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
2000-01-10
2002-06-11
Moore, Margaret G. (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...
C428S447000, C524S731000, C524S853000, C524S852000, C524S849000, C524S863000, C524S864000, C524S775000, C524S776000
Reexamination Certificate
active
06403711
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a low temperature flexible, water-repellant polysiloxane containing copolymer particles dispersed therein. More specifically, the present invention relates to the copolymer particles being formed in situ by polymerizing at least two different types of monomers in the polysiloxane which is curable at low temperatures; for example, an ambient temperature, upon exposure to moisture. Cured sealants containing the copolymer-polysiloxane have high elongation properties.
BACKGROUND OF THE INVENTION
Curable polyorganosiloxane, also known as silicone compositions have been used as sealants, caulks, adhesives, and in other similar applications because of their excellent water repellency, good adhesion, chemical and biological inertness, and good weather resistance. Such compositions generally contain a reactive polyorganosiloxane, crosslinking agents, and crosslinking catalysts. Polyorganosiloxane compositions are, however, relatively expensive and do not always provide satisfactory physical properties such as toughness and strength. In order to improve the physical properties of polyorganosiloxane compositions, various inorganic filler materials such as silica, diatomaceous earth, calcium carbonate, iron oxide and the like have been added. The use of such additives, however, has often resulted in an undesirably high viscosity which adversely affects the ease of application of the composition. In order to reduce the viscosity of filled polyorganosiloxane compositions to an acceptable level, organic solvents or non-reactive organosiloxanes can be used. However, this can result in undesirable shrinkage, or the release of environmentally undesirable organic components into the atmosphere or staining problems due to the non-reactive siloxane extrudate.
U.S. Pat. No. 4,138,387 to Bluestein relates to a polyolefin filled-organo polysiloxane composition which are allegedly stable dispersions comprised of a continuous phase of essentially ungrafted organo polysiloxane and a discontinuous phase of finely divided solid particles of a homopolymer or copolymer prepared from an organic monomer or monomers. The composition, however, is generally unacceptable as a sealant inasmuch as it has low elongation such as a maximum of only about 190 percent.
SUMMARY OF THE INVENTION
Curable dispersed copolymer-polysiloxane compositions are prepared by the in situ free radical polymerization in a polysiloxane fluid of at least two different classes of monomers, e.g. a first class of monomers which are capable of forming a polymer having a low Tg and a second class of monomers which are capable of forming a polymer having a high Tg. The copolymer, which can be either a thermoplastic or a thermoset, is generally a dispersed phase in the form of particles, the surface thereof generally having substantially high Tg polymers. The use of small amounts of a thixotrope renders the dispersed copolymer polysiloxane composition non-slump. The composition is generally viscous and is moisture curable. Utilization of the two different classes of monomers yields synergistic results upon cure in that the dispersed copolymer-polysiloxane composition has very high elongation as well as a 100% modulus of less than 50 psi. The composition also exhibits good flexibility and excellent weathering. Unlike previous reinforcing filler technology, the in situ polymerized particles have the unique characteristics of both reinforcing (strengthening) as well as plasticizing (increasing elasticity) the cured silicone network. Another attribute of the composition of the present invention is that they have good viscosity aging resistance before cure. Accordingly, the composition is suitable for use as a binder in caulks and sealants.
DETAILED DESCRIPTION OF THE INVENTION COPOLYMER-POLYSILOXANE
The dispersed copolymer-polysiloxane compositions of the present invention are generally made by reacting two or more different monomers in the presence of a polysiloxane fluid. The polysiloxane fluid generally contain a total of two or more reactive functional groups on the polymer chain, preferably at the terminal portion thereof.
The polysiloxane fluid desirably is an organo polysiloxane of the formula
where R
1
and R
2
, independently, is an alkyl having from 1 to 8 carbon atoms, desirably from 1 to 4 carbon atoms with methyl being preferred, or is an aromatic group or substituted aromatic group having from 6 to 10 carbon atoms with phenyl being preferred, and “n” is such that the weight average molecular weight of the polysiloxane is from about 2,000 to about 200,000 and desirably from about 15,000 to about 80,000 grams/mole. It is to be understood that the above polymers also contain, as noted above, two or more reactive functional groups (X) therein. The functional groups, independently, can be OH, or OR
3
, or N(R
4
)
2
, or
or an
group, where R
3
through R
12
, are, independently, an alkyl having from about 1 to about 8 carbon atoms. The amount of the functional groups, i.e. m, is 1, 2, or 3. The one or more R groups, independently, is an alkyl having from 1 to 8 carbon atoms or an aromatic or an alkyl-aromatic having from 6 to 20 carbon atoms and optionally containing one or more functional groups thereon such as amine, hydroxyl, etc. A polysiloxane fluid can furthermore contain a blend of two or more different polysiloxanes and/or polysiloxanes having different viscosities. The polysiloxanes are generally a viscous liquid and are commercially available, e.g. Masil® SFR 6,000 from PPG Corporation and Wacker 6LV from Wacker Corporation.
The organopolysiloxane fluid generally constitutes a reactive continuous phase containing a discontinuous phase therein which comprises copolymer particles made in situ by free radical polymerization. Desirably, two or more, and preferably two types of monomers are utilized wherein one, if homopolymerized, forms a low Tg polymer and the other, if homopolymerized, forms a high Tg polymer. As noted above, the copolymer can either be a thermoplastic, or if crosslinked, a thermoset.
The one or more monomers utilized which otherwise would form a polymer having a low Tg, i.e. generally from about −70° C. to about 0° C. and desirably from about −55° C. to about −10° C., include the various alkyl acrylates, and the like. The alkyl acrylate monomers generally have an alkyl portion which contains from 1 to 18 carbon atoms, and desirably from 1 to 8 carbon atoms. Examples of such suitable acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, 1-ethyl propyl acrylate, 1-methyl pentyl acrylate, pentyl acrylate, hexyl acrylate, 2-ethylhexly acrylate, and the like, with n-butyl acrylate being highly preferred. A small amount of approximately 20 percent or less and desirably from about 2 to 8 percent by weight of the various alkyl acrylates can contain functional groups thereon. Such groups include hydroxyl, epoxy, acetoacetyl, acrylamide, and the like, are preferably terminal groups and serve to improve adhesion to various substrates such as metals, concrete, wood, etc.
One or more monomers are also utilized which otherwise would form a polymer having a high Tg, i.e. generally from about 1° C. or 5° C. to about 150° C. and desirably from about 20° C. to about 120° C. Such monomers include vinyl esters, acrylonitrile or derivatives thereof, vinyl substitute aromatics, alkyl methacrylates, vinyl chloride, vinylidene chloride, and the like. The non-vinyl portion of the vinyl ester generally contains a total of from 2 to about 10 carbon atoms, desirably from about 2 to about 8 carbon atoms with acetate, i.e. vinyl acetate, being highly preferred. With respect to the acrylonitrile monomers, while the same is generally utilized, alkyl derivatives thereof containing from 1 to about 6 carbon atoms such as methyl acrylonitrile, ethyl acrylonitrile, etc. can also be utilized. The vinyl substituted aromatics generally contain from 8 to about 12 carbon atoms and specific examples include styr
Beers Melvin Dale
Feng Ta-Min
Yang Wei-Yeih
Calloway Valerie L.
Dunlap Thoburn T.
Hudak & Shunk Co. L.P.A.
Moore Margaret G.
Noveon IP Holdings Corp.
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