WO2019245154A1 - Cation exchange membrane comprising polymer support and manufacturing method therefor - Google Patents

Abstract

The present invention relates to a cation exchange membrane comprising: a support containing ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-glycidyl methacrylate copolymer (EGMA), or the like; and a cation exchanger, wherein the support and the cation exchanger form an interpenetrating polymer network structure. The cation exchange membrane of the present invention has excellent thermal stability and mechanical characteristics, and the manufacturing method for the cation exchange membrane of the present invention implements a simplified process, and thus is economical and lowers the failure rate, leading to excellent productivity.

Description

Cation exchange membrane comprising polymer support and method for preparing same

The present invention relates to a cation exchange membrane and a method for producing the same, and more particularly, to a cation exchange membrane having excellent thermal stability and mechanical properties, and a simplified process, and to a method for producing a cation exchange membrane having excellent productivity with low productivity and low defect rate.

Ion exchange membranes such as NEOSEPTA (ASTOM Corp. Japan) and SELEMION (Asahi Glass Company, Japan), which are conventionally used, are copolymerized with a support made of PVC spun fiber and styrene-divinylbenzene monomer by paste method. Ion exchange membranes prepared by sulfonation have relatively good electrochemical properties and are widely used worldwide.

However, due to the high level of difficulty in spinning, only a few companies make fiber from PVC, which is difficult to supply due to the high cost of fiber. The paste method is a method of impregnating and coating a woven support on a paste mixed with a PVC powder and a monomer. Air gaps generated by unimpregnation may remain as pin holes later to degrade the performance of the ion exchange membrane. It is a tricky process that requires attention.

In addition, due to the low thermal stability of the PVC material that thermal decomposition at low temperature (40 ℃), the use temperature of the ion exchange membrane must be limited to 40 ℃ or less, the temperature limit of the treated water is eventually for cooling Pretreatment equipment is required to increase the cost of the overall ion exchange system. In addition, in the case of the ion-exchange membrane containing a PVC material, some plasticizers are used to overcome brittleness, which may be difficult to apply to the food field because the plasticizer may be eluted at a high temperature.

Therefore, it is necessary to develop an ion exchange membrane including a new material as a support that is easily supplied and has excellent thermal stability and mechanical properties without degrading the performance of the ion exchange membrane.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cation exchange membrane having excellent thermal stability and mechanical properties in view of the problems of the prior art.

It is still another object of the present invention to provide a method for producing a cation exchange membrane which is economical and has low productivity due to a simplified process.

The cation exchange membrane of the present invention is a support comprising one or more of the compounds represented by the following formula (1) and (2); And a cation exchanger, wherein the support and the cation exchanger can form an interpenetrating polymer network structure.

[Formula 1]

In Formula 1,

R is a C1 acetoxyl group or a C1 to C4 acrylic ester group,

m and n are the number of repetitions of the repeating unit,

m: n is from 100: 5 to 100: 50,

The number average molecular weight (Mn) is 3,000 to 500,000.

[Formula 2]

In Formula 2,

R is a C1 to C4 acrylic ester group,

m and n are the number of repetitions of the repeating unit,

m: n is from 100: 5 to 100: 50,

The number average molecular weight (Mn) is 3,000 to 500,000.

In the formula (1), the compound represented by R is an aceoxyl group may be preferably an ethylene-vinyl acetate copolymer (EVA).

In Formula 1, the compound represented by R is an acrylic ester group may be at least one selected from ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), and ethylene-butyl acrylate copolymer (EBA).

The compound represented by Formula 2 may be at least one selected from ethylene-methyl methacrylate copolymer (EMMA) and ethylene-glycidyl methacrylate copolymer (EGMA).

The cation exchanger may be a polymer having a sulfonic acid functional group and polymerized with one or more monomers selected from styrene, divinylbenzene, α-methyl styrene, methyl styrene, t-butyl styrene, and chloromethyl styrene.

The thickness of the support may be 0.01 to 1 mm.

In addition, the method for producing a cation exchange membrane of the present invention is (a) a solution for polymerization comprising at least one monomer selected from styrene, divinylbenzene, α-methyl styrene, methyl styrene, t-butyl styrene, chloromethyl styrene and an initiator. Preparing a mixture by immersing a support including at least one of the compounds represented by Formulas 1 and 2 below; (b) polymerizing the mixture to produce a base film; (c) sulfonating the base membrane to prepare a cation exchange membrane into which sulfonic acid functional groups are introduced.

In step (a), the support can be swollen.

The swelling degree of the swelled support may be 10 to 60%.

The temperature of step (a) may be below the onset temperature of the initiator.

The initiator may be at least one selected from Benzoyl peroxide (BPO) and Azobisisobutyronitrile (AIBN).

The temperature of step (a) is 10 to 70 ° C., and may be performed for 1 to 10 hours.

The polymerization temperature of step (b) may be 70 to 140 ° C., and the polymerization time may be 4 to 18 hours.

Step (c) may be performed by immersing the base membrane in a solution containing at least one selected from sulfuric acid, chloro sulfuric acid, and dichloroethane (DCE).

(d) washing the cation exchange membrane into which the sulfonic acid functional group is introduced may be further washed with deionized water, and then immersing in a NaOH solution to neutralize unreacted sulfonic acid.

The polymerization solution is 100 parts by weight of styrene monomer; 2 to 25 parts by weight of divinylbenzene monomer; And 0.1 to 2.5 parts by weight of a polymerization initiator.

The cation exchange membrane of the present invention is excellent in thermal stability and mechanical properties, the production method of the cation exchange membrane of the present invention is a simplified process, economical, low defect rate is excellent in productivity.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail. In the following description of the present invention, detailed descriptions of related well-known configurations or functions may be omitted.

The terms or words used in the specification and claims are not to be construed as being limited to conventional or dictionary meanings, but should be construed as meanings and concepts corresponding to the technical matters of the present invention.

The embodiments described in the specification and the configuration shown in the drawings are preferred embodiments of the present invention, and do not represent all of the technical idea of the present invention, various equivalents and modifications that can replace them at the time of the present application are There may be.

The cation exchange membrane of the present invention is a support comprising one or more of the compounds represented by the following formula (1) and (2); And a cation exchanger, wherein the support and the cation exchanger can form an interpenetrating polymer network structure.

[Formula 1]

In Formula 1,

R is a C1 acetoxyl group or a C1 to C4 acrylic ester group,

m and n are the number of repetitions of the repeating unit,

m: n is from 100: 5 to 100: 50,

The number average molecular weight (Mn) is 3,000 to 500,000.

[Formula 2]

In Formula 2,

R is a C1 to C4 acrylic ester group,

m and n are the number of repetitions of the repeating unit,

m: n is from 100: 5 to 100: 50,

The number average molecular weight (Mn) is 3,000 to 500,000.

In the formula (1), the compound represented by R is an aceoxyl group may be preferably an ethylene-vinyl acetate copolymer (EVA).

In Formula 1, the compound represented by R is an acrylic ester group may be an ethylene-methyl acrylate copolymer (EMA), an ethylene-ethyl acrylate copolymer (EEA), an ethylene-butyl acrylate copolymer (EBA), or the like.

The compound represented by Formula 2 may be ethylene-methyl methacrylate copolymer (EMMA), ethylene-glycidyl methacrylate copolymer (EGMA), or the like.

The cation exchanger may be a polymer having a sulfonic acid functional group and polymerized with one or more monomers selected from styrene, divinylbenzene, α-methyl styrene, methyl styrene, t-butyl styrene, and chloromethyl styrene.

Preferably styrene-divinylbenzene copolymer having sulfonic acid functionality.

The thickness of the support may be 0.01 to 1 mm, preferably 0.05 to 0.4 mm, more preferably 0.1 to 0.2 mm.

When the thickness of the support is less than 0.01 mm, the thickness may be too thin to decrease the function of supporting the cation exchange membrane, and when the thickness is greater than 1 mm, the electrical resistance may increase due to the difference in sulfonation degree.

Hereinafter, a method of manufacturing the cation exchange membrane of the present invention will be described in detail.

First, styrene, Divinylbenzene , α- methyl  Styrene, methyl  At least one monomer selected from styrene, t-butyl styrene, chloromethyl styrene, and Initiator  A mixture is prepared by immersing a support including at least one of the compounds represented by the following Chemical Formulas 1 and 2 in the polymerization solution containing (step a).

[Formula 1]

In Formula 1,

R is a C1 acetoxyl group or a C1 to C4 acrylic ester group,

m and n are the number of repetitions of the repeating unit,

m: n is from 100: 5 to 100: 50,

The number average molecular weight (Mn) is 3,000 to 500,000.

[Formula 2]

In Formula 2,

R is a C1 to C4 acrylic ester group,

m and n are the number of repetitions of the repeating unit,

m: n is from 100: 5 to 100: 50,

The number average molecular weight (Mn) is 3,000 to 500,000.

The support may be swelled by being immersed in the polymerization bath.

The swelling degree of the swelled support may be 10 to 60%, preferably 20 to 50%, more preferably 30 to 40%.

The swelling degree is calculated as in Equation 1 below.

[Equation 1]

Swelling degree = ((monomer weight + initiator weight) / (weight of z + monomer weight + initiator weight)) x 100%

Here, z is the weight of at least one of the compounds represented by the formula (1) to (2).

The degree of swelling is an important parameter influencing the electrical and mechanical properties of the ion exchange membrane. The higher the swelling degree, the higher the ion exchange capacity (IEC) and the lower the electrical resistance value, but the excessively swelling of more than 60% can easily break the ion exchange membrane even under small impact or stress.

The ratio of the polar groups R of the compounds represented by Formulas 1 and 2 may be controlled by the swelling temperature and the swelling time. If the content of the polar group R is too high (in the ratio of m: n in the formulas 1 and 2, n is greater than 50 when m is 100), the compounds represented by the formulas (1) and (2) are dissolved or Low chemical properties, the main chain can be eroded away in the sulfonation process (step c) to be described later. If the content of the polar group R is too low (in the ratio of m: n in the formula 1 and 2, n is less than 5 when m is 100), the monomer is difficult to penetrate into the interior of the compound represented by the formula (1) and (2) swelling degree Low has a problem that the electrical resistance value increases.

The compound represented by Formulas 1 and 2 may have a thickness of 0.01 to 1 mm, preferably 0.05 to 0.4 mm, more preferably 0.1 to 0.2 mm.

When the thickness of the compound represented by Formulas 1 and 2 is less than 0.01 mm, the thickness may be too thin to decrease the function of supporting the cation exchange membrane, and when the thickness is greater than 1 mm, a sulfonation process to be described later (step c) Due to the difference in the degree of sulfonation inside and outside the electrical resistance value can be increased.

The temperature of step (a) may be less than the initiation temperature of the initiator, the initiator may be BPO (Benzoyl peroxide), Azobisisobutyronitrile (AIBN), anionic polymerization initiator, cationic polymerization initiator, latent polymerization initiator and the like, but preferably It may be a BPO.

The temperature of step (a) may be between 10 and 70 ° C., preferably between 20 and 60 ° C., more preferably between 30 and 50 ° C. The execution time of step (a) may be performed for 0.1 to 10 hours, preferably 1 to 5 hours, more preferably 2 to 4 hours. However, the temperature and time of step (a) is not limited thereto and may vary depending on the type of initiator.

Further, in step (a), a small amount of a polymerization inhibitor (10 to 500 ppm based on the weight of the monomer) may be added to the polymerization solution so that the compound swells in the monomer state.

The polymerization solution is preferably 100 parts by weight of styrene monomer; 2 to 25 parts by weight of divinylbenzene monomer; And 0.1 to 2.5 parts by weight of a polymerization initiator.

Next, the mixture is polymerized to prepare a base film (step b).

The polymerization temperature of step (b) may be 70 to 140 ° C., preferably 75 to 120 ° C., more preferably 80 to 100 ° C. The polymerization time of step (b) may be carried out for 4 to 18 hours, preferably 6 to 16 hours, more preferably 8 to 14 hours. However, the polymerization temperature and time of step (b) is not limited thereto, and may vary depending on the type of monomer and initiator.

The base film formed by the polymerization is formed of an interpenetrating polymer network (IPN) structure, thereby forming a polymer film having a very homogeneous, flexible and excellent mechanical properties.

remind Basement membrane Sulfonated  Sulfonate functional group introduced Cation exchange membrane  To manufacture (step c).

In more detail, sulfonation is performed by immersing the base membrane in a solution containing sulfuric acid, chloro sulfuric acid, dichloroethane (DCE), nitrobenzene, and the like.

Preferably, sulfonation is performed by immersing the base membrane for 1 to 4 hours at room temperature in a solution in which 1 to 5% by weight of chlorosulfuric acid is uniformly stirred in 95 to 99% by weight of dichloroethane (DCE).

Since the cation exchange membrane prepared by the sulfonation may have an unreacted sulfonic acid, it may be further washed with deionized water and then immersed in NaOH solution to neutralize the unreacted sulfonic acid (step d).

At this time, the osmotic shock due to the sudden absorption of water in the washing / neutralization process (osmotic shock) is accompanied. When the existing PVC or hard material is used as a support, the impact may break the cation exchange membrane. However, due to the inherent flexibility and elasticity, the polymer support having the polar group of the present invention is not broken even by osmotic shock, so that the defect rate is low and the productivity is excellent.

EXAMPLE

Hereinafter, a preferred embodiment of the present invention will be described. However, this is for illustrative purposes and the scope of the present invention is not limited thereby.

Example 1

EVA (EVA2030, Hanwha) was made to a thickness of 0.12mm using a Blown Film Extruder to prepare a support. The support was swelled by immersion for 1 hour at 40 ° C. in a polymer solution containing 95% by weight of styrene monomer, 5% by weight of divinylbenzene monomer and 0.5% by weight of polymerization initiator.

Next, the base film was prepared by polymerization at 80 ° C. for 12 hours. A cation exchange membrane was prepared by immersing the base membrane in a solution obtained by uniformly stirring 2 wt% chlorosulfuric acid in 98 wt% dichloroethane (DCE) at room temperature for 2 hours.

Next, after washing with deionized water (deionized water) and neutralized unreacted sulfonic acid for 4 hours in 2M NaOH solution.

Example 2

EMA (Elvaloy 1218AC, DuPont) to Blown Film Extruder using The support was prepared by making thickness 0.12mm. The subsequent step was to prepare a cation exchange membrane in the same manner as in Example 1.

Example 3

EGMA (LOTADER AX8840, ARKEMA) to Blown Film Extruder To a thickness of 0.12 mm to prepare a support. The subsequent step was to prepare a cation exchange membrane in the same manner as in Example 1.

Comparative Example 1

Cation exchange membrane CMX (ASTOM Corp. Japan) prepared using a PVC support was used as Comparative Example 1.

Comparative Example 2

A cation exchange membrane CMV (Asahi Glass Company, Japan) prepared using a PVC support was used as Comparative Example 2.

[Test Example]

Test Example: Measurement of Cation Exchange Membrane

(1) Electric resistance: The cation exchange membranes of Examples 1 to 3, Comparative Examples 1 and 2 were soaked in 0.5N NaCl solution for 24 hours or more so that the electrolyte solution and the cation exchange membrane were in equilibrium. The resistance was measured using an LCR meter.

(2) Water swelling ratio: The cation exchange membranes of Examples 1 to 3, Comparative Examples 1 and 2 were cut into 2 cm x 2 cm, soaked in distilled water for 24 hours or more to reach an equilibrium state, and then cation exchange membranes. The moisture of the surface was removed and the weight (W _wet ) of the wet state was measured. The wet cation exchange membrane was placed in a drying oven (60 ° C.) to measure the weight (W _dry ) after drying for 24 hours, and the water content (W) was calculated using Equation 2 below.

[Equation 2]

W = (W _wet -W _dry ) / W _dry

(3) Ion transport water: Ion transport water is charged in both electrolyte baths with different concentrations of electrolyte (0.001M, 0.005M NaCl), and the potential difference (Em) between the cation exchange membranes is measured. The ion transport was calculated by substitution.

[Equation 3]

Em = (RT / F) × (2t _m -1) × ln (C ₁ / C ₂ )

In Equation 3, R is the gas constant, F is the faraday constant, T is the absolute temperature, C ₁ is the high concentration of the solution, C ₂ is the low concentration of the solution, Em is the average potential obtained, and t _m is the ion transport of the cation exchange membrane. Indicates.

(4) Burst strength

Burst strength was tested by the ballbusting method of KS K 0350 using a tensile tester.

According to the experimental method described above, the properties of the cation exchange membranes of Examples 1 to 3, Comparative Example 1 and Comparative Example 2 were measured and shown in Table 1 below.

division	Electrical resistance (Ω · ㎠)	Moisture content (%)	Ion transport water (-)	Burst strength (kpa)
Example 1	1.82	46.6	0.98	1,500
Example 2	2.1	41.3	0.98	1,180
Example 3	2.4	35.4	0.98	940
Comparative Example 1	3	30	0.98	490
Comparative Example 2	2.5	22.5	0.92	392

Referring to Table 1, the electrical resistance and ion transport water of the cation exchange membranes prepared according to Examples 1 to 3 show comparable or better characteristics than the cation exchange membranes of Comparative Examples 1 and 2. In particular, the bursting strength of the cation exchange membranes prepared according to Examples 1 to 3 was 100-300% or more superior to the commercial cation exchange membranes of Comparative Examples 1 and 2.

(5) Thermal stability

The cation exchange membranes of Example 1 and Comparative Example 1 were placed in a 80 ° C. forced convection oven for 100 hours, and then the brittleness and burst strength change of the cation exchange membrane were tested and shown in Table 2 below.

division	Before heating		After heating
	When folded	Burst strength (kpa)	When folded	Burst strength (kpa)
Example 1	Unbreakable	1,500	Unbreakable	1,490
Comparative Example 1	Unbreakable	490	fracture	360

Referring to Table 2, Example 1 showed little change in physical properties before and after heating, while Comparative Example 1 had a phenomenon of breaking when the ion exchange membrane was folded in half after 100 hours at 80 ° C. It was confirmed that about 25% reduction compared to the state. This phenomenon in which the strength of Comparative Example 1 falls is presumed to be a change in physical properties due to thermal decomposition of PVC material.

Therefore, it can be seen that the cation exchange membrane of the present invention is excellent in thermal stability and mechanical properties.

Claims (16)

1. A support comprising at least one of the compounds represented by Formulas 1 and 2 below; And

   It includes a cation exchanger;

   Wherein said support and said cation exchanger form an interpenetrating polymer network structure.

   [Formula 1]

   

   In Formula 1,

   R is a C1 acetoxyl group or a C1 to C4 acrylic ester group,

   m and n are the number of repetitions of the repeating unit,

   m: n is from 100: 5 to 100: 50,

   The number average molecular weight (Mn) is 3,000 to 500,000.

   [Formula 2]

   

   In Formula 2,

   R is a C1 to C4 acrylic ester group,

   m and n are the number of repetitions of the repeating unit,

   m: n is from 100: 5 to 100: 50,

   The number average molecular weight (Mn) is 3,000 to 500,000.
2. The method of claim 1,

   In Formula 1, the compound represented by R is an aceoxyl group is a cation exchange membrane, characterized in that the EVA (ethylene-vinyl acetate copolymer).
3. The method of claim 1,

   In Formula 1, the compound represented by R is an acrylic ester group is a cation exchange membrane, characterized in that at least one selected from EMA (ethylene-methyl acrylate copolymer), EEA (ethylene-ethyl acrylate copolymer), EBA (ethylene-butyl acrylate copolymer).
4. The method of claim 1,

   Compound represented by Formula 2 is a cation exchange membrane, characterized in that at least one selected from EMMA (ethylene-methyl methacrylate copolymer), EGMA (ethylene-glycidyl methacrylate copolymer).
5. The method of claim 1,

   The cation exchanger has a sulfonic acid functional group,

   Cation exchange membrane, characterized in that at least one monomer selected from styrene, divinylbenzene, α-methyl styrene, methyl styrene, t-butyl styrene and chloromethyl styrene is a polymerized polymer.
6. The method of claim 1,

   Cation exchange membrane, characterized in that the thickness of the support is 0.01 to 1 mm.
7. (a) 1 of compounds represented by formulas (1) and (2) in a polymerization solution containing at least one monomer selected from styrene, divinylbenzene, α-methyl styrene, methyl styrene, t-butyl styrene, and chloromethyl styrene and an initiator Preparing a mixture by dipping a support comprising at least one species;

   (b) polymerizing the mixture to produce a base film;

   (c) sulfonating the base membrane to prepare a cation exchange membrane into which sulfonic acid functional groups are introduced;

   Method for producing a cation exchange membrane comprising.
8. The method of claim 7, wherein

   In step (a), the cation exchange membrane production method, characterized in that the support is swollen.
9. The method of claim 8,

   The swelling degree of the swelled support is a method for producing a cation exchange membrane, characterized in that 10 to 60%.
10. The method of claim 7, wherein

    The temperature of step (a) is a method for producing a cation exchange membrane, characterized in that less than the start temperature of the initiator.
11. The method of claim 10,

    The initiator is a method for producing a cation exchange membrane, characterized in that at least one selected from BPO (Benzoyl peroxide) and AIBN (Azobisisobutyronitrile).
12. The method of claim 11,

    The temperature of step (a) is 10 to 70 ℃, the method for producing a cation exchange membrane, characterized in that carried out for 1 to 10 hours.
13. The method of claim 7, wherein

    The polymerization temperature of step (b) is 70 to 140 ℃, the polymerization time is a method for producing a cation exchange membrane, characterized in that 4 to 18 hours.
14. The method of claim 7, wherein

    Step (c) is carried out by immersing the base membrane in a solution containing at least one selected from sulfuric acid, chloro sulfuric acid and dichloroethane (DCE).
15. The method of claim 7, wherein

    After step (c),

    (d) washing the cation exchange membrane into which the sulfonic acid functional group is introduced, followed by deionized water, and then immersing in a NaOH solution to neutralize unreacted sulfonic acid.
16. The method of claim 7, wherein the polymerization solution is

    100 parts by weight of styrene monomer;

    2 to 25 parts by weight of divinylbenzene monomer; And

    0.1 to 2.5 parts by weight of the polymerization initiator;

    Method for producing a cation exchange membrane comprising a.