Patent Application
20160230050
Pressure sensitive adhesives (PSAs) are an important class of materials. Generally, PSAs adhere to a substrate with light pressure (e.g., finger pressure) and typically do not require any post-curing (e.g., heat or radiation) to achieve their maximum bond strength. A wide variety of PSA chemistries are available. PSAs, particularly silicone PSAs offer one or more of the following useful characteristics: adhesion to low surface energy (LSE) surfaces, quick adhesion with short dwell times, wide use temperature (i.e., performance at high and low temperature extremes), moisture resistance, weathering resistance (including resistance to ultraviolet (UV) radiation, oxidation, and humidity), reduced sensitivity to stress variations (e.g., mode, frequency and angle of applied stresses), gentleness to skin, aiid resistance to chemicals (e.g., solvents and plasticizers) and biological substances (e.g., mold and fungi).
Fluorinated release coatings are often used with PSAs, particularly silicone PSAs, to provide desired release properties. In some embodiments, the desired release force is no greater than 50 g/25 mm, e.g., no greater than 30 g/25 mm at 180 degrees peel angle and 230 cm/min (90 inches/min). However, the selection of fluorinated release coatings available to achieve the desired release performance is limited, particularly for wet-cast (e.g., solvent-based, water-based, and hot melt coated) PSAs. For example, few release materials provide stable, consistent, smooth release of an adhesive.
The most common fluorinated release coatings are fluorosilicone materials with pendent RfCH2CH2— group made from Rf—CH═CH2, wherein Rf is typically a CF3— or a CF3CF2CF2CF2— group. However, commercially available fluorosilicone release coatings are typically more expensive, lite reasons for high cost of commonly used fluorosilicone release materials are believed to related a) the lower reactivity of RfCH═CH2 to low yield hydrosilylation reactions, and b) the preparation from expensive Rf—I with two steps, i) addition to ethylene to form RfCH2CH2—I and ii) elimination of HI.
The present disclosure provides novel fluoroalkyl silicones that can be used as release materials or can also be blended with one or more additional low surface energy materials (e.g., fluoropolymers, polyacrylatea with pendent Rf group, lower cost fluoroalkyl silicones and non-fluorinated silicones) while maintaining the desired low release characteristics of the instant fluorosilicone material. In addition, in some embodiments, high blend ratios of low surface energy materials may be used without detrimentally affecting the re-adhesion force of the adhesive after removal of the blended release materials comprising the present fluorosilicones.
Applicants have identified high reactive fluorinated alkenes for high yield of hydrosilylation products (from hydrosilicones) and subsequently providing novel fluoroalkyl silicones having similar or better performance to current products at reduced cost.
The present disclosure relates to novel fluoroalkyl silicones and use thereof as release materials. In another aspect, the present disclosure provides release liners comprising a substrate and the release material according to the present disclosure bonded to a major surface of the substrate. In another aspect, the present disclosure providers a crosslinked or uncrosslinked coating comprising the fluoroalkyl silicone release material.
In yet another aspect, the present disclosure provides adhesive articles comprising an adhesive having a first major surface and a second major surface, wherein the first major surface of the adhesive is in contact with a release material according to the present disclosure. In some embodiments, the adhesive articles further comprise a first substrate (or backing) having a first major surface and a second major surface, wherein the release material is bonded to the first major surface of the first substrate. In some embodiments, the second major surface of the adhesive is in contact with the second major surface of the first subsuate. In some embodiments, the second major surface of the adhesive is in contact with a second, independently selected release material bonded to the second major surface of the first substrate. In some embodiments, the adhesive articles further comprise a second substrate, wherein the second major surface of the adhesive is in contact with a major surface of the second substrate.
In some embodiments, the adhesive comprises a silicone adhesive. In some embodiments, the silicone adhesive comprises a poly(diorganosiloxane). In some embodiments, the silicone adhesive comprises a polydiorganosiloxane-polyurea block copolymer. In some embodiments, the silicone adhesive comprises a polydiorganosiloxane-polyoxamide copolymer. In some embodiments, the silicone adhesive further comprises a tackifler. In other embodiments, the adhesive comprises an acrylate adhesive.
In another aspcct the present disclosure provides a method of making the fluoroalkyl silicones by the hydrosilylation reaction between a perfluoroalkyl alkenyl ether and a hydrosilicone.
The present disclosure provides novel fluoroalkyl silicones of the formula:
wherein
each R1 independently an alkyl or aryl;
Rf is a perfluoroalkyl group, optionally substituted by one or more in-chain —O-, —S- or —NRf1-heteroatoms, where Rf1 is a perfluoroalkyl, preferably a C1-C6 perfluoroalkyl;
R3is —H, —OR4; where R4is a C1-C4alkyl
n is 0 to 2000;
m may be zero, preferably al least 2;
p may be zero, preferably 10 to 2000;
n+m+p is at least one;
q is at least 3;
R5 is H, alkyl, aryl, —(CH2)n—O—CF2CHF—O—Rf, or R3;
wherein the fluoroalkyl silicone has at least one Rf group of the formula —(CH2)q—O—CF2CHF—O—Rf, preferably at least two Rf groups, either as R5 and/or in the siloxane unit with the subscript m. In some embodiments p is at least one, preferably at least 2. Rf may contain 1 to 8, preferably 1 to 6, most preferably 3 to six, perfluorinated carbon atoms.
In some embodiment the ratio of m to p is from 100:0 to 5:95, preferably the ratio of m to p is from 50:50 to 20:80.
The disclosed fluoroalkyl silicones contain pendent or terminal —(CH2)q—O—CF2CHF—O—Rf. group, which may further contain reactive hydrosilane groups (H—Si), alkoxysilane groups (R4O—Si), alkyl silane groups (Si—R1), either as R5 and/or in the siloxane unit with the subscript p. In some embodiments the alkyl and alkoxy groups of the silicone can be long chains (e.g. C16-C50), either as R5 and/or in the siloxane unit with the subscript p.
The novel fluoroalkyl silicone of Formula I may be prepared by hydrosilylation in the prcscncc of a hydrosilylation catalyst, of a perfluoroalkyl alkenyl ether compound of the formula:
Rf—O—CHFCFf—O—(CH2)q−2CH═CH2, II
wherein
Rf is a perfluoroalkyl group, optionally substituted by one or more in-chain —O—, —S— or —NRf1— heieroatoms, where Rf1 is a perfluoroalkyl; with a hydrosilicone of the formula:
where
each R1 is independently an alkyl or aryl;
n is 0 to 2000; preferably al least 10;
v may be zero:
R6 is H, alkyl or aryl;
with the proviso that the hydrosilicone contains at least one Si—H group, preferably at least two Si—H groups. Thus the silicone unit with the subscript “v” of Formula III may be at least one, preferably at least 2, and/or R6 can be H.
All or a portion of the Si—H groups of the hydrosilicone may be reacted with the alkenyl ether of Formula II. In some embodiments, unreacted hydrosilyl (Si—H) groups may be converted to other useful functional groups, as described herein.
The fluoroalkyl silicone of Formula I have a Mw of at least 400, preferably at least 1000. In some embodiments, the Mw may be 2000 or greater. In some embodiments, the Mw may be limited to 1,000,000 or less; preferably limited to 500,000 or less. In some embodiments n, m and p are each greater than one and where the ratio of n to m is greater than one, preferably the ratio of n to m is greater than 10. In some embodiments, R3 is H, ami the ratio of m to p is from 100:0 to 5:95. In some embodiments, R3 is OR4 (prepared as described herein).
The fluoroalkyl silicone of Formula I is prepared, in part, with at least one hydrostlicone having a plurality of Si—H groups as represented by Formula III. Examples of useful Si—H group containing silicones include hydride terminated polydimethylsiloxanes having the formula HMe2SiO(SiMe2O)nSiMe2H (CAS 70900-21-9); hydride terminated methylhydrosiloxane-dimethylsiloxane copolymers having the formula HMe2SiO(SiMe2O)n(SiMeHO)qSiMe2H (CAS 69013-23-6); trimethylsiloxane terminated polyethylhydrosiloxanes having the formula Me3SiO(SiMeHO)qSiMe3 (CAS 63148-57-2); trimethylsiloxane terminated methylhydrosiloxane-dimethylsiloxane copolymers having the formula Me3SiO(SiMe2O)n(SiMeHO)qSiMe3 (CAS 68037-59-2); triethylsiloxane terminated polyethylhydrosiloxanes having the formula Et3SiOSiEtHO)qSiEt3 (CAS 24979-95-1); hydride terminated poly(phenyl-dimelhylhydrosiloxysiloxanes) having the formula HSiMe2O(SiPh(OSiMe2H)O)qSiMe2H; aill commercially available from vendors such as, for example, Gelest, Inc. or Dow Cornming Corp. with different molecular weights.
It will be appreciated that the Rf group of the fluoroalkyl compound of Formula II may be linear or branched or a combination thereof. The perfluoroalkyl alkenyl ether compounds of Formula II, in turn, may be prepared by reaction of a perfluoro(alkyl vinyl ether) compound of the formula:
Rf—O—CF═CF2 IV
with a compound of the formula:
H—O—(CH2)q−2CH═CH2, VI
where q and Rf are as previously defined.
The reaction between compounds IV and VI is described in US 2005/0113609 (Furakawa et al.) incorporated herein by reference. The perfluoro(alkyl ether) of Formula IV, in turn, may be prepared by fluoride ion catalyzed addition of a perfluorinated acid fluoride to hexafluoropropylene oxide, followed by decarboxylation, according to the techniques describe in U.S. Pat. No. 6,255,536 (Worm et al.), incorporated herein by reference. Perfluorinated acid fluoride may be obtained from hexafluoropropene oxide by reaction with MF or by electrochemical fluorination process as described in U.S. Pat. No. 6,482,979 (Hintzer et al.), incorporated herein by reference. Alternatively, the perfluorinated acid fluorides may be prepared by electrochemical fluorination of alcohols, acids or esters as known in the art.
Commercial available perfluorovinyl ethers of Formula IV are, for example, CF3OCF═CF2, CF3CF2CF2OCF═CF2 and CF3OCF2CF2CF2OCF═CF2.
In the presence of the hydrosilylation catalyst, the compounds of Formula II are hydrosilated by the hydrosilicone of Formula III to produce the fluoroalkyl silicones of Formula I. All or a portion of the Si—H groups may undergo the hydrosilylation with the compound of Formula II. In the following Scheme I, subscription “q” represent the number of original in-chain hydrosilane units, m the number of those in-chain units substituted by hydrosilylation, and subscript s is the number of in-chain Si—H groups remaining. In addition, where R6 is H, all or a portion of those terminal Si—H groups may undergo hydrosilylation to provide terminal Rf groups m the R7. In some embodiments, all of the Si—H groups, whether terminal or in-chain, will be converted to —(C3H6—OCF2CHFORf groups. It will further be understood that hydrosilylation of the fluoroalkyl alkenyl ether of Formula II can yield two propyl isomers: propylene (Si—(CH2)3—) and isopropvlene (Si—CH(CH3)CH2—) when q=3. These two isomers are illustrated genetically as —C3H6— as part of —(CH2)q—.
where
each R1 is independently an alkyl or aryl;
n is 0 to 2000;
m may be zero, preferably at least 1;
s may be zero;
R6 is H, alkyl or aryl;
R7 is H, alkyl, aryl or —(C3H6)—OCF2CHF—O—Rf,
q is at least 3; and
Rf is a perfluoroalkyl group, optionally substituted by one or more in-chain —O-, —S- or —NRf1-heteroatoms, where Rf1 is a perfluoroalkyl;
with the proviso that the starting material of Formula III contain at least one, preferably at least two Si—H groups, and with the prov iso that the product of Formula V contains at least one, preferably at least two —(C3H6)—OCF3CHFORf groups, whether in-chain represented by the units with subscript m, and/or one or both of the R7 groups may be —(C3H6)—OCF2CHFORf groups. Additionally, where there is partial hydrosilylation of the compounds of Formula II, the product of Scheme I will further contain in-chain Si—H groups, represented by the units with subscript s, and/or one or both of the R7 groups may be H. It will be understood that the unit with the subscript “s” represents the propotion of Si—H groups not reactcd by hydrosilation (i.e. m+s=v).
Alternatively, the fluoroalkyl silicones of the formula I can be made by hydrosilylation of perfluoroalkyl alkenyl ether compound of the formula II with either H—Si(R1)X2 to form RfO—CHFCF2—O—(CH2)qSiR1X2, wherein X is a hydrolysable group (e.g. Cl, CH3C(O)O— CH3O— and CH3CH2O—), following hydrolysis condensation polymerization; or cyclic hydrosilane, —[O—SiR1H]w-, to form cyclic silane substituted with Rf—O—CHFCF2—O—(CH2)q—, wherein w is 3 or 4, following by ring opening polymerization, as known from reported literatures.
Regarding the hydrosilylation reaction, numerous patents teach the use of various complexes of cobalt, rhodium, nickel, palladium, or platinum as catalysts for hydrosilylation reactions. For example, U.S. Pat. No. 4,288,345 (Ashby et al) discloses as a catalyst for hydrosilylation reactions a platinum-siloxane complex. Additional platinum-siloxane complexes are disclosed as catalysts for hydrosilylation reactions in U.S. Pat. Nos. 3,715,334, 3,775,452, and 3,814,730 (Karstedt et al). U.S. Pat. No. 3,470,225 (Knorre et al) discloses production of organic silicon compounds by addition of a compound containing silicon- bonded hydrogen to organic compounds containing at least one non-aromatic double or triple carbon-to-carbon bond using a platinum compound of the empirical formula PtX2(RCOCR′COR″)2 wherein X is halogen. R is alkyl, R′ is hydrogen or alkyl, and R″ is alkyl or alkoxy.
The catalysts disclosed in the foregoing patents are characterized by their high catalytic activity. Other platinum complexes for accelerating the aforementioned thermally-activated addition reaction include: a platinacyclobutane complex having the formula (PtCl2C3H2 (U.S. Pat. No. 3,159,662, Ashby); a complex of a platinous salt and an olefin (U.S. Pat. No. 3,178,464, Pierpoint); a platinum-containing complex prepared by reacting chloroplatinic acid with an alcohol, ether, aldehyde, or mixtures thereof (U.S. Pat. No. 3,220,972, Lamorcaux); a platinum compound selected from trimethylplatinum iodide and hexamethyldiplatinum (U.S. Pat. No. 3,313,773. Lamoreaux); a hydrocarbyl or halohydrocarbyl nitrile-platinum (II) halide complex (U.S. Pat. No. 3,410,886, Joy); a hexamethyl-dipyridine-diplatinum iodide (U.S. Pat. No. 3,567,755, Seyfried et al); a platinum curing catalyst obtained from the reaction of chloroplatinic acid and a ketone having up to 15 carbon atoms (U.S. Pat. No. 3,814,731, Nitzsche et al); a platinum compound having the general formula (R′)PtX2 where R′ is a cyclic hydrocarbon radical or substituted cyclic hydrocarbon radical having two aliphatic carbon-carbon double bonds, and X is a halogen or alkyl radical (U.S. Pat. No. 4,276,252, Kreis et al); platinum alkync complexes (U.S. Pat. No. 4,603,215, Chandra et al,); platinum alkenylcyclohexene complexes (U.S. Pat. No. 4,699,813, Cavezzan); and a colloidal hydrosilylation catalyst provided by the reaction between a silicon hydride or a siloxane hydride and a platinum (0) or platinum (II) complex (U.S. Pat. No. 4,705,765, Lewis).
Although these platinum complexes and many others are useful as catalysts in processes for accelerating the hydrosilylation, processes for promoting the ultraviolet or visible radiation-activated addition reaction between these compounds may be preferable in some instances. Platinum complexes that can be used to initiate ultraviolet radiation-activated hydrosilylation reactions have been disclosed, e.g., platinum azo complexes (U.S. Pat. No. 4,670,531, Eckberg); (η4-cyclooctadiene)diarylplatinum complexes (U.S. Pat. No. 4,530,879, Drahnak); and (η5-cyclopentadicnyOtrialkylplatinum complexes (U.S. Pat. No. 4,510,094, Drahnak). Other compositions that are curable by ultraviolet radiation include those described in U.S. Pat. Nos. 4,640,939 and 4,712,092 and in European Patent Application No. 0238033. U.S. Pat. No. 4,916,169 (Boardman et al) describes hydrosilylation reactions activated by visible radiation. U.S. Pat. No. 6,376,569 (Oxman et al.) describes a process for the actinic radiation-activated addition reaction of a compound containing silicon-bonded hydrogen with a compound containing aliphatic unsaturation, said addition being referred to as hydrosilylation, the improvement comprising using, as a platinum hydrosilylation catalyst, an (η5-cyclopentadienyl)tri(σ-aliphatic)platinum complex, and, as a reaction accelerator, a free-radical photoinitiator capable of absorbing actinic radiation, i.e., light having a wavelength ranging from about 200 nm to about 800 nm. The process can also employ, as a sensitizer, a compound that absorbs actinic radiation, and that is capable of transferring energy to the aforementioned platinum complex or platinum complex/free-radical photoinitiator combination, such that the hydrosilylation reaction is initiated upon exposure to actinic radiation. The process is applicable both to the synthesis of low molecular weight compounds and to the curing of high molecular weight compounds, i.e., polymers.
Combinations of the hydrosilylation catalysts and photocatalysts and/or curing methods may also be used.
The catalyst is typically present in an amount that is effective to catalyze the hydrosilylation reaction. More typically, the catalyst is present in amounts sufficient to provide as little as one part of catalyst, or less, per million pans of the Si—H groups of the silicone polymer. On the other hand, amounts of the catalyst sufficient to provide as high as 1 to 10, or more, parts of catalyst per 1,000 parts of the Si—H groups of the silicone polymer may also be used. All or a portion of the Si—H groups may be functionalized with the perfluoroalkyl group.
In the presence of the hydrosilylation catalyst, hydrosilylation of hydrosilicone of Formula III with the compounds of Fonuula II readily produce the fluoroalkyl silicones of Formula I in high yield under mild conditions, such as at room temperature. The fluoroalkyl allyl ether of formula II demonstrated high reactivity to hydrosilicones, and the reaction may be controlled by slowly addition of hydrosilicone into the solution of fluoroalkyl allyl ether and catalyst—with or without solvent. In contrary, almost no product was observed from C4F9CH═CH2 under similar conditions, indicating the significantly higher reactivity of perfluoroalkyl alkenyl ether in comparison with perfluoroalkylethylene.
Regarding the product of Formula V of Scheme I, the Si—H functional fluoroalkyl silicones may be used as a crosslinking agent, such as to thermally crosslink with silicones or fluorinated silicones having a plurality of ethylenically unsaturated bonds in a subsequent hydrosilylation reaction. In some embodiments, the fluoroalkyl silicone may be subsequently crosslinked by vinyl substituted silicones: i.e. silicone having a plurality of vinyl groups.
The non-fluorinatcd organopolysiloxane polymers (vinyl silicones) comprising an average of at least two ethylenically unsaturated organic groups may be formulated with the fluoroalkyl silicone of Formula V. In some embodiments, the non-fluorinated organopolysiloxane polymer has a vinyl equivalent weight of no greater than 60,000 grams per equivalent, e.g., no greater than 20,000, or even no greater than 10,000 grams per equivalent. In some embodiments, the non-fluorinatcd organopolysiloxane polymer has a vinyl equivalent weight of 2000 to 5000 grams per equivalent, e.g., 2000 to 4000 grams per equivalent, or even 2500 to 3500 grams per equivalent.
Exemplary non-fluorinated organopolysiloxane polymers include those comprising a triorganosiloxy endblocked polydiorganosiloxane polymer. In some embodiments, the non-fluorinatcd organopolysiloxane polymer comprises R2SiO2/2units (i.e., “D” units) and R3SiO1/1 units (i.e., “M” units), wherein each R group independently represents a saturated or ethylenically unsaturated, substituted or unsubstituted hydrocarbon radical, provided that at least two R groups contain terminal ethylenic unsaturation.
The ethylenically unsaturated radicals are independently selected from the group consisting of the vinyl radical and higher alkenyl radicals represented by the formula —R′—CH═CH wherein R′ denotes —(CH2)w—; and w has the value of 1-48.
In some embodiments, trace amounts of non-linear siloxane units, i.e., SiO4/2units (i.e., “Q” units) and RSiO3/2, units (i.e., “T” units); may be present wherein R is as described above. In some embodiments, trace amounts of other silicon-bonded radicals, such as hydroxyl and alkoxyl may also be present.
Exemplary non-fluorinatcd organopolysiloxane polymer comprising an average of at least two ethylenically unsaturated organic groups include those having the formula MviDxMvi wherein M represents M units, D represents D units, the superscript “vi”indicates the presence of vinyl-functional groups, and x is the degree of polymerization. Commercially available MviDxMvi, non-fluorinated organopolysiloxane polymers include those available under the trade designations DMS-V from Gelest Inc. (e.g., DMS-V03, DMS-V05, DMS-V21, DMS-V22, DMS-V25, DMS-V35, and DMS-V41).
Examples of useful silicone having a plurality of vinyl groups include vinyl terminated polydimethylsiloxanes having the formula H2C═CHSiMe2O(SiMe2O)nSiMe2CH═CH2 (CAS 68083-19-2); vinyl terminated dimethylsiloxane-diphenylsiloxane copolymers having the formula H2C═CHSiMe2O(SiMe2O)n(SiPh2O)mSiMe2CH═CH2 (CAS: 68951-96-2); vinyl terminated polyphenylmethylsiloxanes having the formula H2C═CHSiMePhO(SiMePhO)nSiMePhCH═CH2 (CAS: 225927-21-9); vinyl-phenylmethyl terminated vinylphenylsiloxane-methylphcnylsiloxane copolymers (CAS: 8027-82-1); vinyl terminated trifluoropropylmethylsiloxane-dimethylsiloxane copolymers having the formula H2C═CHSiMePhO(SiMe2O)2(SiMe(CH2CH2CF2)mSiMePhCH═CH2 (CAS: 68951-98-4); H2C═CHSiMe2O—(SiMe2O)n(SiMe(CH2CH2CF3)O)mSiMe2CH═CH2, H2C═CHSiMe2O—(SiMe2O)n(SiMe(CH2CH2C4F9)O)mSiMe2CH═CH2, vinyl terminate dimethylsiloxane-diethylsiloxane copolymers having the formula H2C═CHSiMe2O(SiMe2O)n(SiEt2O)nSiMe2CH═CH2; trimethylsiloxy terminated vinylmethylsiloxane-dimethylsiloxane copolymers Me3SiO(SiMe2O)n(SiMe(CH═CH2)O)mSiMe3 (CAS: 67762-94-1); vinyl terminated vinylmethylsiloxane-dimethylsiloxane copolymers having the formula H2C═CH(SiMe3O)n(SiMeCH═CH3O)mSiMe3CH═CH2 (CAS: 68063-18-1); vinylmethylsiloxane homopolymers (cyclic and linear) having the formula Me3SiO(SiMe(CH═CH2)O)nSiMe3; and vinyl T-structure polymers having the formula MeSi[O(SiMe2O)mSiMe2CH═CH2]3; all commercially available from vendors such as, for example, Gelest, Inc., Morrisville, Pa. or Dow Coming Corp., Midland. Mich. Additional useful silicones having a plurality of vinyl groups include a vinyl-terminated fluorosilicone that is commercially available under the trade designations “SYL-OFF Q2-7785” and “SYL-OFF Q2-7786” from Dow Corning Corp.
In some embodiments, the Si—H group of Formula V, Scheme I may be converted to alkyl groups by subsequent hydrosilylation of an olefin of the formula: CH2═CHCH2—R4 where R4 is H or C1-C50 alkyl in the presence of a hydrosilylation catalyst.
Again with regard to the silicone of Formula V, Scheme I the Si—H groups may be converted to alkoxide groups (Si—H→Si—OR4) and the alkoxy-functional fluoroalkyl silicone can be subsequently hydrolysis-condensation crosslinked by siloxane formation. Generally, the hydrides are reacted with an alcohol of the formula R4—OH to convert all or a portion of the Si—H groups to Si—OR4 groups, where R4 is a C1-C50 alkyl, preferably a short alkyl group for easy hydrolysis. Thus the present disclosure provides crosslinkable, fluoroalkyl silicones of the formula:
wherein
n is 0 to 2000,
m may be zero, preferably at least one;
s may be zero;
t may be zero, preferably at least one;
R8 is H, alkyl or aryl, —(CH2)q—OCF2CHFORf or OR4, where R4 is C1-C50 alkyl;
q is at least 3; and
Rf is a perfluoroalkyl group, optionally substituted by one or more in-chain —O-, —S- or —NRf1-heteroatoms, where Rf1 is a perfluoroalkyl;
with the proviso that the silicone contains at least one, preferably at least two Si—OR4 groups and the silicone contains at least one —(CH2)q—O—CF2CHF—O—Rf group. In Formula IV, the unit with the subscript t may be at least one, preferably at least two, and/or R8 may be —OR4. Further, if only a portion of the Si—H groups are convened to alkoxysilanc groups (Si—OR4), then s may be at least one, and/or a potion of R8 may be H. Further, the unit with the subscript m may be at least one, and/or a portion of the R8 groups may be —(CH2)q—O—CF2CHF—O—Rf. In some embodiments R4 is lower-chain alkyl (C1-C16, preferably C1-C4). In other embodiments R4 is long-chain alkyl (C18-C50)
Subsequently, these alkoxide groups (Si—OR4) may be hydrolyzed by moisture, then crosslinked by dehydration, which can be catalyzed by a acid, or acid from a photoacid generator (PAG) initiated by photo irradiation, or a thermal acid generator initiated by heating to form siloxane Si—O—Si crosslinked polymers. The acid generator is preferably free of amines or ammonium compounds. The crosslinking of alkoxide substituted silicones by photo irradiation in the presence of PAG is described in U.S. Pat. No. 6,129,980 or WO 9840439 (Liu et al.). incorporated herein by reference.
The conversion of all or a portion of the Si—H groups in the silicone to alkoxide groups by reacting the hydropolysiloxane with an alcohol in the presence of at least one of a Pd(0) and Pt(0) catalyst according to the methods of U.S. Ser. No. 61/739,277(Rathore et al.) filed 19 Dec. 2012 and incorporated herein by reference.
A wide variety of acid generating materials can be used in the practice of the invention to catalyze the moisture curing reaction, including onium salts such as sulfonium and iodonium salts. Activating the acid generating material liberates an acid that initiates and accelerates crosslinking of the moisture-curable composition through the formation of Si—O—Si crosslinks. Activation may be accomplislied by irradiating the composition with, for example, ultraviolet, visible light, electron beam or microwave radiation. While heat may be used to activate the acid generating material, the compositions of the invention advantageously do not require this and thereby can avoid undesirable damage to heat sensitive substrates.
Although the acid generating material described above is preferred due to the controlled curability it provides, it has been found that condensation catalysts, such as strong organic acids, weak Lewis acids, weak organic bases and metal chelates can also be used in the preparation of the novel silicone pressure-sensitive adhesive. Another preferred class of condensation catalyst is the strong organic acids having pKa values of less than about 3 and the anhydrides and ammonium salts thereof described in U.S. Pat. No. 5,286,815. Examples of useful strong organic acids and derivatives include trichloroacetic acid, cyanoacetic acid, malonic acid, nitroacetic acid, dichloroacetic acid, difluoroacetic acid, trichloroacetic anhydride, dichioroacetic anhydride, difluoroacctic anhydride, iriethylammoniimi trichloroacetate, trimethylammonium trichloroacetate, and mixtures thereof.
The condensation catalyst or an acid generating material is used in amounts of about 0.5 to about 20 parts by weight, based on 100 parts by weight of the alkoxy functional silicone.
The fluoroalkyl silicone of Formula IV contains both Si—OR4and Si—H functional groups are dual curable, which may be controllably cured initially via Si—H with a vinyl silicone, then moisture or photo-acid cured from Si—OR4or vioe versa.
The fluoroalkyl silicone release materials of Formula I can be blended with one or more additional low surface energy materials (e.g., a fluoropolymer or silicone) while maintaining the desired low release characteristics of the fluorosilicone material, even when the additional low surface energy material itself is not a release material. In addition, in some embodiments, high blend ratios may be used without detrimentally affecting the readhesion force of the adhesive after removal for the blended release materials of the present disclosure.
Exemplary low surface energy materials that may be blended with the fluoroalkyl silicone release polymer of Formula I include additional fluorosilicone polymers, including those described herein, as well as non-fluorinated silicones and fluoropolymers.
Fluoropolymers can be prepared from a wide variety of fluorinated ethylenes and non-fluorinated monomers. As used herein, the term “fluorinated” includes both perfluorinated and partial Iy-fluorinated materials.
Generally, any known fluorosilicone release polymer may be used. The term “fluorosilicone” means a silicone material comprising at least some fluorine atoms on a pendent groups (i.e. fluoroalkyl). Exemplary fluorosilicone release coatings include release coating compositions derived from organopolysiloxanes having fluorine containing organic groups and alkenyl groups an organohydrogcnsiloxane crosslinking agent and a platinum-containing catalyst. Other fluorosilicone release coatings may be derived from, e.g., organopolysiloxanes having fluorine containing organic groups and silicon-bonded hydrogen groups, an alkenyl functional organopolysiloxane and a platinum-containing catalyst.
A number of useful commercially available fluorosilicone polymers are available from Dow Corning Corp. (Midland, Mich.) under the SYL-OFF and the SYL-OFF ADVANTAGE series of trade designations including, e.g., SYL-OFF Q2-7785 and SYL-OFF Q2-7786. These fluorosilicone polymers are particularly useful in forming release coating compositions when combined with a suitable crosslinking agent. One useful crosslinking agent is available under the SYL-OFF Q2-7560 trade designation from Dow Coming Corp. Other useful crosslinking agents are disclosed in U.S. Pat. No. 5,082,706 (Tangney) and U.S. Pat. No. 5,578,381 (Hamada et al.). Other fluorosilicone polymers ate commercia available from General Elcctric Co. (Albany, N.Y.), Wacker Chemie (Germany), Akrosi (Menasha. Wis.), and Loparex (Willowbrook, Ill.). Other fluorosilicone polymers are available from Momentive (FSR2000), and Siliconature (Scotchpak 9741 and M117)
One class of fluoropolymers is based upon fluorinated olefmk monomers such a tetrafluoroethylene (TFE), hexafluoropropylcne (HFP), vinyl fluoride (VF), vinylidene a fluoride (VDF). In some embodiments, the fluoroolefin-based fluoropolymers may be homopolymers or copolymers of fluorinated oleflnic monomers. In some embodiments, the fluoroolefin-based fluoropolymers may be copolymers of one or more fluorinated oleflnic monomers and one or more other monomers, including, e.g., non-fluorinated olefins such as ethylene, chlorinated olefins such as chlorotrifluoroethylene, and fluorinated vinyl ethers such as trifluoromethylvinylether.
In some embodiments, the fluoroolefin-based polymers may be amorphous fluoropolymers. As used herein, amorphous fluoropolymers are materials that exhibit essentially no crystallinity or possess no significant melting point as determined for example by differential scanning calorimetry (DSC). In some embodiments, the amorphous fluoropolymers are eiastomcric. In some embodiments the elastomeric fluoropolymers may comprise, e.g.,interpolymerized units derived from VDF, HFP, and, optionally. TFE monomers. Examples of such are commercially available from 3M Company under the trade names Dyneon™ Fluoroclastomcr FC 2145 and FT 2430, Additional amorphous fluoropolymers include, e.g., VDF-chlorotrifluoroethylene copolymers, commercially available under the trade name Kel-F™ 3700, from 3M Company.
In some embodiments, the fluoroolefin-based polymers may be homopolymers and copolymers that do exhibit crystalline melting point. Exemplary crystalline fluoropolymers includc those based on fluorinated monomers such as TFE or VDF such as polyvinylidene fluoride (PVDF), available commercially from 3M Company as Dyneon™ PVDF, or thermoplastic copolymers of TFE such as those based on the crystalline microstructure of TFE-HFP-VDF, e.g., those available from 3M under the trade name Dyneon™ Fluoroplastic THV™ 220.
In some embodiments, the fluoroolefin-based polymers may include PVDF-containing fluoroplastic materials having very low molar levels of HFP such as those sold under the trade name Dyneon™ PVDF 6010 or 3100, available from Dyneon LLC, of St. Paul, Minn.; and Kynar™ 740,2800,9301, available from Elf Atochem North America Inc.
A separate class of fluoropolymers useful in some embodiments of the present disclosure are fluoroacrylate polymers, which are based upon (meth)acrylatcs (i.e., acrylatcs and/or methacrylates) having pendant fluoroalkyl groups. Fluoroacrylate polymers derived from fluoroacrylate monomers and multi-(meth)acrylates such a polyethylene glycol diacrylate (PEGDA) or 1,6-hexanediol diacrylate (HDDA) will form nonlinear (e.g., branched and/or crosslinked) fluoropolymers. Fluoroacrylate polymers derived from fluoroacrylate monomers and mono-(meth)acrylates such as C1-C50 acrylatcs (e.g., C4-C20 acrylates such as butyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, and octadecyl acrylate) form linear fluoropolymers.
Such fluoroacrylate monomers can be polymerized to yield a fluorinated acrylic polymer as described in U.S. Pat. No. 7,199,197 (Caldwell et al.) and U.S. Pat. No. 7,297,210 (Qui et al.). The fluoroacrylate monomers can also be copolymerized with one or more comonomers such as mono-(meth)acrylaxe monomers to produce linear fluoropolymers according to some embodiments of the present disclosure. In some embodiments, the comonomer may be an alkyl mono-(meth)acrylatc. In some embodiments, the alkyl mono-(meth)acrylate is a C1-C50, e.g., a C4 to C20, alkyl mono-(meth)aciylatc. Representative examples of useful alkyl mono-(meth)actylates include methyl(meth)acrylate, butyl(meth)acrylate, isobutyl (meth)acrylate, hexyl(meth)acrylate, dodecyl(meth)acrylate, octadecyl(meth)acrylate, and 2-ethylhexyl(meth)acrylate.
The ratio of fluoroalkyl silicone release composition to flooropolymcr (e.g., linear fluoroacrylate polymer or fluoroolefinic polymer) can vary widely. For example, in some embodiments, the weight ratio of the fluoroalkyl silicone release polymer of Formula I to the linear fiuoropolymer is no greater than 10:1, no greater than 5:1, or even no greater than 3:1. In some embodiments, it may be desirable to minimize the amount of the relatively expensive fluoroalkyl silicone release polymer of Formula I, while retaining the required release and readhesion properties. In some embodiments, the weight ratio of the fluoroalkyl silicone release polymer of Formula I to the linear fiuoropolymer is no greater than 1:1, no greater than 1:5, no greater than 1:10, or even no greater than 1:20. For example, in some embodiments the weight ratio of the fluoroalkyl silicone release polymer of Formula I to the linear fiuoropolymer is between 10:1 and 1:20, e.g., between 3:1 and 1:20, inclusive; between 2:1 and 1:10, inclusive (e.g., between 1:1 and 1:10, inclusive), or even between 2:1 and 1:3.
In other embodiments, the fluoroalkyl silicone of Formula I may be blended with non-fluorinated silicone polymers, including vinyl-substituted (described supra), hydrogen (Si—H) substituted silicone polymers, and non-ftinctional silicone polymers. As previous described for the vinyl-substituted silicone polymers, the hydrogen-substituted and non-functional silicone polymers may comprise M, D, T and Q units. Vinyl-substituted and hydrogen-substituted (Si—H) silicone polymers are described in U.S. Pat. No. 7,279,210 (Qiu et al.), incorporated herein by reference.
The present disclosure further provides coating compositions comprising the fluoroalkyl silicone of Formula I in a suitable solvent. In some embodiments, the disclosure provides crosslinkable coating compositions comprising the fluoroalkyl silicone of Formula I and a crosslinking agent in a stable solvent. In other embodiments, the fluoroalkyl silicone of Formula IV, containing hydrolysable Si—OR4 groups, is self- crosslinking by formation of siloxane bonds.
The term “coatable” or “coatable composition” means that the composition is soluble or dispersible in solvents or water and is substantially gel-free and, that it can be applied to a substrate using standard coating methods, and that it forms a film upon heating or curing. The coatable compositions of the invention can be used to impart release properties to a wide variety of substrates.
The coatable compositions we preferably diluted or dispersed in a liquid (for example, water and/or an organic solvent) before coating a substrate. Preferably, the coating compositions contain from about 5 to about 15 percent solids (more preferably, about 2 to about 10 percent), based upon the weight of the coating composition.
The coatable compositions can be applied to fibrous substrates (for example, woven, knit and non-woven fabrics, textiles, carpets, leather, or paper) to impart water- and oil-repellency. The coatable compositions can be applied to a substrate (or articles comprising a substrate) by standard methods such as, for example, spraying, padding, dipping, roll coating, brushing, or exhaustion.
The composition can then be dried to remove any remaining water or solvent. Preferably, the coated composition is heated to a temperature between about 100° C. and about 175° C. The coatable compositions are useful as release coatings, and can be applied to surfaces requiring release properties from adhesives. Surprisingly, dried coatable compositions of the invention show significant solvent resistance. The coatable compositions can therefore be used as release coatings for solvent cast adhesives.
Substrates suitable for release coatings include, for example, paper, metal sheets, foils, non-woven fabrics, polvolefin coated paper, and films of thermoplastic resins such as polyesters, polyamides, polyolefins, polycarbonates, and polyvinyl chloride. Release coating compositions can be applied to suitable substrates by conventional coating techniques such as, for example, wire-wound rod, direct gravure, offset gravure, reverse roll, air-knife, and trailing blade coating. The resulting release coating compositions can provide effective release for a wide variety of pressure sensitive adhesives such as, for example, natural rubber based adhesives, silicone based adhesives, acrylic adhesives, and other synthetic film-forming elastomeric adhesives.
C3F7OCHFCF2OCH2CH═CH2 (PE5) was made from C3F7OCF═CF2 and HOCH2CH═CH2 by similar procedures described in US Patent Publication No. 2005/0113609, except that 1,2-dimethoxycthane (from GFS Chemicals, Inc.) was used as solvent.
1,2-dimethoxycthane was obtained from GFS Chemicals, Inc., Powell, Ohio. “Syl-Off 7048” is a 100 weight percent solids silanc crosslinker (said to comprise methylhydrogen cyclosiloxane, Viscosity—30 centistokes) having H—Si equivalent weight of 60, obtained from Dow Coming Corporation, Midland, Mich., under the trade designation “Syl-Off® 7048”.
“Pt-Cat” (Karstedt catalyst) was bis(1,3-divinyl-1,1,3,3-tetrametyldisiloxane) platinum(0) (2 wt % platinum in xylene), purchased from Gelest, Inc., Morrisville, Pa. and kept in the dark before use.
“Q2-7785” is an 80 wt % solution of fluorosilicone polymer dispersed in heptane, obtained from Dow Corning Corporation, Midland, Mich., under the trade designation of “Syl-Off® Q2-7785”, having the following structure:
“Q2-7786” is a 100 wt % fluorosilicone polymer obtained from Dow Corning Corporation, Midland, Mich., under the trade designation of “Syl-Off® Q2-7786”. having the following structure:
“Q2-7560” is a 100 wt % crosslinker, obtained from Dow Corning Corporation, Midland, Mich., under trade designation “Syl-Off® Q2-7560” having the following structure:
The silicone coat weight of a 3.69 centimeter diameter sample of coatcd substrate was determined by comparing samples of coatcd and uncoated substrates using an EDXRF spectrophotometer (obtained from Oxford Instruments. Elk Grove Village, Ill. under trade designation OXFORD LAB X3000).
Unreacted silicone extractables were measured on cured thin film formulations of Example and Comparative Example samples described below to ascenain the extent of silicone crosslinking immediately after the coatings were cured. The percent extractable silicone, (i.e., the unreacted silicone extractables), a measure of the extent of silicone cure on a release liner, was measured by the following method: The coated substrate sample was cured at then immersed in and shaken with methyl isobutyl ketone (MIBK) for 5 minutes, removed, and allowed to dry. The silicone coating weight was measured again. Silicone ex tradables were attributed to the weight difference between the silicone coar weight before and after extraction with MIBK as a percent using the following formula:
Extractable Silicone %=(a−b)/a*100%
Where a=initial coating weight (before extraction with MIBK); and
b=final coating weight (after extraction with MIBK).
Every number is the average of at least two tests.
An IMASS SP2000 slip peel tester (obtained from IMASS Inc., Accord, MA) was used for all release tests. Tests were performed at 21° C. at 50% RH. A piece of 2.54 cm wide 3M Tape 610 (commercially available from 3M Company, St. Paul, Minn. under trade designation “Scotch® Premium Cellophane Tape 610”) was laminated to the sample coatings with a 2 kg rubber roller, then peeled at an angle of 180° at the speed of 2.29 m per minute in 5 seconds. Typically, 3 measurements were made and the mean reported.
The 3M Tape 610 strips peeled in the Release test were laminated to a steel plate with a 2 kg rubber roller. An IMASS SP2000 slip peel tester was used to peel the tape at an angle of 180° at the speed of 30 cm per minute in 10 seconds. Typically, 3 measurements were made and the mean reported. When measuring re-adhesion for a sample, re-adhesion value of a pristine sample of 3M Tape 610 which was not contacted with release coatings was also determined (as an internal control) and the data tor the control was reported along with the data for corresponding samples.
Coated films prepared in Examples and Coated Examples described below were rinsed for 1 minute with hand agitation in an isopropanol (IPA) bath prior to water and hexadecane (HD) contact angles measurements. Measurements were made using a VCA-2500XE video contact angle analyzer (available from AST Products, Billerica, Mass.). Reported values are the average of at least 3 drops; each drop was measured twice. Drop volumes were 5 μL for static measurements and 1-3 μL for advancing and receding. For HD, only advancing and receding contact angles are reponed because static and advancing values were found to be nearly equal.
Pt-Cat [40 ppm] and C3F7OCF2CHFOCH2CH═CH2(8.3 g) was mixed together in a 100 mL round bottom flask followed by dropwisc addition of the Syl-Off 7048 (5 g) through a dropping funnel at room temperature. The addition of Syl-Off 7048 resulted in the evolution of heat after 20-60 seconds of stirring. The mixture was stirred for an additional 30 minutes followed by the analysis of the mixture by FT-IR (Si—H at ˜2160 cm−1 reduced) and 1H NMR (Si—H at 4.5 ppm reduced). To isolate the product, any unreactcd/residual C3F7OCF2CHFOCH2CH═CH2 was then evaporated using vacuum. Yield—99% and the ratio of n:m was 33:67. Chemical shift of 1H-NMR: 5.8-5.9 (broad split peak); 4.57 (—SiH); 3.9 (b); 1.76 (b), 1.47 (b), 1.02 (broad), 0.63 (broad); 0.24 (broad, —SiCH3) ppm.
PE2 was prepared in the same manner as PE1 except that Pt-Cat [40 ppm] and C3F7OCF2CHFOCH2CH═CH2 (28 g) was mixed together in a 100 mL round bottom flask followed by drop wise addition of the Syl-Off 7048 (5 g) through a dropping funnel at room temperature. Yield—99% and the ratio of n:m is 100:0. Chemical shift of 1H-NMR: 5.8-5.9 (broad split peak); 3.9 (b); 1.76 (b), 1.47 (b), 1.02 (broad), 0.63 (broad); 0.24 (broad, —SiCH3) ppm.
PE3 was prepared in the same maimer as PE1 except that Pt-Cat [40 ppm] and C3F7OCF2CHFOCH2CH═CH2 (16 g) was mixed together in a 100 mL round bottom flask followed by drop wise addition of the Syl-Off 7048 (5 g) through a dropping funnel at room temperature. Yield—99% and the ratio of n:m is 67:33. Chemical shift of 1H-NMR: 5.8-5.9 (broad split peal;); 4.57 (—SiH); 3.9 (b); 1.76 (b), 1.47 (b), 1.02 (broad), 0.63 (broad); 0.24 (broad, —SiCH3) ppm. Preparative Example 4 (PE4) Preparation of —[SiMe(C3H6OCHFCF2OC3F7)n-O]—[SiMeH—O]p-, n/m/p=0.3/0.37/0.33
PE4 was prepared in the same manner as PE1 except that Pt-Cat [40 ppm] and C3F7OCF2CHFOCH2CH═CH2 (5.4 g) was mixed together in a 100 mL round bottom flask followed by drop wise addition of the Syl-Off 7048 (5 g) through a dropping funnel at room temperature. Yield—99% and the ratio of n/m/p=0.30/0.37/0.33. Chemical shift of 1H-NMR: 5.8-5.9 (broad split peak); 4.57 (—SiH); 3.9 (b); 1.76 (b), 1.47 (b), 1.02 (broad), 0.63 (broad); 0.24 (broad, —SiCH3) ppm.
PE5-PE13 fluorinated alkenes were made according to the following reaction with different Rf and different space linkages as shown below by similar procedures described in US Patent Publication No. 2005/0113609, except that 1,2-dimethoxyethane (from GFS Chemicals, Inc.) was used as solvent. The PE5-PE13 fluorinated alkenes were consequently useful for making various fluorinated silicones.
Rf—OCF═CF2+HO—(CH2)x-CH═CH2→Rf—OCHFCF2—O—(CH2)x-CH═CH2
EX1-EX19 coating solutions were prepared by first dissolving PE1, Q2-7785, and Q2-7786 thoroughly in a mixture of heptane/ethyl acetate (80:20 mixture by weight) to result in 10 or 20 wt % solutions then mixing PE1 solution with either Q2-7785 solution or Q2-7786 solution thoroughly. The concentration of the PE1/Q2-7785 mixture or PE1/Q2-7786 mixture in the coating solution was either 10 or 20% by weight.
CE1-CE12 coating solutions were prepared by first dissolving Q2-7560, Q2-7785, and Q2-7786 thoroughly in a mixture of heptane/ethyl acetate (80:20 mixture by weight) to result in 10 or 20 wt % solutions then mixing Q2-7560 solution with either Q2-7785 solution or Q2-7786 solution thoroughly. The concentration of the Q2-7560/Q2-7785 mixture or Q2-7560/Q2-7786 mixture in the coating solution was either 10 or 20% by weight.
The resulting EX1-EX 19 and CE1-CE12 coating solutions were then coated on a 2-mil (0.058 millimeter (mm)) thick polyester terephthalate (PET) film (obtained from Mitsubishi Polyester Film, Greer, S.C., under the trade designation “Hostaphan™ 3SAB”, which has one side chemically treated or primed to improve the adhesion of silicone coatings) with different size of Mayer bars for different coating weights. All coatings were cured at 120° C. for 2 minutes in an oven equipped with solvent exhaust. Table 1, below, summarizes the compositions of the coating solutions as well as the size number of Meyer bars used for preparing the coatings.
The % Extractable Silicone lest was run for the EX1-4 and CE1-CB4 samples using the method described above. The results are summarized below in Table 2.
The water and hexadecane contact angle measurements were done for EX5-EX9 and CE5-CE8 samples using tlve methods described above. The results are summarized below in Table 3.
Release testing of EX10-EX 19 and CE9-CE12 were done using the methods described above. The results are summarized below in Table 4.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2014/058529 | 10/1/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61886829 | Oct 2013 | US |
