Organic compounds -- part of the class 532-570 series – Organic compounds – Four or more ring nitrogens in the bicyclo ring system
Reexamination Certificate
2002-01-30
2004-09-28
Tucker, Philip (Department: 1712)
Organic compounds -- part of the class 532-570 series
Organic compounds
Four or more ring nitrogens in the bicyclo ring system
C525S507000, C525S523000, C528S089000, C528S090000, C528S094000, C528S408000, C544S196000, C558S076000, C558S086000, C558S215000, C564S230000
Reexamination Certificate
active
06797821
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an active-hydrogen-containing phosphorus compound for cross-linking a resin and for imparting flame-retardancy to the cured resin, and in particular to a cured frame-retardant epoxy resin prepared by reacting the hardener with a di- or poly-functional epoxy resin via an addition reaction between the active hydrogen and the epoxide group. It also relates to an epoxy resin made from the active-hydrogen-containing phosphorus compound and epihalohydrin.
BACKGROUND OF THE INVENTION
Typical hardeners for epoxy resins and advanced epoxy resins are phenol-formaldehyde novolac resin, dicyandiamide, methylenedianiline, diaminodiphenyl sulfone, phthalic anhydride, and hexahydrophthalic anhydride, etc. The advanced epoxy resins and cured epoxy resins prepared with these hardeners do not have flame retardancy, and thus can not meet the safety requirements.
Several approaches for modification of epoxy backbone for enhancing the thermal properties of epoxy resins have been reported. Aromatic bromine compounds in conjunction with antimony oxide are widely used as a flame retardant for epoxy resins. Tetrabromobisphenol A is a typical example of the aromatic bromine compounds used as a flame retardant for epoxy resins. An excess amount of epoxy resin is reacted with tetrabromobisphenol A to prepare an advanced epoxy resin having two terminal epoxide groups, as shown in the following formula:
wherein Ep is a bi-radical group of the backbone of the epoxy resin, and m is an integer of 1-10. The advanced epoxy resin can be used in preparing a flame-retardant printed circuit board (FR-4) by impregnating glass fibers with the advanced epoxy resin and heating the resulting composite to cure the advanced epoxy resin. Furthermore, the advanced epoxy resin can be employed to encapsulate microelectronic devices, in which the advanced epoxy resin is cured at a high temperature with a curing agent, so that an encapsulant having a flame-retardant property is formed. Typical examples can be found in U.S. Pat. No. 3,040,495 (1961); U.S. Pat. No. 3,058,946 (1962); U.S. Pat. No. 3,294,742 (1966); U.S. Pat. No. 3,929,908 (1975); U.S. Pat. No. 3,956,403 (1976); U.S. Pat. No. 3,974,235 (1976); U.S. Pat. No. 3,989,531 (1976); U.S. Pat. No. 4,058,507 (1997); U.S. Pat. No. 4,104,257 (1978); U.S. Pat. No. 4,170,711 (1979); and U.S. Pat. No. 4,647,648(1987)].
Although the tetrabromobisphenol A-containing advanced epoxy resin shows flame retardant property, major problems encountered with this system are concerned with the generation of toxic and corrosive fumes during combustion such as dioxin and benzofuran.
The flame retardant having a small molecular weight tends to lower the mechanical properties of the epoxy resins, and migrate/vaporize from the epoxy resins such that the flame retardancy thereof diminishes.
It is an object of this invention to provide a phosphorus-containing flame retardant hardener for cross-linking a resin and for imparting flame-retardancy to the cured resin.
It is another object of this invention to provide advanced epoxy resins and cured epoxy resins with good thermal stability, superior heat resistance, and without environmental problem, which are suitable for use in making printed circuit boards and in semiconductor encapsulation applications.
It is also an object of this invention to provide phosphorus-containing flame-retardant epoxy resins which are suitable for use in making printed circuit boards and in semiconductor encapsulation applications.
SUMMARY OF THE INVENTION
In order to accomplish the aforesaid objects, a flame-retardant hardener containing one of the following phosphorus-containing rigid groups was synthesized in the present invention:
wherein R
1
and R
2
independently are H, C1~C18 alkyl, C6~C18 aryl, C6~C18 substituted aryl, C6~C18 aryl methylene, or C6~C18 substituted aryl methylene; and Ar is an un-substituted or substituted phenyl or phenoxy radical. The hardener of the present invention is prepared by bounding the phosphorus-containing rigid group to bisphenol-A (BPA), diamonodiphenyl methane (DDM), diaminodiphenyl sulfone (DDS), melamine (MA) or dicyandiamide (DICY). The phosphorus-containing bisphenol-A of the hardeners of the present invention can be reacted with an excess amount of epoxy resin to prepare a flame-retardant advanced epoxy, which is suitable for use in making printed circuit boards.
The present invention also provides a flame-retardant epoxy resin by reacting the hardener of the present invention with an excess of epihalohydrin in the presence of an alkali metal hydroxide.
The present invention also provides a cured flame-retardant epoxy resin by using the hardener of the present invention and a cured flame-retardant epoxy resin from the flame-retardant epoxy resin of the present invention. The cured flame-retardant epoxy resins so prepared have a high glass transition temperature (Tg), high decomposition temperature and high elastic modulus, and are free of toxic and corrosive fumes during combustion, and thus are suitable for printed circuit board and semiconductor encapsulation applications.
REFERENCES:
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patent: 4389520 (1983-06-01), Gannon et al.
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Chem. Abstract of JP2000344788, 2000.*
Chem. Abstract of JP0812692, 1996.*
Chun-ShanWang and Jeng-Yueh Shieh, “Synthesis and Properties of Epoxy Resins Containing 2-(6-oxid-6H-dibenz (c,e)(1,2)oxaphosphorin-6-yl)1,4-benzenediol,” Polymer vol. 39, No. 23, pp. 5819-5826, Nov. 1998.
Brochure of Schill & Seilacher entitled “Reactive, halogen-free flame retardants for epoxies,” in free circulation since Sep. 1997 (see p. 24).
Abstract of a lecture held in London at the conference Addcon World '98 in Nov. 1998, which abstract has also been published (ISBN: 1-85957-149-2, 6 pages).
Copy of an article entitled “New developments in flame retartded adhesives,” published in Sep. 1989 in the journal “Kleben & Dichten, Adhesion” (Engl. gluing & sealing, Adhesion).
Japanese Kokai JP-60, 161, 993 (85, 161, 993), together with the corresponding summary in Patent Abstracts of Japan and Chemical Abstracts (total of 6 pages).
Lin Ching Hsuan
Shieh Jeng-Yueh
Wang Chun-Shan
Aylward D.
Jackson Walker L.L.P.
Tucker Philip
Wang Chun-Shan
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