Gas separation: processes – Solid sorption – Inorganic gas or liquid particle sorbed
Patent
1997-11-14
2000-05-09
Spitzer, Robert
Gas separation: processes
Solid sorption
Inorganic gas or liquid particle sorbed
95116, 961175, 96135, 96153, 55512, B01D 5304, B01D 5328
Patent
active
060598603
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to polyolefin articles containing sorptive materials and methods of using such articles.
BACKGROUND OF THE INVENTION
Sorptive materials such as desiccants can be supplied in a loose granular form but this can lead to contamination of product with which they come into contact. To overcome this problem, sorptive materials have been supplied as sachets with the particulate sorbent enclosed in a porous material. However, this can lead to clumping of the sorbent in one area of the sachet and consequent inefficient use of the sorbent. To overcome this problem, the sorptive material has been provided as a sachet having multiple discrete connected smaller areas.
Sorptive materials have also been incorporated into polyolefin films, particularly where the sorptive material is used in a multilayer construction to protect a moisture-sensitive layer such as a film of an ethylene/vinyl alcohol copolymer. However, in such constructions the sorptive material absorbs water vapor at appreciable rates only when heated during a retort process.
To overcome such problems, films have been developed wherein the films have a polymeric matrix with a system of interconnecting micropores and are loaded with particulate sorbent material which may be a desiccant material. Such films are produced by forming a melt blend of the sorbent particles, the polymer and a selected diluent, extruding the film and removing the diluent. The water to be sorbed, generally as water vapor, can then rapidly contact the particulate material through the pores of the polymeric matrix, and sorption of the water by the particulate material can be achieved. However, when the sorbent particulate material is thus available for sorption of the water, the film must be carefully stored prior to use to prevent premature sorption of environmental water vapor and should be protected with a dry atmosphere during manufacturing and converting.
In addition to desiccants for sorption of water, there is also need to sorb other materials such as carbon dioxide and acidic gases and a wide variety of organic materials.
U.S. Pat. No. 4,550,123 teaches textile quality polymeric fibers or thin films made porous by extraction of a diluent included during manufacture of the fiber or film. This reference does not contemplate fibers or films in which a wax is retained in the fiber or film during use of the fiber or film. This reference states in column 3, lines 21-27, the yarns, fibers or films so formed, are extracted with a suitable solvent or solvents for removal of the diluent. This extraction porosifies the polymer leaving the sorbent particles in an active state accessible to vapors, liquids or solutes present on or at the surface of the matrix.
U.S. Pat. No. 4,626,252 discloses backing sheets for a diaper which are made from a stretched extruded film made from a polyolefin, a wax like hydrocarbon polymer and a filler. Presumably the particles are included to assist in formation of pores with film when the film is stretched.
SUMMARY OF THE INVENTION
The present invention relates to a sorptive article comprising a polyolefin, a wax which is miscible with the polyolefin at the melt temperature of the polyolefin but phase separates on cooling of the article, and particulate sorbents distributed in the article. Optionally, the articles of the invention may also contain a dispersant for the sorbent. The sorptive articles may be in the form of films, fibers, pellets, beads and other convenient shapes. The sorptive films of the invention can be used as formed or the films may be layered or laminated with other films and materials.
The present invention further provides a method for removing moisture or other materials from air or an object in the environment comprising providing proximate to said air or object a sorptive article comprising a polyolefin, a wax compound which is miscible with the polyolefin at the melt temperature of the polyolefin but phase separates on cooling of the article, and sorptive particles distribut
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3M Innovative Properties Company
Spitzer Robert
Tamte Roger R.
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