A functional masterbatch for recyclable heat shrink film and a method for preparing the same

Abstract

The application provides a functional masterbatch for a recyclable heat-shrinkable film, which is used for adding to polyester recycled particles and performing a melt modification treatment on the polyester recycled particles, wherein the functional masterbatch is composed of a polyester carrier and diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecanol stearate and magnesium carbonate. In addition, the application further provides a preparation method of the functional masterbatch. The recyclable material obtained by adding the functional masterbatch to the polyester recycled particles and performing the melt modification treatment can be directly used for preparing a heat-shrinkable film. The prepared heat-shrinkable film has excellent performance, meets the recycling rate of environmental protection requirements, does not need to make too many adjustments to the existing production process, has a simple process, and can basically maintain the quality of the original heat-shrinkable film.

Description

Technical Field

[0001] This application relates to the technical field of preparing heat shrink film from waste plastic products, and particularly to a functional masterbatch for recyclable heat shrink film and its preparation method. Background Technology

[0002] Heat shrink film is a type of outer packaging material that can significantly shrink in size after heating, and is widely used for the outer packaging of various consumer and industrial products. The materials used in heat shrink film are mainly various thermoplastic films. Initially, PVC shrink film was dominant, but as market demand continued to grow, PVC shrink film gradually decreased, while various multilayer co-extruded heat shrink films such as PE, PP, PET, PETG, and POF developed rapidly and became the mainstream in the market. PVC produces large amounts of harmful gases such as hydrogen chloride and dioxins when burned, causing air pollution and hindering recycling. PE is prone to aging and discoloration, and has a poor heat shrinkage rate. PP is relatively hard, with poor tear and puncture resistance, and is not resistant to low temperatures. Polyester-type heat shrink films such as PET and PETG are non-toxic, odorless, have good mechanical properties, and are environmentally friendly, leading to their rapid development and application.

[0003] For example, CN 109401212 B discloses a polyester composition, a method for preparing the polyester composition, and a heat-shrinkable film and a method for preparing the same. Specifically, based on the total weight of the components, the polyester composition contains the following components: (1) 51-99% by weight of polyester A; (2) 1-49% by weight of polyester B. The heat-shrinkable film made using the polyester composition provided by the prior art can not only have a high heat shrinkage rate, but its heat shrinkage rate can also vary within a wide range to meet different needs; furthermore, the heat-shrinkable film provided by the prior art has suitable heat-sealing strength, a smooth film surface, good gloss, is degradable, can be repeatedly thermoplasticized, and is recyclable.

[0004] CN 103172990 B discloses a method for preparing a heat-shrinkable copolyester film. A multi-component dicarboxylic acid and a multi-component diol are reacted with a catalyst, stabilizer, antistatic agent, chain extender, anti-adhesion agent, or modifier via esterification and polycondensation reactions to obtain a multi-component copolyester. Multi-component copolyester chips are then produced through melt extrusion, stretching, and granulation processes. Finally, a heat-shrinkable copolyester film is obtained through melt extrusion, die casting, transverse far-infrared stretching, cooling and shaping, winding, and slitting processes. The high-shrinkage heat-shrinkable copolyester film prepared by this prior art possesses high strength and heat shrinkage properties, excellent transparency, extensibility, and toughness, good gloss, uniform shrinkage, and is non-toxic, odorless, and easily recyclable. The product is suitable for labeling various containers and for direct packaging of food, beverages, electronic appliances, machinery, hardware, and other products.

[0005] CN 101531079 B discloses a polyester heat-shrinkable film with balanced heat shrinkage properties and its manufacturing method. The film has a three-layer structure: a top layer, a core layer, and a bottom layer. The core layer is composed of polyethylene terephthalate (PET). The top and bottom layers contain 15-25% by weight of masterbatch, with the remainder being copolymerized modified polyester. The masterbatch is a mixture of copolymerized modified polyester and synthetic silica, with synthetic silica comprising 15-25% by weight and the remainder being copolymerized modified polyester. This prior art film exhibits balanced longitudinal and transverse heat shrinkage. At a temperature of 90-100°C, the longitudinal heat shrinkage rate is approximately 65%, and the transverse heat shrinkage rate is approximately 70%. The longitudinal and transverse tensile strengths are 240-260 MPa. This prior art heat-shrinkable polyester film process is mature and highly operable, particularly suitable for two-step stretching polyester film production lines.

[0006] CN 103203934 B discloses a heat-shrinkable copolyester film, comprising an A-layer surface layer mainly composed of PETG copolyester, a B-layer core layer composed of PET / PBT copolyester, and a C-layer bottom layer composed of PCTG copolyester. The film is prepared by extruding PETG copolyester chips, PCTG copolyester chips, and PET / PBT copolyester chips using a screw extruder. Compared with conventional heat-shrinkable polyester films, the three-layer co-extruded transversely stretched copolyester heat-shrinkable film prepared by this prior art has high light transmittance and unidirectional heat shrinkage rate, good gloss, strong stability, uniform shrinkage, and excellent transparency, extensibility, and toughness. It can be produced on existing BOPET film production lines, and the product is suitable for labeling various containers and direct packaging of food and beverages, electronic appliances, machinery, or hardware products.

[0007] As can be seen from the above-mentioned existing technologies, all existing heat shrink films can provide good heat shrink performance.

[0008] However, with the rise of environmentalism in Europe and America, developed countries have enacted strict laws on plastic recycling, mandating that plastic products or components must meet recyclability requirements. This includes requiring that some plastic products contain a certain proportion of recycled materials, or that the plastic products themselves be made from recycled materials. Heat shrink film, commonly used as the outermost disposable packaging material for products, is most easily identified as a source of white pollution (plastic waste), and therefore receives special attention regarding its recyclability. Recently, heat shrink film manufacturers and exporters have received feedback from importers in Europe and America, urging them to quickly improve existing heat shrink film production by increasing the proportion of recycled materials in the raw materials. Summary of the Invention

[0009] The technical problem to be solved by this application is to provide a functional masterbatch for recyclable heat shrink film and a method for preparing the same, so as to reduce or avoid the problems mentioned above.

[0010] To address the aforementioned technical problems, this application proposes a functional masterbatch for recyclable heat-shrinkable film, which is added to recycled polyester granules to perform melt modification on the recycled polyester granules. The functional masterbatch is composed of a polyester carrier and diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecyl stearate, and magnesium carbonate.

[0011] Preferably, the content of each component in the functional masterbatch is as follows: 100-150 parts by weight of polyester carrier, 25-30 parts by weight of diethyl phenylphosphonate, 5-10 parts by weight of sodium dodecylbenzenesulfonate, 15-20 parts by weight of tridecyl stearate, and 5-10 parts by weight of magnesium carbonate.

[0012] Preferably, the polyester carrier is polyethylene terephthalate and its copolymers.

[0013] Preferably, the recycled polyester particles are transparent particles obtained by crushing, decolorizing, and washing PET bottles or heat-shrink film labels, and the particle size of the recycled polyester particles is 50-200 μm.

[0014] This application also proposes a method for preparing the above-mentioned functional masterbatch, wherein the preparation method includes the following steps: uniformly mixing granular polyester carrier with diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecyl stearate and magnesium carbonate, and then melting and extruding the mixture through an extruder and pelletizing it to obtain the functional masterbatch.

[0015] Preferably, the preparation method further includes the following steps: drying the polyester carrier at 65℃~75℃ for 4 hours, grinding magnesium carbonate to a particle size of 0.3~0.5μm and drying it at 65℃~75℃ for 4 hours, and drying sodium dodecylbenzenesulfonate at 65℃~75℃ for 4 hours.

[0016] Preferably, the preparation method further includes the following steps: adding the dried polyester carrier, magnesium carbonate, sodium dodecylbenzenesulfonate and other components of the functional masterbatch into a high-speed mixer for pre-dispersion and mixing at a speed of 1000-1500 rpm for 15-30 minutes to form a mixture.

[0017] Preferably, the preparation method further includes the following steps: melt extruding the mixture through a single screw extruder, followed by water-cooled granulation.

[0018] Preferably, the temperature of the extruder heating zone is 265℃~275℃.

[0019] The functional masterbatch of this application can be added to polyester recycled granules to perform melt modification treatment on the polyester recycled granules. The recyclable material obtained after melt modification treatment can be directly used to prepare heat shrink film. The heat shrink film produced has excellent performance, which not only meets the recycling rate required by environmental protection, but also does not require too much adjustment to the existing production process. The process is simple and can basically maintain the quality of the original heat shrink film. Detailed Implementation

[0020] In order to have a clearer understanding of the technical features, objectives and effects of this application, the specific implementation methods of this application will now be described in detail.

[0021] Based on the environmental protection requirements described in the background section, it is necessary to improve the existing production of heat shrink film by utilizing a certain proportion of recycled materials as one of the raw materials for producing qualified heat shrink film. However, the polyester composition and content of various recycled PET bottles and labels vary greatly, and their aging levels are inconsistent. Some materials inherently possess high heat shrinkability, while others do not. Therefore, simply using physical methods to melt and granulate recycled materials as masterbatch will affect the performance of the produced heat shrink film. For example, indicators such as heat shrinkage rate, light transmittance, and tensile strength will fluctuate significantly, the product color will be yellowish, and there may even be an odor. Consequently, masterbatch obtained from physical recycling can only be used for low-end heat shrink products, such as for making heat shrink tubing, and cannot meet the requirements of high-quality heat shrink film.

[0022] In view of this, this application proposes a functional masterbatch for recyclable heat-shrinkable film. By adding the functional masterbatch of this application to recycled polyester granules and performing melt modification treatment on the recycled polyester granules, the polyester granules with added functional masterbatch are melt-modified into polyester chips, which can then be used as recyclable material for producing heat-shrinkable film. Adding the recyclable material to the heat-shrinkable film raw materials in a certain proportion can produce heat-shrinkable film containing recyclable material. The recycled polyester granules can be transparent granules obtained by crushing, decolorizing, and washing PET bottles or heat-shrinkable film labels. The particle size of the recycled polyester granules is preferably 50–200 μm.

[0023] The recyclable material obtained from the functional masterbatch of this application can be mixed with the raw materials of heat-shrinkable film in a certain proportion. For example, the proportion of recyclable material can be 5% to 95% wt of the total mass of the raw materials to meet export requirements. The heat-shrinkable film can be produced using any existing suitable preparation process and raw material formulation. For example, the recyclable material obtained from the functional masterbatch of this application can be used in the preparation method of heat-shrinkable copolyester film disclosed in CN103172990B proposed by the applicant. This method uses multi-component dicarboxylic acid and multi-component diol, in the presence of catalyst, stabilizer, antistatic agent, chain extender, anti-adhesion agent or modifier, to produce multi-component copolyester through esterification and polycondensation reactions; multi-component copolyester chips are produced through melt extrusion, stretching and granulation processes; and heat-shrinkable copolyester film is produced through melt extrusion, die casting, transverse far-infrared stretching, cooling and shaping, winding and slitting processes. The recyclable material can be added at the esterification reaction stage or at the polycondensation reaction stage. The multi-component copolyester chips obtained by melt extrusion meet environmental protection requirements for recycling rate. They can be directly stretched into single-layer heat shrink film by melt extrusion, or they can be prepared into the surface, core, or bottom layer of multi-layer composite heat shrink film through multi-layer co-extrusion.

[0024] Alternatively, the recyclable material obtained from the functional masterbatch of this application can be used in the heat-shrinkable polyester film disclosed in CN112297555B by the applicant. This heat-shrinkable polyester film consists of layers A, B, and C, with layers A and C respectively disposed on both sides of layer B. Layers A and C are a polyester surface layer and a polyester bottom layer containing functional material chips, while layer B is a polyester core layer without functional material chips. The polyester composition of layers A and C is the same as that of layer B. The recyclable material of this application can be applied to the middle layer, i.e., layer B, of a three-layer heat-shrinkable polyester film. This eliminates the need to adjust the composition of the existing surface and bottom layers, meeting the environmental protection requirements for recycling rate without requiring excessive adjustments to the production process. The process is simple and can basically maintain the quality of the original heat-shrinkable film. Of course, those skilled in the art can also use the recyclable material to prepare the surface and bottom layers of a three-layer heat-shrinkable polyester film.

[0025] As can be seen from the foregoing description, the functional masterbatch of this application can be considered as a functional additive to be added to polyester recycled granules. After being uniformly mixed with polyester recycled granules, the polyester recycled granules are melt-modified by melting, so that the aged and deteriorated components in the polyester recycled granules can be recombined into new polyester monomers. Then the melt is filtered to remove impurities, and finally, through extrusion, stretching and granulation processes, recyclable material chips are obtained.

[0026] The functional masterbatch for recyclable heat-shrinkable film of this application is composed of a polyester carrier and diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecyl stearate, and magnesium carbonate. In one specific embodiment, the functional masterbatch of this application can be prepared by the following method: granular polyester carrier, diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecyl stearate, and magnesium carbonate are uniformly mixed, and then melt-extruded and pelletized using an extruder to obtain the functional masterbatch of this application. Preferably, the content of each component in the functional masterbatch is: 100-150 parts by weight of polyester carrier, 25-30 parts by weight of diethyl phenylphosphonate, 5-10 parts by weight of sodium dodecylbenzenesulfonate, 15-20 parts by weight of tridecyl stearate, and 5-10 parts by weight of magnesium carbonate.

[0027] The polyester carrier in the functional masterbatch of this application can be formed by polycondensation of diacids and diols. The diacid components include, but are not limited to, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 3,4'-diphenyl ether dicarboxylic acid, hexahydrophthalic acid, 2,7-naphthalenedicarboxylic acid, phthalic acid, 4,4'-methylenebisbenzoic acid, oxalic acid, malonic acid, succinic acid, methylsuccinic acid, glutaric acid, adipic acid, 3-methyl adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, 1,11-undecanedicarboxylic acid, 1,10-decanedicarboxylic acid, undecanediic acid, 1,12-dodecanedicarboxylic acid, hexadecanediic acid, docosanodiic acid, tetradecanediic acid, dimer acids, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,1-cyclohexanediacetic acid, fumaric acid, and maleic acid. These acids can be used alone or in combination. For example, the diol components include, but are not limited to, ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, glycol, diethylene glycol, triethylene glycol, poly(ethylene ether) glycol, poly(butylene ether) glycol, branched glycol, hexanediol or combinations or derivatives thereof, 1,4-cyclohexanediol, 1,5-pentanediol, 3-methyl-2,4-pentanediol, neopentanediol, 2-methyl-1,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,5-ethyl-1,3-hexanediol, 2,2-diethyl-1,3-propanediol, and 1,3-hexanediol. These alcohols can also be used alone or in combination.

[0028] The polyester carrier in the functional masterbatch of this application can also be formed from hydroxycarboxylic acids and their esterifying derivatives or cyclic esters. Hydroxycarboxylic acid components include, but are not limited to, lactic acid, citric acid, malic acid, tartaric acid, glycolic acid, 3-hydroxybutyric acid, p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, and 4-hydroxycyclohexanecarboxylic acid. Esterifying derivatives of hydroxycarboxylic acids include, but are not limited to, dimethyl terephthalate, dimethyl isophthalate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl 3,4'-diphenyl ether dicarboxylate, dimethyl hexahydrophthalate, dimethyl 2,7-naphthalenedicarboxylate, dimethyl phthalate, dimethyl 4,4'-methylenebisbenzoate, dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl azelaate, dimethyl 1,3-cyclohexanecarboxylate, and dimethyl 5-sulfoisophthalate. These components can be used alone or in combination. Furthermore, cyclic esters include, but are not limited to, ε-caprolactone, β-propiolactone, β-methyl-β-propiolactone, δ-valerolactone, glycolide, and lactide. Cyclic esters can also be used alone or in combination.

[0029] In one specific embodiment, the polyester carrier used in this application is preferably polyethylene terephthalate (PET), polybutylene terephthalate, polypropylene terephthalate, poly(1,4-cyclohexanediol) terephthalate (PCT), polyethylene naphthalate, polybutylene naphthalate, polypropylene naphthalate, and copolymers thereof. Particularly preferred are polyethylene terephthalate (PET) and copolymers thereof.

[0030] The polyester carrier preparation method of this application takes PET as an example. A preferred preparation method includes the following steps: First, terephthalic acid or dimethyl terephthalate is reacted with ethylene glycol via esterification or transesterification to obtain diethyl terephthalate. Then, under high temperature and vacuum conditions, a condensation reaction is carried out using a catalyst to polycondense diethyl terephthalate into polyethylene terephthalate (PET). In specific embodiments, terephthalic acid, ethylene glycol, cyclohexanediol, a catalyst, and a heat stabilizer can be used as raw materials for the esterification reaction; or terephthalic acid, ethylene glycol, isophthalic acid, a catalyst, and a heat stabilizer can be used as raw materials for the esterification reaction. The catalyst can be any compound selected from Ti / Si non-heavy metal catalysts and antimony trioxide, and its addition amount is 0.01% to 0.09% of the polyester mass. The heat stabilizer can be any one of phosphoric acid compounds, such as phosphoric acid, phosphorous acid, polyphosphoric acid, trimethyl phosphate, triphenyl phosphate, and triethyl phosphate, and its addition amount is 0.0003 to 0.030% of the polyester mass.

[0031] In another specific embodiment of this application, the polyester carrier of this application can be prepared by the following method: 5.0 kg of terephthalic acid, 2.2 kg of ethylene glycol, and 1.10 g of germanium dioxide are added to a 20 L general-purpose polymerization reactor. Esterification reaction is carried out at 230–265 °C and 0.2–0.3 MPa (gauge pressure). When the water output reaches 1200 ml, the pressure is released to atmospheric pressure, and 1.025 g of triphenyl phosphate is added. The mixture is stirred at atmospheric pressure for 10 minutes. The temperature is raised and the pressure is lowered to below 280 °C and below 100 Pa. After a reaction of 1–3 hours, the mixture is extruded, pelletized, and dried to finally obtain the polyester carrier.

[0032] Corresponding to the above-described method for preparing the polyester carrier, the functional masterbatch of this application can be obtained simultaneously with the preparation of the polyester carrier. For example, taking PET as the polyester carrier, the preparation method of the functional masterbatch of this application may include the following steps: First, terephthalic acid or dimethyl terephthalate is esterified with ethylene glycol to obtain diethyl terephthalate. Then, under high temperature and vacuum conditions, a condensation reaction is carried out using a catalyst to condense diethyl terephthalate into a PET polyester carrier. In the above steps, other components besides the polyester carrier can be added to the functional masterbatch during the esterification reaction stage or during the condensation reaction stage. Finally, a melt containing the PET polyester carrier and other components is generated. The melt is extruded and pelletized to obtain the functional masterbatch of this application. In this specific embodiment, terephthalic acid, ethylene glycol, cyclohexanediol, a catalyst, and a heat stabilizer can be used as raw materials for the esterification reaction; or terephthalic acid, ethylene glycol, isophthalic acid, a catalyst, and a heat stabilizer can be used as raw materials for the esterification reaction. The catalyst can be any compound selected from Ti / Si-based non-heavy metal catalysts and antimony trioxide, and its addition amount is 0.01% to 0.09% of the polyester mass. The heat stabilizer can be any phosphoric acid compound, such as phosphoric acid, phosphorous acid, polyphosphoric acid, trimethyl phosphate, triphenyl phosphate, or triethyl phosphate, and its addition amount is 0.0003% to 0.030% of the polyester mass.

[0033] Similarly, in another specific embodiment of this application, the functional masterbatch of this application can be prepared by the following method: terephthalic acid, ethylene glycol, and germanium dioxide are added to a general polymerization reactor, and an esterification reaction is carried out at 230-265°C and 0.2-0.3 MPa (gauge pressure). After esterification, the pressure is released to atmospheric pressure, and triphenyl phosphate and other components of the functional masterbatch except for the polyester carrier are added. The mixture is stirred at atmospheric pressure for 10 minutes, and the temperature is raised and the pressure is lowered to below 280°C and below 100 Pa. After a reaction of 1-3 hours, the mixture is finally extruded, pelletized, and dried to obtain the functional masterbatch.

[0034] Examples 1-3

[0035] The following table shows the raw material proportions by weight for preparing functional masterbatch 1-3.

[0036] Polyester carrier 100 (PET) 125 (PETG) 150 (PET) Diethyl phenylphosphonate 25 28 30 Sodium dodecylbenzenesulfonate 5 7 10 Tridecyl stearate 15 18 20 Magnesium carbonate 5 8 10

[0037] The polyester carrier in the above embodiments was dried at 65℃~75℃ for 4 hours. Magnesium carbonate was ground to a particle size of 0.3~0.5μm and dried at 65℃~75℃ for 4 hours. Sodium dodecylbenzenesulfonate was dried at 65℃~75℃ for 4 hours. The dried polyester carrier, magnesium carbonate, sodium dodecylbenzenesulfonate and other components in the embodiments were added to a high-speed mixer for pre-dispersion and mixing at a speed of 1000~1500rpm for 15~30 minutes to form a mixture. The mixture was then melt-extruded through a single-screw extruder. The heating zone temperature of the extruder was 265℃~275℃. After water cooling and granulation, functional masterbatches 1-3 were finally obtained.

[0038] Examples 4-6

[0039] Transparent granules obtained from the crushing, decolorization, and washing of recycled PET bottles are used as recycled polyester granules. These granules, with an average particle size of 100–150 μm, are uniformly mixed with functional masterbatches 1–3, and then melt-extruded and pelletized to obtain recyclable material. The recyclable material is then subjected to melt co-extrusion, die casting, transverse far-infrared stretching, cooling and shaping, winding, slitting, and stretching to obtain a 50 μm thick heat-shrinkable film.

[0040] In Example 4, recycled polyester granules and functional masterbatch 1 were mixed in a weight ratio of 4:1 to obtain heat shrink film 4. In Example 5, recycled polyester granules and functional masterbatch 2 were mixed in a weight ratio of 4:1 to obtain heat shrink film 5. In Example 6, recycled polyester granules and functional masterbatch 3 were mixed in a weight ratio of 4:1 to obtain heat shrink film 6. The obtained heat shrink films 4-6, when sealed and stored at room temperature for one week, showed no obvious odor.

[0041] The performance parameters of heat shrink films 4-6 were measured respectively and are shown in the table.

[0042]

[0043] As can be seen from the above performance parameters, the recycled polyester particles, after being modified by adding the functional masterbatch of this application, can be directly used to prepare heat shrink film. The resulting heat shrink film has excellent performance, meets the recycling rate required by environmental protection, does not require too much adjustment to the existing production process, has a simple process, and can basically maintain the quality of the original heat shrink film.

[0044] Comparative Examples 1-3

[0045] For comparison, the raw material ratios shown in the table below by weight are used to prepare comparative functional masterbatches 1-3.

[0046] Polyester carrier 100 (PET) 125 (PETG) 150 (PET) Diethyl phenylphosphonate 0 40 43 Sodium dodecylbenzenesulfonate 8 0 14 Tridecyl stearate 25 28 0 Magnesium carbonate 5 8 10

[0047] Comparative Examples 4-7

[0048] Using the same process, comparative heat shrink films 4-6 with a thickness of 50 μm were prepared. In Comparative Example 4, recycled polyester granules and comparative functional masterbatch 1 were mixed in a weight ratio of 4:1 to obtain comparative heat shrink film 4. In Comparative Example 5, recycled polyester granules and comparative functional masterbatch 2 were mixed in a weight ratio of 4:1 to obtain comparative heat shrink film 5. In Comparative Example 6, recycled polyester granules and comparative functional masterbatch 3 were mixed in a weight ratio of 4:1 to obtain comparative heat shrink film 6. In Comparative Example 7, no functional masterbatch was added, and a comparative heat shrink film 7 with a thickness of 50 μm was directly prepared from recycled polyester granules. The prepared comparative heat shrink films 4-7, when sealed and stored at room temperature for one week, showed a noticeable odor.

[0049] The performance parameters of heat shrink films 4-7 were measured and compared respectively, as shown in the table below.

[0050]

[0051] Those skilled in the art should understand that although this application is described by way of multiple embodiments, not every embodiment contains only one independent technical solution. This description is merely for clarity, and those skilled in the art should understand the specification as a whole and consider the technical solutions involved in each embodiment as being able to be combined with each other to form different embodiments to understand the scope of protection of this application.

[0052] The above description is merely an illustrative embodiment of this application and is not intended to limit the scope of this application. Any equivalent changes, modifications, and combinations made by those skilled in the art without departing from the concept and principles of this application shall fall within the scope of protection of this application.

Claims

1. A heat-shrinkable film, prepared from recyclable material, wherein the recyclable material is obtained by adding a functional masterbatch to recycled polyester granules and then performing a melt modification treatment on the recycled polyester granules, characterized in that... The functional masterbatch is composed of a polyester carrier, diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecyl stearate, and magnesium carbonate. The content of each component in the functional masterbatch is as follows: 100-150 parts by weight of polyester carrier, 25-30 parts by weight of diethyl phenylphosphonate, 5-10 parts by weight of sodium dodecylbenzenesulfonate, 15-20 parts by weight of tridecyl stearate, and 5-10 parts by weight of magnesium carbonate. The polyester carrier is polyethylene terephthalate and its copolymers.

2. The heat-shrinkable film as described in claim 1, characterized in that, The recycled polyester particles are transparent particles obtained by crushing, decolorizing, and washing PET bottles or heat-shrink film labels, and the particle size of the recycled polyester particles is 50-200µm.

3. A heat-shrinkable film as described in claim 1, characterized in that, The preparation method of the functional masterbatch includes the following steps: uniformly mixing granular polyester carrier with diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecyl stearate and magnesium carbonate, and then melting and extruding the mixture through an extruder and pelletizing it to obtain the functional masterbatch.

4. The heat-shrinkable film as described in claim 3, characterized in that, The preparation method further includes the following steps: drying the polyester carrier at 65℃~75℃ for 4 hours, grinding magnesium carbonate to a particle size of 0.3~0.5μm and drying it at 65℃~75℃ for 4 hours, and drying sodium dodecylbenzenesulfonate at 65℃~75℃ for 4 hours.

5. The heat-shrinkable film as described in claim 4, characterized in that, The preparation method further includes the following steps: adding the dried polyester carrier, magnesium carbonate, sodium dodecylbenzenesulfonate and other components of the functional masterbatch into a high-speed mixer for pre-dispersion and mixing at a speed of 1000-1500 rpm for 15-30 minutes to form a mixture.

6. The heat-shrinkable film as described in claim 5, characterized in that, The preparation method further includes the following steps: melting and extruding the mixture through a single screw extruder, followed by water-cooled granulation.

7. The heat-shrinkable film as described in claim 6, characterized in that, The temperature of the extruder heating zone is 265℃~275℃.

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