Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2003-01-13
2003-09-23
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C523S218000, C524S436000, C524S493000, C524S588000, C525S479000, C528S031000, C528S032000
Reexamination Certificate
active
06623864
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention deals with organopolysiloxane-based compositions that are used to prepare silicone rubbers that are flame retardant and to the use of such rubbers. More specifically, this invention deals with flame retardant rubbers that are useful as coatings, for example, as marine deck coatings, firewall construction and fireblanket applications. The materials of this invention are resin reinforced silicone polymers used in conjunction with ceramic hollow spheres and they have demonstrated good performance in burn tests.
The rubbers are prepared by curing a composition comprising liquid dimethylvinyl end blocked polydimethylsiloxane polymers, organopolysiloxane resins, hollow ceramic spheres having a specific particle size, fillers, and a crosslinker in the form of a liquid organohydrogensiloxane in the presence of a catalyst for the crosslinking reaction. Prior to the cure, these materials have the attribute of being liquid silicone rubbers that are easily pourable and castable which allows the materials to be self-leveling. Optionally, adhesion promoters can be added prior to curing to permit adhesion to a desired substrate.
PRIOR ART
One patent, U.S. Pat. No. 4,269,753 that issued to Mine, et al on Sep. 18, 1980 deals with a fire resistant coating comprised of a mixture of siloxanes containing vinyl groups, siloxanes containing SiH groups, ceramic forming fillers, such as ZnO, Al2O3 or mica and a platinum catalyst. Hollow spheres as part of the composition are not disclosed nor suggested. Also, this composition does not deal with resin reinforcement.
Mine, et al also have issued a patent, U.S. Pat. No. 4,396,757, that issued on Sep. 18, 1980 that deals with fire resistant coating compositions comprising vinyl containing siloxane polymers, ceramic forming fillers, and an organoperoxide as a curing agent. This material does not cure via platinum catalyzed silicon hydride addition to unsaturated compounds, does not deal with resin reinforcement, and does not deal with hollow glass spheres in the composition.
U.S. Pat. No. 4,286,013 issued to Daroga, et al, on Aug. 25, 1981 deals with a flame barrier sheet that is comprised of curable diorganopolysiloxane gum coatings containing hollow glass microspheres.
In Great Britain patent GB9223636 to Hluchan, et al, there is disclosed a sealant composition that is comprised of a silicone resin, a filler, a ceramic fire retardant, a smoke suppressant and an intumescent compound. This material is used to seal penetrations and opening in walls, floors and ceilings, such as around pipes and the like. Upon exposure to heat, the intumescent compound converts the material to a sealing compound.
U.S. Pat. No. 5,861,451, that issued to Schroeder, et al on May 6, 1998 deals with an aqueous silicone emulsion that forms an elastomer upon dehydration that is composed of diorgansiloxane polymer, a crosslinker comprised of a linear aminoxy-functional siloxane, a cyclic aminoxy-functional siloxane, water, surfactants, aluminum trihydrate, fumed titanium dioxide, zinc borate, magnesium oxide or a ceramic filler that is used to seal openings in structural building components to reduce the amount of smoke that may pass through the opening.
None of the prior art discussed supra deals with a resin reinforced, liquid silicon material that contains hollow ceramic spheres that is useful for flame retardancy.
THE INVENTION
This invention deals with a silicone composition that is useful for curing into a silicone rubber flame retardant material. With more specificity the invention comprises a silicone composition comprising (A) 0.50 to 4.50 weight percent of a liquid dimethyl vinyl end blocked polydimethylsiloxane polymer having an average molecular weight in the range of 9300 to 12,600 and a vinyl group content in the range of 0.35 to 0.60 weight percent. The component (B) is 2.00 to 10.00 weight percent of a blend of from 55:45 to 65:35 of a liquid dimethylvinyl end blocked polydimethylsiloxane polymer having an average molecular weight in the range of 27,000 to 36,800 and having a vinyl group content in the range of 0.18 to 0.25 weight percent and, an organopolysiloxane resin consisting essentially of (i) R
1
2
(CH
2
═CH)SiO
0.5
units; (ii) R
2
3
SiO
0.5
units and (iii) SiO
4/2
units, wherein the molar ratio of the combination of (i) and (ii) units to (iii) units is from 0.6 to 1.1, and the concentration of (i) units is from 0.2 to 8 weight percent based on the weight of said organopolysiloxane resin, and R
1
and R
2
are each selected from the group consisting of alkyl groups containing from 1 to 4 carbon atoms and phenyl, with the proviso that at least 95 percent of the R
1
and R
2
groups are methyl groups and the total mixture has a weight percent vinyl content in the range of from 0.40 to 0.60. Component (C) is about 14.00 to 55.00 weight percent of a blend of from 60:40 to 70:30 of a liquid dimethylvinyl end blocked polydimethylsiloxane polymer having an average molecular weight in the range of 48,000 to 65,000 and having a vinyl group content in the range of 0.075 to 0.10 weight percent and, an organopolysiloxane resin consisting essentially of (i) R
1
2
(CH
2
═CH)SiO
0.5
units, (ii) R
2
3
SiO
0.5
units and (iii) SiO
4/2
units wherein the molar ratio of the combination of (i) and (ii) units to (iii) units is from 0.6 to 1.1, and the concentration of (i) units is from 0.2 to 8 weight percent based on the weight of said organopolysiloxane resin, and R
1
and R
2
are each selected from the group consisting of alkyl groups containing from 1 to 4 carbon atoms and phenyl, with the proviso that at least 95 percent of the R
1
and R
2
groups are methyl groups and the total mixture has a weight percent vinyl content in the range of from 0.40 to 0.60;
Component (D) is 0 to 0.45 weight percent of a silanol endblocked methylvinyl/dimethyl polysiloxane copolymer containing in the range of 8.0 to 14.0 weight percent vinyl groups, while component (E) is 1.00 to 4.00 weight percent of a crosslinker in the form of a liquid organohydrogensiloxane in an amount sufficient to provide from 1 to 3 silicon-bonded hydrogen atoms per vinyl group present in components (A), (B), (C), and (D) combined, said organohydrogensiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule and consisting essentially of units selected from the group consisting of methylhydrogensiloxy, dimethylsiloxy, dimethylhydrogensiloxy, trimethylsiloxy and SiO
4/2
units;
Component (F) is from 1.50 to 35.0 weight percent of hollow ceramic spheres having a mean particle size of 5 to 500&mgr; and a bulk density in the range of 0.35 g/cm
3
to 0.45 g/cm
3
.
Component (G) is comprised of about 8.0 to 30.00 weight percent of a filler having at least 90% of the particles with an average mesh size of 270 or greater selected from the group consisting of quartz and magnesium oxide.
Finally, component (H) is 0.05 to 0.40 weight percent of a catalyst.
The weight percent of components (A), (B), (C), (D), (E), (F), (G), and (H) are based on the total weight of components (A), (B), (C), (D), (E), (F), (G), and (H) in the composition.
Turning now to the specifics of the components, the vinyl end blocked polydimethylsiloxanes of this invention are well known materials to those skilled in the art. They are commercially available in a wide range of molecular weights and vinyl content. The viscosities of these materials range from about 100 cps to about 75,000 cps, measured at a temperature of 25° C. and they can be represented by the formula
wherein R is methyl or phenyl and at least 95% of the R groups are methyl. Preferably, 100% of the R groups are methyl.
Of this category of components, component (A) is used in the range of 0.5 to about 4.5 weight percent, it being noted that all percentages of components are based on the total weight of the components (A) to (H) in the composition. A preferred range for this component is a range of about 0.9 to about 4.0 weight percent. The materials that are useful in this invention have an average molec
Gallmeyer Jimmy H.
Sweet Randall P.
Dow Corning Corporation
McKellar Robert L.
Moore Margaret G.
LandOfFree
Silicone composition useful in flame retardant applications does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Silicone composition useful in flame retardant applications, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Silicone composition useful in flame retardant applications will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3059566