Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-10-04
2003-02-11
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S161000, C524S162000, C524S409000, C524S410000, C524S537000, C524S611000
Reexamination Certificate
active
06518357
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a flame retardant (FR) halogen-free aromatic polycarbonate (PC) composition.
Many applications require that a polycarbonate composition be flame retardant and combine ease of processing with good optical properties. Typically, flame retardancy is obtained through the use of additives, which are halogen or heavy metal-containing compositions that may form toxic materials when heated. There is an increasing awareness of the effects of these materials and increasing demand for polycarbonate compositions that do not contain potentially toxic flame retardant additives.
Siloxane additives are known to enhance flame retardant properties of polycarbonate compositions. Compression molded {fraction (1/16)} inch bars of polycarbonate compositions with siloxane additives that have condensed triorganosiloxy units can pass the UL94 test with VO rating. See “Flammability of Plastic Materials Bulletin” of Jan. 24, 1980. Aromatic polyester siloxane-containing polycarbonate compositions also exhibit flame retardant properties. However, these polycarbonate compositions can be difficult to process due to incompatibility of the siloxane additive with the polycarbonate.
There is a need for a flame retardant additive for polycarbonate compositions that is sufficiently flame-retardant to obtain a satisfactory UL94 rating, that does not form toxic materials, that imparts good flow as measured by a satisfactory high melt flow index value, that does not affect optical properties, and that improves processibility. Particularly, there is a need for a flame retardant polycarbonate composition that meets UL94 requirements for VO rating at {fraction (1/16)} inch thickness. Additionally, there is a need for fabrication materials that will emit low smoke and heat when burning.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a polycarbonate composition comprising components (A) and (B) wherein component (A) comprises a polycarbonate and component (B) comprises a silsesquioxane.
The present invention further provides a method of making a flame retardant composition comprising providing a polycarbonate and incorporating a flame retardant amount of a silsesquioxane into the polycarbonate.
DETAILED DESCRIPTION OF THE INVENTION
As used hereinafter, the term “flame retardant” means reduced or eliminated in tendency to ignite when exposed to a low-energy flame. The term “UL94 V0” when used in conjunction with “flame retardant” means that a described polycarbonate composition can satisfy the UL94 requirements for VO flammability, as described in the “Flammability of Plastic Materials Bulletin” of Jan. 24, 1980. In this test, a 5 inch by ½ inch by {fraction (1/16)} inch polycarbonate test bar containing an amount of a flame retardant additive is suspended vertically over a ¾ inch Bunsen Burner flame. A material meets requirements for a UL94 V0 rating when a test bar satisfies the following 5 tests: (1) a test bar of the material does not burn with flaming combustion for more than 10 seconds after application of a test flame, (2) no set of five test bars exhibits a total flaming combustion time exceeding 50 seconds for 10 flame applications, (3) no test bar of the material burns with flaming or glowing combustion up to the holding clamp, (4) no test bar drips flaming particles that ignite dry absorbent surgical cotton located 12 inches (305 millimeters) below the bar, and (5) no test bar exhibits glowing combustion that persists for more than 30 seconds after twice applying and removing the test flame.
The polycarbonate composition of the invention contains a silsesquioxane elastomer resin. Silsesquioxanes are siloxanes of the formula R(SiO
3/2
)
n
wherein n equals an even number higher than or equal to 4, for example 4, 6, 8, etc. and R is independently at each occurrence phenyl, C
1
-C
8
alkyl, cycloalkyl, vinyl, or combinations of the same. The silsesquioxanes are cage-like hybrid molecules of silicon and oxygen with similarities to both silica and silicone. When mixed with virtually any ordinary polymer, they bond to the organic molecules and to one another, forming large chains that weave through the polymer. The result may be a nanostructured organic-inorganic hybrid polymer.
The SiO
3/2
units are assembled into spherical, highly symmetric cage-compounds. Terminal R units are not incorporated into the silicate framework. These structural characteristics led to the name spherosiloxanes. The spherosiloxane class of silsesquioxane shows a broad variety. Many different terminal substituents (organic and inorganic, e.g., R=alkyl, aryl, hydroxy, chlorine) are known. The SiO
3/2
unit is synthetically accessible to n in a range between about 4 and about 18. Suitable silsesquioxane elastomer resins in the invention include silsesquioxanes of the following formula (I):
wherein R is independently at each occurrence the same or different moiety selected form the group consisting of phenyl, C
1
-C
8
alkyl, cycloalkyl, vinyl, and combinations thereof. Preferably, R is selected from phenyl, vinyl, methyl, and combinations thereof. The silsesquioxane in the present invention is typically made via copolymerization of phenylsilsesquioxane with dimethylsiloxane to form a (phenyl-silsesquioxane)-co-(dimethyl siloxane) of the general formula, T
Ph
x
D
y
wherein D has the formula (CH
3
)
2
SiO
2/2
, T has the formula (C
6
H
5
)SiO
3/2
, subscript x is in a range between about 0.1 and about 1, and subscript y is in a range between about 0.1 and about 1. A further example of a silsesquioxane in the present invention is a poly(phenyl vinyl silsesquioxane) of the general formula (RSiO
3/2
)
x
(RSiO
3/2
)
y
(RSiO
3/2
)
z
where R is independently at each occurrence phenyl, C
1
-C
8
alkyl, cycloalkyl, and vinyl; and x+y+z is the total degree of polymerization of the resin. These and related materials are prepared by hydrolysis condensation of either RSiCl
3
or RSi(OR′)
3
. For example, if a 9:1 mole ratio of (C
6
H
5
)SiCl
3
and vinylSiCl
3
are hydrolyzed and condensed, then a poly ((C
6
H
5
)SiO
3/2
)
0.9x
(vinylSiO
3/2
)
0.1x
resin is obtained.
Among the polycarbonates that can be rendered flame retardant in the practice of the present invention are included aromatic polycarbonates formed, for example, by phosgenating the following bisphenols: p,p′-bisphenol A, m,p-bisphenol A, o,p-bisphenol A, spirobindane bisphenol, tetramethylbisphenol A and tetramethylbiphenol. Copolycarbonates containing the aforementioned bisphenols as a major bisphenol constituent are also included. Preferably, the aromatic polycarbonate is a bisphenol A polycarbonate having an intrinsic viscosity (IV) in a range between about 0.35 deciliters per gram (dl/g) and about 1.8 dl/g in chloroform at 25° C.
Aromatic polycarbonate resins are, in general, prepared by reacting a dihydric phenol with a carbonate precursor or a carbonate ester. Suitable dihydric phenols for preparing polyestercarbonates include those represented by the formula XII:
HO—D—OH (XII)
wherein D is a divalent aromatic radical. Preferably, D has the structure of formula XIII;
wherein A represents an aromatic group such as phenylene, biphenylene, naphthylene, etc.; and E may be an alkylene or alkylidene group such as methylene, ethylene, ethylidene, propylene, propylidene, isopropylidene, butylene, butylidene, isobutylidene, amylene, amylidene, isoamylidene, etc. Where E is an alkylene or alkylidene group, it may also consist of two or more alkylene or alkylidene groups connected by a moiety different from alkylene or alkylidene, such as an aromatic linkage; a tertiary amino linkage; an ether linkage; a carbonyl linkage; a silicon-containing linkage; or a sulfur-containing linkage such as sulfide, sulfoxide, sulfone, etc.; or a phosphorus-containing linkage such as phosphinyl, phosphonyl, etc. In addition, E may be a cycloaliphatic group (e.g., cyclopentylidene, cyclohexylidene, 3,3,5-trimethylcyclohexylidene, methylcyclohexylidene, 2-[2.2.1]-bicyclohept
Campbell John Robert
Lewis Larry Neil
Rajagopalan Padmavathy
Bennett Bernadette M.
Johnson Noreen C.
LandOfFree
Flame retardant polycarbonate-silsesquioxane compositions,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flame retardant polycarbonate-silsesquioxane compositions,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flame retardant polycarbonate-silsesquioxane compositions,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3157750