	US 7,338,692 B2
	Microporous PVDF films
Samantha D. Smith, Minneapolis, Minn. (US); Gene H. Shipman, Cottage Grove, Minn. (US); Robert M. Floyd, Maplewood, Minn. (US); Harold Todd Freemyer, Woodbury, Minn. (US); Steven J. Hamrock, Stillwater, Minn. (US); Michael A. Yandrasits, Hastings, Minn. (US); and David G. S. Walton, Honolulu, Hi. (US)
Assigned to 3M Innovative Properties Company, St. Paul, Minn. (US)
Filed on Sep. 12, 2003, as Appl. No. 10/661,908.
Prior Publication US 2005/0058821 A1, Mar. 17, 2005
Int. Cl. B32B 1/08 (2006.01); B32B 27/06 (2006.01); B32B 27/28 (2006.01); B32B 3/12 (2006.01); B32B 3/26 (2006.01)

U.S. Cl. 428—36.9 [428/35.7; 428/304.4; 428/315.5; 428/421]

9 Claims

1. A shaped article comprising:

a) polyvinylidene fluoride or copolymers thereof;

b) a sufficient quantity of nanometer-sized nucleating agent to initiate crystallization of the polyvinylidene fluoride or copolymers thereof at a significantly greater number of crystallization sites as compared to crystallization without the nucleating agent;

c) a diluent with which the polyvinylidene fluoride or copolymers thereof are miscible, and in which the polyvinylidene fluoride or copolymers thereof will dissolve at or above the melting temperature of the polyvinylidene fluoride or copolymers thereof, and will phase separate upon cooling to a temperature at or below the crystallization or phase separation temperature of the polyvinylidene fluoride or copolymers thereof;

wherein the diluent is glyceryl triacetate;

wherein the shaped article is microporous and has been oriented in at least one direction at a stretch ratio of at least approximately 1.1 to 1.0; and

wherein the sufficient quantity of nucleating agent is between approximately 0.2 percent to approximately 2.5 percent by weight of the polyvinylidene fluoride or copolymers thereof.