GB2045788A - Method for coating a substrate using a curable silicone release composition - Google Patents
Method for coating a substrate using a curable silicone release composition Download PDFInfo
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- GB2045788A GB2045788A GB8005377A GB8005377A GB2045788A GB 2045788 A GB2045788 A GB 2045788A GB 8005377 A GB8005377 A GB 8005377A GB 8005377 A GB8005377 A GB 8005377A GB 2045788 A GB2045788 A GB 2045788A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
- B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
- C08L83/04—Polysiloxanes
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
- C09D183/04—Polysiloxanes
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
- C08G77/04—Polysiloxanes
- C08G77/12—Polysiloxanes containing silicon bound to hydrogen
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
- C08G77/04—Polysiloxanes
- C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
Abstract
An improved coating process comprises applying to a substrate certain curable silicone release compositions which have a ratio of silicon- bonded hydrogen radicals to silicon- bonded vinyl radicals of 2-10 and comprise a vinyl-terminated polydiorgano- siloxane, a vinyl-containing, xylene- soluble siloxane resin copolymer, a methylhydrogenpolysiloxane and a hydrosilylation catalyst. The high SiH/ SiVi ratio permits the effective lowering of the otherwise-high viscosity of the composition, thereby improving its application to flexible substrates, such as paper, by roller-coating methods.
Description
SPECIFICATION
Method for coating a substrate using a curable silicone release composition.
This invention relates to an improved process for coating a substrate using a curable silicone release composition. More specifically, this invention relates to a new substrate-coating process which uses a silicone release composition which cures rapidly, has improved resistance to abrasion and rub-off in the cured form and yet has a viscosity at room temperature which permits its application to the substrate by standard coating methods, without the need to use a volatile thinning medium such as a solvent or a dispersant.
The term "adhesive materials" as employed herein means materials having a lasting sticky nature, such as pressure sensitive adhesives, foodstuffs, asphalt, pitch and raw rubber, in contrast to temporary sticky materials which become non-sticky, such as cements and moulding compositions.
The application of curable silicone release compositions to substrates to aid in the release of adhesive materials therefrom is old and well known in the coatings art. However, most, if not all, curable silicone compositions that have been used in the release coatings art suffer from a property trade-off which affects the viscosity of the curable composition, the release behaviour of the cured coating and the abrasion resistance of the cured coating.
Specifically, with respect to the silicone compositions which cure by way of a catalyzed reaction of silicon-bonded vinyl radicals with silicon-bonded hydrogen radicals, this property trade-off can be summarized in the following manner. Solventless, low-viscosity coating compositions, such as those disclosed in U.S. Patents Nos. 3,928,629 and 4,071,644 are based on low-molecular weight, vinyl-containing polymers and, therefore, frequently lack the necessary strength, in the cured state, to survive vigorous abrasion and flexing forces. Using a higher molecular weight polymer, instead of the low molecular weight polymer, such as is disclosed in U.K. Patent No. 1,240,520, is known to provide increased strength to the cured coating; however, the viscosity of the uncured composition is correspondingly increased, resulting in difficulty in applying the curable composition to a substrate.Low viscosity is thereby sacrificed for increased strength. Cured silicone release compositions, whether based on a high or low molecular weight polymer, have excellent release characteristics and are desired as adhesive i.e., non-stick, coatings. However, in many instances such as in the preparation of a release backing for pressure-sensitive adhesive labels, easy release is not desired. To control the adhesive release behaviour of a silicone composition and to provide additional strength, it has been taught in U.S. Patent No. 4,123,604to mix a vinyl-containing resin with the curable silicone composition. Whether this resin is mixed with a low molecular weight polymer or a high molecular weight polymer, a considerable increase in the viscosity of the compositions results.To obtain a solventless, low-viscosity curable release composition from such a resin-containing mixture, a very low molecular weight, vinyl-containing polymer, including vinyl-containing cyclopolysiloxanes, must be used, thereby sacrificing abrasion resistance for controlled release.
Of course, an obvious way to decrease the viscosity of a curable silicone release composition is to dissolve or disperse the composition in a volatile thinning medium. However, this expedient is undesirable from at least two aspects. First, environmental considerations suggest that it may be undesirable to vent a solvent to the atmosphere during the preparation and/or use of the release composition. Second, recovery of a solvent from a release composition may be a prohibitively expensive process for the manufacturer and/or user of the release composition.
We have sought to provide an improved process for coating substrates which provides abrasionresistance, adhesive-releasing coatings from solventless coating compositions.
We have found that this can be achieved by applying to a surface of a substrate, from which adhesive release is desired, certain fast-curing, tough silicone compositions having a high ratio of silicon-bonded hydrogen radicals to silicon-bonded vinyl radicals. Certain of the curable silicone compositions which are used in the process of this invention have been disclosed as a marking ink composition and as a repair composition for surface imperfections on translucent silicone rubber articles. Other compositions useful herein appear to be new.
Thus, this invention provides a process for coating a substrate to provide release of adhesive materials therefrom, which process comprises applying a curable silicone release composition to a surface of a substrate and thereafter curing the applied composition, the composition being obtained by mixing components consisting essentially of (I) a polydiorganosiloxane having the general formula ViR2SiO(R 2SiO)x(RViSiO)vSiR2Vi wherein x and y are integers whose sum has an average value sufficient to provide the polydiorganosiloxane with a viscosity at 25"C. of at least 1.0 pascal-second, Vi represents a vinyl radical and each R represents, independently, a monovalent radical selected from methyl, phenyl and saturated hydrocarbon radicals having from 2 to 6 carbon atoms, the total number of organic radicals in the polydiorganosiloxane consisting of at least 95 percent methyl radicals and no more that 1 percent vinyl radicals; (II) a xyiene-soluble copolymer of (CH3)3SiO1/2, (CH3)2(CH2=CH)SiO/2 and SiO4/2 siloxane units, the copolymer having from 1 to 5 percent by weight of vinyl radicals, bsed on the weight of the copolymer, and a total of from 0.6 to 1.1 of said (CH3)3SiO1/2 plus (CH3)2(CH2=CH)SiO1,2 siloxane units for every SiO4/2 siloxane unit; (III) a methylhydrogenpolysiloxane, soluble in the mixture of components (I) and (il), and having an average of at least three silicon-bonded hydrogen radicals per molecule, the hydrogen radicals being bonded to separate silicon atoms; and (IV) a catalytic amount of a hydrosilylation catalyst, the components being mixed in sufficient amount of provide, in the curable silicone release composition, from 10 to 70 parts by weight of component (Il) for every 100 parts by weight of components (I) plus (II) and from 2 to 10 silicon-bonded hydrogen radicals for every silicon-bonded vinyl radical.
The four essential components, i.e., pdlydiorganosiloxane (I), xylene-soluble copolymer (11), methylhydrogenpolysiloxane (III) and hydrosilylation catalyst (IV), which are mixed to form the curable silicone composition which is used as a curable release agent in the improved process of this invention are all generally known in the organopolysiloxane art:
The polydiorganosiloxane (I) is a vinyl-endblocked linear polymer having the general formula ViR2SiO(R 2SiO),-(RViSiO),SiR2Vi.
Each R represents, independently, a methyl radical, a phenyl radical or a saturated hydrocarbon radical having 2 to 6, inclusive carbon atoms such as alkyl radicals, ethyl, propyl, isopropyl, butyl and hexyl and cycloaliphatic radicals, e.g. cyclohexyl. At least 95 percent of all organic radicals in polydiorganosiloxane (I) are the methyl radical. Preferably, each terminal silicon atom of the polydiorganosiloxane (I) bears at least one methyl radical. To avoid overcuring of the release composition, the total number of vinyl radicals in the polydiorganosiloxane (I) should not exceed 1 percent of all of the siiicon-bonded organic radicals therein.
Examples of preferred siloxane units which form the polydiorganosiloxane (I) include ViMe2SiO1,2, PhMeViSiO112, Me2SiO2 and MeViSiO2/2. Examples of other siloxane units suitable for use in the polydiorganosiloxane (I! include PhViSiOu2, Ph2SiO2z2, PhMeSiOu2, ViEtSiOu2 and MeEtSiO2,2 siioxane units.
Herein the symbols Me, Et Ph and Vi represent respectively, the methyl, ethyl, phenyl and vinyl radical.
Examples of preferred polydiorganosiloxanes (I) to be used in the process of this invention include ViMe2SiO(Me2SiO)x(SiMe2Vi; ViPhMeSiO(Me2SiO)xSiMePhVi; ViMe2SiO(Me2SiO)x(ViMeSiO)ySiMe2Vi; and ViPhMeSiO(Me2SiO)x(Vi MeSiO)ySiMePhVi.
The average value of the sum total of x and yin the above formulae is such that the viscosity of the resulting polydiorganosiloxane is at least 1.0 pascal-seconds (1000 centipoise) at 25"C. Preferred results, such as rapid cure rate of the curable composition and high abrasion resistance of the cured release coating, are obtained when the viscosity of the vinyl-endblocked polydiorganosiloxane is at least 25 pascal-seconds.
There is no known upper limit to the viscosity of polydiorganosiloxane (I) unless a solventless coating composition is desired, in which case an upper viscosity limit is approximately 100 pascal-seconds.
The exact average value for the sum total of x and ywhich will produce a desired viscosity at 25"C for polydiorganosiloxane (I) depends upon the amounts and types of R radicals present therein. For example for the above-delineated preferred vinyl-endblocked polydiorganosiloxanes, an average value for the sum total ofx and y of approximately 225 will provide a viscosity of 1.0 pascal-seconds and an average value of approximately 695 will provide a viscosity of 25 pascal-seconds, both measured at 25"C.
Polydiorganosiloxanes (I) are well known in the organosilicon polymer art and may be prepared by any suitable method. While the preparation of the polydiorganosiloxane (I) needs no further elaboration here, it should be noted that, depending upon the particular polydiorganosiloxane (I) which is prepared and particular method for its preparation that is used, there may be coproduced therewith up to about 15 percent by weight of cyclopolydiorganosiloxanes.A large portion of the cyclopolydiorganosiloxanes may be volatile at temperatures up to 1 500C. It is to be noted that the suitability of vinyl-endblocked polydiorganosiloxane (I) for use in the process of this invention is determined by its viscosity at 25 C, as delineated above, and does not depend upon either the presence or absence therein of the above-described amounts of coproduced cyclopolydiorganosiloxanes. That is to say, the vinyl-endblocked polydiorganosiloxane (I) may be optionally freed of any volatile cyclopolydiorganosiloxanes, if desired, without having a detrimental effect on the process of this invention.
For the purposes of this invention, however, the viscosity and the amount of vinyl-endblocked polydiorganosiloxane (I) which is used, and which is further delineated below, are based on polydiorganosiloxane which has been devolatilized at 1 500C for 1 hour.
While the polydiorganosiloxane (I) is stated to be linear and to bear only hydrocarbon radicals on the silicon atoms, it may contain small amounts of non-linear siloxane units, i.e. Six4,2 ViSiO3,2 and Rio3/2 siloxane units wherein R is as previously defined and trace amounts of other silicon-bonded radicals, such as hydroxyl and alkoxyl, which are normally incidentaily present in commercial polydiorganosiloxanes. The use of such a polydiorganosiloxane is within the scope of the present invention, although, preferably, the polydiorganosiloxane (I) is free of such non-linear siloxane units and other radicals.
The xylene-soluble copolymer (II) of (CH3)3SiO112 siloxane units, (CH3)2(CH2=CH)SiOa,2 siloxane units and
SiO4/2 siloxane units is well known in the organosilicon polymer art. The copolymer is a solid, resinous material which is prepared as, and usually, but not necessarily, used as, a solution in an organic solvent.
Typical solvents that are used with copolymer (II) include benzene, toluene, xylene, methylene chloride, perchloroethylene and naphtha mineral spirits.
The copolymer (II) contains from 1 to 5, preferably 1.5 to 3.5, percent by weight of vinyl radicals, based on the weight of the copolymer, and from 0.6 to 1.1 of the siloxane units bearing organic radicals for every
SiO4/2 siloxane units. Thus, in copolymer (II), for every Six4,2 units there is a total of from 0.6 to 1.1 (CH3)3SiO"2 units plus (CH3)2(CH2=CH)SiO112 units.
The copolymer (II) is preferably prepared by an adaptation of the procdure described in U.S. Patent No.
2,676,182 whereby a silica hydrosol is treated at low pH with a source of trimethylsiloxane units, such as hexamethyldisiloxane ortrimethylchlorosilane and a source of dimethylvinylsiloxane units, such as divinyltetramethyldisiloxane or demethylvinylchlorosilane. Alternatively, a suitable mixture of hydrolyzable trimethyl-substituted, dimethylvinyl-substitutd and silanesfree from organic radicals, such as chlorosilanes and/or alkoxysilanes, may by cohydrolyzed. In this alternate procedure, the resulting cohydrolyzate is preferably subsequently treated with a suitable silylating agent, such as hexamethyldisilazane or divinyltetramethyldisilazane, to reduce the hydroxyl content of the resulting resinous copolymer to less than 1 percent by weight. Minor amounts of diorganosilxane units may be present in the copolymer (II).
Methylhydrogenpolysiloxane (III) operates as a'curing agent for the mixture of the polydiorganosiloxane (I) and the xylene-soluble copolymer (II) and therefore must be soluble therein and must contain an average of at least three, preferably more than three, silicon-bonded hydrogen radicals per molecule. The term "methylhydrogenpolysiloxane" means that at least three, but preferably all, silicon atoms therein which bear the hydrogen radicals also bear at least one methyl radical. For efficient curing of the mixture of components (I) and (it), it is preferred that no silicon atom in (lli) bear more than one silicon-bonded hydrogen radical.Methylhydrogenpolysiloxane (III) may also contain silicon-bonded phenyl radicals and silicon-bonded alkyl radicals having from 2 to 6 carbon atoms, provided that it is soluble in the mixture of components (I) and (II).
The methylhydrogenpolysiloxane (III) is preferably a fluid having a low viscosity, such as less than 0.1 pascal-seconds at 25"C, thereby considerably and desirably decreasing the initial, i.e. uncatalyzed, viscosity of the mixture of the polydiorganosiloxane (I) and copolymer (II) when mixed therewith. It is desirable to decrease the viscosity of the mixture of components (I) and (II) because application of the resulting curable composition onto, and adhesion of the subsequently cured composition to, a substrate is aided thereby.The viscosity of the mixture of components (I) and (II) can be considerably decreased by the use of a low viscosity methylhydrogenpolysiloxane as component (III) because the curable silicone compositions which are uniquely operative in the process of this invention have an unusually high ratio of silicon-bonded hydrogen radicals to silicon-bonded vinyl radicals, further delineated below, thereby permitting the use of relatively large amounts of any particular methylhydrogenpolysiloxane (III).
Preferred siloxane units which for the methylhydrogenpolysiloxane (III) include Me3SiO112, Me2HSiO112, Me2SiO2/2, MeHSiO212, MeSiO312, and Six4/2. Methylhydrogenpolysiloxane (III) may also further comprise other siloxane units, such as HSiO3j2, PhHSiOV2, PhMeSiOu2 and PhSiO3,2, provided that the resulting methylhydrogenpolysiloxane is soluble in the mixture of components (I) and (II).
Examples of methylhydrogenpolysiloxane (III) which are operative in the process of this invention include, but are not limited to, siloxanes consisting of Me3SiO/2 units and MeHSiO212 units, siloxanes consisting of Me3SiO112 units, Me2SiO2,2 units and MeHSiO212 units siloxanes consisting of HMe2SiO"2 units, MeSiO212 units and MeHSiO2,2 units, siloxanes consisting of SiO412 units Me3SiO/2 units and HMe2SiO112 units, siloxanes consisting of SiO412 units and HMe2SiO1,2 units, siloxanes consisting of HMeSiO212 units and siloxanes consisting of HMeSiO212 units and Me2SiO212 units.
Specific examples of suitable methylhydrogenpolysiloxanes which may be used as component (III) in the process of this invention include (HMe2SiO)4Si, (MeHSiO)4 MeSi(OSiMe2H)3, PhSi(OSiMe2H)3, and preferably, higher molecular weight fluid siloxanes having the average formulae Me3SiO(MeHSiO)35SiMe3,
Me3SiO(Me2SiO)3(MeHSiO)5SiMe3 and HMe2SiO(Me2SiO)3(MeHSiO)5SiMe2H. The higher molecular weight methylhydrogenpolysiloxanes are preferred as a curing component for a silicone release composition because they have a low volatility and will remain with and more effectively cure the silicon release composition at elevated temperatures.
Methylhydrogenpolysiloxanes are well known in the organosilicon polymer art; their preparation therefore needs no further elaboration here. As in the case of the preparation of vinyl-endblocked polydiorganosiloxanes, it should be noted that the preparation of methylhydrogenpolysiloxanes comprising diorganosiloxane units may produce small amounts of cyclopolydiorganosiloxanes. The presence or absence of these cyclopolydiorganosiloxane species in the methylhydrogenpolysiloxane is of no importance to this invention as long as the methylhydrogenpolysiloxane has an average of at least 3 silicon-bonded hydrogens per molecule.
Component (IV) is any hydrosilylation catalyst which is effective to catalyze the addition reaction of silicon-bonded hydrogen radicals with silicon-bonded vinyl radicals in conventional manner. Typically, component (IV) is an active metal-containing composition such as a platinum-containing compound or a rhodium-containing compound. Examples of these active metal compositions include chloroplatinic acid, platinum deposited on a substrate,platinum complexed with organic liquids, such as ketones, vinylsiloxanes and ethylene, and complexes of rhodium halides. Preferably, the hydrosilylation catalyst is soluble in the curable silicone release composition.
The platinum-containing catalysts may also contain an inhibitor to moderate its catalytic activity at room temperature, in conventional manner, if desired. Rhodium-containing catalysts do not need room temperature inhibiting.
Hydrosilylation catalysts and their inhibitors are well known in the organosilicon art and need no further delineation herein. Further details are disclosed in U.S. Patents Nos. 2,823,218; 3,419,593; 3,445,420; 3,890,359; 3,697,473; 3,814,731; and 4,123,604.
The vinyl-containing components of the curable silicone release composition are mixed in amounts sufficient to provide from 10 to 70 parts by weight of the xylene-soluble copolymer (II) for every 100 parts by weight of the mixture of vinyl-endblocked polydiorganosiloxane (I) plus copolymer (II). A preferred combination of properties, for the cured release agent, such as premium release aggressive acrylic adhesives and high film strength, is obtained when the curable composition contains a mixture of components (I) and (II) which is from 20 to 60 percent by weight of component (II).
The desired amounts of components (I) and (Il) are used on a non-volatile basis. This is easily achieved by subjecting samples of the polydiorganosiloxane, which frequently contains volatile cyclopolydiorganosiloxanes, and xylene-soluble copolymer, which is usually prepared and handled in xylene, to a devolatilization procedure at 150"C for 1 hour in order to determine the non-volatile content of each and using a sufficient quantity of each material to obtain the desired amount of the vinyl-end-blocked polydiorganosiloxane (I) and xylene-soluble copolymer (ill) in the curable composition.
The amount of methylhydrogenpolysiloxane (III) to be mixed when preparing the curable silicone release composition is simply the amount which will provide from 2 to 10 silicon-bonded hydrogen radicals for every silicon-bonded vinyl radical in the composition and the desired viscosity for the silicone release composition. For any given resin concentration in the resin plus polymer mixture, the amount of methylhydrogenpolysiloxane (III) which is needed to obtain a suitable coating viscosity for the curable composition is related to the viscosity of the polymer (I).Thus, a curable composition comprising a polydiorganosiloxane (I) having a viscosity of 5 pascal-seconds may have a suitable coating viscosity when the SiH/SiVi ratio is 2.0; whereas a curable composition containing the same amount of resin but comprising a polydiorganosiloxane (I) having a viscosity of 100 pascal-seconds may require a SiH/SiVi ratio of 10.0 to provide a suitable coating viscosity for the curable composition. A preferred value for this ratio of hydrogen radicals to vinyl radicals is from 2 to 5 wherein the hydrogen gassing, sometimes observed at higher ratios, is usually avoided.
The number of the silicon-bonded hydrogen radicals and the silicon-bonded vinyl radicals should be measured by suitable analytical techniques.
The amount of hydrosilylation catalyst to be used in the curable silicone release composition is simply that amount which will catalyze the addition of silicon-bonded hydrogen to silicon-bonded vinyl and provide the desired cure time at a particular curing temperature for the curable silicone release compositions. A suitable catalytic amount of hydrosilylation catalyst can be determined by simple experimentation. A compositionsoluble, platinum-containing catalyst is typically used in a sufficient amount to provide from 0.5 to 20 parts by weight of platinum for every one million parts by weight of components (I) plus (II) plus (Ill). A composition-soluble, rhodium-containing catalyst is typically used in sufficient amount to provide from 5 to 40 parts per million of rhodium, on the same weight basis.
The curable silicone release composition may further contain up to 95 percent by weight, based on the weight of the curable composition, of a volatile thinning medium having a normal boiling point of less than 150"C, such as a dispersant or a solvent, to aid in mixing and using the composition, if desired. A volatile thinning medium is advantageously employed when further reduction in the viscosity of the curable silicone composition beyond that conferred by the methylhydrogenpolysiloxane, is desired. Conveniently, the thinning medium is the solvent in which the xylene-soluble copolymer (II) is normally prepared and handled.
Organic thinning media should be free of aliphatic unsaturation.
The curable silicone release composition may further contain additional components which do not adversely interfere with the curing of the composition or its use as a release agent, such as pigments, rheology-control additives, substrate-adhesion promoters and adjuvants to control substrate penetration by the release composition.
The curable silicone release composition is prepared by mixing the desired amounts of the four essential components and any additional components in any suitable manner such as by stirring, blending and!or tumbling and in any suitable order. Preferably, the methylhydrogenpolysiloxane (III) and the hydrosilylation catalyst (IV) are brought together in a final mixing step.
For example, the curable silicone release composition can conveniently be obtained by preparing two non-curing compositions which, when blended in proper proportions, will give rise to the curable silicone release composition. Typically, one of the non-curable compositions comprises a portion of the polydiorganosiloxane (I), the xylene-soluble copolymer (it), optionally containing its processing solvent such as xylene, and the methylhydrogenpolysiloxane (Ill) and another of the non-curing compositions comprises the balance of the polydiorganosiloxane (I) and the hydrosilylation catalyst (IV) and any inhibitor.
Alternatively, one of the non-curing compositions may comprise all of the components except the methylhydrogenpolysiloxane, which constitutes another non-curing composition to be mixed with the first non-curing composition at the proper time.
Any solid substrate may be treated by the process of this invention to provide release of adhesive materials therefrom. Examples of suitable substrates include cellulosic materials, such as paper, cardboard, and wood; metals, such as aluminum, iron and steel; siliceous materials such as ceramics, glass and concrete; and synthetics, such as polyester and polyepoxide. To assure proper curing and adhesion of the curable silicone release composition, the substrate to which it is applied should be clean and free of materials which undesirably inhibit the cure of the release composition, such as materials containing amines, mercaptans and phosphines.
The process of this invention is particularly useful for coating flexible substrates, such as paper, aluminium foil, and tapes to provide controlled release of pressure-sensitive adhesive materials, such as aggressive acrylic adhesives. The curable silicone release composition may be applied in a thin layer to the surface of the flexible substrate to provide a coating with a mass of approximately one gram per square metre of coated surface. In the cured state, many of these coatings will release aggressive acrylic adhesives with a force of no more than 38.61 newtons/metre as measured by the method described in the examples. It is to be understood that thinner or thicker coatings of the release composition may be applied to the substrate, if desired.In the paper coating art, the amount of release coating will generally be applied in an amount between 0.1 and 2.0 grams per square metre of surface.
In the process of the invention, the curable silicone release compositions may be applied to a substrate by any suitable means, such as by brushing, dipping, spraying, rolling and spreading. Flexible substrates, such as paper, may also be coated by any of the well known rolling methods, such as by a trailing blade coater, kiss rolls, gravure rolls and offset printing rolls as desired.
For general applications a practical upper viscosity limitation for the curable silicone release composition is approximately 100 pascal-seconds; however, for coating flexible substrates by rolling methods, a practical upper viscosity limitation is approximately 50 pascal-seconds, preferably 10 pascal-seconds at 25 C. In many instances, the release compositions used in the process of this invention have a viscosity which is useful in the roller methods of coating without comprising a significant amount; for example, less than 5 percent by weight, of a volatile thinning medium.
After application to a substrate, the curable silicone release composition is allowed to cure and any volatile thinning medium is allowed to evaporate. Preferably, the curing and evaporating are accelerated by the application of heat to the applied composition. Heating, usually limited to temperatures less than 300"C, preferably less than 200"C, may be accomplished by any suitable means; however, the curable silicone release composition should not be heated much above room temperature before it is applied because it will rapidly gel and become unusable.
The invention is further illustrated by the following Examples.
For this disclosure, all viscosities were measured in centipoise at 25"C and were converted to pascal-seconds by multiplying by 0.0001 and rounding off. Adhesive release was measured in grams/inch and was converted to newtons/metre by multiplying by 0.3860885 and rounding off. Tensile strength was measured in pounds/square inch and was converted to mega-pascals by multiplying by 6.894757 x 10-3 and rounding off. All parts, percentages and ratios are by weight unless otherwise indicated.
These examples illustrate the viscosity-lowering that is obtained by using a high SiH/SiVi ratio in a curable, vinyl resin-containing silicone release composition.
Examples
Release agents, designated by letters A to L in the Table, were prepared by mixing sufficient polydiorganosiloxane and resin copolymer solution to provide the indicated ratio of non-volatile polydiorganosiloxane to non-volatile resin copolymer. The polydiorganosiloxane consisting of 91 percent of a non-volatile methylphenylvinylsiloxane-endblocked polydimethylsiloxane having a viscosity of approximately 65 pascal-seconds at 25"C and 9 percent volatile cyclic polydimethylsiloxanes.
The resin copolymer solution consisted of 34.5 percent xylene and 65.5 percent of a non-volatile resin copolymer having (CH3)3SiO112, (CH3)2(CH2=CH)SiO,2 and SiO4/2 siloxane units wherein the mol ratio of the sum of the methyl- and vinyl-bearing siloxane units to the Six4,2 siloxane units had a value of 0.7 and the vinyl content was 1.7 percent. The resulting mixtures were devolatilized for 3 hours under reduced pressure and at steam temperatures and, after being cooled, were mixed with sufficient methylhydrogenpolysiloxane to provide the indicated ratio of silicon-bonded hydrogen radicals to silicon-bonded vinyl radicals and 0.004 percent methylbutynol as a platinum-catalyzed cure control additive. The methylhydrogenpolysiloxane had the average formula Me3SiO(Me2SiO)3(MeHSiO)sSiMe3.
The viscosities of these mixtures were then measured with a rotating spindle viscometer at 25"C and are recorded in the Table. The percent viscosity decrease is based on the viscosity of the corresponding comparative composition (A, E or 1).
Samples were prepared for tensile strength and elongation measurements by catalyzing the devolatilized mixture of vinyl-containing polymer vinyl-containing resin copolymer, methylhydrogenpolysiloxane and cure control additive with 0.012 percent of the platinum-containing catalyst containing 0.6 percent platinum.
The platinum-containing catalyst was a complex of H2PtCl6.6H2O and divinyltetramethyldisiloxane, prepared according to U.S. Patent No. 3,419,593. The catlyzed compositions were poured into 7.6 cm x 12.7 cm x 60 mil chases and were heated at 70"C for 15 minutes and at 177"C for 5 minutes. The cured samples, after being cooled, were cut into "dog-bone" samples. Tensile strength and elongation were measured according to
ASTM D-412, using these "dog-bone" samples, and are recorded in the Table.
Adhesive release was measured on compositions A, C, E and G, except that the mixtures of polydiorganosiloxane and resin copolymer solution were not devolatilized before being mixed with methylhydrogenpolysiloxane and catalyst and applied to a substrate.
Catalyzed formulations A, C, E and G were coated into 40 pound supercalendared kraft paper using a blade coater at 35 p.s.i. pressure to give approximately 0.8 grams of coating per square metre of surface. The applid coatings were heated at 1 63"C for 60 seconds to cause curing. A coating was considered to be cured if a piece of adhesive tape would stick to itselfafter having first been adhered to the coating and then removed and its adhesive-bearing surface doubled back on itself. All coatings passed this cure test. The abrasion resistance of each cured formulation was determined by rubbing the cured coating with the index finger to see if rub-off occurred. No rub-off occurred. All coatings therefore passed this test for abrasion resistance.
Each cured release coating was prepared for release testing according to the following procedure. The cured release coating was coated with adhesive using a solution of a commercial acrylic adhesive. The acrylic adhesive solution was applied to the cured coating at a wet thickness of 3 mils (76.2 Fm) using a Bird
Bar. The applied adhesive was air-dried at room temperature for one minute, heated at 70"C for 30 seconds and then cooled to room temperature again for 1 minute. A sheet of 60 pound matte litho was applied to the dried adhesive and the resulting laminate was rolled with 4.5 pound rubber-coated roller and aged for 20 hours at 70 C.
Release testing of the laminates was accomplished by cooling the aged laminates to room temperature, cutting the cooled laminates into 1 inch (25.4 mm) wide strips and pulling the matte/adhesive lamina from the kraft paper/coating lamina at an angle of 1800 (x radians) at 400 inches/minute (0.17 m/s). The force, in grams per inch, that was required to separate the laminae was noted. A composition that results in a release value of no more than 38.61 N/m using this test is considered to display premium release.
The following Table summarizes the release values (converted from grams/inch to newtons/metre) which were obtained.
TABLE
Release Agent
Polydiorganosiloxane (Parts) SiH (mols)
Ref. Resin Copolymer (Parts) SiVi (Mols)
A(1) 80/20 1/1
B -do- 2.5/1
C -do- 4/1
D -do- 10/1 (E)1 60/40 1/1
F -do- 2.5/1
G -do 4/1
H -do- 10/1 (1)1 40/60 1/1
J -do- 2.5/1
K -do- 4/1
L -do- 10/1
TABLE (continued)
Properties
Viscosity Tensile Elongation Adhesive
Ref. Pa.s %Decrease (MPa) (%) Release (N/m) A(1) 41.9 - 2.14 250 9.65
B 33.8 19 1.92 250
C 25.8 38 1.48 280 9.65
D 14.4 66 0.83 310 (E)1 44.6 - 3.47 140 17.4
F 26.9 40 3.54 110
G 16.5 63 3.01 170 27.0
H 4.6 90 0.35 90 (1)1 566 - 1.74 40
J 62 89 1.40 30
K 17.2 97 1.21 40
L 1.8 99 Brittle Brittle (I) For Comparison Purposes
Claims (5)
1. A process for coating a substrate to provide release of adhesive materials therefrom, the process comprising applying a curable silicone release composition to a surface of the substrate and thereafter curing the applied composition, wherein the composition is obtained by mixing components consisting essentially of
(I) a polydiorganosiloxane having the general formula ViR2SiO(R2SiO)x(RViSiO)ySiR2Vi wherein x and y are integers whose sum has an average value sufficient to provide the polydiorganosiloxane with a viscosity at 25 "C of at least 1.0 pascal-seconds, Vi represents a vinyl radical and each R represents, independently, a monovalent radical selected from methyl, phenyl and saturated hydrocarbon radicals having from 2 to 6 carbon atoms, at least 95% of the total number of organic radicals in the polydiorganosiloxane being methyl radicals and no more than 1 percent being vinyl radicals; (II) a xylene-soluble copolymer of (CH3)3SiO112, (CH3)2(CH2=CH)SiO1/2 and SiO4/2 siloxane units, the copolymer having from 1 to 5 percent by weight of vinyl radicals, based on the weight of the copolymer, and a total of from 0.6 to 1.1 of said (CH3)3SiOr,2 plus (CH3)2(CH2=CH)SiO112 siloxane units for every SiO4/2 siloxane unit; (III) a methylhydrogenpolysiloxane, soluble in the mixture of components (I) and (II), and having an average of at least three silicon-bonded hydrogen radicals per molecule, the hydrogen radicals being bonded to separate silicon atoms; and
(IV) a catalytic amount of a hydrosilylation catalyst, the components being mixed in sufficient amounts to provide, in the curable silicone release composition, from 10 to 70 parts by weight of component (II) for every 100 parts by weight of components (I) plus (II) and from 2 to 10 silicon-bonded hydrogen radicals for every silicon-bonded vinyl radical.
2. A process according to Claim 1 wherein the curable silicone release composition contains from 20 to 60 parts by weight of xylene-soluble copolymer for every 100 parts by weight of the mixture of the polydiorganosiloxane (I) and xylene-soluble copolymer (II).
3. A process acording to claim 1 or 2, wherein the curable silicone release composition further contains a volatile thinning medium.
4. A process according to claim 1, substantially as herein described with reference to any of the specific
Examples.
5. A substrate coated with a composition by a process according to any of claims 1 to 4.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US1722879A | 1979-03-05 | 1979-03-05 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2045788A true GB2045788A (en) | 1980-11-05 |
| GB2045788B GB2045788B (en) | 1983-05-11 |
Family
ID=21781441
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8005377A Expired GB2045788B (en) | 1979-03-05 | 1980-02-18 | Method for coating a substrate using a curable silicone release composition |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS55139452A (en) |
| CA (1) | CA1129270A (en) |
| DE (1) | DE3005742C2 (en) |
| FR (1) | FR2450642B1 (en) |
| GB (1) | GB2045788B (en) |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2142925A (en) * | 1983-07-07 | 1985-01-30 | Gen Electric | Transparent membrane structures |
| AU584984B2 (en) * | 1985-02-22 | 1989-06-08 | Toray Silicone Co. Ltd. | Composition for coating optical communication glass fiber |
| EP0358370A2 (en) * | 1988-08-26 | 1990-03-14 | Dow Corning Corporation | Optically clear reinforced organosiloxane compositions |
| US5468828A (en) * | 1993-11-05 | 1995-11-21 | Dow Corning Limited | Silicone release composition |
| US5468816A (en) * | 1993-11-05 | 1995-11-21 | Dow Corning Limited | Silicone release compositions |
| WO2004107458A2 (en) * | 2003-06-03 | 2004-12-09 | Wacker-Chemie Gmbh | Encapsulating composition for led |
| WO2007066011A1 (en) * | 2005-12-09 | 2007-06-14 | Bluestar Silicones France | Anti-fouling polyaddition silicone varnish, application of said varnish to a support and support treated thus |
| WO2013070897A1 (en) * | 2011-11-08 | 2013-05-16 | Dongchan Ahn | Organopolysiloxane compositions and surface modification of cured silicone elastomers |
| EP3149094B1 (en) | 2014-05-27 | 2020-10-28 | Momentive Performance Materials Inc. | Release modifier composition |
| CN114058290A (en) * | 2021-11-18 | 2022-02-18 | 四川富彩科技有限公司 | Solvent-free organic silicon release agent with ultralow release force and preparation method thereof |
Families Citing this family (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4322518A (en) * | 1980-12-02 | 1982-03-30 | Dow Corning Corporation | Curable silicone compositions comprising liquid resin and uses thereof |
| ATE66008T1 (en) * | 1982-09-10 | 1991-08-15 | Gen Electric | METHOD FOR PREPARING AN ANTIADH|SIVEN DIORGANOPOLYSILOXA COMPOSITION. |
| US4537829A (en) * | 1984-09-20 | 1985-08-27 | Dow Corning Corporation | Curable silicone compositions comprising resins |
| JPH0641562B2 (en) * | 1985-05-16 | 1994-06-01 | 東レ・ダウコーニング・シリコーン株式会社 | Curable organopolysiloxane composition |
| US4611042A (en) * | 1985-10-03 | 1986-09-09 | Dow Corning Corporation | Resinous copolymeric siloxanes containing alkenyldimethylsiloxanes |
| JPH0637614B2 (en) * | 1986-07-15 | 1994-05-18 | 東レ・ダウコ−ニング・シリコ−ン株式会社 | Silicone pressure sensitive adhesive composition |
| US5110882A (en) * | 1986-11-28 | 1992-05-05 | Dow Corning Toray Silicone Company, Ltd. | Silicone pressure-sensitive adhesive composition |
| US4861670A (en) * | 1987-12-15 | 1989-08-29 | General Electric Company | Marine foulant release coating |
| US5082706A (en) * | 1988-11-23 | 1992-01-21 | Dow Corning Corporation | Pressure sensitive adhesive/release liner laminate |
| US5281656A (en) * | 1992-12-30 | 1994-01-25 | Dow Corning Corporation | Composition to increase the release force of silicone paper release coatings |
| FR2901800B1 (en) * | 2006-05-31 | 2008-08-29 | Rhodia Recherches & Tech | CROSS-LINKABLE SILICONE COMPOSITION FOR THE PRODUCTION OF ANTI-ADHERENT COATINGS FOR POLYMERIC FILMS |
| KR101620123B1 (en) | 2008-07-30 | 2016-05-12 | 블루스타 실리콘즈 프랑스 에스에이에스 | Silicone composition for coating a flexible support intended to form a crosslinked coating having increased attachment, mechanical strength and reactivity |
| FR2946981A1 (en) | 2009-06-19 | 2010-12-24 | Bluestar Silicones France | SILICONE COMPOSITION RETICULABLE BY DEHYDROGENOCONDENSATION IN THE PRESENCE OF A METAL CATALYST |
| JP5470454B2 (en) | 2009-06-19 | 2014-04-16 | ブルースター・シリコーンズ・フランス・エスアエス | Silicone compositions suitable for crosslinking by dehydrogenative condensation in the presence of non-metallic catalysts |
| KR101346478B1 (en) | 2009-06-19 | 2014-01-02 | 블루스타 실리콘즈 프랑스 에스에이에스 | Silicone composition which is cross-linkable by dehydrogenative condensation in the presence of a non-metal catalyst |
| EP2443177B1 (en) | 2009-06-19 | 2014-04-02 | Bluestar Silicones France | Silicone composition which is cross-linkable by dehydrogenative condensation in the presence of a metal catalyst |
| FR2957604A1 (en) | 2010-03-22 | 2011-09-23 | Bluestar Silicones France | CROSS-LINKABLE SILICONE COMPOSITION FOR THE PRODUCTION OF ANTI-ADHERENT COATINGS FOR FLEXIBLE SUPPORTS AND ADDITIVE PROMOTER FOR HITCHING CONTAINED IN THIS COMPOSITION |
| US9150755B2 (en) | 2011-07-07 | 2015-10-06 | Bluestar Silicones France Sas | Silicone composition that can be cross-linked by means of dehydrogenative condensation in the presence of a carbene-type catalyst |
| US10155883B2 (en) | 2014-06-27 | 2018-12-18 | Dow Silicones Corporation | Silicone release coating composition and low release force emulsion silicone release coating for films and papers having cured release coating |
| EP3353252B1 (en) | 2015-09-25 | 2019-09-11 | ELKEM SILICONES France SAS | Crosslinkable silicone composition for the production of non-stick coatings for flexible substrates and an attachment-promoting additive contained in this composition |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1476314A (en) * | 1973-06-23 | 1977-06-10 | Dow Corning Ltd | Coating process |
| US3900617A (en) * | 1973-11-27 | 1975-08-19 | Gen Electric | Method of rendering flexible sheet material non-adherent and article produced thereby |
| CA1064640A (en) * | 1975-08-18 | 1979-10-16 | Robert W. Sandford (Jr.) | Polysiloxane release coating of a substrate |
| DE2736499C2 (en) * | 1977-08-12 | 1990-03-29 | Wacker-Chemie GmbH, 8000 München | Process for the production of coatings which repel tacky substances |
| JPS55110155A (en) * | 1979-02-16 | 1980-08-25 | Toray Silicone Co Ltd | Organopolysiloxane composition forming releasable film |
-
1979
- 1979-12-18 CA CA342,133A patent/CA1129270A/en not_active Expired
-
1980
- 1980-02-15 DE DE3005742A patent/DE3005742C2/en not_active Expired
- 1980-02-18 GB GB8005377A patent/GB2045788B/en not_active Expired
- 1980-02-18 JP JP1895180A patent/JPS55139452A/en active Pending
- 1980-03-03 FR FR8004705A patent/FR2450642B1/en not_active Expired
Cited By (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2142925A (en) * | 1983-07-07 | 1985-01-30 | Gen Electric | Transparent membrane structures |
| AU584984B2 (en) * | 1985-02-22 | 1989-06-08 | Toray Silicone Co. Ltd. | Composition for coating optical communication glass fiber |
| EP0358370A2 (en) * | 1988-08-26 | 1990-03-14 | Dow Corning Corporation | Optically clear reinforced organosiloxane compositions |
| EP0358370A3 (en) * | 1988-08-26 | 1991-04-10 | Dow Corning Corporation | Optically clear reinforced organosiloxane compositions |
| AU630366B2 (en) * | 1988-08-26 | 1992-10-29 | Dow Corning Corporation | Optically clear reinforced organosiloxane compositions |
| US5468828A (en) * | 1993-11-05 | 1995-11-21 | Dow Corning Limited | Silicone release composition |
| US5468816A (en) * | 1993-11-05 | 1995-11-21 | Dow Corning Limited | Silicone release compositions |
| WO2004107458A3 (en) * | 2003-06-03 | 2005-01-20 | Wacker Chemie Gmbh | Encapsulating composition for led |
| WO2004107458A2 (en) * | 2003-06-03 | 2004-12-09 | Wacker-Chemie Gmbh | Encapsulating composition for led |
| KR100704883B1 (en) | 2003-06-03 | 2007-04-09 | 와커 헤미 아게 | Encapsulating composition for led |
| CN100363428C (en) * | 2003-06-03 | 2008-01-23 | 瓦克化学股份公司 | Encapsulating composition for LED |
| WO2007066011A1 (en) * | 2005-12-09 | 2007-06-14 | Bluestar Silicones France | Anti-fouling polyaddition silicone varnish, application of said varnish to a support and support treated thus |
| FR2894591A1 (en) * | 2005-12-09 | 2007-06-15 | Rhodia Recherches & Tech | ANTI-SOILING POLYADDITION SILICONE VARNISH, APPLICATION OF THIS VARNISH ON A SUBSTRATE AND SUBSTRATE THUS TREATED |
| US8329307B2 (en) | 2005-12-09 | 2012-12-11 | Bluestar Silicones France | Anti-fouling polyaddition silicone varnish, application of this varnish to a support and support thus treated |
| WO2013070897A1 (en) * | 2011-11-08 | 2013-05-16 | Dongchan Ahn | Organopolysiloxane compositions and surface modification of cured silicone elastomers |
| EP3149094B1 (en) | 2014-05-27 | 2020-10-28 | Momentive Performance Materials Inc. | Release modifier composition |
| CN114058290A (en) * | 2021-11-18 | 2022-02-18 | 四川富彩科技有限公司 | Solvent-free organic silicon release agent with ultralow release force and preparation method thereof |
| CN114058290B (en) * | 2021-11-18 | 2023-08-08 | 成都富彩新材料有限公司 | Solvent-free organosilicon release agent with ultralow release force and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3005742C2 (en) | 1982-04-15 |
| GB2045788B (en) | 1983-05-11 |
| FR2450642A1 (en) | 1980-10-03 |
| CA1129270A (en) | 1982-08-10 |
| JPS55139452A (en) | 1980-10-31 |
| FR2450642B1 (en) | 1985-07-19 |
| DE3005742A1 (en) | 1980-09-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |