Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
2001-08-09
2004-01-13
Zitomer, Fred (Department: 1713)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S223000, C428S473500, C428S474400, C428S476300, C428S537500, C428S308800, C521S134000, C526S242000, C526S250000
Reexamination Certificate
active
06677033
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the polymerization of fluoropolymers into porous substrates. The fluoropolymer/substrate network that is present on the surface of the substrate and is also deposited into the substrate at appreciable depths. Depending upon the proportion of fluoropolymer relative to substrate, the fluoropolymer may provide a protective coating for the substrate and/or the substrate may improve the physical properties of the fluoropolymer.
TECHNICAL BACKGROUND OF THE INVENTION
Porous materials have a host of uses. Common uses for leather and porous polyurethane are to produce clothing and furniture. Common uses for wood include use as a building material and for the production of furniture. Polyimide compositions are known to have unique performance characteristics, which make them suitable for uses in the form of bushings, seals, electrical insulators, compressor vanes, brake linings, and others as described in U.S. Pat. No. 5,789,523. Para-oriented aromatic polyamides (para-aramids) are used to make fiber substrates that are useful for wear resistant application.
All of the porous materials described may degrade and decay over time by staining, wetting, warping, tearing or wearing. It is desirable to treat porous materials to improve resistance to wear, tear, creep, decay, and degradation by wetting, staining and warping, and to improve durability while maintaining the appearance of the materials.
For many years, textiles have been chemically treated to improve water and oil repellency. Different applications are commercially available to protect different kinds of substrates from oil and water staining. For example, Scotchgard® brand protector for fabrics sold by the 3M Company, and Teflon® Fabric Protector sold by E. I. du Pont de Nemours and Company, are available to consumers for use with textiles and fabrics. The use of granular fluoro-compounds is also discussed in Japanese Patent 05318413. The invention involves a method whereby a raw wood material is impregnated with a fluorinated microparticles having a diameter of 5 microns and a compound which changes to insoluble cured resin.
Other references include the treatment of microporous materials with fluoroacrylate to achieve permanent water and oil repellency. For example, U.S. Pat. No. 5,156,780 teaches a method for treating microporous substrates to achieve water and oil repellency while maintaining porosity. In the '780 method, the substrates are impregnated with a solution of monomer in a carrier solvent. The carrier solvent is first substantially removed from the substrate for the express purpose of leaving the monomer as a thin conformal coating on all internal and external substrate surfaces. In this manner, the monomer is converted to polymer and the polymer does not block the pores or restrict flow in subsequent use as a filtration membrane.
If enough fluoromonomer is polymerized into a porous structure, a point is reached at which there is more fluoropolymer than substrate and the composition can be considered a filled fluoropolymer. Fluoropolymers such as PTFE are commonly filled with substances such as glass fibers, graphite, asbestos, and powdered metals (Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Edition, Volume 11, John Wiley and Sons, New York, pages 626 and 630). The filler is generally added for the purpose of improving some property of the fluoropolymer, such as creep or hardness.
Most often, filled fluoropolymers are made by physically mixing the fluoropolymer with the filler or by coagulating an aqueous fluoropolymer emulsion on the filler, but such methods have their problems. Adhesion of fluoropolymer to filler can be quite poor, particularly if the fluoropolymer does not wet the filler and penetrate its pores and finer surface features. Fluoropolymer melts can be very stiff making mixing/dispersion poor and nonuniform. Mechanical mixing can degrade some fillers, for example by breaking fine fibers. It is desirable to polymerize fluoromonomer onto the surface and into the pores of a substrate to achieve intimate fluoropolymer/substrate interpenetration and dispersion with minimal mechanical stress.
SUMMARY OF THE INVENTION
Disclosed in this invention is a process for preparing a fluoropolymer/substrate composition, comprising:
in the case of gaseous fluoromonomer
(a) contacting a porous substrate with a solution comprising an initiator dissolved in a suitable solvent;
(b) exposing said substrate and said initiator to gaseous fluoromonomer under polymerization temperature and pressure conditions wherein the fluoromonomer polymerizes into said substrate;
or in the case of liquid fluoromonomer
(a) preparing a solution comprising initiator and liquid fluoromonomer;
(b) contacting a porous substrate with said solution; and
(c) polymerizing the liquid fluoromonomer under polymerization temperature and pressure conditions wherein the fluoromonomer polymerizes into said substrate, optionally in the presence of gaseous fluoromonomer.
Also disclosed is a composition of matter made by a process for preparing a fluoropolymer/substrate composition, comprising:
in the case of gaseous fluoromonomer
(a) contacting a porous substrate with a solution comprising an initiator dissolved in a suitable solvent;
(b) exposing said substrate and said initiator to gaseous fluoromonomer under polymerization temperature and pressure conditions wherein the fluoromonomer polymerizes into said substrate;
or in the case of liquid fluoromonomer
(a) preparing a solution comprising initiator and liquid fluoromonomer;
(b) contacting a porous substrate with said solution; and
(c) polymerizing the liquid fluoromonomer under polymerization temperature and pressure conditions wherein the fluoromonomer polymerizes into said substrate optionally in the presence of gaseous fluoromonomer.
A further disclosure of the present invention is a composition of matter, comprising: a substrate having a surface wherein the substrate further comprises polymerized fluoropolymer, and wherein the substrate is an open pore structure having interconnecting pores throughout said substrate, and wherein fluoropolymer is present within and on the surface of said composition at a level from about 0.1 percent to about 300 percent of the weight of said substrate.
Also disclosed is the use of these compositions as filler materials for other polymers.
DETAILED DESCRIPTION OF THE INVENTION
The present invention discloses a fluoropolymer/substrate composition. The presence of fluoropolymer in the composition provides a protective material for the substrate and may also add aesthetic qualities to the substrate. A further advantage of the fluoropolymer/substrate composition is that the physical properties of the fluoropolymer are improved.
Also disclosed in the present invention is a method for preparing intimately interpenetrated fluoropolymer/substrate compositions that improve the functional lifetime and/or the appearance of any or all the components. The method disclosed for making the fluoropolymer/substrate composition leaves the initiator and the initiator carrier solvent in the substrate during polymerization and uses undiluted monomer or, in the preferred embodiment, gaseous monomer, to penetrate and block all pores to the greatest depth possible. In the present invention, the polymerized fluoromonomer partially or completely fills and blocks the pores of the substrate.
Coating the surface and blocking the pores of a substrate with fluoropolymer prevents or slows degradation by wetting and penetration of the substrate by agents such as water, acids, bases, foodstuffs, and cosmetics, thereby preventing staining, warping, and unwanted chemical or physical property changes in the substrate. As a case in point, the Ultrasuede®/PTFE composition of Example 8 below wets less readily than untreated Ultrasuede™. Coating the surface and blocking the pores of a substrate with fluoropolymer can also slow mechanical degradation by such means as abrasion, creep, or tearing. As a case in point, the polyimide/PTFE composition
Bloom Joy Sawyer
Lee Kiu-Seung
Wheland Robert Clayton
E. I. du Pont de Nemours and Company
Zitomer Fred
LandOfFree
In situ fluoropolymer polymerization into porous substrates does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with In situ fluoropolymer polymerization into porous substrates, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and In situ fluoropolymer polymerization into porous substrates will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3256950