U.S. patent application number 09/753843 was filed with the patent office on 2001-09-27 for method for producing water based coating compositions.
Invention is credited to Kobayashi, Kazuo, Morita, Yoshitsugu, Tanaka, Ken.
Application Number | 20010025080 09/753843 |
Document ID | / |
Family ID | 18575835 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010025080 |
Kind Code |
A1 |
Kobayashi, Kazuo ; et
al. |
September 27, 2001 |
Method for producing water based coating compositions
Abstract
An efficient method is provided for producing water based
coating compositions that are capable of forming highly scratch and
abrasion resistant matte coatings in which crosslinked silicone
particles are well dispersed. The method involves addition to a
water based coating composition of a waterborne suspension of
crosslinked silicone particles having an average diameter of
0.1-200 .mu.m. The method is characterized in that the suspension
is a waterborne crosslinked silicone particle suspension provided
by effecting crosslinking of a condensation reaction crosslinkable
silicone composition comprising (A) an organopolysiloxane
containing at least two silanol groups in each molecule, (B) a
crosslinker, and (C) a condensation reaction catalyst. The
crosslinking is effected in the emulsified composition in an
aqueous solution of an anionic surfactant.
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 CO1232
P.O. Box 994
Midland
MI
48686-0994
US
|
Family ID: |
18575835 |
Appl. No.: |
09/753843 |
Filed: |
January 3, 2001 |
Current U.S.
Class: |
524/588 |
Current CPC
Class: |
C09D 201/00 20130101;
C09D 201/00 20130101; C08L 83/00 20130101 |
Class at
Publication: |
524/588 |
International
Class: |
C08J 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 29, 2000 |
JP |
JP2000-054603 |
Claims
1. A method of making a water based coating composition comprising
adding a waterborne suspension of crosslinked silicone particles
that have an average diameter of 0.1-200 .mu.m to a water based
coating composition, the waterborne suspension of crosslinked
silicone particles being prepared by crosslinking a condensation
reaction crosslinkable silicone composition containing (A) an
organopolysiloxane having at least two silanol groups in its
molecule, (B) a crosslinker, and (C) a condensation reaction
catalyst, crosslinking being carried out in an emulsion containing
(A)-(C) and an aqueous solution of an anionic surfactant.
2. A method according to claim 1 in which condensation reaction
catalyst (C) is the last component added to the emulsion.
3. A method according to claim 1 in which condensation reaction
catalyst (C) is an emulsion prepared by emulsifying a tin (II) salt
of organic acid having no more than 10 carbon atoms in water using
an anionic surfactant.
4. A method according to claim 3 in which the average particle size
of the tin (II) salt in the emulsion is no more than 10 .mu.m.
5. A method according to claim 4 wherein the tin (II) salt is tin
(II) octanoate.
6. A method according to claim 1 wherein crosslinker (B) is a
silane having at least three silicon bonded hydrolyzable groups in
its molecule or a partial hydrolysis and condensation product
thereof.
7. A method according to claim 1 wherein the condensation reaction
crosslinkable silicone composition contains (D) an
organoalkoxysilane having an alkyl group of at least five carbon
atoms, a (meth)acrylic group, an epoxy group, a mercapto group, an
amino group, an alkenyl group, or partial hydrolysis and
condensation products thereof.
8. A method according to claim 1 wherein the water based coating
composition is selected from the group consisting of a water based
polyurethane resin coating composition, a water based alkyd resin
coating composition, a water based epoxy resin coating composition,
a water based acrylic resin coating composition, a water based
silicone modified epoxy resin coating composition, a water based
silicone modified polyester resin coating composition, a water
based silicone resin coating composition, and a water based amino
alkyd resin coating composition of an amino resin and an alkyd
resin.
9. A water based coating composition prepared according to the
method in claim 8.
10. A method of making a water based coating composition comprising
adding a waterborne suspension of crosslinked silicone particles
that have an average diameter of 0.1-200 .mu.m to a water based
coating composition, the waterborne suspension of crosslinked
silicone particles being prepared by crosslinking a condensation
reaction crosslinkable silicone composition containing (A) an
organopolysiloxane having at least two silanol groups in its
molecule, (B) a crosslinker, and (C) a condensation reaction
catalyst, crosslinking being carried out in an emulsion containing
(A)-(C) and an aqueous solution of an anionic surfactant,
condensation reaction catalyst (C) being a tin (II) salt of an
organic acid having no more than 10 carbon atoms.
11. A method according to claim 10 in which condensation reaction
catalyst (C) is the last component added to the emulsion.
12. A method according to claim 10 in which condensation reaction
catalyst (C) is an emulsion prepared by emulsifying a tin (II) salt
of organic acid having no more than 10 carbon atoms in water using
an anionic surfactant.
13. A method according to claim 12 in which the average particle
size of the tin (II) salt in the emulsion is no more than 10
.mu.m.
14. A method according to claim 13 wherein the tin (II) salt is tin
(II) octanoate.
15. A method according to claim 10 wherein crosslinker (B) is a
silane having at least three silicon bonded hydrolyzable groups in
its molecule or a partial hydrolysis and condensation product
thereof.
16. A method according to claim 10 wherein the condensation
reaction crosslinkable silicone composition contains (D) an
organoalkoxysilane having an alkyl group of at least five carbon
atoms, a (meth)acrylic group, an epoxy group, a mercapto group, an
amino group, an alkenyl group, or partial hydrolysis and
condensation products thereof.
17. A method according to claim 10 wherein the water based coating
composition is selected from the group consisting of a water based
polyurethane resin coating composition, a water based alkyd resin
coating composition, a water based epoxy resin coating composition,
a water based acrylic resin coating composition, a water based
silicone modified epoxy resin coating composition, a water based
silicone modified polyester resin coating composition, a water
based silicone resin coating composition, and a water based amino
alkyd resin coating composition of an amino resin and an alkyd
resin.
18. A water based coating composition prepared according to the
method in claim 17.
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 relates to a method for producing water based
coating compositions. More particularly, the invention is directed
to an efficient method for producing water based coating
compositions that have the ability to form highly scratch and
abrasion resistant matte coatings in which crosslinked silicone
particles are well dispersed.
BACKGROUND OF THE INVENTION
[0005] Japanese Laid Open (Kokai or Unexamined) Patent Application
Number Hei 2-113079 (113,079/1990)/EP 0 365 009 A2 (Apr. 25, 1990),
discloses blending crosslinked silicone particles into coating
compositions to produce coating compositions that form matte
coatings.
[0006] Since a uniform dispersion is not obtained when crosslinked
silicone particles are blended into a water based coating
composition, Japanese Laid Open (Kokai or Unexamined) Patent
Application Number Hei 5-9409 (9,409/1993)/U.S. Pat. No. 5,708,057
(Jan. 13, 1998), teaches a method for preparing water based coating
compositions in which crosslinked silicone particles are blended as
a waterborne suspension into water based coating compositions.
[0007] Japanese Laid Open (Kokai or Unexamined) Patent Application
Number Hei 11-140191 (140,191/1999) teaches that waterborne
crosslinked silicone particle suspensions of crosslinked silicone
particles, nonionic surfactant, ionic surfactant, and water, can be
blended into water based coating compositions.
[0008] A problem with preparing water based coating compositions
using waterborne crosslinked silicone particle suspensions is that
the application of the resulting water based coating compositions
produces matte coatings that have unacceptable scratch and abrasion
resistance.
BRIEF SUMMARY OF THE INVENTION
[0009] Therefore, the object of this invention is to provide an
efficient method for producing water based coating compositions
that are able to form highly scratch and abrasion resistant matte
coatings in which crosslinked silicone particles are well
dispersed.
[0010] In particular, the method involves producing water based
coating compositions by the addition to a water based coating
composition of a waterborne suspension of crosslinked silicone
particles that have an average diameter of 0.1 to 200 .mu.m.
Furthermore, the method for producing water based coating
compositions is characterized in that the suspension is a
waterborne suspension of crosslinked silicone particles afforded by
effecting crosslinking of a condensation reaction crosslinkable
silicone composition comprising (A) an organopolysiloxane that
contains at least two silanol groups in each molecule, (B) a
crosslinker, and (C) a condensation reaction catalyst. The
crosslinking is effected in the emulsified composition in an
aqueous solution of an anionic surfactant.
[0011] 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
[0012] Not applicable.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The water based coating compositions comprise a coating
resin component emulsified in water. The water based coating
composition should have the ability to form a coating or film upon
drying or curing of the coating resin component when water is
removed after its application. The nature of the composition is not
otherwise critical.
[0014] The water based coating composition can be exemplified by
ambient temperature curing water based coating compositions,
ambient temperature drying water based coating compositions, and
water based coating compositions that cure upon the application of
heat. The coatings of this invention can be used in the protection
of substrate surfaces, altering the appearance of substrate
surfaces, or changing the character of substrate surfaces, ranging
from pigmented paints to varnishes and unpigmented coatings. The
water based coating composition can for example comprise a water
based polyurethane resin coating composition, a water based alkyd
resin coating composition, a water based epoxy resin coating
composition, a water based acrylic resin coating composition, a
water based silicone modified epoxy resin coating composition, a
water based silicone modified polyester resin coating composition,
a water based silicone resin coating composition, or a water based
amino alkyd resin coating composition of an amino resin and an
alkyd resin.
[0015] The method for making water based coating compositions
begins with preparation of a waterborne crosslinked silicone
particle suspension containing crosslinked silicone particles
having an average particle size of 0.1 to 200 .mu.m. This is
accomplished by the crosslinking of a condensation reaction
crosslinkable silicone composition which comprises (A) an
organopolysiloxane that contains at least two silanol groups in
each molecule, (B) a crosslinker, and (C) a condensation reaction
catalyst. Crosslinking is carried out in an aqueous solution of an
anionic surfactant with the condensation reaction crosslinkable
silicone composition (A)-(C) being present in an emulsified
state.
[0016] Organopolysiloxane (A) is the main or base component of the
condensation reaction crosslinkable silicone composition and it
should contain at least two silanol groups in each molecule. The
silanol groups in component (A) are preferably present in the
molecular chain terminal positions. Silicon bonded organic groups
in component (A) can be exemplified by substituted and
unsubstituted monovalent hydrocarbyl groups among which are 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 halogenated alkyl groups such as 3-chloropropyl
and 3,3,3-trifluoropropyl.
[0017] The molecular structure of component (A) can be, for
example, straight chain, partially branched straight chain,
branched chain, or network. Preferably, it is straight chain or
partially branched straight chain. While the viscosity of component
(A) at 25.degree. C. is not critical, it is preferably 5 to
1,000,000 mPa.multidot.s, more preferably 5 to 10,000
mPa.multidot.s, and particularly preferably 5 to 1,000
mPa.multidot.s. The physical properties of the obtained crosslinked
silicone particles become increasingly impaired as the viscosity of
component (A) at 25.degree. C. declines below the lower limit of
these ranges. The ability to emulsify the composition in water is
compromised when the upper limit of the ranges is exceeded.
[0018] The crosslinker (B) is the component that functions to
crosslink the condensation reaction crosslinkable silicone
composition, and this is accomplished by condensing with silanol
groups in component (A). The crosslinker (B) can be (i) a silane
that contains at least three silicon bonded hydrolyzable groups in
each molecule, or partial hydrolysis and condensation products of
such a silane, or crosslinker (B) can be (ii) an organopolysiloxane
that contains at least three silicon bonded hydrogen atoms in each
molecule.
[0019] The silicon bonded hydrolyzable groups in component (B)(i)
can be alkoxy groups such as methoxy, ethoxy, or methoxyethoxy;
oxime groups such as methyl ethyl ketoxime; acetoxy groups; or
aminoxy groups. The silane or siloxane comprising component (B)(i)
can be exemplified by alkoxysilanes such as methyltrimethoxysilane,
ethyltrimethoxysilane, methyl tris(methoxyethoxy)silane,
tetramethoxysilane, and tetraethoxysilane, and the partial
hydrolysis and condensation products of these alkoxy silanes; oxime
silanes such as methyltris(methyl ethyl ketoxime)silane,
ethyltris(methyl ethyl ketoxime)silane, and tetra(methyl ethyl
ketoxime)silane, and the partial hydrolysis and condensation
products of these oxime silanes; acetoxy silanes such as
methyltriacetoxysilane, ethyltriacetoxysilane, and tetra
acetoxysilane, and the partial hydrolysis and condensation products
of these acetoxysilanes; and aminoxy silanes such as
methyltris(trimethylaminoxy)s- ilane,
ethyltris(trimethylaminoxy)silane, and
tetra(trimethylaminoxy)silan- e, and the partial hydrolysis and
condensation products of these aminoxy silanes. Alkoxy silanes and
their partial hydrolysis and condensation products are preferred,
and alkyl polysilicates afforded by the partial hydrolysis and
condensation of tetraalkoxysilanes are particularly preferred.
[0020] The silicon bonded organic groups present in component
(B)(ii) can be exemplified by substituted and unsubstituted
monovalent hydrocarbyl groups, among which are 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 halogenated alkyl groups such as 3-chloropropyl and
3,3,3-trifluoropropyl. The molecular structure of component (B)(ii)
can be straight chain, partially branched straight chain, branched
chain, network, or cyclic. Organopolysiloxanes encompassed by
component (B)(ii) can be exemplified by trimethylsiloxy endblocked
methylhydrogen polysiloxanes, trimethylsiloxy endblocked
dimethylsiloxane/methylhydrogen siloxane copolymers,
dimethylhydrogensiloxy endblocked dimethylsiloxane/methylhydrogen
siloxane copolymers, cyclic methylhydrogen polysiloxanes, and by
organopolysiloxanes afforded by replacing all or part of the methyl
groups in any of the preceding siloxanes with other alkyl groups
such as ethyl or with aryl groups such as phenyl.
[0021] Component (B) should be present in the condensation reaction
crosslinkable silicone composition in an amount sufficient to
crosslink the condensation reaction crosslinkable silicone
composition. In more specific terms, it is present preferably at
0.1 to 50 weight parts per 100 weight parts of component (A). The
content of component (B) below the lower limit of the range runs
the risk of failing to obtain an acceptable crosslinking of the
condensation reaction crosslinkable silicone composition, while a
content of component (B) above the upper limit of the range runs
the risk of impairing the physical properties of crosslinked
silicone particles obtained.
[0022] The condensation reaction crosslinkable silicone composition
may optionally contain a component (D), which component (D) can be
an organoalkoxysilane containing an alkyl group of five or more
carbon atoms, a (meth)acrylic group, an epoxy group, a mercapto
group, an amino group, or an alkenyl group. Component (D) can also
be a partial hydrolysis and condensation product of such
organoalkoxysilanes. Optional component (D) can be exemplified by
alkyl group containing alkoxysilanes such as
pentyltrimethoxysilane, hexyltrimethoxysilane, and
octyltrimethoxysilane; (meth)acryl functional alkoxysilanes such as
3-methacryloxypropyltrimethoxysilane,
3-methacryloxypropylmethyldimethoxy- silane, and
3-methacryloxypropyldimethylmethoxysilane; epoxy functional
alkoxysilanes among which are compositions such as
3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyl
dimethoxysilane, 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane,
2-(3,4-epoxycyclohexyl) ethylmethyl dimethoxysilane,
4-oxiranylbutyltrimethoxysilane, 4-oxiranylbutyltriethoxysilane,
4-oxiranylbutylmethyldimethoxysilane,
8-oxiranyloctyltrimethoxysilane, 8-oxiranyloctyltriethoxysilane,
and 8-oxiranyloctylmethyldimethoxysilane; mercapto functional
alkoxysilanes such as 3-mercaptopropyltrimethoxysilan- e and
3-mercaptopropylmethyldimethoxysilane; amino functional
alkoxysilanes such as 3-aminopropyltrimethoxysilane,
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,
N-(2-aminoethyl)-3-aminop- ropylmethyl dimethoxysilane, and
3-anilinopropyltrimethoxysilane; and alkenyl functional
alkoxysilanes such as vinyltrimethoxysilane, allyltrimethoxysilane,
and hexenyltrimethoxysilane. The partial hydrolysis and
condensation products of any of these compounds can also be
employed as optional component (D).
[0023] While the content of component (D) in the condensation
reaction crosslinkable silicone composition is not critical,
component (D) is preferably used in an amount that provides 0.1 to
10 weight percent of (D) in the condensation reaction crosslinkable
silicone composition, and more preferably 05 to 5 weight percent of
(D) in the condensation reaction crosslinkable silicone
composition. A content of component (D) below the lower limit of
the range runs the risk of producing crosslinked silicone particles
with a poor adherence for organic resins. A content of component
(D) above the upper limit of the range runs the risk of impairing
the physical properties of the crosslinked silicone particles
obtained.
[0024] The condensation reaction crosslinkable silicone composition
may also contain other components among which are reinforcing
fillers such as precipitated silica, fumed silica, calcined silica,
and fumed titanium oxide; nonreinforcing fillers such as quartz
powder, diatomaceous earth, abestos, aluminosilicate, iron oxide,
zinc oxide, and calcium carbonate; fillers treated with
organsilicon compounds such as organochlorosilanes,
organoalkoxysilanes, organosilazanes, or organsiloxane oligomers;
pigments; epoxy and/or amino functional organic compounds; heat
stabilizers; flame retardants; plasticizers; and noncrosslinkable
organopolysiloxanes.
[0025] The anionic surfactant emulsification of the condensation
reaction crosslinkable silicone composition in water is carried out
using an emulsifying device such as a colloid mill, homomixer, or
homogenizer. The absence of the condensation catalyst (C) from the
condensation reaction crosslinkable silicone composition enables
thorough emulsification and even application of some heating during
emulsification. As a consequence, thorough emulsification of the
condensation reaction crosslinkable silicone composition in water
can be achieved, which in turn enables a small average particle
size to be obtained, making possible production of crosslinked
silicone particles with little variation in size.
[0026] The anionic surfactant used for emulsifying the condensation
reaction crosslinkable silicone composition in water can be an
alkylbenzene sulfonate salt such as hexylbenzene sulfonate,
octylbenzene sulfonate, decylbenzene sulfonate, dodecylbenzene
sulfonate, cetylbenzene sulfonate, and myristylbenzene sulfonate;
sulfonate salts such as alkylnaphthalene sulfonates,
sulfosuccinates, n-olefin sulfonates, and N-acyl sulfonates;
carboxylate salts such as soaps, N-acylamino acid salts,
polyoxyethylene carboxylates, polyoxyethylene alkyl ether
carboxylates, and acylated peptides; sulfate ester salts such as
sulfated oils, salts of alkyl sulfates, salts of alkyl ether
sulfates, salts of polyoxyethylene sulfates, salts of sulfates of
polyoxyethylene alkylaryl ethers, and salts of alkylamide sulfates;
salts of alkyl phosphates, salts of polyoxyethylene phosphates,
salts of polyoxyethylene alkyl ether phosphates, salts of
polyoxyethylene alkylaryl ether phosphates; and mixtures
thereof.
[0027] The anionic surfactant is used in an amount that provides
0.05 to 20 weight percent, preferably 0.1 to 10 weight percent
anionic surfactant in the emulsion of the condensation reaction
crosslinkable silicone composition. The use of an anionic
surfactant in an amount below the lower limit of the range runs the
risk of the resulting emulsion having reduced stability. The use of
anionic surfactant in excess of the upper limit of the range runs
the rise of imposing limitations on application of crosslinked
silicone particles obtained.
[0028] To obtain compositions suitable for use according to the
invention, it is necessary that the average particle size of
emulsion particles be 0.1 to 500 .mu.m when the condensation
reaction crosslinkable silicone composition is being emulsified in
water. It is difficult to prepare an emulsion with an average
particle size below the lower limit of the range, while an emulsion
in which the average particle size exceeds the upper limit of the
range has poor stability. The content of the condensation reaction
crosslinkable silicone composition in the emulsion is 10 to 90
weight percent, preferably 20 to 80 weight percent, in the
emulsion. A condensation reaction crosslinkable silicone
composition content below the lower limit of the range impairs
dewatering of the emulsion and recovery of crosslinked silicone
particles, and can result in limitations on applications of the
waterborne crosslinked silicone particle suspension. A composition
content in excess of the upper limit of the range risks impairing
the handling characteristics of the resulting waterborne
crosslinked silicone particle suspension.
[0029] A characteristic feature of the invention is the addition of
a tin (II) salt of an organic acid containing no more than ten
carbon atoms to the emulsion as the condensation reaction catalyst
(C). The use of an organotin compound or a tin (II) salt of an
organic acid with more than ten carbon atoms encounters problems of
inadequate crosslinking in the condensation reaction crosslinkable
silicone composition, and failure of crosslinking to occur. The
preferred tin (II) salt of an organic acid containing no more than
ten carbon atoms is preferably a tin (II) salt of a saturated
aliphatic acid containing no more than ten carbon atoms, such as
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.
[0030] While the invention encompasses direct addition of tin (II)
salt of organic acid catalyst, hereafter referred to as tin (II)
salt, to the emulsion of the condensation reaction crosslinkable
silicone composition, the tin (II) salt is preferably added to the
emulsion of the condensation reaction crosslinkable silicone
composition in the form of a separate emulsion prepared in advance
by emulsification of the tin (II) salt in water using an
emulsifying agent. The use of an emulsion of tin (II) salt results
in a substantial acceleration of the crosslinking reaction in the
condensation reaction crosslinkable silicone composition, and
enables production of crosslinked silicone particles with uniform
particle size. The emulsion of tin (II) salt can be prepared by
direct emulsification of tin (II) salt in water using an anionic
surfactant.
[0031] When it is desired to prepare a uniform emulsion of the tin
(II) salt, the tin (II) salt can be diluted in an organic solvent
and then emulsified in water using an anionic surfactant. The
anionic surfactant used for emulsification of the tin (II) salt can
be the same type of anionic surfactant as mentioned above. The
anionic surfactant is used for emulsification of the tin (II) salt
in an amount of 0.01 to 1,000 weight parts per 100 weight parts of
the tin (II) salt. When the tin (II) salt is to be preliminarily
diluted in an organic solvent, the organic solvent should be a
ketone such as acetone and methyl ethyl ketone, or an alcohol
containing no more than 4 carbon atoms such as methanol, ethanol,
n-propanol, isopropanol, and tert-butanol. Lower alcohols are
preferred. The tin (II) salt emulsion can be prepared using an
emulsifying device such as a colloid mill or homogenizer.
[0032] The amount of tin (II) salt is not critical, but it is
preferably added at 0.01 to 20 weight parts, particularly 0.1 to 10
weight parts, in each case per 100 weight parts of the condensation
reaction crosslinkable silicone composition. Addition of the tin
(II) salt in an amount below the lower limit of the range runs the
risk of failing to obtain an adequate acceleration of crosslinking
in the condensation reaction crosslinkable silicone composition.
Addition of the tin (II) salt in excess of the upper limit of the
range runs the risk of compromising the physical properties of the
crosslinked silicone particles obtained.
[0033] The addition of tin (II) salt to the emulsion of the
condensation reaction crosslinkable silicone composition serves to
accelerate the crosslinking reaction in the condensation reaction
crosslinkable silicone composition. However, crosslinking will
still proceed slowly when the temperature of the emulsion is too
low. Conversely, the stability of the emulsion will be reduced when
its temperature is too high. Therefore, the temperature of addition
of the tin (II) salt is preferably from 5 to 70.degree. C.
[0034] Crosslinked silicone particles prepared according to the
invention should have a spherical shape and an average particle
size of 0.1 to 500 .mu.m. The crosslinked silicone particles have
the capacity to impart an excellent impact resistance and blocking
resistance to organic resins. In addition, the crosslinked silicone
particles should have a type A durometer hardness of 10-95, as
determined by Japanese Industrial Standard (JIS) K 6253-1997,
preferably a hardness of 20-90, to avoid scratching or abrasion of
organic resin film surfaces produced when the film is rubbed.
[0035] Water based coating compositions according to the invention
can be prepared simply by intermixing a water based coating
composition with a separately prepared waterborne dispersion of
cured condensation curable silicone particles. Water based coating
compositions can also be prepared by producing the coating resin
component in a waterborne dispersion of cured condensation curable
silicone particles. When a water based coating composition having a
high total solids concentration is desired, it is preferred to use
a waterborne dispersion of cured condensation curable silicone
particles that has a high concentration of cured condensation
curable silicone particles, or to produce the coating resin
component in the waterborne dispersion of cured condensation
curable silicone particles. The level of addition of the waterborne
crosslinked silicone particle suspension with respect to the water
based coating composition is not critical, but the waterborne
crosslinked silicone particle suspension is preferably used in an
amount that provides 0.01 to 10 weight parts of crosslinked
silicone particles from the suspension per 100 weight parts of
solids in the coating composition.
[0036] Water based coating compositions according to the invention
may contain other components in addition to the water based
dispersion of cured condensation curable silicone particles, such
as inorganic particles, thickeners, and pigments.
[0037] Water based coating compositions according to the invention
can be applied by coating methods used in the application of
organic solvent based coating compositions, such as spray coating,
electrostatic coating, immersion coating, curtain flow coating,
roll coating, and shower coating.
EXAMPLES
[0038] The following working examples are set forth in order to
illustrate this invention in more detail. Viscosity values in the
examples were measured at 25.degree. C., and properties of the
crosslinked silicone particles were measured using the following
methods. Durometer of Crosslinked Silicone Particles
[0039] A crosslinked silicone sheet with a thickness of 1 mm was
prepared by maintaining a condensation catalyst containing
condensation crosslinking silicone composition for one week at
25.degree. C. to effect crosslinking. Type A durometer hardness was
measured on the crosslinked silicone according to the protocol of
JIS K 6253-1997 using a micro hardness testing device of H. W.
Wallace Co.
[0040] Average Particle Size of Crosslinked Silicone Particles
[0041] The average particle size was determined for a waterborne
crosslinked silicone particle dispersion using a laser diffraction
instrument for measuring particle size distributions. The
instrument was a Model LA-500 of Horiba Seisakusho. The median
diameter, i.e., the particle diameter corresponding to 50 percent
of the cumulative distribution, was measured with the instrument
and was used as the average particle size of the crosslinked
silicone particles.
[0042] Average Particle Size of the Condensation Catalyst
Emulsion
[0043] The average particle size of the condensation catalyst
emulsion was measured using a laser scattering submicron particle
analyzer. The device was a Model N4 instrument of Coulter
Electronics.
Reference Example 1
[0044] 84.7 weight parts of adimethylpolysiloxane with 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
produced by partial hydrolysis and condensation of
tetraethoxysilane, and 4.8 weight parts of
3-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 was further emulsified to
homogeneity using a colloid mill, and diluted with 58 weight parts
of pure water to produce an emulsion of a condensation reaction
crosslinkable silicone composition.
[0045] To the emulsion was added a condensation catalyst emulsion
having an average particle size of 1.2 .mu.m. The condensation
catalyst emulsion was prepared by emulsification of one weight part
tin (II) octanoate in an aqueous solution of 9.75 weight parts of
pure water and 0.25 weight part sodium polyoxyethylene lauryl
sulfate anionic surfactant.
[0046] The combined emulsion mixture was allowed to stand for one
day which resulted in the production of a uniform and gel free
waterborne suspension of crosslinked silicone particles. The
composition was designated suspension (A). When suspension (A) was
filtered through a 200 mesh screen, the amount of retained
crosslinked silicone particles was no more than 0.1 weight percent
of the total amount filtered. The crosslinked silicone particles in
suspension (A) were rubbery and had a type A durometer hardness of
60 and an average particle size of 2 .mu.m.
Reference Example 2
[0047] 84.7 weight parts of a dimethylpolysiloxane with the formula
HO((CH.sub.3).sub.2SiO).sub.11H, 10.5 weight parts of ethyl
polysilicate with the formula
(C.sub.2H.sub.5O).sub.12Si.sub.5O.sub.4 produced 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 of 30 weight parts of
pure water and one weight part of sodium polyoxyethylene lauryl
sulfate anionic surfactant. The mixture was further emulsified to
homogeneity using a colloid mill, and diluted with 58 weight parts
of pure water to produce an emulsion of condensation reaction
crosslinkable silicone composition.
[0048] A condensation catalyst emulsion having an average particle
size of approximately 1.2 .mu.m was added to the emulsion of
condensation reaction crosslinkable silicone composition. The
condensation catalyst emulsion was prepared by emulsification of
one weight part of tin (II) octanoate in an aqueous solution of
9.75 weight parts of pure water and 0.25 weight part of sodium
polyoxyethylene lauryl sulfate anionic surfactant. The combined
emulsions were allowed to stand for one day which resulted in
production of a uniform and gel free waterborne suspension of
crosslinked silicone particles designated suspension (B). When
suspension (B) was filtered through a 200 mesh screen, the amount
of crosslinked silicone particles retained on the screen was no
more than 0.1 weight percent of the total amount filtered. The
crosslinked silicone particles in suspension (B) were rubbery and
had a type A durometer hardness of 60 and an average particle size
of 2 .mu.m.
Reference Example 3
[0049] A composition (I) was prepared by mixing 20 weight parts of
a dimethylhydrogensiloxy endblocked methylhydrogen polysiloxane
with a viscosity of 10 mPa.multidot.s, 5 weight parts of
3-glycidoxypropyltrimet- hoxysilane, and 95 weight parts of a
dimethylpolysiloxane with the formula
HO((CH.sub.3).sub.2SiO).sub.35H.
[0050] A composition (II) was prepared by mixing 5 weight parts of
3-glycidoxypropyltrimethoxysilane, 1.0 weight part of dibutyltin
dioctoate, and 95 weight parts of a dimethylpolysiloxane with the
formula HO((CH.sub.3).sub.2SiO).sub.35H.
[0051] Compositions (I) and (II) were placed in separate holding
tanks, and the tanks were cooled to -10.degree. C. 500 weight parts
of composition (I) and 500 weight parts of composition (II) were
mixed to homogeneity by passage through a static mixer manufactured
by Tokushu Kika Kabushiki Kaisha. The mixture was transferred to a
high speed stirred mixer, and 9,000 weight parts of ion exchanged
water, and 20 weight parts of ethylene oxide adduct of
trimethylnonanol, a nonionic surfactant sold under the name
Tergitol.RTM. TMN-6 by Union Carbide Corporation, were poured into
the mixer at the same time. Stirring was carried out at 1,400 rpm,
followed by passage through a colloid mill, to prepare an emulsion
of condensation reaction crosslinkable silicone composition. The
emulsion was maintained for two days at room temperature to produce
a waterborne suspension of crosslinked silicone particles
designated suspension (C). When suspension (C) was filtered through
a 200 mesh screen, the amount of crosslinked silicone particles
retained on the screen was 0.5 weight percent of the total amount
filtered. The crosslinked silicone particles in suspension (C) were
rubbery and had an A durometer hardness of 42 and an average
particle size of 3 .mu.m.
Reference Example 4
[0052] 84.7 weight parts of a dimethylpolysiloxane with the formula
HO((CH.sub.3).sub.2SiO).sub.11H, 10.5 weight parts of ethyl
polysilicate with the formula
(C.sub.2H.sub.5O).sub.12Si.sub.5O.sub.4 produced by partial
hydrolysis and condensation of tetraethoxysilane, and 4.8 weight
parts of 3-glycidoxypropyltrimethoxysilane were mixed to
homogeneity. The mixture was emulsified in an aqueous solution of
30 weight parts of pure water and 0.5 weight part ethylene oxide
adduct on trimethylnonanol, a nonionic surfactant sold under the
name Tergitol.RTM. TMN-6 by Union Carbide Corporation. The
composition was further emulsified to homogeneity using a colloid
mill and then diluted with 58 weight parts of pure water producing
an emulsion of a condensation reaction crosslinkable silicone
composition.
[0053] 0.5 weight part of sodium polyoxyethylene lauryl sulfate
anionic surfactant was added to the emulsion. The emulsion was
mixed with a condensation catalyst emulsion having an average
particle size of 1.2 .mu.m. The condensation catalyst emulsion was
prepared by emulsifying one weight part of tin (II) octanoate in an
aqueous solution of 9.75 weight parts of pure water and 0.25 weight
part of sodium polyoxyethylene lauryl sulfate anionic surfactant.
The composition was allowed to stand for 1 day resulting in a
uniform and gel free waterborne suspension of crosslinked silicone
particles designated suspension (D). When suspension (D) was
filtered through a 200 mesh screen, the amount of crosslinked
silicone particles retained on the screen was 1.9 weight percent of
the total amount filtered. Crosslinked silicone particles in
suspension (D) were rubbery and had an A durometer hardness of 60
and an average particle size of 4 .mu.m.
Examples 1 and 2 and Comparative Examples 1 and 2
[0054] Each waterborne crosslinked silicone particle suspension
(A)-(D) prepared and described in Reference Examples 1-4 was added
to a water based urethane resin paint manufactured by Kansai Paint
Co., Ltd., and to a water based acrylic resin paint also
manufactured by Kansai Paint Co., Ltd.. The suspensions were added
in an amount to provide 1.5 weight parts of crosslinked silicone
particles for each 100 weight parts of solids in the respective
paint. In each case, addition of the suspension to the paint was
followed by shaking 50 times to yield a water based coating
composition. Each of the water based coating compositions were
applied to a polyethylene terephthalate (PET) film and dried by
heating for 10 minutes at 100.degree. C. to produce a paint film
with a thickness of 15 .mu.m.
[0055] Using a light microscope at 1000 .times. magnification, each
paint film was examined for the existence of pinholes due to escape
of crosslinked silicone particles from the paint film surface, and
for the occurrence of crosslinked silicone particles which had
segregated to the paint film surface. A value of + was assigned to
films with an absence of pinholes and crosslinked silicone
particles segregated to the coating film surface; and a value of
.times. was assigned when either or both of these phenomena were
observed. Table 1 shows the evaluation of the paint films.
1 TABLE 1 Comparative Comparative Example 1 Example 2 Example 1
Example 2 waterborne cross- A B C D linked silicone particle
suspension urethane resin + + x x acrylic resin + + x x
[0056] The flattening performance of each paint film surface was
also evaluated using the scale + for strong flattening activity and
particle aggregates of no more than 30 .mu.m; .DELTA. for some
flattening activity present and particle aggregates of no more than
30 .mu.m; and .times. for little flattening activity. Table 2 shows
this evaluation of the paint films.
2 TABLE 2 Comparative Comparative Example 1 Example 2 Example 1
Example 2 waterborne cross- A B C D linked silicone particle
suspension urethane resin + + + .DELTA. acrylic resin + + .DELTA.
.DELTA.
[0057] The occurrence of scratching of the paint film surfaces was
evaluated after each paint film surface had been rubbed five times
with a piece of polypropylene resin. The occurrence of scratching
was evaluated using the scale + for no scratching of the paint
film; .DELTA. for small scratches in the paint film; and .times.
for large scratches in the paint film. Table 3 shows the results of
this evaluation of the paint films.
3 TABLE 3 Comparative Comparative Example 1 Example 2 Example 1
Example 2 waterborne cross- A B C D linked silicone particle
suspension urethane resin + + x x acrylic resin + + .DELTA.
.DELTA.
[0058] In view of the above, it can be seen that the method of the
invention for producing water based coating compositions provides
very efficiently produce water based coating compositions that can
form highly scratch and abrasion resistant coatings in which the
crosslinked silicone particles are thoroughly dispersed.
[0059] 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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