U.S. patent application number 11/852676 was filed with the patent office on 2008-03-13 for silicone rubber composition for extrusion molding.
This patent application is currently assigned to Shin -Etsu Chemical Co., Ltd.. Invention is credited to Daichi Todoroki.
Application Number | 20080064811 11/852676 |
Document ID | / |
Family ID | 39170563 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080064811 |
Kind Code |
A1 |
Todoroki; Daichi |
March 13, 2008 |
SILICONE RUBBER COMPOSITION FOR EXTRUSION MOLDING
Abstract
Provided is a silicone rubber composition for extrusion molding,
including: (A) 100 parts by mass of an organopolysiloxane
represented by an average composition formula (1):
R.sup.1.sub.nSiO.sub.(4-n)/2 (in the formula, R.sup.1 represents
identical or different, unsubstituted or substituted monovalent
hydrocarbon groups, and n represents a positive number within a
range from 1.95 to 2.04), (B) 0 to 50 parts by mass of a vinyl
group-containing silicon compound, (C) 5 to 100 parts by mass of a
reinforcing silica, and (D) an effective quantity of a curing
agent, in which the vinyl group content relative to the combination
of the components (A) through (D) is at least 1.0.times.10.sup.-4
mol/g. The composition yields a cured product for which the elastic
modulus increases across a temperature range from 30 to 110.degree.
C. and which is therefore capable of reducing the temperature
dependency of acrylic optical fibers. The composition is suitable
for extrusion molding.
Inventors: |
Todoroki; Daichi;
(Annaka-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Shin -Etsu Chemical Co.,
Ltd.
Chiyoda-ku
JP
|
Family ID: |
39170563 |
Appl. No.: |
11/852676 |
Filed: |
September 10, 2007 |
Current U.S.
Class: |
524/588 ;
427/162 |
Current CPC
Class: |
C08L 83/04 20130101;
C08G 77/20 20130101; C08G 77/16 20130101; C08L 83/04 20130101; C08L
83/00 20130101; Y10T 428/31663 20150401; C08G 77/18 20130101; C08G
77/12 20130101 |
Class at
Publication: |
524/588 ;
427/162 |
International
Class: |
C08L 83/04 20060101
C08L083/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 2006 |
JP |
2006-244945 |
Claims
1. A silicone rubber composition for extrusion molding, comprising:
(A) 100 parts by mass of an organopolysiloxane represented by an
average composition formula (1) shown below:
R.sup.1.sub.nSiO.sub.(4-n)/2 (1) (wherein, R.sup.1 represents
identical or different, unsubstituted or substituted monovalent
hydrocarbon groups, and n represents a positive number within a
range from 1.95 to 2.04), (B) 0 to 50 parts by mass of a vinyl
group-containing silicon compound, (C) 5 to 100 parts by mass of a
reinforcing silica, and (D) an effective quantity of a curing
agent, wherein a vinyl group content relative to a combination of
components (A) through (D) is at least 1.0.times.10.sup.-4
mol/g.
2. The composition according to claim 1, wherein a rate of elastic
modulus variation R for a cured product of the composition,
calculated using a formula shown below:
R=(E.sub.100-E.sub.30)/E.sub.30.times.100 (wherein, E.sub.30
represents an elastic modulus of the cured product at 30.degree.
C., and E.sub.100 represents an elastic modulus of the cured
product at 100.degree. C.), is at least 5%.
3. The composition according to claim 1, wherein the component (B)
is at least one selected from the group consisting of vinyl
group-containing silanes and vinyl group-containing silazanes.
4. The composition according to claim 1, wherein the specific
surface area of the component (C) measured using the BET method is
50 m.sup.2/g or greater.
5. The composition according to claim 1, wherein the curing agent
of the component (D) is at least one curing agent selected from the
group consisting of: (i) an organic peroxide, and (ii) a
combination of an organohydrogenpolysiloxane and a platinum group
metal-based catalyst.
6. The composition according to claim 1, further comprising (E) 0.5
to 50 parts by mass of an organosilane or organopolysiloxane
represented by a formula (3) shown below:
R.sup.4O(SiR.sup.3.sub.2O).sub.mR.sup.4 (3) (wherein, R.sup.3
represents identical or different, unsubstituted or substituted
monovalent hydrocarbon groups, m represents a positive number
within a range from 1 to 50, and each R.sup.4 represents,
independently, an alkyl group or a hydrogen atom), per 100 parts by
mass of the component (A).
7. A cured product obtained by curing the composition defined in
claim 1, wherein a rate of elastic modulus variation R for the
cured product, calculated using a formula shown below:
R=(E.sub.100-E.sub.30)/E.sub.30.times.100 (wherein, E.sub.30
represents an elastic modulus of the cured product at 30.degree.
C., and E.sub.100 represents an elastic modulus of the cured
product at 100.degree. C.), is at least 5%.
8. An extrusion molded product comprising the cured product defined
in claim 7.
9. A method for reducing the temperature dependency of an acrylic
optical fiber sensor, comprising: disposing a cured product of the
composition defined in claim 1 between a target material that is to
be measured using the acrylic optical fiber sensor, and the acrylic
optical fiber sensor.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a silicone rubber
composition for extrusion molding that yields a cured product for
which the elastic modulus increases across a temperature range from
30 to 110.degree. C.
[0003] 2. Description of the Prior Art
[0004] Tests are being conducted in which special optical fiber
sensors are embedded within high-performance structural materials
such as composite materials, and these sensors are then used to
continually monitor the structural materials for distortion and the
like. For example, a method has been disclosed for measuring the
internal distortion within a fiber-reinforced composite material
laminate by embedding the sensor portion of an optical fiber
interferometer within the layers of a fiber-reinforced composite
material laminate, and then using the sensor portion to measure the
change in intensity of interference light (see patent reference 1).
Furthermore, a method of embedding an optical fiber in an epoxy
resin cast article such as an insulating molding for a high-voltage
instrument is also known (see patent reference 2). Moreover, a
method of embedding an optical fiber as a sensor within a plastic,
metal, ceramic, concrete, a composite material that has been
reinforced using an inorganic fiber such as SiC or a reinforcing
fiber such as stainless steel fiber, or a laminate comprising a
single material or a number of different materials, is also known
(see patent reference 3).
[0005] Known collision sensors include falling rock sensors (see
patent reference 4) and vehicle collision sensors (see patent
references 5 to 7).
[0006] Acrylic optical fibers exhibit superior flexural strength
and are more readily processed than silica-based optical fibers or
glass-based optical fibers, and are consequently used in a wide
variety of fields. However, the elastic modulus of acrylics
decreases with increasing temperature, meaning acrylic optical
fibers have a large temperature dependency, and are therefore
unsuitable for use as optical fiber sensors.
[0007] Silicone rubbers exhibit excellent weather resistance and
electrical properties, have a low compression set, and exhibit
superior properties of heat resistance and cold resistance and the
like, and are consequently widely used as matrix materials. By
using a liquid silicone rubber for which the elastic modulus
increases with increasing temperature, the temperature dependency
of an acrylic optical fiber sensor can be significantly reduced,
but the workability of such compositions is poor, and they are not
suitable for mass production.
[0008] [Patent Reference 1] JP 4-361126 A
[0009] [Patent Reference 2] JP 11-165324 A
[0010] [Patent Reference 3] JP 2001-082918 A
[0011] [Patent Reference 4] JP 2002-267549 A
[0012] [Patent Reference 5] U.S. Pat. No. 5,335,749
[0013] [Patent Reference 6] WO 01/23224 A1
[0014] [Patent Reference 7] JP 2006-500284 A
SUMMARY OF THE INVENTION
[0015] An object of the present invention is to provide a silicone
rubber composition for extrusion molding, (a) which yields a cured
product for which the elastic modulus increases across a
temperature range from 30 to 110.degree. C. and which is therefore
capable of reducing the temperature dependency of acrylic optical
fibers, and (b) which is suitable for extrusion molding.
[0016] As a result of intensive investigation aimed at achieving
the above object, the inventors of the present invention discovered
that by ensuring that the vinyl group content within an entire
silicone rubber composition is at least 1.0.times.10.sup.-4 mol/g,
a cured product could be obtained for which the elastic modulus
increases across the temperature range from 30 to 110.degree. C.,
and they were therefore able to complete the present invention.
[0017] Accordingly, a first aspect of the present invention
provides a silicone rubber composition for extrusion molding,
comprising:
[0018] (A) 100 parts by mass of an organopolysiloxane represented
by an average composition formula (1) shown below:
R.sup.1.sub.nSiO.sub.(4-n)/2 (1)
(wherein, R.sup.1 represents identical or different, unsubstituted
or substituted monovalent hydrocarbon groups, and n represents a
positive number within a range from 1.95 to 2.04),
[0019] (B) 0 to 50 parts by mass of a vinyl group-containing
silicon compound,
[0020] (C) 5 to 100 parts by mass of a reinforcing silica, and
[0021] (D) an effective quantity of a curing agent, wherein
[0022] the vinyl group content relative to the combination of the
components (A) through (D) is at least 1.0.times.10.sup.-4
mol/g.
[0023] A second aspect of the present invention provides a cured
product obtained by curing the above composition, wherein a rate of
elastic modulus variation R for the cured product, calculated using
a formula shown below:
R=(E.sub.100-E.sub.30)/E.sub.30.times.100
(wherein, E.sub.30 represents an elastic modulus of the cured
product at 30.degree. C., and E.sub.100 represents an elastic
modulus of the cured product at 100.degree. C.), is at least
5%.
[0024] A third aspect of the present invention provides an
extrusion molded product comprising the above cured product.
[0025] A fourth aspect of the present invention provides a method
for reducing the temperature dependency of an acrylic optical fiber
sensor, comprising:
[0026] disposing a cured product of the above composition between a
target material that is to be measured using the acrylic optical
fiber sensor, and the acrylic optical fiber sensor.
[0027] According to a silicone rubber composition for extrusion
molding of the present invention, a molded product can be obtained
for which the elastic modulus increases across the temperature
range from 30 to 110.degree. C. A cured product of the composition
of the present invention is useful in reducing the temperature
dependency of acrylic optical fiber sensors.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] As follows is a more detailed description of the present
invention. In the present invention, viscosity values represent
values measured using a rotational viscometer.
[Component (A)]
[0029] The organopolysiloxane of the component (A) is represented
by an average composition formula (1) shown below:
R.sup.1.sub.nSiO.sub.(4-n)/2 (1)
(wherein, R.sup.1 represents identical or different, unsubstituted
or substituted monovalent hydrocarbon groups, and n represents a
positive number within a range from 1.95 to 2.04).
[0030] In the above formula (1), examples of R.sup.1 include
identical or different, unsubstituted or substituted monovalent
hydrocarbon groups, typically of 1 to 20 carbon atoms, and
preferably of 1 to 12, and even more preferably 1 to 8, carbon
atoms. Specific examples of R.sup.1 include alkyl groups such as a
methyl group, ethyl group, propyl group or butyl group; cycloalkyl
groups such as a cyclohexyl group; alkenyl groups such as a vinyl
group, allyl group, butenyl group, or hexenyl group; aryl groups
such as a phenyl group or tolyl group; aralkyl groups such as a
.beta.-phenylpropyl group; and groups in which either a portion of,
or all of, the hydrogen atoms bonded to carbon atoms within the
above hydrocarbon groups have been substituted with a halogen atom
or a cyano group or the like, such as a chloromethyl group,
trifluoropropyl group or cyanoethyl group.
[0031] In the above formula (1), n represents a positive number
within a range from 1.95 to 2.04, and is preferably from 1.98 to
2.02. If the value of n is not within this range from 1.95 to 2.04,
then the cured product of the resulting composition may not exhibit
satisfactory rubber-like elasticity.
[0032] The molecular chain terminals of the organopolysiloxane of
the component (A) are preferably terminated with trimethylsilyl
groups, dimethylvinylsilyl groups, dimethylhydroxysilyl groups,
methyldivinylsilyl groups or trivinylsilyl groups or the like, and
are most preferably terminated with silyl groups that contain at
least one vinyl group (such as dimethylvinylsilyl groups,
methyldivinylsilyl groups and trivinylsilyl groups).
[0033] The organopolysiloxane of the component (A) contains at
least two alkenyl groups bonded to silicon atoms within each
molecule, and more specifically, from 0.001 to 10 mol %, and
preferably from 0.01 to 5 mol %, of the R.sup.1 groups are alkenyl
groups. These alkenyl groups are preferably vinyl groups or allyl
groups, and vinyl groups are particularly preferred.
[0034] The average polymerization degree of the organopolysiloxane
of the component (A) is preferably at least 100, is even more
preferably within a range from 3,000 to 100,000, and is most
preferably from 4,000 to 20,000. The average polymerization degree
can be determined by measuring the number average molecular weight
by GPC (gel permeation chromatography), using polystyrenes as
molecular weight markers, and then calculating the polymerization
degree using the formula shown below.
Average polymerization degree=number average molecular
weight/molecular weight of a repeating unit within the component
(A)
[0035] In those cases where the component (A) comprises a plurality
of different repeating units, the term "molecular weight of a
repeating unit within the component (A)" used within the above
formula refers to the number average molecular weight of that
plurality of repeating units.
[0036] The organopolysiloxane of the component (A) may use either a
single compound, or a mixture of two or more organopolysiloxanes
with different average polymerization degrees or molecular
structures or the like.
[Component (B)]
[0037] The vinyl group-containing silicon compound of the component
(B) is an optional component that may be used as necessary within
the present invention. The component (B) may use either a single
compound, or a mixture of two or more different compounds. Examples
of the component (B) include vinyl group-containing silanes and
vinyl group-containing silazanes.
[0038] Specific examples of suitable vinyl group-containing silanes
include vinyltrichlorosilane, vinyltrimethoxysilane,
vinyltriethoxysilane, and p-styryltrimethoxysilane. An example of
suitable vinyl group-containing silazane is
1,3-divinyl-1,1,3,3-tetramethylsilazane.
[0039] The quantity added of the component (B) is typically not
more than 50 parts by mass (namely, from 0 to 50 parts by mass),
and preferably not more than 20 parts by mass (namely, from 0 to 20
parts by mass), per 100 parts by mass of the component (A). If this
quantity exceeds 50 parts by mass, then the resulting silicone
rubber composition is prone to developing adhesiveness. In those
cases where the component (B) is added to the composition of the
present invention, the lower limit for the quantity added is
typically at least 0.01 parts by mass per 100 parts by mass of the
component (A).
[Component (C)]
[0040] The reinforcing silica of the component (C) is used to
ensure that a silicone rubber with excellent mechanical strength is
obtained. The specific surface area of the reinforcing silica of
the component (C) is preferably 50 m.sup.2/g or greater, and is
even more preferably within a range from 100 to 400 m.sup.2/g. The
specific surface area is measured using the BET method. The
component (C) may use either a single material, or a combination of
two or more different materials.
[0041] Examples of the reinforcing silica of the component (C)
include any of the silica materials that have conventionally been
used as reinforcing fillers for silicone rubbers, and specific
examples include fumed silica and precipitated silica.
[0042] These reinforcing silica materials may be used in untreated
form, or if required, may be subjected to a preliminary surface
treatment using an organopolysiloxane, organopolysilazane,
chlorosilane, or alkoxysilane or the like.
[0043] The blend quantity of the component (C) is typically within
a range from 5 to 100 parts by mass, and is preferably from 10 to
70 parts by mass, per 100 parts by mass of the organopolysiloxane
of the component (A). If this blend quantity is too large, then the
workability of the resulting silicone rubber composition tends to
deteriorate. In contrast, if the blend quantity is too small, then
the cured product obtained by curing the silicone rubber
composition may not exhibit satisfactory levels of mechanical
strength such as tensile strength and tear strength.
[Component (D)]
[0044] The component (D) may employ any conventional curing agent
used during either normal pressure hot air vulcanization or steam
vulcanization of a silicone rubber. Examples of preferred curing
agents for the component (D) include (i) organic peroxides, (ii)
conventional combinations of an organohydrogenpolysiloxane and a
platinum group metal-based catalyst that act as an addition
reaction curing agent for the silicone rubber, as well as
combinations of (i) and (ii). Of these possibilities, organic
peroxides are particularly desirable. In any of the above cases,
the component (D) is used in an effective quantity.
(i) Organic Peroxides
[0045] A silicone rubber can be produced with ease by subjecting
the composition of the present invention to heat curing in the
presence of an organic peroxide. This organic peroxide may use
either a single compound, or a combination of two or more different
compounds. Specific examples of suitable organic peroxides include
chlorine-free organic peroxides such as benzoyl peroxide,
para-methylbenzoyl peroxide, ortho-methylbenzoyl peroxide,
2,5-dimethyl-2,5-di-t-butylperoxyhexane, t-butyl peroxybenzoate,
dicumyl peroxide, and cumyl-t-butyl peroxide. In the case of normal
pressure hot air vulcanization, acyl-based organic peroxides such
as benzoyl peroxide, para-methylbenzoyl peroxide and
ortho-methylbenzoyl peroxide are particularly preferred.
[0046] The quantity added of the organic peroxide is preferably
within a range from 0.1 to 10 parts by mass, and even more
preferably from 0.3 to 5 parts by mass, per 100 parts by mass of
the organopolysiloxane of the component (A). Provided the quantity
falls within this range, the level of cross-linking is
satisfactory, and the curing rate can be increased easily by
increasing the quantity of the organic peroxide, which is desirable
from an economic viewpoint.
(ii) Combinations of an Organohydrogenpolysiloxane and a Platinum
Group Metal-Based Catalyst
[0047] Platinum Group Metal-Based Catalyst
[0048] In those cases where the composition of the present
invention is cured via an addition reaction, an aforementioned
combination of an organohydrogenpolysiloxane and a platinum group
metal-based catalyst (ii) is used. The platinum group metal-based
catalyst used in this addition reaction is a catalyst that promotes
an addition reaction between the aliphatic unsaturated groups (such
as alkenyl groups or diene groups) within the component (A) and the
vinyl groups within the component (B), and the silicon atom-bonded
hydrogen atoms (namely, SiH groups) of the
organohydrogenpolysiloxane within the curing agent (ii). The
platinum group metal-based catalyst may use either a single
catalyst or a combination of two or more different catalysts.
[0049] Examples of the platinum group metal-based catalyst include
simple platinum group metals and compounds thereof, and those
materials conventionally used as catalysts within addition
reaction-curable silicone rubber compositions can be used. Specific
examples of such catalysts include fine particles of platinum metal
adsorbed to a carrier such as silica, alumina or silica gel,
platinic chloride, chloroplatinic acid, an alcohol solution of
chloroplatinic acid hexahydrate, as well as palladium catalysts and
rhodium catalysts, although of these, catalysts containing platinum
are preferred.
[0050] The quantity added of the platinum group metal-based
catalyst need only be sufficient to enable effective acceleration
of the aforementioned addition reaction, and a typical quantity,
calculated as a quantity of the platinum group metal relative to
the quantity of the organopolysiloxane of the component (A), is
within a range from 1 ppm (by mass, this also applies below) to 1%
by mass, and a quantity from 10 to 500 ppm is preferred. Provided
the quantity falls within this range, the addition reaction can be
satisfactorily accelerated, curing occurs satisfactorily, and the
rate of the addition reaction can be increased easily by increasing
the quantity of the catalyst, which is desirable from an economic
viewpoint.
[0051] Organohydrogenpolysiloxane
[0052] The organohydrogenpolysiloxane may be a straight-chain,
cyclic or branched structure, provided it contains two or more, and
preferably three or more, SiH groups within each molecule. The
organohydrogenpolysiloxane may use either a single compound, or a
combination of two or more different compounds. Examples of this
organohydrogenpolysiloxane include conventional
organohydrogenpolysiloxanes used as cross-linking agents within
addition reaction-curable silicone rubber compositions, and
specific examples include the organohydrogenpolysiloxanes
represented by the average composition formula (2) shown below.
R.sup.2.sub.pH.sub.qSiO.sub.(4-p-q)/2 (2)
(wherein, R.sup.2 represents identical or different, unsubstituted
or substituted monovalent hydrocarbon groups, and p and q are
positive numbers that satisfy 0.ltoreq.p<3, 0<q.ltoreq.3, and
0<p+q.ltoreq.3, and preferably satisfy 1.ltoreq.p.ltoreq.2.2,
0.002.ltoreq.q.ltoreq.1, and 1.002.ltoreq.p+q.ltoreq.3)
[0053] In the above average composition formula (2), examples of
R.sup.2 include identical or different, unsubstituted or
substituted monovalent hydrocarbon groups, preferably of 1 to 12
carbon atoms, and even more preferably of 1 to 8 carbon atoms, and
these groups preferably contain no aliphatic unsaturated bonds.
Specific examples of R.sup.2 include alkyl groups such as a methyl
group, ethyl group, or propyl group; cycloalkyl groups such as a
cyclohexyl group; alkenyl groups such as a vinyl group, allyl
group, butenyl group, or hexenyl group; aryl groups such as a
phenyl group or tolyl group; aralkyl groups such as a benzyl group,
2-phenylethyl group, or 2-phenylpropyl group; and groups in which
either a portion of, or all of, the hydrogen atoms within the above
hydrocarbon groups have been substituted with halogen atoms or the
like such as fluorine atoms, including a 3,3,3-trifluoropropyl
group.
[0054] In those cases where this organohydrogenpolysiloxane is a
straight-chain structure, the SiH groups may be located solely at
the molecular chain terminals, solely at non-terminal positions, or
may also exist at both of these locations. Furthermore, the
viscosity of this organohydrogenpolysiloxane at 25.degree. C. is
preferably within a range from 0.5 to 10,000 mm.sup.2/s, and is
even more preferably from 1 to 300 mm.sup.2/s.
[0055] Specific examples of this type of organohydrogenpolysiloxane
include the compounds with the structural formulas shown below.
##STR00001##
(wherein, k represents an integer from 2 to 10, and s and t each
represent an integer from 0 to 10)
[0056] The blend quantity of the above organohydrogenpolysiloxane
is preferably sufficient that for each 1 mol of the combination of
aliphatic unsaturated bonds (such as alkenyl groups or diene
groups) within the component (A) and vinyl groups within the
component (B), the quantity of SiH groups within the
organohydrogenpolysiloxane is within a range from 0.5 to 5 mols,
and even more preferably from 0.8 to 4 mols. Provided the blend
quantity falls within this range, the level of cross-linking is
satisfactory, and the mechanical strength following curing is
adequate. This blend quantity can usually be achieved by adding
from 0.1 to 50 parts by mass of the above
organohydrogenpolysiloxane per 100 parts by mass of the component
(A).
[Other Components]
[0057] In addition to the components described above, an
organosilane or organopolysiloxane represented by a formula (3)
shown below (hereafter referred to as the component (E)) may also
be added to the composition of the present invention if
required.
R.sup.4O(SiR.sup.3.sub.2O).sub.mR.sup.4 (3)
(wherein, R.sup.3 represents identical or different, unsubstituted
or substituted monovalent hydrocarbon groups, m represents a
positive number within a range from 1 to 50, and each R.sup.4
represents, independently, an alkyl group or a hydrogen atom)
[0058] The component (E) contains alkoxy groups or hydroxyl groups
at the molecular chain terminals. This component (E) functions as a
treatment agent for treating the reinforcing silica of the
component (C). The component (E) may use either a single compound,
or a combination of two or more different compounds.
[0059] In the above formula (3), examples of R.sup.3 include alkyl
groups such as a methyl group, ethyl group, propyl group or butyl
group; cycloalkyl groups such as a cyclohexyl group; alkenyl groups
such as a vinyl group, allyl group, butenyl group, or hexenyl
group; aryl groups such as a phenyl group or tolyl group; aralkyl
groups such as a .beta.-phenylpropyl group; and groups in which
either a portion of, or all of, the hydrogen atoms bonded to carbon
atoms within the above hydrocarbon groups have been substituted
with a halogen atom or a cyano group or the like, such as a
chloromethyl group, trifluoropropyl group or cyanoethyl group, and
from the viewpoint of achieving favorable compatibility with the
organopolysiloxane of the component (A), the R.sup.3 groups are
preferably the same as the monovalent hydrocarbon groups R.sup.1,
or the combination of R.sup.1 groups, employed within the component
(A).
[0060] In the above formula (3), examples of R.sup.4 include a
hydrogen atom, or an alkyl group such as a methyl group, ethyl
group, propyl group or butyl group.
[0061] In the formula (3), the average polymerization degree m is
within a range from 1 to 50, and is preferably within a range from
2 to 30. Provided the value of m is within this range, the effect
of the component (E) as a treatment agent for treating the
reinforcing silica of the component (C) can be satisfactorily
realized. The average polymerization degree can be determined in
the manner described above.
[0062] In those cases where the component (E) is added to the
composition of the present invention, the blend quantity is
preferably within a range from 0.5 to 50 parts by mass per 100
parts by mass of the component (A). Provided the blend quantity is
within this range, the resulting silicone rubber composition can be
prevented from developing adhesiveness, kneading of the composition
is facilitated, and replasticization can be more readily
suppressed.
[0063] In addition to the components described above, if required,
the composition of the present invention may also include ground
quartz, non-reinforcing silica such as crystalline silica, carbon
blacks such as acetylene black, furnace black and channel black,
fillers such as calcium carbonate, other additives such as
colorants, tear strength improvers, heat resistance improvers,
flame retardancy improvers, acid receivers, and thermal
conductivity improvers, and release agents or filler dispersants
such as the various alkoxysilanes, and particularly phenyl
group-containing alkoxysilanes or the hydrolysis-condensation
products thereof, diphenylsilanediol, carbon functional silanes,
and low molecular weight siloxanes that contain silanol groups.
[Vinyl Group Content]
[0064] In the present invention, the vinyl group content relative
to the combination of the components (A) through (D) is at least
1.0.times.10.sup.-4 mol/g, and is preferably within a range from
1.0.times.10.sup.-4 to 1.0.times.10.sup.-2 mol/g. If the content is
less than 1.0.times.10.sup.-4 mol/g, then the cured product of the
resulting composition is less likely to exhibit an increasing
elastic modulus across the temperature range from 30 to 110.degree.
C.
[Rate of Elastic Modulus Variation]
[0065] The composition of the present invention yields a cured
product for which the elastic modulus increases across the
temperature range from 30 to 110.degree. C. Specifically, the
composition yields a cured product for which the rate of elastic
modulus variation R, calculated using the formula shown below:
R=(E.sub.100-E.sub.30)/E.sub.30.times.100
(wherein, E.sub.30 represents the elastic modulus of the cured
product at 30.degree. C., and E.sub.100 represents the elastic
modulus of the cured product at 100.degree. C.), is preferably at
least 5%. The elastic modulus is measured using a solid
viscoelasticity measurement apparatus, at a frequency of 30 Hz and
a rate of temperature increase of 5.degree. C./minute.
[Production Method]
[0066] The silicone rubber composition of the present invention can
be obtained by uniformly mixing the components described above
using a rubber kneader such as a two roll mill, Banbury mixer, or
dough mixer (kneader) or the like. A heat treatment (for example,
mixing under heating at 80 to 250.degree. C.) may also be conducted
if required. All of the components may be mixed together
simultaneously at room temperature, or the components (A) to (C)
and any other components may be mixed together first under heat,
and the component (D) then mixed into the resulting mixture at room
temperature.
[Extrusion Molding]
[0067] The silicone rubber composition obtained in this manner can
be molded by extrusion molding in accordance with the intended
application of the composition. The curing temperature may be
selected in accordance with factors such as the nature of the
curing agent, the extrusion method employed, and the thickness of
the target molded article, but is typically within a range from 80
to 500.degree. C.
[Applications]
[0068] By disposing a cured product of the composition of the
present invention between a target material that is to be measured
using an acrylic optical fiber sensor, and the acrylic optical
fiber sensor, the temperature dependency of the acrylic optical
fiber sensor can be reduced. In such cases, the cured product may
be sandwiched between the material and the acrylic optical fiber
sensor, an acrylic optical fiber sensor that has been
surface-coated with the cured product may be embedded within the
material, or the acrylic optical fiber sensor (which may be either
surface-coated with the cured product or not surface-coated) may be
embedded within a material in which the surface that contacts the
optical fiber sensor has been coated with the cured product.
EXAMPLES
[0069] As follows is a description of specifics of the present
invention using a series of examples and comparative examples,
although the present invention is in no way limited by the examples
presented below. Unless stated otherwise, operations were conducted
at room temperature (25.degree. C.).
Example 1
[0070] 100 parts by mass of an organopolysiloxane consisting of
99.431 mol % of dimethylsiloxane units, 0.544 mol % of
methylvinylsiloxane units and 0.025 mol % of dimethylvinylsiloxane
units, and with an average polymerization degree of approximately
8,000, 20 parts by mass of a fumed silica with a BET specific
surface area of 200 m.sup.2/g (product name: Aerosil (a registered
trademark) 200, manufactured by Nippon Aerosil Co., Ltd.), 4 parts
by mass of a dimethylpolysiloxane having silanol groups at both
terminals and with an average polymerization degree of 15, 0.45
parts by mass of vinyltrimethoxysilane, and 0.01 parts by mass of
1,3-divinyl-1,1,3,3-tetramethyldisilazane were placed in a kneader
and subjected to kneading under heating at 180.degree. C. for two
hours, thus yielding a base compound. To 100 parts by mass of this
base compound was added 0.8 parts by mass of
1,6-hexanediol-t-butylperoxycarbonate as a cross-linking agent, and
the resulting mixture was mixed uniformly using a two roll mill,
yielding a composition 1.
Example 2
[0071] 100 parts by mass of an organopolysiloxane consisting of
99.5 mol % of dimethylsiloxane units, 0.475 mol % of
methylvinylsiloxane units and 0.025 mol % of dimethylvinylsiloxane
units, and with an average polymerization degree of approximately
8,000, 22 parts by mass of a fumed silica with a BET specific
surface area of 300 m.sup.2/g (product name: Aerosil 300,
manufactured by Nippon Aerosil Co., Ltd.), 0.5 parts by mass of
vinyltrimethoxysilane, 3 parts by mass of a methylvinylpolysiloxane
with an average polymerization degree of 15 and a vinyl group
content of 0.0013 mol/g, and 0.01 parts by mass of
1,3-divinyl-1,1,3,3-tetramethyldisilazane were placed in a kneader
and subjected to kneading under heating at 180.degree. C. for two
hours, thus yielding a base compound. To 100 parts by mass of this
base compound was added 0.8 parts by mass of
1,6-hexanediol-t-butylperoxycarbonate as a cross-linking agent, and
the resulting mixture was mixed uniformly using a two roll mill,
yielding a composition 2.
Example 3
[0072] 100 parts by mass of an organopolysiloxane consisting of
99.85 mol % of dimethylsiloxane units, 0.125 mol % of
methylvinylsiloxane units and 0.025 mol % of dimethylvinylsiloxane
units, and with an average polymerization degree of approximately
8,000, 1 part by mass of a dimethylpolysiloxane with both molecular
chain terminals blocked with dimethylvinylsiloxy groups and with a
viscosity at 25.degree. C. of 5,000 mPa.s, 1 part by mass of an
organopolysiloxane resin consisting of 6.5 mol % of
(CH.sub.3).sub.2(CH.sub.2.dbd.CH)SiO.sub.1/2 units, 54 mol % of
SiO.sub.2 units and 39.5 mol % of (CH.sub.3).sub.3SiO.sub.1/2
units, 22 parts by mass of a fumed silica with a BET specific
surface area of 300 m.sup.2/g (product name: Aerosil 300,
manufactured by Nippon Aerosil Co., Ltd.), 0.5 parts by mass of
vinyltrimethoxysilane, 3 parts by mass of a methylvinylpolysiloxane
with an average polymerization degree of 15 and a vinyl group
content of 0.0013 mol/g, and 0.01 parts by mass of
1,3-divinyl-1,1,3,3-tetramethyldisilazane were placed in a kneader
and subjected to kneading under heating at 180.degree. C. for two
hours, thus yielding a base compound. To 100 parts by mass of this
base compound was added 0.8 parts by mass of
1,6-hexanediol-t-butylperoxycarbonate as a cross-linking agent, and
the resulting mixture was mixed uniformly using a two roll mill,
yielding a composition 3.
Comparative Example 1
[0073] 84 parts by mass of an organopolysiloxane consisting of
99.85 mol % of dimethylsiloxane units, 0.125 mol % of
methylvinylsiloxane units and 0.025 mol % of dimethylvinylsiloxane
units, and with an average polymerization degree of approximately
8,000, 16 parts by mass of an organopolysiloxane consisting of
99.985 mol % of dimethylsiloxane units and 0.025 mol % of
dimethylvinylsiloxane units, and with an average polymerization
degree of approximately 8,000, 47 parts by mass of a fumed silica
with a BET specific surface area of 200 m.sup.2/g (product name:
Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.), 20 parts by
mass of a dimethylpolysiloxane having silanol groups at both
terminals and with an average polymerization degree of 15, and 0.15
parts by mass of vinyltrimethoxysilane were placed in a kneader and
subjected to kneading under heating at 180.degree. C. for two
hours, thus yielding a base compound. To 100 parts by mass of this
base compound was added 0.8 parts by mass of
1,6-hexanediol-t-butylperoxycarbonate as a cross-linking agent, and
the resulting mixture was mixed uniformly using a two roll mill,
yielding a composition 4.
Comparative Example 2
[0074] 100 parts by mass of an organopolysiloxane consisting of
99.85 mol % of dimethylsiloxane units, 0.125 mol % of
methylvinylsiloxane units and 0.025 mol % of dimethylvinylsiloxane
units, and with an average polymerization degree of approximately
8,000, 40 parts by mass of a precipitated silica with a BET
specific surface area of 201 m.sup.2/g (product name: NIPSIL (a
registered trademark)-LP, manufactured by Nippon Silica Industry
Co., Ltd.), and 8 parts by mass of a dimethylpolysiloxane having
silanol groups at both terminals and with an average polymerization
degree of 15 were placed in a kneader and subjected to kneading
under heating at 180.degree. C. for two hours, thus yielding a base
compound. To 100 parts by mass of this base compound was added 0.8
parts by mass of 1,6-hexanediol-t-butylperoxycarbonate as a
cross-linking agent, and the resulting mixture was mixed uniformly
using a two roll mill, yielding a composition 5.
Comparative Example 3
[0075] 60 parts by mass of a dimethylpolysiloxane with both
molecular chain terminals blocked with dimethylvinylsiloxy groups
and with a viscosity at 25.degree. C. of 5,000 mPa.s, 15 parts by
mass of a dimethylpolysiloxane with both molecular chain terminals
blocked with dimethylvinylsiloxy groups and with a viscosity at
25.degree. C. of 1,000 mPa.s, 25 parts by mass of an
organopolysiloxane resin consisting of 6.5 mol % of
(CH.sub.3).sub.2(CH.sub.2.dbd.CH)SiO.sub.1/2 units, 54 mol % of
SiO.sub.2 units and 39.5 mol % of (CH.sub.3).sub.3SiO.sub.1/2
units, 4.4 parts by mass of a methylvinylpolysiloxane with an
average polymerization degree of 15 and a vinyl group content of
0.0013 mol/g, 10 parts by mass of a methylhydrogenpolysiloxane
having SiH groups at both molecular chain terminals and at
non-terminal positions within the molecular chain (SiH group
content: 0.0060 mol/g) and with an average polymerization degree of
17, and 0.25 parts by mass of a complex of chloroplatinic acid and
divinyltetramethyldisiloxane (platinum atom concentration: 1% by
mass) as a hydrosilylation catalyst were mixed together in a two
roll mill, yielding a composition 6.
[Preparation of Test Specimens and Test Sheets]
[0076] Each of the compositions 1 to 5 was subjected to press
curing for 10 minutes under conditions including a temperature of
165.degree. C. and a pressure of 100 kgf/cm.sup.2, and was then
subjected to secondary vulcanization at 200.degree. C. for 4 hours,
thus preparing test sheets and test specimens appropriate for each
of the measurements described below. The composition 6 was
subjected to press curing for 10 minutes under conditions including
a temperature of 120.degree. C. and a pressure of 100 kgf/cm.sup.2,
and was then subjected to secondary vulcanization at 150.degree. C.
for one hour, thus preparing test sheets and test specimens
appropriate for each of the measurements described below.
[Elastic modulus, Rate of Elastic Modulus Variation]
[0077] A test specimen with a thickness of 2 mm, a width of 5 mm
and a length of 20 mm was used. Using a solid viscoelasticity
measurement apparatus (manufactured by Yoshimizu Corporation), the
elastic modulus of the test specimen was measured at a frequency of
30 Hz and a rate of temperature increase of 5.degree. C./minute.
The rate of elastic modulus variation (%) was calculated using the
formula below:
[(Elastic modulus at 110.degree. C.)-(elastic modulus at 30.degree.
C.)]/(elastic modulus at 30.degree. C.).times.100
[0078] The results are shown in Table 1.
[Density, Hardness, Tensile Strength, and Breaking Elongation]
[0079] Test sheets prepared in accordance with JIS K 6249 were
measured for density, hardness, tensile strength, and breaking
elongation in accordance with the methods described in JIS K 6249.
The results are shown in Table 1.
[Rebound Resilience]
[0080] A test specimen prepared in accordance with JIS K 6255 was
measured for rebound resilience in accordance with the method
described in JIS K 6255. The results are shown in Table 1.
[Extrusion Performance]
[0081] Using an extruder of 60 mm.PHI., each of the compositions 1
to 5 was extruded in a circular cylindrical form from a circular
die with a diameter of 2.5 mm, and then cured at 200.degree. C.,
and those compositions for which no foaming was detectable were
evaluated as having favorable extrusion performance and were
recorded in Table 1 using the symbol O. If foaming was noticeable,
then the extrusion performance was evaluated as poor, and was
recorded in Table 1 using the symbol .DELTA.. The composition 6 was
liquid, and could therefore not be extruded. It is recorded in
Table 1 using the symbol x.
TABLE-US-00001 TABLE 1 Comparative Comparative Comparative Example
1 Example 2 Example 3 example 1 example 2 example 3 Vinyl group
content (mol/g) 1.0 .times. 10.sup.-4 2.5 .times. 10.sup.-4 3.2
.times. 10.sup.-4 2.1 .times. 10.sup.-5 1.5 .times. 10.sup.-5 2.9
.times. 10.sup.-4 Elastic modulus (MPa) 30.degree. C. 2.8 4.8 4.1
5.7 3.1 2.7 Rate of elastic modulus 16 17 15 -17 9 25 variation (%)
Density (g/cm.sup.3) 1.08 1.09 1.08 1.16 1.15 1.02 Hardness
(durometer A) 54 63 54 61 51 58 Tensile strength (MPa) 5.9 3.8 3.9
9.2 7.8 8.2 Breaking elongation (%) 260 120 220 560 360 130 Rebound
resilience (%) 84 87 84 53 74 78 Extrusion performance
.largecircle. .largecircle. .largecircle. .largecircle. .DELTA.
X
* * * * *