Note: Descriptions are shown in the official language in which they were submitted.
5~
-1- 60SI-1340
SILICONE RltV' S E3~IBITI21G RP~PID AD~ESION DEVELOPMENT
The present invention relates to compositlons
for enhancing the bonding of silicones to substrates.
More particularly, it relates to a self-bonding, two
part, room temperature vulcani2able (RTV) silicone
composition comprising a silylating agent.
~
Room temperature two-part ~ulcanizing silicone
compositions are presently widely known. For example,
Hyde, United states Patent No. Z,571,039 di closcs
preparing an organosiloxane by compounding a readily
deformable acid pol~mer comprising a polysiloxane and an
acidic compound with a filler, and then reacting the
compounded material with a silane o~ the formula
RnSi(OR' )~-n where R is a monovalent hydrocarbon radical
free of aliphatic unsaturation, ~' is an al~yl radical of
less than 9 carbon atom~ and n has a value of 0 to 1.
~erridge, United State~ Pate~t No. 2,843,555
disclo c~ an organopolysiloxan~ composition convertible
at room temp~rature to the cured, solid, Pla~tic state
comprising (a) a linear, fluid organopolysiloxane
containing terminal silicon-~onded hydroxy groups and
havin~ an average of about two oryanic group~ per silicon
atom, (b) an alkyl silicate, and (c) a metallic salt of
an organic car~ox~lic acld.
The compositlons are u~2ful as sealants,
electrical insulation, coa~ing~, dental cementt caulking
: - compounds, expansion joints, gaskets, shock absorbers,
adhesive3 and in many o~her applications.
~ ¢ ~ 3~
-2- 60SI-1340
Presently, two-part condensation cure RTV's are
typically comprised of an "A" component consist~ng of (1)
a dihydroxy or silanol terminated polydiorganosiloxane;
(2) a reinforcing filler such as CaC03~ fumed silica, or
ground quartz; and (3) water; and a "B" component
containing (1) an adhesion promoter; (2) a T or Q
functional crosslinker; and (3) a condensation cure
catalyst. Combining the "A" an~ "B" components in a
pred~ter~ined ratlo initiates the cure.
It i~ also known (e.g. from published Japanese
Patent application No. 1-152532, filed June 15, 19~9)
that high strength and high modulus water resistant
silicone rubber compositions can be obtained by adding to
a dealcoholization-type RTV silicone rubber composition,
a colloidal calcium carbonate filler surface-treated with
a rosin acid.
Despite the improved adhesion of the silicones
of the prior art, silicone adhe~ives continue to be
precluded from many indu~trial application~ due to their
slower rate of adhesion. It would therefore represent a
notable advance in the state of the art ~f a two-part
silicone adhe~ive could be prepared having an increased
rate at which the silicone adhesive develops 100%
cohe3ive fa~ lure to plastic substrates, such as
polycarbonate, without adversely affecting other cure or
physical properties.
It has now surprislngly been ~ound that the
addition of a silylat1ng agent to the "B" component of a
two part sillcone adhesive significantly reduces the time
required for the sealant to develop 10~% cohesive failure
to polycarbonate.
::
' P'
.
-3- 60SI-1340
Furthermore, the addition of a sllylatlng agent
such a~ HMDZ does not inhibit the cure of the interior
portions of a large volume of sealan (no "deep section"
cur~ inhibition). This is particularly surprising since
it is well known to those skilled in the art that HMDZ is
~n active silylating agent which converts a reactive
silanol polymer to a chemically iner~ M-~topped fluid as
shown in (I).
SiOH + (cH3)3siNHsi(cH3)3 ~ iOSi(CH3)3 + H2NSl(CH3)3 (I)
It is expected that the silylation reaction of (I) would
favorably compe~e wi~h the condensation (~cure~3 reaction
shown in (II).
SiOH + (RO)3SiOSi --~ SlOSi(O~2OSi + ROH (II)
where R is methyl, ethyl, propyl, etcO
It has been found that polycarbonate samples
sealed with prior art silicone sealants tend to lose
their adhesion after either accelerated heat aging or
extended periods o~ time a~ room temperature. This
adhesion loss has been attributed, at least in part, to
2S "crazing" of the polycarbonate by exposure to NH3 formed
by the reaction of HMDZ with the condensation cure by-
product, methanol. Surprisingly, it has now been found
that no obvious polycarbonate "crazing" appears in
polycarbonate specimen~ sealed with two part RTVs of the
pr0~e~t invention having the neces~ary component-~ for
ammonia formation, HMDZ and an alcohol (methanol, ethanol
or propanol).
-4- 60SI-1340
~ ccording to the present invention there is
provided a self bonding room temperature vulcanizing
composition having improved adhesion to substrates
comprlsing: A. a polymeric component comprlsing (1) a
silanol chain stopped polydiorganosiloxane; and (ii) an
effective amount of water; and B. a catalyst component
comprising (i) an effective amount of a silylating agent
having at lea~t one labile or leaving monovalent or
divalent group attached to silicon by silicon-nitrog~n
linkages and which silylating aq~nt is select~d from the
group consisting of silane and organopolysiloxane; (ii)
an eff~ctive curing amount of a condensation cure
catalyst; and (iii) an effective amount of a crosslinking
agent. Preferably th~ polymeric component A of the RTV
composi~ion furth~r comprise~ A(iii) an effec~ive amount
of a filler. Al~o pre~erably th* ca~aly~t component B of
the RT~ composition further compri~e~ B~iv) an effec ive
amount of an adhe~ion promoter.
Also accord~ng to the presen~ invention there
is provided a method for forming 2 sel~ bonding room
temperature vulcanizing composition having improved
adhesion to substrates comprising: A. preparing a
polymeric component c~mprising (i) a silanol chain
stopped polydiorganosiloxane, and (ii) an ef~ective
amount of water; and B. preparing a catalyst component
compri~ing (i) an effective amount of a silyla~ing agent
having at lea~t one lablle or leaving monovalent or
divalent sroup a tached to s~licon by silicon-nitrogen
linkages and which silylating agent î~ selec~ed from the
group consisting of silane and organopolysiloxane; (ii)
an effective curlng amount of a condensation cure
ca~alyst; and (iil~ an ef~ec~ive amount of a crosslinking
agQnt; and C. combin~ng and mixing A. and B. to cure the
~r,~ t'r~2
~5~ o~SI-1340
polydiorganosiloxane. Pr~ferably the polymeric component
prepared in step A furth~r comprises A~iii) an effective
amount of a filler. Also preferably th~ catalyst
component prepared in step B further comprises (iv) an
effective amount of an adhesion promoter.
In pref~rred embodiments, ~he silanol
terminated polydiorganosiloxane comprises a silanol
terminated dimethylpolysiloxane; the silylating agent
comprises hexamethyldisilazane; th~ condensation cure
catalyst comprises a tin compound; the crosslinking agent
is selected from tetra(n-propyl)silica~e,
tetraethylsilicate, partially condensed ethylsilicate and
methyltrimethoxysilane; the filler comprises ground
and/or precipitated calcium carbonate, fumed silica,
ground quartz or mixture~ thereof; and th~ adhesion
promo~er i5 selected from gamma-glycidoxypropyltri-
m~thoxysilane, 3-aminopropyl-triethoxy~ilane, 1,3,5-
tris(3-trimethoxysilylpropyl)-isocyanurate and mixtures
thereof.
DETAILED D~SCRIP~GN OF ~HE PRES-NI : ~N710N
The silanol chain-stopped polydiorganosiloxanes
A(i) for use in the present invention may be represented
by the formula-
~Rl ~
t 1 2
\R /n
wherein R~ and R2 are each organic rad~cals o up to 20,
and pre~erably up to 8 carbon atom~, selected from
hydrocarbyl, halohydrocarbyl and cyano lower alkyl and n
i~ a number that varie~ generally from about 10 to about
15,000, preferably from 100 to 3,000, and more preferably
from 300 to 1,500.
' ~
-6- 60SI-1340
The silanol chain-stopped polydiorganosiloxanes
are well known in the art and they may be prepared by
known methods, such as describ~d in Be~rs, United States
Patent No. 3,382,205 and include composition containing
different Rl an~ ~2 groupsO For example, in formula (1)
the Rl groups can be methyl, while the R groups can be
phenyl and/or beta-cyano-ethyl and/or trifluoropropyl.
Furthermore, within the scope of the definition of
polydiorganosiloxane~ useful in thi~ invention are
copolymers of various types of diorgansiloxane units,
such as silanol chain-stopped copolymers of dimethyl-
siloxane unit~, diphenylsiloxane units, and methylphenyl
siloxane units,, or, for example, copolymers of
dimethylsiloxane units, methylphenyl-siloxane units and
methylvinyl siloxane units. Pre~erably, at lea~t 50% of
the R1 and R2 groups of the silanol chain-stopped
polydiorganosiloxane~ are alkyl, e.g. me~hyl group~.
In the above formula (1), Rl and ~2 can b~, for
example, mononuclear aryl, ~uch as phenylt benzyl, tolyl,
xylyl and ethylphenyl; halogen-sub~tltuted mononuclear
aryl such as 2,5-dichlorophenyl, 4-bromophenyl, 2,5-
difluorophenyl, 2,4,~-trichlorophenyl and 2,5-dibromo-
phenyl; alkyl such as methyl, ethyl, n-propyl, isopropyl,
n-butyl, sec-butyl, isobutyl, tertbutyl, amyl, hexyl,
heptyl~ octyl; alkenyl such a~ vinyl, allyl, n-butenyl-l,
n-butenyl-2, n-pentenyl-2, n-hexenyl-2, 2,3-dimethyl-
butenyl-2, n-heptenyl; alkynyl such as propargyl, 2-
butynyl; haloalkyl such a3 chloromethyl, iodomethyl,
bromomethyl, fluoromethyl, chloroethyl, iodo~thyl,
bromoethyl, fluoro~thyl, trichloromethyl, diiodoethyl,
tribromomethyl, trifluoromethyl, dichloroethyl, chloro-n-
propyl, bromo-n-propyl, 3,3,3-trifluoropropyl,
iodoisopropyl, bro~o-n-butyl, bromo-tert-bu~yl, 1,3,3-
trtchlorobutyl, 1,3,3-tribromobutyl~ chloropentyl,
bromophenyl, 2,3-dichloropsntyl, 3,3-dibromophenyl,
chlorohexyl, 1,4-dichlorohexyl, 3,3-dibromohexyl,
r~
-7- 60SI-1343
bromooctyl; haloalkenyl such as chlorovinyl~ bromovinyl,
chloroallyl, bromoallyl, 3-chloro-n-butenyl-1, 3-chloro-
n-pentenyl-l, 3-fluoro-n-heptenyl-1, 1,3,3-trichloro-n-
heptenyl-5, 1,3,5-trichloro-n-octenyl-6, 2,3,3-
trichloromethylpentenyl-4; haloalkynyl such as
chloropropsrgyl, bromopropargyl; cy~loalkyl, cycloalkenyl
and alkyl and halogen substituted cycloalkyl and
cycloalkenyl such as cyclopentyl, cyclohexyl,
cycloheptyl, cyclooctyl, 6-methyl-cyclohexyl, 3,3-
dichlorocyclohexyl, 2,6-dibromocy~loheptyl, 1-
cyclopentenyl, 3-methyl-1-cyclopentenyl, 3,4-dime~hyl-1-
cyclopentenyl, 5-methyl-5-cyclopentenyl, 3,4-dichloro-5-
cyclopentenyl, 5-(tert-butyl)-1-cyclopentenyl, 1-
cyclohexenyl, 3-methyl-1-cyclohexenyl, 3,4-dimethyl-1-
cyclohex0nyl; and cyano lower alkyl such as cyanomethyl,
beta-cyanoethyl, gamma-cyanopropyl, delta-cyanobutyl and
gamma cyanoisobutyl.
Further, i~ is contempla~ed that a mix~ure of
various silanol chain-stopped polydiorganosiloxanes may
also be employed as the silanol chain stopped
polydiorganosiloxane component A(i).
The silanol chain-stopped polydiorganosiloxanes
employed in the practice of the present invention may
vary from low vi~co~ity thln fluids to viscous gums,
depending on the value of n and the nature of the
particular organic groups represented by Rl and R2 of
formula (1).
The viscosity of the silanol chain stopped
polydiorganosiloxanes thus varies broadly, e.g., in the
range of 20 to 1,000,000 cps at 25C. Preferably it will
be in the range o~ 1,000 to 200,000 cps, and especially
pre~era~ly from about 2,000 to about 60,000 cps at 25C.
-8- 60SI-1340
In preferred features of the present invention,
the polymeric component comprise~ from about 30 to about
99 weight percent and more preferably from about 50 to
about 90 weight percent of silanol chain stopped
polydiorganosiloxane A(i).
Polymeric component A also comprises component
A(ii), an effective amount of water. Preferably, ~he
polym~rlc component A(ii) comprises from about 0.01 to
about 0.5 weight percent water based on the weight of
said silanol chain stopped polydiorgano siloxane A(i).
Further, in preferr~d embodiments, where a filler A(iii)
is employed, the necessary water can be present adsorbed
on the filler.
The silylating agents ~(i) of the present
invention are known to those skllled in the art. The
preferred silylating agents for use in the practice of
the pre~ent invention are those having at least one
labile or leaving monovalent or divalent group attached
to silicon by silicon-nitrogen linkages and selected from
silane and organopolysiloxane.
Preferred silyating agents are those having a
boiling point of at least 25C, and are included wi~hin
the formula
(R3)~SiX~ (2)
where X is an organic leaving group, pre~erably
carbamato, amido, amino, ureido, or imido, R3 is selected
from Cl13 monovalent or divalent hydrocarbon radicals and
substituted C1l3 monovalent or divalent hydrocarbon
radicals, and a has a value of 0 to 3 inclusive. These
silanes include, for example, but are not limited to: -
N,O-bis(trimethylsilyl)car~amate;
N,O-bis(trimethyl~ilyl)tri1uoroacetamide;
N,N-bis(trimethylsLlyl)ure~; and
- N-methyl-N-dimethylsilyltrifluoroacetamide.
-9- 60SI-1340
In the fonl~ulas of the silicon-nitrogen
compound and ~he silico~.e nitrogen polymer that follow,
the R" and R"' radicals may be selected from hydxogen and
any monovalen~ hydrocarbon radicals including fluoroalkyl
radicals. Examples of the xadicals from which the R" and
R"' can be selected are, for instance, alkyl radicals
such as methyl, ethyl, propyL, etc., cycloalkyl radicals
such as cyclohexyl, cycloheptyl, etc., mononuclear aryl
radicals such as phenyl, methylphenyl, ethylphenyl, etc.,
alkenyl radlcals such as vinyl, allyl, etc., fluoroalkyl
radical~ such as 3,3,3-trifluoropropyl, and R"' may also
be alkoxy such as methoxy, ethoxy, propoxy and butoxy.
Generally, the R" and R"' radicals may have from 1 to 12
car~on atoms and more preferably tha radicals may have
from 1 to 8 carbon atoms.
In addition to the above described
ilicon-nitrogen materials, th~re are al80 included in
the pre~ent invention, silicon-nitrogen materials having
divalent hydrocarbon radicals attached to silicon atsms
through sllicon-carbon linkages. For example, also
included among the ~ilicon-nitrogen materials that can be
employed in the practlce of the invention, are
arylenesilazanes, such as phenylene silazanes, and
alkylenesilazanes such a~ methylenesilazanes. In
addition, variou~ other silicon-n~trogen materials,
containing divalent hydrocar~on radicals are alco
contemplated including copolymers and terpolymers such as
silicon-nitrogen materials containing intercondensed
silox~ne unit~ and silarylenesilazane units,
intercondens~d silazane units, silarylene~iloxane units,
and siloxane units, etc. The silicon-nitrogen polymer~
that can ~e employed in the practlce of the present
invention can include silicon-nitrogen polymers in the
form of silazane/siloxane copolymers having a~ least 3
mole percent of chemically combined ~ila7.y unit~ and up
to 97 mole percent of combined siloxy unit
~r~ q ?~
-lO- 60SI-1340
Accordingly, the sllazane polymers can
include cyclics consi~ting of chemically combined
R"' / R"
--SiI~
R"'
uni~s where R" and R"' are as previously defined to
provide for a ratio of 1.5 to 3.0 of the sum of the R"'
and R2"N radical for silicon atoms in the silazane
polymer.
The definition of a silazane polymer includes
linear polymers having at least one unit of the class
consisting of
R"
(R"2N)~R"')2 SiN -
units and
R~
(~" ' )3 Si~l--
units where R" and R"' are a~ previously defined to
provide for a ratio of 1.5 to 3 o the ~um o~ the R"' and
R2"N radicals per silicon atoms in the silazane polymer.
Further silazane polymers, which are included
within the definition of the above poly~ers comprise
linear polymers con~isting essentially of
R"' R"
-- SiN --~
units where R" and R"' are defined to provide for a ratio
of 1.5 to 3.0 of the sum of the R"' and R2"N radicals per
silicon atom in the silazane polymer.
In addition, the silazane polymers include
polymers ha~ing at lea~t one unit selected from the class
con~isting of
R"' ~ R"
(R")2N _ SiN -
unit~ and
'~
~ 60SI-1340
(R"'~2Si - N
units where R" and R"' are as previously defined to
provide a ratio of 1.5 to 3 of the sum of the R"' and R2"N
radicals per silicon atom in the silazane polymerO
In addition the ~ilazane polymers can comprise
also polymers having a sufficient amsunt of units
selected from
R"' R" R"'~ R" I ~
- SiN - SiN - SiN
R"' l I
where R" and R"' are as previously defined to provide for
a ratio of 1.5 to 3 o~ the sum of the R" ' and R2"N
radicals per silicon atom in the silazan~ polymer.
The silazane/siloxane copolymer can also be in
the form of cyclics and con~ist of chemically comblned
~2"'5iO units and
R"'~ R"
- SlN -~
R""
units where R" and R"' are a~ previously defined
Linear slloxane copolymers are also included
where the mole p~rcent of
(R"')~S~ 2
unit~ can be a~ high as 97 mole percent with the balance
of the units being selec~ed from
R" R"l R" R"
(R"')c S~N - (R~ iO- (R")2N~ N -
R"' R"'
where R" and R"~ are as previously defined to provide for
a ratio of the sum o~ R~ R2"N rad~cal~ per sillcon of
the siloxane copolymer from 1.5 to 3.
Other linear sila~anes that are included wLthin
th~ scope of the above formula~ are ones having the
formula
J ~ ' 2
-12- 60SI-1340
R"~ / R~ ' R"
( R ) 3tSiN ~ Si--N t ( Si ( R )
R ~n
wh~re R" and R"' are as previously defined, n is 0 or an
integer and is preferably from 0 to 20 inclusive, and d
is a whole number aqual to 0 to 1 inclu~ive and where d
i~ equal to 0 and n is prPferably equal to 3 to 7,
in~lusive.
Illustrating the silazan2s that can be employed
in the practice of the present invention within the scope
of the above formulas are hexamethylcyclotrisilazane,
octamethyltetrasilazane, trimethyltrlphenylcyclotri-
silazane, trivinyltrimethylcyclotrisilazane, etc. Other
silazanes within the scope of the above formulas are as
follows:
CH H CH H CH
~ 3 1 ~ 3 ~ ~ 3
CH3 - Si - N - Si - N - Si - CH3
~H3 CH3 CH3
CH3 C~3 CH3 ICH3 CH3
CH3- Si - N - Si - N - Si - ~H3
C~3 CH3 CH3
There can be phenyl,
vinyl, 3,3,3-tri-
fluoropropyl and
variou~ alkyl groups
on the middle Si
atoms (ethyl, propyl,
hutyl)
C~3~ C~3 CH3 C~3 ~ CH3
N - Si - N -Si - N
C~3~ CH3 C~3 ~C~3
,
,
-13- 60SI-1340
CH3 CH3
CH3~ Si - O - Si - CH,
CH3 N N CH3
CH3~ Si O ~ Si - C~3
C~3 C~3
/ CH3 H
-Si - N
N~
- Si - N
H / x
ln addition to the silazanes o~ the above formulas, there
is also included polysiloxanes having terminal silylamine
units or silazane units as shown by the formula
R" / R"'\ R"' R"
l l l l
ZN - - SlO- - SiN - 2
R~/ R"'
where R" and R"' are as defined previously, Z is a me~ber ~ :
selected from R" and SiR3"' where R'! And R"' and n are a~
defined previously. The polysiloxane compounds of the
above formula may be prepared by ~aking ammonia or an
amine and reacting it at a temperature wi~hin the range
of betwe~n about 0 to 60 C. with a halogenated
polysiloxane having the formula
~ R"' \ R"'
xtsio t si~
\ R~ / R"'
where R"' and n are as de~lned abeve and ~ is a halogen
radical such a~ chloro or bromo. If a terminal silazane
radical is desired, for example, a molar amount of
(R"'13SiX can be reacted along wi~h th~ halogenat~d
poly~iloxane, at lea~t equi~alent ~o the mole~ of halogen
radical~ contained th~rein. It will, of course, be
appreciated that amines of the formula
. ,
, .
-14- 60SI-1340
H2NR ~l
are utilized for forming the silazy chain-stopped
polysiloxanes of the invention where R" is as defined
above, whlle in th~ case when materials are de~ired
having terminal silyl amine radicals, amlnes, including
amine~ of the above for~ula, can be employed having at
leas~ one hydrogen available for reactlon to produce the
desired polysiloxane.
The halogen chain-stopped polyd~organosiloxanes
of the above formula can be made by conventional
procedures such as by the controlled hydrolysis of a
diorg~nodihalo~ilane, for example, dimethyldiehloro~ilane
as taught in Patnode, U.S. Pa~. No. 2, 381, 3fi 6 and Hyde
U.S. Pat~ Nos. 2,629,726 and 2,902,507. Another
procedure that ca~ be employed involves eguilibrating a
mixture of a dlorganodlchlorosilane and a cyclic
~0 polydiorganosiloxane in the presence of a metal catalyst
such a3 ferric chlorlde as shown in Sauer U.S. Pat. No.
2,421,653. Although variou~ procedures utilized in
forming the above poly~iloxanes are not critical,
generally it ha~ been found de~irable to maintain the
halogen con ent o~ the re~ulting chain-stopped
polysiloxane in the range of about 0.4 to about 35
percent, by weight, and preferably from about 5 to about
percent by weight. The halogen chain-stopped
poly~iloxane is preferably in the ~orm of a chlorinated
chain-stopped polydimethylsiloxane.
Included among the amine~ which can be employed
with the h logenated polysiloxane~ are ammonia, methyl
amine, aniline, dimethyl amine, ethylphenyl amine,
methylethyl amine, et~.
-15~ 60SI-1340
The proce~ for producing the re~t of the
sllazane compounds and silazane polymers is well known to
a worker skilled in the art.
The silicon nitrogen materials can be volatile
liquids, or gu~my, resinous or crystalline sollds,
depending upon such factors as ~he molecular weight and
the nature and average func~ionality of their respective
chemically combined units. Thsse silicon-nitrogen
materials include for example, silyl amlnes, silazanes
and fluid polymerY consisting e3~entially of
intercondensed siloxane unit~ and silazane units
terminated by trioganosiloxane units, polymers consisting
e~sentially of intercondensed siloxane units with or
lS without silazane units terminated by silyl amine units,
etc. Typical of the methods, th~t can be employed to
make the materials that can be used in the present
invention include tha method shown by R.O. Sauer, et al.
J.A.C.S., Vol. 68, 1~46, p. 241-44, and in U.S. Pat. Nos.
2,462,635 - Haber, 2,885,370 ~ Grozos et al., 2,573,417,
and 2,579,418 - Cheronis. Examples of the polymers
containing intercondensed siloxane and silazane units,
and poly~iloxane3 terminated by silyl am$ne units ~hat
are operable in the present in~ention are chown in U.S.
Pa~. Nos. 2,503,919-Patnode, and 2,865,91~-Hurwitz et al.
Some of the silyl amine~ that can be employed in the
practice of the invention are shown in U.S. Pat. Nos.
2,429,983-Johannson, 2,807,635-Breedervelt et al. and
2,758,127-Gold~chmidt e~ al., etc.
Accordingly, the proce3s for producing such
polymers and compounds is well known.
~ 7~. ~
-16- 60SI-1340
As an example, there is given here a process
for preparing hexamethylcyclotrisilazane. This is
prepared by taking dimethyldichlorosilane, adding it to
a satura~ed solution of ammonia in benzene while
agitating the mixture. During the subse~uent addition of
the dimethyldichloro~ilane ammonia can be bubbled through
the mixture while the temperature i5 maintained below
50. Additional ammonia wa~ bubbled through the mixture
until no further ammonium chloride is prec~pitated. The
product can be recovered by stripping off the benzene
under vacuum. Utilizing such a method, there can be
obtained hexamethylchlorotrisilazane as well as
trisilazane. Similar methods can be employed to produce
any of the above compounds for wh~ch formulas were given
above.
Fluoroalkyl- ubstitu~ed silazane compounds can
also be prepared by a similar method a~ disclosed in the
patent application of Matsumotot Ser. No. 195~579 filed
on Oct. 8, 1990.
The existence oP such silyl-nitrogen compounds
and silyl nitrogen polymers a~ well a~ their me~hods of
preparation is disclosed in U.S. Pat. No. 3,243,404 to
which a worker skilled in the art can refer to for more
information.
In addition to the foregoing silyl-nitrogen
compounds and silyl-nitrog~n polymers disclosed above,
there can also be utllized in the in~ant invention silyl
amines of the formula
R20
H - Si - (N(R )2)~-g-h
wh~re R20 i8 a radical selected from the class consisting
of C(1a) monovalent hydrocarbon radicals and Cl,~) alkoxy
radicals and fluoroalkyl radicals, and R~ i5 selected
from hydrogen and a C(~o monovalent hydrocarbon radical,
and g is a whole number that varies from 1 to 3, h i~ a
."
,
;~ '
-17- 60SI-1340
whole number that varies from 0 ko 2 and the sum of h +
g does not ~xc~cd 3. Compounds coming within the scope
of the above formula are for in tance methyl
di(methylamino)silane, tris(methylamlno)sllane,
methyl bis(diethylamino)silane as well as the following,
tris(diethylamino)silane
methylbis(dimethylamino)silane
tri(ethylamino~silane
ethyl di (methylamino)silane
ethyl di (ethylamino)silane
ethyl bis(dimethylamino)~ilane
Such amines are disclosed in U.S. Pat. No.
3,243,404 and can be produced by the methods disclosed
in that patent. The only difficulty with the hydride
amines is that they do tend to liberate hydrogen upon
standing and also they tend to impart the undesirable
odor of amines to the compo~ition. However, if this is
not a problem, then they can be tolerated in the in~tant
composition. Preferably, the silyl-nitrogen compounds
such as hexamethyldisilazane and the re~t, are utilized
in a concentration of 0.5 to 10 parts by weight per 100
parts of the base organopolysiloxane polym~x.
Examples of fluorosilicone silazane compounds
within the scope of the above formulas are, for instance,
compounds su~h as one~ having the formulas
(c~3cH2cH2(~H3)si)2NH
(CF3CH2CH2~CH3)SiNH)
CH3
(CH3)3Si - N - Si - N Si(CH3)3
~ 2
CH2
CF3
;~!r,r~
-18- 60SI-1340
(CF3C~2C~2(~H3)2Si)2N CH3
~CF3CH2C~2(CH3) SiN ~
L CH3 J 3
rCF3C~2CH2(~H3) SiN
L CH3 ~
Preferably, the silyating agen~s are
organosilazane~ and/or cycloorganosilazane~ such as
hexamethyldisilazane, 1,3-divinyl-1,1,3,3-t~tramethyldi-
silazane, hexamethylcyclotxisilazane, octamethylcy~lo-
tetrasilazane and mixtures of any of ~he foreyoing. Most
preferred i~ hexamethyldlsilazane.
The silylating agents are employed in the
present composition in amount~ ran~iny from about 0.1
to about 10, more preferably from about ~.5 to about 5
percent by weight based on the total weight of the B
component. ~09t pr~ferred is whers th~ silylating agent
is pre~ent in an amount ranging from 0.1 to 1 part by
weight bas~d on 100 parts by weight of silanol chain
stopped polydiorganosiloxane A(i)o
~ he condensation cure cataly~t B(i$) may be any
known to be useful for promoting the reaction between the
silanol chain stopped diorganopolyslloxane and the
crossllnking ag~nt. The con~ensation catalysts are
generally selected from tin compounds, ~ircsnium
compounds and titanium compounds, or mix~ures thereof,
although other metal and nonm~tal catalysts are useful in
the prac~ice of the present inven~ion.
Effective amounts of the condensa~ion ca~alysts
which can be u3ed in the pract~ce of the present
inventlon to facilitate the cure of the RTV compos tlons
aret for example, 0.001 to 205 part based on the weight
of 100 part3 of the silanol chain stopped polydiorgano-
siloxane component. More particularly a~d by way o~
illustration, the conden~ation catalyst may be a tin
compound, for example, di~utyltlndilaurate;
dibutyltindiacetate; dibutyltinmethoxide,
.
. ~. . ,~.
~: . ., . , ~ .
..
-l9- 60SI-1340
dibutyltinbis(ace~ylacetona~e), carbomethoxyphenyltin-
tris-suberate; tin octoate; isobutyltin triceroate;
dimethyltindibutyrate; dimethyltindineodecanoate;
triethyltintartrate; d~butyltin di~enzoa~e; dibutyltin
oxide; tin oleate; tin naphthena~e; butyltintri-2-
ethylhexoate; tinbutyrate; and mixtures of any of the
foregoing. The preferred condensation catalysts are tin
compounds and dibutyltinph~halate, dibutyltindiacetate
1~ and dibutyltindilaurate are par~icularly preferred.
Titanium compounds which can be used in the
practice of ~he pr~ent invention are, for example, 1,3-
dioxypropanetitanium bis(acatylacetonate); diisopropoxy-
titanium bis~acetylacetonate); titanium naphthenate;
tetrabutyltitanate; tetra-2-e~-hylhexyltltanate; tetra-
phenyltitanate; tetraoctadecyltitanate; ethyltriethano-
aminotltanate. In addition bsta-dicarbonyltltan1um
compounds as shown by Weyenberg, United 5tates Patent No.
3,334,067 can be used a~ condensation catalysts in the
present invention.
Zirconium compounds, for example, zirconium
octoa~e, also can be used.
Further examples of metal condensation
catalysts are, for example, lead 2-ethyloctoate; iron 2-
ethylh~xoate; cobalt 2-ethylhexoate; mangane~e 2-
ethylhexoate; zinc 2-ethylhexoate; antimony octoate,
bismuth naphthenate; zinc naph~henate; zinc stearate and
mixtures of any of the foregoing.
Exampls~ of nonmetal condensation catalysts are
hexylammonium acetate and benzyltrimethylammonium ace~ate
and mixtures thereof.
The compositions of the presen~ invention also
preferably comprise a cros~linking a~ent B(iii),
e~pecially a trifunctional ("T") or tetrafunctional ("Q"3
hydroxy re~ctive silane. These are generally of the
formula
~r,,~ t~,~
-20- 60SI-1340
R~Si(oR5)5~ (4)
wherein R4 is an organic radical of up to 8 carbon atoms
selec~ed from hydrocarbyl, halohydrocarbyl and cyano
lower alkyl and R5 is an organic radical of 1 to 30 carbon
atoms selected from hydrocarbyl and halohydrocarbyl, and
m ha~ a value of 0 to 3 and pr~ferably 0 to 1.
Illu~trative organotrialkoxy silanes useful as
crosslinkers in th~ present invention include
CH3Si(OcH3)3
CH3Si(OcH2c~3) 3
CH3Si(Oc~zcH2c~3)3
CH3C~2Si(O~3)3
CH3CH2si(OcH2cH3)3
CH2=CHzSi(OCH3)~
~ Si(ocH3) 3
C~3~H2~H2cH2c~2cH2~2cH2si(O~H3) 3
CF3cH2~i(OcH3)3
; (CH3)Si(OCH2CH2CH2CH3) 3
NCCH2CH25i(OCH3)3
2S These organotrialkoxysilanes are ~ui~ably dascribed by
Barridge in United States Patent No. 2,184,555l assigned
to the same a~ignee a~ the present invention.
Illus rative of useful organotriacyloxysilane
cros~linking agent~ for u~e in the pre~ent invention are
tha following:
c~3si(oC()c~3)3
CH3CH2Si(Oc(O)~H3)3
CH2=C~2si(O~(o)cH3~3
~ Si(OC(O)CH3)3
CH3Si(OC(~)(cHz)5cH3)3
i .
, .
-21- 60SI-1340
~ Si(OC(O)(CHz)~CH3)3
CH3(CH2)6CH2si(~c(~)(cH2)4cH3)3
CF3(CH2)2Si(OC(O) (CH2)4CH3)3
NCC~2CH2Si(OC(O)(CH2)4CH3)3
CH3si(oc(o)cH(c2Hs) (CH2)CH3)3
CH35i(OC(O) ~ ) 3
These silanes are also w211 known in the art
and can ~e made by techniques disclosed, for example, in
Beers, United States Patent ~o. 3,382,205, assigned to
the same assignee a~ the present invention.
Preferably, in the crosslinking agent, m has a
value of 0 and the Rreferred silanes for use in the
invention are tetra(n-propyl)silicate, tetraethyl-
silicate, "partially condensed" ethylsilicate -available
commercially from Union Carbide, AXZO or HULS as ES-40 or
Silbond 40.
Th~ crosslinking agents B(ii) are used in
effective amounts to ensure a substantially cured
composition. Preferably from about 0.25 to about S parts
by weight of crosslinking agent B(ii) based on 100 parts
by weight of the silanol chaln stopped polydiorgano-
siloxane A(i) is employed.
The compositions of the present invention may
also comprise as part of polymeric compon~nt A a Piller
or an extender A(iii~. Illustrative of the many fillers
whlch can be employed with the compositions of the
present invention are titanium dioxide, li~hophone, zinc
oxide, zirconium silicate, silica aerogel, iron dioxide,
diatomaceous earth, calc~um carbonat~, ~um~d silica,
linear or cycllc polysiloxane treated sillca, silazane
treated sillca, precipltated silica, glas3 flbers,
magnesium oxide, chromic oxide, zirconium oxide, aluminum
. . , :
.
~.r J.~ ~r~ r~
J ~ ,`,t ~
-22- 60SI-1340
oxide, crushed quartz, calcined clay, a~bestos, carbon,
graphite, cork, cot~on, synthetic fibers, etc. Among the
most use~ul fillers are calcium carbonat2 alone, or mixed
with fumed silica. Also preferred is a mixture of ground
and precipitated or colloidal calcium carbona~e.
Organosilicone- or silazane-treated silica fillers, such
as those described in Lucas, Unlted States Patent No.
2,938,009; Lichtenwalner, United States Patent No.
3,004,859; and Smith, United States Pstent No. 3,635,743,
are also particularly suitable for use in the R~V
compositions of th~ present invention~ The fillers are
generally employed in any effective amount. Preferably
they are employed in amounts ranging from about 5 to
about 200 parts, and more preferably, from about 10 to
about 150 parts by weight per 100 parts of the silanol
chain-s~opped polydiorganosiloxane component.
The cataly t ~omponent B of the compositions of
the present invention can also comprise B(iv) a wide
variety of adhesion promoters a~ is known to those
skilled in the art. Preferred adhesion promo~ers are
~ilyl maleates, silyl fumarates, silyl succinates, silyl
i~ocyanurate~ and mlxture-~ ~hereof. Generally, such
adhesion promoters may be utilized anywhere up to an
effective amount in the composltion which can vary
somewhat from adh~slon promoter to adhesion promoter.
Too much of the adhesion promoter will not yield any
further desirable results and in soma instances may
detract from the physical properties of th~ cured RTV
composition. Accordingly, generally the adhesion
promoter is utilized at a conc~ntration of anywhere from
0.1 to 10 parts and more preferably from 0.1 to 5 parts
by weight per 100 parts by weight of the silanol chain
stopped polydiorganosiloxane A(i).
,
-23- 60SI-1340
A suitable adhesion promoter is one of the
following general formula:
Rt
(R )3 t Si ` Z ~5)
where R6 and R' are Cl 8 monovalent hydrocarbon radicals,
t varies from 0 to 3 and Z is a saturated, unsaturated or
aromatic hydrocarbon residue which may be fur~her
functionalized by a member selected from the class
consi~ting of amino, ether, epoxy, iscyanato, cyano,
acryloxy and acyloxy and combinations thereof.
In one instance, the ~dhe~ion promoter is an
amine adhesion promoter of ~he for~ula:
Rt R9
(R6O) ~ SL - R3 N - R10 (6)
where R5 and R7 ar~ Cl9 monovalent hydrocarbon radicals,
t varies from Q to 3, and R8 i~ a C2 12 divalent
hydrocarbon radical, and R9 and Rl are selec ed from the
clas~ consisting of hydrogen, amine radicals, and Cl~ :
hydrocarbon substituted amine radicals and Cl 8 monovalent
hydrocarbon groups and mixtures thereof.
Specifically, R~ is selected fro~ alkylene and
arylene substituted or unsubstituted divalent hydrocarbon
radicals of 2-12 carbon atoms and more pref~rably from 2-
8 carbon atom~. The xadical~ R9 a~d Rl can be hydrogen
or any of the Cl~ monovalent hydrocarbon radicals
dlsclosed for the R5 and R7 radicals. However,
preferably, they can be selected from amine radical~ a~d
substituted amine radical8, such a~ for in~ance,
aminoethyl. Tt i8 po8tulated that mo~t of the s$rictly
amine or nitrogen func~ionalized adh~ion promoter~ of
Unit~d States Pa~ent No. 3,888,815 which are disclo~ed ln
that patent can bo utLlized a~ adhe31On promoters in the
,
.
,
~r ~
-24- 60SI-1340
instant case. For a full~r d~scription of such
compounds, one is referred to the disclosure of the
foregoing Bess~mer et al. patent, United States Patent
No. 3,888,815. Such compounds can be made, for instance,
as set forth in the discloqures of United States Patent
Nos. 2,930,809 and 2~971,864, bo~h of which are
incorporated herein by reference. Preferred compounds
within the formula above are for instance, 3-(2-
- 10 aminoethylamino)propyltrimethoxy silane. Other compounds
are gamma-aminopropyltriethoxysilane and gamma-
aminopropyltrimethoxysilane. other preferred amine
adhesion promoters that can be utilized in the instant
invention are as follows:
gamma-aminopropylmethyldiethoxysilane;
gamma-aminopropylmethyldim2thoxys ilane;
bis(3-(triethoxysilyl)propyl)amlne;
bis(3-(triethoxy~ilyl)propyl)ethylenediamine;
3- ( 2-aminoethylamino) -propyldimethoxy-t-
butoxysilane;
methacryloxyethylaminopropyltrim~thoxysilane;
methylaminopropyltrimethoxysilane;
methylamlnopropyltriethoxysilane;
(N,N-dimethyl-3-amino)propyltrimethoxysilane;
N,N~dimethylaminophenyltriethoxy~ilane; and
N,N-dimethylaminoe~hyldimethoxysilane.
Accordingly, although most silanes
functionalized by amine~ were not experimen~ed with, it
is envisloned that most silanes functionalized by amines
should operate in the instant invention as adhesion
promoters.
Another adhesion promoter that can be utilized
in the instant inven~ion are ths isocyanurate adhesion
promoters of the formula
-
.5.~
-25- 60SI-1340
( ~120 ) _ Rl1 N ~ ~N/ (7)
/~ C ~
o N o
G
where G is s~lected from R1l or tR12)3 b - Si - Rl3
radicals, styryl, vinyl, allyl, chloroallyl,
cyclohexenyl, R13 i8 a C2 12 divalent hydrocarbon radical
selected from alkylenearylene, alkylene, cycloalkylene
and halo-substituted divalent hydrocarbon radicals, and
R11 and R12 are selected ~rom the same radicals a~ Rs and
R~ and also cyano alkyl, and b varie~ from 0 to 3.
For more information as to such compound~, one
i~ referred to the di clo~ure o~ Be~rs, United States
Patent No. 4,100,129 and Berger, United States Patent No.
3,8210218 which are hereby incorporated by reference.
The most preferred of thece adhe~ion promoters
are 1,3,5-tristrimethoxysilylpropylisocyanurat~ and bis-
1,3-trimethoxysilylpropylisocyanurate. Again, much
detail will not be given a~ ~o the preparation of such
compounds. The radical R12 can be selecte~ from any
divalent hydrocarbon radical sub3tituted or unsub~tituted
so long as it doe~ not interfere with the adhesion
promoter activitie~ of the compound. It should be noted
that highly complicated compounds are not de~red as they
are far more difficul to prepare and thus more expensive
to obtain. Oth~r specific compounds are:
1,3,5-tristrimethoxysilyIpropyli~ocyanurate;
1,3,5-tristrimethoxysilylethyll~ocyanura~e;
: 1,3,5-trisms~hyldimethoxysilylpropylisocyanurate;
and
1,3,5 trl~methyldiethoxy~Llylypropylisocyanurate.
I . . ~ . .
.
.
-26- 60SI-1340
Another adhesion promoter compound which may be
utilized in the instant invention is, for instance, an
eth~r adhe~ion promoter having the general formula:
(R )3-t Si - RaO - Rl4 - CH ~CH (8~
wherein R6 and R' and t are a~ previou~ly defined, R3 is
a C212 divalent hydrocarbon radical, R~4 is a C212 divalent
hydrocarbon radical and R~5 is selected from the cla~
consisting of hydrogen and a Cl 8 monovalent hydrocarbon
radical. The radicaL R8 and Rl~ can be any divalent
hydrocarbon radlcal~ such as alkylene radicals, arylene
radicals, alkylenearylene radicals, both saturated and
un~aturated a3 disclo~ed previously for the other
compounds, and can be substituted or un~ubstituted with
various group~ such as halogen group~, ether group~,
e~ter groups, and other hydrocarbsn group~. The radical
R1~ can be hydrogen or a monovalent hydrocarbon group as
previously defined for ~6 and R' and i3 most pr~ferably
hydrog~n. The mo~t pre~erred of the~e compounds is
gamma-glycidoxy propyltrim~thoxysilane. Other specific
compounds which are pre~erred as adhe~ion promoters in
the in~tant invention are for instance;
gamma-glycidoxypropylmethyldimethoxysilane;
gam~a-glycidoxypropyltriethoxysilane;
gamma-glycidoxypropylmethyldiethoxysilane; and
beta-glycidoxyethyltrimethoxysilane.
The~e compounds can be made by silicone producer~ as
d~cribed in the literature or obtained from specialty
chemical supply houses.
Another ~roup of compound~ which are u~eful a~
adhesion promoter~ within the ~cope of the present
invention are epoxy functlonalized and have the formula:
-27- 60SI-1340
(R )3 t Si R3 Q (9)
where R6, R7 and t are as previously defined, Ra is a C2 l2
divalent hydrocarbon radical and Q is an epoxy func~ional
radical having a saturated hydrocarbon ring appended
thereto. The radical Ra can be any divalent hydrocarbon
radical substitu~ed or un~ubstitu~ed, saturated or
unsaturated with substituent groups being selected from
monoralent hydrocarbon groups, halogen groups, ether
groups, ester groups, etcO It should he understood that
in all foregoing formulas of adhesion promoters in this
application, the R8 can be any divalent radical of 2 to
12 carbon atoms having monovalent hydrocarbon radicals,
halogen radicals, e~ter radlcals, and other radicals
sub~tituent there~o and Ra rad~cals can be satura~ed or
un~aturated and sub~tltuted or unsu~3tituted. Specific
examples of such radicals are alkylene and arylene
radicals and alkylenearylene combination radicals. A
specific adhesion promoter of this t~pe is beta-(3,4-
epoxycyclohexyl)ethyltrimethoxysilane. Other compounds
of this type are as follows:
gamma-~3,4 epoxycyclohexyl~propyltrimethoxysilane;
beta-(3,4-epoxycyclohexyl)ethyltriethoxysilane;
beta-(3~ 4-epoxycyclohexyl) ethylmethyldi-
methoxysilane;
beta-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane;
gamma-(3~4-epoxycyclohexyl)propylmethyldimethoxy-
silane;
beta-(3~4-epoxycyclohexyl)ethyltris(methoxye~h
silane.
' ~ :' ' I ~ ,
,
. . .
., . , ~ ,
-
-28- 60SI-1340
It should be noted that the Z radical in
formula (5) al50 can be an unsaturated radical such as
vinyl or allyl radical of 2-12 carbon atoms and can be
substituted, unsubstituted, with groups such as
monovalent hydrocarbon radicals, halogen groups, ester
groups and ether groups. Preferably, Z is a Cz 12 olefinic
hydrocarbon group such as vinyl allyl. The prefer:red
compound coming within the scope of the above definition
is vinyltrimethoxysilane. Other compounds coming within
the scope of formula ( 5 ) above are as follows:
virlyltriethoxy~ilarl~;
allyltrimethoxysilane;
allyltriethoxysilane;
~inylmethyldiethoxysilane;
vlnyltrimethoxysilane; and
vinyltris(2-methoxyethoxy)silane.
~no~her group of adhesion promoters coming
within the scope o~ formula (5) above are the cyano
functionalized compounds of the formula:
(R O)3~ Si - R C ~-~ (10)
- 25 where R6, R7 and t are as previously defined and R3 is a
C2 12 divalent hydrocarbon radical and may be any of the R8
radicals previously defined in this application; that is
saturated or unsaturated, substituted or un~ubstituted.
A preferred speciflc compound with the scope of formula
(10) above i~ gamma-cyanopropyltrimethoxy~ilane. Other
specific compounds are as follow~:
3-(cyanoethoxy)-3-methylbutenyltrimethoxysilane;
beta-cyanoethylmethyldimethoxysilane;
beta-cyanoethyltriethoxysilane;
beta-cyanoethyltrimethoxysilane;
2-cyanoethylmethyldiethoxysilane;
3-cyanopropyltriethoxy~ilane;
-29- 60~I-1340
3-cyanopropylmethyldlmethoxysilane and
anoethyltris~methoxyethoxy)silane~
Another group of compounds coming within the
scope of formula (5) above and whlch may ~e utilized as
adhesion promoters are the ac~yloxy functionalized
compounds of the formula
Rl7 o Rt7
Rl8CH =- C --C--O -- Ra _ S i ( oR6 ~ 3 ,~ ( 11 )
where R6, R7 and t are as previously defined. In formulas
(S) - (10), t can vary from 0 to 3 and R3 is a C2~2
divalent hydrocarbon radical a~ previously defined.
Further, Rl6 and Rl7 are selected from the class consisting
of hydrogen, Cl a monovalen~ hydrocarbon radicals, and
mixtures thereof. It should be noted ~hat R16 and Rl7 can
be sub~tituted or unsubstituted. A pre ~rred compound
comins within the s~ope of formula (ll) above is gamma-
methacryloxypropyltrimethoxysilane. Other preferred
compounds of formula (11) which can be utllized in the
practice of the present inventlon are: -
gamma-acryloxypropyltrimethoxysilane;
gamma-acryloxypropyltriethoxysilane;
gamma-methacryloxypropyltri~thoxysilane;
ga~ma-me~hacr~loxypropyltris(methoxyethoxy)cilane;
gamma-methacryloxypropylmethyldlmethoxysilane; and
beta-methacryloxyethyltrimethoxysilane.
Furthermore, mo t of the above chemicals can be
obtained from specialty chemical houses such as HULS
America, Levittown PA; Union Carbide, CT; Dow-Corning,
MI; and Silar Laboratorles, NY.
The composlt~ons o~ the present inv~ntion are
generally prepared by flrst preparing a polymeric
component A comprising (1) a silanol stopped
polydiorganosiloxane; (Li) an effective amount of water;
. , ' ' ' ::
-30- 60SI-1340
and optionally (iii) an effective amount of a filler.
Next a catalyst componen~. ~ is prepared comprising (i) an
ef~ective amoun~ of a silylating agen~ having at least
one labile monovalen~ or divalent group attached to
silicon by silicon-nitrogen linkages and selected from
silane and organopolysiloxane, (ii) an ef~ec~iYe amoun~
o a condensat$on cure catalyst, and (iii) an effective
amount of a crosslinking age~t; and optionally (iv) an
effective amount of an adhesion promoter.
~ h~ two components A and B are then admixed in
an admixing device as is known to tho~e skilled in the
art, at conditions to e~fect the curing of the
polydiorganosiloxane. Preferably, the components A and
B are admixed in a ratio of from about 80 to about 120
parts by weight of polymeric component A to from about 5
to ahout 20 parts by weight of cataly~t component B.
More preferred is a we~ght ratio o~ from about 90 to
about 110 parts by weight A to from about 5 to about 15
parts by weight ~.
It is also contemplated that other additives
such as pigment~, stabilizers, plastlcizer~ and the like
can be added to the compo~itions of the present
inventlon.
The novel two part room tempexature
vulcanizable silicone compositions o~ the subject
invention are partlcularly suitable for ga~eting,
adhesive and sealing applicatlons where excellent
adhesion to a variety of substrate~ i~ important. For
example, the compo~itions are useful in OEM assembly and
indu~tr~al caulking and seal~ng in building, fac~ories,
transportation vehicl~s, and the like and w1th substrates
such as ma~onry, gla~s, plastics such a~ polyearbonate,
metal, wood, and the like. The compositions are also
advantageous in having excellent rate~ o~ application,
~ r?~r ~2
31- 60SI-1340
making them readily suitable for application in automatic
dispen~ing equipment under standard conditions.
DESC~IPTION OF THE PREFE~RED EMBODIMENTS
The following example~ illustrate the present
invention. They ar~ not to be con~trued ~o limit the
scope of the appended claims in any manner whatsoever.
E~MPLES 1 2
A 30 mm Werner Pfleiderer Twin Screw Extruder
wa~ u~ed to compound an RTV base ("A" component)
comprised of 30 weight percen of 5000 eps
polydimethylsiloxanediol, 23.7 weight percent of 25,000
cp~ polydimethylsiloxanediol, and 47.3 weight percent of
a fatty acid tr~ated preclpitated CaCO3 (BET ~pecific
surface area of 16-20 m2~g, average particle size of 0.05
- 0~1 microns). Thls ba~e exhlbited a ~oeing flow of
0.50 inches, viscosity (Brook~ield RVF vi~cometer, No. 7
spindle at 2 rpm) of 590 Kcps, and specific gravity of
1.369 g/c~.
The same extruder was u~ed to compound a paste
catalyst ("B" component) co~prised of 64.5 weight percent
of 10,000 cps trimethylsilyl endstopped
polydimethylsiloxana, 10 weight percent of
octamethylcyclotetra~iloxane (D~, trea~ed fumed silica
(average BET surface area = 200 m2/g), 2 weigh~ percent of
"Black Masterbatch" (50 weight pQrcent carbon black in
300 cp~ dimethylvinyl terminated polydlmethylsiloxane),
15 weight percent of 3-aminopropyltriethoxysilane, 2.5
weigh~ percent of 1,3,5-tris(3-trimethy~ilylpropyl)-
isocyanurate, 5 weight percent tetra(n-propyl)silicate,
and 1 weight percent "solubilized" dlbutyltin oxide.
. ~ , .
-32- 60SI-1340
The ~A~ and ~B~ components are combined and
mixed (via a 5emco Catalyzer) at a weight ratio of 100
part~ by weight base to ~ par~s by weight catalyst. This
5 RTV is deqignated A* in ~able 1.
A second RTV, Example 1, was prepared from 100
parts by weight of the same base "A" component as
described above and catlayzed with 8 parts by weight of
the same paste ca~alyst "B" as described above to which
1.0 weight percent of hexamethyldisilazane ( D Z) had
been added.
A third RTY, Example 2, was prepared from 100
parts by weight of the same base "A" componen~ as
described above and catalyzed wi h 8 parts by weight of
the same paste catalyst "B" to which 2.0 weight percent
of HMD~ and 0.3 weight percent "solubilized" dibutyltin
oxide had been added.
~ he R~Y composition is then applied to a
polycarbonate substrate from the air actuat2d Semco tube
via a 1/8 inch orifice.
The cure and physical properties of the three
RTVs is set forth below in Ta~le 1.
1 0 ~ ~` U'i ~D ~ O~ O Ll'~ O I O o
O ~ ~ O ~ ~ U~ 'i O I O O
o ~ ~ ~ _I ~ o o
~ O
--t ~
O C~ O O W O ~ 'i O ~3 0 0 0
~r o r~ ~ O O
~ r o o ~ o
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-35- 60SI-1340
As can b~ seen from Table 1 above, the addition
of HMD2 to the sealant reduces the time required to
develop adhesion to polycarbona~e. After 24 hours, the
tensile strength of a polycarbonate lap shear specimen
sealed with the R~V of Example 1, containing 0.07 weight
percent of HMDZ, i~ approximately 43% greater than an
identical example sealed wlth the sealant of Example A*
which does not contain ~he HMDZ. Furthermore, ~he
sealant of Example 2 displays a full 100% cohesive
failure to polycarbonate af~er 24 hours.
It is importan~ to note that the ultimate
polycarbonate adhesive tensile strength of all 3 RTVs (7
day cuxe) is nearly identical. In all cases, 1 day after
the R~Vs were prepared the in~erior of a 1.5 inch
diameter cylinder of R~V (2 inches from the end) were
completely cured.
No "crazing" of polycarbona~e or loss of
tensile value wa ob~erved for polycarbonate lap shears
sealed with the RTV sealant of Example 2 and sub~ect~d to
arcelerated heat aglng (7 day cure and 7 days at 100C).
XAMP~ES 3-10
A 30 mm Werner Pfleiderer Twin Screw Extruder
wa~ used to compound an RTV ba~e ("A" component)
comprised of 50 weigh~ percent of a 10,000 cps blend of
an ~ 3,000 cps polydlmethylsiloxanediol and an ~ 30,000
cps polydimethyl~iloxanediol, 25 weigh~ percent of a
rosin acid coated precip~tated CaCo3 (BET specfic surface
area of 14-18 m2/g and average particle size of 0.05-0.1
micron) and 25 weight percent of a s~earic acid coated
ground Ca~o3 (~pecific surface area of 6 m2/g and mean
particle size of z 2 mlcrons).
r;; r ~
36- 60SI-1340
Elght liquid catalyst solution~ ("B" component)
were prepared by combining the concentrations of 10,000
cps trimethylsilyl endstopped polydlmethylsiloxane, 3-
aminopropyltriethoxysilane, tetra(n-propyl)silicate,
~olubiliz~d dibutyltinoxide and hexamethyldisilazane as
set forth in Table 2 below.
Twenty four RTVs were prepared. Each of ~hese
were comprised of 100 parts by weigh~ of the ba~e "A"
component de~cribed above and 8 parts by weight of liquid
cataly~t aged for either 2 day~ at ambient conditions
(RTVs 3A-lOA, Seri~ A), 7 days at ambient conditions
plus 7 days at 70C (RTVs 3B-lOB, Series B), or 14 days
a~ 70C (~TVs 3C-lOC, Series Cl. The resul~s tabulated
in Table 2 demonstra e that additlon of HMDZ to the
liquid catalyst causes no furkher deleterious impact on
shelf life, a~ mea~ured by cure rat~ before and after
accelerated aging, than th2 "control" catalyst formula~ed
without ~MDZ.
rhe Shore A values displayed in Table 2 were
obtained for RTVs which were cataly~ed, cured and stored
in relatively imperm~able polypropylene Semco tubes prior
to measurement. In this configuration, cure by-products
and volatile components could not escape from the R~V,
thu~ si~ulating the "worst ca~e scenario" for an adhesive
application. A cxo~-section, ~ ~" height x l~" diameter
cylinders of cured RTV silicone sliced and remove~ from
the center o~ the Semco tube~ was u~ad for the hardness
measurement. The nearly equivalent values obtainded for
RTVs containing equal 3-aminopropyltrlmethoxysilane
concen~rations regardle~ of HMDZ level, (RTV 3A vs. 4A,
SA or 6A and RTVs 7A vs. 8A, 9A or lOA) demonstra~es that
the silazane doe~ not effectlvely compete with silanol
polymer to inhibit cure in deep section~ or confined
geometrie~.
,
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-39- 60SI-1340
The above patents, patent applicatlons and
tes~ methods are hereby incorpora~ed by reference.
Many variations of the pres~nt invention
will suggest themselves to those skilled in this art in
light of the above detailed de~cription. All such
obvious modifications are within the full intended scope
of the appended claim~.
.
