Preparation method of flame-retardant transparent PETG (Polyethylene Terephthalate Glycol) heat-shrinkable label film

Abstract

The invention belongs to the technical field of thermal shrinkage label films, and particularly relates to a preparation method of a flame-retardant transparent PETG thermal shrinkage label film, the PETG thermal shrinkage label film is of an ABA three-layer co-extrusion structure, the thermal shrinkage label film contains an ionic liquid flame retardant and modified transparent powder, and the specific preparation method is provided. The problem that an existing transparent PETG label film is poor in flame retardance is solved, the ionic liquid flame retardant and the transparent powder are used for forming a dual-flame-retardant system, the flame retardance of the PETG label film is greatly improved, meanwhile, the refractive index of the ionic liquid flame retardant and the refractive index of the transparent powder are similar to that of PETG resin, and transparency of the label film is not affected.

Description

Technical Field

[0001] The invention belongs to the technical field of heat shrinkable label films, and particularly relates to a method for preparing a flame-retardant and transparent PETG heat shrinkable label film. Background Art

[0002] As an important base film product for shrink labels, PETG heat-shrinkable label film has broad market applications and promising development prospects. PETG is a modified PET material with an oxygen index between 20% and 25%, making it flammable and generating significant smoke during combustion. Consequently, its processing, storage, transportation, use, and post-processing present fire hazards. Therefore, improving its flame retardancy has positive effects and practical value for PETG heat-shrinkable label film. However, in actual use, PETG heat-shrinkable label film requires printing of exquisite designs and text, and good transparency facilitates the presentation of trademark designs. Therefore, while improving flame retardancy, PETG heat-shrinkable label film must also maintain transparency.

[0003] Adding flame retardants to PETG is a common method for achieving flame retardancy in heat-shrinkable PETG films. However, current flame retardants primarily include organic halogens, such as decabromodiphenyl ether (BDPO); phosphate esters, such as triphenyl phosphate; and nitrogen-based flame retardants, such as melamine. Other flame retardants include inorganic phosphorus-based flame retardants, such as red phosphorus and phosphates; hydroxides, such as aluminum hydroxide and magnesium hydroxide; and inorganic nanomaterials, such as talc and silica powder. These flame retardants have poor compatibility with PETG. Direct addition not only degrades the surface and mechanical properties of the finished product but also significantly reduces the transparency of the PETG film. Therefore, the market urgently needs a PETG heat-shrinkable label film that combines both flame retardancy and transparency. Summary of the Invention

[0004] In response to the problems in the prior art, the present invention provides a method for preparing a flame-retardant transparent PETG heat-shrinkable label film, which solves the problem of poor flame retardancy of the existing transparent PETG label film. An ionic liquid flame retardant and a transparent powder are used to form a dual flame retardant system, which greatly improves the flame retardant properties of the PETG label film. At the same time, the refractive index of the ionic liquid flame retardant and the transparent powder is relatively close to that of the PETG resin, and does not affect the transparency of the label film.

[0005] In order to achieve the above technical objectives, the technical solution of the present invention is: The invention discloses a method for preparing a flame-retardant transparent PETG heat-shrinkable label film. The PETG heat-shrinkable label film has an ABA three-layer co-extrusion structure, wherein A is a surface layer, i.e., an upper and a lower surface layer, and the upper and lower layers have the same thickness; and B is an intermediate layer, i.e., a core layer.

[0006] The A layer is composed of PETG resin, ionic liquid flame retardant, modified transparent powder and flame retardant open masterbatch, and the mass ratio of the A layer is: 100 parts of PETG resin, 2-3 parts of ionic liquid flame retardant, 3-5 parts of modified transparent powder, and 2-3 parts of flame retardant open masterbatch.

[0007] The ionic liquid flame retardant used is the transparent PET flame retardant ER-M5100 from New Materials (Hangzhou) Co., Ltd. Ionic liquids are liquids in the form of ions, composed of organic cations and organic or inorganic anions. Due to the strong intermolecular Coulombic forces between the anions and cations, ionic liquids have a high decomposition temperature of 170-430°C. They exhibit excellent thermal stability and are non-flammable. Adding them to PETG effectively improves the thermal stability of the composite material. Ionic liquids containing halogen, tetrafluoroborate, and hexafluorophosphate anions contain flame-retardant elements such as halogen, nitrogen, and phosphorus, providing excellent flame retardancy.

[0008] The modified transparent powder adopts silanol modified transparent powder; transparent powder is a non-metallic mineral with high transparency, acid resistance and corrosion resistance. Transparent powder has high transparency and a refractive index close to that of PETG. However, transparent powder itself is an inorganic material with limited surface activity. As the use time increases and the PETG material ages, the surface inertness of the transparent powder becomes prominent, resulting in a decrease in mechanical properties. Therefore, the silanol modified transparent powder can form a silicon-oxygen structure on the surface of the transparent powder. The silicon-oxygen structure contains silicon hydroxy groups. The silicon-oxygen structure on the surface of the transparent powder can effectively improve connectivity and set the silicon-oxygen structure into a three-dimensional network structure, thereby improving the internal penetration effect of the PETG material, thereby achieving the fixation of the transparent powder. The preparation method of the silanol modified transparent powder comprises the following steps: a. 1. Blend the transparent powder with ethanol, put it into a grinder for grinding, and spray dry it to obtain transparent powder particles. The mass ratio of the transparent powder to ethanol is 2:4-5, the stirring speed of the blending is 300-500r / min, the grinding temperature is 5-10°C, the grinding pressure is 5-8MPa, the spraying speed of the spray drying is 10-20mL / min, the spraying area is 50-100cm2, and the temperature is 80-100°C. In this step, the transparent powder is wet-ground using ethanol as a solvent to refine the transparent powder, and the ethanol is removed by spray drying to form transparent powder fine particles. a2. The powder particles are placed in an alkaline solution, then filtered and allowed to stand for 10-20 minutes, washed and dried to obtain a hydroxylated transparent powder, wherein the mass ratio of the transparent powder to the alkaline solution is 1:5-8, and the pH of the alkaline solution is 9-10. The standing temperature is 50-60°C, and the drying temperature is 50-70°C. In this step, the transparent powder is surface treated with the alkaline solution to activate the surface of the transparent powder to form a silanol structure. At the same time, after standing and washing and drying, the silanol groups are distributed on the surface of the transparent powder. a3, (3-chloropropyl)trichlorosilane is added to ethanol to form a dispersion, and then the hydroxylated transparent powder is added and stirred, and filtered to obtain a coated transparent powder. The concentration of (3-chloropropyl)trichlorosilane in ethanol is 100-300 g / L, the concentration of the hydroxylated transparent powder in the dispersion is 50-100 g / L, and the stirring speed is 300-500 r / min. This step utilizes the solubility and dispersibility of (3-chloropropyl)trichlorosilane in ethanol to completely open the structure of (3-chloropropyl)trichlorosilane. During the process of adding and removing the hydroxylated transparent powder, the ethanol containing (3-chloropropyl)trichlorosilane forms a liquid film and is distributed on the surface of the hydroxylated transparent powder. a4, allowing the coated transparent powder to stand for 2-4 hours, then heating and allowing it to stand for 1-2 hours to obtain a silanol-modified transparent powder.The static atmosphere is a mixture of nitrogen and water vapor, with a volume ratio of 9-10:1, and the temperature is 20-30°C. The elevated static temperature is 200-230°C. This step utilizes the ability of water vapor in the atmosphere to dissolve in ethanol and react with (3-chloropropyl)trichlorosilane to form hydroxyl structures. These hydroxyl structures can then react with the transparent powder to form silanol groups, which then undergo a polycondensation reaction, forming a surface siloxane structure. The silanol-modified transparent powder prepared by this process utilizes silanol polycondensation to form a surface coating structure containing a large number of silanol structures and alkyl side chains with hydroxyl groups. The transparent powder is also activated by alkalization to enhance its connectivity with the (3-chloropropyl)trichlorosilane hydrolyzate.

[0009] The flame retardant open masterbatch is a silica PETG masterbatch, and the mass ratio of the flame retardant open masterbatch is: 100 parts of PETG powder, 25 parts of silica micropowder, 8 parts of dimethyl silicone oil, and 3 parts of antioxidant 1010, wherein the PETG powder is PETG resin subjected to freeze-grinding treatment and then passed through a 60-mesh sieve, and the D50 of the silica micropowder is 1.2 μm. The preparation method of the flame retardant open masterbatch is to put the weighed raw materials into a high-speed mixer and mix them for 5-8 minutes. After sufficient mixing, the mixture is added to a twin-screw granulation extruder for extrusion and granulation to obtain the flame retardant open masterbatch, and the extrusion temperature is 240-260°C.

[0010] The B layer is composed of PETG resin, ionic liquid flame retardant, modified transparent powder and recycled material, and the weight ratio is: 100 parts of PETG resin, 1.3-1.8 parts of ionic liquid flame retardant, 1.3-2.4 parts of modified transparent powder, and 10 parts of recycled material. The recycled material is recycled online from the edge yarn.

[0011] The method for preparing the flame-retardant transparent PETG heat shrinkable label film comprises the following steps: Step 1: adding PETG resin, ionic liquid flame retardant, modified transparent powder and flame retardant open masterbatch according to a ratio into a first extruder for plasticization and extrusion to obtain a layer A melt raw material; the plasticization temperature is 248-270° C.; Step 2: adding PETG resin, ionic liquid flame retardant, modified transparent powder and recycled pellets according to a ratio into a second extruder for plasticization and extrusion to obtain a B layer melt raw material; the plasticization temperature is 248-270° C.; In step 3, the melt materials for layer A and layer B are piped into a film preparation mechanism to form a PETG heat-shrinkable label film. The film forming mechanism consists of a die pre-distributor, a casting die, a sheeting mechanism, a transverse stretching system (including a trimming mechanism), a traction system, a winding system, and a slitting system. The temperature of the die pre-distributor and the casting die is 265-270°C, the transverse stretch ratio is 5, and the stretching temperature is 85-95°C. In this step, the melt material for layer A enters the corresponding flow channel of the die pre-distributor through a pipe and is divided into two streams, forming the upper and lower surface layers A. The B layer melt raw material enters the middle flow channel of the die head pre-distributor through the pipeline to form the middle layer B. The raw materials of the A and B layers form a material flow with an ABA three-layer structure after passing through the distributor. It is then cast into an ABA structure PETG sheet through the casting die and the casting mechanism. It is then made into a flame-retardant transparent PETG heat shrinkable label film product through the steps of transverse stretching, pulling, winding, and slitting.

[0012] The thickness ratio of each layer of the PETG heat shrinkable label film is 10:80:10.

[0013] It can be seen from the above description that the present invention has the following advantages: 1. The present invention solves the problem of poor flame retardancy of existing transparent PETG label films by forming a dual flame retardant system using ionic liquid flame retardants and transparent powder, which greatly improves the flame retardant properties of the PETG label film. At the same time, the refractive index of the ionic liquid flame retardant and the transparent powder is relatively close to that of the PETG resin, and does not affect the transparency of the label film.

[0014] 2. The present invention uses transparent powder to replace the ionic liquid flame retardant, which effectively reduces the problem of high activity of the ionic liquid flame retardant and improves the weather resistance and stability of the label film. DETAILED DESCRIPTION

[0015] The present invention is described in detail with reference to the embodiments, but no limitation is imposed on the claims of the present invention.

[0016] Example 1 A method for preparing a flame-retardant transparent PETG heat-shrinkable label film, wherein the PETG heat-shrinkable label film has an ABA three-layer co-extrusion structure, wherein A is a surface layer, i.e., an upper and lower surface layer, and the upper and lower layers have the same thickness; and B is an intermediate layer, i.e., a core layer.

[0017] The A layer is composed of PETG resin, ionic liquid flame retardant, modified transparent powder and flame retardant open masterbatch, and the mass ratio of the A layer is: 100 parts of PETG resin, 2 parts of ionic liquid flame retardant, 3 parts of modified transparent powder and 2 parts of flame retardant open masterbatch.

[0018] The ionic liquid flame retardant is the transparent PET flame retardant ER-M5100 produced by New Materials (Hangzhou) Co., Ltd.

[0019] The modified transparent powder adopts silanol modified transparent powder; the preparation method of the silanol modified transparent powder comprises the following steps: a1, blending the transparent powder with ethanol, putting it into a grinder for grinding, spray drying to obtain transparent powder particles, the mass ratio of the transparent powder to ethanol is 2:4, the stirring speed of the blending is 300r / min, the temperature of the grinding treatment is 5°C, the grinding pressure is 5MPa, the spray speed of the spray drying is 10mL / min, the spray area is 50cm2, and the temperature is 80°C; a2, putting the transparent powder particles into alkali solution, filtering and standing for 10min, washing and drying to obtain hydroxylated transparent powder, the mass ratio of the transparent powder to the alkali solution is 1:5, and the alkali solution The pH value is 9, the standing temperature is 50°C, and the drying temperature is 50°C; a3, (3-chloropropyl)trichlorosilane is added to ethanol to form a dispersion, and then the hydroxylated transparent powder is added and stirred, and a coated transparent powder is obtained after filtration; the concentration of the (3-chloropropyl)trichlorosilane in ethanol is 100 g / L, the concentration of the hydroxylated transparent powder in the dispersion is 50 g / L, and the stirring speed is 300 r / min; a4, the coated transparent powder is allowed to stand for 4 hours, and the temperature is increased and allowed to stand for 2 hours to obtain a silanol-modified transparent powder; the standing atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 10:1, the temperature is 20°C, and the temperature of the heated standing is 230°C.

[0020] The flame retardant open masterbatch is a silica PETG masterbatch, and the mass ratio of the flame retardant open masterbatch is: 100 parts of PETG powder, 25 parts of silica micropowder, 8 parts of dimethyl silicone oil, and 3 parts of antioxidant 1010, wherein the PETG powder is PETG resin subjected to freeze-grinding treatment and then passed through a 60-mesh sieve, the D50 of the silica micropowder is 1.2 μm, and the preparation method of the flame retardant open masterbatch is to put the weighed raw materials into a high-speed mixer and mix for 5 minutes, and after sufficient mixing, add the mixture into a twin-screw granulation extruder for extrusion granulation to obtain the flame retardant open masterbatch, and the extrusion temperature is 240°C.

[0021] The B layer is composed of PETG resin, ionic liquid flame retardant, modified transparent powder and recycled material, and the weight ratio is: 100 parts of PETG resin, 1.3 parts of ionic liquid flame retardant, 1.3 parts of modified transparent powder, and 10 parts of recycled material. The recycled material is recycled online for edge yarn.

[0022] The method for preparing the flame-retardant transparent PETG heat shrinkable label film comprises the following steps: Step 1: adding PETG resin, ionic liquid flame retardant, modified transparent powder and flame retardant open masterbatch according to a ratio into a first extruder and plasticizing and extruding to obtain a layer A melt raw material; the plasticizing temperature is 270° C.; Step 2: adding PETG resin, ionic liquid flame retardant, modified transparent powder and recycled pellets according to a ratio into a second extruder for plasticization and extrusion to obtain a B layer melt raw material; the plasticization temperature is 270° C.; Step 3: The A layer melt raw material and the B layer melt raw material are respectively fed into a film preparation mechanism through pipelines to be processed into a PETG heat shrinkable label film. The film forming mechanism consists of a die pre-distributor, a casting die, a casting mechanism, a transverse stretching system (including a trimming mechanism), a traction system, a winding system, a slitting system, and the like. The temperature of the die pre-distributor and the casting die is 270° C., the transverse stretching ratio is 5, and the stretching temperature is 95° C.

[0023] The thickness ratio of each layer of the PETG heat shrinkable label film is 10:80:10.

[0024] Example 2 A method for preparing a flame-retardant transparent PETG heat-shrinkable label film, wherein the PETG heat-shrinkable label film has an ABA three-layer co-extrusion structure, wherein A is a surface layer, i.e., an upper and lower surface layer, and the upper and lower layers have the same thickness; and B is an intermediate layer, i.e., a core layer.

[0025] The A layer is composed of PETG resin, ionic liquid flame retardant, modified transparent powder and flame retardant open masterbatch, and the mass ratio of the A layer is: 100 parts of PETG resin, 3 parts of ionic liquid flame retardant, 5 parts of modified transparent powder and 2.5 parts of flame retardant open masterbatch.

[0026] The ionic liquid flame retardant is the transparent PET flame retardant ER-M5100 produced by New Materials (Hangzhou) Co., Ltd.

[0027] The modified transparent powder adopts silanol-modified transparent powder; the preparation method of the silanol-modified transparent powder comprises the following steps: a1, blending the transparent powder with ethanol, putting the mixture into a grinder for grinding, spray drying to obtain transparent powder particles, wherein the mass ratio of the transparent powder to the ethanol is 2:5, the stirring speed of the blending is 500r / min, the temperature of the grinding treatment is 10°C, the grinding pressure is 8MPa, the spray speed of the spray drying is 20mL / min, the spray area is 100cm2, and the temperature is 100°C; a2, putting the transparent powder particles into alkali solution, filtering and standing for 20min, washing and drying to obtain hydroxylated transparent powder, wherein the mass ratio of the transparent powder to the alkali solution is 1:8, and the alkali solution is 1:10. The pH value of the liquid is 9, the standing temperature is 60°C, and the drying temperature is 70°C; a3, (3-chloropropyl)trichlorosilane is added to ethanol to form a dispersion, and then the hydroxylated transparent powder is added and stirred, and the coating transparent powder is obtained after filtration; the concentration of the (3-chloropropyl)trichlorosilane in the ethanol is 300 g / L, the concentration of the hydroxylated transparent powder in the dispersion is 100 g / L, and the stirring speed is 500 r / min; a4, the coating transparent powder is allowed to stand for 2 hours, and the temperature is increased and allowed to stand for 1 hour to obtain a silanol-modified transparent powder; the standing atmosphere is a mixed atmosphere of nitrogen and water vapor with a volume ratio of nitrogen to water vapor of 9:1, the temperature is 20°C, and the temperature of the heating and standing is 230°C.

[0028] The flame retardant open masterbatch is a silica PETG masterbatch, and the mass ratio of the flame retardant open masterbatch is: 100 parts of PETG powder, 25 parts of silica micropowder, 8 parts of dimethyl silicone oil, and 3 parts of antioxidant 1010, wherein the PETG powder is PETG resin subjected to freeze-grinding treatment and then passed through a 60-mesh sieve, the D50 of the silica micropowder is 1.2 μm, and the preparation method of the flame retardant open masterbatch is to put the weighed raw materials into a high-speed mixer and mix for 8 minutes, and after sufficient mixing, add the mixture into a twin-screw granulation extruder for extrusion granulation to obtain the flame retardant open masterbatch, and the extrusion temperature is 260°C.

[0029] The B layer is composed of PETG resin, ionic liquid flame retardant, modified transparent powder and recycled material, and the weight ratio is: 100 parts of PETG resin, 1.8 parts of ionic liquid flame retardant, 2.4 parts of modified transparent powder, and 10 parts of recycled material. The recycled material is recycled online for edge yarn.

[0030] The method for preparing the flame-retardant transparent PETG heat shrinkable label film comprises the following steps: Step 1: adding PETG resin, ionic liquid flame retardant, modified transparent powder and flame retardant open masterbatch according to a ratio into a first extruder and plasticizing and extruding to obtain a layer A melt raw material; the plasticizing temperature is 270° C.; Step 2: adding PETG resin, ionic liquid flame retardant, modified transparent powder and recycled pellets according to a ratio into a second extruder for plasticization and extrusion to obtain a B layer melt raw material; the plasticization temperature is 270° C.; Step 3: The A layer melt raw material and the B layer melt raw material are respectively fed into a film preparation mechanism through pipelines to be processed into a PETG heat shrinkable label film. The film forming mechanism consists of a die pre-distributor, a casting die, a casting mechanism, a transverse stretching system (including a trimming mechanism), a traction system, a winding system, a slitting system, and the like. The temperature of the die pre-distributor and the casting die is 270°C, the transverse stretching ratio is 5, and the stretching temperature is 90°C.

[0031] The thickness ratio of each layer of the PETG heat shrinkable label film is 10:80:10.

[0032] Example 3 A method for preparing a flame-retardant transparent PETG heat-shrinkable label film, wherein the PETG heat-shrinkable label film has an ABA three-layer co-extrusion structure, wherein A is a surface layer, i.e., an upper and lower surface layer, and the upper and lower layers have the same thickness; and B is an intermediate layer, i.e., a core layer.

[0033] The A layer is composed of PETG resin, ionic liquid flame retardant, modified transparent powder and flame retardant open masterbatch, and the mass ratio of the A layer is: 100 parts of PETG resin, 2.5 parts of ionic liquid flame retardant, 4 parts of modified transparent powder and 3 parts of flame retardant open masterbatch.

[0034] The ionic liquid flame retardant is the transparent PET flame retardant ER-M5100 produced by New Materials (Hangzhou) Co., Ltd.

[0035] The modified transparent powder adopts silanol modified transparent powder; the preparation method of the silanol modified transparent powder comprises the following steps: a1, blending the transparent powder with ethanol, putting it into a grinder for grinding, spray drying to obtain transparent powder particles, the mass ratio of the transparent powder to ethanol is 2:5, the stirring speed of the blending is 400r / min, the temperature of the grinding treatment is 8°C, the grinding pressure is 7MPa, the spray speed of the spray drying is 15mL / min, the spray area is 80cm2, and the temperature is 90°C; a2, putting the transparent powder particles into alkali solution, filtering and standing for 15min, washing and drying to obtain hydroxylated transparent powder, the mass ratio of the transparent powder to the alkali solution is 1:7, and the alkali solution The pH value is 10, the standing temperature is 55°C, and the drying temperature is 60°C; a3, (3-chloropropyl)trichlorosilane is added to ethanol to form a dispersion, and then the hydroxylated transparent powder is added and stirred, and a coating transparent powder is obtained after filtration; the concentration of the (3-chloropropyl)trichlorosilane in ethanol is 200 g / L, the concentration of the hydroxylated transparent powder in the dispersion is 80 g / L, and the stirring speed is 400 r / min; a4, the coating transparent powder is allowed to stand for 3 hours, and the temperature is increased and allowed to stand for 2 hours to obtain a silanol-modified transparent powder; the standing atmosphere is a mixed atmosphere of nitrogen and water vapor, and the volume ratio of nitrogen to water vapor is 9:1, the temperature is 25°C, and the temperature of the heating and standing is 220°C.

[0036] The flame retardant open masterbatch is a silica PETG masterbatch, and the mass ratio of the flame retardant open masterbatch is: 100 parts of PETG powder, 25 parts of silica micropowder, 8 parts of dimethyl silicone oil, and 3 parts of antioxidant 1010, wherein the PETG powder is PETG resin subjected to freeze-grinding treatment and then passed through a 60-mesh sieve, the D50 of the silica micropowder is 1.2 μm, and the preparation method of the flame retardant open masterbatch is to put the weighed raw materials into a high-speed mixer and mix for 7 minutes, and after sufficient mixing, add the mixture into a twin-screw granulation extruder for extrusion granulation to obtain the flame retardant open masterbatch, and the extrusion temperature is 250°C.

[0037] The B layer is composed of PETG resin, ionic liquid flame retardant, modified transparent powder and recycled material, and the weight ratio is: 100 parts of PETG resin, 1.5 parts of ionic liquid flame retardant, 2.2 parts of modified transparent powder, and 10 parts of recycled material. The recycled material is recycled online for edge yarn.

[0038] The method for preparing the flame-retardant transparent PETG heat shrinkable label film comprises the following steps: Step 1: adding PETG resin, ionic liquid flame retardant, modified transparent powder and flame retardant open masterbatch according to a ratio into a first extruder and plasticizing and extruding to obtain a layer A melt raw material; the plasticizing temperature is 260° C.; Step 2: adding PETG resin, ionic liquid flame retardant, modified transparent powder and recycled pellets according to a ratio into a second extruder for plasticization and extrusion to obtain a B layer melt raw material; the plasticization temperature is 270° C.; Step 3: The A layer melt raw material and the B layer melt raw material are respectively fed into a film preparation mechanism through pipelines to be processed into a PETG heat shrinkable label film. The film forming mechanism consists of a die pre-distributor, a casting die, a casting mechanism, a transverse stretching system (including a trimming mechanism), a traction system, a winding system, a slitting system, and the like. The temperature of the die pre-distributor and the casting die is 270°C, the transverse stretching ratio is 5, and the stretching temperature is 90°C.

[0039] The thickness ratio of each layer of the PETG heat shrinkable label film is 10:80:10.

[0040] Comparative Example 1 A method for preparing a flame-retardant transparent PETG heat-shrinkable label film, wherein the PETG heat-shrinkable label film has an ABA three-layer co-extrusion structure, wherein A is a surface layer, i.e., an upper and lower surface layer, and the upper and lower layers have the same thickness; and B is an intermediate layer, i.e., a core layer.

[0041] The A layer is composed of PETG resin, ionic liquid flame retardant, transparent powder and flame retardant open masterbatch, and the mass ratio of the A layer is: 100 parts of PETG resin, 2.5 parts of ionic liquid flame retardant, 4 parts of transparent powder and 3 parts of flame retardant open masterbatch.

[0042] The ionic liquid flame retardant is the transparent PET flame retardant ER-M5100 produced by New Materials (Hangzhou) Co., Ltd.

[0043] The flame retardant open masterbatch is a silica PETG masterbatch, and the mass ratio of the flame retardant open masterbatch is: 100 parts of PETG powder, 25 parts of silica micropowder, 8 parts of dimethyl silicone oil, and 3 parts of antioxidant 1010, wherein the PETG powder is PETG resin subjected to freeze-grinding treatment and then passed through a 60-mesh sieve, the D50 of the silica micropowder is 1.2 μm, and the preparation method of the flame retardant open masterbatch is to put the weighed raw materials into a high-speed mixer and mix for 7 minutes, and after sufficient mixing, add the mixture into a twin-screw granulation extruder for extrusion granulation to obtain the flame retardant open masterbatch, and the extrusion temperature is 250°C.

[0044] The B layer is composed of PETG resin, ionic liquid flame retardant, transparent powder and recycled material, and the weight ratio is: 100 parts of PETG resin, 1.5 parts of ionic liquid flame retardant, 2.2 parts of transparent powder, and 10 parts of recycled material. The recycled material is recycled online from the edge yarn.

[0045] The method for preparing the flame-retardant transparent PETG heat shrinkable label film comprises the following steps: Step 1: adding PETG resin, ionic liquid flame retardant, transparent powder and flame retardant open masterbatch according to a ratio into a first extruder and plasticizing and extruding to obtain a layer A melt raw material; the plasticizing temperature is 260° C.; Step 2: adding PETG resin, ionic liquid flame retardant, transparent powder and recycled pellets according to a ratio into a second extruder for plasticization and extrusion to obtain a B layer melt raw material; the plasticization temperature is 270° C.; Step 3: The A layer melt raw material and the B layer melt raw material are respectively fed into a film preparation mechanism through pipelines to be processed into a PETG heat shrinkable label film. The film forming mechanism consists of a die pre-distributor, a casting die, a casting mechanism, a transverse stretching system (including a trimming mechanism), a traction system, a winding system, a slitting system, and the like. The temperature of the die pre-distributor and the casting die is 270°C, the transverse stretching ratio is 5, and the stretching temperature is 90°C.

[0046] The thickness ratio of each layer of the PETG heat shrinkable label film is 10:80:10.

[0047] Comparative Example 2 A method for preparing a flame-retardant transparent PETG heat-shrinkable label film, wherein the PETG heat-shrinkable label film has an ABA three-layer co-extrusion structure, wherein A is a surface layer, i.e., an upper and lower surface layer, and the upper and lower layers have the same thickness; and B is an intermediate layer, i.e., a core layer.

[0048] The A layer is composed of PETG resin and open-mouthed smooth masterbatch, and the mass ratio of the A layer is: 100 parts of PETG resin and 2.5 parts of open-mouthed smooth masterbatch.

[0049] The B layer is composed of PETG resin and recycled material, and the mass ratio thereof is: 100 parts of PETG resin and 10 parts of recycled material.

[0050] The preparation method of the flame-retardant transparent PETG heat shrinkable label film is the same as that of Example 3.

[0051] Performance testing The films of Examples 1-3 and Comparative Examples 1-2 were used as test samples for performance testing, and the results are as follows:

[0052] The above data demonstrate that this technical solution effectively improves the flame retardancy of the label film while also ensuring its transparency. A comparison of Examples 1-3 and Comparative Example 2 demonstrates that both the ionic liquid flame retardant and the modified transparent powder effectively enhance the flame retardancy of the label film without affecting the transparent powder. While Comparative Example 1 exhibits good transparency initially, it develops a milky white color and even begins to shed powder over time due to aging of the resin material. Therefore, modification of the transparent powder effectively enhances the weather resistance and stability of the label film.

[0053] It is understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced with equivalents to achieve the same technical effects; as long as the use requirements are met, they are all within the scope of protection of the present invention.

Claims

1. A method for preparing a flame-retardant transparent PETG heat shrinkable label film, characterized in that: The PETG heat shrinkable label film is an ABA three-layer co-extrusion structure, wherein A is the surface layer, i.e., the upper and lower surface layers, and the upper and lower layers have the same thickness; B is the middle layer, i.e., the core layer.

2. The method for preparing the flame-retardant transparent PETG heat shrinkable label film according to claim 1, wherein: The A layer is composed of PETG resin, ionic liquid flame retardant, modified transparent powder and flame retardant open masterbatch, and the mass ratio of the A layer is: 100 parts of PETG resin, 2-3 parts of ionic liquid flame retardant, 3-5 parts of modified transparent powder, and 2-3 parts of flame retardant open masterbatch.

3. The method for preparing the flame-retardant transparent PETG heat shrinkable label film according to claim 2, wherein: The ionic liquid flame retardant is the transparent PET flame retardant ER-M5100 produced by New Materials (Hangzhou) Co., Ltd.

4. The method for preparing the flame-retardant transparent PETG heat shrinkable label film according to claim 2, wherein: The modified transparent powder is silanol modified transparent powder.

5. The method for preparing the flame-retardant transparent PETG heat shrinkable label film according to claim 2, wherein: The flame retardant opening masterbatch is a silicon dioxide PETG masterbatch.

6. The method for preparing the flame-retardant transparent PETG heat shrinkable label film according to claim 5, wherein: The mass ratio of the flame retardant open masterbatch is: 100 parts of PETG powder, 25 parts of silicon dioxide powder, 8 parts of dimethyl silicone oil, and 3 parts of antioxidant 1010.

7. The method for preparing the flame-retardant transparent PETG heat shrinkable label film according to claim 1, wherein: The B layer is composed of PETG resin, ionic liquid flame retardant, modified transparent powder and recycled material, and the mass ratio thereof is: 100 parts of PETG resin, 1.3-1.8 parts of ionic liquid flame retardant, 1.3-2.4 parts of modified transparent powder and 10 parts of recycled material.

8. The method for preparing the flame-retardant transparent PETG heat shrinkable label film according to claim 1, wherein: The method for preparing the flame-retardant transparent PETG heat shrinkable label film comprises the following steps: Step 1: adding PETG resin, ionic liquid flame retardant, modified transparent powder and flame retardant open masterbatch according to a ratio into a first extruder for plasticization and extrusion to obtain a layer A melt raw material; the plasticization temperature is 248-270° C.; Step 2: adding PETG resin, ionic liquid flame retardant, modified transparent powder and recycled pellets according to a ratio into a second extruder for plasticization and extrusion to obtain a B layer melt raw material; the plasticization temperature is 248-270° C.; Step 3: The A layer melt raw material and the B layer melt raw material are respectively fed into a film preparation mechanism through pipelines to be processed into a PETG heat shrinkable label film. The film forming mechanism is composed of a die pre-distributor, a casting die, a casting mechanism, a transverse stretching system (including a trimming mechanism), a traction system, a winding system, a slitting system, and the like. The temperature of the die pre-distributor and the casting die is 265-270°C, the transverse stretching ratio is 5, and the stretching temperature is 85-95°C.

9. The method for preparing the flame-retardant transparent PETG heat shrinkable label film according to claim 8, wherein: The thickness ratio of each layer of the PETG heat shrinkable label film is 10:80:10.

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