Silicone-based, curable, printable, hydrophobic coating compositions and processes for using the same

Silicone-based, high solids, curable, printable, hydrophobic or release coatings or inks comprise a vinyl or hydroxyl chainstopped diorganopolysiloxane; and organic hydrogenpolysiloxane as a curing agent or crosslinker; and a curing catalyst such as a soluble compound of platinum or rhodium, or for hydroxyl chainstopped compositions only, a soluble compound of zinc, manganese, zirconium, cobalt or nickel. Up to about 45% of a vinyl or hydroxyl chainstopped organopolysiloxane resin ("MQ resin") may be included to impart better adhesion to the substrate and/or any pigments used. The combination of chainstopped polysiloxane and organic hydrogenpolysiloxane is characterized by a viscosity at 25.degree. C. of at least about 10,000 centistokes and not more than about 60,000 centistokes. Addition of other printing components such as pigments, rheological additives, reducing oils, fillers, waxes and the like may raise the apparent viscosity of a printing varnish or ink beyond the required range without departing from the invention so long as the viscosity of the basic vehicle from which the ink or varnish was prepared lies within the required range.

BACKGROUND OF THE INVENTION 
This invention relates generally to coatings and specifically to a 
printable silicone-based printing varnish or ink for use with printing 
system such as lithography, letterpress, letterset, silk screen, etc. 
There is a wide variety of uses for a printed silicone-based, hydrophobic 
and/or release coating. Areas can be selectively printed for water 
repellency and/or release properties with other areas unprinted to permit 
other processing incompatible with such a coating. Additionally, such a 
hydrophobic and/or release coating or ink which is compatible with 
pigmentation, dyes and the like and which is selectively printable has a 
wide variety of uses including over-printing. All uses to which a 
printable coating may be put are included within the context of the 
present invention although not specifically catalogued herein. 
Silicone-based release coatings are well known but have not been used in 
printing by lithography letterpress, silk screen, or the like, all of 
which presently employ oil-based inks. 
Oil-based printing inks and varnishes constitute a major portion of all 
inks and varnishes in use by the printing industry today. Such inks and 
varnishes employ drying oils such as linseed oil, chinawood oil, etc., in 
conjunction with rosin-based resins such as modified phenolics, maleic 
modified rosin esters, etc., and hydrocarbon resins. For heat-set inks, 
hydrocarbon resins and rosin-based resins with or without drying oils are 
dissolved in petroleum-based oils, usually straight run middle distillates 
or hydrotreated middle distillates. Final formulations for the actual 
printing inks and varnishes have been prepared by the millions, and are 
routinely developed by those skilled in the art. "The Printing Ink 
Handbook" (1980) compiled by the Product and Technical Publications 
Committees of the National Association of Printing Ink Manufacturers, 
Inc., Harrison, N.Y., provides descriptions of various aspects of printing 
processes and inks and a glossary of terms used in the printing ink 
industry. This publication is expressly incorporated herein by reference. 
Conventional printing inks and varnishes are commonly characterized as 
falling into two broad categories, "paste inks" and "fluid inks." Paste 
inks are relatively high solids compositions which are viscous and tacky. 
Letterpress, offset lithographic, letterset, intaglio and silk screen inks 
are all paste inks. Fluid inks are low viscosity liquids which contain 
large amounts of volatile solvents. Flexographic and gravure inks are 
typical fluid inks. 
Among paste inks, letterpress, offset lithographic and letterset inks and 
varnishes are relatively "long," i.e., they can be drawn out into a long 
thread without breaking; while silk screen and intaglio inks and varnishes 
are relatively "short" and "buttery," i.e., a thread cannot be drawn from 
them without breaking. 
Paste inks and varnishes for lithographic and letterpress printing are 
commonly measured for viscosity and yield utilizing a falling rod 
viscometer in accordance with ASTM Method 4040-81 at a shear rate of 2500 
sec..sup.-1 
"Tack," (expressed in gram-meters) is a measure of the internal cohesion of 
an ink film and thus its resistance to splitting between two rapidly 
moving surfaces (rolls) rather than transferring from one to the other is 
measured in accordance with ASTM Method D4361-84 on the Inkometer, an 
instrument made by the Thwing-Albert Company, Philadelphia, PA. This 
instrument can be operated at different speeds, and is also used to 
determine the effect of speed (revolutions per minute) on ink 
characteristics such as "misting" or "flying," "spitting" and distribution 
of the ink or varnish on the rollers of the instrument. "Mist" is a fine 
mist or spray of ink or varnish thrown off the rapidly moving surfaces 
(rollers) of the Inkometer or a printing press. "Spit" is blobs of ink or 
varnish thrown off the rollers. Spitting is characteristic of excessively 
viscous compositions. Experience has shown that observations of misting, 
spitting, or poor ink distribution on the Inkometer are strongly 
indicative that similar behavior will be observed on a printing press at 
similar speeds. 
These oil-based printing inks and varnishes and their primary organic 
components are generally incompatible with silicone oils and resins. The 
solubility characteristics of silicone oils and resins are so limited that 
a successful printing ink or varnish vehicle based on silicones must be 
substantially composed of silicone ingredients. 
The only reactive silicone coatings applied to the surface of substrates 
that are similar to substrates utilized in the printing, publication, 
packaging, and converting industries are silicone "release" coatings. 
These release coating compositions have tradionally been solvent solutions 
or aqueous emulsions of reactive silicone polymers, wherein the fluid 
composition used for application to a substrate usually contained 3% to 
15% reactive silicon polymer. 
The equipment used for application of these release compositions to the 
substrate are Mayer rod coaters, roller coaters, reverse roll coaters, air 
knife coaters, trailing blade coaters, gravure roll coaters and the like. 
These coating systems apply 100% continuous coverage to the substrate. 
With the advent of "solventless" reactive silicon polymers for release 
coatings as described in U.S. Pat. Nos. 4,071,644, 3,922,443, 3,936,581 
and 3,928,629 the preferred method of coating is by offset gravure 
utilizing differential roll speeds. This method applies 100% continuous 
coverage to the substrate. 
In brief, all of the efforts to develop release coating materials have been 
directed to compositions which will readily afford a continuous or 100% 
coverage to a substrate regardless of the method of application employed. 
The requirement for 100% coverage directs one to compositions which have 
good flow properties so that flow of the coating after application will 
ensure that any pinholes, minor skips, etc. are covered by the 
post-application flow out before curing. 
These requirements are different from the flow properties required for a 
satisfactory printing ink or varnish. Printing requires that the applied 
material remain exactly as printed with as little post-application flow as 
is possible, preferably none at all. Any significant flow out will destroy 
the sharpness of the image, and in multicolor printing will lead to 
running or mixing of one color with another at boundaries where two (or 
more) colors meet. In addition, the printing ink or varnish must have 
sufficient internal cohesion or tack to allow it to transfer as completely 
as possible from one surface to another in the printing process and to 
retain definition throughout the various steps which are required to 
ultimately transfer it to the substrate which is to be printed. Therefore, 
printed areas should have a continuous coating, and the unprinted areas 
left uncovered. 
Thus the balance of properties for a printing ink or varnish is a far more 
complex matter than that required for the continuous coating processes of 
the prior art systems, with the added proviso that while the internal 
cohesion and flow-resistant properties must be high enough to allow 
definition to be retained in the printing process they cannot be too high, 
or poor distribution will occur and the ink or varnish will be unusable. 
The balance of properties will vary from one printing process to another, 
but given a vehicle which is operative according to the present invention, 
formulation for a particular printing system is readily accomplished by 
those skilled in the art. 
For these reasons, the well-known silicone-based release coatings exhibit 
qualities which make them unsuitable for printing techniques such as 
offset lithography, letterpress, etc. For instance, the silicone release 
coating disclosed in U.S. Pat. No. 4,071,644 includes a two-part, curable, 
solventless composition, one part of which is a hydroxyl (silanol) 
chainstopped polysiloxane exhibiting preferably a viscosity of from 300 to 
1000 ctsk. at 25.degree. C. and the other part of which is an organic 
hydrogenpolysiloxane exhibiting a viscosity of from 10 to 100 ctsk. at 
25.degree. C. In another species of the invention disclosed in Example 2 
in U.S. Pat. No. 4,071,644, a vinyl chainstopped polysiloxane fluid is 
disclosed and exhibits a viscosity of 300-1000 ctsk. at 25.degree. C. 
U.S. Pat. No. 3,922,443 discloses a two-part solventless system, one part 
of which is a hydroxyl chainstopped diorganopolysiloxane which has a 
viscosity not greater than 1,000 centipoise at 20.degree. C. (the abstract 
states not greater than 5,000 centipoise), and the other part an 
organophydrogenpolysiloxane which has a viscosity not greater than 100 
centipose at 20.degree. C. The specific dimethylpolysiloxane employed has 
a viscosity of 940 centipoise at 20.degree. C., and the formulated 
composition a viscosity of 740 centipoise at 20.degree. C. 
U.S. Pat. No. 3,936,581 also describes a two-part solventless system based 
on a hydroxyl chainstopped diorganopolysiloxane and an 
organohydrogenpolysiloxane. The preferred diorganopolysiloxane has a 
viscosity not less than 50 centipoise at 20.degree. C., and the specific 
dimethylpolysiloxane employed has a viscosity of 140 centipoise. The 
patent also describes a solvent-based system which employs a 
dimethylpolysiloxane having a viscosity of 19,900 centipoise. Again the 
direction of the teaching of this patent is to a low-viscosity formulation 
to be applied to a substrate by prior art methods. 
U.S. Pat. No. 3,900,617 discloses in Example 1 a vinyl chainstopped 
polysiloxane fluid having a viscosity of 4000 centistokes at 25.degree. C. 
which is cross-linked with hydrogenpolysiloxane as disclosed in U.S. Pat. 
No. 4,071,644. This is employed as an aqueous emulsion which is unsuitable 
for printing systems referred to above. 
A quite similar two-part solventless, curable silicone release coating is 
disclosed in U.S. Pat. No. 3,928,629 which composition exhibits a maximum 
viscosity of 4000 ctsk. at 25.degree. C. 
While U.S. Pat. No. 3,900,617 broadly discloses the use of aqueous emulsion 
employing vinyl chainstopped polysiloxanes which may exhibit viscosities 
up to 750,000 centistokes, the vinyl chainstopped polysiloxane 
specifically exemplified therein has a viscosity of 4000 ctsk. 
Furthermore, the aqueous emulsion is totally unsuitable for use in 
processes such as lithography which require the use of inks or varnishes 
which are immiscible with water. 
All of the above compositions are based on relatively low molecular weight 
vinyl or hydroxyl chainstopped polydimethylsiloxanes which exhibit 
near-Newtonian viscosity behavior (i.e., they exhibit near constant 
viscosity at all but the very highest shear rates). Paste inks are 
characterized by non-Newtonian viscosity characteristics and exhibit a 
significantly higher viscosity at zero or low shear than under the high 
shear conditions of printing. In other words, paste inks become more fluid 
under shear. High viscosity at low shear means that the ink will resist 
static flow and retain a sharp image or definition in the printed image. 
Low viscosity at high shear allows good distribution of the ink or varnish 
on the rollers and printing plate. Therefore, the compositions of U.S. 
Pat. Nos. 3,900,617; 3,922,443; 3,928,629; 3,936,581 and 4,071,644 lack 
the properties required for paste inks and varnishes. They also exhibit a 
highly undesirable tendency to mist or fly excessively. Misting or flying 
leads to ink or varnish on undesired portions of the material being 
printed, on the printing press itself, and in the atmosphere and on the 
surfaces of the workplace. The presence of silicone oil in unwanted areas 
is particularly unacceptable because it can spoil not only the work in 
progress, but later projects as well. In addition, low viscosity fluids 
will run out of the ink fountains (open-bottomed troughs) used on many 
printing presses. Although some of these problems may be remedied by the 
addition of a high molecular weight silicone gum, the misting tendency 
cannot be suppressed by this technique. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, it has been found that 
silicone-based solventless hydrophobic and/or release compositions based 
on vinyl or hydroxyl chainstopped polysiloxanes having viscosities between 
specified limits can be made into printable coatings which may be 
pigmented or not and applied by offset lithographic, letter press and 
other printing processes which presently employ oil-based inks. 
Formulations falling outside the preferred viscosity range may also be 
formulated into printing inks and varnishes which are limited to use at 
slower press speeds. 
A silicon-based, high solids, curable, printable, hydrophobic or release 
coating or ink of the present invention comprises a vinyl or hydroxyl 
chainstopped diorganopolysiloxane; an organic hydrogenpolysiloxane as a 
curing agent or crosslinker; and a curing catalyst such as a soluble 
compound of platinum or rhodium, or for hydroxyl chainstopped compositions 
only, a soluble compound of zinc, manganese, zirconium, cobalt or nickel. 
Up to about 45% of a vinyl or hydroxyl chainstopped organopolysiloxane 
resin ("MQ resin" described hereinafter), may be included to impart better 
adhesion to the substrate and/or any pigments used. In most cases when a 
pigmented ink is to be prepared, it will be necessary to include an MQ 
resin to ensure that the pigment is bound by the vehicle and does not dust 
or rub off. If a top-coat is applied to a pigmented coating, the MQ resin 
may be omitted, as the top-coat may prevent dusting or rub off. The 
combination of chainstopped polysiloxane and organic hydrogenpolysiloxane 
(herein called the vehicle) is characterized by a viscosity at 25.degree. 
C. of at least about 10,000 centistokes and not more than about 60,000 
centistokes. Also within the scope of the invention are somewhat higher 
viscosity vehicles which have had their viscosity adjusted to fall within 
the required range by the addition of an appropriate amount (not more than 
about 20%) of a relatively high boiling saturated hydrocarbon diluent. 
Addition of other printing components such as pigments, rheological 
additives or fillers, waxes and the like may raise the apparent viscosity 
of a printing varnish or ink beyond the required range without departing 
from the invention so long as the viscosity of the basic vehicle from 
which the ink or varnish is prepared lies within the required range. 
Accordingly, final printing inks and varnishes are prepared by formulating 
the vehicle with pigments, waxes, rheological addivitives or fillers, etc. 
in manners well understood by those skilled in the art of ink formulation. 
DETAILED DESCRIPTION OF THE INVENTION 
Chainstopped polydimethylsiloxanes having molecular weights which give 
viscosities in excess of 10,000 centistokes exhibit limited non-Newtonian 
viscosity behavior at shear rates characteristic of those observed in 
printing presses. This non-Newtonian behavior is observed at lower and 
lower shear rates as the molecular weight increases, and at very high 
molecular weights (500,000 centistoke fluids) the polydimethylsiloxanes 
are non-Newtonian at substantially all shear rates. 
It has been found that the viscosity of a silicone-based ink vehicle can be 
correlated with the performance of a printing ink or varnish prepared from 
it. If the viscosity of the vehicle is too low, excessive misting will 
occur and with very low viscosities, excessive flow out will occur. If the 
viscosity of the vehicle is too high, the vehicle and compositions derived 
from it show poor ink distribution on the rollers and/or are subject to 
excessive spitting. 
It is also characteristic of high viscosity linear polydimethylsiloxanes 
that their rheology is relatively independent of the nature of their end 
groups (chainstoppers). Since a wide variety of trimethylsilyl 
chainstopped polydimethylsiloxanes is readily available, they are 
particularly convenient for determining the optimum viscosity range 
(molecular weight) for use in printing processes. Four such products were 
tested on the Inkometer with the results shown in Table I. 
TABLE I 
______________________________________ 
Viscosity Speed 
(cstk.) 
Tack (rpm) Remarks: 
______________________________________ 
5,000 6.2 @ 1 min. to 5.6 @ 9 min. 
1200 very 
heavy mist 
400 very 
heavy mist 
30,000 10.5 @ 1 min. to 10.3 @ 10 min. 
800 no mist 
10.9 @ 1 min. to 10.5 @ 10 min. 
1200 no mist 
60,000 8.2 @ 1 min. to 8.5 @ 10 min. 
800 no mist 
9.9 @ 1 min. to 5.4 @ 10 min. 
1200 spitting 
100,000 
4.2 @ 1 min. to 4.2 @ 10 min. 
800 no 
visual mist 
5.4 @ 1 min. to 5.3 @ 6 min. 
1200 spitting 
______________________________________ 
Since 400 rpm corresponds to an approximate press speed of 314 feet per 
minute (fpm), excessive misting at that speed indicates a composition 
which would require too slow a press speed to be economically acceptable 
for many users. A composition which does not mist at 400 rpm but does at 
1200 rpm (about 942 fpm) may be suitable for use at economical press 
speeds. A composition which does not mist at 1200 rpm will be suitable for 
use at most press speeds used in the industry. Inkometer testing may also 
be done at even higher speeds such as 2000 rpm (about 1570 fpm). High 
viscosity systems generally show failure at high speeds because of 
spitting or poor distribution on the Inkometer roller (or both). Neither 
property is acceptable to the printing industry. 
A series of compositions based on vinyl or hydroxyl (OH) chainstopped 
polydimethylsiloxanes was evaluated on the Inkometer and for Laray 
viscosity with the results shown in Table II. Because the addition of 
crosslinker or curing agent (trimethylsilyl) chainstopped 
polymethylhydrogensiloxane) reduces the viscosity of the system slightly, 
tests were run with and without the addition of 5-10% crosslinker. 
TABLE II 
__________________________________________________________________________ 
Laray-2500 sec..sup.-1 
Viscosity Tack @ 1200 rpm 
Misting, spitting observed 
Viscosity 
Yield 
(centipoise) 
Chainstopper 
Crosslinker 
1 min. 
5 min. 
400 rpm 
1200 rpm 2000 rpm 
(Poise) 
Stress 
__________________________________________________________________________ 
7,700 
OH -- -- -- heavy mist 
-- -- -- -- 
7,700 
OH 5% 8.8 -- heavy mist 
-- -- -- -- 
9,600 
OH -- 9.0 8.2 med. mist 
sl. mist -- 75 598 
9,600 
OH 5% 8.4 7.8 med. mist 
sl. mist -- 71 451 
13,000 
vinyl -- -- -- mist -- -- -- -- 
16,000 
vinyl -- 10.2 
10.0 none none mist -- -- 
16,000 
vinyl 5% 9.6 9.6 none mist -- -- -- 
(2 min.) 
18,000 
OH -- 10.6 
10.2 none none v. slight 
110 1248 
18,000 
OH 5% 10.0 
9.8 none none v. slight 
97 1211 
18,000 
OH 10% 9.2 9.0 none none v. slight 
83 842 
19,850 
vinyl -- 10.8 
10.6 none none slight 
93 1664 
19,850 
vinyl 5% 10.4 
10.0 none none slight 
77 1346 
22,000 
OH -- 10.4 
10.0 none none none -- -- 
30,000 
vinyl -- 11.4 
10.0 none none spits 123 2236 
poor dist. 
30,000 
vinyl 5% 10.8 
10.6 none none slight 
104 2115 
good dist. 
31,250 
OH -- 11.0 
10.8 none none spits 144 3451 
31,250 
OH 5% 10.4 
10.2 none none spits 128 2475 
34,000 
OH -- 11.4 
10.8 none none sl. build-up 
41,000 
OH -- 10.6 
10.2 none spits, 162 4358 
build-up 
41,000 
OH 5% 10.8 
10.6 none v. sl. mist 
spits, 
140 3992 
build-up 
42,000 
vinyl -- 10.6 
10.4 none none spits, 
138 4812 
build-up 
42,000 
vinyl 5% 11.0 
10.6 none none spits, 
126 4086 
build-up 
48,860 
OH -- none poor distribution 
163 5198 
48,860 
OH 5% 10.4 
10.2 none spits, 156 4108 
build-up 
48,860 
OH 10% 10.6 
10.2 none none spits, 
-- -- 
build-up 
51,000 
vinyl -- 10.4 
9.4 none spits, -- -- 
(2 min.) poor distribution 
51,000 
vinyl 5% 10.8 
10.4 none spits, -- -- 
(4 min.) poor distribution 
54,500 
OH -- 10.6 
-- none spits, 175 5710 
build-up 
54,500 
OH 5% 11.0 
10.8 none spits, 148 5377 
(3 min.) build-up 
59,250 
vinyl -- 8.4 none very poor distribution 
-- -- 
59,250 
vinyl 5% 8.4 none spits, -- -- 
very poor distribution 
60,670 
vinyl -- 8.0 none very poor distribution 
-- -- 
60,670 
vinyl 5% 9.6 none very poor distribution 
-- -- 
__________________________________________________________________________ 
Tables I and II show clearly that compositions based on polysiloxanes 
having viscosities below about 10,000 centistokes show unacceptable 
misting at an Inkometer speed corresponding to a press speed of about 300 
fpm. However, at very slow speeds they may yield acceptable prints albeit 
at printing speeds which probably would be uneconomic. If the base fluid 
viscosity is at least about 15,000 centistokes, press speeds of about 1000 
fpm may be obtained without misting. Viscosities higher than about 60,000 
centistokes show poor ink distribution at economical press speeds and are, 
therefore, less desirable, although acceptable results may be obtained at 
slower, less economical press speeds. 
Table II also shows significant non-Newtonian behavior at shear rates 
characteristic of letterpress, letterset and lithographic printing 
processes for compositions using fluids having viscosities of about 10,000 
centipoise or more. As static viscosity increases, the Laray viscosities 
deviate increasingly from the static viscosities. The Inkometer and Laray 
data also show that fluids having viscosities of about 10,000 centipoise 
or more meet the requirements recognized by the printing industry for 
letterpress, letterset and lithographic inks. 
The high solids curable vehicle compositions for printing inks and 
varnishes of the invention comprise: 
a. a vinyl chainstopped diorganopolysiloxane, or a hydroxyl chainstopped 
diorganopolysiloxane, or mixtures thereof; 
b. an organic hydrogenpolysiloxane curing agent or crosslinker; 
c. from 0 to about 45% of a vinyl chainstopped organopolysiloxane resin, 
hydroxyl chainstopped organopolysiloxane resin, or mixtures thereof; and 
d. a catalyst for curing said composition. 
The high solids curable printing ink and varnish compositions comprise the 
above compositions (a, b, c and d) plus 
e. one or more printing components. 
The preferred vinyl chainstopped diorganopolysiloxanes are vinyl 
chainstopped polysiloxanes having units of the formula (I): 
##STR1## 
wherein each R is individually selected from: alkyl such as methyl, ethyl, 
octyl, etc.; cycloalkyl such as cyclohexyl, cyclopentyl, etc.; aryl such 
as phenyl, tolyl, xylyl, etc.; aralkyl such as benzyl, phenethyl, etc.; or 
halogenated aryl such as chlorophenyl, bromophenyl, chloronaphthyl, etc.; 
R.sup.1 is a divalent organic bridging group such as alkylene, arylene, or 
aralylene; Z is 0 or 1, and X and Y have values such that the polysiloxane 
has a viscosity between about 10,000 to about 60,000 centistokes at 
25.degree. C. 
The more preferred vinyl chainstopped polysiloxanes (I above) are those 
wherein R is substantially methyl and Z is 0 where X and Y have values 
which will give a viscosity between about 15,000 and about 50,000 
centistokes at 25.degree. C. Most preferred are those which have a 
viscosity between about 20,000 and about 40,000 centistokes at 25.degree. 
C. 
The preferred hydroxyl chainstopped diorganopolysiloxanes are silanol 
chainstopped polysiloxane having the formula (II): 
##STR2## 
wherein R is the same as described above and t has a value such that the 
polysiloxane has a viscosity between about 10,000 and about 60,000 
centistokes. 
The more preferred hydroxyl chainstopped polysiloxanes (II above) are those 
wherein R is substantially methyl and t has a value which will give a 
viscosity between about 15,000 and about 50,000 centistokes at 25.degree. 
C. Most preferred are those which have a viscosity between about 20,000 
and about 40,000 centistokes at 25.degree. C. 
The best results are obtained when the silanol contains essentially no 
residual alkalinity. When excessive alkalinity is present, an unstable 
formulation may result which has a short shelf-life. A simple test for 
excessive alkalinity is to add about 10% crosslinker to a portion of the 
material to be tested. The viscosity of the mixture is taken after mixing, 
and the mixture is then allowed to stand, and the viscosity is compared 
daily to the original viscosity. If the viscosity changes moderately after 
the first day and there is no subsequent significant change, the material 
will be acceptable. 
The preferred organic hydrogenpolysiloxane curing agent or crosslinker has 
the formula (III): 
##EQU1## 
wherein R is a described above, a is 0 to 3, b is 0.005 to 2.0 and a plus 
b is 0.8 to 3; 
The organic hydrogenpolysiloxane (curing agent or crosslinker) can vary 
broadly in structure and it may comprise a mixture of materials. One 
characteristic is that it contains a plurality of silicon-bonded hydrogen 
atoms per molecule which act to crosslink the other polysiloxane 
component(s). It may be linear or cyclic in nature. Particularly useful is 
a linear methylhydrogen polysiloxane or a methyl hydrogen-dimethyl 
polysiloxane copolymer. Although the crosslinker may be added at any stage 
in the preparation of a printing ink or varnish, in general, addition is 
withheld until shortly before the formulation is to be used. This 
precaution ensures maximum shelf-life for the relatively costly 
formulation. The addition is easily accomplished by merely stirring in the 
desired amount shortly before use. Usually from 1 to 10% by weight of the 
reactive organosilicon species of the crosslinking organohydrogen 
polysiloxane is required. 
The vinyl or hydroxyl chainstopped organopolysiloxane resins 
(conventionally called "MQ resins") are very complex structures comprising 
a three-dimensional condensed silicate structure having random 
trimethylsiloxy groups and either vinyldimethylsiloxy groups (vinyl MQ) or 
hydroxyl groups (MQ) attached to free valences of the silicate structure. 
The MQ resins may be prepared by reacting approprate chlorosilanes with 
acidified water glass as taught in U.S. Pat. No. 2,676,182, by 
cohydrolysis of appropriate chlorosilanes with silicon tetrachloride, or 
by cohydrolysis of ethyl orthosilicate or a condensed ethyl silicate and 
an appropriate monoalkoxytriorganosilane. 
A typical vinyl MQ resin is prepared by exhaustively reacting a mixture of 
trimethylsilyl chloride and vinyldimethylsilyl chloride with acidified 
water glass in the manner taught in U.S. Pat. No. 2,676,182. A vinyl MQ 
resin is present as about 40% by weight of a mixture with vinyl 
chainstopped polydimethylsiloxane sold by the General Electric Company as 
"SS-4305." 
A typical MQ resin is prepared by reacting trimethylsilyl chloride with 
acidified water glass as taught in U.S. Pat. No. 2,676,182. MQ resin 
suitable for use in the present invention may be prepared by adding a 
preferred hydroxyl or vinyl chainstopped polysiloxane of the invention to 
"SR 545 Silicone Resin," a solution of MQ resin in toluene sold by the 
General Electric Company and stripping the aromatic solvent under reduced 
pressure at a temperature below about 100.degree. C. Use of excessive heat 
may cause the MQ resin (or silanol chainstopped polysiloxane if used) to 
polymerize to such an extent that the mixture gels. 
The vehicles prepared from the above components are formulatd into printing 
inks and varnishes by incorporation of printing components such as 
pigments, waxes, rheological additives or fillers and the like into the 
vehicle. The principles involved in ink formulation as well understood by 
those skilled in the art. 
Inks are colored by the addition of printing pigments to a base vehicle. 
Broadly, pigments fall into a few general classes; black pigments such as 
furnace, thermal and channel blacks; white pigments such as titanium 
dioxide, zinc sulfide, zinc oxides, lithopones, alumina, calcium 
carbonate, etc.; inorganic or mineral pigments such as chrome colors, 
cadmium yellows and red, vermillion, Prussian blue, etc.; metallic 
powders; organic colors which constitute an enormous range of materials; 
soluble organic dyes; and mixtures thereof. The choice of colors is such 
that each formulator is skilled in the choice of appropriate pigments for 
the desired result. In general, the compositions of the present invention 
may be used with all types of pigments, but care must be taken to ensure 
that the pigment does not interfere with the catalytic action of curing 
catalyst especially when platinum is used as a curing catalyst. When 
silanol chainstopped silicones are used in the vehicle, some of the 
mineral pigments based on transition metals may cause premature thickening 
or even curing of the inks. Also, sometimes organic pigments have 
sufficiently active amino or acidic groups to cause premature reaction. A 
simple test may be used to check whether a pigment is suitable. A small 
amount of the vehicle is mixed with the pigment and the curing 
characteristics are determined by a "draw down", preparing a thin coating 
with a spatula or glass rod on a suitable substrate, which is then cured. 
Additional portions may be stored and tested at invervals to determine 
shelf-life. If there is interference with catalysis, the draw-downs will 
not cure. When pigments cause premature reaction with silanol-base fluids, 
significant thickening will occur with the passage of time, and eventually 
the system will become too thick to allow draw-downs to be prepared. The 
amount of printing pigment employed may vary very greatly depending on the 
nature of the pigment, the depth of color desired, the nature of the 
substrate and other variables, all of which are well-understood by those 
skilled in the art. 
In general the amount used wil be no more than about 20 to 35% of the 
formulation, depending on the nature of the pigment and its rheological 
effects. 
Other printing components or additives which may be used in formulating 
varnishes and inks include "waxes," lubricants, reducing oils, rheological 
additives and fillers. 
"Waxes" are used to prevent "set-offs" (transfer of ink from a printed 
surface to a surface laid on it), to improve slip, and to impart scuff 
resistance. Printing waxes include paraffin and microcrystalline waxes, 
Fischer-Tropsch waxes, polyethylene waxes, waxes based on 
tetrafluoroethylene polymers and copolymers, fatty acid amides, mineral 
waxes such as montan wax, and natural waxes such as beeswax and Carnauba 
wax. Waxes may be added to the varnish or ink at any convenient stage in 
manufacture. The amount of wax, if any, to be used for a particular 
formulation is judged by the formulator who is skilled in the art. 
Generally, the amount used will not be more than about 4% of the 
formulation. 
Reducing oils or diluents are hydrocarbon oils which are used in this 
invention to adjust tack, viscosity and flow characteristics. They are 
also used to adjust penetration of a porous substrate by the ink or 
varnish. Mineral spirits may be used, but their rather high vapor pressure 
makes the use of higher molecular weight hydrocarbons more desirable. 
Because aromatic hydrocarbons attack rubber components used in printing 
machinery, oils which are substantially free of aromatics are preferred. 
Particularly preferred are high-boiling hydrotreated oils such as 
"Magiesols" sold by the Magie Bros. Oil Co., Franklin Park, IL. These oils 
may be used in amounts up to about 20% by weight of the vehicle to adjust 
tack or bulk viscosity or both, as well as to adjust penetration in the 
finished formulation. 
Rheological additives are high surface-area silicas or silicate-aluminates 
which cause an apparent thickening of a varnish or ink when added in small 
amounts (0.1-5% by weight). Rheological additives include silicas such as 
"Cab-O-Sils" sold by the Cabot Corporation, bentonite clays, etc. Fumed 
silicas are particularly preferred. Care must be exercised in using 
rheological aids in silicone-based systems to avoid adding excessive 
amounts. When too much (more than about 5%) is added to the vehicles of 
the present invention, excessive thickening will occur, rendering the 
resulting composition unsuitable for use as a printing ink or varnish. 
Fillers are used to bulk printing inks and reduce their cost. They are 
relatively low surface area minerals such as clays, blanc-fixe, calcium 
carbonate, etc. which exhibit low surface activity. Fillers may be used in 
amounts up to about 20%. 
Pigments and additives may sometimes be incorporated into a vehicle by 
merely adding them to the vehicle with good agitation. Materials which are 
more difficult to disperse well may be incorporated by use of three-roll 
mills, ball mills, sand mills, shot mills, colloid mills, Baker-Perkins 
mixers, Cowles dissolvers, and the like, as is well-known in the printing 
ink industry. 
For vehicles which contain vinyl chainstopped components the curing 
catalyst employed in the present invention can be any of the well known 
platinum or rhodium catalysts which are effective for catalyzing the 
reaction between silicon-bonded vinyl groups and silicon-bonded hydrogen. 
These materials include the various finely divided elemental platinum 
catalysts, such as those described in Bailey, U.S. Pat. No. 2,970,150; the 
chloroplatinic acid catalysts described in Speier, U.S. Pat. No. 
2,823,218, the platinum-hydrocarbon complexes described in Ashby, U.S. 
Pat. No. 3,159,601 and U.S. Pat. No. 3,139,662, the platinum alcoholate 
catalysts disclosed in Lamoreaux, U.S. Pat. No. 3,220,972, as well as the 
platinum and rhodium catalysts described in the earlier referenced U.S. 
Pat. Nos. 3,922,443; 3,936,581; 3,928,629; 3,900,617 and 4,071,644. Use of 
inhibited catalysts is strongly preferred, and often may be essential for 
good shelf-life. Regardless of the type of platinum or rhodium catalyst 
employed, the catalyst is used in an amount sufficient to provide from 
about 10.sup.3 to 10.sup.6 gram atoms of metal per mole of silicon-bonded 
vinyl groups in the composition. On another basis, a useful range of 
catalyst will provide one metal atom for each 100 to 1,000,000 
silicon-bonded vinyl groups in the vinyl chainstopped polysiloxane. 
Preferably, the platinum or rhodium catalyst will be an inhibited catalyst 
present in an amount sufficient to provide from 5 to 500 parts per million 
or more of platinum or rhodium based on the weight of vinyl chainstopped 
polyorganosiloxane component. More preferably an inhibited platinum 
catalyst will be present in the amount sufficient to provide from about 25 
to 50 parts per million of platinum based on the weight of 
polyorganosiloxane component. The catalyst may be added to the formulation 
at any stage in the preparation of the printing ink or varnish. If the 
formulation already contains the organohydrogenpolysiloxane curing agent, 
it may be desirable to withhold the addition of catalyst until shortly 
before the ink or varnish is to be used, since earlier addition may 
significantly shorten the shelf-life of the printing ink or varnish. When 
the addition is withheld until shortly before use, it is convenient to add 
the catalyst as a solution or dispersion of catalyst in an inert solvent 
or in a portion of vinyl chainstopped polysiloxane which conveniently may 
be a portion of the vinyl chainstopped polysiloxane used in the 
formulation. 
The compositions which contain only silanol chainstopped polysiloxanes may 
be cured using the platinum catalysts described above or more preferably 
with 0.1-5% or more by weight as metal of transition metals such as zinc, 
manganese, zirconium, cobalt or nickel in the form of organic soluble 
salts (usually organic carboxylates). Suitable compounds include the 
neodecanaote, naphthenate, octoate and tallate salts of the above 
elements, commonly available as catalysts and as driers for paints and 
printing inks. The corresponding salts of transition metals such as iron 
and tin are not well suited for the high solids systems of this invention 
because they are so active that premature curing occurs. Other transition 
metal salts such as those of the rare earth metals, chromium and copper 
are not active enough to be useful at practical concentrations. 
When preparing a printing ink or varnish which includes predominantly 
hydroxyl chainstopped polysiloxane components practical considerations of 
shelf-life usually make it desirable to withhold the addition of catalyst 
until as close to the time of use as is practicable. Solutions or 
dispersions of catalyst in an inert solvent are particularly convenient to 
use, and they may be mixed with the ink or varnish formulation by merely 
stirring the desired amount into the formulation. The choice and amounts 
of catalyt used are governed by the end use of the formulation, its 
desired pot-life and the cure time utilized. 
The following are examples of the compositions and processes of the present 
invention. They are illustrative and the claims are not to be construed as 
limited thereby. 
All parts are by weight unless specified otherwise. 
Certain terms are used in the Examples as follows: 
"PDMS" is polydimethylsiloxane 
"MO" is hydroxyl chainstopped organopolysiloxane resin 
"vinyl MQ" is vinyl chainstopped organopolysiloxane resin 
"cstk" is centistoke, and may be used interchangeably with centipoise for 
PDMS fluids 
"ppm" is parts per million 
"rpm" is revolutions per minute 
"tack" is expressed in gram-meters

EXAMPLE I 
A vehicle suitable for formulation into a printing varnish for use as a top 
coat or release coating was prepared as follows: 
A solution of 18 parts by weight of a high molecular weight pendant vinyl 
polydimethylsiloxane gum (General Electric SE-33) in 82 parts of a 425 
centistoke vinyl chainstopped polydimethylsiloxane (General Electric 
SS-4300 from which inhibitor was omitted) was prepared by mixing in a 
Baker-Perkins mixer. This solution "A" exhibited a viscosity of about 
92,000 centistokes. 
Forty-one parts of a 60% solution of hydroxyl chainstopped 
organopolysiloxane (MQ resin) in toluene (General Electric SR-545) was 
mixed with 24.7 parts of a 425 centistoke vinyl chainstopped 
polydimethylsiloxane (General Electric SS-4310), 17.8 parts of a 39% 
solution of vinyl MQ resin in vinyl chainsstopped polydimethylsiloxane 
(General Electric SS-4305), and 16.3 parts of solution "A". This mixture 
was heated to strip off the toluene solvent, to yield 83.4 parts of 
vehicle "B". 
The vehicle "B" was formulated into a printing varnish by adding 2.9 parts 
of a Fischer-Tropsch wax (Shamrock Chemical S-379 H), 2.9 parts fumed 
silica (Cab-O-Sil HS-5, Cabot Corporation) and 3.2 parts tetrabutyl 
titanate (a dispersant for the fumed silica) to 91 parts of vehicle "B". 
The mixture was homogenized on a three-roll mill. This mixture was tested 
on the Inkometer at 1200 rpm. The tack was 17.0 after one minute. The 
varnish was completed by the addition with stirring of 5% by weight of 
polymethylhydrogensiloxane (General Electric 4300c). The complete varnish 
exhibited a tack of 14.0 after 1 minute and 13.0 after 2 minutes. 
EXAMPLE II 
A suitable vehicle for a pigmented coating or ink consists by weight, 
essentially of approximately: 
______________________________________ 
55% to 88% chainstopped polysiloxane 
12% to 45% an MQ polymethylsiloxane resin solution 
in toluene(on a dry basis). 
______________________________________ 
Preferably when vinyl chainstopped dimethylpolysiloxane (G.E. 4300) is 
employed with polymethylsiloxane MQ-vinyl modified resin solution (G.E. 
4305), they appear in a ratio of about 3:1 to 2:1 by weight 4300 to 4305 
but any ratio or even pure 4300 or pure 4305 may be employed. 
The chainstopped polysiloxane and the MQ resin solution in toluene is mixed 
on a solution or wet basis in amounts, by weight, of approximately 20% to 
75% of the said solution, which is approximately 40% toluene, with the 
balance chainstopped polysiloxane. The mixture is rapidly agitated and 
heated to drive-off the toluene. As a practical matter, the two 
constituents can be gradually mixed while the toluene is drawn off but at 
a rate sufficiently slow that the said MQ resin remains in the liquid 
state, it being solubilized in the chainstopped polysiloxane. 
The vehicle includes the catalyst and catalyst retardant if needed. 
A specific formulation was prepared as follows: 
______________________________________ 
60% MQ resin in toluene (G.E. SR-545) 
1815 grams 
39% vinyl MQ resin in 425 cstk. vinyl 
1869 grams 
chainstopped PDMS containing inhibited 
platinum catalyst (G.E. SS-4305) 
A material similar to solution A of Example I, 
723 grams 
but prepared using an inhibited 450 cstk. 
vinyl chainstopped PDMS (G.E. 4310) 
______________________________________ 
This mixture was heated with rapid agitation to drive off the toluene to 
yield about 3680 grams of vehicle. 
EXAMPLE III 
A blue pigmented, coating or ink formulation was prepared as follows: 
______________________________________ 
Product of Example II 3338 grams 
blue pigment (Uhlich #0500) 
711 grams 
Fischer-Tropsch wax (Shamrock S-379 H) 
137 grams 
tetrabutyl titanate (dispersant) 
192 grams 
39% vinyl MQ resin in vinyl chainstopped 
547 grams 
PDMS containing platinum catalyst 
(G.E. SS-4305 from which inhibitor was 
omitted) 
Solution A of Example I 547 grams 
425 cstk. vinyl chainstopped PDMS 
140 grams 
(G.E. SS-4300 from which inhibitor 
was omitted) 
TOTAL 5612 grams 
______________________________________ 
This mixture was homogenized on a three-roll mill. Shortly before use 6% by 
weight of polymethylhydrogen polysiloxane (G.E. 4300 C) was added as 
crosslinker. The formulation was tested on the Inkometer at 1200 rpm. The 
tack was 18.0 after 20 seconds, 17.8 after 60 seconds, and 17.0 after 120 
seconds. Because an uninhibited catalyst was used, the shelf- or pot-life 
was about three hours. 
EXAMPLE IV 
The product of Example III was used on a commercial five-color, web-fed 
perfecting press to print offset and lithocoated papers from a pictorial 
plate at speeds of about 600 fpm. The press was equipped with a 12 foot 
hot air tunnel which was adjusted for a control reading of 
385.degree.-415.degree. F. A sheeter at the end of the tunnel cut the 
product into sheets. The finished product showed clear definition of all 
the fine details of the plate, good depth of color, and generally met all 
requirements for a commercially acceptable print. However, at the printing 
speed selected there was more misting than would be commercially 
desirable. 
For a portion of the print test, the paper feed was rearranged so that the 
paper passed between the printing plate and the blanket, creating a direct 
lithographic ("di-litho") printing system. Circumstantially, a reverse 
image was printed, but the results otherwise were of commercial quality. 
If a negative plate had been employed, a normal positive print would have 
been obtained. 
A similar preparation using a black pigment which omitted the MQ resin and 
the wax of the above formulation also performed satisfactorily yielding 
clean, sharp prints of a commercial quality. However, because no MQ resin 
was included in the formula, the prints chalked or dusted. This shows that 
for pigmented systems it may be necessary to include resin for optimum 
pigment adhesion. 
EXAMPLE V 
The product of Example I was used on the same five-color press employed in 
Example IV under the same operating conditions using a solid-color plate 
having about the same image size as the pictorial plate used in Example 
IV. A sharply defined image was obtained and the coating was fully cured. 
In another experiment, the product of Example III was fed to the press from 
the first ink station to print the pictorial image, and the product of 
Example I from the second ink station to print the solid image to make a 
wet-on-wet print. After curing in the tunnel, top-coated prints were 
obtained which had good definition, perfect registration, and met all 
requirements for a commercial product. 
EXAMPLE VI 
A series of organic-soluble transition metal compounds was evaluated for 
catalytic activity in the reaction of hydroxyl chainstopped PDMS with 
polymethylhydrogen siloxane. A mixture of 100 parts 30,000 cstk. PDMS with 
10 parts polymethylhydrogensiloxane (General Electric 4300 c) was 
prepared. Sufficient transition metal solution to yield the concentration 
shown below was added to an aliquot of the polysiloxane mixture with 
stirring. A portion was withdrawn and used to prepare a drawdown on 
release paper. The drawdown was placed in a forced air oven at 400.degree. 
F. for the time indicated. At the end of that time the drawdown was 
removed from the oven and allowed to cool. "Scotch" tape (#610) was 
applied to the drawdown. The "Scotch" tape was then removed, applied to a 
piece of untreated paper, and then stripped from the untreated paper. If 
the "Scotch" tape peeled firmly, it indicated that the drawdown had not 
cured sufficiently to prevent migration of material from the drawdown to 
the tape. If the "Scotch" tape removed fibers from the untreated paper, 
the cure was judged complete. 
The catalyzed mixtures were tested for pot-life by allowing them to stand 
at room temperature and examining them from time to time for evidence of 
gelling (excessive thickening). 
All of the transition metal compound solutions were obtained from Mooney 
Chemicals, Inc. The results are shown in the following Table III: 
TABLE III 
__________________________________________________________________________ 
% Metal 
Cure Degree of 
Compound in Mixture 
Time Cure Pot-life 
__________________________________________________________________________ 
"CEM ALL" copper 
0.24 2 min. 
none catalyst 
precipitated 
0.24 30 
sec. 
none 
cobalt neodecanoate 
0.24 20 
sec. 
complete 
gelled within 
15 hr. 
0.24 15 
sec. 
complete 
manganese octoate 
0.24 20 
sec. 
complete 
at least 15 hr. 
rare earth octoate 
0.24 1 min. 
none unreactive 
chromium octoate 
0.16 1 min. 
poor gelled after 
8 hr. 
0.24 1 min. 
poor 
nickel octoate 
0.16 not tested at least 
24 hr. 
0.24 30 
sec. 
none 
0.36 30 
sec. 
questionable 
0.48 30 
sec. 
complete 
at least 
24 hr. 
zinc octoate 
0.36 30 
sec. 
complete 
at least 
23 hr. 
0.24 30 
sec. 
complete 
zirconium octoate 
0.24 35 
sec. 
complete 
at least 
10 hr. 
iron naphthenate 
0.24 not tested gelled within 
2 hr. 
0.12 30 
sec. 
no cure gelled within 
1 hr. 
dibutyltin dilaurate 
gelled while mixing 
__________________________________________________________________________ 
These tests indicate that nickel and zinc catalysts tested afford a good 
combination of cure speed and shelf-life. The cobalt, manganese and 
zirconium catalysts afford good cure speeds but somewhat shorter 
shelf-lives. Copper and chromium are less useful, while rare earths are 
inactive. The iron and tin catalysts tested were too reactive to be 
useful. 
Example VII 
A blue ink suitable for use in lithographic or offset printing was prepared 
as follows: 
A mixture of: 
______________________________________ 
39% solution of vinyl MQ resin dissolved 
46 parts 
in 30,000 cstk. vinyl chainstopped 
PDMS (viscosity 29,250 cstk.) 
34% phthaloblue pigment (Magruder Color Co.) 
40 parts 
dispersed in another portion of the 
above solution in a Baker-Perkins mixer, 
and the expelled water decanted 
inhibited platinum catalyst (500 ppm) 
10 parts 
in 30,000 cstk. vinyl chainstopped PDMS 
tetraoctyl titanate (dispersant) 
2.5 parts 
powdered fluorocarbon resin (Shamrock SST-2) 
1.5 parts 
______________________________________ 
was homogenized on a three-roll mill. The product misted slightly on the 
Inkometer at 2000 rpm, but not all at 1200 rpm. At 1200 rpm the tack was 
13.0 after one minute and 12.6 after five minutes. The Laray viscosity at 
2500 sec..sup.-1 and 25.degree. C. was 126, the yield stress 3369 
dynes/cm..sup.2 
Nine parts polymethylhydrogensiloxane (G.E. 4300 c) were stirred into the 
above product and the fully formulated ink was tested on a "Little Joe" 
two-color proofing press (made by "Little Joe" Color Swatcher, Inc. 
Somerville, NJ), using a solid print plate. The prints were cured in a 
forced air oven at 400.degree. F. for thirty seconds. Excellent prints 
with good definition and high resistance to chalking were obtained. 
EXAMPLE VIII 
A clear varnish suitable for use in lithographic or offset printing was 
prepared as follows. 
A mixture of: 
______________________________________ 
30,000 cstk. vinyl chainstopped PDMS 
100 parts 
fumed silica (Cab-O-Sil HS-5) 
2 parts 
was homogenized in a Baker-Perkins 
mixer, and processed on a three- 
roll mill. Then 
polymethylhydrogen siloxane 
5 parts 
inhibited platinum catalyst 
25 ppm pt 
______________________________________ 
were added. A drawdown of the completed varnish cured in 30 seconds at 
400.degree. F. The varnish misted very slightly at 2000 rpm, and not at 
all at 1200 rpm. The Inkometer readings at 1200 rpm were; 1 min. 11.4, 2 
min. 11.2, 3 min. 11.0, 4 min. 10.8, and 5 min. 10.8. The Laray viscosity 
at 25.degree. C. and 2500 sec..sup.-1 was 136 poise, the yield stress was 
3690 dynes/cm..sup.2 
The varnish was printed using a solid-image plate on the "Little Joe" press 
used in Example VI using the same conditions. Excellent prints were 
obtained. 
A blue ink of this invention and the varnish of this Example were also 
printed wet-on-wet on the "Little Joe". Excellent registration of the 
solid varnish image on top of the blue picture was obtained, and the 
printing product met all commercial requirements. 
EXAMPLE IX 
A clear varnish suitable for use in lithographic or offset printing was 
prepared as follows. 
______________________________________ 
30,000 cstk. silanol chainstopped PDMS 
100 parts 
polymethylhydrogensiloxane 
(Gen. Electric SS-4300 c) 
5 parts 
zinc octoate (18% as zinc) 
2 parts 
in mineral spirits 
______________________________________ 
was mixed by stirring. The resulting varnish was drawndown and cured in one 
minute at 400.degree. F. It had a shelf-life in excess of 24 hours. 
The Inkometer readings at 1200 rpm were: 1 min. 12.2, 2 min. 12.2, 3 min. 
12.0, 4 min. 11.8, and 5 min. 11.6 There was no misting, but slight 
buildup and spitting, which indicated that a press speed below about 900 
feet/min. would be the maximum which would give satisfactory results. 
The Laray viscosity was 136 poise, and the yield stress 3974 
dynes/cm..sup.2 at 2500 sec..sup.-1 and 25.degree. C. 
Printing this varnish as a single print was done in the same fashion as in 
Example VIII with excellent results. 
EXAMPLE X 
A red ink suitable for use in lithographic printing was prepared as 
follows. 
Fifty-seven parts of a 70% solution of MQ resin in toluene (General 
Electric SR-545) were added to sixty parts of a 30,000 centistoke hydroxyl 
(silanol) chainstopped PDMS. The resulting mixture was placed in a 
rotating vacuum flask. The flask was heated to not more than 90.degree. C. 
in a water bath and attached to a vacuum pump to remove substantially all 
of the toluene from the mixture. One hundred parts of a 40% solution of MQ 
resin in silanol chainstopped PDMS were obtained. This mixture exhibited a 
viscosity of 61,000 cstk. at 25.degree. C. The Laray viscosity was 286 
poise and the yield stress 6221 at 2500.sup.-1 sec. This material was 
further formulated as below: 
______________________________________ 
14 parts red pigment (Uhlich RD 5210 BON) 
25 parts 40% MQ in PDMS prepared above 
57.5 parts 18,000 cstk. silanol chainstopped PDMS 
1.5 parts powdered polytetrafluoroethylene 
(Shamrock SST-2) 
2.0 parts fumed silica (Cab-O-Sil HS-5) 
______________________________________ 
This mixture was processed on a three-roll mill to yield a red ink base. 
The ink was completed by stirring in 10 parts of polymethylhydrogensiloxane 
(General Electric SS-4300 c) and 2.66 parts of solution of zinc octoate 
containing 18% zinc in mineral spirits (Mooney Chemical). The complete 
formulation showed no misting on the Inkometer at 1200 and 2000 rpm. The 
tack at 1200 rpm was 9.6 at 1 minute and 9.2 at 5 minutes. The Laray 
viscosity was 165 poise at 25.degree. C. at 2500.sup.-1 sec. The yield 
stress was 4312. The Inkometer and Laray data defined the ink as 
satisfactory for use in printing. 
The shelf-life of the complete formulation was more than 24 hours. 
EXAMPLE XI 
A blue silk screen ink was prepared as follows: 
______________________________________ 
34% phthaloblue pigment in a 39% solution of 
13.5 parts 
vinyl MQ resin in a 30,000 cstk. vinyl 
chainstopped PDMS 
4% Cab-O-Sil in a 30,000 cstk. vinyl 
76.5 parts 
chainstopped PDMS 
0.05% platinum containing complex inhibited 
10.0 parts 
with 2% butyl allyl maleate in 30,000 cstk. 
vinyl chainstopped PDMS 
TOTAL 100.0 parts 
______________________________________ 
were homogenized on a three-roll mill. 
Nine parts of polymethylhydrogensiloxane were mixed into the above 
formulation by stirring. 
Samples of the ink were silk-screened on supercalendered release paper and 
Velvo C.sub.2 S paper using a 200 Monotex screen, available from Advance 
Process Supply Co., Long Island City, N.Y. The silk screen print was line 
work consisting of copy and a pictorial subject. It was fully cured at 
400.degree. F. for one minute. 
EXAMPLE XII 
A clear silk screen varnish was prepared as follows: 
______________________________________ 
30,000 centistoke vinyl chainstopped PDMS 
89 parts 
fumed silica (Cab-O-Sil HS-5) 
1 part 
platinum complex inhibited with 
10 parts 
butyl allyl maleate in 
30,000 cstk. vinyl chainstopped 
PDMS 
TOTAL 100 parts 
______________________________________ 
were homogenized on a three-roll mill. 
Five parts of polymethylhydrogensiloxane were stirred into the above 
formulation. 
Samples of the varnish were silk-screened on supercalendered release paper 
and Velco C.sub.2 S paper using silk screen of the previous Example and 
fully cured at 400.degree. F. for 45 seconds. The varnish showed good 
definition, gloss and adhesion on both papers. 
EXAMPLE XIII 
A red ink suitable for use in intaglio printing was prepared by blending 
the following mixture on a three-roll mill. 
______________________________________ 
18,000 cstk. hydroxyl chainstopped PDMS 
50 parts 
70 cstk. hydroxyl chainstopped PDMS 
28 parts 
red pigment (Uhlich RD-5210) 
15 parts 
fumed silica (Cab-O-Sil HS-5) 
5 parts 
powdered fluorocarbon resin (du Pont DLX-6000) 
1 part 
powdered fluorocarbon resin (Shamrock SST-2) 
1 part 
______________________________________ 
When the blending was completed 4.8 parts polymethylhydrogensiloxane (Gen. 
Electric 4300 C) and 4.1 parts zinc octoate solution (18% zinc, Mooney 
Chemical) were stirred into the mixture. A portion of the resulting ink 
was wiped on a N.P.I.R.I. "grind gauge" so as to fill the engraved 
division lines leaving the surface clean. A piece of paper was placed on 
the gauge and squeegeed with a rubber roller. When the paper was lifted 
off the gauge, all of the ink in the grooves had been transferred to the 
paper. The paper was then placed in a forced air oven at 400.degree. F. 
for 30 seconds. The print which resulted faithfully reproduced the image 
of the grooved grind gauge, and showed good adhesion. 
The fully formulated ink had a shelf-life of one week. 
EXAMPLE XIV 
An uncatalyzed mixture of a 30,000 centistoke vinyl-chainstopped PDMS, 2% 
Cab-O-Sil HS-5 and 5% crosslinker had a tack at 1200 rpm of 11.0 after one 
minute through four minutes, and 10.8 after five minutes. When 10% 
Magiesol 40 was added to the same mixture, the tack was 10.2 over a 
five-minute period. 
With traditional varnishes, the same reduction of tack would require only 
about 1% reducing oil.