Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FILLED SILICONE COMPOSITION AND CURED SILICONE
PRODUCT
[0001] The present invention relates to a method of preparing a hydrophobic
partially
aggregated colloidal silica, particularly to a method comprising reacting a
silica sol
comprising at least one hydrophilic partially aggregated colloidal silica with
an organosilicon
compound. The present invention also relates to the hydrophobic partially
aggregated
colloidal silica prepared by the method, a filled silicone composition
containing the
hydrophobic partially aggregated colloidal silica and to a cured silicone
product formed from
the composition.
[0002] Silica fillers are widely used in the rubber industry to reinforce
various silicone and
organic elastomers. These fillers improve the mechanical properties, for
example, hardness,
tensile strength, elongation, modulus, and tear resistance, of the vulcanized
rubber. However,
finely divided silica fillers, such as colloidal silica, tend to agglomerate
and are hard to
disperse in uncured elastomer compositions. Consequently, silica fillers are
often treated
with an organosilicon compound to render the surface hydrophobic. Treatment
reduces the
tendency of the filler particles to agglomerate and also prevents premature
crepe hardening.
[0003) Silicones are useful in a variety of applications by virtue of their
unique
combination of properties, including high thermal stability, good moisture
resistance,
excellent flexibility, high ionic purity, low alpha particle emissions, and
good adhesion to
various substrates. In particular, silicones containing a reinforcing filler,
such as treated silica,
are commonly employed in applications requiring exceptional mechanical
properties. For
example, filled silicones are widely used in the automotive, electronic,
construction,
appliance, and aerospace industries.
[0004) Methods of preparing hydrophobic non-aggregated colloidal silica are
known in the
art. For example, Castaing et al. disclose a method of preparing nano-sized
hairy grains by
grafting long polydimethylsiloxane chains onto silica particles having a
radius of about 15
nm (Europhys. Lett., 1996, 36 (2), 153-158).
[0005] U.S. Patent No. 6,025,455 to Yoshitake et al. discloses a process of
producing a
hydrophobic organosilica sol which comprises aging a reaction mixture at 0 to
100 °C in the
state that an alkali present in the reaction mixture is removed or is
neutralized with an acid in
an equivalent amount or more, thereby forming a silylation-treated silica sol
having a
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hydrophobic colloidal silica dispersed therein, the reaction mixture
comprising: (a) a
hydrophilic colloidal silica having a specific surface area of from 5.5 to 550
m2/g in Si02
concentration of from 5 to 55% by weight, (b) a silylating agent of a
disiloxane compound
and/or monoalkoxysilane compound in a millimolar ratio of from 0.03 to 2 in
terms of Si
atom per 100 m2 of a surface of the hydrophilic colloidal silica, and (c) a
medium, as a
residue thereof, comprising a mixed solvent comprising a hydrophobic organic
solvent
having a solubility of water of from 0.1 to 12% by weight and an alcohol
having 1 to 3
carbon atoms in a weight ratio of from 0.05 to 20 to the hydrophobic organic
solvent, and
water in an amount of 1 S% by weight or less based on the weight of the
medium.
[0006] Kwan et al. disclosed the synthesis of colloidal silica by silylation
of an aqueous
suspension of colloidal silica with either chlorosilanes or disiloxanes in the
presence of acid
and isopropyl alcohol, without aggregation of the silica particles and a
silicone composition
containing a vinyl-terminated polydimethylsiloxane, and Si-H functional
crosslinker, the
hydrophobic colloidal silica, and a platinum catalyst. (156th ACS Rubber
Division Meeting,
Orlando, Fl., September 1999, Paper 96).
[0007] U.S. Patent No. 6,051,672 to Burns et al. discloses a method for making
hydrophobic
non-aggregated colloidal silica comprising reacting an aqueous suspension of a
hydrophilic
non-aggregated colloidal silica having an average particle diameter greater
than about 4 nm
with a silicon compound at a pH less than about 4 in the presence of a
sufficient quantity of a
water-miscible organic solvent to facilitate contact of the hydrophilic non-
aggregated
colloidal silica with the silicon compound at a temperature within a range of
about 20 to 250
°C for a time period sufficient to form a hydrophobic non-aggregated
colloidal silica. U.S.
Patent No. 6,051,672 also describes a silicone rubber composition comprising
the
hydrophobic non-aggregated colloidal silica.
[0008] Although the aforementioned references describe various methods of
producing
hydrophobic non-aggregated colloidal silica, they do not teach the method or
the hydrophobic
partially aggregated colloidal silica of the present invention.
[0009] Furthermore, silicone compositions comprising hydrophobic non-
aggregated
colloidal silica in accordance with the present invention cure to form
silicone products having
a wide range of mechanical properties, high concentrations, for example, 60%
w/w, of
hydrophobic non-aggregated colloidal silica are typically required to achieve
superior
mechanical properties. Consequently, there is a need for a filled silicone
composition
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containing a low concentration of hydrophobic colloidal silica that cures to
form a silicone
product having excellent mechanical properties.
[0010) The present invention is directed to a method of preparing a
hydrophobic partially
aggregated colloidal silica, the method comprising reacting (a) a silica sol
comprising at least
one hydrophilic partially aggregated colloidal silica with (b) an
organosilicon compound
selected from (i) at least one organosilane having the formula RIaHbSiX4_a-b,
(ii) at least
one organocyclosiloxane having the formula (R12Si0)m, (iii) at least one
organosiloxane
having the formula R13Si0(R1 Si0)nSiRl3, and (iv) a mixture comprising at
least two of (i)
(ii), and (iii), in the presence of (c) water (d) an effective amount of a
water-miscible organic
solvent, and (e) an acid catalyst, to produce the hydrophobic partially
aggregated colloidal
silica and an aqueous phase, wherein Rl is hydrocarbyl or substituted
hydrocarbyl; X is a
hydrolysable group; a is 0, 1, 2, or 3; b is 0 or 1; a + b = 1, 2, or 3,
provided when b = 1, a + b
= 2 or 3; m has an average value of from 3 to 10; and n has an average value
of from 0 to 10.
DRAWING
[0011] Figure 1 is shows an electron micrograph (TEM, magnification: 100,000)
of the
hydrophobic partially aggregated colloidal silica of Example 1.
DESCRIPTION
[0012) Component (a) is a silica sol comprising at least one hydrophilic
partially
aggregated colloidal silica. As used herein, the term "silica sol" refers to a
stable suspension
of hydrophilic partially aggregated colloidal silica particles in water, an
organic solvent, or a
mixture of water and a water-miscible organic solvent. Also, as used herein,
the term
"hydrophilic" means the silica surface has silanol (Si-OH) groups capable of
hydrogen
bonding with suitable donors, such as adjacent silanol groups and water
molecules. In other
words, the silanol groups produced during manufacture of the silica have not
been modified,
for example, by reaction with an organosilicon compound. Further, as used
herein, the term
"partially aggregated colloidal silica" refers to colloidal silica comprising
particles having a
ratio Dl/D2 of at least 3, where Dl is the mean diameter of the colloidal
silica particles
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measured by a dynamic light-scattering method and D2 is the mean diameter of
the colloidal
silica particles as determined by a nitrogen adsorption method, and D 1 has a
value of from 40
to 500 nm. The value of D1 may be determined using a conventional light-
scattering
apparatus according to the well known method described in J. Chem. Phys. 1972,
57 (11),
4814. The value of D2 may be calculated according to the equation D2 = 2720/5,
where S is
the specific surface area of the colloidal silica as determined by nitrogen
absorption
according to the Brunauer-Emmett-Teller (BET) method. Additionally, aqueous
silica sols
typically have a pH of from 7 to 11.
[0013] Examples of silica sols suitable for use as component (a) include, but
are not limited
to, a moniliform silica sol disclosed by Watanabe et al. in European Patent
Application No.
EP 1114794 A1 and an elongated-shaped silica sol disclosed by Watanabe et al.
in U.S.
Patent No. 5,597,512. The moniliform (rosary- or pearl necklace-shaped) silica
sol has an
Si02 concentration of from 1 to SO% (w/w) and contains liquid medium-dispersed
moniliform colloidal silica particles having a ratio D1/D2 of at least 3,
wherein the
moniliform colloidal silica particles comprise spherical colloidal silica
particles having a
mean diameter of from 10 to 80 nm and metal oxide-containing silica bonding
the spherical
colloidal silica particles, wherein the spherical colloidal silica particles
are linked in rows in
only one plane; and D 1 and D2 are as defined above, wherein D 1 has a value
of from 50 to
500 nm. The length of the moniliform colloidal silica particles is typically
at least five times
the mean diameter of the spherical colloidal silica particles, as determined
by electron
micrographs. The silica bonding the spherical colloidal silica particles
contains a small
amount, 0.5 to 10% (w/w), of a divalent or trivalent metal oxide, based on the
weight of Si02
in the silica bonding the spherical colloidal silica particles, depending on
the method of
preparing the moniliform silica sol.
[0014] The moniliform silica sol typically contains not greater than 50%
(w/w), preferably
5 to 40% (w/w), of Si02. The viscosity of the silica sol is typically from
several mPa.s to
about 1,000 mPa.s at room temperature.
[0015] Examples of moniliform silica sol include the aqueous suspensions of
colloidal
silica sold by Nissan Chemical Industries, Ltd. (Tokyo, Japan) under the trade
names
SNOWTEX-PS-S and SNOWTEX-PS-M, described in the Examples section below.
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[0016] The moniliform silica sol may be prepared as described in detail by
Watanabe et al.
in European Patent Application No. EP 1114794 A1. Briefly stated, the method
comprises:
(a) adding an aqueous solution containing a water-soluble divalent metal salt
or a water-
soluble trivalent metal salt singly or in admixture to an active silicic acid-
containing aqueous
colloidal liquid or an acidic silica sol having a mean particle diameter of
from 3 to 8 nm, each
containing 0.5 to 10% (w/w) of Si02 and having a pH of from 2 to 6, in an
amount of from 1
to 10% (w/w) as a metal oxide based on Si02 in the aqueous colloidal solution
of active
silicic acid or acidic silica sol and mixing them; (b) adding acidic spherical
silica sol having a
mean diameter of from 10 to 80 nm and a pH 2 to 6 to the mixed liquid (a)
obtained in step
(a) in such an amount that a ratio of a silica content (A) derived from the
acidic spherical
silica sol to a silica content (B) derived from the mixed liquid (b), AB
(weight ratio), is 5 to
100 and the total silica content (A+B) of a mixed liquid (b) obtained by
mixing the acidic
spherical silica sol with the mixed liquid (a) has an Si02 concentration of
from 5 to 40%
(w/w) in the mixed liquid (b) and mixing them; (c) adding an alkali metal
hydroxide, water-
soluble organic base or water-soluble silicate to the mixed liquid (b)
obtained in step (b) such
that the pH is 7 to 11 and mixing them; and (d) heating the mixed liquid (c)
obtained in step
(c) at 100 to 200 °C for 0.5 to 50 hours (hereafter referred to as h).
[0017] The elongated-shaped silica sol has an Si02 concentration of from 6 to
30% (w/w)
and contains elongated-shaped amorphous colloidal silica particles having a
ratio D 1 /D2 of at
least 5, wherein D1 and D2 are as defined above for the moniliform colloidal
silica particles
and D1 has a value of from 40 to 300 nm; and the particles are elongated in
only one plane
and have a uniform thickness along the elongation within the range of from S
to 20 nm, as
determined using an electron microscope. The colloidal silica particles are
substantially
amorphous silica, but they may contain a small amount, typically 1500 to 8500
ppm, of an
oxide of calcium or magnesium, or both, based on the weight of Si02 in the
silica sol. In
some cases, the silica particles may contain a slight amount of oxides of
other polyvalent
metals in addition to the oxides of calcium and/or magnesium. The total
concentration of
metal oxides is typically from 1500 to 15000 ppm, based on the weight of Si02
in the silica
sol. Examples of polyvalent metals include strontium, barium, zinc, tin, lead,
copper, iron,-
nickel cobalt, manganese, aluminum, chromium, yttrium, and titanium.
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[0018] The elongated-shaped silica sol may be prepared as described in detail
by Watanabe
et al. in U.S. Patent No. 5,597,512. Briefly stated, the method comprises: (a)
mixing an
aqueous solution containing a water-soluble calcium salt or magnesium salt or
a mixture of
said calcium salt and said magnesium salt with an aqueous colloidal liquid of
an active silicic
acid containing from 1 to 6% (w/w) of Si02 and having a pH in the range of
from 2 to 5 in an
amount of from 1500 to 8500 ppm as a weight ratio of Ca0 or Mg0 or a mixture
of Ca0 and
Mg0 to Si02 of the active silicic acid; (b) mixing an alkali metal hydroxide
or a water-
soluble organic base or a water-soluble silicate of said alkali metal
hydroxide or said water-
soluble organic base with the aqueous solution obtained in step (a) in a molar
ratio of
Si02/M20 of from 20 to 200, where Si02 represents the total silica content
derived from the
active silicic acid and the silica content of the silicate and M represents an
alkali metal atom
or organic base molecule; and (c) heating at least a part of the mixture
obtained in step (b) to
60 °C or higher to obtain a heel solution, and preparing a feed
solution by using another part
of the mixture obtained in step (b) or a mixture prepared separately in
accordance with step
(b), and adding said feed solution to said heel solution while vaporizing
water from the
mixture during the adding step until the concentration of Si02 is from 6 to
30% (w/w). The
silica sol produced in step (c) typically has a pH of from 8.5 to 11.
[0019] Component (a) may be a silica sol comprising a single hydrophilic
partially
aggregated colloidal silica as described above or a silica sol comprising two
or more such
colloidal silicas that differ in at least one property, such as surface area,
pore diameter, pore
volume, particle size, and particle shape.
[0020] Component (b) is at least one organosilicon compound selected from
(b)(i), (b)(ii),
and (b)(iii), described below, or a mixture (b)(iv) comprising at least two of
(b)(i), (b)(ii), and
(b)(iii), as noted above.
[0021] Component (b)(i) is at least one organosilane having the formula
RlaHbSiX4_a-b~
wherein R1 is hydrocarbyl or substituted hydrocarbyl; X is a hydrolysable
group; a is 0, 1, 2,
or 3; b is 0 or 1; and a + b = 1, 2, or 3, provided when b = 1, a + b = 2 or
3. The hydrocarbyl
groups and substituted hydrocarbyl groups represented by R1 typically have
from 1 to 20
carbon atoms, preferably from 1 to 10 carbon atoms, more preferably from 1 to
6 carbon
atoms. Acyclic hydrocarbyl and substituted hydrocarbyl groups containing at
least 3 carbon
atoms may have a branched or unbranched structure.
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[0022] Examples of hydrocarbyl groups include, but are not limited to, alkyl,
such as
methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl,
1,1-
dimethylethyl, pentyl, 1-methylbutyl, 1-ethylpropyl, 2-methylbutyl, 3-
methylbutyl, 1,2-
dimethylpropyl, 2,2-dimethylpropyl, hexyl, heptyl, octyl, nonyl, decyl,
undecyl, dodecyl,
tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl;
cycloalkyl, such as
cyclopentyl, cyclohexyl, and methylcyclohexyl; aryl, such as phenyl and
naphthyl; alkaryl,
such as tolyl and xylyl; aralkyl, such as benzyl and phenethyl; alkenyl, such
as vinyl, allyl,
and propenyl; arylalkenyl, such as styryl and cinnamyl; and alkynyl, such as
ethynyl and
propynyl.
[0023] Examples of substituents in the substituted hydrocarbyl groups
represented by R1
include -OH, -NH2, -SH, -C02H, -O(O=C)CR2, -(R2)N(O=)CR2, and -S-S-R2, wherein
R2
is C1 to Cg hydrocarbyl.
[0024] As used herein, the term "hydrolysable group" means the Si-X group may
react with
water to form an Si-OH group. Examples of hydrolysable groups include, but are
not
limited to, -Cl, Br, -OR3, -OCH2CH20R3, CH3C(=O)O-, Et(Me)C=N-O-,
CH3C(=O)N(CH3)-, and -ONH2, wherein R3 is C1 to Cg hydrocarbyl or halogen-
substituted
hydrocarbyl.
[0025] Examples of hydrocarbyl groups represented by R3 include, but are not
limited to,
unbranched and branched alkyl, such as methyl, ethyl, propyl, 1-methylethyl,
butyl, 1-
methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, pentyl, 1-methylbutyl, 1-
ethylpropyl, 2-
methylbutyl, 3-methylbutyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, hexyl,
heptyl, and
octyl; cycloalkyl, such as cyclopentyl, cyclohexyl, and methylcyclohexyl;
phenyl; alkaryl,
such as tolyl and xylyl; axalkyl, such as benzyl and phenethyl; alkenyl, such
as vinyl, allyl,
and propenyl; axylalkenyl, such as styryl; and alkynyl, such as ethynyl and
propynyl.
Examples of halogen-substituted hydrocarbyl groups include, but are not
limited to, 3,3,3-
trifluoropropyl, 3- chloropropyl, chlorophenyl, and dichlorophenyl.
[0026] Examples of organosilanes include, but are not limited to, SiCl4,
CH3SiC13,
CH3CH2SiCl3~ C6HSSiCl3, (CH3)2SiC12, (CH3CH2)2SiCl2~ (C6H5)2SiC12, (CH3)3SiCl,
CH3HSiC12, (CH3)2HSiCl, SiBr4, CH3SiBr3, CH3CH2SiBr3~ C6HSSiBr3, (CH3)2SiBr2,
(CH3CH2)2SiBr2~ (C6H5)2SiBr2~ (CH3)3SiBr, CH3HSiBr2, (CH3)2HSiBr, Si(OCH3)4,
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CH3Si(OCH3)3, CH3Si(OCH2CH3)3, CH3Si(OCH2CH2CH3)3, CH3Si[O(CH2)3CH3]3,
CH3CH2Si(OCH2CH3)3, C6HSSi(OCH3)3, C6HSCH2Si(OCH3)3, C6HSSi(OCH2CH3)3
CH2=CHSi(OCH3)3, CH2=CHCH2Si(OCH3)3, CF3CH2CH2Si(OCH3)3,
(CH3)2Si(OCH3)2, (CH3)2Si(OCH2CH3)2, (CH3)2Si(OCH2CH2CH3)2,
(CH3)2Si[O(CH2)3CH3]2~ (CH3CH2)2Si(OCH2CH3)2~ (C6H5)2 Si(OCH3)2~
(C6HSCH2)2Si(OCH3)2, (C6H5)2Si(OCH2CH3)2~ (CH2=CH)2Si(OCH3)2,
(CH2=CHCH2)2Si(OCH3)2, (CF3CH2CH2)2Si(OCH3)2, (CH3)3SiOCH3,
CH3HSi(OCH3)2, (CH3)2HSiOCH3, CH3Si(OCH2CH20CH3)3,
CF3CH2CH2Si(OCH2CH20CH3)3, CH2=CHSi(OCH2CH20CH3)3,
CH2=CHCH2Si(OCH2CH20CH3)3, and C6HSSi(OCH2CH20CH3)3,
(CH3)2Si(OCH2CH20CH3)2, (CF3CH2CH2)2Si(OCH2CH20CH3)2,
(CH2=CH)2Si(OCH2CH20CH3)2, (CH2=CHCH2)2Si(OCH2CH20CH3)2,
(C6H5)2Si(OCH2CH20CH3)2, CH3Si(OAc)3, CH3CH2Si(OAc)3, CH2=CHSi(OAc)3,
(CH3)2Si(OAc)2, (CH3CH2)2Si(OAc)2, (CH2=CH)2Si(OAc)2,
CH3Si[ON=C(CH3)CH2CH3]3, (CH3)2Si[ON=C(CH3)CH2CH3]2, CH3Si[NHC(=O)CH3]3,
C6HSSi[NHC(=O)CH3]3, (CH3)2Si[NHC(=O)CH3]2, and Ph2Si[NHC(=O)CH3]2, wherein
OAc
is CH3C(=O)O- and Ph is phenyl.
[0027] Component (b)(i) may be a single organosilane or a mixture comprising
two or more
different organosilanes, each having the formula RIaHbSiX4_a-b, wherein R1, X,
a, and b are
as defined above. Methods of preparing organosilanes suitable for use as
component (b)(i)
are well known in the art; many of these organosilanes are commercially
available.
[0028] Component (b)(ii) is at least one organocyclosiloxane having the
formula
(R12Si0)m, wherein R1 is as defined and exemplified above for component (b)(i)
and m has
an average value of from 3 to 10, preferably from 3 to 8, more preferably from
3 to 5.
[0029] Examples of organocyclosiloxanes include, but are not limited to,
hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and
decamethylcyclopentasiloxane.
(0030] Component (b)(ii) may be a single organocyclosiloxane or a mixture
comprising
two or more different organocyclosiloxanes that differ in at least one
property, such as
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structure, viscosity, average molecular weight, siloxane units, and sequence.
Methods of
preparing organocyclosiloxanes suitable for use as component (b)(ii) are well
known in the
art; many of these organocyclosiloxanes are commercially available.
[0031) Component (b)(iii) is at least one organosiloxane having the formula
R13Si0(RlSiO)nSiRl3, wherein Rl is as defined and exemplified above for
component
(b)(i) and n has an average value of from 0 to 10, preferably from 0 to 8,
more preferably
from 0 to 4. Examples include, but are not limited to, hexamethyldisiloxane,
hexaethyldisiloxane, 1,3-divinyl-1,1,3,3-tetramethyldisiloxane,
octamethyltrisiloxane, and
decamethyltetrasiloxane.
[0032] Component (b)(iii) may be a single organosiloxane or a mixture
comprising two
or more different organosiloxanes that differ in at least one property, such
as structure,
viscosity, average molecular weight, siloxane units, and sequence. Methods of
preparing
organosiloxanes suitable for use as component (b)(iii) are well known in the
art; many of
these organosiloxanes are commercially available.
1 S [0033] Component (b) may be a single organosilicon compound represented by
components
(b)(i), (b)(ii), and (b)(iii), or a mixture comprising at least two of the
components.
[0034] Component (d) is at least one water-miscible organic solvent. As used
herein, the
term "water-miscible" means the organic solvent is either substantially
miscible or
completely miscible (i.e., miscible in all proportions) with water. For
example, the solubility
of the water-miscible organic solvent in water is typically at least 90 g/100
g of water at 25
°C.
[0035) Examples of water-miscible organic solvents include, but are not
limited to,
monohydric alcohols such as methanol, ethanol, 1-propanol, and 2-propanol;
dihydric
alcohols such as ethylene glycol and propylene glycol; polyhydric alcohols
such as glycerol
and pentaerythritiol; and dipolar aproptic solvents such as N,N-
dimethylformamide,
tetrahydrofuran, dimethylsulfoxide, and acetonitrile. Component (d) may be a
single water-
miscible organic solvent or a mixture comprising two or more different water-
miscible
organic solvents, each as defined above.
[0036] Component (e) is at least one acid catalyst that promotes reaction of
the hydrophilic
partially aggregated colloidal silica with the organosilicon compound,
component (b).
Although the acid catalyst is typically added as a separate component to the
reaction mixture,
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in some cases it may be produced in situ. For example, when component (b) is
an
organosilane containing a hydrolysable group such as chloro, a portion or all
of the acid
catalyst may be generated by reaction of the chlorosilane with water or the
hydroxy groups of
the hydrophilic partially aggregated colloidal silica.
5 [0037] Examples of acid catalysts include inorganic acids such as
hydrochloric acid,
sulfuric acid, nitric acid, and hydrofluoric acid; and organic acids such as
acetic acid, oxalic
acid, and trifluoroacetic acid. The acid may be a single acid or a mixture
comprising two or
more different acids.
[0038] The method of the present invention may be carried out in any standard
reactor
10 suitable for contacting silica with an organosilicon compound in the
presence of water and an
acid catalyst. Suitable reactors include glass and Teflon-lined glass
reactors. Preferably, the
reactor is equipped with an efficient means of agitation, such as a stirrer.
[0039] The silica sol, component (a), is typically added to a mixture
comprising the
organosilicon compound, water, the water-miscible organic solvent, and the
acid catalyst.
Reverse addition, i.e., addition of a mixture comprising the organosilicon
compound to the
silica sol is also possible. However, reverse addition may result in formation
of larger
aggregates of the colloidal silica.
[0040] The rate of addition of the silica sol to the mixture containing the
organosilicon
compound is typically from 1 to 3 ml/min for a 0.5 litre reaction vessel
equipped with an
efficient means of stirring. When the rate of addition is too slow, the
reaction time is
unnecessarily prolonged. When the rate of addition is too fast, the colloidal
silica may form
larger aggregates.
[0041] The suspension of the hydrophilic partially aggregated colloidal silica
and the
organosilicon compound are typically reacted at a temperature of from 20 to
150 °C,
preferably from 40 to 120 °C, more preferably from 60 to 100 °C.
When the temperature is
less than 40 °C, the rate of reaction is typically very slow.
[0042] The reaction is carried out for a period of time sufficient to produce
the hydrophobic
partially aggregated colloidal silica, and an aqueous phase. The reaction time
depends on a
number of factors including the nature of the hydrolysable groups in the
organosilicon
compound, structure of the organosilicon compound, agitation of the reaction
mixture,
concentration of the hydrophilic partially aggregated colloidal silica, and
temperature. The
reaction time is typically from several minutes to several hours. For example,
the reaction
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11
time is typically from 0.1 to 2 h at a temperature of from 40 to 120
°C, preferably from 0.5 to
1 h at a temperature of from 60 to 100 °C. The optimum reaction time
may be determined by
routine experimentation using the methods set forth in the Examples below.
[0043] The concentration of the hydrophilic partially aggregated colloidal
silica of
component (a) in the reaction mixture is typically from 1 to 20% (w/w),
preferably from 1 to
10% (w/w), more preferably from 1 to 5% (w/w), based on the total weight of
the reaction
mixture.
[0044] The mole ratio of the organosilicon compound, component (b), to the
hydrophilic
partially aggregated colloidal silica (Si02) of component (a) is typically
from 0.1 to 5,
preferably from 0.2 to 3, more preferably from 0.5 to 2. When the mole ratio
of component
(b) to the hydrophilic partially aggregated colloidal silica is less than 0.1,
the treated silica
may not exhibit hydrophobic properties. When the mole ratio is greater than 5,
the
hydrophobic colloidal silica may not precipitate from the aqueous phase, as
described below.
[0045] The concentration of water, component (c), in the reaction mixture is
typically from
20 to 60% (w/w), preferably from 20 to 50% (w/w), more preferably from 20 to
40% (w/w),
based on the total weight of the reaction mixture. When component (a) is an
aqueous silica
sol, a portion or all of component (c) may be supplied by the silica sol.
(0046] The water-miscible organic solvent, component (d), is present in an
effective
amount in the reaction mixture. As used herein, the term "effective amount"
means the
concentration of component (d) is such that (i) the organosilicon compound is
soluble in the
aqueous reaction mixture containing the water-miscible organic solvent, and
(ii) the partially
aggregated colloidal silica particles in the reaction mixture are stable,
i.e., the particles do not
form larger aggregates. Aggregation of the hydrophilic partially aggregated
colloidal silica
particles may be detected by comparing the size and shape of the hydrophobic
colloidal silica
particles with the size and shape of the hydrophilic partially aggregated
colloidal silica
particles of component (a) using electron microscopy. The concentration of
component (d) is
typically from about 5 to about 35% (v/v), preferably from 10 to 30% (v/v),
more preferably
from 20 to 30% (v/v), based on the total volume of the reaction mixture. When
the
concentration of component (d) is less than 5% (v/v), the treated silica may
not exhibit
hydrophobic properties. When the concentration of component (d) is greater
than 35% (v/v),
the hydrophobic colloidal silica may not precipitate from the aqueous phase,
as described
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below. The effective amount of component (d) may be determined by routine
experimentation using the methods in the Examples below.
[0047] The concentration of component (e) is sufficient to maintain the pH of
the reaction
mixture at a value less than 4. For example, the concentration of component
(e) is typically
from 10 to 60% (w/w), preferably from 10 to 40% (w/w), based on the total
weight of the
reaction mixture. When the concentration of component (e) is less than 10%
(w/w), the rate
of reaction may be too slow for commercial applications. When the
concentration of
component (e) is greater than 60% (w/w), additional washing steps may be
required to
remove the acid from the hydrophobic partially aggregated colloidal silica.
[0048] The hydrophobic partially aggregated colloidal silica typically
precipitates from the
aqueous phase. As used herein, the term "precipitates" means the hydrophobic
partially
aggregated colloidal silica forms a deposit that is insoluble in the aqueous
phase. For
example, the hydrophobic colloidal silica may float to the top of the aqueous
phase, settle to
the bottom of the aqueous phase, or collect on the walls of the reaction
vessel. The
hydrophobic silica is typically separated from the aqueous phase by removing
(for example,
draining or decanting) the aqueous phase or the hydrophobic silica.
[0049] The hydrophobic silica, isolated as described above, is typically
washed with water
to remove residual acid. The water may further comprise a water-miscible
organic solvent,
such as 2-propanol. The concentration of the water-miscible organic solvent in
the aqueous
wash is typically from 10 to 30% (v/v). The hydrophobic silica may be washed
by mixing it
with water and then separating the hydrophobic silica from the water. The
organic phase is
typically washed from one to three times with separate portions of water. The
volume of
water per wash is typically from two to five times the volume of the
hydrophobic partially
aggregated colloidal silica.
[0050] The washed hydrophobic silica is typically dried by suspending it in a
water-
immiscible organic solvent and then removing the organic solvent using a
process such as
evaporating or spray drying. As used herein, the term "water-immiscible" means
the organic
solvent is slightly miscible or completely immiscible with water. For example,
the solubility
of water in the solvent is typically less than about 0.1 g/100 g of solvent at
25 °C. The
organic solvent may be any aprotic or dipolar aprotic organic solvent that is
immiscible with
water. Preferably, the organic solvent forms a minimum boiling azeotrope with
water. If the
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13
organic solvent does not form an azeotrope with water, the organic solvent
preferably has a
boiling point greater than the boiling point of water.
[0051] Examples of water-immiscible organic solvents include, but are not
limited to,
saturated aliphatic hydrocarbons such as n-pentane, hexane, n-heptane,
isooctane and
dodecane; cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane;
aromatic
hydrocarbons such as benzene, toluene, xylene and mesitylene; cyclic ethers
such as
tetrahydrofuran (THF) and dioxane; ketones such as methyl isobutyl ketone
(MIBK);
halogenated alkanes such as trichloroethane; and halogenated aromatic
hydrocarbons such as
bromobenzene and chlorobenzene. The water-immiscible organic solvent may be a
single
organic solvent or a mixture comprising two or more different organic
solvents, each as
defined above.
[0052] Additionally, before removing the water-immiscible organic solvent, as
described
above, the suspension of the hydrophobic silica in the organic solvent may be
distilled to
remove water. The distillation may be carried out at atmospheric or sub-
atmospheric
1 S pressure at a temperature that depends on the boiling point of the water-
immiscible organic
solvent. The distillation is typically continued until the distillate is free
of water.
[0053] Under certain conditions, the hydrophobic partially aggregated
colloidal silica
remains suspended in the aqueous phase of the reaction mixture. In this case,
the aqueous
suspension of the hydrophobic silica is typically treated with a water-
immiscible organic
solvent in an amount sufficient to form a non-aqueous phase comprising the
water-
immiscible organic solvent and the hydrophobic silica. Suitable water-
immiscible organic
solvents are described above. The concentration of the water-immiscible
organic solvent is
typically from 5 to 20% (v/v), preferably from 10 to 20% (v/v), based on the
total volume of
the aqueous suspension.
[0054] The non-aqueous phase is typically separated from the aqueous phase by
discontinuing agitation of the mixture, allowing the mixture to separate into
two layers, and
removing the aqueous or non-aqueous layer.
[0055] The non-aqueous phase, isolated as described above, is typically washed
with water
to remove residual acid. The water may further comprise a water-miscible
organic solvent,
such as 2-propanol. The concentration of the water-miscible organic solvent in
the solution is
typically from l0 to 30% (v/v). The non-aqueous phase may be washed by mixing
it with
water, allowing the mixture to separate into two layers, and removing the
aqueous layer. The
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14
organic phase is typically washed from one to three times with separate
portions of water.
The volume of water per wash is typically from two to five times the volume of
the non-
aqueous phase.
[0056] The hydrophobic silica is typically dried by removing the water-
immiscible organic
solvent using a method such as evaporating or spray-drying.
[0057] Additionally, before removing the water-immiscible organic solvent, the
non-
aqueous phase may be distilled to remove water. The distillation may be
carried out at
atmospheric or sub-atmospheric pressure at a temperature that depends on the
boiling point of
the water-immiscible organic solvent. The distillation is typically continued
until the
distillate is free of water.
[0058] The hydrophobic partially aggregated colloidal silica prepared by the
method of the
present invention typically has a surface area of from 20 to 300 m2/g,
preferably from 50 to
200 m2/g, more preferably from 50 to 150 m2/g, as determined by nitrogen
adsorption
according to the BET method. Also, the hydrophobic colloidal silica typically
has a pore
diameter of from 50 to 300 ~, preferably from 100 to 250 ~$, more preferably
from 150 to
250 t~; and a pore volume of from 0.5 to 1.5 ml/g, preferably from 0.5 to 1.0
ml/g, as
determined by nitrogen adsorption methods. Moreover, the hydrophobic colloidal
silica
comprises particles having a size and shape approximating the size and shape
of the
hydrophilic colloidal silica particles of component (a).
[0059] The method of the present invention produces hydrophobic partially
aggregated
colloidal silica in high yield from commercially available starting materials.
Moreover, the
method may be conveniently controlled to produce hydrophobic silica having a
wide range of
hydrophobicity, surface area, pore diameter, and pore volume.
[0060] The hydrophobic partially aggregated colloidal silica improves the
mechanical
properties of silicone and organic elastomers (i.e., cross-linked polymers).
In particular, a
low concentration of the silica imparts excellent mechanical properties, such
as durometer
hardness, tensile strength, elongation, modulus, and tear strength, to a
silicone elastomer
compared with hydrophobic non-aggregated colloidal silica. The potential
advantages of low
silica concentrations include shorter formulation time, lower cost, and lower
viscosity.
[0061] The hydrophobic silica of the present invention may be used as a
reinforcing or
extending filler in organic polymer compositions, such as epoxy resins and
phenolic resins,
and silicone compositions, such as sealants, adhesives, encapsulants, and
conformal coatings.
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[0062] The method of the present invention produces hydrophobic partially
aggregated
colloidal silica in high yield from commercially available starting materials.
Moreover, the
method may be conveniently controlled to produce hydrophobic silica having a
wide range of
hydrophobicity, surface area, pore diameter, and pore volume.
5 [0063] The hydrophobic partially aggregated colloidal silica improves the
mechanical
properties of silicone and organic elastomers (i.e., cross-linked polymers).
In particular, a
low concentration of the silica imparts excellent mechanical properties, such
as durometer
hardness, tensile strength, elongation, modulus, and tear strength, to a
silicone elastonier
compared with hydrophobic non-aggregated colloidal silica. The potential
advantages of low
10 silica concentrations include shorter formulation time, lower cost, and
lower viscosity.
[0064] The hydrophobic silica of the present invention may be used as a
reinforcing or
extending filler in organic polymer compositions, such as epoxy resins and
phenolic resins,
and silicone compositions, such as sealants, adhesives, encapsulants, and
conformal coatings.
[0065] In a further aspect of the present invention, there is provided a
filled silicone
15 composition comprising:
(A) a curable silicone composition; and
(B) 5 to 60% (w/w) of a hydrophobic partially aggregated colloidal silica.
[0066] The present invention is also directed to a cured silicone product
comprising a
reaction product of the above-described filled silicone composition.
[0067] Component (A) is a curable silicone composition. Curable silicone
compositions
and methods for their preparation are well known in the art. Examples of
curable silicone
compositions include, but are not limited to, hydrosilylation-curable silicone
compositions,
peroxide curable silicone compositions, condensation-curable silicone
compositions, epoxy-
curable silicone compositions; ultraviolet radiation-curable silicone
compositions, and high-
energy radiation-curable silicone compositions. For example, a suitable
hydrosilylation-
curable silicone composition typically comprises (i) an organopolysiloxane
containing an
average of at least two silicon-bonded alkenyl groups per molecule, (ii) an
organohydrogensiloxane containing an average of at least two silicon-bonded
hydrogen
atoms per molecule in an amount sufficient to cure the composition, and (iii)
a
hydrosilylation catalyst. The hydrosilylation catalyst may be any of the well
known
hydrosilylation catalysts comprising a platinum group metal, a compound
containing a
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16
platinum group metal, or a microencapsulated platinum group metal-containing
catalyst.
Platinum group metals include platinum, rhodium, ruthenium, palladium, osmium
and
iridium. Preferably, the platinum group metal is platinum, based on its high
activity in
hydrosilylation reactions.
[0068] The hydrosilylation-curable silicone composition may be a one-part
composition or
a multi-part composition comprising the components in two or more parts. Room-
temperature vulcanizable (RTV) compositions typically comprise two parts, one
part
containing the organopolysiloxane and catalyst and another part containing the
organohydrogensiloxane and any optional ingredients. Hydrosilylation-curable
silicone
compositions that cure at elevated temperatures may be formulated as one-part
or multi-part
compositions. For example, liquid silicone rubber (LSR) compositions are
typically
formulated as two-part systems. One-part compositions typically contain a
platinum catalyst
inhibitor to ensure adequate shelf life.
[0069] A suitable peroxide-curable silicone composition typically comprises
(i) an
organopolysiloxane and (ii) an organic peroxide. Examples of organic peroxides
include,
diaroyl peroxides such as dibenzoyl peroxide, di-p-chlorobenzoyl peroxide, and
bis-2,4-
dichlorobenzoyl peroxide; dialkyl peroxides such as di-t-butyl peroxide and
2,5-dimethyl-
2,5-di-(t-butylperoxy)hexane; diaralkyl peroxides such as dicumyl peroxide;
alkyl aralkyl
peroxides such as t-butyl cumyl peroxide and 1,4-bis(t-
butylperoxyisopropyl)benzene; and
alkyl amyl peroxides such as t-butyl perbenzoate, t-butyl peracetate, and t-
butyl peroctoate.
[0070] A condensation-curable silicone composition typically comprises (i) an
organopolysiloxane containing an average of at least two hydroxy groups per
molecule; and
(ii) a tri- or tetra-functional silane containing hydrolysable Si-O or Si-N
bonds. Examples of
silanes include alkoxysilanes such as CH3Si(OCH3)3, CH3Si(OCH2CH3)3,
CH3Si(OCH2CH2CH3)3, CH3Si[O(CH2)3CH3]3, CH3CH2Si(OCH2CH3)3,
C6HSSi(OCH3)3, C6HSCH2Si(OCH3)3, C6HSSi(OCH2CH3)3, CH2=CHSi(OCH3)3,
CH2=CHCH2Si(OCH3)3, CF3CH2CH2Si(OCH3)3, CH3Si(OCH2CH20CH3)3,
CF3CH2CH2Si(OCH2CH20CH3)3, CH2=CHSi(OCH2CH20CH3)3,
. CH2=CHCH2Si(OCH2CH20CH3)3, C6HSSi(OCH2CH20CH3)3, Si(OCH3)4,
Si(OC2H5)4, and Si(OC3H~)4; organoacetoxysilanes such as CH3Si(OCOCH3)3,
CH3CH2Si(OCOCH3)3, and CH2=CHSi(OCOCH3)3; organoiminooxysilanes such as
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17
CH3Si[O-N=C(CH3)CH2CH3]3, Si[O-N=C(CH3)CH2CH3]4, and CH2=CHSi[O-
N=C(CH3)CH2CH3]3; organoacetamidosilanes such as CH3Si[NHC(=O)CH3]3 and
C6HSSi[NHC(=O)CH3]3; aminosilanes such as CH3Si[NH(s-C4H9)]3 and CH3Si(NHC6H~
1)3;
and organoaminooxysilanes.
[0071] A condensation-curable silicone composition may also contain a
condensation
catalyst to initiate and accelerate the condensation reaction. Examples of
condensation
catalysts include, but are not limited to, amines; and complexes of lead, tin,
zinc, and iron
with carboxylic acids. Tin(II) octoates, laurates, and oleates, as well as the
salts of dibutyl
tin, are particularly useful. The condensation-curable silicone composition
may be a one-part
composition or a multi-part composition comprising the components in two or
more parts.
For example, room-temperature vulcanizable (RTV) compositions may be
formulated as one-
part or two-part compositions. In the two-part composition, one of the parts
typically
includes a small amount of water.
[0072] A suitable epoxy-curable silicone composition typically comprises (i)
an
organopolysiloxane containing an average of at least two epoxy-functional
groups per
molecule and (ii) a curing agent. Examples of epoxy-functional groups include
2
glycidoxyethyl, 3-glycidoxypropyl, 4-glycidoxybutyl, 2,(3,4-
epoxycyclohexyl)ethyl, 3-(3,4-
epoxycyclohexyl)propyl, 2,3-epoxypropyl, 3,4-epoxybutyl, and 4,5-epoxypentyl.
Examples
of curing agents include anhydrides such as phthalic anhydride,
hexahydrophthalic anhydride,
tetrahydrophthalic anhydride, and dodecenylsuccinic anhydride; polyamines such
as
diethylenetriamine, triethylenetetramine, diethylenepropylamine, N-(2-
hydroxyethyl)diethylenetriamine, N,N'-di(2-hydroxyethyl)diethylenetriamine, m-
phenylenediamine, methylenedianiline, aminoethyl piperazine, 4,4-
diaminodiphenyl sulfone,
benzyldimethylamine, dicyandiamide, and 2-methylimidazole, and triethylamine;
Lewis acids
such as boron trifluoride monoethylamine; polycarboxylic acids;
polymercaptans;
polyamides; and amidoamines.
[0073] A suitable ultraviolet radiation-curable silicone composition typically
comprises (i)
an organopolysiloxane containing radiation-sensitive functional groups and
(ii) a
photoinitiator. Examples of radiation-sensitive functional groups include
acryloyl,
methacryloyl, mercapto, epoxy, and alkenyl ether groups. The type of
photoinitiator depends
on the nature of the radiation-sensitive groups in the organopolysiloxane.
Examples of
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photoinitiators include diaryliodonium salts, sulfonium salts, acetophenone,
benzophenone,
and benzoin and its derivatives.
[0074] A suitable high-energy radiation-curable silicone composition comprises
an
organopolysiloxane polymer. Examples of organpolyosiloxane polymers include
S polydimethylsiloxanes, poly(methylvinylsiloxanes), and
organohydrogenpolysiloxanes.
Examples of high-energy radiation include y-rays and electron beams.
[0075] Component (B) is at least one hydrophobic partially aggregated
colloidal silica as
hereinbefore described.
[0076] The hydrophobic partially aggregated colloidal silica of component (1)
may be a
single hydrophobic partially aggregated colloidal silica or a mixture
comprising two or more
such silicas differing in at least one property, such as surface area, pore
diameter, pore
volume, and hydrophobicity, particle size, and particle shape.
[0077] The concentration of component (B) in the filled silicone composition
is typically
from 5 to 60% (w/w), preferably from 10 to 50% (w/w), more preferably from 20
to 40%
(w/w), based on the total weight of the silicone composition. When the
concentration of
component (B) is less than 5% (w/w), the cured silicone product typically does
not exhibit
improved mechanical properties relative to the unfilled composition. When the
concentration
of component (B) is greater than 60% (w/w), the composition may be too viscous
for certain
applications. The effective amount of component (B) may be determined by
routine
experimentation using the methods in the Examples below.
[0078] The filled silicone composition of the present invention may comprise
additional
ingredients, provided the ingredient does not prevent the composition from
curing to form a
silicone product having superior mechanical properties. Examples of additional
ingredients
include, but are not limited to, hydrosilylation catalyst inhibitors, dyes,
pigments, adhesion
promoters, anti-oxidants, heat stabilizers, UV stabilizers, flame retardants,
surfactants, flow
control additives, and inorganic fillers.
[0079] The filled silicone composition of the instant invention is typically
prepared by
mixing components (A) and (B) and any optional ingredients in the stated
proportions at
ambient temperature with or without the aid of an organic solvent. Mixing may
be
accomplished by any of the techniques known in the art such as milling,
blending, and
stirring, in either a batch or continuous process. Alternatively, component
(B) may be
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19
combined with the individual components of the curable silicone composition of
component
(A) in any order.
[0080] A cured silicone product according to the present invention comprises a
reaction
product of the filled silicone composition comprising components (A) and (B),
described
above. The filled silicone composition may be cured by exposure to ambient
temperature,
elevated temperature, moisture, or radiation, depending on the particular cure
mechanism.
For example, one-part hydrosilylation-curable silicone compositions are
typically cured at an
elevated temperature. Two-part hydrosilylation-curable silicone compositions
are typically
cured at room temperature or an elevated temperature. One-part condensation-
curable
silicone compositions are typically cured by exposure to atmospheric moisture
at room
temperature, although cure may be accelerated by application of heat and/or
exposure to high
humidity. Two-part condensation-curable silicone compositions are typically
cured at room
temperature; however, cure may be accelerated by application of heat. Peroxide-
curable
silicone compositions are typically cured at an elevated temperature. Epoxy-
curable silicone
compositions are typically cured at room temperature or an elevated
temperature. Depending
on the particular formulation, radiation-curable silicone compositions are
typically cured by
exposure to radiation, for example, ultraviolet light, gamma rays, or electron
beams.
[0081] The filled silicone composition of the present invention has numerous
advantages
including low VOC (volatile organic compound) content and good flow. Moreover,
the
filled silicone composition cures to form a cured silicone product having
excellent
mechanical properties, such as durometer hardness, tensile strength,
elongation, modulus, and
tear strength, at relatively low concentrations compared with a similar
silicone composition
lacking the hydrophobic partially aggregated colloidal silica. The potential
advantages of
low filler concentrations include shorter formulation time, lower cost, and
lower viscosity.
[0082] The filled silicone composition of the present invention has numerous
uses
including adhesives, sealants, encapsulants, and molded articles, such as o-
rings.
[0083] Unless otherwise noted, all parts and percentages reported in the
examples are by
weight.
[0084] Examples 1 to 13 and Table 1 comprise methods of preparation in
accordance with
the present invention and physical characteristics of the resulting
hydrophobically partially
aggregated colloidal silicas respectively. The following methods and materials
were
employed in examples 1 to 13:
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Measurement of Surface Area, Pore Diameter, and Pore Volume
[0085] The surface area (m2/g), pore diameter (t~), and pore volume (ml/g) of
a
hydrophobic partially aggregated colloidal silica were determined by nitrogen
adsorption
using a Micrometrics ASAP 2010 Analyzer.
Analysis of Hydrophobic Partially Aggregated Silica
[0086] The extent of surface treatment (% w/w) was determined by digesting
samples of
the treated silica in the presence of potassium hydroxide and
tetraethoxysilane and then
analyzing the digest by gas chromatography using a flame ionization detector
and an octane
internal standard to determine the concentrations of the various silane
species. The amount
10 of Si02 was determined by difference.
[0087] Immediately before analysis, the silica sample was dried in an oven at
150 °C for 24
h. After cooling the sample to room temperature, the silica was manually
pulverized to
eliminate large clumps of silica. Approximately 0.03 to 0.05 g of the treated
silica and 0.03
to 0.06 g of octane (internal standard) were combined in a reaction vial. To
the mixture was
15 added 4 ~ 0.05 g of tetraethyoxysilane and a single pellet of potassium
hydroxide. A
microscale stir bar was placed in the reaction vial, which was sealed with a
rubber septum. A
23-gauge syringe needle (3.8 cm) was inserted through the septum and brought
into contact
with the bottom of the vial. A 26-gauge syringe needle (0.95 cm) was inserted
into the
septum to act as a vent needle. Nitrogen was passed through the longer needle
at a rate of
20 about 150 ml/min until gas bubbles were no longer observed in the mixture.
The vent needle
was removed and the vial was pressurized to 10 psi (68.95 mPa) with nitrogen.
The vial was
placed into an aluminum block at a temperature of 125 °C. After
stirring the reaction mixture
for 1 h, the vial was removed from the aluminum block and then allowed to
stand in air for 15
min. The vial was placed in an ice bath for about 10 min during which time the
septum was
removed from the vial. Dry carbon dioxide was bubbled through the reaction
mixture for 3
min, during which time a precipitate formed, indicating neutralization of the
base. The
mixture was centrifuged at 3000 rpm for 10 min to separate the precipitate
from the liquid
layer. The pH of the supernatant liquid was measured with pH paper to confirm
neutralization of the base (i.e., pH 6 to 8). When the pH was greater than 8,
additional carbon
dioxide was bubbled through the liquid to complete neutralization. The sample
was
transferred to a gas chromatography vial for analysis.
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21
[0088) Gas Chromatographic analysis was carried out using an Agilent 6890 Gas
Chromatograph equipped with a flame ionization detector and a DB-1 capillary
column (30
m x 250 ~m x 1 pm). The analysis was performed using a split of 50:1, an inlet
temperature
of 270 °C, a detector temperature of 280 °C, helium carrier gas
at a constant flow of 1.0
ml/min, an internal standard consisting of 20,000 to 30,000 ppm of octane in
tetraethoxysilane, and the following temperature profile: hold at 50 °C
for 1 min, increase to
200 °C at a rate of 4 °C/min, increase to 300 °C at a
rate of 20 °C/min, and hold at 300 °C for
min.
[0089] The weight percent of the triorganosiloxane and diorganosiloxane groups
on the
10 surface of the treated silica was calculated according to the following
equation:
wt% _ (A)(Rf)(Wt,std)(Purity std)(102)
(A,std)(Rf,std)(Wt,samp)
where:
A = Area of peak for silicon-containing group, arbitrary units
Wt,std = Weight of internal standard (octane), mg
Purity,std = Purity of internal standard (octane), wt%
A,std = Area of peak for internal standard (octane), arbitrary units
Rf,std = Response factor for internal standard (octane)
Wt,samp = Weight of sample, mg
Rf = A std Rf std~R)(Wt red
(A,)(Wt,std)(Purity,std)
where:
R - MW of silicon-containingr~rou~
Mw of reference material (trimethylethoxysilane)
Wt. Ref = Weight of reference material (trimethylethoxysilane), mg
[0090] Examples 14 onwards are presented to further illustrate the coated
silicone rubber
article and method of the present invention, but are not to be considered as
limiting the
invention, which is delineated in the appended claims. The following methods
and materials
were employed in the examples:
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22
Preparation of Silicone Rubber Samples
[0091] The silicone composition was compression molded using a stainless steel
mold
(internal dimensions: 12.7 x 12.7 x 0.16 cm), a pressure of 5000 psi (34.5
MPa), and the
conditions of temperature and time specified in the Examples below.
Measurement of Tensile Strength, Elongation, and Young's Modulus
[0092] Tensile strength at rupture (MPa), ultimate elongation (%), and Young's
modulus
(MPa) of a silicone rubber test specimen were determined according to ASTM
Standard D
412-98a using an Instron Model 5500 R Tensile Tester and dumbbell-shaped test
specimens
(4.5 x 1 cm). Young's modulus was calculated from the stress-strain curve
according to
ASTM Standard E 111-97. Reported values for tensile strength, elongation, and
Young's
modulus each represent the average of five measurements made on different
silicone test
specimens cut from the same silicone rubber sample.
Measurement of Tear Strength
[0093] Type B tear strength (kN/mm) of a silicone rubber test specimen was
determined
according to ASTM Standard D 624-00 using an Instron Model 55008 Tensile
Tester.
Reported values of tear strength represent the average of three measurements
made on
different test specimens cut from the same silicone rubber sample.
Measurement of Durometer Hardness
[0094] The durometer hardness of a silicone rubber test specimen was
determined
according to ASTM Standard D 2240-02 using a Conveloader Model CV-71200 Shore
Type
A Durometer. Three test specimens from the same silicone sample were stacked
to achieve a
total thickness of about 0.5 cm. Reported values for durometer hardness
represent the
average of three measurements performed at different locations on the same
silicone rubber
test specimen.
Measurement of Extrusion Rate
[0095] The extrusion rate (g/min) of a silicone composition absent the
Catalyst and
Inhibitor was determined according to ASTM Standard C 1183-91 using a pressure
of 90 psi
(0.62 MPa).
Measurement of Light Transmittance
[0096] The percent transmittance of a silcone rubber test specimen was
determined using an
XL-211 Hazegard Hazemeter equipped with a tungsten-halogen lamp.
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23
[0097] The following chemical substances were used in the examples:
Polymer A: a dimethylvinylsiloxy-terminated poly(dimethylsiloxane) having a
viscosity
of about 55 Pas at 25 °C.
Polymer B: a dimethylvinylsiloxy-terminated
poly(dimethylsiloxane/methylvinylsiloxane) having an average of 145
dimethylsiloxane units
and 3 methylvinylsiloxane units per molecule, and a viscosity of 0.35 Pas at
25 °C.
Cross-linking Agent: a trimethylsiloxy-terminated
poly(dimethylsiloxane/methylhydrogen-siloxane) having an average of three
dimethylsiloxane units and five methylhydrogensiloxane units per molecule and
containing
about 0.8% of silicon-bonded hydrogen atoms.
Inhibitor: 1-Ethynyl-1-cylcohexanol.
Catalyst: a mixture consisting of 92% of a dimethylvinylsiloxy-terminated
poly(dimethylsiloxane) having a viscosity of about 0.45 Pas at 25 °C, 7
% of 1,3-divinyl-
1,1,3,3-tetramethyldisiloxane, and 1 % of platinum complex of 1,3-
divinyltetramethyldisiloxane.
Silica Filler A: an aqueous suspension of colloidal silica sold under the
trade name
SNOWTEX-PS-S by Nissan Chemical Industries (Tokyo, Japan). The suspension
consists of
13% (w/w) of amorphous silica (Si02), less than 0.2% (w/w) of Na20, and water.
The
suspension has a viscosity of 10 mPa~s at 25 °C, a pH of 10.1, a
specific gravity of 1.08 at 20
°C, and a particle size of about 125 nm (dynamic light-scattering
method).
Silica Filler B: an aqueous suspension of colloidal silica sold under the
trade name
SNOWTEX-PS-M by Nissan Chemical Industries (Tokyo, Japan). The suspension
consists
of 21 % (w/w) of amorphous silica (Si02), less than 0.2% (w/w) of Na20, and
water. The
suspension has a viscosity of 9 mPa~s at 25 °C, a pH of 9.7 a specific
gravity of 1.14 at 20 °C,
and a particle size of about 127 nm (dynamic light-scattering method).
Silica Filler C: an aqueous suspension of colloidal silica sold under the
trade name
SNOWTEX-UP by Nissan Chemical Industries (Tokyo, Japan). The mixture consists
of 20
(w/w) of amorphous silica (Si02), less than 0.35% (w/w) of Na20, and water.
The
suspension has a viscosity of 12.5 mPa~s at 25 °C, a pH of about 10.4,
and a specific gravity
of 1.13 at 20 °C.
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Example 1
[0098) Concentrated hydrochloric acid (300 ml), 1 litre of deionized water,
750 ml of 2-
propanol, 300 ml of hexamethyldisiloxane, and 20 ml of 1,3-
divinyltetramethyldisiloxane
were combined in a 5 litre flask equipped with a mechanical stirrer. Silica
Filler A (1 litre)
was slowly added to the flask during a period of 30 min. The resulting
suspension was stirred
at 75 °C for 2 h, during which time the hydrophobic colloidal silica
separated from the
aqueous phase. The aqueous phase was removed and the remaining hydrophobic
colloidal
silica was washed with 1 litre of a solution of isopropanol (25 v/v%) in
deionized water. The
aqueous wash was removed and the washing procedure was repeated. After the
second wash
was removed, 2.5 litre of toluene was added to the flask. The flask was fitted
with a Dean-
Stark trap and the suspension was distilled until the distillate was free of
water. The
suspension was spray-dried in a Buchi B-191 Mini Spray Drier using compressed
nitrogen,
an aspirator setting of 50%, a pump setting of 50%, an inlet temperature of
220 °C, and an
outlet temperature of 140 °C, to produce 120 g of hydrophobic partially
aggregated colloidal
silica. The physical properties and composition of the hydrophobic colloidal
silica are shown
in Table 1. Reference may be had to Figure 1 which shows an electron
micrograph (TEM,
magnification: 100,000) of the hydrophobic partially aggregated colloidal
silica of this
Example 1.
Example 2
[0099] A hydrophobic partially aggregated colloidal silica was prepared using
the method
of Example 1, except that the volume of hexamethyldisiloxane was 305 ml and
the volume of
1,3-divinyltetramethyldisiloxane was 30 ml. The yield of hydrophobic colloidal
silica was
120 g. The physical properties and composition of the hydrophobic colloidal
silica are shown
in Table 1.
Example 3
[0100] A hydrophobic partially aggregated colloidal silica was prepared using
the method
of Example l, except that the volume of 1,3-divinyltetramethyldisiloxane was
35 ml. The
yield of hydrophobic colloidal silica was 120 g. The physical properties and
composition of
the hydrophobic colloidal silica are shown in Table 1.
Example 4
[0101] A hydrophobic partially aggregated colloidal silica was prepared using
the method
of Example l, except that the volume of concentrated HCl was 200 ml, the
volume of
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deionized water was 900 ml, 150 ml of chlorotrimethylsilane was used in place
of
hexamethyldisiloxane and 15 ml of chlorodimethylvinylsilane was used in place
of 1,3-
divinyltetramethyldisiloxane. The yield of hydrophobic colloidal silica was 51
g. The
physical properties and composition of the hydrophobic colloidal silica are
shown in Table 1.
5 Example 5
[0102] Concentrated hydrochloric acid (200 ml), 0.9 litre of deionized water,
750 ml of 2-
propanol, 150 ml of chlorotrimethylsilane, 10 ml of chlorodimethylvinylsilane,
10 ml of
chloromethylphenylvinylsilane, 10 ml of chlorodimethylphenylsilane, and 10 ml
of
chlorodiphenylmethylsilane were combined in a 5 litre flask. Silica Filler A
(1 litre) was
10 slowly added to the flask during a period of 30 min. The resulting
suspension was stirred at
75 °C for 1 h and then at room temperature overnight. Toluene (500 ml)
was added to the
flask to effect separation of the hydrophobic colloidal silica from the
aqueous phase. The
aqueous phase.was removed and the remaining suspension of hydrophobic
colloidal silica
was washed with 1 litre of a solution of isopropanol (25 v/v%) in deionized
water. The
15 aqueous wash was removed, the flask was fitted with a Dean-Stark trap, and
the suspension
was distilled until the distillate was free of water. The suspension was spray-
dried in a Buchi
B-191 Mini Spray Drier using compressed nitrogen, an aspirator setting of 50%,
a pump
setting of 50%, an inlet temperature of 220 °C, and an outlet
temperature of 140 °C, to
produce 114 g of hydrophobic partially aggregated colloidal silica. The
physical properties
20 and composition of the hydrophobic colloidal silica are shown in Table 1.
The weight
percent of phenyl-containing organosiloxy groups was not determined.
Example 6
[0103] Water (1 litre), 750 ml of 2-propanol, and 300m1 of concentrated
hydrochloric acid
were combined in a 5 litre flask equipped with a mechanical stirrer. Silica
Filler A (1 litre)
25 was slowly to the flask during a period of 30 min. Simultaneously, a
mixture of 313 ml of
dichlorodimethylsilane and 30.Sm1 dichloromethylvinylsilane was added slowly
to the flask
during the same 30-min period. The resulting suspension was stirred at 75
°C for 2 h, during
which time the hydrophobic colloidal silica separated from the aqueous phase.
The aqueous
phase was removed, 1 litre of a solution of 2-propanol (33 v/v%) in deionized
water was
added to the flask, and the mixture was rapidly stirred for 1 min. The aqueous
wash was
removed and the washing procedure was repeated. After the second wash was
removed, 2
litres of toluene was added to the flask. The flask was fitted with a Dean-
Stark trap, and the
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suspension was distilled until the distillate was free of water. The
suspension was spray-
dried in a Buchi B-191 Mini Spray Drier using compressed nitrogen, an
aspirator setting of
50%, a pump setting of 50%, an inlet temperature of 220 °C, and an
outlet temperature of 140
°C, to produce 225 g of hydrophobic partially aggregated colloidal
silica. The physical
properties and composition of the hydrophobic colloidal silica are shown in
Table 1.
Example 7
[0104) A mixture consisting of 562.7 ml of water, 750 ml of 2-propanol, 300 ml
of
hexamethyldisiloxane, and 300 ml of concentrated hydrochloric acid was added
to 1043.5 g
of Silica Filler A (diluted with water to 10% w/w SiOz) in a 5 litre flask
equipped with a
mechanical stirrer. After stirring for one hour at 75 °C, the aqueous
solution was allowed to
cool to room temperature. Methyl isobutyl ketone (500 ml) was added to the
stirred mixture
to effect separation of the hydrophobic colloidal silica from the aqueous
phase, which was
then removed. Methyl isobutyl ketone (100 ml) and 500 ml of a solution of 2-
propanol (33%
v/v) and water were added to the flask, followed by removal of the aqueous
phase. The
preceding step was repeated using 150 ml of methyl isobutyl ketone and 500 ml
of the
solution of 2-propanol and water. After the aqueous phase was removed, 1500 ml
of methyl
isobutyl ketone was added to the flask. The flask was fitted with a Dean-Stark
trap and the
suspension was distilled until the distillate was free of water. The remaining
slurry was
poured into an 18 x 25-cm Pyrex evaporating dish and the solvent was allowed
to evaporate
overnight. The hydrophobic colloidal silica was further dried in an air-
circulating oven at
150 °C for 23 hours. The physical properties and composition of the
hydrophobic colloidal
silica are shown in Table 1.
Example 8
[0105] Concentrated HCl (300 ml), 1 litre of deionized water, 750 ml of 2-
propanol, 300 ml
of hexamethyldisiloxane, and 20 ml of 1,3-divinyltetramethyldisiloxane were
combined in a
5 litre flask. Silica Filler B (700 ml) was slowly added to the flask during a
period of 50 min.
The resulting suspension was stirred at 75 °C for 1 h, during which
time the hydrophobic
colloidal silica separated from the aqueous phase. The aqueous phase was
removed and the
remaining hydrophobic colloidal silica was washed with 1 litre of a solution
of 2-propanol
(25 v/v%) in deionized water. The aqueous wash was removed and the washing
procedure
was repeated. After the second wash was removed, 2.6 litres of toluene was
added to the
flask. The flask was fitted with a Dean-Stark trap, and the suspension was
distilled until the
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27
distillate was free of water. The suspension was spray-dried in a Buchi B-191
Mini Spray
Drier using compressed nitrogen, an aspirator setting of 50%, a pump setting
of 50%, an inlet
temperature of 220 °C, and an outlet temperature of 140 °C, to
produce 70 g of hydrophobic
partially aggregated colloidal silica. The physical properties and composition
of the
hydrophobic colloidal silica are shown in Table 1.
Example 9
[0106] A mixture consisting of 1300 ml of concentrated hydrochloric acid, 200
ml of
chlorotrimethylsilane and 10 ml of chlorodimethylvinylsilane was added to 400
ml of Silica
Filler B in a 5 litre flask equipped with a mechanical stirrer. The resulting
suspension was
stirred at 63 °C for 1 h, during which time the hydrophobic colloidal
silica separated from the
aqueous phase. The aqueous phase was removed, 1 litre of deionized water was
added to the
flask, and the reaction mixture was rapidly stirred for 1 min. The aqueous
phase was
removed and 500 ml of toluene was added to the flask. The flask was fitted
with a Dean-
Stark trap, and the suspension was distilled until the distillate was free of
water. The
remaining toluene/xerogel slurry was poured into an 18 x 25-cm Pyrex
evaporating dish and
the solvent was allowed to evaporate overnight. The silica was further dried
in an air
circulating oven at 120 °C for 10 hours. The physical properties and
composition of the
hydrophobic colloidal silica are shown in Table 1.
Example 10
[0107] Concentrated hydrochloric acid (300 ml), 1 litre of deionized water,
750 ml of 2-
propanol, 300 ml of hexamethyldisiloxane, and 20 ml of 1,3-
divinyltetramethyldisiloxane
were combined in a 5 litre flask. A mixture consisting of Silica Filler A (720
ml) and 265 ml
of Silica Filler B was slowly added to the flask during a period of 30
minutes. The resulting
suspension was stirred at 75 °C for 2 h, during which time the
hydrophobic colloidal silica
separated from the aqueous phase. The aqueous phase was removed and the
hydrophobic
colloidal silica was washed with 1 litre of a solution of 2-propanol (25 v/v%)
in deionized
water. The aqueous wash was removed and 2.7 litres of toluene was added to the
flask. The
flask was fitted with a Dean-Stark trap, and the suspension was distilled
until the distillate
was free of water. The suspension was spray-dried in a Buchi B-191 Mini Spray
Drier using
compressed nitrogen, an aspirator setting of 50%, a pump setting of 50%, an
inlet
temperature of 220 °C, and an outlet temperature of 140 °C, to
produce 110 g of hydrophobic
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28
partially aggregated colloidal silica. The physical properties and composition
of the
hydrophobic colloidal silica are shown in Table 1.
Example 11
[0108] Concentrated hydrochloric acid (300 ml), 1 litre of deionized water,
750 ml of 2-
propanol, 300 ml of hexamethyldisiloxane, and 15 ml of 1,3-
divinyltetramethyldisiloxane
were combined in a 5 litre flask. A mixture consisting of Silica Filler A (250
ml) and 500 ml
of Silica Filler B was slowly added to the flask during a period of 60
minutes. The resulting
suspension was stirred at 75 °C for 2 h, during which time the
hydrophobic colloidal silica
separated from the aqueous phase. The aqueous phase was removed and the
hydrophobic
colloidal silica was washed with 500 ml of a solution of 2-propanol (40 v/v%)
in deionized
water. The aqueous wash was removed and the washing procedure was repeated.
After the
second wash was removed, 2.5 litres of toluene was added to the flask. The
flask was fitted
with a Dean-Stark trap, and the suspension was distilled until the distillate
was free of water.
The suspension was spray-dried in a Buchi B-191 Mini Spray Drier using
compressed
nitrogen, an aspirator setting of 50%, a pump setting of 50%, an inlet
temperature of 220 °C,
and an outlet temperature of 140 °C, to produce 45 g of hydrophobic
partially aggregated
colloidal silica. The physical properties and composition of the hydrophobic
colloidal silica
are shown in Table 1.
Example 12
(0109] Concentrated HCl (300 ml), 1 litre of deionized water, 750 ml of 2-
propanol, 300 ml
of hexamethyldisiloxane, and 20 ml of 1,3-divinyltetramethyldisiloxane were
added to a 5
litre flask. Silica filler C (680 ml) was slowly added to the flask during a
period of SO min.
The resulting suspension was stirred at 75 °C for 1 h, during which
time the hydrophobic
colloidal silica separated from the aqueous phase. The aqueous phase was
removed and the
hydrophobic colloidal silica was washed with 1 litre of a solution of 2-
propanol (25 v/v%) in
deionized water. The aqueous wash was removed and the washing procedure was
repeated.
After the second wash was removed, 2.6 litres of toluene was added to the
flask. The flask
was fitted with a Dean-Stark trap and the suspension was distilled until the
distillate was free
of water. The suspension was spray-dried in a Buchi B-191 Mini Spray Drier
using
compressed nitrogen, an aspirator setting of 50%, a pump setting of 50%, an
inlet
temperature of 220 °C, and an outlet temperature of 140 °C, to
produce 105 g of hydrophobic
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29
partially aggregated colloidal silica. The physical properties and composition
of the
hydrophobic colloidal silica are shown in Table 1.
Example 13
[0110] A mixture consisting of 1 litre of concentrated hydrochloric acid, 100
ml of
chlorotrimethylsilane, and 5 ml chlorodimethylvinylsilane was added to 250 ml
of Silica
Filler C. The resulting suspension was stirred at 60 °C for 1 h, during
which time the
hydrophobic colloidal silica separated from the aqueous phase. The aqueous
phase was
removed, 500 ml of deionized water was added to the flask, and the mixture was
rapidly
stirred for 1 min. The aqueous wash was removed, 610 ml of deionized water was
added to
the flask, and the mixture was rapidly stirred for 1 min. The aqueous wash was
removed, 1
litre of water was added to the flask, and the mixtuxe was stirred rapidly for
1 min. The
aqueous wash was removed and 1 litre of toluene was added to the flask. The
flask was fitted
with a Dean-Stark trap and the suspension was distilled until the distillate
was free of water.
The remaining slurry was poured into an 18 x 25-cm Pyrex evaporating dish and
the solvent
was allowed to evaporate overnight. The treated silica was further dried in an
air-circulating
oven at 120 °C for 19 hours. The physical properties and composition of
the hydrophobic
colloidal silica are shown in Table 1.
Example 14
[0111] A silicone composition was prepared by first adding the hydrophobic
colloidal silica
of Example 1 to a mixture consisting of 90% of Polymer A and 10% of Polymer B
in an
amount sufficient to achieve a concentration of 28% (w/w), based on the weight
of the final
silicone composition. The silica was added to the mixture at a rate of 1 g/min
in a Haake
Rheocord System 90 Mixer equipped with a Rheomix 600 mixing head with sigma
mixing
blades operating at 50 revolutions per minute (rpm). After the addition was
complete, the
mixture was mixed at 60 °C for 1 h and then allowed to cool to 40
°C during a period of 20
min. Crosslinking Agent was added to the mixture in an amount sufficient to
provide 1.5
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N N ~ N M oo O ~ --~
O O O O O ~~ O O O O O O p
O O D O D O O O O O O O O
~ ~_
V) O O O O ~~ ~t O O O O O O O
' O O O O O O~ O O O O O O O
VJ ~ O O O O O M O O O O O O O
O
M M ~ 00 V7 ~ M O (~ 00 01 N o0
M ~ N M O ~~ N O O ~~ N
O O O O O M O O O O O O O
O
cn N
' ~n ,-
~ ~_
c~ ~~ ~ ~ ~' N O O ~t M O~ ~ l~ 01
O ~ N ~ M M N O O ~~ .-~ .~ .-. N N
O O O O D O O O O O O O O
'-'N
O ~ O ~
O M ~O ~ V7 ~ ~
M
~ M ~ ~t ~ O ~ N M M M V7
00
N
Ov N v~ ~ 01 Ov 01 ~' M o0 N O~
O v~ N O ~~ O~ ~O t~ O v7 I~ ~1
~~ O ~-~ '~ ~ O O O O ~~ O O O
.~"."
~ N ~ ~ O ~ ~ I~ M o0 N M_
N ~ N N ~ N ~ N N N N ~ O
t,
O
~,
c~
N
~.
N M o0 \O N 00 l0 N M 00
~ N M ~ v7 ~ ~ M I~ ~ ~ ~~ O ~ 01
V ~ ~ ~ rr
w
~,
O
N
J
1" O N M
N M ~' V1 ~O l~ 00 Oy, ,-
J W
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31
silicon-bonded hydrogen atoms per vinyl group in Polymer A and Polymer B
combined, to
produce a silicone base. After mixing for 30 min, 0.15 ml of Inhibitor was
added to the silicone
base. Catalyst was then added to the mixture in sufficient amount to provide
from 10 to 1 S ppm
of platinum metal, based on the weight of the final silicone composition. The
extrusion rate of
the silicone base was 61 g/min.
Examples 1 Sa and 15b
[0112] In Example 1 Sa, a sample of the silicone composition of Example 14 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and I50 °C
for 10 min. In Example 15b, a sample of the silicone composition of Example 14
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 2.
Example 16
[0113] A silicone composition was prepared using the method of Example 14,
except that the
concentration of the hydrophobic colloidal silica was 30% (w/w). The extrusion
rate of the
silicone base was 37 g/min.
Examples 17a and 17b
[0114] In Example 17a, a sample of the silicone composition of Example 16 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 17b, a sample of the silicone composition of Example 16
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 2.
Example 18
[0115] A silicone composition was prepared using the method of Example 14,
except that the
concentration of the hydrophobic colloidal silica was 34% (w/w). The extrusion
rate of the
silicone base was 11 g/min.
Examples 19a and 19b
[0116] In Example 19a, a sample of the silicone composition of Example 18 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to S
min and 150 °C
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for 10 min. In Example 19b, a sample of the silicone composition of Example I
8 was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 2.
Example 20
[0117] A silicone composition was prepared using the method of Example 14,
except that the
concentration of the hydrophobic colloidal silica was 30% (w/w) and the
mixture of Polymer A,
Polymer B, and hydrophobic colloidal silica was mixed at room temperature for
1 h instead of 60
°C for 1 h, immediately before addition of the Cross-linking Agent. The
extrusion rate of the
silicone base was 46 g/min.
Examples 21 a and 21 b
[0118] In Example 21 a, a sample of the silicone composition of Example 20 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 21 b, a sample of the silicone composition of Example
20 was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for I 0 min, and 200 ° for 1 h. The physical
properties of the silicone rubber
products are shown in Table 2.
Table 2
Young's Modulus
DurometerTensile (MPa) Tear Light
Hardness StrengthElongationat Elongation= StrengthTrans.
Example(Shore (MPa) (%) 50% 100% 200% (N/mm) (%)
A)
15a 42 5.18 437 0.710 1.33 2.25 40.63 85
15b 47 5.99 499 1.17 1.90 2.94 - 79
17a 41 6.22 702 0.686 1.34 2.19 47.63 86
17b 47 6.31 537 1.14 1.91 2.98 - 78
19a 46 7.82 715 1.15 1.92 2.94 43.61 85
19b 52 8.27 605 1.49 2.40 3.56 - 83
21 a 47 5.29 421 1.06 1.87 3.07 43.43 83
21 b 48 5.75 407 1.18 2.05 3.36 - 82
- denotes the property was not measured
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Example 22
[0119] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example 1 was replaced with 28% (w/w) of the
hydrophobic
colloidal silica of Example 2. The extrusion rate of the silicone base was 45
g/min.
Examples 23a and 23b
[0120] In Example 23a, a sample of the silicone composition of Example 22 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 23b, a sample of the silicone composition of Example 22
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 1 SO °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 3.
Example 24
[0121] A silicone composition was prepared using the method of Example 22,
except that the
concentration of the hydrophobic colloidal silica was 28% (w/w). The extrusion
rate of the
silicone base was 23 g/min.
Examples 25a and 25b
[0122] In Example 25a, a sample of the silicone composition of Example 24 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 25b, a sample of the silicone composition of Example 24
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to S
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 3.
Example 26
[0123] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example 1 was replaced with 30% (w/w) of the
hydrophobic
colloidal silica of Example 3. The extrusion rate of the silicone base was 44
g/min.
Examples 27a and 27b
[0124] In Example 27a, a sample of the silicone composition of Example 26 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 27b, a sample of the silicone composition of Example 26
was
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34
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 3.
Example 28
[0125] A silicone composition was prepared using the method of Example 26,
except that the
concentration of the hydrophobic colloidal silica was 28% (w/w). The extrusion
rate of the
silicone base was 77 g/min.
Examples 29a and 29b
[0126] In Example 29a, a sample of the silicone composition of Example 28 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 29b, a sample of the silicone composition of Example 28
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 1 SO °C for 10 min, and 200 °C for I h. The physical
properties of the silicone rubber
products are shown in Table 3.
Table 3
Young's Modulus
DurometerTensile (MPa) Tear Light
Hardness StrengthElongationat Elongation StrengthTrans.
=
Example(Shore (MPa) (%) 50% 100% 200%(N/mm) (%)
A)
23a 48 5.13 406 1.09 1.79 2.88_ 83
23b 50 4.95 365 1.22 1.98 3.1433.27 79
25a 47 4.27 389 1.30 1.84 2.68- g3
25b SO 4.94 374 1.400.9 2.20 3.2134.68 82
27a 45 4.96 463 0.92 1.72 2.8141.51 82
27b 51 5.25 364 1.37 2.18 3.38- g2
,
29a 41 4.61 4S3 0.85 1.43 2.3536.08 82
29b 48 5.30 408 1.12 1.85 2.99_ 8I
- ucm~es one property was not measured
Example 30
[0127] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example 1 was replaced with 30% (w/w) of the
hydrophobic
colloidal silica of Example 4. The extrusion rate of the silicone base was 52
g/min.
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Examples 31 a and 31 b
[0128] In Example 31 a, a sample of the silicone composition of Example 30 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 31 b, a sample of the silicone composition of Example
30 was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 4.
Example 32
[0129] A silicone composition was prepared using the method of Example 30,
except that the
concentration of the hydrophobic colloidal silica was 34% (w/w). The extrusion
rate of the
silicone base was 20 g/min.
Examples 33a and 33b
[0130] In Example 33a, a sample of the silicone composition of Example 32 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 33b, a sample of the silicone composition of Example 32
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 4.
Example 34
[0131] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example 1 was replaced with 34% (w/w) of the
hydrophobic
colloidal silica of Example 5. The extrusion rate of the silicone base was 59
g/min.
Examples 35a and 35b
[0132] In Example 35a, a sample of the silicone composition of Example 34 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 1 SO °C
for 10 min. In Example 35b, a sample of the silicone composition of Example 34
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 4.
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Table 4
Young's Modulus
DurometerTensile (MPs) Tear Light
HardnessStrengthElongationat Elongation StrengthTrans.
=
Example(Shore (MPs) (%) 50% 100% 200% (N/mm) (%)
A)
31 a 42 5.20 530 0.94 1.51 2.39 36.60 82
31 b 48 5.78 460 1.24 1.92 2.99 - 79
33a 50 6.27 509 1.32 2.07 3.14 38.53 81
33b 53 6.45 455 1.63 2.45 3.63 - 75
35a 49 6.12 500 1.10 1.91 3.14 39.58 79
35b 49 6.57 527 1.322 2.08 3.28 - 78
- uom~G~ me pruper~y was not measures
Example 36
[0133] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example I was replaced with 30% (w/w) of the
hydrophobic
colloidal silica of Example 6. The extrusion rate of the silicone base was 110
g/min.
Examples 37a and 37b
[0134] In Example 37a, a sample of the silicone composition of Example 36 was
compression
molded under a continuous pressure of 34.5 MPs at room temperature for 3 to 5
min and I 50 °C
for 10 min. In Example 37b, a sample of the silicone composition of Example 36
was
compression molded under a continuous pressure of 34.5 MPs at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 5.
Example 38
[0135] A silicone composition was prepared using the method of Example 36,
except that the
concentration of the hydrophobic colloidal silica was 38% (w/w). The extrusion
rate of the
silicone base was 44 g/min.
Examples 39a and 39b
[0136] In Example 39a, a sample of the silicone composition of Example 38 was
compression
molded under a continuous pressure of 34.5 MPs at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 39b, a sample of the silicone composition of Example 38
was
compression molded under a continuous pressure of 34.5 MPs at room temperature
for 3 to 5
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min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table S.
Example 40
[0137] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example I was replaced with 25% (w/w) of the
hydrophobic
colloidal silica of Example 7 and the mixture of Polymer A, Polymer B, and
hydrophobic
colloidal silica was mixed at room temperature for 1 h instead of 60 °C
for 1 h, immediately
before addition of the Cross-linking Agent.
Examples 41 a and 41 b
[0138] In Example 41a, a sample of the silicone composition of Example 40 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and I50 °C
for 10 min. In Example 41 b, a sample of the silicone composition of Example
40 was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for I 0 min, and 200 °C for I h. The physical
properties of the silicone rubber
products are shown in Table 5.
Table 5
Young's Modulus
DurometerTensile (MPa) Tear Light
Hardness StrengthElongationat Elongation StrengthTrans.
=
Example(Shore (MPa) (%} 50% 100% 200% (N/mm) (%)
A)
37a 16 0.32 82 p,2g _ _ - 70.
37b 19 0.37 75 0.38 - - 0.88 73
39a 36 1.01 64 O,gg _ _ - 69
39b 42 1.26 59 1.10 - - 1.93 67
41a 40 4.27 481 0.74 1.25 2.11 - g6
41 b 42 4.60 421 0.92 1.54 2.57 - g6
- UG11VLGJ II IC pruper~y was not measured
Example 42
[0139] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example 1 was replaced with 34% (w/w) of the
hydrophobic
colloidal silica of Example 8. The extrusion rate of the silicone base was 84
g/min.
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Examples 43a and 43b
[0140] In Example 43a, a sample of the silicone composition of Example 42 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 43b, a sample of the silicone composition of Example 42
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to S
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 6.
Example 44
[0141] A silicone composition was prepared using the method of Example 42,
except that the
concentration of the hydrophobic colloidal silica was 38% (w/w). The extrusion
rate of the
silicone base was 40 g/min.
Examples 45a and 45b
[0142] In Example 45a, a sample of the silicone composition of Example 44 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 45b, a sample of the silicone composition of Example 44
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 6.
Example 46
[0143] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example 1 was replaced with 34% (w/w) of the
hydrophobic
colloidal silica of Example 9.
Examples 47a and 47b
[0144] In Example 47a, a sample of the silicone composition of Example 46 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 47b, a sample of the silicone composition of Example 46
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 6.
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Example 48
[0145] A silicone composition was prepared using the method of Example 46,
except that the
mixture of Polymer A, Polymer B, and hydrophobic colloidal silica was mixed at
room
temperature for 1 h instead of 60 °C for 1 h, immediately before
addition of the Cross-linking
Agent.
Examples 49a and 49b
[0146] In Example 49a, a sample of the silicone composition of Example 48 was
compression
molded under a continuous pressure of 34.5 MPs at room temperature for 3 to S
min and 150 °C
for 10 min. In Example 49b, a sample of the silicone composition of Example 48
was
compression molded under a continuous pressure of 34.5 MPs at room temperature
for 3 to S
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 6.
Example SO
[0147] A silicone composition was prepared using the method of Example 46,
except that the
concentration of the hydrophobic colloidal silica was 43% (w/w). A sample of
the silicone
composition was compression molded under a continuous pressure of 34.5 MPs at
room
temperature for 3 to 5 min and 150 °C for 10 min. The physical
properties of the silicone rubber
product are shown in Table 6.
Table 6
Young's
Modulus
DurometerTensile (MPs) Tear Light
Hardness StrengthElongation at Elongation= StrengthTrans.
Example(Shore (MPs) (%) 50% 100% 200% (N/mm) (%)
A)
43a 41 5.67 651 0.771.23 2.01 36.08 78
43b 43 6.54 574 0.951.51 2.48 - 72
45a 45 6.93 659 1.001.62 2.58 41.15 78
45b 51 7.03 563 1.251.92 2.99 - 73
47a 47 6.01 586 0.911.41 2.39 - 79
47b 50 5.03 408 1.051.64 2.79 - 7g
49a 52 5.94 457 1.121.77 3.01 - g0
49b 54 6.11 409 1.191.92 3.35 - 79
50 53 8.47 612 1.442.24 3.53 - g I
- ucmuo~ me 1J1V~.IGILy was not measures
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Example 51
[0148] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example 1 was replaced with 30% (w/w) of the
hydrophobic
colloidal silica of Example 10. The extrusion rate of the silicone base was 68
g/min.
Examples 52a and 52b
[0149] In Example 52a, a sample of the silicone composition of Example 51 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 52b, a sample of the silicone composition of Example 51
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 7.
Example 53
[0150] A silicone composition was prepared using the method of Example 51,
except that the
concentration of the hydrophobic colloidal silica was 34% (w/w). The extrusion
rate of the
silicone base was 26 g/min.
Examples 54a and 54b
[0151] In Example 54a, a sample of the silicone composition of Example 53 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 54b, a sample of the silicone composition of Example 53
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 7.
Example 55
[0152] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example 1 was replaced with 25% (w/w) of the
hydrophobic
colloidal silica of Example 1 I . The extrusion rate of the silicone base was
150 g/min.
Examples 56a and 56b
[0153] In Example 56a, a sample of the silicone composition of Example 55 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 56b, a sample of the silicone composition of Example 55
was
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compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 7.
Example 57
[0154] A silicone composition was prepared using the method of Example 55,
except that the
concentration of the hydrophobic colloidal silica was 34% (w/w). The extrusion
rate of the
silicone base was 60 g/min.
Examples 58a and 58b
[0155] In Example 58a, a sample of the silicone composition of Example 57 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 58b, a sample of the silicone composition of Example 57
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 7.
Table 7
Young's Modulus
DurometerTensile (MPa) Tear Light
Hardness StrengthElongationat Elongation StrengthTrans.
=
Example(Shore (MPa) % 50% 100% 200%(kN/mm)(%)
A)
52a 42 6.16 567 0.88 1.52 2.5542.03 82
52b 45 5.52 441 1.10 1.83 2.99- 76
54a 49 6.65 530 1.06 1.99 3.2540.28 81
54b 51 6.79 467 1.48 2.38 3.66- 80
56a 38 4.33 440 0.60 1.09 2.00- -
56b 39 4.81 438 0.57 1.12 2.1423.64 78
58a 39 6.27 670 0.79 1.35 2.21- 81
58b 43 6.39 545 1.050.8 1.76 2.8341.15 80
- denotes the property was not measured
Example 59
(0156] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example 1 was replaced with 30% (w/w) of the
hydrophobic
colloidal silica of Example 12. The extrusion rate of the silicone base was
163 g/min.
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Examples 60a and 60b
[0157] In Example 60a, a sample of the silicone composition of Example 59 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 60b, a sample of the silicone composition of Example 59
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 8.
Example 61
[0158] A silicone composition was prepared using the method of Example 59,
except that the
concentration of the hydrophobic colloidal silica was 34%(w/w). The extrusion
rate of the
silicone base was 105 g/min.
Examples 62a and 62b
[0159] In Example 62a, a sample of the silicone composition of Example 61 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 62b, a sample of the silicone composition of Example 61
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 8.
Example 63
[0160] A silicone composition was prepared using the method of Example 59,
except that the
concentration of the hydrophobic colloidal silica was 38% (w/w). The extrusion
rate of the
silicone base was 56 g/min.
Examples 64a and 64b
[0161] In Example 64a, a sample of the silicone composition of Example 63 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to S
min and 150 °C
for 10 min. In Example 64b, a sample of the silicone composition of Example 63
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, I 50 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 8.
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Example 65
[0162] A silicone composition was prepared using the method of Example 14,
except that the
hydrophobic colloidal silica of Example 1 was replaced with 39% (w/w) of the
hydrophobic
colloidal silica of Example 13.
Examples 66a and 66b
[0163] In Example 66a, a sample of the silicone composition of Example 65 was
compression
molded under a continuous pressure of 34.5 MPa at room temperature for 3 to 5
min and 150 °C
for 10 min. In Example 66b, a sample of the silicone composition of Example 65
was
compression molded under a continuous pressure of 34.5 MPa at room temperature
for 3 to 5
min, 150 °C for 10 min, and 200 °C for 1 h. The physical
properties of the silicone rubber
products are shown in Table 8.
Table 8
Young's Modulus
DurometerTensile (MPa) Tear Light
Hardness StrengthElongationat Elongation StrengthTrans.
=
Example(Shore (MPa) % 50% 100% 200% (kN/mm)(%)
A)
60a 37 2.75 285 0.85 1.42 2.30 15.24 86
606 42 3.14 248 1.25 1.90 2.90 - 79
62a 38 3.00 321 0.86 1.51 2.39 14.54 89
62b 44 3.68 329 1.17 1.92 2.91 - 82
64a 44 2.80 247 1.23 1.88 2.66 - 85
64b 48 2.65 190 1.141.3 1.992.92 14.89 87
66a 53 4.78 405 1.30 2.17 - - 87
66b 56 4.62 350 1.41 2.34 - - 85
- denotes the property was not measured
