KR101317641B1 - Manufacturing method of polyamideimide-based porous membrane - Google Patents

Abstract

The present invention relates to a method for producing a polyamideimide-based porous membrane.
The present invention is a polyamideimide-based porous membrane having excellent strength and high air permeability by applying a polymer solution consisting of a polar solvent, polyamideimide and pore control agent to a support, dried at high temperature, solidified and heat treated at high temperature Provide a method.
The polyamide-imide porous membrane of the present invention is excellent in strength and air permeability, and thus may be usefully applied to a separator for secondary batteries.

Description

MANUFACTURING METHOD OF POLYAMIDEIMIDE-BASED POROUS MEMBRANE

The present invention relates to a method for producing a polyamide-imide porous membrane, and more particularly, a polymer solution consisting of a polar solvent, a polyamide-imide, and a pore control agent is applied to a support, dried at high temperature, solidified, and then heat-treated at high temperature. It relates to a method for producing a polyamide-imide porous membrane having excellent strength and high air permeability.

The polyamideimide has a heat deformation temperature of 278 ° C. and a long service temperature of 200 ° C. or more, and has excellent heat resistance and excellent mechanical strength. In addition, it is widely used in parts that require characteristics such as wear resistance, flame resistance, and radiation resistance.

As a method of dissolving and forming a film of the polyamideimide polymer material, a method of forming a film after blending polyetherimide with a polyamideimide in Japanese Patent Laid-Open No. 11-90194 is proposed. However, the above method is a method of manufacturing a hollow fiber membrane through a dry method has a disadvantage that the tensile strength is insufficient to form into a flat film used in the secondary battery through this.

Korean Patent Publication No. 2006-0120267 discloses polyolefin after adding glycols to polyamideimide resin solution to add homogeneity of pore size and adding ketones and alcohols mixed with water to adjust pore size and distribution of porous membrane. Disclosed is a porous film for secondary batteries produced by applying to a nonwoven series. However, the polyamide-imide membrane prepared by the above method is insufficient to be used as a secondary battery membrane due to insufficient tensile strength, and also has a problem of insufficient air permeability.

It is an object of the present invention to provide a method for producing a polyamideimide-based porous membrane having excellent strength and high air permeability.

In order to achieve the above object, the present invention comprises the steps of applying a polymer solution dissolved in a polar solvent, polyamideimide and pore control agent on a support to form a polymer membrane; Forming pores on top of the polymer film applied on the support; Drying the polymer film applied on the support at a temperature of 50 to 100 ° C. to remove the solvent; Immersing the polymer membrane in a coagulation bath to solidify it, and then peeling the polymer membrane from the support; It provides a method for producing a polyamideimide-based porous membrane comprising the step of curing the polymer membrane at a temperature of 150 to 300 ℃.

At this time, it is preferable to form pores in the upper layer of the polymer membrane by injecting air maintaining a temperature of 20 to 60 ℃ and a relative humidity of 80 to 95% to the polymer film coated on the support.

In addition, the polyamideimide-based porous membrane has a thickness of 10 to 100㎛, pore size of 0.01 to 1.0㎛ and provides a method for producing a polyamideimide-based porous membrane, characterized in that the tensile strength is 500 to 1500kgf / ㎠.

According to the present invention, a polymer solution composed of a polar solvent, a polyamideimide and a pore control agent is applied to a support, dried at high temperature, solidified and heat treated at high temperature to obtain a polyamideimide-based porous membrane having excellent strength and high air permeability. It can provide a manufacturing method.

In addition, according to the present invention, it is possible to provide a method for producing a polyamide-imide-based porous membrane having an excellent tensile strength of 500 to 1500kgf / ㎠ and an average pore size increases and a high air permeability of 200 to 500 seconds / 100cc. .

Hereinafter, the present invention will be described in more detail.

The present invention comprises the steps of applying a polymer solution dissolved in a polar solvent, polyamideimide and pore control agent on a support to form a polymer membrane; Forming pores on top of the polymer film applied on the support; Drying the polymer film applied on the support at a temperature of 50 to 100 ° C. to remove the solvent; Immersing the polymer membrane in a coagulation bath to solidify it, and then peeling the polymer membrane from the support; It provides a method for producing a polyamideimide-based porous membrane comprising the step of curing the polymer membrane at a temperature of 150 to 300 ℃.

Hereinafter, the steps for configuring the polyamideimide-based porous membrane will be described in detail.

The first step of the present invention is to form a polymer membrane by applying a polymer solution in which a polar solvent, polyamideimide (PAI) and a pore regulator are dissolved on a support.

The polar solvent is used to dissolve the polyamideimide and pore control agent, preferably an aprotic polar solvent is used, specifically N-methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfide and dimethylacetamide Any one or more selected from the group consisting of can be mixed and used.

The polyamideimide is a polymer containing both an amide bond and an imide bond in a molecule, and refers to a polymer having as an essential component a repeating unit represented by the following Chemical Formula 1.

,

또는 이들의 혼합물이고, n은 50 내지 1000의 정수이다.Where Ar is

,

Or a mixture thereof, n is an integer from 50 to 1000.

The polyamideimide is an imide-based material, has a property of dissolving in a solvent, and is excellent in heat resistance, chemical resistance, mechanical strength, and electrical insulation, and is a preferred material for use in secondary battery separators.

The polyamideimide preferably contains 10 to 50 parts by weight with respect to 100 parts by weight of a polar solvent, wherein if the content of polyamideimide is less than 10 parts by weight, the viscosity of the polymer solution is weak and the strength and physical properties of the prepared porous membrane are increased. There is a tendency to decrease, and when it exceeds 50 parts by weight, the viscosity becomes strong, making the film formation difficult, and the air permeability of the produced film is reduced, which is undesirable.

The pore control agent to smooth the flow of ions by adjusting the pore size in the range of 0.1 to 1 ㎛ average pore size, using a hydrophilic material and specifically selected from the group consisting of polyvinylpyrrolidone and polyethylene glycol The above can be mixed and used. Preferably polyvinylpyrrolidone is used, more preferably polyvinylpyrrolidone having a molecular weight ranging from 10,000 to 500,000.

The pore modifier is particularly high in affinity with water, and when added to a polymer solution, the affinity with water, which is a non-solvent solution, increases the formation of pores. Water moves toward the pores, resulting in large pore formation. If the molecular weight of the pore regulator is less than 10,000 does not affect the pore size, and if the molecular weight exceeds 500,000, the polymer content in the solution is increased to increase the viscosity to decrease the pore size.

The pore control agent is preferably dissolved 1 to 50 parts by weight based on 100 parts by weight of a polar solvent. If the pore regulator is less than 1 part by weight, the pore size does not affect the pore size. If the content exceeds 50 parts by weight, the resistance to water at the time of phase separation increases, so that the difference in composition of each phase is decreased, and the polymer content in the solution is increased. As the viscosity increases, the pores decrease again.

Polyetherimide (PEI) may be further added to the polymer solution, and the polyetherimide is a polymer having an ether bond and an imide bond in the molecule at the same time, and the repeating unit represented by the following Chemical Formula 2 is an essential component. Refers to a polymer.

Wherein n is an integer from 20 to 200.

The polyetherimide is an imide-based material, has a property of dissolving in a solvent, and is excellent in heat resistance, chemical resistance, mechanical strength, and electrical insulation, and is a preferred material for use in secondary battery separators.

At this time, it is preferable to include 1 to 50 parts by weight of polyamideimide based on 100 parts by weight of the polar solvent. If the content of the polyamideimide is less than 1 part by weight, it does not affect the strength and physical properties of the prepared porous membrane, and if it exceeds 50 parts by weight, the viscosity becomes stronger, making film formation difficult and reducing the air permeability of the prepared membrane, which is not preferable. .

The polymer solution is coated on a support to form a polymer film, and the support may be made of a material such as glass, stainless steel, aluminum, copper alloy, polyethylene terephthalate (PET) sheet, or the like. The method of applying the polymer solution on the support is not particularly limited, and conventional methods used in the art may be used, and specifically, gravure coat, bar coat, spray coat, spin coat, knife coat, roll coat or Various methods, such as a die coat, can be used.

The second step in the method for producing a polyamideimide-based porous membrane of the present invention is to form pores on top of the polymer film applied on the support, the temperature is 20 to 60 ℃ to the polymer film applied on the support in the first step And spraying air maintaining a relative humidity of 80 to 95% to form pores in the upper layer of the polymer membrane. When the humidified air is sprayed, the solvent gradually escapes according to the relative humidity and the exposure time, thereby increasing the pore size and thinning the membrane.

The injection speed of the air is carried out at 1 to 20m / min, the air exposure time is performed for 5 seconds to 10 minutes. If the injection speed of the air is less than 1m / min, the formation of pores is not smooth, if it exceeds 20m / min is not preferable because scratches on the surface of the membrane affects the pore formation. In addition, the exposure time to the air during the air injection is preferably carried out for 5 seconds to 10 minutes, less than 5 seconds it is preferable that the residence time for solidification is sufficiently controlled because the pore formation of the surface is insufficient. At this time, the pore of the membrane is significantly larger than 10 minutes, so that the pores are formed in the applied polymer solution and the strength is also significantly decreased. When the membrane is produced without keeping the air at constant temperature and humidity, the surface of the membrane becomes uneven and the thickness, strength, pore size, etc. of the membrane cannot be controlled.

In the method for producing a polyamide-imide-based porous membrane of the present invention, the third step is to dry the polymer membrane coated on the support in the second step in a high temperature oven for 12 to 48 hours at a temperature of 50 to 100 ℃ condition, As the solvent slowly withdraws with time and exposure time, the strength of the porous membrane becomes stronger. In this case, when the drying temperature is less than 50 ° C., the solvent does not completely fall out, and thus the strength is lowered. When the drying time exceeds 100 ° C., the bonding between the support and the polymer membrane becomes strong, which makes it difficult to peel off.

In the method for producing a polyamideimide-based porous membrane of the present invention, the fourth step is to solidify the polymer membrane by immersing it in a coagulation bath, and then peeling the membrane from the support. In this case, the coagulation solution of the coagulation bath may be used by mixing water or alcohol such as methanol, ethanol, isopropyl alcohol, ethylene glycol with good compatibility with water.

In the production method of the present invention, a post-process may be further performed by immersing the peeled polymer membrane in a washing tank to extract the residual solvent components contained in the membrane matrix to form pores.

The final step in the method for producing a polyamideimide-based porous membrane of the present invention is to cure the polymer membrane peeled from the support at a temperature of 150 to 300 ℃, put in a high temperature oven for 30 minutes to 24 hours depending on the temperature and exposure time The heat treatment improves the strength of the porous membrane while the polyamide-imide polymer is cured. At this time, if the temperature is less than 150 ℃ polyamideimide polymer is not cross-linked there is a problem that the strength is not improved, if the temperature exceeds 300 ℃ there is a problem that the polymer is excessively cured and the film is broken.

Hereinafter, embodiments of the present invention will be described.

The following examples are merely illustrative of the present invention, but the scope of the present invention is not limited to the following examples.

≪ Example 1 >

To 160 mL of N-methylpyrrolidone (NMP) was added 30 g of polyamideimide (Sorvey Corporation, Torlon-4000T) slowly to uniformly disperse, and then heated to 80 ° C. Thereafter, 10% by weight of polyvinylpyrrolidone (Across, K29-32, Mw 68,000) was added as a pore regulator, followed by stirring for 24 hours to prepare a polymer solution.

Next, the polymer solution was cast on a glass support at a rate of 50 mm / sec uniformly so as to have a thickness of 20 μm. After exposure to air for 3 minutes using a gradient device at a temperature of 30 ° C. and a relative humidity of 95%, the coated solution was treated to adjust pores. Porous membranes were prepared.

Next, the support and the porous membrane are solidified by passing through an upper layer of distilled water coagulation bath, and then the porous membrane is peeled off from the support, the remaining solvent component contained in the porous membrane is extracted in a washing tank, and thermally cured at a temperature of 230 ° C. Amidimide porous membrane was prepared.

<Example 2>

A polyamideimide porous membrane was prepared in the same manner as in Example 1 except that 10% by weight of polyvinylpyrrolidone (Across, K90, Mw 360,000) was added.

<Example 3>

A polyamideimide porous membrane was prepared in the same manner as in Example 1, except that 5% by weight of polyvinylpyrrolidone (Across, K90, Mw 360,000) was added.

<Example 4>

A polyamideimide porous membrane was prepared in the same manner as in Example 1 except that 30 g of polyetherimide was further added to the polymer solution.

&Lt; Comparative Example 1 &

To 160 mL of N-methylpyrrolidone (NMP) was added 30 g of polyamideimide (Sorvey Corporation, Torlon-4000T) slowly to uniformly disperse, and then heated to 80 ° C. Thereafter, 10% by weight of polyvinylpyrrolidone (Across, K29-32, Mw 68,000) was added as a pore regulator, followed by stirring for 24 hours to prepare a polymer solution.

Next, the polymer solution was cast on a glass support at a rate of 50 mm / sec uniformly so as to have a thickness of 20 μm. After exposing to air for 3 minutes using a gradient apparatus at a temperature of 30 ° C. and a relative humidity of 95% to treat pores by treating the coated solution, a porous polymer was prepared by drying the coated polymer solution on a support at room temperature.

Next, the support and the porous membrane were solidified by passing through the upper layer of distilled water coagulation bath, the porous membrane was separated from the support, and the remaining solvent component contained in the porous membrane was extracted in the washing tank to prepare a polyamideimide porous membrane.

Comparative Example 2

A polyamideimide porous membrane was prepared in the same manner as in Example 1 except that the polymer solution coated on the support was dried at room temperature.

&Lt; Comparative Example 3 &

The polyamideimide porous membrane was prepared in the same manner as in Example 1 except that the peeled porous membrane was not subjected to a 230 ° C. heat treatment.

<Experimental Example 1>

For the polyamideimide porous membranes prepared in Examples 1 to 4 and Comparative Examples 1 to 3, the film thickness was measured by a micrometer (Sony), and 0 to 60 psi through a filter tester (Capillary flow porometer, PMI). The air permeability and average pore diameter were measured under pressure. After cutting the porous polyamide-imide membrane to a certain size, the tensile strength of the membrane in the casting direction (MD, machine direction) and the casting perpendicular direction (TD, Transverse direction) were measured using a tensile strength measuring instrument (Lloyd's Co.). It is listed in Table 1 below.

thickness
(탆) Average pore size
(탆) Specularity
(Sec / 100cc) MD tensile strength
(kgf / cm2) TD tensile strength
(kgf / cm2) Example 1 15 0.09 221 780 661 Example 2 24 0.06 481 1013 945 Example 3 13 0.08 305 1377 1106 Example 4 22 0.08 339 1074 800 Comparative Example 1 18 0.11 535 122 99 Comparative Example 2 23 0.18 452 638 591 Comparative Example 3 15 0.16 330 351 206

As shown in Table 1, in the case of the polyamideimide porous membranes of Examples 1 to 4 dried at a high temperature and heat treated at a high temperature in the polyamideimide porous membrane manufacturing process, the same procedure as in Comparative Examples 1 to 3 It was confirmed that both MD tensile strength and TD tensile strength were significantly improved than the polyamideimide porous membrane.

As described above, according to the present invention, a polyamideimide-based porous membrane having an excellent tensile strength of 500 to 1500 kgf / cm 2 and at the same time having an average pore size is increased has a high air permeability of 200 to 500 seconds / 100 cc. It can be usefully applied as a secondary battery separator by controlling the size of the pore and the thickness of the membrane through the method of spraying the type of additives and humidified air.

Although the present invention has been described in detail only with respect to the embodiments described, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, and such modifications and modifications belong to the appended claims.

Claims (3)

A polymer solution obtained by dissolving a polar solvent, polyamideimide, and a pore control agent selected from the group consisting of N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, and a mixture of two or more of them is applied onto a support. Forming a film;
Forming pores on top of the polymer film applied on the support;
Drying the polymer film applied on the support at a temperature of 50 to 100 ° C. to remove the solvent;
Immersing the polymer membrane in a coagulation bath to solidify it, and then peeling the polymer membrane from the support;
Curing the polymer membrane to a temperature of 150 to 300 ° C;
The method of claim 1, wherein the polymer membrane has a thickness of 10 to 100 µm, a pore size of 0.01 to 1.0 µm, and a tensile strength of 500 to 1500 kgf / cm 2. The polyamideimide of claim 1, wherein air is maintained at a temperature of 20 to 60 ° C. and a relative humidity of 80 to 95% to the polymer film coated on the support to form pores in the upper layer of the polymer film. Method for producing a porous membrane. delete