Note: Descriptions are shown in the official language in which they were submitted.
;7~L'7
-1- 60SI-311
ULTRAVIOLET I,IG~T CURABLE ACRYLIC
FUNCTIONAL SILICONE COMPOSITIONS
Field of the Invention
The present invention is related to acrylic
functional silicones and polyorganosiloxane copolymeric
compositions which are curable or crosslinkable upon
exposure to ultraviolet light or radiation, and which
are particularly useful in silicone based release
coating applications.
Background of the Invention
Silicone release compositions, and especially
paper release compositions, are widely used as coatings
which release pressure-sensitive adhesives for labels,
transfer tapes, decorative 1~m; n~tesl and the like. Such
silicone products are most commonly sold as dispersions
of reactive high molecular weight polysiloxane gums in
organic solvents, such as tolueneO A crosslinking or
curing catalyst is then added to the dispersed low-solids
mixture, the coating blend is applied to the substrate
whichis then passed through an oven to evaporate the
carrier solvent and cure the silicones to a relatively
non-adherent release surface. This process requires a
large thermal energy input in order to properly evaporate
the solvents and effect the crosslinking reaction at
commercially viable rat~s.
3~'7~7
- 2 - 60SI-311
Rising energy costs coupled with stringent environ-
mental regulation of solvent emissions have made the
use of solvent-borne silicone release agents increasingly
uneconomical. While solventless or emulsion-borne silicone
compositions can solve the environmental problems, high oven
temperatures and expensive energy usage are still required
for their proper application.
Radiation-curable silicone release compositions
successfully address both the energy and environmental
problems inherent in the use of traditional solvent-
dispersed silicones. For example, an ultraviolet (UV)
radiation-curable solventless silicone release composition
eliminates the need for energy-intensive ovens as well as
expensive solvent recovery apparatus. Such materials are
not unknown; considerable litera-ture in the field of
UV-curable silicone compositions has been noted in recent
years, although commercial introduction of such products
has not yet occurred. Applicant's Canadian Application
Serial No. 365,247 filed November 21, 1980, describes epoxy-
functional silicone compositions which are curable upon
exposure to ultraviolet radiation and which utilize certain
bis-aryl halonium salts as photoinitiators.
Several other UV-cure silicone systems have been
described. Patents issued to R.V. Viventi (U.S. 3,816,282
issued June 6, 1974), Bokerman et al. (U.S. 4,052,529 issued
October 4, 1977), and Colquhoun et al. (4,070,526 issued
January 25, 1978) are representative of those compositions
wherein omega-mercaptoalkyl substituents attached to
polysiloxanes add -to vinyl-functional siloxanes in a
free-radical process in the presence of certain photo-
sensitizers upon UV irradiation. However, those silicone
materials which include mercaptoalkyl func-tional protoactive
substituents also posses an o~fensive odor (associated with
the mercaptan group) which persists in the cured material.
~;!
60SI-311
The present invention provides newly developed radiation-
curable silirone paper release cl _~sitions which do not require
scarce or P~r~nqlve inputs. These novel compositions are
comprised of acrylic or m~thacrylic-dimethylsilicone fluids which
S will cure via well-known free radical processe~ when irradlated
with W light in the presenc~ of standard photoinitiators.
Acrylic-functional si~icon~ are ~h~ ~ve~ not a new
COI,C~pt. R. ~. Mercker described polymer~ prepared fro~ acryloxy-
methyl and methacryloxy~ethyl substituted organosilicone i , u.dsin U.S. 2,956,044 which issued October 11, 1960. Merker's
syntheses of acryloxymethyl-substituted sili~on~ r~quired chloro~
methyl-substitu~ed organosiljco~e~ as inputs~ Such 5ilicon~ are
themselve~ prepared by h~ tion o~- methyl-substituted sili-
I5 cone3 or by reaction o~ h~si~ with Grignard leage~-L~
fol7~ued by hyd~olysis in order to ~oduce the desire~ polymer.
Neither of these processes i~ well-suited to large scale
co~mercial production, and chloromethyl-substituted silicone
pol~mers and ~. rs are scarce and e~pensive materials
Anothes synthetic route to acrylic-sil~y~ne compositions is
taught by Nordstrom and Zelek ~.S. 3~50,811 which issued
March 3, 1972). The Nordstro~ et al. synthesis involve~ the
reaction of ~ g~ hydro~yalkylacrylates or methacrylate~ with
silanol-con~a;n;n~ silicon~ in the presence o~ co~n~ation
catalys~s such as tetrai-~opLo~yltitanate. In praotice, the
resulting acryloxy-substituted poly~ers are severely lLmited ~ince
the reactive acrylic group3 are con~i~ed to the ~hain~Lu~er
position ~i.e. at the endR of the linear polymer molecule~). The
lack of reactive sites on ~he polymer chains cause~ the free-
radical crossl in~ing reaction between the acrylic moieties to
7 6osI-3
-4-
proceed very 510wly, rendering such co~lpo~itions impractical for
high-speed proces~ing operations co~mon in the paper convertin~
industry.
U.S. Patent 4,201,803 - Cully et al, disclose~ paper
release compo~itions curable by radiation consis~ing of acrylo~y-
group-cont~inin~ silicn~ fluid plu~ polyacrylic-crosglinki~
agent~ and pho~s~n~it$zers a~,needed. Although the Cully et al.
diR¢105Ure i8 related to the composition~ of the present in~en-
tion, there are ~ignificant differences bet~een the materials
described by Cully et al. and those disclosed in the present
application~ Most L~pOrtant~ the Cully et al. disclosure
specifies that their coating composition must consist of tw~
parts: the acrylo~y-functional silicon~ fluid plu~ at lsast 10
(with 50~ bsing preferr~d3 of a polyacrylate . - -r such a~
trimethylolpropane triacrylate ~i.e. a non-silicone reactive
diluent~ The coating compo~ition~ of the presant invention do
not require reactive diluents or crosslinkers while providing
useful rates of cure~ Nor are such ma~erials required for good
release propertieg. Furthermore, the compositions of the pre~ent
invention provide useful release chara~eristics yet consist
solely of an ~crylic-functional silicone fluid with photo
sensitizers as needed. ~dditionally, although the Cully et al~
disclosure does not specify any particular preferred mod* of
manufacture of the acrylic~si l~ne fluids described therein, the
examples provided by Cully et al~ appear to suggest that hydrosi-
lation addition of allyl(meth)acrylate to hydride ~luids is the
synthetio route utilized. Wherea~, on the other hand, a signifi-
cant feature of the pre~ent disGlosure is the production of
acrylic-Eunctional ~ilicones via consecutive addition o~
tmeth)allYlchloride and acrylic acid to hydride Eluids a~
described herein below.
60S~31
--5--
The COmpQSitions of the present invention herein describ~d
do no~ su~fer from any of the inherent disadvantages discussed
above. All of the inputs for synthesis of these W -curable paper
release composltions are inexpensi~e and readily av~ hle. The
synthesis itself is an easy stepwise procedure which ca~ be
performed in a qingle reaction vessel i~ desired.
It i~ therefore an object of the present in~ention to
provide novel acrylic functional ~ilicone composition~ and copoly-
mers which are capable o~ being crosslinked upon exposure toultraviolet radiation..
It is another object to provide a~rylic-~unctional
polyorganosilox~nes and copolymers of such silo~anes by a proces~
compri~ing the steps of addin~ allylchloride ~na acrylic acid
to hydride-can~aining si~ An~
It is another object to pro~ide processes for the synthesis
of acrylic functional silicones for use in release coating appll~
cations~
It is another ob~ect to provide ultraviolet light curable
acrylic Punctional silicone releas2 coating compo~ition and
methods for use.
These and other object~ will b~come apparent to those
~killed in th~ art upon consideration o~ the--following descrip~
tion, e~ample~ and claim~.
60SI 311
--6--
Summary of the Invention
The present invention provides acrylic functional silicone
co~po~itions and silicone release coatings made ~rom such compo-
3itions as well a~ processes for providing the same~
An acrylic ~unctional polyorgano~3t~ne composition of the
pre~ent invention is comprised of the reaction pLOdU~L of a number
of constituent ingredients~ me rela~ive proportions of these
components are not at all critical and may be varied over a wide
range to provide acrylic-silicone composition~ having varied
properties. The ~ethod described below describes a simple and
preferred two-Rtep synthesis, bu~ it will be recognized that
alterations in the synthetic procedure can ~e ac omplished if
desired without detracting fro~ the spirit of the present
invention.
The instant acrylic functional polyorganosiloY~ne composi~
tion~ will ha~e a first cl :~n~ comprised of an omega-halo
alkene and preferably an omega-chloro-l-alkene such aR allyl
cbloridet 4-chloro-1-butene, 10-chloro l-decene, and othes
analogou~ unsaturated halogen-containing hydrocarbons.
Of course~ it will be recognized that mixtuses of such
omega-halo-alkenes will also be useful. Ordinarily9 from 0.5 to
50 weight percent of such allcenes will be used compared to the
2 5 total weight o~- ~he--- acrylic--functional- silicone- composition
reaction prod~ctO
The next ~ nt i5 a dialkylhydrogen chain~to~ed
polydialkyl alkylhydrogensi~ e cop~lym~r~ Such a hydrogen
~a~ 7
7 - 60SI-311
functional siloxane will ordinarily have the ~eneral
formula:
R ~ R ~ ~ R ~ R
t i ~yt ~ ~ z
wherein each R represents, independently, a monovalen-t
hydrocarbon radical such as methyl, ethyl, phenyl or tri-
fluoropropyl, but will ordinarily be a methyl radical, R'
represents, independently, the same monovalent hydrocarbon
radicals as for R but may additionally represent a hydrogen
atom, y plus z is an integer of, approximately 25 to 600
such that the si~oxane fluid has a viscosity of 20 to 5000
centipoise at 25C and preferably 100 to 500 centipoise.
Such hydrogen functional siloxane fluids are primarily
linear and will therefore have an R to Si ra-tio of
approximately 2 to 1. However, minor and insignificant
amounts of mono and trifunc-tional siloxane uni-ts, some
of which may also contain hydrogen, might also be included
without seriously detracting from the usefulness of such
fluids. These siloxane fluids will ordinarily have 0.5 to
50 weight percent hydrogen-siloxy functionality, and are
made by processes well known in the art.
The alkene component and the hydrogen functional
siloxane component are reacted in a precious metal
catalyzed addition cure reaction which is a partial cure or
precrosslinking reaction described in detail below. Such
catalysts are well known in the silicone art and will
ordinarily be a platinum metal complex effec-tive for adding
hydrogen to the double bond of the alkene. Ordinarily
approxima-tely 50 parts platinum metal per million parts of
siloxane will be effective to promote this hydrosilation
reaction. Examples are those exemplified in U.S.
Patents 3,220,972; 3,~14,730; 3,775,452 and 3,715,334.
A 1~
i7~
- 8 - 60SI-311
particularly useful are those platinum catalysts derived
from chloroplatinic acid which has been treated with
tetramethyldivinyldisiloxane, as described in
u.s. 3,81a,730.
The final component of the reaction mixture is an
acrylic monomer which adds the acrylic functionality to
the silicone compositions of the present invention. A
wide variety of acrylic monomers are effective, including
acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate,
2-hydroxyethyl methacrylate, and other (meth)acrylic acid
estexs containing a reactive hydroxyl group, including
multifunctional acrylic monomers such as pentaerythritol
triacrylate. Ordinarily, approxima-tely 0.2 to 30 weight
% of this acrylic material based upon the weight of the
total reaction product will be effective for provlding an
acrylic-siloxane copolymer having 0.5 to 50% acrylic
siloxy functionality.
The acrylic-silicone release coaiing compositions are
comprised of the above described acrylic silicone fluid
which is further comprised of an amount of Eree radical
photoinitiator which is effective for curing a 0.1 to
5.0 mil coating of said composition to a non~adherent
film on a substrate such as paper upon exposure to an
amount of ultraviolet or electron beam radiation which
is effective for curing such coatings.
Approximately 1.0 to 10.0% by weight based upon
the entire coating composition will ordinarily be an
effective amount of photoinitiator. Among the particularly
useful free radical photoinitiators are included diethoxy-
acetophenone, benzophene, Michler's ketone, t-butylbenzoin
e-ther and certain combinations of amines and
aryl ketones well known to -those skilled in the art.
7~7
60S~ 311
_g_
The proce~s for providing the acrylic ~unctional
polyorganosiloY~n~ c ~ition~ of the present invention
ordinarily comprises the ~tep~ of reacting (A) 1 to 50 parts by
weight of an omega-halo-alkene, (~ 50 to 99 parts by weight of a
S dialkylhydrogen ch~in topped polydialkyl-alkylhydrogen s~loYAne
copolymer; (C) an amount o~ precious metal catalyst e~e~tive for
catalysiny a hydro~ilation reaotion bet..een saLd alkene and said
S~1~Y~nP copolymer; and ~D~ 0.2 to 30 part~ by weight of an
acrylic functional -: effective for providing a si 70~n~
copolymer having 0.5 to 50 weight percent acrylic siloxy unitsO
Description o~ the Invention
The symbol - Si is well k~own in the silico~e art and
s~ tically depicts the- non-reactive or non-functional portion
of a large silicone polymerO Ordina~ily, the major portion o~ a
si1i~ molecule (e.g. a dimethylsiloxy chain) does ~ot take part
i~curing or `~rossl inking reactions nor in synthese~ ~involving
the p~odu Lion of copolymersO ~hus the reactive species (e.g.
hyd~ogen and vinyl, epoxy or acrylic rad;:c~l~) which may be
attached to the polymeric backhone are chemically more interesting
~or su~h reactions. Thus _ Si~ represents a large ilicone
polymer having at lea~t one reactive or functional hydsogen
~5 attache~ thereto, either on the chain or at its terrin~ Pre-
crosslinki~g~ o this int~ !~iate p~lymer can be accomplished by
~Imul~neou~ly reacting a dimethylvinyl-s-o~ped linear dimethyl-
~llicons fluid and (meth)allyl' chloride with a polymer con~inin~
one or more alkyl-hydrogen siloxy units or dialkylhydrogen silyl
chain-stopping units.
97
60SI-311
--10--
The expression "pre-crosslinking~ represents a partial cure
or crosslinkln~ reaction whlch i~ controllably allowed to proceed
at an early stag~ in ~he synthe~is o~ th~se si lioo~P materialsO
Thi9 partial cro~linking serves the very usef~l purpose of enab-
S ling a ~a~t, tigh~ and complete final cure to take place with
relatively very little ene~gy input apon ~Yro~llr~ to a small
amount of ultraviol~t lightD Since the silicQ~e material i~ only
partially crossl;n~ed, ~.~., rp~ecLo~slinked~ it is ~till work-
able a~ a coating ~-~ sition yet qui~e o~r~hl~ of a quick cure ~o
a final non-adherent surface such as a release coatins.
In general terms, acrylic functional silicone polymers are
provided as follows: first allylchloride is reacted with an
- Si~-functional dim2thyl si~icon~ fluid in the presence of a
cat~lytic a~un~ of ~ group VIII preeious metal hydrosilatio~
catalyst, thereby yi~ i n~ a- g~mma-chloL~pL~pyl-functional
dimethyl.cili~onP copolymer via ~tandard hydroqilation additiond
Next the resultant gamma-chlo~op.~yl-methyl silicone fluid
i~ trea~ed with acrylic acid, methacrylic acid, or 2-hydroxyethyl
acrylate or methacrylate in the pre~ence of a tertiary base such
a~ triethylamine ~Et3N) or pyridine to yield an acrylic
functional silic~n~ polym~r. Thi~ series of reaction can be
depicted.in the following fashion:
Si~ + ClC~2C~ ' C~2~-~iC~2C~2~2
~2) - SiCH~CH2C~zCl ~ HOOCC~ = C~2 + Et3N ~-i~
-i~ Et3N-HCl~ + SiC~2C~2c~zOocc~ = C~2
3~ The amine hydrochloride salt i8 a solid precipitate which can be
easily r~ vcd by ~iltration. Any omega-chloto l~alkene C~D b~
7~'~
60S~-311
utilized in place of allylchloride in step [1] (e.g.~ 4-chloro-1
butene, 10-chloro-1-decene, etc.) but allylchloride is inexpensive
and easily obtained and is preferred.
S Persons s~ e~ in the art will rec~gnize that this
pLocedure o~fers several advan~age~ over previously described
syntheses o~ acrylic-functional 3ilicQ~. Mo~t imp~rtant; this
proce~ versatlles acrylic-functional Si7iC~n~S ca~ be
prepared with up to lQO~ acrylic ~unc~ n~ y either on the
polymer chains or as chainstoppers; also, the polymer may easily
be modified by inclusion of other vinyl-functional groups (such as
. vinyl-stopped polysil~Y~nes) with allylchloride in the hydro-
silation step. m e re~ultant acrylic-functional silicone are
hydrolytically ~table, since the acrylic moiety i~ bonded to
silicn~ through an alkyl group rather than through an oxygen
atom7 Another adYantage i~ tha~ the inte -d;ate g - chloro-
propyl-substituted siloxanes need not be isolated; the total
amount of acrylic functionality in the product will be determined
by the amount and nature of the -- SiH present in the input
.Q;lico~ fluid~
C.L. S~hilling and C.S. ~qchhack, XIV Organosilicon
SymposiLun, Fort Worth, Texaq? M~rch 28~ 1980, have described
important difference~ in reactivity between methallyl or allyl
c _~L ` and = Si~-cont~inln~ substances in platin-L~n-catal-
yzed add~tion reaction~. It wa reported that methallyl ~ L '~
provide higher yields of hydrosilation products than do the allyl
counterpart~ and that these higher yields result fro~ le~s exten-
sive side reaction- such as isomeri~ation and el;~;~AtionO
'7~
60SI-311
-12-
The above-described two-stage synthesis o~ acrylic-functional
~ilicone pol~mer fluid~ can be repeated with a processin9
difference being the substitu1:ion of methallyl chloride
( 2 ( 3) 2 ) for allyl chloride (C~2 =C~C~2Cl~ in
the ~irst ~tep of the syn~he~is. Examples 4 and S below
demon~trate the utility of this methallyl c:hloride approach.
These two example~ can be ch~mically represented by this reaction
scheme:
(1) ~+C~ ( 3) 2 ~ ~ 2 ( 3) 2
(2)--SiC~2cH(c~3)c~2cl~0cc~ 2 3
~ Et3N-~c~ 2C~(C~3) 2 It 2
m ese syntheses ~ay be carried out in a single reaction flask~
which simplif ies processiDg . It should also be pointed out that
the reagents utili~ed (methallyl chl~ride, acrylic acid, and
triethylamine) are all inexpenqive and commercially a~ailable
material30 The use o~ methallyl chloride in place of allyl-
chloride does not preclude the use of 2-hydro~yethylacrylate or
other hydroxy-containing acrylates or methacrylate~ rather than
acrylic acid5 also, any tertiary amine hydrogenchloride acceptor
may be substituted for triethylamine without affecting the
product. It has also been es~hlishe~ that multifunction21
acrylate ~-u ? rs containing Gne or more hydroxyl groups may be
u~ed in plac~ of the hydroxyl-con~Ainin~ monofunctional acrylate
i~n -r~t heretofore specified as th~ ~ource of reactiv~
photo-crosslinkin~le acrylate functionality~ ~xa~ple 10 below i~
illu~trati~e of this effect~ The reaction of ~ gamma-chloro~
f-~7
~OS~-311
-13-
isopropyl~functional siloxane with pentaerythritoltriacrylate
(PET~3 in the presence of an amin~ can be represented in this
fashion:
--si ~ Cl + ~o~2C(C~2 ~ C~ 2 3 3 --3D
~--si ~ o ctC~2 ~ C~ = C~2)3 3
wherein each mole of PETA reacting pro~ides 3 moles of acrylate.
In order that those skilled in the ar~ may better practice
the te~chings of the present invention, the following e~ampl~3 are
yiven for purposes o~ illustrating the inventio~ and are n~t
intended to limit the invention. ~nless othe~ise specified~ all
s~eights are given by percent.,
Description of the Pre~erred Emkodiments
~ E~ample l:
35 grams of allylchl~ride were dissolved ia 300 grams
he~ne in a 2 liter flask eguipped with overhead ~tirrer, re~lux
condenser, and thermometer~ Sufficient platinu~ cataly~t
( 2 6 complexed with tetramethyldivinyldisiloxane~ was
added to provide approxi~ately lO par~ platinum per million parts
reactant material. Next 300 gram~- o~ -a dimethylhydroge~-stopped
linear polydimethylmethylhydrosiloy~ne copoly~es fluid havifig- an
approximate visco~ity of 80 centipoise and containing 805~ -~ Si~
functionality (as a perce~t of methylhydrogen s.ilo~y units~ were
slowly added to the allylchloride solution~ Following this
, 7~7
hnSI 311
-14-
addition, the reaction mixture was refluxed at ~9 for 20 hours
with co~tinued stirring, at which point infrared analysis detected
no ~nreacted ~ Si~ groups~ The hexane and excess allyl cbloride
were ~hen removèd b~ s~ripping at 70 and 30 ~m ~g pressure for
two hours, leaving ~ hazy fluid product of 100 Cp5~ viscosity.
Next, 150 grams o thi~ fluid pLodUct were dispersed in 150 grams
toluene with 0.01 gram hydroquinone. ~ mi~ctur~ of 15 grams
a~rylic asid and 21- gr~m3 triethyla~ine were addeds a~d ~h~
complete reaction mix~ure was stirred under a nitrogen purge at
loo for 30 minutes~ ~ white precipi~ate was formed during the
reaction. Following the reaction, the produc~ was fil~ered and
the toluene stripped~ of~, affording a cloudy brown acrylic
functional silicone fluid having a viscoslty of 620 centipoise.
~xamPle 2:
30 gram~ allylchlo~ide and24 grams o~ a 150 centipoise
dimethylvinyl-stopped linear dimethyl fluid and 0.05 grams of the
sa~ platinum catalyst u~ilized in Example 1 were dissolv~d in 1
liter of toluene in a 3 liter flask~ Next, 300 gram~ of a
dimethylhydrogen-stopped linear polydimethyl-methylhydrosilo~n~
copolymer, having a viscosity of 12U centipoise and containing
6.2~ Me~ functionality were slowly added to the allyl chloride
mixture with ~tirring. F311Owi~g thi~ addition, the ~atalyzed
reaction mixture was refluxed at 100 to llO~C for 2 hours, at
which point no unreacted -- Si~ wa~ det~cted. The toluene 501~ent
was stripped of~ to yield a clear fluid prod~ct. 200 grEms of the
above product were d ispe.rsed in 600 grams toluene w~h 15 gra~
acrylic acid and 1 gram ~ydro~uinone~ 17 gram o~ pyridine w~r~
3 510wly added to the stirred solution under N~ atmosphere at roo~
temperat~re. A cryst~ ne white precipitate de~elcped immedi~
ately upon additio~ o~ _he pyridineO After stirring at 25 30 C
~ 7'~ 7 60SI-311
-15-
for aR hour under the nitrogen atmosp~lere, the solution was
filtered, and the filtra~e wa~ then stripped to remove toluene
solvent. A hazy white acrylic Eunctional silicone fluid product
was obtained, having a visco~ity of 340 cPntipoi~ev
s
Exa~ple ~
50 gram~ allylchloride and 40 grams dime~hyl ~inyl-~Lo~d
linear dimethyl fluid and . 05 grams of the same pla~in~ catalyst
were dis~olved in 1500 gram~ toluene. 500 grams of the --SiM-
functional fluid utilized in Example 2 above were slowly added to
the stirring mixture; following ~his addition~ the complete
reaction mixture was refll~Yed at 95 110 C for 4 hours at which
time no unreactPd _ Si~ was detectedO ~nreacted allylchlorid* wa~
then stripped ~ff, and su~icie3lt toluelle ~ai remov~d under ~acuum
to increase the solid~; content s:~f the product solution to 509~ by
weight. Tnen, 3~8 grams of thi~ solutior~ wer~ transfe~red to a 1
liter flask, and 19 grams o~ 2-hydroxyethylacrylate and ~1 grams
hydroquinone were adde~l. 13 grams of pyridin~ were then addedl. to
2 0 . the reaction mixture under a nitrogen purge at 26 C. ~s in the
examples above, a cryst~ll ine pre~ipitate for~ed a8 the amine wa~
added~ Following the addition of pyridine, the total reaction
mass wa~ filtered, and tol~n~ stripped out o~ the filtrate to
furnish a hazy acrylic ~unctional silicone ~luid pr~ucL having a
2 5 viscosity of 500 centipoise.
Example 4-
Another acrylic ~unctional polysilo~ne was prepared in a
fashion analogous to Example 3, except that 2-hydro~yethyl-
methacrylate wa~ substituted in this synthe~i~ for
2 hydroxyethylacrylate in the previous 3ynthQ~i~, yielding a
methacrylic-function~l sili~one fluid PL~dUCLO
60SI--311
E~camp.l~ 5O
33û gral~a o~ - the ~Si}~ :Eluild utilized in ~ Le 2 were
~lowly added to a solutlon o~ 33 gram~ allyl chls: ride a~d 26 gram~
of l~h~? vinQl ~luid utilized in ~ 2 and ,.1 gra~ oiE the ~
platinula cataly~3~ in 5f;10 gram5 tc~ïu~n~n Af1:er re~ g 'chis
mix~ure a1~ 110C~ fo~ 4 hou~ all rea~tiv~ --Si~ wa~ c~n~
Alt thi~ polnt any e2cc:ess allyl chloride wa~ removed by stirring
the rea~:tion mixtuse under 25 m~ }~ vacuum ~or 30 minute3 at
34 C. Next, 25 grams ac~ylis: acid were then added with .05
grams hydr~ui none. 35 gram~ triethylamin~ were slowly adde~d ~o
the reac~ion mixture under a nitrog~n pu~ege at 32 pot
temperat:ure~, The coloplete mixture Wa8 ~ n-e ~ to Ytir ~o~ 16
hour~ at roo~ te~p~ratur2~, ~hen to~n~n~ wa~s r~ ~_d by va~utam
3trip at loo&- The final PL~;IIICL wa~ ob~ ~9 a~ a clear
yellow visco~ls luid a~ter removal of Et3N EIC1 precipitate via
filtration.. It should be rloted that the proo~.sing described
above ~Ja~3 a one kettle pLOCe:l&~
Ultraviolet evaluation~ described herein were accomplished
using a PPG model 1202AN W Proc~sor. The PPG device u~ s
2 0 two ~anovia medium-pr~sure mercury qapor W soul.ces delivering
300 watt~/~quare inch ~c~ powor to irradi~ted surface~.
SalDple3 to be ~xpo~fl to W light are af~ixes~ to a rigid ~arri~r
board, then paæ~ed under t~e lamp~ on a cvl ve~x~:r belt whi;:h opeE-
ates at vari~ble speedæ from 5 to- 500 ft~miDute resulting in
2 5 expo~ur~ tiMes var3!ing from about 6 to 0. 06 S~CQr~S for any ind~
vidual pa~s u~3er the lamp~.
60SI-31l
~17-
The effica~y of these acryli~ or methacrylic-functional
~$1icone fluids as W -curable paper release coatings wa~ deter-
mined in the follo~ing fa~hion: lO gram s~nple~ o~ candidate
fluid~ were cataly~ed with 0.5 grams of Trigonal 14 ~trademark of
Noury Chemical Corporation) W cataly~t. Trigonal 14 is a
stand~rd benzoin eth~r-derived fr~e-radic~l photoinitiator.
Catalyzed blends w~re applied a~ 0O5 ~il coating~ to 4~ x 10~
section~ of 40 pound s~percalendered ~ra~ (SCR) ~tock by mean~ of
a doctor blade. Samples so coated were loaded onto the moving
io conveyer and exposed to the W radiation under inert atmosphere
for varyin~ amounts of time dependent on line s~eed.
Following e~po~ure, ~he re~ultant films were evaluated ~or
cure and for their potential as relea~e agentQ by qu~litatiYely
determ;nin~ the resp~sti~e film~' rub~off, s~ear~ and ~igration
characteristic.~,
Rub-off occurs when a cured silicone coating will not
adhere to a sub3~rate and can b~ rubbed of~ in little ba11s of
29 silicone by u~ing finger pres~ure. Smear i8 defin~d as an incom-
p1etely cured coating which displays an ob~ious, permanent streak
when a finger is firmly pressed across it. ~igration is detected
by the Scotch ~regi-qtered trademark of the ~ Company) cellophane
tape test. The coating is considered to be well~cured and
migration-free i~ a piece of Scotch tape will stick to itself
after having ~ir-~t been firmly pres~ed t~ the coating, then
removed and doubled back on itself, If A CoatiDg i~ miyration-
free by mean~ o~ the Scotch tape test, it is presumed t~ be a
relea~e coating, a~ it ha~ been shown to adhere to the s~b~trate
with an adhesive force much greater ~han the adhesive ~or~e
betwee~ the cur~d ~ ltion and ~he rsl~a~ed a9~re~sive ~cotch
tape adhe~ive.
ll.~Dti747 60SI-311
--18--
When catalyzed ~nd coated as de~;cribed above, all of the
candidate material3 synthesized irs Examples 1 through 5 ~ere found
to cure to non-adherent coatings on SC~ he W exposure times
required for cure to smear-, rub-off-, and migra'cion-free surfaces
S are noted in the table belows
W Activ~ Mini UV ~E~81lr*
Fluid Functionali~r* Pc~r Cure
Example 1 ~}~2CH2c~20occ~3=c 2 3.0 sec.
Example 2 -ci~2C~2c~2cc~[2 1. 5 sec,
E~cample 2 2 2 2 2 =C~2 lo S sec,
ExalDple 4 C:~2C~I2CH20C~ 2Q~c (C~3) ~2 5 ~ O sec
Example 5 -C}I2c~2ca20Qct~2 1. 5 secO
Reactive group attached to silicon atoms in the dimethyl
silicone fluids.
~y~min~tion of the aforemen~ioned data r~ve31~ that acrylic-
functional silicones will cure faster than analogous methacrylic
functional silicones under otherwise identical condition~. Also,
'pre-cros~l~nked' acrylic-functional polymer~ lin which a vinyl-
stopped dlmethyl fluid wa~ mi~ed with allyohlorid~ in the
hydrosilation addition step of t~e synthese~) show significantly
faster cure rate~ than strictly linear polymers.
Example 6:
64 ml. o~ methallyl c:hloride (u9ed as furni5h~d by Aldrich
Ch~ ical t::o.~ and 0.5 gralo~ of a platinum-oct5rl Al~Qh~)l comple~c (a~
prepared in accordance with the disclosure of 1108~ 3,220~9723 ~hich
3 7f~ ~ 6OSI-3l:L
provides, appro~imately, 20 ppm pLatinum were dissolved in 200 ml.
of toluene in a 1 liter flask. 200 gram~ ~f a 95 centipoise
viscosity dimethylhydrogen-chainstopp~d polydimethylmethylhydro-
gensiloxane copolymer fluid containing ~.9~ Me~ siloxy uni~s were
slowly added to the ~t.irred toluene solution over a 30 minut~
period. Follo~ing thi~ addition the complete reaction mixture was
re1uxed at 95-110C for 15 hours; at which point no unreacted
Si~ could b~ de~e~ted by inPrared spectsoscopy~ Exce~ m~thallyl
chloride was re~oved under ~acuum 2t 50 C. 2~ gram~ o~ acrylic
acid were then added to the flask along with 0~01 gra~ hydro-
guinone~ 33 grams of triethylamine were slowly dropped into the
reaction mixture under a nitrogen atmosphere~ A white precipitate
was n~ted a3 svon as tho amine w2s introduced, additionally, a~
exotherm was observed at this time raising th~ flask t~mperature
from 25 to 50 C~ Following additio~ of the amine ~he reac~a~s
~ere heated to 113C fos ona hour. Toluene solven~ plu~
unreacte~ acrylic acid and triethylamine were removed by stripping
the product mixture in vacu~ at 150 . Filte~ing the fla6k
content~ afforded 150 gram~ of a clear~ pale yello~
acrylic-functional silicone ~luid produ~t, ha~ing a viscosity of
217 centi~oise.
Exa~pl~ 7:
51 ml. of methallyl chloride, .05 graMs of th~ platinwm
catalyst utili~ed in Example 6 were dispe~sed in lS0 gram~ toluene~
to which solu~ion 287 gram~ of a 150 centipoi~e visc08i~y dimethyl-
3C hydrogen-chainstopped polydimethylmethyl hydrogen-s;7O~re ~opoly
mer fluid con~ini~ 7.3% ~thylhydrogenslloxy units were qlowly
7 ~
60$I-311
--~0--
added. Refluxing this solution at 115 for 16 hours removed all
reactive ~ Sl~ fro~ the reaction mixture. After stripping off
exces~ methallylchloride, 25 grams acrylic acid, ,01 grams
hydroquinone, and 35 gram~ triethylamin~ were added to the ~eaction
S fla3k a~ de~cribed in Example 1. F~llowing the ensuing reaction~
the solve~t and e~e~R re ctants were stripped o~f in vacuo, the
product filtered to furnish - 240 gra~ of a ha~y yello~
acrylic-functional silicone fluid having a 570 ce~tipoise vi8c08ity.
Cure result~ a~e comparable to those reported for
composition~ prepared via allylchloride addition described in
previous exa~ple~.
E~ample 8:
Because the Gure mechanism fos acrylic materials
free radical initiated, election beam irradiatio~ will also cure
these acrylic-silicone release fluids~ Materials prepared in this
fashion~ when mixed with effective quantities o~ standard photo-
initiators and coated onto paper substrates, will cure to non-
adherent surfaces when irradiated with either ultraviolet light or
electron beam radiation in an inert atmosphere. For example r 10
gram samples of the acrylic-functional silicone fluids of Exam~les
~5 6 and 7 were each mixed with OA5 grams diethoxyacetophenone (DEAP9
Upjohn Co.) and the mixtur~s were applied to 40 lb9 SCR paper with
a doctor blade. These coatings were cured by paqsing them under
~ocused ultraviol.et radiation supplied by two Hano~ia medium
pres ure mercury vapor W lamps deli~eri~ 30n watt ~inch
radiation housed in a PPG model 1202 AN Pro~esso~D Cure was
qualitatively de~ined as formation of a -smear-, mi~ration-~ and
~ 7~ ~0~I-3~1
-21-
rub-off free non-adherent surface as described aboveO Quantita-
tive measurements o~ the release propertie~ o~ cured film~ of the
new co~position~ were al~o ob~ained. After ~be cured ~ilicone
coated 5CX sampIes w*re aged at ambien~ conditions for 16 hour~, a
6 mil thick layer uf. an aggres~ive SBR preqsure ~ensitive adhesive
obtained from Coate~ P.oaui~t-~, IncO was applied on top o~ the
qil1con~ layer, then Gure~ fo~ 10 minut~ at r~o~ temperatur~ ~d
2 IDinUte8 at 150~; ~ second sheet of SC~ .~tQC~ wa~ ~then fir~ly
pres3e~ onto the adhesi~e layer. Lamina so prepared were cut int~
2x9 inch strip~ and aged at 75 F for at least one ho~rO Release
testing o~ these laminates was then accomplished by pulling the
SC~/silicone lamina fro~ the SR/adhesive lamina a~ an angle o~
180 at a rate o 400 inches per minute. Th~ fo~ce required to
separat2 the two l~mina wa~ recorded in gram~. Results of a
~V-cure and relea~ te~ting are sum~arized belowo
Compo~ition W Cure Time Release
Example 6 3.0 sec. 50-70 grams
EXam~le 7 1~5 sec. 60-80 grams
BcamE~l~ 9:
The following example~ illustrate how air inhibition of
acrylic-3ilicone cure ca~ be overcome by proper choice o~ photo-
sensitizers. A composition was prepared in fashion analogou~ to
Example 7 above resulting in a 549 centipois~ viscoqi~y fluid
peo~u~L containing 10 mcle ~ acryloxy-~ub~tituted siloY~ne groups
randomly sequenced along the linear chainq of the pol~mer. 10
grams of this material were mixed with 0.4 gra~s o~ a 50% solutio~
o~ b~nzophenone iD. N-vinylpyrrolldin~n~ plu8 0.3 gram~
74~
605I-311
N-methyldi~thanolamineO Suc~ a combination of photosensitizer~
and photoacti~atorQ is well known to persons ~killed iD the art
and their use i~ taught in U.S~ Patent 3,795,807. This coating
bath was applied to specimenQ of 40 lb. SCR with a doctor blade,
the coated paper wa~ then P~p~se~ to two ~ano~ia medium presRure
mercury ultraviolet lamp~ mounted in a PPG Proce~sor a~ described
previously, except that an air a; -_~`ere was selected rather tha~
nitrogen. Smear-~ree aDd migration-free non-adherent coatingB
were o~tained upon O.S seconds exposure to W radiation under
these conditions. 60 to 100 grams release versus a Coated
Products aggressive SBR wet adheei~e was observed for thiQ cured
material (release wa~ determined as described previously)~ By way
of comparison, when the same composi~ion as found in E~ample 7 was
catalyzed with diethoxyacetophenon~, it would ~ot cur~ in an air
enviornment.
Example 10:
An acrylic silicone ~relea~e compositi~n was made in the
following fashion: 200 grams of a 220 centipois~ viscosity
~5 dimethylhydroge~siloxy-stopped polydimethylmethylhydrogensil~Y~ne
copolymer fluid having 8 wt. % methylhydroge~ siloxy units on the
polymer chain were weighed into a 1 liter fla3k. A total of
approximately 0.27 moles re tive ~ Si~ functionality was
present. 20 grams methallylchloride and O . 05 grams of the same
platinum catalyst utilized in EXample 1 were then added and the
mixture wa~ re~luxed in- 250- gra~s toluene---fo 90 mi-nutesO At the
end of ~hi~ reflu~ period le53 than 0.1 wt % unreacted ~Si~
could be detected, and exce~ methallychlorid~ was then removed by
distillation of 50 ml of solvent and th~ exces3 ~ethallychloride
~9 '~ ^3
~ ~ ~ 60SI~311
-23-
at atmospheric pressureO Next, 17 grams acrylic acid (0.24 moles)
and 9 grams p~taerythritol triacrylate (0.03 moleY) were then
added to the reaction flask, th~n 36 gram3 triethylamine wer~
~lowly added to the stirring reaction mixture at a pot temperatur~
of 90 C. An exothermic reaction and a precipita~e of
triethyli inehydr~chlsrid~ occurred as ~he amin~ wa~ added to the
reaction mixtur~. The pL~Juc~ was then v~-. 3tripped to 1~0 C
and filtered to yi~ld 143 gram~ cf- a cloudy yellow me~hacryli~
silicone fluid prod~ of 525 centipoi~e visco~ity. Cure
performance of the acrylic-silicone was tested by blending 10
parts o~ this fluid with 0~5 parts diethoxyacetophenone (DEAP),
this mixture ~a~ coated onto 40 lb. SC~ paper with a doctor blade,
and the silicone film was exposed to two focu~ed m~dium-pressure
mercury Yapor ultraviolet lamp~ ia an inert atmosphere for a
period of tlme suf~ici~nt to cure the ~ilicone to a non-adherent
rel~a e coating a~ descri~ed pre~iouslyO Exposure times a~ brie.f
as 0.15 seconds were sufficient to cure this mat~rial to
smear-free and migration-free non-adherent surfaces. Faster cure
was possible, but the resultant silicon~ fiLms were then easily
2 0 rubbed-off of the paper substrates.
It should b~ noted that this exampl~ illustrates the use o~
acrylic acid and PETA in an 8~1 molar ratio a~ twin sources o~
reactive acrylic unctionality. I~ principle, it should be
2 5 pos3ible to blend PETA (or similar hydroxy-containing multi-
functional - -rs gucb a~ trimethylolpropanediacrylate) with
a~rylic acid (or similar monofunctio~al ~1 ~s such a~
beta-hydroxyethylacrylate~ in different molar ratio5~ or to
utili~e PETA alone, for the preparation of acrylic-silicone fluids
according to the practic~ of this invention.
