Polyester heat shrink film containing reclaimed materials and preparation method thereof

Abstract

The invention provides a polyester heat shrink film containing reclaimed materials and a preparation method thereof, and belongs to the technical field of polymer synthetic films. The polyester heat shrinkage film is prepared from the following raw materials: recycled PET polyester particles, PET polyester chips and modified master batch, the modified master batch is prepared from polyethylene glycol terephthalate-1, 4-cyclohexanedimethanol ester, triphenyl phosphate, a polyethylene glycol block copolymer, nano silicon dioxide and hyperbranched polyesteramine; the polyethylene glycol block copolymer is prepared from polyethylene glycol and gamma-valerolactone under the action of a catalyst; the hyperbranched polyesteramine is prepared from trimethylolpropane, methyl crotonate and diethylenetriamine. The product has the characteristics of excellent unidirectional shrinkage resistance, low haze and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer synthetic membranes, and particularly relates to a polyester heat shrinkable film containing recycled materials and a preparation method thereof. Background Art

[0002] Heat shrinkable films are usually used for the storage, transportation and outer packaging of various food and beverages, electronics and electrical appliances, pharmaceutical and daily chemical products. They are characterized by significantly shrinking in size after heating and are a widely used plastic packaging material. At present, countries around the world pay more and more attention to environmental protection and circular economy. Many countries and regions have issued various directives or documents, putting forward requirements for the proportion of recycled components in plastic products. Therefore, the plastic packaging products industry must also attach importance to and increase the proportion of recycled materials in products. With the progress of technology, heat shrinkable films made of various materials such as PETG, PET, and PP have emerged one after another, gradually replacing PVC materials, especially in scenarios where recyclable packaging is required, and their advantages in recycling are significant.

[0003] Due to the inconsistent quality and different aging conditions of PET recycled materials, or some recycled materials have been processed multiple times, resulting in a wide molecular weight distribution, and the PDI is usually greater than 2.5. According to the existing PET heat shrinkable film preparation process, if too much recycled material is added, microscopically, there will be insufficient entanglement of chain segments and low molecular chain orientation degree, resulting in a decrease in the mechanical properties of the film, causing poor unidirectional anti-shrinkage performance, high haze and other adverse phenomena. This is not conducive to the packaging of high-curvature containers, especially in the precise packaging industries such as heat shrink labels.

[0004] Chinese Patent CN117165043A discloses a functional masterbatch for recyclable heat shrinkable films and a preparation method thereof. The heat shrinkable film prepared by this method has a high tensile strength, and the characteristic is that the biaxial shrinkage rate is relatively high. Chinese Patent CN117836137B discloses a recyclable heat shrinkable film for recyclable containers, which has a high shrinkage rate. When heated to 100 °C, the entire recyclable shrink label can shrink by 1% to 90%, but it does not mention whether it can not shrink in a single direction, and only states that its product can be recycled, and does not mention adding recycled materials in its preparation process.

[0005] At present, there is little research on unidirectional anti-shrinkage polyester films containing recycled materials in the market. The PET heat shrinkable films containing recycled materials prepared by the existing technology generally have poor unidirectional anti-shrinkage performance and high haze. Summary of the Invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a polyester heat shrinkable film containing recycled materials and a preparation method thereof, achieving the following invention objectives: preparing a polyester heat shrinkable film with a high proportion of recycled materials, excellent unidirectional anti-shrinkage performance, low haze and high tensile strength.

[0007] To achieve the above object, the following technical solutions are adopted: A polyester heat-shrinkable film containing recycled materials, the raw materials of which include recycled PET polyester particles, PET polyester chips, and a modified masterbatch; The modified masterbatch is prepared from polyethylene terephthalate-1,4-cyclohexanedimethanol ester, triphenyl phosphite, polyethylene glycol block copolymer, nano-silica, and hyperbranched polyester amine.

[0008] The hyperbranched polyester amine is prepared from trimethylolpropane, methyl crotonate, and diethylenetriamine.

[0009] The polyethylene glycol block copolymer is prepared from polyethylene glycol and γ-valerolactone under the action of a catalyst.

[0010] The weight ratio of the recycled PET polyester particles, PET polyester chips, and the modified masterbatch is: 600-750 parts of recycled PET polyester particles, 250-300 parts of PET polyester chips, and 70-85 parts of the modified masterbatch.

[0011] Further, the mass ratio of the polyethylene terephthalate-1,4-cyclohexanedimethanol ester, triphenyl phosphite, polyethylene glycol block copolymer, nano-silica, and hyperbranched polyester amine is (80-95):(10-18):(8-12):(5-10):(3-8).

[0012] Further, the molar ratio of the trimethylolpropane, methyl crotonate, and diethylenetriamine is 1:(2-4):(0.3-0.5).

[0013] Further, the molar ratio of the polyethylene glycol and γ-valerolactone is 1:(3-5).

[0014] Further, the catalyst is stannous octoate, and the addition amount is 0.1%-0.4% of the mass of the polyethylene glycol.

[0015] A preparation method of a polyester heat-shrinkable film containing recycled materials, including the steps of preparing a polyethylene glycol block copolymer, preparing a hyperbranched polyester amine, preparing a modified masterbatch, melt blending, casting into a film, and stretching and shaping; Further, the preparation of the hyperbranched polyester amine: includes the synthesis of dendritic molecules and an amidation reaction step; the synthesis of the dendritic molecules: adding trimethylolpropane and methyl crotonate into a reactor, introducing nitrogen for protection, starting stirring and heating, the reaction temperature is 50-60°C, and the reaction time is 4-8 hours; Further, for the amidation reaction: after the synthesis reaction of the dendrimer is completed, diethylenetriamine is added dropwise to the reactor. After the addition is completed, heating is started, and the temperature is raised to 80-90 °C, and the reaction continues for 6-10 hours; Further, for the preparation of the modified masterbatch: polyethylene terephthalate-1,4-cyclohexanedimethanol ester, triphenyl phosphite, polyethylene glycol block copolymer, nano-silica, and hyperbranched polyester amine are kneaded, and the kneading is carried out for 30-40 min at a temperature of 220-230 °C.

[0016] Further, for the preparation of the polyethylene glycol block copolymer: polyethylene glycol and γ-valerolactone are added to the reactor, stirring is started, nitrogen protection is introduced, the temperature is raised to 110-130 °C, a catalyst is added, and after reacting for 6-8 hours, a polyethylene glycol block copolymer is obtained.

[0017] The number average molecular weight of the polyethylene glycol block copolymer is 5000-15000 g / mol.

[0018] Further, for the melt blending: recycled PET polyester particles, PET polyester chips, and the modified masterbatch are melt extruded through a twin-screw extruder; the temperature of the preheating section hopper of the twin-screw extruder is 80-90 °C, the plasticizing and melting section is 250-260 °C, and the die head extrusion section is 270-275 °C.

[0019] Further, for the recycled PET polyester particles, the ash content is less than 0.1%, and the impurity content is less than 0.2%.

[0020] Further, the PET polyester chips are new PET polyester materials.

[0021] Further, for the stretching and setting: it includes longitudinal stretching and transverse stretching; longitudinal stretching: the stretching ratio is 0.5-4.5 times, and the stretching temperature is 80-100 °C; transverse stretching: the stretching temperature is 95-110 °C, and the stretching ratio is 2.5-5.5 times.

[0022] Compared with the prior art, the present invention has achieved the following beneficial effects: A polyester heat-shrinkable film containing recycled materials prepared by the present invention has a longitudinal shrinkage rate as low as 2.1%-3.1% and a transverse shrinkage rate of up to 72%-76% on the basis of a recycled material content of 60%-70%, and the haze is lower than 5%. Description of the Drawings

[0023] Appendix Figure 1 It is the nuclear magnetic resonance hydrogen spectrum (H-NMR) diagram of the "preparation of polyethylene glycol block copolymer" step of the present invention.

[0024] Appendix Figure 2This is the infrared spectrum (FTIR) graph before the reaction in the step of "preparation of hyperbranched polyesters and polyamines" of the present invention.

[0025] Appendix Figure 3 This is the infrared spectrum (FTIR) graph after the reaction in the step of "preparation of hyperbranched polyesters and polyamines" of the present invention. Detailed implementation manners

[0026] To make the objectives, technical solutions and advantages of the present invention clearer, the following will further describe the implementation manners of the present invention in detail. It should be understood that the specific implementation manners described herein are only for explaining and interpreting the present invention, and are not used to limit the present invention.

[0027] Example 1 Preparation method of a polyester heat shrinkable film containing recycled materials Step 1 Preparation of polyethylene glycol block copolymer Add polyethylene glycol and γ-valerolactone into a dry reactor, start stirring, introduce nitrogen for protection, heat up to 130 °C, add stannous octoate, and after reacting for 6 hours, obtain a polyethylene glycol block copolymer. The number-average molecular weight of the polyethylene glycol block copolymer is 5000 g / mol.

[0028] The molar ratio of the amounts of polyethylene glycol and γ-valerolactone used is 1:3.

[0029] The amount of stannous octoate added is 0.2% of the mass of polyethylene glycol.

[0030] Step 2 Preparation of hyperbranched polyesters and polyamines ① Synthesis of dendritic molecules: Add trimethylolpropane and methyl crotonate according to the ratio into a dry reactor, introduce nitrogen for protection, start stirring and heating, control the stirring rate at 300 rpm, and control the temperature at 55 °C, and react for 5 hours.

[0031] ② Amidation reaction: After the synthesis reaction of dendritic molecules is completed, keep stirring on, add diethylenetriamine dropwise to the reactor, and start heating after the addition is completed, heat up to 80 °C, and keep the temperature for reaction for 10 hours.

[0032] The molar ratio of the amounts of trimethylolpropane (TMP), methyl crotonate (MC) and diethylenetriamine (DETA) used is 1:2.0:0.5.

[0033] ③ Purification: Cool the reaction solution obtained in step ② to room temperature, slowly pour it into ethanol at -5 °C, and stir for 30 minutes. Filter the stirred reaction solution, and the obtained solid product is dried to obtain a white powdery hyperbranched polyesters and polyamines. The drying temperature is 50 °C, the vacuum is ≤ -0.065 MPa, and the drying time is 12 hours.

[0034] Step 3 Preparation of modified masterbatch Mix PETG, triphenyl phosphite, polyethylene glycol block copolymer, nano-silica, and hyperbranched polyester amine evenly, then add them to an internal mixer and mix for 35 min at a set temperature of 226 °C. Feed the melt after mixing into a twin-screw granulator through a hot melt gear pump. After extrusion and pelletizing by the twin-screw granulator, a modified masterbatch with a particle size of 3 mm is obtained.

[0035] The weight part ratio of the raw materials used is as follows: 80 parts of polyethylene terephthalate-1,4-cyclohexanedimethanol ester (PETG), 13 parts of triphenyl phosphite, 10 parts of polyethylene glycol block copolymer, 10 parts of nano-silica, and 3 parts of hyperbranched polyester amine (HPEA).

[0036] Step 4, melt blending Mix the recycled PET polyester particles, PET polyester chips (new PET polyester materials), and the modified masterbatch evenly, and convey them through a hopper to a twin-screw extruder for melt extrusion. The temperature settings for each section of the twin-screw extruder are as follows: the temperature of the hopper in the preheating section is 80 °C, the conveying section is 225 °C, the plasticizing and melting section is 260 °C, the vacuum exhaust section is 250 °C, the homogenizing and metering section is 255 °C, and the die head extrusion section is 270 °C. A coat-hanger type flat die head is selected for the die head, and the die lip gap is 1.5 mm.

[0037] The weight part ratio of the raw materials used is as follows: 600 parts of recycled PET polyester particles, 300 parts of PET polyester chips, and 85 parts of the modified masterbatch.

[0038] The recycled PET polyester particles have an ash content of less than 0.1% and an impurity content of less than 0.2%, and are purchased from Foshan Yaotaiyuansu Industry Co., Ltd.

[0039] Step 5, casting into film The melt extruded from the die head contacts the surface of a rapidly rotating quenching roll vertically in a curtain shape, and the melt is extended into a film by the quenching roll; cooling water is connected in the quenching roll, and the temperature of the cooling water is controlled at 20 °C. After cooling, the film is peeled off from the surface of the quenching roll and enters the stretching and shaping section.

[0040] Step 6, stretching and shaping After the film is peeled off from the surface of the quenching roll, it is sequentially introduced into a longitudinal stretching machine and a transverse stretching machine through a set of traction rolls.

[0041] The control parameters of the longitudinal stretching machine are: stretching ratio 0.5 times, temperature 88 °C.

[0042] The control parameters of the transverse stretching machine are: stretching ratio 2.5 times, temperature 95 °C.

[0043] After stretching, the diaphragm is heat-set. The temperature of the diaphragm is raised to 190 °C by infrared heating, and then cooled down to 170 °C in gradients, with each gradient being 10 °C and each gradient temperature lasting for 5 seconds. After heat-setting, it is cooled to room temperature. After edge trimming and winding, a polyester heat-shrinkable film containing recycled materials is obtained.

[0044] Example 2 Preparation method of a polyester heat-shrinkable film containing recycled materials Step 1: Preparation of polyethylene glycol block copolymer Polyethylene glycol and γ-valerolactone are added to a dry reactor. Stirring is started, nitrogen is introduced for protection, the temperature is raised to 115 °C, and stannous octoate is added. After reacting for 7.5 hours, a polyethylene glycol block copolymer is obtained. The molar ratio of PEG to γ-valerolactone is 1:3.8.

[0045] The addition amount of stannous octoate is 0.1% of the mass of polyethylene glycol.

[0046] The prepared polyethylene glycol block copolymer: the number-average molecular weight is 9000 g / mol.

[0047] Step 2: Preparation of hyperbranched polyester amine ① Synthesis of dendritic molecules: Trimethylolpropane and methyl crotonate are added to a dry reactor according to the ratio. Nitrogen is introduced for protection, stirring is started and heated, the stirring rate is controlled at 200 rpm, and the temperature is controlled at 60 °C for 8 hours of reaction.

[0048] ② Amidation reaction: After the synthesis reaction of dendritic molecules is completed, stirring is kept on, diethylenetriamine is added dropwise to the reactor, and after the addition is completed, heating is started, the temperature is raised to 85 °C, and the reaction is kept at this temperature for 7.5 hours.

[0049] The molar ratio of the amounts used of trimethylolpropane (TMP), methyl crotonate (MC) and diethylenetriamine (DETA) is 1:4.0:0.3.

[0050] ③ Purification: The reaction solution obtained in step ② is cooled to room temperature and slowly poured into ethanol at -5 °C, and stirred for 30 minutes. The stirred reaction solution is filtered by suction, and the solid product obtained is dried to obtain a white powdery hyperbranched polyester amine. The drying temperature is 50 °C, the vacuum is ≤ -0.065 MPa, and the drying time is 12 hours.

[0051] Step 3: Preparation of modified masterbatch PETG, triphenyl phosphite, polyethylene glycol block copolymer, nano-silica and hyperbranched polyester amine are mixed evenly and then added to a mixer. Mixing is carried out for 30 min at a temperature of 230 °C. The melt after mixing is fed to a twin-screw granulator through a hot melt gear pump, and after extrusion and pelletizing by the twin-screw granulator, a modified masterbatch with a particle size of 2.5 mm is obtained.

[0052] The weight parts ratio of the raw materials used is as follows: 85 parts of polyethylene terephthalate-1,4-cyclohexanedimethanol ester (PETG), 10 parts of triphenyl phosphite, 8 parts of polyethylene glycol block copolymer, 8 parts of nano-silica, and 6 parts of hyperbranched polyester amine (HPEA).

[0053] Step 4, melt blending Mix the recycled PET polyester particles, PET polyester chips, and modified masterbatch evenly, and convey them to a twin-screw extruder through a hopper for melt extrusion. The temperature settings for each section of the twin-screw extruder are as follows: the temperature of the preheating section hopper is 90 °C, the conveying section is 235 °C, the plasticizing and melting section is 250 °C, the vacuum exhaust section is 240 °C, the homogenizing and metering section is 265 °C, and the die head extrusion section is 275 °C. The die head is a hanger-type flat die head with a die lip gap of 1.5 mm.

[0054] The weight parts ratio of the raw materials used is as follows: 650 parts of recycled PET polyester particles, 260 parts of PET polyester chips, and 78 parts of modified masterbatch.

[0055] The ash content of the recycled PET polyester particles is less than 0.1%, and the impurity content is less than 0.2%. They are purchased from Foshan Yaotai Yuansu Industry Co., Ltd.

[0056] Step 5, casting film formation The melt extruded from the die head contacts the surface of the rapidly rotating quenching roll vertically in a curtain shape, and the melt is extended into a film through the quenching roll; cooling water is connected in the quenching roll, and the temperature of the cooling water is controlled at 15 °C. After cooling, the film is peeled off from the surface of the quenching roll and enters the stretching and setting section.

[0057] Step 6, stretching and setting After the film is peeled off from the surface of the quenching roll, it is sequentially introduced into a longitudinal stretching machine and a transverse stretching machine through a traction roll group.

[0058] The control parameters of the longitudinal stretching machine are: stretching multiple 4.3 times, temperature 100 °C.

[0059] The control parameters of the transverse stretching machine are: stretching multiple 2.8 times, temperature 100 °C.

[0060] After stretching, the film is heat-set. The temperature of the film is raised to 190 °C by infrared heating and then cooled down to 170 °C in a gradient manner, with each gradient being 10 °C and each gradient temperature lasting for 5 seconds; after heat-setting, it is cooled to room temperature, and after trimming and winding, a polyester heat-shrinkable film containing recycled materials is obtained.

[0061] Example 3 A preparation method of a polyester heat-shrinkable film containing recycled materials Step 1, preparation of polyethylene glycol block copolymer Polyethylene glycol and γ-valerolactone were added to a dry reactor. Stirring was started, nitrogen was introduced for protection, and the temperature was raised to 110 °C. Stannous octoate was added, and after reacting for 8 hours, a polyethylene glycol block copolymer was obtained. The number-average molecular weight of the polyethylene glycol block copolymer was 11,000 g / mol. The molar ratio of the amounts of polyethylene glycol and γ-valerolactone used was 1:4.2.

[0062] The amount of stannous octoate added was 0.4% of the mass of polyethylene glycol.

[0063] Step 2: Preparation of hyperbranched polyesteramine ① Synthesis of dendritic molecules: Trimethylolpropane and methyl crotonate were added to a dry reactor according to the ratio. Nitrogen was introduced for protection, stirring was started and heating was carried out. The stirring rate was controlled at 500 rpm and the temperature was controlled at 60 °C, and the reaction was carried out for 4 hours.

[0064] ② Amidation reaction: After the synthesis reaction of dendritic molecules was completed, stirring was kept on, and diethylenetriamine was added dropwise to the reactor. After the addition was completed, heating was started and the temperature was raised to 80 °C, and the reaction was kept at this temperature for 8.5 hours.

[0065] The molar ratio of the amounts of trimethylolpropane (TMP), methyl crotonate (MC) and diethylenetriamine (DETA) used was 1:3.3:0.4.

[0066] ③ Purification: The reaction solution obtained in step ② was cooled to room temperature and slowly poured into ethanol at -5 °C, and stirred for 30 minutes. The stirred reaction solution was filtered by suction, and the obtained solid product was dried to obtain a white powdery hyperbranched polyesteramine. The drying temperature was 50 °C, the vacuum was ≤ -0.065 MPa, and the drying time was 12 hours.

[0067] Step 3: Preparation of modified masterbatch PETG, triphenyl phosphite, polyethylene glycol block copolymer, nano-silica and hyperbranched polyesteramine were mixed evenly and then added to a mixer. Mixing was carried out for 40 min at a temperature of 223 °C. The melt after mixing was fed to a twin-screw granulator through a hot melt gear pump, and after extrusion and pelletizing by the twin-screw granulator, a modified masterbatch with a particle size of 3.3 mm was obtained.

[0068] The weight part ratio of the raw materials used was: polyethylene terephthalate-1,4-cyclohexanedimethanol ester (PETG) 90 parts, triphenyl phosphite 16 parts, polyethylene glycol block copolymer 9 parts, nano-silica 6 parts, hyperbranched polyesteramine (HPEA) 8 parts.

[0069] Step 4: Melt blending The recycled PET polyester particles, PET polyester chips, and modified masterbatch are mixed evenly and conveyed to a twin-screw extruder through a hopper for melt extrusion. The temperatures of each section of the twin-screw extruder are set as follows: the temperature of the hopper in the preheating section is 90 °C, the conveying section is 230 °C, the plasticizing and melting section is 255 °C, the vacuum exhaust section is 250 °C, the homogenizing and metering section is 260 °C, and the die head extrusion section is 275 °C. The die head is a hanger-type flat die head with a die lip gap of 1.5 mm.

[0070] The weight part ratio of the raw materials used is: 700 parts of recycled PET polyester particles, 280 parts of PET polyester chips, and 74 parts of modified masterbatch.

[0071] The recycled PET polyester particles have an ash content of less than 0.1% and an impurity content of less than 0.2%, and are purchased from Foshan Yaotaiyuanshu Industry Co., Ltd.

[0072] Step 5: Cast film The melt extruded from the die head vertically contacts the surface of the rapidly rotating quenching roll in a curtain shape, and the melt is extended into a film by the quenching roll; cooling water is connected in the quenching roll, and the temperature of the cooling water is controlled at 18 °C. After cooling, the film is peeled off from the surface of the quenching roll and enters the stretching and shaping section.

[0073] Step 6: Stretching and shaping After the film is peeled off from the surface of the quenching roll, it is sequentially introduced into a longitudinal stretching machine and a transverse stretching machine through a traction roll group.

[0074] The control parameters of the longitudinal stretching machine are: stretching ratio 3.9 times, temperature 80 °C.

[0075] The control parameters of the transverse stretching machine are: stretching ratio 3.2 times, temperature 105 °C.

[0076] After stretching, the film is heat-set. The temperature of the film is raised to 190 °C by infrared heating and then cooled down to 170 °C in a gradient manner, with each 10 °C as a gradient and each gradient temperature lasting for 5 seconds; after heat-setting, it is cooled to room temperature, and after trimming and winding, a polyester heat-shrinkable film containing recycled materials is obtained.

[0077] Example 4: A preparation method of a polyester heat-shrinkable film containing recycled materials Step 1: Preparation of polyethylene glycol block copolymer Polyethylene glycol and γ-valerolactone are added to a dry reactor, stirring is started, nitrogen protection is introduced, the temperature is raised to 120 °C, stannous octoate is added, and after reacting for 6.5 hours, a polyethylene glycol block copolymer is obtained. The number average molecular weight of the polyethylene glycol block copolymer is 15000 g / mol.

[0078] The molar ratio of the amount of polyethylene glycol to γ-valerolactone used is 1:5.

[0079] The addition amount of stannous octoate is 0.3% of the mass of polyethylene glycol.

[0080] Step 2: Preparation of hyperbranched polyester amine ① Synthesis of dendritic molecule: Trimethylolpropane and methyl crotonate are added to a dry reactor according to the ratio, nitrogen is introduced for protection, stirring is started and heating is carried out. The stirring rate is controlled at 400 rpm, the temperature is controlled at 50 °C, and the reaction is carried out for 6 hours.

[0081] ② Amidation reaction: After the synthesis reaction of the dendritic molecule is completed, stirring is kept on, diethylenetriamine is added dropwise to the reactor. After the addition is completed, heating is started and the temperature is raised to 90 °C, and the reaction is kept at this temperature for 6 hours.

[0082] The molar ratio of the amounts of trimethylolpropane (TMP), methyl crotonate (MC) and diethylenetriamine (DETA) used is 1:2.6:0.5.

[0083] ③ Purification: The reaction solution obtained in step ② is cooled to room temperature and slowly poured into ethanol at -5 °C, and stirred for 30 minutes. The stirred reaction solution is filtered by suction, and the obtained solid product is dried to obtain a white powdery hyperbranched polyester amine. The drying temperature is 50 °C, the vacuum is ≤ -0.065 MPa, and the drying time is 12 hours.

[0084] Step 3: Preparation of modified masterbatch PETG, triphenyl phosphite, polyethylene glycol block copolymer, nano-silica and hyperbranched polyester amine are mixed evenly and then added to an internal mixer, and kneaded for 40 min at a set temperature of 220 °C. The kneaded melt is fed to a twin-screw granulator through a hot melt gear pump, and after extrusion and pelletizing by the twin-screw granulator, a modified masterbatch with a particle size of 3.5 mm is obtained.

[0085] The weight part ratio of the raw materials used is: polyethylene terephthalate-1,4-cyclohexanedimethanol ester (PETG) 95 parts, triphenyl phosphite 18 parts, polyethylene glycol block copolymer 12 parts, nano-silica 5 parts, hyperbranched polyester amine (HPEA) 5 parts.

[0086] Step 4: Melt blending The recycled PET polyester particles, PET polyester chips and modified masterbatch are mixed evenly and conveyed to a twin-screw extruder through a hopper for melt extrusion. The temperature of each section of the twin-screw extruder is set as follows: the temperature of the preheating section hopper is 90 °C, the conveying section is 233 °C, the plasticizing and melting section is 257 °C, the vacuum exhaust section is 245 °C, the homogenizing and metering section is 265 °C, and the die head extrusion section is 273 °C. The die head is a hanger-type flat die head, and the die lip gap is 1.5 mm.

[0087] The weight ratio of the raw materials used is as follows: 750 parts of recycled PET polyester particles, 250 parts of PET polyester chips, and 70 parts of modified masterbatch.

[0088] The recycled PET polyester particles have an ash content of less than 0.1% and an impurity content of less than 0.2%, and are purchased from Foshan Yaotai Yuansu Industry Co., Ltd.

[0089] Step 5: Cast film The melt extruded from the die head vertically contacts the surface of the rapidly rotating quenching roll in a curtain shape, and the melt is extended into a film through the quenching roll; cooling water is connected in the quenching roll, and the temperature of the cooling water is controlled at 16 °C. After cooling, the film is peeled off from the surface of the quenching roll and enters the stretching and shaping section.

[0090] Step 6: Stretching and shaping After the film is peeled off from the surface of the quenching roll, it is sequentially introduced into the longitudinal stretching machine and the transverse stretching machine through the traction roll group.

[0091] The control parameters of the longitudinal stretching machine are: stretching ratio 4.5 times, temperature 95 °C.

[0092] The control parameters of the transverse stretching machine are: stretching ratio 5.5 times, temperature 110 °C.

[0093] After stretching, the film is heat-set. The temperature of the film is raised to 190 °C by infrared heating, and then cooled down to 170 °C in a gradient manner, with each 10 °C as a gradient and each gradient temperature lasting for 5 seconds; after heat-setting, it is cooled to room temperature, and after trimming and winding, a polyester heat-shrinkable film containing recycled materials is obtained.

[0094] Comparative example 1 Step 1: Melt blending The recycled PET polyester particles and PET polyester chips are mixed evenly and conveyed to a twin-screw extruder through a hopper for melt extrusion. The temperatures of each section of the twin-screw extruder are set as follows: the temperature of the hopper in the preheating section is 90 °C, the conveying section is 230 °C, the plasticizing and melting section is 255 °C, the vacuum exhaust section is 250 °C, the homogenizing and metering section is 260 °C, and the die head extrusion section is 275 °C. The die head is a hanger-type flat die head, and the die lip gap is 1.5 mm.

[0095] The weight ratio of the raw materials used is as follows: 600 parts of recycled PET polyester particles, 300 parts of PET polyester chips.

[0096] Step 2: Cast film The melt extruded from the die head vertically contacts the surface of the rapidly rotating quenching roll in a curtain shape, and the melt is extended into a film through the quenching roll; cooling water is connected in the quenching roll, and the temperature of the cooling water is controlled at 18 °C. After cooling, the film is peeled off from the surface of the quenching roll and enters the stretching and shaping section.

[0097] Step 3: Stretching and shaping After the diaphragm is peeled off from the surface of the quenching roll, it is successively introduced into the longitudinal stretching machine and the transverse stretching machine through the traction roll group.

[0098] The control parameters of the longitudinal stretching machine are: stretching multiple 3.9 times, temperature 80 °C.

[0099] The control parameters of the transverse stretching machine are: stretching multiple 3.2 times, temperature 105 °C.

[0100] After stretching, the diaphragm is heat-set. The temperature of the diaphragm is raised to 190 °C by infrared heating, and then cooled down to 170 °C in a gradient manner, with each 10 °C as a gradient and the temperature at each gradient lasting for 5 seconds; after heat-setting, it is cooled to room temperature, and after edge trimming and winding, a polyester heat-shrinkable film containing recycled materials is obtained.

[0101] Performance Test (I) Mechanical and Optical Property Tests The mechanical and optical properties of the products prepared in Examples 1-4 and Comparative Example 1 were tested, and the test results and test reference standards are shown in Table 1.

[0102] Table 1 Test Results of Mechanical and Optical Properties

[0103] Analyzing the data in Table 1, it can be seen that the transverse shrinkage rate of Examples 1 to 4 is 72% to 76%, the longitudinal shrinkage rate is 2.1% to 3.1%, the longitudinal tensile strength is 82 MPa to 95 MPa, the transverse elongation at break is 354% to 389%, and the transverse tensile strength is 137 MPa to 150 MPa. The data shows that the polyester heat-shrinkable film containing recycled materials obtained by the present invention has excellent unidirectional anti-shrinkage performance and mechanical properties. At the same time, due to its low haze, it can well meet the requirements of the fine packaging industry. In Comparative Example 1, the heat-shrinkable film obtained without adding the modified masterbatch during the preparation of the heat-shrinkable film has different degrees of decline in its tensile strength, shrinkage rate and elongation at break compared with Examples 1 to 4. The longitudinal shrinkage is high, and the haze data is also higher than that of Examples 1 to 4. This shows that the modified masterbatch provided by the present invention has a significant effect on improving the mechanical properties and optical properties of the PET polyester heat-shrinkable film containing recycled materials.

[0104] (II) Anti-aging Performance Test The products prepared in Examples 1-4 and Comparative Example 1 were subjected to light aging treatment according to GB / T 43297-2023.

[0105] Parameters of the xenon lamp aging chamber: irradiation intensity: 0.5 W / m² @ 340 nm, chamber temperature: 50 °C ± 2 °C, relative humidity: 50% ± 10%, irradiation time: 240 hours.

[0106] After the irradiation is completed, the mechanical properties and optical properties of the products prepared in Examples 1-4 and Comparative Example 1 are tested, and the test results are shown in Table 2; Table 2 Test Results of Mechanical Properties and Optical Properties after Aging Test

[0107] Analyzing the data in Table 2, it can be seen that after aging treatment, the transverse shrinkage rate of Examples 1-4 is 69% - 72%, the longitudinal shrinkage rate is 2.6% - 3.7%, the longitudinal tensile strength is 79 MPa - 90 MPa, the longitudinal elongation at break is 87% - 90%, the transverse tensile strength is 130 MPa - 139 MPa, the haze is 3.8% - 4.5%, and the attenuation of optical properties and mechanical properties is small; after aging treatment, the transverse tensile strength of Comparative Example 1 drops to 55 MPa, the longitudinal tensile strength drops to 48 MPa, and the haze increases to 10.7%; it shows that the PET polyester heat shrinkable film containing recycled materials provided by the present invention has excellent anti-aging performance.

[0108] The polyethylene glycol block copolymer obtained in the step of "preparation of polyethylene glycol block copolymer" of the present invention can be confirmed by nuclear magnetic resonance hydrogen spectrum (H-NMR). The nuclear magnetic resonance hydrogen spectrum (H-NMR) diagram is as attached Figure 1 shown, and the product can be determined by the characteristic peaks of polyethylene glycol (PEG) and γ-valerolactone.

[0109] The hyperbranched polyesteramine obtained in the step of "preparation of hyperbranched polyesteramine" of the present invention can be confirmed by infrared spectroscopy (FTIR) detection. The infrared spectroscopy (FTIR) diagrams before and after the reaction are as attached Figures 2 - 3 shown. It can be seen from the infrared spectroscopy (FTIR) diagram that after the reaction is completed, the ester group signal at 1720 cm -1 weakens, and the amide bond signal at 1650 cm -1 strengthens, indicating that hyperbranched polyesteramine is obtained.

[0110] Unless otherwise specified, the ratios described in the present invention are all mass ratios, and the percentages described in the present invention are all mass percentages. Obviously, there are many specific implementation methods that can be changed under the concept of the present invention. It should be stated here that any changes made under the inventive concept of the present invention will fall within the protection scope of the present invention.

Claims

1. A polyester heat shrinkable film containing recycled materials, characterized in that: Raw materials include recycled PET polyester granules, PET polyester chips, and modified masterbatch; The modified masterbatch is prepared from polyethylene terephthalate-1,4-cyclohexanedimethanol ester, triphenyl phosphite, polyethylene glycol block copolymer, nano silicon dioxide, and hyperbranched polyester amine; The polyethylene glycol block copolymer is prepared from polyethylene glycol and γ-valerolactone under the action of a catalyst; The hyperbranched polyester amine is prepared from trimethylolpropane, methyl crotonate and diethylenetriamine.

2. The polyester heat shrinkable film containing recycled materials according to claim 1, characterized in that: The weight ratio of the recycled PET polyester particles, PET polyester chips and modified masterbatch is: 600-750 parts of recycled PET polyester particles, 250-300 parts of PET polyester chips and 70-85 parts of modified masterbatch.

3. The polyester heat shrinkable film containing recycled materials according to claim 1, characterized in that: The mass ratio of polyethylene terephthalate-1,4-cyclohexanedimethanol ester, triphenyl phosphite, polyethylene glycol block copolymer, nano-silica and hyperbranched polyester amine is (80-95): (10-18): (8-12): (5-10): (3-8).

4. The polyester heat shrinkable film containing recycled materials according to claim 1, characterized in that: The molar ratio of trimethylolpropane, methyl crotonate and diethylenetriamine is 1: (2-4): (0.3-0.5).

5. The polyester heat shrinkable film containing recycled materials according to claim 1, characterized in that: The molar ratio of polyethylene glycol to gamma-valerolactone is 1:(3-5); the catalyst is stannous octoate, and the added amount is 0.1%-0.4% of the mass of polyethylene glycol.

6. The method for preparing a polyester heat shrinkable film containing recycled materials according to any one of claims 1 to 5, characterized in that: The method comprises the steps of preparing polyethylene glycol block copolymer, preparing hyperbranched polyester amine, preparing modified masterbatch, melt blending, casting film and stretching and shaping; the melt blending comprises: melt extruding recycled PET polyester particles, PET polyester chips and modified masterbatch through a twin-screw extruder; the twin-screw extruder adopts a preheating section hopper temperature of 80-90°C, a plasticizing melting section temperature of 250-260°C and a die extrusion section temperature of 270-275°C.

7. The method for preparing a polyester heat shrinkable film containing recycled materials according to claim 6, characterized in that: The preparation of the polyethylene glycol block copolymer comprises the following steps: adding polyethylene glycol and γ-valerolactone into a reactor, stirring, introducing nitrogen for protection, heating to 110-130° C., adding a catalyst, and reacting for 6-8 hours to obtain the polyethylene glycol block copolymer.

8. The method for preparing a polyester heat shrinkable film containing recycled materials according to claim 6, characterized in that: The preparation of the hyperbranched polyesteramine includes the steps of synthesis of dendritic molecules and amidation reaction. The synthesis of the dendritic molecules includes adding trimethylolpropane and methyl crotonate into a reactor, introducing nitrogen protection, starting stirring and heating, the reaction temperature is 50-60°C, and the reaction time is 4-8 hours. The amidation reaction: After the synthesis reaction of the dendrimer molecule is completed, diethylenetriamine is added dropwise to the reactor. After the addition is completed, heating is started to increase the temperature to 80-90° C. and the reaction is continued for 6-10 hours.

9. The method for preparing a polyester heat shrinkable film containing recycled materials according to claim 6, characterized in that: Preparation of the modified masterbatch: polyethylene terephthalate-1,4-cyclohexanedimethanol ester, triphenyl phosphite, polyethylene glycol block copolymer, nano silicon dioxide, and hyperbranched polyester amine are kneaded for 30-40 minutes at a temperature set at 220-230°C.

10. The method for preparing a polyester heat shrinkable film containing recycled materials according to claim 6, characterized in that: The stretching and shaping includes longitudinal stretching and transverse stretching; longitudinal stretching: the stretching ratio is 0.5-4.5 times, and the stretching temperature is 80-100°C; transverse stretching: the stretching temperature is 95-110°C, and the stretching ratio is 2.5-5.5 times.

Images