A multilayer co-extruded biaxially oriented film and its preparation method and application

Abstract

The application discloses a kind of multilayer co-extrusion biaxial stretching film and preparation method and application thereof, belong to high polymer material field, the film is biaxial stretching film for AB structure, A layer is high ductility PET layer, B layer is PP layer, A layer and B layer are fused extrusion by series screw extruder, two layers of raw materials pass through the co-extrusion die equipped with co-extrusion adapter, electrostatically attached on the casting sheet of cold drum.The application obtains a kind of PET / PP multilayer co-extrusion biaxial stretching film, film-forming is good, with good physical mechanical properties, reaches the national standard of BOPP, and does not include traditional adhesive process, reduces the use of adhesive, reduces cost at the same time, is conducive to safety and health, also conducive to environmental protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high molecular material, in particular to a kind of multilayer co-extrusion biaxial stretching film and its preparation method and application. BACKGROUND

[0002] In plastic soft packaging material, food packaging is its largest application market, with the improvement of consumption level, the requirement of food packaging is more and more demanding, which promotes the development of high barrier multifunctional packaging film material. In the general sense, the structure of packaging film product depends on the functional requirements of packaging film. For food packaging, the packaging material generally has good oxygen and water vapor barrier ability, good heat sealing performance, certain sterilization and heat resistance, strong mechanical property, good printing performance and optical performance. PET polyester is often used as one of the materials of multilayer composite film due to its excellent comprehensive performance.

[0003] The conventional PET composite film for food packaging commonly used has PET / VMPET / LLDPE structure or PET / VMCPP structure, which needs to prepare a raw film separately, and then bond by adhesive. The volatilization of adhesive and solvent used in the production process of the multilayer composite film easily causes environmental pollution.

[0004] When the film is prepared by multilayer co-extrusion processing mode, the multilayer film is once extruded, the process is simple, energy is saved, production efficiency is high, cost is low, environment is protected, adhesive is not used between layers, there is no residual solvent problem, the film has no odor, and it is suitable for food and medical device packaging. However, PET polyester and PP and other polyolefin materials have large differences in melting point and stretching ratio, and it is difficult to form a film by melt co-extrusion processing mode. SUMMARY

[0005] In view of the above shortcomings of the prior art, the purpose of the present application is to provide a kind of multilayer co-extrusion biaxial stretching film and preparation method and application, to PET and PP two layers co-extrusion biaxial stretching film.

[0006] The purpose of the present application can be realized by the following technical scheme:

[0007] A kind of multilayer co-extrusion biaxial stretching film, the biaxial stretching film is AB structure, A layer is high ductility PET layer, B layer is PP layer, the elongation at break of the material MD is 170-200%, TD is 68-80%;Tensile strength MD is 220-280MPa, TD is 300-330MPa.

[0008] In the technical scheme of the present application, the melting point of the high-ductility PET copolyester is between 177-231 DEG C; the maximum transverse stretching ratio of the high-ductility PET copolyester is 7.2-8.6 times (test conditions: the copolyester chip is dried, extruded into a 150 μm thick sheet, and after being placed for one day, unidirectional stretching is carried out on a stretching testing machine; the stretching conditions of the thick sheet are preheating temperature 140 DEG C and preheating time 20 s).

[0009] In the technical scheme of the present application, the high-ductility PET is produced by using terephthalic acid, isophthalic acid, polyaliphatic diacid glycol ester and ethylene glycol as raw materials by direct esterification-melt polycondensation method.

[0010] In some preferred technical schemes, the total mass of terephthalic acid, isophthalic acid and polyaliphatic diacid glycol ester in the raw materials is 100%, and the mass ratio of terephthalic acid, isophthalic acid and polyaliphatic diacid glycol ester is 80-85:5-15:5-15.

[0011] In some preferred technical schemes, the molar ratio of dihydric alcohol to diacid is 1-1.5:1, the dihydric alcohol is ethylene glycol, and the diacid is terephthalic acid and isophthalic acid.

[0012] In some preferred technical schemes, the polyaliphatic diacid glycol ester can be one or more of polypropylene glycol adipate (PEP), polyethylene glycol succinate (PEB), polyethylene glycol glutarate (PEG), polyethylene glycol adipate (PEA), polyethylene glycol suberate (PES) and the like.

[0013] In the technical scheme of the present application, the thickness ratio of the PET layer of layer A to the PP layer of layer B is 1-10:1-10.

[0014] In the technical scheme of the present application, the catalyst used in the direct esterification-melt polycondensation method is ethylene glycol antimony, the antimony atom accounts for 100-300 ppm of the total polyester mass, the esterification reaction temperature is 250-260 DEG C, the polycondensation reaction temperature is 280-285 DEG C, and the polycondensation reaction pressure is below 100 pa of absolute pressure.

[0015] A preparation method of the above multilayer co-extrusion biaxial stretching film, layer A and layer B are melt-extruded through a series connection screw extruder, the two layers of raw materials pass through a co-extrusion die head provided with a co-extrusion adapter, and are electrostatically attached on a cold drum to cast a sheet; the thick sheet obtained after extrusion is sequentially subjected to longitudinal stretching by 3-5 times, transverse stretching by 6-8 times, heat setting, relaxation, traction and winding to form a multilayer co-extrusion biaxial stretching film with a thickness of 20-30 μm.

[0016] In the technical scheme of the present application: the A layer is a high-ductility PET layer, which has a processing temperature similar to that of BOPP and plays a role of outer layer printing. The B layer is a PP layer, which plays a role of heat sealing.

[0017] After the multilayer co-extrusion biaxial stretching film is prepared, the BOPP layer can be subjected to an aluminum plating treatment, so that the film has a certain barrier property to meet the requirements of food packaging.

[0018] Unconventional test method:

[0019] The maximum stretching ratio of the high-ductility PET is evaluated by a stretching testing machine. The copolyester chip is dried and extruded into a 150 μm thick sheet, which is placed for one day and then subjected to unidirectional stretching on the stretching testing machine. The stretching conditions of the thick sheet are a preheating temperature of 140 ℃, a preheating time of 20 s, and a maximum ratio of the maximum stretching ratio in the transverse direction after the longitudinal stretching of 4.0 times.

[0020] The film-forming property of the multilayer co-extrusion biaxial stretching film is evaluated by a stretching testing machine. The continuous thick sheet obtained by multilayer co-extrusion is cut into a 10 cm x 10 cm thick sheet, which is preheated at a preheating temperature of 140 ℃ for 20 s, and then subjected to longitudinal stretching of 4.0 times and transverse stretching of 7.0 times, and then is set at 190 ℃ for 3 s. No film breaking phenomenon in 10 times of biaxial stretching test indicates that the product has excellent film-forming property, which is indicated by ○; film breaking less than or equal to 3 times indicates that the product has good film-forming property, which is indicated by Δ; film breaking more than 3 times or failure to form a film indicates that the product has poor film-forming property, which is indicated by ×.

[0021] Effects of the present application

[0022] The present application obtains a PET / PP multilayer co-extrusion biaxial stretching film, which has good film-forming property, good physical and mechanical properties, and reaches the national standard of BOPP. The film does not contain a traditional gluing process, reduces the use of adhesives, and reduces the cost, which is beneficial to safety and health and environmental protection.

[0023] In the technical scheme of the present application: PTA is terephthalic acid, IPA is isophthalic acid, PEA is polyethylene adipate, PEB is polyethylene succinate, and PEG is polyethylene glutarate. DETAILED DESCRIPTION

[0024] The present application is further described below in combination with examples, but the protection scope of the present application is not limited thereto:

[0025] Example 1

[0026] The product A layer is a high ductility PET copolyester, the total mass of terephthalic acid, isophthalic acid and aliphatic dibasic acid glycol ester is 100%, terephthalic acid is 80%, isophthalic acid is 10%, and polyethylene adipate (PEA) is 10%. The molar ratio of glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is glycol antimony, in which the total mass of antimony atoms is 200 ppm. The conventional esterification reaction is carried out at 256°C by direct esterification-melt polycondensation, and after the esterification is completed, the polycondensation reaction is carried out at 283°C under an absolute pressure of 100 Pa or less. After the reaction is completed, the copolyester chip is obtained by extrusion, drawing, cutting and drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm is 190°C. The copolyester chip is dried and extruded into a 150 μm thick sheet, which is placed for one day and then stretched on a stretching tester. The stretching conditions of the thick sheet are preheating temperature 140°C, preheating time 20 s, and maximum transverse stretching ratio 8.0.

[0027] The product B layer is a PP layer.

[0028] The A layer and the B layer are melt-extruded by a series screw extruder, and the co-extrusion ratio is 1:1 (mass ratio). The extrusion temperature is 280°C, and the two layers of raw materials pass through a co-extrusion die equipped with a co-extrusion adapter, and are electrostatically attached to a cold drum to cast a sheet. The sheet is stretched longitudinally by 4 times, transversely by 7 times, heat set, relaxed, pulled, and wound to form a multilayer co-extruded biaxially stretched film with a thickness of 25 μm. The A layer is 12 μm, and the B layer is 13 μm.

[0029] The co-extruded film has excellent film-forming properties, with a longitudinal elongation at break of 200%, and a tensile strength of 220 MPa; a transverse elongation at break of 80%, and a tensile strength of 300 MPa.

[0030] Example 2

[0031] The product A layer is a high-ductility PET copolyester, the total mass of terephthalic acid, isophthalic acid and aliphatic diacid glycol ester in the raw material is 100%, terephthalic acid accounts for 85%, isophthalic acid accounts for 5%, and polyethylene adipate accounts for 10%. The alcohol-acid molar ratio of ethylene glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the antimony atom accounts for 200 ppm of the total polyester mass. The conventional esterification reaction is carried out at 256°C by direct esterification-melt polycondensation method, after the esterification is completed, the polycondensation reaction is carried out at 283°C under an absolute pressure of 100 Pa or less, after the reaction is completed, the copolyester chips are obtained through extrusion, drawing, pelletizing and drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm is 225°C. The copolyester chips are dried and extruded into 150 μm thick sheets, after being placed for one day, unidirectional stretching is carried out on a stretching testing machine, the stretching conditions of the thick sheets are preheating temperature of 140°C, preheating time of 20 s, and maximum transverse stretching ratio of 7.2.

[0032] The product B layer is a PP layer.

[0033] The A layer and the B layer are melt-extruded through a series screw extruder, the co-extrusion ratio is 1:1. The extrusion temperature is 280°C, the two layers of raw materials pass through a co-extrusion die equipped with a co-extrusion adapter, and are electrostatically attached on a cold drum to cast a thick sheet. The thick sheet is longitudinally stretched by 4 times, transversely stretched by 7 times, heat set, relaxed, pulled and wound to form a multilayer co-extrusion biaxial stretching film with a thickness of 25 μm. The A layer is 12 μm, and the B layer is 13 μm.

[0034] The prepared co-extrusion film has good film-forming property, the longitudinal breaking elongation is 170%, and the tensile strength is 280 MPa; the transverse breaking elongation is 68%, and the tensile strength is 324 MPa.

[0035] Example 3

[0036] The product A layer is a high-ductility PET copolyester, the total mass of terephthalic acid, isophthalic acid and aliphatic diacid glycol ester in the raw material is 100%, terephthalic acid accounts for 85%, isophthalic acid accounts for 5%, and polyethylene adipate accounts for 10%. The alcohol-acid molar ratio of ethylene glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the antimony atom accounts for 200 ppm of the total polyester mass. The conventional esterification reaction is carried out at 256°C by direct esterification-melt polycondensation method, after the esterification is completed, the polycondensation reaction is carried out at 283°C under an absolute pressure of 100 Pa or less, after the reaction is completed, the copolyester chips are obtained through extrusion, drawing, pelletizing and drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm is 225°C. The copolyester chips are dried and extruded into 150 μm thick sheets, after being placed for one day, unidirectional stretching is carried out on a stretching testing machine, the stretching conditions of the thick sheets are preheating temperature of 140°C, preheating time of 20 s, and maximum transverse stretching ratio of 7.2.

[0037] Product B layer is PP layer.

[0038] A layer and B layer are melt extruded by series screw extruder, co-extrusion ratio is 1:1. Extrusion temperature is 280°C, two layer raw materials are electrostatically attached on casting sheet on cold drum by co-extrusion die head with co-extrusion adapter. Thick sheet is longitudinally stretched 4 times, transversely stretched 7 times, heat set, relaxed, pulled, and wound to form multilayer co-extrusion biaxial stretched film with thickness of 25 μm. A layer is 12 μm, B layer is 13 μm.

[0039] The prepared co-extrusion film has excellent film forming property, longitudinal breaking elongation is 195%, tensile strength is 225 MPa; transverse breaking elongation is 78%, tensile strength is 30 MPa.

[0040] Example 4

[0041] Product A layer is high ductility PET copolyester, the total mass of terephthalic acid, isophthalic acid, and aliphatic dibasic acid glycol ester in raw material is 100%, terephthalic acid accounts for 85%, isophthalic acid accounts for 10%, polyethylene adipate accounts for 5%. The alcohol-acid molar ratio of ethylene glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the total polyester mass accounts for 200 ppm of antimony atoms. The copolyester chip is obtained by direct esterification-melt polycondensation method at 256°C for conventional esterification reaction, after esterification, polycondensation reaction is carried out at 283°C under absolute pressure of 100 Pa or less, after reaction, the copolyester chip is obtained after extrusion, stretching, granulation, and drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm is 225°C. The copolyester chip is dried and extruded into a 150 μm thick sheet, after one day, uniaxial stretching is carried out on a stretching testing machine, the stretching conditions of the thick sheet are preheating temperature of 140°C, preheating time of 20 s, and maximum transverse stretching ratio of 7.4.

[0042] Product B layer is PP layer.

[0043] A layer and B layer are melt extruded by series screw extruder, co-extrusion ratio is 1:1. Extrusion temperature is 280°C, two layer raw materials are electrostatically attached on casting sheet on cold drum by co-extrusion die head with co-extrusion adapter. Thick sheet is longitudinally stretched 4 times, transversely stretched 7 times, heat set, relaxed, pulled, and wound to form multilayer co-extrusion biaxial stretched film with thickness of 25 μm. A layer is 12 μm, B layer is 13 μm.

[0044] The prepared co-extrusion film has good film forming property, longitudinal breaking elongation is 177%, tensile strength is 268 MPa; transverse breaking elongation is 70%, tensile strength is 330 MPa.

[0045] Example 5

[0046] Product A layer is high ductility PET copolyester, the total mass of terephthalic acid, isophthalic acid, and aliphatic diacid glycol ester in the raw material is 100%, terephthalic acid accounts for 80%, isophthalic acid accounts for 15%, and polyethylene adipate accounts for 5%. The alcohol acid molar ratio of ethylene glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the antimony atom accounts for 200 ppm of the total polyester mass. The conventional esterification reaction is carried out at 256°C by direct esterification-melt polycondensation method, after the esterification is completed, the polycondensation reaction is carried out at 283°C under an absolute pressure of 100 Pa or less, after the reaction is completed, the copolyester chip is obtained after extrusion, drawing, granulation, and drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm is 188°C. The copolyester chip is dried and extruded into a 150 μm thick sheet, after being placed for one day, uniaxial stretching is carried out on a stretching testing machine, the stretching conditions of the thick sheet are preheating temperature 140°C, preheating time 20 s, and the maximum transverse stretching ratio is 8.0.

[0047] Product B layer is a PP layer.

[0048] The A layer and the B layer are melt extruded through a series screw extruder, and the co-extrusion ratio is 1:1. The extrusion temperature is 280°C, the two layers of raw materials pass through a co-extrusion die equipped with a co-extrusion adapter, and are electrostatically attached to a cold drum to cast a sheet. The sheet is longitudinally stretched by 4 times, transversely stretched by 7 times, heat set, relaxed, pulled, and wound. The co-extruded film prepared has good film forming property, the longitudinal breaking elongation is 197%, and the tensile strength is 223 MPa; the transverse breaking elongation is 80%, and the tensile strength is 305 MPa.

[0049] Example 6

[0050] Product A layer is high ductility PET copolyester, the total mass of terephthalic acid, isophthalic acid, and aliphatic diacid glycol ester in the raw material is 100%, terephthalic acid accounts for 80%, isophthalic acid accounts for 15%, and polyethylene adipate accounts for 5%. The alcohol acid molar ratio of ethylene glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the antimony atom accounts for 200 ppm of the total polyester mass. The conventional esterification reaction is carried out at 256°C by direct esterification-melt polycondensation method, after the esterification is completed, the polycondensation reaction is carried out at 283°C under an absolute pressure of 100 Pa or less, after the reaction is completed, the copolyester chip is obtained after extrusion, drawing, granulation, and drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm is 188°C. The copolyester chip is dried and extruded into a 150 μm thick sheet, after being placed for one day, uniaxial stretching is carried out on a stretching testing machine, the stretching conditions of the thick sheet are preheating temperature 140°C, preheating time 20 s, and the maximum transverse stretching ratio is 8.0.

[0051] Product B layer is a PP layer.

[0052] Layer A and layer B were melt-extruded by series screw extruders with a co-extrusion ratio of 1:1. The extrusion temperature was 280°C, and the two layers of raw materials were electrostatically attached on a cold drum by a co-extrusion die head with a co-extrusion adapter to cast a thick sheet. The thick sheet was longitudinally stretched by 4 times, transversely stretched by 7 times, heat set, relaxed, pulled, and wound to form a multilayer co-extruded biaxially stretched film with a thickness of 25 μm. The thickness of layer A was 12 μm, and the thickness of layer B was 13 μm.

[0053] The prepared co-extruded film had excellent film-forming properties, with a longitudinal elongation at break of 197% and a tensile strength of 228 MPa; a transverse elongation at break of 78% and a tensile strength of 310 MPa.

[0054] Example 7

[0055] Layer A of the product was a high-ductility PET copolyester, and the total mass of terephthalic acid, isophthalic acid, and aliphatic dibasic acid ethylene glycol ester in the raw material was 100%, with terephthalic acid accounting for 80%, isophthalic acid accounting for 10%, and polyglutaric acid ethylene glycol ester (PEG) accounting for 10%. The alcohol-acid molar ratio of ethylene glycol to the total of terephthalic acid and isophthalic acid was 1.2. The catalyst was ethylene glycol antimony, with antimony atoms accounting for 200 ppm of the total mass of the polyester. The copolyester chip was obtained by performing a conventional esterification reaction at 256°C by direct esterification-melt polycondensation, performing a polycondensation reaction at 283°C under an absolute pressure of 100 Pa or less after the esterification was completed, and then performing extrusion, drawing, pelletizing, and drying after the reaction was completed. The intrinsic viscosity of the copolyester was 0.79 dL / g, and the Tm was 193°C. The copolyester chip was dried and extruded to form a 150 μm thick sheet, which was placed for one day and then subjected to uniaxial stretching on a stretching tester. The stretching conditions for the thick sheet were a preheating temperature of 140°C, a preheating time of 20 s, and a maximum transverse stretching ratio of 8.0.

[0056] Layer B of the product was a PP layer.

[0057] Layer A and layer B were melt-extruded by series screw extruders with a co-extrusion ratio of 1:1. The extrusion temperature was 280°C, and the two layers of raw materials were electrostatically attached on a cold drum by a co-extrusion die head with a co-extrusion adapter to cast a thick sheet. The thick sheet was longitudinally stretched by 4 times, transversely stretched by 7 times, heat set, relaxed, pulled, and wound to form a multilayer co-extruded biaxially stretched film with a thickness of 25 μm. The thickness of layer A was 12 μm, and the thickness of layer B was 13 μm.

[0058] The prepared co-extruded film had excellent film-forming properties, with a longitudinal elongation at break of 198% and a tensile strength of 226 MPa; a transverse elongation at break of 79% and a tensile strength of 305 MPa.

[0059] Reference Example 1

[0060] Product A is a high-elongation PET copolyester. The raw materials consist of 100% terephthalic acid, isophthalic acid, and ethylene glycol aliphatic dicarboxylic acid, with 75% terephthalic acid, 10% isophthalic acid, and 15% polyethylene adipate. The molar ratio of ethylene glycol to the total terephthalic acid and isophthalic acid is 1.2. The catalyst is antimony glycolate, with antimony atoms comprising 200 ppm of the total polyester mass. A conventional esterification reaction is carried out at 256°C via direct esterification-melt polycondensation. After esterification, a polycondensation reaction is performed at 283°C and below 100 Pa. After the reaction, the product is extruded, stretched, pelletized, and dried to obtain copolyester chips. The copolyester has an intrinsic viscosity of 0.79 dL / g and a Tm of 177°C. The copolyester chips were dried and extruded to form 150μm thick sheets. After being left to stand for one day, they were subjected to uniaxial stretching on a tensile testing machine. The stretching conditions for the thick sheets were: preheating temperature 140℃, preheating time 20s, and maximum transverse stretch ratio of 8.6.

[0061] The B layer of the product is a PP layer.

[0062] Layers A and B are melt-extruded using a tandem screw extruder, with a co-extrusion ratio of 1:1. The extrusion temperature is 280℃. The two layers of raw material are electrostatically attached to a cooling drum and cast into a sheet using a co-extrusion die equipped with a co-extrusion adapter. The sheet is then stretched 4 times longitudinally and 7 times transversely, followed by heat setting, relaxation, traction, and winding to produce a 25μm thick multilayer co-extruded biaxially oriented film. Layer A is 12μm thick, and Layer B is 13μm thick.

[0063] The resulting co-extruded film exhibits good film-forming properties, with a longitudinal elongation at break of 230% and a tensile strength of 186 MPa; and a transverse elongation at break of 87% and a tensile strength of 281 MPa.

[0064] Reference example 2

[0065] Product A is a high-elongation PET copolyester. The raw materials consist of 100% terephthalic acid, isophthalic acid, and ethylene glycol aliphatic dicarboxylic acid, with 75% terephthalic acid, 15% isophthalic acid, and 10% polyethylene adipate. The molar ratio of ethylene glycol to the total terephthalic acid and isophthalic acid is 1.2. The catalyst is antimony glycolate, with antimony atoms comprising 200 ppm of the total polyester mass. A conventional esterification reaction is carried out at 256°C via direct esterification-melt polycondensation. After esterification, a polycondensation reaction is performed at 283°C and below 100 Pa. After the reaction, the product is extruded, stretched, pelletized, and dried to obtain copolyester chips. The copolyester has an intrinsic viscosity of 0.79 dL / g and a Tm of 180°C. The copolyester chips were dried and extruded to form 150μm thick sheets. After being left to stand for one day, they were subjected to uniaxial stretching on a tensile testing machine. The stretching conditions for the thick sheets were: preheating temperature 140℃, preheating time 20s, and maximum transverse elongation ratio 8.1.

[0066] Product B layer is PP layer.

[0067] A layer and B layer are melt extruded by series screw extruder, the co-extrusion ratio is 1:1. The extrusion temperature is 280℃, the two layer raw materials are attached on the casting sheet on the cold drum by the co-extrusion die head with co-extrusion adapter. The thick sheet is broken when stretched in two directions, and cannot be made into film.

[0068] The co-extrusion film made has good film forming property, the elongation at break in longitudinal direction is 220%, the tensile strength is 180MPa; the elongation at break in transverse direction is 90%, the tensile strength is 270MPa.

[0069] Reference Example 3

[0070] Product A layer is PET polyester commercially available, the intrinsic viscosity of the copolyester is 0.645dL / g, Tm is 250℃. The copolyester chip is dried and extruded to make 150μm thick sheet, which is stretched on the stretching tester after one day, the stretching condition of the thick sheet is preheating temperature 140℃, preheating time 20s, the maximum stretching ratio in transverse direction is 4.4.

[0071] Product B layer is PP layer.

[0072] A layer and B layer are melt extruded by series screw extruder, the co-extrusion ratio is 1:1. The extrusion temperature is 280℃, the two layer raw materials are attached on the casting sheet on the cold drum by the co-extrusion die head with co-extrusion adapter. The thick sheet is broken when stretched in two directions, and cannot be made into film.

[0073] Reference Example 4

[0074] Product A layer is high ductility PET copolyester, the total mass of terephthalic acid and aliphatic dibasic acid glycol ester in the raw material is 100%, terephthalic acid accounts for 95%, polyethylene adipate accounts for 5%. The alcohol acid molar ratio of ethylene glycol and terephthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the antimony atom accounts for 200ppm of the total polyester mass. The copolyester chip is obtained by direct esterification-melt polycondensation method, the conventional esterification reaction is carried out at 256℃, the polycondensation reaction is carried out at 283℃ under absolute pressure below 100Pa after the esterification is finished, and the copolyester chip is obtained after extrusion, drawing, granulation and drying. The intrinsic viscosity of the copolyester is 0.70dL / g, Tm is 236℃. The copolyester chip is dried and extruded to make 150μm thick sheet, which is stretched on the stretching tester after one day, the stretching condition of the thick sheet is preheating temperature 140℃, preheating time 20s, the maximum stretching ratio in transverse direction is 5.0.

[0075] Product B layer is PP layer.

[0076] A layer and B layer were melt extruded by series screw extruder, the co-extrusion ratio was 1:1. The extrusion temperature was 280°C, the two layer raw materials were electrostatically attached on the chill drum by co-extrusion die with co-extrusion adapter. The thick sheet broke when biaxially stretched, and could not be formed into film.

[0077] Reference Example 5

[0078] The product A layer was high ductility PET copolyester, the total mass of terephthalic acid and aliphatic diacid glycol ester in the raw material was 100%, terephthalic acid accounted for 90%, and polyethylene adipate accounted for 10%. The alcohol acid molar ratio of ethylene glycol to terephthalic acid was 1.2. The catalyst was ethylene glycol antimony, in which the antimony atoms accounted for 200 ppm of the total polyester mass. The conventional esterification reaction was carried out at 256°C by direct esterification-melt polycondensation method, after the esterification was completed, the polycondensation reaction was carried out at 283°C under an absolute pressure of 100 Pa or less, after the reaction was completed, the copolyester chips were obtained after extrusion, drawing, granulation and drying. The intrinsic viscosity of the copolyester was 0.79 dL / g, and the Tm was 213°C. The copolyester chips were dried and extruded to form a 150 μm thick sheet, after being placed for one day, uniaxial stretching was carried out on a stretching testing machine, the stretching conditions of the thick sheet were preheating temperature of 140°C, preheating time of 20 s, and maximum stretching ratio in the transverse direction of 6.4.

[0079] The product B layer was PP layer.

[0080] A layer and B layer were melt extruded by series screw extruder, the co-extrusion ratio was 1:1. The extrusion temperature was 280°C, the two layer raw materials were electrostatically attached on the chill drum by co-extrusion die with co-extrusion adapter. The thick sheet broke when biaxially stretched, and could not be formed into film.

[0081] Reference Example 6

[0082] The product A layer was high ductility PET copolyester, the total mass of terephthalic acid and aliphatic diacid glycol ester in the raw material was 100%, terephthalic acid accounted for 85%, and polyethylene adipate accounted for 15%. The alcohol acid molar ratio of ethylene glycol to terephthalic acid was 1.2. The catalyst was ethylene glycol antimony, in which the antimony atoms accounted for 200 ppm of the total polyester mass. The conventional esterification reaction was carried out at 256°C by direct esterification-melt polycondensation method, after the esterification was completed, the polycondensation reaction was carried out at 283°C under an absolute pressure of 100 Pa or less, after the reaction was completed, the copolyester chips were obtained after extrusion, drawing, granulation and drying. The intrinsic viscosity of the copolyester was 0.79 dL / g, and the Tm was 209°C. The copolyester chips were dried and extruded to form a 150 μm thick sheet, after being placed for one day, uniaxial stretching was carried out on a stretching testing machine, the stretching conditions of the thick sheet were preheating temperature of 140°C, preheating time of 20 s, and maximum stretching ratio in the transverse direction of 7.2.

[0083] Product B layer is PP layer.

[0084] A layer and B layer are melt extruded by series screw extruder, the co-extrusion ratio is 1:1. The extrusion temperature is 280°C, the two layer raw materials are electrostatically attached on the casting sheet on the cold drum by the co-extrusion die head with co-extrusion adapter. The thick sheet is broken when biaxially stretched, and cannot be formed into film.

[0085] Reference Example 7

[0086] Product A layer is high ductility PET copolyester, the total mass of terephthalic acid and aliphatic dibasic acid glycol ester in the raw material is 100%, terephthalic acid accounts for 80%, polyethylene adipate accounts for 20%. The alcohol acid molar ratio of ethylene glycol to terephthalic acid is 1.2. The catalyst is ethylene glycol antimony, and the antimony atom accounts for 200ppm of the total polyester mass. The copolyester chip is obtained by direct esterification-melt polycondensation method at 256°C for conventional esterification reaction, and after esterification, the polycondensation reaction is carried out at 283°C under absolute pressure of 100Pa or less. After the reaction is completed, the copolyester chip is obtained by extrusion, drawing, granulation and drying. The intrinsic viscosity of the copolyester is 0.79dL / g, and the Tm is 186°C. The copolyester chip is dried and extruded into a 150μm thick sheet, and after being placed for one day, it is uniaxially stretched on a stretching tester. The stretching conditions of the thick sheet are preheating temperature of 140°C, preheating time of 20s, and maximum transverse stretching ratio of 8.5.

[0087] Product B layer is PP layer.

[0088] A layer and B layer are melt extruded by series screw extruder, the co-extrusion ratio is 1:1. The extrusion temperature is 280°C, the two layer raw materials are electrostatically attached on the casting sheet on the cold drum by the co-extrusion die head with co-extrusion adapter. The thick sheet is broken when biaxially stretched, and cannot be formed into film.

[0089] The co-extrusion film prepared has excellent film forming property, the elongation at break in the longitudinal direction is 220%, and the tensile strength is 176MPa; the elongation at break in the transverse direction is 102%, and the tensile strength is 246MPa.

[0090] Reference Example 8

[0091] Product A layer is high ductility PET copolyester, the total mass of terephthalic acid and isophthalic acid in raw material is 100%, terephthalic acid accounts for 95%, isophthalic acid accounts for 5%. The molar ratio of glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the total polyester mass accounts for 200ppm of antimony atoms. The conventional esterification reaction is carried out at 256℃ by direct esterification-melt polycondensation method, after esterification, the polycondensation reaction is carried out at 283℃ under absolute pressure of 100Pa or less, after the reaction, the copolyester chip is obtained by extrusion, drawing, cutting, drying. The intrinsic viscosity of copolyester is 0.7dL / g, Tm is 240℃. The copolyester chip is dried and extruded into 150μm thick sheet, after one day, the unidirectional stretching is carried out on the stretching testing machine, the stretching conditions of the thick sheet are preheating temperature 140℃, preheating time 20s, the maximum stretching ratio of transverse direction is 4.7.

[0092] Product B layer is PP layer.

[0093] A layer and B layer are melt extruded by series screw extruder, the co-extrusion ratio is 1:1. The extrusion temperature is 280℃, the two layer raw materials pass through the co-extrusion die equipped with co-extrusion adapter, and are electrostatically attached on the cold drum to cast the sheet. The sheet breaks the film when bidirectional stretching, and cannot form film.

[0094] Reference Example 9

[0095] Product A layer is high ductility PET copolyester, the total mass of terephthalic acid and isophthalic acid in raw material is 100%, terephthalic acid accounts for 90%, isophthalic acid accounts for 10%. The molar ratio of glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the total polyester mass accounts for 200ppm of antimony atoms. The conventional esterification reaction is carried out at 256℃ by direct esterification-melt polycondensation method, after esterification, the polycondensation reaction is carried out at 283℃ under absolute pressure of 100Pa or less, after the reaction, the copolyester chip is obtained by extrusion, drawing, cutting, drying. The intrinsic viscosity of copolyester is 0.79dL / g, Tm is 231℃. The copolyester chip is dried and extruded into 150μm thick sheet, after one day, the unidirectional stretching is carried out on the stretching testing machine, the stretching conditions of the thick sheet are preheating temperature 140℃, preheating time 20s, the maximum stretching ratio of transverse direction is 5.4.

[0096] Product B layer is PP layer.

[0097] A layer and B layer are melt extruded by series screw extruder, the co-extrusion ratio is 1:1. The extrusion temperature is 280℃, the two layer raw materials pass through the co-extrusion die equipped with co-extrusion adapter, and are electrostatically attached on the cold drum to cast the sheet. The sheet breaks the film when bidirectional stretching, and cannot form film.

[0098] Reference Example 10

[0099] Product A layer is high ductility PET copolyester, the total mass of terephthalic acid and isophthalic acid in raw material is 100%, terephthalic acid accounts for 85%, isophthalic acid accounts for 15%. The molar ratio of glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the antimony atom accounts for 200 ppm of the total polyester mass. The conventional esterification reaction is carried out at 256°C by direct esterification-melt polycondensation method, after esterification, the polycondensation reaction is carried out at 283°C under absolute pressure below 100 Pa, after the reaction, the copolyester chip is obtained after extrusion, drawing, granulation, drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm is 210°C. The copolyester chip is dried and extruded into a 150 μm thick sheet, after placing for one day, uniaxial stretching is carried out on a stretching testing machine, the stretching conditions of the thick sheet are preheating temperature 140°C, preheating time 20 s, and the maximum stretching ratio in the transverse direction is 6.2.

[0100] Product B layer is PP layer.

[0101] A layer and B layer are melt extruded by serial screw extruder, the co-extrusion ratio is 1:1. The extrusion temperature is 280°C, the two layers of raw materials pass through the co-extrusion die equipped with co-extrusion adapter, and are electrostatically attached on the cold drum to cast the sheet. The sheet breaks when stretched in two directions, and cannot be formed into a film.

[0102] Reference Example 11

[0103] Product A layer is high ductility PET copolyester, the total mass of terephthalic acid and isophthalic acid in raw material is 100%, terephthalic acid accounts for 80%, isophthalic acid accounts for 20%. The molar ratio of glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the antimony atom accounts for 200 ppm of the total polyester mass. The conventional esterification reaction is carried out at 256°C by direct esterification-melt polycondensation method, after esterification, the polycondensation reaction is carried out at 283°C under absolute pressure below 100 Pa, after the reaction, the copolyester chip is obtained after extrusion, drawing, granulation, drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm is 192°C. The copolyester chip is dried and extruded into a 150 μm thick sheet, after placing for one day, uniaxial stretching is carried out on a stretching testing machine, the stretching conditions of the thick sheet are preheating temperature 140°C, preheating time 20 s, and the maximum stretching ratio in the transverse direction is 7.0.

[0104] Product B layer is PP layer.

[0105] A layer and B layer were melt-extruded by connecting screw extruders, and the co-extrusion ratio was 1:1. The extrusion temperature was 280°C, and the two layers of raw materials were electrostatically attached to a cold drum by a co-extrusion die equipped with a co-extrusion adapter to cast a thick sheet. The thick sheet was longitudinally stretched by 4 times, transversely stretched by 7 times, heat set, relaxed, pulled, and wound to produce a multilayer co-extruded biaxially stretched film having a thickness of 25 μm. The A layer was 12 μm, and the B layer was 13 μm.

[0106] The co-extruded film produced had good film-forming properties, with a longitudinal elongation at break of 215% and a tensile strength of 180 MPa; a transverse elongation at break of 100% and a tensile strength of 250 MPa.

[0107] Reference Example 12

[0108] The A layer of the product was a high-ductility PET copolyester, and the total mass of terephthalic acid, isophthalic acid, and aliphatic dibasic acid glycol ester in the raw material was 100%, with terephthalic acid accounting for 90%, isophthalic acid accounting for 5%, and polyethylene adipate accounting for 5%. The alcohol-acid molar ratio of ethylene glycol to the total of terephthalic acid and isophthalic acid was 1.2. The catalyst was ethylene glycol antimony, with antimony atoms accounting for 200 ppm of the total mass of the copolyester. The copolyester chip was obtained by performing a conventional esterification reaction at 256°C by direct esterification-melt polycondensation, performing a polycondensation reaction at 283°C under an absolute pressure of 100 Pa or less after the esterification was completed, and then performing extrusion, drawing, pelletizing, and drying after the reaction was completed. The intrinsic viscosity of the copolyester was 0.79 dL / g, and the Tm was 220°C. The copolyester chip was dried and extruded to produce a 150 μm thick sheet, which was placed for one day and then uniaxially stretched on a stretching tester. The stretching conditions for the thick sheet were a preheating temperature of 140°C, a preheating time of 20 s, and a maximum transverse stretching ratio of 8.0.

[0109] The B layer of the product was a PP layer.

[0110] A layer and B layer were melt-extruded by connecting screw extruders, and the co-extrusion ratio was 1:1. The extrusion temperature was 280°C, and the two layers of raw materials were electrostatically attached to a cold drum by a co-extrusion die equipped with a co-extrusion adapter to cast a thick sheet. The thick sheet was longitudinally stretched by 4 times, transversely stretched by 7 times, heat set, relaxed, pulled, and wound to produce a multilayer co-extruded biaxially stretched film having a thickness of 25 μm. The A layer was 12 μm, and the B layer was 13 μm.

[0111] Reference Example 13

[0112] The product A layer is a high-ductility PET copolyester, the total mass of terephthalic acid, isophthalic acid, and aliphatic diacid glycol ester in the raw material is 100%, terephthalic acid accounts for 75%, isophthalic acid accounts for 5%, and polyethylene adipate accounts for 20%. The alcohol-acid molar ratio of ethylene glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the antimony atom accounts for 200 ppm of the total polyester mass. The conventional esterification reaction is carried out at 256°C by direct esterification-melt polycondensation, after the esterification is completed, the polycondensation reaction is carried out at 283°C under an absolute pressure of 100 Pa or less, after the reaction is completed, the copolyester chip is obtained through extrusion, drawing, granulation, and drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm disappears. The copolyester chip is dried and extruded into a 150-μm-thick sheet, after being placed for one day, the unidirectional stretching is carried out on a stretching testing machine, the stretching conditions of the thick sheet are a preheating temperature of 140°C, a preheating time of 20 s, and a maximum stretching ratio in the transverse direction of 8.8.

[0113] The product B layer is a PP layer.

[0114] The A layer and the B layer are melt-extruded through a series connection screw extruder, the co-extrusion ratio is 1:1. The extrusion temperature is 280°C, the two layers of raw materials pass through a co-extrusion die head provided with a co-extrusion adapter, and are electrostatically attached on a cold drum to cast a sheet. The sheet breaks the film when being bidirectionally stretched, and cannot be formed into a film.

[0115] Reference Example 14

[0116] The product A layer is a high-ductility PET copolyester, the total mass of terephthalic acid, isophthalic acid, and aliphatic diacid glycol ester in the raw material is 100%, terephthalic acid accounts for 75%, isophthalic acid accounts for 5%, and polyethylene adipate accounts for 20%. The alcohol-acid molar ratio of ethylene glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is ethylene glycol antimony, in which the antimony atom accounts for 200 ppm of the total polyester mass. The conventional esterification reaction is carried out at 256°C by direct esterification-melt polycondensation, after the esterification is completed, the polycondensation reaction is carried out at 283°C under an absolute pressure of 100 Pa or less, after the reaction is completed, the copolyester chip is obtained through extrusion, drawing, granulation, and drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm disappears. The copolyester chip is dried and extruded into a 150-μm-thick sheet, after being placed for one day, the unidirectional stretching is carried out on a stretching testing machine, the stretching conditions of the thick sheet are a preheating temperature of 140°C, a preheating time of 20 s, and a maximum stretching ratio in the transverse direction of 8.8.

[0117] The product B layer is a PP layer.

[0118] The A layer and the B layer are melt-extruded through a series connection screw extruder, the co-extrusion ratio is 1:1. The extrusion temperature is 280°C, the two layers of raw materials pass through a co-extrusion die head provided with a co-extrusion adapter, and are electrostatically attached on a cold drum to cast a sheet. The sheet breaks the film when being bidirectionally stretched, and cannot be formed into a film.

[0119] Reference Example 15

[0120] The product A layer is a high ductility PET copolyester, the total mass of terephthalic acid, isophthalic acid and aliphatic dibasic acid glycol ester is 100%, terephthalic acid accounts for 75%, isophthalic acid accounts for 20%, and polyethylene adipate accounts for 5%. The molar ratio of glycol to the total of terephthalic acid and isophthalic acid is 1.2. The catalyst is glycol antimony, in which the total mass of antimony atoms accounts for 200 ppm of the total polyester. The conventional esterification reaction is carried out at 256℃ by direct esterification-melt polycondensation, after the esterification is completed, the polycondensation reaction is carried out at 283℃ under an absolute pressure of 100 Pa or less, and after the reaction is completed, the copolyester chip is obtained after extrusion, drawing, cutting, and drying. The intrinsic viscosity of the copolyester is 0.79 dL / g, and the Tm disappears. The copolyester chip is dried and extruded into a 150 μm thick sheet, which is placed for one day and then stretched uniaxially on a stretching tester. The stretching conditions of the thick sheet are preheating temperature 140℃, preheating time 20 s, and maximum transverse stretching ratio 8.6.

[0121] The product B layer is a PP layer.

[0122] The A layer and the B layer are melt-extruded through a series screw extruder, and the co-extrusion ratio is 1:1. The extrusion temperature is 280℃, and the two layers of raw materials pass through a co-extrusion die equipped with a co-extrusion adapter, and are electrostatically attached to a cold drum to cast a thick sheet. The thick sheet breaks the film when stretched in two directions, and cannot form a film.

[0123] The standard for performance testing is as follows:

[0124] The maximum stretching ratio of the high ductility PET is evaluated by a stretching tester. The copolyester chip is dried and extruded into a 150 μm thick sheet, which is placed for one day and then stretched uniaxially on a stretching tester. The stretching conditions of the thick sheet are preheating temperature 140℃, preheating time 20 s, and the maximum transverse stretching ratio after stretching the longitudinal direction by 4.0 times.

[0125] The film-forming property of the multi-layer co-extruded biaxially stretched film is evaluated by a stretching tester. The continuous thick sheet obtained by multi-layer co-extrusion is cut into a 10 cm x 10 cm thick sheet, which is preheated at 140℃ for 20 s by a stretching tester, and then stretched by 4.0 times in the longitudinal direction, and stretched by 7.0 times in the transverse direction, and then set at 190℃ for 3 s. No film breaking occurs in 10 biaxial stretching tests, indicating that the product has excellent film-forming property, indicated by ○; film breaking is less than or equal to 3 times, indicating that the product has good film-forming property, indicated by Δ; film breaking is more than 3 times or cannot form a film, indicating that the product has poor film-forming property, indicated by ×.

[0126] The elongation at break and tensile strength are tested according to the national standard GB / T 1040.1-2018 "Determination of tensile properties of plastics".

[0127]

[0128]

[0129] The test results of the embodiments and reference examples of the present application are listed in Table 1. The present application uses modified PET polyester and PP to perform co-extrusion stretching to obtain a kind of double-layer biaxial stretching film product, which has better film-forming property and can be used in the packaging field to reduce the process, achieve energy saving and consumption reduction, reduce cost, and reduce organic reagent pollution and other problems. The PET component is modified by in-situ copolymerization of two kinds of monomers to achieve the purpose of co-extrusion stretching with PP. The polyester fatty aliphatic diacid glycol ester monomer used has a long straight chain structure, which is similar to the structure of PP, improves the compatibility with PP material, solves the problems of poor compatibility of PET and PP material, poor film-forming property of the prepared film, and low mechanical properties of the film, and the polyester structure also plays a role in improving the thermal stability of the overall material. The IPA monomer used has a polar aromatic structure, which plays a role in reducing the melting point while maintaining the softening point of the PET material, reducing the difficulty of PET and PP co-extrusion processing, and not significantly reducing the mechanical properties of PET itself. Compared with reference examples 1, 2, 13, 14, and 15, the mechanical strength of the film is affected, which is manifested as an increase in elongation at break of more than 80%, a decrease in tensile strength of less than 200 MPa in MD and less than 300 MPa in TD, and a significant decrease in mechanical properties. Compared with reference examples 3, 4, 5, 6, 8, 9, and 10, the film-forming property of the reference examples within the scope of the present application is poor and difficult to form a film. Compared with reference examples 7 and 11, when only one of isophthalic acid or polyester fatty aliphatic diacid glycol ester is used as the modified component, the mechanical properties of the film are significantly reduced.

Claims

1. A multilayer coextruded biaxially-stretched film, characterized in that: The biaxial stretching film has an AB structure, the A layer is a high ductility PET layer, and the B layer is a PP layer, the film has a breaking elongation MD of 170-200%, a TD of 68-80%, a tensile strength MD of 220-280 MPa, and a TD of 300-330 MPa; The high ductility PET is produced by using terephthalic acid, isophthalic acid, polyaliphatic diacid glycol ester and ethylene glycol as raw materials by a direct esterification-melt polycondensation method; The total mass of terephthalic acid, isophthalic acid and polyaliphatic diacid glycol ester is 100%, and the mass ratio of terephthalic acid, isophthalic acid and polyaliphatic diacid glycol ester is 80-85:5-15:5-15; The total mole ratio of ethylene glycol to terephthalic acid and isophthalic acid is 1:1 to 1.5:

1.

2. The multilayer co-extruded biaxially-stretched film according to claim 1, characterized in that: The melting point of the high ductility PET copolyester is between 177-231℃.

3. The multilayer co-extruded biaxially-stretched film according to claim 1, characterized in that: The maximum transverse stretching ratio of the high ductility PET copolyester is 7.2-8.6 times.

4. The multilayer co-extruded biaxially-stretched film according to claim 1, characterized in that: The polyaliphatic diacid glycol ester is one or more of polypropanedioic acid glycol ester, polybutanedioic acid glycol ester, polyglutaric acid glycol ester, polyadipic acid glycol ester, polyheptanedioic acid glycol ester and polyoctanedioic acid glycol ester.

5. The multilayer co-extruded biaxially-stretched film according to claim 1, characterized in that: The thickness ratio of the PET layer of the A layer to the PP layer of the B layer is 1-10:1-10.

6. A process for the production of the multilayer co-extruded biaxially stretched film according to claim 1, characterized by the fact that: The A layer and the B layer are melt-extruded by a series screw extruder, the two layers of raw materials are attached to a cold drum by electrostatic adhesion through a co-extrusion die head provided with a co-extrusion adapter, and the thick sheet obtained after extrusion is sequentially subjected to longitudinal stretching by 3-5 times, transverse stretching by 6-8 times, heat setting, relaxation, traction and winding to form a multilayer co-extrusion biaxial stretching film with a thickness of 20-30μm.

7. Application of the multilayer co-extrusion biaxial stretching film of claim 1 in food packaging.

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