Daniel J Marquardt DeceasedColumbia, IL

4487911, Dec 11, 1984

Jun 30, 1980

6/164488

Daniel J. Lange - St. Louis MO
Daniel J. Marquardt - Columbia IL

The P. D. George Company - St. Louis MO

C08G 6932
C08G 7310
C08G 7312
C08G 7314

528125

A stable solution of an aromatic polyamic acid of controlled molecular weight, of the type capable of being converted to polyimides, which undergoes relatively little change in viscosity or gelling over extended periods of time at room temperature. Such solution may be prepared by reacting impure aromatic dianhydride with aromatic diamine in a suitable solvent where the ratio of active aromatic diamines is approximately equimolar. Such solution may also be prepared by a two step process which comprises: Step I-Reacting a dianhydride of high purity (99+%) with a diamine in a molar ratio of about 0. 95/1 dianhydride/diamine to yield a viscosity below about 10,000 cps, for example from about 2,000 to 6,000 at about a 10-15% solution. Step II-Then adding to I about 0. 05 mole of a less pure dianhydride such as from about 97-99% pure dianhydride to yield a 10-15% solution of polyamic acid having a viscosity of about 10,000 cps.

4819683, Apr 11, 1989

Jan 29, 1988

7/150341

Brian W. Buffham - Merseyside, GB2
Daniel J. Marquardt - Waterloo IL

Petrolite Corporation - St. Louis MO

F16K 1714

137 71

A pressure release device for sealably mounting on a vessel adapted to contain a fluid under pressure not to exceed a predetermined maximum pressurization limit. The device comprises: (a) a pressure release conduit having an inlet and an outlet and providing an escape passage for the fluid to move from an outlet opening of the vessel through the inlet end of the conduit and out the outlet end of the conduit; (b) a recloseable self-activated fluid pressure release valve disposed in the outlet end of the conduit; (c) a nonrecloseable disc having a portion rupturable into fragments when the pressurization limit is exceeded and being disposed within the conduit between the outlet opening of the vessel and the release valve; and (d) a porous member disposed in the conduit between the disc and the release valve, the porous member having a total cross sectional open area at least about the sum of the cross sectional area of the rupturable portion of said disc and the cross sectional area of the outlet opening, such that when the disc ruptures in response to the pressurization limit being exceeded, fragments are restrained by the porous member from moving to the release valve, yet substantial clogging of the porous member is prevented such that the porous member maintains a cross sectional open area of at least about the cross sectional area of the outlet opening and the flow of the fluid through the conduit to the release valve is not substantially impeded.