Porous fluorine-based resin composite membrane and manufacturing method therefor

Abstract

The present disclosure relates to a porous fluorine-based resin composite membrane having excellent water repellency and oil repellency, and a method for producing the same.

Claims

1. A method for producing a porous fluorine-based resin composite membrane comprising the steps of: providing a porous fluorine-based resin layer having pores therein, preparing a coating solution including a (co)polymer containing a repeating unit derived from a perfluoroalkyl acrylate having 1 to 10 carbon atoms and a perfluoroalkanoic acid having 3 to 10 carbon atoms, coating the coating solution onto at least one surface of the porous fluorine-based resin layer and an outer surface of the pores to produce a coating layer, and decomposing the perfluoroalkanoic acid having 3 to 10 carbon atoms from the coating layer.

2. The method for producing a porous fluorine-based resin composite membrane according to claim 1, wherein the (co)polymer includes a (co)polymer of perfluoroalkyl acrylate having 1 to 10 carbon atoms, alkyl acrylate having 1 to 10 carbon atoms, vinyl chloride, and a crosslinkable monomer.

3. The method for producing a porous fluorine-based resin composite membrane according to claim 2, wherein the crosslinkable monomer is a monomer having a hydroxyl group, a carboxyl group, an epoxy group, or a nitrogen-containing functional group, wherein the nitrogen-containing functional group is an isocyanate group, urethane, amine, amide, or urea.

4. The method for producing a porous fluorine-based resin composite membrane according to claim 1, wherein the coating solution includes 2 to 10% by weight of the (co)polymer and 5 to 15% by weight of the perfluoroalkanoic acid having 3 to 10 carbon atoms.

5. The method for producing a porous fluorine-based resin composite membrane according to claim 1, wherein the coating solution further includes an amine compound or ammonia.

6. The method for producing a porous fluorine-based resin composite membrane according to claim 5, wherein the amine compound or ammonia is contained in an amount of 0.1 to 5% by weight based on the total weight of the perfluoroalkanoic acid having 3 to 10 carbon atoms and amine compound or ammonia.

7. The method for producing a porous fluorine-based resin composite membrane according to claim 1, wherein the coating solution further includes an organic solvent or water.

8. The method for producing a porous fluorine-based resin composite membrane according to claim 1, wherein the step of coating the coating solution onto the at least one surface of the porous fluorine-based resin layer and the outer surface of the pores is performed as a single step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an electron microscope photograph (SEM) of (a) any one surface and (b) another surface forming the remaining part, of the porous fluorine-based resin membrane of Example 1 of the present disclosure. (1 K magnification)

DETAILED DESCRIPTION OF THE EMBODIMENTS

(2) The present disclosure will be described in more detail by way of the examples provided below. However, the following examples are for illustrative purposes only and the scope of the present invention is not limited to or by the examples.

(3) In the following Examples or Comparative Examples, TG-5673 available from Daikin Industries was used as a (co)polymer containing a repeating unit derived from a perfluoroalkyl acrylate having 1 to 10 carbon atoms, and perfluorohexanoic acid (PFHA) was used as a perfluoroalkanoic acid having 3 to 10 carbon atoms.

Preparation Example: Preparation of Porous Fluorine-Based Resin Layer

(4) A uniaxially-stretched porous fluorine-based resin layer was produced through preform-extrusion-calender & drying-MD stretching-heat setting.

(5) That is, 100 parts by weight of polytetrafluoroethylene powder (CD145E, manufactured by AGC Co.) was mixed with 22 parts by weight of a liquid lubricant (product name: “Isopar H”, manufactured by Exxon Co.) to prepare a single-layer preform.

(6) Then, the single-layer preform was extruded at a rate of 50 mm/min at a temperature of 50° C. to prepare a sheet having a thickness of about 300 μm. The prepared sheet was heated at a temperature of about 200° C. to completely dry and remove the liquid lubricant.

(7) Then, after the drying process, the preform was uniaxially stretched under the conditions in Table 1 below. The fabric refers to a uniaxially stretched porous fluorine-based resin layer, and an oil repellency grade of the fabric was 4 grade level.

(8) TABLE-US-00001 TABLE 1 Thickness, μm 190 Porosity, % 65.1 Pore size mean/max, nm 315/720 Gurley, sec 49 Water pressure resistance, MPa 0.190 Pore size was measured by Capillary Flow Porometry (CFP) method.

Example 1

(9) TG-5673 available from Daikin Industries was dissolved in a solvent such that the solid content was 5 parts by weight. As the solvent, isopropyl alcohol and water were used in an amount of 9 and 76 parts by weight in the entire blending.

(10) 9.5 parts by weight of perfluorohexanoic acid (PFHA) and 0.5 part by weight of ammonia were used to prepare a mixture in which the total content of fluorohexanoic acid and ammonia was 10 parts by weight.

(11) To the solution in which the TG-5673 solid was dissolved, a mixture of perfluorohexanoic acid and ammonia was added to prepare a coating solution.

(12) The coating solution prepared above was coated onto one surface of the porous fluorine-based resin layer of the Preparation Example using a Mayer bar, and then dried at 160° C. for 5 minutes to produce a porous fluorine-based resin composite membrane.

Example 2

(13) A porous fluorine-based resin composite membrane was produced by performing the same method as in Example 1, except that the coating solution having the composition shown in Table 2 below was used.

Comparative Example 1

(14) A porous fluorine-based resin composite membrane was produced by performing the same method as in Example 1, except that the coating solution having the composition shown in Table 2 below was used.

Comparative Example 2

(15) A porous fluorine-based resin composite membrane was produced by performing the same method as in Example 1, except that hydrocarbon-based hexanoic acid (HA) was used instead of fluorine-based perfluorohexanoic acid, and a coating solution having the composition shown in Table 2 below was used.

(16) TABLE-US-00002 TABLE 2 Comparative Comparative Coating solution Example 1 Example 2 Example 1 Example 2 TG-5673 5.00 2.80 5.00 5.00 Solid content (wt %) PFHA (wt %) 9.50 9.50 0 0 HA (wt %) 0 0 0 9.50 Ammonia 0.50 0.50 0 0.50 Isopropyl alcohol 9.00 9.00 9.00 9.00 Water 76.00 78.20 86.00 76.00

Experimental Example

(17) The following properties were measured or evaluated for the porous fluorine-based resin composite membranes produced in the Examples and Comparative Examples, and the results are summarized in Table 3 below.

(18) (1) Oil Repellency Grade (AATCC-118)

(19) According to the measurement method specified in AATCC-118, the oil repellency grade of the porous fluorine-based resin composite membrane was measured using a straight chain hydrocarbon solvent.

(20) At this time, any one surface of the porous fluorine-based resin composite membrane was represented by a first surface, and another surface forming the remaining part was represented by a second surface.

(21) (2) Air Permeability

(22) The air permeability was measured using a Gurley-type Densometer (No. 158) available from Toyoseiki, based on the measurement method (JIS Gurley) specified in Japanese Industrial Standards.

(23) More specifically, the air permeability was defined as the time (unit: second/100 mL) required for 100 mL of air to pass through a 1-inch square membrane under a constant air pressure of 4.8 inch.

(24) TABLE-US-00003 TABLE 3 Comparative Comparative Example 1 Example 2 Example 1 Example 2 Oil repellency grade 8 6 8 8 of first surface Oil repellency grade 8 6 4 4 of second surface Air permeability 24 26 130 95 (sec/100 cc)

(25) As a result of the experiment, in the case of Examples 1 and 2 using a coating solution containing a perfluorohexanoic acid and ammonia in a (co)polymer containing a repeating unit derived from a perfluoroalkyl acrylate having 1 to 10 carbon atoms, it was confirmed that the oil repellency grade of the first and second surfaces in the obtained porous fluorine-based resin composite membrane was 6 or more, respectively, and the oil repellency grade of the first and second surfaces showed symmetry with each other.

(26) In contrast, in the case of Comparative Examples 1 and 2, it was confirmed that the oil repellency grade of the second surface was reduced compared to the first surface. Thereby, it was found that the porous fluorine-based resin composite membrane according to the present disclosure had coating layers formed on both sides of the porous fluorine-based resin layer and the outer surfaces of the pores, so that both sides of the produced porous fluorine-based resin composite membrane had excellent water repellency and oil repellency.

(27) In addition, it was confirmed that the air permeability of Examples 1 and 2 was 24 sec/100 cc and 26 sec/100 cc, which were extremely low values as compared with Comparative Examples 1 and 2, and thus had very excellent air permeability.

(28) Therefore, it has been found that the porous fluorine-based resin composite membrane of the present disclosure had excellent air permeability, and could effectively prevent water permeability even while having high permeability to liquids other than gas and water.