WO2021118544A1

WO2021118544A1 - Alkoxy group-containing silicones with reactive functional groups of defined reactivity

Info

Publication number: WO2021118544A1
Application number: PCT/US2019/065586
Authority: WO
Inventors: Timothy B. MCCORMACK; Daniel Calimente
Original assignee: Wacker Chemie Ag
Priority date: 2019-12-11
Filing date: 2019-12-11
Publication date: 2021-06-17

Abstract

Organopolysiloxanes with reactive functional groups which dominate reactivity of the organopolysiloxane are prepared by a cohydrolysis involving alkoxy-functional silanes or siloxanes and hydroxyl-functional reagents, such that the resulting polymers contain less than 10 weight percent of unreacted alkoxy groups, and a ratio of non-reactive groups to silicon of greater than 1:1.

Description

ALKOXY GROUP-CONTAINING SILICONES WITH REACTIVE FUNCTIONAL GROUPS OF DEFINED REACTIVITY

BACKGROUND OF THE INVENTION

1 - Field of the Invention

The present invention pertains to reactive organopolysiloxanes (silicones) bearing alkoxy groups, and reactive functional groups which dominate the overall reactivity of the reactive silicone. The reactive silicones arc prepared through hydrolytic condensation of hydrolyzable precursors. The invention further pertains to curable compositions containing the reactive organopolysiloxanes, and to their use, particularly in coatings and encapsulants. 2. Description of the Related Art

Silicones having reactive organic functional groups such as hydroxya!kyi, aminoalkyl, isocyanatoalkyi and the like are biown. Such reactive silicones may be prepared, for example, by hydrosilylating an ethylenically unsaluratcd compound also bearing a desired reactive group, for example allylamine or isocyaoatoethylmetbacrylaie with a silane or polysiloxane bearing silicon-bonded hydrogen (ΞSi-K). A desirable characteristic of these reactive silicones is that (hey react exclusively through the reactive organic functionality to form macromolccules having the desired properties. However, a disadvantage is that more expensive Si-H functional organosilicon compounds must be used to prepare them, and that ethylenically unsaturated compounds bearing the desired reactive group may not be available, may not have the desired stability, or are available at only relatively high cost.

A further disadvantage is that hydrosilylation generally employs a noble metal hydrosilylation catalyst, generally a platinum-based catalyst, which adds to the expense, if the hydrosilylation reaction is not complete, unreacted ethylenically unsaturated reactants must be removed, e.g. by subjecting the product mixture to stripping or vacuum, which is not always effective unless the temperature is raised. For some reactive groups, however, raising the t temperature is contraindicated, as the reactive functional groups may react or condense. Furthermore, if the final product contains unreacted Si-H groups, these may give rise to storage problems, especially if water is present. Reaction with water can liberate explosive hydrogen gas.

In U.S. Patent 5,814,703, highly branched silicones having aminoalkyl, epoxyalkyl, or elhylenically unsaturated groups are prepared, not by hydrosilylation, but by hydrolytic condensation of a functional diaLkoxysi!ane or trialkoxysilane with a non -functional dialkoxysiiane or trialkoxysilane, optionally together with tetra-alkoxysilanes. These highly branched reactive silicones contain minimally 10 mol percent of “T-units," RSiO_3/2, which form branching sites. Moreover, they contain a limited amount of non-functionai hydrocarbon groups relative to the number of silicon atoms. Due to these requirements and preparation method, the desired reactive functional group is accompanied by a large quantity of non-hydrolyzed alkoxy groups. These reactive silicones may be used to form hard coatings what admixed with a non- functional polymer resin, or preferably, a reactive, crosslinkablc polymer resin.

It has been found, however, that reactive silicones such as those disclosed in U.S. 5,814,703, have numerous drawbacks. First, the relatively high proportion of alkoxy groups allows the silicone, once the organic reactive groups have reacted, to further crosslink in the presence of moisture, which is unavoidable in coatings and articles intended for normal use. Thus, the chemical bonds formed are only partially the result of reaction of the intended organic functional groups. “Designed reactivity” under such conditions is impossible to achieve. Moreover, under conditions of high humidity, the alkoxy groups may react even prior to reaction of the organic functional groups, decreasing mobility of the growing polymer chains to the extent that a proportion of the functional groups may remain unreacted. Furthermore, the products, particularly when used in sections thicker than thin films, show evidence of cracking, shrinkage, and voids (from outgassing of condensation reaction alcohol) which may occur even as early as during initial cure. Such compositions are completely unsuitable as encapsulants for electronic devices, for example. Finally, these reactive silicones display poor compatibility with many polymers, as a result of which a homogeneous coating composition is difficult or even impossible to obtain, or which may be subject to phase-out into silicone-rich and silicone-poor regions in the cured product. It would be desirable to provide reactive silicone polymers by a method which avoids hydrosilylation and its disadvantages, yet provides a greater degree of defined reactivity. It would be further desirable to provide reactive silicone resins which are flexible and exhibit little tendency to crack or develop voids during cure or thereafter, and which exhibit greater compatibility with organic polymers.

SUMMARY OF THE INVENTION

It has now been surprisingly and unexpectedly discovered that if the number of non- reactive silicon-bonded organic groups in a reactive silicone is increased beyond a ratio of 1 per silicon atom, and the residual alkoxy group content is kept below 10 weight percent, that a greater degree of defined reactivity, lesser tendency to crack during or after cure, and greater compatibility with organic polymers can be simultaneously obtained. This is achieved by synthesis of the reactive silicone by careful selection of the hydrolyzable precursor reactants such that the ratio of non-functional groups to silicon in the reactive silicone polymer is greater than 1:1, and the alkoxy content is less than 10 weight percent, while having a reactive functionality greater than 2 on average per molecule, this functionality selected from among epoxy, amino, carboxylic acid, and (metb)acrylic functionalities.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT (S)

The first embodiment of the present invention is a reactive organopolysiloxanc prepared by hydrolytic condensation, comprising on average a) at least two reactive functional groups per molecule, selected from the group consisting of epoxy, amino, carboxy, and (meth)acrylate groups, and mixtures thereof the functional groups bonded to silicon atoms in the reactive organopolysiloxanes, and b) alkoxy groups, in a concentration of less than 10 weight percent based on the total weight of the reactive organopolysiloxanes calculated on the basis of methoxy groups, and c) non-reactive optionally substituted hydrocarbon groups Si-C bonded to silicon atoms of the reactive organopolysiloxanc, the non-rcactive optionally substituted hydrocarbon groups present in a ratio of >1 hydrocarbon group per atom of Si in the reactive organnopolysiloxane, and wherein the at least two reactive functional groups are introduced into the reactive organopolysiloxane by one of the following two condensation processes i) or ii) i) condensing a plurality of alkoxysilanes or their partial hydrolysates, with at least one organic compound comprising a hydroxyl group and a reactive functional group consisting of epoxy, amino, carboxy, and (meth)acrylate groups, and mixtures thereof and with at least one second aikoxysilane or second partial hydrolysate bearing 1, 2, or 3 non-reactive, optionally substituted hydrocarbon groups, or ii) condensing a silanol-stopped or alkoxysilyl-stopped organopolysiloxane or their partial hydrolysates, with at least one organic compound comprising a hydroxyl group and a reactive functional group consisting of epoxy, amino, carboxy, and (meth)acryiate groups, and mixtures thereof, and optionally with an aikoxysilane bearing 1 , 2, or 3 non-reactive, optionally substituted hydrocarbon groups.

Preferably the at least two reactive functional groups per molecule are selected from the group consisting of amino, carboxy, and (meth)acrylale groups, more preferably from acrylate and methacrylate groups. Preferably, the reactive functional groups are the same or of the same type of functional groups.

The second embodiment of the present invention is a curable composition, comprising A) at least one of the above mentioned reactive organopolysiloxanes, and a catalyst effective to cause polymerization of the respective reactive functional groups, or

B) at least one of the above mentioned reactive organopolysiloxanes, and at least one curing agent bearing complementary reactive functional groups reactive with the reactive functional groups of the above mentioned reactive or ga n op oly si 1 ox a n es, and optionally a catalyst effective to catalyze the reaction of the reactive functional groups with the complementary reactive functional groups; or

C) at least a first of the above mentioned reactive organopolysiloxanes, and at least a second at least one of the above mentioned reactive organopolysiloxanes bearing complementarity reactive functional groups reactive with the reactive functional groups of the first reactive organopolyslloxane, and optionally a catalyst effective to catalyze the reaction of die reactive functional groups of the first reactive organopolysiloxanes with the second reactive orgauopolysiloxane. in a preferred embodiment the curable composition comprising at least one reactive rganopolysiloxane with acrylate and/or methacrylate groups and i) further comprising a free radical initiator effective to polymerize the (meth)acrylate groups, or ii) further comprising an Si-II functional crosslinker and an effective amount of ahydrosilylation catalyst.

The third embodiment of the present invention is the process for the preparation of the above mentioned reactive organopolyslloxane comprising on average a) at least two inactive functional groups per molecule, selected from the group consisting of epoxy, amino, carboxy, and (methacrylate groups, and mixtures thereof, the functional groups bonded to silicon atoms in the reactive organopolysiloxanes, and b) alkoxy groups, in a concentration of less than 10 weight percent based on the total weight of the reactive organopolysiloxanes calculated on the basis of methoxy groups, and c) non-reactive optionally substituted hydrocarbon groups Si-C bonded to silicon atoms of the reactive orgauopolysiloxane, the non-reactive optionally substituted hydrocarbon groups present in a ratio of >1 hydrocarbon group per atom of Si in the reactive orgauopolysiloxane, and wherein the at least two reactive functional groups are introduced into the reactive organopolysiloxane by one of the following two condensation processes i) or ii) i) condensing a plurality of alkoxysilanes or their partial hydrolysates, with at least one organic compound comprising a hydroxyl group and a reactive functional group consisting of epoxy, amino, carboxy, and (meth)acrylate groups, and mixtures thereof, aud with at least one second alkoxysilane or second partial hydrolysate bearing 1, 2, or 3 non-reaetive, optionally substituted hydrocarbon groups, or ii) condensing a siianol-stopped or alkoxysilyl-stopped organopolysiloxane or their partial hydrolysates, with at least one organic compound comprising a hydroxyl group and a reactive functional group consisting of epoxy, amino, carboxy, and (meth)acrylate groups, and mixtures thereof, and optionally with an alkoxysilane bearing 1, 2, or 3 non-reactive, optionally substituted hydrocarbon groups.

The reactive silicones of the present invention are prepared by the eohydroiytic condensation of hydroxy bearing reagents bearing reactive epoxy, amino, carboxylic acid, or (meth)acrylic groups with stlanol or alkoxy functional polysiloxanes and silanes bearing nonfunctional groups. The usage of hydroxy terminated reagents facilitates a low alkoxy content, less than 10 weight percent calculated as melhoxy groups based on the total weight of the reactive silicone, preferably less than 9 weight percent, and preferably also in the range of 1 to 8 weight percent, more preferably 2 to 8 weight percent, and also 2 to 7 weight percent, and more than 1 non-functional group per silicon atom, on average, in the reactive silicone, more preferably on average 1.1 to 1.5 non-functional groups per silicon atom. If other than methoxy groups are present, the appropriate weight percent are calculated as if the alkoxy groups present were methoxy groups. Another advantage of the use of hydroxy bearing reagents is that it allows the direct condensation of the functional group containing reagent to the siloxanc. Prior art using alkoxy silanes and alkoxy siloxanes requires an intermediate hydrolysis step of some of these alkoxy groups for the condensation reaction to proceed. This hydrolysis step can be unpredictable and lead to the undesirable self-coudensatiou of some of the reaction components.

Most preferably, the reactive functional groups arc supplied by hydrolytic condensation of a hydroxy bearing reagents bearing the desired functional group, tor example 2-hydroxyethyi acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, when, for example an acrylate group is the desired functionality. Hydroxy bearing epoxy, amino, carboxylic acid, methacrylate, ethylaerylate, and other alkylacrylatc reagents may be used in analogous fashion to prepare the respective functional silicones. Also, preferably, an alkoxysilane or alkoxypolysiloxanc bearing non-functional groups, most preferably an alkoxypolysiloxane, optionally together with an alkoxysilane, is used to provide the non-functional groups.

By "non-functional” group is meant an organic group R with little or no reactivity under expected preparation conditions, and subsequently under curing conditions. Such groups include, but are not limited to, Si-C bonded, optionally substituted hydrocarbon groups, examples of which are alkyl groups, alkenyl groups (when the reactive group is other than a (meth)acrylic group), aryl groups, aralkyl groups, and alkaryl groups, where the alkyl groups may be linear or branched or cyclic. "Non-functional” groups do not include Si-0 bonded alkoxy groups, Si-N bonded nitrogen-containing groups, and silicon-bonded halogen.

Suitable R groups are, for example, linear alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, ocladecyl, etc ., branched alkyl groups such as 2-butyl, and ethylhexyi; cycloalkyl groups such as cyclopentyl, cyclohexyl, methylcyclohexyl, and cyclohexylmcthyl; alkenyl groups such as vinyl, co-hexene, and allyl, preferably vinyl; aryl groups such as phenyl and napthy!; alkaryl groups such as tolyl and xylyl; and aryhlkyl groups such as benzyl, and the α- and β- phenylethyl groups. This list is non-limiting.

Examples of substituted non-reactive groups are halo-substituted hydrocarbon groups such as fluonaated and chlorinated hydrocarbon groups, for example, perfluoropropyl, chloropropyl, chloroethyl, o-, m-, and p-chlorophenyl, and· the like, and hydrocarbon groups substituted with cyano groups, hydroxyl groups or alkoxy groups (including polyoxyalkylene groups).

The reactive silicones of the present invention contain M units, D units, optionally T units, and optionally Q units, defined as follows:

R¹ _aR_b(OR²)cSiO_1/2 (M) where a, b, and c are each 0 to 3 and the sum of a+b+c is 3;

R¹ _aR_b(OR²)cSiO_2/2 (D) where a, b, and c are each 0 to 2 and the sum of a+b+c is 2;

R¹ _aR_b(OR²)cSiO_3/2 (T) where a, b, and c are 0 or 1 and th e sum of a+b+c is 1; and

SiO4/2 (Q).

In these formulae, R is a non-reactive group as previously defined, R^! is a reactive functional group which contains an epoxy group, amino group, carboxylic acid group, or (meth)acrylate group in each case Si-0 bonded to silicon; and OR² is an Si-0 bonded alkoxy group, R² being the same as R.

The reactive silicones may thus be described as

M_mD_eT₀Qp where M, D, T, and Q are defined as above, where M is such that all chain ends are terminated with M groups, n is 1 to 10,000, preferably 2 to 1000, and more preferably 2 to 100, 0 is 0 0 to 100, preferably 1 to 20, and most preferably 2 to 15; and p is 0 to 10, preferably 0 to 5, and more preferably 0 to 3. Most preferably, the silicones contain no Q units, or only those present as an unavoidable consequence of the hydrolytic condensation. On average, each molecule contains at least two reactive functional groups R¹, and the proportion of alkoxy groups, calculated on the basis of methoxy groups, is less than 10 weight percent, By (meth)acrylic group is meant an acrylate or methacrylate bound to the organopotysiloxane.

The reactive organopolysiloxanes are generally liquids, for example with a viscosity of 50 cps to I0⁶ cps, more preferably 100 cps to 10^s cps, and may be described as lightly to moderately branched organopolysiloxanes, but can be described as silicone resins, which are highly branched, network like polymers dominated by T and Q groups, and which are generally solids.

The reactive organopolysiloxanes of the present invention arc prepared by condensation of hydroxy bearing reagents containing the desired functional group, with alkoxy-fvmctional reactants, optionally also with Si-OH functional polymers. Any suitable method of preparation may be used, but two methods are preferably used. In the first of these methods, which may be termed an ab initio synthesis, the principle reactants are silanes, optionally also using alkoxy- rich partial hydrolysates of these silanes, along with a hydroxyl bearing reagent bearing the desired epoxy, anhydride, amino, carboxylic acid, or (alkyl)acrylate group. Each silane contains at least one condensable group, preferably a lower alkyl alfcoxy group, more preferably methoxy, ethoxy, or butoxy groups, or m ixtures of these.

Hereafter, the synthesis will be illustrated for acrylate and methacrylate group-containing reactive organosiloxancs, employing acrylate and methacrylate group-containing reactants, i.e. those containing A_(m)a groups, and more particularly A’(m)n-B-groups as hereafter defined. However the synthetic methods are equally applicable for epoxy group-containing reactive organopolysiloxanes where A(m> and A_(m)o~B- are replaced by E and E'-B respectively, amino group-containing reactive organopolysiloxanes where A_(m)a and A'_(m)n-B- are replaced by A and A'-B-, carboxy group-containing reactive organopolysiloxanes where A_(m)a and A'_(m)a -B- are replaced by Ac and Ac'-B, respectively. It is noted that unless extreme care is taken with respect to reaction conditions, particularly pH, it is generally impossible to prepare reactive organopolysiloxanes containing more than one type of reactive functionality selected from epoxy, amino, and carboxylic, since these groups are generally inter-reactive.

Examples of hydroxyl bearing acrylates as listed previously 2-hydroxycthyl acrylate, 2- hydroxypropyl acrylate, 4-hydroxybutyl acrylate, etc.

Suitable hydroxy bearing alkylacrylales include 2-hydroxyethyl methacrylate, 2- hydroxypropyl methacrylate, 4-hydroxybotyl methacrylate, and corresponding hydroxyalkylated ethyl, propyl, and butyl acrylates,

Suitable hydroxyl bearing epoxies include glyeidol.

Suitable hydroxyl terminated amino reagents include 3-atnino-l -propanol, 4-amino -1- butanol, 5-amino- 1 -pcntanol, 6-amino- i-hcxanol, etc.

Suitable hydroxyl bearing carboxylic acids include, for example, 3-hydroxypropanoic acid, 2-hydroxybutanoic acid, 6-hydroxyhexanoic acid, 8-hydroxyootanoic acid, 9- hydroxynonanoic acid, 10-hydroxydecanoic acid, 11-hydroxyundecanoic acid, and others.

In addition to the functional silanes bearing E, A, Ac or A(_m), groups, non-functional silanes are also used. These are preferably conventional mono-, di-, tri-_> and tetro-atkmysilanes having the formula

ReSi(OR²)(4.0) where R and R² are as previously defined, and e is 0, 1, 2, or 3. Examples include alkyltrimethoxysiianes, dialkyldimethoxysilanes, and trialkylmethoxysilanes, and their ethoxy analogs; phenyltrimeth oxysilane, phenyldimethylmethoxysilane, diphenyldimethoxysilane, diphenlmethylmethoxysilane, phenyldimethylmethoxysilane and their ethoxy analogs, and the like. For increased compatibility with relatively non-polar substances, for example in coatings containing relatively non-polar reactive or non-reactive polymers, the alkyl groups in the aIkyialkoxysilanes may be long chain alkyl groups or cycle alkyl groups such as C₆-C₂₀ alkyl groups, preferably C8.18 alkyl groups, and C5.20 cycloalkyl groups such as cyclohexyl, methylcyciohexyl, cyclohcxylmethyl, norboroyl, and the like. Aryl groups such as napthyl, anthryl, etc. may be present, as well as aryl group-containing compounds such as biphenyl, 4- (phenylmethyl)phenyl, and the like.

The trialkoxysilancs and tetraalkoxysilanes such as tetraethoxysilanes and tetramethoxysilane may be used to impart branching. As indicated previously, highly branched structures are not preferred, as these are generally of high viscosity or are solids, and as the large number of siloxane bonds may make it impossible to achieve a ratio of non-functional groups to silicon of more than 1:1. However, some of the multi-alkoxy functional compounds may remain in part uncondensed, for example at the polymer termini or along the polymer chain as alkoxy groups.

To increase the ratio of non-functional R groups to silicon, the molar amounts of trialkoxy and tetralkoxysilanes are reduced, and the amounts of dialkoxysilancs and monoalkoxysilanes arc correspondingly increased. The silane mixture is condensed, in one or a plurality of steps, by addition of water, generally with the aid of an acidic or basic condensation catalyst such as an alkali metal hydroxide. Methods and conditions of condensation of silanes are well known in the art. Liberated alcohol is removed, for example as an overhead, and the amount of water collected, e.g. in a cooled condenser, may be used to assess the progress of condensation. Adding greater amounts of water will result in a greater degree of condensation, higher molecular weight, and a reduction in residual alkoxy group content, and the reverse is also true.

When plural steps are used in the synthesis, one or more of the silanes may be partially hydrolyzed to produce an alkoxy-rich intermediate product, which can then be further reacted (hydrolyzed) by itself or with addition of the same or other silanes. Such multistep addition can be used to tailor the polymer structure, and to some degree, the location of the reactive functional groups in the final polymer structure.

In the second preparation method, which is preferred, a preformed, alkoxy-fu nctional organopolysiloxane is employed. This preformed organopolysiloxane may be, for example, a partial hydrolysate of one or more starting silanes. The remaining hydroxy bearing reagent, silanes, water, and catalyst, when required, arc added, and further condensation takes place onto tile preformed organopoiysiloxanes. This method has the advantage of employing readily available, partially condensed organopoiysiloxanes having a defined structure, thus being able to more accurately synthesize desired product structures. This method is used in the Examples. Rather than an alkoxy-functional polymer, an α,ω-silanoi stopped organopoiysiloxanes may be used, either directly, or after reaction with an alkoxysilane to produce alkoxysilyl end groups.

The reactive organopoiysiloxanes have numerous uses, for example in coatings, as molded resins, impregnants, hydrophobing compositions, encapsulates, etc. In these uses, the reactive organopoiysiloxanes are generally used with a hardener, or curative, or with a curing catalyst,

A hardener" or “curative" or “curing agent" as used herein is a compound, which may be of low molecular weight, or “monomeric," or oligomeric or polymeric, which provides complementary reactive groups with which the reactive groups of the reactive silicone reach The hardener and reactive organopoiysiloxanes may each be of low functionality such that predominately linear chain extension lakes place, producing a generally flexible product, or one or both of the hardener or reactive silicone may be of higher functionality such that extensive crosslinking takes place, producing a harder and generally less flexible product

When the reactive functional group of the reactive organopoiysiloxanes is the epoxy group, suitable complementary reactive groups of the hardener are, for example, hydroxyalkyl groups, isocyanate groups, anhydride groups, carboxylic acid groups, primary and secondary amino groups, phenol/formaldehyde condensates, inelamineZformaldehyde condensates, and similar condensates, and the like. Such complementary reactive groups are well known in the art of epoxy resins. Hie hardener may be a “monomeric" organic compound of tow molecular weight such as bisphcnol A, ethylene glycol, methylenedianiline ("MDA”), etc., or may be oligomeric or polymeric, such as polyethyleneimines or addition polymers containing residues of acrylic acid, methacrylic acid, maleic anhydride, or the like. See, e.g. EPOXY RESINS: CHEMISTRY AND TECHNOLOGY, Clayton May, Ed., Marcel Dekker, © 1988, and HANDBOOK OF EPOXY RESINS, Henry Lee, et ai, McGraw-Hill, © 1967. For amino reactive groups, complementary reactive groups include epoxy groups, isocyanate groups, cyanate groups, anhydride groups, etc., and may be of low or high molecular weight, monomeric, oligomeric, or polymeric.

For each of these systems, it is also possible to use a complementary reactive organopolysiloxane as the hardener. For example, a curable composition with very high silicone content can be created by using an amino-functional organopolysiloxane with either or both of an isocyanate-functional organopolysiloxane and/or an epoxy-functional organopolysiloxanes. Such systems may also contain other hardeners, and may contain a catalyst as well.

Suitable complementary groups for carboxy functionality include isocyanate groups, amino groups, hydroxyl groups, and the like, whereas for (meth)acrylic groups, the complementary groups may be (meth)acrylic groups or other ethyienically unsaturated groups, or Si-H functional silanes and organopolysiloxanes. The (meth)acrylic group-ftmctional organopolysiloxanes may also be cured without a complementary-reactive crosslinker, for example by free radical polymerization using standard free radical initiators such as peroxides, hydroperoxides, azo compounds, or photocatalysts. When Si-H functional crosslinkers or ctiring agents are used, standard hydrosilylation catalysts, particularly platinum, iridium and rhodium, and their compounds may be used and more particularly platinum and its compounds, for example tire K arstedt catalyst.

The term “catalyst” as used herein refers to substances which facilitate reaction but are not complementary reactive, e.g. the catalyst is not generally chemically bonded in the cured product, as distinguished by hardeners which do become a substantial part of the product Epoxy-functional, isocyanate-functional, and (meth)acry la te-functi onal systems may all be catalyzed. For epoxy systems, suitable catalysts sue those known in the art, and include acids, bases, and tertiary amines, as well as a variety of metal compounds, both organic and inorganic. While amino-functional and anhydride-functional organopolysiloxanes generally require a hardener to cure, epoxy- and isocyanate-functional organopolysiloxanes may be cured catalytically without use of a hardener, as may also (meth)acrylate-functional organopolysiloxanes. The curable compositions may also contain uon-reactive polymers, generally film forming polymers, and may produce homogenous cured compositions or interpenetrating polymer network compositions. By the term “non-reactive polymers’¹ is meant polymers which have no complementary reactive groups or such a low concentration of such groups that a solid, cured composition cannot be obtained without the use of either or both of a separate hardener or catalyst Examples of such polymers are polyvinylacetate, polyvinyl chloride, other polyvinyl ester polymers, polyacrylates, including polyacrylates with a very small proportion of residual unsaturaled acrylic acid or metbacrylic acid groups, polyvinyl acetais, polycarbonates, polyether sulfones, polyurethanes, polyureas, polyamides, and the like. It is preferred fhar the non-reactive polymers have a very minor amount of reactive groups so that despite being unable to cure the composition, the polymer becomes covalently bonded within the composition.

Along with traditional curing methods the curable compositions of the invention may also be cured using high-energy radiation from a radiation source. Many types of radiation are suitable for this purpose, for instance election beams (E-Beam), γ-rays, X-rays, UV light such as that having wavelengths in the range from 200 to 400 nm, and visible light such as that having a wavelength of from 400 to 600 nm, i.e. "halogen light". Ultraviolet light can be generated, for example, in xenon lamps, mercury low-pressure lamps, mercury medium-pressure lamps or mercury high-pressure lamps and cxcimer lamps. Preferably UV light and electron beams is used.

In the embodiments cured using UV light curing photopolymerization initiators are used. Known photopolymerization initiators that may be used in the present invention, include but are not limited to 2,2-dimethoxy- 1 -hydroxy - cyclohexyl - phenyl - ketone, 1- [4- (2-hydroxyelhoxy) - phenyl] -2-hydroxy-2-roethyl-1 -propan- 1 -one, 2 -methyl-1- [4- (methylthio) phenyl] -2- morpholinopropan-l-one , 2-benzyl-2-dimethylamino-l- (4-morphol!nophenyL) - btttanone-1, bis (2,4,6-trimethyIbenzoyI) - phenyl phosphine oxide, 2-hydroxy-l- {4- [4- (2-hydroxy-2- mxethyl - propionyl) - benzyl] - phenyl) -2-methyl - propane, 1,2-octanedione, 1- [4- (phenylene

Thio) 2- (O-benzoyl oxime)], 2-hydroxy-2-methyl-l -phenyl propane- 1 -one, phenylglyoxylate butyric acid methyl ester, 2,4,6-trimcthyI benzoyl - diphenyl, or combinations thereof. Also phosphine oxide and the like, as long as it is able to absorb the light generated from the light source used for photocuring. The above compounds are commercially available, IRGACURE ™ 651, 184, 2959, the 907, the 369, fee 379, the 819, the 127, fee OXE01.02, DAROCUR ™ 1173, fee MBF, fee TPO (manufactured by BASF Japan Co., Ltd.), ESACURE ® KIP 150, same TZT, same ΚTΌ46, the 1001M, fee KB l, the KS300, the KL200, the TPO, (he IΓΧ, the EDB (manufactured by Japan Siber Hegner Co., Ltd.), and the like.

The content of the ph otopolymerizali on initiator in the curable composition of the present invention is preferably from 0.5 to 20% by weight relative to the polymerizable compound, and more preferably from 1% to 10% by weight relative to the polymerizable compound.

The inventive composition may also be cured with high energy radiation, such as electron beam radiation or cobalt 60. A variety of procedures for E-beam curing are well-known. The cure depends on the specific equipment used to deliver the electron beam, and those skilled in the art can define a dose calibration model for the equipment used. However, curing of the inventive composition may generally be accomplished in the range of 2 to 20 megarads. Such radiation curing may be done without initiators but accelerators, such as trialylcyanurate isocyanurate may be added.

It is also possible to cure the siloxane compositions of the invention exclusively thermally, in which case the addition of free-radical-forming peroxides or azo compounds (CE) is preferred. Examples of components (CE) which may be added are, preferably, lauroyl peroxide, benzoyl peroxide, 2,4-diohlorobenzoyl peroxides, azobisisobutyroniirile, hydroperoxides such as tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-dihydroperoxyhexane, 2,5- dimethyi-2_>5-dihydropcroxy-3-hexyne, and pinene hydroperoxide; diaikyl peroxides such as diisobutyl peroxide, di-tert-butyl peroxide, di-tert-amyl peroxide, tert-butyl cumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert- butylperoxy) -3 -hexyn e, alpha, alpha'-bis(tert-butylperoxy)-di(iso butylperoxy)benzene, 1,1- bis(tertbutylperoxy)-3,3,5-trimethylcyclohexane, n-butyl 4,4'-bis(tertbuly1peroxy)vaIerate, 2,2- bis(4_>4-di-tcrt-butyjperoxycyclohexyl)propattc_> 2,2-bis(tert-butylpcroxy)butanc, and 1 , 1 -di(tert- butylperoxy)cyclohexane; diacyl peroxides such as decanoyl peroxide, lauroyl peroxide, stearoyl peroxide, suceinyl peroxide, benzoyl peroxide, p~eh1orobenzoyl peroxide, o- chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and oclanoyl peroxide; peroxy esters such as tert-butyl peroxyacetate, tert-butyl pcroxy-2-ethylhexanoate, tert-bntyl peroxylaurate, tcrt-butyl pcroxybenzoate, di-tert-butyl diperoxyphthalate, 2,5-dimetliyl-2,5- di(b«nzoylperoxy)hcxane, tert-butylperoxymaleic acid, tert-butylperoxyisopropyi carbonate, tcrt-butylpcroxypivalattt, and tcrt-butyjperoxy neodecanoate; peroxy dicarbonates such as diisopropy^] peroxydicarbonatc and di-2-ethylhexyl pcroxydioarbonate; and ketone peroxide.

Peroxide curing is preferably carried out at a temperature of from -70°C to 200°C, particularly preferably from -40°C to 150°C, and at the pressure of the surrounding atmosphere, i.e. from 900 hPa to 1100 hPa. 'The surrounding atmosphere can here be air, nitrogen, xenon or another protective gas. The amount of the organic peroxide added to the inventive composition as a curing agent is usually in the range thorn 0.1 to 5 parts by weight per 100 parts by weight of the organopolysiloxane.

Curable compositions which comprise the reactive organopolysiloxanes may take numerous forms. They may contain a condensation catalyst in an amount effective to polymerize the organopolysiloxanes through a single kind of reactive group. Examples of such compositions include reactive organopolysiloxanes bearing isocyanate groups, epoxy groups, or (mcth)acrylic groups.

The compositions may also include a reactive organopolysiloxane and a compound which reacts with the reactive functional groups of the reactive organopolysiloxanes, i.e. contains complimentary reactive groups. The compound containing the complimentary reactive groups may be a monomeric, oligomeric, or polymeric organic compound, or may be a complementary reactive organosilane or oligomeric or polymeric organopolysiloxane, including silicone resins. The complimentary reactive organopolysiloxanes themselves may be a reactive organopolysiloxane as disclosed herein, or may be a non-inventive organopolysiloxane, for example one containing more than 20 weight percent alkoxy groups, or containing no alkoxy groups. One example of the latter are the commercially available ammoalkyl-fbnciional organopolysiloxanes where the amino alkyl groups may be terminal, pendant, or both terminal and pendant. The curable compositions may also contain non-inventive organopolysiloxanes bearing the same type of reactive group as the inventive organopolysiloxane, or monomeric, oligomeric, or polymeric organic compounds bearing the same type of reactive functional group. One example of such a curable system, for example, might include as a first reactive component an inventive epoxy- functional reactive organopolysiloxane and a bisphenol A-type epoxy resin, and as a second component an aminoalkyl-functional organopolysiloxane, a di- or polyamine, or a mixture of these. Such mixtures are made possible by the inventive reactive organopolysiloxanes which have high compatibility with other purely organic or substantially purely organic compounds.

When catalysts are used, these are advantageously formulated as a second component. It is possible, for example, to provide the catalyst dissolved or dispersed in a suitable solvent, in an organopolysiloxane, including non-reactive organopolysiloxanes which may serve as an extender or plasticizer, in a paraffinic or naphthenic oil, or the like. In some cases, when the catalyst is activatablc only at elevated temperature, or when an inhibitor is present, or in aqueous compositions where reaction takes place only after evaporation of water or after coalescence of the organic (including organosilicon) phase, the catalyst may be included in the composition, resulting in a one component system.

The curable compositions may be “neat” in the sense that they contain no solvent or are not in the form of a dispersion, e.g. an aqueous dispersion, or may be formulated with a solvent or dispersing liquid. Preferable solvents arc those with a low global warming potential such as tertiary butylaeetate, but conventional solvents such as alcohols, ethers, esters, paraffinic hydrocarbons, and aromatic solvents such as toluene and xylene may also be used,

The reactive organopolysiloxanes may be prepared and used as an aqueous dispersion, with or without additional ingredients. In such cases, dispersions may be prepared by using high shear mixers, generally with the aid of a surfactant. For storage stable composi tions, a surfactant which does not bear complementarily reactive groups and which does not function as a catalyst is preferably selected. Anionic, cationic, and zwller ionic catalysts may be used, depending upon the nature of the reactive organopolysiloxanes, but non-ionic surfactants such as polyoxyalfcylated glycols or alcohols are preferred. The curable compositions are generally two- component compositions in which each component simultaneously does not include the reactive organopolysiloxanes and hardener or catalyst

The curable compositions may include numerous additives, including antistais, fragrances, biocides, dyes, pigments, tillers, UV and/or thermal stabilizers, coalescing agents, glossing agents, flattening agents, plasticizers, electrically conducting additives such as carbon black, adhesion promoters, hydrophobing agents such as waxes, silicone oils, and fluorine- containing compounds, and other additives generally used.

When used as coatings, plural component compositions, particularly two component compositions arc preferably employed. One component, for example, may contain the reactive organopolysiloxane and other non-reactive components such as dyes, pigments, non-rcactive polymer, etc., dispersed in water, and a second component may contain catalyst and/or hardener, reactive or non-reactive polymer, dyes, pigments, etc. The components are mixed prior to use, and applied to a substrate by any suitable method, including brushing, spraying, dipping, roll coating, doctor blade coating, curtain coating, and the like, and are then allowed to dry and cure. Cure, and optionally drying, advantageously take place at elevated temperature, e.g. up to 350"C, preferably no more than 250°C, and yet more preferably no more than 200°C.

In some preferred compositions, it is desirable to reduce or eliminate the use of epoxy- functional trialkoxysilanes, and to use epoxy-functional dialkoxysilanes. It has been surprisingly and unexpectedly discovered that cured polymers prepared from inventive organopolysiloxane polymers synthesized in this way, although exhibiting reduced hardness, achieve maximum hardness faster than when the functional organopolysiloxane is prepared using trialkoxysilanes. In addition, volatiles arc reduced by about 33%. Such compositions are well suited for encapsulation or the preparation of thick moldings. Preferred systems of this nature include an aminoalkyl-functional organopolysiloxane free of alkoxy groups, and an inventive epoxysiloxane.

In the examples described below, all parts and percentages are, unless indicated otherwise, by weight. Unless indicated otherwise, the following examples are carried out at the pressure of the surrounding atmosphere, he. at about 1000 hPa, and at room temperature, i.e. at about 20°C, or at a temperature which is established on combining the reactants at room temperature without additional heating or cooling. In the following, all viscosities relate to the dynamic viscosity at a temperature of 20°C and a shear rate l s^-1. The following examples illustrate the invention without having a limiting effect.

Examples

Examples 1-3:

Alkoxy- functional organopolysiloxane, non-fonctional silane, and 2- hydroxyethyl acrylate are charged to a 500 ml reaction flask and blanketed with nitrogen gas. To begin hydrolytic condensation, dodecyibcnzosulfonic acid was slowly added. The contents were stirred without heating for 15 minutes, following which the temperature was increased to 55°C. The reaction mixture was refluxed at 55°C until the appropriate amount of alcohol was collected in a cooled trap. The charges and product properties are reported in Table 1.

Table 1

¹SILRES® 10232 is a methoxy-functional methyl/phenyl organopoiysiloxane containing about 20 weight percent alkoxy groups, available from Wacker Chemical Corp., Adrian, Michigan. ¹SILRES® MSE100 is a methoxy- functional methyl organopoiysiloxane containing about 30 weight percent alkoxy groups, available from Wacker Chemical Corp., Adrian, Michigan.

Examples 4-10:

Following the procedure of Examples 1 -3, additional reactive silicones were prepared. The starting materials and amounts, in percentage by weight, and the epoxy and alkoxy contents of the final products in weight percent are presented in Table 2.

mples 11-18

Coatings were prepared from the inventive reactive silicones from Examples 4 and ccording to Table 3 using 5 wet mil drawdown bar on untreated aluminum panels.

Table 3

DDA is 1,6-bexanediol diacrylate and is available from BASF. PGDA is dipropylcneglyeol diacrylate and is available from BASF. MPTA is trimethylolpropane triacrylate and is available from BASF. peedcure 2022 is liquid formulated blend of photoiuitiators available from Lambson. As can be seen from the Table 3, no appreciable post-hardening was observed except when film received minima] light cure intensities. Observed “softening" is attributed to segmental siloxane bond rotation which is common with polymer matrices based on siloxaac chemistry such as in self-healing coatings.

All films were clear and glossy, demonstrating the compatibility of those reactive siloxanes with commonly used acrylate monomers.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A reactive organopolysiloxane prepared by hydrolytic condensation, comprising on average a) at least two reactive functional groups per molecule, selected from group consisting of epoxy, amino, carboxy, and (mcth)acrylate groups, and mixtures eof, the functional groups bonded to silicon atoms in the reactive organopoiysiloxanes. b) alkoxy groups, in a concentration of less than 10 weight percent based on the total weight of the reactive organopoiysiloxanes calculated on the basis of methoxy groups, and c) non-reactive optionally substl luted hydrocarbon groups Sl-C bonded to silicon atoms of the reactive organopolysiloxane, the non-reactive optionally substituted hydrocarbon groups present in a ratio of >1 hydrocarbon group per atom ol'Si in the reactive organopolysiloxane, and wherein the at least two reactive functional groups are introduced into the reactive organopolysiloxane by one of the following two condensation processes i) or ii) i) condensing a plurality of alkoxysilanes or their partial hydrolysates, with at least one organic compound comprising a hydroxyl group and a reactive functional group consisting of epoxy, amino, carboxy, and (meth)acrylate groups, and mixtures thereof, and with at least one second alkoxysilane or second partial hydrolysate bearing 1, 2, or 3 non-reactive, optionally substituted hydrocarbon groups, or ii) condensing a silanll-stopped or alkoxysilyl-stopped organopolysiloxane or their partial hydrolysates, with at least one organic compound comprising a hydroxyl group and a reactive functional group consisting of epoxy, amino, carboxy, and (meth)acrylate groups, and mixtures thereof, and optionally with an alkoxysi!ane bearing 1, 2, or 3 non-reactive, optionally substituted hydrocarbon groups.

2. The reactive organopolysiloxane of claim t, wherein the reactivectional group are selected from the group consisting of epoxy, acrylate and methacrylateups.

3. The reactive organopolysiloxanes of claim 1, wherein the reactivectional group are selected from the group consisting of acrylate and methacrylateups.

4, A curable composition, comprising

A) at least one reactive organopolysiloxanes of claim 1 to 3, and a catalyst effective to cause polymerization of the respective reactive functional groups, or

B) at least one reactive organopolysiloxane of claim 1 to 3, and at least one curing agent bearing complementary reactive functional groups reactive with the reactive functional groups of the reactive organopolysiloxane of claim 1 to 3, and optionally a catalyst effective to catalyze the reaction of the reactive functional groups with the complementary reactive functional groups; or

C) at least a first reactive organopolysiloxane of claim 1 to 3, and at least a second reactive organopolysiloxane of claim 1 to 3 bearing complementarily reactive functional groups reactive with the reactive functional groups of the first reactive organopolysiloxane, and optionally a catalyst effective to catalyze the reaction of the reactive functional groups of the first reactive organopolysiloxanes with the second reactive organopolysiloxane.

5. The curable composition of claim 4, comprising at least one reactive anopolysiloxane of claim 3 and i) further comprising a free radical initiator effective to polymerize the th)acrylate groups, or ii) further comprising an Si-H functional crosslinkcr and an effective ount of a hydrosilylation catalyst.

6. A process for the preparation of a reactive organopolysiloxanemprising on average a) at least two reactive functional groups per molecule, selected from group consisting of epoxy, amino, oarboxy, and (meth)acrylate groups, and mixtures eof, the functional groups bonded to silicon atoms in the reactive organopolysiloxancs, b) alkoxy groups, in a concentration of less than 10 weight percent ed on the total weight of the reactive organopolysiloxancs calculated on the basis of hoxy groups, and c) non-reactive optionally substituted hydrocarbon groups Si-C bonded ilicon atoms of the reactive organopolysiloxane, the non-reactivc optionally substituted rocarbon groups present in a ratio of>l hydrocarbon group per atom of Si in the reactive anopolysiloxane, and wherein the at least two reactive functional groups are introduced into the reactive organopolysiloxane by one of the following two condensation processes i) or ii) i) condensing a plurality of aikoxysilanes or their partial hydrolysates, with at least one organic compound comprising a hydroxyl group and a reactive functional group consisting of epoxy, amino, carboxy, and (meth)acrylate groups, and mixtures thereof, and with at least one second alkoxysilane or second partial hydrolysate bearing 1, 2, or 3 non-reactive, optionally substituted hydrocarbon groups, or ii) condensing a silanol-stopped or alkoxysilyl-stopped organopolysiloxane or their partial hydrolysates, with at least one organic compound comprising a hydroxyl group and a reactive functional group consisting of epoxy, amino, carboxy, and (meth)acrylate groups, and mixtures thereof, and optionally with an alkoxysilane bearing 1, 2, or 3 non-reactive, optionally substituted hydrocarbon groups.

7. A coating prepared by

-applying a curable composition of claim 4 or 5 to a substrate in a desired thickness, -curing the curable composition.

8. The coating of claim 7 wherein the curing is initiated via radiationm a radiation source.

9. The coating of claim 8 wherein the radiation is selected from UV- t and electron beams.