Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-09-21
2001-08-21
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C427S386000, C428S413000, C428S418000, C523S427000, C525S524000
Reexamination Certificate
active
06277903
ABSTRACT:
BACKGROUND OF INVENTION
This application relates to flexible epoxy coatings which have sound damping properties and to processes for applying such coatings to substrates and
Many transportation vehicles, electronic device apparatuses, and machines are subjected to noise and vibration due to the environments within which they are placed or used. Such noise and vibration can present problems in their use or function and may be annoying or harmful to the users of such devices or apparatuses. Therefore, there is a need to reduce the impact of such noise and vibration on the apparatuses, devices and users thereof. In many applications, noise and vibration is reduced by placing in or fixing to such vehicles or devices extensional dampers. Extensional dampers are composite pads comprised of a viscoelastic polymer or resin, filler and additive composition layer having on one side of such layer a pressure sensitive or hot melt adhesive. These are applied to the vibrating substrate. Such plates are difficult to affix to or shape around odd shaped parts, such as the interior of automobiles.
In addition, certain coatings are placed in or sprayed on parts of the underside exterior painted surfaces of such transportation vehicles. Such coatings are usually used for corrosion protection by providing abrasion or stone-impact resistance for the painted surfaces.
Typically such coatings are tough, elastic polyvinyl chloride based and do not provide significant noise and vibration reduction. In some embodiments, epoxy or modified epoxy resin formulations are used as electro-deposition coatings for corrosion protection. Unfortunately, epoxy or modified epoxy resin formulations typically form brittle or highly cross-linked networks, at thickness' which have limited effect with respect to reducing the impact of noise and vibration on the user of such devices.
What is needed is a multifunctional coating which provides noise and vibration reduction in combination with corrosion protection and anti-abrasion properties. What is further needed is such a coating which is sprayable and can easily be placed or coated on odd shaped objects.
SUMMARY OF INVENTION
The invention is a multifunctional, sprayable coating having noise and vibration attenuation or absorption properties. Such composition comprises from about 10 to about 60 percent of the flexible epoxy resin, from about 5 to about 40 percent by weight of a liquid bisphenol based epoxy resin formulation, and a curing agent for the epoxy moieties of the two resins.
In another embodiment, the invention is a method of coating a substrate to improve the noise and vibration properties of the substrate, which process comprises spraying the above defined composition on to a substrate and curing the resin on such substrate.
In yet another embodiment the invention is a coated substrate described hereinbefore having enhanced noise and vibration attenuation.
The coatings of the invention provide for good noise and vibration attenuation, excellent corrosion resistance, impact resistance and abrasion resistance. The process of the invention allows for coating irregular shaped objects in a cost effective way and allows complete surface contact of the coating on the substrate.
DETAILED DESCRIPTION OF THE INVENTION
Important in developing a coating which has good sound abatement properties, abrasion resistance, impact resistance, corrosion resistance and substrate wet out, is the selection of the epoxy resins used in the formulation or coating. More particularly a balance of flexible epoxy resins and rigid epoxy resins achieves the desired results. As used herein, rigid epoxy resins refer to epoxy resins having bisphenol moieties in the backbone of the epoxy resin. Representative of preferred bisphenol resins useful in this invention are those disclosed in U.S. Pat. No. 5,308,895 at column 8, line 6 and represented by Formula 6, relevant portions of such patent are incorporated herein by reference. Preferably the rigid epoxy resin is a liquid epoxy resin or a mixture of a solid epoxy resin dispersed in a liquid epoxy resin. The most preferred rigid epoxy resins are bisphenol-A based epoxy resins and bisphenol-F based epoxy resins.
Flexible epoxy resins as used herein refer to epoxy resins having elastomeric chains in the backbone. Representative of such elastomeric chains are polyether chains which are preferably prepared from one or more alkylene oxides. Representative examples of these flexible epoxy resins are those described in U.S. Pat. No. 5,308,895 at column 8, line 9 and formula 9 and the description thereof following, relevant portions of such description are incorporated herein by reference. Preferably the flexible epoxy resin contains in its backbone ethylene oxide, propylene oxide or a mixture thereof.
The mixture of flexible and rigid epoxy resins should be such that the peak glass transition temperature of the formulation, as determined by dynamic mechanical measurements of the loss modulus, is about −30° C. or greater and preferably about 10° C. or greater. Preferably the peak glass transition temperature is about 100° C. or less and more preferably about 50° C. or less. In a preferred embodiment, the glass transition should be a broad and high glass transition with respect to temperature and frequency, preferably the breadth of the glass transition temperature is greater than about 80° C. and more preferably about 100° C. Preferably the flexible epoxy resin is present in the formulation in an amount of about 10 percent by weight or greater, more preferably about 20 percent by weight or greater, even more preferably about 25 percent by weight or greater based on the weight of the formulation. Preferably the amount of the flexible epoxy resin present in the formulation is about 60 percent by weight or less and more preferably about 50 percent by weight or less. A preferred flexible epoxy resin is DER™ 732 epoxy resin available from The Dow Chemical Company.
The amount of rigid epoxy resin present is preferably about 5 percent by weight or greater and more preferably about 10 percent by weight or greater based on the weight of the formulation. The amount of rigid epoxy resin present in the formulation is preferably about 40 percent by weight or less and more preferably about 30 percent by weight or less based on the weight of the formulation.
The formulation should have a viscosity such that the formulation is sprayable using a airless sprayer which atomizes the formulation. Preferably the formulation has a viscosity of about 150,000 centipoise or less and more preferably about 100,000 centipoise or less.
The formulation further comprises a curing agent for the epoxy resin. The curing agent can be any curing agent useful with epoxy resins and known to one skilled in the art. Representative curing agents are disclosed in U.S. Pat. No. 5,308,895 at column 11, line 8 to column 12 line 47 incorporated herein by reference. More preferably the curing agent is an amine terminated polyether, such as Jeffamine amine terminated polyether available from Huntsman Chemical, anhydrides, including dianhydrides, and cyandiamides or dicyandiamides and derivatives thereof. Most preferred curing agents are the dicyandiamides and the derivatives thereof. The choice of the curing agent will effect the form of the composition, whether it is a one-part or a two-part composition, shelf stability, final performance properties and the curing temperature of the composition. For a two-component composition, an amine terminated polyether or an anhydride curing agent may be used. For a one-component formulation, a dicyandiamide curing agent may be used.
The curing agent in relation to the epoxy resin is used in an amount such that the ratio of epoxy groups to epoxy reactive groups is about 0.7 to 1 to about 1.3 to 1. The curing agent may be present in an amount of from about 0.5 to about 7 percent by weight based on the amount of the total formulation. It is preferable that there be a slight excess of epoxy moieties to epoxy reactive moieties such that the range is about
Hoffman Dwight K.
Hong Xiao
Hsu Gloria
Sophiea Daniel P.
Sellers Robert E. L.
Sims Norman L.
The Dow Chemical Company
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