Silicone release coatings using liquid resins

Abstract

An article includes a substrate and a curable silicone release coating composition; wherein the curable silicone release coating composition is a film that has a thickness of 2 micrometers or less and coats at least part of at least one surface of the substrate; and wherein the curable silicone release coating composition contains the following components: (a) an alkenyl-functional organopolysiloxane; (b) a silylhydride-functional organopolysiloxane; (c) a hydrosilylation catalyst; (d) a hydrosilylation inhibitor; and (e) a liquid silicone resin having an average chemical structure (I): [R3SiO1 / 2]a[R2R'SiO1 / 2]b[R2SiO2 / 2]c[R'SiO3 / 2]d[RSiO3 / 2]eXz with a weight-average molecular weight that is 10,000 grams per mole or less.

Description

[0001] SILICONE RELEASE COATINGS USING LIQUID RESINS

[0002] FIELD

[0003] The present invention relates to silicone release coatings prepared from silicone release coating compositions containing liquid MT resins.

[0004] INTRODUCTION

[0005] Silicone release coatings are silicone-based coatings that are designed for temporarily adhering adhesive materials in a way that protects the adhesive surface of the material until applying the adhesive material to desired surface. An adhesive material can reside with its adhesive layer on the silicone release coating and the silicone release coating allows easy and controllable removal of the adhesive material for adhesion to a desired surface.

[0006] Silicone release coatings reside as a film, typically a film having a thickness of 2 micrometers or less, on a substrate. Fabrication of silicone release coatings requires coating a substrate with a film of curable silicone release coating composition and then curing the film to form a release coating having a thickness of only 2 micrometers or less. Curable silicone release coating compositions are usually liquids that can be readily coated onto a substrate in the desired thickness.

[0007] Silicone release coatings are cured films of curable silicone release coating compositions that usually comprise curable silicone components and a release modifier. The curable silicone components are often hydrosilylation-curable siloxanes. The release modifier commonly comprises MQ resins as the active component. MQ resins can enhance release properties and adjusting the concentration of MQ resins in a curable silicone release coating composition can allow for tuning the release properties of a resulting silicone release coating.

[0008] While MQ resins are desirable as release modifiers, they offer challenges. For instance, synthesis of MQ resins typically involves generating an MQ resin in an organic solvent, typically a volatile organic (V OC) solvent, which is undesirable in a curable silicone release coating composition for handling and application purposes. MQ resins are often solids that typically are prepared in an organic solvent and require dispersing in a diluent followed by removal of the organic solvent in order to mix with the curable silicone coating components to form a curable silicone release coating composition. Diluents, even if they are not volatile organic materials, typically reside as migratable components in a final release coating unless they polymerize into the release coating, and migratable components are undesirable. Even with more recent development of liquid MQ resins, the use of solvent during synthesis or formulating MQ resins is undesirable for the release coating application. It would be desirable to identify a silicone resins that is suitable as a release modifier in silicone release coatings but that does not require an MQ resin. Moreover, it is desirable to identify such a silicone resin that is also a liquid to avoid need to disperse in solvents or diluents for formulating.

[0009] SUMMARY

[0010] The present invention provides a curable silicone release coating composition that does not require use of MQ resin, or any resin containing Q siloxane units. Instead, the curable silicone release coating composition of the present invention comprises a particular liquid MT silicone resin as the release modifier active component. The liquid MT silicone resin can be formulated into a curable silicone release coating composition without use of a solvent or diluent, which allows avoiding having to strip organic solvent or having migratable diluent when using the liquid resin. Curable silicone release coating compositions of the present invention are suitable for applying as coatings that are 2 micrometers thick or less on a surface of a substrate.

[0011] Once cured on the substrate, the curable silicone release coating composition forms a release coating. Desirable performance properties of the resulting release coating include the following: (i) less than 10% extractables in the Extractables Test, described herein below; (ii) immediate or 12 hour rub-off resistance (ROR) of >75% and 7 Day ROR of >80% as determined by the ROR Test, described herein below; (iii) Release Performance per the Release Performance Test herein below after 7 days that is at least 20 grams per inch (g / in) at a pull off rate of 0.3 meters per minute (m / min), at least 55 g / in at 10 m / min, at least 80 g / in at 100 m / min, and at least 55 g / in at 300 m / min; and (iv) Release Performance per the Release Performance Test herein below after one month that is at least 40 g / in at 0.3 m / min, at least 70 g / in at 10 m / min, at least 90 g / in at 100 m / min, and at least 85 g / in at 300 m / min.

[0012] In a first aspect, the present invention is an article comprising a substrate and a curable silicone release coating composition; wherein the curable silicone release coating composition is a film that has a thickness of 2 micrometers or less and that coats at least part of at least one surface of the substrate; and wherein the curable silicone release coating composition comprises the following components: (a) an alkenyl-functional organopolysiloxane that contains an average of at least 2 alkenyl groups per molecule; (b) a silylhydride-functional organopolysiloxane that contains an average of at least 2 SiH groups per molecule; (c) a hydrosilylation catalyst; (d) a hydrosilylation inhibitor; and (e) a liquid silicone resin having an average chemical structure (III):

[0013] [R3SiOl / 2]a[R2R’SiOl / 2]b[R2SiO2 / 2]c[R’SiO3 / 2]d[RSiO3 / 2]eXz (III) where: (i) the liquid silicone resin has a weight- average molecular weight, as determined by gel permeation chromatography using polystyrene standards, that is 10,000 grams per mole or less; (ii) X refers to a combination of all siloxane units that contain an SiOZ group, where Z is in each occurrence selected from hydrogen and alkyl groups; (iii) R is independently in each occurrence selected from alkyl groups having from one to 8 carbon atoms; (iv) R’ is independently in each occurrence selected from alkenyl groups having from 2 to 8 carbon atoms; (v) subscript a is the mole ratio of R3SiOi / 2 siloxane units in the molecule and has a value in a range of 0.23 to 0.40;

[0014] (vi) subscript b is the mole ratio of R2R’SiOi / 2 siloxane units in the molecule and has a value in in a range of 0 to 0.3; (vii) subscript c is the mole ratio of R2SiC>2 / 2 siloxane units in the molecule and has a value in a range of 0 to 0.1; (viii) subscript d is the mole ratio of R’SiO3 / 2 siloxane units in the molecule and has a value in a range of 0.03 to 0.2; (ix) subscript e is the mole ratio of SKL / i siloxane units in the molecule and has a value in a range of 0.4 to 0.7 ; and (x) subscript z has a values such that the molar concentration of SiOZ groups is 10 mole-percent or less, with mole-percent relative to total moles of silicon atoms in the molecule; where mole ratio of siloxane units are relative to the total moles of siloxane units. The curable silicone release coating composition can be in a cured state where the curable silicone release coating composition has been cured by hydrosilylation reactions between the alkenyl-functional organopolysiloxane alkenyl groups and the silylhydride-functional organopolysiloxane SiH groups to form a silicone release coating that is a film having a thickness of 2 micrometers or less that coats at least a portion of a surface of the substrate.

[0015] In a second aspect, the present invention is a process for preparing a silicone release coating, the process comprising: (a) providing a curable silicone release coating composition as described in any one previous claim; (b) providing a substrate; and (c) coating the curable silicone release coating composition onto the substrate as a film of curable silicone release coating that is 2 micrometers thick or less on the substrate. The process can further comprise curing the film of curable silicone release coating composition to form a silicone release coating on the substrate.

[0016] The process of the present invention is useful for making the article of the present invention, and both are useful in forming or serving as silicone release coatings.

[0017] DETAILED DESCRIPTION

[0018] Test 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. The following test method abbreviations and identifiers apply herein: ASTM refers to ASTM International methods; END refers to European Norm; DIN refers to Deutsches Institut fur Normung; ISO refers to International Organization for Standards; and UL refers to Underwriters Laboratory.

[0019] Products identified by their tradename refer to the compositions available under those tradenames on the priority date of this document.

[0020] “Multiple” means two or more. “And / or” means “and, or as an alternative”. All ranges include endpoints unless otherwise indicated.

[0021] “Average value” when referencing a value describing a molecule refers to the average value of a sample of molecules since it is generally difficult to measure the value of a single molecule.

[0022] “Cx-y” refers to having from x to y number of carbon atoms.

[0023] “Siloxane” and “silicone” refer to molecules comprising at least one siloxane (Si-O-Si) bond. Herein, “siloxane” can be a “polysiloxane” having multiple siloxane bonds or a siloxane having only one siloxane bond. Polysiloxanes comprise multiple siloxane units linked together through siloxane bonds. Siloxane units can be characterized by the designation M, D, T or Q. There are two generally accepted usages of MDTQ nomenclature: GE method and an NMR method. Usage herein is in accordance with the following method. Unless expressly stated otherwise: “M” correspond to R3SiOi / 2 siloxane units; “D” corresponds to the combination of R SiO2 / 2 and R2(OZ)SiOi / 2 siloxane units; “T” corresponds to the combination of RSiOa / 2, R(OZ)SiO2 / 2, and R(OZ)2SiOi / 2 siloxane units; “Q” corresponds to a combination of (OZ)3SiOi / 2, (OZ)2SiO2 / 2, (OZ)SiO3 / 2, and SiO4 / 2 siloxane units; and “R” is independently in each occurrence selected from hydrocarbyl groups and can be an alkyl or aryl. Preferably, R is selected from a group consisting of Ci-8 alkyls (such as methyl, ethyl, propyl, methyl, butyl, pentyl, hexyl, heptyl, octyl) and C6-20 aryls (including phenyl and benzyl). “OZ” is -OH or -OR, where R is as described above.

[0024] Notably, an oxygen atom having a multiple of “1 / 2” subscript is an oxygen of a siloxane bond that is shared with a silicon atom of two siloxane units including the one of the subject siloxane unit. The numerator of the subscript indicates how many shared oxygen atoms are attached to the silicon atom. For example, SiOs / 2 has three siloxane bonded oxygen atoms.

[0025] The M, D and T notations can include a superscript indicating what R groups are bound to the silicon atom of the siloxane unit or what group has replaced an R group bound to the silicone atom. If no superscript notation is used, then it is assumed the R groups are all methyl groups. For instance, TPrrefers to a T unit where the R group is an n-propyl group. Tphunit refers to a T unit where the R group is a phenyl group. D, DIc-VIcand DMe2 each refer to a D unit with two methyl R group on the silicon atom. opll-Icand Dphboth refer to a D unit with one phenyl R group and one methyl R group on the silicon atom. Dph,phand Dph2 both refer to a D unit with two phenyl R group on the silicon atom. MMe,Me,Meand MMe3 both refer to a M unit with three methyl R group on the silicon atom. DHrefers to a D siloxane unit where one of the R groups has been replaced with hydrogen.

[0026] Chemical formula designations for polysiloxanes using M, D, T, Q nomenclature typically have subscripts associated with the siloxane unit designator that can either refer to the average mole ratio of that siloxane unit relative to all siloxane units in the molecule or the average number of the associate siloxane units in the molecule. When the subscript associated with a siloxane unit is greater than or equal to one, then the subscript refers to the average number of those siloxane units in the molecule. When the subscript associated with a siloxane unit is less than one then the subscript refers to the average mole ratio of that siloxane unit relative to the number of moles of all siloxane units in the molecule. An absence of a subscript implies a subscript value of one. Determine chemical structures of siloxanes, including OZ content and relative amounts of each siloxane unit, using silicon- 29 (“ Si) nuclear magnetic resonance (NMR) spectroscopy with a 500 MHz Bruker Avance Neo spectrometer equipped with an Agilent premium shielded 11.7 T magnet and a Bruker He-cooled multinuclear 10 mm C / Pt / Si / N-H-D observe cry oprobe at 25 °C using TopSpin 4.3.0. Perform data processing using MestReNova software version 14.3.2-32681.

[0027] “Organopolysiloxane” refers to a polysiloxane that has at least one organic group bound to a silicon atom of the poly siloxane.

[0028] “Silicone resin” refers to a polysiloxane that where the sum of T and Q siloxane units is at least 30 mole-percent (mol%) of the total number of siloxane units in the siloxane. A silicone resin can be free of T units as long as the number of Q siloxane units is at least 30 mol% of the total number of siloxane units in the siloxane. Similarly, the silicone resin can be free of Q siloxane units provided that the total number of T siloxane units is at least 30 mol% of the total number of siloxane units in the siloxane.

[0029] An “MQ resin” is a resin that has as siloxane units primarily, and typically exclusively, M and Q siloxane units. An “MT resin” is a resin that has as siloxanes units primarily, and typically exclusively, M and T siloxane units. Usually an MQ resin has minimal or no T siloxane units and can have minor amounts of D siloxane units or can be free of D siloxane units. Similarly, an MT resin has minimal or no Q siloxane units and can have minor amounts of D siloxane units or be free of D siloxane units.

[0030] “Silicone polymer” refers to a polysiloxane that contains a sum of T and Q siloxane units that is less than 30 mol%, typically 20 mol% or less, and can be 15 mol% or less, 10 mol% or less, 5 mol% or less, or even zero mol% of the total number of siloxane units in the polysiloxane. A “Q-branched” silicone polymer is a silicone polymer that contains one or more than one Q siloxane unit, but fewer than 10 mol% of a sum of T and Q siloxane units.

[0031] Unless otherwise stated, determine molecular weight of silicone resins by gel permeation chromatography (GPC). Preparing samples in certified tetrahydrofuran at 1% w / w, filter with a 0.145 micrometer polytetrafluoroethylene syringe filter and analyze against polystyrene standards. Use 3rdorder relative calibration based on 12 polystyrene standards ranging in molecular weights from 580 to 1,735,00 Daltons. The chromatographic equipment consists of a Viscotek GPCmax VE2001 Solvent / Sample Module equipped with a vacuum degasser, a Viscotek VE3580 RI detector, and two (300 millimeter x 7.5 millimeter) Polymer Laboratories Mixed C columns (molecular weights separation range of 200 to 3,000,000) preceded by a guard column. Perform the separation using certified grade tetrahydrofuran programmed to flow at 1.0 milliliters per minute, injection volume is 100 microliters, and columns and detector are heated to 35 °C. Data collection occurs for 30 minutes and perform processing using OmniSEC software. Report number average molecular weights (Mn).

[0032] In a first aspect, the present invention is an article comprising a substrate and a curable silicone release coating composition. The curable silicone release coating composition is in the form of a film that covers at least part of a surface of the substrate and that has a thickness of 2 micrometers or less and can have a thickness of 1.5 micrometer or less, even one micrometer or less.

[0033] In the broadest scope of the invention, the substrate can be any solid material and in any form. Typically, the substrate is a sheet that has a width and a length that is at least 10 times, more typically at least 100 times its thickness. The substrate can be, for example, a polymeric sheet or a sheet containing cellulosic material. Sheets have primary surfaces, which are surfaces defined by the width and length dimensions and generally perpendicular to the thickness dimension. For sheet substrates, curable silicone release coating composition typically coats at least a portion of, and can coat entirely coat a primary surface of a substrate sheet.

[0034] The curable silicone release coating composition can reside on the substrate in either an uncured state or in a cured state. Upon curing, the curable silicone release coating composition becomes a “silicone release coating”. The curable silicone release coating composition is curable using hydrosilylation chemistry. Upon curing, the silicone release coating resides on the substrate as a film that has a thickness of 2 micrometers or less.

[0035] The curable silicone release coating composition prior to curing comprises the following components: (a) an alkenyl-functional organopolysiloxane; (b) a silylhydride-functional (SiH- functional) organopolysiloxane; (c) a hydrosilylation catalyst; (d) a hydrosilylation inhibitor; and (e) a liquid silicone resin. The curable silicone release coating composition can be free of silicone resin that contains Q siloxane units. The curable silicone release coating composition can be free of organic solvent.

[0036] Alkenyl-Functional Organopolysiloxane

[0037] The alkenyl-functional organopolysiloxane contains an average of at least 2 alkenyl groups per molecule. The alkenyl groups are desirably terminally unsaturated. Preferably, the alkenyl groups contain 2 or more, and can contain 3 or more, 4 or more 5 or more, 6 or more, even 7 or more carbon atoms while at the same time typically contain 8 or fewer, and can contain 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, even 3 or fewer carbon atoms. Typically, the alkenyl groups are selected from vinyl, allyl and hexenyl groups. The alkenyl-functional organopolysiloxane can be all of one type or can be a combination or more than one type of alkenyl-functional organopolysiloxane.

[0038] The alkenyl-functional organopolysiloxane can comprise or consist of one or a combination or more than one Q-branched silicone polymer. For example, the alkenyl- functional organopolysiloxane can comprise, or consist of a Q-branched silicone polymer. The Q-branched silicone polymer can an average chemical structure (I):

[0039] M^y^DdD^^d’Q (I) where:

[0040] “alkenyl” refers to an alkenyl group as described in the previous paragraph;

[0041] M^kenyi js an a]kyi functionalized M siloxane unit; subscript “m” refers to the average number of Mlllkcinylsiloxane units per molecule and has a value of 2 or more, and can be 3 or more, even 4 or more while at the same time is typically 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, even 4 or less;

[0042] D is a D siloxane unit and subscript “d” is the average number of D siloxane units per molecule and has a value of 50 or more, and can be 75 or more, 100 or more, 110 or more, 120 or more, 130 or more, 140 or more, 150 or more, 175 or more, 200 or more, even 225 or more, while at the same time is typically 300 or less, and can be 275 or less, 250 or less, 227 or less, 200 or less, 175 or less, 150 or less, 140 or less, 130 or less, even 120 or less. paikenyi -s an ai]enyi_functionai£) siloxane group; and subscript d’ is the average number of Dalkenylsiloxane units per molecule and typically has a value of zero or more, and can be one or more, even 2 or more, while at the same time is typically 5 or less, 4 or less, 3 or less, 2 or less, even one or less.

[0043] The alkenyl groups in chemical structure (I) can be C2-6 alkenyl groups including vinyl, allyl, and hexenyl.

[0044] Examples of suitable Q-branched alkenyl functional polyorganosiloxanes include one or any combination of more than one Q-branched polymer having the following average chemical structures: MVI4D |2OQ. MvSo.28 M0Zvx4 D4303Q12, and MheX2Di4o.93Dhex2 where MV1refers to a vinyl-functional M siloxane unit, Mozrefers to an OZ-functional M siloxane unit, Mhexrefers to a hexenyl functional M siloxane unit, and Dhexrefers to a hexenyl functional D siloxane unit.

[0045] Typically, the concentration of alkenyl-functional organopolysiloxane is in a range of 55 to 85 weight-percent (wt%), and can be 55 wt% or more, 60 wt% or more, 65 wt% or more, 70 wt% or more, 75 wt% or more, even 80 wt% or more, while at the same time is typically 85 wt% or less, and can be 80 wt% or less, 75 wt% or less, 70 wt% or less, 65 wt% or less, even 60 wt% or less, with wt% relative to weight of curable silicone release coating composition.

[0046] SiH-Functional Organopolysiloxane

[0047] The SiH-functional organopolysiloxane contains an average of at least 2 SiH groups per molecule. The SiH-functional silicone can be free of alkenyl groups, even unsaturated groups altogether. The SiH-functional organopolysiloxane serves as a crosslinker where the SiH groups react with alkenyl groups in the alkenyl-functional organopolysiloxane as the curable silicone release coating composition cures to form a silicone release coating.

[0048] The SiH-functional organopolysiloxane is desirably a linear silicone polymer. The SiH- functional organopolysiloxane can have an average chemical structure (II):

[0049] [(CH3)3SiO]2[(CH3)2SiO]d[(CH3)HSiO]d’ (II) where: subscript d has a value in a range of zero to 50, and can be zero or more, 2 or more, 4 or more, 8 or more, 10 or more, 15 or more, 18 or more, 20 or more, 25 or more, 30 or more, 35 or more, 40 or more, even 45 or more, while at the same time is typically 50 or less, and can be 40 or less, 30 or less, 20 or less, even 10 or less; and subscript d’ has a value in a range of 10 to 80, and can be 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, 35 or more, 40 or more, 42 or more, 45 or more, 50 or more, 60 or more, even 65 or more, while at the same time is typically 80 or less, and can be 70 or less, 65 or less, 60 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, 20 or less, even 10 or less.

[0050] The SiH-functional organopolysiloxane can be a single SiH-functional organopolysiloxane or can be a combination of multiple SiH-functional organopolysiloxanes. For example, the SiH-functional organopolysiloxane can be a combination of SiH-functional organopolysiloxanes having the following average chemical structures: [(CH3)3SiO]2[(CH3)2SiO]i8[(CH3)HSiO]42 and [(CH3)3SiO]2[(CH3)HSiO]65.

[0051] The concentration of SiH-functional silicone in the curable silicone release coating composition is desirably sufficient to provide a molar ratio of SiH groups relative to alkene groups from the alkene-functional silicone (SiH / C=C ratio) that is greater than 0.80 and that can be 1.00 or more, 1.10 or more, 1.20 or more, 1.30 or more, 1.40 or more, 1.50 or more, 1.60 or more, 1.70 or more, even 1.80 or more, while at the same time is typically 5 or less, 4 or less, 3 or less, 2 or less, and can be 1.90 or less, or even 1.80 or less.

[0052] Desirably, the concentration of SiH-functional silicone is in a range of 3-10 wt% of the weight of the curable silicone release coating composition. Usually, the concentration of SiH- functional silicone is 3 wt% or more, and can be 4 wt% or more, 5 wt% or more, 6 wt% or more, 7 wt% or more, 8 wt% or more, even 9 wt% or more, while at the same time is typically 10 wt% or less, and can be 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, even 4 wt% or less, with wt% relative to weight of curable silicone release coating composition.

[0053] Hydrosilylation Catalyst

[0054] The hydrosilylation catalyst can be any known in the art. For example, the hydrosilylation catalyst can be selected from the group consisting of: a metal selected from Pt- group metals of platinum, rhodium, ruthenium, palladium, osmium, and iridium; a compound of platinum, rhodium, ruthenium, palladium, osmium, and iridium; a complex of the complexed metal with an organopolysiloxane; and any of the previous options microencapsulated in a matrix or core / shell type structure. Examples of suitable hydrosilylation catalysts are a metal selected from platinum, rhodium, ruthenium, palladium, osmium, and iridium; a compound such as, for example, chloridotris (triphenylphosphane) rhodium (I) (Wilkinson's Catalyst), a rhodium diphosphine chelate such as [l,2-bis(diphenylphosphino)ethane] dichlorodirhodium or [1,2- bis(diethylphospino)ethane] dichlorodirhodium, chloro platinic acid (Speier's Catalyst), chloroplatinic acid hexahydrate, platinum dichloride; a complex of a compound described above with organopolysiloxanes or platinum compounds microencapsulated in a matrix or core / shell type structure. Complexes of platinum with organopolysiloxanes include 1,3-diethenyl-l, 1,3,3- tetramethyldisiloxane complexes with platinum (Karstedt's Catalyst).

[0055] The concentration of hydrosilylation catalyst is sufficient to catalyze the curing reaction of the curable silicone release coating. Typically, the concentration of hydrosilylation catalyst is sufficient to provide platinum-group metal component at a concentration of greater than 0.01 weight parts per million (ppm), and can be 0.1 ppm or more, 1.0 ppm or more, 10 ppm or more, 50 ppm or more, 60 ppm or more, 70 ppm or more, 80 ppm or more, 90 ppm or more, 100 ppm or more, 500 ppm or more, 1000 ppm or more, 2000 ppm or more, 3000 ppm or more, 4000 ppm or more, 5000 ppm or more , 6000 ppm or more, even 8000 ppm or more, while at the same time is typically 10,000 ppm or less, 8000 pm or less, 6000 ppm or less, 5000 ppm or less, 4000 ppm or less, 3000 ppm or less, 2000 ppm or less, 1000 ppm or less, 500 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, even 70 ppm or less relative to weight parts of curable silicone release coating composition.

[0056] Hydrosilylation Inhibitor

[0057] Examples of suitable hydrosilylation inhibitors include those selected from the group consisting of: acetylenic alcohols; silylated acetylenic compounds; cycloalkenylsiloxanes; ene- yne compounds; triazoles; phosphines; mercaptans; hydrazines; amines; fumarates such as dialkyl fumarates, dialkenyl fumarates, and dialkoxyalkyl fumarates; maleates, nitriles, ethers, and combinations of two or more of the aforementioned materials. Suitable acetylenic alcohols include dimethyl hexynol, and 3,5-dimethyl-l-hexyn-3-ol, methyl butynol such as l-butyn-3-ol, l-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. Suitable cycloalkenylsiloxanes include methylvinylcyclosiloxanes exemplified by l,3,5,7-tetramethyl-l,3,5,7- tetravinylcyclotetrasiloxane, l,3,5,7-tetramethyl-l,3,5,7-tetrahexenylcyclotetrasiloxane, combination thereof. Suitable ene-yne compounds include 3-methyl-3-penten- 1-yne, 3,5- dimethyl-3-hexen-l-yne. Suitable triazoles include benzotriazole. Suitable amines include tetramethyl ethylenediamine. Silylated acetylenic compounds include (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 1- butyn-3-oxy)dimethylhexenylsilane, (3-methyl- 1-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)dimethylphenyls dimethylvinylsilane, (3 -phenyl- 1 -buty n-3-oxy )dimethylhexeny Isilane, (cyclohexyl- 1 -ethyn- 1 - oxy)dimethylhexenylsilane, (cyclohexyl- 1 -ethyn- 1 -oxy (dimethylvinylsilane, (cyclohexyl- 1 - ethyn- l-oxy)diphenylmethylsilane, (cyclohexyl- 1 -ethyn- l-oxy)trimethylsilane, and combinations thereof.

[0058] The amount of inhibitor is typically greater than zero weight-percent (wt%) and can be 0.001 wt% or more, 0.0025 wt% or more, 0.01 wt% or more, even 0.05 wt% or more, while at the same time is typically 5 wt% or less, and can be 3 wt% or less, one wt% or less, 0.5 wt% or less, or even 0.025 wt% or less based on the weight of the curable silicone release coating composition.

[0059] Liquid Silicone Resin

[0060] The liquid silicone resin is a liquid at 25 °C and 101 kilopascals pressure. The liquid silicone resin has an average chemical structure (III):

[0061] [R3SiOl / 2]a[R2R’SiOl / 2]b[R2SiO2 / 2]c[R’SiO3 / 2]d[RSiO3 / 2]eXz (III) where, for chemical structure (III): the liquid silicone resin has a number-average molecular weight, as determined by gel permeation chromatography using polystyrene standards, that is 10,000 grams per mole or less and can be 7500 or less, 7000 or less, 6500 or less, 6000 or less, 5500 or less, 4500 or less, 4000 or less, 3500 or less, 3000 or less, 2500 or less, even 2000 or less, while at the same time is typically 1000 or more, and can be 1500 or more, 2000 or more, 2500 or more, 3000 or more, 3500 or more, 4000 or more, 4500 or more, even 5000 or more;

[0062] X refers to a combination of all siloxane units that contain an SiOZ group, where Z is in each occurrence selected from hydrogen and alkyl groups;

[0063] R is independently in each occurrence selected form alkyl groups having from one to 8 carbon atoms, and can be selected from, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl groups; R’ is independently selected from alkenyl groups having from 2 to 8 carbon atoms, and can be selected from, for example, vinyl, allyl, and hexenyl groups; subscript a is the mole ratio of R3SiOi / 2 siloxane units in the molecule and has a value in a range of 0.23 to 0.40; subscript b is the mole ratio of R2R’SiOi / 2 siloxane units in the molecule and has a value in in a range of 0 to 0.3; subscript c is the mole ratio of R i O2 / 2 siloxane units in the molecule and has a value in a range of 0 to 0.1 ; subscript d is the mole ratio of R’SiOs / 2 siloxane units in the molecule and has a value in a range of 0.03 to 0.2; subscript e is the mole ratio of RSiOs / 2 siloxane units in the molecule and has a value in a range of 0.4 to 0.7; subscript z has a value such that the molar concentration of SiOZ groups is 10 mole-percent or less, with mole-percent relative to total moles of silicon atoms in the molecule; and wherein the mole ratio of siloxane units are relative to the total moles of siloxane units in the molecule.

[0064] The concentration of liquid silicone resin is in a range of 5 to 60 wt%, and can be 5 wt% or more, 10 wt% or more, 15 wt% or more, 20 wt% or more, 25 wt% or more, 30 wt% or more, 35 wt% or more, 40 wt% or more, 45 wt% or more, 50 wt% or more, even 55 wt% or more, while at the same time is typically 60 wt% or less, even 55 wt% or less, 50 wt% or less, 45 wt% or less, 40 wt% or less, 35 wt% or less, 30 wt% or less, 25 wt% or less, 20 wt% or less, 15 wt% or less, even 10 wt% or less, with wt% relative to curable silicone release coating composition weight.

[0065] Optional Components

[0066] The curable silicone release coating composition can comprise, or be free of, any one or any combination of additional optional components. For example, the curable silicone release coating composition can comprise any one or any combination of more than one component selected from solvents, additional release agents, adhesions promoters, and fumed silica.

[0067] While the curable silicone release coating composition can comprise solvent or solvents, the curable silicone release coating is desirably free of organic solvent, and more desirably free of any solvent. Suitable adhesion promoters include reaction products of a vinyl alkoxysilane and an epoxy-functional alkoxysilane; reaction products of a vinyl acetoxysilane and epoxy-functional alkoxysilane; and a combination (for example, physical blend and / or a reaction product) of a polyorganosiloxane having at least one aliphatically unsaturated hydro carbon group and at least one hydrolyzable group per molecule and an epoxy-functional alkoxysilane (for example, a combination of a hydroxy-terminated, vinyl functional polydimethylsiloxane with glycidoxypropyltrimethoxysilane). Suitable concentrations of adhesion promoters is typically zero wt% or more and can be 0.01 wt% or more, 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, even 0.5 wt% or more while at the same time is typically 2 wt% or less, and can be one wt% or less, 0.9 wt% or less, 0.8 wt% or less, 0.7 wt% or less, even 0.6 wt% or less based on the weight of the curable silicone release coating composition.

[0068] In a second aspect, the present invention is a process for preparing a silicone release coating. The process comprises; (a) providing a curable silicone release coating composition as described hereinabove for the first aspect of the invention; (b) providing a substrate; and (c) coating the curable silicone release coating composition onto the substrate as a film of curable silicone release coating that is 2 micrometers thick or less on the substrate. The process can further include curing the film of curable silicone release coating composition to form a silicone release coating on the substrate.

[0069] The substrate can be a sheet material and coating can occur in any method suitable for coating a sheet, including a continuous coating process comprising coating a web of sheet material with the curable silicone release coating composition. The process can include doctoring or rolling the coating once it has been applied to the substrate in order to establish a film that is 2 micrometers or less in thickness.

[0070] EXAMPLES

[0071] Table 1 presents the components other than the liquid silicone resins for use in the following samples. Table 2 presents the components for use in synthesizing the liquid silicone resins used in the sample and the synthetic method for the liquid silicone resins follows Table 2. Table 1

[0072] SYL-OFF is a trademark of Dow Silicones Corporation.

[0073] Synthesis of liquid resins Table 2 lists the materials for use in preparing liquid resins for samples of the present invention. Following Table 2 is the synthetic route for making the liquid resins, 18 in total. In the chemical formulae for the liquid resins “Vi” refers to a vinyl functionalization, “hex” refers to a hexenyl functionalization, and “Me” refers to a methyl group bound to the siloxane unit. Table 2

[0074] Synthesis of Liquid Silicone Resin (LSR) 1

[0075] Fit a 3-liter (3-L), 4-neck round bottom flask with a thermocouple, polytetrafluoroethylene stir paddle attached to a glass stir rod, a Dean Stark apparatus attached to a water-cooled condenser, and an addition funnel. Load into the flask 176.94 grams (g) Silane 3, 699.97 g Silane 1, and 69.19 g Silane 2. Apply a nitrogen blanket. Add 0.473 g Acid Catalyst at 25 °C and then add 227 g of deionized water slowing using an addition funnel allowing an exotherm to raise the flask content temperature to 61 °C. Heat the flask to maintain a temperature of 65 °C for one hour. Add 272.87 g of Solvent 1 followed by 1.645 g of a solution of 45.5 wt% Base Catalyst in distilled water. Distill off 270.25 g volatiles. Add another 272.35 g Solvent 1. Distill off 213.30 g of volatiles. Add 213.40 g more Solvent 1. The Dean Stark trap fills with Solvent 1. Heat at reflux for 7 hours. Cool to 60 °C and then add 0.675 g glacial acetic acid. Stir at 25 °C for 8-12 hours. Pressure filter the flask contents through a 142 millimeter diameter Magna Nylon Supported Plain 0.45 micron filter. Strip the resulting product to dryness using a rotovap at an oil bath temperature of 80 °C and a vacuum to a pressure of approximately 0.13 kilopascals (one millimeter Hg). Upon reaching full vacuum, continue rotovap for one hour to obtain the final product LSR 1.

[0076] Synthesis of LSRs 2-8 and 10-16

[0077] Prepare in similar manner as Liquid Silicone Resin 1, but with modifications to the amounts of each components as shown in Table 3 with amounts of each component in grams. Table 3

[0078] Synthesis of LSR 9

[0079] Into a one-liter, 2-neck round bottom flask add 208.42 g of Silane 1 and 10.00 g Silane 2. Add 0.114 g of Acid Catalyst at 25 °C. Add 49.94 g deionized water slowly using an addition funnel. Heat to 65 °C for 30 minutes. Distill out 96.46 g methanol, targeting 60% of the amount that could have been produced. Add 131.65 g of Solvent 1. Add 47.50 g of Silane 3. Heat to 55 °C for 3 hours. Distill off 69.36 g of volatiles. Add 0.46 g of calcium carbonate to neutralize the Acid Catalyst. Stir 8-12 hours at 25 °C. Remove remaining methanol using a rotovap under vacuum at an oil bath temperature of 80 °C. Cool to 25 °C and then pressure filter through a 47 millimeter diameter Magna Nylon Supported Plain 0.45 micron filter. Strip the resulting product to dryness using a rotovap and an oil bath temperature of 80 °C and a vacuum to a pressure of approximately 0.13-0.26 kilopascals (one to two millimeter Hg). Continue to rotovap for one hour after reaching full vacuum to obtain Liquid Silicone Resin 9.

[0080] Synthesis of LSR 17

[0081] Into a 3-L, 4-neck round bottom flask add 592.58 g of Silane 1 and 67.20 g Silane 7, and 219.23 g Silane 3. Add 0.440 g of Acid Catalyst at 25 °C. Heat to 70 °C for 3 hours. Cool to 45 °C and add 176.33 g deionized water slowly using an addition funnel. Heat to 65 °C for 3 hours. Distill out 293.5 g of methanol. Add 891 g of Solvent 1. Add 1.65 g of Base Catalyst (45 wt% in water). Distill off 207 g of volatiles. Add 207 g Solvent 1. Distill off 40 g volatiles. Add 40 g Solvent 1 and add an equal amount into the Dean Stark apparatus. Heat at reflux for 7 hours. Coo to 60 °C and then add 0.700 g Neutralizing Agent. Stir at 25 °C for 8-12 hours. Pressure filter through a 142 millimeter Magna Nylon Supported Plain 5.0 micron filter. Strip the resulting product to dryness using a rotovap using an oil bath temperature of 100 °C and a vacuum to 0.13 -0.26 kilopascals (one to two millimeter Hg) pressure. Continue to rotovap for one hour after reaching full vacuum to obtain final product Liquid Silicone Resin 17.

[0082] Synthesis of LSR 18

[0083] Into a 3-L, 4-neck round bottom flask add 725.40 g of Silane 1 and 67.20 g Silane 7, and 140.03 g Silane 3. Add 0.466 g of Acid Catalyst at 25 °C. Heat to 70 °C for 3 hours. Cool to 45 °C and add 215.86 g deionized water slowly using an addition funnel. Heat to 65 °C for 3 hours. Distill out 293.5 g of methanol. Add 891 g of Solvent 1. Add 1.62 g of Base Catalyst (45 wt% in water). Distill off 207 g of volatiles. Add 207 g Solvent 1. Distill off 40 g volatiles. Add 40 g Solvent 1 and add an equal amount into the Dean Stark apparatus. Heat at reflux for 7 hours. Cool to 60 °C and then add 0.700 g Neutralizing Agent. Stir at 25 °C for 8-12 hours. Pressure filter through a 142 millimeter Magna Nylon Supported Plain 5.0 micron filter. Strip the resulting product to dryness using a rotovap using an oil bath temperature of 100 °C and a vacuum to 0. 13-0.26 kilopascals (one to two millimeter Hg) pressure. Continue to rotovap for one hour after reaching full vacuum to obtain final product Liquid Silicone Resin 18.

[0084] Table 4 provides properties for the Liquid Silicone Resins. “Vi” refers to a vinyl group.

[0085] “Hex” refers to a hexenyl group.

[0086] Table 4

[0087] Formulating Curable Silicone Release Coating Compositions

[0088] Tables 5, 6, 7, and 8 present formulations for sample curable silicone release coating compositions. Amounts of each component are listed in wt% relative to total composition weight. Table 5 lists reference samples. Table 6 lists formulations with 20 wt% liquid resin for hand coating characterization. Table 7 lists formulations with 10 wt% liquid resin for pilot coating characterization. Table 8 lists formulations with 20 wt% liquid resin for pilot coating characterization.

[0089] For those formulations that list “Coating 1” as a component, prepare the coating composition by blending together 97.75 wt% AFO-1, 2 wt% AFO-2, and 0.25 wt% of Hydrosilylation Inhibitor and then use that blend as “Coating 1”.

[0090] Prepare the curable silicone release coating compositions by combining all of the components except catalyst together and mixing using a dental mixer at 3500 revolutions per minute for 30 seconds. Add the catalyst component and mix with the dental mixer at 3500 revolutions per minute for another 30 seconds to obtain the curable silicone release coating composition.

[0091] Table 5 - Reference Samples Table 6 - Hand Coating Samples with 20 wt% Liquid Resin

[0092] Table 7 - Pilot Coating Samples with 10 wt% Liquid Resin

[0093] Table 8 - Pilot Coating samples with 20 wt% Liquid Resin Coating Substrates

[0094] Handsheet Coating

[0095] Use Samples 1-9 to coat 60 gram per square meter (g / m2) weight UPM glassine paper substrate using a Euclid Single Roll Lab hand Coater (a manual unit with precision air regulator and air gauge). Coat the substrate with a coat weight of 1.3 g / m to obtain a coating thickness in a range of 1.2 to 1.4 micrometers. The coating on the substrate was cured in a Bluemax two zone oven at a temperature of 204 °C for 25 seconds. After curing, the substrates have a release coating of curable silicone release coating composition that has been cured. Pilot Coating

[0096] Use Samples 10-23 and A-F to coat 60 g / m weight UPM glassine paper substrate using a Bluemax three roll offset gravure coater. Coat the substrate with a coat weight of 1.3 g / m2to obtain a coating thickness in a range of 1.2 to 1.4 micrometers. The coating on the substrate was cured in a Bluemax two zone oven at a temperature of 204 °C for 4 seconds. After curing, the substrates have a release coating of curable silicone release coating composition that has been cured.

[0097] Characterizing Release Coatings

[0098] Characterize the release coating formed from the curable silicone release coating compositions with the following characterization tests. Results are in Table 9.

[0099] Extractables Test

[0100] Determine the amount of extractables in the cured release coating by taking a sample of the cured release coating on the glassine substrate and cut it into three sample discs using a die cutter (3.49 centimeter diameter discs). Handle the samples only with tweezers to minimize contamination and / or damage. Analyze each disc by x-ray fluorescence (XRF) spectroscopy to determine an initial coat weight (WS). Place each disc into individual bottles (100 milliliter bottle) containing 40 milliliters of methyl isobutyl ketone, cap the bottle, and allow it to rest at 25 °C for 30 minutes. Remove each sample disc from the solvent and place each disc, coated sample side up, on a clean surface of tissue paper and allow residual methyl isobutyl ketone to evaporate (without blotting or wiping). Analyze each disc by XRF spectroscopy to determine a final coat weight (Wfs). Determine the %Extractables for each sample as the percent change in coat weight after the solvent soak using the formula:

[0101] %Extractables = [ ( W's- W^ / W^] x 100%

[0102] The %Extractables indicates how much non-cured components is extractable from the release coating. Lower %Extractables values are more desirable, with a target value that is below 10%.

[0103] Rub-Off Resistance (ROR) Test

[0104] Evaluate the anchorage strength of a release coating to a substrate using the ROR Test. Conduct the ROR test at two times per sample: (1) 12 hours (Samples 1-9) or immediately (Samples A-F and 10-19) after curing the release coating onto the substrate; and (2) after storing a cured sample at 23 °C and 50 % relative humidity for 7 days after curing. For each ROR test evaluate two 3.49 centimeter diameter discs cut from a sample of cured release coating on the glassine substrate. Determine initial coat weight (W^) on each sample using XRF spectroscopy as described above. Abrade each sample disc with a 44 millimeter felt under 1.9 kilogram load with four cycles of the felt using automated abrading equipment similar to a Taber- type abrasion test as described in ASTM D4060-19. After abrading, analyze the samples by XRF spectroscopy to determine a final coat weight (Wfa). Calculate a ROR% using the following formula:

[0105] ROR% = [Wfa / W ] x 100%

[0106] ROR% indicate how strong the release coating adheres to the substrate, with a higher ROR% corresponding to a strong adherence to the substrate. Target performance is a ROR% that is greater than 75% for the immediately tested sample and greater than 80% for the sample aged 7 days.

[0107] Release Performance Test

[0108] Laminate a sheet of release coating on glassine substrate with a piece of 25 millimeter by 200 millimeter Tesa 7475 industrial standard tape applied to the release coating. Age the sample under 20 gram per square centimeter weight at 23 °C and 50 % relative humidity for a specified period of time (7 days or 1 month) after applying the Tesa tape. Cut the laminated sheets into three strips that are 2.54 centimeters wide and 20 centimeters long for testing at each peel rate (total of 12 strips). Testing in triplicate for each peel rate, evaluate the release performance of the Tesa 7475 industrial standard tape from the release coating with an IMASS SP-2100 slip / peel tester at a peel rate of 0.3 meters per minute (m / min) and an IMASS XPE-1100W slip / peel tester at peal rates of 10 m / min, 100 m / min and 300 m / min. Use a 180° peel angle each sample and measure the force required to peel the release coating / glassine substrate from the tape in grams per inch (g / in). Target performance is:

[0109] 7 Day Aging: at least 20 g / in at 0.3 m / min; at least 55 g / in at 10 m / min, at least 80 g / in at 100 m / min, and at least 55 g / in at 300 m / min.

[0110] 1 Month Aging: at least 20 g / in at 0.3 m / min; at least 55 g / in at 10 m / min, at least 80 g / in at 100 m / min, and at least 55 g / in at 300 m / min.

[0111] Table 9 presents characteristics of the samples described hereinabove. “%Extr” is %Extractables. Release values are provided for 0.3 m / min, 10 m / min, 100 m / min, and 300 m / min (units for the rates are not included in the table, just the numerical value). Table 9

[0112] * Sample did not cure sufficiently to test.

[0113] — means not measured.

[0114] ** these samples were actually measured 12 hours after curing (T= 12 hours) rather than immediately after curing (T=0).

Claims

CLAIMS:

1. An article comprising a substrate and a curable silicone release coating composition; wherein the curable silicone release coating composition is a film that has a thickness of 2 micrometers or less and that coats at least part of at least one surface of the substrate; and wherein the curable silicone release coating composition comprises the following components:(a) an alkenyl-functional organopolysiloxane that contains an average of at least 2 alkenyl groups per molecule;(b) a silylhydride-functional organopolysiloxane that contains an average of at least 2 SiH groups per molecule;(c) a hydrosilylation catalyst;(d) a hydrosilylation inhibitor; and(e) a liquid silicone resin having an average chemical structure (III):[R3SiOi / 2]a[R2R’SiOi / 2]b[R2SiO2 / 2]c[R’SiO3 / 2]d[RSiO3 / 2]eXz(III) where:(i) the liquid silicone resin has a weight-average molecular weight, as determined by gel permeation chromatography using polystyrene standards, that is 10,000 grams per mole or less;(ii) X refers to a combination of all siloxane units that contain an SiOZ group, where Z is in each occurrence selected from hydrogen and alkyl groups;(iii) R is independently in each occurrence selected from alkyl groups having from one to 8 carbon atoms;(iv) R’ is independently in each occurrence selected from alkenyl groups having from 2 to 8 carbon atoms;(v) subscript a is the mole ratio of RsSiOi / i siloxane units in the molecule and has a value in a range of 0.23 to 0.40;(vi) subscript b is the mole ratio of R2R’SiOi / 2 siloxane units in the molecule and has a value in in a range of 0 to 0.3;(vii) subscript c is the mole ratio of R2SiO2 / 2 siloxane units in the molecule and has a value in a range of 0 to 0.1 ;(viii) subscript d is the mole ratio of R’SiO3 / 2siloxane units in the molecule and has a value in a range of 0.03 to 0.2;(ix) subscript e is the mole ratio of RSiOs / 2 siloxane units in the molecule and has a value in a range of 0.4 to 0.7;(x) subscript z has a values such that the molar concentration of SiOZ groups is 10 mole-percent or less, with mole-percent relative to total moles of silicon atoms in the molecule; where mole ratio of siloxane units are relative to the total moles of siloxane units.

2. The article of claim 1 , wherein the curable silicone release coating composition is free of silicone resin that contains Q siloxane units.

3. The article of any one previous claim, wherein the curable silicone release coating composition comprises:(a) 55 to 85 weight-percent of the alkenyl- functional organopolysiloxane;(b) 3 to 10 weight-percent of the silylhydride- functional organopolysiloxane;(c) 0.01 to 10,000 weight-parts per million weight parts of curable silicone release coating composition;(d) 0.05 to one weight-percent of the hydrosilylation inhibitor; and(e) 5 to 60 weight-percent of the liquid silicone resin; where weight-percent values are relative to curable silicone release coating composition weight.

4. The article of any one previous claim, wherein the alkenyl-functional organopolysiloxane comprises an alkenyl-functional Q-branched polymer.

5. The article of any one previous claim, wherein the alkenyl group of the alkenyl- functional organopolysiloxane is selected from a group consisting of vinyl groups and hexenyl groups.

6. The article of any one previous claim, wherein each R’ is selected from vinyl and hexenyl groups.

7. The article of any one previous claim, wherein the curable silicone release coating composition is free of organic solvent.

8. The article of any one previous claim, wherein the curable silicone release coating composition has been cured by hydrosilylation reactions between the alkenyl-functional organopolysiloxane alkenyl groups and the silylhydride-functional organopolysiloxane SiH groups to form a silicone release coating that is a film having a thickness of 2 micrometers or less that coats at least a portion of a surface of the substrate.

9. A process for preparing a silicone release coating, the process comprising:(a) providing a curable silicone release coating composition as described in any one previous claim;(b) providing a substrate; and(c) coating the curable silicone release coating composition onto the substrate as a film of curable silicone release coating that is 2 micrometers thick or less on the substrate.

10. The process of claim 9, wherein the process further comprises curing the film of curable silicone release coating composition to form a silicone release coating on the substrate.

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