CA1256239A - Dual cure silicone compositions - Google Patents

Abstract

60SI-896/0043p/GLL:mz NOVEL DUAL CURE SILICONE COMPOSITIONS

ABSTRACT OF THE DISCLOSURE

There is provided a method for making curable compositions containing silicon-bonded hydrogen atoms and silicon-bonded acrylate radicals, the improvement comprising adding at least one free radical type initiator and at least one precious metal or precious metal-containing hydrosilation catalyst so that crosslinking can be effected by two different mechanisms.
Curable compositions and articles made therefrom are also provided.

Description

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60SI ~96 NOVEL DUAL CURE SIL][CONE COMPOSITIONS
sackground of the Invention The present invention generally relates to compositions which are curable by two different mechanisms. More particularly, the present invention relates to compositions which cure by both a free radical photoinitiated crosslinking reaction and a platinum catalyzed thermal hydrosilation reaction.
Silicone compositions have become widely accepted as protective coatings for electronic components mounted on circuit boards. The misture resistance, thermal stability and resistivity of silicones make them ideal for this purpose. Previously developed silicone conformal coatings have been heat curable and furnished in organic solvents, however high energy costs as well as safety and environmental considerations have led to the development of such alternate technologies as ultraviolet radiation curable silicone conformal coatings.

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60SI-896/0043p/GLL:mz Both heat curable and U~curable silicone conformal coat-in~s have certain disadvantages. The use of heat curable con-formal coatings risks damaging many fragile, heat sensitive electronic components. Consequently, thermal cure cycles can be extremely long, which in turn reduces production of coated - circuit boards. On the other hand, while radiation curable silicone conformal coatings speed processing and avoid damaging the electronic components, in many instances a eomplete cure of the conformal coating is not effected due to what is called the Ushadow effect". Briefly, the shadow eff ect is caused by com-ponents mounted on circuit boards which, because they project off the surface of the board, cast shadows and thereby prevent effectiYe curing. While persons skilled in the art can over-come much of the shadow effect with mirrors, there can be crevices and the like where ultraviolet light simply cannot penetrate and thus where UY-curable compositions cannot be rured.

In view of the foregoing, the skilled artisan will appre-ciate that it is highly desirab7e to have available a composi-tion which is both UY-curable and thermally curable (either at room temperature or at elevated temperatures) in order to over-come such shortcomings.

It is also desirable that such compositions can be utili~ed in other applications, for example, as silicone release coat-ings.

Platinum catalyzed addition curable silicone compositions are well known in the art. For example, Grenoble in U.S.

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60SI-896/0043p/GLL:mz Patent No. 3,900,617 disclosed that flexible sheet ~aterial can be rendered non-adherent to surfaces which nonmally adhere thereto by coating the sheet material with a coating composi-tion formed from (1) a vinyl chainstopped polysiloxane, (2) a hydrogen-containing polysiloxane and (33 a platinum catalyst effective to cause copolymerization of (1) and (2).

Other variations of such technology are disclosed in U.S.
Patent Nos. 4,2~6,870 and 4,340,647 to Eckberg~ both of which are assigned to the same assignee as the present 1 0 invention .

Ohto et al., U.S. Patent ~o. 3,865,588, discloses photo-polymerizable compositions which contain at least one organo-polysiloxane having an unsaturated radical of the formula Rl R2 I
HC = C - C - O -Il o I5 where pl is a hydrogen atom, a phenyl radical or a halogen substituted phenyl radical and R2 is a hydrogen atom or a methyl radical. Exemplary of such radicals are the acryloxy radical, methacryloxy radical, cinnamoyloxy radical or a halo-genated cinnamoyloxy radical.

~0 In U.S. Patent No. 3,726,710 to Berger et al. there is dis-closed a composition comprising a vinyl group containing poly-organosiloxane having a sensitizer added thereto and which is curable by exposing it to high intensity ultraviGlet rays.

:' ' ' . ' ' '. - , 60SI~-8~6/0043p/GLL:mz Hatanaka et al., U.S. Patent No. 4,451,634, discloses sili-cone elastomeric compositions suitable for ultraviolet ray curing comprising (A) 100 parts by weight of a polyorganosilox-ane of the general formula (CH3)2RlSiO ~~~~~ R2 SiO ~ SiR (CH3j2 wherein Rl represents hydrogen or a monovalent radical selected from methyl, vinyl and hydroxy, R2 represents hydrogen or a substituted or unsubstituted monovalent hydrocar-bon radical, 0.02 - 49.g5% based on the total number of Rl - 10 and R groups are vinyl radicals, 0.05 - 49.98~ based on the total number of Rl and R2 groups are hydrogen, and n represents a number from 10 to 10,000; (B) 0.5 to 10 parts by ~eight of a polyorganosiloxane having the formula (R )b (CH2 = CH)a SiO 4-a-b wherein R3 i5 a substituted or unsubstituted monovalent hydrocarbon radical other than vinyl, a represents a number of 0.01 c a c 1 on average, b represents a number of 0 c b 3 on average, and a + b is a number from 1 to 3; and (C) 0.1 to 10 parts by weight of a peroxy ester of the formula wherein R4 is a substituted or unsubstituted monovalent ali-phatic radical and R5 is a substitut.ed or unsubstituted monovalent aromatic radical.

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60SI-896/D043p/GLL:rnz Eckberg et al., Cdn. Application Serial No. 469,075 riled Nov. 30, 19~49 and assigned to the same assignee as the present invention, discloses an ultraviolet radiation curable composition comprising: (A) a diorganopolysiloxane comprising units of the formula RR'SiO, wherein R is hydrogen or a Cl 8 alkyl radical and R' is hydrogen, a Cl 8 alkyl radical or a monovalent mercaptoalkoxyalkyl-functional organic radical of 2 to 20 carbon atoms, ~B) a polysiloxane consisting of from 0.5 to 100 mole percent of vinyl functional siloxane units of the formula (CH2 = CH)Rn SiO(3 n)/2~ where R is hydrogen or a Cl 8 alkyl radical and n has a value of O to 2~ inclusive~
and (C) a catalytic amount of photoinitiator~

Nowhere, however, to applicant's knowledge, is there dis-closed or suggested a silicone composition which cures by both a free radical catalyzed UY-hydrosilation reaction and platinum catalyzed hydrosilatton reaction, and thereby avoids the shortcomings of those compositions which cure by only one of the recited mechanisms.

Summary of the Invention It is one object of the present invention to provide compo-sitions which are curable by both a free radical photoinitiated crosslinking reaction and a precious metal cataly2ed hydrosila~
tion reaction.

It is another object of the present invention to provide articles such as circuit boards and the like having such compo-sitions cured thereon.

Another object of the present invention is to provide methods for making the foregoing compositions and articles.

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605I-896/0043p/GLL:mz In accordance with a preferred embodiment of the present invention there is provided a curable composition comprising:

(A) a polysiloxane having the general formula:

(I) Rl _ Si _ SiO ~ SiO 5 i T ; -J x R R R

wherein each R is an independently selected substituted or unsubstituted monovalent hydrocarbon radical haYing from 1 to 20 carbon atoms; Rl is hydrogen, a hydroxyl radical, or a substituted or unsubstituted, saturated or unsaturated hydro-carbon or hydrocarbonoxy radical having from 1 to 2Q carbon at-oms; A is an acrylate radical having the general formula:

(II) HC = C - C - 0 - R4 -R2 and R3 are, independently, hydrogen or a substituted or unsubstituted hydrocarbon radical, R4 is a divalent hydro-carbon radical having from 1 to 10 carbon atoms; x is a number such that there is from about 0.1 to about 50 mole percent acrylate-containing siloxy units, y is a number such t~at there is present from about 0 to about 50 mole percent hydrogen-containing siloxy units; and x ~ y + z is a number - ' - . ' .' ' .
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60SI-896/0043p/GLL:mz such that the viscosity of said polysiloxane is from about 25 centipoise to about 2~500,000 centipoise at 25C;

(B) a free radical type photoinitiator;

(C) a precious metal or precious metal containing hydrosi-lation catalyst;

(D) when y equals ~ero, an organohydrogenpolysiloxane, (E) optionally, an olefin-containing polysiloxane, and (F) optionally, a hydrosilation inhibitor.

Most preferably, the polysiloxane of Fonmula I includes up to about 20 mole percent alkenyl-containing siloxy units~ This is due to the fact that a precious metal catalyzed SiH addition to an acrylate radical of Formula II is very slow in comparison with an SiH addition to an alkenyl radical such as, for example, vinyl or allyl. Accordingly9 prompt thenmal curing is insured by including alkenyl radicals in the system, either as part of the polysiloxane of Formula I or as separate component (E)n The artisan can therefore appreciate that preferably the siloxane of Formula I has the general structure R ~ A ~ ~ H ~ ~ R ~ ~ R5 ~ R

Rl_ SiOJ~SiO ~U~SiO ~SiO~ S i O ~ S j R \ R J \ R J ~R ~ \2 ~ R

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60SI 896/0043p/GLL:mz where R, Rl, A, x, y and z are as previously defined, R5 is an olefinically unsaturated hydrocarbon radical, preferably vinyl, and w is a number such that there is present up to 20 mole percent alkenyl-containing siloxy units. Those of ordinary skill in the art will, of course, appreciate that there are many available variations in which to provide the silicon-bonded acrylate, hydrogen and alkenyl moieties.

Description of th nvention In its broadest aspect, the present invention involves adding both a radical type photoinitiator or photocatalyst and a precious metal or precious metal-containing hydrosilation catalyst to a curable composition having silicon-bonded hydrogen atoms and silicon-bonded acrylate radicals of the general fonmula:

HC - C - C 0 - R4 _ o where R2 and R3 are, independently, hydrogen or a substitu-ted or unsubstituted hydrocarbon radical, preferably methyl, and R4 is a divalent hydrocarbon radical having from l to lO
carbon at~ms. The si 1 icon-bonded hydrogen atoms and the silicon-bonded acrylate radicals can be on the same or differ ent polysiloxane chains. What is essential to the present invention is that, because of the presence of a photocatalyst, the silicon-bonded hydrogen atoms and siliconbonded acrylate radicals will crosslink upon exposure to ultraviolet radiation, .

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605I-896/0043p/GLL:mz _g_ and that~ because of the presence of a precious metal or precious metal-containing catalylst, the silicon-bonded hydrogen atoms and the silicon-bonded acrylate radicals or silicon-bonded alkenyl radicals will crosslink at room temperature or elevated temperatures.

~ n a preferred embodiment of the present invention there is provided a curable composition comprising:

(A) a polysiloxane having the general formula:

R~ SiO~ jo~ioJ si_Rl wherein each R is an independently selected sub~tituted or unsubstituted monovalent hydrocarbon radical having from 1 to 20 carbon atoms; Rl is hydrogen, a hydroxyl radical9 or a substituted or unsubstituted hydrocarbon or hydrocarb~no~y radical having from 1 to 20 carbon atoms; A is an acrylate radical having the general fonmula:
R~ R3 ~:
HC = C - C 0 - R4 -I
O
where R2 and R3 are~ independently, hydrogen or a substitu-ted or unsubstituted hydrocarbon radical; R4 is a divalent hydrocarbon radical having from 1 to 10 carbon atoms; x is a number such that there is present from about 0.1 to about 50 mole percent acrylate-containing siloxy units; y is a number such that there is present from about 0 to about 50 mole '.,. ~ ~, '' ' ' ' ', ': , .

~25~i23~3 60SI-896/0043p/GLL:mz percent hydrogen-containing siloxy units; and x ~ y + z is a number such that the viscosity of said polysiloxane is from about 25 centipoise to about 2,~00,000 centipoise at 25DC;

(B) a free radical type photoinitiator;

(C) a precious metal or precious metal containing hydrosi-lation catalyst;

(D) optionally, an organohydrogenpolysiloxane;

(E) optionally, an olefin-containing polysiloxane; and (F) optionally, a hydrosilation inhibitor.

In a more preferred embodiment the curable composition of the present invention includes up ~o about 20 mole percent alkenyl-containing siloxy units. Such alkenyl-containing siloxy units, which preferably are vinyl, are preferably included because a precious metal catalyzed SiH addition to an acrylate radical of Formula II is slow in comparison with an SiH addition to an alkenyl radical such as vinyl or allyl.
Hence, the inclusion of alkenyl groups insures more rapid thermal curing of the composition. The artisan will therefore appreciate that preferably the siloxane of Formula I has the structure Rl 5j ~ 5io ~ 5jO ~ 5jo ~ 5~0 ) Si - R
x R R R

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~2~6239 60SI-896/0043p/GLL:mz where R, Rl, A9 x, y and z are as previously defined, R5 is an olefinically unsaturated hydrocarbon radical, pr~ferably vinyl, and w is a number such that there is present up to 20 mole percent alkenyl-containing siloxy units. Of course, it is still within the intended scolpe of the present invention to include such alkenyl radicals on a separate polysiloxane.

It should be noted that for purposes of the present inven tion the term "hydrogen-containing siloxy units" means ~hat hydrogen is bonded directly to silicon.

Polysiloxane (A) of this invention is represented by the above Formula I, wherein the R groups can be any substituted or unsubstituted hydrocarbon radical having from l to 20 carbon atoms, for example9 alkyl radicals such as methyl~ ethyl, propyl, butyl, pentyl, hexyl, octyl and decyl, alkenyl radicals such as vinyl and allyl; cycloalkyl radicals such as cyclohexyl and cycloheptyl; aryl radicals such as phenyl;
aralkyl radicals such as beta-phenylethyl; and any of such radicals wherein a part or all of the hydrogen atoms are replaced, for example, by halogen atoms such as fluorine, chlorine or bromine; cyanoethyl radicals or 3,3,3 trifluoro-propyl radicals. From the viewpoint of availability and ease of synthesis, it is preferable that substantially all of the R
radicals be either methyl or methyl and phenyl.

The Rl radicals can be any of the foregoing R radicals and, in addition, can also be a hydrogen atom, hydroxyl radical or a hydrocarbonoxy radical having from l to 20 carbon atoms such as, for example, methoxy, ethoxy and propoxy.

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60SI-896/0043p/GLL:mz The A moieties have the general formula:

HC = C ; C - 0 - R4 Il where R2 and R3 are selected, independently, from the group consisting of hydrogen and substituted or unsubstituted hydro-carbon radicals; R4 is a divalent hydrocarbon radical having from 1 to 10 carbon atoms. Examples of organofunctional groups reprPsented by A include atryloxy, methacryloxy, cinnamoyl, and crotonate and any other organic groups which crosslink in the presence of photo or thermal generated free radicals and which include the G = C structure. Preferably, R4 is a divalent radical having from 2 to 5 carbon atoms and most preferably has

3 carbon atoms. Preferably R~ and R3 are, independently, hydrogen or a Cl 3 hydrocarbon radital.

It is not necessary that polysiloxane (A) contain silicon-bonded hydrogen atoms and silicon-bonded acrylate radicals in the same molecule. However, when y in Formula I is zero it is necessary to provide silicon-bonded hydrogen atoms in the form of a separate organohydrogenpolysiloxane as described more fully hereinbelow. The number of acrylate-containing siloxy units is generally from about 0.1 to about 50 mole percent based on the total number of siloxy units in polysiloxane (A).
The number of hydrogen-containing siloxy units must be suffi-cient to react with substantially all of the acrylate-contain-in~ siloxy units and~or substantially all of the siloxane bonded alkenyl groups. Generally, there is from about 0.1 to 50 mole pert:ent hydrogen-containing siloxy units based on the total number of siloxy units in polysiloxane (A).

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~5~ 3 605I-896/0043p/GLL:mz i Those skilled in the ~rt will be able to adjust the number of hydrogen-containing siloxy units and acrylate or alkenyl containing siloxy units to obtain a cured composition having predetermined properties.

The artisan will appreciate that the value for x can be zero in Formula I provided that in such case R will be an acrylate radical of Formula II. It is also possible to employ a mixture of polymers, for example, polymers having hydrogen only on the polymer chain and acrylate radicals in the terminal positions. Similarly, it is possible to utilize a mixture wherein hydrogen is present only at the terminal positions and acrylate radicals only on the polymer chain. Other variations will be obviDus to those of ordinary skill in the art.

As stat~d earlier, the value of y in For~ula I can be zero provided that silicon-bonded hydrogen atoms are provided from another source. When y = 0, a preferred composition has w greater than zero such that the polymer of Formula I includes acrylate and alkenyl functionality. However, it should be understood that in practicing the present invention it is merely necessary to provide silicon-bonded hydrogen atoms and silicon-bonded acrylate radicals in combination with a free radical type photoinitiator and a precious metal or precious metal-containing hydrosilation catalyst.

When the number of silicon-bonded hydrogen atoms or acrylate radicals is less than the above-said ranges, respectively, the adhering ability of the cured composition is reduced. When the number of ~hese substituents is more than the above said ranges, respectively, thermal resistance is . ~ .

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60SI-896/0043p/6LL:mz -l4-reduced or the curing rate is inadequate. When the number of silicon-bonded hydrogen atoms and silicon-bonded acrylate radicals is within the stated ranges, no fo~ming occurs-upon exposure to ultraviolet radiation due to generation of hydrogen gas and the composition is sufficiently "set" after brief exposure to UV radiation to allow the coated article to be placed elsewhere for thermal curing. Thermal curing, for purposes of the instant application, includes subjecting the composition to elevated temperatures or merely allowing the precious metal ca$alyzed hydrosilation reaction to take place at room temperature.

The number of diorganosiloxy groups present in polysiloxane (A3 is not critical and can be anywhere from zero to about 99.8 mole percent. Generally there should be sufficient dior~anosiloxy units to proYide polysiloxane (A) a viscosity of from about 25 centipoise to about 2,500,000 centipoise at 25C. It is particularly preferred that some of the R groups of polysiloxane (A) be alkenyl radicals such as vinyl. It has been found that optimum results are obtained when the number of vinyl-containing siloxy units is from about l to about lO mole percent based on the number of siloxy units in polysiloxane (A).

The artisan will appreciate that in addition to the-difunctional units illustrated in Formula I, there may also be present trifunctional siloYy units of the formula R SiOl 5, where R is as previously detined~ and/or tetrafunctional 5ilo%y units of the formula SiO~. The number of such units employed, if any, will depend upon the particular application under consideration and can readily be detenmined by one of ordinary skill in the art without undue experimentation.
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60SI 896~0043p/GLL:~z In a preferred embodiment of the present invention there is present from about 2 to about 20 mole percent acrylate-contain-ing 5iloxy units, from about 2 to about 20 mole percent hydrogen-containing siloxy units, ~rom about 2 to about 10 mole percent vinyl-containing siloxy units, and the viscosity of polysiloxane (A) is from about 100 centipoise to about ~000 centipoise at 25~C.

Free radical type photoinitiators or photocatalysts are well known in the art. Photoinitiator (B) of the present lû invention can be any known silicone compatible free radical type photoinitiator effective fDr promoting crosslinking between unsaturated silicon-bonded groups sueh as acrylate and vinyl and silicon-bonded hydrogen atoms.

Especially preferred photoinitiators for promoting cross-linking between unsaturated groups and SiH groups are disclosed by Eckberg et al,-in Canadian Patent Application Serial Number 469,075 which application was filed on -November 30,-1984-and which application is assigned to the same assignee as the present invention. Briefly, Eckberg et al. disclose that combinations of certain perbenzoate esters having the general formula:
o (III) R5 - - - IC ~ Z

where R5 is a monovalent alkyl or aryl group and Z is hydrogen, alkyl, halogen, nitro, amino, or amido and .
-- ~ ' ~ ,'" . ' 60SI-896/0043p/GLL:mz pho~osensitizers such as benzophenone photocatalyze the additinn reaction of SiH group!i and unsaturated groups bonded to siloxy units. The nature oF the Z substituent will affect the stability of the peroxy bond; an electron-poor substituent stabilizing the peroxy bond and an electron rich substituent making the peroxy bond more reactive. These perbenzoate esters may be synthesized in known ways, such as by reacting benzoyl halides with hydroperoxides (see, e.g. the descriptions in Blomquist and Berstein, J. Amer. Chem. Soc., 73, ~546 (1951)).
Preferred perben20ate esters include t-butylperbenzoate and its para-substitu~ed derivatives, t-butylper-p-nitrobenzoate, t-butylper-p-methoxybenzoate, t~butylper-p-methylben20ate and t-butylper-p-chlorobenzoate.

The amDunt of photoinitiator employed is not critical, so long as proper crosslinking is achieved. As with any catalyst, it is preferable to use the smallest effective amount possible. 6enerally ~ he amount of photoinitiator can be anywhere from about to about 10 parts by weight based on 100 parts by weight of polysiloxane (A~. More preferably~ the photocatalyst level is from about 1 to about 5 parts by weight per 100 parts by weight polysiloxane (A).

Other photoinitiators, whose suitability for use in a particular situation can easily be ascertained by the artisan, are described in U.S~ Patent Nos. 3,759,807, 3,968i305, 3,966,573, 4,113,592, 4,131,529, 4,310,600, and 4,348,462.
Diethoxyacetophenone is an examplP of a silicone soluble photo-initiator particularly useful in photocatalyzing crosslinking of acryloxy-containing silicones.

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60SI-896/0043p/GLL:mz Component (C) can be any precious metal or pr~cious metal-containing catalyst effective for initiating a thenmal hydrosilation cure reaction. Especially included are all of the well known platinum and rhodium catalysts which are effective for catalyzing tne addition reaction between silicon-bonded hydrogen atoms and silicon-bonded olefinic groups. Examples of platinum or platinum-containing complexes, which are the most preferred of the precious metal catalysts, include platinum metal on charcoal, the platinum hydrocarbon complexes described in U.S. Patent Nos. 3,159,601 and 3,159,662 to Ashby, the platinum alcoholate catalysts described in U.S.
Patent No. 3,220,970 to Lamoreaux, the platinum complexes described in U.S. Patent No. 3,814,730 to Karstedt, and the platinum chloride-olefin complexes described in United States-Patent Number 3,814,730 to Karstedtr and the platinum chloride-olefin complexes described in-~nited States Patent No. 3,516,946 to M~dic The most preferred catalyst for facilitating the thermal hydrosilation reaction are the Ashby catalysts described in U.S. Patent Nos. 3,159,501 and 3,159,662. Other platinum metal and platinum-containing catalysts which can be employed in the present invention are well known to those skilled in the art.

~ydrosilation catalysts other than those based on platinum may also be used to effect thenmal curing. For example, complexes of the metals rhodium, ruthenium1 palladium, osmium and irridium can be utilized. Of the non-platinum based catalysts, those based on rhodium are most preferred. The preparation and description of preferred rhodium catalysts are set forth in U.S. Patent No. 4,347,346 to Eckberg.

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- - . -9L 2~6~2~3 60SI-896/0043p/GLL:mz As with photoinitiator (B), the amount of precious metal or precious-metal containing catalyst (C) is not critical so long as proper crosslinking is achieved. Typically, the amount of precious metal or precious metal-containing catalyst is from about 10 to about 500 ppm as metal atoms based on polysiloxane (A) If the optional organohydrogenpolysiloxane (D) and vinyl containing polysiloxane (E) are included it may be desirable to utilize a greater amount of catalyst (C). Of course, the skilled artisan can determine the appropriate amount of catalysts (8) and (C) without undue experimentation. The artisan will also appreciate that it is within the scope of the present invention to employ mixtures of the various photo-catalysts and precious metal or precious metal-containing catalysts.

Organohydrogensiloxane (D)-can be either a fluid, resin or mixture thereof which those skilled in the art utilize as a crosslinking agent in addition curable silicone systems.
Particularly useful organohydrogenpolysiloxanes for practieing the present invention are trimethyl chainstopped polymethylhy-drogensiloxane fluids having from approximately lOX to 100~ SiH
groups, any remaining groups being dimethylsiloxy units, and having a viscosity in the range from about 10 to about 1000 centipoise at 25~C. However, any organohydrogenpolysiloxane having the general fonmula (IV) RaHb SiO 4 a b is within the srope of the present invention. Such organohy-drogenpolysiloxanes are well known in the art, fcr example, as , described in U.S. Patent Nos. 3,344,111 an~ 3,436,366.

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2 ~9 60SI-896/0043p/GLL:mz Among the radicals included within R of Forrnula III are alkyl such as methyl, ethyl and propyl; cycloalkyl such as cyclopentyl, cyclohexyl and cycloheptyl, aryl such as phenyl, naphthyl, tolyl and xylyl, aral kyl such as phenylethyl and phenylpropyl; and substituted radicals of any of the fore-going, for example, halogen substituted and cyanoalkyl substituted.

Other organohydrogenpolysiloxane fluids are well known in the art and are described in greater detail in United States Patent Number which issued to Grenoble and --Eckberg.
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It is possible to utilize an organohydrogenpolysiloxane resin in place of, or in addition to, the organohydrogenpoly-siloxane fluid. Such organohydrogenpolysiloxane resins are aiso well known in the art, for example, as described in Unlted States Patent Number 4,041,010 to Jeram. Briefly-, organohydrogenpolysiloxane resins comprise either . ._-R
H _ li0.5 units and SiO2 units, where the R

ratio of R ~ H units to SiO2 units ranges from 1.0 to 2.7 and where R is as previously defined, or .

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60SI-896/0043p/GLL:mz R
H - 5iO0 5units, R2SiO units, and SiO~ units, R

where the ratio of R + H units to SiQ2 units ranges from 1.2 to 2.0 and where R is as previously defined.

If an organohydrogenpolysilloxane is employed, it can be employed in any amount to obtain specific properties in the cured product. Generally, it should be utilized in a range of from about 1.0 parts by weight to about 10 parts by weight per 100 parts by weight of polysiloxane (A). In a preferred embodiment there is utilized a mixture of organohydrogenpoly-siloxane fluid and organohydrogenpolysiloxane resin. While no particular ratio o~ fluid to resin is requireJ, a~ratio of from a~out 0.1 parts fluid per part resin on a weight basis to about 10 parts fluid per part resin on a weight basis has been found to provi~e compositions suitable for use as a coating composition.

Another optional component for practicing the instant invention is olefin~containing polydiorganosiloxane (E). As with organohydrogenpolysiloxane (D), olefin-containing poly-diorganosiluxane (E) can be either a fluid or a resin and preferably is a mixture thereof. Most preferably component (E) is a vinyl-containing polydiorganosiloxane. A typical vinyl-containing polydiorganosiloxane fluid has the formula:
~ R ~ ~R5 ~
(V) H2C = CH ~ SiO t 51 ~ sIi ~ 1 CH ~ CH2 . . ' , . , .- .
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60SI-896/~043p/GLL:mz wherein R is as previously defined; R5 is a radical having alkenyl unsaturation, preferably vinyl; and a and b are positive integers such that the Yinyl chainstopped polysiloxane has up to about 20% by weight RS groups. The viscosity of such a polysiloxane ranges from about 50 to about 100,000 centipoise at 2~C. Such polysiloxane fluids are also described in U.S. Patent No. 4,448,813 to Grenoble and Eckberg.

Vinyl-containing silicone resins are also known in the art, for example, as described in U.S. Patent No. 4,041,010 to Jeram. 6enerally these resins are selected from the class consisting of resins having YiR2SiOo 5 units and SiO2 units where the ratio of hydrocarbon substituents to Si varies from 0.8 to 2.7 and resins having ViR2SiOo 5 units, R2SiO
units and SiQ2 units where the ratio of hydrocarbon substituents to Si varies from 0.8 to 2.4. For more specific details relating to such resins and their preparation the reader is referred to the cited Jeram patent No. 4,041,010.

If a vinyl-containing polysiloxane is employed in the present invention it can be utilized in any amount. As the artisan will appreciate, including precious metal or precious metal-containing catalyst (C) in the same package as polysilox-ane (A) will result in product gelation or curing before it reaches the consumer provided polysiloxane (A) includes silicon-bonded hydrogen atoms. Accordingly, in a commercial environment, olefin-containing polysiloxane (E) serves primarily as a carrier of precious metal catalyst (C). Thus, in one embodiment of the present invention, the curable composition is provided in two or more packages; one package including therein the alkenyl-containing polysiloxane, precious .

3L 2~ 2 3~i 60SI-896/0043p/GLL:mz metal catalyst and optional inhibitor, and the other package containing the remaining in~redients. Such two package systems are well known in the art. A particularly preferred multi-component packaging system can be adapted from the teachings of 6renoble and Eckberg in U.S. Patent No. 4,448,815.

It is also contemplated that: a hydrosilation inhibitor (F) can be included in the curable composition of the present invention in order to extend the work life of the composition.
One example of a suitable inhibitor is disclosed in U.S. Patent IO No. 4,256,870 wherein Eckberg teaches the use of organic esters of maleic acid to selectively retard the thermal addition cure reaction.

Eckberg discloses in U.S. Patent No. 4,262,107 that other suitable inhibitor compounds are certain acetylenic compounds, olefinic carboxylic acid esters of aliphatic alcohols such as vinyl acetate, alkenyl isocyanurates and mixtures thereof.

In United States Patent~No. 4,476rl66 which issue October 9, 19-84 ., and assigned to the same assignee as the present invention, Eckberg discloses that a blend of a ~icar-boxylic acid ester having carbon to carbon unsaturation and an ole,inic carboxylic acid ester of an aliphatic alcohol is particularly effective as an inhibitor.
. . . , -- .
In another aspect of -the present invention there are provided methods for making the curable compositions of the present invention and methods for making articles having the compositions cured thereon.

.
, -- : : - - . .
.~ .
' ' ' ' ' 3~
60SI 896/0043p/GLL:mz The curable compositions are prepared merely by combining the various ingredients or by mixing the pac~ages in which the various ingredients were provided. The articles of ~he present invention are prepared by apl~lying such composition to a substrate such as a circuit board if it is to be used as a confonmal coating, or to a fllexible sheet material such as Mylar ~ or paper if it is to be used as a release coating, thereafter exposing the coated substrate to ultraviolet radia-tion sufficient to set the composition, and finally allowing curing to be completed by exposing the article to either room temperature or elevated temperature. Of course, the higher the temperature, the more rapidly complete cure will take place.

In order that those skilled in the art might be better able to practice the present invention, the following examples are given by way of illustration and not by way of limitation. All parts are by weight unless otherwise indicated.

Example 1 To a one liter flask there was added 15~ grams dimethyldi-ch10rosilane (1.2 moles) and 42 grams methylvinyldichlorosilane (0.3 mole). These monomers were then hydrolyzed with 24 grams water (1.33 moles) dispersed in 33 grams acetone oYer a 75 minute period at 18 - 24~C. The reaction mixture was main-tained at 20C for 40 minutes and at 40C for 40 minutes before beiny stripped under 33 mm vacuum at 105C for 15 minutes to provide 107 grams of a Cl-stopped linear copolymer. The linear chloro-stopped species was then treated with 114 grams methylmethacryloxypropyldichlorosilane (0.47 moles), ~3 grams ,- ~

.~ ' . ' ' ` ' .

~j6;23~
60SI-8g6/0043p/GLL :mz ~24-methyltrichlorosilane (0,36 molles), and 54 grams of a 70D
centipoise silanol endstopped linear d~methylpolysiloxane fluid, and hydrolyzed with 130 grams water in a reaction medium of l:l toluene:aretone at 54-6~C. This resulted in 264 ~rams of a clear 392 centipoise fluid designated polysiloxane (Al). End group analysis revealed 2.0X hydroxyl functionality as OH. 150 grams of this fluid (approximately 0.18 mo1es OH) were then hydrolyzed with ~8.3 grams trimethylchlorosilane (0.35 mole) in excess water at 60C.
IO Solvent and byproduct (Me3 SiOo 5)2 were removed in vacuo to furnish a final product designated polysiloxane (A2) having a viscosity of about l75 centipoise at ~5C and a hydroxyl content of about 0.l2%.

These polysiloxanes (e.g. Al and A2) were evaluated for UV cure performance. Comparative properties of interest are set forth in Table I.

Tabl e Visc., l~a~i~u~ Co~pat{billty~
Co~ tion ,~ ~t~ ~ ~'~
2 A12 392 2.0 1.5 ~/8 Incompatlble A 175 0.12 1.0 ~/s Preely ~i~cible in propor~ion~
* 2 ~il c~ating on supercalendared kraft (SCK) stock, 400- watts per square inch UV power, nitrogen atmosphere, 4X diethoxyacetophenone (DEAP) photoinitiator. nCure~ is defined as smear-free coating.
** MDHM = methylhydrogenpolysiloxane having a viscosity of about 25 cps. at 25C; x 'Z'20.

-, - , , ' :.

, Ei 23~

60SI-~96/0043ptGLL:mz Thermal cure studies were then conducted on the following blends:

a.) 100 parts polysiloxane (A2) + 4 parts MDHM +
100 ppm Pt-containing catalyst as Pt.

b.) 90 parts polysiloxane (A2) ~ 10 parts MDHM +
100 ppm Pt-containing catalyst at Pt.

c.) 90 parts polysiloxane (A2) + 10 parts MDXHM + 50 ppm Pt-containing catalyst at Pt.

The results of such thermal cure studies are set forth in Table II.

Table II
.

~ini~ual 15D ~C
Blend A~ e a SO ~ec. 3.5 ~our~
b lS ~ec. 20 ~inutes c 15 ~cO 35 ninutes 1 ~ 3at~ng~ ~n ~C~ stoc~. Cure defined as above.

, ,. ., . : .

- -6~
60SI-896/0043p/GLL:mz Addition of 4X DEAP to blend (c) enabled UV cure comparable to polysiloxane (A2) despite the presence of 10 percent methylhydrogenpolysiloxane crosslinking agent. Blend (c) was then applied in a layer 5 mil thick to a stainless steel Q
panel and passed through a UV processor at 50 feet per minute under a nitrogen atmosphere and 400 watts per square inch lamp power. Areas kept in shadow were obserYed to cure to a non-tacky surface after being left undisturbed at 25C in the dark for 20 hours. Exposed areas were fully UV-cured immediately on exposure. This example illustrates the most preferred embodi-ment of the present invention.

The preferred~packaging of such a dual cure composition would be to place in package A the UV curable polymer9 photo;
initiaLor and precious metal or precious metal-containing catalyst, and to place in package B the organohydrogenpoly~
siloxane crosslinking agent. A small amount of inhibitor such as butylallylmaleate or vinylacetate may also be included in package A.
:
Example 2 In this example 25 grams of a 20 cps methylhydrogenpoly-siloxane fluid, 30 grams sym-tetramethyltetravinylcyclotetra-siloxane and 445 grams octamethylcyclotetrasiloxane were equil-ibrated under nitrogen at 83C for 18.5 hours with 5 grams Filtrol 20 acid clay catalyst to furnish a 2000 centipoise fluid having the general fonmula MDH Dyi DzM

.
: . . ' ' . .

:, .' ~ ~ -, ~L2~;6:239 60SI-B96/~043p/GLL:mz where D is a dimethylsiloxy unit, DH is 3 methylhydrogen-siloxy unit and DVi is a methylvinyl silsxy unit. 100 grams of a methacrylate ~unctional silane having the fonmula Cl O
3 Sl (CH2)3 C l CH2 Cl CH3 were added to the equilibrate as well as 0.05 gram di-t-butyl-hydroquinone. The mixture was agitated for one hour at 83C
and then filtered to remove the heterogeneGus equilibration catalyst. The fluid so obtained was a 70 centipoise fluid having 3.22 weight percent hydrolyzable chloride as chain-stopper. 100 grams of such 70 cps. chloro-stopped fluid were then added to a 500 ml flask (0.0882 mole Cl) along with 50 ~rams toluene. The solution was agitated at 39C as 1.56 grams water (0.0867 mole) dissolved in 20 grams acetone were slowly added over a ten minute period. The temperature was maintained a~ 30-35C for thirty minutes following the water addition.
Twenty five grams water were then added to consume any remain-ing hydroly~able chloride. The product mixture was transferred to a separatory funnel, the aqueous layer discarded, and the organic layer washed with 100 ml of 5X aqueous sodium bicarbon-ate. 85 grams of a 700 centipoise fluid designated polysilox-ane (A3) were obtained a~ter 120C, 15 mm vacuum stripping, and having the fonmula -- . . . .

- , ~ . .
: . :. . ., . -60SI-896/0043p/GLL:mz -?8-HOtSiOt SiO--~ SiO ~ SiO 1 SiO

\ (CH2)3 ~ CH3 / ~ CH3 Jb \CH3 ~ c(CH2)3 J
O O
C = O C = O
CH C
3 . CH3 - C

~H2 CH2 where the molecular weight is about 11,000, and where b is approximately equal to c which is approximately equal to 1/8 a.

Ultraviolet cure characteristics were determined by preparing 2 coating bath oonsisting of 10 parts polymer, 2.5 parts benzophenone and 4 parts diethoxyacetophenone. Cure studies were conducted under 400 watts per square inch focused total UV power in a PPG model 1202 QC Processor. The results are set ~orth in Table III.

.. . . .

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.
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.

3L 2~;S 2 3~

60SI-896/0043p/GLL:mz Ta~le III

Coat~n~ Cure Substr~te Th7ckness Atmos~here Line 5peed coating; smears with press~re.
SC~ Thin fi7m Air 20 fp~ ~ n SCK ! mil N2 loo fpm Exee~lent cure to . sme~r- ree coating; oood anchorage :
SCK I mi7 N2 2DQ fpm Cured to mi~rat~on-free coating; smears with ~ .
pressure PEK 4 mil N2 lO0 fpm Excellent cure t~
smear-free;~~ossy, tough ~oatin~, ~ood anchorage.
NOrES: SCK ~ 40~ream supercalendered kraft paper PEK ~ polyethylenelaminated kraft paper 'Thin film' i5 ~ 1.5 grams/meterZ

'' ' ' ' -, - , ..

~25 6~

60SI 896/0043p/GLL:mz The observation that the cured coatings do not migrate tc Scotch ~ ~610 cellophane tape suggested that the compositions of the present invention will function as release coatings.
Accordingly~ a coating ~ath was prepared ~s follows: 10 grams of the abo~e-described polysiloxane (A3), 0.25 grams benzo-phenone, and 0.4 grams diethaxyacetophenone dispersed in 50 grams acetone and ~ grams hexane. This mixture was coated onto SCK using a ~8 wire-wound rod and then cured under exposure to 400 watts/inch2 UV radiation at 100 feet per minute line speed under nitrogen. 5even miles of an aggressive SBR
adhesive (Fasson SS-l) were coated and cured onto the silicone layer, then top~coated with another layer of S~K. Two inch wide tapes were prepared and the silicone layer delaminated from the adhesive layer at a 180 angle and 400 ~eet per minute pull speed. 70 to ~0 grams force was required to separate the lamina which represents good release perfonmance.

The thenmal cure perfor~ance of polysiloxane (A3) was then tested. Nine grams of polysiloxane (A3) was combined with one gram of a 400 centipoise vinyl endstopped di~ethyl-polysiloxane and 300 ppm of a platinum~containing hydrosilation catalyst (as platinum metal). The result was a clear fluid containing 30 ppm catalyst at Pt metal, Cure performance was assessed on SCK substrate at 150C. The results are provided ~ -in Table IV.

Table IY
Thickness Oven Dwell Ti~e Re~arks 1 mil 50U cured to ~ on-free, smear-free csating I mil 30~ , with slight migration, Thin fil~ 30~ cured to ~igration-free release (As defined ~bove) . .
. - , , ~
~", , :- .:
. .
, 2 3~

60SI-896/0043p/GLL:mz The foregoinQ illustrates that polysiloxane (A3) can combine both UY curing and thermial curing so as to overcome the "shadow effect" suffered by prior art compositions which utilize only UY curing. this example also illustrates that the rate of UY curing release coatings can be increased since complete cure will be effected afterwards by thermal curing.

Example 3 In this example 850 ~rams of dimethyldichlorosilane (6.6 moles), 92 grams methylhydrogendichloros~lane ~0.8 moles), and 86 grams methylvinyldichlorosilane (0.6 mole) were treated with a dispersion of 130 grams water (7.22 moles) in 180 grams - acetone by slow addition of the aqueous phase over a 150 minute period. The temperature was maintained at 16-26~C during the addition. The hydrilyzate was stripped to 100C, 40 mm vacuum to furnish 504 grams of a 120 oentipoise ~luid haYing 6.04 weight percent DH units and 0.4 weight percent ~ydrolyzable chloride (as HCl). 200 grams of this chloride-stopped fluid was cambined wi~h 2DD gr~ms of methylmethacryloxypropyldi-chlorosilane and 200 grams of a ~00 cps. silanol stopped dimethylpolysiloxane fluid in a blend of 400 ml acetone and 400 ml toluene. The mixture was then treated with 300 ml water by dropwise addition over a 7~ minute period at 4~-60C. Follow-ing hydrolysis, the product mixture ~as transferred to a separatory funnel, the aqueous layer dis~arded and the organio phase washed with 300 ml of a 5X NaHC03 solution. Stripping the organic phase of solvent and light ends at 100C, 25 mm vacuum, afforded 4~4 grams of polysiloxane (A4~. To poly~
siloxane ~A4) there was added 9.1 grams benzophenone and 18.2 grams diethoxyacetopheRone. The final produot was a 160 .

-- ;

;6Z3~

60SI~896/0043p/GLL:mz centipoise fluid having 3.0 we~ght percent DH units. It is convenient to prepare the Cl-DH DVi-D-Cl precursor fluid ;n situ, then carry out the cohydrolysis with the acrylic functional silane in the same pDt. This eliminates the need to isolatP the hydrolytically unstable chloride-stopped polydimethyl-methylhydrogen-methyl- vinylsiloxane intermediate.

In situ preparation of the chloride stopped precursor was employed to prepare polysiloxane (A5) as follows: 136 grams dimethyldichlorosilane (1.054 moles), 3S grams methylhydrogen-~` 10 dichlorosilane (0.304 mole) and 21 grams methylvinyldichloroO
silane (0.149 mole) were hydrolyzed via a one hour addition of 23.3 grams water (1.29 moles) dispersed in 32.3 grams acetone at 18-25~C. Stripping this material afforded 90 grams of a fluid containing 0.15X hydrolyzable chloride. This chloride-stopped polymer was then trPated with 150 ml toluene and 150 ml acetone, 90 grams methylmethacryloxypropyldichlorosilane, 45 grams of a silanol endstopped dimethylpolysiloxane having a viscosity of about 700 cps., and 45 grams methyltrichloro-silane. The silane solution was then hydrolyzed with 12~ ml water via addition over a period of 45 minutes at 45-58C. The resultant polysiloxane (A5) had a viscosity of about 4~0 cps.
and included 4.05% DH units (217 grams yield). To polysilox-ane (A ) there was added 4.9 grams benzophenone and 8.6 grams diethoxyacetophenone.

A third polymer, designated polysiloxane (A6), was prepared as was polysiloxane (A ) except that the reactants (85 grams Cl-DDHDVi-Cl fluid, 85 grams methylmethacrylic-dichlorosilane, 64 grams 470 cps. silanol endstopped polydimethylsiloxane and 21 grams methyltrichlorosilane3 were .~ . , .

. - " ~

... , . . . . :
-, : ,. ;. .

~25~23~3 60SI-895/0043p/GLL:mz such so as to provide 209 grams of 130 cps. product having 5.8X
DH units. To polysiloxane (A6) there was added 2 weight percent benzophenone and 4 weight percent diethoxyacetophen-one. All three of the compositions based on polysiloxane 5(A4)~ (A5) and (A6) were c~mplete one-part products for UY-cure applications. Qualitative UY cure perf~rmance was assessed as in Example 2. The results are set forth in Table V.

Table V

Th~cknes~ Atmo~Phere ~ a~
A' 2 mil N2100 fpm Cured to ~mear-free glo sy coating 200 fpm _ndercured smear~ badly Air5 fpm Cured to smear-free glossy co~tinq.
A5 2 mil N22no fpm Cured to smear-free glossy~
hard coatingO
~300 ipm Cured; slight ~e~r AiE30 fpm ~ -AS 2 mil ~100 fpm ~red to ~mear-free glo~y co~ting Il 9200 fpm ~ - some s~ear.
Air10 fpm Cured; slight ~ear .

~2~ 3 ~

~Q5I-896/0043p/GLL:mz Next a catalyst mixture was prepared as follows: 490 grams of a 400 Cp5 blend of 95 parts dimethylvinyl_stopped dimethyl fluid and 5 parts soft (M~ 3007000) dimethylvinyl endstopped dimethyl silicone gum were combined with a platinum~containing catalyst su~ficient to furnish 300 ppm Pt metal. To this mixture was added 11.8 grl~ms (2 weight percent) benzophenone.
This fluid proved to be compatible with methacrylated polysi-loxanes (A4), (A5) and (A ) to yield clear mixtures.

Thermal cure was ascertained by blending one part o~ the I0 catalyst blend with 9 parts of each of polysilaxanes (A4), (A5) and (A6). There was 30 ppm catalyst as Pt metal in e~ch blend. A 2 ml thick coating of each experimental eompo~i-tion was applied on SCK substrate and placed in a forced air ov~n maintained at 150C. The thermal cure results are set forth in Table VI.

Table VI

Oven Dwell I ~e~.
A4 30 nder~ured; smear~
- 60 Cured~ mear 2 ~ " 90 ~!~; no s~ear A5 20 Under~:ured; smearls ~ no ~raear A6 20 ~o cure observed ~ 30 lJnder~:ur~d; 13lDear~
Co~Plete ~ure DO ss~le~r . , , ~
' ' ' . ' ' ','. ' - ' . '' ' '': ' ' ' ' ' ', ':

-, ~25623g 60SI-B96/0043p/GLL:mz A ~shadow effect~ experiment was then carried out using a 9:1 blend of polysiloxane (A5) and the above-described catal-yst mixture. Four ml thick coatings were applied to stainless steel panels, and a one inch L-shaped metal piece was then placed across the coated panel so as to effectively block ultraviolet radiation from reaching the composition across a one inch wide strip. The coatings were exposed to 400 watts focused UV radiation in a nitrDgen atmosphere. Exposed areas cured to smear-free, glossy surfaces at 100 feet per minute line speed. Unexposed areas were wet a~ter removal from the VY
processor, but oured to tack-free surfaces after )6 hours at 25C in the dark.

Example 4 These dual curable (meth)acrylated silicone polymers can be prepared in many ways besides the high-acid reverse hydrolyses illustrated in some o~ the previous examples. A dual-cure com-position designated A7 was synthesized in this fashion:

48g of methylmethacryloxyprQpyldichlorasilane (0.2 moles) +
79 methylvinyldichlorosilane (0.05 moles) ~ 2089 dimethyldi-chlorosilane (1.75 moles) were dispersed in 300 cc of toluene, then the silane solution slowly added to 10009 of water over a 2.5 hour period at a temperature of 25-40C. The organic phase obtained from the ~ow-acid hydrolysis was stripped to 150C, 28 mm to yield g59 of low molecular weight silanol-stopped poly-2~ siloxanes represented as HO ~ DDViDMA ~ OH. Silanol content was about 5 weight percent as OH. This hydrolyzate was in turn dispersed in 3009 toluene, heated to reflux (113~C)~
when 0.89 stannous octoate was added. After 10 minutes at - - ~ - :
, - .
.
' ' ''- ~" ~

- ~ , , . . : -. , , . ~ .

, : :

3~ 6 Z 3 60SI-896/0043p/GLL:m~

113C about 0.6 ml H20 had formed and was tr~pped out in a Claisen apparatus. The reaction mixture was cooled to 70C, 209 (.17 mole) of dimethylvinylchlorosilane added follcwed by dropwise addition of 50 cc H2~ at 70~C to convert silanol chainstopper to MYi chainstopper. The product was worked up by washing with 5X NaHC03 solution ~aqueous), isolated by a 90C strip at 15 ~m ~acuum. 989 of MVi ~ DDViDMA) MVi were finally treated with 3.99 diethoxyacetophenone photo-initiator and sufficient soluble platinum catalyst to 1 0 furnish ~, 25 ppm Pt. The complete blended pr~duct ~as a ele~r 57 cps. fluid. (Persons skilled in the art will see that the viscosity of th;s product can be controlled by monitoring the amount of water ccndensed during the tin octoate-bodying step.) 2 mil coatings of the product A cured to a smear-free, 1~ glossy surface on SCK substrate when exposed to 400 watts/square inch focused ultraviolet power at 1~0 ft/min. line s~eed in nitrogen. 100 parts of A blended with 4 parts of 25 cps. trimethylsiloxy-stopped polymethylhydrogen fluid cured tG a smear and migration-free coating when applied at 2 mil .hickness on SCK paper upon 30 seconds dwell time at lSO~C;
the UV-cure performance of the 100:4 blend proved indistin-guishable from $hat of the unblended A7 product. The blended mixture was a clear fluid which set up to a soft gel in 2 hours at 25~C.

The example A7 demonstrated that this invention is not limited by its mode of processing~ and that compositions of which these examples are representative fall within the scope of this application however they might be prepared.

.

: ~, - . -- . - , .
.. . . :.' .

Claims (49)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a curable composition containing polymers having silicon-bonded hydrogen atoms and polymers having silicon-bonded acrylate radicals, the improvement comprising at least one part by weight per 100 parts by weight of said polymers having silicon-bonded hydrogen atoms and polymers having silicon-bonded acrylate radicals of at least one free radical photoinitiator and at least one precious metal-containing hydrosilation catalyst for effecting crosslinking of said silicon-bonded hydrogen atoms and said silicon-bonded acrylate radicals.

2. A curable composition comprising:
(A) a polysiloxane having the general formula:

wherein each R is an independently selected substituted or unsubstituted monovalent hydrocarbon radical having from 1 to 20 carbon atoms; R1 is hydrogen, a hydroxyl radical or a substituted or unsubstituted hydrocarbon or hydrocarbonoxy radical having from 1 to 20 carbon atoms; A is an acrylate radical having the general formula:
where R2 and R3 are, independently, hydrogen or a sub-stituted or unsubstituted monovalent hydrocarbon radical;
R4 is a divalent hydrocarbon radical having from 1 to 10 carbon atoms; x is a number such that there is present from about 0.1 to about 50 mole percent acrylate-containing siloxy units; y is a number such that there is present from about 0 to 50 mole percent hydrogen-containing siloxy units with the proviso that if y is 0 there is present an organohydrogenpolysiloxane; and x+y+z is a number such that the viscosity of said poly-siloxane is from about 25 centipoise to about 2,500,000 centipoise at 25°C;
(B) at least one part by weight per 100 parts by weight of said polysiloxane of a free radical photo-initiator; and (C) a precious metal-containing hydrosilation catalyst.

3. The composition of claim 2 wherein y is zero, further comprising an organohydrogenpolysiloxane.

4. The composition of claim 2 wherein substantially all of the R radicals are selected from the group consisting of methyl, vinyl and phenyl radicals.

5. The composition of claim 2 wherein R2 and R3 are, independently, selected from the group consisting of hydrogen and C1-3 monovalent hydrocarbon radicals and R4 is a C1-3 divalent hydrocarbon radical.

6. The composition of claim 2 wherein up to about 20 mole percent of the R radicals of the units are vinyl radicals.

7. The composition of claim 2 wherein x is a number such that there is present from about 2 to about 20 mole percent acrylate-containing siloxy units; y is a number such that there is present from about 2 to about 20 mole percent hydrogen-containing siloxy units, and x+y+z is a number such that the viscosity of polysiloxane (A) is from about 200 centipoise to about 5000 centipoise at 25°C.

8. The composition of claim 2 wherein the free radical photoinitiator has the general formula:

where R5 is a monovalent alkyl or aryl group and Z is hydrogen, alkyl, halogen, nitro, amino or amido.

9. The composition of claim 8 wherein the free radical photoinitiator is selected from the group consisting of t-butylperbenzoate, t-butylper-p-nitrobenzoate, t-butylper-p-methoxybenzoate, t-butylper-p-methylbenzoate, and t-butylper-p-chlorobenzoate.

10. The composition of claim 9 wherein the free radical photoinitiator is t-butylperbenzoate.

11. The composition of claim 8 wherein the free radical photoinitiator further comprises a sensitizer which is an aromatic compound having at least one benzene ring which is alpha to a carbonyl group.

12. The composition of claim 11 wherein the sensitizer is benzophenone.

13. The composition of claim 1 or 2 wherein the precious metal-containing hydrosilation catalyst is selected from the group consisting of platinum metal, a platinum complexes, rhodium metal and rhodium complexes.

14. The composition of claim 1 or 2 wherein the free radical photoinitiator is present in an amount of from about 1 to about 10 parts by weight per 100 parts by weight polysiloxane (A) and the precious metal-containing catalyst is present in an amount of from about 10 ppm to about 500 ppm as precious metal based on polysiloxane (A).

15. The composition of claim 2 further comprising an organohydrogenpolysiloxane.

16. The composition of claim 2 further comprising a vinyl-containing polysiloxane.

17. The composition of claim 2 further comprising an organohydrogenpolysiloxane and a vinyl-containing polysiloxane.

18. The composition of claim 2 or 17 further comprising an inhibitor effective for preventing curing of said composition at temperatures below the heat cure temperature.

19. A curable composition comprising:
(A) a polysiloxane having the general formula:

wherein substantially all of the R radicals are selected from the group consisting of methyl, vinyl and phenyl radicals; R1 is selected from the group consisting of hydrogen atoms, hydroxyl radicals, methyl radicals and methoxy radicals; A is an acrylate radical having the general formula wherein R2 and R3 are, independently, selected from the group consisting of hydrogen and C1-3 hydrocarbon radicals; R4 is a C1-3 divalent hydrocarbon radical;
R5 is an olefinically unsaturated hydrocarbon radical, w is a number such that there is present up to 20 mole percent of siloxy units having olefinically unsaturated hydrocarbon radicals, x is a number such that there is from about 2 to about 20 mole percent acrylate-containing siloxy units; y is a number such that there is from zero to about 20 mole percent hydrogen-containing siloxy units; and w+x+y+z is a number such that the viscosity of said polysiloxane varies from about 100 centipoise to about 5000 centipoise at 25°C;
(B) from 1 to 10 parts by weight per 100 parts by weight polysiloxane (A) of a free radical photo-initiator selected from the group consisting of t-butyl-perbenzoate, t-butylper-p-nitrobenzoate, t-butylper-p-methoxybenzoate, t-butylper-p-methylbenzoate, t-bu-tylper-p-chlorobenzoate, benzophenone, t-butylanthraquinone and diethoxyacetophenone;
(C) from 10 ppm to 500 ppm based on polysiloxane (A) of a platinum-containing hydrosilation catalyst, as platinum metal;
(D) optionally, an organohydrogenpolysiloxane;
(E) optionally, a vinyl-containing polydiorgano-siloxane; and (F) an inhibitor effective for preventing curing of said composition at temperatures below the heat cure temperature.

20. In a method for making a curable composition containing polymers having silicon-bonded hydrogen atoms and polymers having silicon-bonded acrylate radicals, the improvement comprising adding at least one part by weight per 100 parts by weight of said polymers having silicon-bonded hydrogen atoms and polymers having silicon-bonded acrylate radicals of at least one free radical photoinitiator and at least one precious metal-containing hydrosilation catalyst for effecting crosslinking of said silicon-bonded hydrogen atoms and said silicon-bonded acrylate radicals.

21. A method for making a curable composition comprising mixing:
(Al a polysiloxane having the general formula:

wherein each R is an independently selected substituted or unsubstituted monovalent hydrocarbon radical having from 1 to 20 carbon atoms; R1 is hydrogen, a hydroxyl radical or a substituted or unsubstituted hydrocarbon or hydrocarbonoxy radical having from 1 to 20 carbon atoms; A is an acrylate radical having the general formula:
where R2 and R3 are, independently, hydrogen or a substituted or unsubstituted monovalent hydrocarbon radical; R4 is a divalent hydrocarbon radical having from 1 to 10 carbon atoms; x is a number such that there is present from about 0.1 to about 50 mole percent acrylate-containing siloxy units; y is a number such that there is present from about 0 to 50 mole percent hydrogen-containing siloxy units with the proviso that if y is 0 there is present an organo-hydrogenpolysiloxane; and x+y+z is a number such that the viscosity of said polysiloxane is from about 25 centipoise to about 2,500,000 centipoise at 25°C;
(B) at least one part by weight per 100 parts by weight of said polysiloxane of a free radical photo-initiator; and (C) a precious metal-containing hydrosilation catalyst.

22. The method of claim 21 wherein y is zero, further comprising an organohydrogenpolysiloxane.

23. The method of claim 21 wherein substantially all of the R radicals are selected from the group consist-ing of methyl, vinyl and phenyl radicals.

24. The method of claim 21 wherein R2 and R3 are, independently, selected from the group consisting of hydrogen and C1-3 monovalent hydrocarbon radicals and R4 is a C1-3 divalent hydrocarbon radical.

25. The method of claim 21 wherein up to about 20 mole percent of the R radicals of the units are vinyl radicals.

26. The method of claim 21 wherein x is a number such that there is present from about 2 to about 20 mole percent acrylate-containing siloxy units; y is a number such that there is present from about 2 to about 20 mole percent hydrogen-containing siloxy units; and x+y+z is a number such that the viscosity of polysiloxane (A) is from about 100 centipoise to about 5000 centipoise at 25°C.

27. The method of claim 21 wherein the free radical photoinitiator has the general formula:

where R5 is monovalent alkyl or aryl group and z is hydrogen, alkyl, halogen, nitro, amino or amido.

28. The method of claim 27 wherein the free radical photoinitiator is selected from the group consisting of t-butylperbenzoate, t-butylper-p-nitro-benzoate, t-butylper-p-methoxbenzoate, t-butylper-p-methylbenzoate, and t-butylper-p-chlorobenzoate.

29. The method of claim 28 wherein the free radical photoinitiator is t-butylperbenzoate.

30. The method of claim 27 wherein the free radical photoinitiator further comprises a sensitizer which is an aromatic compound having at least one benzene ring which is alpha to a carbonyl group.

31. The method of claim 30 wherein the sensitizer is benzophenone.

32. The method of claim 20 or 21 wherein the precious metal-containing hydrosilation catalyst is selected from the group consisting of platinum metal, platinum complexes, rhodium metal and rhodium complexes.

33. The methods of claim 20 or 21 wherein the free radical photoinitiator is present in an amount of from about 1 to about 10 parts by weight per 100 parts by weight polysiloxane (A) and -the precious metal-contain-ing catalyst is present in an amount of from about 10 ppm to about 500 ppm as precious metal based on polysiloxane (A).

34. The method of claim 21 further comprising mixing an organohydrogenpolysiloxane.

35. The method of claim 21 further comprising a vinyl-containing polysiloxane.

36. The method of claim 21 further comprising an organohydrogenpolysiloxane and a vinyl-containing polysiloxane.

37. The method of claim 21 or 36 further comprising an inhibitor effective for preventing curing of said composition at temperatures below the heat cure temperature.

38. A method for making a curable composition comprising mixing:
(A) a polysiloxane having the general formula wherein substantially all of the R radicals are selected from the group consisting of methyl, vinyl and phenyl radicals; R1 is selected from the group consisting of hydrogen atoms, hydroxyl radicals, methyl radicals and methoxy radicals; A is an acrylate radical having the general formula wherein R2 and R3 are, independently, selected from the group consisting of hydrogen and C1-3 hydrocarbon radicals;

R4 is a C1-3 divalent hydrocarbon radical; R5 is an olefinically unsaturated hydrocarbon radical, w is a number such that there is present up to 20 mole percent of siloxy units having olefinically unsaturated hydro-carbon radicals, x is a number such that there is from about 2 to about 20 mole percent acrylate-containing siloxy units; y is a number such that there is from zero to about 20 mole percent hydrogen-containing siloxy units; and w+x+y+z is a number such that the viscosity of said polysiloxane varies from about 100 centipoise to about 5000 centipoise at 25°C;
(B) from 1 to 10 parts by weight per 100 parts by weight polysiloxane (A) of a free radical photo-initiator selected from the group consisting of t-butyl-perbenzoate, t-butylper-p-nitrobenzoate, t-butylper-p-methoxybenzoate, t-butylper-p-methylbenzoate, and t-butylper-p-ehlorobenzoate, benzophenone, t-butylanthra-quinone and diethoxyacetophenone;
(C) from 10 ppm to 500 ppm based on polysiloxane (Al of a platinum-containing hydrosilation catalyst, as platinum metal;
(D) optionally, an organohydrogenpolysiloxane;
(E) optionally, a vinyl-containing polydiorgano-siloxane; and (F) an inhibitor effective for preventing curing of said composition at temperatures below the heat cure temperature.

39. An article of manufacture comprising:
(a) 100 parts by weight of component A and (b) 1 to 100 parts by weight of component B, wherein component (A) comprises a mixture of (i) one or more polysiloxanes having silicon-bonded acrylate radicals; (ii) at least one part by weight per 100 parts by weight of polysiloxane of a free radical photo-initiator; (iii) a precious metal-containing hydrosilation catalyst; and component B comprises an organohydrogen-polysiloxane and wherein component A and component B are contained separate from one another.

40. An article of manufacture comprising:
(a) 100 parts by weight of component A and (b) 1 to 100 parts by weight of component B, wherein component A comprises a mixture of (i) one or more polysiloxanes having silicon-bonded acrylate radicals and silicon-bonded hydrogen atoms and (ii) at least one part by weight per 100 parts by weight of poly-siloxane of a free radical photoinitiator; and component B
comprises a precious metal-containing hydrosilation catalyst dispersed in a vinyl-containing polysiloxane;
and wherein component A and component B are contained separate from one another.

41. The article of claim 40 wherein component A
is a mixture of a polysiloxane having silicon-bonded acrylate radicals, a polysiloxane having silicon-bonded hydrogen atoms, and a free radical type photoinitiator.

42. An article of manufacture prepared by the steps comprising:
I. mixing, so as to form a curable composition composition comprising:
(A) a polysiloxane having the general formula:

wherein each R is an independently selected substituted or unsubstituted monovalent hydrocarbon radical having from 1 to 20 carbon atoms; R1 is hydrogen, a hydroxyl radical or a substituted or unsubstituted hydrocarbon or hydro-carbonoxy radical having from 1 to 20 carbon atoms; A is an acrylate radical having the general formula:

where R2 and R3 are, independently, hydrogen or a substituted or unsubstituted monovalent hydrocarbon radical; R4 is a divalent hydrocarbon radical having from 1 to 10 carbon atoms; x is a number such that there is present from about 0.1 to about 50 mole percent acrylate-containing siloxy units; y is a number such that there is present from about 0 to 50 mole percent hydrogen-containing siloxy units with the proviso that if y is 0 there is present an organohydrogenpolysiloxane;
and x+y+z is a number such that the viscosity of said polysiloxane is from about 25 centipoise to about 2,500,000 centipoise at 25°C;
(B) at least one part by weight per 100 parts by weight of polysiloxane of a free radical photo-initiator; and (C) a precious metal-containing hydrosilation catalyst;
II. applying a coating of said curable composi-tion to a substrate; and III. curing said caoting to said substrate by exposing the coated substrate to a source of ultraviolet radication and thereafter thermally curing said coating.

43. The article of claim 42 wherein the substrate is paper.

44. The article of claim 42 wherein the substrate is a circuit board.
45. A method for making an article of manufacture, comprising:
I. mixing, so as to form a curable composition comprising:
(A) a polysiloxane having the general formula:

Claim 45 continued:

wherein each R is an independently selected substituted or unsubstituted monovalent hydrocarbon radical having from 1 to 20 carbon atoms; R1 is hydrogen, a hydroxyl radical or a substituted or unsubstituted hydrocarbon or hydrocarbonoxy radical having from 1 to 20 carbon atoms;
A is an acrylate radical having the general formula:

where R2 and R3 are, independently, hydrogen or a sub-stituted or unsubstituted monovalent hydrocarbon radical;
R4 is a divalent hydrocarbon radical having from 1 to 10 carbon atoms; x is a number such that there is present from about 0.1 to about 50 mole percent acrylate-containing siloxy units; y is a number such that there is present from about Q to 50 mole percent hydrogen-containing siloxy units with the proviso that if y is 0 there is present an organohydrogenpolysiloxane;
and x+y+z is a number such that the viscosity of said polysiloxane is from about 25 centipoise to about 2,500,000 centipoise at 25°C;:
(B) at least one part by weight per 100 parts by weight of polysiloxane of a free radical photoinitiator;
and (C) a precious metal-containing hydrosilation catalyst; and II. applying a coating of said curable composition to a substrate; and III. curing said coating to said substrate by exposing the coated substrate to a source of ultraviolet radiation and thereafter thermally curing said coating.

46. The method of claim 45 wherein the substrate is paper.

47. The method of claim 45 wherein the substrate is a circuit board.

48. The method of claim 45 wherein thermal curing is effected at room temperature.

49. The method of claim 45 wherein thermal curing is effected at an elevated temperature.