Hydrosilylation pressure sensitive adhesive composition with 1-cod

Abstract

A one-component pressure sensitive adhesive composition contains: (a) a silicone resin; (b) a linear silicone with an average of at least two terminal alkenyl groups per molecule; (c) a reactive diluent with a terminal alkenyl group; (d) a crosslinker having at least two silylhydride groups per molecule; (e) 1-COD hydrosilylation catalyst; (f) optionally hydrosilylation inhibitor; and (g) less than 10 weight-percent non-reactive organic solvent relative to one-component pressure sensitive adhesive composition weight.

Description

[0001] HYDROSILYLATION PRESSURE SENSITIVE ADHESIVE COMPOSITION WITH 1-COD

[0002] FIELD

[0003] The present invention relates to hydrosilylation curable silicone pressure sensitive adhesive composition that contains a platinum (II) co-alkenyl complex with 1,5 -cyclooctadiene known as 1-COD as the catalyst.

[0004] INTRODUCTION

[0005] Pressure sensitive adhesive (PSA) compositions are curable compositions that, upon curing, form a PSA. Generally, PSA compositions useful for coating onto a substrate and then curing to form a PSA on the substrate. A common type of curing chemistry for PSA compositions is hydrosilylation where silicones with carbon-carbon double bond (C=C) functionality react with crosslinkers containing silylhydride (SiH) functionality in the presence of a hydrosilylation catalyst. Karstedt’s catalyst is perhaps the most widely used hydrosilylation catalyst in these systems, yet there are challenges with using Karstedt’s catalyst that are desirable to overcome. Karstedt’s catalyst tends to be highly effective at inducing a hydrosilylation reaction meaning hydrosilylation reactions occur rapidly in the presence of Karstedt’s catalyst. As a result, PSA compositions using Karstedt’s catalyst have a short workability timeframe once the catalyst is introduced into the PSA composition. Similarly, PSA compositions containing Karstedt’s catalyst cannot easily be compounded and stored for any reasonable period of time, which hinders formulating PSA compositions as one-component systems.

[0006] It is possible to add inhibitors such as 1-ethynyl-l -cyclohexanol (ETCH) to PSA composition containing Karstedt’s catalyst in order to slow the rapid curing reaction. ETCH inhibits Karstedt’s catalyst from catalyzing hydrosilylation reactions at lower temperatures, but allows the reaction to proceed at elevated temperatures. Use of inhibitors offer their own challenges to PSA compositions with Karstedt’s catalyst. Often, the complex of inhibitor and catalyst is not soluble in the components of the PSA composition, especially those compositions with little to no solvent. Such incompatibility can result in the inhibitor / catalyst complex phase separating and even settling out of the PSA composition as a precipitate over time, thereby causing the PSA composition to become less reactive over time. This deactivation is manifest as a reduction in shelf life for the PSA composition because over time as the inhibitor / catalyst separates from the PSA composition, the PSA composition decreases in usefulness due to decreased reactivity and that renders the PSA composition unable to cure completely if at all. Additionally, the inhibitor / catalyst complex can result in undesirable discoloration of the PSA composition.

[0007] It is desirable to enhance handleability, versatility and ease of use for PSA compositions to identify a PSA composition that can be formulated as a one-component system that contains reactants and catalyst together, but that can be formulated with an inhibitor without experiencing diminished reactivity over time (Shelf Life Stability) and that does not experience discoloration to the extent experienced by a similar PSA composition containing Karstedt’ s catalyst (Color Stability).

[0008] SUMMARY

[0009] The present invention surprisingly provides a one-component PSA composition that contains reactants and catalyst together, but that can be formulated with an inhibitor without experiencing diminished reactivity over time (that is, demonstrates Shelf Life Stability) and that does not experience discoloration (that is, demonstrates Color Stability) in the presence of inhibitor. Even more beneficial and surprising, the PSA composition of the present invention can contain less than 10 weight-percent, even less than 5 wt% non-reactive organic solvent based on the PSA composition weight and still achieve these results.

[0010] The present invention is a result of discovering that these results unexpectedly occur when using as a hydrosilylation catalyst “1-COD”, which is a platinum (11) co-alkenyl complex with 1,5-cyclooctadiene having the following structure (“Vi” is a vinyl group):

[0011] 1 -COD is a known catalyst for hydrosilylation reactions, but it has not been known to solve all of the problems discovered with the present invention, particularly Shelf Life Stability and Color Stability, let alone solve these problems in a reactive composition as complex as a PSA composition and while in the presence of little to no non-reactive organic solvent.

[0012] In a first aspect, the present invention is a one-component pressure sensitive adhesive composition comprising the following active components: (a) 50 to 80 weight-percent of a silicone resin containing R3SiOi / 2and SiO4 / 2siloxane units, where each R is independently selected from hydrocarbyl groups having from one to 20 carbons, wherein the silicone resin is free of non-aromatic alkenyl groups and up to 5 mole-percent of the oxygen atoms on the SiO4 / 2siloxane units participate in SiOZ linkages where Z is selected from hydrogen and alkyl groups having from one to 6 carbon atoms; (b) 15 to 40 weight-percent of a linear silicone with an average of at least two terminal alkenyl groups per molecule; (c) zero to 7 weight-percent of a reactive diluent with a terminal alkenyl group; (d) a crosslinker having at least two silylhydride groups per molecule at a concentration sufficient to provide a molar ratio of silylhydride to alkenyl groups in the one-component pressure sensitive adhesive composition that is in a range of 1: 1 to 40: 1; (e) 1-COD hydrosilylation catalyst at a concentration sufficient to provide a platinum concentration in a range of 15 to 250 weight parts per million weight parts of reactive pressure sensitive adhesive composition; (f) zero to one weight-percent of a hydrosilylation inhibitor; and (g) less than 10 weight-percent non-reactive organic solvent; where weight- percent values are relative to weight of one-component pressure sensitive adhesive composition.

[0013] In a second aspect, the present invention is a process for preparing a pressure sensitive adhesive comprising the steps: (a) providing the one-component pressure sensitive adhesive composition of any one of claims 1-6; and (b) heating the one-component pressure sensitive adhesive composition to a temperature of at least 60 degrees Celsius and allowing the one- component pressure sensitive adhesive composition to cure.

[0014] Composition of the present invention are useful as PSA compositions, which are useful for creating PSA coatings.

[0015] DETAILED DESCRIPTION

[0016] 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 fiir Normung; ISO refers to International Organization for Standards; and UL refers to Underwriters Laboratory.

[0017] Products identified by their tradename refer to the compositions available under those tradenames on the priority date of this document.

[0018] “Multiple” means two or more. “And / or” means “and, or as an alternative”. All ranges include endpoints unless otherwise indicated.

[0019] “Silicone” refers to a polysiloxane, which is a molecule that comprises multiple siloxane units. Identification of siloxane units often utilize abbreviations M, D, T and Q. M-type siloxane units refer to units having the chemical formula: Ra3SiOi / 2- D-type siloxane units refer to units having the chemical formula: Ra2SiO2 / 2- T-type siloxane units refer to units having the chemical formula: RaSiOs / 2. Q-type siloxane units refer to units having the chemical formula: SiO.4 / 2. In these general formulae, each Rais independently in each occurrence selected from a hydrogen, hydrocarbyl group (substituted or non-substituted), hydroxyl, alkoxyl, or essentially any other group bound to the silicon atom. The O’s refer to oxygen atoms bound the silicon that are shared with a silicon atom of another siloxane unit or a Z group (a hydrogen or alkyl). The subscript is a multiple of Vi to reflect that the oxygen is bound to and therefor shared with this silicon atom and another functionality such as an -Z group or silicon atom of another siloxane unit also having a multiple of Yi in the denominator - both siloxane units reflect ownership of Vi of the same oxygen atom. The number in the oxygen subscript reflects how many oxygens are bound to the specified silicon atom that are also bound to another siloxane unit silicon atom. Typically, there are subscripts associated with the siloxane units themselves to indicate the relative amounts of the siloxane unit in the molecule. If the subscripts associated with siloxane units are greater than one, then the subscript refers to the average number of those siloxane units in the molecule. If the subscript associated with siloxane units is less than one, then the subscript refers to the average molar ratio of the siloxane unit associated with the subscript relative to total moles of all siloxane units in the molecule. Subscripts of one are typically left unstated so if a siloxane unit does not include a subscript it is understood to have a subscript of one. A chemical formula for a silicone typically lists the siloxane units in blocks, but that does not necessarily imply block polymerization (that is, that the siloxane units exist in the molecule as blocks) but rather are presented in block for convenience to indicate how much of each siloxane unit is present total in the polymer.

[0020] A “resinous polysiloxane”, also referred to as a “silicone resin” or simply “resin”, contains 30 mole-percent (mol%) or more and can contain 50 mol% or more, 70 mol% or more, 90 mol% or more , even 100 mol% of Q-type, T-type or a sum of Q-type and T-type siloxane units. In contrast, a “non-resinous” silicone, which is often referred to simply as a “polymeric”, or “linear” silicone, siloxane or polysiloxane, contains less than 30 mol% of a combination Q- type and T-type siloxane units and often contains only siloxane groups selected from M-type and D-type siloxane units.

[0021] “Silyl hydride” functionality refers to having a hydrogen atom bonded directly to a silicon atom to form an SiH group.

[0022] Determine number average molecular weight (Mn), weight-average molecular weight (Mw) and molecular weight distribution of silicone resin by gel phase chromatography (GPC) using an Agilent Technologies 1260 Infinity chromatograph and ethyl acetate as a solvent. The chromatograph uses two columns, Agilent PLgel Mixed-D and PLgel Mixed E columns. Calibrate the chromatograph using polystyrene standards. Prepare samples by dissolving sample material (resin) in toluene (approximately 20 milligrams per milliliter) and then immediately analyzing the material by GPC using a flow rate of one milliliter per minute and a column temperature of 35 degrees Celsius (°C).

[0023] One-Component PSA Composition

[0024] In a first aspect, the present invention is a one-component pressure sensitive adhesive (PSA) composition. A PSA composition is a composition that is curable to a pressure sensitive adhesive. The PSA composition of the present invention is curable using hydrosilylation chemistry. The PSA composition of the present invention is a “one-component” PSA composition, which means that all of the components of the PSA composition are present together as a fully formulated PSA composition without immediately reacting (that is, it has some shelf stability). A “one-component” PSA composition is in contrast to a “two-part” PSA composition, which keeps reactive components of the PSA composition in two separate compositions during storage and then the two separate compositions are mixed together to form a fully formulated PSA composition just prior to use.

[0025] The one-component PSA composition of the present invention comprises: (a) a silicone resin; (b) a linear silicone; (c) optionally a reactive diluent; (d)a crosslinker; (e) a hydrosilylation catalyst; (f) optionally, a hydrosilylation inhibitor; and (g) less than 10 weight-percent organic solvent based on the one-component PSA composition weight.

[0026] (a) Silicone Resin

[0027] The silicone resin of the present invention contains RsSiOi / z and SiO4 / 2 siloxane units, where each R is independently selected from hydrocarbyl groups having from one to 20 carbons. The R groups can contain one or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more 8 or more, 9 or more, even 10 or more while at the same time contains 20 or fewer, and can contain 18 or fewer, 16 or fewer, 14 or fewer, 12 or fewer, even 10 or fewer carbon atoms. The silicone resin is free of non-aromatic alkenyl groups and can be free of any alkenyl groups. The silicone resin can consist of R3SiOi / 2 and SiO.4 / 2 siloxane units, making it a “MQ” resin.

[0028] Regardless of whether the silicone resin is a MQ resin or comprises siloxane units other than M and Q siloxane units, up to 5 mole-percent (mol%) of the oxygen atoms in the SiC>4 / 2 siloxane units participate in SiOZ linkages, where Z is selected form hydrogen and alkyl groups having from one to 6 carbon atoms. That means zero mol% or more, one mol% or more, 2 mol% or more, 3 mol% or more, even 4 mol% or more while at the same time 5 mol% or fewer, 4 mol% or fewer, 3 mol% or fewer, 2 mol% or fewer, even one mol% or fewer of the oxygen atoms in the SiO4 / 2 siloxane units participate in such SiOZ linkages (such as silanol linkages). Determine the concentration of SiOZ content (“OZ content”) as a mol% of a resin using silicon-29 ( Si) nuclear magnetic resonance (NMR) spectroscopy. Collect NMR spectra using an Agilent 500 megahertz DD2 (mi-MR-06) system equipped with a 16 mm silicone free AutoX probe or on a Varian Inova NMR (mi-MR-04) spectrometer with a proton operational frequency of 400 megahertz. Prepare samples in deuterated chloroform with 0.02 molar chromium (III) acetylacetonate (Cr(acac)s). The OZ content is the sum of the moles of alkoxyl and hydroxyl groups bound to silicon atoms stated as a percent relative to moles of silicon atoms in the molecule. Determine OZ content from the Si NMR spectrum of the molecule by identifying the peaks corresponding to the different siloxane units (M, D, and T) based on pre-determined assignments known in the art, integrating those peaks to determine relative molar concentrations of the functional groups. The OZ content is the sum of the products of molar concentration of each functional group multiplied by the number of OZ groups associate with each functional group.

[0029] Desirably, the silicone resin has a weight-average molecular weight (Mw) in a range of 8,400 to 29,000 Daltons (Da). The Mw of the silicone resin can be 10,000 Da or more, 12,000 Da or more, 14,000 Da or more, even 16,000 or more while at the same time is typically 29,000 Da or less, or even 27,000 Da or less, 25,000 Da or less, 23,0000 Da or less, 21,000 Da or less, 19,000 Da or less, or even 17,000 or less.

[0030] One suitable silicone resin is a trimethylsilyl-capped MQ resin having a Mn of approximately 3700 Daltons and a Mw of approximately 16,800 Daltons with an OZ content in the form of SiOH of approximately 4. 1 mol%.

[0031] The concentration of silicone resin in the PSA composition of the present invention is desirably 50 weight-percent (wt%) or more and can be 55 wt% or more, 60 wt% or more, 65 wt% or more, 70 wt% or more, even 75 wt% or more while at the same time is generally 80 wt% or less, and can be 75 wt% or less, 70 wt% or less, 65 wt% or less, 60 wt% or less, even 55 wt% or less of the one-component PSA composition.

[0032] (b) Linear Silicone

[0033] The linear silicone of the present invention has an average of at least two terminal alkenyl groups per molecule. Terminal alkenyl groups are attached to silicon atoms of M type siloxane units. Desirably, the linear silicone of the present invention has one or more than one alkenyl group on different ends of the linear molecule thereby forming an alkenyl endblocked silicone. Desirably, the alkenyl groups are vinyl groups. The linear silicone can be, for example, one or any combination or more than one vinyl- endblocked polydimethylsiloxane having the following chemical structure:

[0034] Vix(CH3)(3-X)SiO[(CH3)2SiO]ySiViz(CH3)(3-z) (I) where:

[0035] Vi refers to a vinyl group; x and z are each independently an average value in a range of 1 to 3 and can be one or more, even two or more while at the same time 3 or less, or even 2 or less; and y has an average value in a range of 125 to 175 and can be 125 or more, 130 or more, 135 or more, 140 or more, 145 or more, 150 or more, 155 or more, 160 or more, 165 or more, even 170 or more while at the same time is typically 175 or less, and can be 170 or less, 165 or less, 160 or less, 155 or less, even 150 or less.

[0036] The linear silicone is desirably present at a concentration of 15 wt% or more and can be present at a concentration of 20 wt% or more, 25 wt% or more, 30 wt% or more, even 35 wt% or more while at the same time is present at a concentration of 40 wt% or less, and can be present at a concentration of 35 wt% or less, 30 wt% or less, 25 wt% or less, or even 20 wt% or less relative to weight of the one-component PSA composition.

[0037] (c) Reactive Diluent

[0038] The one-component PSA composition of the present invention can comprise a reactive diluent or can be free of reactive diluent. The reactive diluent is desirably an unsaturated hydrocarbon, typically a linear alkene. Preferably, the reactive diluent is a terminally unsaturated linear hydrocarbon selected from one or any combination or more than one compound having the following chemical structure:

[0039] CH3(CH2)nCH=CH2(II) where subscript n has an average value that is typically 5 or more, 6 or more 7 or more, 8 or more 9 or more 10 or more, 11 or more, 12 or more, 14 or more 16 or more, and can be 18 or more while at the same time is typically 20 or less, and can be 18 or less, 16 or less, 14 or less, 13 or less, 12 or less or even 11 or less.

[0040] The concentration of reactive diluent in the one-component PSA composition of the present invention is typically zero wt% or more, and can be one wt% or more, 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% or more, even 6 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, 4 wt% or less, 3 wt% or less, 2 wt% or less, or even one wt% or less relative to one- component PSA composition weight. (d) Crosslinker

[0041] The one-component PSA composition of the present invention comprise a crosslinker. The crosslinker has an average of at least two silyhydride (SiH) groups per molecule. Desirably, the crosslinker is a linear silicone, even more desirably a linear silicone with pendant SiH groups as opposed to terminal SiH groups. Pendant SiH groups are on siloxane units other than M type siloxane units.

[0042] The crosslinker can be a trimethylsiloxy terminated polymethylhydrogen siloxane copolymer. The trimethylsiloxy terminated polymethylhydrogen siloxane copolymer can have the following chemical structure:

[0043] Me3SiO-[Me2SiO]a-[HMeSiO]b-SiMe3 (III) where:

[0044] “Me” refers to a methyl group; subscript a typically has an average value that is one or more, and can be a value of 2 or more, even 3 or more while at the same time is typically a value of 10 or less, and can be a value of 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, even 4 or less; and subscript b typically has an average value of 2 or more, and can be a value of 3 or more, 4 or more, 5 or more, even 6 or more while at the same time is typically a value of 10 or less, and can be 9 or less, 8 or less, or even 7 or less.

[0045] The concentration of crosslinker in the one-component PSA composition is sufficient to provide a molar ratio of SiH groups (from the crosslinker) to alkenyl groups in the one- component PSA composition that is in a range of 1: 1 to 40: 1, and that can be 1: 1 or more, 2: 1 or more, 3: 1 or more, 4: 1 or more, 5: 1 or more, 6:1 or more, 7:1 or more, 8: 1 or more, 9: 1 or more, 10:1 or more, 15: 1 or more, 20:1 or more, 25: 1 or more, 30:1 or more, even 35:1 or more while at the same time is 40: 1 or less, and can be 35: 1 or less, 30: 1 or less, 25:1 or less, 20:1 or less; 15:1 or less, 10: 1 or less, even 5: 1 or less.

[0046] (e) Hydrosilylation Catalyst

[0047] The one-component PSA composition of the present invention comprises 1-COD as a hydrosilylation catalyst. Surprisingly, the present invention has at least partially been a result of discovering surprisingly benefits of using 1-COD as a hydrosilylation catalyst in one-component PSA compositions. One of the surprising results is that the one-component PSA composition can comprise hydrosilylation inhibitor at the same time as the 1-COD hydrosilylation catalyst while retaining reactivity to hydrosilylation over time. Additionally, the one-component PSA composition of the present invention does not experience discoloration in the presence of inhibitor, which is also a problem associated with other platinum-based hydrosilylation catalysts.

[0048] The concentration of 1-COD hydrosilylation catalyst in the one-component PSA composition of the present invention is sufficient to provide a platinum concentration in a range of 15 to 250 weight parts per million weight parts of one-component PSA composition (PPM), and can be sufficient to provide a concentration of platinum of 15 PPM or more, 20 PPM or more, 25 PPM or more, 50 PPM or more, 75 PPM or more, 100 PPM or more 125 PPM or more, 150 PPM or more, 175 PPM or more, 200 PPM or more, or even 225 PPM or more while at the same time 250 PPM or less, even 200 PPM or less, 190 PPM or less, 180 PPM or less, 170 PPM or less, 160 PPM or less, or evenl55 PPM or less.

[0049] The one-component PSA composition can be and desirably is free of platinum hydrosilylation catalysts other than 1-COD, such as Karstedt’s catalyst.

[0050] (f) Hydrosilylation Inhibitor

[0051] The one-component PSA composition of the present invention can and desirably does contain a hydrosilylation inhibitor. Hydrosilylation inhibitor can be desirable to slow or delay reactivity of a one-component PSA composition in order to inhibit gelling of a one-component PSA composition during storage. However, as mentioned previously herein, the combination of hydrosilylation inhibitor and platinum-containing hydrosilylation catalyst can also result in detrimental effects such as discoloration or diminished reactivity of a one-component PSA composition containing such a combination. Surprisingly, the one-component PSA composition of the present invention can contain both hydrosilylation inhibitor and 1-COD hydrosilylation catalyst without suffering from discoloration or significant reduction in reactivity.

[0052] Examples of suitable hydrosilylation inhibitors include any one or any combination of more than one of acetylene-type compounds such as 2-methyl-3-butyn-2-ol; 3-methyl-l-butyn-3- ol; 3,5-dimethyl- l-hexyn-3-ol; 2-phenyl-3-butyn-2-ol;3-phenyl- l-butyn-3-ol; 1-ethynyl-l- cyclohexanol; 1 , l-dimethyl-2-propynyl)oxy)trimethylsilane; methyl(tris(l,l-dimethyl-2- propynyloxy))silane; and 1-ethynyl-l -cyclohexanol (ETCH); ene-yne compounds such as 3- methyl-3-penten-l-yne and 3,5-dimethyl-3-hexen-l-yne; triazols such as benzotriazole; hydrazine-based compounds; phosphines-based compounds; mercaptane-based compounds; cycloalkenylsiloxanes including methylvinylcyclosiloxanes such as 1,3, 5, 7-tetramethyl-l, 3, 5, 7- tetravinyl cyclotetrasiloxane and 1,3, 5, 7-tetramethyl-l, 3, 5, 7-tetrahexenyl cyclotetrasiloxane.

[0053] The concentration of hydrosilylation inhibitor is zero wt% or more, and can be 0.05 wt% or more, 0.10 wt% or more, 0.15 wt% or more, 0.20 wt% or more, 0.25 wt% or more, even 0.29 wt% or more while at the same time is typically one wt% or less, and can be 0.90 wt% or less, 0.80 wt% or less, 0.70 wt% or less, 0.60 wt% or less, 0.50 wt% or less, 0.40 wt% or less, even 0.30 wt% or less relative to weight of the one-component PSA composition.

[0054] (g) Non-Reactive Organic Solvent

[0055] The one-component PSA composition of the present invention can comprise very little non-reactive organic solvent, which makes it desirable in applications where residual organic solvent is undesirable. Non-reactive organic solvent refers to organic solvent that does not participate in hydrosilylation reactions. For instance, the reactive diluent participates in hydrosilylation reactions so does not qualify as a non-reactive organic solvent.

[0056] Non-reactive organic solvents can be aromatic or aliphatic. Examples of aromatic non- reactive organic solvents include benzene, toluene, xylene, and combinations thereof. Examples of aliphatic non-reactive organic solvents include pentane, hexane, heptane, octane, nonane, decane and combinations thereof.

[0057] The one-component PSA composition of the present invention can contain less than 10 wt%, and preferably contains 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less, or even one wt% or less non-reactive organic solvent relative to weight of the one-component PSA composition. The one-component PSA composition of the present invention can be free of non-reactive organic solvent.

[0058] Process for Preparing a PSA

[0059] In a second aspect, the present invention is a process for preparing a PSA comprising the following steps: (a) providing the one-component PSA composition of the first aspect of the present invention; and (b) heating the one-component PSA composition to a temperature of at least 60 °C and allowing the one-component PSA composition to cure. Preferably, heat the one- component PSA composition in step (b) to a temperature of 80 °C or higher, 90°C or higher, 100 °C or higher, 110 °C or higher, 120 °C or higher, 130 °C or higher, 140 °C or higher, even 150°C or higher while at the same time typically to a temperature of 250 °C or less, preferably 200 °C or less, even 180 °C or less to cure the one-component PSA composition.

[0060] The process of the second aspect can further comprise coating the one-component PSA composition onto a substrate after step (a) and prior to step (b). This additional step results in a cured PSA coating on the substrate.

[0061] EXAMPLES

[0062] Table 1 lists the components for preparing the samples in this section. Table 1

[0063] DOWSIL is a trademark of The Dow Chemical Company.

[0064] PSA Stock Mixture Prepare a PSA Stock Mixture by combining 287.22 grams (g) of Silicone Resin, 107.02 g of Linear Silicone and 14.63 g of Reactive Diluent into a single neck, one-liter flask. Load the flask onto a rotovap that has a dry ice condenser and hot oil bath set at 150 °C. Draw a vacuum on the flask (< 133 Pascal pressure) while rotating at 25 revolutions per minute for one hour in order to strip out volatiles such as non-reactive organic solvents. Catalyst Solutions

[0065] Prepare a Benchmark Catalyst solution by combining 0.501 g Karstedt’s Catalyst and 22.104 g Solvent.

[0066] Prepare a 1-COD Catalyst solution by combining 0.501 g of 1-COD Catalyst and 36.88 g Solvent. PSA Intermediate Composition

[0067] Prepare a Benchmark PSA Intermediate Composition by combining 250.00 g of PSA Stock Mixture, 0.650 g of Inhibitor and 8.00 g of Benchmark Catalyst solution.

[0068] Prepare a 1-COD PSA Intermediate Composition by combining 250.00 g of PSA Stock, Mixture, 0.642 g of Inhibitor and 8.02 g of 1-COD Catalyst solution.

[0069] Benchmark PSA Composition - Karstedt’s Catalyst

[0070] Prepare a one-component PSA composition by combining 26.02 g of Benchmark PSA Intermediate Composition and 1.43 g of Crosslinker.

[0071] Inventive PSA Composition - 1-COD Catalyst

[0072] Prepare a one-component PSA composition by combining 26.02 g of 1-COD PSA Intermediate Composition and 1.43 g of Crosslinker.

[0073] Table 2 identifies the composition of the Benchmark PSA Composition and the Inventive PSA Composition showing the amount of components in both grams (g) and wt% values.

[0074] Table 2

[0075] *Silicone resin values are for the resin solids of the Silicone Resin because the xylene is removed after forming the PSA Stock Mixture and prior to forming the complete PSA Composition. This table does not include xylene as it is not present in the PSA compositions.

[0076] Characterization of the one-component PSA Compositions

[0077] Both the Benchmark PSA Composition and the Inventive PSA Composition were characterized for Color Stability, Reactivity Stability, Tack and Adhesion using the following procedures. Color Stability

[0078] The color of each PSA Composition was monitored over time to determine whether the color changed.

[0079] To understand the compatibility between catalyst and inhibitor, the PSA stock mixture and the Conventional or 1-COD catalyst solutions and inhibitor, as the case may be, were combined and mixed to give a mixture. Each mixture was aged at RT under air in a capped vial. The color change of each mixture was monitored visually over time. At certain times as noted in Table 3 (and Table 4 for Reactivity Stability), crosslinker was added to each mixture to provide the Benchmark PSA composition and Inventive PSA composition, and the composition was mixed on dental mixer at 3500 RPM for 30 seconds. Each composition was then analyzed via differential scanning calorimetry (DSC) and for appearance over time via visual inspection. DSC was measured via a TA DSC-2500 DSC by heating each sample composition from 40 °C to 200 °C under N2 protection. In each of the compositions, the content of platinum was the same at 150-151 PPM, and the total ratio of silicon-bonded hydrogen atoms to silicon-bonded vinyl groups was the same atl.9 / 1 mol / mol (SiH to SiVi). Tables 3 and 4 below describe color change and the DSC data at time intervals for the compositions of benchmark PSA composition and inventive PSA composition, respectively.

[0080] The results of the Color Stability test are in Table 3. Ideally, the composition start and remain close to colorless. As revealed in Table 3, the combination of the benchmark catalyst solutions and inhibitor caused undesirable precipitation and color changes over time for the composition of benchmark PSA composition, which is undesirable and problematic in the release coating industry as a whole. In contrast, no obvious color change or precipitation was observed with the combination of the 1-COD catalyst solutions and inhibitor over time resulting in clear inventive PSA composition.

[0081] Table 3

[0082] Reactivity Stability

[0083] Cure performance stability of PSA composition is also critical to the industry desires for PSA compositions. Thus, the reactivity of the PSA compositions was evaluated by using an DSC characterization to determine if the PSA compositions remain reactive over time. This evaluation determines the storage stability of the PSA compositions with respect to hydrosilylation reactivity - does the PSA composition decrease in reactivity over time.

[0084] Differential Scanning Calorimetry (DSC) is a powerful technique used to analyze the reactivity of curable coating systems. It measures the heat flow associated with thermal transitions in materials, offering insights into their curing behavior. When applied to a curable coating system, DSC can provide valuable information on the curing process by measuring parameters like peak temperature (Tpeak) and 95% conversion temperature (T95). Tpeak: This represents the maximum heat flow or the peak temperature observed during the curing process of the coating system. It corresponds to the point where the curing reaction is at its most active or exothermic, indicating the maximum rate of reaction and energy release during curing. T95: This indicates the temperature at which 95% of the conversion or curing process has occurred. It reflects the point at which most of the material has undergone the curing reaction, signifying the near-completion of the curing process. By analyzing these parameters using DSC, one can assess the reactivity and curing behavior of the coating system. Understanding Tpeak and T95 provides insight into reactivity of the tested PSA system.

[0085] As shown by Table 4, when the composition of Benchmark PSA composition including the conventional Catalyst and Inhibitor mixture was aged, the cure performance became increasingly worse - both Tpeak and T95 dramatically increased over time. Further still, color change and precipitation also increased over. In contrast, the inventive Catalyst has no compatibility issues with the Inhibitor, as demonstrated by the Inventive PSA composition including the 1-COD catalyst and inhibitor mixture was aged which has no cure performance change (both Tpeaand T95 remained almost unchanged) over time.

[0086] Table 4 Tack and Adhesion

[0087] Confirm the PSA composition serve as pressure sensitive adhesives one cured by evaluating their tack and adhesion in the following tests.

[0088] For each of the Benchmark and Inventive PSA Compositions, use a 1.5 mil application bar to draw a PSA composition film down onto a 2 mil polyester (PET) sheet sing a vacuum coating board. Cure each PSA composition film at 150 °C for 5 minutes. Allows the cured samples to age for 24 hours at 21 °C and 50% relative humidity prior to testing. Then cut the samples of cured PSA film on PET sheet into 1 inch wide strips for tack and adhesion testing.

[0089] Tack Testing

[0090] Conduct Tack Testing according to ASTM D2979. Test samples on a PT-1000 Probe Tack Tester with a dwell time of 1.0 seconds. Make 10 measurements, discard the high and low values and then average the remaining 8 to obtain a tack value in grams.

[0091] The results of the Tack test are in Table 5. The PSA needs to maintain a tack greater than 100 grams for optimal performance. Results show that both the Inventive PSA composition and Benchmark PSA meet this threshold.

[0092] Table 5

[0093] Adhesion Testing

[0094] Conduct Adhesion Testing using a Peel adhesion (180°) method according to PSTC-101 standards. Apply sample strips to a clean stainless steel panel (5 centimeters by 15 centimeters; 2 inches by 6 inches) using a 2 kilogram roller. Allow the samples to dwell for 20 minutes at 21 °C and 50 % relative humidity. Evaluate the samples by pulling at 180 ° peel angle at a rate of 30.5 centimeter (12 inches) per minute using a TMI Release and Adhesion Tester. Take the average of three measurements for each sample and report results with units of grams per inch. The results of the Adhesion test are in Table 6. The PSA needs to maintain an adhesion greater than 1000 grams per inch for optimal performance. Results show that both the Inventive

[0095] PSA composition and Benchmark PSA meet this threshold.

[0096] Table 6

Claims

CLAIMS:What is claimed is1. A one-component pressure sensitive adhesive composition comprising the following active components:(a) 50 to 80 weight-percent of a silicone resin containing R3SiOi / 2 and SiO4 / 2 siloxane units, where each R is independently selected from hydrocarbyl groups having from one to 20 carbons, wherein the silicone resin is free of non-aromatic alkenyl groups and up to 5 mole-percent of the oxygen atoms on the SiO4 / 2 siloxane units participate in SiOZ linkages where Z is selected from hydrogen and alkyl groups having from one to 6 carbon atoms;(b) 15 to 40 weight-percent of a linear silicone with an average of at least two terminal alkenyl groups per molecule;(c) zero to 7 weight-percent of a reactive diluent with a terminal alkenyl group;(d) a crosslinker having at least two silylhydride groups per molecule at a concentration sufficient to provide a molar ratio of silylhydride to alkenyl groups in the one-component pressure sensitive adhesive composition that is in a range of 1:1 to 40:1;(e) 1-COD hydrosilylation catalyst at a concentration sufficient to provide a platinum concentration in a range of 15 to 250 weight parts per million weight parts of reactive pressure sensitive adhesive composition;(f) zero to one weight-percent of a hydrosilylation inhibitor; and(g) less than 10 weight-percent non-reactive organic solvent; where weight-percent values are relative to weight of one-component pressure sensitive adhesive composition.

2. The one-component pressure sensitive adhesive composition of claim 1, wherein the one- component pressure sensitive adhesive composition comprises from 0.05 to one weight- percent hydrosilylation inhibitor based on one-component pressure sensitive adhesive composition weight.

3. The one-component pressure sensitive adhesive composition of any one previous claim, wherein:(a) the linear silicone is a vinyl-endblocked poly dimethylsiloxane;(b) the reactive diluent is a linear alkene; and(c) the crosslinker is trimethylsiloxy terminated polydimethylsiloxane polymethylhydrogensiloxane copolymer.

4. The one-component pressure sensitive adhesive composition of any one previous claim, wherein the silicone resin is an MQ resin having a weight- average molecular weight in a range of 8,400 to 29,000 Daltons and has a silanol content of 4 mole-percent.

5. The one-component pressure sensitive adhesive composition of any one previous claim, wherein the linear silicone with at least two terminal alkenyl groups per molecule has a chemical structure: Vix(CH )(3_X)SiO[(CH3)2SiO]ySiViz(CH3)(3_Z) where Vi refers to a vinyl group, x and z are each independently a value in a range of 1 to 3 and y is a value in a range of 125 to 175.

6. The one-component pressure sensitive adhesive composition of any one previous claim, wherein the crosslinker has the chemical composition: (CH3)3SiO[(CH3)2SiO]a[(CH3 HSiO]bSi(CH3)3 where subscript a has an average value in a range of 2 to 5 and subscript b has an average value in a range of 5 to 8.

7. The one-component pressure sensitive adhesive composition of any one previous claim, wherein the one-component pressure sensitive adhesive composition is free of platinum hydrosilylation catalyst other than 1-COD.

8. A process for preparing a pressure sensitive adhesive comprising the steps:(a) providing the one-component pressure sensitive adhesive composition of any one of claims 1-6; and(b) heating the one-component pressure sensitive adhesive composition to a temperature of at least 60 degrees Celsius and allowing the one-component pressure sensitive adhesive composition to cure.

9. The process of claim 8, further comprising coating the one-component pressure sensitive adhesive composition onto a substrate after step (a) and prior to step (b).

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