Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-11-28
2002-11-26
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S194000, C525S195000, C525S196000, C525S232000, C525S238000, C525S240000, C427S386000, C428S500000, C524S515000, C524S521000, C524S525000
Reexamination Certificate
active
06486259
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to ebonite coatings for metal substrates. More particularly, it relates to an ebonite tape.
BACKGROUND ART
There is a pervasive and continuing need for protecting metals from corrosive chemical action, such as in metal pipes, stacks, chimneys, bridges, chemical plant constructions, ship hulls, and containers for aggressive chemicals, to name just a few applications. In addition to having a high resistance to chemical action, an ideal coating has certain other properties: the raw materials required to produce the coating are preferably commercially available, inexpensive and non-hazardous; the coating should have the ability to be easily applied to the metal; the coating adheres strongly to many different metals; the coating should be strong, hard, abrasion resistant and thermostable; and the hardening process of the coating can be performed in contact with moisture, does not require extreme or long heating, and does not release toxic fumes. An ideal metal coating may have many additional properties, depending on the particular application or purpose of the coating.
The most widespread anticorrosive coatings possessing many of the above properties are polyurethanes and epoxide resins (see for example,
Coating Systems: A guidance Manual For Field Surveyors,
American Bureau of Shipping and Affiliated Companies, 1995). These coatings have good chemical resistance to many substances, have adhesion to metals that is satisfactory for many purposes, and have good mechanical properties. Neither polyurethanes nor epoxide resins, however, satisfy all the criteria for an ideal coating for metal. In particular, although polyurethanes have outstanding oil-gasoline resistance, a unique combination of favorable physical-mechanical properties, and strong adhesion to some metals, they are not stable under elevated temperature, alkaline hydrolysis:, and persistent tension. Epoxide resins, although they have outstanding adhesion to some metals, do not have a satisfactory resistance to acids, certain solvents, temperature changes, and vibration. One of the most significant problems associated with both epoxide resins and polyurethanes is their susceptibility to underfilm corrosion associated with defects in the coating surface. Because these coatings are bonded to the metal only by adhesive bonding, these bonds can be broken by the introduction of moisture, solvents or other substances.
As is known from rubber chemistry (
Encyclopedia of Polymer Science
&
Technology,
John Wiley & Sons, N.Y., vol 12, p.161, 1970), solid ebonite, commonly known as hard rubber, is a polymer material with sulfur content used for vulcanization. Ebonite, like elastomeric or flexible rubber, is made from a combination of sulfur with polydienes (unsaturated rubbers containing double bonds). The sulfur and polydienes are combined with some auxiliary additives and heated to produce vulcanization. Typical mass ratios of sulfur to rubber are 2:100 for elastomeric rubber and 40:100 for hard rubber. Due to the large degree of sulfide cross-linking formed in the vulcanization process, solid ebonite is a hard, non-flexible, plastic-like material possessed of unique chemical resistance to aggressive substances such as acids, alkalis, salt solutions, oil, and gasoline. In addition, solid ebonite has good mechanical properties. Consequently, these conventional rubbers are commonly used as materials for fuel tanks, containers for aggressive substances, and other applications. In spite of these advantages, however, solid rubbers can not be easily applied to metal surfaces, they release toxic fumes during vulcanization, and they require a long time to harden.
More than 30 years ago liquid rubbers were synthesized. (See Alan R. Luxton, “The Preparation, modification and application of non-functional liquid polybutadienes”,
Rubber Chemistry and Technology,
54 (1981) 3, 596-626.) Like earlier rubbers, liquid rubbers are formed from compounds such as polybutadiene, polyisoprene, butadiene-styrene, and butadiene-nitrile. In contrast to the hard rubbers, which are made from such compounds having molecular weights on the order of 100,000 to 500,000, the liquid rubbers are made from such compounds having molecular weights of only 2,000 to 4,000. Consequently, the low molecular weight rubbers permit castable processing by pouring, spreading, spraying, or rolling, while providing similar properties as the hard rubbers after curing. Liquid rubber, therefore, may be used to more easily coat metal surfaces.
Liquid ebonite mixture (LEM) compositions are disclosed by Figovsky in WO 0,006,639 issued Feb. 10, 2000, and liquid rubber based ebonite coating has been disclosed by Rappoport in U.S. Pat. No. 5,766,687 issued Jun. 16, 1998 and U.S. Pat. No. 5,997,953 issued Dec. 7, 1999. The liquid ebonite compositions have advantage of applying, by brushing, rolling or spraying a thin layer to coat any surface with complex geometry, such as bolts and anchors. The liquid coatings can usually stick to the substrate directly without using additional primer or adhesive. However, it is usually inconvenient and messy to handle. Furthermore, the coating is heated by hot air or steam to typically 160° C. to 180° C. for vulcanization.
Ebonite rubber sheets have been produced for coating metal substrates. The ebonite rubber sheets of prior art are either extruded or calendered to give a relatively thick layer, typically greater than 0.0.625 inch, which is easy to handle and can be cut into any desired shapes. However, due to its thickness and high modulus, the rubber sheets of prior art can only be applied by laying them onto a substrate without stretching. It is usually very craft sensitive to lay and join rubber sheets neatly to provide a complete surface coverage. In addition, such sheets can not effectively coat a substrate with complex geometry, such as bolts and anchors. Furthermore, an adhesive or primer is invariably required to fix and bond rubber sheets onto the substrate. In addition, similar to liquid ebonite coating, the same vulcanization condition is required to cure the laid rubber sheet.
There is a need, therefore, for an ebonite tape that will overcome the disadvantages of the prior art, while maintaining all ebonite key properties, such as chemical resistance and tenacious bonding to metal.
SUMMARY
Disadvantages associated with the prior art are overcome by an ebonite tape formed by either a single component mixture or a two-component mixture.
According to a first embodiment of the present invention, an ebonite tape is made by a single component mixture. The mixture includes unsaturated polymers, a vulcanization agent, a vulcanization activator, a solubilizer for the vulcanization agent, and a vulcanization accelerator. Unsaturated polymers can be polybutadiene, polyisoprene, or poly(butadiene-co-acrylonitrile), which contain high amount of unsaturation (typically double bonds) in the backbones for forming linkage with a high loading of the vulcanization agent. The mass parts of unsaturated polymers in the mixture are 100. Unsaturated polymers may or may not contain functional groups, such as hydroxyl, epoxy or acrylic, and may be partially epoxidized.
A preferable vulcanization agent is sulfur, with mass parts of approximately 15-50, preferably 30-50. A solubilizer for sulfur preferably contains polyamine, such as aliphatic, cycloaliphatic, amidoamide, and polyamide amine, with the mass parts approximately 1.5-6. The vulcanization accelerator preferably contains thiuram disulfide, such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetraisobutylthiuram disulfide, and tetrabenzylthiuram disulfide, and its mass parts is approximately 3-5. The thiuram disulfide will react with polyamine and causes the mixture to gel at ambient condition.
The vulcanization activator may contain zinc oxide or zinc stearate, and its mass parts are approximately 5-35. The mixture further includes a viscosity reducer for adjusting the viscosity of the mixture and the
Betts, III William L.
Change Rong Jong
3L&T, Inc.
Lumen Intellectual Property Services Inc.
Nutter Nathan M.
LandOfFree
Ebonite tape does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ebonite tape, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ebonite tape will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2994009