Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
1997-01-31
2003-12-16
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S413000, C427S386000, C524S474000, C524S490000, C525S097000, C525S098000, C526S280000, C526S281000, C526S283000
Reexamination Certificate
active
06663970
ABSTRACT:
FIELD OF THE INVENTION
The instant invention relates to a blending of hydrocarbon resin into epoxy resin and subsequently curing the epoxy to form a modified thermoset alloy of hydrocarbon resins in a cured epoxy matrix. Hydrocarbon resins of utility in the instant invention are formed by an alkylation reaction between cyclic diolefins such as dicyclopentadiene (DCPD) and aromatic solvents.
The alloys of the instant invention are of particular utility as binders for use with matrix materials, such as glass fabrics, for use in making laminate products for electronics.
BACKGROUND OF THE INVENTION
Epoxy resins are commonly used as binders for making glass fabric reinforced laminate products for electronics applications. In these applications, epoxy resin, combined with a curative, is applied in liquid form (neat or as a solution) to glass fabric. The fabric containing the epoxy is then dried at elevated temperatures to remove volatiles from the epoxy and to partially cure the epoxy thereby yielding an intermediate product typically termed a “prepreg”. Laminates can be constructed from prepregs by layering sheets of prepreg in various combinations and orientations and typically placing copper foil layer on one or both of the outside layers of the laminate to form a laminate structure. The laminate structure is then compressed with the application of heat and pressure to form electronic laminate products comprised of metal foil(s) bonded to cured epoxy/glass fabric sheets.
Typically, epoxies used in electronic laminate are Bisphenol A diglycidylether epoxy resins where a required amount of bromine has been reacted onto an epoxy molecule to confer flame retardance to cured product. Laminate produced from this type of epoxy is typically classified as FR-4 type.
Cured epoxy resins provide several desirable properties required for electronic laminate application such as infusibility, high glass transition temperature, solvent resistance, adhesion to copper, flame retardance, among other characteristics. However epoxy resins are inherently polar in character, and this polarity causes other undesirable properties commonly associated with epoxy resins such as high moisture absorption and higher dielectric constant and dissipation factor (higher than measured for many common polymers).
One potential technique for producing a material which retains the desirable attributes of epoxy resin and desirable attributes associated with a non-polar material is to form an alloy of non-polar polymer(s) blended into and cured with the epoxy resin itself. An example of such an alloy is a product produced and sold by General Electric as Getek® polymer. The alloy comprises an alloy of polyphenyleneether (PPE) polymer mixed with an epoxy resin, where this alloy is applied and used as the binder in electronic laminate products. While this alloy offers some property advantages, it suffers from the fact that the PPE polymer and epoxy resin are highly incompatible. This incompatibility leads to both processing problems and product variability. The latter problem is attributed to difficulties associated with consistent formation of a desired phase separation between the PPE and epoxy.
One solution to this problem is to use a non-polar hydrocarbon polymer which is soluble and compatible with epoxy resins. However non-polar polymers such as polypropylene, polyethylene, polystyrene, PPE, or hydrocarbon rubbers such as polyisoprene, polybutadiene, and the like are incompatible with epoxy resins. Compatibility can be improved by reducing the molecular weight of the polymer. One type of non-polar low molecular weight polymer are materials typically classified as hydrocarbon resins. Examples of such hydrocarbon resins include Kristalex® 3100 resin or Picco® 5140 resin available from Hercules Incorporated. These materials are low molecular weight polymers derived from pure styrenic monomers in the former case or mixed unsaturated aromatic feedstocks in the latter case. However even low MW oligomers such as these hydrocarbon resins display poor solubility and compatibility with epoxy resins.
BRIEF DESCRIPTION OF THE INVENTION
The instant invention relates to an epoxy/alkylation-type hydrocarbon resin alloy comprising an epoxy resin, an alkylation-type hydrocarbon resin, and a curative. The epoxy resin may be a Bisphenol A diglycidylether epoxy resins where a required amount of bromine has been reacted onto an epoxy molecule. The alkylation-type hydrocarbon resin is characterized as a product formed by an alkylation reaction between a cyclic diolefin and aromatic solvent. One particularly effective alkylation-type hydrocarbon resin in this invention is the alkylation resin formed by the reaction of dicyclopentadiene (DCPD) with alkylnaphthalene solvent. The resin exhibits a high glass transition temperature (Tg) at very low number average molecular weight values (MW), less than about 10,000, preferably less than 5,000, most preferably less than 3,000, measured by size exclusion chromatography. The alkylation-type hydrocarbon resin is added to the epoxy resin at levels up to about 25% by weight, preferably between about 10% to 25% by weight, more preferably about 17.5% to 20% by weight.
The instant invention also relates to a process of producing an epoxy/alkylation-type hydrocarbon resin alloy comprising the steps of: dissolving an alkylation-type hydrocarbon resin in a liquid epoxy to form a mixture; adding a curative to the alkylation-type hydrocarbon resin/epoxy mixture; impregnating a matrix with the alkylation-type hydrocarbon resin/epoxy mixture containing the curative; and advancing the epoxy's cure to provide the epoxy/alkylation-type hydrocarbon resin alloy.
Additionally, the invention relates to a prepreg comprising; a matrix impregnated with the epoxy/alkylation-type hydrocarbon resin alloy as well as laminates produced from such prepregs.
DETAILED DESCRIPTION OF THE INVENTION
Alkylation hydrocarbon resins is an alternate way to hydrophobically modify the properties of epoxy materials. use of an alkylation-type hydrocarbon resin reduces processing difficulties associated with PPE alloys and forms a product which is hydrophobically modified.
One particularly effective alkylation-type hydrocarbon resin for this application is the alkylation resin formed by the reaction of dicyclopentadiene (DCPD) with alkylnaphthalene solvent, described in U.S. Pat. No. 5,391,670. Because of the rigid molecular structure of this material, it exhibits a high glass transition temperature (Tg) at very low number average molecular weight values (MW), less than about 10,000, preferably less than 5,000, most preferably less than 3,000, measured by size exclusion chromatography. Because of its aromatic character and low MW, the alkylation-type hydrocarbon resin can be readily dissolved into various epoxy resins and easily processed into resin impregnated glass cloth prepreg for ultimate conversion into electronic laminate products. These epoxy/alkylation-type hydrocarbon resin alloys retain high Tg values with minimal increase in thermal expansion. Incorporation of the non-polar alkylation-type hydrocarbon resin into an epoxy reduces moisture sensitivity and improves dielectric properties of the epoxy relative to the unmodified epoxy. Because of compatibility between in the epoxy and alkylation resin, other important properties such as degree of cure, solvent resistance, mechanical properties, thermal stability, and adhesive characteristics are not deteriorated despite the fact that the alkylation-type hydrocarbon resin does not co-cure with the epoxy matrix and retains its thermoplastic characteristics in epoxy/alkylation-type hydrocarbon resin alloy.
Alkylation-type hydrocarbon resin formed by the alkylation reaction between cyclic diolefins such as dicyclopentadiene (DCPD) and aromatic solvents exhibit almost universal solubility in a range of solvents and are highly soluble and compatible in various types of epoxy resins. Because of this high degree of compatibility, up to 25 vol % of alkylation-type hydrocarbon resin can be
Dawson Robert
Eastman Chemical Resins Inc.
Graves, Jr. Bernard J.
Keehan Christopher M.
Owen Polly C.
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