A bidirectional stretched polyamide film for power battery and a preparation method thereof

Abstract

The application relates to the technical field of film packaging, and particularly discloses a bidirectional-stretching polyamide film for power batteries, which comprises, from top to bottom, an upper surface layer, a middle layer and a lower surface layer; the upper surface layer comprises, in terms of mass fraction, 1-10 parts of anti-sticking master batches, 5-40 parts of nylon copolymer A and 50-94 parts of nylon copolymer B; the middle layer comprises, in terms of mass fraction, 5-40 parts of nylon copolymer B and 60-95 parts of nylon copolymer C; and the lower surface layer comprises, in terms of mass fraction, 1-10 parts of anti-sticking master batches, 5-40 parts of nylon copolymer A and 50-94 parts of nylon copolymer B. The bidirectional-stretching polyamide film has a thickness of 10-30 microns, the upper surface layer and the lower surface layer have a thickness of 1-4 microns, and the middle layer has a thickness of 2-28 microns. The bidirectional-stretching polyamide film prepared by the application has excellent comprehensive performance, good punching depth and toughness, is easy to process, has simple production process, high production efficiency and easy industrialization, and can be widely used in the packaging field of power battery aluminum-plastic composite films.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thin film packaging, in particular to a biaxially oriented polyamide film for power battery and a preparation method thereof. BACKGROUND

[0002] The biaxially oriented polyamide film is also called biaxially oriented nylon film, namely BOPA film. It is widely used in various packaging fields of food, daily necessities, electronic products, medical products and the like, and occupies a pivotal position, because it has excellent mechanical properties, gas barrier property, electrical insulation, optical performance, easy printing, oil resistance, chemical solvent resistance and wide temperature use range. In the application of electronic products, lithium ion power battery is praised as the "green chemical energy" of the 21st century, and is widely used in 3C consumer electronics, power battery, energy storage and many other fields. As a key material of soft-pack lithium ion battery, the aluminum-plastic film has very high scientific and technological content, and the performance of the aluminum-plastic film directly determines the quality of the lithium ion battery.

[0003] The aluminum-plastic film can be roughly divided into three layers: the inner layer is a heat sealing layer, generally using polypropylene material, the middle layer is an aluminum foil, which can prevent the penetration of water vapor from the outside of the battery and the leakage of the internal electrolyte; the outer layer is a protective layer, which is mostly made of nylon material, has strong mechanical properties and toughness, prevents damage to the battery by external force, and protects the battery. The development and research of high-quality aluminum-plastic film is the key to the successful development of soft-pack lithium ion battery, which is an indispensable important component of soft-pack lithium ion battery. At present, two processes, hot method and dry method, are mainly used to prepare composite aluminum-plastic film. The hot method composite process refers to hot melt adhesive as the binder to hot composite the aluminum foil and the heat sealing layer CPP film material. The advantage is that the product has good weather resistance, no need to use a large amount of organic solvent in the production process, more environmentally friendly, and more suitable for large-scale continuous production. However, the traditional hot method composite process needs high-temperature hot pressing and bonding, which causes damage to the flexibility of the substrate, and needs high-temperature curing storage, which consumes time and energy. As one of the most critical materials of aluminum-plastic film, biaxially oriented polyamide film is self-evident in importance. The current domestic technology is not mature, and the core technology is mainly controlled by Japan. Not only is the price expensive, but also it is often subject to neck.

[0004] Therefore, it is a technical problem to be solved to provide a biaxially oriented polyamide film for power battery, which has simple production process, is environmentally friendly and energy-saving, and has excellent performance. SUMMARY

[0005] The present application aims to overcome the defects existing in the prior art, and provides a bidirectional stretching polyamide film for power batteries and a preparation method thereof.

[0006] To achieve the above object, one of the technical solutions of the present application is:

[0007] A bidirectional stretching polyamide film for power batteries, comprising a three-layer structure, sequentially comprising an upper surface layer, a middle layer and a lower surface layer from top to bottom, the upper surface layer comprises 1-10 parts by mass of anti-sticking masterbatch, 5-40 parts by mass of nylon copolymer A and 50-94 parts by mass of nylon copolymer B, the middle layer comprises 5-40 parts by mass of nylon copolymer B and 60-95 parts by mass of nylon copolymer C, and the lower surface layer comprises 1-10 parts by mass of anti-sticking masterbatch, 5-40 parts by mass of nylon copolymer A and 50-94 parts by mass of nylon copolymer B.

[0008] Further, the nylon copolymer A is obtained by polymerization of caprolactam monomer, omega-undecyl amino acid, pure water, catalyst and capping agent.

[0009] Further, the caprolactam monomer, omega-undecyl amino acid, pure water, catalyst and capping agent are 10-94 parts by mass, 10-80 parts by mass, 10-60 parts by mass, 0.5-5 parts by mass and 0.5-5 parts by mass, respectively.

[0010] Further, the catalyst is benzoic acid, and the capping agent is adipic acid.

[0011] Further, the nylon copolymer B is obtained by polymerization of adipic acid, hexamethylene diamine, polyether, pure water and catalyst.

[0012] Further, the adipic acid, hexamethylene diamine, polyether, pure water and catalyst are 10-50 parts by mass, 10-50 parts by mass, 10-90 parts by mass, 1-50 parts by mass and 0.1-5 parts by mass, respectively.

[0013] Further, the polyether is a double-end amino polyether, and the catalyst is sodium hypophosphite.

[0014] Further, the nylon copolymer C is obtained by polymerization of polyamide hard segment, polyether amine soft segment, pure water and catalyst.

[0015] Further, the polyamide hard segment, polyether amine soft segment, pure water and catalyst are 10-80 parts by mass, 10-70 parts by mass, 1-50 parts by mass and 0.1-5 parts by mass, respectively.

[0016] Still further, the polyamide hard segment is a polyamide 6-66 copolymer salt, the polyether amine soft segment is shown below, and the catalyst is benzoic acid.

[0017]

[0018] Further, the nylon copolymer A is prepared by the following method:

[0019] Step 1: Put caprolactam monomer, omega-undecyl amino acid, pure water, catalyst, and end-capping agent into a high-pressure reactor, vacuumize for 5-200 minutes, introduce nitrogen for 5-60 minutes, and circulate 1-10 times to ensure that the components are under nitrogen protection, and control the pressure in the high-pressure reactor to be maintained at 0.1-2.5 MPa;

[0020] Step 2: Heat the high-pressure reactor to 220-290°C, and at the same time, start stirring at a speed of 30-150 r / min, and keep the temperature and pressure under the above conditions for 2-20 hours, then release the gas to reduce the pressure to normal pressure, and at the same time, reduce the temperature to 30-100°C;

[0021] Step 3: Discharge the material and cut it into particles by casting and granulating, and then dry it at 80-130°C to obtain the desired nylon copolymer A.

[0022] Further, the nylon copolymer B is prepared by the following method:

[0023] Step 1: Put adipic acid, hexamethylene diamine, polyether, pure water, and catalyst into a high-pressure reactor, vacuumize for 10-120 minutes, introduce nitrogen for 5-40 minutes, and circulate 3-10 times to ensure that the components are under nitrogen protection, and control the pressure in the high-pressure reactor to be maintained at 0.1-1.5 MPa;

[0024] Step 2: Heat the high-pressure reactor to 200-265°C, and at the same time, start stirring at a speed of 30-150 r / min, and keep the temperature and pressure under the above conditions for 2-24 hours, then release the gas to reduce the pressure to normal pressure, and at the same time, reduce the temperature to 30-100°C;

[0025] Step 3: Discharge the material and cut it into particles by casting and granulating, and then dry it at 80-150°C to obtain the desired nylon copolymer B.

[0026] Further, the nylon copolymer C is prepared by the following method:

[0027] First step: Put polyamide hard segment, polyether amine soft segment, pure water and catalyst into high-pressure reactor, vacuum for 20-120 minutes, introduce nitrogen for 5-60 minutes, and circulate 2-10 times, ensure that each component is under nitrogen protection condition, and control the pressure in the high-pressure reactor to maintain at 0.1-2MPa;

[0028] Second step: Mix and stir at 60-80℃ for 0.5-2 hours, and the stirring speed is controlled at 30-150r / min.

[0029] Third step: Further stir at a temperature of 140-220℃ for 1-6 hours, and the stirring speed is controlled at 20-120r / min, then slowly release the small molecular products in the system;

[0030] Fourth step: Increase the temperature of the high-pressure reactor to 180-260℃, and the pressure is kept below 1kPa, and further react for 2-24 hours;

[0031] Fifth step: Release the pressure to normal pressure, and reduce the temperature to 30-100℃.

[0032] Sixth step: Cut the material into particles through belt casting, and dry at 80-120℃ to obtain the required nylon copolymer C.

[0033] Further, the anti-sticking master batch comprises 1-10 parts of a lubricant, 2-15 parts of an anti-sticking agent and 75-97 parts of the nylon copolymer A by mass fraction, and the anti-sticking master batch is obtained by melting extrusion, drawing, cooling, particle cutting and drying of the anti-sticking master batch through a double-screw extruder at a temperature of 230-270℃.

[0034] Further, the lubricant is selected from one or a combination of several of erucic acid amide, PE wax and ethylene bis-stearamide, and the anti-sticking agent is selected from one or a combination of several of talc, silicon dioxide, calcium carbonate, kaolin and diatomite.

[0035] Further, the thickness of the biaxially stretched polyamide film is 10-30μm; wherein the thickness of the upper and lower surface layers is 1-4μm; and the thickness of the intermediate layer is 2-28μm.

[0036] In order to achieve the above purpose, the second technical scheme of the present application is:

[0037] A preparation method of a biaxially stretched polyamide film for power battery, comprising the following steps:

[0038] S1: Dry all raw materials, and control the moisture content of the raw materials to be below 600ppm;

[0039] S2: the raw materials of the upper layer, the middle layer and the lower layer are mixed according to the formula proportion respectively, and then are extruded by the respective extruders at the temperature of 230-280 DEG C, and are discharged through the clothes hanger type die;

[0040] S3: the melt is attached on the cold drum by the low pressure air knife to form a thick sheet, wherein the thickness of the thick sheet is 100-350 mu m, and the temperature of the cold drum is 10-30 DEG C;

[0041] S4: the thick sheet is preheated, is stretched in the longitudinal direction at the temperature of 45-68 DEG C, and then is cooled after being shaped, and the stretching ratio of the longitudinal stretching is 2.5-3.8 times;

[0042] S5: the film after the longitudinal stretching is sent into the transverse stretching machine, the preheating temperature is 60-90 DEG C, the stretching temperature is 70-155 DEG C, and the stretching ratio is 3.0-4.5 times;

[0043] S6: the film after the stretching is subjected to heat setting treatment, wherein the setting temperature is 185-221 DEG C, the setting time is 1-60 s, and then the film is cooled and is subjected to the corona treatment, and the power of the corona treatment is 5-18 Wmin / m 2 , and is wound up;

[0044] S7: the biaxially stretched polyamide film after being wound up is cut according to the requirement, and finally the biaxially stretched polyamide film for the power battery is obtained, and the thickness of the film is 10-30 mu m.

[0045] Compared with the prior art, the beneficial effects of the present application are that:

[0046] 1. the polyamide 6-66 copolymer salt in the nylon copolymer C of the present application is used as the hard segment, the polyether amine is used as the soft segment, the soft segment has the elasticity of rubber, and the hydrogen chain and the crystalline micro area formed by the block polyamide hard segment can realize physical crosslinking, so that it can be melt processed at a certain temperature, and it shows elasticity below the melting temperature, so that the addition of the substance can improve the toughness of the product and improve the depth of the film;

[0047] 2. the omega-undecyl amino acid component in the nylon copolymer A of the present application exists in a large number of non-polar methylene groups, the existence of the groups greatly enhances the flexibility of the molecular chain of the nylon copolymer A, and the toughness is good;

[0048] 3. the addition of the omega-undecyl amino acid component in the nylon copolymer A of the present application increases the proportion of methylene groups in the molecule, greatly reduces the influence of the hydrophilic group, and thus overcomes the shortcomings of ordinary polyamide 6, such as large water absorption, poor dimensional stability and difficult to guarantee the mechanical properties, so as to ensure the optimization of the film performance;

[0049] 4. The structure of the nylon copolymer B in the application is similar to that of the nylon copolymer C, which is a copolymer composed of soft segments and hard segments, and is helpful to the improvement of the toughness of the film;

[0050] 5. The three kinds of nylon copolymers used in the application are used for film toughening, and the nylon copolymers have excellent compatibility with the nylon system, avoiding the problem of poor film toughening effect caused by dispersion or agglomeration between different components, and the nylon copolymers themselves have the advantages of high temperature resistance, friction resistance, good dimensional stability, anti-creep stability, low moisture absorption, good softness, high elastic recovery rate; especially in a low temperature environment of-40.0~0℃, the impact strength and flexibility remain unchanged, and excellent low temperature toughening effect is achieved; under relatively low stress, the nylon copolymer has better tensile stress compared with high molecular products with the same hardness, so the thickness of the product can be thinned, and it is especially suitable for the toughening modification of ultra-thin polyamide film products; various nylon copolymers realize the optimization of performance and cost through the complementation of properties;

[0051] 6. The biaxially stretched polyamide film prepared in the application has low moisture absorption performance due to the low moisture absorption performance of the two surface layer materials, and the design of the two surface layers can significantly reduce the moisture absorption performance of the film, while protecting the moisture absorption of the middle layer. Through this design, the cost of the film can also be reduced;

[0052] 7. The biaxially stretched polyamide film prepared in the application has excellent comprehensive performance, good impact depth and toughness, and is easy to process, has simple production process, high production efficiency, and is easy to realize industrialization; can be widely used in the packaging field of power battery aluminum-plastic composite film, and has good market application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description.

[0054] Figure 1 The structure of the biaxially stretched polyamide film for power battery in the application is shown in the figure;

[0055] In the figure: 10 is the lower surface layer, 20 is the middle layer, and 30 is the upper surface layer. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical scheme and advantages of the application more clear and obvious, the following will describe the application in more detail in combination with the drawings and specific embodiments, but the protection scope of the application is not limited to these embodiments. The same reference signs in the text always represent the same elements, and similar reference signs represent similar elements.

[0057] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "horizontal", "vertical", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the perspective view in the drawings, only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation on the present application.

[0058] A bidirectional stretch polyamide film for power battery, comprising a three-layer structure, from top to bottom comprising an upper surface layer, an intermediate layer and a lower surface layer in turn, the components of the upper surface layer comprise 1-10 parts of anti-sticking master batch, 5-40 parts of nylon copolymer A, 50-94 parts of nylon copolymer B by mass fraction, the components of the intermediate layer comprise 5-40 parts of nylon copolymer B, 60-95 parts of nylon copolymer C by mass fraction, the components of the lower surface layer comprise 1-10 parts of anti-sticking master batch, 5-40 parts of nylon copolymer A, 50-94 parts of nylon copolymer B by mass fraction.

[0059] The nylon copolymer A is obtained by polymerization reaction of caprolactam monomer, omega-undecyl amino acid, pure water, catalyst and end-capping agent.

[0060] The caprolactam monomer, omega-undecyl amino acid, pure water, catalyst and end-capping agent are 10-94 parts, 10-80 parts, 10-60 parts, 0.5-5 parts and 0.5-5 parts respectively by mass fraction.

[0061] The catalyst is benzoic acid, and the end-capping agent is adipic acid.

[0062] The nylon copolymer B is obtained by polymerization reaction of adipic acid, hexamethylene diamine, polyether, pure water and catalyst.

[0063] The adipic acid, hexamethylene diamine, polyether, pure water and catalyst are 10-50 parts, 10-50 parts, 10-90 parts, 1-50 parts and 0.1-5 parts respectively by mass fraction.

[0064] The polyether is a double-end amino polyether, and the catalyst is sodium hypophosphite.

[0065] The nylon copolymer C is obtained by polymerization reaction of polyamide hard segment, polyether amine soft segment, pure water and catalyst.

[0066] The polyamide hard segment, polyether amine soft segment, pure water and catalyst are 10-80 parts, 10-70 parts, 1-50 parts and 0.1-5 parts respectively by mass fraction.

[0067] The polyamide hard segment is a polyamide 6-66 copolymer salt, the polyether amine soft segment is shown below, and the catalyst is benzoic acid.

[0068]

[0069] The preparation method of the nylon copolymer A is as follows:

[0070] First step: the caprolactam monomer, omega-undecyl amino acid, pure water, catalyst, and end-capping agent are added into a high-pressure reaction kettle, vacuum is drawn for 5-200 minutes, nitrogen is introduced for 5-60 minutes, and circulation is performed for 1-10 times, so as to ensure that the components are in nitrogen protection condition, and the pressure in the high-pressure reaction kettle is controlled to be maintained at 0.1-2.5 MPa;

[0071] Second step: the high-pressure reaction kettle is heated to 220-290 ℃, and stirring is started at the same time, the stirring speed is controlled to be 30-150 r / min, and the temperature is reduced to 30-100 ℃ under the condition of heat preservation and pressure maintenance reaction for 2-20 hours.

[0072] Third step: the material is discharged and cut into particles through belt casting, and dried at 80-130 ℃ to obtain the required nylon copolymer A.

[0073] The preparation method of the nylon copolymer B is as follows:

[0074] First step: adipic acid, hexamethylene diamine, polyether, pure water, and a catalyst are added into a high-pressure reaction kettle, vacuum is drawn for 10-120 minutes, nitrogen is introduced for 5-40 minutes, and circulation is performed for 3-10 times, so as to ensure that the components are in nitrogen protection condition, and the pressure in the high-pressure reaction kettle is controlled to be maintained at 0.1-1.5 MPa;

[0075] Second step: the high-pressure reaction kettle is heated to 200-265 ℃, and stirring is started at the same time, the stirring speed is controlled to be 30-150 r / min, and the temperature is reduced to 30-100 ℃ under the condition of heat preservation and pressure maintenance reaction for 2-24 hours.

[0076] Third step: the material is discharged and cut into particles through belt casting, and dried at 80-150 ℃ to obtain the required nylon copolymer B.

[0077] The preparation method of the nylon copolymer C is as follows:

[0078] First step: the polyamide hard segment, the polyether amine soft segment, pure water, and a catalyst are put into a high-pressure reaction kettle, vacuum is drawn for 20-120 minutes, nitrogen is introduced for 5-60 minutes, and circulation is performed for 2-10 times, so as to ensure that the components are in nitrogen protection condition, and the pressure in the high-pressure reaction kettle is controlled to be maintained at 0.1-2 MPa;

[0079] Second step: mixing and stirring at 60-80℃ for 0.5-2 hours, with stirring speed controlled at 30-150r / min.

[0080] Third step: further stirring at 140-220℃ for 1-6 hours, with stirring speed controlled at 20-120r / min, and then slowly releasing small molecule products in the system;

[0081] Fourth step: heating the high-pressure reactor to 180-260℃, keeping the pressure below 1kPa, and further reacting for 2-24 hours;

[0082] Fifth step: releasing the pressure to normal pressure, and reducing the temperature to 30-100℃.

[0083] Sixth step: casting and granulating the material, and drying at 80-120℃ to obtain the desired nylon copolymer C.

[0084] The anti-sticking master batch comprises 1-10 parts of a lubricant, 2-15 parts of an anti-sticking agent, and 75-97 parts of the nylon copolymer A by mass fraction, and is obtained by melt extrusion, drawing, cooling, granulation, and drying of the anti-sticking master batch through a double-screw extruder at a temperature of 230-270℃.

[0085] The lubricant is selected from one or a combination of several of erucic acid amide, PE wax, and ethylene bis-stearamide, and the anti-sticking agent is selected from one or a combination of several of talc, silicon dioxide, calcium carbonate, kaolin, and diatomite.

[0086] The biaxially stretched polyamide film has a thickness of 10-30μm, wherein the upper and lower surface layers have a thickness of 1-4μm, and the intermediate layer has a thickness of 2-28μm.

[0087] A preparation method of a biaxially stretched polyamide film for power batteries, comprising the following steps:

[0088] S1: drying all raw materials, and controlling the water content of the raw materials to be below 600ppm;

[0089] S2: mixing the raw materials of the upper surface layer, the intermediate layer, and the lower surface layer according to the formula proportion, and then melt plasticizing and extruding through respective extruders at a temperature of 230-280℃, and flowing out through a clothes hanger type die;

[0090] S3: using a low-pressure air knife to attach the melt to a cold drum to form a thick sheet, wherein the thickness of the thick sheet is 100-350μm, and the temperature of the cold drum is 10-30℃;

[0091] S4: preheating the thick sheet, longitudinally stretching at a temperature of 45-68℃, and then performing shaping and cooling, and the stretching ratio of the longitudinal stretching is 2.5-3.8 times.

[0092] S5: the longitudinally stretched film is sent into a transverse stretching machine, the preheating temperature is 60-90℃, the stretching temperature is 70-155℃, and the stretching ratio is 3.0-4.5 times;

[0093] S6: the stretched film is subjected to heat setting treatment, wherein the setting temperature is 185-221℃, the setting time is 1-60s, then the film is cooled and subjected to corona treatment, and the power of the corona treatment is 5-18Wmin / m 2 and is wound up;

[0094] S7: the wound biaxially stretched polyamide film is cut according to requirements, and finally a biaxially stretched polyamide film for power battery is obtained, the thickness of the film is 10-30μm.

[0095] Example 1

[0096] A biaxially stretched polyamide film for power battery comprises a three-layer structure, from top to bottom, an upper surface layer, a middle layer and a lower surface layer. The upper surface layer comprises 5 parts of anti-sticking master batch, 25 parts of nylon copolymer A and 70 parts of nylon copolymer B by mass fraction. The middle layer comprises 20 parts of nylon copolymer B and 80 parts of nylon copolymer C. The lower surface layer comprises 5 parts of anti-sticking master batch, 25 parts of nylon copolymer A and 70 parts of nylon copolymer B. The nylon copolymer A is obtained by polymerization of caprolactam monomer, ω-undecyl amino acid, pure water, catalyst and blocking agent, and the components are caprolactam monomer 60 parts, ω-undecyl amino acid 40 parts, pure water 30 parts, catalyst 15 parts and blocking agent 0.8 parts by mass fraction. The catalyst is benzoic acid, and the blocking agent is adipic acid. The nylon copolymer B is obtained by polymerization of adipic acid, hexamethylene diamine, polyether, pure water and catalyst, and the components are adipic acid 20 parts, hexamethylene diamine 20 parts, polyether 60 parts, pure water 30 parts and catalyst 1 part by mass fraction. The polyether is double-end amino polyether, and the catalyst is sodium hypophosphite. The nylon copolymer C is obtained by polymerization of polyamide hard segment, polyether amine soft segment, pure water and catalyst, and the components are polyamide hard segment 50 parts, polyether amine soft segment 50 parts, pure water 20 parts and catalyst 1 part by mass fraction. The polyamide hard segment is polyamide 6-66 copolymer salt, the polyether amine soft segment is shown below, and the catalyst is benzoic acid. The anti-sticking master batch comprises 6 parts of slip agent, 10 parts of anti-sticking agent and 84 parts of nylon copolymer A by mass fraction. The slip agent is selected from ethylene bis-stearamide. The anti-sticking agent is selected from silicon dioxide. The anti-sticking master batch is obtained by melt extrusion, drawing, cooling, granulation and drying of the double-screw extruder at a temperature of 250℃. The thickness of the biaxially stretched polyamide film is 25μm, wherein the thickness of the upper surface layer and the lower surface layer is 2μm, and the thickness of the middle layer is 21μm.

[0097]

[0098] The preparation method of the nylon copolymer A is as follows:

[0099] First step: the caprolactam monomer, omega-undecyl amino acid, pure water, catalyst, end-capping agent are added into the high-pressure reaction kettle, vacuumed for 100 minutes, nitrogen is introduced for 30 minutes, and circulated for 5 times, to ensure that each component is in the nitrogen protection condition, and the pressure in the high-pressure reaction kettle is controlled to maintain 1 MPa;

[0100] Second step: the high-pressure reaction kettle is heated to 260°C, and stirring is started at the same time, and the stirring speed is controlled at 100 r / min, and the pressure is maintained for 10 hours under the condition, and the temperature is reduced to 60°C while the pressure is released to normal pressure;

[0101] Third step: discharge and cut the material into particles through belt casting, and dry at 90°C to obtain the required nylon copolymer A.

[0102] The preparation method of the nylon copolymer B is as follows:

[0103] First step: adipic acid, hexamethylene diamine, polyether, pure water and catalyst are added into the high-pressure reaction kettle, vacuumed for 80 minutes, nitrogen is introduced for 30 minutes, and circulated for 6 times, to ensure that each component is in the nitrogen protection condition, and the pressure in the high-pressure reaction kettle is controlled to maintain 1 MPa;

[0104] Second step: the high-pressure reaction kettle is heated to 235°C, and stirring is started at the same time, and the stirring speed is controlled at 65 r / min, and the pressure is maintained for 18 hours under the condition, and the temperature is reduced to 60°C while the pressure is released to normal pressure;

[0105] Third step: discharge and cut the material into particles through belt casting, and dry at 85°C to obtain the required nylon copolymer B.

[0106] The preparation method of the nylon copolymer C is as follows:

[0107] First step: the polyamide hard segment, polyether amine soft segment, pure water and catalyst are put into the high-pressure reaction kettle, vacuumed for 70 minutes, nitrogen is introduced for 30 minutes, and circulated for 9 times, to ensure that each component is in the nitrogen protection condition, and the pressure in the high-pressure reaction kettle is controlled to maintain 0.8 MPa;

[0108] Second step: mixed and stirred at 65°C for 1 hour, and the stirring speed was controlled at 80 r / min.

[0109] Third step: further stirring at a temperature of 200°C for 5 hours, and the stirring speed was controlled at 100 r / min, and then the small molecular products in the system were slowly released;

[0110] Fourth step: the high pressure reactor is heated to 230℃, the pressure is kept at 0.8kPa, and the reaction is further carried out for 18 hours;

[0111] Fifth step: the pressure is reduced to normal pressure, and the temperature is reduced to 60℃.

[0112] Sixth step: the material is cut into particles through casting belt and dried at 90℃ to obtain the required nylon copolymer C.

[0113] A preparation method of a biaxially stretched polyamide film, comprising the following steps:

[0114] S1: dry all raw materials, and control the moisture content of the raw materials to be below 600ppm;

[0115] S2: mix the raw materials of the upper layer, the middle layer and the lower layer according to the formula proportion respectively, then melt and plasticize and extrude through the respective extruders at a temperature of 255℃, and flow out through a clothes hanger type die;

[0116] S3: use a low-pressure air knife to attach the melt to a cold drum to form a thick sheet, wherein the thickness of the thick sheet is 280μm, and the temperature of the cold drum is 15℃;

[0117] S4: preheat the thick sheet, longitudinally stretch at a temperature of 55℃, then cool and set, and the longitudinal stretching ratio is 2.8 times;

[0118] S5: send the film after longitudinal stretching into a transverse stretching machine, the preheating temperature is 75℃, the stretching temperature is 95℃, and the stretching ratio is 3.9;

[0119] S6: heat set the stretched film, wherein the setting temperature is 202℃, the setting time is 6s, then the film is cooled and treated by corona, and the corona treatment power is 12Wmin / m 2 , and is wound up;

[0120] S7: cut the biaxially stretched polyamide film for power battery after winding according to requirements, and finally obtain the biaxially stretched polyamide film for power battery, and the film thickness is 25μm.

[0121] Example 2

[0122] The application discloses a bidirectional stretching polyamide film for a power battery, which comprises a three-layer structure from top to bottom, namely an upper surface layer, a middle layer and a lower surface layer, wherein the upper surface layer comprises 2 parts of anti-sticking master batch, 10 parts of nylon copolymer A and 88 parts of nylon copolymer B; the middle layer comprises 30 parts of nylon copolymer B and 70 parts of nylon copolymer C; and the lower surface layer comprises 2 parts of anti-sticking master batch, 10 parts of nylon copolymer A and 88 parts of nylon copolymer B. The nylon copolymer A is obtained through polymerization reaction of caprolactam monomer, omega-undecyl amino acid, pure water, a catalyst and a blocking agent, and each component comprises 17 parts of caprolactam monomer, 50 parts of omega-undecyl amino acid, 30 parts of pure water, 2 parts of the catalyst and 1 part of the blocking agent. The catalyst is benzoic acid, and the blocking agent is adipic acid. The nylon copolymer B is obtained through polymerization reaction of adipic acid, hexamethylene diamine, polyether, pure water and a catalyst, and each component comprises 15 parts of adipic acid, 15 parts of hexamethylene diamine, 40 parts of polyether, 29 parts of pure water and 1 part of the catalyst. The polyether is a double-end amino polyether, and the catalyst is sodium hypophosphite. The nylon copolymer C is obtained through polymerization reaction of polyamide hard segment, polyether amine soft segment, pure water and a catalyst, and each component comprises 30 parts of polyamide hard segment, 50 parts of polyether amine soft segment, 19 parts of pure water and 1 part of the catalyst. The polyamide hard segment is a polyamide 6-66 copolymer salt, the polyether amine soft segment is shown in the description, and the catalyst is benzoic acid. The anti-sticking master batch comprises 2 parts of a lubricant, 5 parts of an anti-sticking agent and 93 parts of nylon copolymer A. The lubricant is selected from erucic acid amide. The anti-sticking agent is selected from talc. The anti-sticking master batch is obtained through melt extrusion of a double-screw extruder at a temperature of 235 DEG C, drawing, cooling, granulation and drying. The thickness of the bidirectional stretching polyamide film is 25 microns, wherein the thickness of the upper surface layer and the lower surface layer is 1.5 microns, and the thickness of the middle layer is 22 microns.

[0123]

[0124] The preparation method of the nylon copolymer A is as follows:

[0125] Step 1: the caprolactam monomer, the omega-undecyl amino acid, the pure water, the catalyst and the blocking agent are added into a high-pressure reaction kettle, vacuum is drawn for 10 minutes, nitrogen is introduced for 10 minutes, and circulation is carried out twice, so that the components are ensured to be in the nitrogen protection condition, and the pressure in the high-pressure reaction kettle is controlled to be maintained at 0.5 MPa;

[0126] Step 2: the high-pressure reaction kettle is heated to 230 DEG C, meanwhile, stirring is started, the stirring speed is controlled to be 50 r / min, and under the condition, the pressure is maintained for 8 hours, the temperature is reduced to 90 DEG C, and the pressure is reduced to normal pressure;

[0127] Step 3: the material is discharged and granulated through belt casting, and is dried at 100 DEG C, so that the required nylon copolymer A is obtained.

[0128] The preparation method of the nylon copolymer B is as follows:

[0129] Step 1: Put adipic acid, hexamethylene diamine, polyether, pure water and catalyst into a high-pressure reaction kettle, vacuumize for 15 minutes, introduce nitrogen for 8 minutes and circulate 5 times to ensure that the components are under nitrogen protection and the pressure in the high-pressure reaction kettle is controlled to maintain 0.3 MPa;

[0130] Step 2: Increase the temperature of the high-pressure reaction kettle to 210℃, and start stirring at the same time, with the stirring speed controlled at 120r / min, and keep the temperature and pressure for 23 hours under this condition, then release the pressure to normal pressure, and reduce the temperature to 40℃;

[0131] Step 3: Discharge the material and cut it into particles through belt casting, and dry it at 95℃ to obtain the desired nylon copolymer B.

[0132] The preparation method of the nylon copolymer C is as follows:

[0133] Step 1: Put polyamide hard segment, polyether amine soft segment, pure water and catalyst into a high-pressure reaction kettle, vacuumize for 30 minutes, introduce nitrogen for 10 minutes and circulate 3 times to ensure that the components are under nitrogen protection and the pressure in the high-pressure reaction kettle is controlled to maintain 0.5 MPa;

[0134] Step 2: Mix and stir at 70℃ for 1.5 hours, with the stirring speed controlled at 40r / min.

[0135] Step 3: Further stir at a temperature of 150℃ for 1.5 hours, with the stirring speed controlled at 30r / min, and then slowly release the small molecular products in the system;

[0136] Step 4: Increase the temperature of the high-pressure reaction kettle to 190℃, and keep the pressure at 0.5kPa, and further react for 5 hours;

[0137] Step 5: Release the pressure to normal pressure while reducing the temperature to 40℃.

[0138] Step 6: Cut the material into particles through belt casting, and dry it at 105℃ to obtain the desired nylon copolymer C.

[0139] A preparation method of a biaxially stretched polyamide film, comprising the following steps:

[0140] S1: Dry all raw materials, and control the moisture content of the raw materials to be below 600ppm;

[0141] S2: Mix the raw materials of the upper layer, the middle layer and the lower layer according to the formula proportion respectively, then melt and plasticize through the respective extruders at a temperature of 250℃, and flow out through a clothes hanger type die;

[0142] S3: The melt is adhered to the cold drum to form a thick sheet using a low-pressure air knife, wherein the thickness of the thick sheet is 250 μm, and the temperature of the cold drum is 18°C;

[0143] S4: The thick sheet is preheated, stretched longitudinally at a temperature of 58°C, and then cooled by setting, wherein the stretching ratio of the longitudinal stretching is 2.9 times;

[0144] S5: The film after the longitudinal stretching is sent to a transverse stretching machine, wherein the preheating temperature is 80°C, the stretching temperature is 120°C, and the stretching ratio is 3.7;

[0145] S6: The film after the stretching is subjected to heat setting treatment, wherein the setting temperature is 200°C, and the setting time is 10 s, and then the film is cooled and subjected to a corona treatment, wherein the power of the corona treatment is 10 Wmin / m 2 , and is wound up;

[0146] S7: The wound bidirectional-stretching polyamide film for power batteries is slit according to requirements, and finally the bidirectional-stretching polyamide film for power batteries is obtained, wherein the thickness of the film is 25 μm.

[0147] Example 3

[0148] The application discloses a bidirectional stretching polyamide film for a power battery, which comprises a three-layer structure from top to bottom, namely an upper surface layer, a middle layer and a lower surface layer, wherein the upper surface layer comprises 8 parts of anti-sticking master batch, 38 parts of nylon copolymer A and 54 parts of nylon copolymer B in terms of mass fraction; the middle layer comprises 10 parts of nylon copolymer B and 90 parts of nylon copolymer C; and the lower surface layer comprises 8 parts of anti-sticking master batch, 38 parts of nylon copolymer A and 54 parts of nylon copolymer B. The nylon copolymer A is obtained through polymerization of caprolactam monomer, omega-undecyl amino acid, pure water, a catalyst and a blocking agent, and each component comprises 74 parts of caprolactam monomer, 12 parts of omega-undecyl amino acid, 12 parts of pure water, 1.5 parts of the catalyst and 1 part of the blocking agent in terms of mass fraction. The catalyst is benzoic acid, and the blocking agent is adipic acid. The nylon copolymer B is obtained through polymerization of adipic acid, hexamethylene diamine, polyether, pure water and a catalyst, and each component comprises 25 parts of adipic acid, 25 parts of hexamethylene diamine, 40 parts of polyether, 9.5 parts of pure water and 0.5 parts of the catalyst in terms of mass fraction. The polyether is a double-end amino polyether, and the catalyst is sodium hypophosphite. The nylon copolymer C is obtained through polymerization of polyamide hard segment, polyether amine soft segment, pure water and a catalyst, and each component comprises 40 parts of polyamide hard segment, 40 parts of polyether amine soft segment, 19.5 parts of pure water and 0.5 parts of the catalyst in terms of mass fraction. The polyamide hard segment is a polyamide 6-66 copolymer salt, the polyether amine soft segment is shown in the description, and the catalyst is benzoic acid. The anti-sticking master batch comprises 8 parts of a lubricant, 8 parts of an anti-sticking agent and 84 parts of nylon copolymer A in terms of mass fraction. The lubricant is selected from erucic acid amide. The anti-sticking agent is selected from silicon dioxide. The anti-sticking master batch is obtained through melt extrusion of a double-screw extruder at a temperature of 260 DEG C, drawing, cooling, granulation and drying. The thickness of the bidirectional stretching polyamide film is 25 microns, wherein the thickness of the upper surface layer and the lower surface layer is 2.5 microns, and the thickness of the middle layer is 20 microns.

[0149]

[0150] The preparation method of the nylon copolymer A is as follows:

[0151] Step 1: the caprolactam monomer, the omega-undecyl amino acid, the pure water, the catalyst and the blocking agent are added into a high-pressure reaction kettle, vacuum is drawn for 180 minutes, nitrogen is introduced for 50 minutes, and circulation is carried out for 8 times, so that the components are ensured to be in nitrogen protection condition, and the pressure in the high-pressure reaction kettle is controlled to be maintained at 2 MPa;

[0152] Step 2: the high-pressure reaction kettle is heated to 280 DEG C, meanwhile, stirring is started, the stirring speed is controlled to be 120 r / min, and under the condition, heat preservation and pressure preservation reaction is carried out for 18 hours, air is discharged to reduce the pressure to normal pressure, meanwhile, the temperature is reduced to 35 DEG C;

[0153] Step 3: the material is discharged and cast into a belt for granulation, and then dried at 110 DEG C to obtain the required nylon copolymer A.

[0154] Further, the scheme for the bidirectional stretching polyamide film for power battery, the nylon copolymer B, the preparation method is as follows:

[0155] First step: put adipic acid, hexamethylene diamine, polyether, pure water and catalyst into the high-pressure reaction kettle, vacuumize for 50 minutes, introduce nitrogen for 20 minutes, and circulate 8 times, ensure that each component is in the nitrogen protection condition, and control the pressure in the high-pressure reaction kettle to maintain 1.2MPa;

[0156] Second step: raise the temperature of the high-pressure reaction kettle to 255℃, while starting stirring, control the stirring speed at 35r / min, and keep the temperature and pressure for 6 hours under this condition, release the pressure to normal pressure, and reduce the temperature to 80℃ at the same time;

[0157] Third step: discharge the material and cut it into particles through belt casting, dry it at 100℃ to obtain the required nylon copolymer B.

[0158] The preparation method of the nylon copolymer C is as follows:

[0159] First step: put polyamide hard segment, polyether amine soft segment, pure water and catalyst into the high-pressure reaction kettle, vacuumize for 100 minutes, introduce nitrogen for 50 minutes, and circulate 6 times, ensure that each component is in the nitrogen protection condition, and control the pressure in the high-pressure reaction kettle to maintain 1.2MPa;

[0160] Second step: mix and stir at 75℃ for 1.8 hours, control the stirring speed at 120r / min.

[0161] Third step: further stir at the temperature of 180℃ for 3 hours, control the stirring speed at 80r / min, and then slowly release the small molecular products in the system;

[0162] Fourth step: raise the temperature of the high-pressure reaction kettle to 250℃, keep the pressure at 0.3kPa, and further react for 10 hours;

[0163] Fifth step: release the pressure to normal pressure, and reduce the temperature to 90℃ at the same time.

[0164] Sixth step: cut the material into particles through belt casting, dry it at 90℃ to obtain the required nylon copolymer C.

[0165] A preparation method of a bidirectional stretching polyamide film, comprising the following steps:

[0166] S1: dry all raw materials, control the moisture content of the raw materials to be below 600ppm;

[0167] S2: The raw materials of the upper layer, the middle layer and the lower layer are mixed according to the formula proportion respectively, and then are melt plasticized and extruded through the respective extruders at a temperature of 260℃, and are discharged through a clothes hanger type die;

[0168] S3: The melt is attached to a cold drum to form a thick sheet by using a low-pressure air knife, wherein the thickness of the thick sheet is 300μm, and the temperature of the cold drum is 15℃;

[0169] S4: The thick sheet is preheated, stretched longitudinally at a temperature of 56℃, and then is cooled and shaped, and the stretching ratio of the longitudinal stretching is 3 times;

[0170] S5: The film after the longitudinal stretching is sent to a transverse stretching machine, the preheating temperature is 85℃, the stretching temperature is 125℃, and the stretching ratio is 3.6;

[0171] S6: The stretched film is heat set treated, wherein the setting temperature is 207℃, the setting time is 15s, and then the film is cooled and treated by corona, and the power of the corona treatment is 15Wmin / m 2 , and is wound up;

[0172] S7: The wound bidirectional stretched polyamide film for power battery is cut according to requirements, and finally the bidirectional stretched polyamide film for power battery is obtained, and the thickness of the film is 25μm.

[0173] Comparative Example 1

[0174] A polyamide film includes a three-layer structure, from top to bottom, an upper layer, a middle layer and a lower layer. The upper layer includes 5 parts of anti-sticking master batch, 95 parts of PA6 by mass fraction. The middle layer includes 100 parts of PA6. The lower layer includes 5 parts of anti-sticking master batch, 95 parts of PA6. The anti-sticking master batch includes 6 parts of slip agent, 10 parts of anti-sticking agent and 84 parts of PA6 by mass fraction. The slip agent is selected from ethylene bis-stearamide. The anti-sticking agent is selected from silicon dioxide. The anti-sticking master batch is obtained by melt extrusion, drawing, cooling, granulation and drying of the double screw extruder at a temperature of 250℃. The thickness of the film is 25μm; wherein the thickness of the upper layer and the lower layer is 2μm; the thickness of the middle layer is 21μm.

[0175] A preparation method of a polyamide film is the same as that of Example 1.

[0176] Comparative Example 2

[0177] A kind of polyamide film, including three-layer structure, from top to bottom, upper surface layer, middle layer and lower surface layer, upper surface layer includes 5 parts of anti-adhesion master batch, 95 parts of nylon copolymer B by mass fraction.The middle layer includes 20 parts of nylon copolymer B, 80 parts of nylon copolymer C.The lower surface layer includes 5 parts of anti-adhesion master batch, 95 parts of nylon copolymer B.Nylon copolymer B is obtained by polymerization reaction of adipic acid, hexamethylene diamine, polyether, pure water and catalyst, each component includes 20 parts of adipic acid, 20 parts of hexamethylene diamine, 60 parts of polyether, 30 parts of pure water, 1 part of catalyst by mass fraction.Polyether is double-end amino polyether, and catalyst is sodium hypophosphite.Nylon copolymer C is obtained by polymerization reaction of polyamide hard segment, polyether amine soft segment, pure water and catalyst, each component includes 50 parts of polyamide hard segment, 50 parts of polyether amine soft segment, 20 parts of pure water, 1 part of catalyst by mass fraction.Polyamide hard segment is polyamide 6-66 copolymer salt, polyether amine soft segment is shown as follows, and catalyst is benzoic acid.Anti-adhesion master batch includes 6 parts of slip agent, 10 parts of anti-adhesion agent and 84 parts of PA6 by mass fraction.Slip agent is selected from ethylene bis-stearamide.Anti-adhesion agent is selected from silicon dioxide.Anti-adhesion master batch is obtained by melt extrusion of double-screw extruder at a temperature of 250 DEG C, drawing, cooling, granulating and drying.A biaxially stretched polyamide film has a thickness of 25 μm;Among them, the thickness of the upper surface layer and the lower surface layer is 2 μm;The thickness of the middle layer is 21 μm.

[0178]

[0179] The preparation method of nylon copolymer B is as follows:

[0180] First step: adipic acid, hexamethylene diamine, polyether, pure water and catalyst are added into high-pressure reaction kettle, vacuum is extracted for 80 minutes, nitrogen is introduced for 30 minutes, and circulation is carried out 6 times, to ensure that each component is under nitrogen protection condition, and the pressure in high-pressure reaction kettle is controlled to maintain at 1 MPa;

[0181] Second step: the high-pressure reaction kettle is heated to 235 DEG C, while stirring is started, and the stirring speed is controlled at 65 r / min, and under this condition, the temperature is kept for 18 hours, and the pressure is reduced to normal pressure while the temperature is reduced to 60 DEG C;

[0182] Third step: discharge the material and cut the granules, and dry at 85 DEG C to obtain the required nylon copolymer B.

[0183] The preparation method of nylon copolymer C is as follows:

[0184] First step: polyamide hard segment, polyether amine soft segment, pure water and catalyst are put into high-pressure reaction kettle, vacuum is extracted for 70 minutes, nitrogen is introduced for 30 minutes, and circulation is carried out 9 times, to ensure that each component is under nitrogen protection condition, and the pressure in high-pressure reaction kettle is controlled to maintain at 0.8 MPa;

[0185] Second step: mixing and stirring at 65℃ for 1 hour, stirring speed controlled at 80r / min.

[0186] Third step: further stirring at 200℃ for 5 hours, stirring speed controlled at 100r / min, then slowly releasing small molecule products in the system;

[0187] Fourth step: heating the high-pressure reactor to 230℃, pressure maintained at 0.8kPa, further reaction for 18 hours;

[0188] Fifth step: releasing the pressure to normal pressure, and reducing the temperature to 60℃.

[0189] Sixth step: casting and granulating the material, and drying at 90℃ to obtain the desired nylon copolymer C.

[0190] A method for preparing a polyamide film is the same as that in Example 1.

[0191] Comparative Example 3

[0192] A polyamide film includes a three-layer structure, from top to bottom, an upper surface layer, a middle layer, and a lower surface layer. The upper surface layer includes 5 parts of anti-sticking masterbatch and 95 parts of nylon copolymer A by mass fraction. The middle layer includes 100 parts of nylon copolymer C. The lower surface layer includes 5 parts of anti-sticking masterbatch and 95 parts of nylon copolymer A. The nylon copolymer A is obtained by polymerization of caprolactam monomer, ω-undecyl amino acid, pure water, catalyst, and blocking agent. The components include 60 parts of caprolactam monomer, 40 parts of ω-undecyl amino acid, 30 parts of pure water, 15 parts of catalyst, and 0.8 parts of blocking agent by mass fraction. The catalyst is benzoic acid, and the blocking agent is adipic acid. The nylon copolymer C is obtained by polymerization of polyamide hard segment, polyether amine soft segment, pure water, and catalyst. The components include 50 parts of polyamide hard segment, 50 parts of polyether amine soft segment, 20 parts of pure water, and 1 part of catalyst by mass fraction. The polyamide hard segment is polyamide 6-66 copolymer salt, the polyether amine soft segment is shown below, and the catalyst is benzoic acid. The anti-sticking masterbatch includes 6 parts of lubricant, 10 parts of anti-sticking agent, and 84 parts of nylon copolymer A by mass fraction. The lubricant is selected from ethylene bis-stearamide, and the anti-sticking agent is selected from silicon dioxide. The anti-sticking masterbatch is obtained by melt extrusion, drawing, cooling, granulation, and drying of the double-screw extruder at a temperature of 250℃. The biaxially stretched polyamide film has a thickness of 25μm. The thickness of the upper surface layer and the lower surface layer is 2μm, and the thickness of the middle layer is 21μm.

[0193]

[0194] The preparation method of the nylon copolymer A is as follows:

[0195] First step: Put caprolactam monomer, omega-undecyl amino acid, pure water, catalyst and end-capping agent into a high-pressure reactor, vacuumize for 100 minutes, introduce nitrogen for 30 minutes and circulate 5 times to ensure that each component is under nitrogen protection and the pressure in the high-pressure reactor is maintained at 1 MPa;

[0196] Second step: Increase the temperature of the high-pressure reactor to 260°C while starting stirring at a speed of 100 r / min, and keep the temperature and pressure for 10 hours, then release the pressure to normal pressure and reduce the temperature to 60°C;

[0197] Third step: Release the material and cut it into particles by casting and drying at 90°C to obtain the desired nylon copolymer A.

[0198] The preparation method of nylon copolymer C is as follows:

[0199] First step: Put polyamide hard segment, polyether amine soft segment, pure water and catalyst into a high-pressure reactor, vacuumize for 70 minutes, introduce nitrogen for 30 minutes and circulate 9 times to ensure that each component is under nitrogen protection and the pressure in the high-pressure reactor is maintained at 0.8 MPa;

[0200] Second step: Mix and stir at 65°C for 1 hour at a stirring speed of 80 r / min.

[0201] Third step: Further stir at a temperature of 200°C for 5 hours at a stirring speed of 100 r / min, then slowly release the small molecular products in the system;

[0202] Fourth step: Increase the temperature of the high-pressure reactor to 230°C and keep the pressure at 0.8 kPa for further reaction for 18 hours;

[0203] Fifth step: Release the pressure to normal pressure while reducing the temperature to 60°C.

[0204] Sixth step: Cut the material into particles by casting and dry at 90°C to obtain the desired nylon copolymer C.

[0205] A preparation method of a polyamide film is the same as that of Example 1.

[0206] Comparative Example 4

[0207] A kind of polyamide film, including three-layer structure, from top to bottom, upper surface layer, middle layer and lower surface layer, upper surface layer includes 5 parts of anti-adhesion master batch, 25 parts of nylon copolymer A, 70 parts of nylon copolymer B by mass fraction;Middle layer includes 100 parts of nylon copolymer B;Lower surface layer includes 5 parts of anti-adhesion master batch, 25 parts of nylon copolymer A, 70 parts of nylon copolymer B.Nylon copolymer A is obtained by polymerization reaction of caprolactam monomer, omega-undecyl amino acid, pure water, catalyst, blocking agent, each component is by mass fraction, including 60 parts of caprolactam monomer, 40 parts of omega-undecyl amino acid, 30 parts of pure water, 15 parts of catalyst, 0.8 parts of blocking agent.Catalyst is benzoic acid, and the blocking agent is adipic acid.Nylon copolymer B is obtained by polymerization reaction of adipic acid, hexamethylene diamine, polyether, pure water and catalyst, each component is by mass fraction including 20 parts of adipic acid, 20 parts of hexamethylene diamine, 60 parts of polyether, 30 parts of pure water, 1 part of catalyst.Polyether is double-end amino polyether, and catalyst is sodium hypophosphite.Anti-adhesion master batch includes 6 parts of slip agent, 10 parts of anti-adhesion agent and 84 parts of nylon copolymer A by mass fraction, and slip agent is selected from ethylene bis-stearamide, and anti-adhesion agent is selected from silicon dioxide.Anti-adhesion master batch is obtained by melt extrusion, drawing, cooling, granulating and drying of double-screw extruder at 250 DEG C.The thickness of biaxially stretched polyamide film is 25 μm;Among them, the thickness of upper surface layer and lower surface layer is 2 μm;The thickness of middle layer is 21 μm.

[0208] The preparation method of nylon copolymer A is as follows:

[0209] First step: caprolactam monomer, omega-undecyl amino acid, pure water, catalyst, blocking agent are added into high-pressure reaction kettle, vacuum extraction is carried out for 100 minutes, nitrogen is introduced for 30 minutes, and circulation is carried out for 5 times, to ensure that each component is under nitrogen protection condition, and the pressure in high-pressure reaction kettle is controlled to maintain 1 MPa;

[0210] Second step: the high-pressure reaction kettle is heated to 260 DEG C, while stirring is started, and the stirring speed is controlled at 100 r / min, and under this condition, the temperature is kept for 10 hours, and the pressure is reduced to normal pressure, while the temperature is reduced to 60 DEG C;

[0211] Third step: discharge and granulate, and dry at 90 DEG C to obtain the required nylon copolymer A.

[0212] The preparation method of nylon copolymer B is as follows:

[0213] First step: adipic acid, hexamethylene diamine, polyether, pure water and catalyst are added into high-pressure reaction kettle, vacuum extraction is carried out for 80 minutes, nitrogen is introduced for 30 minutes, and circulation is carried out for 6 times, to ensure that each component is under nitrogen protection condition, and the pressure in high-pressure reaction kettle is controlled to maintain 1 MPa;

[0214] Second step: the high-pressure reactor is warmed up to 235℃, while the stirring is started, the stirring speed is controlled at 65r / min, and the reaction is kept under the above conditions for 18 hours, the pressure is released to normal pressure, and the temperature is reduced to 60℃;

[0215] Third step: the material is discharged and cut into particles through cast strip and dried at 85℃ to obtain the desired nylon copolymer B.

[0216] A method for preparing a polyamide film is the same as in Example 1.

[0217] Comparative Example 5

[0218] A polyamide film includes a three-layer structure, from top to bottom, an upper surface layer, a middle layer, and a lower surface layer. The upper surface layer includes 5 parts of anti-sticking masterbatch and 95 parts of PA6 by mass fraction. The middle layer includes 100 parts of nylon copolymer C. The lower surface layer includes 5 parts of anti-sticking masterbatch and 95 parts of PA6. The nylon copolymer C is obtained by polymerization of polyamide hard segment, polyether amine soft segment, pure water, and catalyst. The components include 50 parts of polyamide hard segment, 50 parts of polyether amine soft segment, 20 parts of pure water, and 1 part of catalyst by mass fraction. The polyamide hard segment is polyamide 6-66 copolymer salt. The polyether amine soft segment is shown below. The catalyst is benzoic acid. The anti-sticking masterbatch includes 6 parts of slip agent, 10 parts of anti-sticking agent, and 84 parts of PA6 by mass fraction. The slip agent is selected from ethylene bis-stearamide. The anti-sticking agent is selected from silicon dioxide. The anti-sticking masterbatch is obtained by melt extrusion, drawing, cooling, granulation, and drying of a double-screw extruder at a temperature of 250℃. The biaxially stretched polyamide film has a thickness of 25μm. The upper surface layer and the lower surface layer have a thickness of 2μm. The middle layer has a thickness of 21μm.

[0219]

[0220] The preparation method of the nylon copolymer C is as follows:

[0221] First step: the polyamide hard segment, the polyether amine soft segment, the pure water, and the catalyst are put into the high-pressure reactor, vacuum is drawn for 70 minutes, nitrogen is introduced for 30 minutes, and circulation is performed 9 times to ensure that the components are under nitrogen protection, and the pressure in the high-pressure reactor is controlled to maintain at 0.8MPa;

[0222] Second step: mixing and stirring at 65℃ for 1 hour, the stirring speed is controlled at 80r / min.

[0223] Third step: further stirring at a temperature of 200℃ for 5 hours, the stirring speed is controlled at 100r / min, and then the small molecular products in the system are slowly released;

[0224] Fourth step: the high-pressure reactor is warmed up to 230℃, the pressure is kept at 0.8kPa, and the reaction is further carried out for 18 hours.

[0225] Fifth step: release the pressure to normal pressure, and reduce the temperature to 60℃.

[0226] Sixth step: cast the material into strands and dry at 90℃ to obtain the desired nylon copolymer C.

[0227] A method for preparing a polyamide film is the same as that of Example 1.

[0228] Comparative Example 6

[0229] A polyamide film includes a three-layer structure from top to bottom, an upper surface layer, a middle layer, and a lower surface layer. The upper surface layer includes 5 parts of anti-sticking masterbatch and 95 parts of nylon copolymer B by mass fraction. The middle layer includes 100 parts of nylon copolymer B. The lower surface layer includes 5 parts of anti-sticking masterbatch and 95 parts of nylon copolymer B. The nylon copolymer B is obtained by polymerization reaction of adipic acid, hexamethylene diamine, polyether, purified water, and a catalyst. Each component includes 20 parts of adipic acid, 20 parts of hexamethylene diamine, 60 parts of polyether, 30 parts of purified water, and 1 part of catalyst by mass fraction. The polyether is a double-end amino polyether, and the catalyst is sodium hypophosphite.

[0230] The preparation method of the nylon copolymer B is as follows:

[0231] First step: add adipic acid, hexamethylene diamine, polyether, purified water, and a catalyst into a high-pressure reaction kettle, vacuumize for 80 minutes, introduce nitrogen for 30 minutes, and circulate 6 times to ensure that each component is under nitrogen protection and the pressure in the high-pressure reaction kettle is maintained at 1 MPa.

[0232] Second step: heat the high-pressure reaction kettle to 235℃, and start stirring at a speed of 65 r / min. Maintain the temperature and pressure for 18 hours, release the pressure to normal pressure, and reduce the temperature to 60℃.

[0233] Third step: discharge the material, cast it into strands, and dry at 85℃ to obtain the desired nylon copolymer B.

[0234] The anti-sticking masterbatch includes 6 parts of a lubricant, 10 parts of an anti-sticking agent, and 84 parts of PA6 by mass fraction. The lubricant is selected from ethylene bis-stearamide, and the anti-sticking agent is selected from silicon dioxide. The anti-sticking masterbatch is obtained by melt extrusion, drawing, cooling, granulation, and drying of a double-screw extruder at a temperature of 250℃. The biaxially stretched polyamide film has a thickness of 25 μm, wherein the thickness of the upper and lower surface layers is 2 μm, and the thickness of the middle layer is 21 μm.

[0235] A method for preparing a polyamide film is the same as that of Example 1.

[0236] Comparative Example 7

[0237] A polyamide film comprising a three-layer structure, from top to bottom, an upper surface layer, a middle layer and a lower surface layer, the upper surface layer comprising 5 parts of anti-sticking masterbatch, 95 parts of nylon copolymer A by mass fraction; the middle layer comprising 100 parts of PA6; the lower surface layer comprising 5 parts of anti-sticking masterbatch, 95 parts of nylon copolymer A. The nylon copolymer A is obtained by polymerization of caprolactam monomer, omega-undecyl amino acid, pure water, catalyst and blocking agent, and each component comprises 60 parts of caprolactam monomer, 40 parts of omega-undecyl amino acid, 30 parts of pure water, 15 parts of catalyst and 0.8 parts of blocking agent by mass fraction. The catalyst is benzoic acid, and the blocking agent is adipic acid. The anti-sticking masterbatch comprises 6 parts of slip agent, 10 parts of anti-sticking agent and 84 parts of nylon copolymer A by mass fraction, the slip agent is selected from ethylene bis-stearamide, and the anti-sticking agent is selected from silicon dioxide. The anti-sticking masterbatch is obtained by melt extrusion, drawing, cooling, granulation and drying of the double-screw extruder at a temperature of 250°C. The thickness of the biaxially stretched polyamide film is 25μm; wherein the thickness of the upper surface layer and the lower surface layer is 2μm; the thickness of the middle layer is 21μm.

[0238] The preparation method of the nylon copolymer A is as follows:

[0239] First step: caprolactam monomer, omega-undecyl amino acid, pure water, catalyst and blocking agent are added into a high-pressure reaction kettle, vacuumed for 100 minutes, nitrogen is introduced for 30 minutes, and circulated for 5 times, to ensure that each component is under nitrogen protection condition, and the pressure in the high-pressure reaction kettle is controlled to maintain 1MPa;

[0240] Second step: the high-pressure reaction kettle is heated to 260°C, while the stirring is started, and the stirring speed is controlled at 100r / min, and under this condition, the pressure is maintained for 10 hours, the gas is released to reduce the pressure to normal pressure, and the temperature is reduced to 60°C;

[0241] Third step: the material is discharged and cast into particles, and dried at 90°C to obtain the required nylon copolymer A.

[0242] A polyamide film is prepared by the method of Example 1.

[0243] Comparative Example 8

[0244] A kind of polyamide film, including three-layer structure, from top to bottom in turn is upper surface layer, middle layer and lower surface layer, upper surface layer includes 5 parts of anti-adhesion master batch, 25 parts of nylon elastomer, 70 parts of PA6 according to mass fraction;Middle layer includes 20 parts of nylon elastomer, 80 parts of PA6;Lower surface layer includes 5 parts of anti-adhesion master batch, 25 parts of nylon elastomer, 70 parts of PA6. Nylon elastomer is selected from pebax 7233 of Arkema. Anti-adhesion master batch includes 6 parts of slip agent, 10 parts of anti-adhesion agent and 84 parts of PA6 according to mass fraction, slip agent is selected from ethylene bis-stearamide, and anti-adhesion agent is selected from silicon dioxide. Anti-adhesion master batch is obtained after being melt-extruded by double screw extruder at the temperature of 250 DEG C, drawing, cooling, granulating and drying. The thickness of biaxially stretched polyamide film is 25 μm;Among them, the thickness of upper surface layer and lower surface layer is 2 μm;The thickness of middle layer is 21 μm.

[0245] A kind of polyamide film is prepared according to the method of embodiment 1.

[0246] Comparative example 9

[0247] A kind of polyamide film, including three-layer structure, from top to bottom in turn is upper surface layer, middle layer and lower surface layer, upper surface layer includes 5 parts of anti-adhesion master batch, 25 parts of elastomer POE-g-MAH, 70 parts of PA6 according to mass fraction;Middle layer includes 20 parts of elastomer POE-g-MAH, 80 parts of PA6;Lower surface layer includes 5 parts of anti-adhesion master batch, 25 parts of elastomer POE-g-MAH, 70 parts of PA6. Elastomer POE-g-MAH is selected from Jia Yirong CMG5805-L. Anti-adhesion master batch includes 6 parts of slip agent, 10 parts of anti-adhesion agent and 84 parts of PA6 according to mass fraction, slip agent is selected from ethylene bis-stearamide, and anti-adhesion agent is selected from silicon dioxide, and anti-adhesion master batch is obtained after being melt-extruded by double screw extruder at the temperature of 250 DEG C, drawing, cooling, granulating and drying. The thickness of biaxially stretched polyamide film is 25 μm;Among them, the thickness of upper surface layer and lower surface layer is 2 μm;The thickness of middle layer is 21 μm.

[0248] A kind of polyamide film is prepared according to the method of embodiment 1.

[0249] The polyamide films prepared in the above embodiments 1-3 and comparative examples 1-9 are tested for performance according to the following method:

[0250] (1) Tensile strength performance test: test according to the requirements of GB / T 1040.3 "Determination of tensile properties of plastics-Part 3: test conditions for films and sheets" standard;

[0251] (2) Punch depth performance test: 40 film samples are tested for punch depth until the maximum punch depth at which the film does not crack is the test value;

[0252] (3) Puncture resistance test: the test was performed according to the standard of ASTM D4833 "Index Puncture Resistance of Geomembranes and Related Products";

[0253] (4) Moisture absorption dimensional elongation: the film was first placed in a vacuum drying oven at 85°C for 24 hours, and then the length L0 of the center was measured. Then the sample was placed in an environment of 60% RH / 25°C for 24 hours, and then the length L1 was measured again. The moisture absorption elongation was S=(L1-L0) / L0*100%.

[0254] The specific test results are shown in Table 1. As can be seen from Table 1, the bidirectional stretched polyamide film for power batteries prepared in Examples 1-3 has better toughness and processing performance compared with the film prepared by the conventional method in Comparative Examples 1-9, while still maintaining excellent tensile strength, moisture absorption elongation, etc., and can meet the market demand in different power battery packaging fields.

[0255] Table 1 Performance test results of polyamide films prepared in Examples 1-3 and Comparative Examples 1-9

[0256]

[0257]

[0258] Although the terms such as substrate layer, upper surface layer, intermediate layer, etc. are used more frequently in this document, the possibility of using other terms is not excluded. The use of these terms is only for the convenience of describing and explaining the essence of the present application; any interpretation of them as any kind of additional limitation is contrary to the spirit of the present application.

[0259] The above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A biaxially stretched polyamide film for power cells, characterized in that, From top to bottom, the upper surface layer, the middle layer and the lower surface layer are sequentially included, the upper surface layer includes 1-10 parts by mass of anti-sticking master batch, 5-40 parts by mass of nylon copolymer A and 50-94 parts by mass of nylon copolymer B, the middle layer includes 5-40 parts by mass of nylon copolymer B and 60-95 parts by mass of nylon copolymer C, and the lower surface layer includes 1-10 parts by mass of anti-sticking master batch, 5-40 parts by mass of nylon copolymer A and 50-94 parts by mass of nylon copolymer B; the nylon copolymer A is obtained by polymerization of caprolactam monomer, omega-undecyl amino acid, pure water, catalyst and blocking agent; the nylon copolymer B is obtained by polymerization of adipic acid, hexamethylene diamine, polyether, pure water and catalyst, and the nylon copolymer C is obtained by polymerization of polyamide hard segment, polyether amine soft segment, pure water and catalyst.

2. The biaxially oriented polyamide film according to claim 1, wherein The thickness of the biaxially stretched polyamide film is 10-30 μm, the thickness of the upper surface layer and the lower surface layer is 1-4 μm, and the thickness of the middle layer is 2-28 μm.

3. The biaxially oriented polyamide film according to claim 1, wherein In the nylon copolymer A, the caprolactam monomer, omega-undecyl amino acid, pure water, catalyst and blocking agent are respectively 10-94 parts by mass, 10-80 parts by mass, 10-60 parts by mass, 0.5-5 parts by mass and 0.5-5 parts by mass.

4. The biaxially oriented polyamide film according to claim 3, wherein The catalyst is benzoic acid, and the blocking agent is adipic acid.

5. The biaxially oriented polyamide film according to claim 1, wherein In the nylon copolymer B, the adipic acid, hexamethylene diamine, polyether, pure water and catalyst are respectively 10-50 parts by mass, 10-50 parts by mass, 10-90 parts by mass, 1-50 parts by mass and 0.1-5 parts by mass.

6. The biaxially oriented polyamide film according to claim 1, wherein The polyether is a double-end amino polyether, and the catalyst is sodium hypophosphite.

7. The biaxially oriented polyamide film according to claim 1, wherein In the nylon copolymer C, the polyamide hard segment, polyether amine soft segment, pure water and catalyst are respectively 10-80 parts by mass, 10-70 parts by mass, 1-50 parts by mass and 0.1-5 parts by mass.

8. The biaxially oriented polyamide film according to claim 7, wherein The polyamide hard segment is polyamide 6-66 copolymer salt, the catalyst is benzoic acid, and the polyether amine soft segment has the following structure: 。 9. The biaxially oriented polyamide film according to claim 1, wherein The anti-sticking master batch includes 1-10 parts by mass of lubricant, 2-15 parts by mass of anti-sticking agent and 75-97 parts by mass of nylon copolymer A, and is obtained by The anti-sticking master batch is obtained by melting extrusion, drawing, cooling, granulation and drying of the double screw extruder at a temperature of 230-270 ℃, the lubricant is one or more of erucic acid amide, PE wax and ethylene bis-stearamide, and the anti-sticking agent is one or more of talc, silicon dioxide, calcium carbonate, kaolin and diatomite.

10. A process for the production of a biaxially stretched polyamide film according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: S1: drying raw materials of the upper surface layer, the middle layer and the lower surface layer; S2: mixing the raw materials of the upper surface layer, the middle layer and the lower surface layer according to their component proportions, respectively, then melting and plasticizing extrusion of the raw materials through respective extruders at a temperature of 230-280 ℃, and then obtaining a melt by flowing out of a clothes hanger type die; S3: using a low-pressure air knife to attach the melt to a cold drum to form a thick sheet, the thickness of the thick sheet is 100-350 μm, and the temperature of the cold drum is 10-30 ℃; S4: the thick sheet is preheated, stretched longitudinally at a temperature of 45-68℃, and then cooled to set the shape, the stretching ratio of the longitudinal stretching being 2.5-3.8 times; S5: the film after the longitudinal stretching is sent to a transverse stretching machine, the preheating temperature being 60-90℃, the stretching temperature being 70-155℃, and the stretching ratio being 3.0-4.5 times; S6: the film after the stretching is heat-set at a temperature of 185-221℃ for 1-60s, and then cooled and treated by corona discharge at a power of 5-18 W·min / m², and wound up; S7: the biaxially stretched polyamide film after the winding is cut according to requirements to obtain a biaxially stretched polyamide film with a thickness of 10-30 μm for power batteries.

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