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Timestamp: 2018-06-21 05:45:56
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US5468826A - Adhesion promoting additives and curable organosiloxane compositions containing same - Google Patents
Adhesion promoting additives and curable organosiloxane compositions containing same Download PDF
US5468826A
US5468826A US08240426 US24042694A US5468826A US 5468826 A US5468826 A US 5468826A US 08240426 US08240426 US 08240426 US 24042694 A US24042694 A US 24042694A US 5468826 A US5468826 A US 5468826A
US08240426
The present invention provides organosiloxane copolymers comprising SiO4/2 units, silicon-bonded hydrolyzable groups, epoxy or acryloxyalkyl groups and silicon-bonded hydrogen atoms. The copolymers are particularly useful as adhesion promoting additives in organosiloxane compositions that cure by a platinum group metal-catalyzed hydrosilation reaction at temperatures up to 100° C.
This invention relates to new multifunctional organosilicon copolymers and their use as adhesion additives in curable organosiloxane compositions. Preferred compositions cure by a platinum group metal catalyzed hydrosilation reaction at temperatures of up to 100° C.
The curing characteristics of organosiloxane compositions and the properties of the cured materials obtained from these compositions are desirable for a variety of end use applications, particularly in the electrical and electronics areas. The cured materials are useful as protective coatings, potting materials and encapsulants for integrated circuits and other electronic devices and as coatings for printed circuit boards.
A shortcoming of organosiloxane compositions, particularly those that cure by a platinum group metal catalyzed hydrosilation reaction, is their inability to develop strong adhesion to many substrates, particularly plastics and certain metals. One method for remedying this deficiency is by using primer compositions or adhesion promoting additives containing one or more silanes and/or organosiloxanes with a plurality of silicon-bonded hydrolyzable groups and at least one organofunctional substituent that is bonded to silicon through at least one carbon atom.
Primer compositions are applied to substrates to which adhesion is desired prior to application of the curable organosiloxane composition. Adhesion promoters may also be present in the curable organosiloxane composition.
Adhesion promoting additives described in the prior art typically contain at least two functional groups.
U.S. Pat. Nos. 3,772,026 and 3,873,334 teach acyloxy functional silanes which additionally have silicon hydride or alkenyl functionality respectively. Although the acyloxy functionality is very reactive, it liberates corrosive acetic acid upon reaction with hydroxyl groups present at the surface of the substrate or with ambient moisture.
U.S. Pat. No. 4,196,273 teaches use of unsaturated alkoxysilanes, such as vinyltrimethoxysilane, as adhesion additives. Adhesion is not demonstrated at temperatures below 100° C. and only adhesion to glass is demonstrated at 100° C. U.S. Pat. No. 4,329,273 teaches use of partially hydrolyzed unsaturated alkoxysilanes. Curing of compositions containing these adhesion promoting additives did not occur at ambient laboratory temperatures, but cure at 100° C. was demonstrated.
U.S. Pat. No. 4,082,726 teaches organosilicon compounds containing epoxy functional dialkoxysilyl groups and at least one alkenyl radical or hydrogen atom bonded to silicon in the organosilicon compound. Adhesion with compositions containing these compounds is demonstrated after cure at between 100°-200° C. U.S. Pat. No. 4,087,585 teaches physical blends of epoxy functional alkoxysilanes with silanol functional fluids containing alkenyl functionality. Cure was obtained at elevated temperatures. Multifunctional organosilanes containing ethylenic unsaturation, epoxy functionality, and alkoxy functionality are taught in U.S. Pat. No. 4,732,932. U.S. Pat. No. 5,106,933 teaches use of mixtures of alkoxysilanes.
U.S. Pat. Nos. 4,659,851, 4,719,262, and 4,906,686 teach reaction products of unsaturated alcohols with alkoxysilanes as adhesion promoting additives. The resultant Si-O-C bond between the unsaturated alcohol and alkoxysilane would be susceptible to hydrolysis such that the adhesion could be decreased upon exposure to moisture.
U.S. Pat. No. 4,077,943 teaches using an organohydrogensiloxane containing epoxy functionality as the curing agent for organosiloxane compositions. Japanese Laid Open Patent Application (JLOPA) 1/085,224 teaches accelerating the development of adhesion using organosiloxanes containing epoxy functional silsesquioxane units and optional ethylenic unsaturation, but no Si(OR)3 functional groups. JLOPA 4/311,766 teaches adhesion promoting additives containing a) siloxane units with at least one alkoxysilylalkyl group, b) siloxane units with at least one terminally unsaturated alkenyl radical; c) trialkoxysiloxy units and d) SiO4/2 units. JLOPA 2/18452 describes adhesion promoters that include organosilicon compounds containing two silicon-bonded alkoxy groups and at least one epoxy group and organosilicon compounds containing at least one alkoxy group and at least two ethylenically unsaturated double bonds per molecule.
U.S. Pat. No 4,786,701 teaches adhesion promoters which are hydrolysis reaction products of tetraalkoxysilanes, alkenyl or silicon hydride functional organopolysiloxane, and optional (meth)acryloxy functional alkoxysilanes. U.S. Pat. No. 4,677,161 teaches silicon hydride functional SiO2 resins containing residual alkoxy groups, however no Si(OR)3 groups are present.
None of the aforementioned patents demonstrate that adhesion can be achieved at temperatures below 100° C. or to a variety of substrates.
One objective of this invention is to define a group of organosilicon compounds that impart adhesion between a) elastomers and other products prepared by curing organosiloxane compositions and b) a variety of organic and inorganic substrates that the compositions are in contact with during curing. Preferred additives impart adhesion at curing temperatures of up to 100° C.
The objectives of the present invention can be achieved by the presence in the curable organosiloxane composition of a specified group of organosiloxane copolymers comprising SiO4/2 units, silicon-bonded hydrolyzable groups, epoxy or (meth)acryloxyalkyl groups and either silicon-bonded hydrogen atoms or alkenyl radicals.
This invention provides an improved curable organosiloxane composition, said composition comprising
(B) a curing agent in an amount sufficient to cure said composition; and
(C) a curing catalyst in an amount sufficient to promote curing of said composition;
where said composition cures using a reaction selected from the group consisting of hydrosilation reactions catalyzed by platinum group metals and compounds thereof, reactions of silicon-bonded hydrogen atoms with silanol groups, and free radical reactions initiated by the decomposition of a photolytically unstable compound.
The improvement comprises the presence in the curable composition of
(D) an amount sufficient to achieve adhesion to substrates in contact with said composition during curing thereof of an adhesion promoting additive comprising at least one organosiloxane copolymer corresponding to the general formula
{XR.sup.1.sub.2 SiO.sub.1/2 }.sub.a {SiO.sub.2 }.sub.b {(R.sup.2 O).sub.3 SiR.sup.3 (R.sup.1).sub.2 SiO.sub.1/2 }.sub.c {R.sup.4.sub.x R.sup.5.sub.y SiO.sub.(4-x-y)/2 }.sub.d {R.sup.1.sub.v (R.sup.2 O).sub.w SiO.sub.(4-v-w)/2 }.sub.e {R.sup.2 O.sub.1/2 }.sub.f {HO.sub.1/2 }.sub.g
wherein each R1 is individually selected from monovalent hydrocarbon radicals that are substantially free of ethylenic unsaturation and contain from 1 to 10 carbon atoms, R2 is an alkyl radical containing 1 to 10 carbon atoms, R3 is a divalent hydrocarbon radical containing from 2 to 10 carbon atoms, each R4 is individually selected from the group consisting of monovalent hydrocarbon radicals containing an epoxy, acryloxyalkyl or methacryloxyalkyl group, R5 is R1 OR2 ; X is hydrogen or an alkenyl radical, a, b, c, d, e, f and g represent mole fractions with a total value of 1, a, b, c, and d are all greater than zero, e, f and g are 0 or a positive number less than 1; x is 1, 2, or 3; y is 0, 1, or 2; x+y is 1, 2 or 3; v and w are each 0, 1, 2, or 3; and v+w is 1, 2 or 3.
The adhesion promoting additives of the present compositions are novel compounds and constitute one embodiment of the present invention.
2) the generation of free radicals on the polyorganosiloxane initiated by the photoinduced decomposition in the presence of ultraviolet radiation of photosensitive compounds such as alpha-hydroxy ketones.
The characterizing feature of the present organosiloxane compositions is the adhesion-promoting additive, referred to hereinafter as ingredient D. This ingredient can be defined as an organosiloxane copolymer containing a combination of repeating units that distinguish it from prior art organosiloxane copolymers.
The required units that constitute the ingredient D are diorganohydrogensiloxy or diorganoalkenylsiloxy (XR1 2 SiO1/2) (I), trialkoxysilylalkyldiorganosiloxy [(R2 O)3 SiR3 Si(R1)2 O1/2 ] (II), siloxane units containing a silicon-bonded epoxyalkyl, acryloxyalkyl or methacryloxyalkyl group, represented by R4 in the formula R4 x R5 y SiO4-x-y (III), and SiO4/2 units (IV). X represents hydrogen or an alkenyl radical. Alkenyl radicals represented by X preferably contain from 2 to 12 carbon atoms and are terminally unsaturated. X is most preferably hydrogen, vinyl or 5-hexenyl.
The optional units that can be present in this copolymer are siloxane units containing 1) at least one silicon-bonded hydrocarbon radical and/or alkoxy group or 2) a silicon-bonded hydroxyl group.
The monovalent hydrocarbon radicals represented by R1 contain from 1 to 10 carbon atoms, can contain substituents such as halogen atoms, and are substantially free of ethylenic unsaturation. These hydrocarbon radicals include but are not. limited to alkyl such as methyl, ethyl, n-propyl, n-butyl and n-decyl; haloalkyl such as chloromethyl and 3,3,3-trifluoropropyl; cycloalkyl such as cyclohexyl; aryl such as phenyl and naphthyl; alkaryl such as tolyl and xylyl; and aralkyl such as benzyl. When more than 1 R1 is present on a silicon atom, these can be identical or different. R1 is preferably selected from methyl, ethyl, 3,3,3-trifluoropropyl and phenyl, this preference being based on the availability and cost of the starting materials, typically the corresponding chlorosilanes, used to prepare the copolymer.
OR2 represents an alkoxy group containing from 1 to 10 carbon atoms, and is preferably methoxy or ethoxy, this preference being based on the low boiling points of the alcohols formed upon hydrolysis of this alkoxy group during curing of organosiloxane compositions containing the present adhesion promoters and their reactivity, which promotes adhesion.
R3 represents a divalent hydrocarbon radical containing from 2 to 10 carbon atoms, and includes but is not limited to alkylene such as ethylene and propylene, cycloalkylene such as cyclohexylene, and arylene such as phenylene. R3 is preferably ethylene based on the availability of the intermediates used to prepare this unit of the present copolymers.
R4 represents a monovalent radical containing an epoxy, acryloxyalkyl or methacryloxyalkyl group that is bonded to silicon through at least one carbon atom that is not part of the functional group. Preferred embodiments of R4 include 3-glycidoxypropyl, 3-epoxycyclohexylmethyl and 3-methacryloxypropyl. In preferred R4 x R5 y SiO4-x-y units, R5 is methoxy or ethoxy, x is 1, and y is 2. These preferences are based on the availability of the intermediates for preparing these units of the present copolymers and the high level adhesion imparted by the copolymers to curable organosiloxane compositions.
In the present copolymers the XR1 2 SiO1/2 or I units constitute from 5 to 50 percent, preferably from 25 to 40 percent of the total units the (R2 O)3 SiR3 Si(R1)2 O1/2 or II units constitute from 3 to 30 percent, preferably from 10 to 20 percent of the total units, the units containing silicon-bonded epoxyalkyl or (meth)acryloxyalkyl groups, or III units, constitute from 3 to 30 percent, preferably from 10 to 20 percent, of the total units and the SiO4/2 units (IV units) from 10 to 50 percent, preferably from 35 to 45 percent, of the total units.
The total of all the aforementioned optional units typically constitute from 0 to 30 percent of the total units present in the copolymer.
The organosiloxane copolymers referred to in this specification as ingredient D can be prepared by cohydrolysis of a mixture of at least four silanes. Each one of the silanes is a precursor for one of the four types of required repeating units and any of the silicon-containing optional unit present in the final adhesion additive.
For example, the precursor of unit I can be a diorganohydrogensilane containing silicon-bonded halogen or alkoxy as the hydrolyzable group; unit II can be derived from a tetrachlorosilane or an alkylorthosilicate; and unit IV from a silane containing at least one silicon-bonded epoxyalkyl or (meth)acryloxyalkyl radical and at least one silicon-bonded hydrolyzable group. The precursor of unit III, a silane containing an alkenyl radical such as vinyl and three hydrolyzable groups, is reacted with the product of the cohydrolysis reaction.
Methods for hydrolyzing mixtures of silanes in the presence of controlled amounts of water to form organosiloxane copolymers are sufficiently described in the literature that a detailed description in this specification is not required.
A preferred method for preparing the organosiloxane copolymers used as ingredient D of the present curable compositions utilizes the reaction of known organosiloxane copolymers containing diorganohydrogensiloxy (HR1 2 SiO1/2) and SiO4/2 units with a mixture of an alkenyltrialkoxysilane and an ethylenically unsaturated organic epoxide such as allylglycidyl ether. Copolymers of this type are described in U.S. Pat. No. 4,707,531.
Preferred intermediate copolymers have the general structure {HMe2 SiO1/2 }1.82 {SiO2 }1.00.
The reaction is typically conducted in the presence of a hydrosilation catalyst such as a metal from the platinum group of the periodic table or a compound of one of these metals. The combined concentrations of alkenyltrialkoxysilane and organic epoxide compound is typically sufficient to react with from 10 to 80 percent of the silicon-bonded hydrogen atoms present in the intermediate copolymer. In preferred copolymers the alkenyltrialkoxysilane constitutes from 30 to 60 percent of this total.
It may be desirable to include in the reaction mixture for preparing ingredient D a liquid diluent that may also function as a solvent for the reactants. Suitable diluents include aliphatic and aromatic hydrocarbons that are liquid at ambient temperature and boil within the range of from 50° to about 150° C. Representative diluents include hexane, heptane and liquid aromatic hydrocarbons such as toluene and xylene.
In preferred compositions the concentration of ingredient D is typically from 1 to 10, preferably from 2 to 5 weight percent, based on the total weight of the curable composition.
The present adhesion promoting additives are particularly useful in organosiloxane compositions that cure by a platinum group metal-catalyzed hydrosilation reaction at temperatures below about 100° C. The additives are also useful in organosiloxane compositions that cure in the presence of free radicals generated by the photoinduced decomposition of a one of the known types of photoinitiators.
The adhesion to certain substrates such as glass and aluminum, achieved using the present adhesion additives, particularly those containing silicon-bonded trialkoxysilylethyl groups, can be improved by combining the adhesion additive with from 1 to 5 percent, based on the weight of the curable organosiloxane composition, of a silane containing at least three alkoxy groups. Preferred silanes are alkenyltrialkoxysilanes, where the alkenyl radical contains from 2 to 10 carbon atoms, and alkyl orthosilicates. Allyltrimethoxysilane and ethyl orthosilicate are particularly preferred for use in combination with the present adhesion additives.
The Polyorganosiloxane (Ingredient A)
The polyorganosiloxane ingredient, referred to hereinafter as ingredient A, of preferred curable organosiloxane compositions of this invention is the principal ingredient of these compositions. Because these compositions cure by a hydrosilation reaction, ingredient A contains at least two silicon-bonded alkenyl radicals in each molecule.
Preferred embodiments of ingredient A are polydiorganosiloxanes represented by the general formula I ##STR1## where each R7 is individually selected from monovalent hydrocarbon radicals and alkenyl radicals, R8 represents a vinyl or other alkenyl radical, and n represents a degree of polymerization equivalent to a viscosity of at least 100 centipoise (0.1 Pa.s), preferably from 0.1 to 10 Pa.s.
The hydrocarbon radicals represented by R7 are either unsubstituted or can contain substituents such as halogen atoms that will not adversely affect the storage stability and curing of the present compositions or the properties of cured articles prepared from these compositions.
The two R7 substituents on each of the silicon atoms in formula I can be identical or different, and can contain from. 1 to about 20 carbon atoms. A range of from 1 to 10 carbon atoms is preferred based on the availability of the corresponding monomers. Most preferably at least one of the hydrocarbon radicals on each silicon atom is methyl, and any remainder are vinyl, phenyl and/or 3,3,3-trifluoropropyl, this preference being based on the availability of the reactants typically used to prepare the polydiorganosiloxane and the properties of cured elastomers prepared from these polydiorganosiloxanes. For the same reasons, R8 is preferably vinyl or 5-hexenyl
Representative embodiments of ingredient A containing ethylenically unsaturated hydrocarbon radicals only at the terminal positions include but are not limited to dimethylvinylsiloxy-terminated polydimethylsiloxanes, dimethylvinylsiloxy-terminated polymethyl-3,3,3-trifluoropropylsiloxanes, dimethylvinylsiloxy-terminated-dimethylsiloxane/3,3,3-trifluoropropylmethylsiloxane copolymers and dimethylvinylsiloxy-terminated-dimethylsiloxane/methylphenylsiloxane copolymers.
The Organohydrogensiloxane Curing Agent (Ingredient B).
The silicon-bonded organic groups present in ingredient B are selected from the same group of monovalent hydrocarbon and halogenated hydrocarbon radicals as the organic groups of ingredient A, with the proviso that the organic groups in ingredient B must be substantially free of ethylenic or acetylenic unsaturation. The molecular structure of ingredient B can be straight chain, branch-containing straight chain, cyclic, or network.
While the molecular weight of ingredient B is not specifically restricted, viscosities in the range of 3 to 10,000 centipoise (0,003 to 10 Pa.s) at 25 degrees Centigrade are preferred.
The Hydrosilation Reaction Catalyst (Ingredient C)
Platinum Catalyst Inhibitors
Known platinum catalyst inhibitors include the acetylenic compounds disclosed in U.S. Pat. No. 3,445,420, which issued on May 20, 1969 to Kookootsedes et al. Acetylenic alcohols such as 2-methyl-3-butyn-2-ol constitute a preferred class of inhibitors that will suppress the activity of a platinum-containing catalyst at 25° C. Compositions containing these catalyst inhibitors typically require heating at temperatures of 70° C. or above to cure at a practical rate.
Typical additives include but are not limited to non-reinforcing fillers such as quartz, alumina, mica and calcium. carbonate; pigments such as carbon black and titanium dioxide; dyes, flame retardants, and heat and/or ultraviolet light stabilizers. Resinous organosiloxane copolymers can be used in place of or in combination with one or more reinforcing fillers to improve the physical properties of the cured organosiloxane composition.
A preferred type of resinous copolymer contains repeating units of the general formula SiO4/2 in addition to triorganosiloxy units of the general formulae R9 3 SiO1/2 and diorganovinylsiloxy units of the general formula CH2 ═CH(R10)2 SiO1/2. In these formulae R9 and R10 are individually monovalent hydrocarbon or substituted monovalent hydrocarbon radicals as previously defined for the R7 radicals of ingredient A.
The resinous copolymers can be prepared as described in U.S. Pat. No. 2,676,182, which issued to Daudt and Tyler on Apr. 20, 1954 and is hereby incorporated in this specification by reference thereto. The copolymers described in this patent contain from 2 to 23 percent by weight of hydroxyl groups, which is considerably above the maximum level of about 0.8 weight percent preferred for precursors of the present copolymers. The hydroxyl content of the precursor can be conveniently reduced to the desired level by employing a higher concentration of triorganosiloxy units than the concentration range taught by Daudt et al.
To maximize storage stability the curable compositions are preferably kept in closed containers until used. If greater storage stability is desired, the preferred compositions can be packaged in two or more containers with the organohydrogensiloxane (ingredient B) and the platinum group metal catalyst (ingredient C) in separate containers.
Depending upon the types and concentrations of polyorganosiloxane and curing agent, cured organosiloxane materials prepared using the present compositions can vary in properties from brittle resins to elastomers to gels, and are useful in a variety of end-use applications as coatings or as molded or extruded articles. Unfilled materials are particularly useful as adhesives, protective coatings, encapsulants and potting compositions for protecting delicate electronic devices such as transistors and integrated circuits from damage by moisture and other materials present in the environment that can adversely affect operation of the device. The compositions can be used to coat either the individual devices or a circuit board containing a number of these devices together with other electronic components.
Curing of the preferred compositions commences when ingredients A, B and C are combined. One advantage of the present adhesion promoting compositions is the absence of substantial retardation of the hydrosilation reaction used to cure these preferred compositions.
Organosiloxane compositions containing the present adhesion additives cohesively bond to a variety of organic and inorganic substrates during curing at temperatures as low as 25° C. The ability of the present compositions to develop adhesion when cured at these relatively low temperatures make them suitable for application to substrates that cannot withstand the elevated temperatures of 100° C. or higher required to cure organosiloxane compositions containing some prior art adhesion additives that inhibit platinum group metal catalysts.
Unlike many prior art adhesion promoters, the initial adhesion imparted by preferred adhesion additives is not adversely affected to any substantial extent when substrates coated using the present compositions are exposed to moisture. This is particularly desirable when the compositions are used to coat and seal electronic devices such as semiconductor devices and integrated circuits whose performance can be adversely affected by moisture and other contaminants to which these devices can be exposed to during use.
The following general procedure was used for preparation of the present organosiloxane copolymers:
The dimethylhydrogensiloxy/SiO4/2 copolymer used as the starting material for preparing the copolymers contained 60 mole percent of dimethylhydrogensiloxy units. This copolymer was prepared as described in U.S. Pat. No. 4,707,531 and was dried over molecular sieves.
Vinyltrimethoxysilane was used as received.
Hexenyltrimethoxysilane was freshly distilled from sodium methoxide.
Toluene was reagent grade and freshly distilled from calcium hydride.
The platinum catalyst was a reaction product of platinic chloride and sym-tetramethyldivinyldisiloxane that had been diluted with toluene to achieve a platinum content of 0.99 weight percent.
Other chemicals were purchased from commercial suppliers and used as received.
The required amount of copolymer was weighed into a 250 ml-capacity glass reactor, followed by 50 g toluene. The reactor was then equipped with a magnetic stirrer, thermometer, temperature controller, addition funnel, water cooled condenser, and a gas inlet tube. All the glassware had been dried at 120° C. prior to use.
The ethylenically unsaturated reactants were then weighed into the additional funnel and diluted to 50 ml total volume with toluene. A mixture of 4% oxygen in nitrogen was introduced into the reactor through the gas inlet tube while the reactants were weighed into the addition funnel. Following this operation the same gas mixture was introduced through a syringe needle that extended below the surface of the liquid in the reactor and the platinum catalyst was added. The reaction mixture was then heated. When the temperature of the reaction mixture reached 100° C. the unsaturated compounds were added over 1-2 hours. Samples were periodically withdrawn from the reaction mixture and monitored to determine the extent of reaction using gas/liquid chromatography (GC). Heating was continued until the reaction was more than 95% complete. Volatile liquids were then removed under a pressure of less than 10 mm Hg and a temperature 100° C.
Adhesion Additive D1 was prepared using 32.9 g of the (CH3)2 HSiO1/2 /SiO4/2 copolymer, 7.43 g allylglycidyl ether, 9.67 g vinyltrimethoxysilane, and 29 microliters of the platinum catalyst solution.
Adhesion Additive D2 was prepared using 30.79 g of the same copolymer used to prepare D1, 6.96 g allylglycidyl ether, 12.25 g hexenyltrimethoxysilane, and 29 microliters of the platinum catalyst solution.
Adhesion Additive D3 was prepared using 29.41 g of the same copolymer used to prepare additive D1, 8.88 g limonene oxide, 11.71 g hexenyltrimethoxysilane, and 29 microliters of the platinum catalyst solution.
Adhesion Additive D4 was prepared for comparative purposes using 35.82 g of the same organohydrogensiloxane used as ingredient B, 6.16 g allylglycidyl ether, 8.02 g vinyltrimethoxysilane, and 29 microliters of the platinum catalyst solution.
Adhesion Additive D5 was prepared for comparative purposes by reacting 33.93 g of the organohydrogensiloxane used as ingredient B with 5.83 g allylglycidyl ether and 10.24 g hexenyltrimethoxysilane in the presence of 29 microliters of the platinum catalyst solution.
The molar quantities of epoxy- and alkenyl-substituted silanes added were each equivalent to 20% of the silicon-bonded hydrogen atoms in the initial copolymer with which the silanes are reacted.
Adhesion additive D6 was allyltrimethoxysilane and Adhesion additive D7 was ethyl orthosilicate. Both of these additives were used for comparative purposes.
Six curable compositions containing the present adhesion additives at two concentration levels and four comparative compositions were prepared by making a physical blend of the ingredients. The amounts of the various adhesion additives were equivalent to equimolar quantities of each additive.
The ingredient referred to as A was a dimethylvinylsiloxy-terminated polydimethylsiloxane with a viscosity of 2.2 Pa.s;
Ingredient B was a trimethylsiloxy-terminated organosiloxane copolymer containing an average of five methylhydrogensiloxane units and three dimethylsiloxane units per molecule with a silicon-bonded hydrogen atom content of about 0.8 weight percent.
Each of the compositions contained 0.253 part of a catalyst that was a reaction product of hexachloroplatinic acid and sym-tetramethyldivinyldisiloxane that had been diluted with a liquid dimethylvinylsiloxy terminated polydimethylsiloxane in an amount sufficient to achieve a platinum content of 0.6 weight percent; as a catalyst inhibitor, 0.083 part by weight of cyclic methylvinylsiloxanes; and 0.15 part of tetrabutyl titanate to facilitate reaction of the adhesion additive.
TABLE 1______________________________________Composition    1       2       3     4     5     6______________________________________Ingredient A    146     144     146   144   146   144(Parts)Ingredient B    2.4     1.6     2.4   1.6   2.4   1.6(Parts)Additive D1      D1      D2    D2    D3    D3Parts of 2.1     4.1     2.2   4.4   2.3   4.6Additive______________________________________
TABLE 2______________________________________Composition C1      C2        C3    C4______________________________________Ingredient A       146     144       146   144(Parts)Ingredient B       2.4     1.6       2.4   1.6(Parts)Additive    D4      D4        D5    D5Parts       1.9     3.8       2.0   4.0Additive______________________________________
Films of each composition measuring 0,008 in (0.2 mm) were applied to each of the substrates using a draw-down bar. The coatings were allowed to cure under ambient conditions or in a forced air oven at 70° C. for 30 minutes followed by additional curing at room temperature for the time periods specified in Tables 3 and 4. The cured coatings were then tested to determine adhesion.
The adhesion test consisted of scratching the cured coating with the blade of a metal spatula to determine whether the coating could be removed without leaving a residue on the surface (adhesive failure, AF) or whether failure occurred within the coating layer, resulting in at least a portion of the coating material in the test area adhering to the substrate (cohesive failure, CF). On some samples the coating exhibited adhesive failure in one area and cohesive in another area (AF/CF).
The substrates on which the curable compositions were evaluated were glass microscope slides (glass) or panels measuring 7.6 by 12.7 cm. and formed from type 3003 H14 alloy mill finish aluminum available from Q-Panel (aluminum).
The results of the adhesion tests are summarized in Table 3 for the samples cured under ambient conditions and Table 4 for the samples cured at 70° C.
TABLE 3______________________________________Room Temperature AdhesionCom-po-   Glass           Aluminumsition 1 day   3 day   7 day 1 day  3 day  7 day______________________________________1     CF      CF      CF    AF     AF/CF  CF/WD2     CF      CF      CF    AF     AF/CF  CF/WD3     CF      CF      CF    CF/WE  CF     CF4     CF      CF      CF    CF/WD  CF     CF5     CF      CF      CF    CF/WE  CF/WE  CF/WD6     CF      CF      CF    CF/WE  CF/WD  CF/WDC1    CF      CF      CF    CF/WE  CF/WE  CFC2    CF      CF      CF    CF/WE  CF/WE  CFC3    CF      CF      CF    CF/WE  CF/WD  CFC4    CF      CF      CF    CF     CF     CF______________________________________
TABLE 4______________________________________Oven Cured AdhesionCom-po-   Glass           Aluminumsition Initial 1 day   3 day Initial                              1 day  3 day______________________________________1     CF      CF      CF    CF/WE  CF/WD  CF2     CF      CF      CF    CF/WE  CF/WD  CF3     CF      CF      CF    CF     CF     CF4     CF      CF      CF    CF     CF     CF5     CF      CF      CF    CF/WD  CF/WD  CF6     CF      CF      CF    CF/WD  CF     CFC1    CF      CF      CF    CF/WD  CF     CFC2    CF      CF      CF    CF/WD  CF/WD  CFC3    CF      CF      CF    CF     CF     CFC4    CF      CF      CF    CF     CF     CF______________________________________
All of the adhesion additives tested ultimately provided cohesive failure to both substrates under both curing conditions.
A number of preferred adhesion additives of this invention were evaluated using a 2-part curable organosiloxane composition.
Part 1 of the composition contained 52 parts of a dimethylvinylsiloxy-terminated polydimethylsiloxane having a viscosity of 0.4 Pa.s at 25° C., 46 parts of quartz with an average particle size of 5 microns, 0.9 part of zinc oxide, 0.5 part carbon black and 0.2 part of a reaction product of hexachloroplatinic acid and sym-tetramethyldivinyldisiloxane that has been diluted with a liquid dimethylvinylsiloxy terminated polydimethylsiloxane in an amount sufficient to achieve a platinum content of 0.7 weight percent.
Part 2 of the composition contained 46 parts of the same dimethylvinylsiloxy-terminated polydimethylsiloxane as part 1, 47 parts of the same quartz filler, 6 parts of a trimethylsiloxy-terminated polydiorganosiloxane having an average of five methylhydrogensiloxane units and three dimethylsiloxane units per molecule with a silicon-bonded hydrogen atom content of 0.8 weight percent and 0.5 part of cyclic methylvinylsiloxanes as a platinum catalyst inhibitor.
The curable compositions also contained one of the adhesion additives identified in the preceding section of this specification and all but one of the compositions (C5) contained 0.15 part of tetrabutyl titanate. The concentrations of parts 1 and 2 of a curable organosiloxane composition, defined in example 2, and the adhesion additives are; listed in Table 5.
TABLE 5______________________________________Composition     C5      C6      7    8    9    C7   C8______________________________________Part 1 (Parts)     7.50    7.50    9.53 9.53 9.53 9.53 9.53Part 2 (Parts)     7.50    7.49    5.46 5.46 5.46 5.46 5.46Additive Type     None    None    D1   D2   D3   D4   D5Additive (Parts)     --      --      0.41 0.44 0.46 0.38 0.40______________________________________
Compositions C5, C6, C7, and C8 are for comparative purposes. The concentrations of adhesion additives provided equimolar amounts of the additive in each composition. The adhesion of the cured compositions was evaluated as described in Example 1 and the results are recorded in Tables 6 and 7.
TABLE 6__________________________________________________________________________Room Temperature Adhesion   Glass         AluminumComposition   1 day        3 day             7 day                 1 day                      3 day                           7 day__________________________________________________________________________C5      CF/WD        CF/WD             CF  AF   AF   AFC6      AF/CF        AF   AF  CF/WE                      AF   AF7       AF   AF   AF  AF   AF   AF8       CF   CF/WD             CF  CF/WD                      CF   CF9       CF   CF/WD             CF  CF/WD                      AF/CF                           CFC7      CF/WD        CF/WD             CF  AF   AF   AFC8      CF   CF   CF  AF/CF                      AF/CF                           CF/WD__________________________________________________________________________
TABLE 7__________________________________________________________________________Oven Cured Adhesion   Glass         AluminumComposition   Initial        1 day             3 day                 Initial                      1 day                           3 day__________________________________________________________________________C5      CF/WD        CF   CF  AF   AF   AFC6      AF   AF   AF  AF   AF   AF7       AF   AF   AF  AF   AF   AF8       CF/WD        CF   CF  AF   CF/WD                           CF9       CF/WD        CF   CF  AF   AF/CF                           CFC7      AF   CF/WE             CF  AF   AF   CF/WEC8      AF   CF/WD             CF  AF   CF/WD                           CF__________________________________________________________________________
This example demonstrates the beneficial effect of using the present adhesion additives in combination with silanes containing at least three alkoxy groups per molecule.
Each of the curable compositions contained 9.53 parts of Part 1 of example 2, 5.48 parts of Part 2, and 0.015 part of tetrabutyl titanate. Additive D2 was the additive of the present invention and additive D5 in compositions C9, C10 and C11 was used for comparative purposes. The ingredients of the compositions are summarized in Table 8.
TABLE 8______________________________________Composition     10     11     12     C9   C10  C11______________________________________Additive  D2     D2     D2     D5   D5   D5Pts. Additive     0.44   0.44   0.44   0.40 0.40 0.40Silane    D6     D7     D6/D7  D6   D7   D6/D7Parts Monomer     0.38   0.38   0.19/0.19                          0.38 0.30 0.19/0.19Ingredient B     0.80   --     0.40   0.80 --   0.40______________________________________
The concentrations of adhesion additives were selected to provide an equal molar amount of each. The adhesion of these compositions was tested as described in a preceding section of this specification and the results are recorded in Tables 9 and 10.
TABLE 9__________________________________________________________________________Room Temperature Adhesion  Glass          AluminumComposition  1 day       3 day            7 day                 1 day                      3 day                           7 day__________________________________________________________________________10     CF/WD       CF/WD            CF/WD                 CF/WD                      CF/WD                           CF/WD11     CF   CF   CF   AF/CF                      AF/CF                           AF/CF12     CF   CF/WD            CF   CF/WD                      AF/CF                           CFC9     CF/WD       CF/WD            CF   AF   AF   AFC10    AF/CF       AF   AF   CF/WE                      AF   AFC11    AF   AF   AF   AF   AF   AF__________________________________________________________________________
TABLE 10__________________________________________________________________________Oven Cured Adhesion  Glass          AluminumComposition  Initial       1 day            3 day                 Initial                      1 day                           3 day__________________________________________________________________________10     CF/WD       CF/WD            CF   CF/WE                      CF   CF11     AF   CF/WD            CF   AF   CF/WD                           CF12     CF/WD       CF   CF   AF   AF/CF                           CFC9     CF/WD       CF   CF   AF   AF   AFC10    AF   AF   AF   AF   AF   AFC11    AF   AF   AF   AF   AF   AF__________________________________________________________________________
1. An organosiloxane copolymer corresponding to the general formula
wherein each R1 is individually selected from monovalent hydrocarbon or halogenated hydrocarbon radicals that are substantially free of ethylenic unsaturation and contain from 1 to 10 carbon atoms;
each R2 is individually selected from alkyl radicals containing 1 to 10 carbon atoms;
R3 is a divalent hydrocarbon radical containing from 2 to 10 carbon atoms;
each R4 is individually selected from monovalent hydrocarbon radicals containing an epoxy, acryloxyalkyl or methacryloxyalkyl group;
R5 is R1 or OR2 ;
X is hydrogen or an alkenyl radical;
a, b, c, d, e, f and g represent mole fractions with a total value of 1;
a, b, c, and d are all greater than zero;
e, f and g are 0 or a positive number less than 1;
x+y is 1, 2or3;
v and w are each 0, 1, 2, or 3;
and v+w is 1, 2 or 3.
2. A copolymer according to claim 1 wherein
each R1 is individually selected from methyl, phenyl, and 3,3,3-trifluoropropyl;
each OR2 and R5 is individually selected from methoxy and ethoxy;
R3 is selected from the group consisting of ethylene, propylene, cyclohexylene and phenylene;
R4 is selected from the group consisting of 3-glycidoxypropyl, 3-epoxycyclohexylmethyl and 3-methacryloxypropyl; the alkenyl radicals represented by X contain from 2 to 12 carbon atoms;
x is 1; y is 2;
the XR1 2 SiO1/2 units constitute from 5 to 50 percent of the total units in said copolymer;
the (R2 O)3 SiR3 (R1)2 SiO1/2 units constitute from 3 to 30 percent of the total units in said copolymer;
the R4 x R5 y SiO.sub.(4-x-y)/2 units constitute from 3 to 30 percent of the total units in said copolymer; and
the SiO4/2 units constitute from 10 to 50 percent, of the total units in said copolymer.
3. A copolymer according to claim 2 wherein the XR1 2 SiO1/2 units are selected from the group consisting of dimethylhydrogensiloxy and dimethylvinylsiloxy and constitute from 25 to 40 percent of the units in said copolymer; the (R2 O)3 SiR3 (R1)2 SiO1/2 units are trimethoxysilylethyldimethylsiloxy; and
the R4 x R5 y SiO.sub.(4-x-y)/2 units are 3-glycidoxypropyldimethylsiloxy.
4. In a curable organosiloxane composition comprising
wherein the combination of curable polyorganosiloxane, curing agent and curing catalyst is selected from the group consisting of
1) polyorganosiloxanes containing at least two alkenyl radicals per molecule as the reactive group; as the curing agent, organohydrogensiloxanes containing an average of at least more than two silicon-bonded hydrogen atoms per molecule as the reactive groups; and a curing catalyst selected from metals from the platinum group of the periodic table or compounds thereof; and
2) polyorganosiloxanes containing silanol groups as the reactive group; as the curing agent, organohydrogensiloxanes containing at least three silicon-bonded hydrogen atoms per molecule as the reactive group; and a curing catalyst selected from metals from the platinum group of the periodic table or compounds thereof;
(D) an adhesion promoting additive in an amount sufficient to achieve adhesion to a substrate in contact with said composition during curing thereof, wherein said additive comprises at least one organosiloxane copolymer corresponding to the general formula ##STR2## wherein each R1 is individually selected from monovalent hydrocarbon or halogenated hydrocarbon radicals that are substantially free of ethylenic unsaturation and contain from 1 to 10 carbon atoms;
x+y is 1, 2 or 3;
5. A composition according to claim 4 wherein said composition is cured by a hydrosilation.
6. A composition according to claim 5 wherein each R1 is individually selected from methyl, phenyl, or 3,3,3-trifluoropropyl;
OR2 and R5 are individually selected from methoxy or ethoxy; R3 is selected from the group consisting of ethylene, propylene, cyclohexylene or phenylene;
x is 1; y is 2; the XR1 2 SiO1/2 units constitute from 5 to 50 percent of the total units in said copolymer;
the (R2 O)3 SiR3 (R1 2)SiO1/2 units constitute from 3 to 30 percent of the total units in said copolymer;
7. A composition according to claim 6 wherein the XR1 2 SiO1/2 units are selected from the group consisting of dimethylhydrogensiloxy and dimethylvinylsiloxy;
the (R2 O)3 SiR3 (R1)2 SiO1/2 units are trimethoxysilylethyldimethylsiloxy;
the R4 x R5 y SiO.sub.(4-x-y)/2 units are 3-glycidoxypropyldimethylsiloxy;
from 25 to 40 percent of the units of said copolymer contain a silicon-bonded hydrogen atom.
8. A composition according to claim 7 wherein said composition further comprises an organotitanium compound as a catalyst to promote hydrolysis of said adhesion promoting additive.
9. A composition according to claim 7 wherein said adhesion promoting additive further comprises from i to 5 weight percent, based on the weight of said composition, of a silane containing at least three alkoxy groups.
10. A composition according to claim 9 wherein said silane is selected from the group consisting of alkenyltrialkoxysilanes and alkyl orthosilicates.
11. A composition according to claim 4 wherein said polyorganosiloxane contains at least two alkenyl radicals per molecule as the reactive group, said curing agent comprises at least one organohydrogensiloxane containing an average of more than two silicon-bonded hydrogen atoms per molecule as the reactive group, and
said curing catalyst is selected from metals from the platinum group of the periodic table or compounds thereof, and the curing temperature of said composition is up to 100° C.
12. A composition according to claim 11 wherein said composition is packaged in at least two containers, said organohydrogensiloxane and said curing catalyst being located in separate containers.
13. A composition according to claim 11 wherein
said polyorganosiloxane is a polydiorganosiloxane exhibiting a viscosity greater than 0.1 Pa.s at 25° C.;
the viscosity of said organohydrogensiloxane at 25° C. is from 0.003 to 10 Pa.s;
the organic groups bonded to the silicon atoms of said polydiorganosiloxane and said organohydrogensiloxane in addition to said reactive groups are monovalent unsubstituted or substituted hydrocarbon radicals;
the concentration of said organohydrogensiloxane provides a molar ratio of silicon-bonded hydrogen atoms to alkenyl radicals in said composition of from 0.5 to 2; and the concentration of said curing catalyst is equivalent to from 1 to 50 parts by weight of platinum group metal per million parts by weight of the combination of said polyorganosiloxane and said organohydrogensiloxane.
14. A composition according to claim 13 wherein said polydiorganosiloxane is represented by the general formula ##STR3## wherein each R7 is individually selected from monovalent hydrocarbon radicals, R8 represents a vinyl or other alkenyl radical, and n represents a degree of polymerization equivalent to a viscosity of at least 100 centipoise (0.1 Pa.s).
US08240426 1994-05-10 1994-05-10 Adhesion promoting additives and curable organosiloxane compositions containing same Expired - Lifetime US5468826A (en)
US08240426 US5468826A (en) 1994-05-10 1994-05-10 Adhesion promoting additives and curable organosiloxane compositions containing same
EP19950302947 EP0682058A3 (en) 1994-05-10 1995-05-01 Adhesion promoting additives and curable organosiloxane compositions containing same.
JP11193495A JPH08143672A (en) 1994-05-10 1995-05-10 Adhesion promoting additive and curable organosiloxane composition containing same
US5468826A true US5468826A (en) 1995-11-21
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US08240426 Expired - Lifetime US5468826A (en) 1994-05-10 1994-05-10 Adhesion promoting additives and curable organosiloxane compositions containing same
US (1) US5468826A (en)
EP (1) EP0682058A3 (en)
JP (1) JPH08143672A (en)
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