CN106953054B - Long carbon chain polyamide porous membrane and preparation method and application thereof - Google Patents

Abstract

The invention relates to a long carbon-chain polyamide porous membrane, a preparation method and application thereof. The porous membrane is a sheet-like structure of uniform thickness, and the sheet-like structure has a plurality of micropores that are basically independent of each other. The porous membrane is prepared by using long carbon chain polyamide, and the long carbon chain polyamide is an aliphatic polyamide with a carbon chain length greater than 10 between two adjacent amide groups in the molecule, wherein the The micropores are elliptical-like, and the long axes of at least two elliptical-like shapes are close to a straight line or parallel; or the micropores are elliptical-like, and several elliptical-like structures form several micropores on the sheet-like structure. Cluster distribution, most ellipse-like long axes are basically in one direction. The use of the long carbon chain polyamide in the present invention can have good affinity with the polar electrolyte in the lithium battery, and at the same time the long carbon chain polyamide has higher melting point, thermal decomposition temperature and softening temperature. It has advantages in lithium-ion battery separators and water treatment membranes.

Description

A kind of long carbon chain polyamide porous membrane and its preparation method and use

technical field

The present invention relates to a kind of porous film and its preparation method and use, in particular, to a kind of long carbon chain polyamide porous film and its preparation method and use

Background technique

Porous membrane is an advanced separation technology, which has been widely used in various fields because of its simple operation, high efficiency, energy saving, and low pollution. Polyamide is an engineering plastic with excellent comprehensive properties, and polyamide filtration membranes have also been widely used in laboratory, industrial and life filtration treatment. But for common polyamide, it contains polar amide groups, and the density of amide groups is high, which leads to its strong water absorption, and the mechanical properties of polyamide will be greatly reduced after water absorption, which greatly limits the polyamide. The service life of amide filtration membrane and its application in some specific fields.

Another important application field of porous membrane is lithium ion battery separator. With the continuous development of energy technology, lithium ion battery has been widely used in various fields, from computers, mobile phones to electric vehicles, lithium ion batteries play a pivotal role. It has excellent properties such as high operating voltage, high energy density, long cycle life, and low pollution. As an important part of a lithium-ion battery, the separator is a layer of microporous membrane material between the positive electrode and the negative electrode, which is used to block the physical contact between the positive and negative electrodes, while allowing the ions in the electrolyte to migrate freely while the electrons in the battery cannot pass through. , even if the current is blocked, the battery separator plays an important role. The polymer separator with a porous structure melts at a higher temperature, which leads to the closure of the porous structure and the rapid increase of the impedance to block the current. This temperature is called resistance. Shut-Down temperature, also known as self-closing temperature. In addition, after the pores of the separator are closed, if the battery temperature continues to rise, when the heat-resistant temperature of the separator is exceeded, the separator will be completely melted and destroyed, causing the positive and negative electrodes to directly contact and short-circuit. This temperature is called break-out )temperature. The separator material significantly affects the energy, power density, cycle life and safety performance of the battery, and its structural optimization plays an important role in improving the comprehensive performance of the battery. Polyolefins are widely used in lithium-ion battery separator materials due to their high mechanical strength and good chemical stability. At present, commercial lithium battery separator materials mainly use polyethylene (PE), polypropylene (PP) microporous films and PP/PE multilayer composite film, due to the low melting temperature (such as the self-closing temperature of PE diaphragm is 130-140 ℃, the self-closing temperature of PP diaphragm is about 170 ℃), in some cases, such as the external temperature is too high, In the case of excessive discharge current or thermal inertia during the heating process of the electrolyte, even if the current is blocked, the temperature of the battery may continue to rise, so the diaphragm may be completely destroyed and the battery will be short-circuited, causing the battery to explode or catch fire, Therefore, the safety of using PE diaphragm and PP diaphragm is low. In addition, the diaphragm material also has the following disadvantages. Because the polarity of polyolefin is small and the surface energy is low, and the electrolyte is an organic solvent with high polarity, the wettability of polyolefin and electrolyte is poor, resulting in most electrolytes. The liquid exists in the gap, which is easy to cause electrolyte leakage.

The patent application with the application number of 201510126639.9 discloses a preparation method of a hydrophilic polyolefin microporous membrane for lithium ion batteries. The polyolefin microporous membrane is coated with a 1,1,-disubstituted aromatic olefin monomer. The prepared block copolymer, wherein one segment of the block copolymer contains a hydrophilic group, and the other segment has good affinity with the polyolefin membrane, making it compatible with the polyolefin microporous membrane and the lithium battery. The electrolytes in the pool have good affinity. However, in this method, the adhesion between the coating and the substrate and its complex process optimization are important problems faced by this technology.

The patent with the application number of 200680039461.3 discloses a polyolefin multi-layer microporous film and its manufacturing method, as well as a battery separator, a polyolefin three-layer microporous film, which has two surface layers formed by polyethylene resin. The porous layer, and the microporous layer forming the inner layer containing polypropylene and a heat-resistant resin having a melting point or glass transition temperature of 180-260° C., thereby improving the heat resistance of the microporous film.

The patent with the application number of 200810185300.6 discloses a method for preparing a microporous polyolefin multi-layer film. The multi-layer film is formed by mixing polyethylene, a diluent and a heat-resistant filler to form a film, thereby improving the thermal stability of the polyolefin. , but the weight and shedding of the filler seriously affect the performance of this type of material.

Long carbon chain polyamide has the advantages of good flexibility, low water absorption, good dimensional stability, excellent chemical resistance, wear resistance, corrosion resistance, low temperature impact resistance, and good electrical insulation. It is widely used in machinery , electronic appliances, automobiles, information, textiles, aerospace and other fields are the development directions of key research at home and abroad. So far, there have been no patents or reports on the preparation of porous membranes with long carbon chain polyamides.

In view of the above reasons, the present invention is proposed.

SUMMARY OF THE INVENTION

The first object of the present invention is to provide a long carbon chain polyamide porous membrane.

The second object of the present invention is to provide a method for preparing the porous membrane.

The third object of the present invention is to provide the use of the porous membrane.

To achieve the first object of the present invention, the present invention adopts the following technical solutions:

A long carbon-chain polyamide porous membrane, characterized in that the porous membrane is a sheet-like structure of uniform thickness, and the sheet-like structure has a plurality of micropores that are basically independent of each other, and the porous membrane It is prepared by using long carbon chain polyamide, and the long carbon chain polyamide is an aliphatic polyamide whose carbon chain length between two adjacent amide groups in the molecule is greater than 10, wherein

The micropores are elliptical-like, and the long axes of at least two elliptical-like shapes are close to a straight line or parallel;

Alternatively, the micropores are elliptical-like, and several ellipses-like structures form several micropore clusters distributed on the sheet-like structure, and the major axes of most of the elliptical-like shapes are basically in one direction.

The porous membrane with this structure has high electrical conductivity and high mechanical strength in the battery separator, and the electrolyte is not easy to leak, which is beneficial to the migration of carriers.

Since the hydrogen bonding between polyamide molecular chains is the determining factor for its structure and performance, long carbon chain polyamides have longer methylene chains, low hydrogen bond density, and better flexibility of the molecular chains, so they have toughness Good, and long carbon chain polyamide, low melting point, low water absorption, good mechanical properties, high bonding strength, low density, good impact performance, etc., so it is a material with good mechanical properties and dimensional stability. Due to the high water absorption rate of polyamide, after water absorption, the dimensional change is large, the rigidity is sharply reduced, the tensile strength and bending strength are reduced, and the electrical properties are also deteriorated, which greatly limits the application range. Ideal material for making filter membranes.

In addition, the amide bond in the long carbon-chain polyamide molecular chain is a polar bond, there is a large cohesive energy between the bonds, and hydrogen bonds can be formed between the molecules, so that the molecular arrangement is more regular, so that the polymer has a higher crystallinity. Methylene is non-polar, and its presence makes the molecular chain softer, because the various properties of nylon depend on the relative ratio of methylene to amide in its molecular chain. The greater the ratio of amide to methylene, The higher the polarity of the polyamide, the higher the polarity of the organic solvent is generally used in the electrolyte. Therefore, the affinity between the separator and the electrolyte is better, so the battery is not prone to leakage. This kind of material is used in the preparation of lithium ion. It has advantages in battery separator. In addition, the distribution density of amide groups and methylene groups in the long carbon chain polyamide is not uniform, which affects the hydrogen bond density and has a higher melting point.

Preferably, in the first direction, the long axes of a plurality of the ellipse-like shapes are substantially arranged in a straight line, and in the second direction perpendicular to the first direction, the long axes of the ellipse-like shapes are substantially Parallel distribution; preferably in the second direction perpendicular to the first direction, the elliptical-like dislocation distribution;

Or the long axis of the ellipse-like shape that forms the microporous cluster is a straight line or the long axes are parallel, preferably the ellipse-like shape is dislocated to form a microporous cluster, and preferably the central part of the microporous cluster is a micropore with a small aperture .

Preferably, the length of the long axis of the ellipse-like shape is much larger than the length of the short axis.

Preferably, the long carbon chain polyamide is one or more of pure long carbon chain polyamides, long carbon chain polyamides containing additives, polyamide alloys or polyamide nanocomposite materials. The melting point of the chain polyamide is 180°C-230°C, and the melt index is 0.5-20 g/10min, preferably 1-10 g/10min.

Among them, additives include nucleating agents, antioxidants, chain extenders, polyamide alloy materials include polymer materials such as PP, PA, and reinforcing materials such as glass fibers and whiskers, and nanocomposite materials include carbon nanotubes, montmorillonite, carbon black, etc.

Preferably, the long carbon chain polyamide is one or more of nylon 610, nylon 612, nylon 1010, nylon 1012 or nylon 1212, preferably nylon 1012 or/and nylon 1212. .

Preferably, the long carbon chain polyamide porous film is a single-layer film or a multi-layer composite film, and the pore size of the long carbon chain polyamide porous film is 0.01 μm-5 μm.

Among them, the single-layer film is a uniaxially stretched long carbon chain polyamide single-layer film, and the mechanical strength of the single-layer film in the stretching direction is greater than the mechanical strength in the vertical stretching direction; the multi-layer composite film is composed of a single-layer film. The composite film consists of a single-layer film in each orientation direction with excellent tensile strength, or a biaxially oriented long carbon chain polyamide porous film.

For realizing the second purpose, the present invention adopts following technical scheme:

A preparation method of a long carbon chain polyamide porous membrane, the preparation method comprises the following steps:

Described preparation method comprises the steps:

(1) prepare long carbon chain polyamide flat sheet;

(2) The above-mentioned flat sheet is placed in the stretching equipment for one-step stretching or two-step stretching.

Preferably, the flat sheet preparation method in step (1) is a melt extrusion method or a hot pressing method, and the extrusion or hot pressing temperature is 200°C-300°C, preferably 220°C-270°C.

Preferably, the one-step stretching in step (2) is to place the flat sheet on a stretching device for 5-15 minutes at an isothermal temperature, and the isothermal temperature is 10-170° C., and then at this temperature, the stretching rate is 5-500 μm/s in one direction. Or biaxially stretched to 10%-650% to obtain the porous film; the two-step stretching is to place the flat sheet on the stretching equipment for 5-15 minutes at an isothermal temperature, and the isothermal temperature is T ₁ . Stretching unidirectionally or biaxially at a rate of 5-500 μm/s to ε ₁ , the obtained stretched sample is held at a temperature T ₂ , isothermally for 5-15 min, and then at a stretching rate of 5-500 μm/s unidirectionally or bidirectionally at this temperature Stretching to ε ₂ to obtain the porous film, ₁₀ ° _{C≤T1≤T2≤170} °C, ₁₀ % _{≤ε1≤ε2≤650} %, preferably the stretching rate is 10μm/s-100μm/s.

Among them, the uniaxial stretching method is as follows: on the one hand, it can be prepared by a one-step stretching method. First, a long carbon chain polyamide extruded film is prepared, and then the sample is placed on the stretching equipment for 5-15 minutes at the same temperature, and then the film is carried out at a certain rate. Stretching in one direction yields a spline with a stretch ratio ε. On the other hand, it can be prepared by a two-step stretching method. The long carbon chain polyamide extruded film sample is placed on the stretching equipment, isothermally held at _a temperature of T1 for 5-15 min, and then uniaxially stretched at a certain rate to a stretching ratio of ε1, then the stretched sample was isothermally held at temperature T2 for 5-15 min, and then uniaxially stretched at a certain rate to a draw ratio of _ε2 . The controllability of the porous pore size can be achieved by adjusting the isothermal temperature and stretching ratio.

The biaxial stretching method is as follows: on the one hand, it can be prepared by a one-step stretching method. First, a long carbon chain polyamide extruded film is prepared, and then the sample is placed on the stretching equipment for isothermal 5-15min, and then biaxially stretched at a certain rate. , a spline with a stretch ratio ε is obtained. On the other hand, it can be prepared by a two-step stretching method. The long carbon chain polyamide extruded film sample is placed on the stretching equipment, isothermally held at a temperature T ₁ for 5-15 min, and then biaxially stretched at a certain rate to a stretching ratio of ε ₁ , then the stretched sample was isothermally held at temperature T ₂ for 5-15 min, and then biaxially stretched at a certain rate to a stretch ratio of ε ₂ . The controllability of the porous pore size can be achieved by adjusting the isothermal temperature and stretching ratio.

The stretching method does not require any additives or solvents in the molding process, so the entire molding process is environmentally friendly and the product is of high purity.

To achieve the third object of the present invention, the present invention adopts the following technical solutions:

An application of the long carbon chain polyamide porous membrane of the present invention in the following fields:

(1) Lithium-ion battery separator;

(2) Water filtration membrane.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The long carbon chain polyamide contains a long methylene chain, and its water absorption rate is low, and it has good dimensional stability compared with ordinary polyamide, which overcomes the mechanical properties of traditional polyamide filter membranes due to water absorption. Reduced defects.

(2) The long carbon chain polyamide contains polar amide groups, which can be quickly infiltrated by the organic electrolyte in the lithium ion battery, and has good wettability.

(3) The melting point and softening temperature of long carbon chain polyamide are higher than those of PP and PE (PA1012 has a melting point of 190 °C and a softening temperature of 156 °C), and has a higher film breaking temperature and suitable closed cell temperature. Appropriate closed-cell temperatures are all increased by 20%, providing more reliable safety performance in lithium-ion battery separator applications.

(4) The long carbon chain polyamide has excellent mechanical properties similar to ordinary polyamides, and can meet the strength requirements of water filtration membranes and lithium battery separators.

(5) The preparation method of the porous film is a flat sheet stretching method, which does not require a solvent compared with methods such as thermally induced phase separation, and the preparation process is simple and environmentally friendly.

Description of drawings

Figure 1: Scanning electron microscope image of the microstructure of Example 2 of the present invention.

Figure 2: Scanning electron microscope image of the microstructure of Example 3 of the present invention.

Figure 3: Scanning electron microscope image of the microstructure of Example 4 of the present invention.

Figure 4: Scanning electron microscope image of the microstructure of Example 7 of the present invention.

Figure 5: Scanning electron microscope image of the microstructure of Example 22 of the present invention.

Figure 6: Scanning electron microscope image of the microstructure of Example 23 of the present invention.

Detailed ways

The embodiments in the following examples can be further combined or replaced, and the examples are only to describe the preferred embodiments of the present invention, and not to limit the concept and scope of the present invention. Various changes and improvements made to the technical solutions of the present invention by professional and technical personnel all belong to the protection scope of the present invention.

Example 1

(1) First prepare a PA1012 extrusion film, the melting point of PA1012 is 190°C, the melt index is 20g/min, the melt extrusion method is adopted, and the extrusion temperature is 210°C;

(2) Put the above-mentioned extruded film on the stretching equipment and isothermally for 5min, the isothermal temperature is 10°C, and then uniaxially stretch at this temperature with a stretching rate of 5 μm/s, and the stretching elongation is 10%, A PA1012 porous membrane was obtained with a tensile breaking strength of 49.1 MPa and a pore size of 0.01 μm.

Example 2

(1) First prepare a PA1012 extrusion film, the melting point of PA1012 is 190°C, the melt index is 15g/min, the melt extrusion method is adopted, and the extrusion temperature is 220°C;

(2) Put the above-mentioned extruded film on the stretching equipment and isothermally for 10min, the isothermal temperature is 60°C, and then stretch uniaxially at this temperature with a stretching rate of 20 μm/s, and the tensile elongation is 200%, The PA1012 porous film was obtained, with a tensile breaking strength of 50.3 MPa and a pore size of 1 μm. The scanning electron microscope image of the microstructure is shown in Figure 1. It can be seen from Figure 1 that the micropores are elliptical-like, and the long axes of at least two elliptical-like shapes are close to one line. straight or parallel.

Example 3

(1) First prepare a PA1012 extrusion film, the melting point of PA1012 is 190°C, the melt index is 1 g/min, the melt extrusion method is adopted, and the extrusion temperature is 250°C;

(2) Put the above-mentioned extruded film on the stretching equipment for 15 minutes at the isothermal temperature, and the isothermal temperature is 100°C, and then uniaxially stretch at the stretching rate of 50 μm/s at this temperature, and the tensile elongation is 200%, The PA1012 porous film was obtained, with a tensile breaking strength of 49.5 MPa and a pore size of 2 μm. The scanning electron microscope image of the microstructure is shown in Figure 2. It can be seen from Figure 2 that the micropores are elliptical-like, and the long axes of at least two elliptical-like shapes are close to one line. straight or parallel.

Example 4

(1) First prepare the PA1012 extrusion film, the melting point of PA1012 is 190°C, the melt index is 0.5g/min, the melt extrusion method is adopted, and the extrusion temperature is 260°C;

(2) Put the above-mentioned extruded film on the stretching equipment for 8 minutes at an isothermal temperature, and the isothermal temperature is 100°C, and then uniaxially stretch at a stretching rate of 10 μm/s at this temperature, and the tensile elongation is 650%, The obtained PA1012 porous film has a self-tensile breaking strength of 53.3 MPa and a pore size of 5 μm. The scanning electron microscope image of the microstructure is shown in Figure 3.

It can be seen from FIG. 3 that in the first direction, the long axes of the plurality of ellipse-like shapes are basically arranged in a straight line, and in the second direction perpendicular to the first direction, the long axes of the ellipse-like shapes are The axes are distributed substantially parallel; in the second direction perpendicular to the first direction, the dislocation distribution of the ellipse-like shape, the length of the long axis of the ellipse-like shape is much greater than the length of the short axis.

Example 5

(1) First prepare a PA1012 extrusion film, the melting point of PA1012 is 190°C, the melt index is 10g/min, the melt extrusion method is adopted, and the extrusion temperature is 230°C;

(2) put the above-mentioned extruded film on the stretching equipment and isothermally for 10min, the isothermal temperature is 170°C, and then biaxially stretch at this temperature with a stretching rate of 100 μm/s, and the tensile elongation is 400%, to obtain The PA1012 porous membrane has a tensile breaking strength of 52.3MPa and a pore size of 4μm.

Example 6

(1) First prepare a PA1012 extrusion film, the melting point of PA1012 is 190°C, the melt index is 20g/min, the melt extrusion method is adopted, and the extrusion temperature is 210°C;

(2) Put the above-mentioned extruded film on the stretching equipment for 10 minutes isothermally, and the isothermal temperature is 30°C, and then stretch uniaxially at the stretching rate of 400 μm/s at this temperature, and the tensile elongation is 200%, A PA1012 porous membrane was obtained with a tensile breaking strength of 50.3 MPa and a pore size of 2 μm.

Example 7

1) First prepare a PA612 extrusion film, the melting point of PA612 is 190°C, the melt index is 15g/min, the melt extrusion method is adopted, and the extrusion temperature is 220°C;

(2) Put the above-mentioned extruded film on the stretching equipment for 10 minutes isothermally, and the isothermal temperature is 30°C, and then uniaxially stretch at this temperature with a stretching rate of 500 μm/s, and the tensile elongation is 200%, The obtained PA612 porous film has a tensile breaking strength of 50.1 MPa and a pore size of 2 μm. The scanning electron microscope image of the microstructure is shown in Figure 4.

It can be seen from FIG. 4 that in the first direction, the long axes of a plurality of the ellipse-like shapes are basically arranged in a straight line, and in the second direction perpendicular to the first direction, the long axes of the ellipse-like shapes are The axes are distributed substantially parallel; in the second direction perpendicular to the first direction, the dislocation distribution of the ellipse-like shape, the length of the long axis of the ellipse-like shape is much greater than the length of the short axis.

Example 8

(1) First prepare a PA1012 hot-pressed film, the melting point of PA1012 is 190°C, the melt index is 5g/min, the hot-pressing method is adopted, and the hot-pressing temperature is 250°C;

(2) Put the above-mentioned extruded film on the stretching equipment for 10 minutes at an isothermal temperature, and the isothermal temperature is 150° C., and then biaxially stretch at this temperature with a stretching rate of 450 μm/s, and the stretching elongation is 500% to obtain The PA1012 porous membrane has a tensile breaking strength of 51.3 MPa and a pore size of 4 μm.

Example 9

(1) First prepare a PA1012 hot-pressed film, the melting point of PA1012 is 190°C, the melt index is 3g/min, the hot-pressing method is adopted, and the hot-pressing temperature is 220°C;

(2) Put the above-mentioned extruded film on the stretching equipment for 9 minutes at an isothermal temperature of 100°C, and then stretch uniaxially at this temperature at a stretching rate of 90 μm/s, with a tensile elongation of 300%, A PA1012 porous membrane was obtained, with a self-tensile breaking strength of 50.5 MPa and a pore size of 3 μm.

The following are Examples 10-21, the operation steps are as in Example 1, and the specific process parameters and performance indicators are shown in Table 1 and Table 2.

Table 1 Processing technology and basic performance parameters of Examples 10-15

Table 2 Processing technology and basic performance parameters of Examples 16-21

Example 22

(1) First prepare a PA1012 extrusion film, the melting point of PA1012 is 190°C, the melt index is 20g/min, the melt extrusion method is adopted, and the extrusion temperature is 220°C;

(2) Put the obtained extruded film on the stretching equipment for 10 minutes at an isothermal temperature, and the isothermal temperature T ₁ is 30 °C, and then uniaxially stretch at a stretching rate of 20 μm/s at this temperature, and the elongation ε ₁ is 200%, and then let the previously obtained tensile sample be isothermal for ₁₀ min at a temperature T of 100 °C, and then uniaxially stretched at this temperature at a tensile rate of 20 μm/s, with a tensile elongation of ε ₂ of 400 %, the porous film was obtained with a tensile breaking strength of 49.5 MPa and a pore size of 0.9 μm. The scanning electron microscope image of the microstructure is shown in Figure 5.

It can be seen from FIG. 5 that in the first direction, the long axes of the plurality of ellipse-like shapes are basically arranged in a straight line, and in the second direction perpendicular to the first direction, the long axes of the ellipse-like shapes are The axes are distributed substantially parallel; in the second direction perpendicular to the first direction, the dislocation distribution of the ellipse-like shape, the length of the long axis of the ellipse-like shape is much greater than the length of the short axis.

Example 23

(1) First prepare a PA1012 extrusion film, the melting point of PA1012 is 190°C, the melt index is 15g/min, the melt extrusion method is adopted, and the extrusion temperature is 220°C;

(2) The obtained extruded film was placed on the stretching equipment for 8 minutes at an isothermal temperature of 30°C, and then biaxially stretched at a stretching rate of 50 μm/s at this temperature, with an elongation rate of 200%, and then let The tensile sample obtained above was isothermally held at a temperature of 100 ° C for 10 minutes, and then biaxially stretched at a stretching rate of 20 μm/s at this temperature, and the tensile elongation was 400% to obtain the porous film, which was tensile fractured. The strength is 51.4MPa, the aperture is 4μm, and the scanning electron microscope image of the microstructure is shown in Figure 6.

It can be seen from Fig. 6 that the long axis of the ellipse-like shape of the formed microporous cluster is a straight line or the long axes are parallel, and the elliptical-like dislocation distribution forms a microporous cluster, and the central part of the microporous cluster is a micropore with a small aperture. .

Example 24

(1) First prepare the PA1012 extrusion film, the melting point of PA1012 is 190°C, the melt index is 0.5g/min, the melt extrusion method is adopted, and the extrusion temperature is 260°C;

(2) Put the obtained extruded film on the stretching equipment for 15 minutes at an isothermal temperature of 40°C, and then uniaxially stretch at a stretching rate of 100 μm/s at this temperature, with an elongation rate of 100%, and then Let the stretched sample obtained above be isothermal for 10 minutes at a temperature of 100 °C, and then stretched at a stretching rate of 80 μm/s at this temperature, with a tensile elongation of 200%, to obtain the porous film described above. The strength is 50.8MPa, and the pore size is 4μm.

Example 25

(1) First prepare a PA1012 extrusion film, the melting point of PA1012 is 190°C, the melt index is 1 g/min, the melt extrusion method is adopted, and the extrusion temperature is 250°C;

(2) The obtained extruded film was placed on the stretching equipment for 14 minutes at an isothermal temperature of 40°C, and then uniaxially stretched at a stretching rate of 90 μm/s at this temperature with an elongation of 400%, and then Let the stretched sample obtained above be isothermal for 10 minutes at a temperature of 100 °C, and then stretched at a stretching rate of 200 μm/s at this temperature, with a tensile elongation of 650%, to obtain the porous film described above. The tensile fracture The strength is 52.1MPa, and the pore size is 5μm.

The following are Examples 26-31 and 32-37, the operation steps are as in Example 22, and the specific process parameters and performance indicators are shown in Table 3 and Table 4.

Table 3 Processing technology and basic performance parameters of Examples 26-31

Table 4 Processing technology and basic performance parameters of Examples 32-37

The following are the water absorption properties of the long carbon chain polyamide (Table 5) and the long carbon chain polyamide and its mechanical properties after water absorption (Table 6).

Table 5 Water absorption parameters of long carbon chain polyamide after soaking in boiling water for 5h

Table 6 Mechanical properties of long carbon chain polyamide before and after water absorption for 5h

Claims (11)

1. A long carbon-chain polyamide porous membrane, characterized in that, the porous membrane is a sheet-like structure of uniform thickness, and the sheet-like structure has a plurality of micropores that are substantially independent of each other, and the porous membrane is The film is prepared from long carbon chain polyamide, and the long carbon chain polyamide is an aliphatic polyamide whose carbon chain length between two adjacent amide groups in the molecule is greater than 10, wherein, The micropores are elliptical-like, and the long axes of at least two elliptical-like shapes are close to a straight line or parallel; Or the micropores are oval-like, several oval-like clusters form several microporous clusters on the sheet-like structure, and the major axes of most oval-like shapes are basically in one direction; In the first direction, the long axes of the plurality of ellipse-like shapes are substantially arranged on a straight line, and in the second direction perpendicular to the first direction, the long axes of the ellipse-like shapes are distributed substantially parallel; Or the long axis of the ellipse-like shape forming the microporous cluster is a straight line or the long axes are parallel; The long carbon chain polyamide has a melting point of 180°C-230°C and a melt index of 0.5-20g/10min; Described long carbon chain polyamide is nylon 1012 or/and nylon 1212; The long carbon chain polyamide porous film is a single-layer film or a multi-layer composite film, and the pore size of the long carbon chain polyamide porous film is 0.01 μm-5 μm. 2 . The long carbon-chain polyamide porous membrane according to claim 1 , wherein in the second direction perpendicular to the first direction, the elliptical-like dislocations are distributed. 3 . 3 . The long carbon-chain polyamide porous membrane according to claim 1 , wherein the elliptical-like dislocation distribution forms microporous clusters. 4 . 4 . The long carbon-chain polyamide porous membrane according to claim 1 , wherein the central part of the microporous cluster is a micropore with a small pore size. 5 . 5 . The long carbon chain polyamide porous membrane according to claim 1 , wherein the melt index of the long carbon chain polyamide is 1-10 g/10min. 6 . 6. the preparation method of the long carbon chain polyamide porous membrane described in any one of claim 1-5, is characterized in that, described preparation method comprises the steps: (1) prepare long carbon chain polyamide flat sheet; (2) The above-mentioned flat sheet is placed in the stretching equipment for one-step stretching or two-step stretching. 7 . The preparation method according to claim 6 , wherein the flat sheet preparation method in step (1) is a melt extrusion method or a hot pressing method, and the extrusion or hot pressing temperature is 200° C.-300° C. 8 . 8 . The preparation method according to claim 7 , wherein the extrusion or hot pressing temperature is 220° C.-270° C. 9 . 9. preparation method according to claim 6, is characterized in that, in step (2), one step stretching is to place the flat sheet on the stretching equipment and isothermal 5-15min, the isothermal temperature is 10-170 ℃, then in This temperature is stretched to 10%-650% unidirectionally or biaxially at a stretching rate of 5-500μm/s to obtain the porous film; the two-step stretching is to place the flat sheet on the stretching equipment for 5-15min at the same temperature, The isothermal temperature is T1, and at this temperature, the tensile rate is 5-500μm/s unidirectionally or biaxially stretched to ε1, and the obtained tensile sample is isothermally held at the temperature T2 for 5-15min, and then stretched at this temperature. The rate of 5-500μm/s unidirectional or biaxial stretching ε2 to obtain the porous film, 10°C≤T1≤T2≤170°C, 10%≤ε1≤ε2≤650%. 10 . The preparation method according to claim 9 , wherein the stretching rate is 10 μm/s-100 μm/s. 11 . 11. An application of the long carbon-chain polyamide porous membrane of any one of claims 1-5 in the fields of lithium ion battery separators and water filtration membranes.

Images