Hydrophilizing agent for hydrophobic porous membrane, and method for hydrophilizing hydrophobic porous membrane and test method using this agent

Abstract

A hydrophilizing agent for a hydrophobic porous membrane, wherein the agent contains a surfactant, and the surfactant has a frothability such that the bubble height immediately after frothing, as measured according to the Ross-Miles method (JIS K 3362), using a 0.1 wt % aqueous solution of the surfactant at 25° C., is 40 mm or less, and preferably has a frothability such that the bubble height five minutes after frothing is 20 mm or less; a method for hydrophilizing a hydrophobic porous membrane using this hydrophilizing agent; and a method for testing and hydrophilizing a membrane module using this hydrophilizing agent.

1 . A hydrophilizing agent for a hydrophobic porous membrane, wherein the agent contains a surfactant, and the surfactant has a frothability such that the bubble height immediately after frothing, as measured according to the Ross-Miles method (JIS K 3362), using a 0.1 wt % aqueous solution of the surfactant at 25° C., is 40 mm or less. 
     
     
         2 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 , wherein the surfactant has the frothability such that the bubble height immediately after frothing is 30 mm or less. 
     
     
         3 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 , wherein the surfactant has a frothability such that the bubble height five minutes after frothing, as measured according to the Ross-Miles method (JIS K 3362), using a 0.1 wt % aqueous solution of the surfactant at 25° C., is 20 mm or less. 
     
     
         4 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 3 , wherein the surfactant has the frothability such that the bubble height five minutes after frothing is 15 mm or less. 
     
     
         5 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 , wherein the surfactant has a static surface tension of 30 mN/m or less when a 0.1 wt % aqueous solution of the surfactant is used. 
     
     
         6 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 5 , wherein the surfactant has the static surface tension of 29 mN/m or less. 
     
     
         7 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 , wherein the surfactant is a nonionic surfactant. 
     
     
         8 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 , wherein the surfactant is acetylene glycol, ethoxylated acetylene glycol, or a mixture of these. 
     
     
         9 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 , wherein the surfactant is selected from the group of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 3,6-dimethyl-4-octyn-3,6-diol, 3,5-dimethyl-1-hexyn-3-ol, 2,5,8,11-tetramethyl-6-dodecyn-5,8-diol, and ethoxylates of these. 
     
     
         10 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 , wherein the surfactant is contained in an amount of 0.05 to 5 wt % with respect to the entire hydrophobic porous membrane hydrophilizing agent. 
     
     
         11 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 , wherein the agent further contains a solvent. 
     
     
         12 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 11 , wherein the solvent is water. 
     
     
         13 . The hydrophilizing agent for a hydrophobic porous membrane according to  claim 11 , wherein the hydrophobic porous membrane is formed from polyvinylidene fluoride. 
     
     
         14 . A method for hydrophilizing a hydrophobic porous membrane, comprising a step of bringing a hydrophobic porous membrane into contact with the hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 . 
     
     
         15 . The method for hydrophilizing a hydrophobic porous membrane according to  claim 14 , further comprising a step of drying the hydrophobic porous membrane that has come into contact with the hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 . 
     
     
         16 . The method for hydrophilizing a hydrophobic porous membrane according to  claim 14 , wherein the adhesion proportion of the hydrophilizing agent is 0.01 to 1.0 wt %. 
     
     
         17 . A method for testing a membrane module having a main body, an inlet and outlet provided to the main body, and a hydrophobic porous membrane provided inside the main body, the method comprising the steps of:
 (1) immersing the membrane module in the hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 ;   (2) introducing a test gas through the inlet, allowing the gas to pass through the hydrophobic porous membrane, and discharging the gas through the outlet; and   (3) observing bubbles discharged from the membrane module.   
     
     
         18 . The method for testing a membrane module according to  claim 17 , wherein the step (2) is conducted by:
 (i) introducing the test gas through the inlet of the membrane module while everything beyond the outlet is closed off;   (ii) gradually pressurizing the test gas;   (iii) using the pressurized test gas to push water out of the pores in the hydrophobic porous membrane; and   (iv) discharging the test gas out through the hydrophobic porous membrane.   
     
     
         19 . A method for testing and hydrophilizing a membrane module having a main body, an inlet and outlet provided to the main body, and a hydrophobic porous membrane provided inside the main body, the method comprising the steps of:
 (1) immersing the membrane module in the hydrophilizing agent for a hydrophobic porous membrane according to  claim 1 ;   (2) introducing a test gas through the inlet, allowing the gas to pass through the hydrophobic porous membrane, and discharging the gas through the outlet;   (3) observing bubbles discharged from the membrane module; and   (4) drying the membrane module.   
     
     
         20 . The method for testing and hydrophilizing a membrane module according to  claim 19 , wherein the step (2) is conducted by:
 (i) introducing the test gas through the inlet of the membrane module while everything beyond the outlet is closed off;   (ii) gradually pressurizing the test gas;   (iii) using the pressurized test gas to push water out of the pores in the hydrophobic porous membrane; and   (iv) discharging the test gas out through the hydrophobic porous membrane.