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
2002-02-01
2003-10-28
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S479000, C525S187000, C525S523000, C528S012000, C528S017000, C528S018000, C528S014000, C528S034000, C528S038000, C528S411000, C528S412000, C528S413000, C528S414000, C528S409000
Reexamination Certificate
active
06639025
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to epoxy resin based compositions useful for protective coatings and the like and, more specifically, to elastomer-modified epoxy siloxane polymer compositions having improved properties of flexibility, weatherability, and chemical resistance.
BACKGROUND OF THE INVENTION
Epoxy siloxane compositions useful for application as coating materials are well known, and have gained commercial acceptance as protective and decorative coatings for steel, aluminum, galvanizing, wood and concrete in maintenance, marine, construction, architectural, aircraft and product finishing markets. While epoxy-based compositions have long been known for their desired properties of good adherence to substrates, corrosion resistance, and chemical resistance, and weatherability, they have suffered from less than ideal properties of weatherability and related gloss retention. Epoxy siloxane compositions were developed to provide improved properties of weatherability and gloss retention without sacrificing the desired properties of corrosion resistance and chemical resistance.
U.S. Pat. No. 4,250,074 discloses a known epoxy siloxane composition comprising an interpenetrating polymer network (IPN) of intertwined epoxy polymers and polysiloxane polymers. The composition is prepared by simultaneously polymerizing, at substantially balanced reaction rates, a mixture of epoxy resin and silane groups to form two intertwined networks of polymerized epoxy and polysiloxane throughout a resulting coating. An amine curing agent is used to form the polymerized epoxy network, and water is distributed throughout the mixture to cause hydrolytic polycondensation of silane groups to form the polysiloxane. While this epoxy siloxane coating composition displayed improved properties of weatherability, corrosion and chemical resistance when compared to conventional nonsiloxane-containing epoxy resin compositions, it is known to be somewhat brittle, lacking a desired degree of impact resistance, flexibility and abrasion resistance for certain applications.
U.S. Pat. No. 5,618,860 discloses a known epoxy polysiloxane composition for use as a coating. The composition is prepared by combining a non-aromatic epoxy resin with a difunctional aminosilane hardener, an organotin catalyst, and an optional pigment. The so-formed epoxy polysiloxane composition provided improved properties of weatherability, chemical and corrosion resistance, and impact resistance when compared to conventional nonsiloxane-containing epoxy resin compositions. While this epoxy siloxane coating composition provided such improved performance properties, like the epoxy siloxane composition discussed above, it too is known to be somewhat brittle, lacking a desired degree of impact resistance, flexibility and abrasion resistance for certain applications.
It is, therefore, desired that an epoxy siloxane composition be developed that is both capable of providing the desired properties of weatherability, corrosion and chemical resistance already associated with epoxy siloxane compositions, while also providing improved properties of impact resistance, flexibility and abrasion resistance. It is desired that epoxy siloxane compositions of this invention provide improved resistance to cracking and delamination when applied in the form of coatings.
SUMMARY OF THE INVENTION
An elastomer-modified epoxy siloxane composition is prepared, according to principles of this invention, by combining in the presence of water: (1) a silicone intermediate preferably in the form of an alkoxy or silanol-functional polysiloxane; with (2) an epoxy resin preferably having more than one 1,2-epoxide groups per molecule, and an epoxide equivalent weight in the range of from 100 to about 5,000; (3) an elastomeric resinous intermediate having a functionality selected from the group consisting of hydroxyl, isocyanate, carboxyl, epoxy, mercaptan, and amine, and being selected from the group of resins consisting of butenes, polybutenes, butadienes, polybutadienes, nitrites, acrylonitiriles, polysulfides, and combinations thereof; and (4) a polyfunctional amine curative agent. An optional organometallic catalyst can be used to facilitate cure at ambient temperature conditions.
The elastomer-modified epoxy siloxane composition may comprise in the range of from about 1 to 40 percent by weight silicone intermediate, 1 to 15 percent by weight polyfunctional amine, 5 to 60 percent by weight epoxy resin, and 1 to 25 percent by weight elastomeric resinous intermediate.
These above-identified ingredients undergo hydrolysis and polycondensation reactions when combined in the presence of water to form elastomer-modified epoxy polymers or elastomer-modified polysiloxane polymers, depending on the choice of elastomeric resinous intermediate, that copolymerize with polysiloxane polymers and/or epoxy polymers to form a fully-cured elastomer-modified epoxy siloxane polymer composition. Ultimately, the chemical and physical properties of the elastomer-modified epoxy siloxane compositions of the present invention are affected by judicious choice of epoxy resin, silicone intermediate, polyfunctional amine hardener, and pigment. Elastomer-modified epoxy siloxane compositions of this invention are unique, when compared to conventional epoxy polysiloxane compositions, in that the incorporated elastomer serves to provide an improved degree of flexibility, impact resistance, crack resistance, and abrasion resistance to finally-cured coatings formed therefrom. These improved properties are provided without detracting from the desired properties of weatherability, chemical and corrosion resistance.
DETAILED DESCRIPTION OF THE INVENTION
Elastomer-modified epoxy siloxane compositions of this invention are prepared, according to one example, by reacting an epoxy-containing ingredient with a polyamine or aminosilane ingredient to form a cured epoxysilane polymer, and reacting the aminosilane ingredient with a silicone intermediate to form a polysiloxane polymer. Epoxy siloxane compositions of this invention are referred to as being “elastomer-modified” due to the additional reaction of an elastomeric resin with the epoxy-containing ingredient, the silicone intermediate, or the aminosilane or polyamine depending on the type of elastomeric resin functionality. Elastomer-modified epoxy siloxane compositions of this invention provide improved properties of impact resistance, flexibility, and abrasion resistance when compared to conventional nonelastomer-modified epoxy siloxane compositions.
Elastomer-modifier epoxy siloxane compositions are prepared, according to principles of this invention, by combining in the presence of water;
(a) an aromatic or nonaromatic epoxy resin having at least two 1,2-epoxide groups; with
(b) an alkoxy or silanol-functional silicone intermediate;
(c) a polyfunctional amine;
(d) a reactive elastomeric resinous intermediate; and
(e) an optional organometallic catalyst
Elastomer-modified epoxy siloxane compositions of this invention may also contain other components such as optional pigments and/or solvents, rheological modifiers, plasticizers, thixotropic agents, antifoam agents and solvents and the like to achieve the desired properties sought by the user.
With respect to the epoxy resin ingredient, useful epoxy resins include more than one 1,2-epoxy group per mole and may be saturated or unsaturated, aliphatic, cycloaliphatic, or heterocyclic. The epoxide resins generally contain glycidyl ester or glycidyl ether groups, have a weight per epoxide (i.e., an epoxide equivalent weight) of from 100 to 5,000, and have a reactivity of about two. The epoxy resin is preferably provided in liquid rather than solid form.
Example epoxy resins useful for forming compositions of this invention include glycidyl polyethers of polyhydric phenols which are derived from an epihalohydrin, e.g., epichlorohydrin, and a polyhdric phenol. Examples of such polyhydric phenols include resorcinol, hydroquinone, bis(4-hydroxyphenyl)-2,2-propane, or bisphenol A as it is commonly called
Ameron International Corporation
Dawson Robert
Jeffer Mangels Butler & Marmaro LLP
Peng Kuo-Liang
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