| 摘要 |
PROBLEM TO BE SOLVED: To provide porous membranes with multiple zones having different pore sizes.SOLUTION: A porous membrane includes a first zone, the first zone including a crystallizable polymer; and a first nucleating agent, the first nucleating agent having a first concentration in the first zone, the first zone having a first average pore size; and a second zone, the second zone including a crystallizable polymer; and a second nucleating agent, the second nucleating agent having a second concentration in the second zone, the second zone having a second average pore size. The crystallizable polymer is the same in the first zone and the second zone. The first average pore size is not the same as the second average pore size. The first nucleating agent and the second nucleating agent are the same or different, and the first concentration and the second concentration of the agents are the same or different, with the proviso that the first nucleating agent and the first concentration are not the same as the second nucleating agent and the second concentration. |
