CN112405935A

CN112405935A - Matte black polyamide film for lithium ion battery, black master batch of matte black polyamide film and preparation method of black master batch

Info

Publication number: CN112405935A
Application number: CN202011301342.9A
Authority: CN
Inventors: 廖贵何; 刘运锦; 林新土; 贾露; 李智尧; 陈曦
Original assignee: Xiamen Changsu Industrial Co Ltd
Current assignee: Xiamen Changsu Industrial Co Ltd
Priority date: 2020-11-19
Filing date: 2020-11-19
Publication date: 2021-02-26
Anticipated expiration: 2040-11-19
Also published as: CN114654700A; CN112405935B; CN114654700B

Abstract

The invention discloses a matte black polyamide film for a lithium ion battery, black master batch thereof and a preparation method thereof. The film sequentially comprises a matte black polyamide upper surface layer, a polyamide middle layer and a black polyamide lower surface layer from top to bottom. The upper surface layer comprises 1-20 parts of black master batch, 1-20 parts of toughening agent, 1-20 parts of matte agent, 1-5 parts of additive and 35-96 parts of polyamide in parts by weight; the middle layer is 100 parts of polyamide; the lower surface layer comprises 1-20 parts of black master batch, 1-20 parts of toughening agent, 1-5 parts of additive and 55-97 parts of polyamide. The black master batch is prepared by processing under the combination condition of a special threaded element and a specific screw rod, and then the film is prepared, so that the film has low glossiness and soft effect, the black auxiliary agent is uniformly distributed, has no granular sensation, is easy to identify the process defects in production, and is particularly suitable for the field of high-grade lithium ion battery packaging.

Description

Matte black polyamide film for lithium ion battery, black master batch of matte black polyamide film and preparation method of black master batch

Technical Field

The invention belongs to the technical field of film flexible packaging, and particularly relates to a matte black polyamide film for a lithium ion battery, a black master batch of the matte black polyamide film and a preparation method of the black master batch.

Background

The lithium ion battery package has two modes of hard shell package and soft shell package. The soft package lithium ion battery has the characteristics of high safety, small size, light weight, flexible design and the like, and is widely applied to different electronic products and energy storage products, such as mobile phones, tablet computers, wearable intelligent equipment, electric bicycles, electric motorcycles, Bluetooth headsets and the like. As an encapsulation film used for a soft package lithium ion battery, the common structure thereof is as follows: nylon layer, gluing agent layer, aluminium lamination, gluing agent layer and heat-seal CPP layer. The nylon layer is one of key materials, has high technical barrier, is always monopolized by foreign enterprises, and not only is required to have certain strength, but also is required to provide certain toughness and punching depth capability, and can ensure that the aluminum layer has good deformation capability.

The importance of the nylon layer in the soft lithium battery packaging film is thought to be important. However, at present, the nylon layer is generally transparent, which is not beneficial to finding appearance defects in the manufacturing process of the packaging composite film. Such as breakage or micro-cracks at the deep-drawn corners, a great safety hazard exists in the application of the battery product. Therefore, the current mature technical route is to print a layer of black ink and coat a layer of matte oil on the nylon layer.

However, the application of the above technical solutions, while solving the problems, has resulted in some disadvantages. If two processes are added in the preparation process, the material cost is greatly increased; uncertainty exists in the thickness in the printing and coating processes, so that certain risk exists in the quality stability of the packaging film; the process route causes the reduction of a certain degree of deep drawing capability; a large amount of solvent is used in the printing and coating processes, so that the energy consumption is increased and the environment is polluted. Today, the environmental protection is more and more important, the method becomes a problem and is a technical scheme which is not beneficial to long-term development.

The Chinese patent application with the publication number of CN110564142A, namely 'a black matte polyamide film for lithium battery outer packaging and a preparation method thereof', mentions that the problem is solved by adding an organic black coloring agent, but because the decomposition temperature of the organic black coloring agent is in the processing temperature range of a polyamide product, the product has the hidden danger of decomposition, so that the film product has heavy smell, the downstream use is influenced, and the performance of the product is reduced; in addition, the color shade of the film produced by the organic black colorant is bluish violet, and for the film product, the film product has some differences with the current mature product, and the acceptance of customers is obviously reduced.

Therefore, how to obtain a matte black polyamide film for a lithium ion battery, which not only has a soft visual effect, but also is beneficial to identifying appearance defects in a manufacturing process of an encapsulating film, is a problem to be solved at present.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a matte black polyamide film for a lithium ion battery, a black master batch and a preparation method thereof, and solves the problem of coloring of the polyamide film for the lithium ion battery in the background technology.

One of the technical schemes adopted by the invention for solving the technical problems is as follows: the preparation method of the black master batch is provided, and the black master batch is prepared by adopting a double-screw extruder under the combination condition of a special thread element and a special screw, wherein the special thread element comprises a conveying block, a conventional kneading block, a special multi-head kneading thread block and a toothed disc, and the special screw combination condition is as follows:

75/75A,90/90,90/90,90/90,75/75,45/45,45/45,K30/5/75,K30/5/45,K30/5/45,K30/5/45,K30/5/45L,30/30L,75/75,75/75,90/90,90/90,90/90,90/90,DKB90/7/75,DKB90/7/75,DKB90/7/75,DKB90/7/75,DKB90/7/75,K45/5/75L,K90/5/45,60/60,K45/5/75,K90/5/45,K90/5/45,K90/5/45,30/30L,60/60,60/60,60/60,60/60,K45/5/45,K45/5/45,K45/5/45,60/60,60/60,C1,C2,C1,CY,90/90,75/75,75/75,75/75,75/75,75/75,75/75,60/60,60/60；

where K is the conventional kneading screw element, DKB is the special multi-start kneading screw element, L is the reverse screw block, C1 and C2 are toothed disks, and CY is a circular disk.

In a preferred embodiment of the present invention, the preparation method comprises the following steps:

s1, adding 1-40 parts by mass of black coloring agent, 0.01-2 parts by mass of super dispersant, 0.1-5 parts by mass of wax powder and 1-10 parts by mass of coupling agent into a high-speed stirrer, and stirring for 2-5 min to obtain a mixture P;

s2, adding 43-97.89 parts of polyamide through a main feeding screw, and adding the mixture P through a side feeding scale;

s3, setting the temperature of an extruder at 180-270 ℃, and melting and plasticizing the material through a double-screw extruder, wherein the rotating speed of the extruder is 500-800 rpm;

s4, cooling the melt through a neck mold in a water tank at the temperature of 10-50 ℃ to form a brace;

s5, after dewatering and grain cutting by a grain cutting machine, sucking into a drying tank, and drying at 80-110 ℃ for 3-10 h to obtain the black master batch.

In a preferred embodiment of the present invention, the black colorant includes any one of carbon black, graphite, and graphene, or a mixture of at least two of the same.

In a preferred embodiment of the present invention, the coupling agent comprises any one or a mixture of at least two of a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, and a vinyl silane.

In a preferred embodiment of the present invention, the hyperdispersant is DP 310.

In a preferred embodiment of the present invention, the wax powder is any one of or a blend or copolymer of at least two of PE wax, PP wax, low molecular weight ionomer, oxidized polyethylene wax, micro powder wax, fischer tropsch wax, ethylene acrylic acid copolymer, and polyester wax.

In a preferred embodiment of the present invention, the ratio of the length to the diameter of the twin-screw extruder is 50: 1-80: 1.

the second technical scheme adopted by the invention for solving the technical problems is as follows: the matte black polyamide film for the lithium ion battery is provided, and a matte black polyamide upper surface layer, a polyamide intermediate layer and a black polyamide lower surface layer are sequentially arranged from top to bottom; based on the mass parts, the weight ratio of the components,

the matte black polyamide upper surface layer comprises 1-20 parts of black master batch, 1-20 parts of toughening agent, 1-20 parts of matte agent, 1-5 parts of additive and 35-96 parts of polyamide;

the polyamide middle layer is 100 parts of polyamide;

the lower black polyamide surface layer comprises 1-20 parts of black master batch, 1-20 parts of toughening agent, 1-5 parts of additive and 55-97 parts of polyamide;

the black master batch is prepared by the method.

In a preferred embodiment of the invention, the additive comprises any one of a lubricant, a mouth-opening agent and an antioxidant or a mixture of at least two of the above. Wherein the lubricant comprises any one or a mixture of at least two of erucamide, stearamide, oleamide, ethylene bis-stearamide, ethylene bis-lauramide and silicone powder. The antioxidant comprises one or a mixture of at least two of antioxidant 1010, antioxidant 1098, antioxidant 2246, antioxidant 168, antioxidant 330, antioxidant DNP, antioxidant SEED and antioxidant phosphite. The opening agent comprises any one or a mixture of at least two of magnesium carbonate, alumina, silica, calcium carbonate, talcum powder, barium carbonate, diatomite, titanium dioxide, kaolin and organic silicon resin.

In a preferred embodiment of the present invention, the polyamide comprises any one of nylon 6, nylon 66, nylon 610, nylon 612, nylon 1010, nylon 1212, nylon 11, nylon 12, nylon MXD6, nylon 6I, nylon 5T, nylon 6T, nylon 9T, nylon 10T, or a blend or copolymer of at least two thereof.

In a preferred embodiment of the present invention, the toughening agent comprises any one of or a blend or copolymer of at least two of a maleic anhydride grafted ethylene-butene copolymer, a maleic anhydride grafted ethylene-octene copolymer, a maleic anhydride grafted polystyrene-based thermoplastic elastomer, and a polyamide block elastomer.

In a preferred embodiment of the present invention, the matte agent comprises any one or a blend or copolymer of at least two of silicone polymer, crosslinked methyl methacrylate polymer, crosslinked polystyrene, magnesium oxide, calcium oxide, ferric oxide, ethylene propylene copolymer, ethylene butene copolymer, ethylene hexene copolymer, ethylene octene copolymer, propylene butene copolymer, and poly 4-methyl-1-pentene.

In a preferred embodiment of the present invention, the total thickness of the thin film is 10 to 60 μm; the matte black polyamide upper surface layer and the black polyamide lower surface layer are 1-5 microns thick, and the polyamide middle layer is 8-50 microns thick.

The third technical scheme adopted by the invention for solving the technical problems is as follows: the preparation method of the matte black polyamide film for the lithium ion battery comprises the following steps:

the first step is as follows: drying all raw materials, and controlling the moisture content of the raw materials to be below 600 ppm;

the second step is that: mixing the raw materials of the upper surface layer, the middle layer and the lower surface layer according to a formula ratio, uniformly dispersing the raw materials by a high-speed stirrer, melting, plasticizing and extruding the raw materials at 230-290 ℃ by respective extruders, and flowing out of a T-shaped die;

the third step: attaching the melt to a cold drum by using a low-pressure air knife to form a thick sheet, wherein the thickness of the thick sheet is 100-400 mu m, and the temperature of the cold drum is 10-45 ℃;

the fourth step: immersing the thick sheet into a water tank at the temperature of 20-100 ℃ for pretreatment;

the fifth step: heating the thick sheet, and then performing synchronous biaxial stretching on the polyamide film by adopting Brookner magnetic suspension synchronous biaxial stretching equipment, wherein the stretching temperature is 160-220 ℃, and the stretching ratio is 2.7 x 2.7-3.6 x 3.6;

and a sixth step: carrying out heat setting treatment on the stretched film, wherein the setting temperature is 170-235 ℃, the setting time is 5-50 s, then carrying out cooling and corona post-treatment on the film, and the corona treatment power is 8-15 Wmin/m²And rolling;

the seventh step: and cutting the rolled biaxially-oriented polyamide film according to the requirement to finally obtain the matte black polyamide film, wherein the thickness of the film is 10-60 mu m.

Compared with the background technology, the technical scheme has the following advantages:

(1) the film prepared by the scheme reduces two procedures of black printing and matte coating, thereby not only reducing the problem of environmental pollution, but also obviously reducing the use cost of raw materials;

(2) and the screw combination conditions of the double-screw extruder are specially designed and combined, so that substances such as carbon black, graphene and the like which are very difficult to disperse are perfectly dispersed.

(3) The special multi-head kneading thread block is added in the screw combination of the double-screw extruder, so that the defect of a common kneading thread element is overcome, the design is more flexible, and the double-screw extruder is particularly suitable for homogenizing and mixing. The melting and mixing efficiency is improved as compared to the normal kneading blocks due to their increased ability to stretch, fold and extrude the material in a compact kneading cycle, not only eliminating shear peaks, but also allowing more uniform transfer of energy to the processed material, with shorter energy input requirements for uniformity and strength increase (50% less than standard kneading blocks). Therefore, the use of the special multi-head kneading thread block can not only realize excellent dispersion effect on materials, but also reduce energy consumption, finally improve output and capacity, improve product quality and improve overall production efficiency;

(4) the dispersed toner is further distributed through a toothed disc element in a screw combination of the double-screw extruder to form black master batch with perfect dispersion and uniform distribution, so that the uniform performance, uniform coloring, small addition amount and no agglomeration of the film are ensured;

(5) the middle layer is made of polyamide, so that the aluminum layer has certain strength, certain toughness and punching depth capability can be maintained and provided, the influence of the toughening agent added in the middle layer on the reduction of the strength of the film is reduced, and the aluminum layer can be ensured to have good deformation capability;

(6) only the black master batches are added on the two surface layers, and the middle layer is not added, so that the use of the black master batches and the adverse effect on the performance are reduced;

(7) the matte effect of the matte agent is good, and the addition amount is small;

in conclusion, the matte black polyamide film for the lithium ion battery provided by the scheme realizes perfect dispersion of toner which is difficult to disperse through the special threaded element and the special screw combination design and the preparation of the black master batch, and further the matte black polyamide film is prepared. The prepared film has high strength, good deep punching capability, good matte effect and soft visual effect, and is beneficial to identifying appearance defects in the manufacturing process of the packaging film. Functional layers of the film are mutually matched and coordinated to form an inseparable organic whole, and the biaxially oriented polyamide film which is black, matte, high in strength and good in punching depth performance is provided and is widely applied to the field of packaging of various lithium ion batteries.

Drawings

FIG. 1 is a schematic view of a special multi-start kneading screw element of example 1;

FIG. 2 shows specific screw combination conditions of example 1.

Detailed Description

It is to be understood that the terms "upper" and "lower" are used merely for convenience in describing the present invention and for simplicity in description, and are not intended to indicate or imply that the devices or elements so referred to must be in a particular orientation, constructed and operated, and are not to be considered limiting.

Example 1

The matte black polyamide film for the lithium ion battery comprises a three-layer film structure, wherein a matte black polyamide upper surface layer, a polyamide middle layer and a black polyamide lower surface layer are sequentially arranged from top to bottom. The upper surface layer comprises, by mass, 5 parts of black master batch, 10 parts of toughening agent, 5 parts of matte agent, 2 parts of additive and 78 parts of polyamide; the middle layer is 100 parts of polyamide; the lower surface layer comprises 5 parts of black master batch, 10 parts of toughening agent, 2 parts of additive and 83 parts of polyamide.

In this example, the additives are selected from three of lubricants, opening agents, and antioxidants as 1: 2: 1 proportion of a mixture, the lubricant being selected from erucamide; the antioxidant is selected from three of antioxidant 1098, antioxidant 168 and antioxidant SEED according to the ratio of 2: 1: 2 ratio of the mixture; the opening agent is selected from silicon dioxide;

in this example, the polyamide is selected from nylon 6; the toughening agent is selected from polyamide block elastomers; the matte agent is selected from three of organic silicon polymer, crosslinked methyl methacrylate polymer and poly 4-methyl-1-pentene with the weight ratio of 1: 1: 3 ratio of the blend;

wherein, the length-diameter ratio of the black master batch is 52: the double-screw extruder of 1 is processed and prepared under the condition of specific screw combination, and the preparation method comprises the following steps:

s1, adding 30 parts of black coloring agent, 0.05 part of super dispersant, 2 parts of wax powder and 2 parts of coupling agent into a high-speed stirrer, and stirring at a high speed for 3min to obtain a mixture P; wherein the black colorant is selected from carbon black; the coupling agent is selected from silane coupling agents; the super dispersant is selected from DP 310; the wax powder is selected from two of Fischer-Tropsch wax and ethylene acrylic acid copolymer according to the weight ratio of 1: 2 ratio of the mixture;

s2, adding 65.95 parts of polyamide through a main feeding screw, and adding the mixture P through a side feeding scale;

s3, setting the temperature of an extruder at 240 ℃, and melting and plasticizing the material through a double-screw extruder at the rotating speed of 600 rpm;

s4, cooling the melt through a neck mold in a water tank at the temperature of 30 ℃ to form a brace;

s5, after being granulated by a dewatering granulator, sucking the granules into a drying tank, drying the granules at 90 ℃ for 5 hours, and then bagging and packaging the granules to obtain black master batches;

referring to FIGS. 1 and 2, this example was prepared using a twin-screw extruder under special screw elements including a conveying block, a conventional kneading block, a special multi-start kneading screw block and a toothed disc, and under special screw combination conditions as follows:

The specific preparation method of the matte black polyamide film comprises the following steps:

the first step is as follows: drying all the raw materials, and controlling the moisture content of the raw materials to be below 600 ppm.

The second step is that: the raw materials of the upper surface layer, the middle layer and the lower surface layer are respectively mixed according to the formula proportion, are uniformly dispersed by a high-speed stirrer, are melted, plasticized and extruded at the temperature of 265 ℃ by respective extruders, and flow out through a T-shaped die head.

The third step: and attaching the melt to a cold drum by using a low-pressure air knife to form a thick sheet, wherein the thickness of the thick sheet is 170 mu m, and the temperature of the cold drum is 25 ℃.

The fourth step: the slabs were pre-treated by immersion in a water bath at 60 ℃.

The fifth step: heating the thick sheet, and then performing synchronous biaxial stretching on the polyamide film by adopting Brookner magnetic suspension synchronous biaxial stretching equipment, wherein the stretching temperature is 180 ℃, and the stretching ratio is 3.1 x 3.1.

And a sixth step: heat setting the stretched film at 210 deg.c for 8 sec, cooling and corona post-treatment at 10Wmin/m²And rolling.

The seventh step: cutting the rolled biaxially-oriented polyamide film according to the requirement to finally obtain the matte black polyamide film, wherein the total thickness of the film is 15 mu m; wherein the thicknesses of the polyamide upper surface layer and the polyamide lower surface layer are both 2 micrometers; the thickness of the intermediate layer was 11 μm.

Example 2

The matte black polyamide film for the lithium ion battery is of a three-layer film structure and sequentially comprises a matte black polyamide upper surface layer, a polyamide middle layer and a black polyamide lower surface layer from top to bottom. The upper surface layer comprises, by mass, 3 parts of black master batch, 10 parts of toughening agent, 3 parts of matte agent, 2 parts of additive and 82 parts of polyamide; the middle layer is 100 parts of polyamide; the lower surface layer comprises 3 parts of black master batch, 10 parts of toughening agent, 2 parts of additive and 85 parts of polyamide.

In this example, the additives are selected from three of lubricants, opening agents, and antioxidants as 1: 2: 1 ratio of the mixture; the lubricant is selected from erucamide; the antioxidant is selected from three of antioxidant 1098, antioxidant 168 and antioxidant SEED according to the ratio of 2: 1: 2 ratio of the mixture; the opening agent is selected from silicon dioxide;

in this example, the polyamide is selected from nylon 6; the toughening agent is selected from polyamide block elastomers; the matte agent is selected from three of silicone polymer, crosslinked methyl methacrylate polymer and poly 4-methyl-1-pentene in a ratio of 0.5: 0.5: 4 ratio of the blend.

s1, adding 30 parts of black coloring agent, 0.08 part of super dispersant, 2 parts of wax powder and 3 parts of coupling agent into a high-speed stirrer, and stirring at a high speed for 3min to obtain a mixture P; wherein the black colorant is selected from carbon black; the coupling agent is selected from silane coupling agents; the super dispersant is selected from DP 310; the wax powder is selected from two of Fischer-Tropsch wax and ethylene acrylic acid copolymer according to the weight ratio of 1: 2 ratio of the mixture;

s2, adding 64.92 parts of polyamide through a main feeding screw, and adding the mixture P through a side feeding scale;

s3, setting the temperature of an extruder at 235 ℃, and melting and plasticizing the materials by using a double-screw extruder, wherein the rotating speed of the extruder is 700 rpm;

this example was prepared using a twin screw extruder with special screw elements comprising a conveying block, a conventional kneading block, a special multi-start kneading screw block and a toothed disc and with specific screw combinations as follows:

The second step is that: the raw materials of the upper surface layer, the middle layer and the lower surface layer are respectively mixed according to the formula proportion, are uniformly dispersed by a high-speed stirrer, are melted, plasticized and extruded at the temperature of 260 ℃ by respective extruders, and flow out through a T-shaped die head.

The third step: the melt was attached to a cold drum using a low pressure air knife to form a slab, wherein the slab had a thickness of 175 μm and the cold drum was at a temperature of 20 ℃.

The fourth step: the slabs were pre-treated by immersion in a water bath at 55 ℃.

The fifth step: heating the thick sheet, and performing synchronous biaxial stretching on the polyamide film by using Brukner magnetic suspension synchronous biaxial stretching equipment, wherein the stretching temperature is 185 ℃, and the stretching ratio is 3.3 x 3.3.

And a sixth step: the stretched film is subjected to heat setting treatment, wherein the setting temperature is 205 ℃, the setting time is 10s, then the film is subjected to cooling and corona post-treatment, and the corona treatment power is 10Wmin/m²And rolling.

The seventh step: cutting the rolled biaxially-oriented polyamide film according to the requirement to finally obtain the matte black polyamide film, wherein the total thickness of the film is 15 mu m; wherein the thickness of the polyamide upper surface layer and the thickness of the polyamide lower surface layer are both 1.8 mu m; the thickness of the intermediate layer was 11.4 μm.

Comparative example 1

A commercially available BOPA film, printed black and coated with a matte finish.

Comparative example 2

The matte black polyamide film for the lithium ion battery is also of a three-layer film structure, and the three-layer structure sequentially comprises a matte black polyamide upper surface layer, a polyamide middle layer and a black polyamide lower surface layer from top to bottom. The upper surface layer comprises, by mass, 5 parts of black master batch, 10 parts of toughening agent, 5 parts of matte agent, 2 parts of additive and 78 parts of polyamide; the middle layer is 100 parts of polyamide; the lower surface layer comprises 5 parts of black master batch, 10 parts of toughening agent, 2 parts of additive and 83 parts of polyamide.

In this comparative example, the additives were selected from three of lubricants, opening agents, and antioxidants as 1: 2: 1 ratio of the mixture; the lubricant is selected from erucamide; the antioxidant is selected from three of antioxidant 1098, antioxidant 168 and antioxidant SEED according to the ratio of 2: 1: 2 ratio of the mixture; the opening agent is selected from silicon dioxide;

in this comparative example, the polyamide was selected from nylon 6; the toughening agent is selected from polyamide block elastomers; the matte agent is selected from three of organic silicon polymer, crosslinked methyl methacrylate polymer and poly 4-methyl-1-pentene with the weight ratio of 1: 1: 3 ratio of the blend;

in addition, the black master batch of the comparative example adopts a black master batch with the length-diameter ratio of 52: the double-screw extruder of 1 is processed and prepared under the condition of specific screw combination, and the preparation method comprises the following steps:

s1, adding 30 parts of black coloring agent, 0.05 part of super dispersant, 2 parts of wax powder and 2 parts of coupling agent into a high-speed stirrer, and stirring at a high speed for 3min to obtain a mixture P; the black colorant is selected from carbon black; the coupling agent is selected from silane coupling agents; the super dispersant is selected from DP 310; the wax powder is selected from two of Fischer-Tropsch wax and ethylene acrylic acid copolymer according to the weight ratio of 1: 2 ratio of the mixture;

the black master batch of the comparative example employs the following combination of a common screw element and a screw, and the screw elements included therein are a conveying block and a conventional kneading block. The combination is as follows:

75/75A,90/90,90/90,90/90,75/75,45/45,45/45,K30/5/75,K30/5/45,K30/5/45,K30/5/45,K30/5/45L,30/30L,75/75,75/75,90/90,90/90,90/90,90/90,K90/5/75,K90/5/75,K90/5/75,K90/5/75,K90/5/75,K45/5/75L,K90/5/45,60/60,K45/5/75,K90/5/45,K90/5/45,K90/5/45,30/30L,60/60,60/60,60/60,60/60,K45/5/45,K45/5/45,K45/5/45,60/60,60/60,45/45,45/45,45/45,45/45,90/90,75/75,75/75,75/75,75/75,75/75,75/75,60/60,60/60；

where K is the conventional kneading screw element and L is the reverse screw block.

Then, a matte black polyamide film with the total thickness of 15 μm was prepared by the same method as example 1; wherein the thicknesses of the polyamide upper surface layer and the polyamide lower surface layer are both 2 micrometers; the thickness of the intermediate layer was 11 μm.

Comparative example 3

The matte black polyamide film for the lithium ion battery in the comparative example is of a three-layer film structure, and the three-layer structure sequentially comprises a matte black polyamide upper surface layer, a polyamide middle layer and a black polyamide lower surface layer from top to bottom. The upper surface layer comprises, by mass, 5 parts of black master batch, 10 parts of toughening agent, 5 parts of matte agent, 2 parts of additive and 78 parts of polyamide; the middle layer is 100 parts of polyamide; the lower surface layer comprises 5 parts of black master batch, 10 parts of toughening agent, 2 parts of additive and 83 parts of polyamide.

In this comparative example, the additives were selected from three of lubricants, opening agents, and antioxidants as 1: 2: 1 ratio of the mixture; the lubricant is selected from erucamide; the antioxidant is selected from three of antioxidant 1098, antioxidant 168 and antioxidant SEED according to the ratio of 2: 1: 2 ratio of the mixture; the opening agent is selected from silicon dioxide; the polyamide is selected from nylon 6; the toughening agent is selected from polyamide block elastomers; the matte agent is selected from three of organic silicon polymer, crosslinked methyl methacrylate polymer and poly 4-methyl-1-pentene with the weight ratio of 1: 1: 3 ratio of the blend.

s1, adding 30 parts of black coloring agent, 0.05 part of super dispersant, 2 parts of wax powder and 2 parts of coupling agent into a high-speed stirrer, and stirring at a high speed for 3min to obtain a mixture P; the black colorant is selected from organic aniline black; the coupling agent is selected from silane coupling agents; the super dispersant is selected from DP 310; the wax powder is selected from two of Fischer-Tropsch wax and ethylene acrylic acid copolymer according to the weight ratio of 1: 2 ratio of the mixture;

the black master batch is prepared by adopting a double-screw extruder under the conditions of special thread elements and special screw combination, wherein the special thread elements comprise a conveying block, a conventional kneading block, a special multi-head kneading thread block and a toothed disc, and the special screw combination conditions are as follows:

Comparative example 4

The matte black polyamide film for the lithium ion battery in the comparative example is of a three-layer film structure, and the three-layer structure sequentially comprises a matte black polyamide upper surface layer, a polyamide middle layer and a black polyamide lower surface layer from top to bottom. The upper surface layer comprises, by mass, 5 parts of black master batch, 10 parts of toughening agent, 5 parts of matte agent, 2 parts of additive and 78 parts of polyamide; the middle layer is composed of 90 parts of polyamide and 10 parts of toughening agent; the lower surface layer comprises 5 parts of black master batch, 10 parts of toughening agent, 2 parts of additive and 83 parts of polyamide.

Wherein, the additive is selected from three of lubricant, opening agent and antioxidant according to the proportion of 1: 2: 1 ratio of the mixture; the lubricant is selected from erucamide; the antioxidant is selected from three of antioxidant 1098, antioxidant 168 and antioxidant SEED according to the ratio of 2: 1: 2 ratio of the mixture; the opening agent is selected from silicon dioxide; the polyamide is selected from nylon 6; the toughening agent is selected from polyamide block elastomers; the matte agent is selected from three of organic silicon polymer, crosslinked methyl methacrylate polymer and poly 4-methyl-1-pentene with the weight ratio of 1: 1: 3 ratio of the blend.

The length-diameter ratio of the black master batch is 52: the double-screw extruder of 1 is processed and prepared under the condition of specific screw combination, and the preparation method comprises the following steps:

the black master batch of the comparative example is prepared by a twin-screw extruder under the conditions of special thread elements and special screw combination, wherein the special thread elements comprise a conveying block, a conventional kneading block, a special multi-head kneading thread block and a toothed disc, and the special screw combination conditions are as follows:

Comparative example 5

The matte black polyamide film for the lithium ion battery is of a three-layer film structure, and the three-layer structure sequentially comprises a matte black polyamide upper surface layer, a polyamide middle layer and a black polyamide lower surface layer from top to bottom. The upper surface layer comprises, by mass, 5 parts of black master batch, 10 parts of toughening agent, 5 parts of matte agent, 2 parts of additive and 78 parts of polyamide; the middle layer is 95 parts of polyamide and 5 parts of black master batch; the lower surface layer comprises 5 parts of black master batch, 10 parts of toughening agent, 2 parts of additive and 83 parts of polyamide.

The length-diameter ratio of the black master batch is 52: 1, processing and preparing the double-screw extruder under the condition of specific screw combination, wherein the preparation method comprises the following steps:

Comparative example 6

The matte black polyamide film for the lithium ion battery is of a three-layer film structure, and the three-layer structure sequentially comprises a matte black polyamide upper surface layer, a polyamide middle layer and a black polyamide lower surface layer from top to bottom. The upper surface layer comprises, by mass, 5 parts of black master batch, 10 parts of toughening agent, 5 parts of matte agent, 2 parts of additive and 78 parts of polyamide; the middle layer is 100 parts of polyamide; the lower surface layer comprises 5 parts of black master batch, 10 parts of toughening agent, 2 parts of additive and 83 parts of polyamide.

Wherein, the additive is selected from three of lubricant, opening agent and antioxidant according to the proportion of 1: 2: 1 ratio of the mixture; the lubricant is selected from erucamide; the antioxidant is selected from three of antioxidant 1098, antioxidant 168 and antioxidant SEED according to the ratio of 2: 1: 2 ratio of the mixture; the opening agent is selected from silicon dioxide; the polyamide is selected from nylon 6; the toughening agent is selected from polyamide block elastomers; the matte agent is selected from silicon dioxide.

the black master batch is prepared by adopting a double-screw extruder under the combination condition of a special thread element and a special screw, wherein the special thread element comprises a conveying block, a conventional kneading block, a special multi-head kneading thread block and a toothed disc, and the special screw combination condition is as follows:

The relevant performances of the above examples and comparative examples were tested, and the specific result data are shown in the following table:

note:

(1) tensile strength was tested in accordance with the requirements of Standard GB/T1040.3 determination of tensile Properties of plastics (part 3: test conditions for films and sheets).

(2) Light transmittance: the test is carried out according to the requirements of GB/T2410-2008 standard.

(3) And (3) testing the punching depth performance: and (3) carrying out a depth punching test on 40 film samples until the maximum value of the depth punching when the film does not crack is the test value.

(4) Gloss was measured according to ASTM D2457 Standard Test Method for Specular Gloss of Plastic Films and Solid Plastics.

(5) And (3) thickness performance test: according to reference GB/T6672-2001, determination of the thickness of Plastic films and sheets: mechanical measurements "require testing.

(6) And (3) testing the covering property: and vertically and fixedly clamping a 30 x 30cm film, and observing the definition of a point light source of the backlight module at a distance of 1m to judge the covering performance of the film. The point light source can not be seen completely, and a uniform surface light source is presented, which shows that the coverage of the film is very good and is marked by 'excellent'; point light sources cannot be seen, and a non-uniform surface light source is presented, which indicates that the coverage of the film is good and is marked by "∘"; a slight point light source can be seen, and the light and shade change is presented, which indicates that the coverage of the film is general and is marked by □; point light sources can be clearly seen, which indicates that the film has poor covering property and is marked by X;

(7) black performance test: the blackness test is carried out by using a spectrophotometric colorimeter, and the L value is from 0 to 100 to represent that the L value is from black to white. The L value is less than or equal to 25, which indicates that the blackness is very good and is marked by 'very good'; the value L is more than 25 and less than or equal to 27, which means that the black color is good and marked by a mark of "-"; l value more than 27 and less than or equal to 29 represents black medium, and is marked by □; an L value > 29 indicates a black color difference, which is denoted by "X".

(8) Testing the black distribution uniformity: a single film of 40 x 60cm is laid on a white light source LED detection lamp box of 60W, and the light transmission conditions of the films at different positions are observed to judge the black distribution uniformity condition of the film. The light transmission conditions at each position are basically consistent, which indicates that the black is uniformly distributed and marked with 'excellent'; slight difference exists in the light transmission conditions of different positions, but the light transmission conditions are not obvious, which indicates that the black distribution is good and is marked by a mark; the light transmission difference at different positions is obvious, which shows that the black distribution is general and is marked by □; the light transmission conditions at different positions are very different, and some parts are completely black and opaque, some parts are transparent, or the parts are transparent or opaque in a sheet mode, so that the black distribution is not uniform, the agglomeration phenomenon is caused, and the mark is marked by X.

From the above table, compared with the biaxially oriented polyamide film produced by the traditional method, the matte black polyamide film for the lithium ion battery has the advantages that the black master batch is uniformly dispersed and has high coverage rate while the glossiness is kept, and the matte black polyamide film has better punching depth performance and tensile strength and can meet the requirements of the lithium ion battery packaging market.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of black master batch is characterized by comprising the following steps: the special screw element is prepared by a double-screw extruder under the conditions of special screw elements and special screw combination, wherein the special screw elements comprise a conveying block, a conventional kneading block, a special multi-head kneading screw block and a toothed disc, and the special screw combination conditions are as follows:

2. The method for preparing the black master batch according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:

3. The method for preparing the black master batch according to claim 1, wherein the method comprises the following steps: the black colorant comprises any one of carbon black, graphite and graphene or a mixture of at least two of the carbon black, the graphite and the graphene.

4. The method for preparing the black master batch according to claim 1, wherein the method comprises the following steps: the coupling agent comprises any one or a mixture of at least two of silane coupling agent, titanate coupling agent, aluminate coupling agent and vinyl silane.

5. The method for preparing the black master batch according to claim 1, wherein the method comprises the following steps: the hyperdispersant is DP 310.

6. The method for preparing the black master batch according to claim 1, wherein the method comprises the following steps: the wax powder is any one or a blend or copolymer of at least two of PE wax, PP wax, low molecular weight ionomer, oxidized polyethylene wax, micro powder wax, Fischer-Tropsch wax and ethylene acrylic acid copolymer polyester wax.

7. The method for preparing the black master batch according to claim 1, wherein the method comprises the following steps: the length-diameter ratio of the double-screw extruder is 50: 1-80: 1.

8. a matte black polyamide film for a lithium ion battery is characterized in that: a matte black polyamide upper surface layer, a polyamide middle layer and a black polyamide lower surface layer are sequentially arranged from top to bottom; based on the mass parts, the weight ratio of the components,

the polyamide middle layer is 100 parts of polyamide;

the black master batch is prepared by the method of any one of claims 1 to 7.

9. The matte black polyamide film for lithium ion batteries according to claim 8, wherein: the additive comprises any one or a mixture of at least two of a lubricant, a mouth-opening agent and an antioxidant.

10. The matte black polyamide film for lithium ion batteries according to claim 9, wherein: the lubricant comprises any one or a mixture of at least two of erucamide, stearamide, oleamide, ethylene bis-stearamide, ethylene bis-lauramide and silicone powder.

11. The matte black polyamide film for lithium ion batteries according to claim 9, wherein: the antioxidant comprises one or a mixture of at least two of antioxidant 1010, antioxidant 1098, antioxidant 2246, antioxidant 168, antioxidant 330, antioxidant DNP, antioxidant SEED and antioxidant phosphite.

12. The matte black polyamide film for lithium ion batteries according to claim 9, wherein: the opening agent comprises any one or a mixture of at least two of magnesium carbonate, alumina, silica, calcium carbonate, talcum powder, barium carbonate, diatomite, titanium dioxide, kaolin and organic silicon resin.

13. The matte black polyamide film for lithium ion batteries according to claim 8, wherein: the polyamide comprises any one of nylon 6, nylon 66, nylon 610, nylon 612, nylon 1010, nylon 1212, nylon 11, nylon 12, nylon MXD6, nylon 6I, nylon 5T, nylon 6T, nylon 9T and nylon 10T or a blend or copolymer of at least two of the above.

14. The matte black polyamide film for lithium ion batteries according to claim 8, wherein: the toughening agent comprises any one of or a blend or copolymer of at least two of maleic anhydride grafted ethylene-butylene copolymer, maleic anhydride grafted ethylene-octene copolymer, maleic anhydride grafted polystyrene thermoplastic elastomer and polyamide block elastomer.

15. The matte black polyamide film for lithium ion batteries according to claim 8, wherein: the matte agent comprises any one or a blend or a copolymer of at least two of organic silicon polymer, crosslinked methyl methacrylate polymer, crosslinked polystyrene, magnesium oxide, calcium oxide, ferric oxide, ethylene propylene copolymer, ethylene butene copolymer, ethylene hexene copolymer, ethylene octene copolymer, propylene butene copolymer and poly 4-methyl-1-pentene.

16. The matte black polyamide film for lithium ion batteries according to claim 8, wherein: the total thickness of the film is 10-60 mu m; the matte black polyamide upper surface layer and the black polyamide lower surface layer are 1-5 microns thick, and the polyamide middle layer is 8-50 microns thick.

17. The preparation method of the matte black polyamide film for the lithium ion battery as claimed in any one of claims 8 to 14, wherein the preparation method comprises the following steps: the method comprises the following steps: