Note: Descriptions are shown in the official language in which they were submitted.
8CS-3417
1 1 62~
This invention relates to non-opaque abrasion
and chemical solvent resistant thermoset organopolysiloxane
coated shaped polycarbonate articles wherein the
organopolysiloxane top coat is uniformly and tenaciously
adhered to the polycarbonate substrate. More
particularly, the present invention relates to an
organopolysiloxane coated polycarbonate article
having a primer layer comprised of from about 25 to
about 85 weight percent thermoset acrylic polymer
and from about 15 to about 75 weight percent of at
least one ultraviolet light screening compound
disposed between the polycarbonate substrate and the
organopolysiloxane top coat.
BACKGROUND OF THE INVENTION
The use of transparent glazing materials
utilizing polycarbonate resin as a structural component
for windows, windshields and the like are well known.
While these polycarbonate resins are easily fabricated
into the desired shape and have excellent physical
and chemical properties, such as being less dense than
glass and having more breakage resistance than glass,
their abrasion and chemical solvent resistance is
relatively low.
In order to overcome this relatively low
abrasion resistance and to otherwise improve the
surface characteristics of the polycarbonate,
various coatings have been applied onto the
polycarbonate substrates. U.S. Patent 3,582,398
H.R. Ringler - issued June 1, 1971 describes a
fabricated polycarbonate part having improved optical
properties consisting of a polycarbonate substrate
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~ 3 62~ 8Cs~3417
having a transparent coating thereon consisting of a
thermoplastic polymethylmethacrylate. U.S. Patent
4,061,652 - S.F. Schroeter, issued December 6, 1977,
describes a coating for polycarbonate resins comprised
of (i) an acrylic resin which is a mixture of
olefinically unsaturated organic monomers in
combination with an acrylic polymer, and (ii) certain
urethanes of hydroxybenzotriazoles and
hydroxybenzophenones in combination with certain
catalysts. U.S. Patents 3,451,838 - A~Jo Burzynski,
issued June 24, 1969j 3,983,997 - H.A. Clark, issued
October 19, 1976 and 4,027,073- H.A. Clark, issued
May 31, 1977 disclose organopolysiloxane coating
compositions and techniques for the application of
these organopolysiloxane coatings onto polycarbonate
surfaces. While these coatings have many desirable
properties, e.g., they are hard, abrasion xesistant,
and chemical solvent resistant, these organopolysiloxane
coatings do not in all instances possess the requisite
degree of uniform adherence to and durability on
these polycarbonate surfaces. U.S. 3,707,397
D.F. Gagnon, issued December 26, 1972 describes a
process for providing a hard coating on, inter alia,
polycarbonate articles, said process including priming
the polycarbonate surface with an adhesion promoting
thermosettable acrylic and applying an organopolysiloxane
onto the primed surface. This reference further
teaches that the thickness of the thermosettable
acrylic polymer primer layer varies between 0.01 mil
up to as much as 0.5 mil or even more.
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However, organopolysiloxane coated
polycarbonate articles which contain a thermoset
acrylic primer have suffered from the problem of loss
of adhesion of the organopolysiloxane top coat to
the primed polycarbonate substrate upon exposure to
weathering.
It has now been discovered that, if the
primer layer is loaded with high amounts of
ultraviolet light absorbers, i.e., contains from
about 15 to about 75 weight percent of at least
one ultraviolet lîght screening or absorbing compound,
then the adhesion of the organopolysiloxane top coat
is not deleteriously affected upon exposure to
weathering.
DESCRIPTION OF THE INVENTION
This invention relates to non-opaque
organopolysiloxane coated polycarbonate articles
having an adhesion promoting primer layer comprised
of from about 25 to about 85 weight percent of a
thermoset acrylic polymer and from about 15 to
about 75 weight percent of at least one ultraviolet
light absorbing compound disposed between the
polycarbonate surface and the thermoset
organopolysiloxane top coat.
In the practice of the present invention,
prior to the application of the organopolysiloxane
top coat to the polycarbonate surface, -the surface
is first primed by the application thereon of a
primer layer of controlled thickness containing a
thermoset acrylic polymer.
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~ 1 ~2~$ 8CS-3~17
The aromatic carbonate polymers of the instant
invention are known compounds and have recurring units
of the formula:
A
- R - C - R - O - C - O (I)-
B O
wherein each -R- is selected from the group consisting
of phenylene, halo-substituted phenylene and alkyl
substituted phenylene; and A and B are each selected
from the group consisting of hydrogen, hydrocarbon
radicals, free from aliphatic unsaturation and of
radicals which together with the adjoining -C- atom
form a cycloalkane radical, the total number of
carbon atoms in A and B being up to 12.
These aromatic carbonate polymers may be
prepared by methods well known in the art and described
in U.S. Patents 3,989,672 - J.H. Vestergarrd, issued
November 2, 1976; 3,275,601 - H. Schnell, issued
September 27, 1966; and, 3,028,365 - H. Schnell
et al, issued April 3, 1962.
In the practice of -this invention, any of
the aromatic polycarbonates can be employed herein.
However, particularly useful are the aromatic
polycarbonates prepared by reacting a dihydric
phenol, such as bisphenol-A (2,2-bis~4-hydroxyphenyl)
propane) with a carbonate precursor. Typical oE
some of the dihydric phenols that may be employed
in the practice of this invention are
bis(4-hydroxyphenyl)methane, 2,2-bis~4-hydroxyphenyl)
propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane,
4,4-bis-(4-hydroxyphenyl)heptane,
~ 1 6 2 4 ~ 3 8CS-3417
2,2-(3,5,3',5'-tetrabromo-4,~'-dihydroxydiphenyl)propane,
(3,3'-dichloro-4,4'-dihydroxydiphenyl)me-thane. Other
dihydric phenols of the bisphenol type are also
available and are disclosed in U.S. Patent Nos.
2,99 ,835 - E.P. Goldberg, issued September 12, 1961;
3,028,365 - H. Schnell et al, issued April 3, 19~2;
and, 3,334,154 - J.K.S. Kim, issued August l, 1967.
In addition, the reaction is earried out
with the carbonate precursor in the presence of a
molecular weight regulator, an acid acceptor and a
catalyst. The preferred carbonate precursor generally
employed in preparing earbonate polymers is earbonyl
ehloride. However, other carbonate precursors may
be employed and this includes other carbonyl halides,
carbonate esters or haloformates.
The acid acceptors, molecular weight
regulators and catalysts employed in the process of
preparing polycarbonates are well known in the art
and may be any of those eommonly used to prepare
polyearbonates.
The thermosettable aerylie polymers whieh
are contained in the primer compositions are well
known in the art. Exemplary thermosettable acrylics
which may be utilized in the practice of this
invention are set forth in Encyclopedia of Polymer
Science and Technology, Vol. 1, Interscience Publishers,
John Wiley & Sons, Inc., at p. 273 et seq., and in
the Chemistry of Organic Film Formers, by
D.H. Solomon, John Wiley & Sons, Inc., 1967, at
page 251 et seq., and the references cited therein.
1 3 62~4g
8CS-3417
Generally, the term, thermosettahle acrylics, as used herein
includes an acrylic polymer or copolymer having reactive functional
groups which are capable of reacting between themselves to erfect
a cross-linkage thereof. These functional groups may be the same,
provided they are of the type which will react between themselves,
or the polymer or copolymer may contain two or more different types
of reactive functional groups, such as, for example, an epoxide
group and a carboxyl groupO The term, thermosettable acrylics,
also includes acrylic polymers or copolymers having a reactive
functional group to which there is added an appropriate
cross-linking agent which reacts wi~h the functional group to
effect cross-linking. The term, thermosettable acrylics, still
further includes a mixture of two or more polymers containing
cross-linkable functional reactive groups. ~hese polymers may be
acrylic polymers or copolymers having reactable, cross-linkable,
functional groups thèreon, or at least one of the polymèrs may be
an acrylic polymer or copolymer having a reactive functional group
and the other polymer or copolymer may be one or more other types
of known polymers having functional groups which are reactive
with the acrylic functional group to provide the thermoset product
as a result of cross-linking.
Typically, the reactions involved in cross-linking the
thermosettable acrylic polymers are reactions between, for example,
epoxide functional groups and amine functional groups; epoxide
2; functional groups and acid anhydride functional groups; epoxide
functional groups and carboxyl functional groups, including
phenolic hydroxyl groups; epoxide functional groups and N-methylol
or N-methylol-ether; sarboxyl functional groups and N-methylol or
N-methylol-ether functional groups; interreaction between carboxyl
_ 6 ~
1 ~ 6 ~
8CS-3417
and isocyanate groups; reactions between hydroxyl, for example
polyols, and isocyanate groups, and reactions between amine groups
and N-methylol or N-methylol-ether groups. In the usual case of
resin mixtures, the acrylic will be present in a major proportion,
i.e., greater than 50 weight percent and, more ~ypically, will be
present in an amount in excess of about 70 percent. The needed
functional group in the acrylic copolymer, which is the foundation
of the thermosettable acrylic polymer, is provided by employing
in the copolymerization a monomer which supplies the needed
reactive functional group into the polymer chain. Usually, this
copolymerizable functional group-supplying monomer will be present
in small amounts, that is, on the order of 25 weight percent or
less, and typically, between about 1 and 20 percent of the monomer
mass which is polymerized. Exemplary of these functional group-
supplying monomers are glycidyl acrylate, glycidyl methacrylate,allyl glycidyl ether, dimethylaminoethyl methacrylate, vinyl
pyridine, tert-butyl-aminoethyl-methacrylate, maleic anhydxide,
itaconic anhydride, allyl alcohol, monoallyl ethers of polyols,
hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxy-
propyl acrylate, acrylamide, methacrylamide, maleamide,N-methylolmethacrylamide, vinyl isocyanate, allyl isocyanate.
Usually, the other monomer which will be polymerized along with the
monomer supplying the functional group is a lower (Cl-C3) alkyl
acrylic ester or mixtures thereof, e.g , methyl acrylate, ethyl
~5 acrylate, methyl methacrylate, ethyl methacrylate, or
mixtures thereof, in an amount ranging between about 75 parts to
about 99 parts and, more typically, between about 80 parts to
about 97 parts.
1 1 ~2~ 8CS-3417
The thermosettable acrylics are in general
applied from primer compositions containing (i) the
thermosettable acrylics and the ultraviolet light
absorber dissolved in an organic or inorganic
solvent, or (ii) an emulsion containing the thermosettable
acrylics, the ultraviolet light screening compound
an alcohol and water. In the case wherein the primer
composition contains a thermosettable acrylic dissolved
in an organic solvent, the solvent should generally be
relatively volatile and inert, i.e., one that will not
readily react with or too deleteriously affect the
polycarbonate substrate, but which is capable of
dissolving the thermosettable acrylic and the
ultraviolet light screening compound.
The primer compositions contain sufficient
thermosettable acrylic polymer and ultraviolet light
screening compound to provide a primer layer containing
from about 2S to about 85 weight percent thermoset
acrylic polymer and from about lS to about 75 weight
percent of the ultraviolet light absorbing compound.
Generally, this requires that the primer compositions
contain from about 1 to about 20 weight percent of
thermosettable acrylic solids and a sufficient amount
of an ultraviolet light absorbing system to provide a
thermosettable acrylic solid to ultraviolet light
absorber, weight ratio of from about 1:0.2 to about 1:3.
The ultraviolet light absorbing system can be one
which contains only one ultraviolet light screening
compound or it can contain a mixture of two or more
ultraviolet light screening compounds.
~ ~ 624~ 8CS-3417
The ultraviolet light screening compounds
are well known in the art and are compounds which act
to absorb or screen out the ultraviolet radiation.
Illustrative of these compounds are those of the
hydroxy benzophenone and benzotriazole series, the
cyanoacrylates, and benzylidene malonates. Examples
of these include: 2-hydroxy-4-n-o toxybenzophenone,
substituted hydroxyphenylbenzotriazole
2-(2'-hydroxy-5'-methylphenyl) benzotriazole,
2-hydroxy~4-methoxybenzophenone,
2,2'-dihydroxybenzophenone,
2,2',4,4'-tetrahydroxybenzophenone,
2,2'-dihydroxy-4,4'-dimethoxybenzophenone,
2,2'-dihydroxy-4,4'-diethoxybenzophenone,
2,2'-dihydroxy-4,4'-dipropoxybenzophenone,
2,2'-dihydroxy-4,4'-dibutoxybenzophenone,
2,2'-dihydroxy-4-methoxy-4'-ethoxybenzophenone,
2,2'-dihydroxy-4-methoxy-4'-propoxybenzophenone,
2,2'-dihydroxy-4-methoxy-4'-butoxybenzophenone,
2-(2'-hydroxy-5'-tert-butylphenyl) benzotriazole,
2-(2'-hydroxy-3'-methyl-5'-tert-butylphenyl) benzotriazole,
2-(2'-hydroxy-5'-cyclohexylphenyl)-benzotriazole,
2-(2'-hydroxy-3',5'-dimethylphenyl) benzotriazole,
ethyl 3,3-diphenyl-3-cyanoacylate, and
octyl 3,3-diphenyl-2-cyanoacrylate. Further examples
of ultraviolet light screening compounds which may be
used in the practice of this invention may be found
in U.S. Patent No. 3,043,709 - L.E. Amborski, issued
July lO, 1962.
The primer compositions of the instant
invention may also optionally contain various flatting
I ~ 62~ 8CS-3417
agents, stabilizers such as antioxidants, surface-
active agents and thixotropic agents. All of these
additives and the use thereof are well known in the art
and do not require extensive discussions. Therefore,
only a limited number will be referred to, it being
understood that any compounds possessing the ability
to function in such a manner, i.e., as a flatting agent,
surface-active agents and stabilizing agents can be
used.
The various surface-active agents, including
anionic, cationic and nonionic surface-active agents
are described in Kirk-Othmer Encyclopedia of Chemical
Technology, Vol. 19, Interscience Publishers, New ~ork,
1969, pp. 507-593, and Encyclopedia of Polymer Science
and Technology, Vol. 13, Interscience Publishers, New
York, 1960, pp. 477-486.
A uniform film of the primer composition
containing the further curable thermosettable acrylic
and the ultraviolet light absorbing system is applied
onto the polycarbonate surface by any of the known
means such as dipping, spraying, roll-coating and the
like. After the formed polycarbonate part is coated
with the primer composition, the inert volatile solvent
is removed by drying the coated article until a
substantial portion of the volatile solvent
evaporates leaving a solid residue, and thereafter
heat is applied to thermoset the thermosettable acrylic,
thereby forming a primer layer or coating containing
the thermoset acrylic and the ultraviolet light absorbing
system on the polycarbonate surface to which the primer
composition was applied. This primer layer contains
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~ 8CS-3417
from about 25 to about 85 weight percent of the thermoset
acrylic polymer and from about 15 to about 75 weight
p rcent of the ultraviolet light absorbing system,
i.e., at least one ultraviolet light screening compound;
preferably from about 25 to about 80 weight percent of
the ultraviolet light absorbing system; more preferably
from about 25 to about 75 weight percent of the thermoset
acrylic polymer and from about 25 to about 75 weight
percent of the ultraviolet light absorbing system; and
most preferably from about 25 to about 70 weight percent
of the thermoset acrylic polymer and from about 30 to
about 75 weight percent of the ultraviolet light
absorbing system.
&enerally, if less than about 15 weight
percent of the ultraviolet light absorber i5 present in
the primer layer, there is no appreciable improvement
upon the durability of adhesion of the silicone top
coat. If the primer layer contains more than about
75 weight percent of an ultraviolet light absorber,
the adhesion promoting properties of the primer begin to
be deleteriously affected.
After the polycarbonate article which is to
be coated with the top coat composition has been primed
by the application of the primer composition and the
evaporation of the solvent component of the primer
composition and the thermosetting of the thermosettable
acrylic, the primed surface of the polycarbonate
article is then coated with the thermosettable
organopolysiloxane top coating. In the practice of
this invention, an organopolysiloxane coating
composition containing a further curable
-- 11 --
8CS-3417
organopolysiloxane is applied onto the cured primer
and is then cured to form a thermoset
organopolysiloxane coating.
The further-curable organopolysiloxane used
in the practice of the instant invention is the hydrolysis
and partial condensation product of a~ least one compound
represented by the general formula
n (4-n) II.
wherein R2 represents a monovalent hydrocarbon radical
and a hologenated monovalent hydrocarbon radical,
Z represents a hydrolyzable group and n may vary from
0 to 2. More specifically, Z is independently a
member such as halogen t alkoxy, acyloxy and aryloxy.
Preferably, R represents an alkyl radical
containing from 1 to about 8 carbon atoms such as
methyl, ethyl, and propyl through octyl (both normal
and isomeric), an alkenyl radical containing from 2 to
about 8 carbon atoms, such as vinyl and the normal
and isomeric forms of propenyl through octenyl, and
the phenyl radical; Z preferably represents an alkoxy
radical containing from 1 to about 8 carbon atoms
such as methoxy, ethoxy, propoxy, heptoxy, octoxy
and the like, an acyloxy radical containing from 2 to
about 9 carbon atoms such as acetoxy, propionoxy,
butyroxy, pentanoxy, hexanoxy, and the like, and a
phenoxy radical; and n varies from 0 to 2.
Preferred compounds of formula II are
silanes of the formula
R aSi(OR )4 aIII.
and silanes of the formula
R bSi(OCOR )4 bIV.
12 -
1 31 ~2~
8CS-3417
wherein R3 and R5 represent a monovalent hydrocarbon
radical and a halogenated monovalent hydrocarbon
radical, preferably an alkyl radical containing from
1 to about a carbon atoms, an alkenyl radical
containing from 2 to about 8 carbon atoms, and the
phenyl radical; R4 and R6 represent monovalent
hydrocarbon radicals and halogenated monovalent
radicals such as alkyl radicals and phenyl radicals,
but are preferably alkyl radicals of 1 to 8 carbon
atoms; a is O or l; and b varies from O to 2.
Upon hydrolysis, the compounds of formula II,
and more specifically those of formulae III and IV,
are converted to the corresponding silanols. Upon
generation of the silanol, there is condensation of
the hydroxyl substituents to form -Si-O-Si- bonding.
The condensation is not complete, but rather the
organopolysiloxane retains a quantity of silicon-
bonded hydroxyl group. This partial condensate can
be characterized as a further-curable, i.e., further
~0 condensable, siloxanol polymer.
The further-curable organopolysiloxane may
be formulated into the top coat composition as a
solution of the further-condensable siloxanol polymer
in water and alcohol by-product as a concentrated
solution of further-condensable siloxanol in water
and alcohol by-product formed by evaporating off a
substantial quantity of the alcohol by-product and
water, or it may be formulated onto the top coat
composition as a solid partially pre-cured product
by evaporating off a substantial amount of alcohol
by-product and water and then partially pre-curing
and solidifying the concentrated product.
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~ ~ ~24~
8CS-3417
Examples of good silicone top coats are the
foregoing alkoxy and aryloxy functional silanes
represented by formula III and acyloxy functional
silanes represented by formula IV. Such alkoxy
functional, aryloxy functional, and acyloxy
functional silanes are well known materials to
silicone manufacturers and are easily obtainable.
With respect to the acyloxy functional
silanes, these materials are generally applied
without any solvent since it has been found that
the use of solvents in the application of such top
coats at times seriously degrades the applied
silicone top coat. Prefexably, the silanes of Formula
IV, that is the acyloxy functional silanes, are
applied at 100~ solids or from 2Q to 100~ solids,
in the case of the acyloxy silanes where the solids
are less than 100~ the silane is simply the water
hydrolysis and partial condensation product of the
foregoing acyloxy functional silanes of Formula IV.
The alkoxy and aryloxy functional silanes of Formula
III are generally applied from a top coat composition
containing solvents in a solids concentration of
from about 20 to 95~ by weight. Examples of solvents
which may be used in the formulation of the top coat
composition include methanol, ethanol, butanol, ethyl
acetate, benzene, toluene, xylene, ethylene glycol
and the like. However, the alkoxy and aryloxy
functional silanes may also, similarly to the
acyloxy functional silan~s, be applied from a top
coat composition which contains no solvents other
than the alcohol by-product and water used to form the
partial hydrolysis and condensation products of these
silanes.
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~ J ~ 2 ~ 8CS-3A17
With respect to the foregoing aryloxy
functional, alkoxy functional and acyloxy functional
silanes mentioned above, such materials are well
known in the art as, for ins-tance, in U.S. Patents
2,888,815 - S.J. Bessmer, issued June 10, 1975 and
3,701,753 - H.P. Shaw, issued October 31, 1972.
One particular class of further-curable
organopolysiloxanes wh.ich are employed in the top
coat compositions of the present invention are the
partial hydrolysis and condensation products of
alkoxy functional silanes, preferably
alkyltrialkoxysilanes, preferably those
alkyltrialkoxysilanes wherein the alkyl group
contains from 1 to about 8 carbon atoms, and
aryltrialkoxysilanes, preferably phenyltrialkoxysilanes,
or mixtures thereof, wherein the alkoxy group contains
from 1 to about 8 carbon atoms, such as, for example,
methoxy, ethoxy, isopropoxy, butoxy, pentoxy, hexoxy,
octoxy, and the like. The further-curable
~0 organopolysiloxanes are generally prepared by a
process wherein the alkyltrial~oxysilane,
aryltrialkoxysilane, or a m~ixture of alkyltrialkoxysilane
and aryltrialkoxysilane is heated in the presence of
water, wherein the molar ratio of water to total
silane is at least about 1.5:1 and in the presence
of an effective amount of a hydrolysis catalyst,
such as a mineral acid, for example, HCl, for about
1 to about 10 hours at a temperature between ambient
and reflux to produce a siloxane partial condensation
product; the partial condensation product is then
concentrated by heating to remove 50 to about 90
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~ 8CS-3417
mole percent alkanol by-product and some water, and
thereafter, the concentrated partial condensation
product is precured by heating at a temperature below
the gel point thereof and generally in the range of
about 70 to 300C to produce the solvent-soluble,
further-curable organopolysiloxane. This pre-cured
solvent-soluble, urther-curable organopolysiloxane
is then dissolved in a suitable solvent to form the
top coat composition and the primed polycarbonate
substrate is then coated with this top coat composition.
The solvent is then evaporated and the residual
further-curable organopolysiloxane is cured to a
thermoset state to provide a uniformly and tenaciously
adhered top coat on the primed polycarbonate substrate.
The curing is effected at elevated temperatures in
the range of about 50 to 135C for times between
about l hour to about 72 hours, depending on the
temperature at which the cure is effected. The
silicone top coat generally shouId be cured preferably
at an elevated temperature to effect the proper cure,
but the temperature should be below the glass
transition temperature of the polycarbonate is
exceeded, then the polycarbonate part may become
deformed and lose its utility.
One particular further-curable organopolysiloxane
that can be employed in the top coat composition of the
instant invention is the partial hydrolysis and
condensation product of methyltriethoxysilane. This
further-curable organopolysiloxane is prepared by
hydrolyzing methyltriethoxysilane with water in -the
presence of an effective amount of a hydrolysis catalyst,
such as HCl, for about l to 10 hours at a temperature
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t ~ ~ 6~8 8CS-3417
generally between 409C and reflux kemperature, to
produce a partial condensation product. This partial
condensation product is then concentrated by heating
to remove some of the alkanol by product and water.
This concentrated product is then partially pre-cured
at a temperature of about 70 to about 300C and
below the gel point thereof and then solidified to
provide a solid, solvent-soluble, further-curable
organopolysiloxane. The solid, solvent-soluble,
further-curable organopolysiloxane is then dissolved
to a desired concentration in a suitable solvent to
form the top coat composition. The top coat composition
is then applied to the primed polycarbonate substrate,
after which the solvent is evaporated and the further-
curable organopolysiloxane finally cured to provide a
hard, abrasion and chemical solvent resistant, thermoset
organopolysiloxane top coat in the polycarbonate
substrate.
Another further-curable organopolysiloxane
which may be employed in the practice of the present
invention is the partial hydrolysis and condensation
product of a mixture of methyltriethoxysilane and
phenyltriethoxysilane. This organopolysiloxane is
prepared by hydrolyzing a mixture of methyltriethoxysilane
and phenyltriethoxysilane with water in the presence of
a hydrolysis catalyst such as HC1 to produce a partial
condensation product. This partial condensation product
is then concentrated by heating to remove a substantial
amount of the alkanol by-product and some water. This
concentrated product is then partially pre-cured by
heating and then solidified to provide a solid,
- 17 -
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solvent-soluble, further-curable organopolysiloxane.
The solid, solvent-soluble, further-curable
organopolysiloxane is then dissolved to a desired
concentration in a suitable solvent to form the top
coat composition containing a further-curable
organopolysiloxane. The top coat composition is
then applied to the primed polycarbonate substrate,
after which the solvent is evaporated and the further-
curable organopolysiloxane is finally cured to provide
a tenaciously and durably adhered, abrasion and chemical
resistant thermoset organopolysiloxane top coat on the
polycarbonate substrate.
These are not the only silicones that may
be utilized in the top coats of the instant invention.
Less preferred silicones which can be utilized to form
the top coats of the present invention are, for instance,
silicone resins composed of trifunctional and difunctional
units, silicone resins composed of trifunctional units,
difunctional units and tetrafunctional units when the
organo substituent groups in the trifunctional units
may be selected from hydrocarbon radicals of 1 to about
8 carbon atoms and are preferably methyl, phenyl and
vinyl; and wherein the organo substituent groups in
the trifunctional units may be selected from hydrocarbon
radicals of 1 to about 8 carbon atoms and are preferab:Ly
methyl, phenyl and vinyl; and wherein the organo
substitutent groups in the difunctional siloxy units
may be selected from hydrocarbon units of from 1 to
about 8 carbon atoms, preferably alkyl radicals, vinyl
radicals and phenyl radicals. Such silicone resins
usually have an organic radical to silicon atom ratio
of 1:1 to 1.9:1; may have a silanol con-tent that varies
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I ~ 62d~ 8CS-3417
anywhere from 4 to 10 weight percent and optionally
may have an alkoxy content that varies from 2 to 4%O
The preparations of such silicone resins which may
be utilized as top coats in the invention of the
instant case are, for instance, to be found in U.S.
Patents, 3,375,223 - D.F. Merrill, issued March 26,
1968; 3,435,001 - D.F. Merrill, issued March 25, 1969;
3,450,672 - D.F. Merrill et al, issued June 17, lg69;
3,790,527 - D.F. Merrill, issued February 5, 1974;
3,832,319 - D.F. Merrill, issued August 27, lg74;
3,865,766 - D.F. Merrill, issued February 11, 1975;
3,887,514 - D.F. Merrill, issued June 3, 1975 and
3,925,276 - W.J. Lampe, issued December 9, 1975.
Particularly prefered, filled further-curable
organopolysiloxane top coat compositions are disclosed
in U.S. Patents 3,986,997 and U.S. Patent 4,027,073.
These compositions comprise a dispersion of colloidal
silica in a lower aliphatic alcohol-water solution of
the partial condensate of a silanol having the formula
R Si(OH)3
wherein R is selected from the group consisting of
alkyl radicals containing from 1 to 3 carbon atoms,
the vinyl radical, the 3,3,3-trifluoropropyl radical,
the gamma-glycioxypropyl radical and the gamma
methacryloxypropyl radical, with at least 70 percent
by weight of said silanol being CH3Si(OH)3. This
composition generally contains from about 10 to about
50 percent by weight of solids, said solids consisting
essentially of a mixture of from about 10 to about
70 percent by weight of colloidal silica and from
about 30 to about 90 percent by weight of the partial
-- 19 --
~ 3 6~
8CS-3~19
condensate of a silanol. The partial condensate of
a silanol, i.e., a siloxanol, is obtained, preferably,
entirely from the condensation of CH3Si(OH)3, however,
the partial condensate may also optionally be comprised
of a major portion which is obtained from the
condensation of CH3Si(OH)3 and a minor portion which
is obtained from the condensation of monoethyltrisilanol,
monopropyltrisilanol, monovinyltrisilanol, mono gamma-
methacryloxy-propyltrisilanol, mono gamma-
glycidoxypropyltrisilanol, or mixtures thereof.
The composition further contains sufficient acid to
provide a pH in the range of 3.0 to 6Ø The pH is
maintained in this range in order to prevent premature
gellation and increase the shelf life of the silica-
filled organopolysiloxane top coat composition and
to obtain optimum properties in the cured coating.
Suitable acids include both organic and inorganic
acids such as hydrochloric, chloroacetic, acetic,
citric, benzoic, formic, propionic, maleic, oxalic,
~0 glycolic and the like. The acid can be added to
either the silane, which hydrolyzes to form the
silanol component of the composition, or the hydrosol
prior to mixing the two components.
The trisilanol component of the top coat
composition of the present invention is generated
in situ by the addition of the corresponding
trialkoxysilanes to aqueous dispersions of colloidal
silica. Suitable trialkoxysilanes are those containing
methoxy, ethoxy, isopropoxy and t-butoxy substituents.
Upon generation of the silanol in the acidic aqueous
medium, there is condensation of the hydroxyl
- 20 -
1 1 ~ 8
8CS-3417
substituents to form -si-o-si bonding. The condensation
is not complete, but rather the siloxane retains an
appreciable quantity of silicon-bonded hydroxyl groups,
thus rendering the organopolysiloxane polymer soluble
in the water-alcohol solvent. This soluble partial
condensate can be characterized as a siloxanol polymer
having at least one silicon-bonded hydroxyl group per
every three -SiO- units. During curing of the top
coating composition on the primer, these residual
hydroxyl groups condense to give a silsesquioxane,
R SiO3/2.
The silica component of the top coat composition
is present in the form of colloidal silica. Aqueous
colloidal silica dispersions generally have a particle
size in the range of 5 to 150 millimicrons in diameterO
These silica dispersions are prepared by methods well
known in the art and are commercially available. It is
preferred to use colloidal silica having-a particle
size in the range of lO to 30 millimicrons in diameter
; 20 in order to obtain dispersions having a greater
stability and to provide top coatings having superior
optical properties.
The silica-filled organopolysiloxane top
coa~ compositions are prepared by adding trialkoxysilanes
to colloidal silica hydrosol and adjusting the pH to a
range of 3.0 to 6.0 by the addition of acid. As
mentioned previously, the acid can be added to either
the silane or the silica hydrosol before the two
components are mixed. Alcohol is generated during the
hydrolysis of the trialkoxy silanes to the trisilanols.
Depeinding upon the percent solids desired in the final
- 21 -
BCS-3417
coating composition, additional alcohol, water, or a
water-miscible solvent can be added. Suitable
alcohols are the lower aliphatic alcohols such as
methanol, ethanol, isopropanol, t-butanol, and
mixtures thereof. Generally, the solvent system
should contain from about 20 to about 75 weight percent
alcohol to ensure solubility of the siloxanol formed
by the condensation of the silanol. If desired, a
minor amount of an additional water-miscible polar
solvent such as acetone, butyl cellosolve, and the
like can be added to the water-alcohol solvent system.
Generally, su-Eficient alcohol or water-alcohol
solvent is added to give a composition containing
from about 10 to about 50 percent by weight of solids,
said solids generally comprising from about 10 to
about 70 percent by weight of colloidal silica and
from about 30 to about 90 percent by weight of the
partial condensate of the silanol. The composition
is allowed to age for a short period of time to
ensure formation of the partial condensate of the
silanol, i.e., the siloxanol. This condensation
occurs upon generation of the silanol in the acidic
aqueous medium through the hydroxyl substituents to
form Si-O-Si bonding. The condensation is not
complete, resulting in a siloxane having an appreciable
quantity of silicon-bonded hydroxyl group.
The top coat compositions containing the
afore-described silicones are simply brushed, dipped,
sprayed or flowed on top of the primer layer that is
applied to the polycarbonate substrate. The solvent,
or alcohol by-product and water, present in the top
coat composition is evaporated and the residual
- 22 -
-
~ 8CS-2317
further curable organopolysiloxane is cured to form
a thermoset organopolysiloxane top coat. Preferably,
the further-curable organopolysiloxane is cured at
ele ated temperatures. Although certain catalysts
may be utilized to accelerate the cure of the further-
curable organopolysiloxane, such catalysts are not
necessary if the further-curable organopolysiloxane
is cured by itself at the elevated temperature for a
sufficient length of time.
PREFERRED_EMBODIMENT OF THE INVENTION
In order that those skilled in the art may
better understand how the present invention may be
practiced, the following examples are given by way of
illustration and not by way of limitation. In the
Examples set forth below, all parts and percentages,
unless otherwise indicated, are on a weight basis.
EXAMPLE 1
An aromatic polycarbonate is prepared by
reacting 2,2-bis(4-hydroxyphenyl)propane and phosgene
in the presence of an acid acceptor and a molecular
weight regulator and having an intrinsic viscosity
o 0.57. The product is then fed to an extruder,
which extruder is operated at about 265C and the
extrudate is comminuted into pellets.
The pellets are then injection molded at
about 315C into test panels of about 4in. by 4 in.
by about 1/8 in. thick.
A further curable organopolysiloxane top
coat composition is prepared as follows: To 100 parts
by weight of a commercially available solution
containing a further-curable organopolysiloxane
- 23 -
8CS~3~17
dissolved in a suitable solvent is added 2 parts by
weight of a commercially available curing catalyst
solution to form a top coat composition. This further-
curable organopolysiloxane is available from Resart-Ihm
A.G., Mainæ, Federal Republic of Germany, as their
Resarix SF/PC/TM and is a solution containing about
32 weight percent of a partial hydrolysis and
condensation product of methyl triethoxysilane
dissolved in an ethanol-tetrahydrofuran-n-butanol-
ethoxyethanol solvent system. The catalyst consists
of a solution containing 2 weight percent of
tetraethylammonium hydroxide dissolved in methanol.
EXAMPLE 2
This Example illustrates a primed, top
coated polycarbonate ar~icle falling outside the scope
of the instant invention in that no ultraviolet light
absorbing compound is present in the primer layer~
A solution of 120 parts by weight of freshly
distilled methyl methacrylate, 2 parts by weight of
methacrylic acid, 0.03 parts by weight of dodecanethiol,
and 0.15 parts by weight of 2,2'-azobisisobutyronitrite
in 360 parts by weight of butoxyethanol is stirred under
nitrogen at 100C for 24 hours.
A thermosettable acrylic primer formulation
hereinafter referred to as "primer formulation A", is
made by combining 10 parts by weight of the afore--
prepared solution, 0.12 parts by weight of a
cycloaliphatic diepoxide, 0.01 parts by weight of
toluenesulfonic acid, and 1 dxop of a flow agent in
32 parts by weight of butoxyethanol and 14 parts by
weight of ethylene glycol diacetate.
- 24 -
-
1 1 62~
8CS-3417
Polycarbonate test panels prepared in
accordance with the procedure of ~xample 1 are flow
coated with this primer formulation A, are drained
for 10 minutes, and then are baked at 125C for 15
minutes. After cooling, the primed test panels are
flow coated with the organopolysiloxane top coat
composition prepared substantially in accordance with
t'ne procedure set forth above. Excess top coat
solution is drained off and the panels are air dried
for 30 minutes. The panels are then baked for 1 hour
at 125C to effect the cure of the further curable
organopolysiloxane. The primed and top coated test
panels are subjected to an adhesion test,-both beore
and after weathering, and he results are set forth
in TABLE I. The adhesion test consists of using a
multiple blade tool to cut parallel grooves about 1 mm
apart through the coating into the substrate, rotating
the sample 90 and repeating the cutting process
thereby forming a grid pattern of 1 mm squares cut
into the coating, and applying an adhesive tape over
the cross-hatched area and quickly pulling said tape
off. A sample fails the adhesion test if any of the
squares in the grid are pulled off. The weathering
consists of placing the test panels in a QU~ TM
accelerated weathering tester, sold by Q-Panel
Company, which is set to cycles of 4 hours of
fluorescent ultraviolet light at about 60C and 4 hours
of dark/condensation at about 45C.
`EX_MPLE 3
A thermosettalbe acrylic primer formulation
containing a hiyh amount of a benzotriazole ultraviolet
~ 25
I ~ ~2A~
8CS-3417
light absorber is prepared by combining 56 parts by weight
of the thermosettable acrylic primer formulation A of
Example 2 with 3 parts by weight of Cyosorb TM 5411
(a benzotriazole ultraviolet light absorber sold by
American Cyanamid). Test panels prepared in accordance
with the procedure of Example l are primed with this
primer formulation and top coated in accordance with the
procedure of Example 2. These primed and top coated
test panels are subjected to the adhesion test, before
and after weathering, and the results are set forth
in TABLE I.
EXAMPLE 4
A thermosettable acrylic primer formulation
containing a high amount of dihydroxybenzophenone
ultraviolet light absorber is prepared by combining 56
parts by weight of the thermosettable acrylic primer
formulation A of Example 2 with 3.5 parts by weight
of 2,~-dihydroxybenzophenone. Test panels prepared in
accordance with the procedure of Example 1 are primed
with this primer formulation and top coated in accordance
with the procedure of Example 2. These primed and top
coated test panels are subjected to the adhesion test,
before and after weatheringr and the results are set
forth in TABLE I.
EXAMPLE 5
-
A thermosettable acrylic primer formulation
containing a high amount of a benzophenone ultraviolet
li ht absorber is prepared by co~;bining 56 parts by
weight of the thermosettable acryli~ primer formulation
A of Example 2 with 3.5 parts by weight of Cyasorb 531
(a benzophenone ultraviolet light absorber sold by
American Cyanamid). Test panels prepared in accordance
- 26 -
I 1 ~2~
8CS-3417
with the procedure of Example 1 are primed with this primer
formulation and top coated in accordance with the procedure
of Example 2. These primed and top coated test panels
are subjected to the adhesion test, before and after
weathering, and the results are set forth in TABLE 1.
EXA~E 6
A thermosettable acrylic primer formulation
containing a high amount of a cyanoacrylate ultraviolet
light absorber is prepared by combining 56 parts by
weight of the thermosettable acrylic primer formulation A
of Example 2 with 3.5 parts by weight of Uvinul TM N-539
(a cyanoacrylate ultraviolet light absorber sold by GAF
Corporation). Test panels prepared in accordance with
the procedure of Example 1 are primed with this primer
formulation and top coated in accordance with the procedure
of Example 2. These primed and top coated test panels
are subjected to the adhesion test, before and after
weathering, and the results are set forth in TABLE I.
EXAMPLE 7
A thermosettable acrylic primer formulation
containing a high amount of a benzylidene malonate
ultraviolet light absorber is prepared by combining 56
parts by weight of the thermosettable acrylic primer
formulation A of Example 2 with 3.5 parts by weight
of Cyasorb W-1988 (a benzylidene malonate ultraviolet
light absorber sold by American Cyanamid). Test panels
prepared in accordance with the procedure of Example 1
are primed with this primer formulation and top coated
in accordance with the procedure of Example 2. These
primed and top coated test panels are subjected to the
adhesion test, before and after weathering, and the
results are set forth in TABLE I.
~ 27
7 3 ~2~ 8CS-3417
EXAMPLE 8
This Example illustrates a primed and top
coated polycarbonate article falling outside the scope
of the instant invention in that no ultraviolet light
absorbing compound is present in the primer layer.
A solution of 20 parts by weight of methyl
methacrylate, 20 parts by weight of ethyl methacrylate,
0.6 parts by weight of methacrylic acid and 0.1 parts by
weight of 2,2'-azobisisobutyronitrile in 160 parts by
weight of butoxyethanol is stirred under nitrogen at
100C for 36 hours.
A thermosettable acrylic primer formulation,
hereinafter referred to as "primer formulation B", is
made by combining 40 parts by weight of the afore-
described solution with 0.5 parts by weight of
hexamethoxymethylmelamine, 0.03 parts by weight of
toluenesulfonic acid, and 160 parts by weight of
butoxy ethanol.
Polycarbonate test panels prepared in
accordance with the procedure of Example 1 are flow coated
with this primer formulation B, are drained for 10 minutes,
and then are baked at 125C for 30 minutes. After
cooling the primed test panels are flow coated with
the organopolysiloxane top coat composition prepared
substantially in accordance with the procedure set
forth above. Excess top coat solution is drained off
and the panels are air dried for 30 minutes. The panels
are then baked for 1 hour at 125C to cure the further-
curable organopolysiloxane. The primed and top coated
test panels are subjected to an adhesion test, before
weathering, after weathering for 144 hours, and after
weathering for 503 hours, and the results are set forth
in TABLE II.
- 28 -
8CS-3417
EXAMPLE 9
This example illustrates a primed and top
coated polycarbonate article falling outside the scope
of the instant invention in that the primer layer
contains about 9 weight percent of an ultraviolet
light absorber.
A thermosettable acrylic primer formulation
containing a low amount of a benzotriazole ultraviolet
light absorber is prepared by combining 20 parts by
weight of the thermosettable acrylic primer
formulation B of Example 8 with 0.08 parts by weight of
Cyasorb 5411 (a benzotriazole ultraviolet light
absorber sold by American Cyanamid). Test panels
prepared in accordance with the procedure of Example 1
are primed with this primer formulation and top coated
in accordance with the procedure set forth in
Example 8. These primed and top coated test panels
are subjected to the adhesion test, before and after
weathering, and the results are set forth in TABLE II.
EXAMPLE 10
A thermosettable acrylic primer formulation
containing a high amount of dihydroxybenzophenone
ultraviolet light absorber is prepared by comhining
19.8 parts by weight of the thermosettable acrylic
primer formulation B of Example 8 with 2.2 parts by
weight of 2,4-dihydroxybenzophenone. Test panels
prepared in accordance with the procedure of Example 1
are primed with this primer formulation and top coated
in accordance with the procedure set forth in Example 8.
These primed and top coated test panels are subjected
to the adhesion test, before and after weathering,
and the results are set forth in TABLE II.
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1 3 5~a~
8CS~3417
EXAMPLE II
A thermosettable acrylic primer formulation
containins a high amount of benzotriazole ultraviolet
light absorber is prepared by combining 19.95 parts by
weight of the thermosettable acrylic primer formulation B
of Example 8 with 1.05 parts by weight of Cyasorb UV-1988
(a benzotriazole ultraviolet light screener sold by
American Cyanamid). Test panels prepared in accordance
with the procedure of Example 1 are primed with this prior
primer formulation and top coated in accordance with the
procedure set forth in Example 8. These primed and top
coated test panels are subjected to the adhesion test,
before and after weathering, and the results are set
forth in TABLE II.
TABLE I
Color of Test
Adhesion Test Adhesion Test Panel After
Before After 144 Hrs. 144 Hours
Example Weatherlng Weathering Weathering
2 Pass Fail Yellow
3 Pass ~Pass Colorless
4 Pass Pass Colorless
Pass Pass Colorless
6 Pass Pass Colorless
7 Pass Pass Colorless
TABLE II
Color of
Adhesion Ad~esion Adhesion Test Panel
Test ~est After' Test After After 144
Before 144 Hrs. of 503 Hrs. of Hours of
Example Weathering Weathering Weathering W
8 Pass Fail Fail Yellow
9 Pass Marginal Fail Yellow
Pass Pass Pass Colorless
11 Pass Pass Pass Colorless
- 30 -
gCS-3417
As can be seen by comparison of Examples 2 and 8
with Examples 3-7 and 10-ll in TABLES I and II above, the
adhesion of the thermoset organopolysiloxane containing
top coat composition to polycarbonate panels primed
with a primer containing a thermoset acrylic polymer
but no ultraviolet light screener rapidly deteriorates
upon exposure to weathering, while the adhesion of
the top coat to a primer containing relatively high
amounts of ultraviolet light screener is not
deleteriously affected by weathering. Example 9, in
which the primer layer contains 9 weight percent of
an ultraviolet light screener, shows that the presence
of relatively small amounts of ultraviolet light
screener in the primer layer is ineffective in
remedying the problem of adhesive failure of the
top coat upon exposure to weathering.
EXAMPLE 12
An aromatic polycarbonate is prepared by
reacting 2,2-bis(4-hydroxyphenol) propane and phosgene
in the presence of an acid acceptor and a molecular
weight regulator and having an intrinsic viscosity of
0.57. The product is then fed to an extruder, which
extruder is operated at about 265C and the ~xtrudate
is comminuted into pellets.
The pellets are then injection molded at
about 315C into test panels of about 4 in. by 4 in.
by about 1/8 in. thick.
A colloidal silica~filled further-curable
organopolysiloxane top coat composition is prepared
as follows: Glacial acetic acid (0.2 grams) is added
to 200 grams of a commercially available a~ueous
- 31 -
~ ~ ~24 ~ ~ 8cs-34l7
dispersion of colloidal silica having an initial
p~ of 3.1 containing 34% SiO2 of approximately 15
millimicron particle size and having a Na2O content
of less than 0.01 weight percent. Methyltrimethoxysilane
(138 grams~ is added to the stirred acidified dispersion
generating methanol and methyltrisilanol. After
standing for about one hour, the pH of the composi~ion
stabilizes at 4.5. The pH of the composition is adjusted
to a range of from 3.7 to 5.6. The composition is aged
for 4 days to ensure formation of the partial condensate
of CH2Si(OH)3 in the silica methanol-water dispersion.
The composition contains 40% solids, half of which is
SiO2 and the other half silicone calculated on the basis
CH3SiO3/2 weight available in the cured composition.
The aged composition is diluted to 25 weight percent
solids by addition of isopropanol.
EXAMPLE 13
This Example illustrates a primed and top
coated polycarbonate article falling outside the scope
of the instant invention in that no ultraviolet light
absorbing compound is present in the primer layer.
A solution of 20 parts by weight of methyl
methacrylate, 20 parts by weight of ethyl methacrylate,
0.6 parts by weight of methacrylic aci and 0.1 parts
by weight of 2,2'-azobisisobutyronitrile in 160 parts
by weight of butoxyethanol i~ stirred, under nitrogen
at 100C for 36 hours.
A thermosettable acrylic primer formulation,
hereinafter referred to as primer formulation B, is
made by combining 40 parts by weight of the afore-
described solution with 0.5 parts by weight of
hexamethoxymethylmelamine, 0.03 parts by weight of
- 32 -
~ ~ ~24~ 8CS-3417
toluenesulfonic acid, and 160 parts by weight of
butoxyethanol.
Polycarbonate test panels prepared in
accordance with the procedure of Example 12 are flow
coated with this primer formulation B, are drained
for 10 minutes, and then are baked at 125C for 30
minutes. After cooling the primed test panels are
flow coated with the colloldal silica filled
organopolysiloxane top coat composition prepared
substantially in accordance with the procedure set
forth above. Excess top coat solution is drained
off and the panels are air dried for 30 minutes.
The panels are then baked for 1 hour at 125C to
cure the colloidal silica filled further-curable
organopolysiloxane. The primed and top coated test
panels are subjected to an adhesion test, before
weathering and after weathering for 503 hours, and
the results are set forth in TABLE III.
The adhesion test consists of using a
multiple blade tool to cut parallel grooves about lmm
apart through the top coat and primer layer into the
substrate, rotating the sample 90 and repeating the
cutting process thereby forming a grid pattern of
lmm squares cut into the coating, and applying an
adhesive tape over the cross-hatched area and quickly
pulling said tape off (a sample fails the adhesion
test if any of the squares in the grid are pulled
off). The weathering consists of placing the test
panels in a Q W accelerating weathering tester, sold
by Q-Panel Company, which is set to cycles of 8 hours
of fluorescent ultraviolet light at about 70C and
4 hours of dark/condensation at about 60 C.
33 -
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~ ~ $24 4 ~ 8CS 3417
EXAMPLE 14
-
This Example illustrates a primed and top
coated polycarbonate article falling outside the scope
of the instant invention in that the primer layer
contains about 3 weight percent of an ultraviolet
light absorber.
A thermosettable acrylic primer formulation
containing a low amount of a benzotriazole ultraviolet
light absorber is prepared by combining 20 parts by
weight of the thermosettable acrylic primer formulation
B of Example 2 with 0.08 parts by weight of Cyasorb
5411 (a benzotriazole ultraviolet light absorber
sold by American Cyanamid). Test panels prepared in
accordance with the procedure of Example 12 are primed
with this primer formulation and top coated in accordance
with the procedure set forth in Example 13. These
primed and top coated test panels are subjected to the
adhesion test, before and after weathering, and the
results are set forth in TABLE III.
EXAMPLE 15
-
~0 A thermosettable acrylic primer formulation
containing a high amount of a cyanoacrylate ultraviolet
light absorber is prepared by combining 19.8 parts by
weight of the thermosettable acrylic primer formulation
B of Example 2 with 2~2 parts by weight of Uvinul N-539
(a cyanoacrylate ultraviolet light absorber sold by
GAF Corporation). Test panels prepared in accordance
with the procedure of Example 12 are primed with this
primer formulation and top coated in accordance with
the procedure set forth in Example 13. These primed
and top coated test panels are subjected to the
adhesion test, before and after weathering, and the
results are set forth in TABIE III.
- 34 -
~ ~2~
8CS-3417
EXAMPLE 16
A thermosettable acrylic primer formulation
containing a high amount of a dihydroxybenzophenone
ultraviolet light absorber is prepared by combining
19.8 parts by weight of the thermosettable acrylic
primer formulation B of Example 2 with 2.2 parts by
weight of 2,4-dihydroxybenzophenone. Test panels
prepared substantially in accordance with the procedure
of Example 12 are primed with this primer formulation
and top coated in accordance with the procedure
set forth in Example 13. These primed and top coated
test panels are subjected to the adhesion test, before
and after weatheringl and the results are set forth in
TABLE III.
EXAMPLE 17
A thermosettable acrylic primer formulation
containing a high amount of a benzophenone ultraviolet
light absorber is made by combining 19.8 parts by
weight of the thermosettable acrylic primer formulation
B of Example 2 with 2.2 parts by weight of Cyasorb 531
ta benzophenone ultraviolet light absorber sold by
American Cyanamid). Test panels prepared in accordance
with the procedure of Example 12 are primed with this
primer formulation and top coated in accordance with
the procedure set forth in Example 13. These primed
and top coated test panels are subjected to the adhesion
test, before and after weathering, and the results are
set forth in TABLE III.
EXAMPLE 18
A thermosettable acrylic primer formulation
containing a high amount of benzotriazole ultraviolet
light screener is made by combining 19.95 parts by
- 35 -
~CS-3417
weight of the thermosettable acrylic primer formulation B
of Example 2 with 1.05 parts by weight of Cyasorb 5411
(a benzotriazole ultraviolet light screener sold by
American Cyanamid). Test panels prepared in accordance
with the procedure of Example 12 are primed with this
primer formulation and top coated in accordance with
the procedure set forth in Example 13. These primed
and top coated test panels are subjected to the adhesion
test, before and after weathering, and the results are
set forth in TABLE III.
TABLE III
Colo~ of
Adhesion Test Test Panel
After 503 After 503
Adhesion Test Hours of Hours of
Example Before Weathering Weathering Weathering
2 Pass Fail Yellow
3 Pass Fail Yellow
4 Pass Pass Colorless
Pass Pass Colorless
6 Pass Pass Colorless
7 Pass Pass Colorless
As can be seen by comparison of Example 13
where the primer layer contains no ultraviolet light
screener) and 14 (where the primer layer contains a
relatively small amount, i.e., 9 weight percent, of an
ultraviolet light screener) with Examples 15-18 (wherein
the primer layer contains high amounts of an ultraviolet
light screener), the presence of relatively high amounts
o~ an ultraviolet light screener in the primer layer
greatly improves the adnesion of the colloidal silica
filled thermoset organopolysiloxane containing top coat
- 36 -
8CS-3~19
to the polycarbonate upon exposure to weathering.
Thus, while in test panels of Examples 13 and 14 the
top coat failed the adhesion test after 503 hours
e~posure to weathering, the adhesion of the top coat
of test panels of Examples 15-18 was not delet~riously
affected by exposure to weathering for this same
period of time.
The foregoing disclosure of this in~ention
is not to be considered as limiting, since many
variations may be made by those skilled in the art
without departing from the scope or spirit of the
foregoing description.
- 37 -
