CN109367044B - High-impact-resistance biaxially oriented polyester/polyamide film and preparation method thereof - Google Patents

High-impact-resistance biaxially oriented polyester/polyamide film and preparation method thereof Download PDF

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CN109367044B
CN109367044B CN201811124333.XA CN201811124333A CN109367044B CN 109367044 B CN109367044 B CN 109367044B CN 201811124333 A CN201811124333 A CN 201811124333A CN 109367044 B CN109367044 B CN 109367044B
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film
polyamide
polyester
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layer
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CN109367044A (en
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宋建新
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Jiangyin Changgen High Technology Material Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
    • B29C71/02—Thermal after-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
    • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
    • B29C55/16—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial simultaneously
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B32B15/085—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B32B15/088—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising polyamides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B32B15/09—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising polyesters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/20—Layered products comprising a layer of metal comprising aluminium or copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
    • B29C71/02—Thermal after-treatment
    • B29C2071/022—Annealing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2077/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2007/00—Flat articles, e.g. films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2009/00—Layered products
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/03—3 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/04—4 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/05—5 or more layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/24—All layers being polymeric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/558—Impact strength, toughness
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/714—Inert, i.e. inert to chemical degradation, corrosion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/10—Batteries

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Sealing Battery Cases Or Jackets (AREA)
  • Laminated Bodies (AREA)

Abstract

The invention discloses a high-impact-resistance biaxially oriented polyester/polyamide film and a preparation method thereof, wherein the method comprises the following steps: a) multilayer coextruded film tube: the multi-layer structure of the membrane tube is polyester/adhesive/(polyamide)n(ii) a b) Rapidly cooling to room temperature after co-extrusion; c) and (3) biaxial stretching: heating the cooled membrane tube to 70-120 ℃, and then stretching in two directions, wherein the stretching ratio is as follows: longitudinal direction 2.5-4.0; transverse: 3.0-4.0; d) and (3) heat treatment: flattening the stretched film tube by a drawing roller, and carrying out annealing heat treatment under the condition of keeping longitudinal and transverse tension; e) and rolling: and cooling the film after the heat treatment, cutting and rolling to obtain a finished product. The high-impact-resistance biaxially oriented polyester/polyamide film disclosed by the invention is excellent in corrosion resistance and cold stamping formability, and is suitable for new energy automobile electricityThe cell packages the outer layer material required for the application.

Description

High-impact-resistance biaxially oriented polyester/polyamide film and preparation method thereof
Technical Field
The invention belongs to the technical field of packaging films, and relates to a high-impact-resistance biaxially oriented polyester/polyamide film, a preparation method thereof and an aluminum-plastic composite film containing the same.
Background
At present, lithium ion batteries are commonly used secondary batteries, are widely applied in the 3C field, and with the development of electric automobiles, higher requirements are put forward on outer packaging materials of the lithium ion batteries. The lithium ion battery outer packaging material used at present is a composite material, and the structure composition of the composite material is as follows: the outer layer substrate layer, the metal barrier layer and the heat sealing layer. Wherein, the outer layer substrate film is required to have good elongation, toughness, tensile strength and isotropy, and the following problems are overcome:
firstly, because the lithium ion battery adopts a cold forming mode, three materials with different performances are easy to strip between layers in the forming process, particularly between an outer-layer substrate layer and a metal barrier layer, and the metal barrier layer is easy to generate defects in the cold forming process;
secondly, when the outer packaging film is subjected to a heat sealing process, the temperature is 180-200 ℃, the time is 2-3s, and interlayer peeling between the outer substrate layer and the metal blocking layer is easy to occur under the condition;
and thirdly, when the lithium battery is used under the condition of high temperature and high humidity, the outer layer substrate film is in direct contact with extremely severe environment, and interlayer peeling is easy to occur.
In addition, the outer substrate film protects the middle metal barrier layer from being scratched, continuous operation can be realized in the processing process without damaging the appearance, the damage of external force to the battery in the use process is prevented, the inside of the battery is protected in the use process of the battery, and the impact shock to the battery caused by falling and the like is avoided. The outer-layer base material film of the outer package for the lithium battery generally adopts a nylon film, but the existing nylon film is easy to absorb moisture and is not corrosion-resistant due to the material performance of the existing nylon film, so that the requirement of the outer-layer base material film of the outer package for the lithium battery is difficult to meet.
Chinese patent (publication No. CN107825794A) discloses a biaxially oriented nylon coextruded film with a polyester surface layer and a method for preparing the same, wherein a tape casting method and a biaxially oriented process are adopted, and whether synchronous stretching or asynchronous stretching is adopted, the orientation in longitudinal and transverse directions is different, so that the mechanical strength of a polyamide film in longitudinal and transverse directions is not uniform, and the mechanical strength of the polyamide film applied in the field of lithium ion batteries needs to be uniform in longitudinal and transverse directions, thereby preventing the peeling risk caused by the non-uniform mechanical strength in longitudinal and transverse directions in the cold forming process.
Disclosure of Invention
Therefore, aiming at the technical problems that in the prior art, a nylon film serving as an outer layer base material layer of a lithium ion battery outer packaging material is easy to strip from a layer, is easy to absorb moisture, is not corrosion-resistant and is difficult to meet requirements, the invention aims to provide a high-impact-resistance biaxially oriented polyester/polyamide film and a preparation method thereof.
The preparation method of the high impact-resistant biaxially oriented polyester/polyamide film comprises the following steps:
a) multilayer coextruded film tube: according to weight, 10 to 20 percent of polyester, 10 to 15 percent of adhesive and 65 to 80 percent of polyamide are respectively melted by a plurality of extruders and then are co-extruded to form the structure of polyester/adhesive/(polyamide)nThe thickness of the multi-layer thin-wall membrane tube is 100-400 mu m, and n is 2-5;
b) rapidly cooling to room temperature after co-extrusion to enable the film tube to be in a highly amorphous state so as to facilitate biaxial stretching;
c) and (3) biaxial stretching: heating the cooled membrane tube to 70-120 ℃, and then stretching in two directions, wherein the stretching ratio is as follows: longitudinal direction 2.5-4.0; transverse: 3.0-4.0; area after stretching: the area before stretching is 10: 1-16: 1;
d) and (3) heat treatment: flattening the stretched film tube by a drawing roller, and annealing heat treatment by adopting a flat plate heating method under the condition of keeping longitudinal and transverse tension, wherein the heat treatment temperature is 80-230 ℃;
e) and rolling: and cutting and rolling the film after heat treatment after cooling to obtain a finished product.
The method comprises the following steps of controlling the formula to be 10-20% of polyester, 10-15% of binder and 65-80% of polyamide; wherein, polyester is used as a corrosion-resistant surface layer, and a binder is used as an intermediate adhesive layer, and the two raw materials are relatively low in dosage; the polyamide is used as a structural layer and a surface layer which is more suitable for being bonded with the metal barrier layer by aluminum platinum, the using amount is relatively large, the polyamide layering, the polyester and the bonding agent are subjected to multi-layer co-extrusion film tube and then subjected to biaxial stretching, the balance of the orientation of the macromolecular chain can achieve the balance of the mechanical strength in two directions, the orientation proportion of the two directions can be easily adjusted, and the good cold stamping performance can be kept. And the polyamide is more flexibly adjusted during layered coextrusion, so that the aim of adjusting the final performance is more conveniently realized.
In addition, in the conventional production process, after the stretching ratio is too large, the material rebounds after the stretching is finished, so that in the conventional production process of the film tube method, the longitudinal stretching ratio and the transverse stretching ratio are generally controlled within 3.0, and the total area ratio is controlled within 9: within 1; the film needs to be fully stretched to meet the performance requirements of the lithium ion battery packaging material, and the stretching ratio is usually 10:1 or more, so that the conventional film tube production method cannot be realized. Therefore, the method adopts the subsequent heat treatment step, and the stretched film is subjected to heat treatment under the tension to eliminate the internal stress, so that the film is shaped, the material rebound is avoided, and the film performance is effectively improved.
In the step a, the specific process of the multilayer co-extruded film tube comprises the following steps: the raw materials of polyester, adhesive and polyamide are distributed and added into a plurality of extruders (specifically, one polyester, one adhesive and n polyamides) and are respectively supplied with different molten material flows after being melted at high temperature, the molten material flows are converged in a die head, a thin-wall tube blank with a multi-layer structure and a closed end is manufactured through an annular die, and then compressed air is introduced to blow the thin-wall tube blank to the required thickness.
Preferably, in step a, n ═ 3, i.e. the polyamide is coextruded in three layers with polyester and binder, the multilayer structure of the coextruded film tube being arranged polyester/binder/polyamide.
Preferably, the polyester is one of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) and polybutylene naphthalate (PBN), or a mixture of two or more polyesters.
Preferably, the binder is one or more of modified polyolefin, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate polymer (EEA) and ethylene-maleic anhydride copolymer (EMA).
Preferably, each layer of polyamide is independently selected from one or more than two of nylon 6, nylon 66, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6, 66-nylon 12 copolymer, nylon MXD, aromatic polyamide, polyamide imide, aromatic polyimide, polyether imide, polymaleimide and polyaminobismaleimide.
In some preferred embodiments of the present invention, the polyester is polyethylene terephthalate, the binder is ethylene-maleic anhydride copolymer, and the polyamide is nylon 6.
Preferably, in step c, the heating method is water heating, hot air heating or infrared heating.
Preferably, in step c, the biaxial stretching process is as follows: heating the cooled membrane tube to a temperature above the glass transition temperature; then longitudinal stretching is carried out, and meanwhile, compressed air is used for carrying out transverse blowing to complete transverse stretching.
Preferably, in step c, the area after stretching: the area before stretching is 13:1 to 16: 1.
Preferably, in the step d, the heat treatment can be performed in two steps, after the biaxially oriented film tube is flattened by a drawing roll, the film tube is heated to 80-180 ℃ to perform pre-annealing treatment under the condition of keeping longitudinal and transverse tension, so that the internal stress of the film is eliminated, the film is prevented from shrinking, and the pre-shrinking phenomenon of the film is eliminated; then further heating to 100-230 ℃ for annealing treatment, recrystallizing the film, eliminating the tissue defect and effectively improving the mechanical property of the film.
Preferably, the thickness of the membrane tube prepared in step a is 150-300 μm.
Preferably, the thickness of the finished film obtained in step e is 10-50 μm.
The invention also aims to provide an aluminum-plastic composite film, which comprises an outer layer, an intermediate layer and an inner layer, wherein the outer layer is adhered to the intermediate layer through an adhesive, and the intermediate layer is adhered to the inner layer through an adhesive; the high-impact-resistance biaxially oriented polyester/polyamide film is characterized in that the outer layer is the high-impact-resistance biaxially oriented polyester/polyamide film, the middle layer is an aluminum foil film, and the inner layer is a polypropylene film. The aluminum-plastic composite film has better mechanical property, is not easy to generate interlayer peeling, and can be used as an outer packaging material of a battery.
The positive progress effects of the invention are as follows:
the method comprises the following steps of controlling the formula to be 10-20% of polyester, 10-15% of binder and 65-80% of polyamide; the polyester is used as a corrosion-resistant surface layer, so that moisture absorption of the film can be effectively avoided, and the corrosion resistance of the film is improved. The polyamide is used as a structural layer and a surface layer which is more suitable for being bonded with the metal barrier layer by aluminum platinum, the using amount is relatively large, the polyamide layering, the polyester and the bonding agent are subjected to multi-layer co-extrusion film tube and then subjected to biaxial stretching, the orientation of the macromolecular chains is balanced to achieve the balance of the mechanical strength in two directions, the orientation proportion of the two directions is easy to adjust, and good cold stamping performance can be kept. And the polyamide is more flexibly adjusted during layered coextrusion, so that the aim of adjusting the final performance is more conveniently realized.
The invention adopts the subsequent heat treatment step, and the stretched film is subjected to heat treatment under the tension to eliminate the internal stress, and is shaped, so that the material springback is avoided, and the performance of the film is effectively improved.
In conclusion, the high-impact-resistance biaxially oriented polyester/polyamide film disclosed by the invention is excellent in corrosion resistance and cold stamping formability, and is suitable for outer layer materials required by new energy automobile battery packaging application.
Detailed Description
The following series of specific examples are given to further illustrate the present invention, but the present invention is not limited to these specific examples, and any modification of the present invention that would be obvious to those skilled in the art to achieve similar results would also be included in the present invention.
Examples 1 to 7
First, film formula
The raw materials and weight ratios of the raw materials of examples 1 to 7 are shown in Table 1. Wherein the polyester in the embodiments 1-5 is preferably polyethylene terephthalate (PET); the binder is preferably ethylene-maleic anhydride copolymer (EMA); the polyamide is preferably nylon 6. Examples 6 and 7 were adjusted for the type of starting material as compared to example 5.
Secondly, the preparation step
a) Multilayer coextruded film tube: melting raw materials at high temperature through a plurality of extruders (one polyester, one binder and three polyamides) according to a formula, supplying molten material flows in five layers according to the arrangement of the polyester/binder/polyamide, converging the molten material flows in a die head, forming a multi-layer thin-wall tube blank with a closed end part and a structure of the polyester/binder/polyamide through an annular die, and introducing compressed air to blow the tube blank to a film tube with the required thickness, wherein the thickness of the film tube is 100-400 mu m;
b) rapidly cooling to room temperature after co-extrusion to enable the film tube to be in a highly random and amorphous state so as to facilitate biaxial stretching;
c) and (3) biaxial stretching: heating the cooled membrane tube to 70-120 ℃, and then stretching in two directions, wherein the stretching ratio is as follows: longitudinal direction 2.5-4.0; transverse: 3.0-4.0;
d) and (3) heat treatment: flattening the stretched film tube by a drawing roller, and carrying out annealing heat treatment in a flat plate heating mode under the condition of keeping longitudinal and transverse tension, wherein the heat treatment temperature is 80-230 ℃;
e) and rolling: and cooling the film after the heat treatment, cutting and rolling to obtain a finished product.
The raw material formulas and process parameters of examples 1 to 7 are specifically shown in table 1.
TABLE 1 raw material formulations and Process parameters for examples 1-7
Figure BDA0001812056340000041
Figure BDA0001812056340000051
Comparative examples 1 to 5
The raw material formulas and process parameters of comparative examples 1 to 4 are shown in table 2, and example 5 is used as a comparison object, except that:
comparative example 1 the starting material used was pure polyamide, otherwise the same as in example 5;
comparative example 2 the starting material used was pure polyester, as in example 5;
comparative example 3 the starting material was the same as in example 5, and the temperature was 240 ℃ during the heat treatment in step d; the rest of the procedure was the same as in example 5;
comparative example 4 the starting material was the same as in example 5 and was cooled directly to room temperature without heat treatment in step d; the rest of the procedure was the same as in example 5;
comparative example 5 a coextruded film was made by casting and biaxial stretching processes, the raw materials, preparation steps and process parameters refer to example 2 of patent CN 107825794A.
TABLE 2 raw material formulation and Process parameters for comparative examples 1-5
Figure BDA0001812056340000052
The films prepared in examples 1 to 7 and comparative examples 1 to 5 were subjected to performance tests, and the results are shown in tables 3 and 4.
TABLE 3 film Performance parameters for examples 1-7
Figure BDA0001812056340000061
TABLE 4 film Performance parameters for comparative examples 1-5
Figure BDA0001812056340000062
Note 1: cold stamping test conditions: firstly, sample size: 10mm by 20 mm; secondly, setting parameters of the punching machine: the pressure is 0.2-0.6MPa, the speed is 20-40mm/s, and the pressure maintaining time is 2-3 s.
Note 2: the corrosion resistance test method comprises the following steps: the films of the examples and the comparative examples were dropped with 1mL of electrolyte on the surface, and left at room temperature for 24h, the electrolyte was composed of Ethylene Carbonate (EC): diethyl carbonate (DEC), dimethyl carbonate (DMC) ═ 1 wt%: 1 wt%: 1 wt%, LiPF 61 mol/L (same method as patent CN 107825794A).
As shown in tables 3 and 4, the high-impact biaxially oriented polyester-polyamide film prepared by the method disclosed by the invention has the advantages of good elongation, toughness and tensile strength, small difference between transverse and longitudinal mechanical properties, excellent corrosion resistance and cold stamping formability, a stamping depth as high as 3-4 mm, greatly improved composite property, capability of being well compounded with a metal barrier layer, avoidance of interlayer peeling phenomenon and suitability for an outer layer material required by new energy automobile battery packaging application. This type of film is more suitable for use in batteries for power vehicles.
And the raw material of the comparative example 1 only adopts polyamide, so the corrosion resistance is poor. Comparative example 2 only polyester was used as a raw material, and cold press formability was poor. Comparative example 3 is too high in heat treatment temperature after stretching, while comparative example 4 is not heat treated after stretching, and the elongation, toughness and tensile strength are greatly influenced, while the proposal of patent CN107825794A is referred to in comparative example 5, although the co-extruded film prepared by casting and biaxial stretching processes has good elongation, toughness and tensile strength and corrosion resistance, the difference between the longitudinal mechanical strength and the transverse mechanical strength, especially the elongation at break is large, and the peeling phenomenon is easy to occur when the co-extruded film is compounded with other materials. As can be seen from Table 4, the punching depths of the comparative examples 1 to 5 all fail to reach 3mm, the cold punching formability is not high, and the composite performance of the metal barrier layer and the metal barrier layer is greatly reduced.
While the preferred embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that the invention is not limited thereto, and that various changes and modifications may be made without departing from the spirit of the invention, and the scope of the appended claims is to be accorded the full range of equivalents.

Claims (6)

1. A preparation method of a high-impact-resistance biaxially oriented polyester/polyamide film is characterized by comprising the following steps:
a) multilayer coextruded film tube: respectively melting 20% of polyester, 15% of adhesive and 65% of polyamide by weight through a plurality of extruders, and then co-extruding a multi-layer thin-wall film tube with a structure of polyester/adhesive/(polyamide) n, wherein the thickness of the film tube is 100-400 mu m;
in step a, n =3, i.e. the polyamide is coextruded with the polyester and the binder in three layers, the multilayer structure of the coextruded film tube being arranged polyester/binder/polyamide;
b) rapidly cooling to room temperature after co-extrusion to enable the co-extruded film tube to be in a highly amorphous state so as to facilitate biaxial stretching;
c) and (3) biaxial stretching: heating the cooled membrane tube to 70-120 ℃, and then stretching in two directions, wherein the stretching ratio is as follows: longitudinal direction 2.5-4.0; transverse: 3.0-4.0; area after stretching: the area before stretching is 10: 1-16: 1;
d) and (3) heat treatment: flattening the stretched film tube by a drawing roller, and annealing heat treatment by adopting a flat plate heating method under the condition of keeping longitudinal and transverse tension, wherein the heat treatment temperature is 80-230 ℃;
e) and rolling: cutting and rolling the film after heat treatment after cooling to obtain a finished product;
the polyester is one or more than two of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polybutylene naphthalate;
the binder is one or more than two of modified polyolefin, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate polymer and ethylene-maleic anhydride copolymer;
each layer of polyamide is independently selected from one or more of nylon 6, nylon 66, nylon 11, nylon 12, nylon 610 and nylon 612.
2. The method of claim 1 wherein the polyester is polyethylene terephthalate, the binder is ethylene-maleic anhydride copolymer, and the polyamide is nylon 6.
3. The method of claim 1, wherein the heating in step c is water heating, hot air heating or infrared heating.
4. The method of claim 1, wherein in step c, the area after stretching is: the area before stretching is 13:1 to 16: 1.
5. A high impact biaxially oriented polyester/polyamide film produced by the process as claimed in any one of claims 1 to 4.
6. An aluminum-plastic composite film comprises an outer layer, an intermediate layer and an inner layer, wherein the outer layer is adhered to the intermediate layer through an adhesive, and the intermediate layer is adhered to the inner layer through an adhesive; characterized in that the outer layer is the high impact biaxial stretching polyester/polyamide film as claimed in claim 5, the middle layer is an aluminum foil film, and the inner layer is a polypropylene film.
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