CA2128865A1 - Mositure curable polysiloxane release coating compositions - Google Patents

Abstract

A release coating composition comprising: a) a polydiorganosiloxane having at least one reactive hydrolyzable group .alpha.
connected to a silicon atom, wherein R3 is a monovalent alkyl group with about 1 to 3 carbon atoms; Z is a monovalent moiety selected from the group consisting of -OR and -R wherein R is an alkyl group having about 1 to 3 carbon atoms; Y is a divalent alkylene linking group comprising about 1 to 12 carbon atoms; Q is a divalent linking group selected from urea, amide, urethane, thiourethane, ether and thioether; t is an integer from 0 to 10; and X is a divalent alkylene linking group comprising about 1 to 12 carbon atoms; b) a component selected from the group of compounds of the general formula (R3O)3 - Si - A, hydrolysates thereof, and mixtures thereof, wherein R3 is as previously defined; A is a monovalent moiety selected from the group consisting of -OR3, alkyl group with about 1 to 20 carbon atoms, and -X-(Q)p - [D-Q]t -(Y)b - SiCOR3)3 wherein X, Q, t, Y and R3 are as previously defined; D is a divalent group selected from alkylene groups with about 2 to 30 carbon atoms; aralkylene groups with about 6 to 30 carbon atoms; arylene groups with about 6 to 30 carbon atoms;
and divalent polymeric segments having a number average molecular weight of about 500 to 10,000 selected from polyether, polyolefin, polyester, polydiene, and mixtures thereof; p is 0 or 1; b is 0 or 1; wherein when t is an integer of 1 to 10, b must equal 1 and p must equal 1; wherein when t=0 and b=0, p must also equal 0;
and c) a component selected from acids having pKa less than about 3, anhydrides of acids having pKa less than about 3, ammonium and lower alkyl ammonium salts of acid having pKa less than about 3, and mixtures thereof. The release coating composition of the invention has excellent shelf stability and pot life and cures rapidly, completely and reliably in atmospheric moisture in a controllable manner when coated on a variety of substrates.

Description

2t2~ S;

MOISTURE CURABLE POLYSILOXANE RELEASE COATING
COMPOSITIONS

5 Field of the lnvention This invention relates to polysiloxane release coating -compositions which cure rapidly and completely in atmospheric moisture in a controllable manna and which have a level of release which can easîly be adjusted from premium to tight.
Back~round of the lnvention In the manufacture of many tape and label products in which a ~-pressure sensitive adhesive is coated on a substrate such as paper or film, an essential component of the construction is the release coating. When a release 15coating is applied on the non-adhesive side of a backing, as in a roll of tape, it - -is commonly referred to as a "low adhesion backsize". The low adhesion backsize allows ~he roll of tape to be unwound with a reasonable amount of force ~about 5 to 15 N/dm). On the other hand, a separate release coated sheet which is contacted with an adhesive coated side of a tape or label is referred to 20 as a "liner", and in such a case, the peel force required to remove the tape or label is usually very low ^ typically less tha~ about 1 to 2 N/dm. For this level of release, which is referred to as premium to easy~ the usual coating material employed is some form of cured polysiloxane. These polysiloxanes are, for the most part, polydimethylsiloxanes substituted with a minimum number of 25 various reactive functional-groups. These polysiloxanes are coated on a substrate and subsequently chemically crosslinlced. Ideally, these polysiloxanesshould provide complete coverage of the substrate, cure completely to an ultra th;n film (about 1 micron~, have reasonable strength, be resistant to abrasion, and strongly adhere to the substrate. Other desirable features of such systems 30 would include long term shelf stability and pot life prior to coating, followed by rapid cure on web, as well as ~he ability to easily adjust the release to higherlevels than premium, if necessary. Few polysiloxane release coatings possess all of these optimal attributes.
Over the years, a number of polysiloxane matenals having 35 different curing chemistries were de~eloped as release liner coatings for pressure sensitive adhesives. One of the first to find widespread acceptance wasa composition comprising high molecular weight silanol terminal ~pobdimethylsiloxane and ~a low molecular weight crosslinking copolymer of WO 93/16142 . PCr/US93/00490 7'i, ~

dimethyl and methyl siloxane. Cure was effected by hea~ing the composition in the presence of organometallic catalysts. Although reliable premium release was provided, the polysiloxane coating suffered from a number of drawbacks; it was useful only on paper, it had to be applied from hydrocarbon solvents, and S finally, the cure was extremely slow, often requiring days for completion.
More recently, several other polysiloxanes have become available, in which fast cure is triggered by exposure to ultraviolet radiation (UV). Such compositions and processes are exemplified by U.S. Patent Nos.
4,563,539 (Gornowicz et al.); 4,359,369 ~Ta~mizawa et al.); 4,554,339 (Hockemeyer et al.); and 4,5g7,987 (Hockemeyer et al.). These patents disclose oligomeric polydimethylsiloxanes substituted with pendant acryloxy ~`alkyl groups which undergo rapid crosslinking using ultraviolet light sensitive photoinitiators in an inert atmosphere. In a similar fashion, U.S. Patent Nos.
4,313,988 (~Coshar et al.) and 4,822,687 (Kessel et al.) disclose polysiloxane 15 compositions with pendant epoxy alkyl substituents which cure in seconds whensuper acids are generated from the UV catalyzed decomposition of certain onium salts. For these polysiloxane compositions, inerting of the coating is notnecessary. In addition to the high speed of cure, these types of polysiloxane compositions offer the advantage of being completely stable before and during 20 coating operations.
- Another curing method which has proven very effective for the preparation of polysiloxane adhesives and sealants is the Hmoisture cureU of alkoxysilane functional polydiorganosiloxanes. In this systemr atmospheric water is utilized to hydrolyæ the alkoxy, especially trialkoxy, silane to -SiOH
25 groups, which subsequently condense with other silanols or alkoxysilane groups to form -Si-~Si- crosslinks. These reactions are catalyzed by certain tin compounds, such as dibutyl tin dilaurate. Although such materials bave been reported useful as release coatings~ as in, for example, U.S. Patent No.
4,269,963 (Homan et al.), they, like the condensation cure silicones, are found 30 to cure too slowly to be practical in most manufacturing operations.
Recently, how~ver, Homan et al. (U.S. Patent Nos. 4,743,474;
4,530,882; and 4,525,566) have disclosed moisture curable silicone compositions consisting of mixtures of predominantly polydiorganosiloxanes having two or more terminal andJor pendant trialkoxysilyl substituents and 35 lesser amounts of tetraalkyl titanate esters which provide silicone release coatings that cure exceptionally rapidly under ambient conditions.

wo 93/16142 2 1 2 ~ i Pcr/US~3/00490 .

Although these composi~ions have indeed solved the problem of slow curing of silane substituted silicones, the actual use of such materials inpractice is not without some formidable difficulties. These practical processingdifficulties are well described by D.J. Huettner in a conference paper entitled "Moisture Curing Silicone Releasei Coating Technology: A Coating Process is --the Missing Component", presented at the 1988 Pressure Sensitive Tape Council Technical Seminar. Huettner states that these silaneltitanate mixtures are so extremely sensitive to ambient moisture that they cure hlstantaneously upon exposure to air, making them almost impossible to coat with ordinary equipment due to premature gelation on the substrate, in the coating equipment, and in the feed tanks. `
Due to the limitations of known silicone release coating compositions, a need exists for a silicone release coating composition which hasexcellent shelf stability, processibility and pot life, and yet which cures rapidly and completely in atmospheric moisture in a controllable manner when coated -on a variety of substrates. A need also exists for a release coating compositionfor which the level of release of the coating can be easily adjusted from premium to tight in a readily predictable and reliable manner. We have found ~`
such a release coadng composition. -Sumn~ary of the Invention This invention provides novel polysiloxane release coating compositions which compositions have excellent shelf stability and pot life and which cure rapidly, completely, and reliably in atmospheric moisture in a controllable manner when coa~ed on a variety of substrates. T}le level of release of release coatings prepared therefrom can be easily adjusted from premium to tight by modifying the polydimethylsiloxane content of the release coating compositions in a readily predictable and reliable marmer.
The present invention provides a moisture-curable release coating composition comprising:
(a) about 1 to about 100 percent by weight of polymer selected from the group consisting of polymers of the general Formula:

R2 Rl R2 1 l l w--[--I i--o- ] ~ o- ~ m- I i--w ( I ) ,.

4- :
and mixtures thereof:
wherein n and m each represent integers, wherein the sum of n plus m is an integer of about 20 to about 5000;
S m has a value ranging from about 0 to about O.l(n+m);
Rl are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, `~
aryl, and substituted aryl;
R2 are monovalent moieties which can be the same or different selected from the group c~nsisting of alkyl, substituted alkyl, aryl, and substituted aryl; .
W are monovalent moieties which can be the same or different selected from the group consis~ing of alkyl, substituted alkyl, aryl, substituted aryl, and reactive hydrolyzable group (R30) 2 -Si- (Y-Q) ,-x-;
1 .
wherein at least about 50% of the total number of silicon atoms excluding those in said reactive hydrolyzable group(s) have two methyl groups bonded theretot and wherein at least one reactive hydrolyzable group 20 (R30) 2- l i_ (Y-Q) I-X-appesrs on each polymer of Formula I and further wherein at least about 25% ;:
of the polymers of Formula 1 in the release coating composition have at least tworeactivehydrolyzablegroups (R30)2-s~ y-Q)l-x;

wherein X are divalent linking groups which can be the same or different selected from the group consisting of alkylene groups comprising about l to about 12 urbon atoms;
Q are divalent linking groups which ~n be the same or different selected from the group consisting of urea, amide, urethane, thiourethane, ether, and thioether groups;
Y are divalent linking groups which can be the same or different select¢d from the group consisting of alkylene groups comprising about 1 to about 12 carbon atoms;
t is an integer of 0 to lO; .

W0 93/16142 ~ f; ~ Pcr/~lss3/oo49o Z are monovalent moie~ies which can be the same or different selected from the group consisting of -OR and -R wherein R is an alkyl group comprising about 1 to about 3 carbon atoms; and R3 is a monovalent alkyl group comprising about 1 to 5 about 3 carbon atoms;
(b) about 0 to about 99 percent by weight of a component selected from the group consisting of compounds and polymers of the general Formula:
(R30) 3-Si-A ( II ) 10 hydrolysates thereof, and mixtures thereof, wherein R3 is as previously defined;
A is a monovalent moiety selected from the group consisting of -oR3, monovalent alkyl groups comprising about 1 to about 20 carbon atoms, and -X-(Q)p-tD-Q],-(Y)b-Si(o~3)3~ wherein 15X, Q, t, Y and R3 are as previously defined; ~:
D is a divalent group which can be the same of different selected from the group consisting of alkylene groups comprising from about 2 to about 30 carbon a~oms; aralkylene groups comprising from about 6 to about 30 carbon atoms; arylene gFOUpS comprising from about 6 to about 30 ca~oon ~-atoms; and divalent polymeric segments ha~nng a number average mole~ular ~ `
weight of about 500 to about 10,000 seleeted from the group consisting of polyether, polyolefin, polyester, polydiene, and mixtures thereof;
p is an integer of from 0 to 1;
b is an integer of from 0 to 1;
whe~ein when t is an integer of 1 to 10, b must equal 1 and p must equal 1;
wherein when t=0 and b--0, p must also equal 0;
wherein the weight percen~es of (a) and (b) are based upon the total weight of (a) plus (b); and (c~ about 1 to about 15 percent by weight based upon the total weight of (a) plus (b) of a eomponent selected from the group consisting of acids having pKas of less than about 3, anhydrides of acids ha~fing pKas of less than about 3, ammonium 3alts of acids having pKas of less than about 3, lower alkyl ammonium salts of acids having pKas of less than about 3, and mixtures thereof.

wo 93/16142 Pcr/uss3/oo49o 6- ~
Cured versions of the composi~ions, release coated sheet matenals, and met~iods of providing release coa~ed sheet materials are also provided.

Detailed Description of the Invention Polysiloxane Component The functional polysiloxanes which comprise component (a) of the invention are represented by Formula I. Examples of preferred polysiloxanes comprise the polysiloxanes selected from the group consisting of polymers of Formula I, wherein R' and R2 each comprise methyl, X and Y
each comprise -CH2CH2CH2-, t equals 1, and Q is selected from the group consisdng of urea groups and thioether groups. These moieties are preferred because of the commercial availability and ease of preparation of starting materials having these functionalities or their precursors. Preferred polysiloxanes comprise at least one trialkoxysilane terminal or pendant group, wherein Z comprises -OCH3 and R3 comprises -CH3 due to the enhanced hydrolytic acdvity of ~he resultant trimethoxysilane terminal andlor pendant groups.
The sum of n plus m must represent an integer of about 20 to about 5000~ in order to provide a funcdonal polysiloxane that yields a release coating having the required release force and rheological properties. If ~e sum of n plus m is much less than about 20, the abhesive pr~perties of a release coating prepared therefrom are diminished due l~o an insufficient number of dimethylsiloxy groups in the polysiloxane chain~ If the sum of n plus m is greater than about 5000, the viscosity of the release coating composition becomes too high for current coating practices and processes. Preferably, the sum of n plus m is an integer of about 70 to about lO00, most preferably about 70 to about 500, a range that balances these release and rheologic~l concerns.
The value of m is less than about O.l(n+m). Among other factors, the release properties of the release coating of the invention is dependent on ~he number of dimethylsiloxane segments in the polymer backbone of the polymer of Formula I. Thus, the number of pendant reactive hydrolyzable groups is restricted to ensure an adequate ratio of dimethylsiloxane repeating units in the functional polysiloxanes of Formula I.

wo93/16142 '2.12~ PCr/US93/00490 Trialkoxysilyl substituted polysiloxanes of Formula 1 can be ~-conveniently prepared from the reaction of appropriate trialkoxysilyl substituted reagents with various functionally reactive polysiloxanes. Thus, a polymer of Formula l wherein the terminal W groups each comprise a methyl group and 5 wherein the pendant W groups comprise thio-linked, trimethoxysilyl functional reactive hydrolyzable groups, may be obtained from the free radically induced addition of, for example, commercially available mercaptopropyl-substituted polysiloxanes with vinyltrimethoxysilane. In a similar fashion, reaction of isocyanatopropyl triethoxysilane with another commercially available 10 polysiloxane having pendant aminopropyl groups provides polymers of Formula I with dipropylurea links. Difunctional polysiloxanes may be formed by the treatment of bis(aminopropyl) terminated polysiloxanes, which can be obtained from commercial sources or prepared via the method described in U.S. Patent No. 5,09l,483, with isocyanatopropyl triethoxysilane. These lS reactants produce polysiloxanes of Formula I wherein each terminal W group comprises a urea-functional trialkoxysilane and m = 0.
U.S. Patent No. 5,09l,483 describes several rnethods for synthesizing organopolysiloxane diamines useful in the preparation of difunctional polysiloxanes useful in the present invendon. In a first method, an2Q organopolysiloxane ~rninated at both chain ends with hydroxy groups? as re~resented by the general Formula H~Si~H III

where R2 is as defined above and e is an integer of about 270 to about lO00, 30 can be subjec~ed to a condensa~ion reaction with a compound represen~ed by the general Formula H-l-X-Si-B IV

wo 93/16142 Pcr/~Jss 5 ; 8-.. , ~,;, where X7 and R2 are as defined above, B is a hydroxy group or a hydroly~able group, and R4 is selected from the group comprising of hydrogen, an alkyl group comprising a~out 1 to about 10 carbon atoms, aryl, and substituted aryl.
A second method involves the reaction of a cyclic organosiloxane, represented -5 by the general Formula ( Si~l~ `
12 v _ ~ ','.

where R2 is as defined above and k is a positive integer of 3 to 8, with an -amine functional endblocker, represented by the general Formula H-l-x-si-o-si-x-N-H VI

.' ', where R4, X, and R2 are as defined above, in tho presence of a basic catalyst 25 such as tetramethylammonium hydroxide or ~ior~anosilanolate. A third method, a modification of the second, is preferred and involves running the reaction in two stages udlizing a minimum amount of an essentially anhydrous amino alkyl functional silanvlate catalyst represen~ed by the general Formula H-l-X~ o M~ VII

where R4, X, and R2 are as defined above and M+ is a cation selected from the group eonsisting of K+, Na+, and tetraorganoammonium ion, with N(CH3)4+
being preferred. In the first stage of the reaction, a low molecular weight organopolysiloxane diamine, represented by the general formula WO 93/16142 PCI'/US93/00490 6~ 7 2~

H--N-X-Si~o-Si ) X - O-Si-X-N-H VIII
1 2 ~ 1 2 where R4, X, and R2 are as defined above and x is an integer of about 4 to about 40, is prepared by r~acting an amine functional disiloxane endblocker represented by Formula VI above with a cyclic organosiloxane represent~d by Formula V in the presence of a catalytic amount of essentially anhydrous amino alkyl functional silanolate represented by Formula VII in an inert atmosphere such as nitrogen or argon. The preferred catalyst for use in this reaction is 3-aminopropyl dimethyl tetramethylammonium silanolate, which can be obtained as a crystalline solid from the reaction of one molar ~uivalent of 1,3^bis(3-aminopropyl) tetramethyldisiloxane with two molar equivalents of tetramethylammonium hydroxide pentahydrate in tetrahydrofuran under reflux, ~ollowed by dIying under vacuum for five hours (0.1 mm) at 60C. The amount of catalyst employed should be less than about O.OS percent, preferably about 0.005 to about 0.03 percent, by weight of the resultant organopolysiloxane diamine. The reaction can be carried out in bulk at a temperature of about 80C to about 90C, and under these conditions is usually complete in about 0.5 to about 2 hours, as judged by substantially complete disappea~ance of the endblocker of the reaction mixture as determined by vapor phase chromatog~aphy. The second stage of the reaction involves the slow addition of the remainder of the cyclic organosiloxane required to achieve the desired molecular weight. This addition is preferably carried out dropwise at such a rate that the eyclic organosiloxane is incorporated into the polymer about as fast as it is added, usually in ~out five to seven hours at the reaction temperature of about 80C to about 90C. By utilizing this two-stage method with a minimum amount of essentially anhydrous eatalyst, organopolysiloxane diamines, useful in the prepa~ation of the difunctional polysiloxanes useful in this invçntion can be consistently pTepaIed having excellent difunctionality with little contamination from monofunctional and nonfunctional polysiloxane impurities.
Finally, for monofunctional polysiloxanes of Formula I in which one terminal W group comprises an alkyl group, m - 0, and the other W
group comprises dialkyl urea linked triethoxysilane, the star~ing monoamine is obtained fron~ the well known anionic polymerization of `:
WO 93/16142 ~r PCr/US93/00490 ?, V

hexamethylcyclotrisiloxane initiated with n-butyl lithium and terminated with the capping reagent, 3-aminopropyl dimethyl fluorosilane, as described in U.S.
Patent No. 5 ,091,483 .
Terrnination of the anionic polymerization is, in general, 5 achieved via direct reaction of the living polymeric anion with fluorine-containing terminating agents, i.e., functionalized fluorosilones, to produce amine terminated polymeric monomers. The termination reaction is carried out by adding a slight molar excess of the terminating agent (relative to the amount of initiator) to the living polymer at the polymerization temperature.
This preferred capping reagent is prepared by combining 1 ,3-bis(aminopropyl)tet~yldisiloxane and a hydrocarbon solvent having a boiling point ranging from about 7SC to about 85C in order to form a `
solution. Suitable hydroca~bon solvcnts include cyclohexane, benzcnc, hcptane, and the like. The solution thus formcd is reacted by combining the solution 15 with at least about a molar e4uivalent of an acidic fluoride reactant, preferably at least about a 5 percent molar excess of an acidic fluoride reactant, such as hydrofluoric acid, potassium bifluoride, ammonium fluoride, or the like, ~ ~`
preferably ammonium fluoride, with azeotr~pic removal of water. This provides the amine hydrofluoride subsdtute~ fluorosilane isolated as the 2~ crystalline hydrofluondc salt precipitate, which can then be convcrted to thcfree amine by headng a slurry of the salt in a water-immisciblc solvent boiling in the range of abou~ 35C to about 50C, c.g., mcthylcne chloride, with about a 1 perccnt molar excess to about a 5 percent molar excess of a compound -seleeted from the group consisdng of monosubstituted or disubsdtuted lower 25 alkylamino silanes and hexamethyl disilazane. The amine-substituted fluorosilane can be se~arated from the solvent by evaporation of the solvent anddistillation of the product under reduced pressure.
The release coating composition of the invention comprises about 1 to about 100 percent by weight of polymer of Formula I, preferably about S -;30 to about 30 percent by weight for use as low adhesion backsizes, and preferably about 50 to about 90 percent by weight for applications requiring ea~er release,based upon the total weight of components (a) plus (b). As indicated ~;previously, component (a) comprises at least about 25 percent of polysiloxane of Pormula 1 which has at least two reactive, hydrolyzable functional silane 35 groups per polymer. Component (a~ can comprise mixtures of difuncIional or multifunctional polysiloxanes of Formula I with polysiloxanes of ~ormula I
having only one hydrolyzable, reactive silane group, i.e., typically a terminal WO 93/16142 PCr/US93J00490 2 1 2 t , "

hydrolyzable reactive silane group. Mixtures of all three, i.e., monofunc~ional,difunc~ional and multifunctional polysiloxanes of Formula I are also possible.
The exact composition is dependent on such factors as the requiremes~ts of the coating process, the release requirernents of the pressure sensitive adhesive S employed, and other associated elements encountered in each particular application.
When component (a) comprises monofunctional polysiloxanes of Formula I blended with difunctional polysiloxanes and/or muldfunctional `~
polysiloxanes, no more than about 75 percent, preferably no more than about 10 60 percent of the polymers of Formula I should comprise monofunctional polysiloxanes. Incorporation of increasing amounts of the monofunctional polysiloxanes of Formula 1 (i.e., having only one reactive trialkoxysilane substituent) in the formulation tends to reduce the surface fnction as well as, in many instances, lower the level of release of the cured release coadng.
15 Incorporation of an excess of monofunctional polysiloxane, however, may lead to a slow and/or incomplete cure. On the other hand, increasing the number of reactive functional groups ia the polysiloxanes of Formula I, or increasing the amount of these multifunctional polysiloxanes in mixtures of monofunctional and difunctional polysiloxanes, tends to have the effect of increasing the rate of 20 cure of the compositions.

Non-Polvsiloxane ContaininP Com~onent The moisture curable selease coating composition of the invention compnses about 0 to about 99 percent by weight of a non-polysiloxane 25 containing component selected from the group consisting of compwnds and polyme~s of Formula II, hydrolysates thereof, and mixtures thereof. If the non-polysiloxane component is included, ~he release coating composition typically comprises about 1 to about 99 percent by weight non-polysiloxane of component (b) and ~out 1 to about 99 percent by weight polysiloxane of 30 componen~ (a) based upon the total weight of (a) plus (b). These non-polysiloxane containing components may be used to adjust the viscosity of the composition or to impart additional desirable characteristics to the cured release coatings. For example, inclusion of up to about S0 percent by weight of component (b) based upon the total weight of components (a) plus (b~
35 provides cured coatings which exhibit the same easy level of release as the pure, cured polysiloxane component (a), but with better mechanical strength and adhesion to substrates. To obtain release coatings with higher levels of wo 93/16142 Pcr/uss3/oo4so ~,; ! ~ ;..' peel adhesion, compositions having significantly greater amounts of ~;
non-polysiloxane component (b), i.e., from about 70 to about 99 percent, preferably about 80 to about 9S percent, based upon the total weight of -components (a) and (b) are utilized. Release coating compositions with these S higher levels of non-polysiloxane component provide increasing levels of release force in a controlled manner.
Examples of useful non-polysiloxane containing components having terminal alkoxysilyl groups include but are not limited to those selectedfrom the group consisting of alkoxysilyl terminated alkanesl alkoxysilyl 10 terminated ethers, alkoxysilyl ~erminated thioethers, tetraalkoxy silyl compounds, trialkoxysilyl terminated polymeric derivatives, such as tnalkoxysilyl terminated polypropylene oxide, polyethylene oxide, polytcllam~ylcne oxide, polycapro!actone, mixtures thereof, and the like. `
- During the cure of a composition of the invention which `
lS comprises components (a~ and (b), wherein (b) is represented by Formula II, in addition to com~ent (c), atmospheric moisture hydrolyzes the silan;e groups of both the funcdonal polysilo~ane(s) of Formula I and the non-polysiloxane component(s) of Formula II to intermediate SiOH groups which ultimately ;~
undergo condensation to form Si-~Si bonds in a random fashion to provide 20~ crosslinked silicate nctworks in which the functional polysiloxanes of Formula I
are chemically bonded to the non-polysiloxane componenu of Formula II.
Thus, the corresponding hydrolysates of the silane funcdonal compounds and polymers of Formula lI, i.e., silicate resins, colloidal silica, etc., can be used ~- in place of or in addition to the compounds and polymers of Formula II in component (b) of the release coating composidon of this invention. If `
hydrolysates are included, the release coating composition preferably comprises about l to about lS percent by weight of a hydrolysate such as colloidal siliea ~- based upon the total weight of components (a) plus (b). Component (b) may optionally also include, in addition to the hydrolysate(s), compounds and/or polymers of Formula II.

Catalyst The release coating composition of the invention comprises about 1 to about IS wdght percent of component (c) based upon the total weight of components (a) plus~(b), wherein component (c) is selected from the group consisting of acids having pKas of less than about 3, anhydrides of acids having ~pKas of less than about 3, ammonium salts of acids having pKas of less wo s3/16t42 Pcr/uss3/oo49o 5~

than about 3, lower alkyl ammonium salts of acids having pKas of less than abo~t 3, and mixtures thereof. Lower alkyl ammonium salts of acids having pKas of less than about 3 refer to the products obtained from the neutralizationof acids having pKas of less than about 3 with amines having alkyl substituents 5 comprising from about l to about 3 carbon atoms. Preferably component (c) comprises an organic acid or a derivative thereof in order to ensure most efficient and effective cure. ;
In order to facilitate a more rapid cure, the release coating composition preferably comprises about 3 to about l0 of component (c) based ~;
10 upon the total weight of components (a) plus (b). Preferably the acid should have a pKa of about 0. l to about l.5 in order to provide a more complete and efficient conversion of thc hydrolyzable alkoxysilane groups present in the relese coatin~ composition. If greatcr than about 15 weight percent of component (c) is included in the release coating composition, no additional benefit is achieved, and the excess acid or acid derivadve component becomes a `
non-incorporated diluent which may actually have a deleterious effect on the pfonnance of the release composidon. On the other hand, if insufficient componcnt (c) is included, the hydrolysis of the alkoxysilane functionalides andsubsequent condcnsation to cured silicatc networks occurs too slowly.
20~ ; Examples of useful acids? anhydrides, and lower alkyl ammonium salts thereof falling within component (c) include but are not }inuted to those selected from the group consisting of trichloroacetic acid, cyanoaceticacid, malonic acid, nitroacedc acid, dichloroacedc acid, difluoroacetic acid, trichloroacedc anhydride, dichloroacetic anhydnde, difluoroacedc anhydride, triethylammonium tTichloroacetate, trimethylammonium trichloroacetate, and mixtures thereof.
C~talyzed by the component (c), the release coadng composidons of the inventdon cure to solid, crosslinked polysiloxane coatings ~ia the hydrolysis of the alkoxysilane endgroups and condensation to silicate networks.
When cast in thin films, as is the case for release coatings, the ~eaction occurs extremely rapidly, typically curing to clear, smear-free, and well anchored coatings in about 60 seconds or less.

Method of Pormin~ Release-Coated Substrates Thc moisture curable release coating compositions of this invention may be applied to subs~ates by most standard coating techniques, e:ither as dilute solutions in organic solvents or as neat liquids. When cast from ~ .

WO 93/16142 rCr/US93/00490 "~J ~ l4-solvent, the component (c) of the composition may be present either as the free acid, as an anhydride, as an ammonium or lower alkyl ammonium salt, such as triethylammonium, or as a mixture thereof. Suitable solvents include but are not limited to volatile organic liquids which will dissolve the compositions of 5 the invention, including but not limited to those solvents selected from the group consisting of alkanes, arenes, chlorinated hydrocar~ons, lower alkanols, and mixtures thereof. If a solvent is utilized, the release coating composition may be included in the solvent at a concentration as low as about 2 percent solids. In the free acid form, curing of the functional polysiloxane occurs 10 almost instantaneously upon evaporation of the solvent from the coated substrate. In the ammonium salt and lower alkyl ammonium salt form, however, the catalyst is inactive, and cure does not take place until the dried coating is heated sufficiently to dissociate the salt and evaporate the amine to -liberate the free acid catalyst and initiate the moisture cure. The temperatureslS required for this will vary depending on the particular acid employed, but generally will range from about 50C to about 1~0C, preferably about 80C to about l 10C.
When coating very high solids solutions (i.e., about 80 percent solids or more) or neat materials, it is essendal to utilize the ammonium salt 20~ f~rm or the lower alkyl ammonium salt form of the acid, or mixtures thereof as component (c). Otherwise, it is not possible to avoid premature reaction with atmospheric moisture and subsequent gellations. With the inactivated ammonium salt, lower alkyl asnmonium salt, or mixtures thereof as component (c), it is thus possible to coat the release coadng composidons of this invention 25 at 100% solids in atmospheric moisture using standard coating techniques, such as gravure, o~fset gravure, and electrospray, without premature curing.
Standard electrospray coating techniques are described in U.S. Patent No.
4,748~043. Cure is then activated by heating the coating as described above.
The release coating compositions of the invention preferably consist essendally 30 of components (a), (b), and (c) and optional solvent or components (a) and (d) and optional solvent, most preferably the release coating compositions of the invention consist of components (a), (b), and (c) and optional solvent or components ~a) and (c) and opdonal solvent.
The release coating composition of this invention can be used as 35 a coating on a substrate, which can be a sheet, a fiber, or a shaped object.
However, the preferred substrates are those used for pressure-sensitive adhesive -products. The composition can be applied to at least one major surface of wo 93/16142 Pcr/uss3/00490 2 1 h ( ` ~

suitable flexible or inflexible backing materials and then cured. Useful flexible backing materials include paper, plastic films such as poly(propylene), poly(ethylene), poly(vinyl chloride), poly(tetralluoroethylene), polyester le.g., poly(ethylene terephthalate)], polyamide film such as duPont's Kapton~, cellulose acetate, and ethyl cellulose, although any surface requiring release toward adhesives can be used. Backings can thus also be of woven fabric formed of threads of synthetic or natural materials such as cotton, nylon, rayon, glass, or ceramic material, or they can be of nonwoven fabric such as air-laid webs of natural or synthetic fibers or blends of these. In addition, suitable backings can be formed of metal, metallized polymeric film, or ceramic sheet mat~rial. Primers can be utilized, but they are not always necessary.
The release coating composition of the invention can also be used as a component in an abrasive article. U.S. Patent Application Serial No.
07/832,474, describes an abrasive article comprising a substrate having on a ;
surface thereof pardcles of an abrasive material secured by a binding medium to form an abrasive surface wherein at least a portion of the abrasive surface has thereon a coating comprising a crosslinked siloxane, the crosslinked siloxane comprising the condensadon reaction product of the release coating composidon of the invendon.
2Q In most cases, the release coating composition of this invention provides coatings which possess the desired level of release immediately upon curing. Thus, the composition is suitable for use in the integrated manufacture of PSA~ated labels and ta~es. The specifie level of release provided upon curing can be controllably varîed through variation in the weight percentage andmolecular weight of the functional polysiloxane of Formula I included in the composition.
A sufficiently high amount of difunctional and~or multifunctional siloxanes (i.e., siloxanes having two or more reactive hydrolyzable groups) must be present to ensure a high and rapid degree of alkoxysilane hydrolysis conversion and complete cure of the polysiloxane. Thus, release co~dngs ! I obtained via the moisture cure of the composition of the invention contain little or no free silicone to adversely affect the tack and peel properties of PSAs which come in contact with them. The release coating composition of the invention cures ~apidly to firmly anchored, highly crosslinked, solvent resistant, 35 tack-*ee coadngs which have utility for a broad range of PSA types, such as `
those based on acrylates, tacl~fied natural rubbers, and tackified synthetic elastomers.

wo 93/16142 Pcr~uss3/0o4so ~'t~ l6-Examples All parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight unless otherwise specified.

S Aged Relçase Value This test measures the effectiveness of the silicone release composition after a period of heat aging. The aged release value is a quantitative measure of the force required to rèmove a flexible adhesive tape :
from a substrate coated with the test composi~on at a specific angle and rate of10 removal. In the following examples this force is expressed in Newtons per decimeter (Nldm) from the following represen~tive examp1es of flexible adhesive tapes:
Tape A - acrylate pressure-sensitive adhesive coated on l.9l cm wide cellulose acetate backing;
lS Tape B - tackified styrene-isoprene block copolymer pressure-sensitive adhesive coated on a l.27 cm wide polypropylene backing;
Tape C - an aggressive acrylate copolymer pressure-sensitive adhesive on a 1.27 cm polyp~opylene backing; and, Tape D - tackified natural rubber eoated on a 1.27 cm wide resin ~ -impregnated creped paper backing.
Aged release testing was conducted by laminatin~ a 2~54 cm by 20.32 cm strip of the coated substrate prepared in the examples coated side up to the stage of an Instrumentors, Inc. slip/peel tester (model 3M90) with doublecoated tape. A l.9 cm by 15.24 em strip of a presswe-sensi~ve adhesive (PSA) coated test tape was rolled down onto the laminate thus forme~ with a 1.82 kg rubber roller. The force required to remove this tape at 180 and 228.6 cm/minute after allowing the test tape to dwell in &ontaet with the coatedsubs~ate for ~wo ~r tilree days at 65C was then measured. The results of these tests are ~eported below.
Aged readhesions were also measured by adhering the freshly peeled tape to a clean glass plate and measu ing the peel adhesion in normal fashion using the same Instrumentors sliplpeel tester indicated above, again peeling at 228.6 cm/min and at a 180 peel angle after allowing the test tape todwell for two to three days at 6SC. These measurements were taken to determine whether a drop in the adhesion value occurred due to undesirable ~-contamination of the adhesive surface by the release coating. Readhesions are Wo 93/16142 Pcr/uss3/00490 reported as a percentage of the force required tO remove the aged sample from a clean glass plate versus the force required to remove a control tape sample from a clean glass plate which has not been adhered to the release coating.

~e 1 Preparation of Aminoalkvl FluQrosilane Terminating A~ent A 500 ml, 3 neck round bottom flask was charged with 49.6 g 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 29.6 g ammonium fluoride, and 300 ml cyclohexane. While heating under reflux, water was removed by means 10 of a Dean-Stark trap. After 18 hours, 4.4 ml of water had been collected, andthe clear, colorless solution was transferred while warm to a 500 ml l-neck round bottom flask. The solvent was distilled on a rotary evaporator to provide 165 g of white solid. This was dissolved in 200 ml of methylene chloride.
Next, 30 g of hexamethyldisilazane was added and the mixture was s~Ted and 15 heated under reflux for S hours. The flask was fitted for distillation and the solvent removed under aspirator vacuum. The product was distilled (boiling point of 70C) at aspirator vacuum to provide 3-aminopropyldimethyl fluorosilane as a clear, colorlexs oil. lhe yield was 54 g (100%), which was determined to be pure by vapor phase chromatography. The structure was ~
20, confirmed by NMR spectroscopy. `

Exan~ple 2 Pre~aration of Mnn~AminoorQ~vl-Tç~ate~ Polvdi~nethv1siloxane `~
First, n-butyl lithium (10 ml, 2.5 M) was added to 7.4 g 25 octamethylcyclotetrasiloxane (D4) under argon to form lithium silanolate initiator. After sdrring for 30 minutes, a soludon of 250 g hexamethylcyclotrisiloxane (D3) in 250 g dry tetrahydrofuran was added following which the composition was slirred at room temperature for 18 hours.
To the resulting viscous syrup of lithium polydimethylsiloxanolate was added ~`30 3.4 g of the 3-aminopropyldime~hyl fluorosilane terminating agent of Example 1. The viscosity rapidly decreased. After s~isring for 2 hours, the solvent was distilled off on a rotary evaporator. The product was filtered to remove lithium fluoride and 250 g of silicone monoamine was provided as a clear, colorless oil. Titration of a sample dissolved in 50/50 isopropyl 35 alcohol/tetrahydrofi~ vith 0.1 N HCI gave a number average molecular ::

wo 93/16142 Pcr/uss3/oo49o ; s ~ 18-~weigh~, Mn, of 9400 (theore~ical Mn = 10,000). A mono-aminopropyl terminated polydimethylsiloxane, Mn = 15000, was also prepared by repeating -the above procedure, but increasing the amount of D3 in the reaction to 375 g.

Example 3 Preparation of Di-AminQ~rQpvl ~ermina~ PolydimethylsilQxanes A 500 ml 3-necked round bottom flask equipped with thermometer, mechanical stirrer, dropping funnel and dry argon inlet was charged with 7.44 g bis(3-aminopropyl3 tetramethyldisiloxane and 36 g of octamethylcyclotetrasiloxane (D4) which had been previously purged for 10 .
minutes with argon. The flask contents were heated to 80C with an oil bath, and a trace (about 0.03 to 0.05 g) of anhydrous 3-aminopropyl dimethyl tetramethylammonium silanolate catalyst was added via a spatula. The composition was sdrred at 80C and after 30 minutes of stirring had become quite viscous. Vapor phase chromatography ~VPC) showed that the end-blocker had completely disappeared. To the resultant reaction mixture (which; consisted of a 1,500 number average molecular weight polysiloxane with aminopropyl ;~i endgroups, cyclic siloxanes and active catalyst) was added dropwise over a hour period 310 g of argon-purged D4, resul~ng in a further rise in the viscosity. Heating the reaction flask contents at 80C was continued overnight.
The catalyst was decomposed by hea~ng at 150C for lt2 hour, and ~e product was stripped at 140C at 0.1 mm pressure until no more volatiles distilled (ca. 1 112 hour), resulting in 310 g of a clear, colorless, visc~us oil (a yield of 88% of theoretical) The number average molecular weighe of the product determined by acid titration was lû,000. Using this procedure, but varying the ratio of endblocker to D4, a silicone diamine with a number average molecular weight of 5,000 was also prepared.

Example 4 PreparatiOn n~i-s~Stitutçd UreaT~ kOX SiLV1 PQ1VSi1~aneS
These inte~nediate trialkoxysilane functional silicones having two groups per chain were prepared from the reaction of the corresponding aminoalkyl substituted silicones with an equivalent stoichiometric amount of isocyanatopropyl triethoxy silane, available from SiLAR Laboratories. Thus, 200 g di-aminopropyl terminated polydimethlsiloxane of 5,000 number average molecular weight of Example 3 was heated in vacuo (15mm Hg) at lOO~C for 10 minutes. The clear, colorless oil was cooled to room temperature under N2, Wo 93/16142 Pcr/uss3/oo49o and 19.76 g isocyanatopropyl triethoxysilane was added with stirring. The mixture was hazy at first, but cleared in lO minutes and became significantly more viscous. In a similar manner, an analogolss di-substituted urea-trialkoxysilyl polysiloxane of lO,000 number average molecular weight was prepared by the reaction or lO0 g of the lO,000 number average molecular weight diamine of Example 3 with 19.76 g isocyanatopropyl triethoxysilane.

Example 5 Preparation of Mon~Substituted Urea-Trialkoxvsilyl Polvsiloxanes In a manner similar to that of Example 4, the analogous mono-substituted polydimethylsiloxanes were produced again by the reaction of i.e., lO0 g of lO,000 number average molecular weight silicone pr~pylamine of -~
Example 2 with 2.47 g isocyanatopropyl triethoxysilane and 150 g of l5,000 number average molecular weight silicone propylamine of Example 2 with -~
I5 2.47 g isocyanatopropyl triethoxysilane.

E~xample 6 Preparation of I~lti-Substituted Urea-Trialko~ysilyl Polvsiloxanes -~
In a manner similar to that of Example 4, 100 g of PS 812, a multi-aminopropyl silicone (equivalent weight 1700) commercially available from Huls Amenca, was converted to the urea-triethoxysilyl polysiloxane with 14.53 g of the isocyanatopropyl triethoxysilane.

J3xamplç 7 Preparati~ ~f Multi-Substituted Sulfido-~Eialkoxysilyl PQlYsiloxanes A mixture of 100 g of PS-849, a trimethylsiloxy terminated polydimethyl c~mercaptopropylmethyl siloxane (- 8,000 number average molecular weight) having about 4 mercaptopropyl groups per chain (commercially available from Huls America Ine.), 8. lS g vinyl trimethoxysilane, and 0.~7 g azo-bis(isobutyronitrile) initiator were dissolved in 69 ml ethyl acetate. The clear solution was purged with N2 for 5 minutes, and heated at 55C for 24 hours. Gas chromatog~aphy of a sample revealed complete incorporation of the vinyl compound. Evaporation of the solvent under reduced pressure provided the product as a colorless, mo~ile oil.

WO 93/ 5 6142 Pcr/US93/00490 , .
"1~ Example 8 Preparation of Di-Substituted TrialkoxvsilYl Thioethers A solution of 11.4 g mercaptopropyl t~imethoxysilane, 9.03 g vinyl trimethoxysilane, and 0.1 g azo bis(i; ~utyronitrile)in 13.0 ml ethyl ace te was purged with nitrogen for 5 mil ~s and the;~ heated ~or 24 hours at 55C. The solution was cooled, the solvent evaporated on a rotary evaporator, and the resulting oil distilled under vacuum. The product was collected and weighed 18.5 g (93% yield). NMR confirrned the structure to be that of the desired trimethoxysilylethyl trimethoxysilylpropyl sulfide.
Example ~
Pre~aradon of Allylene Bis(3-Trialkoxvsilvlpropyl Thio~ Eth~rs To a slurry of 1.51 g 60% NaH in mineral oil (previously washed with hexane) in 40 ml dry tetrahydrofuran, was added 7.79 g 95%
mercaptopropyl trimethoxysilane in 10 ml THF dropwise at 14C to control -~
foaming. After 1 hour at room temperature, 5.88 g 97%
1,12-dibromododecane was added dropwise to the stirred solution. The reaction was al~owed to warm to room temperature, and stirred for 18 hours.
The resulting cloudy mixture was evaporated^to dryness, taken up in hep~ane, filtered, and r~stripped to give the product as a clea~, colorless oil having the expected structure, 1,12-bis (trimethoxysilylpropylthio) dodecane as shown by NMR. ~;

~xam~l~ 10 PreparatiQn~f Di-Substitutedlnalkoxysi!vl Urea-PQlv.~lkvlçn~ Qxides) S g Jeffaminen' D-2000, an amine telminated polypropylene oxide of 2,000 molecular weight available from the Texaco Chemical Co., was treated with 1.4 g isocyana~opropyl triethoxysilane and stirred for 25 minutes to g;ve the oligomeric bis(urea-triethoxysilane).
Prepar~tion of Moisture-Curable Polvsilox~ne ~ele~Coating Comp~sitions ExampJe 11 To a solution of 10 g of the di-substituted urea-trialkoxysilyl polysiloxanes of 5,000 molecular wàght prepared in Example 4 in 10 ml isopropyl alcohol was added 7.0 g of a 10% solution of trichloroacetic acid in isopropyl alcohol~ This was diluted to 10% solids by weight with 30 ml more wo 93/16l42 Pcr/uss3/004so ~ ~ 2 3, 1~

isopropyl alcohol, and was coated on 2 mil polyester film using a #3 Mayer rod. Immediately upon evaporation of the solvent under ambient conditions, a clear, tack-free coahng was obtained. lt adhered well to the substrate, and was quite rubbery in texture. The aged release and readhesion was recorded in Table 1.

Table 1 r _ ~
Release ~NIdm3 Readhesion (%) l ¦ Ex. Tape Sample 3 Da~f, 65C 3 Day, 65C -¦ 11 Tape C _ 5.03 105.0%

Exampl~ 12-14 .
Examples 12-14 demonstrate the use of mixtures of the functional 15 polysiloxanes described above to vary the release properties of the coatings of the invention. A fonnulation consisting of 85% of the di-substituted -urea-trialkoxysilyl polysiloxanes of 5,000 number average molecular weight prepared in Example 4, and 159~o of a 15,000 number average molecular weight mono-substituted urea-trialkoxysilane of Example 5 was prepared by dissolving 20. the two components in isopropyl alcohol at 5 % solids; 7 parts trichlo~oacetic acid by weight of silicone mixture were added, and the solution was coated on polyester film as described in Example 11. Again the material was cured immediately up~n drying~ but in this case, the coadng was much smoother to the touch than that of E~;ample 11. Example 13 was similarly prepared from 25 75% of the di-substituted urea^trialkoxysilyl polysiaoxane of 5,000 number average molecular weight prepared in Example 4 and 25% of a 15,000 number average molecular weight mon~substituted urea-trialkoxysilane of Exarnple 5.
In a similar manner, Example 14 was prepared from equal proportions of the di-substituted and mon~substi~uted trialkoxysilanes. Samples of these release 30 compositions were coated on polyester film as described in Example 11 and aged release and readhesion data were collected and report~ in Table 2.

Wo 93/16142 ~ ~ f.''. Pcr/US93/Oo49O
~ ? `'`"` `

Table 2 Reiease (Nldm) Readhesion (%) Ex. Tape Sample 3 Day, 6SC 3 Day, 65C I
12 Tape C 5.25 _ 91.6% ¦
¦ 13 Tape C 5.25 97.8%
¦ _ 14 ~ Tape C 7.66 91.2%

Example 15 ;
This example illustrates the ability ~o change the release properties of the polysiloxane coadng through altering the molecular weight of the difunctional alkoxysilyl polysiloxane consdtuent. A polydimethylsiloxane release coating was prepared in a manner identical to that found in Example 12, except that the 5,000 number average molecular weight di-substdtuted urea-~rialkoxysilane used in Example 12 was replaced by the 10,000 number average molecu!ar weight polysiloxane of Example 4. Aged release ind readhesion data were collected for this release coating formulation and reported ~;
in Table 3.

20 ~ Table 3 _ Release (N/dm) Readhesion (%) ¦
Ex~ Tape Sam~e 3 Day, 65~ 3 Day, 6SC ¦
Ta~e C 3.06 80~0%
. ~ ~ . ~ I --Exam~les 117 In a further variation, the multifunctional silicones having pendant isocyanato triethoxysilyl substituents, as prepared in Example 6, were incoIporated into the release coating formulation. Example 16 consists of 100% of this polysiloxane~ prepared in the same manner as Example 11.
Example 17, prepared by a similar method, consists of 25% mon~uncdonal compound of 15,000 number average molecular weight of Example 5, 60%
10,000 number average molecular weight di-functional alkoxysilane of Example 4, and 15æ of the above mentioned multifunctional silicone. Again, ~: :
.

WO 93/16142 PCI`/US93/00490 21 2 ~ '`? (';;

excellent release performance with a variety of pressure sensitive adhesives wasobserved. Aged release and readhesion data were collected for this release coating formulation and reported in Table 4.

Table 4 Release (N/dm) Readhesion (%) _ Ex. Tape Sample 3 Da~,r, 65C 3 Day, 65C
16 T A 0.82* _ I ape _ _ ¦ 17 Tape C 0.18 69.9 * denotes 2 day aged release or readhesion Ex~mples 18-19 These examples demonstrate that an altemative strongly acidic 15 compound, in this case cyanoacetic acid, may be substituted for trichloroacetic acid as the catalyst in this release composition. In Example 18, 25% 15,000 number average molecular weight mon~functional compound of Example 5 and 75 % 10,000 number average molecular weight difunctional polysiloxane of ~xample 4 were mixed witli 2% ~ichloroacetic acid as described in 20 Example 11. Example 19 illustrates that the same polysiloxane composition may be effectively cured using 2gb cyanoacetic acid acid catalyst. Aged release and readhesion data were collected for this release coating fonnulation and reported in Table ~. "

Table 5 .. _ ~ ., ". .. ~
Release (Nldm) Readhesion (~o) Ex. Ta~e Sam~le3 Dav 65C 3 Dav 65C
I . . ~......... _ . .. .
_ 18 Ta~e C 0.31 ~.0 _ ¦ 19 Ta~e C _0 35 92.9 Examples 20-21 These examples demonstrate the use of ~ialkyl ammonium salts of the strongly acidic component to delay the hydrolytic cure of the 35 polysiloxane release compositions of this inven~ion. ln Example 20, to a solution of 0.85 g of the difunctional triethoxysilyl-urea terminated silicone of Example 4 (4300 number average molecular weight), and 0.15 g of 15,000 .

Wo 93/16142 ~; Pcr/uss3/oo49o number average molecular weight mono-triethoxysilyl-urea of Example 5 in 9.0 g isopropyl alcohol, was added 0.04 g tnchloroacetic acid and 0.02 g triethylamine. A sample was coated on 2 mil polyester film with #6 Mayer rod and the solvent evaporated at room temperature. After 2 hours, the coating 5 remained an uncured, easily smeared oil; however, this, or a freshly coated film cured in less than 30 seconds when heated with a hot air gun. Similar results were obtained in Example 2l with another formulation consiseing of 1.0 g 85tlS 10,000 number average molecular weight di- and 15,000 number average molecular weight mono-triethoxysilanes, 0.06 g trichloroacetic acid and 10 0.06 g triethylarnine in l9 g isopropyl alcohol, and coated on polyester filmusing #3 Mayer rod. Again, little or no cure occurred until the films were briefly heated in air. Aged release and readhesion data were collected for this release coating formulation and reported in Table 6.

Table 6 _ Release (N/dm) Readhesion (~) ¦ Ex. Tape Sample 3 Day, 65C 3 Day, 65~C
Ta~e C 3.70* 95.4*
_, , ~ 21 Tape A _ 1.30 98.2 * denotes 2 day aged release or readhesion As is evident from the above results, many parameters may be easily valied (polysiloxane molecular weights, relaâve weight ratios of 25 polysiloxane functionalities and structural types, etc.) enabling optimization of properties for partieular applications.

~am21ç~2~
These examples introduce a non-polysiloxane containing 30 component to an alkoxysilyl functional polysiloxane to produce release coatings which display premium aged release when brought into contaet with several representative adhesive tape samples. In Examples 22-24, the multi-functional polysiloxane of Example 6 (78%), 22% of the bis-tsimethoxysilane of Example 8, and 5 parts tnchloroacetic acid were combined and coated as in Example ll.
35 Aged peel adhesions from a variety of pressure-sensitive adhesives tape samples was recorded and may be found in Table 7.

wo 93/16142 ~ ~ 2 ~ 8 ~ j Pcr/us93/00490 Table 7 ~ ~- _ Release (N/dm) Readhesion (%) Ex. Tape Sample 3 Day, 65C 3 Day, 65C
22 T D 2.00 86.7 _ ape _ _ 23 Ta~e A 0.50 101.4 . .
24 Tape B 0.70 97.7 Exam~les 25-28 Example 25 illus~ates the use of a combination of mono- and di-functional polysiloxane components with a non-polysiloxane alkoxysilyl compound. A mixture of 2.0 g of bis urea-triethoxysilyl terminal silicone (5000 number average molecular weight) of Example 4, 5.0 g ~`
mono-urea-triethoxysilyl silicone (15,000 number average molecular weight) of 15 Example 5, and 3.0 g of tetraethoxysilane was diluted to 10% by weight in isopropyl alcohol to provide a formulation consisting of 20% di-functional polysiloxanes, S0% mono-functional polysiloxanes, and 30% reactive diluent.
Tdchloroacetic acid, 0.5 g (5%),was added and a sample of the solution was coated on 2 mil polyester film. Evaporation of the solvent provided a clear, 20- tack free cured release coating. Other fonnula~ions were prepared in which the concentrations of the components was vaned.
Examples 2~29 are prepared in the same manner as Exunple 2S
and demonstrate the effect of altering concentrations of the three cvmponents ofExample 25. Example 26 contains 40% silicone di-silane, 30% silicone 25 mon~silane, and 30% tetraethoxysilane. Example 27 contains 67% di-, 12%
mono-, and 21% tet~ethoxysilane. Example 28 has percentages of 75%, 13%, and 12% of these mon~functional, di-functional, and diluent concentra~ons, res~ectively. Aged peel adhesions and readhesiorls were recorded and may be found in Table 8.

wo s3Jls~42 ~ f~ ~ Pcr/uss3/00490 ~ ~1 t ~
, 26-Table 8 _ _ _ _ Release (N/dm)Readhesion (%) Ex. Ta~e Sam~le 3 Dav, 65C 3 Day, 65C
. ~__ . .
Tape D _ 2.08 _ 139.3 26 Ta~e D 1 70 98.7 . ... . .
27 Ta~e D 2 20 94.9 _ _. . , .... _ 28 Tape D 1.94 98.2 Exam~
A mixture of 5.0 g silicone diamine of Example 3 having 4300 number average molecular weight, and 5.0 g of 15,000 number average molecular weight silicone mono-funcdonal compound of Example 2, was dissolved in 90 g isopropyl alcohol and, while stirring, treated wi~h 0.66 g 15 3-isocyanatopropyl triethoxysilane to form the urea-triethoxysilanes. To thissolution was added dropwise with stirring, 5.5 g of ~alco 2326, a 15~ aqueous dispersion of colloidal silica stabilized with ammonia, available from Nalco Chemical Co; this amounts to 8% solid silica relative to weight of silicones.
Cyanatoacetic acid, 0.5 g (5%),was dissolved in the solution and then coated on 20 ~ polyester film using a ~f3 Mayer rod; the film was placed in a 93C oven for 30 seconds to provide a clear, tack free coating which could not be rubbed off.
Aged peel adhesions and readhesions were recorded and may be found in Table 9.

Table 9 r ~ ~ ~
Release ~Ntdm~ Readhesion (%) L _ Ex. Tape Sample 3 I:)ay, 65C _3 Day, 65C
¦ _ 29~ Tape C 9.57_ 103.3 ~3Q~ .
For these coa~ngs, two formulations were prepared aecording to the method of Example 25; the first consisled of a mixture of 10% af the 5,000 number average molecular weight bis urea-triethoxysilane of Example 4, 70%
35 bis thioether trimethoxysilane of Example 9, and 20~o octyltriethoxysî}ane (Examples 30 and 32). The second (Examples 31 and 33~ had 5% of the W O 93/16142 PC~r/US93/00490 ~ ;r~ -;

di-functional alkoxysilane, 70% of the bis thioether trime~h~xy silane, and 20%
of the octyltriethoxysilane. Both were treated with 5 % trichloroacetic acid andcoated in the usual manner at 5% solids in isopropyl alcohol. As can be seen by the aged release and readhesion data recorded in Table 10, decreasing 5 polysiloxane concen~ation lead to an increase in release when tested against two different pressure-sensitive adhesive tape samples.

Table 10 . ,_ . ... ,.. ,"" ,~_ , _ : _ ~ _~ ~
Release (N/dm) Readhesion (%) ¦ Ex. Tape Sample 3 Day, 65C 3 Day, 65C
¦ 30 Tape D 17.97 93.6 ¦ ~31 Tape D _ 19.00 _ 95.1 1 32 _ Tape C_ _ 4.38 109.2 L 33 Tape C 4.60 ~ lrO~0-4~ . .

Exarnp]e 34 A mixture of 0.5 g SK bis urea-triethoxysilane of Example 4, O~S g 2K polypropylene oxide bis urea-triethoxysilane of Example 10, and - 20~ 0.07 g ~ichloroacetic acid in 9 g isopropyl alcohol was coated on polyester film as described in Example 25. The final coating was smooth and completely clear. Aged peel adhesions and readhesions were recorded and may be found in Table 11.

Table 11 ~ ~ ~. = ., .- ,.~ . _ Release (Nldm) Readhesion (%) ~__~ape Sa~ple 3 Day, 659C_ 3 Day? 65C
¦ 34Tape D_ _ 8.98 _ 91.5 While this invention has been described in connection with speeific embodiments, it should be understood that it is capable of further modification. The claims herein are intended to cover those variations which one skilled in the art would recognize as the chemical equivalent of what has 35 been described here.

Claims (10)

Claims

1. A release coating composition comprising:
(a) about 1 to about 100 percent by weight of polymer selected from the group consisting of polymers of the general Formula:

(I) and mixtures thereof:
wherein n and m each represent integers, wherein the sum of n plus m is an integer of about 20 to about 5000;
m has a value ranging from about 0 to about 0.1(n+m);
R1 arc monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted allyl, aryl, and substituted aryl;
R2 are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl;
W are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, and reactive hydrolyzable group ;

wherein at least about 50% of the total number of silicon atoms excluding those in said reactive hydrolyzable group(s) have two methyl groups bonded thereto, and wherein at least one reactive hydrolyzable group appears on each polymer of Formula I and further wherein at least about 25 %
of the polymers of Formula I in the release coating composition have at least two reactive hydrolyzable groups ;

wherein X are divalent linking groups which can be the same or different selected from the group consisting of alkylene groups comprising about 1 to about 12 carbon atoms;
Q are divalent linking groups which can be the same or different selected from the group consisting of urea, amide, urethane, thiourethane, ether, and thioether groups;
Y are divalent linking groups which can be the same or different selected from the group consisting of alkylene groups comprising about 1 to about 12 carbon atoms;
t is an integer of 0 to 10;
Z are monovalent moieties which can be the same or different selected from the group consisting of -OR and -R wherein R is an alkyl group comprising about 1 to about 3 carbon atoms; and R3 is a monovalent alkyl group comprising about 1 to about 3 carbon atoms;
(b) about 0 to about 99 percent by weight of a component selected from the group consisting of compounds and polymers of the general Formula:
(R3O)3-Si-A (II) hydrolysates thereof, and mixtures thereof, wherein R3 is as previously defined;
A is a monovalent moiety selected from the group consisting of -OR3, monovalent alkyl groups comprising about 1 to about 20 carbon atoms, and X-(Q)p-[D-Q]t-(Y)b-Si(OR3)3, wherein X, Q, t, Y and R3 are as previously defined;
D is a divalent group which can be the same or different selected from the group consisting of alkylene groups comprising from about 2 to about 30 carbon atoms; aralkylene groups comprising from about 6 to about 30 carbon atoms; arylene groups comprising from about 6 to about 30 carbon atoms; and divalent polymeric segments having a number average molecular weight of about 500 to about 10,000 selected from the group comsisting of polyether, polyolefin, polyester, polydiene, and mixtures thereof;
p is an integer of from 0 to 1;
b is an integer of from 0 to 1;
wherein when t is an integer of 1 to 10, b must equal 1 and p must equal 1;

wherein when t=0 and b=0, p must also equal 0;
wherein the weight percentages of (a) and (b) are based upon the total weight of (a) plus (b); and (c) about 1 to about 15 percent by weight based upon the total weight of (a) plus (b) of a component selected from the group consisting of acids having pKas of less than about 3, anhydrides of acids having pKas of less than about 3, ammonium salts of acids having pKas of less than about 3, lower alkyl ammonium salts of acids having pKas of less than about 3, and mixtures thereof.

2. The release coating composition of claim 1 wherein R1 and R2 each comprise methyl groups, X and Y each comprise -CH2CH2CH2-, t equals 1, and Q is independently selected from the group consisting of urea and thioether groups;
wherein each Z moiety comprises -OCH3 and each R3 group comprises -CH3;
wherein the component of Formula II is selected from the group consisting of alkoxysilyl terminated polypropylene oxide, alkoxysilyl terminatedpolyethylene oxide, alkoxysilyl terminated polycaprolactone, alkoxy silyl terminated polytetramethylene oxide, alkoxysilyl terminated alkanes, alkoxysilane terminated ethers, alkoxy terminated thioethers, tetraalkoxy silyl compounds, and mixtures thereof; and wherein the component of element (c) is selected from the group consisting of trichloroacetic acid, cyanoacetic acid, malonic acid, nitroacetic acid, dichloroacetic acid, difluoroacetic acid, trichloroacetic anhydride, dichloroacetic anhydride, difluoroacetic anhydride, triethylammonium trichloroacetate, trimethylammonium trichloroacetate, and mixtures thereof.

3. The release coating composition of claim 1 wherein component (b) comprises about 1 to about 15 percent by weight of colloidal silica based upon the total weight of (a) plus (b).

4. A release coating composition comprising:
(a) about 1 to about 100 percent by weight of polymer selected from the group consisting of polymers of the general Formula:

(I) and mixtures thereof:
wherein n and m each represent integers, wherein the sum of n plus m is an integer of about 70 to about 1000;
m has a value ranging from about 0 to about 0.1(n+m);
R' are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl;
R2 are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl;
W are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted allyl, aryl, substituted aryl, and reactive hydrolyzable group ;

wherein at least about 50% of the total number of silicon atoms excluding those in said reactive hydrolyzable group(s) have two methyl groups bonded thereto, and wherein at least one reactive hydrolyzable group appears on each polymer of Formula I and further wherein at least about 25%
of the polymers of Formula I in the release coating composition have at least two reactive hydrolyzable groups ;

wherein X are divalent linking groups which can be the same or different selected from the group consisting of alkylene groups comprising about 1 to about 12 carbon atoms;
Q are divalent linking groups which can be the same or different selected from the group consisting of urea, amide, urethane, thiourethane, ether, and thioether groups;

Y are divalent linking groups which can be the same or different selected from the group consisting of alkylene groups comprising about 1 to about 12 carbon atoms;
t is an integer of 0 to 10;
Z are monovalent moieties which can be the same or different selected from the group consisting of -OR and -R wherein R is an alkyl group comprising about 1 to about 3 carbon atoms; and R3 is a monovalent alkyl group comprising about l to about 3 carbon atoms;
(b) about 0 to about 99 percent by weight of a component selected from the group consisting of compounds and polymers of the general Formula:
(R3O)3-Si-A (II) hydrolysates thereof, and mixtures thereof, wherein R3 is as previously defined;
A is a monovalent moiety selected from the group consisting of -OR3, monovalent alkyl groups comprising about 1 to about 20 carbon atoms, and -X-(Q)p-[D-Q]t-(Y)b-Si(OR3)3 wherein X, Q, t, Y and R3 are is previously defined;
D is a divalent group which can be the same or different selected from the group consisting of alkylene groups comprising from about 2 to about 30 carbon atoms; aralkylene groups comprising from about 6 to about 30 carbon atoms; arylene groups comprising from about 6 to about 30 carbon atoms; and divalent polymeric segments having a number average molecular weight of about 500 to about 10,000 selected from the group consisting of polyether, polyolefin, polyester, polydiene, and mixtures thereof;
p is an integer of from 0 to 1;
b is an integer of from 1 to 1;
wherein when t is an integer of 1 to 10, b must equal 1 and p must equal 1;
wherein when t=0 and b-0, p must also equal 0;
wherein the weight percentages of (a) and (b) are based upon the total weight of (a) plus (b); and (c) about 3 to about 10 percent by weight based upon the total weight of (a) plus (b) of a component selected from the group consisting of acids having pKas of less than about 3, anhydrides of acids having pKas of less than about 3, ammonium salts of acids having pKas of less than about 3, lower alkyl ammonium salts of acids having pKas of less than about 3, and mixtures thereof.

5. A release coating formed from curing the composition of claim 1.

6. A release coating formed from curing the release coating composition of claim 4.

7. A substrate coated with the release coating of claim 5.

8. A substrate coated with the release coating of claim 6.

9. A method of forming a release coating coated substrate comprising the steps of:
(a) applying to a substrate a layer of a release coating composition, wherein said release coating composition comprises:
(i) about 1 to about 100 percent by weight of polymer selected from the group consisting of polymers of the general Formula:

(I) and mixtures thereof:
wherein n and m each represent integers, wherein the sum of n plus m is an integer of about 20 to about 5000;
m has a value ranging from about 0 to about 0.1(n+m);
R1 are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl;
R2 are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl;

W are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, and reactive hydrolyzable group ;

wherein at least about 50% of the total number of silicon atoms excluding those in said reactive hydrolyzable group(s) have two methyl groups bonded thereto, and wherein at least one reactive hydrolyzable group appears on each polymer of Formula I and further wherein at least about 25%
of the polymers of Formula I in the release coating composition have at least two reactive hydrolyzable groups ;

wherein X are divalent linking groups which can be the same or different selected from the group consisting of alkylene groups comprising about 1 to about 12 carbon atoms;
Q are divalent linking groups which can be the same or different selected from the group consisting of urea, amide, urethane, thiourethane, ether, and thioether groups;
Y are divalent linking groups which can be the same or different selected from the group consisting of alkylene groups comprising about 1 to about 12 carbon atoms;
t is an integer of 0 to 10;
Z are monovalent moieties which can be the same or different selected from the group consisting of -OR and -R wherein R is an alkyl group comprising about 1 to about 3 carbon atoms; and R3 is a monovalent alkyl group comprising about 1 to about 3 carbon atoms;
(ii) about 0 to about 99 percent by weight of a component selected from the group consisting of compounds and polymers of the general Formula:
(R3O)3-Si-A (II) hydrolysates thereof, and mixtures thereof, wherein R3 is as previously defined;

A is a monovalent moiety selected from the group consisting of -OR3, monovalent alkyl groups comprising about 1 to about 20 carbon atoms, and -X-(Q)p-[D-Q]t-(Y)b-Si(OR3)3 wherein X, Q, t, Y and R3 are as previously defined;
D is a divalent group which can be the same or different selected from the group consisting of alkylene groups comprising from about 2 to about 30 carbon atoms; aralkylene groups comprising from about 6 to about 30 carbon atoms; arylene groups comprising from about 6 to about 30 carbon atoms; and divalent polymeric segments having a number average molecular weight of about 500 to about 10,000 selected from the group consisting of polyether, polyolefin, polyester, polydiene, and mixtures thereof;
p is an integer of from 0 to 1;
b is an integer of from 0 to 1;
wherein when t is an integer of 1 to 10, b must equal 1 and p must equal 1;
wherein when t=0 and b=0, p must also equal 0;
wherein the weight percentages of (i) and (ii) are based upon the total weight of (i) plus (ii); and (iii) about 1 to about 15 percent by weight based upon the total weight of (i) plus (ii) of a component selected from the group consisting of ammonium salts of acids having pKas of less than about 3, lower alkyl ammonium salts of acids having pKas of less than about 3, and mixtures thereof;
(b) heating said release coating composition sufficiently to dissociate the component selected from the group consisting of ammonium salts of acids having pKas of less than about 3, lower alkyl ammonium salts of acids having pKas of less than about 3, and mixtures thereof, in order to evaporate ammonia, amine(s), or both, and yield acid(s) having pKas of less than 3; and, (c) exposing said release coating composition to atmospheric moisture sufficient to cure said reactive hydrolyzable groups to form Si-O-Si crosslinks.

10. A method of forming a release coating coated substrate comprising the steps of:
(a) applying to a substrate a layer of a release coating composition, wherein said release coating composition comprises:

(i) about 1 to about 100 percent by weight of polymer selected from the group consisting of polymers of the general Formula:

(I) and mixtures thereof:
wherein n and m each represent integers, wherein the sum of n plus m is an integer of about 20 to about 5000;
m has a value ranging from about 0 to about 0.1(n+m);
R' are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl;
R2 are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl, W are monovalent moieties which can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, substituted aryl, and reactive hydrolyzable group ;

wherein at least about 50% of the total number of silicon atoms excluding those in said reactive hydrolyzable group(s) have two methyl groups bonded thereto, and wherein at least one reactive hydrolyzable group appears on each polymer of Formula I and further wherein at least about 25%
of the polymers of Formula I in the release coating composition have at least two reactive hydrolyzable groups ;

wherein X are divalent linking groups which can be the same or different selected from the group consisting of alkylene groups comprising about 1 to about 12 carbon atoms;

Q are divalent linking groups which can be the same or different selected from the group consisting of urea, amide, urethane, thiourethane, ether, and thioether groups;
Y are divalent linking groups which can be the same or different selected from the group consisting of alkylene groups comprising about 1 to about 12 carbon atoms;
t is an integer of 0 to 10;
Z are monovalent moieties which can be the same or different selected from the group consisting of -OR and -R wherein R is an alkyl group comprising about 1 to about 3 carbon atoms; and R3 is a monovalent alkyl group comprising about 1 to about 3 carbon atoms;
(ii) about 0 to about 99 percent by weight of a component selected from the group consisting of compounds and polymers of the general Formula:
(R3O)3-Si-A (II) hydrolysates thereof, and mixtures thereof, wherein R3 is as previously defined;
A is a monovalent moiety selected from the group consisting of -OR3, monovalent alkyl groups comprising about 1 to about 20 carbon atoms, and -X-(Q)p-[D-Q]t-(Y)b-Si(OR3)3 wherein X, Q, t, Y and R3 are as previously defined;
D is a divalent group which can be the same or different selected from the group consisting of alkylene groups comprising from about 2 to about 30 carbon atoms; alkylene groups comprising from about 6 to about 30 carbon atoms; arylene groups comprising from about 6 to about 30 carbon atoms; and divalent polymeric segments having a number average molecular weight of about 500 to about 10,000 selected from the group consisting of polyether, polyolefin, polyester, polydiene, and mixtures thereof;
p is an integer of from 0 to 1;
b is an integer of from 0 to 1;
wherein when t is an integer of 1 to 10, b must equal 1 and p must equal 1;
wherein when t=0 and b=0, p must also equal 0;
wherein the weight percentages of (i) and (ii) are based upon the total weight of (i) plus (ii); and (iii) about 1 to about 15 percent by weight based upon the total weight of (i) plus (ii) of a component selected from the group consisting of acids having pKas of less than about 3, anhydrides of acids havingpKas of less than about 3, and mixtures thereof; and (b) exposing said release coating composition to atmospheric moisture sufficient to cure said reactive hydrolyzable groups to form Si-O-Si crosslinks.