A heat-shrinkable film recyclate and a method for producing the same

Abstract

The application provides a heat-shrinkable film recyclable material and a preparation method thereof. The heat-shrinkable film recyclable material is prepared by mixing 60-80 wt% polyester recyclable particles and 20-40 wt% functional masterbatch, wherein the polyester recyclable particles are prepared from recycled PET bottles or heat-shrinkable film labels, and the functional masterbatch is composed of a polyester carrier and diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecanol stearate and magnesium carbonate. The preparation method of the recyclable material comprises a preparation step of the functional masterbatch, a preparation step of the polyester recyclable particles and a step of mixing the polyester recyclable particles and the functional masterbatch. The recyclable material prepared by adding the functional masterbatch to the polyester recyclable particles and performing melt modification treatment can be used to prepare a single-layer structure of a heat-shrinkable film, or can be mixed with other polyester raw materials to prepare a single-layer structure of a heat-shrinkable film or one layer of a multi-layer structure of a heat-shrinkable film. The prepared heat-shrinkable film has excellent performance and can meet environmental protection requirements.

Description

Technical Field

[0001] This application relates to the field of plastic product recycling, and more particularly to the technical field of preparing heat shrink film from waste plastic products, and specifically to a recyclable heat shrink film material and its preparation method. Background Technology

[0002] Plastic products are difficult to degrade and easily cause environmental pollution. While a large amount of waste plastic products, such as beverage bottles, are being recycled, most of these bottles are crushed and reused as raw materials for low-end products, making them unsuitable for applications with high aesthetic and environmental requirements. For example, heat-shrink film is a packaging material that shrinks significantly in size when heated and is widely used for packaging various consumer and industrial products. Heat-shrink film used as packaging material typically requires good mechanical properties, high transverse tensile strength, high transparency, and fire resistance. However, ordinary recycled plastics, due to their diverse origins and significant differences in composition between different plastic products, suffer from aging and discoloration, making them unsuitable as raw materials for heat-shrink film production.

[0003] For example, CN 100493903 C discloses a heat-shrinkable polyester film with a multilayer structure, one layer of which uses recycled PET bottle material, while the other layers do not contain recycled material. This prior art considers recycled PET bottle material to be a random mixture of various PET materials with different melt viscosities, molecular weights, molecular weight distributions, monomer compositions, crystallinity, and the presence or absence of additives such as polymerization catalysts. Their physical properties vary significantly from batch to batch. Directly manufacturing heat-shrinkable film using such recycled material cannot yield stable and uniform products. Furthermore, films using more than 45% by mass of recycled material cannot achieve sufficient mechanical strength or heat shrinkability. Therefore, this prior art employs a multilayer structure for the heat-shrinkable film, utilizing layers without recycled material to provide the required mechanical strength and heat shrinkability, thus overcoming the shortcomings of insufficient recycled material performance.

[0004] Therefore, this existing technology uses recycled PET bottles to prepare heat shrink film without thoroughly modifying the recycled raw materials. The original defects are not improved; the defects of the recycled raw material layer are simply covered up with a normal heat shrink layer. The inherent problems of discoloration and transparency of the recycled raw material layer are still perceptible to the senses. Heat shrink film prepared by this existing technology is difficult to enter the consumer market with high quality requirements and can only be used as low-grade packaging material in the industrial field. Summary of the Invention

[0005] The technical problem to be solved by this application is to provide a recyclable heat-shrinkable film and a method for preparing the same, so as to reduce or avoid the problems mentioned above.

[0006] To address the aforementioned technical problems, this application proposes a heat-shrinkable film recyclable material, prepared by mixing 60-80 wt% of recycled polyester granules with 20-40 wt% of functional masterbatch. The recycled polyester granules are prepared from recycled PET bottles or heat-shrinkable film labels. The functional masterbatch is composed of a polyester carrier and diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecyl stearate, and magnesium carbonate.

[0007] 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.

[0008] Preferably, the polyester carrier is polyethylene terephthalate and its copolymers.

[0009] Preferably, the particle size of the recycled polyester particles is 50–200 μm.

[0010] This application also proposes a method for preparing the above-mentioned heat-shrinkable film recyclable material, including a functional masterbatch preparation step, a polyester recycling particle preparation step, and a step of mixing the polyester recycling particles with the functional masterbatch to prepare the recyclable material. The functional masterbatch preparation step includes: firstly, drying 100-150 parts by weight of a polyester carrier at 65°C-75°C for 4 hours; secondly, grinding 5-10 parts by weight of magnesium carbonate to a particle size of 0.3-0.5 μm and drying it at 65°C-75°C for 4 hours; and thirdly, drying 5-10 parts by weight of sodium dodecylbenzenesulfonate at 65°C-75°C for 4 hours. The mixture is dried at 5°C for 4 hours. Then, the dried polyester carrier, magnesium carbonate, sodium dodecylbenzenesulfonate, 25-30 parts by weight of diethyl phenylphosphonate, 5-10 parts by weight of sodium dodecylbenzenesulfonate, and 15-20 parts by weight of tridecyl stearate are added to a high-speed mixer for pre-dispersion mixing at 1000-1500 rpm for 15-30 minutes to form a mixture. The mixture is then melt-extruded through a single-screw extruder at a heating zone temperature of 265°C-275°C, followed by water cooling and granulation to obtain the functional masterbatch.

[0011] Preferably, the preparation steps of the recycled polyester granules include: using transparent granules obtained by crushing, decolorizing, and washing recycled PET bottles or heat-shrink film labels as recycled polyester granules.

[0012] Preferably, the preparation method further includes the following steps: crushing the recycled PET bottles or heat shrink film labels, air-drying them at the same time, and removing low-density and high-density impurities by air separation after air drying; and decolorizing the material after air separation by solvent.

[0013] Preferably, the preparation method further includes the following steps: after decolorization, the liquid is discharged, then water is injected and allowed to stand, and activated carbon is removed by flotation washing; the material after flotation washing is dried, and polyester recycled particles with a particle size of 100-150μm are separated for later use.

[0014] Preferably, the injected water contains 1.5–3% sodium hydroxide by weight of the total water mass and 0.5–1.0% ethanolamine by weight of the total water mass.

[0015] Preferably, the step of preparing recyclable material by mixing polyester recycled particles with functional masterbatch includes: uniformly mixing polyester recycled particles with an average particle size of 100-150 μm with the prepared functional masterbatch in a certain proportion, then feeding the mixture into a single screw extruder, removing impurities by melt filtration and then extruding the mixture, with the extruder heating zone temperature being 265℃-275℃, followed by water cooling granulation, and finally obtaining recyclable material.

[0016] This application describes a process where functional masterbatch is added to recycled polyester granules for melt modification. The resulting recyclable material can be prepared as a single layer of a heat-shrinkable film, or it can be mixed with other polyester raw materials to prepare a single-layer heat-shrinkable film or a layer of a multi-layer heat-shrinkable film. The heat-shrinkable film produced has excellent performance and meets environmental protection requirements. Detailed Implementation

[0017] In order to gain 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.

[0018] To address the limitation of existing technologies that cannot directly produce high-quality heat-shrinkable film from recycled PET bottles, this application proposes a recyclable material for heat-shrinkable film. This material is obtained by melt-modifying recycled polyester granules by adding functional masterbatch. Adding a certain proportion, for example, 5% to 95% wt of the recyclable material to the heat-shrinkable film raw material allows for the production of heat-shrinkable film containing the recyclable material. The recycled polyester granules can be transparent granules obtained from recycled PET bottles or heat-shrinkable film labels after crushing, decolorizing, and washing. The preferred particle size of the recycled polyester granules is 50–200 μm.

[0019] The heat-shrinkable film can be produced using any existing suitable manufacturing process and raw material formulation. For example, the recyclable material prepared in this application can be used in the heat-shrinkable copolyester film preparation method disclosed in CN103172990B, in which a multi-component dicarboxylic acid and a multi-component diol undergo esterification and polycondensation reactions in the presence of a catalyst, stabilizer, antistatic agent, chain extender, anti-adhesion agent, or modifier to produce a multi-component copolyester; multi-component copolyester chips are produced through melt extrusion, stretching, and granulation processes; and heat-shrinkable copolyester film is obtained through melt extrusion, die casting, transverse far-infrared stretching, cooling and shaping, winding, and slitting processes. The recyclable material can be added during the esterification reaction stage or the polycondensation reaction stage. The multi-component copolyester chips obtained after melt extrusion meet environmental protection requirements for recycling rate and can be directly melt-extruded and stretched into a single-layer heat-shrinkable film, or multi-layer co-extruded to prepare the surface, core, or bottom layer of a multi-layer composite heat-shrinkable film.

[0020] Alternatively, the recyclable material prepared in this application can be used in the heat-shrinkable polyester film disclosed in CN112297555B, which consists of layers A, B, and C. Layers A and C are 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 used in the middle layer, 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.

[0021] As can be seen from the above application examples of the recyclable material in this application, the recyclable material is an intermediate product obtained by melt-modifying recycled polyester granules, containing functional masterbatch. This recyclable material containing functional masterbatch can be prepared alone as a single layer of heat-shrinkable film, or it can be mixed with other polyester raw materials to prepare a single-layer heat-shrinkable film or a layer of a multi-layer heat-shrinkable film. This application preferably uses the recyclable material mixed with other polyester raw materials to minimize the performance deficiencies of the recyclable material.

[0022] In one specific embodiment, the recyclable heat-shrinkable film of this application is prepared by mixing 60-80 wt% of recycled polyester particles with 20-40 wt% of functional masterbatch. The recycled polyester particles are prepared from recycled PET bottles or heat-shrinkable film labels. The functional masterbatch consists of a polyester carrier and diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecyl stearate, and magnesium carbonate. In one specific embodiment, the recyclable material of this application can be prepared by the following method: transparent particles obtained by crushing, decolorizing, and washing recycled PET bottles or heat-shrinkable film labels are used as recycled polyester particles. The recycled polyester particles with an average particle size of 100-150 μm are selected and uniformly mixed with the prepared functional masterbatch. Then, the mixture is melt-extruded and pelletized using an extruder to obtain the recyclable material.

[0023] The functional masterbatch of this application can be prepared by the following method: a granular polyester carrier is uniformly mixed with diethyl phenylphosphonate, sodium dodecylbenzenesulfonate, tridecyl stearate, and magnesium carbonate, and then melt-extruded and pelletized using an extruder to obtain the functional masterbatch of this application. The preferred 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] In one specific embodiment of this application, the functional masterbatch 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 can 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 of functional masterbatch 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.

[0030] 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.

[0031] As mentioned above, in a preferred embodiment of this application, the functional masterbatch of this application can be prepared by the following method: 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.

[0032] More specifically, the preparation steps of the functional masterbatch of this application include: First, drying 100-150 parts by weight of polyester carrier at 65℃-75℃ for 4 hours; grinding 5-10 parts by weight of magnesium carbonate to a particle size of 0.3-0.5 μm and drying it at 65℃-75℃ for 4 hours; and drying 5-10 parts by weight of sodium dodecylbenzenesulfonate at 65℃-75℃ for 4 hours. Then, the dried polyester carrier, magnesium carbonate, sodium dodecylbenzenesulfonate, 25-30 parts by weight of diethyl phenylphosphonate, 5-10 parts by weight of sodium dodecylbenzenesulfonate, and 15-20 parts by weight of tridecyl stearate are added to a high-speed mixer for pre-dispersion mixing at 1000-1500 rpm for 15-30 minutes to form a mixture. Next, the mixture is melt-extruded through a single-screw extruder at a heating zone temperature of 265℃-275℃, followed by water-cooled granulation. Finally, the functional masterbatch can be obtained.

[0033] As mentioned above, the recyclable material of this application is prepared by mixing 60-80 wt% of recycled polyester particles with 20-40 wt% of functional masterbatch. Therefore, the method for preparing the recyclable material includes not only the preparation step of the functional masterbatch described above, but also the preparation step of recycled polyester particles and the step of mixing with functional masterbatch to prepare the recyclable material.

[0034] For example, the preparation steps of the polyester recycled granules in this application are as follows: transparent granules obtained by crushing, decolorizing, and washing recycled PET bottles or heat-shrink film labels are used as polyester recycled granules. Typically, recycled PET beverage bottles usually have labels, most of which are heat-shrink film labels tightly bonded to the bottle body, and a small portion use adhesive easy-tear labels. Easy-tear labels have a very low density and are easily sorted and removed after crushing. The caps of recycled PET bottles need to be removed, using only the bottle body. Most existing PET beverage bottles typically use a one-piece molding process for the bottle neck, with the neck and body made of the same material. However, bottles in some special fields, such as injection bottles in the medical field, have different materials for the neck and body, and may contain pathogens, requiring rejection.

[0035] Therefore, the preparation steps of the recycled polyester granules in this application further include: crushing the recycled PET bottles or heat-shrink film labels, air-drying them simultaneously, and then removing low-density and high-density impurities by air separation after air drying. Since beverage bottles may contain residual liquid, air drying is necessary during crushing to prevent the particles from sticking together and becoming difficult to dry. The dried material is then easier to air-separate.

[0036] The material after air classification needs to be decolorized using a solvent. For example, commonly used decolorizing solvents in the art can be selected for decolorization. In one specific embodiment, a decolorizing agent can be prepared from 20-30 wt% propylene glycol diacetate, 50-60 wt% dimethyl sulfoxide, and 10-30 wt% activated carbon. The material and decolorizing agent are soaked in a volume ratio of 1:2 for 10-24 hours, while continuously stirring at a speed of 20-30 rpm.

[0037] After decolorization, the liquid is discharged, and then clean water is added for settling. The activated carbon is then removed by flotation. The preferred mass ratio of material to water is between 1:3 and 1:5. The denser activated carbon, having absorbed the liquid, sinks to the bottom, while the less dense PET particles float. Therefore, the PET particles are easily removed by flotation, thus eliminating the activated carbon. Additionally, flotation can further remove high-density impurities that were not completely removed by air separation. The flotation process also serves a cleaning function and can be repeated multiple times (because activated carbon is dark in color, it is easy to see whether it has been completely removed; therefore, the number of flotation cycles can be selected based on observation).

[0038] During flotation, since the material is also repeatedly washed, it is preferable to add 1.5-3% sodium hydroxide and 0.5-1.0% ethanolamine by mass of the total water mass to the injected water to perform surface treatment on the material, remove the attached solvent as much as possible, and change the surface properties of the material to facilitate subsequent modification treatment.

[0039] The material after flotation washing needs to be dried, and polyester recovery particles with a particle size of 100-150 μm are separated for later use. The moisture content of the prepared polyester recovery particles must be less than 0.1%.

[0040] Finally, the steps for preparing recyclable material by mixing polyester recycled granules and functional masterbatch include: uniformly mixing polyester recycled granules with an average particle size of 100-150 μm with the prepared functional masterbatch in a certain proportion, then feeding the mixture into a single screw extruder, removing impurities by melt filtration and then extruding the mixture. The temperature of the heating zone of the extruder is 265℃-275℃, followed by water cooling and granulation, and finally obtaining recyclable material.

[0041] Examples 1-3

[0042] The following table shows the raw material proportions by weight for preparing functional masterbatch 1-3.

[0043] 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

[0044] 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.

[0045] Examples 4-6

[0046] The prepared polyester recycled particles with an average particle size of 100-150 μm were uniformly mixed with functional masterbatch 1-3, fed into an extruder, and impurities were removed by melt filtration before extrusion and pelleting to obtain recyclable material.

[0047] The recyclable material is melt co-extruded, die-cast, transverse far-infrared stretched, cooled and shaped, wound, slit, and stretched to obtain a heat shrink film with a thickness of 50μm.

[0048] 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 3:1 to obtain heat shrink film 5. In Example 6, recycled polyester granules and functional masterbatch 3 were mixed in a weight ratio of 7:3 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.

[0049] The performance parameters of heat shrink films 4-6 were measured respectively and are shown in the table.

[0050]

[0051] 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.

[0052] Comparative Examples 1-3

[0053] For comparison, the raw material ratios shown in the table below by weight are used to prepare comparative functional masterbatches 1-3.

[0054] 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

[0055] Comparative Examples 4-7

[0056] 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 3:1 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 7:3 to obtain comparative heat shrink film 6. In Comparative Example 7, no functional masterbatch was added, and comparative heat shrink film 7 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.

[0057] The performance parameters of heat shrink films 4-7 were measured and compared respectively, as shown in the table below.

[0058]

[0059] Comparative Examples 8-10

[0060] Using the same process, comparative heat shrink films 8-10 with a thickness of 50 μm were prepared. In Comparative Example 8, only sodium hydroxide was added during the sorting and cleaning of the recycled polyester particles; in Comparative Example 9, only ethanolamine was added; and in Comparative Example 10, neither sodium hydroxide nor ethanolamine was added during the sorting and cleaning of the recycled polyester particles. Similar to Examples 1-3, in Comparative Example 8, recycled polyester particles were mixed with functional masterbatch 1 at a weight ratio of 4:1 to obtain comparative heat shrink film 8. In Comparative Example 9, recycled polyester particles were mixed with functional masterbatch 2 at a weight ratio of 3:1 to obtain comparative heat shrink film 9. In Comparative Example 10, recycled polyester particles were mixed with functional masterbatch 3 at a weight ratio of 7:3 to obtain comparative heat shrink film 10.

[0061]

[0062] The comparison shows that adding sodium hydroxide and ethanolamine during the cleaning process can appropriately improve the performance of the heat shrink film.

[0063] 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.

[0064] 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 method for preparing a heat-shrinkable film recyclable material, wherein the heat-shrinkable film recyclable material is prepared by mixing 60-80 wt% of recycled polyester particles with 20-40 wt% of functional masterbatch; the preparation method includes a step of preparing the functional masterbatch, a step of preparing the recycled polyester particles, and a step of mixing the recycled polyester particles with the functional masterbatch to prepare the recyclable material, characterized in that, The preparation steps of the functional masterbatch include: first, drying 100-150 parts by weight of polyester carrier at 65℃-75℃ for 4 hours; grinding 5-10 parts by weight of magnesium carbonate to a particle size of 0.3-0.5μm and drying it at 65℃-75℃ for 4 hours; and drying 5-10 parts by weight of sodium dodecylbenzenesulfonate at 65℃-75℃ for 4 hours; then, adding the dried polyester carrier, magnesium carbonate, sodium dodecylbenzenesulfonate, 25-30 parts by weight of diethyl phenylphosphonate, and 15-20 parts by weight of tridecyl stearate into a high-speed mixer for pre-dispersion mixing at a speed of 1000-1500 rpm. Mix at rpm for 15-30 minutes to form a mixture; then, melt-extrude the mixture through a single-screw extruder, with the extruder heating zone temperature at 265℃-275℃, followed by water-cooled granulation to obtain the functional masterbatch; the preparation method further includes the following steps: crushing recycled PET bottles or heat shrink film labels, air-drying them simultaneously, and then removing low-density and high-density impurities by air separation; the material after air separation is decolorized by solvent; the decolorization step is: using 20-30 wt% propylene glycol diacetate, 50-60 wt% dimethyl sulfoxide, and 10-30 wt%... A decolorizing agent is obtained by mixing wt% activated carbon; the material and the decolorizing agent are soaked in a volume ratio of 1:2 for 10-24 hours while continuously stirring at a speed of 20-30 rpm; the preparation method further includes the following steps: after decolorization, the liquid is discharged, and then water is injected for standing, and activated carbon is removed by flotation washing; the material after flotation washing is dried, and polyester recovery particles with a particle size of 100-150 μm are separated for later use; 1.5-3% sodium hydroxide and 0.5-1.0% ethanolamine by mass of water are added to the injected water.

2. The preparation method according to claim 1, characterized in that, The steps for preparing recyclable material by mixing polyester recycled particles with functional masterbatch include: uniformly mixing the prepared polyester recycled particles with an average particle size of 100-150μm with the prepared functional masterbatch in a certain proportion, then feeding them into a single screw extruder, removing impurities by melt filtration and then extruding them. The temperature of the heating zone of the extruder is 265℃-275℃, followed by water cooling granulation, and finally preparing recyclable material.

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