. oven to dry to constant weight; Step 2, after mixing the raw materials of each layer, respectively introduce them into different twin-screw extruders, and melt granulate them in the temperature range of 250-290° C. to obtain upper surface layer masterbatch, lower surface layer masterbatch and inner core layer masterbatch respectively; Step 3, pouring the three masterbatches obtained in step 2 into a three-layer co-extrusion film blowing machine, pressing and extruding them in sequence, the extrusion molding temperature is: 200°C for the upper surface layer, 240°C for the inner core layer, and 200°C for the lower surface layer; then undergoing a biaxial stretching treatment, the stretching temperature for longitudinal stretching is 85°C, the stretching ratio is 1.5 times, the stretching temperature for transverse stretching is 105°C, and the stretching ratio is 3 times; then rapidly cooling to 35°C for shaping, to obtain a low shrinkage force PETG composite heat shrinkable film with a thickness of 40 μm.

[0041] Example 3 A low shrinkage force PETG composite heat shrinkable film, comprising an upper surface layer, an inner core layer and a lower surface layer arranged in sequence from top to bottom; wherein the thickness ratio of the upper surface layer, the inner core layer and the lower surface layer is 3:6:3; The inner core layer is a PETG / PBAT composite film, which includes the following components calculated by weight: 80 parts of PETG resin, 40 parts of PBAT resin, 3 parts of plasticizer and 0.6 parts of chain extender.

[0042] Among them, the density of PETG resin is 1.27g / cm 3 , melt index is 10g / 10min (230℃, 2.16kg); density of PBAT resin is 1.2g / cm 3 , the melt index is 3.2g / 10min (300℃, 1.2kg); the plasticizer is tributyl citrate; the chain extender is phthalic anhydride and 2,2'-bis(2-oxazoline) in a mass ratio of 1.5:1.

[0043] The upper and lower surfaces are both PETG films, and the PETG films include the following components calculated by weight: 100 parts of PETG resin, 7 parts of anti-blocking agent, 6 parts of lubricant, 2 parts of antioxidant and 1 part of light stabilizer.

[0044] Among them, the density of PETG resin is 1.27g / cm 3 , the melt index is 10g / 10min (230℃, 2.16kg); the lubricant is polyethylene wax; the antioxidant is a mixture of antioxidant 1098 and antioxidant 168 in a mass ratio of 1:3.6; the light stabilizer is UV-326.

[0045] Wherein, the anti-adhesion agent is modified nano-silicon dioxide, and the preparation method comprises: S1, weigh 1g of 50±10nm nano-silica powder, 0.3g of coupling agent KH-550 and 10g of 60wt% ethanol solution, mix them, heat to 80°C, reflux for 6h, filter and dry to obtain amino nano-silica; S2. Weigh 0.45 g of tris(2-carboxyethyl)isocyanurate and add it to 10 g of dichloromethane. Stir evenly in an ice-water bath, introduce nitrogen as a protective gas, add 0.8 g of N,N'-dicyclohexylcarbodiimide (DCC), stir for 1 h, then warm to room temperature, add 0.98 g of N-hydroxysuccinimide (NHS), stir for 2 h, and obtain an activated reaction solution. S3. Add 1 g of amino-modified nano-silica to the activation reaction solution, stir for 10 hours at room temperature under the protection of nitrogen. After the reaction is completed, remove the solvent under reduced pressure, wash with water 3 times, and dry to obtain modified nano-silica.

[0046] The method for preparing the low shrinkage force PETG composite heat shrinkable film comprises the following steps: Step 1, weigh the raw materials of the upper surface layer, the lower surface layer and the inner core layer respectively, and place them in an oven at 80° C. to dry to constant weight; Step 2, after mixing the raw materials of each layer, respectively introduce them into different twin-screw extruders, and melt granulate them in the temperature range of 250-290° C. to obtain upper surface layer masterbatch, lower surface layer masterbatch and inner core layer masterbatch respectively; Step 3, pouring the three masterbatches obtained in step 2 into a three-layer co-extrusion film blowing machine, pressing and extruding them in sequence, the extrusion molding temperature is: 240°C for the upper surface layer, 260°C for the inner core layer, and 240°C for the lower surface layer; then undergoing a biaxial stretching treatment, the stretching temperature for longitudinal stretching is 90°C, the stretching ratio is 3 times, the stretching temperature for transverse stretching is 110°C, and the stretching ratio is 4.5 times; then rapidly cooling to 50°C for shaping, to obtain a low shrinkage force PETG composite heat shrinkable film with a thickness of 60 μm.

[0047] Comparative Example 1 A PETG composite heat shrinkable film, which is different from Example 1 in that the PETG film components of the upper surface layer and the lower surface layer are different, and the anti-adhesion agent therein is replaced by nano silicon dioxide powder. The PETG film, calculated by weight, includes the following components: 100 parts of PETG resin, 5 parts of nano silicon dioxide powder, 4 parts of lubricant, 1 part of antioxidant and 0.6 parts of light stabilizer.

[0048] Comparative Example 2 A PETG composite heat shrinkable film, which is different from Example 1 in that the PETG film components of the upper surface layer and the lower surface layer are different, and the anti-adhesive agent therein is replaced by amino nano-silicon dioxide, and the preparation process of amino nano-silicon dioxide is the same as that of Example 1. The PETG film comprises the following components calculated by weight: 100 parts of PETG resin, 5 parts of amino nano-silica, 4 parts of lubricant, 1 part of antioxidant and 0.6 parts of light stabilizer.

[0049] Comparative Example 3 A PETG composite heat shrinkable film, which is different from Example 1 in that the PETG film components of the upper surface layer and the lower surface layer are different, and the anti-adhesive agent therein is replaced by a mixture of nano-silicon dioxide and tris(2-carboxyethyl)isocyanurate, and the mass ratio of nano-silicon dioxide to tris(2-carboxyethyl)isocyanurate is 1:0.35. The PETG film, calculated by weight, includes the following components: 100 parts of PETG resin, 3.7 parts of nano-silicon dioxide, 1.3 parts of tris(2-carboxyethyl)isocyanurate, 4 parts of lubricant, 1 part of antioxidant and 0.6 parts of light stabilizer.

[0050] Experimental testing The heat shrinkage rate, strength and heat resistance of the PETG composite heat shrinkable films prepared in Example 1 and Comparative Examples 1-3 were tested.

[0051] Among them, the detection reference standard of tensile strength and elongation at break is ASTM D638 (tensile speed 50 mm / min).

[0052] The test of heat shrinkage and shrinkage stress refers to ISO 14616 (110℃ hot air treatment for 20 seconds).

[0053] The Vicat heat resistance temperature is tested according to ISO 306:2013 (heating rate is 50℃ / h).

[0054] The test results are shown in Table 1 below: Table 1 Test results of PETG composite heat shrink film

[0055] It can be seen from Table 1 above that the transverse tensile strength and heat shrinkage rate of the PETG composite heat shrinkable film prepared in Example 1 are higher than those of the comparative example, indicating that it has high mechanical strength and can perfectly fit complex contours; while the shrinkage stress is minimal, indicating that its shrinkage balance performance is better, while maintaining a high shrinkage rate, reducing stress, achieving more uniform body-fitting shrinkage, and avoiding label wrinkles or ruptures caused by local stress concentration.

[0056] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc., mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0057] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A low shrinkage force PETG composite heat shrinkable film, characterized in that, It includes an upper surface layer, an inner core layer and a lower surface layer arranged in sequence from top to bottom; the upper surface layer and the lower surface layer are both PETG films, and the inner core layer is a PETG / PBAT composite film; Among them, the PETG / PBAT composite film is calculated by weight and includes the following components: 60-80 parts of PETG resin, 20-40 parts of PBAT resin, 1-3 parts of plasticizer and 0.2-0.6 parts of chain extender; Among them, the PETG film is calculated by weight and includes the following components: 100 parts of PETG resin, 3-7 parts of anti-blocking agent, 2-6 parts of lubricant, 1-2 parts of antioxidant and 0.5-1 parts of light stabilizer.

2. The low shrinkage force PETG composite heat shrinkable film according to claim 1, wherein, The thickness ratio of the upper surface layer, the inner core layer and the lower surface layer is 1-3:6:1-3.

3. A low shrinkage force PETG composite heat shrinkable film according to claim 1, characterized in that, The plasticizer is a mixture of one or more of epoxidized soybean oil, epoxidized linseed oil, tributyl citrate, and acetyl tributyl citrate; the lubricant is a mixture of one or more of zinc stearate, calcium stearate, polyethylene wax, and paraffin.

4. A low shrinkage force PETG composite heat shrinkable film according to claim 1, characterized in that The chain extender is phthalic anhydride and 2,2'-bis(2-oxazoline) in a mass ratio of 1.1-1.5:

1.

5. A low shrinkage force PETG composite heat shrinkable film according to claim 1, characterized in that, The anti-adhesion agent is modified nano-silicon dioxide, and the preparation method includes: S1, weigh nano-silica powder, coupling agent KH-550 and ethanol solution, mix them, heat them to 60-80°C, reflux them for 2-6h, filter and dry them to obtain amino-modified nano-silica; S2. Weigh tris(2-carboxyethyl)isocyanurate and add it to dichloromethane. Stir evenly in an ice-water bath, introduce nitrogen as a protective gas, add N,N'-dicyclohexylcarbodiimide, stir for 0.5-1h, then warm to room temperature, add N-hydroxysuccinimide, stir for 1-2h, and obtain an activated reaction solution. S3. Add the amino-modified nano-silica to the activation reaction solution, stir for 5-10 hours at room temperature under the protection of nitrogen. After the reaction is completed, remove the solvent under reduced pressure, wash with water 2-3 times, and dry to obtain modified nano-silica.

6. The low shrinkage force PETG composite heat shrinkable film according to claim 5, characterized in that, In the preparation process of the amino-modified nano-silica, the particle size of the nano-silica is 50±10nm, the mass fraction of the ethanol solution is 30-60wt%, and the mass ratio of the silicon dioxide nano-powder, the coupling agent KH-550 and the ethanol solution is 1:0.1-0.3:5-10.

7. A low shrinkage force PETG composite heat shrinkable film according to claim 5, characterized in that, In the preparation process of the modified nano-silica, the mass ratio of the amino nano-silica, tris(2-carboxyethyl)isocyanurate, N,N'-dicyclohexylcarbodiimide, N-hydroxysuccinimide and dichloromethane is 1:0.25-0.45:0.5-0.8:0.76-0.98:5-10.

8. A low shrinkage force PETG composite heat shrinkable film according to claim 1, characterized in that, The antioxidant is obtained by mixing a main antioxidant and a secondary antioxidant in a mass ratio of 1:1.2-3.6; wherein the main antioxidant is one of antioxidant 1010, antioxidant 1076, and antioxidant 1098; and the secondary antioxidant is antioxidant 168.

9. A low-shrinkage force PETG composite heat-shrinkable film according to claim 1, wherein The light stabilizer is a mixture of one or more of UV-622, UV-770, UV-944, UV-326, UV-328, and UV-1577.

10. A method for preparing the low shrinkage force PETG composite heat shrinkable film according to claim 1, characterized in that, The following steps are involved: Step 1, Weigh the raw materials of the upper surface layer, the lower surface layer and the inner core layer respectively, and place them in an oven at 70-80 °C to dry to constant weight; Step 2, After mixing the raw materials of each layer respectively, introduce them into different twin-screw extruders, and melt granulate them in the temperature range of 250-290 °C to obtain the upper surface layer masterbatch, the lower surface layer masterbatch and the inner core layer masterbatch respectively; Step 3, Add the three kinds of materials obtained in Step 2 into three extruders, and after compounding through a die head, cast and form a sheet. First, carry out biaxial stretching treatment, and then quickly cool and shape to obtain a low shrinkage force PETG composite heat shrinkable film.

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