Acrylated urethane silicone compositions are formed from the reaction of a silicone carbinol, a polyisocyanate and a hydroxy-functional acrylate. These compositions are useful as components of improved radiation-curable coating compositions.

BACKGROUND OF THE INVENTION 
Coatings play a useful role in the manufacture of a great many articles 
which find wide use in nearly all facets of contemporary life. Until 
recently, nearly all coatings were applied with the employment of a 
hydrocarbon based solvent which evaporated leaving a dried coating on the 
article which was to be coated. This system met with increasing disfavor 
as the price of organic solvent increased and as the deleterious 
environmental effects of the evaporated solvent became better understood. 
Systems aimed at solvent recovery to reduce pollution and conserve solvent 
have generally proven to be expensive and energy intensive. In response, 
those skilled in the art have devised a class of coatings termed 
radiation-curable coatings in which, upon exposure to radiation, virtually 
all of the liquid portion of the coating is converted to cured coating 
resulting in little solvent emission. 
Unfortunately many of the radiation-curable coatings which have been 
heretofore manufactured are highly viscous and difficult to apply to the 
substrate requiring dilution of the coating material with volatile 
solvents. A radiation-curable coating which is of such low viscosity so as 
to avoid the use of diluents would be of great advantage. 
SUMMARY OF THE INVENTION 
It has now been found that compositions formed from the reaction of a 
silicone carbinol, a polyisocyanate and a hydroxy-functional acrylate can 
be incorporated in radiation-curable coatings and that the resulting 
coatings are significantly less viscous than the heretofore available 
coatings. 
DESCRIPTION OF THE INVENTION 
The acrylated urethane silicone compositions of this invention are the 
reaction products of a silicone having at least four reactive hydroxyl 
groups in the molecule (a silicone carbinol), an organic polyisocyanate 
and a hydroxyalkyl acrylyl compound; all as hereinafter defined. 
The silicone carbinols useful are those having a plurality of hydroxyl 
groups in the molecule. Particularly useful are the silicone carbinols of 
the grafted copoly type of the formula; 
##STR1## 
wherein R' is an alkylene group having from 1 to 16 carbon atoms; n is an 
integer having a value of 2 or 3; x has an average value of from 1 to 
1000; y has an average value of from 0 to 15; and z has an average value 
of from 4 to 6, preferably 5 to 6. The silicon carbinols having a higher 
hydroxyl functionality, i.e. a higher value of z, are preferred since an 
acrylated urethane silicon having better film properties results when 
silicones of a higher hydroxyl functionality are used. 
The organic polyisocyantes are known compounds and can be represented by 
the general formula Q(NCO).sub.m wherein m has a value of from 2 to 5 and 
Q is the residual organic portion of the molecule to which the isocyanato 
groups are attached. Among those suitable for use in this invention one 
can mention 3,5,5-tri-methyl-1-isocyanato-3-isocyanato-methylcyclohexane, 
di(2-isocyanatoethyl)-bicyclo [2,2,1]-hept-5-ene-2,3-dicarboxylate, 
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane 
diisocyanate, dianisdine diisocyanate, tolidine diisocyanate, 
hexamethylene diisocyanate, the m- and p-xylylene diisocyanates, 
tetramethylene diisocyanate, dicyclohexyl-4,4'-methane diisocyanate, 
cyclohexane-1,4-diisocyanate, 1,5-naphthylene 
diisocyanate,4,4'-diisocyanate diphenyl ether, 2,4,6-triisocyanato 
toluene, 4,4',4"-triisocyanate triphenyl methane, 
diphenylene-4,4-diisocyanate, the polymethylene poly-phenylisocyanates, as 
well as any of the other organic isocyanates known to the average skilled 
chemist. 
The hydroxyalkyl acrylyl compounds suitable for use in producing the 
acrylated urethane silicones are those of the formula 
##STR2## 
wherein X is hydrogen or methyl and R" is a linear or branched divalent 
alkylene having from 2 to about 5 carbon atoms. Illustrative thereof one 
can mention hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxypentyl 
acrylate and the corresponding methacrylates. 
In producing the acrylated urethane silicones one initially produces a 
prepolymer containing free isocyanato groups and then reacts the free 
isocyanato groups with a reactant containing a reactive hydrogen atom. 
Thus, in one embodiment of the reaction, the silicone carbinol is reacted 
with a sufficient excess of organic polyisocyanate to permit reaction of 
all of the hydroxyl groups with isocyanato groups but still have unreacted 
at least one free isocyanato equivalent per mole of prepolymer produced, 
thereby producing an isocyanato terminated prepolymer. Thereafter this 
prepolymer is reacted with the hydroxyalkyl acrylyl compound. In a second 
embodiment of the reaction the prepolymer is produced by initially 
reacting the organic polyisocyanate with the hydroxyalkyl acrylyl compound 
and then reacting the prepolymer with the silicone carbinol. 
In either mode of operation the reaction of the silicone carbinol, 
polyisocyanate and acrylate to form the compositions of this invention can 
be carried out at a temperature of from 0.degree. C. to 125.degree. C. The 
preferred temperature is ambient, i.e. about 20.degree.-30.degree. C. 
The reaction can be carried out at subatmospheric, atmospheric or 
superatmospheric pressure; the preferred pressure is atmospheric. 
The reaction time will vary according to the size of the batch, the 
temperature and pressure and the nature of the particular silicone 
carbinol, polyisocyanate and hydroxy-functional acrylate reactants being 
employed. 
The reaction will proceed uncatalyzed, but a catalyst can be employed to 
expedite it. Such catalysts are well known in the art and include dibutyl 
tin dilaurate, stannous octoate, dioctyl tin diacetate, morpholine, 
triethylene diamine as well as any other suitable urethane catalyst 
recognized in the art. The catalyst, if present, can be in a concentration 
of from 0.01 to 1.0 weight percent, preferably from 0.05 to 0.2 weight 
percent, based on the total weight of the reaction mixture. 
The acrylated urethane silicone compositions of this invention can be used 
as coating compositions either alone or in mixture with other reactive 
monomers, solvents, pigments, fillers and other additives. The coating 
compositions can be applied by conventional means and cured by exposure to 
ultraviolet light or to high energy radiation such as gamma-ray, 
alpha-particle, beta-particle and accelerated electrons or by heat. If 
ultraviolet light is employed the coating composition preferably contains 
a photoinitiator. Illustrative of such photoinitiators one can name 
.alpha.,.alpha.-di-S-butoxyacetophenone, 2,2-diethoxyacetophenone, 
2,2-dimethoxy-2-phenylacetophenone, benzophenone, p-methoxybenzophenone, 
acetophenone, m-chloroacetophenone, propiophenone, xanthone, benzion, 
benzil, benzaldehyde, naphthoquinone, anthraquinone and the like. The 
photoinitiator may be used singly or in mixtures and is present in a 
concentration of from 0 to 10 weight percent preferably from 0.5 to 5 
weight percent based on the weight of the acrylated urethane silicone 
present. 
When heat curing is employed there can be employed free radical initiators 
in a concentration of from about 0.1 to 10 weight percent, preferably from 
0.5 to 5 weight percent based on the weight of the acrylated urethane 
silicone present. Illustrative of such free radical initiators one can 
name di-t-butyl peroxide, dicumyl peroxide, t-butyl hydroperoxide, t-butyl 
peracetate, peracetic acid, perbenzoic acid, benzoyl peroxide, 
dichlorobenzoyl peroxide, azobis(isobutyrontrile), dimethyl 
azobis(isobutyrate) and the like. 
The coatings can be applied to any acceptable substrate such as wood, 
metal, glass, fabric, paper, fiber, plastic that is in any form, e.g. 
sheet, coil, molded, film, panel, tube, etc., by conventional means 
including spray curtain, dip pad, roll-coating and brushing procedures. 
In a typical embodiment isophorone diisocyanate and dibutyl tin dilaurate 
as catalyst are charged to a flask, stirred and heated, while a silicone 
carbinol is added dropwise. After completion of this reaction, 
2-hydroxyethyl acrylate is added dropwise and the mixture is stirred and 
heated for an additional period to complete the reaction. The acrylated 
urethane silicone produced is stabilized with hydroquinone monomethyl 
ether. A coating is produced by blending with 2-(N-methyl-carbamoyl) 
oxyethyl acrylate and .alpha.,.alpha.-di-S-butoxyacetophenone as 
photoinitiator. When applied to release paper and irradiated with 
ultraviolet light, the liquid cured to a polymerized film. 
It was completely unexpected and unobvious to find that the reaction of a 
silicone carbinol having a high hydroxy functionality, a polyisocyanate 
and a hydroxyfunctional acrylate would produce an acrylated urethane 
silicone which has a low viscosity so that it can be easily coated on 
substrates without the use of diluents, and which can be employed in a 
radiation curable composition. Generally, compounds containing a carbinol 
of high hydroxyl functionality also have a high viscosity and require a 
solvent to lower the viscosity for use in coating compositions. The 
invention provides for a composition with good film properties as a result 
of the high functionality and yet with low viscosity, allowing for diluent 
free coating compositions. Therefore, an improved and preferred 
radiation-curable coating is one that is diluent-free. 
The acrylated urethane silicones are especially useful in the formulation 
of low viscosity varnishes for application over conventional ink prints 
while the ink is still in the uncured state, with subsequent curing of the 
varnish by exposure to radiation. The unique properties of the acrylates 
urethane silicones such as a low viscosity/molecular weight ratio good 
flowout performance, good wetting of the ink surface combined with minimal 
miscibility with the ink make them particularly good choices for this 
application in view of the fact that the commonly used organic acrylate 
materials, when used in this application yield varnishes which do not 
provide the desired high level of gloss combined with good film 
properties, such as scratch resistance, flexibility and adhesion, after 
the ink has cured to a solid state by the process of vehicle penetration 
into the substrate and oxidation of the contained drying oils.

The following examples serve to further illustrate the invention. 
EXAMPLE 1 
There were charged to a 500 ml four-neck round-bottom flask, equipped with 
a mechanical stirrer, cooling water bath and dropping funnel, 11.1 grams 
of isophorone diisocyanate and 5 drops of dibutyl tin dilaurate as 
catalyst. While the temperature was maintained at about 20.degree. C. to 
25.degree. C. with the cooling water bath, 7 grams of 2-hydroxyethyl 
acrylate was added dropwise with stirring. When the addition was complete 
the mixture was stirred at room temperature for about 16 hours to complete 
formation of the isocyanato terminated prepolymer. Thereafter 50 grams of 
silicone polycarbinol having a hydroxyl number of 200 mg.KOH/g, a specific 
gravity of 1.06 at 25.degree. C. and a viscosity of 350 centistokes at 
25.degree. C. was added dropwise and the mixture was stirred at ambient 
temperature for about 24 hours. The silicone polycarbinol had the chemical 
formula 
##STR3## 
Thereafter 99 parts of this acrylated urethane silicone was mixed with 1 
part of .alpha.,.alpha.-di-S-butoxyacetophenone as photoinitiator. The 
resulting mixture was coated on release paper and then irradiated for 2.88 
seconds under a nitrogen atmosphere using ultraviolet radiation at a 
wavelength of about 3500 angstrom units. The liquid cured to a dry film, 
and the film was removed from the release paper. 
The film was placed in a constant temperature/humidity chamber overnight. 
The next day a 0.25 inch wide strip was cut and placed in a 1.0 inch gauge 
length crosshead of a stress strain testing machine. The film strip was 
stretched to breakage and the force at failure was used together with the 
width and thickness to calculate the force per unit area at failure. The 
ultimate elongation was calculated using the formula 
##EQU1## 
where L is the length at failure and L.sub.o is the original gauge length. 
The film was found to have a tensile strength of 64 psi and an ultimate 
elongation of 19 percent. 
EXAMPLE 2 
To 49 parts of the acrylated urethane silicone prepared in Example 1 there 
was added 1 part of .alpha., .alpha.-di-S-butoxyacetophenone as 
photoinitiator, resulting in a clear varnish having a viscosity at 
25.degree. C. of about 2000 cps. A sheet of coated offset paper was 
prepared by coating an ink film using a hand proofer with a large charge 
of black ink on its surface so as to obtain two complete roller 
revolutions down the center of the sheet from top to bottom then 
immediately applying the varnish over the ink film with another hand 
proofer equipped with a 180 line/inch quadragravure engraved metering 
roll. The printed and coated paper thus formed was then immediately passed 
through an ultraviolet curing unit delivering a flux of 160 watts per 
square foot, under a nitrogen atmosphere, over a path length of 2 feet. 
The conveyor belt speed was set at 275 ft./min giving an exposure time of 
about 0.44 second. Cure of the varnish was judged to be complete by virtue 
of its resistance of fingernail scratch. The properties of the varnish 
over the ink film were evaluated 20 hours after curing. Flow-out and 
wetting were judged to be good using visual comparative methods. Gloss 
level measured by a 60.degree. C. gloss meter was 72 percent. 
EXAMPLE 3 
There were charged to the apparatus described in Example 1, 8.7 grams of an 
80/20 mixture of 2,4-and 2,6-isomers of toluene diisocyanate and 5 drops 
of dibutyl tin dilaurate as catalyst. While the temperature was maintained 
at about ambient with the cooling water bath, 7 grams of 2-hydroxyethyl 
acrylate was added dropwise with stirring. When the addition was complete 
the mixture was stirred at room temperature for about 3 hours to complete 
the formation of the isocyanato terminated prepolymer. Thereafter 50 grams 
of the silicone polycarbinol described in Example 1 was added dropwise. 
After this addition the mixture was stirred at ambient temperature for 
about 16 hours to form the acrylated urethane silicone composition; after 
which 0.01 grams of hydroquinone monomethyl ether was added as 
polymerization inhibitor. Thereafter 73 parts of the acrylated urethane 
silicone was formulated with 25 parts of the diacrylate derivative of the 
4 mole ethoxylate of 
2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate and 2 parts 
of .alpha.,.alpha.-di-S-butoxyacetophenone as photoinitiator. This 
formulation was applied to coated offset paper and cured using the 
procedure described in Example 2. The resultant dry film was glossy and 
free of surface tack. 
EXAMPLE 4 
There were charged to the apparatus described in Example 1, 35.5 grams of 
isophorone diisocyanate and 5 drops of dibutyl tin dilaurate as catalyst. 
While the temperature was maintained at about ambient with the cooling 
water bath, 20.0 grams of 2-hydroxyethyl acrylate was added dropwise with 
stirring. When the addition was complete the mixture was stirred at room 
temperature for about 4 hours to complete formation of the isocyanato 
terminated prepolymer. Thereafter 50 grams of silicone polycarbinol 
described in Example 1 was added dropwise. After this addition the mixture 
was stirred at ambient temperature for about 16 hours to form the 
acrylated urethane silicone composition. Thereafter 73 parts of this 
acrylated urethane silicone was formulated with 25 parts of 
trimethylolpropane triacrylate and 2 parts of 
.alpha.,.alpha.-di-S-butoxyacetophenone as photoinitiator. The formulation 
had a viscosity of 1010 cps at 25.degree. C. The mixture was applied as a 
varnish over uncured ink and cured following the procedure described in 
Example 3 resulting in a tack-free surface. After the varnish was cured, 
the sheet was aged for about 20 hours and evaluated using the tests used 
in Example 2. The results were as follows 
60.degree. gloss--82% 
flow-out--fair to good 
wetting--good 
EXAMPLE 5 
There were charged to the apparatus described in Example 1, 10.5 grams of a 
mixture of 2,2,4- and 2,4,4-isomers of trimethyl hexamethylene 
diisocyanate and 5 drops of dibutyl tin dilaurate as catalyst. While the 
temperature was maintained at about ambient with the cooling water bath, 7 
grams of 2-hydroxyethyl acrylate was added dropwise with stirring. When 
the addition was complete the mixture was stirred at room temperature for 
about 4 hours to form the isocyanato terminated prepolymer. Thereafter 50 
grams of the silicone polycarbinol described in Example 1 was added 
dropwise. After this addition the mixture was stirred at ambient 
temperature for about 16 hours to complete production of the acrylated 
urethane silicone. Thereafter 73 parts of this acrylated urethane silicone 
was formulated with 25 parts of pentaerythritol acrylate and 2 parts of 
.alpha.,.alpha.-di-S-butoxyacetophenone as photoinitiator. The formulation 
had a viscosity of 2300 cps at 25.degree. C. It was then applied over 
uncured ink and cured following the procedure described in Example 6 
resulting in a clear tack-free film. After the varnish was cured, the 
sheet was aged for 20 hours and evaluated using the tests in Example 2. 
The results were as follows: 
60.degree. gloss--76% 
flow-out--fair 
wetting--good 
EXAMPLE 6 
Four varnishes were prepared using the procedure described in Example 2. 
For comparative purposes, two other varnishes, representing the heretofore 
state of the art were produced and evaluated using the same procedures. 
The compositions of each varnish and the results of the evaluation are 
shown in Table I. 
TABLE I 
______________________________________ 
Varnish (parts by weight) 
A B C D E F 
______________________________________ 
Acrylated 
Urethane 
Silicone of 
Example 1 
39 50 42 17 -- -- 
Polyether 
Urethane 
Oligomer -- -- -- 12 29 -- 
Caprolactone 
Polyol 
Urethane 
Oligomer -- -- -- -- -- 8 
Adduct of 
1 mole 
Isophorone 
Diisocyanate 
and 2 moles 
2-hydroxy- 
ethyl acrylate 
-- -- -- 6 -- 16 
Trimethylol- 
propane 
triacrylate 
61 -- 53 60 66 44 
Phenoxyethyl 
acrylate -- -- 5 5 5 12 
.alpha.,.alpha.-di- 
Sbutoxy- 
acetophenone 
2 2 2 2 2 2 
Compound A 
1 1 1 1 1 1 
Compound B 
-- 50 -- -- -- -- 
60.degree. gloss 
74 78 72 75 67 68 
Flow-out Good Good Fair Good Fair Good 
to to 
Good Good 
Resistance to 
cracking 
when folded 
Good Exc. Exc. Good Fair Fair 
______________________________________ 
Compound A-- 
##STR4## 
Compound B-- The diacrylate derivative of the 4 mole ethoxylate of 
2,2dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate 
This example demonstrates the superior properties of varnishes employing 
the acrylated urethane silicones of this invention particularly the 
resistance to cracking over those of the heretofore present state of the 
art.