Low dust silicone-based paper coating process

Abstract

A process includes the steps: (a) providing a base emulsion; (b) providing a catalyst emulsion; (c) providing a stabilizer selected from silicone polyethers, alkyl alkoxylates, olefinic alkoxylates and polyvinyl alcohols; and (d) combining the base emulsion, catalyst emulsion and stabilizer together to form a curable silicone emulsion.

Description

LOW DUST SILICONE-BASED PAPER COATING PROCESSFIELDThe present invention relates to a process for preparing a curable silicone emulsion and includes a coating process using the curable silicone emulsion.INTRODUCTIONCurable silicone-in-water emulsions (“curable silicone emulsions”) are useful as paper coating formulations. Silicone emulsions are particularly desirable as coatings for bakery paper due to the release performance and water resistance that a cured silicone emulsion provides the bakery paper. Silicone emulsion coatings have fewer health concerns than alternative bakery paper options such as coatings containing chrome complexes or fluoropolymers.Curable silicone emulsions for coatings are commonly cured with hydrosilylation chemistry using a hydrosilylation cure catalyst. To prevent premature curing, curable silicone emulsion composition are typically provided in the form of multiple emulsions to keep the catalyst apart from the reactants until the emulsions are combined. The emulsions are usually blended to form a curable silicone emulsion within 12 hours of coating and curing the curable silicone emulsion composition on a substrate. One of the multiple emulsions (a “base emulsion”) typically comprises an alkenyl-functional siloxane and usually a silicon-hydride (SiH) functional siloxane as a crosslinker. A second of the multiple emulsions (a “catalyst emulsion”) typically comprises a hydrosilylation reaction catalyst and usually a siloxane such as an alkenyl-functional siloxane. Sometimes, a third emulsion (an “antifoam emulsion”) comprising an antifoaming agent is combined with the base emulsion and catalyst emulsion when forming a curable silicone emulsion for coating applications.A challenge with curable silicone emulsions in coating applications such as paper coating applications is that the coating process typically results in formation of dust during the coating process, sufficient dust that the coating equipment must be regularly shut down and cleaned. It is desirable, therefore, to reduce the amount of dust generation in the coating process.Another challenge with curable silicone emulsions is achieving sufficient storage stability to facilitate shipping and storage prior to use. It is desirable for the emulsions to remain stable to coalescence and curing for at least 360 days at 25 degrees Celsius (°C). That is one of the reasons why curable silicone emulsions typically come in the form of multiple emulsions that keep the catalyst apart from the reactants until they are mixed proximate in time to coating a substrate.SUMMARYThe present invention provides a solution to reducing dust formation during a coating process when using curable silicone emulsion coatings. The present invention is partially a result of discovering that shear destabilization of a curable silicone emulsion while coating a substrate is a reason for dust formation. Without being bound by theory, one hypothesis on the relationship to shear stability and dust formation is that shear promotes the coalescence of the curable silicone emulsion dispersed phase of coating, resulting in formation of relatively large “beads” of coating material upon curing. Beads, in turn, cause discontinuity of the cured films and mechanical integrity defects promoting cohesive failure and migration of cured materials into dust onto production elements during the process. Hence, increasing shear stability of the curable silicone emulsion should reduce dust formation. It should also help produce a more uniform coating with higher cohesive strength on the substrate due to a smaller particle size and more homogeneously sized dispersed phase prior to film formation and curing.The process of the present invention includes adding a particular stabilizer to one or more of the silicone emulsions used for making the curable silicone emulsion. When the silicone emulsions are combined with the stabilizer, the result is a curable silicone emulsion that is more stable to shear than a similar curable silicone emulsion without the additive. Notably, the present work has also discovered and demonstrated that the stabilizer needs to be added to the emulsion(s) after the emulsion(s) are made rather than added during or prior to emulsification of the emulsion(s) in order to both optimally improve shear stability of the resulting curable silicone emulsion and ensure a storage stability of at least 360 days. Data herein below shows that a base emulsion that is storage stable for greater than 360 days becomes notably less stable by including stabilizer during formation of the base emulsion instead of after forming the emulsion. To ensure storage stability, the stabilizer should be added after formation of the emulsion, preferably within 12 hours of using the silicone emulsion in a curable silicone emulsion coating application.The stabilizers that have been found successful in increasing shear stability in the process of the present invention are selected from a group consisting of: silicone polyethers, alkyl alkoxylates, olefinic alkoxylates, and polyvinyl alcohols; wherein the silicone polyethers, alkyl alkoxy lates and olefinic alkoxylates have a molecular weight of 3,000 grams per mole (g / mol) or less, preferably 1,000 g / mole or less, as determined by the calculating the sum of the atomic masses for each atom in the molecule.Lower molecular weight stabilizers are desirable because they are easier to mix thoroughly into a silicone emulsion. Typically, the stabilizer is in a form other than being in an emulsion when added to a silicone emulsion.In a first aspect, the present invention is process comprising the following steps: (a) providing a base emulsion comprising water, surfactant, alkenyl-functional siloxane, and SiH- functional siloxane and having a dispersed particle size with a Dv(0.9) value of one micrometer or more and at the same time less than 3 micrometers as measured as a value determined using laser diffraction spectroscopy with a Malvern Mastersizer 3000 instrument; (b) providing a catalyst emulsion comprising water, surfactant, alkenyl-functional siloxane and hydrosilylation catalyst; (c) providing a stabilizer selected from a group consisting of silicone poly ethers, alkyl alkoxylates, olefinic alkoxylates, and polyvinyl alcohols; wherein the silicone polyethers, alkyl alkoxylates and olefinic alkoxylates have a molecular weight of 3,000 grams per mole or less as determined by the calculating the sum of the atomic masses for each atom in the molecule; and (d) combining the base emulsion, catalyst emulsion and stabilizer together to form a curable silicone emulsion.The process of the present invention is useful for preparing a curable silicone emulsion for use as a coating as well as providing a process for coating a substrate with a curable silicone emulsion.DETAILED DESCRIPTIONTest methods refer to the most recent test method as of the priority date of this document when a date is not indicated with the test method number. References to test methods contain both a reference to the testing society and the test method number.Materials identified only by a product name or tradename refer to the material sold under that product name or tradename at the priority filing date of this document unless otherwise stated herein.“Multiple” means two or more. “And / or” means “and, or as an alternative”. All ranges include endpoints unless otherwise indicated. The sum of components in a composition do not exceed 100 weight-percent or volume-percent based respectively on the weight or volume of the composition.“Silicone emulsion” refers to a silicone-in-water emulsion where a silicone phase resides as a dispersed phase in a continuous aqueous phase.“Curable silicone emulsion” refers to a silicone emulsion that can undergo a curing (crosslinking) reaction between silicone components.“Dv(0.9)” refers to a value for a dispersed phase particle size in an emulsion where 90 percent of the volume of the dispersed phase particles are smaller than the Dv(0.9) value. Determine Dv(0.9) values for emulsions herein using laser diffraction spectroscopy with a Malvern Mastersizer 3000 instrument.Determine viscosity for siloxane polymers according to ASTM method D4283-98.In a first aspect, the present invention is a process. The process comprises a process for preparing a curable silicone emulsion. The process can further comprise steps of coating the curable silicone emulsion onto a substrate.The process of the present invention comprises: (a) providing a base emulsion; (b) providing a catalyst emulsion; (c) providing a stabilizer; and (d) combing the base emulsion, catalyst emulsion and stabilizer together to form a curable silicone emulsion. The stabilizer can be added to the base emulsion prior to combining the base emulsion and catalyst emulsion. The stabilizer can be added to the catalyst emulsion prior to combining the base emulsion and catalyst emulsion. The stabilizer can be added to an emulsion resulting from a combination of the base emulsion and catalyst emulsion. In the broadest scope of the invention, there is no restriction on at what point the stabilizer is combined with the base emulsion and catalyst emulsion.(a) Base EmulsionThe base emulsion comprises water, surfactant, alkenyl-functional siloxane and silylhydride (SiH)-functional siloxane.WaterWater serves as the continuous phase of the base emulsion. Water is typically present at a concentration of 30 wt% or more, and can be 35 wt% or more, 40 wt% or more, 42 wt% or more, even 45 wt% or more, while at the same time is typically present at a concentration of 55 wt% or less, 52 wt% or less, 50 wt% or less, 48 wt% or less, 46 wt% or less, even 45 wt% or less, with wt% values based on base emulsion weight.SurfactantSurfactants are useful for stabilizing the components of the present invention as an emulsion and / or dispersion in a water-continuous phase.The surfactant can be nonionic and / or ionic. Preferably, the surfactant is nonionic. Suitable surfactants can be selected from those that are known and the art and are commercially available. Suitable nonionic surfactants include alkylphenols, fatty alcohols or fatty acids with alkylene oxide groups, such as ethylene oxide or propylene oxide groups. Suitable ionic surfactants include anionic surfactants such as sulfates, sulfonates, phosphates, andsulfosuccinates. Suitable surfactants for use herein are exemplified by those described as surfactant (G) in U.S. Patent Application Publication 2007 / 0099007 at paragraphs

[0167] to

[0176] .It can be desirable to use a combination of surfactants. For instance, polyvinyl alcohol (PVA) can be a primary surfactant and a poly(oxy- 1 ,2-ethanediyl) can be a co-surfactant.Examples of surfactants for use in the present invention include those available under the names PVA 40 TAD from BIM Kemi AB and LUTENSOL ™ XP100 (LUTENSOL is a trademark of BASF SE).The concentration of surfactants in the coating composition is typically greater than zero, preferably 10 wt% or more, 12 wt% or more, 14 wt% or more, 15 wt% or more, 16 wt% or more, 18 wt% or more, even 20 wt% or more, while at the same time is typically 25 wt% or less, 22 wt% or less, 20 wt% or less, 18 wt% or less, 16 wt% or less, with wt% values based on base emulsion weight.Alkenyl-functional siloxaneThe alkenyl-functional siloxane polymer preferably has at least two silicon-bonded alkenyl-functional groups per molecule. The alkenyl group is preferably linear having up to 6 carbon atoms, as exemplified by vinyl, allyl or pentenyl, and hexenyl, groups as well as cycloalkenyl groups such as cyclohexenyl. Vinyl groups may be desirable for cost and regulations reasons, especially for food related uses.The organopolysiloxane containing alkenyl groups can contain terminal and / or pendant alkenyl groups. If the organopolysiloxane has terminal alkenyl groups it is an alkenyl-terminated polydiorganosiloxane. The alkenyl-functional siloxane polymer can for example be a linear organopolysiloxane having the general formula:YX2SiO(X2SiO)x(XYSiO)ySiX2Y wherein each X denotes independently a phenyl group or an alkyl or cycloalkyl group having from 1 to 10 carbon atoms, for example, methyl, ethyl, propyl, butyl or cyclohexyl; each Y denotes an alkenyl group; subscript x typically has a value of zero or more, preferably 20 or more, 40 or more, 60 or more, 80 or more, 100 or more, even 120 or more while at the same time is typically 500 or less, and can be 250 or less, 200 or less, 150 or less, 140 or less, 130 or less, even 120 or less; subscript y typically has a value of zero or more, preferably 20 or more, 40 or more, 60 or more, 80 or more, 100 or more, even 120 or more while at the same time is typically 500 or less, and can be 250 or less, 200 or less, 150 or less, 140 or less, 130 or less, even 120 or less; and desirably x and y are such that the organopolysiloxane has a viscosity at 25° C in arange from 5 to 10,000 square millimeters per second (mm / s), more preferably 50 to 500 mm2 / s. The organopoly siloxane containing alkenyl groups can be a linear vinyl end-capped siloxane polymer such as a dimethylvinylsiloxy-terminated polydiorganosiloxane, or a hexenyl terminated polydiorganosiloxane, such as a dimethyl (5-hexenyl)siloxy-terminated polydiorganosiloxane. Preferably, at least 50% of all the X substituents of the alkenyl-functional siloxane polymer are methyl groups, most preferably all being methyl groups. It is possible but not preferred that small amounts (preferably less than 10% of all the substituents present) of other substituents are present, for example hydroxyl groups. Alternatively, the organopolysiloxane containing alkenyl groups is free of substituents extending from the polysiloxane backbone other than hydrocarbyl groups. An example of a suitable linear organopolysiloxane containing alkenyl groups is a linear vinyl end-capped polydimethylsiloxane having an average of 120 dimethylsiloxane units, which is commercially available from Gelest under the name DMS-V22.The alkenyl-functional siloxane polymer can be a branched siloxane comprising one or more Q units of the formula (SiO.4 / 2), from 15 to 995 D units of the formula Rb2SiO2 / 2 and M units of the formula RaRb2SiOi / 2- wherein the Raand Rbsubstituents are selected from alkyl groups having 1 to 6 carbon atoms and alkenyl groups having 2 to 6 carbon atoms. Preferably the Rbsubstituents are alkyl groups, most preferably methyl groups. At least two, and preferably at least three, Rasubstituents in such a Q-branched siloxane are alkenyl groups, as described in EP- A- 1070734. Vinyl groups can be present as methylvinylsiloxane units. Such a siloxane may for example be a poly(dimethylsiloxane-silicate) copolymer having at least three vinyldimethylsilyl-terminated siloxane branches. The branched siloxane can also incorporate other terminal groups such as terminal trimethylsilyl (SiMej) and / or terminal hydroxydimethylsilyl (SiMe2OH) groups. The Q branched siloxane can contain other additional branching groups, for example it can also incorporate units. Branched siloxanes have the advantage that they allow faster cure than linear polymers with similar viscosities.The alkenyl-functional siloxane polymer is typically present at a concentration of 25 wt% or more, 28 wt% or more, 30 wt% or more, 32 wt% or more, 34 wt% or more, even 35 wt% or more while at the same time is typically 45 wt% or less, 40 wt% or less, or even 38 wt% or less with wt% values based on base emulsion weight.The SiH-functional siloxaneThe silylhydride (SiH)-functional siloxane polymer generally contains an average of at least 2 or 3 SiH groups per molecule. The SiH-functional siloxane polymer can have the general formula:Rt3SiOl / 2((CH3)2SiO2 / 2)d(RL2SiO2 / 2)e)SiOl / 2 Rl3 where each R1can be an alkyl group having 1 to 4 carbon atoms or hydrogen, d and e are 0 or any number such that d+e is from 8 to 400. Preferably the SiH-functional siloxane polymer comprises at least two or three methylhydrogensiloxane units. The SiH-functional siloxane polymer can for example be a poly(methylhydrogensiloxane) having trimethylsilyl terminal units or a dimethylsiloxane methylhydrogensiloxane copolymer having trimethylsilyl terminal units. The crosslinking agent can alternatively contain SiH groups in a linked cyclic polyorganosiloxane structure. Such linked cyclic polyorganosiloxanes can be produced by reacting a cyclic polysiloxane containing at least two SiH groups with a compound having aliphatic unsaturation or containing a hydroxy group, for example a silane or polyorganosiloxane having aliphatic unsaturation or containing a hydroxy group as described in US7378482.The SiH-functional siloxane polymer can be an MQ resin consisting of units of the general formula SiO4 / 2 and Rq3SiOi / 2 wherein at least three Rqsubstituents in the MQ resin molecule are hydrogen atoms and the remainder are alkyl groups, or may be a rake or comb polymer comprising a polydiorganosiloxane chain containing one or more T or Q unit having a subchain of diorganosiloxane and organohydrogensiloxane units attached thereto.Preferably, the SiH-functional siloxane polymer has a viscosity of from 5 to 1000 mm2 / s at 25° C, more preferably 20 to 350 mm / s, most preferably 50 to 300 mm / s.The SiH-functional siloxane polymer is typically present at a concentration of 1.0 wt% or more, 1.2 wt% or more, 1.3 wt% or more, 1.4 wt% or more, even 1.5 wt% or more, while at the same time is typically 2.0 wt% or less, 1.8 wt% or less, 1.6 wt% or less, even 1.5wt% or less, with wt% values based on base emulsion weight.Non-reactive siloxane polymerThe base emulsion can comprise a non-reactive siloxane polymer. The non-reactive siloxane polymer is an optional component. It can be desirable to include the non-reactive siloxane polymer to, for example, serve as a surface lubricating agent useful in industrial processes where friction and shear apply. It can also be desirable to minimize or avoid use of non-reactive siloxane polymers because they can be extractable components from resulting cured coating, which can be undesirable particularly in food applications. The non-reactivesiloxane polymer is free of reactive groups such as SiH groups, alkenyl groups, and hydroxyl groups. Typically, the non-reactive siloxane polymer has only hydrocarbyl groups bound the silicon atoms of the siloxane polymer.Typical non-reactive siloxane polymer for use in the present invention are linear trimethyl end-blocked poly dimethylsiloxanes. The non-reactive siloxane polymer can have the following average structure:[(CH3)3SiO][(CH3)2SiO]w[(CH2)3Si] where subscript w is typically 5 or more, and can be 10 or more, 20 or more, 30 or more, 40 or more, 50 or more, 75 or more, 100, or more, 150 or more, even 200 or more and at the same time is typically 120,000 or less, and can be 100,000 or less, 80,000 or less, 70,000 or less, 60,000 or less, 50,000 or less, 40,000 or less, 30,000 or less, 20,000 or less, 10,000 or less, 9000 or less, 8000 or less, 7000 or less, 6000 or less, 5000 or less, 4000 or less, 2000 or less, 1000 or less, 800 or less, 600 or less, even 500 or less. DOWSIL™ 200 fluid products are examples of suitable linear trimethyl end-blocked polydimethylsiloxanes. One example of a suitable linear trimethyl end-blocked polydimethylsiloxane has an average viscosity of 12,500 mm2 / s and is available under the name DOWSIL™ 200 Fluid 12,500 cst from The Dow Chemical Company (DOWSIL is a trademark of The Dow Chemical Company).The concentration of non-reactive siloxane polymer in the coating composition is zero wt% or more and can be 1.0 wt% or more, 1.2 wt% or more, 1.4 wt% or more, 1.6 wt% or more, 1.8 wt% or more, 1.9 wt% or more, even 2.0 wt% or more, while at the same time is typically 2.5 wt% or less, and can be 2.3 wt% or less, 2.1 wt% or less, or even 2.0 wt% or less, with wt% values based on base emulsion weight.InhibitorThe base emulsion can comprise an inhibitor. Inhibitors are hydrosilylation inhibitors can be used for altering when and / or how fast the hydrosilylation reaction occurs. Hydrosilylation inhibitor can be, for example, one or more than one material selected from a group consisting of an acetylenic alcohol, an acetylenic alcohol, an ene-yne compound, a triazole, a phosphine, a mercaptan, a hydrazine, an amine, a fumarate, a maleate, an ether, carbon monoxide, an alkenyl-functional siloxane oligomer, and a combination of two or more thereof.Acetylenic alcohols are exemplified by 3,5-dimethyl-l-hexyn-3-ol, l-butyn-3-ol, 1- propyn-3-ol, 2-methyl-3-butyn-2-ol, 3 -methyl- l-butyn-3-ol, 3 -methyl- l-pentyn-3-ol, 3-phenyl- l-butyn-3-ol, 4-ethyl-l-octyn-3-ol, 3,5-dimethyl-l-hexyn-3-ol, and 1-ethynyl-l -cyclohexanol,and a combination thereof. The acetylenic alcohol can be a silylated acetylenic compound. Without wishing to be bound by theory, it is thought that adding a silylated acetylenic compound reduces yellowing of the reaction product prepared from hydrosilylation reaction as compared to a reaction product from hydrosilylation of starting materials that do not include a silylated acetylenic compound or that include an organic acetylenic alcohol inhibitor, such as those described above. Silylated acetylenic compounds are exemplified by (3-methyl-l -butyn-3- oxy)trimethylsilane, ((l,l-dimethyl-2-propynyl)oxy)trimethylsilane, bis(3-methyl-l-butyn-3- oxy)dimethylsilane, bis(3-methyl-l-butyn-3-oxy)silanemethylvinylsilane, bis((l,l-dimethyl-2- propynyl)oxy)dimethylsilane, methyl(tris(l,l-dimethyl-2-propynyloxy))silane, methyl(tris(3- methyl-l-butyn-3-oxy))silane, (3-methyl-l-butyn-3-oxy)dimethylphenylsilane, (3-methyl-l- butyn-3-oxy)dimethylhexenylsilane, (3-methyl-l -butyn-3-oxy)triethylsilane, bis(3-methyl-l- butyn-3-oxy)methyltrifluoropropylsilane, (3,5-dimethyl-l-hexyn-3-oxy)trimethylsilane, (3- phenyl-l-butyn-3-oxy)diphenylmethylsilane, (3-phenyl-l-butyn-3-oxy)dimethylphenylsilane, (3-phenyl-l-butyn-3-oxy)dimethylvinylsilane, (3-phenyl-l-butyn-3-oxy)dimethylhexenylsilane, (cyclohexyl- 1 -ethyn- 1 -oxy )dimethylhexenylsilane, (cyclohexyl- 1 -ethyn- 1 - oxy)dimethylvinylsilane, (cyclohexyl- 1 -ethyn- 1 -oxy)dipheny Imethylsilane, (cyclohexyl- 1 - ethyn- l-oxy)trimethylsilane, and combinations thereof. The silylated acetylenic compound useful as the inhibitor herein may be prepared by methods known in the art, for example, U.S. Patent 6,677,407 to Bilgrien, et al. discloses silylating an acetylenic alcohol described above by reacting it with a chlorosilane in the presence of an acid receptor.Ene-yne compound include 3-methyl-3-penten-l-yne; 3,5-dimethyl-3-hexen-l-yne; and a combinations thereof. Triazole include benzotriazole.Amines are exemplified by tetramethyl ethylenediamine, 3-dimethylamino-l-propyne, n- methylpropargylamine, propargylamine, 1-ethynylcyclohexylamine, or a combination thereof.Fumarates include dialkyl fumarates such as diethyl fumarate, dialkenyl fumarates such as diallyl fumarate, dialkoxyalkyl fumarates such as bis-(methoxymethyl)ethyl fumarate.Maleates include dialkyl maleates such as diethyl maleate, dialkenyl maleates such as diallyl maleate, and dialkoxyalkyl maleates such as bis-(methoxymethyl)ethyl maleate.The inhibitor may comprise an alkenyl-functional siloxane oligomer, which may be cyclic or linear such as methylvinylcyclosiloxanes exemplified by l,3,5,7-tetramethyl-l,3,5,7- tetravinylcyclotetrasiloxane, l,3,5,7-tetramethyl-l,3,5,7-tetrahexenylcyclotetrasiloxane, 1,3- divinyl-l,3-diphenyl-l,3-dimethyldisiloxane; l,3-divinyl-l,l,3,3-tetramethyldisiloxane; and a combination of two or more thereof.The concentration of hydrosilylation reaction inhibitor in the coating composition is zero wt% or more, and can be 0.05 wt% or more, 0.10 wt% or more, even 0.15 wt% or more, while at the same time is typically 0.30 wt% or less, 0.20 wt% or less, or even 0.15 wt% or less, with wt% values based on base emulsion weight.Acid / Base BufferThe base emulsion can comprise an acid / base buffer, which is a combination of acid and a base that serve as a buffer to maintain the coating composition at a pH of less than 7. In the broadest scope of the invention, the acid / base buffer (buffer) can be any acid / base buffer. The acid / base buffer typically comprises a mono or polyprotic acid and its conjugate base. For example, one example of a suitable buffer comprises HCO v / CO r" and H2PO47HPO42‘ as described as agent F in U.S. Patent Application Publication 2007 / 0099007 at paragraphs

[0145] to

[0147] may be used herein. The buffer can comprise NaCCh and NaHCO v The buffer can comprise citric acid and a citrate salt such as potassium citrate or sodium citrate. The acid / base buffer can be formed by combining a polyprotic acid (such as citric acid) with a base (such as sodium hydroxide) at a molar ratio such that fewer than all of the polyprotic acid is neutralized. One of ordinary skill can choose appropriate relative concentrations of selected acids and bases as well as the required amount of total buffer necessary to achieve a buffer that maintains a pH of less than 7 for a given coating composition. Desirably, the buffer maintains the coating composition at a pH of 7 or less, but it can maintain it at a pH of 6 or less, while at the same time the buffer desirably maintains the coating composition at a pH of 2 or more, even 3 or more, or 4 or more.The amount of the acid / base buffer (combination of acid and its conjugate base) is typically 0 wt% or more, preferably 0. 10 wt% or more, 0.20 wt% or more, 0.30 wt% or more, 0.40 wt% or more, even 0.45 wt% or more, and at the same time is typically 0.80 wt% or less, 7.0 wt% or less, 6.0 wt% or less, even 5.0 wt% or less based on base emulsion weight.BiocideThe base emulsion can comprise a biocide. Biocide is desirable in the present coating composition to inhibit growth of undesirable organisms in the coating composition. It is particularly desirable considering the presence of the alkyl and / or alkenyl succinic anhydride- modified starch component. The coating composition can contain multiple biocides as the biocide component.Suitable biocides include any biocides known in the art. For example, the biocide can be a fungicide, an herbicide, a pesticide, an antimicrobial agent, or a combination of two or more thereof. Exemplary biocides are disclosed, for example, in U.S. Patent 9,221,041.Specific examples of suitable biocides for use in the present invention include those available under the names KATHON™ LXE (KATHON is a trademark of Nutrition & Biosciences USA2, LLC) and BIOBAN™ 1530 (BIOBAN is a trademark of LANXESS Corporation).The concentration of biocide in the coating composition is typically zero wt% or more and can be 0.05 wt% or more, 0.75 wt% or more, 0. 10 wt% or more, 0. 12 wt% or more, even 0.13 wt% or more, while at the same time is typically 0.30 wt% or less, or 0.20 wt% or less, even 0.15 wt% or less, with wt% values based on base emulsion weight.Dispersed Phase Particle SizeThe base emulsion has a dispersed phase with a Dv(0.9) value of one micrometer or more and at the same time less than 3 micrometers, preferably 2 micrometers or less. To prepare the base emulsion it is suitable to blend together the polymer components, then blend in the surfactant(s), then the remaining components other than water. Then emulsify by blending in the water component. Examples, below, describe specific examples of base emulsions. Use sufficient shear in preparing the base emulsion to obtain an emulsion with a dispersed phase with a Dv(0.9) value of one micrometer or more and at the same time less than 3 micrometers, preferably 2 micrometers or less.(b) Catalyst EmulsionThe catalyst emulsion comprises water, surfactant, alkenyl-functional siloxane and hydrosilylation catalyst. The amount of catalyst emulsion in the process of the present invention is typically 0.5 wt% or more, preferably 0.75 wt% or more, and can be 1.0 wt% or more, even 1.25 wt% or more, while at the same time is typically 2.5 wt% or less, and can be 2.0 wt% or less, 1.5 wt% or less, or even 1.25 wt% or less relative to weight of curable silicone emulsion.WaterThe catalyst emulsion is a water continuous emulsion. The amount of water is typically 30 wt% or more, 35 wt% or more, 40 wt% or more, even 45 wt% or more, while at the same time is typically 55 wt% or less, 50 wt% or less, even 46 wt% or less based on catalyst emulsion weight.SurfactantThe catalyst emulsion further comprises a surfactant as described for the base emulsion that is typically present at a concentration of 10 wt% or more, 12 wt% or more, even 14 wt% or more, while at the same time is typically 20 wt% or less, 18 wt% or less, 16 wt% or less, even 15 wt% or less based on catalyst emulsion weight.Non-Aqueous ComponentThe catalyst emulsion contains a non-aqueous component that becomes dispersed in the continuous aqueous phase of the catalyst emulsion. The non-aqueous component typically comprises, or is, a component selected from one or a combination of more than one in a group consisting of alkenyl-functional siloxane and non-reactive siloxane polymer. The alkenyl- functional siloxane and non-reactive siloxane polymer can be selected from those suitable for the base emulsion as described above. Desirably, the catalyst emulsion is free of SiH-functional siloxane, which can react with water in the presence of the hydrosilylation catalyst.The non-aqueous component in the catalyst emulsion typically comprises, or is, an alkenyl-functional siloxane as described for the base emulsion at a concentration of 20 wt% or more, 25 wt% or more, 30 wt% or more, 31 wt% or more 32 wt% or more, even 33 wt% or more, while at the same time typically 45 wt% or less, 40 wt% or less, 38 wt% or less, 36 wt% or less, 35 wt% or less, or even 34 wt% or less, with wt% based on catalyst emulsion weight.Hydrosilylation CatalystThe catalyst emulsion comprises a hydrosilylation catalyst. The hydrosilylation catalyst preferably comprises a platinum group metal that is a group VIII metal such as platinum (Pt), ruthenium, rhodium, palladium, osmium or indium. Suitable hydrosilylation catalysts include complexes or compounds of these platinum group metals, particularly platinum compounds or complexes including chloroplatinic acid, either in hexahydrate form or anhydrous form, and or a platinum-containing catalyst which is obtained by a method comprising reacting chloroplatinic acid with an aliphatically unsaturated organosilicon compound such as divinyltetramethyldisiloxane, platinum acetylacetonate, complexes of platinous halides with unsaturated compounds, for example, ethylene, propylene, organovinylsiloxanes and styrene, hexamethyldiplatinum, alkene-platinum-silyl complexes such as (COD)Pt(SiMeCb)2, where COD is 1,5-cyclooctadiene and Me is methyl, PtCb.PtCh and Pt(CN)3. Alternatively, the catalyst may be a rhodium complex, for example, RhCh(Bu2S)3.Platinum-based hydrosilylation catalysts include compounds and complexes such as platinum (0)-l,3-divinyl-l,l,3,3-tetramethyldisiloxane (Karstedt’s catalyst), PpPtCle, di-p..- carbonyl di-.7i.-cyclopentadienyldinickel, platinum-carbonyl complexes, platinum- divinyltetramethyldisiloxane complexes, platinum cyclovinylmethylsiloxane complexes, platinum acetylacetonate (acac), platinum black, platinum compounds such as chloroplatinic acid, chloroplatinic acid hexahydrate, a reaction product of chloroplatinic acid and a monohydric alcohol, platinum bis(ethylacetoacetate), platinum bis(acetylacetonate), platinum dichloride, andcomplexes of the platinum compounds with olefins or low molecular weight organopolysiloxanes or platinum compounds microencapsulated in a matrix or core-shell type structure. The hydrosilylation catalyst can be part of a solution that includes complexes of platinum with low molecular weight organopolysiloxanes that include 1,3-diethenyl-l, 1,3,3- tetramethyldisiloxane complexes with platinum. These complexes may be microencapsulated in a resin matrix.The concentration of hydrosilylation catalyst can vary depending on the desires and is not particularly limited provide catalyst is ultimately present in the curable silicone emulsion at a sufficient concentration to increase the reaction rate of a hydrosilylation reaction between the alkenyl-functional siloxane polymer and the SiH-functional siloxane polymer in the final curable silicone emulsion. The concentration of actual catalyst compound will vary depending on what catalyst compound is in the coating composition. For the particular Karstedt’ s catalyst composition used in the examples of the present invention, the concentration of the catalyst composition is typically one wt% or more, 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% or more, or even 6 wt% or more, while at the same time is typically 10 wt% or less, 9 wt% or less, 8 wt% or less, or even 7 wt% or less, with wt% values based on catalyst emulsion weight.Acid / Base BufferThe catalyst emulsion can, and desirably does, also comprise an acid / base buffer as described for the base emulsion. The concentration of acid / base buffer is typically 0.20 wt% or more, and can be 0.25 wt% or more, 0.30 wt% or more, 0.35 wt% or more, even 0.40 wt% or more, while at the same time is typically 0.60 wt% or less, 0.50 wt% or less, or even 0.45 wt% or less, with wt% relative to the catalyst emulsion weight.BiocideThe catalyst emulsion can comprise a biocide, as described for the base emulsion. The concentration of biocide is typically 0.05 wt% or more, 0.08 wt% or more, 0.10 wt% or more, 0.12 wt% or more, even 0.13 wt% or more, while at the same time is typically 0.20 wt% or less, 0.18 wt% or less, 0.16 wt% or less, or even 0.14 wt% or less, with wt% based on catalyst emulsion weight.(c) StabilizerAn important feature of the present invention for achieving shear stability in the curable silicone emulsion is addition of a stabilizer to one or more of the base emulsion and catalyst emulsion, or to an emulsion blend of the base emulsion and catalyst emulsion. Notably, any oneof the stabilizers can be in a form other than an emulsion when it is blended with the base emulsion and / or catalyst emulsion.The stabilizer is selected from a group consisting of silicone polyethers, alkyl alkoxylates, olefinic alkoxylates, and polyvinyl alcohols. The silicone polyethers, alkyl alkoxylates and olefinic alkoxylates are limited to those having a molecular weight that is 3,000 grams per mole (g / mol) or less, preferably 2,000 g / mol or less, even more preferably 1 ,000 g / mol or less. Determine molecular weight of the stabilizer from the chemical structure of the stabilizer by adding together the atomic weight of the atoms in the chemical structure. Lower molecular weight stabilizers are desirable to facilitate easy mixing into an emulsion to form a uniform mixture of the stabilizer in the emulsion.Silicone polyethers comprise both a siloxane segment and a polyether segment. Suitable silicone poly ethers typically have a molecular weight that is 3,000 grams per mole (g / mol) or less as determined from the chemical structure of the silicone polyether by adding the atomic masses of the individual atoms in the molecule. Silicone polyethers contain a siloxane segment and a polyether (polyalkylene oxide) segment. The polyether segment typically comprises or consists of ethylene oxide (EO) and / or polypropylene oxide (PO) segments that are terminal or grafted segments on the polyalkylene oxide. Desirably, the poly alkylene oxide component comprises or consists of EO segments. The polyalkylene oxide segment typically comprise terminal hydroxyl (OH) groups, acetoxyl (OAc) groups, or alkoxyl (OR) groups where R is desirably an alkyl group having 3 or fewer, 2 or fewer, preferably one carbon atom. The wt% of siloxane segment is typically 25 to 85 wt% of the silicone polyether weight. The siloxane segment is typically a linear siloxane comprising M-type and D-type siloxane units with a degree of polymerization (number of D-type siloxane units) that is in a range of 2.5 to 25. The silicone polyether typically has a hydrophilic / lipophilic balance (HLB) that is in a range of 8.0 to 18.0, preferably 12.0 to 18.0, as determined by calculating the Cohesive Energy Ratio (CER) using the equation: HLB = (0.925-log(CER) / 0.0963) Determine CER following the well-known approach of Beerbower and Hill as described, for instance, in Encyclopedia of Emulsion Technology Vol. 3, Basic theory, measurement, applications; by Paul Becher (1988) page 81 and 82 with citations 35, 48 and 49; and in C. Holtzcherer and F. Candau, Colloids and Surfaces, 29 (1988) 411-423.One particularly desirable silicone polyether stabilizer is a polyoxyethylene modified heptamethytrisoloxane (7.8 ethylene oxide units on average per molecule with polyglycol H end cap) having an average chemical structure: (CH3)3SiOSi(CH3)2OSi(CH3)2(CH2CH2O)7.sH,which is commercially available under the name DOWS1L™ 67 Additive from The Dow Chemical Company. DOWSIL is a trademark of The Dow Chemical Company. Another particularly desirable silicone polyether stabilizer is a polyoxyethylene modified polydimethylsiloxane (11.2 EO units on average, polyglycol acetate end cap), which is commercially available as XIAMETER™ OFX-5098 Fluid from The Dow Chemical Company. XIAMETER is a trademark of Dow Silicones Corporation.Alkyl alkoxylates are alkoxylates with a terminal alkyl group. Particularly suitable alkyl alkoxylates include alkyl ethoxylates having a general chemical structure: RO(CH2CH2O)eH, where R is an alkyl group typically having 2 or more, preferably 3 or more, can have 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, even 10 or more carbon atoms, while at the same time typically has 30 or fewer, 25 or fewer, 20 or fewer, 15 or fewer, even 10 or fewer carbon atoms; and where subscript e is the average number of (CH2CH2O) units per molecule and typically has a value of 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, even 10 or more, while at the same time typically has a value of 20 or fewer, 15 or fewer, even 10 or fewer. One particularly desirable alkyl alkoxylate stabilizer is poly(oxy-l,2-ethanediyl) with an average chemical structure C10H21 OiClTCFhOjioH, which is commercially available under the name LUTENSOL™ XP100 from BASF. LUTENSOL is a trademark of BASF SE.Alkenyl alkoxylates are alkoxylates with a terminal alkenyl group. Particularly suitable alkyl alkoxylates include alkyl ethoxylates having a general chemical structure: R’O(CH2CH2O)eH, where R’ is an alkenyl-containing group, preferably a terminally unsaturated alkenyl-containing group, typically having 2 or more, preferably 3 or more, can have 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, even 10 or more carbon atoms, while at the same time typically has 30 or fewer, 25 or fewer, 20 or fewer, 15 or fewer, even 10 or fewer carbon atoms; and where subscript e is the average number of (CH2CH2O) units per molecule and typically has a value of 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, even 10 or more, while at the same time typically has a value of 20 or fewer, 15 or fewer, even 10 or fewer. One particularly desirable alkenyl alkoxylate stabilizer is vinyloxybutylpolyethlene, particularly one having an average chemical structure: CH2=CHO(CH2)4O(CH2CH2O)65H, which is commercially available under the name PLURIOL™ A 3090 V from BASF. PLURIOL is a trademark of BASF SE.Polyvinyl alcohol (PVA) stabilizers can be, in the broadest scope of the present invention, any PVA known to stabilizer silicone emulsions. Examples of PVAs are taught, for example, in US patent application 2007 / 0099007 at paragraphs

[0172] and

[0173] . Polyvinylalcohol may be made by saponification of polyvinylacetate, and up to 65 mol % of polyvinylacetate may remain in the polyvinyl alcohol used herein. Alternatively, the polyvinyl alcohol can be 35 mol % to 99 mol% polyvinyl alcohol (with the balance being 65 mol % to 1 mol % polyvinylacetate). Alternatively, the polyvinyl alcohol can be hydrolyzed from 80% to 98%. The polyvinyl alcohol can have a minimum viscosity (as measured according to DIN 53015 I JIS K 6726) of 5 mPa*s at 4 % aqueous solution at 20 °C and alternatively up to 200 mPa*s. Alternatively, the polyvinyl alcohol can have a viscosity of 15 mPa*s to 55 mPa*s. Suitable PVA stabilizers include PVA commercially available as DOWSIL™ PVA SOL 40 TAD from The Dow Chemical Company.The amount of stabilizer used in the process is typically in a range of 0.8 to 5 wt% relative to the weight of base emulsion. Typically, the amount of stabilizer is 0.8 wt% or more, and can be 0.9 wt% or more, 1.0 wt% or more, 1.1 wt% or more, 1.2 wt% or more, 1.4 wt% or more, 1.6 wt% or more, 1.8 wt% or more, 2.0 wt% or more, 2.5 wt% or more, 3.0 wt% or more, 3.5 wt% or more, even 4.0 wt% or more, while at the same time is typically 5.0 wt% or less, and can be 4.5 wt% or less, 4.0 wt% or less, 3.5 wt% or less, 3.0 wt% or less, 2.5 wt% or less, 2.0 wt% or less, 1.5 wt% or less, even 1.1 wt% or less, with wt% relative to weight of base emulsion. When the stabilizer is selected from silicone polyethers, alkyl alkoxylates, and alkenyl alkoxylates it is desirable for the concentration of the stabilizer to be 0.8 wt% or more, and can be 0.9 wt% or more, 1.0 wt% or more, even 1.1 wt% or more, and at the same time is desirable to be 2.0 wt% or less, 1.5 wt% or less, 1.4 wt% or less, 1.3 wt% or less, 1.2 wt% or less, 1.1 wt% or less, or even 1.0 wt% or less, with wt% relative to base emulsion weight.(d) Optional Anti-Foam EmulsionThe process can comprise providing an anti-foam emulsion and combining the anti-foam emulsion with the base emulsion, catalyst emulsion and stabilizer to form a curable silicone emulsion. Anti-foam emulsions typically comprise a water continuous phase, surfactant, and antifoaming agent(s). Examples of suitable anti-foam emulsions include emulsions containing silica and polydimethylsiloxanes. Suitably commercially available anti-foaming components include those available under the tradenames DOWSIL™ 7989, SYL-OFF™ EM 25 7989 ANTIFOAM, XIAMETER™ AFE-0100, XIAMETER™ AFE-1510, XIAMETER™ AFE- 1520, and XIAMETER™ AFE-1530. DOWSIL is a trademark of The Dow Chemical Company. XIAMETER and SYL-OFF are trademarks of Dow Silicones Corporation.The amount of anti-foam emulsion used in the process is typically sufficient to provide anti-foam components at a concentration of zero wt% or more, and can be 0.01 wt% or more, 0.02 wt% or more, 0.03 wt% or more, 0.04 wt% or more, 0.05 wt% or more, 0.06 wt% or more,even 0.07 wt% or more, while at the same time is typically 0.20 wt% or less, and can be 0. 10 wt% or less, 0.08 wt% or less, 0.06 wt% or less, even 0.05 wt% or less, with wt% values based on curable silicone emulsion weight.The curable silicone emulsion desirably has a molar ratio (SiH / C=C ratio) of SiH groups from the SiH-functional siloxane polymer to alkenyl groups from the alkenyl-functional siloxane composition in a range of from 0.9:1 to 8: 1 , more preferably 1.1 : 1 to 4: 1 , more preferably 1.2: 1 to 3.0:1, and most preferably 1.5:1 to 3:1.(e) Optional Additional WaterThe process of the present invention can comprise providing and combining with the base emulsion, catalyst emulsion and stabilizer additional water when forming the curable silicone emulsion. Additional water can be desirable in the process in order to dilute, thereby reducing the viscosity, of the curable silicone emulsion in order to facilitate coating a substrate. Additional water is typically utilized at a concentration of zero wt% or more, and can be 10 wt% or more, 20 wt% or more, 30 wt% or more, 40 wt% or more, even 50 wt% or more, while at the same time is typically 75 wt% or less, 70 wt% or less, or even 60 wt% or less, with wt% relative to curable silicone emulsion weight.The process of the present invention can further comprise a step of coating the curable silicone emulsion onto a substrate. The substrate can be, and desirably is, in sheet form. The process can comprise coating a web of substrate in sheet form with the curable silicone emulsion in a continuous coating process. The coating process is typically followed by curing the curable silicone emulsion on the sheet to form a sheet with a cured silicone coating.When coating a substrate with curable silicone emulsion according to the present invention, it is desirable to combine the stabilizer, base emulsion and catalyst emulsion to form the curable silicone emulsion within 12 hours, preferably within 10 hours, 8 hours, 7 hours, 6 hours, 5 hours, 4 hours, 3 hours, 2 hours, one hour, even within 30 minutes of coating the substrate with the curable silicone emulsion to prevent premature curing or destabilization of the curable silicone emulsion prior to coating the substrate.The process can comprise adding stabilizer to the base emulsion first and then combining the other components to form the curable silicone emulsion. In such a situation is desirable to form the curable emulsion and coat a substrate with the curable silicone emulsion within 12 hours, preferably within 10 hours, 8 hours, 7 hours, 6 hours, 5 hours, 4 hours, 3 hours, 2 hours, one hour, even within 30 minutes of adding the stabilizer to the base emulsion to prevent destabilization of the base emulsion prior to forming the curable silicone composition and coating the substrate with the curable silicone composition.EXAMPLESTable 1 lists the components for use in the samples described herein below.Table 1SYL-OFF is a trademark of Dow Silicones Corporation. DOWSIL is a trademark of The Dow Chemical Company. XIAMETER is a trademark of Dow Corning Corporation. SURFYNOL is a trademark of Evonik Operation s GMBH. LUTENSOL is a trademark of BASF SE.KATHON is a trademark of Nutrition & Biosciences USA 2, LLC. BIOBAN is a trademark of LANXESS Corporation.Preparation of Base Emulsion with and without StabilizerTable 2 presents formulations for base emulsions and, if used, the stabilizer. Add stabilizer either in-situ when preparing the base emulsion or add stabilizer to the base emulsion after forming the emulsion. Table 2 distinguishes between the two options by indicating “in- situ” or “post-add”. Table 2 lists weight-parts of each component.Prepare the base emulsions by mixing the polymer components together, then add the PVA surfactant and Alkyl Alkoxylate components including the stabilizer if “in-situ”, while mixing along with an aqueous solution of the remaining components to form an emulsion. Mix the emulsion sufficiently to achieve a Dv(0.9) value of 1 to 2 micrometers for the emulsion. Mix in any stabilizer that is included “post-addition.”Characterize the storage stability for the base emulsion using the following “Ageing Test”, then mix in any “post-add” components listed in Table 2.Ageing TestPlace samples of an emulsion into 6 individual bottles at 25 degrees Celsius (°C) and store protected from light. Evaluate one of the bottles at intervals of 30 days, 60 days, 90 days, 180 days, 270 days, and 360 days by measuring the particle size (Dv(0.9) for the emulsion using laser diffraction spectroscopy with a Malvern Mastersizer 3000 instrument. The emulsion is considered “stable” if the Dv(0.9) value remains below 3 micrometers, but “unstable” if the Dv(0.9) value exceeds 3 micrometers. Record how many days it takes for the emulsion to become unstable.Table 2Preparation of Catalyst EmulsionTable 3 provides the composition of the Catalyst Emulsion, with amounts for the components listed in wt% relative to the Catalyst Emulsion weight.Table 3Prepare an aqueous acid / base buffer solution by blending the water, Buffer Acid , and Buffer Base components together. Weigh out separately the Vinyl Siloxane and Catalyst, and then mix them together to form a polymer mix. Weigh out separately the PVA Surfactant and Alkyl Alkoxy late and mix them together to form a surfactant mix. Slowly add the surfactant mix to the polymer mix while emulsifying using a high pressure sonolator at 100 bars until obtaining a Dv(0.9) particle size between 1.0 and 2.5 micrometers, preferably between 1.5 and 2.0 micrometers. Determine Dv(0.9) particle size using laser diffraction spectroscopy with a Malvern Mastersizer 3000 instrument. To the emulsion add the buffer solution and biocides while continuing to emulsify. The resulting emulsion is the Catalyst Emulsion.Curable Silicone EmulsionsPrepare curable silicone emulsions by mixing together 23.75 weight-parts of base emulsion, 1.25 weight-parts of the catalyst emulsion, 0.05 weight-parts of Antifoam Emulsion, and then add 41.5 weight-parts water. Mix together gently using a blade mixer to obtain a curable silicone emulsion. The Dv(0.9) remains indistinguishable from that of the base emulsion.Prepare a curable silicone emulsion using each of the base emulsions of Table 2 and then characterize the curable silicone emulsion in the Shear Stability Test described herein below. Shear stability results are in Table 4.Shear Stability TestThe Shear Stability Test is derived from the emulsion stability test in US20050089697 paragraphs

[0238] and

[0239] . Mix the curable silicone emulsion at 1950 revolutions per minute using a blade mixer while maintaining the temperature at 60 °C. After mixing for 6 hours, determine Dv(0.9) for the curable silicone emulsion. If the Dv(0.9) is 13 micrometers or less then the curable silicone emulsion passes the Shear Stability Test. If the Dv(0.9) exceeds 13 micrometers, then the curable silicone emulsion fails the Shear Stability Test.Table 4Sample A corresponds to a reference sample without any additional stabilizer. While the base emulsion of Sample A passes the Ageing Test, the corresponding curable silicone emulsion fails to pass the Shear Stability Test.Samples B and 1 explore use of alkenyl alkoxylate as a stabilizer in the base emulsion by including 1.1 weight-parts alkenyl alkoxylate either In-Situ (B) or Post-Add (1). Sample B fails to pass the Ageing Test even though it passes the Shear Stability Test. Sample 1 passes both the Ageing Test and Shear Stability Test.Samples C and 2 explore use of silicone polyether (SPE) 1 as a stabilizer in the base emulsion by including 2 weight-parts SPE leither In-Situ (C) or Post-Add (2). Sample C fails to pass the Ageing Test and the Shear Stability Test. Sample 2 passes both the Ageing Test and Shear Stability Test.Samples D and E explore use of silicone polyether (SPE) 2, which has a molecular weight greater than 3,000 g / mol, as a stabilizer in the base emulsion by including 1 weight-part SPE 2 either In-Situ (D) or Post-Add (E). Sample D fails to pass the Ageing Test and the Shear Stability Test. Sample E passes the Ageing Test but fails the Shear Stability Test. These samples illustrate a need for the stabilizer to have a molecular weight of 3,000 g / mol or less.Samples F and 3 explores use of alkyl alkoxylate as a stabilizer in the base emulsion by including an additional 1.1 weight-parts alkyl alkoxylate either In-Situ (F) or Post- Add (3). Sample F fails to pass the Ageing Test and the Shear Stability Test. Sample 3 passes both the Ageing Test and Shear Stability Test.Samples G and 4 explores use of PVA Surfactant as a stabilizer in the base emulsion by including an additional 4 weight-parts PVA Surfactant either In-Situ (G) or Post-Add (4). Sample G fails to pass the Ageing Test and the Shear Stability Test. Sample 4 passes both the Ageing Test and Shear Stability Test.The data reveals the benefit of alkyl alkoxylates, alkenyl alkoxylates, SPEs and PVAs as set for as in-scope of the present invention for achieving shear stability in curable silicone emulsions when adding them to emulsions rather than in-situ while preparing emulsions. Theprocess of the present invention also allows preservation of storage stability of emulsions for at least 360 days prior to use.

Claims

CLAIMS:

1. A process comprising the following steps:(a) providing a base emulsion comprising water, surfactant, alkenyl-functional siloxane, and SiH-functional siloxane and having a dispersed particle size with a Dv(0.9) value of one micrometer or more and at the same time less than 3 micrometers as measured as a value determined using laser diffraction spectroscopy with a Malvern Mastersizer 3000 instrument;(b) providing a catalyst emulsion comprising water, surfactant, alkenyl-functional siloxane and hydrosilylation catalyst;(c) providing a stabilizer selected from a group consisting of silicone polyethers, alkyl alkoxylates, olefinic alkoxylates, and polyvinyl alcohols; wherein the silicone polyethers, alkyl alkoxylates and olefinic alkoxylates have a molecular weight of 3,000 grams per mole or less as determined by the calculating the sum of the atomic masses for each atom in the molecule; and(d) combining the base emulsion, catalyst emulsion and stabilizer together to form a curable silicone emulsion.

2. The process of claim 1, wherein the stabilizer is mixed into base emulsion prior to combining the base emulsion and catalyst emulsion.

3. The process of any one previous claim, wherein the concentration of stabilizer is in a range of 0.8 to 5 weight-percent of the weight of base emulsion.

4. The process of any one previous claim, wherein:(a) in the base emulsion,(i) the alkenyl-functional siloxane contains an average of at least 2 alkenyl groups per molecule;(ii) the SiH-functional siloxane contains an average of at least two SiH functionalities per molecule;(b) in the catalyst emulsion,(i) the alkenyl-functional siloxane contains an average of at least 2 alkenyl groups per molecule; and(c) the molar ratio of SiH to alkenyl groups in the curable silicone emulsion is in a range of 1.2 to 3.0.

5. The process of claim 4, wherein:(a) the base emulsion comprises:(i) 30-55 weight-percent water;(ii) 12-20 weight-percent surfactant;(iii) 25-45 weight-percent alkenyl-functional siloxane;(iv) 1.0-2.0 weight-percent SiH- functional siloxane; where weight-percents for the base emulsion components are based on base emulsion weight;(b) the catalyst emulsion comprises:(i) 35-55 weight-percent water;(ii) 12-20 weight-percent surfactant;(iii) 20-40 weight-percent alkenyl-functional siloxane;(iv) 4-8 weight-percent hydrosilylation catalyst composition; where weight-percents for the catalyst emulsion components are based catalyst emulsion weight; and(c) the stabilizer is selected from a group consisting of polyvinyl alcohol and silicone polyethers, alkyl alkoxylates, olefinic alkoxylates; where the silicone poly ethers, alkyl alkoxylates, olefinic alkoxylates have a molecular weight of 1,000 grams per mole or less.

6. The process of any one previous claim, wherein the process further includes providing an antifoam emulsion and mixing that with the base emulsion, catalyst emulsion and stabilizer to form the curable silicone emulsion; where the antifoam emulsion comprising water, surfactant, and an antifoaming agent.

7. The process of any one previous claim, wherein the process further comprises coating the curable silicone emulsion onto a substrate.

8. The process of claim 7, wherein the stabilizer is mixed into base emulsion or a combination of the base emulsion and catalyst emulsion within 12 hours of coating the substrate with a curable silicone emulsion comprising the base emulsion and stabilizer.

9. The process of claim 7 or 8, wherein the substrate is in sheet form and the coating process is a continuous process for coating a web of substrate sheet.

10. The process of any one previous claim, wherein the stabilizer is selected from a group consisting of vinyloxybutylpolyethlene oxide, poly (oxy- 1,2-ethanediyl), polyethylene modified heptamethyltrisiloxane, and polyoxyethylene modified polydimethylsiloxane.

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