Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-06-22
2003-07-01
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S477000, C528S015000, C528S020000, C528S031000, C528S032000
Reexamination Certificate
active
06586535
ABSTRACT:
BACKGROUND OF THE INVENTION
During the process of coating silicone on to paper for release coating applications, the formation of silicone mist (i.e. aerosol) is undesirable. Small mist particles, on the order of 1 to 10 microns are considered to be capable of being inhaled and can be deposited deep within the lungs. Silicone mist can also cause hygiene problems by coating everything in the vicinity of the coating head with a layer of silicone.
Solventless silicone coatings have been disclosed in the art. For example, Chung et al. in U.S. Pat. No. 5,036,117 discloses a curable composition comprising (A) an organosilicon compound having an average of at least two curing radicals per molecule thereof selected from the group consisting of the hydroxy radical and olefinic hydrocarbon radicals, (B) an organohydrogensilicon compound containing an average of at least two silicon-bonded hydrogen atoms per molecule thereof, the amounts of Components (A) and (B) being sufficient to provide a ratio of the number of silicon-bonded hydrogen atoms to the number of silicon-bonded curing radicals of from 1/100 to 100/1, (C) a platinum group metal-containing catalyst in sufficient amount to accelerate a curing reaction among said silicon-bonded curing radicals and said silicon-bonded hydrogen atoms, (D) an inhibitor compound for said accelerated curing reaction in a total amount sufficient to retard the curing reaction at room temperature but insufficient to prevent said reaction at elevated temperature, and (E) a bath life extender compound in a total amount sufficient to further retard the curing reaction at room temperature.
Jones et al. in U.S. Pat. No. 5,125,998 discloses a process, the process comprising the steps of (I) first mixing (A) an inhibitor compound and (B) a platinum group metal-containing catalyst, (II) thereafter adding the mixture of (I) to (C) an organosilicon compound having an average of at least two curing radicals per molecule thereof selected from the group consisting of the hydroxy radical and olefinic hydrocarbon radicals, (III) thereafter adding to the mixture of (II) (D) an organohydrogensilicon compound containing an average of at least two silicon-bonded hydrogen atoms per molecule thereof, the amounts of components (C) and (D) being sufficient to provide a ratio of the number of silicon-bonded hydrogen atoms to the number of silicon-bonded curing radicals of from 1/100 to 100/1; (IV) applying the mixture from (II) to a solid substrate to form a coating; (V) exposing the coating to an energy source selected from the group consisting of (i) heat, and (ii) actinic radiation in an amount sufficient to cure the coating; whereby the amount of component (A) present in the total composition of components (A), (B), (C), and (D), is sufficient to retard any curing reaction at room temperature but insufficient to prevent any reaction at elevated temperatures; and whereby the amount of component (B) is sufficient to accelerate any curing reaction among the silicon-bonded curing radicals and the silicon-bonded hydrogen atoms at elevated temperatures.
Thayer et al. in U.S. Pat. No. 5,281,656 discloses coating compositions comprising (A) an alkenyldiorganosiloxy-terminated polydiorganosiloxane, (B) an alkenyldiorganosiloxy-terminated polydiorganosiloxane-polyorganoalkenylsiloxane copolymer, (C) a hydrogendiorganosiloxy-terminated polydiorganosiloxane, (D) a platinum-containing catalyst, and (D) an inhibitor. Thayer et al. further discloses the amounts of Components (A), (B) and (C) that are used in the compositions, expressed in terms of the ratio of the number of silicon-bonded hydrogen atoms of Component (C) to the number of silicon-bonded alkenyl radicals of Components (A) and (B), are sufficient to provide a value of from 1/2 to 20/1 for said ratio and, preferably, from 1/2 to 2/1, and even more preferably, about 1/1.
Silicone compositions which are useful in suppressing silicone mist have also been described in the art. For example, Chung et al. in U.S. Pat. No. 5,625,023 discloses silicone mist suppressant compositions which are prepared by reacting an organosilicon compound, an oxyalkylene containing compound, and a catalyst. Chung et al. further discloses that these compositions, when added to silicone coatings, reduce the amount of silicone mist in high speed coating processes. These silicone mist suppressant compositions were only partially compatible with silicone and produced a cloudy mixture when added to coating formulations. This partial incompatibility was believed to be critical to the mist-suppression performance of these materials. However, the use of these suppressant also introduced new issues with the coverage and anchorage of the silicone release coating.
SUMMARY OF THE INVENTION
This invention relates to silicone coating composition comprising a solventless silicone coating composition and a liquid silicone mist suppressant composition obtained by a method comprising reacting at least one organohydrogensilicon compound containing at least two silicon-bonded hydrogen groups with a large excess of at least one organoalkenylsiloxane containing at least three silicon-bonded alkenyl groups in the presence of a platinum group metal-containing catalyst.
This invention also relates to a method of reducing mist in a solventless silicone coating which comprises adding to a solventless silicone coating a liquid silicone mist suppressant composition obtained by a method comprising reacting at least one organohydrogensilicon compound containing at least two silicon-bonded hydrogen groups with a large excess of at least one organoalkenylsiloxane containing at least three silicon-bonded alkenyl groups in the presence of a platinum group metal-containing catalyst.
The present invention also relates to the use of the silicone suppressant compositions in processes for preparing a laminate of a substrate and an adhesive wherein the adhesive will release from the substrate.
It is an object of this invention to provide a silicone composition which is capable of mist suppression in silicone coatings employed in high speed coating processes.
DETAILED DESCRIPTION OF THE INVENTION
In a first embodiment, this invention relates to a silcone coating composition comprising (A) a solventless silicone coating composition and (B) a liquid silicone mist suppressant composition having a viscosity of from 150 to 50,000 millipascal-seconds (mPa·s) (1 millipascal-second=1 centipoise) obtained by a method comprising mixing: (a) at least one organohydrogensilicon compound containing at least two silicon-bonded hydrogen groups per molecule, (b) at least one organoalkenylsiloxane containing at least three silicon-bonded alkenyl groups per molecule, and (c) a platinum group metal-containing catalyst which is present in an amount sufficient to provide 1 to 250 weight parts of platinum group metal per million weight parts of (a)+(b), with the proviso that the ratio of the number of silicon-bonded hydrogen atoms of Component (a) to the number of silicon-bonded alkenyl groups of Component (b) is less than or equal to 1:4.6.
Component (A), the solventless silicone coating can be any of the well-known solventless hydrosilylation reaction based compositions known in the art. These solventless silicone coating compositions typically comprise (i) an organosilicon compound containing at least two silicon-bonded alkenyl groups per molecule, (ii) an organohydrogensilicon compound containing at least two silicon-bonded hydrogen atoms per molecule, (iii) a platinum group metal-containing catalyst, and (iv) an inhibitor.
The alkenyl groups of Component (i) are exemplified by vinyl, allyl, 3-butenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 10-undecenyl, 4,7-octadienyl, 5,8-nonadienyl, 5,9-decadienyl, 6,11-dodecadienyl and 4,8-nonadienyl.
Component (i) is exemplified by triorganosiloxy-terminated polydiorganosiloxane-polyorganoalkenylsiloxane copolymers, alkenyldiorganosiloxy-terminated polydiorganosiloxane-polyorganoalkenylsiloxane copolymers, triorganosiloxy-terminate
Clark Joseph Norbert
Van Dort Paul Cornelius
Dawson Robert
Dow Corning Corporation
Robertson Jeffrey B.
Scaduto Patricia M.
Troy Timothy J.
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