High-barrier polyester co-extrusion sheet and preparation method thereof

Abstract

The invention discloses a high-barrier polyester co-extrusion sheet and a preparation method thereof, and belongs to the technical field of high polymer materials. According to the invention, the polyethylene furanoate and the polyethylene glycol terephthalate are used as main raw materials, and under the interaction of the components, the interfacial compatibility and the binding force are obviously improved, so that the mechanical properties of the application are ensured under the condition that a binder is not added, and on the whole, through the interface design of a molecular level and the synergistic interaction of the components, the mechanical properties are greatly improved. The problem that high barrier performance and high toughness are difficult to consider at the same time is solved. Besides, by optimizing the components of the flexibilizer A and the flexibilizer B, mutual crosslinking and chemical bonding among the components can be promoted, the interfacial compatibility is increased, the interfacial adhesion is also increased, and the material has more excellent mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a high-barrier polyester co-extruded sheet and a preparation method thereof. Background Art

[0002] In the packaging industry, PET (polyethylene terephthalate) is widely used. It has good formability and fragrance retention, and can be made into food packaging forms such as boxes, bottles, and bags. However, PET has average barrier properties to water vapor and oxygen. To achieve high barrier properties, it usually needs to be co-extruded with EVOH, or compounded with a co-extruded film containing EVOH. However, PET and EVOH are two different types of materials. Whether co-extruded or compounded sheets, they cannot be directly recycled. As recyclable packaging becomes more and more popular, people are exploring new high-barrier polyester sheet solutions. Polyethylene furanoate is a new type of polyester material with high glass transition temperature, low melting point, and high barrier properties. It also has good compatibility with polyethylene terephthalate and can be incorporated into the PET recycling stream without affecting the performance of the recycled PET.

[0003] On the other hand, terephthalic acid (TPA), the main raw material for the production of PET, is completely dependent on the petrochemical product paraxylene (PX), while furandicarboxylic acid, the main raw material for polyethylene furanoate, comes from bio-based materials such as fructose and starch. Furandicarboxylic acid is synthesized by dehydration of hexose derivatives, oxidation of disubstituted furans, and catalytic conversion of furan derivatives, and then polymerized with petroleum-based or bio-based diols to obtain partially bio-based or fully bio-based polyethylene furanoate materials, which can reduce carbon footprint.

[0004] There are also modified applications of PET materials in the prior art. For example, the Chinese patent publication number CN115926396A proposes to obtain a bottle with high barrier properties by extrusion blow molding of a blend of poly(ethylene furandicarboxylate) and poly(ethylene terephthalate). However, for films and sheets, since the glass transition temperature and melt fluidity of the two materials are different, it is easy to produce crystal points that affect the appearance during the extrusion process due to the mismatch of processing temperature. For another example, the Chinese patent publication number CN117183527A proposes a cast film obtained by co-extrusion of poly(ethylene furandicarboxylate) and poly(ethylene terephthalate), which has good barrier properties and elongation at break. However, using a similar method to co-extrude a sheet, the finished product is relatively brittle and cannot meet the mechanical use requirements of a blister box. Therefore, the above-mentioned problems still need to be solved in the prior art. Summary of the invention

[0005] Based on this, in order to solve one of the above problems, the present invention provides a high barrier polyester co-extruded sheet and a preparation method thereof, and the specific technical scheme is as follows: A high barrier polyester co-extruded sheet, comprising a polyethylene furanoate layer and a polyethylene terephthalate layer connected in sequence; The raw materials for preparing the polyethylene furanoate layer include: polyethylene furanoate and a toughening agent A accounting for 0.5% to 2% of the weight of the polyethylene furanoate, wherein the toughening agent A is at least one of ethylene-glycidyl methacrylate copolymer and glycidyl methacrylate grafted styrene-hydrogenated butadiene copolymer; The raw materials for preparing the polyethylene terephthalate layer include polyethylene terephthalate and a toughening agent B accounting for 0.5% to 2% of the weight of the polyethylene terephthalate, wherein the toughening agent B is prepared by mixing epoxidized calcium carbonate, lignin-polyethylene glycol grafted product and chitosan in a mass ratio of (1 to 7): (1 to 3): (1 to 5).

[0006] Furthermore, the intrinsic viscosity of the polyethylene furanoate is (0.05-0.20) dL / g higher than that of the polyethylene terephthalate; the glass transition temperature of the polyethylene furanoate is 86±5°C, and the melting point is 220±20°C.

[0007] Furthermore, the polyethylene furanoate is prepared by a dehydration condensation polymerization reaction between a polymerizable monomer furan dicarboxylic acid and a polymerizable monomer diol compound.

[0008] Furthermore, the polymerizable monomer furandicarboxylic acid is at least one of 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 2,3-furandicarboxylic acid and 3,4-furandicarboxylic acid.

[0009] Further, the polymerizable monomer diol compound is a cyclic diol and / or an aliphatic diol; The cyclic diol is at least one of cis-1,4-cyclohexanedimethanol, trans-1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanediol, 1,3-cyclohexanediol, 1,2-cyclohexanediol, dicyclopentanediol, 1-methyldicyclopentanediol, 1,5-dimethyldicyclopentanediol, tricyclodecane dimethanol, tetrafluoroterephthalimethanol, tricyclodecanediol, dicycloheptanediol, tricyclopentanediol and tetracyclodiol; The aliphatic diol is at least one of ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol and 2-methyl-1,3-propanediol.

[0010] Furthermore, the polyethylene terephthalate has an intrinsic viscosity of 0.70-0.90 dL / g, a glass transition temperature of 76±5°C, and a melting point of 250±20°C.

[0011] Furthermore, the preparation method of the epoxidized calcium carbonate is: The ball-milled calcium carbonate is added to anhydrous ethanol and ultrasonically dispersed. Then, a catalyst is added and stirred at 65°C to 70°C for 15min to 20min. Epichlorohydrin is added and nitrogen is introduced at 70°C to 80°C for protection. The reaction is carried out for 3h to 5h. The mixture is cooled to room temperature, neutralized, washed and dried to obtain epoxidized calcium carbonate.

[0012] Furthermore, the power of ultrasonic dispersion is 300 W, and the time is 20 min to 30 min.

[0013] In addition, the present invention also provides a method for preparing a high barrier polyester co-extruded sheet, the preparation method comprising the following steps: According to the design of the number of layers of the high barrier polyester co-extruded sheet, the raw materials for the preparation of the polyethylene furanoate layer and the raw materials for the preparation of the polyethylene terephthalate layer are respectively added to the screw extruder, passed through a distributor, and entered the co-extrusion die head, and were cooled and formed by three smooth rollers, trimmed, and rolled to obtain the high barrier polyester co-extruded sheet.

[0014] Further, the extrusion conditions of the polyethylene terephthalate layer are: the temperature of the first zone is 250°C to 280°C, the temperature of the second zone is 250°C to 280°C, and the temperature of the third zone to the sixth zone is 270°C to 290°C; The extrusion conditions of the polyethylene furanoate layer are as follows: the temperature of the first zone is 240°C to 250°C, the temperature of the second zone is 240°C to 250°C, and the temperature of the third to sixth zones is 240°C to 260°C; The temperature of the coextrusion die was set at 240°C~255°C.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses polyethylene furanoate and polyethylene terephthalate as main raw materials. Since the melting point of polyethylene furanoate is lower than that of polyethylene terephthalate, and the intrinsic viscosity of polyethylene furanoate is higher than that of polyethylene terephthalate, it is helpful to improve the fluidity with mutual matching during co-extrusion, and under the interaction of the components, the interface compatibility and bonding force are significantly improved, so that the mechanical properties of the application are guaranteed without adding a binder. Overall, the problem of high barrier performance and high toughness being difficult to take into account is solved through the interface design at the molecular level and the synergistic enhancement of the components.

[0016] 2. The present invention adds toughening agent A to the polyethylene furanoate layer and toughening agent B to the polyethylene terephthalate layer, which not only increases the toughness and strength of the sheet, but also significantly increases the barrier properties of the sheet, and participates in the recycling flow of polyester without affecting the properties of the recycled materials, meeting the use requirements of packaging materials with high barrier requirements. Specifically, toughening agent A reacts with the terminal carboxyl group of polyethylene furanoate without destroying the crystallinity of polyethylene furanoate to form a chemical cross-linking network, which helps to improve the toughness within the layer and also avoids the reduction of barrier properties caused by the migration of toughening agent A. The specific toughening agent B of the present invention is prepared by mixing epoxidized calcium carbonate, lignin-polyethylene glycol graft and chitosan in a specific ratio, and can exert a significant toughening effect. The surface of the epoxidized calcium carbonate is introduced with epoxidized calcium carbonate, which not only has excellent compatibility with polyethylene terephthalate, but also forms a chemical bond with polyethylene furanoate, which not only increases the interface compatibility, but also increases the interface adhesion, so that it has more excellent mechanical properties. In addition, the epoxidized calcium carbonate is uniformly dispersed and filled in the polyethylene terephthalate. The addition of lignin-polyethylene glycol grafts between the polyethylene terephthalate layers can help improve the barrier properties; the addition of lignin-polyethylene glycol grafts can make the molecular chains in the polyethylene terephthalate layer tend to be more regular and uniform, increase the compatibility of the system, and form chemical bonds with epoxidized calcium carbonate to synergize the toughening of epoxidized calcium carbonate, so that the material can more evenly withstand and disperse stress when subjected to external forces, reducing the occurrence of local tearing; chitosan can produce hydrogen bonds with polyethylene terephthalate, synergistically enhance the effect, and avoid the loss of strength caused by single toughening. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0019] A high barrier polyester co-extruded sheet in one embodiment of the present invention comprises a polyethylene furanoate layer and a polyethylene terephthalate layer connected in sequence; The raw materials for preparing the polyethylene furanoate layer include: polyethylene furanoate and a toughening agent A accounting for 0.5% to 2% of the weight of the polyethylene furanoate, wherein the toughening agent A is at least one of ethylene-glycidyl methacrylate copolymer and glycidyl methacrylate grafted styrene-hydrogenated butadiene copolymer; The raw materials for preparing the polyethylene terephthalate layer include polyethylene terephthalate and a toughening agent B accounting for 0.5% to 2% of the weight of the polyethylene terephthalate, wherein the toughening agent B is prepared by mixing epoxidized calcium carbonate, lignin-polyethylene glycol grafted product and chitosan in a mass ratio of (1 to 7): (1 to 3): (1 to 5).

[0020] In one embodiment, the high barrier polyester co-extruded sheet comprises a polyethylene furanoate layer, a polyethylene terephthalate layer and a polyethylene furanoate layer connected in sequence.

[0021] In one embodiment, the high barrier polyester co-extruded sheet comprises a polyethylene furanoate layer, a polyethylene terephthalate layer, a polyethylene furanoate layer, a polyethylene terephthalate layer and a polyethylene furanoate layer connected in sequence.

[0022] In one embodiment, the thickness of the high barrier polyester co-extruded sheet is 200 μm to 1000 μm.

[0023] In one embodiment, the mass ratio of the polyethylene furanoate layer to the polyethylene terephthalate layer is (1-4): (6-9).

[0024] In one embodiment, the intrinsic viscosity of the polyethylene furanoate is (0.05-0.20) dL / g higher than that of the polyethylene terephthalate; the glass transition temperature of the polyethylene furanoate is 86±5°C, and the melting point is 220±20°C. The melting point of the polyethylene furanoate of the present invention is lower than that of polyethylene terephthalate, and the intrinsic viscosity of the polyethylene furanoate used for coextrusion should be slightly higher than that of polyethylene terephthalate so that the fluidity can match each other in the coextrusion die.

[0025] In one embodiment, the polyethylene furanoate is prepared by a dehydration condensation polymerization reaction between a polymerizable monomer furan dicarboxylic acid and a polymerizable monomer diol compound.

[0026] In one embodiment, the polymerizable monomer furandicarboxylic acid is at least one of 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 2,3-furandicarboxylic acid and 3,4-furandicarboxylic acid, preferably 2,5-furandicarboxylic acid.

[0027] In one embodiment, the polymerizable monomer diol compound is a cyclic diol and / or an aliphatic diol; The cyclic diol is at least one of cis-1,4-cyclohexanedimethanol, trans-1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanediol, 1,3-cyclohexanediol, 1,2-cyclohexanediol, dicyclopentanediol, 1-methyldicyclopentanediol, 1,5-dimethyldicyclopentanediol, tricyclodecane dimethanol, tetrafluoroterephthalimethanol, tricyclodecanediol, dicycloheptanediol, tricyclopentanediol and tetracyclodiol; The aliphatic diol is at least one of ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol and 2-methyl-1,3-propanediol, preferably ethylene glycol.

[0028] In one embodiment, the intrinsic viscosity of the polyethylene terephthalate is 0.70-0.90 dL / g, the glass transition temperature is 76±5° C., and the melting point is 250±20° C. The polyethylene terephthalate with such characteristics is used to prepare high barrier polyester co-extruded sheets, which have excellent formability and impact resistance.

[0029] In one embodiment, the reaction formula of the 2,5-furandicarboxylic acid and the ethylene glycol is as follows: .

[0030] In one embodiment, the preparation method of the epoxidized calcium carbonate is: The ball-milled calcium carbonate is added to anhydrous ethanol and ultrasonically dispersed. Then, a catalyst is added and stirred at 65°C to 70°C for 15min to 20min. Epichlorohydrin is added and nitrogen is introduced at 70°C to 80°C for protection. The reaction is carried out for 3h to 5h. The mixture is cooled to room temperature, neutralized, washed and dried to obtain epoxidized calcium carbonate.

[0031] In one embodiment, the average particle size of the calcium carbonate after ball milling is 50nm~100nm.

[0032] In one embodiment, the solid-to-liquid ratio of the calcium carbonate to the anhydrous ethanol is 1:(10-15).

[0033] In one embodiment, the power of ultrasonic dispersion is 300 W and the time is 20 min to 30 min.

[0034] In one embodiment, the catalyst is at least one of triethylamine and nitrous acid.

[0035] In one embodiment, the amount of the catalyst added is 0.5% to 1% of the mass of the calcium carbonate.

[0036] In one embodiment, the amount of epichlorohydrin added is 1% to 10% of the mass of the calcium carbonate.

[0037] In one embodiment, the drying temperature is 90° C. to 100° C., and the drying time is 1 h to 4 h.

[0038] In addition, the present invention also provides a method for preparing a high barrier polyester co-extruded sheet, the preparation method comprising the following steps: According to the design of the number of layers of the high barrier polyester co-extruded sheet, the raw materials for the preparation of the polyethylene furanoate layer and the raw materials for the preparation of the polyethylene terephthalate layer are respectively added to the screw extruder, passed through a distributor, and entered the co-extrusion die head, and were cooled and formed by three smooth rollers, trimmed, and rolled to obtain the high barrier polyester co-extruded sheet.

[0039] In one embodiment, the extrusion conditions of the polyethylene terephthalate layer are: the temperature of the first zone is 250°C to 280°C, the temperature of the second zone is 250°C to 280°C, and the temperature of the third zone to the sixth zone is 270°C to 290°C; The extrusion conditions of the polyethylene furanoate layer are as follows: the temperature of the first zone is 240°C to 250°C, the temperature of the second zone is 240°C to 250°C, and the temperature of the third to sixth zones is 240°C to 260°C; The temperature of the co-extrusion die was set at 240°C~255°C, and the temperatures of the three smooth rollers were 30°C~35°C, 35°C~40°C, and 40°C~45°C, respectively.

[0040] The embodiments of the present invention will be described in detail below with reference to specific examples.

[0041] It should be noted that in the following embodiments, PEF is a polyethylene furanoate layer, and PET is a polyethylene terephthalate layer.

[0042] Embodiment 1: A method for preparing a high barrier polyester co-extruded sheet comprises the following steps: The raw materials for preparing the polyethylene furanoate layer include: polyethylene furanoate and 0.5% by weight of the polyethylene furanoate of glycidyl methacrylate grafted styrene-hydrogenated butadiene copolymer; wherein the intrinsic viscosity of the polyethylene furanoate is 0.90 dL / g; the raw materials for preparing the polyethylene furanoate layer need to be pre-crystallized and dehydrated before being added to the screw extruder, and stirred and dried at 130° C. for 4 hours; The raw materials for preparing the polyethylene terephthalate layer include: polyethylene terephthalate and a toughening agent B accounting for 0.5% of the weight of the polyethylene terephthalate, wherein the toughening agent B is prepared by mixing epoxidized calcium carbonate, lignin-polyethylene glycol grafted product and chitosan in a mass ratio of 2:1:2; wherein the intrinsic viscosity of the polyethylene terephthalate is 0.820 dL / g; the preparation method of the epoxidized calcium carbonate is: at a solid-liquid ratio of 1:10, the ball-milled calcium carbonate is added to anhydrous In ethanol, ultrasonic dispersion is performed at a power of 300 W for 20 minutes, and then 0.5% of triethylamine by weight of the calcium carbonate is added, and the mixture is stirred at 65° C. for 15 minutes, and then 8% of epichlorohydrin by weight of the calcium carbonate is added, and nitrogen is introduced at 70° C. for protection, and the mixture is reacted for 4 hours, cooled to room temperature, neutralized, washed, and dried at 90° C. for 3 hours to obtain epoxidized calcium carbonate; the raw materials for the preparation of the polyethylene terephthalate layer need to be dried in a drying tank at 150° C. for 2 hours before being added to the screw extruder; According to the design of the number of layers of the high barrier polyester co-extruded sheet of the PEF-PET-PEF three-layer structure, the raw materials for the preparation of the polyethylene furanoate layer and the raw materials for the preparation of the polyethylene terephthalate layer are respectively added to the screw extruder, and then pass through the distributor to enter the co-extrusion die head, and are cooled and formed by three rollers, wherein the extrusion conditions of the polyethylene furanoate layer are: the temperature of the first zone is 250°C, the temperature of the second zone is 250°C, and the temperatures of the third zone to the sixth zone are all 255°C; the extrusion conditions of the polyethylene terephthalate layer are: the temperature of the first zone is 250°C, and the temperatures of the second zone to the sixth zone are all 280°C; the temperature of the co-extrusion die head is set to 250°C; trimming and winding are performed to obtain the high barrier polyester co-extruded sheet.

[0043] The thickness of the high barrier polyester co-extruded sheet prepared in Example 1 is 400 μm, wherein the thickness ratio of the PEF layer, the PET layer and the PEF layer is 10:80:10.

[0044] Embodiment 2: A method for preparing a high barrier polyester co-extruded sheet comprises the following steps: The raw materials for preparing the polyethylene furanoate layer include: polyethylene furanoate and 0.5% by weight of the polyethylene furanoate of glycidyl methacrylate grafted styrene-hydrogenated butadiene copolymer; wherein the intrinsic viscosity of the polyethylene furanoate is 0.90 dL / g; the raw materials for preparing the polyethylene furanoate layer need to be pre-crystallized and dehydrated before being added to the screw extruder, and stirred and dried at 130° C. for 4 hours; The raw materials for preparing the polyethylene terephthalate layer include: polyethylene terephthalate and a toughening agent B accounting for 0.5% of the weight of the polyethylene terephthalate, wherein the toughening agent B is prepared by mixing epoxidized calcium carbonate, lignin-polyethylene glycol grafted product and chitosan in a mass ratio of 3:1:1; wherein the intrinsic viscosity of the polyethylene terephthalate is 0.80 dL / g; the preparation method of the epoxidized calcium carbonate is: at a solid-liquid ratio of 1:10, the ball-milled calcium carbonate is added to anhydrous ethyl acetate; alcohol, ultrasonically dispersed at 300W power for 25 minutes, then added triethylamine accounting for 0.6% of the mass of the calcium carbonate, stirred at 70°C for 20 minutes, then added epichlorohydrin accounting for 8% of the mass of the calcium carbonate, and reacted for 4 hours at 80°C under nitrogen protection, cooled to room temperature, neutralized, washed, and dried at 100°C for 2 hours to obtain epoxidized calcium carbonate; the raw materials for the preparation of the polyethylene terephthalate layer need to be dried in a drying tank at 150°C for 2 hours before being added to the screw extruder; According to the design of the number of layers of the high barrier polyester co-extruded sheet with a five-layer structure of PET-PEF-PET-PEF-PET, the raw materials for the preparation of the polyethylene furanoate layer and the raw materials for the preparation of the polyethylene terephthalate layer are respectively added into a screw extruder, passed through a distributor, enter the co-extrusion die head, and are cooled and formed by three smooth rollers, wherein the extrusion conditions of the polyethylene furanoate layer are as follows: the temperature of the first zone is 250°C, the temperature of the second zone is 250°C, and the temperatures of the third zone to the sixth zone are all 255°C; the extrusion conditions of the polyethylene terephthalate layer are as follows: the temperature of the first zone is 250°C, and the temperatures of the second zone to the sixth zone are all 280°C; the temperature of the co-extrusion die head is set to 250°C; trimming and winding are performed to obtain the high barrier polyester co-extruded sheet.

[0045] The thickness of the high barrier polyester co-extruded sheet prepared in Example 2 is 400 μm, wherein the thickness ratio of the PET layer, the PEF layer, the PET layer, the PEF layer and the PET layer is 10:10:60:10:10.

[0046] Embodiment 3: A method for preparing a high barrier polyester co-extruded sheet comprises the following steps: The raw materials for preparing the polyethylene furanoate layer include: polyethylene furanoate and 0.5% by weight of the polyethylene furanoate of glycidyl methacrylate grafted styrene-hydrogenated butadiene copolymer; wherein the intrinsic viscosity of the polyethylene furanoate is 0.90 dL / g; the raw materials for preparing the polyethylene furanoate layer need to be pre-crystallized and dehydrated before being added to the screw extruder, and stirred and dried at 130° C. for 4 hours; The raw materials for preparing the polyethylene terephthalate layer include: polyethylene terephthalate and a toughening agent B accounting for 1% of the weight of the polyethylene terephthalate, wherein the toughening agent B is prepared by mixing epoxidized calcium carbonate, lignin-polyethylene glycol grafted product and chitosan in a mass ratio of 2:1:2; wherein the intrinsic viscosity of the polyethylene terephthalate is 0.82dL / g; the preparation method of the epoxidized calcium carbonate is: at a solid-liquid ratio of 1:10, the ball-milled calcium carbonate is added to anhydrous ethanol The mixture was ultrasonically dispersed at 300 W for 25 min, and then 0.8% triethylamine by weight of the calcium carbonate was added, and the mixture was stirred at 70° C. for 20 min. Then 10% epichlorohydrin by weight of the calcium carbonate was added, and nitrogen was introduced at 70° C. for protection, and the mixture was reacted for 5 h. The mixture was cooled to room temperature, neutralized, washed, and dried at 100° C. for 3 h to obtain epoxidized calcium carbonate. The raw materials for the preparation of the polyethylene terephthalate layer need to be dried in a drying tank at 150° C. for 2 h before being added to the screw extruder. According to the design of the number of layers of the high barrier polyester co-extruded sheet of the PEF-PET-PEF three-layer structure, the raw materials for the preparation of the polyethylene furanoate layer and the raw materials for the preparation of the polyethylene terephthalate layer are respectively added into the screw extruder, passed through a distributor, enter the co-extrusion die head, and are cooled and formed by three rollers, wherein the extrusion conditions of the polyethylene furanoate layer are as follows: the temperature of the first zone is 250°C, the temperature of the second zone is 250°C, and the temperatures of the third zone to the sixth zone are all 255°C; the extrusion conditions of the polyethylene terephthalate layer are as follows: the temperature of the first zone is 250°C, and the temperatures of the second zone to the sixth zone are all 280°C; the temperature of the co-extrusion die head is set to 250°C; trimming and winding are performed to obtain the high barrier polyester co-extruded sheet.

[0047] The thickness of the high barrier polyester co-extruded sheet prepared in Example 3 is 400 μm, wherein the thickness ratio of the PEF layer, the PET layer and the PEF layer is 10:70:20.

[0048] Comparative Example 1: Comparative Example 1 is a single PET layer, and the raw materials for preparing the PET layer include polyethylene terephthalate and 0.5% of the mass of the polyethylene terephthalate by weight of glycidyl methacrylate grafted styrene-hydrogenated butadiene copolymer; the intrinsic viscosity of the polyethylene terephthalate is 0.80 dL / g; the raw materials for preparing the polyethylene terephthalate layer need to be dried in a 150°C drying tank for 2 hours before being added to the screw extruder, and a single screw extruder and a hanger-type die are used to extrude a 400 μm PET sheet. The extrusion conditions of the polyethylene terephthalate layer are as follows: the temperature of the first zone is 250°C, the temperatures of the second to sixth zones are all 280°C, trimming and winding are performed to obtain comparative sample 1.

[0049] The thickness of Comparative Sample 1 was 400 μm.

[0050] Comparative Example 2: The number of layers of the comparative sample of comparative example 2 is designed to be a PET layer, an adhesive layer, an EVOH layer, an adhesive layer and a PET layer, wherein the raw material for preparing the PET layer includes polyethylene terephthalate and a 0.5% by mass of the polyethylene terephthalate glycidyl methacrylate grafted styrene-hydrogenated butadiene copolymer; the intrinsic viscosity of the polyethylene terephthalate is 0.80 dL / g; the raw material for preparing the polyethylene terephthalate layer needs to be dried in a drying tank at 150°C for 2 hours before being added to the screw extruder; the EVOH layer uses Kuraray blister molding grade EVOH SP521B; the adhesive layer uses an adhesive resin, and the adhesive resin is Mitsui adhesive resin AT1955; A three-layer single-screw extruder and a hanger-type co-extrusion die with a dispenser were used, wherein the extrusion conditions for the PET layer were as follows: the temperature of the first zone was 250°C, and the temperatures of the second to sixth zones were 280°C; the extrusion conditions for the bonding layer were as follows: the extrusion temperature of the first zone was 200°C, and the extrusion temperature of the second to sixth zones was 220°C; the extrusion conditions for the EVOH layer were as follows: the temperature of the first zone was 200°C, and the temperature of the second to sixth zones was 220°C; the temperature of the co-extrusion die was 255°C; trimming and winding were performed to obtain comparison sample 2.

[0051] The thickness of Comparative Sample 2 was 400 μm, and the thickness ratio of the PET layer, the adhesive layer, the EVOH layer, the adhesive layer, and the PET layer was 35:10:10:10:35.

[0052] Comparative Example 3: Comparative Example 3 is a composite of a PET layer and an EVOH layer, wherein the raw materials for preparing the PET layer include polyethylene terephthalate and a glycidyl methacrylate grafted styrene-hydrogenated butadiene copolymer accounting for 0.5% of the mass of the polyethylene terephthalate; the intrinsic viscosity of the polyethylene terephthalate is 0.80 dL / g; the raw materials for preparing the polyethylene terephthalate layer need to be dried in a drying tank at 150° C. for 2 hours before being added to the screw extruder; A single screw extruder and a coat hanger die were used to extrude a PET sheet with a thickness of 350 μm. The extrusion conditions were as follows: the temperature of the first zone was 250°C, the temperature of the second to sixth zones was 280°C, and after cooling, the sheets were trimmed and rolled. The PET sheet and the EVOH sheet with a thickness of 50 μm were dry-compounded and aged to obtain comparative sample 3.

[0053] Comparative Example 4: Comparative Example 4 is a single-layer structure, and the raw materials for preparation include polyethylene furanoate and polyethylene terephthalate, the intrinsic viscosity of the polyethylene furanoate is 0.90 dL / g, and the intrinsic viscosity of the polyethylene terephthalate is 0.80 dL / g; The raw materials were mixed and dried at 130°C for 3 hours. The extrusion conditions were as follows: the temperature of the first zone was 250°C, and the temperature of the second to sixth zones was 280°C. A single screw extruder and a coat-hanger die were used. After cooling, the extruder was trimmed and rolled to obtain comparative sample 4.

[0054] The thickness of Comparative Sample 4 was 400 μm.

[0055] Comparative Example 5: Compared with Example 3, toughening agent B is not added in Comparative Example 5, and the rest is the same as Example 3.

[0056] Comparative Example 6: Compared with Example 3, the toughening agent B in Comparative Example 6 is a single epoxidized calcium carbonate, and the rest is the same as Example 3.

[0057] Comparative Example 7: Compared with Example 3, the toughening agent B in Comparative Example 7 is a single lignin-polyethylene glycol graft, and the rest is the same as Example 3.

[0058] Comparative Example 8: Compared with Example 3, the toughening agent B in Comparative Example 8 is a single chitosan, and the rest is the same as Example 3.

[0059] The samples prepared in Examples 1 to 3 and the comparative samples prepared in Comparative Examples 1 to 8 were subjected to performance tests, and the results are shown in Table 1 below.

[0060] Among them, oxygen transmission rate (OTR): Tested in accordance with the test method of national standard GB / T 19789-2021. The test temperature is 23°C and the relative humidity is 0. Five different areas of the sample are selected for testing and the average value is taken. The lower the OTR value, the better the barrier performance.

[0061] Water Vapor Transmission Rate (WVTR): Tested in accordance with the test method of GB / T 26253-2010. Test temperature is 23°C and relative humidity is 50%. Select 5 different areas of the sample for testing and take the average value. The lower the WVTR value, the better the barrier performance.

[0062] Dart impact (Method A) / g: Refer to GB / T9639.1-2008, Method A: The diameter of the dart head is 38±1mm, the dart head material is made of smooth and polished phenolic plastic, and the falling height is 0.66±0.01m.

[0063] Table 1: Performance test results

[0064] From the data analysis of Table 1, it can be seen that the high barrier polyester co-extruded sheet prepared by the present invention has excellent barrier properties and mechanical properties and is recyclable. Adding toughener A and toughener B can promote the describing properties of the component interface and help improve the comprehensive performance of the polyester co-extruded sheet.

[0065] In comparative example 1, there is a single PET layer. The molecular chain of PET is mainly composed of benzene rings and ester groups. The rigid structure of the benzene rings causes the chain segments to be not densely stacked, resulting in poor barrier performance. In addition, the single PET layer lacks a superposition effect, making the barrier performance inferior to that of Example 3. The number of layers in comparative example 2 is designed as a PET layer, an adhesive layer, an EVOH layer, an adhesive layer, and a PET layer. Although it has a certain oxygen permeability, the EVOH layer contains more hydroxyl groups and is easy to form hydrogen bonds with water molecules, resulting in poor water vapor barrier performance. The adhesive layer / EVOH interface is prone to failure, resulting in a decrease in barrier performance. At the same time, EVOH and the adhesive layer cause material heterogeneity and cannot be recycled. Comparative example 3 is a composite of a PET layer and an EVOH layer, with poor oxygen permeability and water vapor permeability, no bio-based materials, and contains EVOH and an adhesive layer, resulting in material heterogeneity and cannot be recycled. Comparative Example 4 is a single-layer structure, in which polyethylene furanoate and polyethylene terephthalate are melt-extruded. Although it is recyclable, the overall performance is poor, and the barrier performance and impact performance are not as good as those of the layered structure design. Comparative Example 5 does not add toughening agent B, resulting in a significant decrease in barrier performance and impact performance, indicating that toughening agent B not only helps to improve barrier performance, but also has a significant promoting effect on overall toughening. Toughening agent B in Comparative Example 6 is a single epoxidized calcium carbonate, toughening agent B in Comparative Example 7 is a single lignin-polyethylene glycol graft, and toughening agent B in Comparative Example 8 is a single chitosan, but the barrier performance and impact performance in Comparative Examples 6 to 8 are significantly worse than those in Example 3, indicating that the present invention has a significant promoting effect on the performance of the polyester co-extruded sheet by compounding the components of toughening agent B and the synergistic effect of the components. The results show that the toughening agent B prepared by mixing a specific proportion of epoxidized calcium carbonate, lignin-polyethylene glycol grafted product and chitosan can exert a significant toughening effect, and the surface of the epoxidized calcium carbonate not only has excellent compatibility with polyethylene terephthalate, but also forms a chemical bond with polyethylene furanoate, which not only increases the interfacial compatibility, but also increases the interfacial adhesion, making it have better mechanical properties. In addition, the epoxidized calcium carbonate is evenly dispersed and filled in the polyethylene terephthalate layer. The addition of lignin-polyethylene glycol grafts can make the molecular chains in the polyethylene terephthalate layer more regular and uniform, increase the compatibility of the system, and form chemical bonds with epoxidized calcium carbonate to synergize the toughening of epoxidized calcium carbonate, so that the material can more evenly withstand and disperse stress when subjected to external forces, reducing the occurrence of local tearing; chitosan can produce hydrogen bonds with polyethylene terephthalate, synergistically enhance the effect, and avoid the loss of strength caused by single toughening.

[0066] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0067] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A high barrier polyester co-extruded sheet, characterized in that: The high barrier polyester co-extruded sheet comprises a polyethylene furanoate layer and a polyethylene terephthalate layer connected in sequence; The raw materials for preparing the polyethylene furanoate layer include: polyethylene furanoate and a toughening agent A accounting for 0.5% to 2% of the weight of the polyethylene furanoate, wherein the toughening agent A is at least one of ethylene-glycidyl methacrylate copolymer and glycidyl methacrylate grafted styrene-hydrogenated butadiene copolymer; The raw materials for preparing the polyethylene terephthalate layer include polyethylene terephthalate and a toughening agent B accounting for 0.5% to 2% of the weight of the polyethylene terephthalate, wherein the toughening agent B is prepared by mixing epoxidized calcium carbonate, lignin-polyethylene glycol grafted product and chitosan in a mass ratio of (1 to 7): (1 to 3): (1 to 5).

2. The high barrier polyester co-extruded sheet according to claim 1, characterized in that: The intrinsic viscosity of the polyethylene furanoate is higher than that of the polyethylene terephthalate by (0.05-0.20) dL / g; the glass transition temperature of the polyethylene furanoate is 86±5°C, and the melting point is 220±20°C.

3. The high barrier polyester co-extruded sheet according to claim 1, characterized in that: The polyethylene furanoate is prepared by a dehydration condensation polymerization reaction between a polymerizable monomer furan dicarboxylic acid and a polymerizable monomer diol compound.

4. The high barrier polyester co-extruded sheet according to claim 3, characterized in that: The polymerizable monomer furandicarboxylic acid is at least one of 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 2,3-furandicarboxylic acid and 3,4-furandicarboxylic acid.

5. The high barrier polyester co-extruded sheet according to claim 3, characterized in that: The polymerizable monomer diol compound is a cyclic diol and / or an aliphatic diol; The cyclic diol is at least one of cis-1,4-cyclohexanedimethanol, trans-1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanediol, 1,3-cyclohexanediol, 1,2-cyclohexanediol, dicyclopentanediol, 1-methyldicyclopentanediol, 1,5-dimethyldicyclopentanediol, tricyclodecane dimethanol, tetrafluoroterephthalimethanol, tricyclodecanediol, dicycloheptanediol, tricyclopentanediol and tetracyclodiol; The aliphatic diol is at least one of ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol and 2-methyl-1,3-propanediol.

6. The high barrier polyester co-extruded sheet according to claim 1, characterized in that: The polyethylene terephthalate has an intrinsic viscosity of 0.70-0.90 dL / g, a glass transition temperature of 76±5°C, and a melting point of 250±20°C.

7. The high barrier polyester co-extruded sheet according to claim 1, characterized in that: The preparation method of the epoxidized calcium carbonate is: The ball-milled calcium carbonate is added to anhydrous ethanol and ultrasonically dispersed. Then, a catalyst is added and stirred at 65°C to 70°C for 15min to 20min. Epichlorohydrin is added and nitrogen is introduced at 70°C to 80°C for protection. The reaction is carried out for 3h to 5h. The mixture is cooled to room temperature, neutralized, washed and dried to obtain epoxidized calcium carbonate.

8. The high barrier polyester co-extruded sheet according to claim 7, characterized in that: The power of ultrasonic dispersion is 300W and the time is 20min~30min.

9. A method for preparing a high barrier polyester co-extruded sheet, characterized in that: The preparation method is used to prepare the high barrier polyester co-extruded sheet according to any one of claims 1 to 8, and the preparation method comprises the following steps: According to the design of the number of layers of the high barrier polyester co-extruded sheet, the raw materials for the preparation of the polyethylene furanoate layer and the raw materials for the preparation of the polyethylene terephthalate layer are respectively added to the screw extruder, passed through a distributor, and entered the co-extrusion die head, and were cooled and formed by three smooth rollers, trimmed, and rolled to obtain the high barrier polyester co-extruded sheet.

10. The preparation method according to claim 9, characterized in that: The extrusion conditions of the polyethylene terephthalate layer are as follows: the temperature of the first zone is 250°C to 280°C, the temperature of the second zone is 250°C to 280°C, and the temperature of the third zone to the sixth zone is 270°C to 290°C; The extrusion conditions of the polyethylene furanoate layer are as follows: the temperature of the first zone is 240°C to 250°C, the temperature of the second zone is 240°C to 250°C, and the temperature of the third to sixth zones is 240°C to 260°C; The temperature of the coextrusion die was set at 240°C~255°C.

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