Silicone pressure sensitive adhesive compositions

Abstract

This invention relates to pressure sensitive adhesive compositions which are obtained by a method comprising reacting a mixture of at least one polydiorganosiloxane, at least one silicone resin copolymer, at least one silanol condensation catalyst, and at least one solvent or plasticizer having a boiling point of at least 200.degree. C., to form a reaction product, and then adding an organic peroxide or azo compound to the resultant reaction product. The silicone pressure sensitive adhesives of this invention are useful in preparing articles such as pressure sensitive tapes, labels, emblems and other decorative or informational signs.

Description

BACKGROUND OF THE INVENTION

This invention relates to silicone pressure sensitive adhesive compositions. More particularly this invention relates to pressure sensitive adhesive compositions obtained by reacting a mixture comprising a polydiorganosiloxane, a silicone resin copolymer, a condensation catalyst, and at least one solvent or plasticizer having a boiling point of at least 200.degree. C. to form a reaction product, and then adding an organic peroxide or azo compound to the reaction product.

Silicone pressure sensitive adhesives (PSA's) are typically produced by either blending or condensing together a silicone resin and a silicone polymer. These types of silicone pressure sensitive adhesives have been disclosed for example in U.S. Pat. Nos. 2,736,721, 2,814,601, 2,857,356, and 3,528,940.

Silicone pressure sensitive adhesives which are produced by adding an amine or a salt of an amine to the silicone resin-silicone polymer blend have been disclosed for example in Great Britain Patent Specification No. 998,232. Silicone pressure sensitive adhesives have also been disclosed which comprise a resin, a polydiorganosiloxane fluid, and a condensation catalyst such as a metal salt of a carboxylic acid for example in U.S. Pat. No. 4,831,070.

European Patent Application No. 0459292 discloses a silicone pressure sensitive adhesive composition comprising a mixture two different pressure sensitive adhesive compositions containing resin and polymer blends.

U.S. Pat. No. 5,248,739 to Schmidt et al. discloses a silicone pressure sensitive adhesive composition produced by mixing together a silicone resin and a polydiorganosiloxane polymer and that these compositions can further comprise an organic peroxide as a crosslinking agent when the polydiorganosiloxane polymer does not contain unsaturated groups.

Great Britain Patent Publication No. 2301829 discloses silicone pressure sensitive adhesive compositions comprising 100 parts of an organopolysiloxane having a viscosity of at least 500,000 centipoise at 25.degree. C., 60 to 300 parts of a silicone MQ resin, and 20 to 2500 parts of a linear or cyclic volatile organosiloxane fluid having a boiling point in the range of about 95.degree. C. to about 250.degree. C. where the organo radicals of the silicone PSA composition are selected from C.sub.1-13 organo radicals which are attached to silicon by carbon-silicon linkages and further discloses that the curing of the silicone PSA composition is by the use of a free-radical initiator such as an organic peroxide.

Conventional peroxide curable silicone pressure sensitive adhesives are typically supplied at 55 to 60% solids by weight in an organic (typically aromatic) solvent diluent. This is done to lower the viscosity of the film forming product, making it easier to handle and apply evenly to a desired substrate. These solvents typically boil at 100 to 140.degree. C., and care is taken to remove them prior to thermal activation by a peroxide initiator.

SUMMARY OF THE INVENTION

It has now been discovered that the addition of a high boiling organic solvent or plasticizer to silicone pressure sensitive adhesive composition can improve the performance of the adhesive.

This invention relates to silicone pressure sensitive adhesive compositions which are obtained by reacting a mixture comprising at least one polydiorganosiloxane, at least one silicone resin copolymer, at least one condensation catalyst, and at least one solvent or plasticizer having a boiling point of at least 200.degree. C. to form a reaction product, and then adding an organic peroxide or azo compound to the reaction product.

It is an object of this invention to provide a silicone pressure sensitive adhesive that exhibits high tack while retaining good peel adhesion.

It is further an object of this invention to provide a silicone pressure sensitive adhesive that is produced by condensing a polydiorganosiloxane in the presence of a silicone resin.

It is further an object of this invention to provide a silicone pressure sensitive adhesive having a high solids content or are solventless which maintain excellent adhesive properties at low viscosities.

It is another object of this invention to provide a silicone pressure sensitive adhesive which will be particularly suitable in adhesive tape constructions.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to a silicone pressure sensitive adhesive composition obtained by a method comprising the steps of (I) reacting a mixture comprising: (A)(i) at least one hydroxyl-terminated polydiorganosiloxane having a viscosity of from 100 to 100,000,000 mm.sup.2 /s at 25.degree. C. or (ii) a mixture of (a) a hydroxyl-terminated polydiorganosiloxane and (b) a polydiorganosiloxane selected from (i) polydiorganosiloxanes terminated with monovalent hydrocarbon radicals free of aliphatic unsaturation or (ii) alkenyl-terminated polydiorganosiloxanes wherein said mixture has a viscosity of from 100 to 100,000,000 mm.sup.2 /s at 25.degree. C., (B) at least one soluble silicone resin consisting essentially of at least one R.sub.3 SiO.sub.1/2 unit and at least one SiO.sub.4/2 unit, wherein R is independently selected from a monovalent hydrocarbon or halohydrocarbon radical free of aliphatic unsaturation and having from 1 to 20 carbon atoms, an alkenyl radical, or a hydroxyl radical wherein the molar ratio of R.sub.3 SiO.sub.1/2 units to SiO.sub.4/2 units is from 0.5:1 to 1.2:1, (C) at least one silanol condensation catalyst selected from the group consisting of liquid catalysts having a boiling point of less than 200.degree. C. and catalysts which are solid at room temperature, and (D) at least one solvent or plasticizer having a boiling point of at least 200.degree. C. to form a reaction product, and (II) adding (E) an organic peroxide or azo compound to the reaction product of (I).

The hydroxyl-terminated polydiorganosiloxane of component (A) is preferably a polydiorganosiloxane having the general formula HOR.sup.1.sub.2 SiO(R.sup.1.sub.2 SiO).sub.a SiR.sup.1.sub.2 OH wherein each R.sup.1 is independently selected from a monovalent hydrocarbon or halohydrocarbon radical having from 1 to 20 carbon atoms or an alkenyl radical. The monovalent hydrocarbon radicals free of aliphatic unsaturation include alkyl radicals exemplified by methyl, ethyl, propyl, pentyl, octyl, undecyl or octadecyl, cycloaliphatic radicals exemplified by cyclohexyl, aryl radicals exemplified by phenyl, tolyl, xylyl, benzyl or 2-phenylethyl, and chlorinated hydrocarbon radicals exemplified by 3-chloropropyl and dichlorophenyl. The alkenyl radicals include vinyl, allyl, butenyl, hexenyl, cyclohexenyl and beta-cyclohexenylethyl. Preferably R.sup.1 is selected from methyl, phenyl, or vinyl. Preferably the hydroxyl-terminated polydiorganosiloxane of component (A) is a compound in which at least 50%, and preferably at least 85%, of the R.sup.1 radicals are methyl radicals.

The average value of subscript "a" above is such that it provides a viscosity at 25.degree. C. of about 100 mm.sup.2 /s (100 centistokes) to about 100,000,000 mm.sup.2 /s (100,000,000 centistokes), the viscosity being a function of the R.sup.1 radicals on the polymer. It is especially preferred that the average value of a is such that it provides an organopolysiloxane component (A) having a viscosity in the range of 1,000 to 50,000,000 mm.sup.2 /s at 25.degree. C., and it is highly preferred that a has a value such that the viscosity of component (A) ranges from 2,000 to 500,000 mm.sup.2 /s when measured at 25.degree. C.

Specific examples of these polydiorganosiloxanes include, but are not limited to, HOMe.sub.2 SiO(Me.sub.2 SiO).sub.a SiMe.sub.2 OH, HOMe.sub.2 SiO(Me.sub.2 SiO).sub.0.94a (Ph.sub.2 SiO).sub.0.06a SiMe.sub.2 OH, HOPh.sub.2 SiO(Me.sub.2 SiO).sub.0.94a (Ph.sub.2 SiO).sub.0.06a SiPh.sub.2 OH, HOMe.sub.2 SiO(Me.sub.2 SiO).sub.0.95a (MeViSiO).sub.0.05a SiMe.sub.2 OH, HOVi.sub.2 SiO(Me.sub.2 SiO).sub.0.95a (MeViSiO).sub.0.05a SiVi.sub.2 OH, or HOR.sub.2 SiO(Me.sub.2 SiO).sub.0.88a (Ph.sub.2 SiO).sub.0.12a SiR.sub.2 OH wherein Me, Vi, and Ph hereinafter denote methyl, vinyl, and phenyl, respectively, and a is as defined above. Component (i) can also be a mixture of two or more different hydroxyl-terminated polydiorganosiloxanes.

Component (A) can also be (ii) a mixture of (a) a hydroxyl-terminated polydiorganosiloxane and (b) a polydiorganosiloxane selected from (i) polydiorganosiloxanes terminated with monovalent hydrocarbon radicals free of aliphatic unsaturation or (ii) alkenyl-terminated polydiorganosiloxanes wherein said mixture has a viscosity of from 100 to 100,000,000 mm.sup.2 /s at 25.degree. C. The hydroxyl-terminated polydiorganosiloxane is as described above including preferred embodiments thereof. The monovalent hydrocarbon radicals free of aliphatic unsaturation and the alkenyl radicals are as described above including preferred embodiments thereof.

Specific examples of polydiorganosiloxanes terminated with monovalent hydrocarbon radicals free of aliphatic unsaturation include, but are not limited to, Me.sub.3 SiO(Me.sub.2 SiO).sub.a SiMe.sub.3, Me.sub.3 SiO(Me.sub.2 SiO).sub.0.95a (MeViSiO).sub.0.05a SiMe.sub.3, Me.sub.3 SiO(Me.sub.2 SiO).sub.0.5a (MePhSiO).sub.0.5a SiMe.sub.3, or Me.sub.3 SiO(Me.sub.2 SiO).sub.0.5a (Ph.sub.2 SiO).sub.0.5a SiMe.sub.3 wherein a has an average value as defined above.

Specific examples of polydiorganosiloxanes terminated with alkenyl radicals include, but are not limited to, ViMe.sub.2 SiO(Me.sub.2 SiO).sub.a SiMe.sub.2 Vi, ViMe.sub.2 SiO(Me.sub.2 SiO).sub.0.95a (MePhSiO).sub.0.05a SiMe.sub.2 Vi, ViMe.sub.2 SiO(Me.sub.2 SiO).sub.0.98a (MeViSiO).sub.0.02a SiMe.sub.2 Vi, PhMeViSiO(Me.sub.2 SiO).sub.a SiPhMeVi, ViMe.sub.2 SiO(Me.sub.2 SiO).sub.0.95a (Ph2SiO).sub.0.05a SiMe.sub.2 Vi, PhMeViSiO(Me.sub.2 SiO).sub.0.8a (MePhSiO).sub.0.1a (Ph.sub.2 SiO).sub.0.1a SiPhMeVi wherein a has an average value as defined above.

If component (A) is (ii) a mixture of (a) and (b) as defined above, the mixture of (a) and (b) can be in weight ratios of (a):(b) of 1:99 to 99:1, is preferably from 90:10 to 10:90, and it is highly preferred that the weight ratio of (a) to (b) is from 70:30 to 30:70.

In component (A) it is also preferred that the molar sum of phenyl and vinyl radicals should not exceed 30% of the silicon atoms. In addition, component (A) can comprise trace amounts of siloxane branching sites, such as R.sup.1 SiO.sub.3/2 units and SiO.sub.4/2 units, provided that the component remains flowable. Component (A) is well known in the art and can be prepared by known methods.

The amount of component (A) in the compositions of this invention is preferably from about 30 parts by weight to about 50 parts by weight, and more preferably from about 37 parts by weight to about 47 parts by weight per 100 parts by weight of components (A)+(B).

Component (B) of this invention is at least one soluble silicone resin consisting essentially of at least one R.sub.3 SiO.sub.1/2 unit (M unit) and at least one SiO.sub.4/2 unit (Q unit), wherein R is independently selected from a monovalent hydrocarbon or halohydrocarbon radical having 1 to 20 carbon atoms, an alkenyl radical, or a hydroxyl group, all of which are as described above. By the term "soluble" it is meant that the silicone resin (B) can be dispersed, substantially completely, in either a hydrocarbon liquid exemplified by benzene, toluene, xylene, heptane and the like or in a silicone liquid such as cyclic or linear polydiorganosiloxanes. Preferably the resin is soluble in component (A), delineated above. Preferably the silicone resin of component (B) is a soluble hydroxy-functional organopolysiloxane resin consisting essentially of M units and Q units. In the hydroxyl functional organopolysiloxane resin the R.sub.3 SiO.sub.1/2 units are bonded to the SiO.sub.4/2 units, each of the latter being bonded to at least one other SiO.sub.4/2 unit. Some of the SiO.sub.4/2 units are bonded to hydroxy radicals resulting in HOSiO.sub.3/2 units, thereby accounting for the silicon-bonded hydroxyl content of the resin. In addition, the resin may contain a small amount of a low molecular weight material comprised substantially of a neopentamer organopolysiloxane having the formula (R.sub.3 SiO).sub.4 Si.

It is preferable that the hydroxy-content of the silicone resin or resin mixture as determined by .sup.29 Si NMR (nuclear magnetic resonance) ranges from 1.0 wt % to 5.0 wt % based on the resin solids content, and preferably 1.5 wt % to 3.5 wt %. However, resins having less than 1.0 wt % hydroxy can be used in this invention.

In the formula for organopolysiloxane resin (B), the monovalent hydrocarbon radicals free of aliphatic unsaturation and the alkenyl radicals are as defined above, including preferred embodiments thereof. Preferably R is independently selected from methyl, phenyl, vinyl, hexenyl, or hydroxyl. Preferably, at least one-third, and more preferably substantially all R radicals in the formula for component (B) are methyl radicals. Examples of preferred R.sub.3 SiO.sub.1/2 units include Me.sub.3 SiO.sub.1/2, ViMe.sub.2 SiO.sub.1/2, PhMe.sub.2 SiO.sub.1/2, or Ph.sub.2 MeSiO.sub.1/2.

The molar ratio of R.sub.3 SiO.sub.1/2 units to SiO.sub.4/2 units is from 0.5:1 to 1.2:1. It is more preferred that the molar ratio of R.sub.3 SiO.sub.1/2 units to SiO.sub.4/2 units be from 0.6:1 to 1:1. The above M:Q molar ratios can be easily obtained by .sup.29 Si NMR. It is preferred that component (B) have a number average molecular weight (Mn) of about 3,000 to 7,500 when measured by gel permeation chromatography (GPC) calibrated against fractionated MQ resin standards. It is especially preferred that the molecular weight of Component (B) is from 3,500 to 6,000.

Component (B) can be prepared by well known methods. It is preferably prepared by the silica hydrosol capping process of U.S. Pat. No. 2,676,182 to Daudt et al., as modified by U.S. Pat. No. 3,627,851 to Brady, and U.S. Pat. No. 3,772,247 to Flannigan, each patent being incorporated herein by reference to teach how to prepare soluble organopolysiloxanes which are useful in this invention. Further, component (B) can be prepared by the cohydrolysis of a trialkyl hydrolyzable silane and alkyl silicate as described in U.S. Pat. No. 2,857,356, to Goodwin herein incorporated by reference for its teaching of how to prepare the resin.

The amount of component (B) in the compositions of this invention is preferably from about 50 parts by weight to about 70 parts by weight, and more preferably from about 53 parts by weight to about 63 parts by weight per 100 parts by weight of components (A)+(B). A preferred embodiment is the addition of a separate high-resin containing polymer-resin mixture to the initial resin-polymer mixture such that the resin content of the proportion of the combined resin and polymer mixture falls within the limits delineated above.

Component (C) of this invention is at least one silanol condensation catalyst selected from the group consisting of liquid catalysts having a boiling point of less than 200.degree. C. and catalysts which are solid at room temperature. The silanol condensation catalyst can be selected from alkali metal hydroxides, alkali metal alkoxides, alkali metal carbonates, alkali metal silanolates, amines, metal salts of amines, carboxylic acids, or metal salts of carboxylic acids so long at the catalyst has the above properties. Component (C) is preferably selected from amines, carboxylic acid salts of organic amines, quaternary ammonium salts, carboxylic acids, and metal salts of carboxylic acids. Amines suitable for use as component (C) include primary amines exemplified by methylamine, ethylamine, propyl amine, hexylamine, butanolamine, and butylamine, secondary amines exemplified by dimethylamine, diethylamine, diethanolamine, dipropylamine, dibutylamine, dihexylamine, ethylamylamine, imidazole, and propylhexylamine, tertiary amines exemplified by trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, methyldipropylamine, tripropanolamine, pyridine, N-methylimidazole, and methylpropylhexylamine. Carboxylic acid salts of organic amines suitable as component (C) are exemplified by diethylammonium acetate, butylammonium octoate, and trimethylammonium laurate. Quaternary ammonium salts suitable as component (C) are exemplified by tetramethylammonium acetate, methylethyldibutylammonium chloride, or dioctadecyldimethylammonium chloride. Carboxylic acids suitable as component (C) are exemplified by acetic acid, propanoic acid, butanoic acid, formic acid, stearic acid, tetradecanoic acid, hexadecanoic acid, dodecanoic acid, decanoic acid, 3,6-dioxaheptanoic acid, and 3,6,9-trioxadecanoic acid. Metal salts of carboxylic acids wherein the metal is selected from the group consisting of Li, Na, K, Ce, and Ca are also suitable for use as component (C). The metal salts of carboxylic acids are exemplified by potassium formate and potassium acetate. Component (C) can also be a combination of two or more different condensation catalysts. It is preferred that component (C) is a tertiary amine.

The amount of component (C) in the compositions of this invention is preferably from about 0.01 parts by weight to about 20 parts by weight, and more preferably from about 0.1 parts by weight to about 5 parts by weight per 100 parts by weight of components (A)+(B).

Component (D) is at least one solvent or plasticizer having a boiling point of at least 200.degree. C. The term "boiling point" for the purposes of this invention denotes the boiling point of a liquid at 760 mm of Hg. The materials of component (D) are exemplified by aliphatic hydrocarbons including dodecane (boiling point (bp) of about 216.degree. C.), tridecane (bp of about 234.degree. C.), tetradecane (bp of about 252.degree. C.), 1-tetradecene (bp of about 256.degree. C.), pentadecane (bp of about 266.degree. C.), hexadecane (bp of about 280.degree. C.), octadecane (bp of about 308.degree. C.), and nonadecane (bp of about 320.degree. C.), glycol ethers exemplified by diethylene glycol ethyl ether (bp of about 202.degree. C.), diethylene glycol butyl ether (bp of about 230.degree. C.), triethylene glycol methyl ether (bp of about 242.degree. C.), triethylene glycol ethyl ether (bp of about 254.degree. C.), triethylene glycol butyl ether (bp of about 283.degree. C.), ethylene glycol phenyl ether (bp of about 245.degree. C.), propylene glycol phenyl ether (bp of about 243.degree. C.), and aromatic based glycol ethers (bp of about 245.degree. C.), esters exemplified by diethylene glycol butyl ether acetate (bp of at least 235.degree. C.), pine oil (bp of at least 212.degree. C.), and mineral seal oil (bp of at least 278.degree. C.), alcohols exemplified by tridecyl alcohol (bp of about 252.degree. C.) and ester alcohols including trimethyl pentane diol isobutyrate (bp of at least 244.degree. C.), ketones exemplified by isophorone (bp of at least 215.degree. C.), kerosenes, naphthas, petrolatums, carboxylic acids having at least six carbon atoms exemplified by nonanoic acid (bp of about 268.degree. C.), caproic acid (also known as hexanoic acid (bp of about 202.degree. C.), caprylic acid (also known as octanoic acid (bp of about 237.degree. C.), oleic acid, linoleic acid, linolenic acid, and N-coco-beta-aminobutyric acid and amines having at least nine carbon atoms exemplified by dodecylamine (bp of about 248.degree. C.), hexadecylamine (bp of about 330.degree. C.), octadecylamine, dimethyldodecylamine, dicocoamine, methyldicocoamine, dimethyl cocoamine, dimethyltetradecylamine, dimethylhexadecylamine, dimethyloctadecylamine, dimethyl tallow amine, dimethylsoyaamine, dimethyl nonylamine, di(hydrogenated-tallow)amine, and methyldi(hydrogenated-tallow)amine. Particularly useful solvents from the standpoint of their physical and chemical properties are the branch-chain isoparaffinic solvents sold by the Exxon Chemical Company under the tradename Exxsol.RTM. D 110, Isopar.RTM. M, or Isopar.RTM. V. It is preferred that the solvent or plasticizer of component (D) have a boiling point of at least 210.degree. C., and it is especially preferred that the solvent or plasticizer of (D) have a boiling point of at least 225.degree. C. It is preferred that component (D) is miscible in components (A) and (B). Miscible as used herein denotes that Component (D) has the ability to dissolve uniformly in the mixture of (A)+(B).

The amount of component (D) to be used is dependent on the type of solvent or plasticizer selected. If a solvent or plasticizer having a boiling point near 200.degree. C. is selected, a greater amount of solvent or plasticizer is required. The amount of component (D) in the compositions of this invention is preferably from about 2 parts by weight to about 40 parts by weight, and more preferably from about 5 parts by weight to about 30 parts by weight per 100 parts by weight of components (A)+(B).

The mixture of step (I) can also further comprise a rare earth metal salt of a fatty acid. Examples of rare earth metals suitable for forming the salt include cerium, lanthanum, praseodymium, with cerium being preferred. The fatty acid generally contains about 6 to 18 carbon atoms, most preferably about 8 carbon atoms. The preferred rare earth metal salt is cerium octoate. The rare earth metal salt is generally used in the compositions of this invention to provide the composition with an amount of rare earth metal within the range of from about 1 to about 1000 parts by weight, and preferably from about 10 to about 250 parts by weight, per one million parts by weight of components (A)+(B). Typically, the rare earth metal salt, if used, is in the form of a 30% solvent solution, 6% of which is composed of the active rare earth metal. Solvents suitable for the rare earth metal solution are solvents having a boiling point of less than 200.degree. C. such as hexane, heptane, toluene, xylene, naphtha, mineral spirits, or ketones.

The reaction product of step (I) is made by reacting a mixture of components (A), (B), (C), and (D). Reacting for the purposes of this invention denotes simply mixing components (A), (B), (C), and (D) and any optional components at room temperature (about 25.degree. C.) or heating a mixture of components (A)-(D) and any optional components at temperatures above room temperature. Preferably a mixture of components (A)-(D) and any optional components are heated at a temperature above 100.degree. C. A preferred embodiment of the reaction process is to pre-neutralize or otherwise pacify catalytic impurities which are introduced with the raw materials which comprise the adhesive reaction product. The reaction product can also be formed by reacting a mixture of components (A), (B), and (C), and then adding component (D), and then optionally heating the resulting product to form a reaction product. The mixing of these components can be enhanced, if desired, by the use of one or more solvents having a boiling point of less than 200.degree. C. in the mixture of step (I), such as benzene, toluene, xylene, naphtha, mineral spirits, cyclic polysiloxanes, or alcohols such as methanol, ethanol, isopropanol, butanol, or n-propanol. The amount of solvent having a boiling point of less than 200.degree. C., if used, ranges from about 60 to 200 parts by weight per 100 parts by weight of components (A)+(B). The mixture of (A)-(D) is generally heated for up to 4 hours at temperatures of from 100 to 180.degree. C., however, the time and temperature are dependent on the selection and concentration of the reaction components. The reaction is essentially complete when the viscosity of the reaction product begins to level off or begins to decrease after achieving a maximum value. The reacting of the mixture of (A)-(D) results in the formation of a reaction product.

When a solvent having a boiling point of less than 200.degree. C. is used, it may be necessary to strip off this solvent after the formation of the reaction product. Methods of stripping volatile components are well known in the art and need no extensive delineation herein. Any method of removing volatile components can be used, such methods exemplified by molecular stills, rotoevaporators, and wipe film evaporators, with the preferred method being rotoevaporators.

It is preferred that the reaction product of step (I) have a solids content of at least 60% and a viscosity of up to 200,000 millipascal-seconds (mPa.s), more preferably has a solids content of at least 75% and a viscosity of up to 150,000 mPa.s, and it is highly preferred that the reaction product of step (I) has a solids content of at least 80% and a viscosity of up to 100,000 mPa.s.

In step (II), component (E) an organic peroxide or azo compound is added to the reaction product of step (I). Examples of preferred organic peroxides which are suitable as component (E) include diacyl peroxides such as benzoyl peroxide or dichlorobenzoyl peroxide. Benzoyl peroxide has been found to be a particularly effective organic peroxide.

Examples of azo compounds suitable as component (E) include azobenzene, azobenzene-p-sulfonic acid, 2,4-dimethyl-4-methoxyvaleronitrile, azobisdimethylvaleronitrile, azobisisobutyronitrile, or azodine, with azobisisobutyronitrile being preferred. Component (E) when added to the product of step (I) can be added as a solution, for example, in an appropriate solvent having a boiling point of less than 200.degree. C. such as benzene, toluene, xylene, naphtha, chlorocarbons, ketones, or mineral spirits.

The amount of Component (E) in the compositions of this invention is preferably from about 0.1 to 5 parts by weight, and more preferably from about 1.5 to 3.5 parts by weight per 100 parts by weight of components (A)+(B).

During or after the formation of the silicone pressure sensitive adhesive composition, small amounts of additional ingredients may be added to the composition so long as they do not materially affect the pressure sensitive adhesive composition. These additional ingredients may be exemplified by, but not limited to, antioxidants, pigments, stabilizers, fillers, and others. It should be apparent to one skilled in the art that a blend of two or more reaction products, each having different amounts of components (A), (B), (C), and/or (D) can be formed in Step (I), and then this blend can be catalyzed according to Step (II).

This invention further relates to an article of manufacture prepared by (I) applying a silicone pressure sensitive adhesive composition to at least one surface of a substrate, wherein the silicone pressure sensitive adhesive composition is as described above including preferred embodiments thereof and (II) heating the silicone pressure sensitive adhesive composition and the substrate to cure the composition. The method can further comprise (III) contacting a solid support with the substrate having the adhesive composition cured thereon after step (II) whereby the solid support and the substrate are adhered together.

The silicone pressure sensitive adhesives of this invention are useful as pressure sensitive adhesives and will readily stick to support a solid support, whether flexible or rigid. These compositions may be applied to a surface by any suitable means such as rolling, spreading, spraying, etc., and cured as described above.

The surface of the support and the substrate to which the support is adhered may be any known solid material such as metals, such as aluminum, silver, copper, iron and their alloys, porous materials such as paper, wood, leather, and fabrics, organic polymeric materials such as polyolefins including polyethylene and polypropylene, fluorocarbon polymers such as polytetrafluoroethylene and polyvinylfluoride, silicone elastomers, silicone resins, polystyrene, polyamides such as Nylon, polyimides, polyesters and acrylic polymers, painted surfaces, siliceous materials such as concrete, bricks, cinderblocks, and glass such as glass cloth. Porous materials such as glass cloth are often impregnated with a substance that will prevent the migration of the silicone pressure sensitive adhesive from one surface to another surface of the support. In this regard, it is also well known to chemically treat, physically treat (for example etching, etc.), or primecoat (adding a curable polysiloxane) the surface of a substrate prior to addition of the silicone PSA to enhance the adhesion of the silicone pressure sensitive adhesive to said surface. The PSA's of the invention are particularly suited to applications wherein good adhesion to a low energy surface (e.g., polyethylene or Teflon.TM.) is desired.

The amount of silicone pressure sensitive adhesive composition to be applied to the surfaces should be sufficient to render the surface definitely tacky to the touch after the removal of any solvent having a boiling point of less than 200.degree. C. After applying it to the surface, the adhesive may be cured by air drying or heating at temperatures of up to 300.degree. C.

Solid supports bearing the cured compositions of this invention are readily adhered to any solid substrate because the silicone pressure sensitive adhesive compositions of this invention have high tack and good adhesive strength.

Useful articles which can be prepared with the silicone pressure sensitive adhesives of this invention include pressure sensitive tapes, labels, emblems and other decorative or informational signs, among others. In particular, the silicone pressure sensitive adhesives are useful in tapes such as a splicing tape in label and paper stock manufacture and converting. An especially useful article is one comprising a flexible or rigid support that can withstand extreme temperatures, hot and/or cold, and carrying on at least one surface thereof the silicone pressure sensitive adhesives of this invention. Such an article makes full use of the stability at high temperatures and the flexibility at low temperatures that the silicone pressure sensitive adhesives of this invention possess.

EXAMPLES

All parts and percentages are on a weight basis and all measurements were obtained at 25.degree. C. unless otherwise indicated. The molecular weight properties of the polydimethylsiloxane polymers below were determined by Gas Phase Chromatography (GPC) in a toluene solvent, and using a polydimethylsiloxane standard.

The apparatus and testing procedures used for the results shown herein are as follows:

Adhesion was measured by applying a 6.times.1 inch strip of a Kapton.TM. or Mylar.TM.-backed adhesive to a clean 2.times.6 inch stainless steel panel using two passes of a 4.5 lb. rubber-coated roller. The force required to remove the tape from the panel was measured with a Keil Tester at an peel angle of 180.degree. at a rate of 12 inches per minute. The values recorded are the average of multiple readings taken during the course of one pull per sample. The Keil Tester is described in TAPPI, vol. 43, No. 8. pages 164A and 165A (Aug. 1960). The readings are reported in units of ounces per inch (oz/in).

Tack was measured on at least five one-inch squares of the Kapton.TM. or Mylar.TM.-backed adhesive using a POLYKEN.RTM. probe tack tester, available from Testing Machines, Inc., Amityville, N.Y. The tack tester has a 0.5 cm diameter stainless steel probe. The test procedure used a 20 gram weight, a dwell time of 1.0 seconds and a pull speed of 0.5 cm per second. The results reported represent the average of at least five readings, expressed in (g)/cm.sup.2.

Non-volatile content, i.e. percent solids, of an adhesive material was determined by heating a two gram sample of the material at 150.degree. C. for one hour and expressing the weight of the residue as a percentage of the original sample weight.

The non-volatile content of the MQ resins was determined by mixing about 1.5 grams of resin solution with about 0.75 grams of a polydimethylsiloxane fluid having a viscosity of 100 centistokes (cS) (100 mm.sup.2 /s), followed by devolatilization at 150.degree. for 2 hours.

The resins in the examples were analyzed using .sup.29 Si n.m.r. to determine the molar ratios of the (CH.sub.3).sub.3 SiO.sub.1/2 units (M) to SiO.sub.4/2 units (Q) in each resin and to determine the hydroxyl content of each resin.

Viscosities were measured in centipoise (cP) (1 cP=1 millipascal-second (mPa.s)) at room temperature (25.degree..+-.2.degree. C.) using a Brookfield rotating disc viscometer fitted with an LV-4 spindle.

The following materials were employed in preparing the compositions in the examples:

POLYMER A was a hydroxyl-endblocked polydimethylsiloxane fluid having a viscosity of about 15,000 mPa.s, a number average molecular weight (Mn) of 38,200, and a weight average molecular weight Mw of 68,470.

POLYMER B was a hydroxyl-endblocked polydimethylsiloxane gum copolymer containing 4 mole % MeViSiO repeat units and having a plasticity of about 59 mils as measured by ASTM D926-27.

POLYMER C was a hydroxyl-endblocked polydimethylsiloxane gum, having a plasticity of about 58 mils as measured by ASTM D926-27.

RESIN A was a benzene-soluble, siloxane resin consisting of (CH.sub.3).sub.3 SiO.sub.1/2 (M) units and SiO.sub.4/2 (Q) units and having an M:Q molar ratio of 0.78:1.0, a hydroxyl content of 2.9 wt %, and the following molecular weight characteristics as determined by GPC in Chloroform, using fractionated MQ resin standards and an IR detector, an Mn of 4,300, an Mw of 14,600, and an Mw/Mn of 3.395.

RESIN B is a benzene-soluble, siloxane resin consisting of (CH.sub.3).sub.3 SiO.sub.1/2 (M) units and SiO.sub.4/2 (Q) units and having a non-volatile content of 63.5%, and a hydroxyl content of <1.0%.

THERMAL STABILITY ADDITIVE was Ten-Cem.TM. (a dispersion of a neodecanoate salt of a rare earth metal in mineral spirits having 6% active metals in the mineral spirits from Mooney Chemicals, Inc., Cleveland, Ohio).

PEROXIDES

Perkadox.RTM. PD-50S-ps-a--a suspension of 50 wt % 2,4-dichlorobenzoyl peroxide in a proprietary polysiloxane fluid supplied by Akzo Chemical.

Benzoyl Peroxide, in granular form, was 98% pure supplied by Aldrich Chemical Company.

Example 1

Approximately 150.1 grams (g) of Resin A, 73.6 (g) of Polymer A, 76.3 (g) of toluene, 20 (g) Exxsol.RTM. D-110 Solvent (a C.sub.9 -C.sub.16 branched chain aliphatic hydrocarbon petroleum distillate having a boiling point ranging from about 237.degree. C. to 277.degree. C. from Exxon Chemical Company, a Division of Exxon Corporation, Houston, Tex.), 4.6 (g) of triethylamine, and 0.06 (g) of a thermal stability additive, were combined in a 500 ml 3-neck flask equipped with stirrer, thermometer, Dean Stark trap, and condenser. The contents were mixed and heated to reflux temperature (about 125.degree. C.) where it was maintained for 4 hours. Water was removed continuously during the reflux step. About 20 (g) of Exxsol.RTM. D-110 was added to the mixture about half way through the stripping process, which was conducted at elevated temperature and at atmospheric pressure. The stripping process was then resumed until the pot temperature reached 205.degree. C. The reaction product was then allowed to cool prior to recovery and storage for evaluation. The resultant PSA had a measured viscosity of about 35,500 mPa.s at about 86% solids.

A portion of the PSA was then catalyzed by adding Perkadox.RTM. PD-50S-ps-a to the reaction product at a level of 2 wt % peroxide solids based on PSA solids, and cast onto 1 mil polyimide (Kapton.TM.) in an amount sufficient to attain a 2 mil dry PSA film on the substrate. The polyimide-supported film was cured for 5 minutes at 204.degree. C. The same catalyzed PSA mixture was also cast onto a sheet of 2 mil Mylar.TM. A, and cured for 5 minutes at 178.degree. C. The samples were then measured for probe tack and 180 degree peel adhesion according to the procedures described above. The results are shown in Table 1 below.

In a separate evaluation, a second portion of the adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at the same level described above, and cast onto sheets of 2 mil polyester (Mylar.TM. A) and 1 mil polyimide (Kapton.TM.). Each sheet was then cured according to a different set of thermal conditions, followed by evaluation of 180 degree Peel Adhesion and Probe Tack as described above. The results are recorded Table 2 below.

Comparative Example 1

Approximately 150.1 (g) of Resin A, 73.6 (g) of Polymer A, 76.3 (g) of toluene, 4.6 (g) of triethylamine, and 0.06 (g) of a thermal stability additive, were combined in a 500 ml 3-neck flask equipped with stirrer, thermometer, Dean Stark trap, and condenser. After refluxing for 4 hours, with continuous removal of water from the process, the mixture was stripped to about 84% solids. The resultant adhesive product was then cooled, recovered, and stored for evaluation.

A portion of the adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at a level of 2 wt % peroxide solids based on PSA solids, and cast onto 1 mil polyimide (Kapton.TM.) in an amount sufficient to attain a 2 mil Dry PSA film on the substrate. The polyimide-supported film was cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 204.degree. C. The same catalyzed PSA mixture was also cast onto a sheet of 2 mil Mylar.TM. A, and cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 178.degree. C. The probe tack and 180 degree Peel Adhesion were then measured according to the methods described above. The results are recorded in Table 3 below.

Comparative Example 2

Approximately 150.1 (g) of Resin A, 73.6 (g) of Polymer A, 76.3 (g) of toluene, 4.6 (g) of triethylamine, and 0.06 (g) of a thermal stability additive, were combined in a 500 ml 3-neck flask equipped with stirrer, thermometer, Dean Stark trap, and condenser. After refluxing for 4 hours, with continuous removal of water from the process, the product was stripped to remove a majority of the aromatic solvents contained in the crude mixture. Approximately 20 (g) of heptane solvent was then added to the stripped product, resulting in a non-volatile content of about 90%. The resultant product was cooled, recovered, and stored for evaluation.

A portion of the adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at a level of 2 wt % peroxide solids based on PSA solids, and cast onto a sheet of 2 mil Mylar.TM. A, in an amount sufficient to attain a 2 mil dry film thickness on the substrate. The polyester-supported film was cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 178.degree. C. Probe Tack and 180 degree Peel Adhesion were then measured according to the methods described above. Results are recorded below.

______________________________________ 180.degree. PEELSUBSTRATE ADHESION PROBE TACK______________________________________2 mil Mylar .TM. A 52 oz/in 998 +/- 38 (g)cm.sup.2______________________________________

Using the same catalyzed mixture, a second polyester sheet was coated and cured for 5 minutes at 178.degree. C. Probe Tack and 180 degree Peel Adhesion were then measured according to the methods described above. Results are recorded below.

______________________________________ 180.degree. PEELSUBSTRATE ADHESION PROBE TACK______________________________________2 mil Mylar .TM. A 49 oz/in 1,098 +/- 82 (g)/cm.sup.2______________________________________

Example 2

Approximately 150.1 (g) of Resin A, 73.6 (g) of Polymer A, 76.3 (g) of toluene, 4.6 (g) of Triethylamine, and 0.06 (g) of a thermal stability additive, were combined in a 500 ml 3-neck flask equipped with stirrer, thermometer, Dean Stark trap, and condenser. The contents were mixed well and heated to reflux temperature where it was maintained for 4 hrs. Water was removed continuously during the reflux step. Approximately 9.5 (g) Exxsol.RTM. D-110 was added to the PSA product and the resulting reaction product (adhesive) was then stripped at atmospheric pressure to approximately 91% solids, cooled, recovered, and stored for evaluation.

A portion of the adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at a level of 2 wt % peroxide solids based on PSA solids, and then cast onto 1 mil polyimide (Kapton.TM.) using the appropriate Bird Bar to attain a 2 mil Dry PSA film on the substrate. The polyimide-supported film was cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 204.degree. C. The same catalyzed PSA mixture was also cast onto a sheet of 2 mil Mylar.TM. A, and cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 178.degree. C. Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above. Results are recorded in Table 4 below.

Example 3

Approximately 150.1 (g) of Resin A, 73.6 (g) of Polymer A, 76.3 (g) of toluene, 4.6 (g) of triethylamine, and 0.06 (g) of a thermal stability additive, were combined in a 500 ml 3-neck flask equipped with stirrer, thermometer, Dean Stark trap, and condenser. The contents were well mixed and heated to reflux temperature where it was maintained for 4 hrs. Water was removed continuously during the reflux step. Approximately 45 (g) Exxsol.RTM. D-110 was added to the reaction product (adhesive), which was then stripped at atmospheric pressure to approximately 76% solids, cooled, recovered, and stored for evaluation at a future date.

A portion of the adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at a level of 2 wt % peroxide solids based on PSA solids, and cast onto 1 mil polyimide (Kapton.TM.) using the appropriate Bird Bar to attain a 2 mil Dry PSA film on the substrate. The polyimide-supported film was cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 204.degree. C. The same catalyzed PSA mixture was also cast onto a sheet of 2 mil Mylar.TM. A, and cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 178.degree. C. The Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above. Results are recorded below in Table 5.

Example 4

Approximately 150.1 (g) of Resin A, 73.6 (g) of Polymer A, 76.3 (g) of toluene, 4.6 (g) of triethylamine, and 0.06 (g) of a thermal stability additive, were combined in a 500 ml 3-neck flask equipped with stirrer, thermometer, Dean Stark trap, and condenser. The contents were well mixed and heated to reflux temperature where it was maintained for 4 hrs. Water was removed continuously during the reflux step. Approximately 20 (g) Isopar.RTM. M (a C.sub.13 -C.sub.14 branched chain aliphatic hydrocarbon petroleum distillate having a boiling point ranging from about 207.degree. C. to 254.degree. C. marketed by Exxon Chemical Company, a Division of Exxon Corporation, Houston, Tex.) was added to the PSA mixture, which was then stripped at atmospheric pressure to approximately 86% solids, cooled, recovered, and stored for evaluation.

A portion of the adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at a level of 2 wt % peroxide solids based on PSA solids, and cast onto 1 mil polyimide (Kapton.TM.) using the appropriate Bird Bar to attain a 2 mil dry PSA film on the substrate. The polyimide-supported film was cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 204.degree. C. The same catalyzed PSA mixture was also cast onto a sheet of 2 mil polyester (Mylar.TM. A), and cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 178.degree. C. The Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above. The results are recorded in Table 6 below.

Example 5

Approximately 150.1 (g) of Resin A, 73.6 (g) of Polymer A, 76.3 (g) of toluene, 4.6 (g) of Triethylamine, and 0.06 (g) of a thermal stability additive, were combined in a 500 ml 3-neck flask equipped with stirrer, thermometer, Dean Stark trap, and condenser. The contents were well mixed and heated to reflux temperature where it was maintained for 4 hrs. Water was removed continuously during the reflux step. Approximately 20 (g) Isopar.RTM. V ((a C.sub.14 -C.sub.18 branched chain aliphatic hydrocarbon petroleum distillate having a boiling point ranging from about 254.degree. C. to 329.degree. C. marketed by Exxon Chemical Company, a Division of Exxon Corporation, Houston, Tex.) was added to the reaction product (adhesive), which was then stripped to approximately 86% solids, cooled, recovered, and stored for evaluation.

A portion of the adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at a level of 2 wt % peroxide solids based on PSA solids, and cast onto 1 mil polyimide (Kapton.TM.) using the appropriate Bird Bar to attain a 2 mil Dry PSA film on the substrate. The polyimide-supported film was cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 204.degree. C. The same catalyzed PSA mixture was also cast onto a sheet of 2 mil Mylar.TM. A, and cured for 2 minutes at 70.degree. C. followed by an additional 2 minutes at 178.degree. C. The Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above. The results are recorded in Table 7 below.

Example 6

Approximately 133.7 (g) of Resin A, 85.5 (g) of polymer A, 80.9 (g) of toluene, 0.06 (g) of a thermal stability additive, and 4.6 (g) triethylamine, were combined and thoroughly blended in a three-necked flask equipped with a stirrer, thermometer, condenser, and Dean Stark Trap. The mixture was heated to reflux, and maintained at reflux, for approximately 4 hrs. Water was continuously removed during the reflux step. Approximately 20 grams of Exxsol.RTM. D-110 Solvent were then added to the reaction product which was then re-heated and stripped at atmospheric pressure to the desired non-volatiles content in the range of 85% solids. The viscosity of the resultant PSA reaction product was determined to be 32,250 mPa.s at 83.9% solids.

Example 7

Approximately 174.0 (g) of Resin A, 56.4 (g) of polymer A, 69.6 (g) of toluene, 0.06 (g) of a thermal stability additive, and 4.6 (g) of triethylamine, were combined and thoroughly blended in a three-necked flask equipped with a stirrer, thermometer, condenser, and Dean Stark Trap. The mixture was heated to reflux, and maintained at reflux, for approximately 4 hrs. Water was continuously removed during the reflux step. Approximately 20 (g) of Exxsol.RTM. D-110 were then added to the reaction product which was then re-heated and stripped at atmospheric pressure to the desired non-volatiles content in the range of 85% solids. The viscosity of the resultant PSA reaction product was determined to be 12,200 mPa.s at 84.8% solids.

Example 8

A PSA blend was prepared by combining 3 parts of the product described in Example 5, per 1 part of the product described in Example 6, then mixing until a uniform dispersion was obtained. The mixture was catalyzed, using a 10% solution of benzoyl peroxide in methyl ethyl ketone at a benzoyl peroxide actives level of 2% based on PSA solids. The catalyzed PSA solution was then cast onto 2 mil Polyester film (Mylar.TM. A) in an amount sufficient to attain a 2 mil, dried PSA film. The cast PSA film was devolatilized for 2 minutes at 70.degree. C., and then cured for 2 additional minutes at 178.degree. C. The resultant PSA film laminate was then cut into 1" wide strips and evaluated for PSA performance. The Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above. The Peel Adhesion of this silicone pressure sensitive adhesive composition was 52 oz/in and the Probe Tack was 1,368 (g)/cm.sup.2.

Example 9

Approximately 133.7 (g) of Resin A, 78.1 (g) of polymer A, 7.4 (g) of polymer B, 80.9 (g) of toluene, 0.06 (g) of a thermal stability additive, and 4.6 (g) triethylamine, were combined and thoroughly blended in a three-necked flask equipped with a stirrer, thermometer, condenser, and Dean Stark Trap. The mixture was heated to reflux and maintained at reflux for approximately 4 hrs. Water was continuously removed during the reflux step. Approximately 20 (g) of Exxsol.RTM. D-110 were added to the reaction product which was then re-heated and stripped at atmospheric pressure to the desired non-volatiles content in the range of 85% solids. The viscosity of the resultant PSA reaction product was determined to be 100,000 mPa.s at 86% solids.

Example 10

Approximately 174.0 (g) of Resin A, 51.5 (g) of polymer A, 4.9 (g) of polymer B, 69.6 (g) of toluene, 0.06 (g) of a thermal stability additive, and 4.6 (g) triethylamine, were combined and thoroughly blended in a three-necked flask equipped with a stirrer, thermometer, condenser, and Dean Stark Trap. The mixture was heated to reflux, and maintained at reflux, for approximately 4 hrs. Water was continuously removed during the reflux step. Approximately 20 (g) of Exxsol.RTM. D-110 were then added to the reaction product, which was then re-heated and stripped at atmospheric pressure to the desired non-volatiles content in the range of 85% solids. The viscosity of the resultant PSA reaction product was determined to be 32,250 mPa.s at 86.4% solids.

Example 11

A PSA blend was prepared by combining 3 parts of the product described in Example 8, per 1 part of the product described in Example 9, then mixing until a uniform dispersion was obtained. The mixture was catalyzed, using a 10% solution of benzoyl peroxide in methyl ethyl ketone, at a benzoyl peroxide actives level of 2% based on PSA solids. The catalyzed PSA solution was then cast onto 2 mil Polyester film (Mylar.TM. A) in an amount sufficient to attain a 2 mil, dried PSA film. The cast PSA film was devolatilized for 2 minutes at 70.degree. C., and then cured for 2 additional minutes at 178.degree. C. The resultant sheet supporting the PSA film was then cut into 1" wide strips and evaluated for PSA performance. The Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above. The Peel Adhesion of this silicone pressure sensitive adhesive composition was 56 oz/in and the Probe Tack was 1,326 (g)/cm.sup.2.

Example 12

Approximately 150.1 (g) of Resin A, 73.6 (g) of polymer A, 58.3 (g) of toluene, 18.0 (g) of tetradecane, 0.06 (g) of a thermal stability additive, and 4.6 (g) triethylamine, were combined and thoroughly blended in a three-necked flask equipped with a stirrer, thermometer, condenser, and Dean Stark Trap. The mixture was heated to reflux, and maintained at reflux, for approximately 4 hrs. Water was continuously removed during the reflux step. The reaction product (adhesive) was then stripped at atmospheric pressure to approximately 86% solids.

A portion of the adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at a level of 2 wt % peroxide solids based on PSA solids. The catalyzed PSA mixture was cast onto 2 mil polyester film (Mylar.TM. A), de-volatilized for 2 minutes at 70.degree. C., and finally cured for an additional 2 minutes at 178.degree. C. The thickness of the PSA film was 1.9 mil. The Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above. The Peel Adhesion of this silicone pressure sensitive adhesive composition was 59 oz/in and the Probe Tack was 1,304 (g)/cm.sup.2.

Example 13

Approximately 150.1 (g) of Resin A, 73.6 (g) of polymer A, 58.3 (g) of toluene, 18.0 (g) of hexadecane, 0.06 (g) of a thermal stability additive, and 4.6 (g) triethylamine, were combined and thoroughly blended in a three-necked flask equipped with a stirrer, thermometer, condenser, and Dean Stark Trap. The mixture was heated to reflux, and maintained at reflux, for approximately 4 hrs. Water was continuously removed during the reflux step. The reaction product (adhesive) was then stripped at atmospheric pressure to approximately 85.5% solids.

A portion of the adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at a level of 2 wt % peroxide solids based on PSA solids. The catalyzed PSA mixture was cast onto 2 mil polyester film (Mylar.TM. A), de-volatilized for 2 minutes at 70.degree. C., and finally cured for an additional 2 minutes at 178.degree. C. The thickness of the PSA film was 1.9 mil. The Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above. The Peel Adhesion of this silicone pressure sensitive adhesive composition was 70 oz/in and the Probe Tack was 1,380 (g)/cm.sup.2.

Example 14

Approximately 150.1 (g) of Resin A, 73.6 (g) of polymer A, 58.3 (g) of toluene, 18.0 (g) of octadecane, 0.06 (g) of a thermal stability additive, and 4.6 (g) triethylamine, were combined and thoroughly blended in a three-necked flask equipped with a stirrer, thermometer, condenser, and Dean Stark Trap. The mixture was heated to reflux, and maintained at reflux, for approximately 4 hrs. Water was continuously removed during the reflux step. The reaction product (adhesive) was then stripped at atmospheric pressure to approximately 86% solids.

A portion of the adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at a level of 2 wt % peroxide solids based on PSA solids. The catalyzed PSA mixture was cast onto 2 mil polyester film (Mylar.TM. A), de-volatilized for 2 minutes at 70.degree. C., and finally cured for an additional 2 minutes at 178.degree. C. The thickness of the PSA film was 1.9 mil. The Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above. The Peel Adhesion of this silicone pressure sensitive adhesive composition was 72 oz/in and the Probe Tack was 1,351 (g)/cm.sup.2.

Example 15

Several samples were prepared by mixing approximately 150.1 (g) of Resin A, 73.6 (g) of polymer A, an amount of toluene, an amount of a solvent having a high boiling point (denoted HBS (High Boiling Solvent) in Table 8), 0.06 (g) of a thermal stability additive, and an amount of catalyst, were combined and thoroughly blended in a three-necked flask equipped with a stirrer, thermometer, condenser, and Dean Stark Trap. Each mixture was heated to reflux, and maintained at reflux, for approximately 4 hrs. Water was continuously removed during the reflux step. Each reaction product was then stripped at atmospheric pressure, and the solids content and viscosity of each sample is recorded in Table 9 below. The amount of toluene, the amount and type of solvent, and the amount and type of catalyst are delineated in Table 8 below. In Table 8, Tem denotes Triethylamine, Dowanol.TM.DPM is dipropylene glycol methyl ether having a boiling point of about 188.degree. C. from Dow Chemical Company, Midland, Mich., Dowanol.TM.TPM is tripropylene glycol methyl ether having a boiling point of about 242.degree. C. from Dow Chemical Company, Midland, Mich., and Dowanol.TM.PPh is propylene glycol phenyl ether having a boiling point of about 242.degree. C. from Dow Chemical Company, Midland, Mich. Dowanol.RTM.TPM was not entirely miscible in the resin-polymer mixture.

A portion of each adhesive was catalyzed with Perkadox.RTM. PD-50S-ps-a at a level of 2 wt % peroxide solids based on PSA solids. Each catalyzed PSA mixture was cast onto 2 mil polyester film (Mylar.TM. A), de-volatilized for 2 minutes at 70.degree. C., and finally cured for an additional 2 minutes at 178.degree. C. The thickness of the PSA film was 1.9 mil. The Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above and the results are shown in Table 9. The Peel Adhesion was measured in oz/in and the Probe Tack was measured in (g)/cm.sup.2.

Example 16

Approximately 80.3 (g) of Resin A, 19.7 (g) of Resin B, 55.7 (g) of polymer C, 144.2 (g) of xylene, 3.0 (g) of triethylamine, 5.0 (g) nonanoic acid, and 0.04 (g) of a thermal stability additive, were combined and thoroughly blended in a three-necked flask equipped with a stirrer, thermometer, condenser, and Dean Stark Trap. The mixture was heated to reflux, and maintained at reflux, for approximately 4 hrs. Water was continuously removed during the reflux step. The reaction product (adhesive) was then stripped at atmospheric pressure, followed by addition of an additional 7.0 (g) of nonanoic acid. The non-volatile content for the resultant PSA was approximately 54.6% solids.

A portion of the adhesive was catalyzed with a 10% solution of benzoyl peroxide in toluene, at a level of 2 wt % peroxide solids based on PSA solids. The catalyzed PSA mixture was cast onto a primed 2 mil Kapton.TM. film, de-volatilized for 2 minutes at 70.degree. C., and finally cured for an additional 2 minutes at 204.degree. C. The thickness of the PSA film was approximately 1.0 mils. The Probe Tack and 180 degree Peel Adhesion were then measured according to the procedures described above. The Peel Adhesion of this silicone pressure sensitive adhesive composition was 20 oz/in, and the Probe Tack was 1,095 (g)/cm.sup.2.

TABLE 1______________________________________SUBSTRATE 180.degree. PEEL ADHESION PROBE TACK______________________________________2 MIL MYLAR .TM. A 51 oz/in 1,286 +/- 47 (g)/cm.sup.21 MIL KAPTON .TM. 33 oz/in 967 +/- 59 (g)/cm.sup.2______________________________________ TABLE 2______________________________________ CURE 180.degree. PEELSHEET TYPE CONDITIONS ADHESION PROBE TACK______________________________________1 MIL KAPTON .TM. 2 min. @ 70.degree. C. 36 oz/in 981 +/- then 2 min. @ 25 (g)/cm.sup.2 204.degree. C.1 MIL KAPTON .TM. 2 min. @ 204.degree. C. 36 oz/in 988 +/- 31 (g)/cm.sup.22 MIL MYLAR .TM. A 2 min. @ 70.degree. C. 56 oz/in 1,334 +/- then 2 min. @ 62 (g)/cm.sup.2 178.degree. C.2 MIL MYLAR .TM. A 2 min. @ 178.degree. C. 55 oz/in 1,262 +/- 88 (g)/cm.sup.2______________________________________ TABLE 3______________________________________SUBSTRATE 180.degree. PEEL ADHESION PROBE TACK______________________________________2 MIL MYLAR .TM. A 51 oz/in 1,101 +/- 43 (g)/cm.sup.21 MIL KAPTON .TM. 28 oz/in 925 +/- 29 (g)cm.sup.2______________________________________ TABLE 4______________________________________SUBSTRATE 180.degree. PEEL ADHESION PROBE TACK______________________________________2 MIL MYLAR .TM. A 55 oz/in 1,338 (g)/cm.sup.21 MIL KAPTON .TM. 32 oz/in 1,058 (g)/cm.sup.2______________________________________ TABLE 5______________________________________SUBSTRATE 180.degree. PEEL ADHESION PROBE TACK______________________________________2 MIL MYLAR .TM. A 71 oz/in 1,442 (g)/cm.sup.21 MIL KAPTON .TM. 42 oz/in 1,097 (g)/cm.sup.2______________________________________ TABLE 6______________________________________SUBSTRATE 180.degree. PEEL ADHESION PROBE TACK______________________________________2 MIL MYLAR .TM. A 52 oz/in 1,111 (g)/cm.sup.21 MIL KAPTON .TM. 29 oz/in 894 (g)/cm.sup.2______________________________________ TABLE 7______________________________________SUBSTRATE 180.degree. PEEL ADHESION PROBE TACK______________________________________2 MIL MYLAR .TM. A 58 oz/in 1,253 (g)/cm.sup.21 MIL KAPTON .TM. 32 oz/in 1,023 (g)/cm.sup.2______________________________________ TABLE 8______________________________________ Toluene HBS HBS Catalyst CatalystSample (grams) Type (grams) Type (grams)______________________________________1 58.3 Dowanol .TM. 18 Pyridine 3.6 DPM2 58.3 Dowanol .TM. 18 Pyridine 3.6 TPM3 40.3 Dowanol .TM. 36 Pyridine 3.6 PPh4 22.3 Isopar .RTM. M 54 Tem 4.65 40.3 Isopar .RTM. M 36 Tem 4.66 76.3 Isopar .RTM. M 0 Tem 4.67 58.3 Octadecane 18 Tem 4.68 58.3 Hexadecane 18 Tem 4.69 58.3 Tetradecane 18 Tem 4.610 22.3 Decane 54 Tem 4.611 22.3 Undecane 54 Tem 4.612 22.3 Dodecane 54 Tem 4.6______________________________________ TABLE 9______________________________________ Peel Probe Viscosity Adhesion TackSample (mPa .multidot. s) % Solids (oz/in) (g/cm.sup.2)______________________________________1 470,000 88 48 8642 1,190,000 89 44 6013 53,000 79 48 1,3044 4,200 73 58 1,1905 11,500 81 63 1,0346 43,500 89 60 1,0017 N/A 86 >70 1,3518 N/A 86 70 1,3809 N/A 86 59 1,30410 16,500 86 46 1,01411 5,500 79 44 95612 2,900 74 48 1,097______________________________________

Claims

1. A silicone pressure sensitive adhesive composition obtained by a method comprising the steps of

(I) reacting a mixture comprising

(A)(i) at least one hydroxyl-terminated polydiorganosiloxane having a viscosity of from 100 to 100,000,000 mm.sup.2 /s at 25.degree. C. or

(ii) a mixture of

(a) a hydroxyl-terminated polydiorganosiloxane and

(b) a polydiorganosiloxane selected from

(i) polydiorganosiloxanes terminated with monovalent hydrocarbon radicals free of aliphatic unsaturation or

(ii) alkenyl-terminated polydiorganosiloxanes wherein said mixture has a viscosity of from 100 to 100,000,000 mm.sup.2 /s at 25.degree. C.;

(B) at least one soluble silicone resin consisting essentially of at least one R.sub.3 SiO.sub.1/2 unit and at least one SiO.sub.4/2 unit, wherein R is independently selected from a monovalent hydrocarbon or halohydrocarbon radical free of aliphatic unsaturation and having from 1 to 20 carbon atoms, an alkenyl radical, or a hydroxyl radical wherein the molar ratio of R.sub.3 SiO.sub.1/2 units to SiO.sub.4/2 units is from 0.5:1 to 1.2:1;

(C) at least one silanol condensation catalyst selected from the group consisting of liquid catalysts having a boiling point of less than 200.degree. C. and catalysts which are solid at room temperature; and

(D) at least one solvent or plasticizer having a boiling point of at least 200.degree. C. to form a reaction product; and

(II) adding (E) an organic peroxide or azo compound to the reaction product of (I).

2. A composition according to claim 1, wherein the hydroxyl-terminated polydiorganosiloxane is a polydiorganosiloxane having the general formula

HOR.sup.1.sub.2 SiO(R.sup.1.sub.2 SiO).sub.a SiR.sup.1.sub.2 OH

wherein each R.sup.1 is independently selected from a monovalent hydrocarbon or halohydrocarbon radical having from 1 to 20 carbon atoms or an alkenyl radical and a has a value such that the viscosity of the polydiorganosiloxane ranges from 1,000 to 500,000 mm.sup.2 /s when measured at 25.degree. C.

3. A composition according to claim 1, wherein (b)(i) is selected from Me.sub.3 SiO(Me.sub.2 SiO).sub.a SiMe.sub.3, Me.sub.3 SiO(Me.sub.2 SiO).sub.0.95a (MeViSiO).sub.0.05a SiMe.sub.3, or Me.sub.3 SiO(Me.sub.2 SiO).sub.0.5a (MePhSiO).sub.0.5a SiMe.sub.3 wherein Me, Vi, and Ph denote methyl, vinyl and phenyl, respectively, and a has a value such that the viscosity of the polydiorganosiloxane ranges from 1,000 to 500,000 mm.sup.2 /s when measured at 25.degree. C.

4. A composition according to claim 1, wherein (b)(ii) is selected from ViMe.sub.2 SiO(Me.sub.2 SiO).sub.a SiMe.sub.2 Vi, ViMe.sub.2 SiO(Me.sub.2 SiO).sub.0.95a (MePhSiO).sub.0.05a SiMe.sub.2 Vi, ViMe.sub.2 SiO(Me.sub.2 SiO).sub.0.98a (MeViSiO).sub.0.02a SiMe.sub.2 Vi, PhMeViSiO(Me.sub.2 SiO).sub.a SiPhMeVi, or PhMeViSiO(Me.sub.2 SiO).sub.0.8a (MePhSiO).sub.0.1a (Ph.sub.2 SiO).sub.0.1a SiPhMeVi, wherein Me, Vi, and Ph denote methyl, vinyl and phenyl, respectively, and a has a value such that the viscosity of the polydiorganosiloxane ranges from 1,000 to 500,000 mm.sup.2 /s when measured at 25.degree. C.

5. A composition according to claim 1, wherein R is independently selected from methyl, phenyl, vinyl, or hydroxyl, the molar ratio of R.sub.3 SiO.sub.1/2 units to SiO.sub.4/2 units is from 0.6:1 to 1:1, and (B) has a number average molecular weight of 3,000 to 7,500.

6. A composition according to claim 1, wherein (C) is selected from alkali metal hydroxides, alkali metal alkoxides, alkali metal carbonates, alkali metal silanolates, amines, carboxylic acid salts of amines, quaternary ammonium salts, carboxylic acids, or metal salts of carboxylic acids.

7. A composition according to claim 1, wherein (C) is selected from trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, methyldipropylamine, tripropanolamine, pyridine, N-methylimidazole, methylpropylhexylamine, acetic acid, propanoic acid, butanoic acid, formic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, stearic acid, potassium formate, or potassium acetate.

8. A composition according to claim 1, wherein (D) is selected from the group consisting of aliphatic hydrocarbons, glycol ethers, esters, alcohols, ester alcohols, ketones, kerosenes, naphthas, petrolatums, carboxylic acids having at least six carbon atoms, and amines having at least nine carbon atoms.

9. A composition according to claim 1, wherein (D) is selected from the group consisting of dodecane, tridecane, tetradecane, 1-tetradecene, pentadecane, hexadecane, octadecane, nonadecane, diethylene glycol ethyl ether, diethylene glycol butyl ether, triethylene glycol methyl ether, triethylene glycol ethyl ether, triethylene glycol butyl ether, ethylene glycol phenyl ether, propylene glycol phenyl ether, aromatic based glycol ethers, diethylene glycol butyl ether acetate, pine oil, mineral seal oil, tridecyl alcohol, trimethyl pentane diol isobutyrate, isophorone, nonanoic acid, caproic acid, caprylic acid, oleic acid, linoleic acid, linolenic acid, dodecylamine, hexadecylamine, octadecylamine, dimethyldodecylamine, dicocoamine, methyldicocoamine, dimethyl cocoamine, dimethyltetradecylamine, dimethylhexadecylamine, dimethyloctadecylamine, dimethyl tallow amine, dimethyl nonylamine, di(hydrogenated-tallow)amine, and methyldi(hydrogenated-tallow)amine.

10. A composition according to claim 1, wherein the mixture of step (I) further comprises a rare earth metal salt of a fatty acid.

11. A composition according to claim 1, wherein the mixture of step (I) further comprises a solvent having a boiling point of less than 200.degree. C.

12. A composition according to claim 10, wherein the mixture of step (I) further comprises a solvent having a boiling point of less than 200.degree. C.

13. A composition according to claim 11, wherein the solvent is selected from benzene, toluene, xylene, alcohols, naphtha, cyclic polysiloxanes, or mineral spirits.

14. A composition according to claim 12, wherein the solvent is selected from benzene, toluene, xylene, alcohols, naphtha, cyclic polysiloxanes, or mineral spirits.

15. A composition according to claim 1, wherein (E) is selected from benzoyl peroxide, dichlorobenzoyl peroxide, azobisisobutyronitrile, or 2,4-dimethyl-4-methoxyvaleronitrile.

16. A composition according to claim 1, wherein step (I) comprises reacting a mixture comprising components (A), (B), and (C), (II) adding component (D) to the product of (I), and optionally (III) heating the product of (II) to form a reaction product.

17. A composition according to claim 1, wherein the reaction product of step (I) has a solids content of at least 60% and a viscosity of up to 200,000 millipascal-seconds (mPa.s).

18. An article of manufacture obtained by a method comprising:

(I) applying a silicone pressure sensitive adhesive composition to at least one surface of a substrate, wherein the silicone pressure sensitive adhesive composition is obtained by a method comprising the steps of

(i) reacting a mixture comprising

(A)(i) at least one hydroxyl-terminated polydiorganosiloxane having a viscosity of from 100 to 100,000,000 mm.sup.2 /s at 25.degree. C. or

(ii) a mixture of

(a) a hydroxyl-terminated polydiorganosiloxane and

(b) a polydiorganosiloxane selected from

(i) polydiorganosiloxanes terminated with monovalent hydrocarbon radicals free of aliphatic unsaturation or

(ii) alkenyl-terminated polydiorganosiloxanes wherein said mixture has a viscosity of from 100 to 100,000,000 mm.sup.2 /s at 25.degree. C.;

(B) at least one soluble silicone resin consisting essentially of at least one R.sub.3 SiO.sub.1/2 unit and at least one SiO.sub.4/2 unit, wherein R is independently selected from a monovalent hydrocarbon or halohydrocarbon radical free of aliphatic unsaturation and having from 1 to 20 carbon atoms, an alkenyl radical, or a hydroxyl radical wherein the molar ratio of R.sub.3 SiO.sub.1/2 units is from 0.5:1 to 1.2:1;

(C) at least one silanol condensation catalyst selected from the group consisting of liquid catalysts having a boiling point of less than 200.degree. C. and catalysts which are solid at room temperature; and

(D) at least one solvent or plasticizer having a boiling point of at least 200.degree. C. to form a reaction product; and

(ii) adding (E) an organic peroxide or azo compound to the reaction product of step (i); and

(II) heating the silicone pressure sensitive adhesive composition and the substrate to cure the composition.

19. An article of manufacture according to claim 18, wherein the article is further obtained by (III) contacting a solid support with the substrate having the adhesive composition cured thereon after step (II) whereby the solid support and the substrate are adhered together.

20. An article of manufacture according to claim 18, wherein step (i) comprises reacting a mixture comprising components (A), (B), and (C), adding component (D), and optionally heating the resulting product to form a reaction product.

21. An article of manufacture according to claim 18, wherein (C) is selected from alkali metal hydroxides, alkali metal alkoxides, alkali metal carbonates, alkali metal silanolates, amines, carboxylic acid salts of amines, quaternary ammonium salts, carboxylic acids, or metal salts of carboxylic acids.

22. An article of manufacture according to claim 18, wherein (D) is selected from the group consisting of aliphatic hydrocarbons, glycol ethers, esters, alcohols, ester alcohols, ketones, kerosenes, naphthas, petrolatums, carboxylic acids having at least six carbon atoms, and amines having at least nine carbon atoms.