Note: Descriptions are shown in the official language in which they were submitted.
. ~233290 SUE
ULTRAVIOLET RADIATION-CURABLE
SILICONE RELEASE COMPOSITIONS
FIELD OF THE INVENTION
This invention relates to ultraviolet radiation-
curable silicone release compositions. More particularly it relates to new photo curable selection polymers and new
photocatalyst-siloxane polymer combinations. Marquette-
alkoxyalkyl-functional polysiloxanes and vinyl-functional
selection terpolymers have been discovered which are
curable on exposure to ultraviolet radiation in the
presence of a photo initiator.
BACKGROUND OF THE INVENTION
Silicone compositions have become widely accepted
as release coatings, which are useful to provide a
surface or material which is relatively non adherent to
other materials which would normally adhere closely
thereto. Silicone release compositions may be used as
coatings which release pressure sensitive adhesives for
labels, decorative laminates, transfer tapes, etc.
Jo
1233Z90 SUE 666
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Silicone release coatings on paper, polyethylene, Mylar ,
and other such substrates are also useful to provide
non-stick surfaces for food handling and industrial
packaging.
Previously developed silicone release products
have been heat-curable, however the high one gyp costs
and safety and environmental considerations associated
with high temperature oven curing has provided the
incentive for developing alternative technologies,
such as ultraviolet radiation-curable silicones.
Ultraviolet (W) radiation is one of the most
widely used types of radiation because of it low cost,
ease of maintenance, and low potential hazard to
industrial users. Typical curing times are much shorter,
and heat-sensitive materials can be safely coated and
cured under W radiation where thermal energy might
damage the substrate.
I
Three basic Uncurable silicone systems have been
developed: ~poxysilicone systems, acrylic-runctional
silicone systems, and mercaptofunctional silicone
systems.
I
Epoxy silicone systems, such as those described in
US. 4,279,717 (Eckberg et Allah and commonly assigned
Canadian application Serial Jo. 428,1~2 which was filed
May 13, 1983, feature epoxy-functional diorgano selection
base polymers catalyzed by opium salt photo initiators.
The compositions exhibit extremely high cure rates but
depend on expensive materials which are not widely
available.
lZ~3~90 SUE 666
Acrylic-~unctional silicone systems sun as
described in commonly assigned cop ending dun Applications
Serial Nos. 399,410 filed March 25, 19~2 and 428,142
filed May 13, 1983, and also modified systems described
in US. 4,048,036 (Prucnal) and US. 4,017,652 (Grubber),
provide serviceable coatings that are W-curable in the
presence of free radical-type photo initiators but require
complex, multi step preparation.
Many mercapto-functional systems are known: For
example, US. 4,064,027 (cant), US. 4,107,390
(Gordon et at.), US. 4,197,173 (Curry et at.), Japan
okay Tokyo Kiwi 79 48,854 (to Takamizawa; Chum.
Abstracts 91: 58888r, 1979), US. 3,661,744 (Kerr et at.),
US. 4,G70,526 (Colquhoun et at.), US. 4,052,529
(Bokerman et at.), US. 3,873,499 Michael et at.),
and US. 3,816,282 (Viventi) disclose Marquette-
functional polysiloxane or polythiol compositions which
are W -curable when combined with an ethylenically
unsaturated organic compounds, which curable csmpusitions
also contain, variously, mercaptoalkyl polysiloxane cure
accelerators, acetophenone-type photosensitizes,
silacyclopentenyl curing agents, cure rate accelerators
and gellation inhibitors. These provide a wide range
of serviceable release coating compositions, however,
the acceptance of this technology has been hindered by
several persistent disadvantages including dependence
on scarce or expensive starting materials, unserviceably
slow curing rates, complex processing, and offensive
odors (associated with the mercaptan group) which
persist in the cured products. Some of these specific
disadvantages have been addressed, for example, in the
cant patent, photosensiti~ers such as acetophenone are
added to assist radiation curing, in Us 4,171,252
(Fantazier), photo polymerization of unsaturated come
, SUE 666
~Z33Z9(~
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pounds is catalyzed by peroxy-napthalenic compounds,
and in the aforementioned Kerr et at. and Colquhoun et at.
patents aromatic kittens are employed to accelerate the
cure; however, there is still a need for improvement and
reduction of costs in mercaptofunctional compositions
and related W-cure technologies.
New mercaptoalkoxyalkyl-functional silicones have
now been discovered which can be synthesized in a two-step,
one-vessel process from readily available, inexpensive
lo materials and which do not emit disagreeable odors. In
addition, it has been discovered that certain perbenzoate
esters are suitable photoinititators for polymerization
reactions between mercqptofunctional compounds and
vinyl-functional compounds; and the cure characteristics
of the novel reactive polysiloxane/photoinitiator blends
ox the present invention may be enhanced or modified by
certain aromatic photosensitizes or by judicious
selection of the molar ratios of reactive ingredients
in such Lindsey
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invent
lion to provide new mercaptofunctional silicone release
coating compositions.
It is a further object of the present invention
25 to provide solvent less silicone release coating
compositions which are curable on brief exposure to
ultraviolet radiation.
~,~3~9~ SUE 666
It is a further object of the present invention
to provide improved reactive polysiloxane/photoinitiator
blends which are simply and inexpensively produced.
These and other objects are accomplished herein
by a mercaptoalkoxyalkyl-functional polysiloxane
capable of curing (i.e., polymerizing or cross linking)
to an adhesive polymeric composition on brief exposure
to ultraviolet radiation when combined with an organic
compound containing ethylenic unsat~ration and a
catalytic amount of a photo initiator comprising: A
diorsanopolysiloxane comprising units of the formula
RR'SiO, where R is hydrogen or Cal 8) alkyd and R' is
hydrogen, Cal 8) alkyd or a monovalent mercaptoalkoxyalkyl-
functional organic radical of from 2 to 20 carbon atoms,
said diorganopolysiloxane having up to about 50% Marquette-
alkoxyalkyl-functional groups and a viscosity of from
about 50 to 10,000 centipoise at 25C.
Also contemplated are mercaptoalkoxyalkyl-function~l
diorganopolysiloxanes prepared by (1) reacting a dialkyl-
hydrogen-chainstopped polydialkyl-alkylhydrogensiloxane
copolymer with an ~-halo-alkene in the presence of a
precious metal hydrosilation catalyst, and (2) reacting
the product of (1) with a hydroxy-functional they'll of
the formula HORATIO, where R" is a diva lent alkaline
or alkyd kitten radical of from 2 to 20 carbon atoms in the
presence of an amine.
Another feature of the present invention is a
corbel silicone release composition comprising:
o
i~33~9 SUE 666
(A) A diorganopolysiloxane comprising units Of
the formula RR'SiO, where R is hydrogen or Cal 8) allele
and R' is hydrogen, Cal 8) alkyd or a monovalent
mercaptoalkoxyalkyl functional organic radical of from 2
to 20 carbon atoms, said diorganopolysiloxane having up
to about 50~ weight mercaptoalkoxyalkyl groups and
a viscosity of from about 50 to 10,000 centipoise at 25C;
(B) A polysiloxane consisting of from about 0.5
to 100 mole percent of vinyl-lunctional selection units
of the formula (CH2=CH)RnSiO3 n/2' where R is hydrogen
or Cal 8) alkyd and n has a value of 0 to 2, inclusive,
any non-vinyl-containing selection units having the
formula R3mSio4 my where R is hydrogen or Cal 8) alkyd
and m has a value of from 0 to 3, inclusive; and
(C) A catalytic amount of a photo initiator.
Especially contemplated are W -curable compositions
wherein the photGinitiator component is a pe~benzoate
ester; and further features include the use of certain
aromatic kittens as photosensitizes to assist curing,
and the discovery of a vinyl-functional polysiloxane
terpolymer which is useful in forming Uncurable release
compositions.
Further embodiments of the present invention will
become apparent to those skilled in the art upon consider-
lion of the following description, examples, and claims.
60S1 666
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DOTTED DESCRIPTION OF THE INVENTION
The present invention provides mercaptoalkoxyalkyl-
functional silicone compositions and silicone release
coaxings made from such compositions, as well as photo-
initiators for such compositions and processes for
providing the compositions and coatings.
The mercaptofunctional polymers of the present
invention are diorganopolysiloxanes comprised of
selection units having substituent groups including
hydrogen atoms, lower alkyd radicals having up to about
8 carbon atoms such as methyl, ethyl, Ripley, isopropyl,
etc., and monovalent mercaptoalkoxyalkyl radicals of
from about 2 to 20 carbon atoms. These polymers may be
advantageously synthesized from a number of constituent
ingredients. The relative proportions of these
constituents are not critical and may be varied over a
wide range to provide mercaptoalkoxyalkyl-functional
polysiloxanes having varied properties. The preferred
synthesis, described below, requires only two steps and
may be carried out in a single reaction vessel, however
it will be recognized that alterations in the synthesis
procedure can be readily devised which are within the
scope of the present invention.
The preferred mercaptoalkoxyalkyl-functional
polymers of the present invention are prepared from a
dialkylhydrogen-chainstopped polydialkyl-alkylhydrogen
selection copolymer. Such SiH-containing polysiloxanes
will ordinarily haze the general formula:
-
z33~9c~ SUE 566
_ 8
R , R \ / R R
Ho Slow Sluice
R H R y R
in which each R represents, independently, a monovalentalkyl radical of from 1 to 8 carbon atoms, preferably
methyl, and zoo is an integer of about 25 to 600 such
that the polysiloxane has a viscosity of about 20 to
5000 centipoise at 25C, preferably 100 to 500 centipoise.
Such hydrogen-functional selection fluids are primarily
linear and will therefore have an R to So ratio of
approximately 2 to 1. These selection fluids will
ordinarily have from about 0.5 to 50 percent by weight
hydrogen-siloxy functionality and are made by processes
well known in the art. Minor amounts of moo- and
tri-functional selection units, some of which may also
contain hydrogen, may also occur in these fluids but
will not seriously detract from their usefulness.
The SiH-containing polysiloxanes are reacted with
an ~-halo-alkene, preferably an w-chloro-l-alkene
such as ally chloride, methallyl chloride, sheller-
butane, 10-chloro-1-decene, and owner analogous
unsaturated halogen-containing hydrocarbons. Mixtures
of such ~-halo-alkenes will also be useful.
1233Z~3~
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_ g
The alkene component and the hydrogen-functional
polysiloxane component are reacted in a precious
metal-catalyzed addition cure reaction. Such catalysts
are well known in the silicone art and will ordinarily
be a platinum metal complex effective to promote
the addition of a -Six moiety to the double bond of
an alkene. Examples of such hydrosilation catalysts
suitable for the purposes herein are described in
United States Patents 3,220,972 (Limericks) issued
November 30, 1965; 3,715,334 (Karlstedt) issued
February 6, 1973; 3,775,452 (Karlstedt) issued
November 27, 1973 and 3,814,730 (Karlstedt) issued
June 4, 1974.
The product of the hydrosilation reaction
described above is finally reacted with a hydroxy-
functional they'll monomer in the presence of an amine.
Suitable thiols have the general formula Horatio in
which R is diva lent alkaline of from 2 to 20 carbon
atoms or diva lent alkyd kitten radicals,
-(Sheehan COO-, of from 2 to 20 carbon atoms.
Preferred compounds are -mercaptoethanol and
-mercaptopropionic acid. For the purposes of the
present invention, sufficient amounts of the
hydroxy-functional they'll monomer should be used to
provide a mercaptioalkoxyalkyl-functional polysiloxane
having from 0.5 to 50 percent by weight
mercaptoalkoxyalkyl sulks functionality. The
above-described synthesis may be illustrated as
follows: _
_
:.
1~33~
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_ 10 _
1) -Six + CH2=CCH2-C~ -I SiCH2fHCH2-Cl
SHEA SHEA
methallyl chloride
2) -SiCH2CHCH2-Cl + HOWE amine _
I
OH
3 -SiCH2CHCH2-O-R-SH
SHEA
o
R is preferably CH2CH2 or CCH2CH2 .
W -curable mercaptoalkoxyalkyl-functional silicone
composition scan be made by combining the above-described
mercaptoalkoxyalkyl-functional polysiloxanes with a
catalytic amount of a photo initiator. Any of the
numerous photo catalysts known to promote a curing-,
it cross linking, reaction between the mercaptofunc-
tonal group and the vinyl-functional group of a vinyl-
containing cross linking compound, marry of which
photo catalysts are discussed n the
previously cited United States Patent Numbers
are suitable. Especially contemplated are the acetophe-
none-type photo initiators such as dimethylhydroxyacetophe-
none, which is commercially obtainable under the trade name
Darker 1173 term. Chemicals, Inc.) A preferred
feature of the present invention, however, stems from
the discovery that certain perbenzoate esters hazing
the general formula:
Wreck
12332~0 SUE 66~i
where R is a monovalent alkyd or aureole group and Z is
H, alkoxy, alkyd, halogen, vitro, amino, primary and
secondary amino, amino, etc. The nature of the Z
substituent will affect the stability of the proxy
bond, an electron-poor substituent stabilizing the
proxy bond, and an electron-rich substituent making
the proxy bond more reactive. These perbenzoate esters
may be synthesized in known ways, such as by reacting
bouncily halides with hydroperoxides. (See, e.g., the
descriptions in Blomquist and Bernstein, J. Amer. Chum.
So., 73,5546 (1951)). Preferred perbenzoate esters
include t-butylperbenzoate and its para-substituted
derivatives, t-butylper-p-nitrobenzoate, t-but~lper-p-
methoxybenzoate, t-butylper-p-methylbenzoate, and
t-butylper-p-chlorobenzoate. T-butylperbenzoate is
most preferred.
The amount of photo initiator employed is not
critical, so long as proper cross linking is achieved.
As with any catalyst, it is preferable to use the
smallest effective amount possible; however, for
purposes of illustration, catalyst levels of from about
1% to 5% by weight of the total composition have been
found suitable.
In addition to the discovery that t-b~tylperbenzoate
(and its derivatives) is an excellent photo catalyst for
radical addition of mercaptofunctional selections to vinyl-
functional selections, it has been discovered that the
effectiveness of t-butylperbenzoate as a photo catalyst
is considerably enhanced when it is combined with certain
photosensitizes soluble in the silicone polymers of the
the instant invention. The use of these photosensitizes
leads to advantages in terms of release performance
ease of processing and lowering costs. The photosensi-
lZ33290 SUE 666~
- 12 _
titers more than double the rate of cure in photoactive
compositions under inert conditions and, surprisingly,
promotes good cure without inverting, which allows
important cost and processing advantages.
The photosensitizes are polyaromatic compounds
having at least two Bunsen rings which may be fused
or bridged by organic radicals or hetero-radicals such
as ox, trio, etc. Preferred among the photosensitizes
Lo tested were benzophenone and t-butylanthraquinone.
Anthracene and thioxanthone were unsuccessful as photo-
sensitizers due to their limited volubility in silicone
solutions. Other photosensitizes compounds related to
those already mentioned will suggest themselves to
persons skilled in the art and are meant to be included
within the scope of the present invention.
In the course of trials testing the effectiveness
of the aforementioned perbenzoate esters and photo-
sensitizers, previously unknown photo reactive terpolymers
were discovered which are capable of curing (on exposure
to W radiation) to adhesive compositions in the presence
of certain radical photosensitizes and without the use
of perbenzoate esters. The terpolymers are mixed
dimethylvinyl- and trimethyl-chainstopped linear
polydimethyl-methylvinyl-methylhydrogen selection
terpolymer fluids and can be synthesized by acid equal-
ration of methyl hydrogen selection fluid, tetramethyl-
tetravinylcyclotetrasiloxane (methylvinyltetramer~ and
octamethylcyclotetrasiloxane (dimethyltetramer), as desk
cried Gore completely in the worming examples (infer).
The W -curable silicone compositions which may be
prepared from the previously described ingredients can be
applied to cellulosic and other substrates including paper,
metal, foil, glass, polyethylene coated Crete PUKE), super-
,. . .
Swiss
SUE 666
- 13 --
calendered raft paper (SUCK), polyethylene films, polyp
propylene films and polyester films. A photo initiated
reaction will cure the silicone compositions to form an
adhesive surface on the coated substrate. Inverting of
the cure environment, such as with nitrogen, may be
desirable where the presence of oxygen is found to
inhibit the curing reaction.
In order that persons skilled in the art may
better understand the practice of the present invention,
the following examples are provided by way of illustration,
and not by way of limitation. All measurements are parts
by weight.
EXAMPLES l-10
Sample A
200 parts by weight of a 90 cups dimethylhydrogen-
chain stopped linear polydimethyl-methylhydrogen selection
fluid having about 9.5% by weight SiH-containing sulks
units about 0.31 moles Six total) were combined with
200 parts by weight Tulane and about 31.5 parts by
weight metnallyl chloride about 0.36 moles). A small
amount of a platinum catalyst was added and the
reaction mixture reflexed at 110C for 14 hours, at
which time infrared examination detected no unrequited
Six functionality. Excess methallyl chloride was removed
by distilling about 6 parts by weight of solvent from
the mixture at one atmosphere pressure. 33 parts by
weight y-mercaptopropionic acid Tao moles) were added
to the reaction vessel and a nitrogen atmosphere
established prior to drops addition of 40 parts by
weight triethylamlne at a temperature of SKYE. A
hazy precipitate taminehydrochloride) formed as the
triethylamine was added. The solvent was stripped under
a vacuum trout 5 mm pressure) at 158C for 30 minutes.
1~332~0 SUE 666
_ 14 -
Filtering the reaction product resulted in 173 parts by
weight of a hazy fluid, ~50 cups viscosity.
Sample B
Another mercaptofunctional polysiloxàne material
was prepared in the same manner as Sample A except that
~-mercaptoethanol (0.31 moles) was substituted for
y-mercaptopropionic acid. 182 parts by weight of a
slightly hazy 190 cups fluid product were obtained.
Sample C
250 parts by weight of a 50 cups SiH-containing
fluid similar to that used in Samples A & B containing
about 6.0 percent by weight SiH-containing sulks units
(0.25 moles total Six) were reacted with about 27 parts
by weight methallyl chloride by refluxing in 250 parts by
weight Tulane for 16 hours in the presence of a
platinum catalyst. After removal of excess methallyl
chloride, 500 parts by weight hexane and 19.5 parts by
weight (0.25 moles) ~-mercaptoethanol were added,
followed by drops addition of 20 parts by weight
pardon (0.26 moles) under nitrogen at 60C. The
precipitate resulting from the amine addition was
filtered from the solution and the filtrate stripped
of solvent and unrequited mercaptoethanol under a
vacuum at 165C for I hours. 226 parts by
weight of a clear, pale yellow 130 cups product were
obtained.
Sample D
250 parts by weight of a 295 cups SiH-containing
fluid having about 7.0 percent by weight SiH-containing
sulks units (0.29 moles total Six) were reacted with
methallyl chloride, then ~-mercaptoethanol and pardon
precisely as in the preparation of Sample C, above.
3 SUE 666
15-
Stripping the reaction product at 165C for 4 hours yielded
237 parts by weight of a clear, pale yellow fluid product,
830 cups viscosity.
It was noted that the prolonged strip cycle at
temperatures above about 160C accomplished the removal
of free (unrequited) mercaptoethanol (leaving an odor-free
product) and the removal of residual pardon hydrochlorate
precipitate by vacuum sublimation (leaving a clear fluid
lo product).
The mercaptoalkoxyalkyl-functional silicones
produced in the above fashion were used to produce ultra-
violet radiation-curable release compositions, as set forth
below:
Coating Composition l: 10 parts Sample B
1 part methylvinyltetramer
(teiramethyl-tetravinyl
cyclotetrasiloxane)
0.5 part dimethylhydroxyaceto-
phenone (Darker 1173).
Coating Composition 2: 8 parts Sample B
2 parts methylvinyltetramer
US 0.5 part dimethylhydroxyaceto-
phenone
Coating Composition 3: 8 parts Sample B
2 parts vinyl terminated
dimethylpolysiloxane
fluid, 200 cups.
0.5 part dimethylhydroxyaceto-
phenone.
:3 Z~2~3Q
SUE 666
~16~
Coating Composition 4: 7 parts Sample D
3 parts sym-Letramethyldivinyl-
disiloxane
0.4 part dimethylhydroxyaceto-
phenone.
Coating Composition 5: 5 parts Sample D
3 parts sym-tetramethyldivinyl-
disiloxane
2 parts vinyl terminal dim ethyl-
methyl vinyl selection fluid,
200 cups
0.4 part dimethylhydro~yaceto-
phenone.
Each coating composition was coated onto 40-lb.
SUCK paper as a thin film with a doctor blade, then
exposed to ultraviolet radiation from two focused medium-
pressure mercury vapor lamps each operating at 30C watts
per square inch mounted in a PUG 1202 SCAN processor.
Exposure times and curing atmosphere were varied to
assess the cure performance of the experimental compost-
lions. The cure was qualitatively determined by noting
the presence or absence of smear, migration, or rub-off,
with the following results:
Coating Cure Exposure
Cc~position _ Time, Sec. Qualitative Cure
1 No 1.5 No smear, no migration, no rub-off
1 Air 1.5 Slight jar, slight muggier., no n~toff
1 No 0-3 No migration, easy rub-off
1 Air 0.3 Slight migration, easy rub-off
1 No 0-07 No migration, eye rub-off
1 Air 0.07 Migrates, rubs off easily
2 No 0-3 Jo migration, rubs off easily
2 Air 0.3 Slight muggier., rubs off easily
3 No 0-3 Slight muggier., rubs off easily
i23329~ SUE 666
3 Air 0.3 NOT CUD
4 1.5 No jar, no migration, no rebuff
4 Air 1.5 Slight err, no migration, slight
rub-off
5 5 No 1.5 No smear, no migration, no rub-off
Air 1.5 Migrates, no rub-off
No 0-3 No migration, easy rub-off
These data indicate that a wide range of vinyl-
functional selections are suitable cross linkers in the
US cure of mercaptoalkoxyalkyl-functional polysiloxanes.
Also, it is apparent that better results are obtained
under a nitrogen atmosphere than in air, which is
predictable given the radical-initiated nature of the
curing reaction. Fully cured (migration-free) coatings
are observed with exposure times as brief as 1.5 seconds,
although anchorage to the SIX paper (evidenced by rub-off)
suffers at shorter exposure times.
It has been previously -sported, in US. 4,139,385
(Crivello), issued on February 13, 1979 , that opium
salt photo catalysts promote poIv~lefin-polythiol cross-
linking; and the following coating compositions were
prepared to test the effectiveness of cat ionic photo-
catalysts with the polymers of eke present invention:
Coating Composition 6: 10 parts Sample B
1 part methylvinyltetramer
0.2 part (C12H25Ph)2ISbF6
(bis(dodecylphenyl) ioaonium
hexafluoroantimonate photo catalyst).
lZ~3~0
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- 18 -
Coating Composition 7: lo parts Sample C
l part methylvinylteramer
0.5 part dimethylhydroxyacetophenone
0.2 part (Classifies 6
Coating Composition 8: 7.5 parts Sample C
0.5 part methylvin~ltetramer
2 parts 1,2-epoxydodecane*
0.4 part dimethylhydroxyacetophenone
0.2 part (Cl2H2sPh)2Isb 6
*I -epoxy monomer added as a cure enhancer (described as
to epoxy silicones in Canadian Apply SUN. 428,142 filed
May 13, 1983.
The performance of these compositions was tested
on super calendered raft paper as in Examples 1-5 with
the following results:
Exposure,
Composition Aim. Sec. Qualitative Cure
6 Air 1.5 No smear, no migration, no
rub-off
6 No 0~3 No smear, no migration,
rubs-off
7 Air 0.3 Slight smear, no
migration, some rub-off
7 N 0.3 No smear, no migration, easy
2 rub-Off
8 Air 1.5 No smear, no migration, no
rub-off
8 No 0 3 No smear, no migration,
easy rub-off
30 using the 'opium salt catalyst in this system allows those
skilled in the art to add an epoxy monomer reactive delineate
(such as the linear epoxide present in Composition 8) to the
vinylsiloxane-mercaptoalkoxyalkylsiloxane mixture n
=
i;2332~
SUE 666
_ 19 -
order to assist anchorage or modify the release character-
is tics of the cured coating.
The quantitative release performance was determined
for two coating compositions by preparing coating baths
as follows: (The Sample compositions were dispersed in
solvent in order to obtain even, low silicone depositions)
Bath 9: 20 parts Sample B
lo 2 parts methylvinyltetramer
l part dimethylhydroxyacetophenone
80 parts hexane.
Bath 10: 20 parts Sample B
2 parts methylvinyltetramer
0.4 part (Cl2H2sPh)2Isb 6
80 parts hexane.
These baths were used to coat SUCK paper using
a #3 wire-wound rod, and the coated paper were then
exposed to W radiation for 0.3 seconds as described above.
Laminates of the cured coatings were prepared by applying
a lo mix coating of Monsanto Gelva 263 aggressive acrylic
adhesive on top of the cured silicone coating and then
pressing an uncoated sheet of SUCK paper onto the adhesive.
2"x9" strips of the laminates were cut, and the
silicone/SCK famine separated from the adhesive/SCR famine
at a 180 angle at 400 ft./minute in a Scott tester. The
release, in grams force needed to separate Ike two famine,
was recorded and the following results obtained:
i ~3Z90 SUE 666
_20 -
Qualitative
Bath Aim. Cure Release grams
9 Aryan muggier., rubs-off 150-190
9 No No muggier., rubs-off 350-450
Air (poor cure) (not recorded)
No No muggier., rubs-off 150-210
Although the cured silicone release coatings did not
appear to be well anchored, as evidenced by rub-off, there
was no observation of the silicone layer being pulled away
preferentially from the SUCK substrate. The results also show
a high release (as opposed to "premium" release, usually <100
grams), especially when cured in an inert atmosphere, suggesting
that the radicals formed in the silicone coating interact
with the acrylic monomers present in the adhesive to
raise the observed release.
EXAMPLES 11 & lea
The efficacy of t-butylperbenzoate as a photo catalyst
so thiol/vinyl addition was demonstrated in the following
comparative trial:
Coating Composition 11: go parts Sample D (described
previously)
. 1.0 parts methylvinyltetramer
0.5 part t-butylperbenzoate.
Coating Composition lea: 9.0 parts Sample D
1.0 part methylvinyltetramer
0.5 parts dimethylhydroxyaceto-
phenone (Darker 1173).
These coating compositions were hand-coated on 40-lb.
super calendered raft paper using a doctor blade, exposed
to ultraviolet light as described above, and finally
35 qualitatively assessed for cure as a release surface, as
1~3Z90 60S~ 666
- 21_
summarized below:
W Exposure
Eye Aim. sec. Qualitative Cure
11 AIR 0.6 Slight sir, no migration, slight
rub-off
11 No 0-3 No smear, no migration, no rub-off
11 No 0.15 No or, no migration, slight
rub off
lea AIR 1.5 Swears, no migration, easily
rubbed of
lea No 1.5 Slight jar, no migration, slight
rebuff
lea No 0 3 us no migration, easily rubbed-
of
From these data, it is apparent that t-butylperbenzoate is
superior to the commercially available Darker 1173
photo initiator in this curable mercapto-vinyl silicone
system.
EXAMPLES 12-14 & AYE
Further investigation into the photo catalytic
qualities of perbenzoate esters was conducted by preparing
the following coating compositions:
5 Coating Composition 12: 10 parts vinyl terminal d methyl
fluid*
0.6 part trim ethyl terminal
methyl hydrogen fluid
0.5 part t-butylperbenzoate.
Coating Composition 13: 10 parts vinyl terminal dim ethyl
fluid
1.0 part trim ethyl terminal
methyl hydrogen fluid
0.5 part t-butylperben~oate
0.5 part dimethylhydrox~yaceto-
phenone.
~Z33~90 SUE 666
_ 22-
Coating Composition 14: 10 parts vinyl-functional
terpolymer3
0.5 part t-butylperbenzoate.
Coating Composition AYE: 10 parts vinyl-functional
terpolymer
0.5 part 2, 5-bis(t-butylperoxy)
hexane (control)
*Dimethylvinyl terminal dim ethyl polysiloxane, 200 cups
viscosity fluid.
-Trim ethyl terminal methyl-hydrogen polysiloxane, about
30 cups viscosity fluid. 3Dimethylvinyl terminal
dimethyl-methylvinyl-methylhydrogen polysiloxane fluid,
ratio of dim ethyl: methyl vinyl: methyl hydrogen units
equals, approximately, 88: 5: 6, 80 cups viscosity
fluid.
Because t-butylperbenzoate may be used to promote
thermally-activated cross linking reactions, the control
composition, AYE, was included in the trial. Bassett-
butylperoxy) hexane has similar thermal activity to
t-butylperbenzoate, so that if the heat generated by the
W curing lamps was responsible for curing the coating
compositions (instead of the ultraviolet radiation), then
the curing characteristics of compositions 14 and AYE
would be similar.
The cure performance in terms of exposure time
required to achieve a tack-free release surface was tested
by the following method:
~3Z~0 SUE 666
-23
Each mixture was applied as a thin film to 40-lb.
super calendered raft (SKYE) paper by hand with a doctor
blade, then exposed to two Hanovia medium pressure
mercury vapor ultraviolet lamps, each operating at 300
watts per square inch focused power, mounted in a PUG QC
1202 AN processor. The following results were observed:
Tack-Free Exposure
Coating Composition Atmosphere time, seconds
12 INERT 0.9
12 AIR No Cure (5.0 sec.)
13 INERT 1.5
13 AIR No Cure (5.0 sec.)
14 INERT 0.3
14 AIR No Cure (5.0 sec.)
AYE INERT No Cure (5.0 Sec.
AYE AIR --
Failure of the control composition to cure even in
an inert cure environment indicates that t-butylperbenzoate
is a photo catalyst for a wide range of vinyl-nydrogen cross-
linking reactions. The cured coating compositions also
exhibited typical release surface characteristics, with
no migration to Scotch #610 adhesive tape but with
a slight tendency to smear. Poor cure in the presence
of oxygen indicates the radical nature of the cross linking
reaction. It is believed that the proxy group bonded
directly to the phenol kitten chromophore through the
carbonyl carbon atom is necessary for photoactivity.
EXAMPLES 15-25
Derivatives of t-butylperbenzoate were synthesized
to evaluate their performance as photo catalysts.
lZ33Z90 SUE 666
_ I _
Nutria Perbenzoate Derivative
33.4 parts by weight of 70~ aqueous t-butylhydro-
- peroxide were placed in a reaction vessel and cooled in
an ice bath. 65 parts by weight of a 30% aqueous solution
of KOCH and 46.4 parts by weight of p-nitrobenzoylchloride
dissolved in 90 parts by weight SCHICK were simultaneously
added to the vessel slowly over a 30-minute period. This
reaction mixture was stirred for 2 hours at 0C, and then
for 3 hours at 25C. The organic layer was separated from
the aqueous layer, transferred to a separator funnel and
twice washed with a I Nikko solution, thrice washed with
water and finally dried over an hydrous McCoy. Removal of
ethylene chloride under a vacuum furnished 30.9 parts by
weight of a crude yellow product, which was recrystallized
from acetone/hexane to furnish yellow crystalline t-butylper-
p-nitrobenzoate. This was designated Dun, or nutria
derivative.
P-methoxy Perbenzoate Derivative
Synthesis of t-butylper-p-methoxybenzoate was
carried out in the same manner as the nutria derivative.
Since the product is a liquid at room temperature,
purification was achieved by dissolving the crude product
in CHICANO, then extracting twice with hexane. The product
was obtained from the acetonitrile layer by removing
C~3CN under a vacuum, to give a 64% yield of a clear,
pale yellow, viscous fluid. This product was designated
Do, or p-methoxy derivative.
P-tolyl Perbenzoate Derivative
T-butylper-p-methylbenzoate was synthesized and
purified precisely as the p-methoxy derivative. Purify-
cation gave an 85% yield of a clear, colorless fluid
product which was designated Do, or p-tolyl derivative.
1233290 SUE 666
P~chloro Perbenzoate Derivative
T-butylper-p-chlorobenzoate was synthesized according
to the procedure used for the nutria derivative. The
tendency of the compound to supercool resulted in the
recovery of a product with a melting point of approximately
10-30C, compared to 49C for this compound known from the
literature. The solid product slowly melted at room
temperature to a clear, pale yellow viscous fluid. No
further effort was made to purify this sample, which was
designated Do, or p-chloro derivative.
In addition to the foregoing syntheses, a number of
reactive silicone terpolymers were prepared by acid-
catalyzed IFiltrol 20, acid treated play) equilibration
of trimethyl-chainstopped methyl hydrogen polysiloxane,
methylvinyltetramer, and dimethyltetramer. Photosensi-
titers were added to the terpolymers to enhance cure,
according to the discovery discussed previously and
demonstrated in Examples 25-56, swooper. These terpolymer
compositions are described below:
Silicone TerpolYmer Compositions
Photosensi-
polymer Wt. D units t. % Do units White D units titer Wt. %
A 75.0 20.0 5.0 A, 0.2
B 77.0 11.3 11.7 BY, 2; A, 0.2
C 88.0 10.0 2.0 BY, 2; A, 0.25
D 48.0 50.0 2.0 BY, 2; A, 0.25
E 45.0 50.0 5.0 BY, 2; A, 0.25
F 45.0 50.0 5.0 BY, 3; A, 0.3
D = dim ethyl sulks units
DO = methyl hydrogen sulks units
DVi = methyl vinyl sulks units
I A = 2-t-butylanthraquinone
.
lZ33290 SUE 666
sup = benzophenone
The relative W-curing performance of the various
para-substituted perbenzoate derivatives was determined
by assessing the the speed and quality of cure of a photo-
sensitized silicone terpolymer combined with various
perbenzoate ester photo catalysts. Low volubility of some
of the perbenzoate derivatives necessitated coating and
curing the compositions out of solvent.
Two coating baths were prepared, as follows:
Bath 15: 20 pow terpolymer C
80 pow hexane
l pow t-butylperbenzoate
Bath 16: 20 pow terpolymer C
80 pow hexane
l pow Dun.
The coating mixtures were applied to SUCK substrates
with a #3 wire-wound rod. Coated samples were exposed
to ultraviolet lamps as 600 watts per square inch under
inert conditions in a PUG QC 1202 AN processor as previously
described until smear- and migra~ion-free adhesive surfaces
were obtained. The unsubstituted perbenzoate-catalyzed
composition (No. 15) cured after 0.6 seconds W exposure;
the Containing composition required 5.0 seconds W
exposure for the same degree of cure.
Another set of coating baths were prepared as
follows:
.,~
1233290 SUE 666
Perbenzoate
Baths Terpolymer Derivative
17 D Do, 5 Wt. %
18 D Do, 5 Wt.
19 D Do S Wt. %
D Control, 5 Wt.
Control = t-butylperbenzoate ~unsubstituted)
Of these solvent less compositions, only the
p-methoxy derivative, Do, formed an opaque mixture in
terpolymer D, the other mixtures remained clear. The
compositions were hand-coated on SIX substrates with
a doctor blade, then cured under inert and ambient
(air) environments as in Eagles 15 & 16, to give the
following results:
Minimum US Exposure Required for Cure
I MacWeek R in Terpolymer D
20 Derivative R Aim. Cure time, sec.
Control H AIR 1.5
Control H INERT 0.3
Do Of AIR 1.5
Do Of INERT 0.3
Do Me AIR 0.6
Do Me INERT C.15
Do Owe AIR 0.6
Owe INERT 0.15
From these data is appears that the perbenzoate ester
catalysts may be qualitatively ranked (in ascending order
of activity): Dun (very low activity), Do roughly eke to
unsubstituted t-butylperbenzoate, and Do roughly equal to Do.
This rank roughly corresponds to thermally-induced pyre
bond dissociation energies observed in the literature,
SUE 666--
33'Z5~0
_28 _
It is believed that higher alkoxy derivatives, e.g.,
p-butoxy, p-ethoxy, or p-dodecyloxy, etc. might overcome
the sublet problems of the p-methoxy derivative, Do.
It was a further discovery during the course of
these trials that the photosensitized sit cone terpolymers
described above were capable of photo curing tug adhesive
coatings without the assistance of a perbenzoate ester
photo initiator.
Solvent-free coating baths were prepared as
follows:
Bath Composition
1521 Terpolymer F alone (contains
photosensitizes: 3 Wt. % BY
and 0.3 Wt. % A)
22 10 pow terpolymer F + 0.5 pow
diethoxyacetophenone (DEEP)
2023 10 pow terpolymer F + 0.5 pow
Trigonal~ 14 (mixture of
isobutyl Bunsen esters;
Norway Chemical Co.)
24 10 pow terpolymer F + 0.5
pow t-butylperbenzoate.
2525 10 pow terpolymer F + 0.5
pow DEEP + 0.5 t-butylper-
bonniest.
Baths 21-24 were clear fluids, while bath 25 was hazy and
partially opaque due to the limited volubility of DEEP
and t-butylperbenzoate mixtures in non-polar silicone
fluids.
The baths were coated on SUCK substrates and cured
as in Examples 17-20, and the minimum W exposure time until
smear- and migration-free coatings were achieved was recorded
lo ~329 SUE 666
Minimum W
sathCure Atmosphere Exposure or Cure sec.
-
21 AIR 1. 5
21 INERT O . 6
22 AIR O . 3
5 2 2 INERT O . 3
23 AIR 1.5
24 AIR 1. 3
24 INERT Owe
AIR 0.3
1025 INERT O . 3
These date suggest that H-abstraction prom the Sigh
bond by the photosensitizes is involved in the curing
mechanism. Benzophenone and t-butylanthraquinone are known
to produce free radicals following excitation by ultraviolet
radiation in the presence of a suitable proton donor.
Combinations of photosensitizes with photo-
initiators capable of generating radical pairs via
u..imoiecular homolysis after photo excitation are
reported to be a means of minimizing oxygen quenching
of radical-induced cross linking by Grubber, US. 4,071,652
which issued January 31,,1978, and this effect is
evident in comparing the performance of Baths 21 and 22,
where DEEP is the photo initiator generating radical pairs.
Also noted is a synergistic effect in combining photo-
sensitizers with perbenzoate photo initiators, when
comparing the performance of Baths 21, 24 and 25. Although
volubility problems evidently interfered with the perform-
ante of Bath E, it is believed that enhanced cure will result from combinations including benzophenone, t-butyl-
anthraquinone, DEEP and t-butylperbenzoate in a mutually
computable medium.
lZ33~0 SUE 666
_ 30-
EXAMPLES 26-56
The following compositions were prepared to show
the effect of certain polyaromatic photosensitizes:
880 parts by weight dimethyltetramer, 50 pa is
by weight methylvinyltetramer, 20 parts by weight of
sym-tetramethyldivinyldisiloxane, and 63 parts by weight
of trimethyl-chainstopped polymethylhydrogensiloxane fluid
(30 cups) were blended together with 5 parts by weight of
an acid clay catalyst (Filtrol 20), then agitated under
a nitrogen atmosphere at 60C for 15 hours. Removing the
catalyst by filtration afforded a mixed dimethylvinyl-
and trimethyl-chainstopped linear polydimethyl-methylvinyl-
methylhydrogensiloxane terpolymer fluid 570 cups), Wheaties designated Sample G.
300 parts by weight of Sample G were stripped of
light ends under a vacuum at 165C for 2 hours. 241 parts
by weight of the product were treated with 1.2 parts by
weight benzophenone and the mixture stirred at 100C for
30 minutes until a clear solution was obtained. The
ben~ophenone remained in solution when the polymer was
cooled to room temperature, to give a 340 cups fluid
product designated Sample H.
Another terpolymer was prepared exactly as
Sample G from the following materials: 1260 parts by
weight dimethyltetramer, 92 parts by weight methyl vinyl-
tetramer, 15 parts by weight sym-te~ramethyldivinyldi-
selection, and 150 parts by weight of the methyl hydrogen
fluid. Filtering and stripping the equilibrate afforded
1240 parts by weight of a 1225 cups fluid, designated
Sample J.
_.
i23325~0 SUE 666
_ 31 -
A composition designated Sample K was prepared con-
sitting of 0.5 weight percent solution of benzophenone in
the Sample J terpolymer.
A composition designated Sample L was prepared
consistilig of a 1.0 weight percent solution of buoyancy-
phenone in the Sample J terpolymer.
A composition designated Sample M was prepared con-
sitting of a 2.0 weight percent solution of benzophenone in
the Sample J terpolymer.
A composition designated Sample N was prepared
consisting of a 4.0 weight percent solution of benzophenone
in the Sample J terpolymer.
A composition designated Sample P was prepared
consisting of a 0.2 weight percent solution of 2-t-butyl-
anthraquinone in the Sample J terpolymer.
It was noted that the benzophenone was quite
soluble in silicone fluids to at least 4 weight percent.
The limits of volubility of the chemically similar
t-butylanthraquinone have not been established, however,
simple experimentation will reveal to the persons skilled in
this art the useful range of volubility for this and other
photosensitizes suitable for the purposes disclosed herein.
Attempts to prepare 0.5 weight percent solutions of anthrax
cent and thioxanthone in the Sample J terpolymer were us-
successful due to their limited volubility in silicones.
Ultraviolet cure analyses were performed using Samples G-P in the following manner. Each sample was
mixed with 5 weight percent p-butylperbenzoate, manually
coated as thin films on 40-lb. super calendered raft
(SUCK) paper with a doctor blade, then passed through a
~;33 SUE 666
_ 32 -
PUG QC 1202 An ultraviolet processor (2 Hanovia medium-
pressure mercury vapor US lamps each capable of operating
at lo, 200 or 300 watts per square inch focused power).
The degree of cure was qualitatively assessed by noting
the presence or absence of smear, migration, and rub-off
in irradiated coatings. After curing the test coatings
prepared from Samples G-P under various cure conditions,
the following results were obtained:
To lamp Ensure to, Cure
Eye ale pcwer,-~tts seconds Aim. elite ivy Cure
26 G 600 0.3 No No smear, no micra-
lion, slight runoff
27 G 600 1.5 AIR NOT CUD
28 H 400 0.3 No No smear, no micra-
lion, slight rough
29 H 600 0.15 No No smear, no micra-
lion, slight rub-off
H 600 1.5 AIR No smear, no micra-
lion, no rub-off
31 J 400 0.3 No No smear, no micra-
lion, slight rub-off
32 J 600 0.15 No No or, no micra-
lion, moderate
rub-off
33 J 600 0.6 AIR NOT CUED
34 K 200 0.6 No No sir, no muggier-
lion, slight r off
X 400 0.1 No No smear, no micra-
lion, moderate
rub-off
36 K 600 0.08 No No smear, no micra-
lion, easy r off
37 L 200 0.3 No No or, no micra-
ton, moderate -off
38 L 400 0.1 No No smear, no micra-
lion, moderate
nephew
- 39 L 600 0.08 No No sneer, no micra-
lion, easy rub-off
- - 1233291~ SUE 666
_ 33 -
queue posture twine, Cure
Example ale power, watts seconds Aim. alitative Cure
M100 0.3 No No smear, no micra-
lion, moderate
rub-off
41 M400 0.1 No I seer, my micra-
lion, moderate
r off
42 M600 0.6 AIR No slrear, no micra-
lion, r off
43 N200 0.3 No No smear, no micra-
lion, moderate
rub-off
44 N600 0.08 No No Of, no micra-
lion, easy rebuff
N600 0.3 No No en, no micra-
lion, no r off
46 N600 0.3 AIR No seer, no micra-
lion, no rub-off
47 P200 0.3 No No sir, no micra-
lion, moderate
r~b-off
48 P600 0.3 No No err, no micra-
lion, no rub-off
49 P600 0.3 AIR No smear, no micra-
lion, no rub-off
P600 0.8 No No smear, no micra-
lion, easy nephew
It it apparent from these results that the presence
of benæophenone or t-butylanthraquinone more than doubles
the rate of cure for the photoactive compositions under
inert conditions, and, surprisingly, permits good cure
(at fairly fast rates) even without inverting the cure
environment. The latter observation can be particularly
important where the expense of providing an inert atoms-
phone for radiation curing is a critical concern of the
particular user. The compositions anchor well to SIX
substrates when W lamps are operated at high intensity
for at least 0.3 seconds exposure. Shorter exposure
provides migration-free adhesive coatings which are
'
.
123329~
SUE 666
-34 -
easily rubbed off, although they are otherwise fully
cured.
Several samples were next assessed for release
performance against common adhesives The following
coating baths were prepared (measurements are in parts
by weight):
Bath Q: 20 pow Sample J
1 pow t-butylperbenzoate
79 pow hexane.
Bath R: 20 pow Sample L
1 pow t-butylperbenzoate
79 pow hexane
Bath S: 20 pow Sample M
1 pow t-butylperbenzoate
79 pow hexane
pa
path T: 20 pow Sample N
1 pow t-butylperbenzoate
79 pow hexane
Bath U: 20 pow Sample P
1 pow t-butylperbenzoate
79 pow hexane
Each of the baths Q-U were coated onto 9"x12"
sheets of SUCK paper with a I wire-wound rod, then
exposed to ultraviolet light in the PUG ultraviolet
processor as previously described. The cured compost-
lions were then coated with a 10 mull layer of Jowl 263
acrylic adhesive (Monsanto) and cured for 15 minutes
at 65C. An uncoated SUCK sheet was then affixed to
..
~Z~33Z9Q SUE 666
_ 35 --
the adhesive layer. These laminates were cut into strips,
and the release in grams recorded as in previous examples,
with the following results:
Iota lamp Exposure, Cure ~itative Release,
S Example Bath or, watts sec. A Cure go
51 Q 100 0.3 No No migration, 55-80
poor anchorage
52 R 100 0.3 No No migration, 50 85
poor anchorage
53 S 600 0.3 AIR No migration, 210-250
good anchorage
54 S 100 0.3 No No migration, 60-90
good anchorage
U 600 0.3 AIR No migration, 110-130
good anchorage
56 U 600 0.3 No No migration, 25-40
good anchorage
Examples 51, 52 and 54 indicate that benzophenone con-
cent ration has little effect on release. Although some of the
cured compositions did not appear to anchor to the sub-
striate particularly well, the separated famine showdown evidence that the silicone layer adhered preferentially
to the aggressive Gelva adhesive.
Examples 53, 55 and 56 indicate that the nature of
2$ the curing environment does have an effect that is not
evident from the previous Examples 26-50: Air cure
apparently leads to a higher release than cure of the
same composition in an inert environment. This difference
in release suggests that varying the amount of nitrogen
in the curing chamber may provide a means of controlling
the release of a silicone composition. It is also
apparent that a low level on anthraquinone (0.2%) is more
effective than benzophenone for promoting t-bu~ylperbenzoate-
catalyzed US cure of the vinyl-runctional terpolymers of
the present invention.
SUE -
SUE 666
_ 36 -
because t-butylper~enzoate is thermally very
stable and can be stored indefinitely at room temperature,
the compositions of the present invention can be packaged
and sold as l-part systems, eliminating preparatory steps
and making the compositions easier to use.
EXAMPLES 57 & 58
Higher alkoxy-substituted perbenzoate photo-
catalysts were synthesized to try to overcome thesolubility problems encountered with the p-methoxy and
p-tolyl derivatives of t-butylperbenzoate:
T-butylper-p-butoxybenzoate was synthesized by
first preparing p-butoxybenzoylchloride according to the
procedure described by Rohrmann and Wischniewski, Arch.
Harm., 292, 787 (1959). 29.1 parts by weight of 4-n-
butoxybenzoate 4-n-butoxybenzoic acid and 71.4 parts
by weight thionylchloride were mixed and agitated at
86C for 1 hour. The resulting clear solution was
stripped of excess thionylchloride under a vacuum at
60C, and the product isolated by vacuum distillation.
30.6 parts by weight of clear viscous fluid by 143-147C/
7mm) were obtained (95 yield). This product was added
slowly to 18 parts by weight of 70~ aqueous t-butylhydro-
peroxide simultaneously with 35 parts by weight of 30%
aqueous potassium hydroxide (also slowly added). Reaction
temperature was maintained at 0-5C during this addition.
the p-butoxy derivative was isolated by dissolution in
acetonitrile, extracting twice with hexane, and removal
of the acetonitrile under a vacuum, resulting in 26.2
parts by weight of a clear, pale yellow fluid product.
the infrared spectrum of the product was consistent with
the structure of the p-butoxy derivative of t-butylper-
benzoats.
1~3Z9(3 SUE 666
_ 37 _
A p-dodecyloxy derivative was prepared in the
same manner as the p-butoxy derivative, using p-dodecyl-
oxybenzoyl chloride. The final product was a viscous
pale yellow liquid at room temperature, and the infrared
spectrum was consistent with the structure of the p-dode-
sulks derivative.
Two silicone release coating compositions were
prepared using the above derivatives by mixing 5 parts
by weight or each derivative, respectively, with 100
parts by weight of a 670 cups linear polydimethyl-methyl-
vinyl-methylhydrogen selection fluid with 7 weight percent
methylvinylsiloxy units, 5.2 weight percent methyl hydrogen
sulks units and the remainder consisting of dim ethyl-
sulks units. In each case, an opaque white mixture resulted. Although both compositions could be cured to
smear- and migration-free release coatings on SUCK substrates
in 0.3 seconds W exposure (at 600 watts/square inch), the
apparent poor compatibility of these two derivatives with
pure silicone terpolymer solutions suggests that they are
not the catalysts of choice for solvent-free release
applications.
EXAMPLES 59-63
Further trials were conducted with terpolymers
prepared according to the present invention in order to
assess cure characteristics and storage stability. Three
new terpolymers having different Si-H/Si-vinyl ratios
were prepared as in previous examples and compared with
terpolymer F (see Examples 15-25):
SUE 666
lZ33~90
_38 -
Mole Ratio
Example Terpolymer Photosensitizes Si-H/Si-vinyl
59 F 3 White BY, 0.3 Wt.% A 14.0
X 2 White BY 2.80
61 Y 2 Wt.% BY 1.50
562 Z 3 White BY Luke
BY = benzophenone
A = t-butylanthraquinone
The release performance of the above terpolymers
was assessed as in previous examples, by preparing coating
baths consisting of 20 parts by weight of a terpolymer~
0.6 pow t-butylperbenzoate and 8 a pow hexane, applying
each coating composition to SIX paper, curing under US
light at 600 watts/square inch for 0.3 seconds inert
atmosphere), and finally preparing laminates using Molly
coatings of aggressive SIR adhesive (Coated Products, Inc.
#495G~ and recording the force required to separate the
famine (400 ft./minute; 180 angle). Release was tested
initially and periodically after aging at 150F. The
following data resulted:
Release Release Release Release
(grams) (grams) (grams) (grams)
Exhume Terpolymer Initial 1 day 1 week 2 weeks
2559 F 30-50 ~500 >500 >500
X 35-45 45-65 140-160 160-180
61 Y 35-50 40-60 85-105 95-120
62 Z 45-65 50-65 65-90 70-90
It is apparent that a large excess of unrequited
Sigh functionality relative to Si-vinyl-functionality will
affect release, probably due to interaction OX the Sue
function with the adhesives. The data suggest that where
stable release is desired, the Si-H~Si-vinyl ratio should
35 be held at lower levels, preferably below about 2/1 for the
SUE 666
_ 39-
terpolymers described herein.
A separate trial to assess storage stability of
a l-part W-curable composition was run by preparing a
coating composition using 100 pow of Terpolymer X (con-
twining benzophenone, I blended with t-butylperbenzoa'e
(5 pow The composition was split into two samples,
one sample being maintained at room temperature in the
dark and the other at 66C also in the dark. The
viscosity of these blends was monitored over time Jo
obtain an indication of storage stability. The following
results were observed:
Storage Tempt Initial 1 Week 2 Weeks 4 Weeks 8 Weeks
25C 560 cups 550 cups 540 cups 550 cups 550 cups
660C 550 cups 4370 cups (golfed) -- --
These data suggest that a storage temperature below
about 30C it recommendable to prevent cure during storage.
EXAMPLES 64 & AYE
A trial comparing the cure performance of reactive
terpolymers prepared according to the present invention
to conventional Uncurable vinyl-functional systems was
run as follows:
A linear polydimethyl-methylvinyl-methylhydrogen
selection terpolymer was prepared having a molar Sue/
Si-vinyl ratio of 2.8 and including 83 weight percent
dimethylsiloxy units was prepared in which 2.5 weight
percent benzophenone was dissolved. A conventional W-
curable, vinyl-functional silicone blend was prepared
consisting of 100 parts by weight of a 200 cups dim ethyl-
vinyl-chainstopped linear polydimethyl-methylvinyl
1233290 SUE 666
-40 -
selection fluid having 5.2 weight percent methyl vinyl
sulks units, combined with 3 parts by weight of a
30 cups trimethyl-chainstopped linear polymethylhydrogen
selection fluid, also containing 2.5 parts by weight
benzophenone.
The cure performance of the two coating blends
was qualitatively tested as described in previous
examples, with the PUG ultraviolet processor operating
with 400 watts/square inch total focused power. The
minimum US exposure time (seconds to obtain a smear-
and-migration-free release coating on SUCK substrates was
recorded:
Exposure Time
CompositionCurinq Aim. for Cure, sec.
64 No 0.3
64 AIR 1.5
AYE No 3.0
(control)
AYE AIR No cure after
(control) 15 sec.
64+3% t-butyl-N~ 0.15
perbenzoate
These data indicate that the instant terpolymer
compositions ax superior in cure efficiency to known
vinyl-functional systems; additionally, there appears to
be a synergistic effect from the combination of buoyancy-
phenone and perbenzoate catalysts, allowing line speeds
20 times faster than those required to fully cure
conventional coatings.
Modifications and variations in the present
invention are obviously possible in light of the fore-
going disclosure. For example, many polyaromatic
; 35 compounds soluble in a given silicone composition and
. ..
.
... . .
1;~33~90
SUE 666
- 41 -
effective as photosensitizes for the purposes described
herein will suggest themselves to persons of ordinary
skill in this art and may be utilized advantageously
with coating compositions prepared in accordance with
the present disclosure. It is understood, however,
that any such incidental change made in the particular
embodiments of the invention are within the full intended
scope of the appended claims.
