Low-density PETG (polyethylene terephthalate glycol) heat-shrinkable label film containing microporous core layer and preparation method of low-density PETG heat-shrinkable label film
By modifying PETG polymer with hollow glass microspheres and co-extruding it with PETG to form a microporous core layer, the density and shrinkage rate problems of PETG heat-shrinkable label film are solved, and a low-density and stable production process is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU GUANGHUI PACKAGE
- Filing Date
- 2026-03-24
- Publication Date
- 2026-05-12
AI Technical Summary
Existing low-density PETG heat shrink label films have problems such as high process difficulty, material delamination and inconsistent shrinkage rate during production, and cannot effectively reduce density, resulting in a decline in recycling value.
Hollow glass microspheres are used as the core filler. They are modified and co-extruded with PETG material to form a microporous core layer. The low density and inert surface micropores of the hollow glass microspheres are utilized, and the compatibility is improved by combining silane coupling agents to achieve a low-density and uniform pore structure.
This technology enables the reduction of the density of PETG heat-shrinkable label film, solves the problems of material delamination and inconsistent shrinkage rates, and improves production stability and recycling value.
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] This invention belongs to the field of heat shrink label film technology, specifically relating to a low-density PETG heat shrink label film containing a microporous core layer and its preparation method. Background Technology
[0002] PETG heat shrink label film is currently the main base film for shrink sleeves. Because both the PET bottle and the PET bottle are made of polyester and have essentially the same density, they cannot be effectively separated during recycling using simple gravity differences. Although they belong to the same material family, their properties differ significantly, making co-extrusion and melt-forming impossible. Furthermore, the PETG label surface, being printed, retains a large amount of ink. The inability to separate the PETG label film from the waste PET bottle leads to contamination, reducing its recycling value. Therefore, reducing the density of the PETG heat shrink label film to create a significant density difference with the waste PET bottle is a crucial area for technological improvement.
[0003] There are two main technologies used for low-density PETG heat-shrinkable label films: using low-density materials such as PP and SBC as the core layer material, or foaming the PETG core layer. However, while using a low-density material for the core layer and co-extruding it with the PETG surface layer effectively reduces the film density, the differences in material properties lead to significant variations in processing techniques, making production control difficult and prone to delamination between different materials within the film. Furthermore, the varying shrinkage properties of different materials result in inconsistent shrinkage rates and other quality issues. PETG heat-shrinkable label films using foamed core layers are prone to problems like bubble breakage and uneven foaming due to the low melt viscosity and poor melt strength of PETG. This makes practical control very difficult, resulting in significant shrinkage variations in the prepared films, hindering industrial application. While supercritical carbon dioxide foaming technology can achieve a relatively uniform foamed structure in the core layer, its production process requires specialized equipment. The extrusion of the core layer material necessitates specific foaming molding devices and stringent process control conditions. Ordinary PETG heat-shrink label film production lines cannot directly process and produce it.
[0004] Therefore, the market urgently needs a low-density PETG heat-shrinkable label film that can be industrially produced and has uniform pores. Summary of the Invention
[0005] To address the problems in the prior art, this invention provides a low-density PETG heat-shrinkable label film with a microporous core layer, which solves the process defects of existing low-density PETG heat-shrinkable label films. It utilizes hollow glass microspheres as a low-density filler in the core layer, and combines this with the surface micropore cracks caused by the inertness of the hollow glass microspheres, thereby achieving a low-density microporous core layer and thus achieving the low-density effect of PETG heat-shrinkable label film.
[0006] To achieve the above technical objectives, the technical solution of the present invention is as follows:
[0007] A low-density PETG heat-shrinkable label film with a microporous core layer has a three-layer co-extrusion structure, with the top and bottom layers being PETG surface layers and the middle layer being a microporous core layer containing hollow glass microspheres modified PETG polymer.
[0008] In the three-layer co-extrusion structure, the top and bottom layers, serving as the surface layers, are primarily made of PETG material, as is the microporous core layer. Therefore, the use of the same PETG material in both the surface and core layers ensures excellent consistency, guaranteeing interlayer compatibility and bonding stability of the heat-shrinkable label film, and reducing interlayer cracks and differences. Hollow glass microspheres, modified to enhance surface activity and bonded to the PETG material, not only ensure uniform dispersion of the microspheres in the core layer but also improve the bonding stability between the microspheres and PETG. The hollow structure of the microspheres results in a lower density, effectively reducing the overall density of the PETG material. Furthermore, the uniform dispersion of the microspheres within the PETG material, combined with the differences between the microspheres and PETG, creates poor interfacial compatibility. Under high-ratio stretching conditions, gaps form between the microspheres and the PETG matrix, creating a microporous structure, further reducing the density of the PETG heat-shrinkable label film.
[0009] The thickness ratio of the three-layer co-extruded structure of the low-density PETG heat-shrinkable label film is 10-15:70-80:10-15.
[0010] The PETG top layer comprises PETG resin and open-face slip masterbatch, with the PETG resin accounting for 97%-98% of the PETG top layer by mass. Further, the PETG resin is made from modified PET chips, specifically CHDM-modified PETG or NPG-modified PETG. The CHDM-modified PETG uses one of the following: Embrace™ copolyester, Embrace™ LV copolyester, GN001, S2008 from SK Corporation of Korea, and K2012 from SK Corporation of Korea. The NPG-modified PETG uses one of the following: FG718H from Yizheng Chemical Fiber, HSF from Jiangsu Solide, and W501 from Jiangyin Huahong. The open-face slip masterbatch uses TA10-08 MB13 from Sucanor GmbH of Switzerland or similar products from other manufacturers.
[0011] The microporous core layer comprises: hollow glass microspheres modified with PETG polymer and recycled materials, wherein the mass percentage of hollow glass microspheres modified with PETG polymer is 92%, and the recycled materials are the trimmed edges of online wires.
[0012] The method for preparing the low-density PETG heat-shrinkable label film includes the following steps: Step 1: PETG resin and open slip masterbatch are put into the first extruder according to the mass ratio, and the surface melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the first extruder is 255-270℃. Step 2: The hollow glass microsphere modified PETG polymer and recycled material are put into the second extruder according to the mass ratio, and the core layer melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the second extruder is 255-270℃. Step 3: The surface layer melt material and the core layer melt material are respectively fed into the film preparation mechanism through pipes to form a PETG heat shrink label film. The film forming mechanism consists of a pre-die distributor, a casting die, a casting mechanism, a transverse stretching system with an edge trimming mechanism, a traction system, a winding system, and a slitting system. In the film preparation mechanism, the surface layer melt material enters the corresponding flow channel of the pre-die distributor through pipes and is divided into two streams to form upper and lower surface layers. The core layer melt material enters the middle flow channel of the pre-die distributor through pipes to form the core layer. The surface layer and the core layer form a three-layer co-extrusion structure after passing through the distributor. After casting and cooling by the casting die and casting mechanism, it is formed into a three-layer co-extrusion PETG sheet. This sheet is then processed by the transverse stretching system, traction system, winding system, and slitting system to produce a low-density PETG heat shrink label film product with a microporous core layer.
[0013] Furthermore, the temperature of the distributor is 265-270℃; the temperature of the casting die head is 265-270℃; the temperature of the casting roller of the casting mechanism is 28℃; the transverse stretching system has a transverse stretching ratio of 5 and a stretching temperature of 85-98℃.
[0014] The hollow glass microsphere-modified PETG polymer involves incorporating hollow glass microspheres into the PETG polymerization reaction and bonding them to the PETG. However, the main component of hollow glass microspheres is borosilicate glass, whose surface does not react significantly with acids and alkalis at room temperature, exhibiting good corrosion resistance and chemical stability. Simultaneously, the surface of the hollow glass microspheres contains a small amount of silanol groups, which, although exhibiting some hydrophilicity, result in low overall chemical activity and poor compatibility with PETG material, leading to a decline in the mechanical properties of the core layer and the entire PETG heat-shrinkable label film. To address this issue, the hollow glass microspheres undergo surface modification and dispersion treatment, and are then homogeneously dispersed in the PETG precursor, participating in the PETG polymerization reaction.
[0015] Therefore, the preparation method of the hollow glass microsphere modified PETG polymer includes the following steps: a1, under room temperature conditions, hollow glass microspheres, silane coupling agent, and ethylene glycol are added to a ball mill and dispersed in the ball mill for 7-8 hours to ensure that the hollow glass microspheres are uniformly dispersed in the ethylene glycol, thereby obtaining a hollow glass microsphere-ethylene glycol dispersion. The mass ratio of the hollow glass microsphere-ethylene glycol dispersion is: 15 parts hollow glass microspheres, 3-5 parts silane coupling agent, and 80-82 parts ethylene glycol. Taking 4 parts of ethylene glycol and 81 parts of ethylene glycol as an example; the hollow glass microspheres have a particle size of 20-25 μm and a density of less than 0.50 g / cm3, specifically using one of 3M's iM16K, HGS19K46, HGS8000X, K42HS, HGS7K32, and S32HS, or similar products from other manufacturers; the silane coupling agent is a [(RO)3-Si-R'] type silane coupling agent dispersant, specifically using A1120's N-β(aminoethyl)-γ-aminopropyltrimethoxysilane; a2. Terephthalic acid, ethylene glycol, neopentyl glycol, catalyst, and stabilizer are prepared in a certain proportion and added to a pulping kettle and mixed evenly. Then, the mixture is sequentially placed into a first esterification kettle and a second esterification kettle for esterification reaction to obtain an esterification reaction solution. The catalyst is antimony glycolate, which is added in small amounts after pre-dissolving in ethylene glycol. The stabilizer is trimethyl phosphite, which is added in small amounts after pre-dissolving in ethylene glycol. The temperature of the first esterification kettle is 253-255℃ and the pressure is 75kPa. The temperature of the second esterification kettle is 252-254℃ and the pressure is atmospheric pressure. a3. A hollow glass microsphere-ethylene glycol dispersion is added to an esterification reaction solution in a certain proportion and then sequentially fed into a first pre-polymerization reactor, a second polymerization reactor, and a final polymerization reactor for continuous polymerization reaction to obtain a PETG polymer melt containing hollow glass microspheres and having a certain intrinsic viscosity. The temperature of the first pre-polymerization reactor is 268-270℃, and the pressure is 14-16 kPa. The temperature of the second pre-polymerization reactor is 271-273℃, and the pressure is 0.43-0.45 kPa, with a stirring speed of 5.5-5.8 rpm. The temperature of the final polymerization reactor is 276-278℃, the pressure is 0.09-0.12 kPa, and the stirring speed is 4.1-4.4 rpm. a4. The PETG polymer melt containing hollow glass microspheres and having a certain intrinsic viscosity is sequentially filtered through a filter, cast into strips, and granulated by a pelletizer to obtain hollow glass microsphere modified PETG polymer granules, namely the hollow glass microsphere modified PETG polymer.
[0016] In the above preparation method, the mass ratio of terephthalic acid, ethylene glycol, neopentyl glycol, and hollow glass microsphere-ethylene glycol dispersion is 84:23-25:15:6, and terephthalic acid and neopentyl glycol are pre-dissolved in ethylene glycol. During the polymerization process, a slight excess of ethylene glycol can prevent excessive cross-linking or branching of molecular chains and effectively end the two ends of polymer chains, ultimately obtaining a uniformly dispersed and stable PETG. The amount of catalyst and stabilizer added is extremely small, and the ratio of their amounts to terephthalic acid is in the millions. Therefore, only a small amount needs to be added during the production process.
[0017] In the preparation of the above-mentioned hollow glass microspheres modified PETG polymer, the presence of silanol groups on the surface of the hollow glass microspheres can form localized high surface activity, leading to easy aggregation of the hollow glass microspheres. The aforementioned silane coupling agent acts as a dispersant, with the chemical formula [(RO)3-Si-R'], where the R group adjacent to the oxygen atom is an electron-donating group (CH3), thereby enhancing the electronegativity of the oxygen atom. The Si-OC bond is relatively active, especially when OMe or OEt is attached to the Si atom. When the silane coupling agent encounters the -OH group on the surface of the hollow glass microspheres, a chemical reaction occurs, removing the ROH. At the same time, the -NH2 and -NH groups on Al120 also form hydrogen bonds with the -OH group on the surface of the hollow glass microspheres. Therefore, the above reaction utilizes the active groups on the silane coupling agent to form a corresponding reaction with the -OH group on the surface of the hollow glass microspheres, thereby coating the surface of the hollow glass microspheres with a chemical film, which not only greatly reduces the aggregation problem but also improves the dispersibility and stability of the hollow glass microspheres. In the entire microporous core layer, hollow glass microspheres are homogeneously dispersed in the PETG material and bonded to the PETG polymer using a modifier with hydroxyl groups on their surface. This improves the bonding stability of the hollow glass microspheres within the PETG polymer. Simultaneously, while the surface of the hollow glass microspheres contains a small amount of silanol groups, the majority remains inert silicate glass. Therefore, when hollow glass microspheres modify PETG polymer as a microporous core layer, under high-ratio stretching conditions, while the hollow glass microspheres form stable bonds using silanol groups and silane coupling agents, gaps still form between the hollow glass microspheres and the PETG material matrix in other areas, creating a microporous structure and still reducing the density of the PETG heat-shrinkable label film.
[0018] As can be seen from the above description, the present invention has the following advantages: 1. This invention solves the process defects of existing low-density PETG heat-shrinkable label films by using hollow glass microspheres as a low-density filler in the core layer. The low-density characteristics of the hollow glass microspheres, combined with the surface micropores and cracks caused by the inertia of the hollow glass microspheres, achieve the low density of the microporous core layer, thereby achieving the low-density effect of PETG heat-shrinkable label films.
[0019] 2. This invention utilizes the dispersibility and functional activity of silane coupling agents to form bonds with a small number of hydroxyl groups on the surface of hollow glass microspheres, resulting in increased local activity and improved compatibility with PETG materials. Therefore, hollow glass microspheres not only improve their connectivity with PETG polymer through modification, preventing a decrease in mechanical strength, but also retain surface inertness, thus maintaining interfacial cracks even under high-ratio stretching and preserving the low density of the PETG heat-shrinkable label film. Detailed Implementation
[0020] The present invention will be described in detail with reference to the embodiments, but the claims of the present invention are not intended to limit the scope of the invention.
[0021] The preparation method of the hollow glass microsphere modified PETG polymer includes the following steps: a1, under room temperature conditions, hollow glass microspheres, silane coupling agent, and ethylene glycol are added to a ball mill and dispersed in the ball mill for 8 hours to ensure that the hollow glass microspheres are uniformly dispersed in the ethylene glycol, thereby obtaining a hollow glass microsphere-ethylene glycol dispersion. The mass ratio of the hollow glass microsphere-ethylene glycol dispersion is: 15 parts hollow glass microspheres, 4 parts silane coupling agent, and 81 parts ethylene glycol. The particle size of the hollow glass microspheres is 20-25 μm, and the density is less than 0.50 g / cm3. Specifically, 3M's iM16K is used. The silane coupling agent is a [(RO)3-Si-R'] type silane coupling agent dispersant, specifically A1120's N-β(aminoethyl)-γ-aminopropyltrimethoxysilane. a2. Terephthalic acid, ethylene glycol, neopentyl glycol, catalyst, and stabilizer are added to a pulping vessel and mixed evenly. Then, the mixture is sequentially placed into a first esterification vessel and a second esterification vessel for esterification reaction to obtain an esterification reaction solution. The catalyst is antimony glycolate, which is added in small amounts after pre-dissolving in ethylene glycol. The stabilizer is trimethyl phosphite, which is added in small amounts after pre-dissolving in ethylene glycol. The temperature of the first esterification vessel is 253-255℃ and the pressure is 75kPa. The temperature of the second esterification vessel is 252-254℃ and the pressure is atmospheric pressure. a3. A hollow glass microsphere-ethylene glycol dispersion is added and sequentially fed into a first prepolymerization reactor, a second polymerization reactor, and a final polymerization reactor for a continuous polymerization reaction, to obtain a PETG polymer melt containing hollow glass microspheres and having a certain intrinsic viscosity. The temperature of the first prepolymerization reactor is 268-270℃, and the pressure is 14-16 kPa. The temperature of the second prepolymerization reactor is 271-273℃, and the pressure is 0.43-0.45 kPa, with a stirring speed of 5.5-5.8 rpm. The temperature of the final polymerization reactor is 276-278℃, the pressure is 0.09-0.12 kPa, and the stirring speed is 4.1-4.4 rpm. a4. A PETG polymer melt containing hollow glass microspheres and having a certain intrinsic viscosity is sequentially filtered, cast into strips, and granulated using a pelletizer to obtain hollow glass microsphere-modified PETG polymer granules, namely, the hollow glass microsphere-modified PETG polymer. The mass ratio of terephthalic acid, ethylene glycol, neopentyl glycol, and hollow glass microsphere-ethylene glycol dispersion is 84:25:15:6, and terephthalic acid and neopentyl glycol are pre-dissolved in ethylene glycol.
[0022] The performance of the hollow glass microspheres modified with PETG polymer prepared by the above method is shown below: Table 1 Performance testing of PETG polymer modified with hollow glass microspheres
[0023] Example 1 A low-density PETG heat-shrinkable label film with a microporous core layer has a three-layer co-extrusion structure, with the top and bottom layers being PETG surface layers and the middle layer being a microporous core layer containing hollow glass microspheres modified PETG polymer.
[0024] The thickness ratio of the three-layer co-extruded structure of the low-density PETG heat-shrinkable label film is 10:80:10.
[0025] The PETG top layer comprises PETG resin and open-face slip masterbatch, wherein the PETG resin accounts for 98% of the mass of the PETG top layer, and the open-face slip masterbatch accounts for 2% of the mass. Specifically, the PETG resin is CHDM-modified PETG, specifically Embrace™ copolyester, and the open-face slip masterbatch is TA10-08 MB13 from Sucanor, Switzerland.
[0026] The microporous core layer comprises: the hollow glass microsphere modified PETG polymer and recycled material, wherein the mass percentage of the hollow glass microsphere modified PETG polymer is 92% and the mass percentage of the recycled material is 8%, and the recycled material is the edge trimming and recycling of online wires.
[0027] The method for preparing the low-density PETG heat-shrinkable label film includes the following steps: Step 1: PETG resin and open slip masterbatch are put into the first extruder according to the mass ratio, and the surface melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the first extruder is 255-270℃. Step 2: The hollow glass microsphere modified PETG polymer and recycled material are put into the second extruder according to the mass ratio, and the core layer melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the second extruder is 255-270℃. Step 3: The surface layer melt material and the core layer melt material are respectively fed into the film preparation mechanism through pipes to process and form a PETG heat shrink label film. The film forming mechanism consists of a pre-die 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. In the film preparation mechanism, the surface layer melt raw material enters the corresponding flow channel of the die pre-distributor through a pipe and is divided into two streams to form upper and lower surface layers; the core layer melt raw material enters the middle flow channel of the die pre-distributor through a pipe to form the core layer; the surface layer and core layer form a three-layer co-extrusion structure after passing through the distributor, and are then cast and cooled by a casting die and a casting mechanism to form a three-layer co-extruded PETG sheet. This sheet is then processed by a transverse stretching system, a traction system, a winding system, and a slitting system to produce a low-density PETG heat-shrinkable label film product with a microporous core layer. The temperature of the distributor is 265-270℃; the temperature of the casting die is 265-270℃; the temperature of the casting roller of the casting mechanism is 28℃; the transverse stretching system has a transverse stretching ratio of 5 and a stretching temperature of 85-98℃.
[0028] Example 2 A low-density PETG heat-shrinkable label film with a microporous core layer has a three-layer co-extrusion structure, with the top and bottom layers being PETG surface layers and the middle layer being a microporous core layer containing hollow glass microspheres modified PETG polymer.
[0029] The thickness ratio of the three-layer co-extruded structure of the low-density PETG heat-shrinkable label film is 15:70:15.
[0030] The PETG top layer comprises PETG resin and open-end slip masterbatch, wherein the PETG resin accounts for 97% of the PETG top layer by mass, and the open-end slip masterbatch accounts for 3% by mass. Specifically, the PETG resin is CHDM-modified PETG, specifically S2008 from SK Corporation of South Korea, and the open-end slip masterbatch is TA10-08 MB13 from Sucanor Corporation of Switzerland.
[0031] The microporous core layer comprises: the hollow glass microsphere modified PETG polymer and recycled material, wherein the mass percentage of the hollow glass microsphere modified PETG polymer is 92% and the mass percentage of the recycled material is 8%, and the recycled material is the edge trimming and recycling of online wires.
[0032] The method for preparing the low-density PETG heat-shrinkable label film includes the following steps: Step 1: PETG resin and open slip masterbatch are put into the first extruder according to the mass ratio, and the surface melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the first extruder is 255-270℃. Step 2: The hollow glass microsphere modified PETG polymer and recycled material are put into the second extruder according to the mass ratio, and the core layer melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the second extruder is 255-270℃. Step 3: The surface layer melt material and the core layer melt material are respectively fed into the film preparation mechanism through pipes to process and form a PETG heat shrink label film. The film forming mechanism consists of a pre-die 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. In the film preparation mechanism, the surface layer melt raw material enters the corresponding flow channel of the die pre-distributor through a pipe and is divided into two streams to form upper and lower surface layers; the core layer melt raw material enters the middle flow channel of the die pre-distributor through a pipe to form the core layer; the surface layer and core layer form a three-layer co-extrusion structure after passing through the distributor, and are then cast and cooled by a casting die and a casting mechanism to form a three-layer co-extruded PETG sheet. This sheet is then processed by a transverse stretching system, a traction system, a winding system, and a slitting system to produce a low-density PETG heat-shrinkable label film product with a microporous core layer. The temperature of the distributor is 265-270℃; the temperature of the casting die is 265-270℃; the temperature of the casting roller of the casting mechanism is 28℃; the transverse stretching system has a transverse stretching ratio of 5 and a stretching temperature of 85-98℃.
[0033] Example 3 A low-density PETG heat-shrinkable label film with a microporous core layer has a three-layer co-extrusion structure, with the top and bottom layers being PETG surface layers and the middle layer being a microporous core layer containing hollow glass microspheres modified PETG polymer.
[0034] The thickness ratio of the three-layer co-extruded structure of the low-density PETG heat-shrinkable label film is 12.5:75:12.5.
[0035] The PETG top layer comprises PETG resin and open-end slip masterbatch, wherein the PETG resin accounts for 98% of the mass of the PETG top layer, and the open-end slip masterbatch accounts for 2% of the mass. Specifically, the PETG resin is NPG-modified PETG, specifically HSF from Jiangsu Solide Co., Ltd., and the open-end slip masterbatch is TA10-08 MB13 from Sucanor, Switzerland.
[0036] The microporous core layer comprises: the hollow glass microsphere modified PETG polymer and recycled material, wherein the mass percentage of the hollow glass microsphere modified PETG polymer is 92% and the mass percentage of the recycled material is 8%, and the recycled material is the edge trimming and recycling of online wires.
[0037] The method for preparing the low-density PETG heat-shrinkable label film includes the following steps: Step 1: PETG resin and open slip masterbatch are put into the first extruder according to the mass ratio, and the surface melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the first extruder is 255-270℃. Step 2: The hollow glass microsphere modified PETG polymer and recycled material are put into the second extruder according to the mass ratio, and the core layer melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the second extruder is 255-270℃. Step 3: The surface layer melt material and the core layer melt material are respectively fed into the film preparation mechanism through pipes to process and form a PETG heat shrink label film. The film forming mechanism consists of a pre-die 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. In the film preparation mechanism, the surface layer melt raw material enters the corresponding flow channel of the die pre-distributor through a pipe and is divided into two streams to form upper and lower surface layers; the core layer melt raw material enters the middle flow channel of the die pre-distributor through a pipe to form the core layer; the surface layer and core layer form a three-layer co-extrusion structure after passing through the distributor, and are then cast and cooled by a casting die and a casting mechanism to form a three-layer co-extruded PETG sheet. This sheet is then processed by a transverse stretching system, a traction system, a winding system, and a slitting system to produce a low-density PETG heat-shrinkable label film product with a microporous core layer. The temperature of the distributor is 265-270℃; the temperature of the casting die is 265-270℃; the temperature of the casting roller of the casting mechanism is 28℃; the transverse stretching system has a transverse stretching ratio of 5 and a stretching temperature of 85-98℃.
[0038] Comparative Example 1 A PETG heat-shrinkable label film has a three-layer co-extruded structure, with the top and bottom layers being PETG surface layers and the middle layer being a PETG core layer containing hollow glass microspheres.
[0039] The thickness ratio of the three-layer co-extruded structure of the PETG heat-shrinkable label film is 12.5:75:12.5.
[0040] The PETG top layer comprises PETG resin and open-end slip masterbatch, wherein the PETG resin accounts for 98% of the mass of the PETG top layer, and the open-end slip masterbatch accounts for 2% of the mass. Specifically, the PETG resin is NPG-modified PETG, specifically HSF from Jiangsu Solide Co., Ltd., and the open-end slip masterbatch is TA10-08 MB13 from Sucanor, Switzerland.
[0041] The PETG core layer containing hollow glass microspheres comprises: PETG resin containing hollow glass microspheres and recycled material, wherein the mass percentage of the PETG resin containing hollow glass microspheres is 92% and the mass percentage of the recycled material is 8%, and the recycled material is the trimmed edge of the online wire. The PETG resin is NPG-modified PETG, specifically HSF from Jiangsu Solide Company, and the hollow glass microsphere content is 8010ppm. It is homogeneously dispersed in molten NPG-modified PETG, and then sequentially filtered, cast into strips, and pelletized by a pelletizer to obtain the PETG resin containing hollow glass microspheres.
[0042] The method for preparing the PETG heat-shrinkable label film includes the following steps: Step 1: PETG resin and open slip masterbatch are put into the first extruder according to the mass ratio, and the surface melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the first extruder is 255-270℃. Step 2: PETG resin containing hollow glass microspheres and recycled material are put into the second extruder according to the mass ratio, and the core layer melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the second extruder is 255-270℃. Step 3: The surface layer melt material and the core layer melt material are respectively fed into the film preparation mechanism through pipes to process and form a PETG heat shrink label film. The film forming mechanism consists of a pre-die 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. In the film preparation mechanism, the surface layer melt raw material enters the corresponding flow channel of the die pre-distributor through a pipe and is divided into two streams to form upper and lower surface layers; the core layer melt raw material enters the middle flow channel of the die pre-distributor through a pipe to form the core layer; the surface layer and core layer form a three-layer co-extrusion structure after passing through the distributor, and are then cast and cooled by a casting die and a casting mechanism to form a three-layer co-extruded PETG sheet. This sheet is then processed by a transverse stretching system, a traction system, a winding system, and a slitting system to produce a low-density PETG heat-shrinkable label film product with a microporous core layer. The temperature of the distributor is 265-270℃; the temperature of the casting die is 265-270℃; the temperature of the casting roller of the casting mechanism is 28℃; the transverse stretching system has a transverse stretching ratio of 5 and a stretching temperature of 85-98℃.
[0043] Comparative Example 2 A PETG heat-shrinkable label film has a three-layer co-extruded structure, with the top and bottom layers being PETG surface layers and the middle layer being a PETG core layer.
[0044] The thickness ratio of the three-layer co-extruded structure of the PETG heat-shrinkable label film is 12.5:75:12.5.
[0045] The PETG top layer comprises PETG resin and open-end slip masterbatch, wherein the PETG resin accounts for 98% of the mass of the PETG top layer, and the open-end slip masterbatch accounts for 2% of the mass. Specifically, the PETG resin is NPG-modified PETG, specifically HSF from Jiangsu Solide Co., Ltd., and the open-end slip masterbatch is TA10-08 MB13 from Sucanor, Switzerland.
[0046] The core layer comprises PETG resin and recycled material, with PETG resin accounting for 92% by mass and recycled material accounting for 8% by mass. The recycled material is the edge trimming and recycling of online edge wires.
[0047] The method for preparing the PETG heat-shrinkable label film includes the following steps: Step 1: PETG resin and open slip masterbatch are put into the first extruder according to the mass ratio, and the surface melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the first extruder is 255-270℃. Step 2: PETG resin and recycled material are fed into the second extruder according to the mass ratio, and the core layer melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the second extruder is 255-270℃. Step 3: The surface layer melt material and the core layer melt material are respectively fed into the film preparation mechanism through pipes to process and form a PETG heat shrink label film. The film forming mechanism consists of a pre-die 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. In the film preparation mechanism, the surface layer melt raw material enters the corresponding flow channel of the die pre-distributor through a pipe and is divided into two streams to form upper and lower surface layers; the core layer melt raw material enters the middle flow channel of the die pre-distributor through a pipe to form the core layer; the surface layer and core layer form a three-layer co-extrusion structure after passing through the distributor, and are then cast and cooled by a casting die and a casting mechanism to form a three-layer co-extruded PETG sheet. This sheet is then processed by a transverse stretching system, a traction system, a winding system, and a slitting system to produce a low-density PETG heat-shrinkable label film product with a microporous core layer. The temperature of the distributor is 265-270℃; the temperature of the casting die is 265-270℃; the temperature of the casting roller of the casting mechanism is 28℃; the transverse stretching system has a transverse stretching ratio of 5 and a stretching temperature of 85-98℃.
[0048] Performance testing Performance tests were conducted using Examples 1-3 and Comparative Example 1 as test samples, and the results are as follows: Table 2 Performance test data of PETG heat shrink label films of Examples 1-3 and Comparative Example 1
[0049] The data comparison above shows that the hollow glass microspheres in this technical solution have low density characteristics, can be homogeneously dispersed in PETG, and participate in the polymerization reaction of PETG after modification by coupling agent to form hollow glass microsphere modified PETG polymer. When used as the core layer of the label film, it can generate interfacial micropores during high-ratio stretching, and at the same time, it can achieve chemical bonding between hollow glass microspheres and PETG resin, solving the problem of decreased mechanical strength, and realizing the low density of PETG heat shrink label film.
[0050] It is understood that the above detailed description of the present invention is for illustrative purposes only and is not intended to limit the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effects; as long as the usage requirements are met, they are all within the protection scope of the present invention.
Claims
1. A low-density PETG heat-shrinkable label film containing a microporous core layer, characterized in that: The low-density PETG heat-shrinkable label film has a three-layer co-extrusion structure, with the top and bottom layers being PETG surface layers and the middle layer being a microporous core layer containing hollow glass microspheres modified PETG polymer.
2. The low-density PETG heat-shrinkable label film with a microporous core layer according to claim 1, characterized in that: The thickness ratio of the three-layer co-extruded structure of the low-density PETG heat-shrinkable label film is 10-15:70-80:10-15.
3. The low-density PETG heat-shrinkable label film with a microporous core layer according to claim 1, characterized in that: The PETG top layer comprises PETG resin and open slip masterbatch, and the PETG resin accounts for 97%-98% of the mass of the PETG top layer.
4. The low-density PETG heat-shrinkable label film with a microporous core layer according to claim 3, characterized in that: The PETG resin is made from modified PET chips, specifically CHDM-modified PETG or NPG-modified PETG; wherein the CHDM-modified PETG is one of Embrace™ copolyester, Embrace™ LV copolyester, GN001, S2008 from SK Corporation of Korea, and K2012 from SK Corporation of Korea; the NPG-modified PETG is one of FG718H from Yizheng Chemical Fiber, HSF from Jiangsu Suolide, and W501 from Jiangyin Huahong.
5. The low-density PETG heat-shrinkable label film with a microporous core layer according to claim 3, characterized in that: The open-ended smooth masterbatch uses TA10-08 MB13 from Sucanor, Switzerland, or similar products from other vendors.
6. The low-density PETG heat-shrinkable label film with a microporous core layer according to claim 1, characterized in that: The microporous core layer comprises: hollow glass microspheres modified with PETG polymer and recycled materials, wherein the mass percentage of hollow glass microspheres modified with PETG polymer is 92%, and the recycled materials are the trimmed edges of online wires.
7. The low-density PETG heat-shrinkable label film with a microporous core layer according to claim 1, characterized in that: The hollow glass microsphere modified PETG polymer is prepared by incorporating hollow glass microspheres into the PETG polymerization reaction and bonding the hollow glass microspheres to the PETG polymer.
8. The low-density PETG heat-shrinkable label film with a microporous core layer according to claim 1, characterized in that: The method for preparing the low-density PETG heat-shrinkable label film includes the following steps: Step 1: PETG resin and open slip masterbatch are put into the first extruder according to the mass ratio, and the surface melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the first extruder is 255-270℃. Step 2: The hollow glass microsphere modified PETG polymer and recycled material are put into the second extruder according to the mass ratio, and the core layer melt raw material is obtained by plasticizing and extruding. The plasticizing and extruding temperature of the second extruder is 255-270℃. Step 3: The surface layer melt material and the core layer melt material are respectively fed into the film preparation mechanism through pipes and processed into PETG heat shrink label film.
9. The low-density PETG heat-shrinkable label film with a microporous core layer according to claim 8, characterized in that: The film forming mechanism consists of a pre-die 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. In the film preparation mechanism, the surface layer melt raw material enters the corresponding flow channel of the pre-die distributor through a pipe and is divided into two streams to form upper and lower surface layers. The core layer melt raw material enters the middle flow channel of the pre-die distributor through a pipe to form the core layer. The surface layer and the core layer form a three-layer co-extrusion structure after passing through the distributor. The three-layer co-extrusion PETG sheet is formed by casting and cooling through the casting die and casting mechanism. The sheet is then processed by the transverse stretching system, traction system, winding system, and slitting system to produce a low-density PETG heat-shrinkable label film product with a microporous core layer.
10. The low-density PETG heat-shrinkable label film with a microporous core layer according to claim 9, characterized in that: The temperature of the distributor in step 3 is 265-270℃; the temperature of the casting die head is 265-270℃; the temperature of the casting roller of the casting mechanism is 28℃; the transverse stretching system has a transverse stretching ratio of 5 and a stretching temperature of 85-98℃.