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
1999-12-08
2001-05-22
Dawson, Robert (Department: 1712)
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...
C524S492000, C528S012000, C528S037000, C528S017000, C528S018000, C528S039000, C556S458000, C556S464000
Reexamination Certificate
active
06235832
ABSTRACT:
FIELD OF THE INVENTION
A room temperature vulcanizing (RTV) silicone composition curable in the presence of moisture with rapid development of green strength. The RTV silicone composition comprises (A) 0 to about 85 weight percent polydiorganosiloxanes comprising on average at least 1.2 chain terminations per molecule selected from the group consisting of hydroxysilyl groups and alkoxysilyl groups; (B) about 10 to 95 weight percent polydiorganosiloxanes comprising on average at least 1.2 chain terminations per molecule selected from the group consisting of hydroxysilyl groups, alkoxysilyl groups, and multi-alkoxysilyl groups, provided that at least one chain termination per molecule comprises a multi-alkoxysilyl group; (C) an effective amount of a condensation catalyst; (D) 0 to about 40 weight percent of an alkoxysilane; and (E) 0 to about 60 weight percent of a filler; provided that the sum of the weight percents of Components (A) and (B) comprises about 20 to 95 weight percent based on the total weight of the RTV silicone composition.
BACKGROUND OF THE INVENTION
Polyorganosiloxane compositions which cure to elastomeric materials at room temperature are well known. Such compositions can be obtained by mixing polydiorganosiloxanes having reactive groups, such as silanol groups, with silane crosslinking agents, for example, alkoxysilanes, acetoxysilanes, oximosilanes, or aminosilanes, and catalysts as necessary. Compositions comprising these ingredients can then be cured by exposure to atmospheric moisture at room temperature.
Moisture curable compositions are well known for their use as sealants. Moisture curable compositions require a significant amount of time, commonly several days, in which to fully cure before reaching maximum strength. In certain applications which utilize sealant in assembly line applications, it is necessary to use a sealant which can rapidly develop green strength. Sealants which rapidly develop green strength have the advantage of allowing the sealant user to handle, package and ship the assembled construction after relatively shorter cure times without damage to the assembled construction, thus increasing production line speed and lowering product inventory. Green strength as defined herein means the strength of the sealant used in an assembled construction before the sealant has fully cured.
The present inventors have unexpectedly determined that RTV silicone compositions comprising about 10 to 95 weight percent based on the total weight of the RTV silicone composition of polydiorganosiloxanes comprising on average at least 1.2 chain terminations per molecule selected from the group consisting of hydroxysilyl groups, alkoxysilyl groups, and multi-alkoxysilyl groups, provided that at least one chain termination per molecule is a multi-alkoxysilyl group rapidly develop green strength upon exposure to moisture.
One objective of this invention is to prepare a RTV silicone composition curable in the presence of moisture with rapid development of green strength.
SUMMARY OF THE INVENTION
The present invention is a RTV silicone composition curable in the presence of moisture with rapid development of green strength. The RTV silicone composition comprises (A) 0 to about 85 weight percent polydiorganosiloxanes comprising on average at least 1.2 chain terminations per molecule selected from the group consisting of hydroxysilyl groups and alkoxysilyl groups; (B) about 10 to 95 weight percent polydiorganosiloxanes comprising on average at least 1.2 chain terminations per molecule selected from the group consisting of hydroxysilyl groups, alkoxysilyl groups, and multi-alkoxysilyl groups, provided that at least one chain termination per molecule comprises a multi-alkoxysilyl group; (C) an effective amount of a condensation catalyst; (D) 0 to about 40 weight percent of an alkoxysilane; and (E) 0 to about 60 weight percent of a filler; provided that the sum of the weight percents of Components (A) and (B) comprises about 20 to 95 weight percent based on the total weight of the RTV silicone composition.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a RTV silicone composition curable in the presence of moisture, comprising
(A) 0 to about 85 weight percent polydiorganosiloxanes comprising on average at least 1.2 chain terminations per molecule selected from the group consisting of hydroxysilyl groups described by formula
—SiR
2
2
OH, (I)
and alkoxysilyl groups described by formula
—Z
y
—SiR
2
x
(OR
3
)
3−x
, (II)
where each R
2
is independently selected from the group consisting of a hydrogen atom and monovalent hydrocarbon radicals comprising 1 to about 18 carbon atoms, each R
3
is an independently selected alkyl radical comprising 1 to about 8 carbon atoms, each Z is independently selected from the group consisting of divalent hydrocarbon radicals comprising about 2 to 18 carbon atoms and a combination of divalent hydrocarbon radicals and siloxane segments described by formula
where R
2
is as defined above, each G is an independently selected divalent hydrocarbon radical comprising about 2 to 18 carbon atoms, and c is a whole number from 1 to about 6, x is 0 or 1, and y is 0 or 1;
(B) about 10 to 95 weight percent polydiorganosiloxanes comprising on average at least 1.2 chain terminations per molecule selected from the group consisting of hydroxysilyl groups, alkoxysilyl groups, and multi-alkoxysilyl groups described by formula
—Z
b
—R
4
(Z—SiR
2
n
(OR
3
)
3−n
)
a
(III)
provided that at least one chain termination per molecule comprises a multi-alkoxysilyl group, where R
2
, R
3
, and Z are as defined above, R
4
is independently selected from the group consisting of a silicon atom and a siloxane radical comprising at least two silicon atoms and each Z is bonded to a silicon atom of R
4
with the remaining valences of the silicon atoms of R
4
being bonded to a hydrogen atom, a monovalent hydrocarbon radical comprising 1 to about 18 carbon atoms, or forming siloxane bonds, n is 0, 1, or 2, a is at least 2, and b is 0 or 1, provided, when b is 0, R
4
is bonded to the polydiorganosiloxane through a siloxane bond;
(C) an effective amount of a condensation catalyst;
(D) 0 to about 40 weight percent of an alkoxysilane described by formula
R
z
Si(OR
1
)
4−z
,
where each R is an independently selected monovalent hydrocarbon radical comprising 1 to about 18 carbon atoms, each R
1
is an independently selected alkyl radical comprising 1 to about 6 carbon atoms, and z is 0, 1, or 2; and
(E) 0 to about 60 weight percent of a filler;
provided that the sum of the weight percents of Components (A) and (B) comprises about 20 to 95 weight percent based on the total weight of the RTV silicone composition.
The polydiorganosiloxanes represented by Component (A) comprise on average at least 1.2 chain terminations per molecule selected from the group consisting of hydroxysilyl groups described by formula (I) and alkoxysilyl groups described by formula (II). The polydiorganosiloxanes may be linear or branched and may be homopolymers, copolymers, or terpolymers. The polydiorganosiloxanes may be a single species or a mixture of different polymers.
The repeating units of the polydiorganosiloxanes include siloxy units such as described by R
2
s
SiO
(4−s)/2
, where s is 0, 1, or 2, and each R
2
is independently selected from the group consisting of a hydrogen atom and monovalent hydrocarbon radicals comprising 1 to about 18 carbon atoms.
The monovalent hydrocarbon radicals represented by R
2
may be substituted or unsubstituted. Examples of monovalent hydrocarbon radicals represented by R
2
include alkyl radicals such as methyl, ethyl, hexyl, 3,3,3-trifluoropropyl, chloromethyl, and octadecyl; alkenyl radicals such as vinyl, allyl, and butadienyl; cycloalkyl radicals such as cyclobutyl, cyclopentyl, and cyclohexyl; cycloalkenyl radicals such as cyclopentenyl and cyclohexenyl; aryl radicals such as phenyl and xylyl; aralkyl radicals such as benzyl; and alkaryl radicals such as tolyl. Preferably each R
2
is ind
Deng Qin
Krahnke Robert Harold
Lower Loren Dale
Lueder Timothy B.
Palmer Richard Alan
Dawson Robert
Dow Corning Corporation
Peng Kuo-Liang
Scaduto Patricia M.
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