METHOD FOR PREPARING A LAMINATE INCLUDING A SILICONE PRESSURE

SENSITIVE ADHESIVE ADHERED TO FLUOROSILICONE RUBBER OR SILICONE

FOAM

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63/317,126 filed on 7 March 2022 and U.S. Provisional Patent Application Serial No.

63/335,735 filed 28 April 2022 under 35 U.S.C. §119 (e). U.S. Provisional Patent Application Serial No. 63,317,126 and 63/335,735 is hereby incorporated by reference.

FIELD

[0002] This invention relates to a method for preparing a silicone pressure sensitive adhesive composition that can be cured to form a silicone pressure sensitive adhesive with strong adhesion to substrates to which conventional silicone pressure sensitive adhesives typically exhibit weak adhesion. More particularly, this invention relates to a method for preparing a peroxide curable silicone pressure sensitive adhesive composition that cures to form a silicone pressure sensitive adhesive with strong adhesion to fluorosilicone rubber or silicone foam. A laminate includes the silicone pressure sensitive adhesive adhered to a substrate comprising a fluorosilicone rubber article or a silicone foam article.

INTRODUCTION

[0003] Current commercially available silicone pressure sensitive adhesives may suffer from the drawback of providing relatively weak adhesion strength to fluorosilicone rubber articles and silicone foam articles. This weak adhesion often fails to meet the application needs where silicone pressure sensitive adhesives are used to bond to these articles, such as in electronics, automotive, and masking tape applications.

SUMMARY

[0004] A method for fabricating a laminate comprising an article selected from the group consisting of a fluorosilicone rubber article and a silicone foam article is provided. The method comprises:

(a) combining, under conditions to effect condensation reaction, starting materials comprising

(P) a bis-hydroxyl-terminated polydiorganosiloxane with a weight average molecular weight of 10,000 g/mol to < 200,000 g/mol measured by GPC,

(R) a hydroxyl-functional polyorganosilicate resin with a weight average molecular weight of 4,000 g/mol to < 10,000 g/mol measured by GPC, where starting materials (R) and (P) and are present in a weight ratio (R)/(P) of 0.76/1 to 2.15/1; and

(S) a solvent, thereby producing a reaction mixture;

(b) adding (C) a condensation reaction catalyst to the reaction mixture, thereby producing a catalyzed reaction mixture;

(c) heating the catalyzed reaction mixture at a temperature of > RT to 145 °C and removing water, thereby forming a silicone pressure sensitive adhesive composition;

(d) coating the silicone pressure sensitive adhesive composition on a surface of a backing substrate,

(e) drying the silicone pressure sensitive adhesive composition,

(f) curing the silicone pressure sensitive adhesive composition to form a silicone pressure sensitive adhesive layer having a surface adhered to the surface of the backing substrate, where the silicone pressure sensitive adhesive layer further comprises an opposing surface opposite the surface of the backing substrate; and

(g) adhering the opposing surface of the silicone pressure sensitive adhesive and a surface of the article selected from the group consisting of the fluorosilicone rubber article and the silicone foam article.

BRIEF DESCRIPTION OF THE DRAWING

[0005] Figure 1 shows a partial cross section of a laminate article 100.

[0006] Figure 2 shows a partial cross section of a laminate article 200.

Reference Numerals

100 partial cross section of a laminate article

101 backing substrate

101b surface of backing substrate 101

102 silicone pressure sensitive adhesive

102a surface of silicone pressure sensitive adhesive 102

102b opposing surface of silicone pressure sensitive adhesive 102

103 fluorosilicone rubber article

103a surface of fluorosilicone rubber article 103

200 partial cross section of a laminate article

201 backing substrate comprising a silicone rubber

201b surface of backing substrate 201

202 silicone pressure sensitive adhesive

202a surface of silicone pressure sensitive adhesive 202

202b opposing surface of silicone pressure sensitive adhesive 202

DETAILED DESCRIPTION [0007] A method for fabricating a laminate comprises:

(1) combining, under conditions to effect condensation reaction, starting materials comprising

(P) a bis-hydroxyl-terminated polydiorganosiloxane with a weight average molecular weight of 10,000 g/mol to < 200,000 g/mol measured by GPC;

(R) a hydroxyl-functional polyorganosilicate resin with a weight average molecular weight of 4,000 g/mol to < 10,000 g/mol measured by GPC;

(S) a solvent; and optionally (N) a neutralizer; where starting materials (R) and (P) and are present in a weight ratio (R)/(P) of 0.76/1 to 2.15/1; thereby producing a reaction mixture; and

(2) adding (C) a condensation reaction catalyst to the reaction mixture, thereby producing a catalyzed reaction mixture;

(3) heating the catalyzed reaction mixture at a temperature of > RT to 145 °C and removing water; optionally (4) recovering a condensation reaction product of (P) and (R); optionally (5) adding up to 4 weight %, based on combined weights of (R) and (P), of (X) a peroxide crosslinking agent, thereby forming a silicone pressure sensitive adhesive composition; optionally (6) treating a surface of a backing substrate;

(7) coating the silicone pressure sensitive adhesive composition on the surface of the backing substrate,

(8) drying the silicone pressure sensitive adhesive composition,

(9) curing the silicone pressure sensitive adhesive composition to form a silicone pressure sensitive adhesive layer having a surface adhered to the surface of the backing substrate, where the silicone pressure sensitive adhesive layer further comprises an opposing surface opposite the surface of the backing substrate; optionally (10) treating a surface of an article selected from the group consisting of a fluorosilicone rubber article and a silicone foam article; and

(11) adhering the opposing surface of silicone pressure sensitive adhesive and the surface of the article.

[0008] Step (1) of the method described above may be performed by any convenient means, such as mixing starting materials comprising (P), (R), (S), and optionally (N) as introduced above and described in detail below, in a batch reactor, optionally with an agitator and jacketing. The condensation reaction may be performed at a temperature of 20 °C to 150 °C, alternatively RT to the reflux temperature of starting material (S), the solvent. The time for reaction depends on various factors including the selection of starting materials and the temperature, however, condensation reaction in step (1) may be performed in, e.g., 0.5 hour to 20 hours, alternatively 1 hour to 10 hours. The condensation reaction may be performed as described, for example, in U.S. Patent 5,916,981 to Cifuentes, et al., by varying the appropriate starting materials to those described below.

(P) Bis -Hydroxyl Terminated Polydiorganosiloxane

[0009] Starting material (P) is the bis-hydroxyl terminated polydiorganosiloxane (Polymer) used in step (1). This Polymer may have formula each R ¹ is an independently selected alkyl group of 1 to 6 carbon atoms, and subscript a represents average number of difunctional siloxane units per molecule, and 250 < a < 3,000, alternatively 270 < a < 2,000. Alternatively, subscript a may be at least 250, alternatively at least 270, alternatively at least 300, alternatively, at least 350, alternatively at least 400, alternatively at least 450, and alternatively at least 500, while at the same time, subscript a may be up to 3,000, alternatively up to 2,500, alternatively up to 2,000, alternatively up to 1,500, alternatively up to 1,100, and alternatively up to 1,000. Examples of alkyl groups for R ¹ include methyl, ethyl, propyl (including n-propyl and isopropyl), butyl (including n-butyl, tert-butyl, sec-butyl, and isobutyl), pentyl (including n-pentyl, cyclopentyl, and branched isomers with 5 carbon atoms), and hexyl (including n-hexyl, cyclohexyl, and branched isomers with 6 carbon atoms). Alternatively, each R ¹ may be methyl or ethyl; alternatively methyl.

[0010] Suitable Polymers for starting material (P) are known in the art and are commercially available from various sources, such as Gelest Inc. of Morrisville, Pennsylvania, USA, and DSC. Examples of suitable Polymers include bis-hydroxyl terminated polydimethylsiloxanes with Mw of 20,000 g/mol to 150,000 g/mol, alternatively 40,000 g/mol to 135,000 g/mol, alternatively 75,000 g/mol to 135,000 g/mol; and alternatively 100,000 g/mol to 140,000 g/mol; where Mw can be measured by GPC.

[0011] The amount of Polymer may be sufficient to provide 32 weight % to 56 weight %, alternatively 37 weight % to 52 weight %, alternatively 42 weight % to 47 weight %, based on combined weights of starting materials (P) the Polymer, (R) the Resin, (N) the neutralizer, and (C) the condensation reaction catalyst.

(R) Polyorganosilicate Resin

[0012] Starting material (R) is the hydroxyl-functional polyorganosilicate resin (Resin) used in step (1). The Resin comprises monofunctional units of formula R^SiOic and tetrafunctional silicate units (“Q” units) of formula SiO4/2, where R ¹ is as described above. Alternatively, the monofunctional units may be exemplified by M units of formula (Me3SiOi/2). The polyorganosilicate resin is soluble in solvents such as those described below as starting material (S), exemplified by aliphatic and/or aromatic hydrocarbons, such as benzene, toluene, xylene, ethyl benzene, heptane, and combinations thereof.

[0013] When prepared, the Resin comprises the monofunctional and tetrafunctional units described above, and the Resin further comprises units with silicon bonded hydroxyl groups and may comprise neopentamer of formula Si(OSiR ¹ 3)4, where R ¹ is as described above, e.g., the neopentamer may be tetrakis(trimethylsiloxy)silane. The concentration of silanol groups present in the Resin may be determined using FTIR spectroscopy according to ASTM Standard E-168- 16. Molar ratio of monofunctional and tetrafunctional units, where said ratio is expressed as {M(resin)}/{Q(resin)}, or M:Q, excluding monofunctional and tetrafunctional units from the neopentamer. M:Q ratio represents the molar ratio of the total number of triorganosiloxy groups (monofunctional units) of the resinous portion of the polyorganosilicate resin to the total number of silicate groups (Q units) in the resinous portion. M:Q ratio may be 0.5:1 to 1.5:1.

[0014] The Mn of the polyorganosilicate resin depends on various factors including the types of alkyl groups represented by R ¹ that are present. The Mn of the polyorganosilicate resin refers to the number average molecular weight measured using GPC, when the peak representing the neopentamer is excluded from the measurement. The Mn of the polyorganosilicate resin may be 2,000 to 3,500 g/mol. The Mw of the polyorganosilicate resin refers to the weight average molecular weight measured using GPC. The Mw of the polyorganosilicate resin may be at least 4,000 g/mol, alternatively at least 5,000 g/mol, alternatively at least 5,500 g/mol, while at the same time the Mw may be < 10,000 g/mol, alternatively up to 9,000 g/mol, alternatively up to 8,500 g/mol. Alternatively, the Mw of the polyorganosilicate resin may be 4,000 g/mol to < 10,000 g/mol; alternatively 5,000 g/mol to 9,000 g/mol; alternatively 5,500 g/mol to 8,500 g/mol.

[0015] The polyorganosilicate resin can be prepared by any suitable method, such as cohydrolysis of the corresponding silanes or by silica hydrosol capping methods. The polyorganosilicate resin may be prepared by silica hydrosol capping processes such as those disclosed in U.S. Patent 2,676,182 to Daudt, et al.; U.S. Patent 4,611,042 to Rivers-Farrell et al.; and U.S. Patent 4,774,310 to Butler, et al. The method of Daudt, et al. described above involves reacting a silica hydrosol under acidic conditions with a hydrolyzable triorganosilane such as trimethylchlorosilane, a siloxane such as hexamethyldisiloxane, or mixtures thereof, and recovering a copolymer having monofunctional units and Q units. The resulting copolymers generally contain from 2 to 5 percent by weight of hydroxyl groups.

[0016] The intermediates used to prepare the polyorganosilicate resin may be triorganosilanes and silanes with four hydrolyzable substituents or alkali metal silicates. The triorganosilanes may have formula R^SiX ¹ , where R ¹ is as described above and X ¹ represents a hydrolyzable substituent such as hydroxyl. Silanes with four hydrolyzable substituents may have formula SiX ² 4, where each X ² is halogen, alkoxy or hydroxyl. Suitable alkali metal silicates include sodium silicate.

[0017] The Resin selected for starting material (R) may have unit formula (R ¹ 3SiOi/2)b(SiO4/2)c(HOi/2)d, where each R ¹ is an independently selected alkyl group of 1 to 6 carbon atoms as described above, subscripts b and c represent mole fractions of monofunctional and tetrafunctional units, respectively, and subscripts b and c have values such that 0.4 < b < 0.5, 0.5 < c < 0.6, and a quantity (b + c) = 1; subscript d represents a quantity of hydroxyl groups in the Resin, and subscript d has a value sufficient to provide the Resin with a hydroxyl content of 2 weight % to 5 weight % and Mw is as described above. Suitable Resins are known in the art and are commercially available, e.g., from DSC. The amount of Resin may be sufficient to provide 43 weight % to 68 weight %, alternatively 48 weight % to 63 weight %, and 53 weight % to 58 weight %, of Resin based on combined weights of starting materials (P), (R), (N), and (C).

[0018] The Resin (R) and Polymer (P) are present in a weight ratio (R)/(P) of 0.76/1 to 2.15/1. Alternatively, (R)/(P) may be 0.93/1 to 1.40/1, and alternatively 1.14/1 to 1.40/1. Alternatively (R)/(P) may be at least 0.76/1, alternatively at least 0.93/1, and alternatively at least 1.14/1, while at the same time (R)/(P) may be up to 2.15/1, alternatively up to 1.72/1, and alternatively up to 1.40/1. Without wishing to be bound by theory, it is thought that (R)/(P) of < 0.76/1 or higher than 2.15/1 may result in a silicone pressure sensitive adhesive that has insufficient adhesion to fluorosilicone rubber or silicone foam, or both.

(S) Solvent

[0019] Starting material (S) is a solvent. The solvent may be added during step (1) and optionally a later step, e.g., step (2), to facilitate introduction of certain starting materials, such as (R) the Resin. Solvents that can be used herein are those that help fluidize the starting materials but essentially do not react with the starting materials. The solvent may be selected based on solubility the starting materials and volatility of the solvent. The solubility refers to the solvent being sufficient to dissolve and/or disperse a starting material. Volatility refers to vapor pressure of the solvent. Without wishing to be bound by theory, it is thought that if the solvent is too volatile (having too high vapor pressure) the solvent may volatilize out of the reaction mixture during step (3) too quickly. However, if the solvent is not volatile enough (too low vapor pressure) too much of the solvent may remain in the condensation reaction product prepared in step (3) and/or water produced as a side product of the condensation reaction may be insufficiently removed during step (3), and when present, step (4).

[0020] Suitable solvents include polyorganosiloxanes with suitable vapor pressures, such as hexamethyldisiloxane, octamethyltrisiloxane, hexamethylcyclotrisiloxane and other low molecular weight polyorganosiloxanes, such as 0.5 to 1.5 cSt DOWSIL™ 200 Fluids and DOWSIL™ OS FLUIDS, which are commercially available from DSC.

[0021] Alternatively, the solvent may comprise an organic solvent. The organic solvent can be a ketone such as acetone, methylethyl ketone, or methyl isobutyl ketone; an aromatic hydrocarbon such as benzene, toluene, ethylbenzene or xylene; an aliphatic hydrocarbon such as heptane, hexane, or octane; a glycol ether such as propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol n-butyl ether, propylene glycol n-propyl ether, or ethylene glycol n-butyl ether, a halogenated hydrocarbon such as dichloromethane, 1,1,1 -trichloroethane or methylene chloride; chloroform; dimethyl sulfoxide; dimethyl formamide, acetonitrile; tetrahydrofuran; white spirits; mineral spirits; naphtha; n-methyl pyrrolidone; or a combination thereof.

[0022] The amount of solvent will depend on various factors including the type of solvent selected and the amount and type of other starting materials selected for use in the method. However, the amount of solvent may range from 1% to 99%, alternatively 2% to 90%, based on the weight of all starting materials in step (1). All or a portion of the solvent may optionally be removed during and/or after step (3). For example, water may form as a side product of the condensation reaction in steps (2) and (3). To progress the reaction, some or all of the water may be removed, e.g., via azeotropic distillation with the solvent.

(N) Neutralizing Agent

[0023] Starting material (N), the neutralizing agent, is optional. The neutralizing agent may comprise a silyl phosphate. Without wishing to be bound by theory, it is thought that the neutralizing agent may be added to scavenge impurities in (R) the Resin and/or (P) the Polymer, described above, before condensation reaction thereof. The neutralizing agent may be, for example, a silyl phosphate. Silyl phosphates, such as bis(trimethylsilyl) hydrogen phosphate, are commercially available from DSC.

[0024] The amount of neutralizing agent depends on various factors including the type of (P) the Polymer and (R) the Resin selected, however, the amount of neutralizer may be 0.005% to 0.02%, alternatively 0.01% to 0.015%, based on combined weights of starting materials (P), (R), (N), and (C).

(C) Condensation Reaction Catalyst [0025] Starting material (C) added in step (2) is a condensation reaction catalyst that can catalyze condensation reaction of the hydroxyl groups of (P) the Polymer and (R) the Resin, described above. The condensation reaction catalyst is not specifically restricted and may comprise an acid, or a base condensation reaction catalyst. For example, suitable base catalysts include metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide, carbonates such as sodium carbonate and potassium carbonate, bicarbonates such as sodium bicarbonate and potassium bicarbonate, metal alkoxides such as sodium methoxide and potassium butoxide, organometallic compounds such as butyl lithium, potassium silanolate, and nitrogen compounds such as ammonia gas, ammonia water, methylamine, trimethylamine and triethylamine. Alternatively, the condensation reaction catalyst may be an acid, e.g., organic acids such as acetic acid, benzoic acid, octanoic acid and citric acid, and mineral acids such as hydrochloric acid, sulfuric acid and phosphoric acid, are suitable. Alternatively, the condensation reaction catalyst may be an acid catalyst, such as an organic acid, e.g., benzoic acid.

[0026] Suitable condensation reaction catalysts are commercially available from various sources, e.g., Sigma Aldrich, Inc. of St. Louis, Missouri, USA and Acros. The amount of catalyst depends on various factors including the type of catalyst select and the temperature for step (1), however, the amount of catalyst may be 0.1% to 0.5%, alternatively 0.25% to 0.3%, based on combined weights of starting materials (P), (R), (C), and (N).

[0027] Step (4) in the method described above is optional. After a condensation reaction product of (P) the Polymer and (R) the Resin forms, the condensation reaction product may further comprise unreacted starting materials, solvent, and water as a side product. In step (4), the condensation reaction product may be recovered, e.g., the solvent, water, and unreacted starting materials may be removed, e.g., by distillation and/or stripping optionally with heating and/or reduced pressure.

[0028] Step (5) in the method described above is optional. The reaction product after step (3), or step (4), when present, may be used to form a silicone pressure sensitive adhesive composition. Alternatively, (X) a peroxide crosslinking agent may be added in step (5) to form the silicone pressure sensitive adhesive composition which may cure faster than when the peroxide crosslinking agent is not present, provided other conditions such as temperature are kept constant.

(X) Peroxide crosslinking agent

[0029] Starting material (X) added when step (5) is present is a peroxide crosslinking agent. The peroxide crosslinking agent may be an organic peroxide or a hydroperoxide, such as benzoyl peroxide; 4-monochlorobenzoyl peroxide; t-butylperoctoate; t-butyl peroxybenzoate, tert-butylperoxybenzoate, tert-butyl cumyl peroxide, tert-butyloxide 2,5-dimethyl-2,5-di-tert- butylperoxyhexane; 2, 4-dichlorobenzoyl peroxide; di-tertbutylperoxy-diisopropyl benzene; 1,1- bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane; 2,5-di-tert-butylperoxyhexane-3,2,5-dimethyl- 2,5-bis(tert-butylperoxy) hexane; cumyl-tert-butyl peroxide; dicumyl peroxide; di-t-butyl peroxide; t-butyl hydroperoxide; cumene hydroperoxide; di-t-amyl peroxide; and combinations of two or more thereof. Additionally, di-peroxide peroxide crosslinking agents may be used alone or in combination with other di-peroxide crosslinking agents. Such di-peroxide peroxide crosslinking agents include, but are not limited to, l,4-bis-(t-butyl peroxycarbo)cyclohexane; l,2-di(t-butyl peroxy )cyclohexane; and 2,5-di(t-butyl peroxy)-3-hexyne. Suitable peroxide crosslinking agents for use as starting material (X) are known in the art and are commercially available from various sources, such as Sigma-Aldrich, Inc. of St. Louis, Missouri, USA.

[0030] Starting material (X) may comprise one peroxide crosslinking agent or a combination of two or more peroxide crosslinking agents. The amount of starting material (X) added in step (5) depends on various factors including the type and amount of peroxide crosslinking agent selected and the selection of (P) the Polymer and (R) the Resin, however, the amount of peroxide crosslinking agent, when present, may be 0.1 weight % to 4 weight %, alternatively 1 weight % to 4 weight %, and alternatively 2 weight % to 3 weight %, based on combined weights of starting materials (P), (R), (C), and (S).

[0031] Step (6) in the method described herein is optional. However, step (6) may be included in the method to improve bonding of the silicone pressure sensitive adhesive to the backing substrate. Therefore, the method for forming the adhesive article may optionally further comprise (6) treating a surface of the backing substrate before applying the silicone pressure sensitive adhesive composition. Treating the surface may be performed by any convenient means, such as applying a primer, or subjecting the surface to corona-discharge treatment, etching, or plasma treatment before applying the silicone pressure sensitive adhesive composition to the surface. Alternatively, treating the surface may comprise applying a primer to the surface of the backing substrate.

[0032] Step (7), coating the silicone pressure sensitive adhesive composition on the surface of the backing substrate can be performed by any convenient means. For example, the silicone pressure sensitive adhesive composition may be applied by gravure coater, comma coater, offset coater, offset-gravure coater, roller coater, reverse-roller coater, air-knife coater, slot die, or curtain coater.

[0033] In the method described herein, steps (7) to (9) may be performed via wet casting or via dry casting. In wet casting, the silicone pressure sensitive adhesive layer may be permanently adhered to the backing substrate, such as the polymeric films and/or foams described below. [0034] The backing substrate can be any material that can withstand the curing conditions used in step (9) to cure the silicone pressure sensitive adhesive composition to form the silicone pressure sensitive adhesive on the surface of the backing substrate. For example, any backing substrate that can withstand heat treatment at a temperature equal to or greater than 120 °C, alternatively 150 °C is suitable. Examples of materials suitable for such backing substrates including polymeric films and/or foams, which may be comprised of polyimide (PI), poly etheretherketone (PEEK), polyethylene naphthalate (PEN), liquid-crystal polyarylate, polyamideimide (PAI), polyether sulfide (PES), polyethylene terephthalate (PET), polycarbonate (PC), polymethylmethacrylate (PMMA), thermoplastic polyurethane (TPU), thermoplastic elastomer (TPE), polyethylene (PE), or polypropylene (PP). Alternatively, the backing substrate may be glass. Alternatively, the backing substrate may be a release liner, for example, when the silicone pressure sensitive adhesive will be used in a dry casting method. The thickness of the backing substrate is not critical; however, the thickness may be 5 pm to 300 pm, alternatively 10 pm to 200 pm. Alternatively, the backing substrate used in step (7) may be selected from the group consisting of PE, PU, TPE, and TPU.

[0035] Step (8) of the method comprises drying the silicone pressure sensitive adhesive composition. Drying may be performed by any convenient means, such as heating at a temperature and for a time sufficient to vaporize all or a portion of the solvent but insufficient to fully cure the silicone pressure sensitive adhesive composition. For example, drying may be performed by, e.g., heating at a temperature of 50 °C to 120 °C, alternatively 70 °C to 100 °C, and alternatively 70 °C to 80 °C for a time sufficient to remove all or a portion of the solvent (e.g., 30 seconds to 1 hour, alternatively 1 minute to 5 minutes).

[0036] After drying, the method further comprises step (9), curing the silicone pressure sensitive adhesive composition to form a laminate article comprising a silicone pressure sensitive adhesive layer having a surface adhered to the surface of the backing substrate, where the silicone pressure sensitive adhesive layer further comprises an opposing surface opposite the surface of the backing substrate.

[0037] Curing the pressure sensitive adhesive composition in step (9) may be performed by heating at a temperature of 80 °C to 200 °C, alternatively 90 °C to 210 °C, alternatively 150 °C to 205 °C, and alternatively 180 °C to 205 °C for a time sufficient to cure the pressure sensitive adhesive composition (e.g., for 30 seconds to an hour, alternatively 1 to 5 minutes). If cure speed needs to be increased or the process oven temperatures lowered, the amount of (X) the peroxide crosslinking agent can be increased. This forms a silicone pressure sensitive adhesive on the surface of the backing substrate. Curing may be performed by placing the coated backing substrate in an oven. The amount of the silicone pressure sensitive adhesive composition to be coated on the backing substrate depends on the specific application, however, the amount may be sufficient such that, after curing, thickness of the silicone pressure sensitive adhesive may be 5 micrometers to 100 micrometers.

[0038] The method described herein may optionally further comprise an additional step after step (9). The additional step comprises applying a removable release liner to the opposing surface of the silicone pressure sensitive adhesive layer opposite the backing substrate, e.g., to protect the silicone pressure sensitive adhesive before use (e.g., when the backing substrate is a polymeric film and/or foam, or glass). The release liner may be applied before, during or after curing the silicone pressure sensitive adhesive composition; alternatively after curing. [0039] The silicone pressure sensitive adhesive prepared in step (9) will adhere to a fluorosilicone rubber article or a silicone foam article, or both. Without wishing to be bound by theory, it is thought that the silicone pressure sensitive adhesive prepared in step (9) may have adhesion to fluorosilicone rubber > 400 gf/in, alternatively at least 900 gf/in, alternatively at least 1,000 gf/in, while at the same time adhesion may be up to 1,100 gf/in, alternatively up to 1,000 gf/in, alternatively up to 950 gf/in, when tested according to the peel adhesion test method described in the EXAMPLES, below. Without wishing to be bound by theory, it is also thought that the silicone pressure sensitive adhesive prepared in step (9) may have adhesion to silicone foam > 300 gf/in, alternatively at least 350 gf/in, alternatively at least 375 gf/in, while at the same time adhesion may be up to 550 gf/in, alternatively up to 510 gf/in, and alternatively up to 475 gf/in, when tested according to the peel adhesion test method described in the EXAMPLES, below.

[0040] While treatment of the article is not required for this adhesion, the method may optionally further comprise step (10), treating a surface of the article, which may facilitate and/or improve adhesion of the silicone pressure sensitive adhesive to the surface of the article. Treating the surface of the article may be performed by any convenient means, such as cleaning the surface of the article, e.g., with an alcohol such as isopropanol, or any of the surface treatments described above in step (6).

[0041] The article may comprise a fluorosilicone rubber or a silicone foam. The fluorosilicone rubber article is not specifically restricted. The fluorosilicone rubber article may have a durometer, Shore A, of 30 to 60 measured by ASTM D2240. Fluorosilicone rubbers (F- LSRs) are known in the art and may be made by known methods, such as those disclosed in U.S. Patent 4,857,564 to Maxson; U.S. Patent 4,882,368 to Elias, et al.; U.S. Patent 5,171,773 to Chaffee, et al.; U.S. Patent 5,824,736 to Kobayashi, et al.; and U.S. Patent Application Publication 2017-0267829 to Drake, et al. Alternatively, the fluorosilicone rubber article may be selected based on the desired end use for the laminate prepared herein. Exemplary fluorosilicone rubbers (F-LSRs) are known in the art and are commercially available. For example, F-LSRs include SILASTIC™ brand F-LSRs available from DSC. These include SILASTIC™ FL 30-9201, SILASTIC™ FL 40-9201, and SILASTIC™ FL 60-9201, which are fluorosilicone liquid silicone rubbers with durometer Shore A values from 30 to 60.

[0042] Alternatively, the article may comprise a silicone foam. The silicone foam may have a durometer Shore 00 value from 10 to 70. The silicone foam may have a density from 0.03 g/cm ³ to 1.5 g/cm ³ . The silicone foam may have a compression of 1 to 100 psi. The silicone foam may have a tensile strength of 1 to 300 psi. Silicone foams, such as open cell silicone foams, are known in the art and are commercially available. For example, articles comprising silicone foams are available from McMaster-Carr of Elmhurst, Illinois, USA. These include McMaster- Carr product names 1652N101-129; 5025T171-176, 181-186, and 191-196; and 87485K212- 216, 221-226, and 231-236. Silicone foams may be prepared by known methods, such as those disclosed in U.S. Patent 5,252,627 to Bauman, et al.; U.S. Patent 5,330724 to Bauman, et al.;

U.S. Patent 5,683,527 to Angell, et al.; and U.S. Patent 5,744,507 to Angell, et al.

[0043] The method described herein further comprises step (11), adhering the opposing surface of silicone pressure sensitive adhesive, as described in step (9), and the surface of the article. Step (11) may be performed by any convenient means, such as contacting the surface of the article and the opposing surface of the silicone pressure sensitive adhesive and applying pressure. If a release liner is used to protect the opposing surface of the silicone pressure sensitive adhesive, the release liner is removed before contacting the surface of the silicone rubber article and the opposing surface of the silicone pressure sensitive adhesive. The resulting product prepared in step (11) is a laminate.

[0044] Alternatively, when dry casting is used in steps (7) to (9) described above, the backing substrate comprises a release liner. The release liner may be removed after step (9) to form the silicone pressure sensitive adhesive layer as a free standing film. Alternatively, the release liner may be removed after step (11). When dry casting is performed, the method may further comprise: optionally (12) treating a surface of a second article (i.e., a second fluorosilicone rubber article or a second silicone foam article); and

(13) adhering the surface of the silicone pressure sensitive adhesive layer (exposed via removal of the release liner) to the surface of the second silicone rubber article.

[0045] The second article comprises a fluorosilicone rubber or a silicone foam, as described above for use in step (11). The second article may be the same as the article used in step (11). Alternatively, the second article may be different from the article used in step (11). In this instance, the laminate article formed by the method has a silicone pressure sensitive adhesive layer sandwiched between the article and the second article, described above.

[0046] Figure 1 shows a partial cross section of a laminate (100) prepared by the method described above. The laminate (100) includes a silicone pressure sensitive (102) having a surface (102a) and an opposing surface (102b). The opposing surface (102b) of the silicone pressure sensitive (102) adheres to the surface (103a) of the fluorosilicone rubber article (103) with a peel adhesion of 400 gf/in as measured by the test method described in the EXAMPLES, below. The silicone pressure sensitive (102) may have a thickness of 10 pm to 200 pm. The silicone pressure sensitive (102) adheres to a backing substrate (101) having a surface (101b). The surface (102a) of the silicone pressure sensitive (102) contacts the surface (101b) of the backing substrate (101). The backing substrate (101) may be selected from the group consisting of PE, PU, TPU, and TPE, which may have a thickness of 10 pm to 200 pm. The fluorosilicone rubber article (103) may be a SILASTIC™ F-LSR, as described above.

[0047] The silicone pressure sensitive adhesive composition may be used in fabrication of the laminate (100) via wet casting. For example, the silicone pressure sensitive adhesive composition may be applied to the surface (101b) of the backing substrate (101) and cured to form the silicone pressure sensitive adhesive (102). Alternatively, the silicone pressure sensitive adhesive composition may be applied to the surface (103a) of the fluorosilicone rubber article (103) and cured to form the silicone pressure sensitive adhesive (102). Alternatively, the silicone pressure sensitive adhesive composition may be applied to a surface of a release liner and cured to form the silicone pressure sensitive adhesive (102). Thereafter, the surface (103a) of the fluorosilicone rubber article (103) may be contacted with the opposing surface (102b) of the silicone pressure sensitive adhesive (102) and the surface (101b) of the backing substrate (101) may be contacted with the surface (102a) of the silicone pressure sensitive adhesive (102). Pressure may be applied to adhere the layers of backing substrate (101), silicone pressure sensitive adhesive (102), and fluorosilicone rubber article (103) together.

[0048] Alternatively, wet casting may be used to prepare a laminate article comprising a backing substrate comprising a fluorosilicone rubber or a silicone foam and a silicone pressure sensitive adhesive described above, and optionally, a (second) article comprising a fluorosilicone rubber or a silicone foam. In this method, the backing substrate may be a fluorosilicone rubber article or silicone foam that is the same as or different from the article used in step (11), described below. Alternatively, the backing substrate may comprise more than one material of construction, such as a mesh (which may be fabricated from a polymeric material, as described above) impregnated with a fluorosilicone rubber. This method for fabricating a laminate article comprises:

(1) combining, under conditions to effect condensation reaction, starting materials comprising

(P) a bis-hydroxyl-terminated polydiorganosiloxane with a weight average molecular weight of 10,000 g/mol to < 200,000 g/mol measured by GPC;

(R) a hydroxyl-functional polyorganosilicate resin with a weight average molecular weight of 4,000 g/mol to < 10,000 g/mol measured by GPC;

(S) a solvent; and optionally (N) a neutralizer; where starting materials (R) and (P) and are present in a weight ratio (R)/(P) of 0.76/1 to 2.15/1; thereby producing a reaction mixture; and

(2) adding (C) a condensation reaction catalyst to the reaction mixture, thereby producing a catalyzed reaction mixture;

(3) heating the catalyzed reaction mixture at a temperature of > RT to 145 °C and removing water; thereby producing a condensation reaction mixture comprising a condensation reaction product of (P) and (R) optionally (4) recovering the condensation reaction product of (P) and (R); optionally (5) adding up to 4 weight %, based on combined weights of (R) and (P), of (X) a peroxide crosslinking agent, thereby forming a silicone pressure sensitive adhesive composition; optionally (6) treating a surface of a backing substrate comprising a fluorosilicone rubber or a silicone foam;

(7) coating the silicone pressure sensitive adhesive composition on the surface of the backing substrate;

(8) drying the silicone pressure sensitive adhesive composition, and

(9) curing the silicone pressure sensitive adhesive composition to form a silicone pressure sensitive adhesive layer having a surface adhered to the surface of the backing substrate, where the silicone pressure sensitive adhesive layer further comprises an opposing surface opposite the surface of the backing substrate. This method may optionally further comprise: optionally (10) treating a surface of an article comprising a fluorosilicone rubber or a silicone foam; and

(11) adhering the opposing surface of silicone pressure sensitive adhesive and the surface of the article.

[0049] Figure 2 shows a partial cross section of a laminate article (200) prepared by the method described above. The laminate article (200) includes a silicone pressure sensitive (202) having a surface (202a) and an opposing surface (202b). The silicone pressure sensitive (202) may have a thickness of 10 pm to 200 . The silicone pressure sensitive (202) adheres to a backing substrate comprising a fluorosilicone rubber (201) and having a surface (201b) with a peel adhesion of > 400 gf/in as measured by the test method described in the EXAMPLES, below. The surface (202a) of the silicone pressure sensitive (202) contacts the surface (201b) of the backing substrate (201). The backing substrate (201) may be a fluorosilicone rubber article, as described above. Alternatively, the backing substrate (201) may comprise a mesh impregnated with a fluorosilicone rubber.

[0050] The silicone pressure sensitive adhesive composition may be used in fabrication of the laminate article (200) via wet casting. For example, the silicone pressure sensitive adhesive composition may be applied to the surface (201b) of the backing substrate (201) and cured to form the silicone pressure sensitive adhesive (202).

EXAMPLES

[0051] The following examples are provided to illustrate the invention to one skilled in the art and are not to be construed to limit the scope of the invention set forth in the claims. Starting materials used in these examples are described in Table 1.

Table 1 - Starting Materials

[0052] In this Reference Example 1 , condensation reaction products (Bodied Resins) were prepared as follows: PDMS polymer, MQ resin, solvent, and neutralizer were combined in a three neck flask at RT. The contents of the flask were stirred at 250 rpm for 20 minutes using a stainless steel stir paddle in the middle neck. Condensation Catalyst was then added with stirring. Another neck was connected to a dean-stark trap and then condenser with city water cooling capability. The last neck contained a thermometer and nitrogen sweep adapter closing the system. Finally, the three-neck flask with the mixture inside was mounted on a heating mantle with temperature control and heated to a reaction temperature of 145 °C. The reaction continued for 3 hours starting from the beginning of refluxing. Bodied Resins IE1 to IE7 and CE1 to CE5 and CE7 to CE17 were prepared according to this procedure.

[0053] In this Reference Example 2, comparative silicone pressure sensitive adhesive composition CE6 was prepared as follows: Starting materials were added to a dental mixer cup and mixed for 30 seconds at 3500 rpm until homogeneous. This cold blend (comparative) PSA was used immediately for coating/curing process.

[0054] In this Reference Example 3, the Peroxide Crosslinking agent was added to form the peroxide curable silicone pressure sensitive adhesive compositions, which were coated on backing substrates and cured as follows: For peroxide curable silicone pressure sensitive adhesive compositions (IE1 to IE7 and CE1 to CE18), Peroxide Crosslinking agent (in toluene) and solvent 1 were added to each composition prepared as described above Reference Examples 1 and 2 in a dental mixer cup to reach a 50 wt% solid level and a 2 wt% Peroxide Crosslinking agent level. The resulting sample was mixed for 30 seconds at 3500 rpm until homogeneous. Each sample was prepared for application testing by coating on to a 2-mil thick sheet of polyester (PET) using a 3-mil coating bar. Each sheet was then cured in an oven at 80°C for 2 minutes, followed by 180°C for 2 minutes.

[0055] The starting materials, and amounts used to prepare each sample, are shown below in Tables 2, 4, and 6.

[0056] In this Reference Example 4, fluorosilicone rubber substrates were fabricated as follows:

[0057] The liquid fluorosilicone rubber (F-LSR) substrates were from DSC, SILASTIC™ FL 40-9201 Part A and Part B were dispensed through a 1:1 ratio meter mix system which supplied a static mixer that fed into an injection molding machine. Mixed material was injected into a 6” X 6” X 0.078” slab mold and cured for 30 seconds at 280 °F. Slabs were removed after mold opened and allowed to cool to room temperature.

[0058] In this Reference Example 5, adhesion of the pressure sensitive adhesives prepared according to Reference Example 3 to the fluorosilicone rubbers prepared according to Reference Example 4 and to the commercially available silicone foam was measured as follows:

[0059] Peel Adhesion: Peel adhesion (180°) was tested according to PSTC-101 standards. The silicone pressure sensitive adhesive coated onto 2-mil polyester film (tape) was laminated onto the silicone rubber surface typically after 1 day following cure. The silicone rubber surface was wiped with Isopropyl Alcohol to clean the surface and allowed to dry under ambient conditions for 5 minutes before the silicone pressure sensitive adhesive was laminated thereto. After laminating, a 2-kg rubber-coated roller was applied to the resulting article (back and forth five times each) and the article was left undisturbed for a dwell time of 20 minutes at room temperature before the peel adhesion test. A TMI Release and Adhesion Tester was used to pull a 1-inch wide tape from the silicone rubber substrate at 12 inches per minute. The adhesion test results are shown below in Tables 3, 5, and 7. In the tables, CE denotes a comparative example, and IE denotes a working example of this invention.

Table 2 - Examples of Bodied Resins of Different R/P

Table 3 - Peel Adhesion Results of Examples in Table 2

[0060] In Tables 2 and 3, bodied resins with different resin to polymer ratio were prepared. When polyorganosilicate resin with the Mw described herein and the (liquid) polymers were used in the silicone pressure sensitive adhesive compositions, these compositions cured to form silicone pressure sensitive adhesives with adhesion > 400 g/inch to F-LSR and > 300 g/inch to silicone foam (all of IE1 to IE6). The highest adhesion silicone pressure sensitive adhesives were produced from compositions with R/P of 0.93/1 to 1.40/1 (IE2, IE3, and IE4). Silicone pressure sensitive adhesives produced from comparative compositions with R/P outside of 0.76/1 to 2.15/1 showed poor adhesion (CE1, CE2) to both F-LSR and silicone foam.

Table 4 - Comparative Examples of Bodied Resins of Different Mw Resins and Polymers

Table 5 - Peel Adhesion Results of Examples in Table 4

[0061] The data in Tables 2 to 5 showed that when R/P ratio was kept constant (at 0.93/1), using resins with Mw that was too high (> 10,000 g/mol) in examples CE3, CE4, and CE7-CE9, or using gum with Mw that was too high in example CE5, in the composition, the resulting silicone pressure sensitive adhesive showed weak adhesion to F-LSR and silicone foam, in comparison to example IE2. Using polyorganosilicate resin with Mw < 10,000 g/mol (IE2, IE3, and IE7) in the compositions produced silicone pressure sensitive adhesives good adhesion to both F-LSR and silicone foam. The cold blend PSA (CE6) showed very weak adhesion to F- LSR and silicone foam, in comparison to silicone pressure sensitive adhesive produced from the composition containing a bodied resin (IE2).

Table 6 - Additional Comparative Examples

Table 7 - Peel Adhesion Results of Examples in Table 6

[0062] The data in Tables 6 and 7 showed that the use of a polyorganosilicate resin with a molecular weight that was too high (> 10,000 g/mol) in the comparative compositions produced pressure sensitive adhesives with weak adhesion to F-LSR and weak adhesion to silicone foam, with adhesion strength < 200 gf/inch to F-LSR and < 150 gf/inch to silicone foam.

Table 8 - Comparative Examples of Commercial Materials

[0063] Under the conditions tested, commercial silicone PSAs showed poor adhesion to both F-LSR and silicone foam, < 350 g/inch to F-LSR and < 300 g/inch to silicone foam as shown in examples CE18 and CE19.

[0064] In this Reference Example 6, samples of laminate articles were prepared in a method involving wet casting (method 2) as follows:

1. Samples of silicone pressure sensitive adhesive compositions were prepared by mixing Peroxide Crosslinking agent (in toluene) and solvent 1 and each of composition IE4 and a commercial PSA (7406-VLO) (prepared as described above) in a dental mixer cup to reach a 50 wt% solid level and a 2 wt% Peroxide Crosslinking agent level. Each resulting sample was mixed for 30 seconds at 3500 rpm until homogeneous.

2. Four sheets of substrate were provided. Two sheets were F-LSR prepared as described above in Reference Example 4. Two sheets were silicone foam as described above. A surface of each substrate was cleaned by wiping with isopropyl alcohol and allowing to dry under ambient conditions for 5 minutes.

3. Each sample of a silicone pressure sensitive adhesive composition was coated on a cleaned surface of a substrate using a 3-mil coating bar. Each coated substrate was then placed in an oven at 80°C for 2 minutes, followed by 180°C for 2 minutes to prepare a laminate of (cured) silicone pressure sensitive adhesive layer on each sheet of substrate.

4. Four additional sheets of substrate were provided; two of F-LSR and two of silicone foam as described above. A surface of each substrate was cleaned by wiping with isopropyl alcohol and allowing to dry under ambient conditions for 5 minutes.

5. One day following step 3, the surface of each silicone pressure sensitive adhesive layer was contacted with the cleaned surface of a substrate from step 4. Each resulting laminate had two F-LSR substrates with a silicone pressure sensitive adhesive between them or two silicone foam substrates with a silicone pressure sensitive adhesive between them. A 2-kg rubber-coated roller was applied to the resulting laminate (back and forth five times each), and the laminate was left undisturbed for a dwell time of 20 minutes at room temperature before the peel adhesion test according to PSTC-101 standards, as described above (except without the polyester film as backing substrate), was performed. A TMI Release and Adhesion Tester was used to pull a 1- inch wide tape from the substrate at 12 inches per minute. Peel adhesion test results are shown below in Table 9.

Table 9 - Peel Adhesion Test Results for Laminate Articles Prepared According to Reference Example 6

[0065] The data in Table 9 show that a silicone pressure sensitive adhesive prepared via a wet casting method, as described herein, has better adhesion to fluorosilicone rubber than a commercially available silicone pressure sensitive adhesive applied to a fluorosilicone rubber article in the same manner.

[0066] In this Reference Example 7, samples of laminate articles were prepared by a method including dry casting (Method 3) as follows:

1. Two samples of silicone pressure sensitive adhesive compositions were prepared by mixing Peroxide Crosslinking agent (in toluene) and solvent 1 and each of composition IE4 and a commercial PSA (7406-VLO) (prepared as described above) in a dental mixer cup to reach a 50 wt% solid level and a 2 wt% Peroxide Crosslinking agent level. Each resulting sample was mixed for 30 seconds at 3500 rpm until homogeneous. 2. Each sample of a silicone pressure sensitive adhesive composition was coated on a fluorosilicone release liner using a 3-mil coating bar. Each coated liner was then placed in an oven at 80 °C for 2 minutes, followed by 180 °C for 2 minutes to prepare a laminate of (cured) silicone pressure sensitive adhesive layer on each fluorosilicone release liner. Each laminate was aged for 1 day at RT.

3. Four sheets of substrate were provided. Two sheets were F-LSR prepared as described above in Reference Example 4. Two sheets were silicone foam as described above. A surface of each substrate was cleaned by wiping with isopropyl alcohol and allowing to dry under ambient conditions for 5 minutes.

4. The surface of each silicone pressure sensitive adhesive layer from step 2 was contacted with the cleaned surface of each substrate from step 3.

5. Four sheets of substrate were provided. Two sheets were F-LSR prepared as described above in Reference Example 4. Two sheets were silicone foam as described above. A surface of each substrate was cleaned by wiping with isopropyl alcohol and allowing to dry under ambient conditions for 5 minutes.

6. One day following step 4, the fluorosilicone release liner was removed from each laminate, and the resulting exposed surface of each silicone pressure sensitive adhesive layer was contacted with the cleaned surface of a substrate from step 5. Each resulting laminate had two F-LSR substrates with a silicone pressure sensitive adhesive between them or two silicone foam substrates with a silicone pressure sensitive adhesive between them. A 2-kg rubber-coated roller was applied to the resulting laminate (back and forth five times each), and the laminate was left undisturbed for a dwell time of 20 minutes at room temperature before the peel adhesion test according to PSTC-101 standards, as described above (except without the polyester film as backing substrate), was performed. A TMI Release and Adhesion Tester was used to pull a 1- inch wide tape from the silicone rubber substrate at 12 inches per minute. Peel adhesion test results are shown below in Table 10.

Table 10 - Peel Adhesion Test Results for Laminate Articles Prepared According to Reference Example 7

[0067] The data in Table 10 show that a silicone pressure sensitive adhesive prepared via a dry casting method, as described herein, has better adhesion to fluorosilicone rubber than a commercially available silicone pressure sensitive adhesive applied to a fluorosilicone rubber article in the same manner. Definitions and Usage of Terms

[0068] All amounts, ratios, and percentages are by weight unless otherwise indicated. The amounts of all starting materials in a composition total 100% by weight. The Summary and the Abstract are hereby incorporated by reference. The articles ‘a’, ‘an’, and ‘the’ each refer to one or more, unless otherwise indicated by the context of specification. The singular includes the plural unless otherwise indicated. The term “comprising” and derivatives thereof, such as “comprise” and “comprises” are used herein in their broadest sense to mean and encompass the notions of “including,” “include,” “consist(ing) essentially of,” and “consist(ing) of. The use of “for example,” “<?.g.,” “such as,” and “including” to list illustrative examples does not limit to only the listed examples. Thus, “for example” or “such as” means “for example, but not limited to” or “such as, but not limited to” and encompasses other similar or equivalent examples.

[0069] It is to be understood that the appended claims are not limited to express and particular compounds, compositions, or methods described in the detailed description, which may vary between particular embodiments which fall within the scope of the appended claims. With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, different, special, and/or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members. Each member of a Markush group may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims.

[0070] Abbreviations used herein are defined in Table 11.

Table 11 - Abbreviations

[0071] The Mn, Mw, and molecular weight distribution of the Polymer and condensation reaction product may be determined by GPC using an Agilent Technologies 1260 Infinity chromatograph and toluene as a solvent. The instrument is equipped with two PLgel Mixed C columns. Calibration was made using polystyrene standards. Samples were made by dissolving polymer in toluene (~10 mg/mL) and then immediately analyzing the material by GPC (1 mL/min flow and 45 °C column temperature).

[0072] The Mn, Mw, and molecular weight distribution of the Resin may be determined by GPC using an Agilent Technologies 1260 Infinity chromatograph and ethyl acetate as a solvent. The instrument is equipped with two columns, Agilent PLgel Mixed-D and PLgel Mixed-E columns. Calibration was made using polystyrene standards. Samples were made by dissolving polymer in toluene (~20 mg/mL) and then immediately analyzing the material by GPC (1 mL/min flow and 35 °C column temperature).