Note: Descriptions are shown in the official language in which they were submitted.
PATENT
2090-30-24
PREPARING_AND COATING A GLASS SUBSTRATE
The present inven~ion is directed to priminq a glass
substrate for coating and subsequently coating the glass
substrate with a polyvinylidene fluoride/acrylic resin
coating containing inorganic pigments.
BACXGROUND OF THE INVENTl N
The present invention is direc~ed to an improved method
of coating a glass substrate with pigmented coatings in
which the resin system is a mixture of a fluorocarbon and a
thermoplastic polyacrylic resin.
Fluorocarbon-based coating compositions have been
recognized to Aave excellent w~-athering propertie~,
including gloss retention, water resistan~e and color
retention. The present invention is directed to coating
glass with a fluorocarbon-based coating composition in a
manner that provides excellent adherence o~ the coating to
the glass. Glass so coated may have widespread application
in curtain walls where they may provide economic ~dvantages
relative to aluminum skins tha~ are curren~ly used.
A lo~g recognized problem of glass coated wi~h a
fluorocarbon-based coating is obtaining adequate adherence
of the coating to the glass.
P~T~I~T
2C90-3C 24
~.S. Patent No. 4,879,345 to Connelly et al., issued
November 7, 1989, teaches a coating composition of a
fluorocarbon, an organosilane, an acrylic resin having
functional groups reactiv~ with the organosilane and (optionally)
pigments and fillers. This coating is applied directly to the
glass surface, and it is theorized that the organosilane forms
bonds between the glass and the functional acrylic resin.
V.S. Patent No. 4,510,282 to Goll, issued April 9, 1985,
teaches a composition which is an aqueous dispersion of
polyvinylidene fluoride (PVDF), acrylic co-polymer and pigment.
Examples are given in which the composition also contains an
organosilane. Thi~ reference t~aches ~at the woxk material
may be pre-treated with gamma-methacryloxypropyltrimethoXy-
silane and then pre-impregnated with up ~o ~hree coa~s of a
PVDF latex prior to adding the coa~ing composition. While
the pre-treatment of the work ma~erial with organosilane may
promote bonding to the PVDF later, the subsequent pre-
impregnation with PVDF later would prevent bonding directly
between the organosilane on the work material and components
of the coating material. Although water-based system5 are
desirable from an emissions and environmen~al point of view,
organosilanes are unstable in the presence of water,
converting to silanols and then to siloxanes. Thus a water-
based coating composition would la k long-term stability,
changing in silane co~position over time.
- The present invention is directed to an improved method
of coating glass with a fluorocarbon-based coating
composition.
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PATEN~
2090-30-24
SUMMARY OF THE_INVENTION
In accordance wi~h the presen~ inv~ntion, a properly
cleaned glass substrate is ~irst primed with a clear, dilute
solution of a mixture of an organosilane and an
organotitanate. A coating composi~ion is applied which
comprises a fluorocarbon resin, an organosilane and/or an
organotitanate~ a thermoplastic polyacrylate resin having no
groups reactive with the organosilane and/or an
organotitanate, and an inorganic pigment, the components
being carried in an organic solvent. Two successive
coatings may be applied to a surface of a glass substrate,
each having a pigment level and being applied to a
sufficient thickness to be fully opaque and thereby give
distinctly differen~ appearances to ~he glass~ which is
coated on only one side, as vie~ed from opposite sides.
DETAILED DESCRIPTION OF CERT~IN PREFERR D EM~ODIMENTS
Fluorocar~ons useful in forming the coating
compositions o~ the present inven~ion include polyvinyl
fluorides, polyvinylidene ~luori~es (PVDF), vinyl fluoride
copolymer~ and vinylidene ~luoride copolymQrs. The
preferred fluorocarbon is po1yvinylidene fluoride. The
copolymers preferably include at least ab~ut 75 wt.% and
preferably at le~st abou~ 90 wt.% vinyl ~luoride or
viny1idene fluoride monomers. Examples of monomers which
may be copoly~erized with vinyl fluoride or vinylidene
fluoride are e~hylene, propylene~ isobutylene, styrene,
difluorochloroethylene, tetrafluoroethylene
trifluoropropylene, h~xafluoropropylene, vinyl formate,
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PATENT
2090~30-24
vinyl acetate, vinyl propionate, viny~ ~utyrate, acrylic
acid and its salts, methyl methacrylate t allyl methacrylate,
acry}onitrile, methacrylonitrile, N-butoxymethyl acrylamide,
allyl acetate and isopropenyl acetate.
The fluorocar~on comprises between abou~ 50 and about
~0 wt. percent of the resins of the coating, the
thermoplastic polyacrylate resin compri~e~ between a~out lo
and about 50 wt. percent of the resi~s. Herein, unless
otherwise ~tated, non-rPsin components will b~ expressed as
parts per hundred (phr) resin based upon the total amount oP
resin, including the fluorocarbon and the polyacrylate.
A mixture of an organosilane and an organotitanate is
used as a primer to treat the glass ~urface. An
organosilane or organotitanate is ~lso incorporated in the
pigmented coating or coatings~
Organosilanes, such as ~hose described in above-
referenced U.S. Patent No. 4,879,345, are useful in the pr~
invention both for applica~ion as a clear pri~er and as a
component of the pigmented coating or coatings. Some
preferred organosilanes for use in ~h~ method of the present
invention are gamma~methacryloxy propyltrimethoxysilane,
gamma-a~inopropyltriethoxysilane, gamma- -
glycidoxypropyltrimethoxysilane, gamma-
~ercaptopropyltrimethoxysilane, beta-3,4-
epoxycyclohexylethyltrimethoxysilane, gamma-
aminopropyltrime~hsxysilane,
aminoethyla~inopropyltrimethoxysilane, gamma~
methacryloXypropyltrimethoxysilane, vinylbenzyl
(trimethoxysilyl) propyl mono hydrochloride, 1,2-bis
(trim~hoxy~ilyl) ethane, phenylaminopropyl~ri~ethoxysilane,
3CH-styrylmethyl-2~amino ~tAylamino propyl~rimethoxysilane
hydrochloride, vinyltrimethoxysilane, N-C3-acryloxy-2-
hydroxypropyl)-3-amino-propyltriethoxy~ilan~,
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PAT~NT
2090-30-2~
N 2(vinylben~ylamino)-ethyl-3-aminopropylkrimathoxysilane
mono hydroqen chloride, 3-(N-styryl~ethyl-2~
aminoethylamino)-propyl rimethoxysilan~ hydrochloride and
triethoxysilyl modifiad polybutadiene.
Suitable organotitana~es include, but are not limited
to, tetraisopropyl titanate, tetrabu~yl titanate, and
tetra~is (2-ethylhexyl) ~itanate. Also, titanate chelates,
such as titanium bis(ethyl-3-oxobutanolato-O1,03)bis(2-
propenolato)-, ethanol, 2, 2' 2"-nitrilotris-,
titanium(4+)salt, and ti~anate (2-),dihydroxy bis [2-
hydroxypropanato (2-)_ol,o2]-, are suitable.
In the pri~er, the organosilane and organoti~anate are
mixed together at a weight ratio of be~ween about 5:1 and
about 1:5, preferably between about 2:1 and about 1:2.
The organosilane/organoti~anate primer is applied to a
glass surface, generally as a dilute, e.g., 2-25 wt.%,
solution in an organic solvent ~5) . The
organosilane/organotitana~ primer is preferably applied to
between about 1.0 and a~out 5.0 ~m. (organosilane plus
organotitanate) per m2. In pigmente~ coating compositions
in accordance with the present invention, organosilane
and/or organotitanate is used at between about 2 and about
12 phr, preferably betw~en about 3 and about 6 phr.
Above-referenced U.S. Patent No. 4,879,345 t~aches that
an acrylate adjuvant resin having functional groups reactive
with the organosilane is necessary to obtain adequate
adhesion. Surprisingly and unexpectedly, it is found that
in a coating composition containing an inorganic pigment or
filler, it is preferreA that the thermoplastic acrylate
resin b~ non-reactive with the organosilane or the
organotitanate of the primer or the organosilane or
organotitanate o~ the coating composition. U.SO Patent No.
4,879,345 proposes thak by using an organosilane-reactive
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PA~ENT
2090-30-24
adjuvant resin, a bond is formed between t.h~ glass and the
adjuvant resin. Although applicants are no~ bound by
theory, evidence applicants have accumulated indicates that
in an inorganic piymen~-con~aining coating composition, a
bond is formed ~hrough the organosilanes and organotitanate
directly between the glass and the inorganic pigment
particles, thereby achieving a s~ronger bond between the
glass and the coating.
Preferred polyacrylates are polymers and copolymers
formed from esterified acrylates having no additional
functional groups, such as esters of acrylic acid and
methacrylic acids with mono-functional alcohols. ~owever,
in accordance with the lnvention, the polyacrylates may have
functional groups, providing they do not co~tain any
significant amounts of functional groups reactive with the
organosilane selected. On an equivalence basis, the
polyacrylate resin should con~ain no more ~han bout 10%
relative to co-reactive groups of the organosilane or
organotitanate in the coating composition and preferably no
co-reactive groups at all. This allows all bonding to take
place b~tween the organo~ilane and organotitanate, both in
the primed glass surface a~d in the coating composition, and
the inorganic pigment or fill2r.
Th~ inorganic pigment or filler i5 us~d at a level of
at least 2 phr, up to about 150 phr. Preferably, the
selected pigment or filler is neither acid nor water
sensitive. Examplec of inorganic fillers useful in the
present invention are silicates; such as mica, aluminum
silicat~ and glass par~iculatest inorganic oxides, such as
titanium dioxide; strontium chromate; and barium sulfate.
It is believed that the excellent glass-to-coating
bonding achieved b~ the method of the present invention is a
result of direct chemical bonding be~ween the glass and some
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PATENT
209~-30-~4
of the inorganic pigment particles. It i5 believed that the
absence of reactive func~ional groups on ~he acrylic resin,
prevents khe depletion of organosilane and organotitanate by
reaction with the polyacrylate resi~ and t:he organosila~e
and organotitanate, which such raaction would result in
bonds that are less s~rong ~han the bonds bgtwe~n the glass
and the inorganic filler ~hrough the organo~ilane and
organotitanate.
The coating composition may contain other components
well known in the art, including W -inhibitors, colorants,
ceramic fiber, and organic pigments. Although organic
pigments may be used in addition to inorganic pigments,
organic pigments are found not to significantly promote
bonding of the coa~ing to the glass. Indeed, if organic
pigments are used in the absence o~ inorganic pigments,
there is insufficient bonding o~ ~he coa~ing to the glass.
The types and amounts of pigments and coloran~s and the
thickn~ss to which the coating is applied de~ermines the
appearance of the final pro~uc~. Typically ~he coa~ing is
applied directly ov~r the primed glas~ ~o a thickness of
between about S and about 50 micr~ns. The appearance o~ the
coating may range from translucent, as is desirable for a
lighting fixture, to fully opaque, as is g~nerally desirable
in curtain wall panel~.
In o~e a~pect of ~he i~ven~ion~ a glass substr~e will
be prim~d, coated with a ~irs~ coa~ing, as described above,
th~ first coating containing suf~icient pigment and bein~
applied to a thickness as to ~ fully opaque and then coated
with a second coating, as da~cribed above, al~o containing
sufficient pigment and being applied to a ~hickness as to be
fully opaque. Through the us~ of different pigments and
colorants, each side of the glass may have entirely
di~ferent appearances. This may be particularly desirable
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PATENT
2090-30-24
in curtain wall panels, particularly t~ose used in the
interior of a building, where a glass panel coated on one
side only, but with two coats, can have entirely different
appearances when viewed from opposite side~s.
Be~t results are obtained when the glass i5 thoro-lghly
cleaned. One very suitable protocol involve~: 1. rinsing
with water, 2. polishing with an abrasive, such as cerium
oxide, 3. rinsing with water, 4. cleaning with a deteryent
solution, 5. rinsing with deionized w~ter, and 6. drying.
The unpigmented organosilane/organotitanate primer is
carried in an organic solvent as is the pigmented coating
composition. Suitable organic solvents include, but are not
limited to toluene, xylene and mixtures thereof.
Preferably, the primer composition is water-~ree
particularly i~ the primer contains organosilane, as water
tends to degrade organosilane. Generally, primer
compositions in accordancP with the inv~ntion are applied at
between about 1 and about 45 percent solids; pigmented
coatings are typically applied at be~ween abou~ 10 and about
55 percent solids. The me~hod of applying the coating may
determine the percent solids of application. The primer is
typically applied by spray coating and then dried prior to
application of the coating co~position. The coating
composition may be applied by a variety of me~hod~, such a~
spray coating~ roller coating, silkscreen, curtain coating,
and electrostatic spray coating, such as that involving
turbodisks and turbobells.
After application, the coating is dried, typically at
elevated temperatures. After the coating(s) is applied and
dried, it is typical to bake the coating to fuse the
resinous material and promote bonding of ~he coating to the
glass. Baking is typically at between abou~ 200 and about
250C~ If more than one coating is applied, baking
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PATE~NT
2090-30 ~4
generally follows application and drylng of the two
coatings.
Coatings produced in accordance with ~he present
invention have proven to be ex~remely stronyly bonded to
glass substrates. It has proven difficul~ to scrape coating
from a glas~ substrate without scraping away glass itself.
Coatings in accordance with the present inven~ion are highly
resistant to water, including boiling water and humid
atmosphere.
The coatings may be applied to any glass substrate.
For curtain wall panels, particularly exterior curtain wall
panels, tempered glass is preferred for safety reasons.
The invention will now be described in greater detail
by way of specific examples.
Examples 1-7
~all parts by weight unless stated otherwise)
Example 1
Tetra ~2-~ethoxyethoxy) silane 2.5 parts
Tetrabutyl titanate 2.5 parts
Tetrapropyl orthosilicate2.5 parts
Naphtha (petroleum light aromatic) 42.5 parts
Toluene 25.0 parts
Example 2 (pigmented coating composition)
parts
Thermoplastic acrylic resin*10.31
(60,000)MW(wt.ave)
Toluene 12.93
Iron oxide 10.30
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PATENT
2090-30_24
"Kynar 500" (PVDF)
Butyl "Cellosolve"2 24-
Di-methyl phthalate 8.77
3-ethoxy propionate 8.25
~3-glycido~xpropyl)trim2thoxysilane 2 o
*polymethylmethacrylate (ACRYLOID B-44 , Rohm & Haas)
Example 3 (pigmented coating composition)
Thermoplastic acrylic resin
(60,000) MW (wt.aveJ 10.54
Mica (3-48 micron)
"Kynar 500"l 8.31
3-ethoxypropiQnate 24.42
Butyl "Cellosolvel'2 11.19
Di-methyl phthalate
Toluene 8.88
Lampblack, iron oxide
(3-glycidoxypropyl)trimethoxysilane 1 96
l. Trade Mark
2. TFade Mark,Butyl "Cellosolve" is ethylene glycol monobutyl
ether (2-butoxyethanol)
3- Trade Mark
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PATENT
2090-30~24
Example 4 (pigmented coating composition)
Ther~oplastic acrylic resin 11.63
(60,000) MW ~wt.ave)
Toluene 12.15
Lampblack 1.90
"Kynar 500"* 27.32
~utyl "Cellosolve"* 9.70
Di-methyl phthalate 9.13
3-ethoxy propionate 10.49
N-2(vinylbenzylamino)-ethyl-3-
aminopropyltrimethoxysilane mono(HCl) 1.96
Example 5 (pigmented coating composition)
Ther~oplastic acrylic resin 8.96
~60,000) MW (wt. ave)
Toluene - 12.97
Titanium dioxide 14.97
"Kynar 500"* 21.07
Butyl "Cellosolve"* 8.80
Di-methyl phthalate ~.29
3-ethoxy propionate 9.70
3-methacryloxypropyl-trimethoxysilane 2.00
* Trade Mark
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PATEN'r
~090-30~2
Example 6
A sur~ace of a sheet of tempered gla~;~; was thoroughly
cleaned. To this surface was applied, ~y spraying/ the
primer o~ Example ~ in an amount suf f icien~ ~o provide th~
organosilane and organoti'canate at a level of ~bou~ 3 gm per
square meter and allowed to air dry.
S~bsequently, the coating composi~ion of example 4
above was applied by sprayir~g to a thicknes~ of about :L25
microns and allowed to air dry. The coa~ed glass was th~n
baked at 245C for 15 min. An opaque uniform ~ilm is
f ormed O
A portion of the glass is submerged in boiling water
~or 2 hours. Anoth~r portion of the glass is submerged in
water for 7 days at 60C. In both case~;, there is no loss
of coating, indicating excellent adhesion.
Example 7
Tempered glass was ~ aned, primed with ~he
2 0 composill:ion of Exa~ple 1 in an amount to provide the
organosilane and organotitanate at a level of about 3 gm per
square meter. Then the coa~ ing compositi.on of Example 4 wa~
applied a~ per Ex~mple ~. Subs~quently, ~he pigmented
coating of Example 7 was applied by spr2~ying over ~he ~irst
coating co~npo~ition to a thickn~;s o~ 125 microns~ Aftex
dryillg/ th~ glass was again ~aked at 24SC fc~r 15 mi:n. When
viewed through the glass the f irs~ oating appears uni~orm
with high gloss and excellent del?~h o~ age and with no
chang~ in appearance caused ~y ~e ses:ond coa~ing. From the
opE30site side, th~ glass c:o ted with two coating
compo~itions app~ars unifo~n with no show-~hrough of the
first coating composition.
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PATENT
2090-30-24
While the invention h~s been described in terms of
certain preferred embodiments, modifications obvious to one
with ordinary skill in t~e art may be ma~ea without depar~ing
from the scope of the present invention.
Various features of the invention are set ~orth in the
following claims.
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