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
2000-05-16
2003-09-02
Sellers, Robert E. L. (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...
C525S496000, C525S497000, C528S149000, C528S150000, C528S158000, C564S015000, C564S016000, C568S017000, C558S076000, C558S082000
Reexamination Certificate
active
06613848
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.
BACKGROUND OF THE INVENTION
Epoxy resins have the excellent characteristics of moisture, solvent and chemical resistance, toughness, low shrinkage on cure, superior electrical and mechanical resistance properties, and good adhesion to many substrates. The versatility in formulation also make epoxy resins widely applicable industrially for surface coatings, adhesive, painting materials, potting, composites, laminates, encapsulants for semiconductors, and insulating materials for electric devices, etc. o-Cresol formaldehyde novolac epoxy (CNE) is the resin typically employed in the encapsulation of microelectronic devices. 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.
The trend of electronics equipment is being miniaturized and becoming thinner, at the same time the scale of integration of large scale integrated circuits (LSICs) is continuing upward, forcing the design toward larger chips, finer patterns, and higher pin counts that are more susceptible to a high-temperature failure. The prevailing surface mount technology (SMT) also causes the devices being subjected to a high temperature. Therefore, the development of a high-temperature reliable, flame-retardant and environmentally friendly epoxy resin for printed circuit board and encapsulant are essential for semiconductor industry.
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 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.
SUMMARY OF THE INVENTION
In order to accomplish the aforesaid objects, a flame-retardant hardener containing one of the following phosphorus groups was synthesized in the prevent invention:
wherein 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 a multi-active-hydrogen-containing compound or resin.
The present invention also provides a cured flame-retardant epoxy resin by using the hardener of the present invention. The cured flame-retardant epoxy resin so prepared has a high glass transition temperature (Tg), high decomposition temperature and high elastic modulus, and is free of toxic and corrosive fumes during combustion, and thus is suitable for printed circuit board and semiconductor encapsulation applications.
DETAILED DESCRIPTION OF THE INVENTION
A phosphorus-containing hardener prepared in accordance with the present invention has a formula selecting from the group consisting of (a), (b), (c) and (d):
wherein
m=1 or 2; m′=0 or 1; p=0~3; R=C1~C4 alkyl or aryl; X=O, S or NH;
wherein Q=—, when Q′ is the latter;
wherein
R
1
, 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;
n′=0~11; Z=—NH
2
, —NHR, or —R; o=1~3; o′=3~10; r=0~6; R, Q and p are defined as above;
wherein R is defined as above and n=0-5;
wherein either all the A or all the A′ in each formula of (a) to (d) are H, and at least one of the A is not H when all the A′ are H in each formula of (a) to (d), and at least one of the A′ is not H when all the A are H in each formula of (a) to (d).
Preferably, R is hydrogen or methyl, and more preferably R is hydrogen.
Preferably,
Preferably, X is —O— or —NH—. More preferably, X is —O—.
Preferably, Y is—, i.e. r is 0.
Preferably, the hardener of the present invention has a structure of the formula (a).
Preferably, the hardener of the present invention has a structure of the formula (b).
Preferably, the hardener of the present invention has a structure of the formula (c).
Preferably, the hardener of the present invention has a structure of the formula (d).
Preferably, all the A′ are H, and
More preferably, only one A is not H.
Preferably, all the A are H, and only one A′ is not H.
Preferably, all the A are H, and
Preferably, all the A are H, and Q′ is
More preferably, Z is —NH
2
.
Preferably, R
1
—C—R
2
is one of the followings:
wherein X′=H or halogen. More preferably, R
1
and R
2
are hydrogen.
The hardener of the present invention can be synthesized by bounding a reactive phosphorus-containing rigid group to a multi-active-hydrogen-containing compound or resin. There are two different schemes for preparing the hardener of the present invention depending on the types of the reactants containing the reactive phosphorus-containing rigid group. The reactants having the following formulas (I) or (II) are used to prepare the hardener having all the A in the formulas (a) to (d) being hydrogen:
by reacting with a multi-active-hydrogen-containing compound or resin having a structure selected from the formulas (III) to (VII) as follows:
wherein R
1
, R
2
, Ar, R, Q′, X, Z, Y, p, o and o′ in (I) to (VII) are defined the same as above.
The reactants having the following formulas (I′) or (II′) are used to prepare the hardener having all the A in the formulas (a) to (d) being hydrogen:
by reacting with a multi-active-hydrogen-containing compound or resin having a structure selected from the formulas (III), (V), (VI) and (VII), wherein Ar in the formula (II′) is defined as above.
The compound (I) may be synthesized by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) with a compound of R
1
CR
2
O, as shown by the following reaction formula (VIII):
The compound (II
Shieh Jeng-Yueh
Wang Chun-Shan
Jackson Walker L.L.P.
National Science Council
Sellers Robert E. L.
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