POLYCARBONATE ARTICLE COATED WITH A PHOTOCURED COATING

ARTICLE EN POLYCARBONATE REVETU D'UN ENDUIT PHOTOCURABLE

English Abstract

8SP 2968
ABSTRACT OF THE DISCLOSURE
A polycarbonate article coated with a
photocured coating comprised of the photoreaction
product of (i) a polythiol, (ii) a polyene, and (iii)
a silicone modified polyester copolymer.

Claims

8SP-2968
The embodiments of the invention in which an exclu-
sive property or privilege is claimed are defined as follows:
1. A polycarbonate article having deposited on the
surface thereof a photocurable composition consisting essentially
of:
(i) a polythiol represented by the general formula
<IMG>
wherein R1 and R2 are organic moieties containing no reactive
carbon-to-carbon unsaturation and a is 2 to 4;
(ii) a polyene represented by the general formula:
<IMG>
wherein R3 is a straight chain aliphatic moiety containing no
reactive carbon-to-carbon unsaturation; and
(iii) a silicone-modified polyester copolymer.
2. The polycarbonate article of claim 1 wherein said
silicone modified polyester copolymer is the reaction product of:
A) a hydroxyl terminated unsaturated polyester of:
1) polycarboxylic acid reactant wherein at least
about 65 mole percent of said polycarboxylic acid
reactant is an .alpha.,.beta.-ethylenically unsaturated poly-
carboxylic reactant and up to about 35 mole percent of
said polycarboxylic acid reactant is a polycarboxylic
acid reactant free from non-benzenoid unsaturation; and
2) an alcohol reactant containing two terminal
hydroxyl groups and a member selected from the group
consisting of allyl ether groups methallyl ether groups
and mixtures thereof in an amount sufficient to provide
at least 0.1 mole of said ether groups per mole of
said ethylenically unsaturated polycarboxylic acid
reactant; and
19

8SP-2968
3) wherein said polyester has an acid number from
about 10 to about 35; and
B. an organopolysiloxane having the average unit formula:
<IMG>
wherein R is selected from the group of lower alkyl radicals
having 1 to 8 carbon atoms; cycloalkyl radicals havlng 5 to 7
carbon atoms in the ring; lower alkenyl radicals having 2 to 8
carbon atoms; mononuclear aryl radical; mononuclear aryl lower
alkyl radicals having 1 to 6 carbon atoms in the alkyl group; and
halogenated derivatives of the above radicals; R' is selected from
the group of alkyl radicals containing 1 to 8 carbon atoms;
mononuclear aryl radicals; acyl radicals of 1 to 8 carbon atoms;
s has a value of 1.0 to 2.0; q has a value of 0 to 1.0; r has a
value of 0 to 1.0; the sum of q + r has a value of 0.01 to 1.0;
and said organopolysiloxane containing at least 0.25% by weight of
OH or OR' groups or a mixture of said OH and OR' groups.
3. The polycarbonate article of claim 2 wherein said poly-
thiol is representec by the general formula
<IMG>
wherein R1 and R2 are straight chain aliphatic moieties containing
no reactive carbon-to-carbon unsaturation and a is 2 to 4.
4. The polycarbonate article of claim 3 wherein R1 and R2
are straight chain aliphatic moieties containing no reactive
carbon-to-carbon unsaturation and containing from 1 to about 20
carbon atoms.
5. The polycarbonate article of claim 4 wherein said poly-
thiol is represented by the formula
<IMG>

8SP-2968
6. The polycarbonate article of claim 2 wherein said
polyene is represented by the formula
<IMG> .
7. The coating composition of claim 5 wherein said
polyene is represented by the formula
<IMG> .
8. The polycarbonate article of claim 1 wherein said
polyene and polythiol are present in stoichiometric amounts.
9. The polycarbonate article of claim 8 wherein said
composition contains, in parts by weight, from about 1 part of
said silicone modified polyester copolymer to about 3 parts of
the combined weights of said polythiol and said polyene to from
about 3 parts of said silicone modified polyester copolymer to
about 1 part of the combined weights of said polythiol and said
polyene.
10. The polycarbonate article of claim 9 wherein said
composition contains, in parts by weight, from about 1 part of
said silicone modified polyester copolymer to about 2 parts of
the combined weights of said polythiol and polyene to from about
2 parts of said silicone modified polyester copolymer to about 1
part of the combined weights of said polythiol and polyene.
11. A coated polycarbonated article coated with coating
consisting essentially of the photo reaction product of:
(i) a polythiol represented by the general formula:
<IMG>
21

8SP-2968
wherein R1 and R2 are organic moieties containing no reactive
carbon-to-carbon unsaturation and a is 2 to 4;
(ii) a polyene represented by the general formula:
<IMG>
wherein R3 is a straight chain aliphatic moiety containing no
reactive carbon-to-carbon unsaturation; and
(iii) a silicone modified polyester copolymer.
12. The coated polycarbonate article of claim 11
wherein said silicone modified polyester copolymer is the
reaction product of:
A) a hydroxyl terminated unsaturated polyester of:
1) polycarboxylic acid reactant wherein at least
about 65 mole percent of said polycarboxylic acid
reactant is an .alpha.,.beta.-ethylenically unsaturated poly-
carboxylic reactant and up to about 35 mole percent of
said polycarboxylic acid reactant is a polycarboxylic
acid reactant free from non-benzenoid unsaturation; and
2) an alcohol reactant containing two terminal
hydroxyl groups and a member selected from the group
consisting of allyl ether groups methallyl ether groups
and mixtures thereof in an amount sufficient to provide
at least 0.1 mole of said ether groups per mole of said
ether groups per mole of said ethylenically unsaturated
polycarboxylic acid reactant; and
3) wherein said polyester has an acid number from
about 10 to about 35; and
B) an organopolysiloxane having the average unit
formula:
<IMG>
22

8SP-2968
wherein R is selected from the group of lower alkyl radicals having
1 to 8 carbon atoms; cycloalkyl radicals having 5 to 7 carbon atoms
in the ring; lower alkenyl radicals having 2 to 8 carbon atoms;
mononuclear aryl radicals; mononuclear aryl lower alkyl radicals
having 1 to 6 carbon atoms in the alkyl group; and halogenated
derivatives of the above radicals; R' is selected from the group
of alkyl radicals containing 1 to 8 carbon atoms; mononuclear
aryl radicals; acyl radicals of 1 to 8 carbon atoms; s has a value
of 1.0 to 2.0; q has a value of 0 to 1.0; r has a value of 0 to
1.0; the sum of q + r has a value of 0.01 to 1.0; and said organo-
polysiloxane containing at least 0.25% by weight of OH or OR'
groups or a mixture of said OH and OR' groups.
13. The coated polycarbonate article of claim 12 wherein
said polythiol is represented by the general formula
<IMG>
wherein R1 and R2 are straight chain aliphatic moieties contain-
ing no reactive carbon-to-carbon unsaturation and a is 2 to 4.
14. The coated polycarbonate article of claim 13 wherein R1
and R2 are straight chain aliphatic moieties containing no
reactive carbon-to-carbon unsaturation and containing from 1 to
about 20 carbon atoms.
15. The coated polycarbonate article of claim 14 wherein
said polythiol is represented by the formula
<IMG>
16. The coated polycarbonate article of claim 12 wherein
said polyene is represented by the formula
<IMG>
23

8SP-2968
17. The coated polycarbonate article of claim 15 wherein
said polyene is represented by the formula
<IMG> .
18. The coated polycarbonate article of claim 11 wherein
said polyene and polythiol are present in stoichiometric amounts.
19. The coated polycarbonate article of claim 18
wherein said composition contains, in parts by weight, from
about 1 part of said silicone modified polyester copolymer
to about 3 parts of the combined weights of said polythiol and
said polyene to from about 3 parts of said silicone modified
polyester copolymer to about 1 part of the combined weights of
said polythiol and said polyene.
20. The coated polycarbonate article of claim 19
wherein said composition contains, in parts by weight, from
about 1 part of said silicone modified polyester copolymer to
about 2 parts of the combined weights of said polythiol and
polyene to from about 2 parts of said silicone modified polyester
copolymer to about 1 part of the combined weights of said
polythiol and polyene.
24

Description

~36(~1~
gSP-2968
This invention is directed to a polycarbonate article coated
with a photocurable coating composition comprised of (1) a poly-
thiol, (ii) a polyene, and (iii) a silicone modified polyester
copolymer. This invention is also directed to a coated polycarbon-
ate article coated with a photocured coating comprising the photo-
reaction product of (i) a polythiol, (ii) a polyene, and (ii) a
silicone modified polyester copolymer.
BACKGROUND OF THE INVENTIO~
Commercial liquid coating compositions are available. Many
of these coating compositions are not suitable for coating poly-
carbonate articles since they are not compatible with the polycar-
bonate. Also, the uncured coating may adversely affect the poly-
carbonate àrticle by stress cracking and crazing it,by causing
crack propogation into the polycarbonate as a result of brittle-
ness of the coating itself and/or by reducing the properties of
the polymer generally such as, for example, impact resistance,
elongation, tensile strength and so on. Further, several coatings
while compatible with the polycarbonate have little or no chemical
barrier properties and/or poor adhesion.
Therefore, a successful coating for polycarbonate articles
must be compatible with the polycarbonate and provide barrier or
other desirable surface properties while maintaining mechanical
or other properties of the polymer substrate and themselves
provide chemically resistant surfaces. Also, the cured coating,
in this particular application, should particularly provide the
coated polycarbonate article with anti-skid properties in addition
to the chemical barrier properties necessary to prevent crazing of
the substrate polycarbonate in chemically aggressive environments
and have improved adhesion to the polycarbonate substrate.
. ~

1136~
8SP-2968
U.S. 4,Q82,891 describes photocurable compositions suitable
for coatings comprising a polythiol and two different polyenes
and poly~arbonate articles coated therewith. The instant invention
provides a polycarbonate article coated wit~ a photocured coating
composition wherein said photocured coating has good adhesion to
the polycarbonate substrate, is tough, and has good anti-skid
properties.
DESCRIPTION OF THE INVENTION
-
The instant invention is concerned with a polycarbonate
article coated with a photocurable composition comprising: (i) a
polythiol, (ii) a polyene, and (iii) a silicone modified polyester
copolymer. The coating, when photocured, is the photo reaction
product of (i) a polythiol, (ii) a polyene, and (iii) a silicone
modified polyester copolymer. The instant invention is thus also
concerned with a coated polycarbonate article coated with a photo-
cured coating which is the photo reaction product of ~i) a poly-
thiol, (ii) a polyene, ana (iii) a silicone modified polyester
copolymer.
Upon curing, the coatings have improved adhesion to the poly-
carbonate substrate and provide a polycarbonate article with
anti-skid properties, chemical resistance, scratch resistance and
chemical barrier properties resulting in stress-crazing resistance.
Also, a polycarbonate article coated with the instant photo-cured
coating retains its inherent desirable physical properties by
which it is distinguished.
The photocurable coating composition comprises:
(i) a polythiol represented by the general formula:
R1 ( R-R2SH) a
wherein Rl and R2 are organic moieties containing no reactive
-- 2 --

~36~1
8SP-2968
carbon-to-carbon unsaturation and a is 2 to 4;
(ii) a polyene represented by the general formula
~ ~ oR3CH=CH2)3
wherein R3 is an organic moiety containing no reactive carbon-to-
carbon unsaturation; and
(iii) a silicone modified polyester which is the reaction
product of a hydroxyl terminated unsaturated polyester of a poly-
carboxylic acid reactant wherein at least about 65 mole ~ of the
polycarboxylic acid reactant is an ~, ~-ethylenically unsaturated
polycarboxylic acid reactant and an alcohol which contains two
terminal hydroxyl groups and alkyl ether and/or methallyl ether
groups, and an organopolysiloxane containing at least 0.25~ by
weight of groups reaCtive with the hydroxyl functional groups of
the polyester.
The photocured coating comprises the photoreaction product of:
(i) a polythiol represented by the general formula:
Rl--t--C-R2SH)a
wherein Rl and R2 are organic moieties containing no reactive
carbon-to-carbon unsaturation and a is 2 to 4;
(ii) a polyene represented by the general formula
~\
~ ~ oR3CH=CH~)3
wherein R3 is an organic moiety containing no reactive carbon-to-
carbon unsaturation; and
(iii) a silicone modified polyester which is the reaction
product of a hydroxyl terminated unsaturated polyester of a
-- 3 --

11360~1
8SP-2968
polycdrboxylic acid reactant wherein at least about 65 mole % of
the polycarboxylic acid reactant is an ~, ~-ethylenically unsat-
urated polycarboxylic acid reactant and an alcohol which contains
two terminal hydroxyl groups and alkyl ether and/or methallyl
ether groups, and an organopolysiloxane containing at least 0.25 ~
hy weight of groups reactive with the hydroxyl functional groups of
- the polyester.
The polythiols of (i) are prepared by reacting an ester of
thiol containing acids of ~he formula HS-R2-COOH wherein R2 is an
organic moiety containing no reactive carbon-to-carbon unsatura-
tion, with polyhydroxy compounds of structure Rl(OH)a wherein
is an organic moiety containing no reactive carbon-to-carbon
unsaturation and a is 2 to 4. These components react under condi-
tions known in the art and as are set forth in U.S. Patent 3,6Cl/7l4,
3,661,744, which issued May 9, 1972~ Preferably-, the poly-
thiol of (i) has the following general formula
Rl ( CH2OC-R2SH)a
wherein Rl and R2 are straight chain aliphatic moieties containing
no reactive carbon-to-carbon unsaturation and a is 2 to 4.
Preferred straight chain aliphatic moieties are those containing
from 1 to about 20 carbon atoms.
The polyenes of (ii) are prepared by methods known in the
art and as set forth in U.S. Patent 3,66~',744, which
issued May 9, 1972. Preferred poly,enes of type (i) have the
following general formula:
/\
~ ~ (oR3CH=CH2)3
N
wherein R3 is an organic moiety containing no reactive carbon-to-

1~36011
~SP-2968
carbon unsaturation. Prefera~ly, R3 is a straight chain aliphatic
moiety containing no reactive carbon-to-carbon unsaturation and
containing from l to about 20 carbon atoms.
The silicone modified polyesters of (ii) are the reaction
products of:
. a hydroxyl terminated unsaturated polyester of:
l. a polycarboxylic acid reactant wherein at least
about 65 mole % of,the polycarboxylic acid reactant is
an ~ , ~-ethylenically unsatura~ed polycarboxylic acid
reactant and up to about 35 mole % of the polycarboxylic
acid reactant is a polycarboxylic acid reactant free
from non-benzenoid unsaturation; and
~. an alcohol reactant containing two terminal hydroxyl
groups and allyl ether groups and/or methallyl ether
groups in an amount sufficient to provide at least 0.1
mole of allyl ether groups and/or methallyl ether groups
per mole of said ethylenically unsaturated polycarboxylic,
acid reactant; and
3. wherein said polyester has an acid number from about
10 to about 35; and
B. an organopolysiloxane having the average unit formula:
(OH) q (OR' ) rRssi4-q-r-S
wherein R is lower alkyl radical having l to 8 carbon atoms;
and/or cycloalkyl radical having 5 to 7 carbon atoms in the
ring; and/or lower alkenyl radical having 2 to 8 carbon atoms;
and/or mononuclear aryl radical; and/or mononuclear aryl
lower alkyl radical having l to 6 carbon atoms in the alkyl
group; and/or halogenated derivatives of the above radicals;
R' is alkyl containing from l to 8 carbon atoms per radical;

1136Qli
8SP-2968
and/or aryl; and/or acyl of l to 8 carbon atoms; s has a
value of 1 to 2; q has a value of 0 to 1.0; r has a value of
0 to 1.0; and the sum of q + r has a value of 0.01 to l; and
containing at least 0.25% by weight of silicon-bonded OH and/
or OR' groups.
These silicone-polyester copolymers and the processes for
their production are known in the art and are set forth in U.S.
Patent 3,919.438, which iss~ued November ll, 1975.
The relative amounts of unsaturated polyes*er and organopoly-
siloxane are generally from about 90 to about 40~ by weight of
unsaturated polyester and correspondingly from about 10 to about
60% by weight of organopolysiloxane based upon the combined weight
of the polyester and organopolysiloxane. The preferred relative
quantities of polyester to organopolysiloxane employed in the
copolymers of the present invention are from about 70% to about
50% by weight of unsaturated polyester and correspondingly from
about 30 to about 50% by weight of organopolysiloxane based upon
the combined weight of the polyester and organopolysiloxane.
The copolymers of the present inventi'on are prepared by
copolymerizing a preformed unsaturated polyester of the type
described above with the required polysiloxane to effect a trans-
esterification between the reactants. The ester interchange
reaction is carried out in the presence of a reaction diluent
which is inert to the reaction (does not adversely affect `either
the reactants or the product). Suitable reaction diluents include
aromatic hydrocarbons such as xylene, benz ~e, and toluene; and
esters such as ethyl acetate and Cellosolv acetate.
The preferred diluents are the aromatic hydrocarbons. The
diluent is usually employed in amounts of at least about l part

1l36~ll
8SP-2968
by weight per 4 parts of reac~ants and preferably at least about
1 part by weight per 3 parts of reactants. The maximum quantity of
diluent is limited only by economical and practical considerations
such as equipment capacities.
In addition, it is preferred to carry out the transesterifica~
tion in the presence of an esterification catalyst. Examples of
such catalysts include the metallic esters of the general formula
M(oR4)4 wherein M is a titanium atom or a zirconium atom and each
R4 is a monovalent hydrocarbon radical or an acyl radical. The
substituents represented by R4 can be alkyl, aryl, alkenyl, aralkyl,
alkaryl, and acyl, The R4 substituents can be the same or
different in a particular compound. Illustrative of suitable
specific catalysts are M(OC6Hs)4, M(OC3H7)4, M(OC4~9)4, M(OC2H5)4~
M(OC2H5)3(0C6Hs)/ M(OCH3)3(oc2H3), M(OCH2C6H5)4~ M(OC5H4~H3)4r and
M(ocH3)(oc2Hs)(oc6H5)(oc4H9)-
The preferred catalysts are the alkyl titanates wherein the
alkyl group contains from 1 to 20 carbon atoms; and the titan um
acylates. Some commercially available titanium acylates are
represented by the formula (R50)3TioR4 wherein R5 is an alkyl
radical or is hydrogen and R4 is an acyl radical. The most pre-
ferred transesterification catalyst for the present invention is
tetraisopropyltitanate. In addition, various known polymeric
titanates and zirconates obtained by the partial hydrolysis and
condensation of the above-described monomeric titanates or
zirconates can be employed.
Generally, the polythiol of (i) and the polyene of (ii) are
used in stoichiometric amounts. The amounts, by weight, of the
silicone modified polyester copolymer, the polythiol and the
polyene present in the coating composition generally range from

- 113601~
8SP-2968
about 1 part by weight of the silicone modified polyester copoly-
mer to about 3 parts by weight of the combined weight of the poly-
thiol and the polyene to from about 3 parts by weight of the
silicone modi~ied polyester copolymer to about 1 part by weight of
the combined weight of the polythiol and the polyene; preferably
from about 1 part by weight of the silicone modified polyester
copolymer to about 2 parts by weight of the combined weight of the
polythiol and the polyene to from about 2 parts by weight of the
silicone modified polyester copolymer to about 1 part by weight of
the combined weights of the polythiol and polyene; and more
preferably from about 1 part by weight of the silicone modified
polyester copolymer to about 1 part by weight of the combined
weights of the polythiol and polyene.
The photocurable composition may be formulated for use as 100
percent solids, or disposed in organic solvents, or as dispersions
- or emulsions in aqueous media, prior to curing.
The curable coating compositions, if in liquid form, prior to
curing may readily be pumped, poured, siphoned, brushed, sprayed,
doctored, or otherwise handled as desired. Following application,
curing in place to the polycarbonate article may be effected
either very rapidly or extremely slowly as desired by manipulation
of the compounding ingredients and the method of curing.
The curing reaction may be initiated by most actinic light
sources that disassociate or abstract a hydrogen atom from an SH
group, or accomplish the equivalent thereof. Generally, the rate
of the curing reaction may be increased by increasing the temper-
ature of the composition at the time of initiation of cure. In
many applications, however, the curing is accomplished convenient-
ly and economically by operating at ordinary room temperature
conditions.
- 8 -

~136011
8SP-2968
By proper choice of type and concentration of photocuring
rate accelerator for initiation, the curing period required for
conversion of the polythiol-polyene-silicone modified polyester
copolymer composition from the liquid to the solid state may be
varied greatly as desired. In combination with suitable acceler-
ators or retarders, the curing period may vary from about a second
or less to about 30 days or more. In general, short curing periods
are achieved in applications where thin films of curable composi-
tions are required, such as in the field of coatings whereas the
long curing periods are achieved and desired where more massive
layers of composition are required, such as in the field of
elastomeric sealants.
A class of actinic light useful herein is ultraviolet light
and other forms of actinic radiation which are normally found in
radiation e~itted from the sun or from artificial sources such as
Type RS Sunlamps, carbon arc lamps, xenon arc lamps, mercury
vapor lamps, tungsten halide lamps and the like. Ultraviolet
radiation may be used most efficiently if the photocurable coating
composition contains a suitable photocuring rate accelerator.
Curing periods may be adjusted to be very short and hence commer-
cially economical by proper choice of ultraviolet source,
photocuring rate accelerator and concentration thereof, tempera-
ture and molecular weight, and reactive group functionality of
the polyene and polythiol.
Conventional curing inhibitors or retarders which may be
used in order to stabilize the components or curable compositions
so as to prevent premature onset of curing may include hydro~uinone;
p-tert-butyl catechol; 2,6-di tert-butyl-p-methylphenol; phenothia-
zine; N-phenyl-2-nephthylamine; inert gas atmosphere such as
helium, argon, nitrogen and carbon dioxide; vacuum; and the like.

1136011
8SP-2968
It is understood to be within the scope of this invention
that the photocuring rate accelerator may be present as a separate
and distinct component such as azobenzene, as a mixture of two or
more separate components, such as benzophenone; benzanthrone;
5 anthrone and dibenzosuberone; carbon tetrachloride and phenanthrene;
and the like, or in chemically combined form within the molecular
structure of either the polyenes or the polythiol.
Specifically useful herein are chemical photocuring rate
accelerators such as benzophenone, acetophenone, acenaphthene-
quinGne, o-methyoxy benzophenone, thioxanthen-9-one, xanthen-9-
one, 7-H-Benz(de)anthracen-7-one, dibenzosuberone, l-naphthaldehyde,
4,4'-bis(dimethylamino) benzophenone, fluorene-9-one, l'-aceto-
naphthane, anthraquinone, l-indanone, 2-tert-butyl anthraquinone,
valerophenone, hexanophenone, 3-phenyl-butyrophenone, p-morpholino-
propiophenone, 4-morpholino-benzophenone, p-diacetylbenzene, 4-
amino-benzophenone, ~'-methoxyacetophenone, benzaldehyde, ~ -
tetralone, 9-acetylphenanthrene, 2-acetyLphenanthrone, lO-thiox-
anthenone, 3-acetylphenanthrene, 3-acetylindole, 1,3,5-triacetyl-
benzene and the like, including blends thereof, to greatly reduce
the exposure times.
The curing rate accelerators are usually added in an amount
ranging from about 0.005 to about 50 percent by weight of the
photocurable composition, with a preferred range being from about
0.05 to about 25 percent by weight. Preferred photocuring rate
accelerators are the aldehyde and ketone carbonyl compounds having
at least one aromatic nucleus attached directly to the -C- group.
The compositions to be cured, i.e., (converted to solid
resins or elastomers) and the photocured compositions, i.e.,
(solid resins or elastomers) in accord with the present invention
-- 10 --

1~36~11
8SP-2968
may, if desired, include such additives as antioxidants, acceler-
ators, dyes, inhibitors, activators, fillers, pigments, antistatic
agents, flame-retardant agents, thickeners, thixotropic agents,
surface-active agents, viscosity modifiers, extendinq oils,
plasticizers, tackifiers and the like within the scope of this
invention. Such additlves are usually preblended with the polyene
or polythiol prior to or during the compounding step. Operable
fillers include natural and synthetic resins, carbon black, glass
fibers, wood flour, clay, silica, alumina, carbonates, oxides,
hydroxides, silicates, glass flakes, glass beads, borates, phos-
phates, diatomaceous earth, talc, kaolin, barium sulfate, calcium
sulfate, calcium carbonate, antimony oxide and the like. The
aforesaid additives may be present in quantities up to 500 parts
or more per 100 parts polymer by weight and preferably about
0.0005 to about 300 parts on the same basis.
A useful method of compounding is to prepare in an ambient
atmosphere by conventional mixing techniques but in the absence
of actinic radiation a composition consisting of polyenes,
antioxidant (to inhibit spontaneous oxygen-initiated curing),
polythiol, silicone modified polyester copolymer, UV sensitizer
or photoinitiator, and other inert additives. This composition
may be stored in the dark for extended periods of time, but on
exposure to actinic radiation (e.g., ultraviolet light, sunlight,
etc.) will cure controllably and in a very short time period to
solid polythioether products.
The coating composition of the instant invention may be
applied to the polycarbonate sur~ace by any conventional coating
technique such as roll, curtain or spray.
-- 11 --

- 1136011
8SP-2968
Tn ~he practice of this invention, any of the aromatic
polycarbonates can be employed herein. These are homopolymers
and copolymers and mixtures thereof that are prepared by reacting
a dihydric phenol with a carbonate precursor. Ty~ical of some of
5 the dihydric phenols that may be employed in the practice of this
invention are bisphenol-A, (2,2-bis(4-hydroxyphenyl) propane),
bis (4-hydroxyphenyl) methane, 2,2-bis(4-hydroxy-3-methylphenyl)
propane, 4,4-bis(4-hydroxyphenyl) heptane, 2,2-(3,5,3',5'-tetra-
chloro-4,4'-dihydroxydiphenyl) propane, 2,2-(3,5,3',5'-tetrabromo-
4,4'-dihydroxydiphenyl) propane, (3,3'-dichloro-4,4'-dihydroxy-
phenyl) methane. Other dihydric phenols of the bisphenol type
are also available and are disclosed in U.S. Patents 2,999,835,
3,028,365 and 3,334,154.
It is, of co~urse, possible to employ two or more different
dihydric phenols or a copolymer of a dihydric phenol with a glycol
or with hydroxy or acid terminated polyester, or with a dibasic
acid in the event a carbonat:e copolymer or interpolymer rather than
a homopolymer is desired for use in the preparation of the aromatic
carbonate polymers of this invention. Also employed in the prac-
tice of this invention may be blends of any of the above materialsto provide the aromatic carbonate polymer.
The carbonate precursor may be either a carbonyl halide, a
carbonate ester or a haloformate. The carbonyl halides which can
be employed herein are carbonyl bromide, carbonyl chloride and
mixtures thereof. Typical of the carbonate esters which may be
employed herein are diphenyl carbonate, di-(halophenyl)carbonates
such as di-(chlorophenyl) carbonate, di-(bromophenyl) carbonate,
di-(trichlorophenyl) carbonate, di-(tribromophenyl) carbonate,
etc~, di-(alkylphenyl) carbonate such as di(tolyl) carbonate,
- 12 -

113601~
8SP-2968
etc., di-(naphthyl) carbonate, di-~chloronaphthyl) carbon2te,
phenyl tolyl carbonate, chlorophenyl chloronaphthyl carbonate,
etc., or mixtures thereof. The haloformates suitable for use
herein include bis-haloformates of dihydric phenols (bischloro-
formates of hydroquinone, etc.) or glycols (bishaloformates of
ethylene glycol, neopentyl glycol, polyethylene glycol, etc.).
While other carbonate precursors will occur to those skilled in
the art, carbonyl chloride, also known as phosgene, is preferred.
Also included are the polymeric derivatives of a dihydric
phenol, a dicarboxylic acid and carbonic acid. These are disclosed
in U.S. Patent 3,169,121 which issued February 9, 1965.
~he aromatic carbonate polymers of this invention may be pre-
pared by employing a molecular weight regulator, an acid acceptor
and a catalyst. The molecular weight regulators which can be
employed in carrying out the process of this invention include
monohydric phenols such as phenol, chroman-T, paratertiary-
butylphenol, parabromophenol, primary and secondary amines, etc.
Preferably, phenol is employed as the molecular weight regulator.
A suitable acid acceptor may be either an organic or an
inorganic acid acceptor. A suitable organic acid acceptor is a
tertiary amine and includes such materials as pyridine, triethyl-
amine, dimethylaniline, tributylamine, etc. The inorganic acid
acceptor may be one which can be either a hydroxide, a carbonate,
a bicarbonate, or a phosphate of an alkali or alkaline earthmetal.
The catalysts which are employed herein can be any of the
suitable catalysts that aid the polymerization of bisphenol-A
with phosgene. Suitable catalysts include tertiary amines such as
for example, triethylamine, tropropylamine, N,N-dimethylaniline,
quaternary ammonium compounds such as, for example, tetraethyl-

113601~
8SP-2968
ammonium bromide, xetyl triethyl ammonium bromide, tetra-n-
heptylammonium iodide, tetra-n-propyl ammonium bromide, tetra-
methylammonium chloride, tetramethyl ammonium hydroxide, tetra-n-
butylammonium iodide, benzyltrimethylammonium chloride and
quaternary phosphonium compounds such as for example, n-butyltri-
phenyl phosphonium bromide and methyltriphenyl phosphonium
bromide.
Also, included herein are branched polycarbonates wherein a
polyfunctional aromatic compound is reacted with the dihydric
phenol and carbonate precursor to provide a thermoplastic
randomly branched polycarbonate.
These polyfunctional aromatic compounds contain at le~st
three functional groups which are carboxyl, carboxylic anhydride,
haloformyl or mixtures thereof. Examples of these polyfunctional
aromatic compounds which may be employed in the practice of
this invention include: trimellitic anhydride, trimellitic acid,
trimellityl trichloride, 4-chloroformyl phthalic anhydride,
pyromellitic acid, pyromellitic dianhydride, mellitic acid,
mellitic anhydride, trimesic acid, benzophenonetetracarboxylic
acid, benzophenonetetracarboxylic anhydride and the like. The
preferred polyfunctional aromatic compounds are trimellitic
anhydride or trimellitic acid, or their haloformyl derivatives.
Also, included herein are blends of a linear polycarbonate
and a branched polycarbonate.
DESCRIPTION OF THE PREFERRED EMBODIMENT
.. . . ..
The following examples are set forth to illustrate more
clearly theprinciple and practice of this invention to those
skilled in the art. Unless otherwise specified, where parts or
percents are mentioned, they are parts or percents by weight.

~36()11
8SP-2968
EXAMPLE 1
A sample of a polycarbonate of 2,2'-bis-(4-hydroxyphenyl)
propane having an intrinsic viscosity of 0.57 deciliters is
molded into test specimens of 4" x 4" x 1/4" and tested for
toughness and stress-crazing.
The toughness of the specimen is determined by moving the
fingernails of a hand back and forth across the test specimen
with medium pressure and observing whether or not the coating
scratches.
The stress-crazing of the 4" x 4" specimen is determined by
placing it on a material, such as an equivalent size of carpet,
placing a steel ball in the center of the combination and applying
a load plate of 100 lbs. to the steel ball. The sample is allowed
to remain under stress for 7 days. The sample of polycarbonate is
then examined around the stress point for any sign of stress
crazing .
The polycarbonate of this example is molded into a test
specimen of 10" x 10" x 1/4" and tested for its anti-skid
properties. The anti-skid rating is determined by placing three
7/8" diameter steel balls, welded together to form a triangle, on
the test specimen and raising one end of the specimen vertically
while keeping the opposite end on the horizontal plane. The
distance in inches to which the edge is raised vertically when the
weight slides down the sample is recorded. A value of 7-8 is
considered acceptable.
The test results are summarized in Table I.
EXAMPLE 2
Sheets of 4" x 4" x 1/4" and 10" x 10" x 1/4", made from the
polycarbonate of Example 1, are coated with a coating which is a

113601:1
8SP-2968
mixture of a stoichiometric amount of a thiol of the formula
R
CH3CH2C-t-CH2oCCH2CH2SH)3
- and a polyene of the formula:
o
~COCH2CH=CH2
~ ~ IOCH2CH=CH~
O
in a thickness in the range of 0.5 mils to 2.5 mils and cured
with ultraviolet light for 60 seconds. The coated sheets are
tested as described in Example 1 and also tested for coating
adhesion.
The coating adhesion is measured on the coated sheet with
scotch tape. In the unscribed coating adhesion test, a strip of
scotch tape is applied to the surface of the coating, taking care
to hold one end of the strip away from the surface. The tape is
removed rapidly by pulling the free end at a 90 angle away from
the surface. Removal of the coating with the tape is considered
adhesion failure. In the scribed coating adhesion test, the
coating surface is scribed with a sharp instrument such as a razor
blade or a Gardner cross-cut (lattice cutting) tester. The
scribed area consists of two sets of parallel scribes 1-2 mm.
apart, perpendicular to each other. The scotch tape is applied
tas above) over the scribed area and removed in the same manner as
above. The coating is then examined for partial or complete
removal of the squares or no change.
EXAMPLE 3
Sheets of 4" x 4" x 1/4" and 10" x 10" x 1/4" made from the
polycarbonate of Example 1, are coated with a coating which is a
mixture of a stoichiometric amount of the thiol of Example 2 and
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1136~
8SP-2968
a poLyene of the formula:
O CH3 O O C~ O
HO LC3~6OCN ~ NCOC3H6 ~ CN ~ ~ r NCOC~S2CII CH2
where n is an integer wherein the molec r weight ls equal to
1000, in a thickness in the range of 0.5 mils to 2.5 mils and
cured with ultraviolet light for 60 seconds. The coated sheets
are tested as described in Examples 1 and 2. The results are set
forth in Table I.
EXA~IPLE 4
To a reaction vessel equipped with a stirrer, a fractionation
column packed with glass helices, a Dean-Stark trap, and a conden-
ser are added 213.30 parts of maleic anhydride, 202.74 parts of
trimethylolpropane monoalkyl ether and 183.96 parts of diethylene
glycol. The reaction mass is heated under a nitrogen atmosphere
to a maximum temperature of 200C. After about 4~ hours, a total
of 33 parts of water of esterification are collected. The
reaction mass is cooled to room temperature and about 567 parts of
an unsaturated polyester having an acid number of 32 are obtained.
169 parts of this polyester and 60 parts of xylene are added
to a reaction vessel e~uipped with a stirrer, a fractionation
column packed with glass helices, a Dean-Stark trap, and a
condenser. The reaction mixture is heated to 110C in about 10
minutes at which time 76 parts of a methoxy chain-stopped linear
polysiloxane containing phenyl and methyl groups; 7% by weight
silicon-bonded methoxy groups, and a viscosity of 1500-3000
centisto~es at 25C; 25 parts of xylene and 0.38 parts of tetra-
isopropyl titanate are added to the reaction vessel. The reaction
mass is heated under a nitrogen atmosphere to a maximum tempera-
ture of 152C. After about 23i hours, 6 parts of methanol are

:1136011 8SP-29~8
collected and external heating of the reaction is stopped. The
reaction mass is distilled under vacuum at a pressure of 20 mm Hg
to a maximum temperature of 145C to remove the xylene. About 239
` parts of a clear copolymer containing 70 weight % of the unsatur-
ated polyester and 30 weight ~ of the organopolysiloxane are
obtained .
EXAMPLE 5
Sheets of 4" x 4" x 1/4" and lO" x 10" x 1/4" made from the
polycarbonate of Example 1 are coa~ed with a coating which con-
tains a mixture of (i) 50 gms. of a mixture o~ a stoichiometric
amount of the thiol of Example 2 and a stoichiometric amount of a
polyene having the formula
~ ~ CH2CH=CH2~ 3
and (ii) 50 gms. of the silicone modified polyester copolymer
prepared substantially in accordance with Example 4 and cured with
ultraviolet light for 60 seconds to give a curea coating about 1.2
mils in thickness. The coated sheets are tested as described in
Examples 1 and 2. The results are set forth in Table I.
TA8LE I
Example 1 Example 2 ExamPle 3 Example 5
~oughness Pass Fail Pass Pass
Stress Crazing Fail Pass Fail Pass
Anti-Skid 3-4 6-8 7-8 7-8
Adhesion N/A Pass Fail Pass
Although the above examples have shown various modifications
of the present invention, other variations are possible in the
light of the above teachings. It is therefore to be understood
that changes may be made in the particular embodiments of the
invention described which are within the full intended scope of
the invention as defined by the appended claims.
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