Preparation method of bamboo-plastic composite PETG thermal shrinkage label film

Abstract

The invention belongs to the technical field of label films, and particularly relates to a preparation method of a bamboo-plastic composite PETG (polyethylene terephthalate glycol) heat-shrinkable label film, which comprises the following steps: taking PETG resin and opening master batch as a layer A, taking PETG resin, bamboo powder master batch containing pretreated bamboo powder, a compatibilizer and a recycled material as a layer B, respectively melting and extruding, then feeding into a film preparation mechanism, and processing and forming the PETG label film. The defects of the bamboo-plastic composite PETG thermal shrinkage label film are overcome, the bamboo powder is modified in the modes of refining, plasma etching and coupling treatment, so that the interfacial compatibility of the bamboo powder and the plastic base material PETG is improved, the bamboo powder master batch is obtained in the mode of melt extrusion granulation, and the dispersity and compatibility of the bamboo powder in the thermal shrinkage label film are effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of label films, and particularly relates to a preparation method of a bamboo-plastic composite PETG heat shrinkable label film. Background Art

[0002] PETG heat-shrinkable label film is the mainstream base film product for shrink labels today. Although it does not contain phthalates and does not pose a potential risk of dioxin disposal, it still faces certain environmental concerns due to practical issues such as its raw material being derived from petroleum and being unable to be recycled with PET bottles.

[0003] Bamboo powder, a simple processed product from bamboo, is a natural, renewable material with excellent biodegradability. It can be added to plastics to create bamboo-plastic composite products, increasing the added value of bamboo materials, reducing plastic usage and waste, and protecting the environment. Therefore, adding bamboo powder to PETG shrink label film not only reduces the use of petroleum-based PETG and increases the bio-based content of the label material, but also effectively reduces the density of the bamboo-plastic composite PETG heat-shrinkable label film, creating a significant density difference with the PET bottle, facilitating simple density separation during recycling. Furthermore, the addition of bamboo powder imparts a natural scent and flavor to the label, giving it a sense of connection to nature.

[0004] However, the most significant challenge in the processing of bamboo powder and PETG composite metamaterials is the significant difference in surface properties between the two materials, resulting in poor interfacial compatibility. Simply coupling bamboo powder with PETG for filling and composite processing results in poor mechanical properties, failing to meet the demands of higher processing and application requirements. Therefore, improving the surface properties of bamboo powder and enhancing its compatibility with the PETG interface are key technical considerations for producing high-quality bamboo-plastic composite PETG heat-shrinkable label films. Summary of the Invention

[0005] In response to the problems in the prior art, the present invention provides a method for preparing a bamboo-plastic composite PETG heat shrinkable label film, which solves the defects of the bamboo-plastic composite PETG heat shrinkable label film. The bamboo powder is modified by means of refinement, plasma etching, and coupling treatment, thereby increasing the interface compatibility between the bamboo powder and the plastic substrate PETG, and bamboo powder masterbatch is obtained by melt extrusion granulation, effectively improving the dispersibility and compatibility of the bamboo powder in the heat shrinkable label film.

[0006] In order to achieve the above technical objectives, the technical solution of the present invention is: A method for preparing a bamboo-plastic composite PETG heat shrinkable label film comprises the following steps: Step 1: Add PETG resin and open masterbatch into the first extruder for plasticization and extrusion to obtain a layer A melt raw material; the plasticization temperature of the first extruder is 250-272° C.; Step 2: Put the PETG resin, bamboo powder masterbatch, compatibilizer, and edge wire recycling into a second extruder for plasticization and extrusion to obtain a B layer melt raw material; the plasticization temperature of the second extruder is 250-272° C.; Step 3, the A layer melt raw material and the B layer melt raw material are respectively introduced into a film preparation mechanism through pipelines to be processed into a PETG label film; the film preparation 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 A layer melt raw material enters the corresponding channel of the die pre-distributor through a pipeline and is divided into two streams to form upper and lower surface layers A; the B layer melt raw material enters the middle flow channel of the die pre-distributor through a pipeline to form an intermediate 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, and are cast into an ABA structure PETG sheet through the casting die and the casting mechanism, and then undergoes transverse stretching, traction, winding, slitting, and the like to make a bamboo-plastic composite PETG heat shrinkable label film product. The temperature of the die pre-distributor is 268-272°C, the temperature of the casting die is 268-272°C, the transverse stretching multiple is 5, and the stretching temperature is 86-98°C.

[0007] The thickness ratio of the ABA three-layer film of the bamboo-plastic composite PETG heat shrinkable label film is 10:80:10.

[0008] The mass ratio of the A layer is: 100 parts PETG resin and 2.5 parts open-cell masterbatch. The open-cell masterbatch is Sukano® TA10-08MB13 from Sukano, Switzerland. The PETG resin is a CHDM-modified PETG product or an NPG-modified PETG product. The CHDM-modified PETG resin is one of Embrace™ copolyester, Embrace™ LV copolyester, GN001, S2008 from SK, Korea, or K2012 from SK. The NPG-modified PETG product is one of Yizheng Chemical Fiber FG718H, Jiangsu Solide Company HSF, and Jiangyin Huahong W-501.

[0009] The mass ratio of the B layer is: 100 parts of PETG resin, 40-60 parts of bamboo powder masterbatch, 10-20 parts of compatibilizer, and 10 parts of recycled material. The recycled material is recycled online by edge wire. The PETG resin is a CHDM-modified PETG product or an NPG-modified PETG product. The CHDM-modified PETG resin is one of Embrace™ copolyester, Embrace™ LV copolyester, GN001, S2008 of South Korea's SK Company, and K2012 of South Korea's SK Company. The NPG-modified PETG product is one of Yizheng Chemical Fiber FG718H, Jiangsu Solide Company HSF, and Jiangyin Huahong W-501. The compatibilizer is AM-g-PETG-g-MA.

[0010] The compatibilizer AM-g-PETG-g-MA is prepared by grafting copolymerization of acrylamide and maleic anhydride on the surface of PETG particles using ammonium cerium nitrate and diisopropylbenzene peroxide as initiators through solution free radical polymerization. The compatibilizer AM-g-PETG-g-MA is prepared by: a1, using 1,3-dioxolane to prepare a 10% by mass 1,3-dioxolane solution of acrylamide and maleic anhydride; a2, mixing 200 parts by weight of PETG chip particles, 150 parts by weight of 10% acrylamide-1,3-dioxolane solution, and 50 parts by weight of 10% maleic anhydride-1,3-dioxolane solution. The reaction mixture was added into a closed reactor, the oxygen therein was replaced with nitrogen, the temperature was raised to 65° C., and the mixture was expanded for 1 hour. Then, 200 parts by weight of anhydrous ethanol, 5 parts by weight of ammonium cerium nitrate, and 1.5 parts by weight of dicumyl peroxide were added to the reactor, stirred evenly, and kept warm for 4 hours. After the reaction, the reactant was filtered and the residual PETG particles were rinsed with distilled water several times to remove the solvent, unreacted initiator and comonomer. The particles were then placed in a container filled with a large amount of distilled water and soaked for 20 minutes. The particles were filtered again, and the residual PETG particles were moved to an oven and dried at 65° C. for 6 hours to obtain a compatibilizer AM-g-PETG-g-MA with a grafting rate of 7-9%.

[0011] The bamboo powder masterbatch is prepared by mixing bamboo powder, PETG powder, an antioxidant and a lubricant in a certain proportion, and the mass ratio of the bamboo powder masterbatch is: 60 parts of bamboo powder, 40 parts of PETG powder, 3 parts of antioxidant and 1 part of lubricant, wherein the bamboo powder is pretreated before use; the PETG powder is obtained by freeze-grinding PETG slice particles and passing through a 40-mesh sieve; the antioxidant is antioxidant 1010 from Tianjin Lianlong New Materials Co., Ltd.; and the lubricant is oxidized polyethylene wax AC-540A from Honeywell. The preparation method of the bamboo powder masterbatch comprises: b1, weighing raw materials according to the proportion, putting all of them into a mixer, stirring at high speed for 5 minutes, and discharging to obtain a mixture; b2, adding the mixture into a twin-screw extruder, heating and plasticizing, and extruding and granulating to prepare the bamboo powder masterbatch. The twin-screw extruder is φ55, with a body temperature of 170-250°C, a pelletizing head temperature of 245-248°C, and a screw speed of 40-45 r / min. The extruded strands are pelletized using a crawler-type air-cooling method and crushed by a pulverizer to avoid excessive moisture content in the bamboo powder masterbatch produced from water-cooled strands, which could affect subsequent film production. The bamboo powder pretreatment includes refinement, etching, and surface coupling treatment.

[0012] Furthermore, the bamboo powder pretreatment method includes the following steps: c1, bamboo powder refining treatment: the commercially available 60-80 mesh bamboo powder is refined using a ZJ-C600 bamboo powder ultrafine grinder to prepare ultrafine bamboo powder with a D90 of 1800 mesh (8.5 μm); as the bamboo powder fineness increases, the bamboo powder density decreases, the density of 1800 mesh bamboo powder is about 0.6, and its bulk density is about 0.36; c2, bamboo powder surface etching: the refined bamboo powder is added to a vacuum drum plasma cleaning machine, and the surface of the bamboo powder particles is impacted at high speed by plasma (high-energy active particles); the energy of the active particles in the plasma is generally close to or exceeds the bond energy of CC or other carbon bonds, and under its high-speed impact, the surface of the bamboo powder particles is etched. The surface of the bamboo powder particles will undergo complex physical and chemical changes. The vacuum drum plasma cleaning machine uses the RD-60 produced by Shanghai Xuanyi Environmental Protection Technology Co., Ltd., with a vacuum chamber volume of φ500x400, a vacuum degree of 50Pa, and a processing time of 40 seconds. c3, bamboo powder surface coupling treatment: first, the coupling agent is dissolved in anhydrous ethanol to prepare a 2% ethanol solution, and the bamboo powder is placed in a high-speed mixer and stirred and heated to 110°C to remove moisture; then, the ethanol solution is sprayed on the bamboo powder using a sprayer. After spraying, the mixture is mixed at high speed for 5 minutes, and the material is discharged and cooled to obtain pretreated bamboo powder. The coupling agent is one of KH550, KH560, and KH570. The amount of ethanol solution used is 3% of the mass of the bamboo powder.

[0013] It can be seen from the above description that the present invention has the following advantages: 1. The present invention solves the defects of bamboo-plastic composite PETG heat shrinkable label film. The bamboo powder is modified by thinning, plasma etching, and coupling treatment, thereby increasing the interfacial compatibility between the bamboo powder and the plastic substrate PETG. The bamboo powder masterbatch is obtained by melt extrusion granulation, effectively improving the dispersibility and compatibility of the bamboo powder in the heat shrinkable label film.

[0014] 2. The present invention utilizes solution polymerization technology, under the joint initiation of ammonium cerium nitrate and dicumyl peroxide, to promote the graft copolymerization of acrylic acid and maleic anhydride on PETG through free radical polymerization, thereby effectively improving the interfacial compatibility between bamboo powder and PETG. 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] The pretreatment method of bamboo powder includes the following steps: c1, bamboo powder refining treatment: the commercially available 60-80 mesh bamboo powder is refined using a ZJ-C600 bamboo powder ultrafine pulverizer to prepare ultrafine bamboo powder with a D90 of 1800 mesh (8.5 μm); c2, bamboo powder surface etching: the refined bamboo powder is added to a vacuum drum plasma cleaning machine, and plasma (high-energy active particles) is used to impact the surface of the bamboo powder particles at high speed; the vacuum drum plasma cleaning machine adopts the RD-6 0, the volume of the vacuum chamber is φ500x400, the vacuum degree is 50Pa, and the treatment time is 40 seconds; c3, bamboo powder surface coupling treatment; first, the coupling agent is dissolved in anhydrous ethanol to prepare a 2% ethanol solution, the bamboo powder is placed in a high-speed mixer, stirred and heated to 110°C to remove moisture; then, the ethanol solution is sprayed on the bamboo powder using a sprayer, and after spraying, it is mixed at high speed for 5 minutes, discharged and cooled to obtain pretreated bamboo powder; the coupling agent is KH550; the amount of ethanol solution used is 3% of the mass of the bamboo powder.

[0017] The preparation method of bamboo powder masterbatch comprises the following steps: b1, weighing bamboo powder, PETG powder, antioxidant, and lubricant according to a ratio of 60 parts bamboo powder, 40 parts PETG powder, 3 parts antioxidant, and 1 part lubricant, wherein the bamboo powder adopts the above-mentioned pretreated bamboo powder, and the PETG powder is obtained by freeze-grinding PETG slice particles and passing through a 40-mesh sieve; the antioxidant is antioxidant 1010 produced by Tianjin Lianlong New Materials Co., Ltd.; and the lubricant is oxidized polyethylene wax AC-540A produced by Honeywell; b2, putting all the above-mentioned weighed raw materials into a mixer, stirring at high speed for 5 minutes, and discharging to obtain a mixture; b3, adding the mixture into a twin-screw extruder, heating and plasticizing, and extruding and granulating to prepare bamboo powder masterbatch, wherein the twin-screw extruder is φ55, has a body temperature of 170-250° C., a granulation die temperature of 245-248° C., and a screw speed of 40-45 r / min.

[0018] The compatibilizer adopts AM-g-PETG-g-MA, which is grafted copolymerized on the surface of PETG particles by solution free radical polymerization using acrylamide and maleic anhydride as graft copolymer monomers, ammonium cerium nitrate and dicumyl peroxide as initiators, to prepare the compatibilizer AM-g-PETG-g-MA. The preparation method of the compatibilizer comprises: a1, using 1,3-dioxolane to respectively prepare a 1,3-dioxolane solution with a mass fraction of 10% by weight of acrylamide and maleic anhydride; a2, mixing 200 parts by weight of PETG chip particles, 150 parts by weight of a 10% acrylamide-1,3-dioxolane solution, and 50 parts by weight of a 10% maleic anhydride-1,3-dioxolane solution. Add them together into a closed reactor, replace the oxygen therein with nitrogen, heat to 65°C, expand for 1 hour, then add 200 parts by weight of anhydrous ethanol, 5 parts by weight of ammonium cerium nitrate, and 1.5 parts by weight of diisopropylbenzene peroxide to the reactor, stir evenly and keep warm for 4 hours, a3. After the reaction is completed, filter the reactants, rinse the residue PETG particles with distilled water several times to remove the solvent, unreacted initiator and comonomer, and then place it in a container filled with a large amount of distilled water and soak and wash for 20 minutes, filter again, move the residue PETG particles to an oven, and dry them at 65°C for 6 hours to obtain a compatibilizer AM-g-PETG-g-MA with a grafting rate of 7-9%.

[0019] Example 1 A method for preparing a bamboo-plastic composite PETG heat shrinkable label film comprises the following steps: Step 1: Weigh the raw materials according to the mass ratio; the mass ratio of the A layer is 100 parts of PETG resin and 2.5 parts of open masterbatch. Among them, the open masterbatch is Sukano®TA10-08MB13 from Sukarno, Switzerland, and the PETG resin is an NPG-modified PETG product, specifically HSF from Jiangsu Solide Company; the mass ratio of the B layer is 100 parts of PETG resin, 40 parts of bamboo powder masterbatch, 10 parts of compatibilizer, and 10 parts of recycled material, wherein the PETG resin is an NPG-modified PETG product, specifically HSF from Jiangsu Solide Company, the bamboo powder masterbatch is the masterbatch prepared above, and the compatibilizer is the compatibilizer AM-g-PETG-g-MA prepared above; Step 2: adding the raw material of layer A into the first extruder for plasticization and extrusion to obtain the melt raw material of layer A; the plasticization temperature of the first extruder is 250-272°C; Step 3: Place the raw material of layer B into a second extruder for plasticization and extrusion to obtain a melt raw material of layer B; the plasticization temperature of the second extruder is 250-272°C; Step 4: The A layer melt raw material and the B layer melt raw material are respectively fed into the film preparation mechanism through pipelines to be processed into a PETG label film. The film preparation mechanism is composed of a die pre-distributor, a casting die, a sheet casting mechanism, a transverse stretching system (including a trimming mechanism), a traction system, a winding system, a slitting system, and the like. The A layer melt raw material enters the corresponding channel of the die pre-distributor through a pipeline and is divided into two streams to form the upper and lower surface layers A. The B layer melt raw material enters the die pre-distributor through a pipeline and is divided into two streams to form the upper and lower surface layers A. The middle flow channel of the device forms the middle layer B. The raw materials of layers A and B pass through the distributor to form a material flow with an ABA three-layer structure. The material is then cast into an ABA structure PETG sheet through a casting die and a sheet casting mechanism. The temperature of the die pre-distributor is 268-272°C, and the temperature of the casting die is 268-272°C. The sheet is then subjected to transverse stretching, pulling, winding, and slitting to produce a bamboo-plastic composite PETG heat shrinkable label film product. The transverse stretching ratio is 5 and the stretching temperature is 86-98°C. The thickness ratio of the ABA three-layer film of the bamboo-plastic composite PETG heat shrinkable label film is 10:80:10.

[0020] Example 2 A method for preparing a bamboo-plastic composite PETG heat shrinkable label film comprises the following steps: Step 1: Weigh the raw materials according to the mass ratio; the mass ratio of the A layer is 100 parts of PETG resin and 2.5 parts of open masterbatch. Among them, the open masterbatch is Sukano®TA10-08MB13 from Sukarno, Switzerland, and the PETG resin is an NPG-modified PETG product, specifically HSF from Jiangsu Solide Company; the mass ratio of the B layer is 100 parts of PETG resin, 50 parts of bamboo powder masterbatch, 20 parts of compatibilizer, and 10 parts of recycled material, wherein the PETG resin is an NPG-modified PETG product, specifically HSF from Jiangsu Solide Company, the bamboo powder masterbatch is the masterbatch prepared above, and the compatibilizer is the compatibilizer AM-g-PETG-g-MA prepared above; Step 2: adding the raw material of layer A into the first extruder for plasticization and extrusion to obtain the melt raw material of layer A; the plasticization temperature of the first extruder is 250-272°C; Step 3: Place the raw material of layer B into a second extruder for plasticization and extrusion to obtain a melt raw material of layer B; the plasticization temperature of the second extruder is 250-272°C; Step 4: The A layer melt raw material and the B layer melt raw material are respectively fed into the film preparation mechanism through pipelines to be processed into a PETG label film. The film preparation mechanism is composed of a die pre-distributor, a casting die, a sheet casting mechanism, a transverse stretching system (including a trimming mechanism), a traction system, a winding system, a slitting system, and the like. The A layer melt raw material enters the corresponding channel of the die pre-distributor through a pipeline and is divided into two streams to form the upper and lower surface layers A. The B layer melt raw material enters the die pre-distributor through a pipeline and is divided into two streams to form the upper and lower surface layers A. The middle flow channel of the device forms the middle layer B. The raw materials of layers A and B pass through the distributor to form a material flow with an ABA three-layer structure. The material is then cast into an ABA structure PETG sheet through a casting die and a sheet casting mechanism. The temperature of the die pre-distributor is 268-272°C, and the temperature of the casting die is 268-272°C. The sheet is then subjected to transverse stretching, pulling, winding, and slitting to produce a bamboo-plastic composite PETG heat shrinkable label film product. The transverse stretching ratio is 5 and the stretching temperature is 86-98°C. The thickness ratio of the ABA three-layer film of the bamboo-plastic composite PETG heat shrinkable label film is 10:80:10.

[0021] Example 3 A method for preparing a bamboo-plastic composite PETG heat shrinkable label film comprises the following steps: Step 1: Weigh the raw materials according to the mass ratio; the mass ratio of the A layer is 100 parts of PETG resin and 2.5 parts of open masterbatch. Among them, the open masterbatch is Sukano®TA10-08MB13 from Sukarno, Switzerland, and the PETG resin is an NPG-modified PETG product, specifically HSF from Jiangsu Solide Company; the mass ratio of the B layer is 100 parts of PETG resin, 60 parts of bamboo powder masterbatch, 20 parts of compatibilizer, and 10 parts of recycled material, wherein the PETG resin is an NPG-modified PETG product, specifically HSF from Jiangsu Solide Company, the bamboo powder masterbatch is the masterbatch prepared above, and the compatibilizer is the compatibilizer AM-g-PETG-g-MA prepared above; Step 2: adding the raw material of layer A into the first extruder for plasticization and extrusion to obtain the melt raw material of layer A; the plasticization temperature of the first extruder is 250-272°C; Step 3: Place the raw material of layer B into a second extruder for plasticization and extrusion to obtain a melt raw material of layer B; the plasticization temperature of the second extruder is 250-272°C; Step 4: The A layer melt raw material and the B layer melt raw material are respectively fed into the film preparation mechanism through pipelines to be processed into a PETG label film. The film preparation mechanism is composed of a die pre-distributor, a casting die, a sheet casting mechanism, a transverse stretching system (including a trimming mechanism), a traction system, a winding system, a slitting system, and the like. The A layer melt raw material enters the corresponding channel of the die pre-distributor through a pipeline and is divided into two streams to form the upper and lower surface layers A. The B layer melt raw material enters the die pre-distributor through a pipeline and is divided into two streams to form the upper and lower surface layers A. The middle flow channel of the device forms the middle layer B. The raw materials of layers A and B pass through the distributor to form a material flow with an ABA three-layer structure. The material is then cast into an ABA structure PETG sheet through a casting die and a sheet casting mechanism. The temperature of the die pre-distributor is 268-272°C, and the temperature of the casting die is 268-272°C. The sheet is then subjected to transverse stretching, pulling, winding, and slitting to produce a bamboo-plastic composite PETG heat shrinkable label film product. The transverse stretching ratio is 5 and the stretching temperature is 86-98°C. The thickness ratio of the ABA three-layer film of the bamboo-plastic composite PETG heat shrinkable label film is 10:80:10.

[0022] Comparative Example 1 A method for preparing a composite PETG heat shrinkable label film comprises the following steps: Step 1: Weigh the raw materials according to the mass ratio; the mass ratio of the A layer is 100 parts of PETG resin and 2.5 parts of open masterbatch. The open masterbatch is Sukano®TA10-08MB13 from Sukarno, Switzerland, and the PETG resin is an NPG-modified PETG product, specifically HSF from Jiangsu Solide Co., Ltd.; the mass ratio of the B layer is 100 parts of PETG resin and 10 parts of recycled material, and the PETG resin is an NPG-modified PETG product, specifically HSF from Jiangsu Solide Co., Ltd.; Step 2: adding the raw material of layer A into the first extruder for plasticization and extrusion to obtain the melt raw material of layer A; the plasticization temperature of the first extruder is 250-272°C; Step 3: Place the raw material of layer B into a second extruder for plasticization and extrusion to obtain a melt raw material of layer B; the plasticization temperature of the second extruder is 250-272°C; Step 4: The A layer melt raw material and the B layer melt raw material are respectively introduced into a film preparation mechanism through pipelines to form a PETG label film. The film preparation 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, and a slitting system. The A layer melt raw material enters the corresponding channel of the die pre-distributor through a pipeline and is divided into two streams to form upper and lower surface layers A. The B layer melt raw material enters the middle flow channel of the die pre-distributor through a pipeline to form an intermediate layer B. The raw materials of the A and B layers form an ABA three-layer structure after passing through the distributor. The material is cast into an ABA structure PETG sheet through the casting die and the casting mechanism. The temperature of the die pre-distributor is 268-272° C., and the temperature of the casting die is 268-272° C. Then, the composite PETG heat shrinkable label film product is made through the steps of transverse stretching, traction, winding, and slitting, wherein the transverse stretching multiple is 5 and the stretching temperature is 86-98° C. The thickness ratio of the ABA three-layer film of the composite PETG heat shrinkable label film is 10:80:10.

[0023] Comparative Example 2 A method for preparing a bamboo-plastic composite PETG heat shrinkable label film comprises the following steps: Step 1: Weigh the raw materials according to the mass ratio. The mass ratio of the A layer is 100 parts PETG resin and 2.5 parts open-cell masterbatch. The open-cell masterbatch is Sukano® TA10-08MB13 from Sukano, Switzerland, and the PETG resin is an NPG-modified PETG product, specifically HSF from Jiangsu Solide. The mass ratio of the B layer is 100 parts PETG resin and 10 parts coupling agent-treated bamboo powder. (Using large amounts of bamboo powder can easily cause film breakage during shrink film stretching, disrupting normal production. Coupling treatment is generally used.) Bamboo powder coupling agent treatment method: Use commercially available 60-80 mesh bamboo powder. First, dissolve the coupling agent in anhydrous ethanol to create a 2% ethanol solution. Place the bamboo powder in a high-speed mixer and stir until the temperature reaches 110°C to remove moisture. Then, use a sprayer to spray the ethanol solution onto the bamboo powder. After spraying, mix at high speed for 5 minutes. Discharge and cool the mixture to obtain the coupling agent-treated bamboo powder. The coupling agent used is KH550. The amount of ethanol solution used is 3% of the weight of the bamboo powder. (Recycle 10 parts.) The PETG resin used is an NPG-modified PETG product, specifically HSF from Jiangsu Solide Company. Step 2: adding the raw material of layer A into the first extruder for plasticization and extrusion to obtain the melt raw material of layer A; the plasticization temperature of the first extruder is 250-272°C; Step 3: Place the raw material of layer B into a second extruder for plasticization and extrusion to obtain a melt raw material of layer B; the plasticization temperature of the second extruder is 250-272°C; Step 4: The A layer melt raw material and the B layer melt raw material are respectively fed into the film preparation mechanism through pipelines to be processed into a PETG label film. The film preparation mechanism is composed of a die pre-distributor, a casting die, a sheet casting mechanism, a transverse stretching system (including a trimming mechanism), a traction system, a winding system, a slitting system, and the like. The A layer melt raw material enters the corresponding channel of the die pre-distributor through a pipeline and is divided into two streams to form the upper and lower surface layers A. The B layer melt raw material enters the die pre-distributor through a pipeline and is divided into two streams to form the upper and lower surface layers A. The middle flow channel of the device forms the middle layer B. The raw materials of layers A and B pass through the distributor to form a material flow with an ABA three-layer structure. The material is then cast into an ABA structure PETG sheet through a casting die and a sheet casting mechanism. The temperature of the die pre-distributor is 268-272°C, and the temperature of the casting die is 268-272°C. The sheet is then subjected to transverse stretching, pulling, winding, and slitting to produce a bamboo-plastic composite PETG heat shrinkable label film product. The transverse stretching ratio is 5 and the stretching temperature is 86-98°C. The thickness ratio of the ABA three-layer film of the bamboo-plastic composite PETG heat shrinkable label film is 10:80:10.

[0024] Performance testing The PETG heat shrinkable label films prepared in Examples 1-3 and the comparative example were used as test samples, and the test results were as follows:

[0025] The above comparison shows that the bamboo powder used in Examples 1-3 is refined, etched and surface coupled to increase the activity of the bamboo powder surface, and a bamboo powder masterbatch composed of bamboo powder and PETG is obtained by melt extrusion granulation, thereby improving the compatibility and dispersibility of the bamboo powder in the entire system; by comparing the data of Comparative Example 1 and Comparative Example 2 with the data of Examples 1-3, it can be seen that from the perspective of mechanical properties, the present technical solution improves the surface activity of the bamboo powder by modification, improves its compatibility and reactivity with PETG, thereby solving the problem of poor interface compatibility between the coupled bamboo powder and the PETG powder, and at the same time can ensure that its mechanical properties are not lower than those of the composite PETG heat shrinkable label film without bamboo powder.

[0026] 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 bamboo-plastic composite PETG heat shrinkable label film, characterized in that: The steps include: Step 1: Add PETG resin and open masterbatch into a first extruder for plasticization and extrusion to obtain a layer A melt raw material; Step 2: Put the PETG resin, bamboo powder masterbatch, compatibilizer, and edge wire recycling into the second extruder for plasticization and extrusion to obtain the B layer melt raw material; Step 3, the A layer melt raw material and the B layer melt raw material are respectively introduced into a film preparation mechanism through pipelines to be processed into a PETG label film; the film preparation mechanism is composed of a die pre-distributor, a casting die, a casting mechanism, a transverse stretching system, a traction system, a winding system, a slitting system and the like; the A layer melt raw material enters the corresponding channel of the die pre-distributor through a pipeline and is divided into two streams to form upper and lower surface layers A, and the B layer melt raw material enters the middle flow channel of the die pre-distributor through a pipeline to form an intermediate 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, and are cast into an ABA structure PETG sheet through the casting die and the casting mechanism, and then undergoes transverse stretching, traction, winding, slitting and other steps to make a bamboo-plastic composite PETG heat shrinkable label film product.

2. The method for preparing the bamboo-plastic composite PETG heat shrinkable label film according to claim 1, wherein: The plasticizing temperature of the first extruder in step 1 is 250-272°C.

3. The method for preparing the bamboo-plastic composite PETG heat shrinkable label film according to claim 1, wherein: The plasticizing temperature of the second extruder in step 2 is 250-272°C.

4. The method for preparing the bamboo-plastic composite PETG heat shrinkable label film according to claim 1, wherein: The temperature of the die pre-distributor in step 3 is 268-272° C., the temperature of the casting die is 268-272° C., the transverse stretching multiple is 5, and the stretching temperature is 86-98° C.

5. The method for preparing the bamboo-plastic composite PETG heat shrinkable label film according to claim 1, wherein: The thickness ratio of the ABA three-layer film of the bamboo-plastic composite PETG heat shrinkable label film in step 3 is 10:80:

10.

6. The method for preparing the bamboo-plastic composite PETG heat shrinkable label film according to claim 1, wherein: The mass ratio of the A layer is: 100 parts of PETG resin and 2.5 parts of open masterbatch.

7. The method for preparing the bamboo-plastic composite PETG heat shrinkable label film according to claim 1, wherein: The mass ratio of the B layer is: 100 parts of PETG resin, 40-60 parts of bamboo powder masterbatch, 10-20 parts of compatibilizer, and 10 parts of recycled material.

8. The method for preparing the bamboo-plastic composite PETG heat shrinkable label film according to claim 7, wherein: The compatibilizer AM-g-PETG-g-MA uses acrylamide and maleic anhydride as graft copolymer monomers, and uses ammonium cerium nitrate and dicumyl peroxide as initiators. The compatibilizer is graft copolymerized on the surface of PETG particles through solution free radical polymerization to prepare the compatibilizer AM-g-PETG-g-MA.

9. The method for preparing the bamboo-plastic composite PETG heat shrinkable label film according to claim 7, wherein: The bamboo powder masterbatch is prepared by mixing bamboo powder, PETG powder, antioxidant and lubricant in a certain proportion, and the bamboo powder is pretreated before use.

10. The method for preparing the bamboo-plastic composite PETG heat shrinkable label film according to claim 9, characterized in that: The mass ratio of the bamboo powder masterbatch is: 60 parts of bamboo powder, 40 parts of PETG powder, 3 parts of antioxidant, and 1 part of lubricant.

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