U.S. patent application number 09/753772 was filed with the patent office on 2001-10-04 for method for producing suspension of crosslinked silicone particles.
Invention is credited to Kobayashi, Kazuo, Morita, Yoshitsugu, Tanaka, Ken.
Application Number | 20010027233 09/753772 |
Document ID | / |
Family ID | 18575834 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010027233 |
Kind Code |
A1 |
Kobayashi, Kazuo ; et
al. |
October 4, 2001 |
Method for producing suspension of crosslinked silicone
particles
Abstract
A suspension containing crosslinked silicone particles with a
lower mean particle diameter and a better dispersion in certain
organic resins is prepared by emulsifying a condensation
crosslinkable silicone composition containing (A) an
organopolysiloxane having at least two silanol groups per molecule
and (B) a crosslinker, but no (C) condensation catalyst, in water
using a surfactant. A tin (II) salt of an organic acid with no more
than ten carbon atoms is then emulsified in water with a
surfactant, and added as the component (C) to the emulsion of
condensation crosslinkable silicone composition. This crosslinks
the emulsion of condensation crosslinkable silicone
composition.
Inventors: |
Kobayashi, Kazuo; (Chiba
Prefecture, JP) ; Morita, Yoshitsugu; (Chiba
Prefecture, JP) ; Tanaka, Ken; (Chiba Prefecture,
JP) |
Correspondence
Address: |
Dow Corning Corporation
Intellectual Property Department
Mail C01232
P. O. Box 994
Midland
MI
48686-0994
US
|
Family ID: |
18575834 |
Appl. No.: |
09/753772 |
Filed: |
January 3, 2001 |
Current U.S.
Class: |
524/588 |
Current CPC
Class: |
Y10T 428/2995 20150115;
Y10T 428/2991 20150115; C08J 2383/04 20130101; C08J 3/26 20130101;
C08J 3/215 20130101 |
Class at
Publication: |
524/588 |
International
Class: |
C08J 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 29, 2000 |
JP |
JP2000-054602 |
Claims
1. A method of making a suspension of crosslinked silicone
particles having a mean particle diameter of 0.1-500 .mu.m
comprising forming a condensation crosslinkable silicone
composition containing an organopolysiloxane (A) having at least
two silanol groups per molecule and a crosslinker (B), but without
a condensation catalyst (C); emulsifying the condensation
crosslinkable silicone composition (A) and (B) in water using a
surfactant; forming an emulsion of a tin (II) salt of an organic
acid with no more than ten carbon atoms, in water using a
surfactant; adding the tin (II) salt emulsion as the condensation
catalyst (C) to the emulsion of the condensation crosslinkable
silicone composition (A) and (B), in order to crosslink the
condensation crosslinkable silicone composition (A) and (B)
resulting in the formation of the suspension of crosslinked
silicone particles having a mean particle diameter of 0.1-500
.mu.m.
2. A method according to claim 1 in which the tin (II) salt
emulsion has a mean particle diameter of no more than 10 .mu.m.
3. A method according to claim 1 in which the tin (II) salt is
formed from a saturated organic fatty acid with no more than 10
carbon atoms.
4. A method according to claim 3 in which the tin (II) salt is tin
(II) octanoate.
5. A method according to claim 1 in which crosslinker (B) is a
silane with at least three silicon bonded hydrolyzable groups per
molecule or a partially hydrolyzed condensate thereof.
6. A method according to claim 1 in which the condensation
crosslinkable silicone composition (A) and (B) includes an
organoalkoxysilane (D) with at least one group selected from the
group consisting of an alkyl group with five or more carbon atoms,
a (meth)acrylic group, an epoxy group, a mercapto group, an amino
group, an alkenyl group, or partially hydrolyzed condensates
thereof.
7. A suspension of crosslinked silicone particles prepared
according to the method defined in claim 1.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO A MICROFICHE APPENDIX
[0003] Not applicable.
FIELD OF THE INVENTION
[0004] This invention is directed to a method for crosslinking a
condensation crosslinkable silicone composition to produce
crosslinked silicone particles. In particular, it relates to a
method for efficiently producing crosslinked silicone particles
with a lower mean particle diameter and better dispersion in
organic resins.
BACKGROUND OF THE INVENTION
[0005] In Japanese Unexamined Patent Applications Kokai No.
63-202658/EP 350 519 (Jan. 17, 1990), Kokai No. 64-70558/EP 304 946
(Mar. 1, 1989), and Kokai No. 10-36674, methods are described for
producing crosslinked silicone particles, in which a condensation
crosslinkable silicone composition containing an organopolysiloxane
with at least two silanol groups per molecule, a crosslinker, and a
condensation catalyst, is crosslinked while emulsified in water
using a surfactant.
[0006] However, when such a condensation crosslinkable silicone
composition is emulsified in water with a surfactant, the
crosslinker and condensation catalyst are mixed as a separately
blended silicone composition is cooled. Unless the silicone
composition mixed in this manner is emulsified in cold water,
problems occur such that the composition continues to undergo
crosslinking while emulsified, making it impossible to achieve a
homogenous emulsion. Crosslinked silicone particles also have a
large mean particle diameter.
[0007] These Kokai applications provide that the condensation
crosslinkable silicone composition can be emulsified in water and
then crosslinked by addition of the condensation catalyst, but
after the condensation crosslinkable silicone composition without
the condensation catalyst has been first emulsified in water using
a surfactant.
BRIEF SUMMARY OF THE INVENTION
[0008] It is therefore an object of the present invention is to
provide a method for crosslinking a condensation crosslinkable
silicone composition to efficiently produce crosslinked silicone
particles with a lower mean particle diameter, and with a better
dispersion in organic resins.
[0009] Thus, the invention relates to a method for producing
crosslinked silicone particles with a mean particle diameter of
0.1-500 .mu.m, in which a condensation crosslinkable silicone
composition containing (A) an organopolysiloxane having at least
two silanol groups per molecule, and (B) a crosslinker, but without
a (C) condensation catalyst, is first emulsified in water using a
surfactant. An emulsion containing a tin (II) salt of an organic
acid with no more than 10 carbon atoms is emulsified in water using
a surfactant, and is added as component (C) to the emulsion of the
condensation crosslinkable silicone composition. This crosslinks
the emulsified condensation crosslinkable silicone composition.
[0010] These and other features of the invention will become
apparent from a consideration of the detailed description.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0011] Not applicable.
DETAILED DESCRIPTION OF THE INVENTION
[0012] In the method of the present invention, a condensation
crosslinkable silicone composition containing (A) an
organopolysiloxane having at least two silanol groups per molecule
and (B) a crosslinker, but no (C) condensation catalyst, is first
emulsified in water with a surfactant.
[0013] Organopolysiloxane (A) is the primary component of the
condensation crosslinkable silicone composition, and should have at
least two silanol groups in its molecule. The silanol groups in
organopolysiloxane (A) are preferably at the terminals of the
molecular chain. Examples of silicon atom bonded organic groups
which can also be present in organopolysiloxane (A) include alkyl
groups such as methyl, ethyl, propyl, and butyl; alkenyl groups
such as vinyl and allyl; aryl groups such as phenyl; aralkyl groups
such as benzyl and phenethyl; cycloalkyl groups such as cyclopentyl
and cyclohexyl ; and substituted monovalent hydrocarbon groups such
as 3-chloropropyl, 3,3,3-trifluoropropyl, and other such
halogenated alkyl groups.
[0014] The molecular structure of organopolysiloxane (A) may be
linear, linear with some branching, branched, or reticulated. While
the viscosity of organopolysiloxane (A) at 25 .degree. C. is not
particularly limited, it is preferably 5-1,000,000 mPa.multidot.s,
more preferably 5-10,000 mPa.multidot.s, and even more preferably
5-1,000 mPa.multidot.s. This is because the physical properties of
the crosslinked silicone particles tend to suffer when the
viscosity of organopolysiloxane (A) at 25.degree. C. is lower than
the minimum of the range, whereas a viscosity over the maximum of
the range makes it more difficult to emulsify the composition in
water.
[0015] A crosslinker (B) is used to crosslink the condensation
crosslinkable silicone composition by condensation with the silanol
groups in organopolysiloxane (A). Examples of suitable crosslinkers
(B) include (i) silanes having at least three silicon atom bonded
hydrolysable groups or partially hydrolyzed condensates thereof,
and (ii) organosiloxanes having at least three silicon atom bonded
hydrogen atoms per molecule.
[0016] The silicon atom bonded hydrolysable groups which may be
present in silanes of crosslinker (B)(i) include alkoxy groups such
as methoxy, ethoxy, and methoxyethoxy; oxime groups such as methyl
ethyl ketoxime; acetoxy groups; and aminoxy groups. Examples of
silanes or siloxanes of crosslinker (B)(i) include alkoxysilanes
such as methyltrimethoxysilane, ethyl trimethoxysilane,
methyltris(methoxy ethoxy)silane, tetramethoxysilane,
tetraethoxysilane, and partially hydrolyzed condensates thereof;
oxime silanes such as methyltris(methyl ethyl ketoxime)silane,
ethyltris(methyl ethyl ketoxime)silane, tetra(methyl ethyl
ketoxime)silane, and partially hydrolyzed condensates thereof;
acetoxysilanes such as methyltriacetoxysilane
ethyltriacetoxysilane, tetracetoxysilane, and partially hydrolyzed
condensates thereof; and aminoxysilanes such as
methyltris(trimethyl aminoxy)silane, ethyltris(trimethyl
aminoxy)silane, tetra(trimethyl aminoxy)silane, and partially
hydrolyzed condensates thereof. Alkoxysilanes and partially
hydrolyzed condensates thereof are preferred, while alkyl
polysilicates which are partially hydrolyzed condensates of
tetralkoxysilanes are particularly preferred.
[0017] Examples of silicon atom bonded organic groups which may be
present in crosslinker (B)(ii) include alkyl groups such as methyl,
ethyl, propyl, and butyl; alkenyl groups such as vinyl and allyl;
aryl groups such as phenyl; aralkyl groups such as benzyl and
phenethyl; cycloalkyl groups such as cyclopentyl and cyclohexyl;
and substituted monovalent hydrocarbon groups such as
3-chloropropyl, 3,3,3-trifluoropropyl, and other such halogenated
alkyl groups.
[0018] The molecular structure of crosslinker (B)(ii) may be
linear, linear with some branching, branched, reticulated, and
cyclic. Some examples of organopolysiloxanes of crosslinker (B)(ii)
include methylhydridopolysiloxanes with trimethylsiloxy groups at
both ends of the molecular chain, dimethylsiloxane
methylhydridosiloxane copolymers with trimethylsiloxane groups at
both ends of the molecular chain, dimethylsiloxane
methylhydridosiloxane copolymers with dimethylhydridosiloxy groups
at both ends of the molecular chain, cyclic
methylhydridopolysiloxanes, and organopolysiloxanes with part or
all methyl groups in the siloxane substituted by alkyl groups such
as ethyl or aryl groups such as phenyl.
[0019] The condensation crosslinkable silicone composition contains
crosslinker (B) in an amount sufficient to crosslink the
condensation crosslinkable silicone composition. Specifically, the
amount crosslinker (B) should be 0.1-50 weight parts per 100 weight
parts of organopolysiloxane (A). The reason is that an amount of
crosslinker (B) less than the minimum range can result in
insufficient crosslinking, whereas an amount more than the maximum
range can result in crosslinked silicone particles with diminished
physical properties.
[0020] The condensation crosslinkable silicone composition may
contain other optional components such as (D) organoalkoxysilanes
containing groups such as C.sub.5 or greater alkyl groups,
(meth)acrylic groups, epoxy groups, mercapto groups, amino groups,
alkenyl groups, or partially hydrolyzed condensates thereof.
Examples of organoalkoxysilane (D) include alkyl group containing
alkoxysilanes such as pentyltrimethoxysilane,
hexyltrimethoxysilane, octyltrimethoxysilane, and partially
hydrolyzed condensates thereof; (meth)acrylic group containing
alkoxysilanes such as 3-methacryloxypropyl trimethoxysilane,
3-methacryloxypropyl methyldimethoxysilane, 3-methacryloxypropyl
dimethylmethoxysilane, and partially hydrolyzed condensates
thereof; epoxy group containing alkoxysilanes such as
3-glycidoxypropyltrimethoxys- ilane, 3-glycidoxypropylmethyl
dimethoxysilane, 2-(3,4-epoxycyclohexyl)eth- yl trimethoxysilane,
2-(3,4-epoxycyclohexyl)ethyl methyldimethoxysilane, 4-oxiranylbutyl
trimethoxysilane, 4-oxiranylbutyl triethoxysilane, 4-oxiranylbutyl
methyldimethoxysilane, 8-oxiranyloctyl trimethoxysilane,
8-oxiranyloctyl triethoxysilane, 8-oxiranyloctyl
methyldimethoxysilane, and partially hydrolyzed condensates
thereof; 3-mercaptopropyltrimethoxys- ilane, 3-mercaptopropyl
methyldimethoxysilane, and partially hydrolyzed condensates
thereof; amino group containing alkoxysilanes such as
3-aminopropyltrimethoxysilane,
N-(2-aminoethyl)-3-aminopropyltrimethoxysi- lane,
N-(2-aminoethyl)-3-aminopropyl methyldimethoxysilane,
3-anilinopropyl trimethoxysilane, and partially hydrolyzed
condensates thereof; and alkenyl group containing alkoxysilanes
such as vinyltrimethoxysilane, allyltrimethoxysilane,
hexenyltrimethoxysilane, and partially hydrolyzed condensates
thereof.
[0021] The content of organoalkoxysilane (D) in the condensation
crosslinkable silicone composition is not particularly limited, but
should preferably be present in the amount of 0.1-10 weight percent
of the condensation crosslinkable silicone composition, more
preferably 0.5-5 weight percent. An organoalkoxysilane (D) content
lower than the minimum of the range can result in crosslinked
silicone particles having poor adhesion with organic resins,
whereas an amount greater than the maximum of the range can result
in crosslinked silicone particles with diminished physical
properties.
[0022] The condensation crosslinkable silicone composition may
contain a reinforcing filler such as precipitated silica, fumed
silica, sintered silica, and fumed titanium oxide; a nonreinforcing
filler such as milled quartz, diatomaceous earth, asbestos, alumino
silicic acid, iron oxide, zinc oxide, and calcium carbonate; a
filler treated with an organosilicon compound such as an
organochlorosilane, organoalkoxysilane, organosilazane, and
organosiloxane oligomer. In addition, the condensation
crosslinkable silicone composition can include a pigment, an
organic compound with an epoxy or amino group, a heat resistant
imparting agent, a flame retardant, plasticizer, or noncrosslinking
type of organopolysiloxane.
[0023] A device such as a colloid mill, homomixer, or homogenizer
can be used to emulsify the condensation crosslinkable silicone
composition in water with a surfactant. Since the condensation
crosslinkable silicone composition does not contain a condensation
catalyst during emulsification, the condensation crosslinkable
silicone composition can be fully emulsified, and can even be
heated to some extent, during emulsification. The condensation
crosslinkable silicone composition can therefore be sufficiently
emulsified in water, which results in the production of crosslinked
silicone particles with a lower mean particle diameter and which
are more uniformly granular.
[0024] Surfactants which can be used include anionic surfactants
such as hexylbenzene sulfonic acid, octylbenzene sulfonic acid,
decylbenzene sulfonic acid, dodecylbenzene sulfonic acid,
cetylbenzene sulfonic acid, myristylbenzene sulfonic acid, and
sodium salts thereof; cationic surfactants such as octyl
trimethylammonium hydroxide, dodecyl trimethylammonium hydroxide,
hexadecyl trimethylammonium hydroxide, octyl dimethylbenzyl
ammonium hydroxide, decyl dimethyl benzylammonium hydroxide,
dioctadecyl dimethylammonium hydroxide, beef tallow
trimethylammonium hydroxide, and coconut oil trimethylammonium
hydroxide; and nonionic surfactants such as polyoxyalkylene alkyl
ethers, polyoxyalkylene alkyl phenols, polyoxyalkylene alkyl
esters, polyoxyalkylene sorbitan esters, polyethylene glycol,
polypropylene glycol, diethylene glycol trimethylnonanol ethylene
oxide adducts, or mixtures of two or more of such surfactants.
Nonionic surfactants and anionic surfactants are most
preferred.
[0025] The surfactant is used in an amount of 0.05-20 weight
percent of the emulsion of condensation crosslinkable silicone
composition, preferably in an amount of 0.1-10 weight percent. A
surfactant content lower than the minimum of the range can result
in an emulsion with a lower stability, whereas an amount greater
than the maximum of the range limits the applications of the
crosslinked silicone particles.
[0026] In the present invention, the condensation crosslinkable
silicone composition should be emulsified in water to produce an
emulsion with a mean particle diameter of 0.1-500 .mu.m. It is
difficult to produce an emulsion with a mean particle diameter
below the minimum of the range, whereas an emulsion with a mean
particle diameter above the range will suffer from poor stability.
The content of the condensation crosslinkable silicone composition
in the emulsion should be 10-90 weight percent of the emulsion,
preferably 20-80 weight percent. If the content of the condensation
crosslinkable silicone composition is below the range, it is more
difficult to dehydrate the emulsion to recover crosslinked silicone
particles, and applications of aqueous suspensions of the
crosslinked silicone particles will be more limited. A content of
condensation crosslinkable silicone composition above the range can
result in an aqueous suspension of crosslinked silicone particles
that is more difficult to handle.
[0027] The invention is characterized by the use as condensation
catalyst (C), an emulsion containing a tin (II) salt of an organic
acid with no more than 10 carbon atoms, emulsified in water using a
surfactant. The condensation catalyst (C) emulsion is added to the
emulsion of the condensation crosslinkable silicone composition.
The use of an organotin compound or a tin (II) salt of an organic
acid with more than ten carbon atoms as the condensation catalyst
(C) will not allow the condensation crosslinkable silicone
composition to sufficiently crosslink and can even result in no
crosslinking at all. In this invention, crosslinking reactions can
be effectively achieved by use of the emulsion containing the
particular tin (II) salt of an organic acid with no more than 10
carbon atoms, emulsified in water using a surfactant. Some examples
of appropriate tin (II) salts of organic acids with no more than
ten carbon atoms are tin (II) acetate, tin (II) 2-ethylhexanoate,
tin (II) neodecanoate, tin (II) 2,4-pentadionate, and tin (II)
octanoate. Tin (II) octanoate is especially preferred.
[0028] The emulsion of the tin (II) salt can be prepared by
emulsifying the tin (II) salt directly in the water using a
surfactant, or by diluting the tin (II) salt in an organic solvent
as a more uniform and fine emulsion and then emulsifying it in
water with a surfactant. The surfactants noted previously can be
used for this purpose. The surfactant should be blended in an
amount of 0.01-1,000 weight parts per 100 weight parts of the tin
(II) salt.
[0029] When the tin (II) salt is diluted with an organic solvent,
the organic solvent can be an alcohol with no more than four carbon
atoms such as methanol, ethanol, n-propanol, isopropanol, and
t-butanol; or a ketone such as acetone or methyl ethyl ketone. The
lower alcohols are preferred. An emulsifier such as a colloid mill
or homogenizer can be used to produce the emulsion of the tin (II)
salt. While the mean particle diameter of the condensation catalyst
(C) emulsion is not limited, a mean diameter of no more than 10
.mu.m is preferred.
[0030] The amount of tin (II) salt used is preferably 0.01-20
weight parts, more preferably 0.1-10 weight parts, per 100 weight
parts of the condensation crosslinkable silicone composition.
Adding it in an amount lower than the range can make it more
difficult to crosslink the condensation crosslinkable silicone
composition, whereas its presence in an amount above the range can
result in crosslinked silicone particles with diminished physical
properties.
[0031] After the emulsion containing the tin (II) salt has been
added to the emulsion of the condensation crosslinkable silicone
composition, the crosslinking reaction of the condensation
crosslinkable silicone composition will proceed. However, if the
temperature of the emulsion is too low, the crosslinking reaction
will progress slowly, whereas a high temperature will compromise
the stability of the emulsion. The temperature of the emulsion
should therefore be 5-70 .degree. C.
[0032] Crosslinked silicone particles thus obtained generally have
a mean particle diameter of 0.1-500 .mu.m and a spherical shape.
Such crosslinked silicone particles, when added to an organic
resin, are able to impart to the organic resin better impact
resistance and better blocking resistance. Additionally, using
crosslinked silicone particles with a type A durometer hardness,
determined according to the protocol of Japanese Industrial
Standard (JIS) K 6253, of 10-95, preferably 20-90, avoids damaging
film surfaces by sliding action between organic resin films.
[0033] Crosslinked silicone particles according to the invention
are in the form of an aqueous suspension, but the suspension can be
dehydrated if desired, when there is a need to obtain only
crosslinked silicone particles. The aqueous suspension of
crosslinked silicone particles can be dehydrated by spraying it
into hot air.
[0034] The surface of the crosslinked silicone particles can be
coated with fine particles of a metal oxide or fine particles of a
silicone resin, to improve dispersion of the crosslinked silicone
particles in organic resins. One example of a method for coating
the surface of the crosslinked silicone particles with a metal
oxide or silicone resin particle is to add the metal oxide sol or a
hydrolyzed silane condensate to the aqueous suspension of the
crosslinked silicone particles, and dehydrate the suspension.
Another method is to manually or mechanically coat the crosslinked
silicone particles with the metal oxide powder or the hydrolyzed
silane condensate.
[0035] Crosslinked silicone particles according to this invention
can be blended with organic resins among which are silicone resins;
polyolefin resins such as polyethylene and polypropylene resins;
epoxy resins; polyurethane resins; urea resins; acrylic resins;
polycarbonate resins; polystyrene resins; and nylon resins. They
can also be blended with a silicone rubber latex, and with a rubber
latex containing polybutadiene or natural organic rubber.
[0036] The crosslinked silicone particles are especially useful as
a flexibilizer for making organic resins or rubbers more impact
resistant, as a surface lubricant for providing organic resin films
with blocking resistance, and as a delustrant for paint. The
crosslinked silicone particles also have excellent compatibility
with organic solvents such as toluene, xylene, mineral spirits,
kerosene, octamethylcyclotetrasiloxane,
decamethylcyclopentasiloxane, and hexamethyldisiloxane. They can
therefore be used as fillers for paints and inks.
EXAMPLES
[0037] The following examples are set forth in order to illustrate
this invention in more detail. The properties of the crosslinked
silicone particles were determined in the following manner.
[0038] Hardness of Crosslinked Silicone Particles
[0039] A condensation crosslinkable silicone composition containing
a condensation catalyst was crosslinked by being allowed to stand
for one week at 25.degree. C. and provided a one mm thick
crosslinked silicone sheet. The type A durometer hardness of the
crosslinked silicone particles according to JIS K 6253 (1997) was
determined using a Wallace microhardness meter manufactured by H.
W. Wallace Co.
[0040] Mean Particle Diameter of Crosslinked Silicone Particles
[0041] An aqueous suspension of crosslinked silicone particles was
measured using a laser diffraction instrument for measuring
particle size distribution. The instrument was a Model LA-500
manufactured by Horiba Seisakusho. The median diameter, i.e., the
particle diameter corresponding to 50 percent of the cumulative
distribution, was used as the mean particle diameter of the
crosslinked silicone particles.
[0042] Mean Particle Diameter of Condensation Catalyst Emulsion
[0043] The mean particle diameter of the condensation catalyst
emulsion was determined using a laser scattering submicron particle
analyzer. The device was a Coulter Model N4 manufactured by Coulter
Electronics.
Example 1
[0044] 84.7 weight parts of a dimethylpolysiloxane of the formula
HO{(CH.sub.3).sub.2SiO}.sub.11H, 10.5 weight parts of ethyl
polysilicate of the formula (C.sub.2H.sub.5O).sub.12Si.sub.5O.sub.4
obtained by partial hydrolysis and condensation of
tetraethoxysilane, and 4.8 weight parts of .gamma.-glycidoxypropyl
trimethoxysilane, were mixed to homogeneity. The mixture was
emulsified in an aqueous solution of 30 weight parts of pure water
and one weight part of the anionic surfactant sodium
polyoxyethylene lauryl sulfate. The ingredients were further
uniformly emulsified using a colloid mill, and 58 weight parts of
pure water was added to dilute the mixture. This provided an
emulsion of a condensation crosslinkable silicone composition.
[0045] One weight part of tin (II) octanoate was emulsified to a
mean particle diameter of about 1.2 .mu.m in an aqueous solution of
0.25 weight part of sodium polyoxyethylene lauryl sulfate anionic
surfactant and 9.75 weight parts of pure water. The resulting
condensation catalyst emulsion was mixed with the emulsion of the
condensation crosslinkable silicone composition, and allowed to
stand for a day. The product was a homogenous, ungelled aqueous
suspension of crosslinked silicone particles. Subsequent filtration
of the aqueous suspension through a 200 mesh screen retained on the
screen less than 0.1 weight percent of crosslinked silicone
particles based on the total amount filtered. The crosslinked
silicone particles were in the form of a rubber having a type A
durometer hardness of 60 and a mean particle diameter of 2
.mu.m.
Example 2
[0046] 84.7 weight parts of a dimethylpolysiloxane of the formula
HO{(CH.sub.3).sub.2SiO}.sub.11H, 10.5 weight parts of ethyl
polysilicate of the formula (C.sub.2H.sub.5O).sub.12Si.sub.5O.sub.4
obtained by partial hydrolysis and condensation of
tetraethoxysilane, and 4.8 weight parts of allyltrimethoxysilane,
were mixed to homogeneity. The mixture was emulsified in an aqueous
solution containing 30 weight parts of pure water and one weight
part of sodium polyoxyethylene lauryl sulfate anionic surfactant.
The mixture was further uniformly emulsified in a colloid mill, and
58 weight parts of pure water was added to dilute the mixture. This
provided an emulsion of condensation crosslinkable silicone
composition.
[0047] One weight part of tin (II) octanoate was emulsified to a
mean particle diameter of about 1.2 .mu.m in an aqueous solution of
0.25 weight part of sodium polyoxyethylene lauryl sulfate anionic
surfactant and 9.75 weight parts of pure water. The condensation
catalyst emulsion was mixed with the emulsion of condensation
crosslinkable silicone composition and allowed to stand for one
day. The result was a homogenous, ungelled aqueous suspension of
crosslinked silicone particles. Filtration of the aqueous
suspension of crosslinked silicone particles through a 200 mesh
screen left less than 0.1 weight percent of crosslinked silicone
particles on the screen, based on the total amount of aqueous
suspension passed through the screen. The crosslinked silicone
particles were a rubber having a type A durometer hardness of 60
and a mean particle diameter of 2 .mu.m.
Example 3
[0048] 84.7 weight parts of a dimethylpolysiloxane of the formula
HO{(CH.sub.3).sub.2SiO}.sub.11H, 10.5 weight parts of ethyl
polysilicate of the formula (C.sub.2H.sub.5O).sub.12Si.sub.5O.sub.4
obtained by partial hydrolysis and condensation of
tetraethoxysilane, and 4.8 weight parts of
.gamma.-mercaptopropyltrimethoxysilane, were mixed to homogeneity.
The mixture was emulsified in an aqueous solution of 30 weight
parts of pure water and one weight part of sodium polyoxyethylene
lauryl sulfate anionic surfactant. The mixture was further
uniformly emulsified in a colloid mill, and 58 weight parts of pure
water was added to dilute the mixture, providing an emulsion of
condensation crosslinkable silicone composition.
[0049] One weight part of tin (II) octanoate was emulsified to a
mean particle diameter of about 1.2 .mu.m in an aqueous solution of
0.25 weight part of sodium polyoxyethylene lauryl sulfate anionic
surfactant, and 9.75 weight parts of pure water. The resulting
condensation catalyst emulsion was mixed with the emulsion of
condensation crosslinkable silicone composition and allowed to
stand for one day, providing a homogenous, ungelled aqueous
suspension of crosslinked silicone particles. Filtration of the
aqueous suspension of crosslinked silicone particles through a 200
mesh screen left less than 0.1 weight percent of crosslinked
silicone particles on the screen, based on the total amount of
aqueous suspension passed through the screen. The crosslinked
silicone particles were a rubber having a type A durometer hardness
of 61 and a mean particle diameter of 2 .mu.m.
Example 4
[0050] 86.3 weight parts of a dimethylpolysiloxane of the formula
HO{(CH.sub.3).sub.2SiO}.sub.11H, 11.3 weight parts of ethyl
polysilicate of the formula (C.sub.2H.sub.5O).sub.12Si.sub.5O.sub.4
obtained by partial hydrolysis and condensation of
tetraethoxysilane, and 2.4 weight parts of
.gamma.-(2-aminoethyl)aminopropyl methyldimethoxysilane, were mixed
to homogeneity. The mixture was emulsified in an aqueous solution
of 30 weight parts of an aqueous solution of 5 weight percent of
polyoxyethylene (9) nonylphenyl ether nonionic surfactant. The
mixture was further uniformly emulsified in a colloid mill, and 59
weight parts of pure water were added to dilute the mixture,
providing an emulsion of condensation crosslinkable silicone
composition.
[0051] One weight part of tin (II) octanoate was emulsified to a
mean particle diameter of about 0.5 .mu.m in an aqueous solution of
9 weight parts of pure water and one weight part of nonionic
surfactant polyoxyethylene (9) nonylphenyl ether, and the resulting
condensation catalyst emulsion was mixed with the emulsion of
condensation crosslinkable silicone composition and allowed to
stand for one day, providing a homogenous, ungelled aqueous
suspension of crosslinked silicone particles. Filtration of the
aqueous suspension of crosslinked silicone particles through a 200
mesh screen left less than 0.1 weight percent of crosslinked
silicone particles on the screen, based on the total amount of
aqueous suspension passed through the screen. The crosslinked
silicone particles were a rubber having a type A durometer hardness
of 63 and a mean particle diameter of 2 .mu.m.
Comparative Example 1
[0052] 84.7 weight parts of a dimethylpolysiloxane of the formula
HO{(CH.sub.3).sub.2SiO}.sub.11H, 10.5 weight parts of ethyl
polysilicate of the formula (C.sub.2H.sub.5O).sub.12Si.sub.5O.sub.4
obtained by partial hydrolysis and condensation of
tetraethoxysilane, and 4.8 weight parts of
.gamma.-glycidoxypropyltrimethoxysilane, were mixed to homogeneity.
One weight part of tin (II) octanoate was added to the mixture and
the components were mixed to homogeneity. The mixture was rapidly
emulsified in an aqueous solution of 30 weight parts of pure water
and one weight part of sodium polyoxyethylene lauryl sulfate
anionic surfactant. The mixture was further uniformly emulsified
using a colloid mill, and 58 weight parts of pure water was added
to dilute the mixture, providing an emulsion of condensation
crosslinkable silicone composition. Crosslinking commenced
immediately after emulsification and portions of the emulsion
separated. The emulsion was allowed to stand for one day providing
an aqueous suspension of crosslinked silicone particles. Filtration
of the aqueous suspension of crosslinked silicone particles through
a 200 mesh screen left 3.7 weight percent of crosslinked silicone
particles on the screen, based on the total amount of aqueous
suspension passed through the screen. The crosslinked silicone
particles were a rubber having a type A durometer hardness of 63
and a mean particle diameter of 15 .mu.m.
Comparative Example 2
[0053] 84.7 weight parts of a dimethylpolysiloxane of the formula
HO{(CH.sub.3).sub.2SiO}.sub.11H, 10.5 weight parts of ethyl
polysilicate of the formula (C.sub.2H.sub.5O).sub.12Si.sub.5O.sub.4
obtained by partial hydrolysis and condensation of
tetraethoxysilane, and 4.8 weight parts of
.gamma.-glycidoxypropyltrimethoxysilane, were mixed to homogeneity.
The mixture was emulsified in an aqueous solution of 30 weight
parts of pure water and one weight part of sodium polyoxyethylene
lauryl sulfate anionic surfactant. The mixed ingredients were
further uniformly emulsified using a colloid mill, and 58 weight
parts of pure water were added to dilute the mixture, providing an
emulsion of condensation crosslinkable silicone composition.
[0054] Two weight parts of a toluene solution of 50 weight percent
stearic acid was emulsified to a mean particle diameter of about 12
m and more in an aqueous solution of 0.25 weight part of sodium
polyoxyethylene lauryl sulfate anionic surfactant and 9.75 weight
parts of pure water. The resulting condensation catalyst emulsion
was mixed with the emulsion of condensation crosslinkable silicone
composition and allowed to stand for one day. However, the
condensation crosslinkable silicone composition was not crosslinked
and the product was an oily substance.
Comparative Example 3
[0055] 84.7 weight parts of a dimethylpolysiloxane of the formula
HO{(CH.sub.3).sub.2SiO}.sub.11H, 10.5 weight parts of ethyl
polysilicate of the formula (C.sub.2H.sub.5O).sub.12Si.sub.5O.sub.4
obtained by partial hydrolysis and condensation of
tetraethoxysilane, and 4.8 weight parts of
.gamma.-glycidoxypropyltrimethoxysilane, were mixed to homogeneity.
The mixture was emulsified in an aqueous solution of 30 weight
parts of pure water and one weight part of sodium polyoxyethylene
lauryl sulfate anionic surfactant. The mixture of ingredients was
further uniformly emulsified using a colloid mill, and 58 weight
parts of pure water were added to dilute the mixture, providing an
emulsion of condensation crosslinkable silicone composition.
[0056] One weight part of dibutyltin dilaurate was emulsified to a
mean particle diameter of about 12 .mu.m or more in an aqueous
solution of 0.25 weight part of sodium polyoxyethylene lauryl
sulfate anionic surfactant and 9.75 weight parts of pure water. The
resulting condensation catalyst emulsion was mixed with the
emulsion of condensation crosslinkable silicone composition and
allowed to stand for one day. However, the condensation
crosslinkable silicone composition was not crosslinked and produced
only an oily substance.
Comparative Example 4
[0057] 84.7 weight parts of a dimethylpolysiloxane of the formula
HO{(CH.sub.3).sub.2SiO}.sub.11H, 10.5 weight parts of ethyl
polysilicate of the formula (C.sub.2H.sub.5O).sub.12Si.sub.5O.sub.4
obtained by partial hydrolysis and condensation of
tetraethoxysilane, and 4.8 weight parts of
.gamma.-glycidoxypropyltrimethoxysilane, were mixed to homogeneity.
The mixture was emulsified in an aqueous solution of 30 weight
parts of pure water and one weight part of sodium polyoxyethylene
lauryl sulfate anionic surfactant. The mixture of ingredients was
further uniformly emulsified in a colloid mill, and 58 weight parts
of pure water was added to dilute the mixture, providing an
emulsion of condensation crosslinkable silicone composition.
[0058] One weight part of tin (II) octanoate was added as drops in
the emulsion of condensation crosslinkable silicone composition.
The mixture was allowed to stand for one day, but the condensation
crosslinkable silicone composition was not crosslinked, resulting
only in an oily substance.
Application Example
[0059] The aqueous suspensions of crosslinked silicone particles
prepared in Examples 1-4 and in Comparative Examples 1-4 were added
in an amount of 1.5 weight parts of crosslinked silicone particles
per 100 weight parts of paint solids in an aqueous urethane resin
paint of Kansai Paint or in an aqueous acrylic resin paint of
Kansai Paint. A coating composition was produced after 50 cycles of
shaking of the mixture. Polyethylene terephthalate (PET) films were
coated with each paint composition, and then heated and dried for
10 minutes at 100.degree. C., forming coated films about 15 .mu.m
thick.
[0060] The coated films were examined using an optical microscope
at a magnification of 1000 to determine the presence of pinholes
caused by crosslinked silicone particles which had fallen from or
otherwise been removed from the coated film. The absence of
pinholes on the coated film was rated O, whereas their presence was
rated x. The results are shown in Table 1.
1TABLE 1 Cross- linked silicone Example Comparative particles 1
Example 2 Example 3 Example 4 Example 1 Urethane .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle. resin
Acrylic .smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. resin
[0061] The coated film surfaces were examined for their delustrant
property. A high degree of delustrant effect and particle
aggregates of no more than 30 .mu.m was rated O, an effective
delustrant property and aggregate particles of more than 30 .mu.m
was rated .DELTA., and a low delustrant effect was rated x. The
results are shown in Table 2.
2TABLE 2 Cross- linked silicone Example Example Example Comparative
particles 1 Example 2 3 4 Example 1 Urethane .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .DELTA. resin Acrylic
.smallcircle. .smallcircle. .smallcircle. .smallcircle. .DELTA.
resin
[0062] The coated film surfaces were examined for the presence of
damage after having being rubbed five times with a piece of
polypropylene resin. An undamaged coated film was rated O, while a
damaged film was rated x. The results are shown in Table 3.
3TABLE 3 Cross- linked silicone Example Example Example Comparative
particles Example 1 2 3 4 Example 1 Urethane .smallcircle.
.smallcircle. .smallcircle. .smallcircle. x resin Acrylic
.smallcircle. .smallcircle. .smallcircle. .smallcircle. x resin
[0063] It should be apparent from the above that the method
according to this invention for making suspension containing
crosslinked silicone particles results in a more efficient
production of the crosslinked silicone particles having a lower
mean particle diameter and better dispersion in organic resins.
[0064] Other variations may be made in compounds, compositions, and
methods described herein without departing from the essential
features of the invention. The embodiments of the invention
specifically illustrated herein are exemplary only and not intended
as limitations on their scope except as defined in the appended
claims.
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