Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric – Nonwoven fabric has an elastic quality
Reexamination Certificate
1998-11-20
2001-10-09
Morris, Terrel (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
Nonwoven fabric has an elastic quality
C442S329000, C442S337000, C442S417000, C428S912000
Reexamination Certificate
active
06300261
ABSTRACT:
The present invention relates to self-healing articles resistant to oxidizing agents useful in the surface conditioning of sheets (e.g., metal sheets) and to processes of making such articles.
BACKGROUND OF THE INVENTION
Rotatable surface conditioning rolls (“mill rolls”) are commonly used in the manufacturing and processing of metal sheets and coils in continuous production lines. During the processing of metal sheets, mill rolls are generally utilized in so-called “wringer applications” as well as “oiler applications”.
In wringer applications, mill rolls and like articles are used to prevent the cross contamination of treating solutions. For example, during manufacture of metal sheets many process operations use a variety of treating solutions designed to variously clean, degrease, remove scale, preserve, rinse, surface etch, lubricate, and/or protect a metal surface. During these operations, it is important that mill rolls prevent the contamination of these often incompatible treating solutions. Thus, mill rolls provide wringing (“damming”) operations at surfaces of metal sheets to remove excess treating solution from metal surfaces as metal strips exit each treatment tank. The wringing operation prevents the inadvertent mixing of treating solutions. Wringer arrangements may include mill rolls made of conventional rotatable rubber or made of non-woven materials as well as wiper bars made of felt or cork.
During a surface conditioning process, metal sheets move rapidly over rotatable mill rolls at a rate of approximately 200-1200 feet/minute. The relatively non-compressible nature of rubber mill rolls, unlike the web construction of non-woven mill rolls, for example, makes them susceptible to cut propagation and other structural damage at the nip of a roll. Additionally, the surfaces of rolls are easily torn, gouged, or cut by edges of splices in the metal sheets. Once damaged, the initial cut, tear, or gouge in the roll will usually enlarge due to compressive forces at the nip and tension forces on either side of the nip. As a roll becomes increasingly damaged, a roll's ability to act as a wringer decreases and treating solutions may pass through the roll. Chemicals of one treatment tank are then inadvertently mixed with chemicals of another chemical treatment tank and may eliminate a surface modification activity of an initially pure chemical. If a treatment tank is contaminated by another chemical, the contaminated chemical mixture will have to be replaced with new chemical or chemicals. Discarding the contaminated chemicals may be difficult, raising environmental concerns. Also, frequent repair (e.g., surface dressing) or replacement of these articles has been required, thereby creating unscheduled production line downtimes with associated losses and costs.
When production lines are stopped, the rolls on the lines become dried as the sheets of metal are no longer moving and carrying liquid to the rolls. Non-woven rolls absorb liquid because they are porous and have a large void volume. The liquid from the surface modification process fills the void volume when the production line is in operation. When the production line operation stops, the liquid in the roll may precipitate and change the physical characteristics of the roll. Typically, the roll becomes stiff and may have to be replaced before production begins.
In some processes of modifying the surface of metal sheets, the last steps may include a passivating treatment comprising oxidizing acids. The oxidizing acids react with the surface of the metal to make the metal surface less reactive with its environment. Unfortunately, the oxidizing acids also react with the rolls and the rolls may loose physical integrity. A roll used in the passivating treatment step usually performs an application function of applying a thin layer of oxidizing acid to the surface of the metal sheets being treated. The application of a uniform layer of oxidizing acid is necessary to avoid problems. Excess oxidizing acid results in spots appearing on the surface of the metal sheets. Not enough oxidizing acid results in paints or other coatings not adhering well to the metal surface.
SUMMARY OF THE INVENTION
The present invention provides self-healing articles, preferably non-woven articles in the form of a roll, suited for the surface conditioning of sheets. These articles, when cut or torn during a surface modification process, are able to maintain wringer characteristics by preventing the passage of treating solution through the roll. Because these non-woven articles act like wringers when damaged, they have an increased life span; and if used, will result in fewer roll replacements and unscheduled production line downtimes. The chances of chemical contamination between treating solutions are also minimized.
The articles of the present invention are also resistant to oxidizing agents, such as chromic acid, nitric acid, or combinations thereof. Chromic acid is used in the steel industry to modify the surface of steel sheets. The articles of the present invention are preferably shaped in the form of a roll and may be used in a passivating treatment step and perform an application function of applying a thin layer of oxidizing acid to the surface of the metal sheets being treated. The layer of oxidizing acid applied is preferably chromic, nitric acid, phosphoric, or combinations thereof.
As mentioned, the present invention provides a self-healing article suited for use in the surface conditioning of sheets. An article comprises a plurality of stacked, compacted web elements, with each web element comprising entangled fibers bonded together at points of mutual contact by a bonding agent. The self-healing article is resistant to oxidizing agents and has a Shore A hardness in the range of 70 to 93 and (preferably, 75 to 85) a void volume in the range of 2 to 30 percent (preferably, 5 to 20 percent). It is preferred that the web is made of non-woven material.
The present invention also provides a self-healing roll, resistant to oxidizing agents, suited for surface conditioning of sheets. The roll comprises a cylindrical body supported on its cylindrical axis for rotation. The cylindrical body comprises a plurality of compacted, stacked, and disc-shaped web elements. Each web element comprises entangled fibers, wherein a bonding agent bonds adjacent fibers in each web element together at points of mutual contact. The roll is resistant to oxidizing agents and has a Shore A hardness in the range of 70 to 93 (preferably, 75 to 85) and a void volume in the range of 2 to 30 percent (preferably, 5 to 20 percent). It is preferred that the web elements are made of non-woven materials.
The present invention also provides a process for making a self-healing and non-woven article suited for the surface conditioning of sheets. The process provides a plurality of non-woven web elements, the web elements comprising entangled fibers bonded at their points of mutual contact by a bonding agent. The plurality of non-woven web elements are stacked into a pile. Optionally, water may be added to the stacked non-woven web elements. The pile of web elements are compacted under a compaction force. The pile of web elements are restrained in its compacted configuration to form an article. The article is self-healing, resistant to oxidizing agents, and has a Shore A hardness in the range of 70 to 93 (preferably, 75 to 85) and a void volume in the range of 2 to 30 percent (preferably, 5 to 20 percent).
The preferred process for making a self-healing and non-woven article suited for the surface conditioning of sheets includes an additional step in addition to those described above. The step comprises heating the pile in its compacted configuration to an elevated temperature to integrally bond the layers.
As used herein:
“Chemically resistant” in referring to the fibers used in the articles of the invention, refers to the ability of a fiber to tolerate exposure to the conditions in use without significant degradation.
“Oxidizing agent” refers to any compound that spontan
Barber Loren L.
Young John B.
3M Innovative Properties Company
Allen Gregory D.
Morris Terrel
Torres Norca L.
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