Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1999-12-02
2002-05-28
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S015000, C528S018000, C528S031000, C528S032000, C528S033000, C528S035000, C524S858000, C524S860000, C524S861000, C524S862000, C524S863000, C525S100000, C525S101000, C525S102000, C525S103000, C525S105000, C525S106000, C522S099000
Reexamination Certificate
active
06395856
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to silicone oligomers useful as coupling agents, crosslinkers and adhesion promoters for curable compositions, for instance free-radically curable filler-organic elastomeric polymer compositions having special application as insulation coatings, to compositions employing the oligomers, and to cured products obtained therefrom.
2. Description of the Prior Art
Silanes are known as coupling agents, crosslinkers and adhesion promoters, and are quite useful in adhesives and coatings. Furthermore, a substantial amount of research has been performed heretofore in connection with silane compounds having a plurality of alkoxy groups and which are useful as coupling agents, crosslinkers and adhesion promoters.
For instance, U.S. Pat. No. 4,179,537 to Rykowski discloses blends of an organofunctional silane, e.g., vinyltrialkoxysilanes, methacryloxyalkyltrialkoxysilanes, vinyltrihalosilanes and the like with a non-organofunctional silane, e.g., alkyltrialkoxysilanes, and the incorporation of such blends into organic resins, e.g., EPDM rubber for improving the adhesion between inorganic substrates such as clay fillers and the resin. This patent fails to disclose, teach or suggest the incorporation of siloxane oligomers in the coupling composition and suggests that the presence of siloxane oligomers in the resin-filler system could have a detrimental effect on coupling efficiency (col. 4, lines 54-63).
Use of silanes having silicon-bonded 2-methoxyethoxy groups as coupling agents, e.g., vinyl-tris-(2-methoxyethoxy)silane (col. 2, lines 44-47) is also described in U.S. Pat. No 4,179,537. Vinyl-tris-(2-methoxyethoxy)silane, has been used industrially for many years as a coupling additive in mineral-filled EPM and EPDM wire and cable insulations. EPM is an ASTM designation for copolymers or ethylene and propylene; EPDM is a terpolymer of ethylene, propylene and a diene monomer such as ethylidene norbornene or 1,4 hexadiene. Vinyl-tris-(2-methoxyethoxy)silane has been extensively used heretofore because it provides a unique balance of elastomer reinforcement and the degree of wet electrical stability required. However, it releases 2-methoxyethanol as a hydrolysis by-product when it is used and, unfortunately, 2-methoxyethanol is now being studied as a suspected teratogen. Consequently coupling agent products based on vinyl-tris-(2-methoxyethoxy)silane are now facing continuing replacement pressure in the marketplace.
U.S. Pat. No 4,950,779, Wengrovius, et al. (General Electric), describes mixtures comprising cyclic, linear and branched alkoxy functional silicone oligomers produced by condensation of organotrialkoxysilanes, such as methyltrimethoxysilane and vinyltrimethoxysilane, using formic acid, optionally with a strong acid catalyst.
U.S. Pat. Nos. 4,499,150 and 4,499,151 teach a copolymer of an ethylenically unsaturated alkoxysilane with another ethylenically unsaturated group made by free radical polymerization. These interpolymers are limited in structure and functionalities because of the formulation chemistry.
U.S. Pat. No. 5,210,168 to Bergstrom et al. (Dow Corning) describes alkoxy functional silicone oligomer mixtures produced from organotrialkyoxysilanes using a carboxylic acid, such as formic acid, using a catalytic amount of a strong acid catalyst.
U.S. Pat. No. 5,282,998 to Horn et al. (Hüls), describes mixtures of linear and cyclic alkoxy functional silicone oligomers produced from vinyltrialkoxysilanes using hydrogen chloride catalyst and water.
U.S. Pat. No. 5,432,246 to Fenn et al. discloses a silane oligomer made from a secondary amino-alkoxy silane, a polyisocyanate and optionally a single isocyanate group. Such oligomers are based on the reaction of the amine with the isocyanate to form a substituted urea. In these oligomers, all the isocyanate groups have reacted with the amine groups, so no such functionalities are present. Further, urea structures may increase viscosity to an undesirable degree.
SUMMARY OF THE INVENTION
The present inventors have found novel silicone oligomers having a plurality of alkoxysilyl groups, and having either at least one unsaturated group attached thereon, or at least one organosilyl functional group bridged to a silicone atom of the oligomer backbone by an Si—C bond, or both. The unsaturated group may be vinyl or some other aliphatically unsaturated hydrocarbon functionality.
These silicone oligomers are useful as coupling agents, crosslinkers and adhesion promoters as well as for crosslinkable organic polymer/filler compositions such as wire cable insulating formulations, as well as other free-radically curable compositions. They have lower volatility than alkoxysilane compounds, making them easier to handle by formulators and potentially safer.
The silicone oligomers of the present invention may be of the formula
[R
3
SiO
1/2
]
m
[O
1/2
SiR
2
O
1/2
]
n
[SiO
3/2
R]
o
[SiO
4/2
]
p
(I)
wherein
each R is selected individually from the group consisting of B, R
1
, —OR
2
, R
3
and R
4
; B is an organosilyl functional group bridged to the Si atom of the siloxane oligomer backbone by a Si—C bond; each R
1
is independently a saturated aliphatic hydrocarbon group of 1 to 16 carbon atoms; each R
2
is independently a group as defined for R
1
or an acyl or aromatic hydrocarbon group; each R
3
is independently a monovalent organic radical containing an aliphatically unsaturated hydrocarbon group and each R
4
is a monovalent organic radical linked to the Si atom of the siloxane oligomer backbone by a Si—C bond, which does not include an aliphatically unsaturated hydrocarbon group and which has thereon one or more members of the group selected from aromatic hydrocarbon, ether, ester, carbamate, thioether, polysulfide, blocked mercaptan, amide, epoxy, cyano or oximato groups; and
with the provisos that
at least one quarter of all R groups are —OR
2
; either at least one silicon atom of the oligomer has an R
3
group thereon or at least one R is a B, or both; if there is a group R
3
which is a vinyl group, there is at least one other group which is a B group, an R
3
group other than vinyl, or an R
4
group; m=2 to 20; n=0 to 50; o=0 to 20; p=0 to 10.
In a further aspect, the invention is a curable composition comprising an oligomer of formula (I) wherein formula has at least one silicone atom of the oligomer which has an R
3
group and at least one R is a B. Such compositions may be formed by mixing concurrently or in any order of succession:
(1) an organic polymer curable by a free radical mechanism;
(2) an inorganic filler;
(3) a siloxane oligomer as described above.
Preferred compositions also include a free radical catalyst system capable of crosslinking the organic polymer. Coating and adhesive compositions which comprise the oligomers of formula (I) may also be prepared.
The siloxane oligomers may be produced with little or no volatiles. They function as suitable, cost effective, replacements for commercial coupling agents used in wire cable insulator formulations, with decreased health hazards.
A further aspect the invention is an article, at least a portion of which comprises a cured composition as described above. Preferred articles are wire cables comprising a conductor and a coating of insulation on the conductor, the coating comprising the cured composition as described above.
DETAILED DESCRIPTION OF THE INVENTION
All patents or other published documents mentioned anywhere herein are expressly incorporated herein by reference in their entirety.
Oligomer Structure
In structure I above, B is an organosilyl functional group, —A—W, which comprises a silyl group W and a divalent linking group A which is attached by an Si—C bonds to group W and to a silicon atom of the siloxane oligomer. Preferably B is internal (i.e. non-terminal) to the oligomer. In one preferred embodiment of the present invention, there is at least one B group per oligomer. For this particular embodiment, more prefer
Osterholtz Frederick D.
Petty Herbert E.
Pickwell Robert
Su Shiu-Chin Huang
Crompton Corporation
Dawson Robert
Dilworth Michael P.
Robertson Jeffrey B.
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