Silicone pressure-sensitive adhesive and method for preparing the same

Abstract

A process for producing a silicone pressure sensitive adhesive is shown and described herein. The process includes reacting an MQ silicone resin with a polydiorganosiloxane in the absence of a solvent. The MQ silicone resin is a solid, solvent-free MQ resin. The reaction may be carried out in the presence of a catalyst, a chain extender, or a combination thereof, and the resulting pressure sensitive adhesive can be dissolved in a solvent to adjust the solids content. The method provides an approach to provide a cleaner adhesive that is substantially free of unwanted and undesirable materials such as aromatic solvents and is substantially free of cyclic siloxane impurities.

Description

[Technical Field]

[0001] The present invention relates to silicone pressure-sensitive adhesives and methods for producing such adhesives. In particular, the present invention relates to silicone pressure-sensitive adhesives that are substantially free of aromatic solvents and / or cyclic siloxanes and methods for producing such adhesives, wherein the method is carried out in the absence of a solvent. [Background technology]

[0002] Silicone pressure-sensitive adhesives are an important category of adhesives used in a wide variety of applications. They are used in high-temperature applications, industrial applications, electronics applications, medical / healthcare applications, and drug delivery applications.

[0003] Many silicone pressure-sensitive adhesives are produced by the solution condensation of branched silicone resin (MQ resin) and polydiorganosiloxane in the presence of a condensation catalyst. This reaction is conventionally carried out in a solvent, most often an aromatic solvent such as benzene, toluene, and / or xylene (BTX solvent), and then cured via peroxide radicals. Another route for forming silicone pressure-sensitive adhesives is the addition curing of vinyl-containing siloxanes and hydride-containing siloxane oligomers using a platinum catalyst.

[0004] In the industry, the more preferred route for preparing silicone pressure-sensitive adhesives is generally the solution condensation method. Solution condensation typically yields pressure-sensitive adhesives with better adhesion and thermal behavior compared to those prepared via two-component addition curing methods. In addition, most MQ resins are obtained in BTX-type solvents, thereby making the process easier to use. The condensation process has several drawbacks, including discoloration and clouding of the adhesive, and the formation of salts / residual ion content based on the neutralization of the condensation catalyst. Nevertheless, condensation-curable silicone pressure-sensitive adhesives are well known in the art and have been documented in the literature.

[0005] U.S. Patent No. 5,726,256 describes the production of silicone PSA using a weak organic acid or metal salt to catalyze the condensation of benzene-soluble MQ resin and polydiorganosiloxane rubber.

[0006] U.S. Patent No. 5,861,472 describes a method for preparing a silicone PSA composition by heating a mixture of a polydiorganosiloxane polymer, a silicone resin copolymer, a heat stabilizer, and an equilibration catalyst such as potassium silanolate in toluene.

[0007] U.S. Patent No. 5,162,410 describes a process for producing hot-melt silicone PSA by homogeneously mixing silicone rubber (phenylmethyl) and MQ resin (in xylene solution) with an ammonium carbonate catalyst and heating the mixture to 100°C. Volatile components are subsequently removed at 100°C.

[0008] International Publication 2007 / 067332A2 describes a sequential method for synthesizing silicone PSA by mixing a hydroxyl-functionalized polydiorganosiloxane polymer with a hydroxyl-functionalized polyorganosiloxane resin and a solvent (xylene). The composition is heated above the evaporation point of the solvent, and all volatile species are removed using a twin-screw extruder.

[0009] U.S. Patent No. 5,175,058 describes a silicone PSA composition comprising a homogeneous mixture of two intermediate compositions of a pressure-sensitive adhesive in toluene.

[0010] U.S. Patent No. 5,602,214 describes a method for synthesizing silicone PSA in toluene, which has excellent peel adhesion strength, high tackiness, and quick-stick properties.

[0011] U.S. Patent No. 10,351,742 describes providing a solvent-free MQ silicone resin for removing aromatic resins and then redissolving the MQ resin in different volatile solvents before mixing and reacting it with a polydiorganosiloxane. The starting MQ resin is treated to remove volatile aromatic solvents and then redissolved in a volatile solvent free of such aromatic solvents before being reacted with the polydiorganosiloxane.

[0012] International Publication No. 2011 / 031452A1 describes a process for creating a silicone PSA by condensing a low-viscosity polyorganosiloxane rubber and slowly adding a silicone MQ resin in a xylene solvent or a silicone fluid during the polymerization process.

[0013] International Publication No. 2018 / 132941A1 describes a process for creating a silicone PSA curable composition at a temperature not exceeding 35°C by mixing a polyorganosiloxane resin with a silanol-terminated polydiorganosiloxane rubber in an organic solvent (a mixture of toluene and xylene) and subsequently mixing this material with an amino-functional alkoxysilane and a phosphate silyl ester compound.

[0014] International Publication No. 2020 / 090781 describes a process for creating a silicone PSA with a reduced residual silanol content by condensation of a base-catalyzed MQ resin and a polyorganosiloxane rubber in n-heptane.

[0015] International Publication No. 2020 / 099999 describes a hot melt process for creating a silicone PSA that minimizes damage and pain to the skin upon removal while having improved adhesion properties. This process involves base-catalyzed condensation of a silanol-terminated linear organopolysiloxane and a silicate MQ resin solid in the presence of a non-functional linear organopolysiloxane, for example using ammonia.

[0016] Despite these various processes, there remains an interest in providing a process for generating cleaner pressure-sensitive adhesives with excellent adhesion properties.

Summary of the Invention

[0017] What is presented below is an overview of the present disclosure to provide a basic understanding of some embodiments. This overview is not intended to identify key or essential elements or to define any limitations on the embodiments or the claims. Furthermore, this overview may provide a simplified overview of some embodiments, which may be described in more detail elsewhere in the present disclosure.

[0018] Provided is a silicone pressure-sensitive adhesive and a method for producing such an adhesive. The silicone pressure-sensitive adhesive is prepared by reacting at least one substantially solid, solvent-free MQ resin with at least one polydiorganosiloxane, wherein the pressure-sensitive adhesive is substantially free of solvents, particularly aromatic solvents, more specifically solvents of the benzene, toluene, and xylene types.

[0019] For the purposes of this application, being substantially free of solvents means that the solvent is <5 ppm and the cyclic substances are <100 ppm. Preferably, the cyclic substances are less than 1 ppm, more preferably <50 ppm, and most preferably less than 20 ppm.

[0020] In one embodiment, the method for making the silicone pressure-sensitive adhesive includes reacting the MQ resin with the polydiorganosiloxane in the presence of a catalyst, where the reaction is solvent-free. The MQ resin used in the reaction is a solid, solvent-free MQ resin.

[0021] In another embodiment, the method involves reacting an MQ resin, a polydiorganosiloxane, and a chain extender selected from hexaalkylcyclotrisilazane or bis(alkylamino)silane in the absence of a solvent to produce a silicone pressure-sensitive adhesive material.

[0022] Provided in one embodiment is a process for producing a pressure-sensitive adhesive, which comprises: reacting at least one MQ silicone resin with at least one polydiorganosiloxane, where the MQ silicone resin is a solid solvent-free resin, and the reaction is carried out in the absence of a solvent.

[0023] In one embodiment, based on the total weight of MQ silicone resin and polydiorganosiloxane, MQ silicone resin is present in an amount of about 40% to about 70% by weight, and polydiorganosiloxane is present in an amount of about 60% to about 30% by weight.

[0024] In one embodiment, the reaction is carried out at a temperature of approximately 25°C to approximately 200°C.

[0025] In one embodiment, the reaction is carried out at a temperature of approximately 50°C to approximately 150°C.

[0026] In one embodiment, the reaction is carried out in the presence of a catalyst, a chain extender, or a combination thereof.

[0027] In one embodiment, the catalyst is selected from hydrochloric acid, phosphoric acid, polyphosphate, carboxylic acid, metal camponate salt, alkali metal oxide, alkali metal alkoxide, alkali metal hydroxide, alkali metal silanolate, alkali metal siloxanolate, alkali metal amide, alkyl metal, ammonia, amine, ammonium hydroxide, quaternary phosphonium hydroxide, or two or more combinations thereof.

[0028] In one embodiment, the process includes at least one chain extender selected from silazanes, metal silanolates, metal siloxanolates, bis(alkylamino)dialkylsilanes, bis(alkylamino)dialkenylsilanes, or two or more combinations thereof.

[0029] In one embodiment, the silazane is selected from disilazane, trisilazane, tetrasilazane, or a combination of two or more of these.

[0030] In one embodiment, the silazane is selected from alkyl or alkenyl-substituted cyclosilazanes, linear alkyl or polyalkyl-substituted polysilazanes, or two or more combinations thereof, with ring sizes of 6 or 8.

[0031] In one embodiment, the silazane is selected from 2,2,5,5-tetramethyl-2,5-disila-1-azacyclopentane, 2,2,6,6-tetramethyl-2,6-disila-1-azacyclohexane, hexamethyldisilazane, 2,2,4,4,6,6-hexamethylcyclotrisilazane, 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane, 2,2,4,4,6,6,8,8-octamethylcyclotetrasilazane, 1,1,3,3-tetramethyldisilazane, 1,3-diethyl-1,1,3,3-tetramethyldisilazane, or two or more combinations thereof.

[0032] In one embodiment, the metal siloxanolate is selected from potassium siloxanolate, lithium siloxanolate, sodium siloxanolate, or a combination of two or more of these.

[0033] In one embodiment, bis(alkylamino)dialkylsilane or bis(alkylamino)dialkenylsilane is bis(methylamino)dimethylsilane, bis(methylamino)diethylsilane, bis(methylamino)divinylsilane, bis(methylamino)di-n-propylsilane, bis(methylamino)diisopropylsilane, bis(methylamino)di-n-butylsilane, bis(methylamino)diisobutylsilane, bis(methylamino)di-sec-butylsilane, bis(methylamino)di-t-butylsilane, bis(methylamino)di -n-neopentylsilane, bis(methylamino)dicyclopentylsilane, bis(methylamino)dicyclohexylsilane, bis(methylamino)di-4-methoxyphenylsilane, bis(methylamino)methylethylsilane, bis(methylamino)methyl-t-butylsilane, bis(methylamino)methylphenylsilane, bis(methylamino)ethyl-t-butylsilane, bis(methylamino)sec-butylmethylsilane, bis(methylamino)sec-butylethylsilane, bis(methylamino)methylcyclopentylsilane, bis(methylamino) (Mino)ethylcyclopentylsilane, bis(methylamino)cyclopentylcyclohexylsilane, bis(methylamino)methylcyclohexylsilane, bis(methylamino)didecahydronaphthylsilane, bis(methylamino)texylmethylsilane, bis(ethylamino)dimethylsilane, bis(ethylamino)diethylsilane, bis(ethylamino)divinylsilane, bis(ethylamino)di-n-propylsilane, bis(ethylamino)diisopropylsilane, bis(ethylamino)di-n-butylsilane, bis(ethylamino)diisobutylsilane Lan, bis(ethylamino)di-sec-butylsilane, bis(ethylamino)di-t-butylsilane, bis(ethylamino)dicyclopentylsilane, bis(ethylamino)dicyclohexylsilane, bis(ethylamino)didecahydronaphthylsilane, bis(ethylamino)methylethylsilane, bis(ethylamino)methyl-t-butylsilane, bis(ethylamino)methylphenylsilane, bis(ethylamino)ethyl-t-butylsilane, bis(ethylamino)sec-butylmethylsilane, bis(ethylamino)sec-butylethylsilane,Bis(ethylamino)methylcyclopentylsilane, bis(ethylamino)cyclopentylcyclohexylsilane, bis(ethylamino)methylcyclohexylsilane, bis(ethylamino)t-butylisobutylsilane, bis(ethylamino)cyclohexyltexylsilane, bis(n-propylamino)dimethylsilane, bis(n-propylamino)diethylsilane, bis(n-propylamino)divinylsilane, bis(n-propylamino)di-n-propylsilane, bis(n-propylamino)diisopropylsilane, bis(n-propylamino)di-n-butylsilane, bis(n-propylamino)di-sec-butylsilane, bis(n-propylamino)di-t-butylsilane, bis(n-propylamino)di-n-neopentylsilane, bis Bis(n-propylamino)dicyclopentylsilane, bis(n-propylamino)dicyclohexylsilane, bis(isopropylamino)dimethylsilane, bis(isopropylamino)diethylsilane, bis(isopropylamino)divinylsilane, bis(isopropylamino)di-n-propylsilane, bis(isopropylamino)diisopropylsilane, bis(isopropylamino)di-n-butylsilane, bis(isopropylamino)diisobutylsilane, bis(isopropylamino)di-sec-butylsilane, bis(isopropylamino)di-t-butylsilane, bis(isopropylamino)dineopentylsilane, bis(isopropylamino)dicyclopentylsilane, bis(isopropylamino)dicyclohexylsilane, or a selection of two or more combinations of these.

[0034] In one embodiment, the process further includes heating to a temperature sufficient to decompose the catalyst and, if a chain extender is used, to remove ammonia by-products, amine by-products, or a combination thereof.

[0035] In one embodiment, the polydiorganosiloxane is of formula: [ka] It has, and in the formula R 4 Each of them is independently selected from alkyl, alkenyl, aromatic, arylalkyl, and fluoroalkyl, R 5 Since is -OH and n+m is 50 or greater, polydiorganosiloxanes have viscosities ranging from approximately 500 cPs to approximately 200,000,000 cPs.

[0036] In one embodiment, the polydiorganosiloxane has a viscosity ranging from about 20,000 cPs to about 200,000,000 cPs.

[0037] In one embodiment, the polydiorganosiloxane has a viscosity ranging from about 25,000 cPs to about 150,000,000 cPs.

[0038] In one embodiment, the polydiorganosiloxane comprises a mixture of two or more polydiorganosiloxanes.

[0039] In one embodiment, a mixture of two or more polydiorganosiloxanes comprises a first polydiorganosiloxane with a first viscosity of about 100,000 cPs to about 450,000 cPs, and a second polydiorganosiloxane with a second viscosity of about 300,000 cPs to about 750,000 cPs, where the second polydiorganosiloxane has a higher viscosity than the first polydiorganosiloxane.

[0040] In one embodiment, the MQ silicone resin is approximately 0.3 to approximately 0.9 g / cm³ 3 It has a density within that range.

[0041] In one embodiment, the MQ silicone resin has a ratio of M units to Q units of 0.2:1 to 1.7:1.

[0042] In one embodiment, the MQ resin contains approximately 2% to approximately 12% free Si-OH functional groups.

[0043] In one embodiment, the process involves treating the reaction by nitrogen sparging.

[0044] In one embodiment, the reaction is carried out under vacuum for a predetermined time.

[0045] In one embodiment, the process involves dissolving a pressure-sensitive adhesive in a non-aromatic solvent.

[0046] In one embodiment, the pressure-sensitive adhesive produced by this process has a cyclic siloxane content of approximately 2000 ppm or less.

[0047] In one embodiment, the pressure-sensitive adhesive produced by this process has an octamethylcyclotetrasiloxane content of about 2000 ppm or less; a decamethylcyclopentasiloxane content of about 2000 ppm or less; and / or a dodecamethylcyclohexasiloxane content of about 2000 ppm or less.

[0048] In one embodiment, the pressure-sensitive adhesive produced by this process has an octamethylcyclotetrasiloxane content of about 1000 ppm or less; a decamethylcyclopentasiloxane content of about 1000 ppm or less; and / or a dodecamethylcyclohexasiloxane content of about 1000 ppm or less.

[0049] In one embodiment, the pressure-sensitive adhesive produced from this process has an octamethylcyclotetrasiloxane content of about 500 ppm or less; a decamethylcyclopentasiloxane content of about 500 ppm or less; and / or a dodecamethylcyclohexasiloxane content of about 500 ppm or less.

[0050] In one embodiment, the pressure-sensitive adhesive produced by this process has an octamethylcyclotetrasiloxane content of about 250 ppm or less; a decamethylcyclopentasiloxane content of about 250 ppm or less; and / or a dodecamethylcyclohexasiloxane content of about 250 ppm.

[0051] The applicant has found that the condensation reaction for producing silicone pressure-sensitive adhesive materials can be carried out in the absence of a solvent. In addition, this method has been found to produce silicone pressure-sensitive adhesives with a low cyclic siloxane content.

[0052] The following description discloses various exemplary embodiments. Some improvements and novel embodiments are explicitly identified, while others may be obvious from the description. [Modes for carrying out the invention]

[0053] The following descriptions refer to exemplary embodiments, examples of which are shown in the description and examples. As will be understood, other embodiments may be used, and structural and functional modifications may be made. Furthermore, features of various embodiments may be combined or modified. Therefore, the following description is presented only as an example and does not limit in any way to the various changes and modifications that may be made to the embodiments described. Many specific details in this disclosure will lead to a full understanding of the subject matter of this disclosure. It should be understood that embodiments of this disclosure may be implemented in other embodiments without necessarily including all embodiments described herein.

[0054] As used in this application, the terms “example” or “exemplary” mean a case or example. The terms “example” or “exemplary” do not indicate that they are important or preferred embodiments or forms. The term “or” is intended to be inclusive, not exclusive, unless the context specifically suggests otherwise. For example, the phrase “A uses B or C” includes all inclusive substitutions (e.g., A uses B; A uses C; or A uses both B and C). Separately, the articles “a” and “one” are generally intended to mean “one or more” unless the context specifically suggests otherwise.

[0055] The silicone pressure-sensitive adhesive produced by this technology is obtained by the reaction of (i) MQ silicone resin free of volatile solvents and (ii) polydiorganosiloxane, where the reaction is carried out in the absence of volatile solvents. This reaction may be carried out in the presence of a catalyst. This catalyst may be removed, for example, by degrading it by heating. The viscosity of the resulting pressure-sensitive adhesive may be adjusted via a suitable non-aromatic solvent.

[0056] MQ resins are provided as resin materials that are substantially free of any volatile solvents. In particular, MQ resins are free of any aromatic solvents, and especially substantially free of benzene, toluene, and / or xylene-type solvents. MQ resins may be in solid form. With respect to the purposes of this application, "solvent-free" means that the solvent content is <5 ppm and the cyclic substance content is <100 ppm. For cyclic substances, the content is preferably less than 100 ppm, more preferably <50 ppm, and most preferably less than 20 ppm.

[0057] MQ resin materials are generally provided or obtained by being placed in an aromatic solvent, such as a BTX type. This solvent can be removed by any suitable method. In one embodiment, solvent-free MQ resin can be provided by removing the solvent via an extrusion process. Such a process is described in U.S. Patent No. 8,017,712, which is hereby incorporated by reference in its entirety. In another embodiment, solvent-free MQ resin can be provided by removing the solvent via a spray drying process as described in U.S. Patent No. 5,324,806.

[0058] The MQ resin is not particularly limited and includes polymers of M units represented by the formula R 1 3SiO 1 / 2 and Q units represented by the formula SiO 4 / 2 . The MQ resin is mainly formed from such M units and Q units, but may contain some residual D units (R 2 2SiO 2 / 2 ) and T units (R 3 SiO 3 / 2 ). Generally, the MQ resin contains less than 20 mol% of D units and T units, less than 15 mol% of D units and T units, less than 10 mol% of D units and T units, less than 5 mol% of D units and T units, and even less than 1 mol% of D units and T units.

[0059] In the MQ resin, R 1 , R 2 , and R 3Each is independently selected from monovalent C1-C6 hydrocarbons, C5-C20 alicyclic radicals, C2-C6 olefinic radicals, and C6-C20 aromatic radicals. Suitable examples of monovalent C1-C6 hydrocarbon radicals include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, and hexyl. Suitable examples of alicyclic radicals include, but are not limited to, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and others. Suitable examples of C2-C6 olefinic radicals include, but are not limited to, vinyl, allyl, and others. Suitable examples of aromatic radicals include, but are not limited to, phenyl. 1 , R 2 , and R 3 Each of the elements can be identical or different within a given M, D, or T unit. In one embodiment, R 1 , R 2 , and / or R 3 Approximately 95 to 100% of the groups are methyl. In one embodiment, R 1 , R 2 , and / or R 3 Substantially all of the groups are unsaturated. In one embodiment, the R of the MQ resin 1 , R 2 , and R 3 The base contains 0 to 0.5 mol% of some unsaturated material.

[0060] Solid solvent-free MQ resins have a concentration of 0.3 to 0.9 g / cm³. 3 It has a density in the range of . The ratio of M units to Q units is about 0.2:1 or greater. In one embodiment, the ratio of M units to Q units is 0.2:1 to 1.7:1. The MQ resin may contain some free Si-OH groups. In embodiments, the MQ resin contains about 2% to about 12% free Si-OH functional groups, about 4% to about 10% free Si-OH functional groups, or about 5% to about 8% free Si-OH functional groups.

[0061] The polydiorganosiloxane is selected from hydroxyl-functionalized polydiorganosiloxanes. The polydiorganosiloxane may also be referred to as silicone rubber in this application. According to this technology, the silicone rubber may be a low molecular weight to high molecular weight rubber.

[0062] In one embodiment, the polydiorganosiloxane is of formula: [ka] It has, and in the formula R 4 Each of them is independently selected from alkyl, alkenyl, aromatic, arylalkyl, and fluoroalkyl, and R 5 is -OH, where n+m is 50 or greater, and polydiorganosiloxanes have viscosities from about 500 cPs to about 200,000,000 cPs. In one embodiment, R 4 The group is independently selected from C1-C10 alkyl, C2-C10 alkenyl, C6-C20 aromatic, C7-C20 arylalkyl, and C1-C10 fluoroalkyl groups. A fluoroalkyl group is one in which one or more of the hydrogen atoms of the alkyl group are substituted with fluorine atoms; in embodiments, the fluoroalkyl group may be selected from perfluorinated alkyl groups. In one embodiment, R 4 Each of them is an alkyl group, and in the embodiment, R 4 Each of them is methyl. In one embodiment, R is located in units of m. 4 The group is alkyl, and in embodiments it is methyl, and also R in the y unit. 4 The group is an aromatic group, and in this embodiment, it is phenyl. For one purpose, polydiorganosiloxanes are available in approximately 500 cPs to approximately 200,000,000 cPs; approximately 25,000 cPs to approximately 150,000,000 cPs; approximately 50,000 cPs to approximately 100,000,000 cPs; approximately 75,000 cPs to approximately 75,000,000 cPs; approximately 1 The viscosity is approximately 00,000 cPs to about 50,000,000 cPs; approximately 125,000 cPs to about 800,000 cPs; approximately 150,000 cPs to about 750,000 cPs; approximately 200,000 cPs to about 500,000 cPs; or approximately 300,000 cPs to about 450,000 cPs. In one embodiment, the polydiorganosiloxane has a viscosity of approximately 50,000 cPs to about 150,000 cPs or approximately 75,000 cPs to about 100,000 cPs. In another embodiment, the polydiorganosiloxane has a viscosity of about 100,000 cPs to about 450,000 cPs; about 150,000 cPs to about 400,000 cPs; or about 200,000 to about 300,000 cPs. In yet another embodiment, the polydiorganosiloxane has a viscosity of about 300,000 cPs to about 750,000 cPs; about 400,000 cPs to about 700,000 cPs; or about 500,000 cPs to about 600,000 cPs. Viscosity may be evaluated using any suitable method. In one embodiment, viscosity is determined by dissolving the resulting PSA molten material in a suitable solvent with a solid content of 60%, and then measuring the viscosity at 25°C using a Brookfield (DV1) viscometer.

[0063] The polydiorganosiloxane may include a blend of polydiorganosiloxanes with different viscosities. In one embodiment, the polydiorganosiloxane comprises a first polydiorganosiloxane with a first viscosity ranging from about 100,000 cPs to about 450,000 cPs, and a second polydiorganosiloxane with a second viscosity ranging from about 300,000 cPs to about 750,000 cPs, where the second polydiorganosiloxane has a higher viscosity than the first polydiorganosiloxane.

[0064] In forming the adhesive, solid MQ resin is present in amounts of approximately 20% to 70% by weight, approximately 25% to 65% by weight, approximately 45% to 60% by weight, or approximately 50% to 55% by weight; and polydiorganosiloxane is present in amounts of approximately 30% to 80% by weight, approximately 35% to 75% by weight, approximately 40% to 55% by weight, or approximately 45% to 50% by weight.

[0065] The catalyst is not particularly limited and may be selected from any suitable condensation catalyst. The condensation catalyst can be, for example, an acid catalyst or a base catalyst. The acid catalyst can be an inorganic acid catalyst or an organic acid catalyst. Examples of inorganic acid catalysts include, but are not limited to, hydrochloric acid, phosphoric acid, and polyphosphate. Examples of organic acid catalysts include, but are not limited to, carboxylic acids, such as, but are not limited to, acetic acid, benzoic acid, propionic acid, but are not limited to, acetic acid, benzoic acid, formic acid, and carboxylic acid metal salts, where the metal is selected from the group consisting of, but is not limited to, Li, Na, K, Ce, and Ca. Non-limited examples of carboxylic acid metal salts include, but are not limited to, potassium formate or potassium acetate. The base catalyst can be selected from, but is not limited to, alkali metal oxides, alkali metal alkoxides, alkali metal hydroxides, alkali metal silanolates, alkali metal siloxanolates, alkali metal amides, alkyl metals, ammonia, amines, and ammonia compounds such as ammonium hydroxide and substituted ammonium hydroxide. An exemplary alkali metal oxide is, but is not limited to, sodium oxide. Examples of suitable alkali metal alkoxides include, but is not limited to, potassium ethoxide, sodium methoxide, lyuthim methoxide, and potassium isopropoxide. Examples of suitable alkali metal hydroxides include, but is not limited to, potassium hydroxide, lithium hydroxide, sodium hydroxide, and cesium hydroxide. Examples of suitable alkali metal amides include, but is not limited to, sodium amide and potassium amide. Examples of suitable alkyl metals include, but is not limited to, butyllithium. Examples of suitable amines include, but is not limited to, triethylamine and allylamine. Examples of suitable ammonium hydroxides include, but is not limited to, quaternary ammonium hydroxides such as tetramethylammonium hydroxide. The base catalyst can alternatively be a quaternary phosphonium hydroxide, such as tetrabutylphosphonium hydroxide, but is not limited to, quaternary phosphonium hydroxide. The base catalyst can alternatively be a salt of a strong base and a weak acid, such as potassium carbonate.

[0066] In one embodiment, the base catalyst can be selected from chain extenders or encapsulants, which are selected from metal siloxanolates, metal silanolates, silazanes, bis(alkylamino)silanes, or combinations of two or more of these. Suitable alkali metal silanolates include, but are not limited to, potassium silanolate, lithium silanolate, and sodium silanolate. Suitable metal siloxanolates include, but are not limited to, potassium siloxanolate, lithium siloxanolate, and sodium siloxanolate. Suitable silazanes include, but are not limited to, bissilazanes, trisilazanes, and tetrasilazanes. Examples of such agents include, but are not limited to, hexamethylcyclotrisilazane, trimethyltrivinylcyclotrisilazane, octamethylcyclotetrasilazane, alkyl or alkenyl-substituted cyclosilazanes with ring size 6 or 8, and linear alkyl or polyalkyl-substituted polysilazanes. Some more specific examples of suitable silazanes include, but are not limited to, 1,1,3,3-tetramethyldisilazane, 1,3-diethyl-1,1,3,3-tetramethyldisilazane, hexamethyldisilazane; cyclic disilazane compounds such as 2,2,5,5-tetramethyl-2,5-disila-1-azacyclopentane and 2,2,6,6-tetramethyl-2,6-disila-1-azacyclohexane; cyclic trisilazane compounds such as 2,2,4,4,6,6-hexamethylcyclotrisilazane and 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane; and cyclic tetrasilazane compounds such as 2,2,4,4,6,6,8,8-octamethylcyclotetrasilazane.

[0067] Examples of suitable bis(alkylamino)dialkylsilanes and bis(alkylamino)dialkenylsilanes include, but are not limited to, bis(methylamino)dimethylsilane, bis(methylamino)diethylsilane, bis(methylamino)divinylsilane, bis(methylamino)di-n-propylsilane, bis(methylamino)diisopropylsilane, bis(methylamino)di-n-butylsilane, bis(methylamino)diisobutylsilane, bis(methylamino)di-sec-butylsilane, bis(methylamino)di-t-butylsilane, Bis(methylamino)di-n-neopentylsilane, bis(methylamino)dicyclopentylsilane, bis(methylamino)dicyclohexylsilane, bis(methylamino)di-4-methoxyphenylsilane, bis(methylamino)methylethylsilane, bis(methylamino)methyl-t-butylsilane, bis(methylamino)methylphenylsilane, bis(methylamino)ethyl-t-butylsilane, bis(methylamino)sec-butylmethylsilane, bis(methylamino)sec-butylethylsilane, bis(methylamino)methylcyclo Pentylsilane, bis(methylamino)ethylcyclopentylsilane, bis(methylamino)cyclopentylcyclohexylsilane, bis(methylamino)methylcyclohexylsilane, bis(methylamino)didecahydronaphthylsilane, bis(methylamino)texylmethylsilane, bis(ethylamino)dimethylsilane, bis(ethylamino)diethylsilane, bis(ethylamino)divinylsilane, bis(ethylamino)di-n-propylsilane, bis(ethylamino)diisopropylsilane, bis(ethylamino)di-n-butylsilane , bis(ethylamino)diisobutylsilane, bis(ethylamino)di-sec-butylsilane, bis(ethylamino)di-t-butylsilane, bis(ethylamino)dicyclopentylsilane, bis(ethylamino)dicyclohexylsilane, bis(ethylamino)didecahydronaphthylsilane, bis(ethylamino)methylethylsilane, bis(ethylamino)methyl-t-butylsilane, bis(ethylamino)methylphenylsilane, bis(ethylamino)ethyl-t-butylsilane, bis(ethylamino)sec-butylmethylsilane,Bis(ethylamino)sec-butylethylsilane, bis(ethylamino)methylcyclopentylsilane, bis(ethylamino)cyclopentylcyclohexylsilane, bis(ethylamino)methylcyclohexylsilane, bis(ethylamino)t-butylisobutylsilane, bis(ethylamino)cyclohexyltexylsilane, bis(n-propylamino)dimethylsilane, bis(n-propylamino)diethylsilane, bis(n-propylamino)divinylsilane, bis(n-propylamino)di-n-propylsilane, bis(n-propylamino)diisopropylsilane, bis(n-propylamino)di-n-butylsilane, bis(n-propylamino)diisobutylsilane, bis(n-propylamino)di- This includes n-neopentylsilane, bis(n-propylamino)dicyclopentylsilane, bis(n-propylamino)dicyclohexylsilane, bis(isopropylamino)dimethylsilane, bis(isopropylamino)diethylsilane, bis(isopropylamino)divinylsilane, bis(isopropylamino)di-n-propylsilane, bis(isopropylamino)diisopropylsilane, bis(isopropylamino)di-n-butylsilane, bis(isopropylamino)diisobutylsilane, bis(isopropylamino)di-sec-butylsilane, bis(isopropylamino)di-t-butylsilane, bis(isopropylamino)dineopentylsilane, bis(isopropylamino)dicyclopentylsilane, bis(isopropylamino)dicyclohexylsilane, or two or more combinations of these.

[0068] If the composition contains such a chain extender, the amount used may be 50% to 175% of the stoichiometric amount, preferably 70% to 120%, and most preferably 90% to 110%, based on the available silanol content.

[0069] In the formation of the adhesive, the catalyst is present in amounts of approximately 0.3% to 10% by weight, approximately 0.5% to 5% by weight, or approximately 1% to 2% by weight.

[0070] A process for producing a silicone pressure-sensitive adhesive comprises (i) mixing a solid, solvent-free MQ resin with a polydiorganosiloxane to form a first mixture; (ii) adding a catalyst to the first mixture to catalyze the reaction between the MQ resin and the polydiorganosiloxane to form a pressure-sensitive adhesive composition; and (iii) removing the catalyst from the pressure-sensitive adhesive composition, wherein the reaction is solvent-free. This process may further comprise (iv) dissolving the pressure-sensitive adhesive composition in a non-aromatic solvent to adjust the solid content as desired.

[0071] The mixing of solid, solvent-free MQ resin and polydiorganosiloxane can be carried out at a temperature suitable for ensuring sufficient mixing and dispersion of the MQ resin into the polydiorganosiloxane. In some embodiments, the mixture of MQ resin and polydiorganosiloxane can be heated to temperatures ranging from about 25°C to about 200°C, from about 50°C to about 150°C, or from about 75°C to about 100°C. In one embodiment, the mixture of MQ resin and polydiorganosiloxane can be heated to temperatures ranging from about 120°C to about 130°C.

[0072] After adding the catalyst to the mixture of MQ resin and polydiorganosiloxane, the mixture can be continuously heated for a sufficient amount of time to complete the condensation / crosslinking reaction. In embodiments, the mixture of MQ resin, polydiorganosiloxane, and catalyst or chain extender can be heated to temperatures of about 60°C to about 200°C, about 75°C to about 175°C, or about 100°C to about 150°C. The heating time may vary. In embodiments, heating can be carried out for any length of time from 1 to 10 hours.

[0073] While not bound by any particular theory, it can be understood that, based on the available silanol functionalities, chain extension may occur via reaction with low molecular weight silanol-terminated fluids, resulting in the situ formation of rubber, followed by condensation with the silanol of MQ to produce a pressure-sensitive adhesive.

[0074] It will be understood that the temperature of the mixture containing the condensation catalyst is lower than the temperature at which the catalyst decomposes, at least initially. The reaction must be kept below the catalyst decomposition temperature for a sufficient length of time to allow the condensation / crosslinking to complete. After the condensation reaction reaches its endpoint, the temperature of the pressure-sensitive adhesive composition can be set to the catalyst decomposition temperature. This allows for easy removal of the catalyst from the system without the need for a separate extraction step or treatment otherwise performed to remove the catalyst. The step for removing the catalyst can also be carried out under a nitrogen atmosphere or using a nitrogen purge to facilitate catalyst removal.

[0075] When using a chain extender, the reaction temperature should be sufficient to react the silanol groups and remove any ammonia or amine by-products that may form, but low enough so that the chain extender does not volatilize and be removed from the system prematurely.

[0076] With regard to the purpose of this application, completion or endpoint of the reaction indicates that the desired melt viscosity has been reached.

[0077] This process can also be carried out under suitable atmospheric conditions that are desired or suitable for promoting adhesive formation. To remove unwanted gases from the system and composition, the system or mixture can be treated with nitrogen sparging. In addition, the mixing of the composition can also be carried out under reduced pressure or vacuum, as desired. In embodiments, mixing can be carried out under pressures of about 0.1 torr to about 760 torr; about 0.5 torr to about 500 torr; about 1 torr to about 250 torr; or about 10 torr to about 100 torr. In one embodiment, mixing is carried out at a pressure of about 0.1 torr to about 100 torr.

[0078] The resulting pressure-sensitive adhesive is suitable for a variety of applications, including those where a conversion process from hot melt is required or beneficial. For applications requiring a solvent, the adhesive may be dissolved in a suitable solvent, as described in more detail below.

[0079] The solids content of the resulting pressure-sensitive adhesive can be adjusted as desired using a suitable solvent. The solids content of the pressure-sensitive adhesive can be selected as desired for a particular purpose or intended application. In one embodiment, the solids content of the pressure-sensitive adhesive can be adjusted from about 30% to about 80%, from about 40% to about 70%, or from about 50% to about 60%. The solvent is preferably a non-aromatic solvent, and more preferably a solvent other than a BTX type solvent. Examples of suitable solvents that may be used to dissolve the pressure-sensitive adhesive include, but are not limited to, hydrocarbon solvents, silicone solvents, esters, ketones, or ethers.

[0080] Suitable examples of aliphatic hydrocarbons include linear, branched, or cyclic aliphatic hydrocarbons having 6 to 16 carbon atoms, such as saturated acyclic aliphatic hydrocarbons (paraffins) like heptane, hexane, octane, isooctane, decane, isodecane, isohexadecane or dodecane or isododecane, and cyclic aliphatic hydrocarbons like cyclohexane, methylcyclohexane or decahydronaphthalene. The aliphatic hydrocarbon solvent can be an alkene, such as heptane, cyclohexadiene, cyclohexane, or 2,5-dimethyl-2,4-hexadiene. A mixture of aliphatic hydrocarbons, such as ISOPAR 登録商標 Mixtures of branched-chain paraffins sold under the same name are also suitable.

[0081] Examples of suitable volatile silicone solvents include, but are not limited to, linear, branched, and cyclic polydiorganosiloxanes, such as polydimethylsiloxanes like linear trimethylsilyl-terminated polydimethylsiloxane having a viscosity of 0.65 to 5 cP at 25°C, and cyclic polydimethylsiloxanes like decamethylcyclopentasiloxane and octamethylcyclotetrasiloxane. Volatile silicone solvents may contain organic groups other than methyl, such as higher alkyl or phenyl groups. One example is 3-octylheptamethyltrisiloxane. In one embodiment, viscosity is determined by melting the resulting PSA molten material in a suitable solvent with a solid content of 60%, and then measuring the viscosity at 25°C using a Brookfield (DV1) viscometer.

[0082] Examples of suitable ester solvents include, but are not limited to, carboxylic acid esters such as alkyl carboxylic acid esters and carbonate esters such as alkyl carbonate esters. For example, volatile solvents include C1-C8 carboxylic acids such as ethyl acetate or butyl acetate. It may contain at least one alkyl ester. Suitable carbonate ester solvents include, but are not limited to, diethyl carbonate and dicaprylyl carbonate.

[0083] Suitable ketone solvents include, but are not limited to, methyl isobutyl ketone (4-methyl-2-pentanone), 2-pentanone, 3-hexanone, and methyl isoamyl ketone (5-methyl-2-hexanone).

[0084] Suitable ether solvents include, but are not limited to, dibutyl ether, volatile polyethers such as 1-(propoxymethoxy)propane, and cyclic ethers such as cyclopentamethyl ether.

[0085] The pressure-sensitive adhesives produced by this process can be used in a wide variety of applications. Silicone pressure-sensitive adhesives prepared by the method of the present invention readily adhere to and support solid supports or substrates, whether flexible or rigid. These pressure-sensitive adhesive compositions may be applied to a surface by any suitable means, such as rolling, spreading, or spraying. The surface of the support and the substrate to which the support is attached may be any known solid material, such as metal, paper, wood, leather, textiles, organic polymer materials, painted surfaces, siliceous materials such as concrete, brick, and concrete blocks, and glass including glass cloth. After application to a surface, the adhesive may be cured by air drying or by heating at a temperature of, for example, up to 300°C.

[0086] In addition, the pressure-sensitive adhesive produced by this technology may contain a low concentration of cyclic siloxane. In embodiments, the pressure-sensitive adhesive contains one or more of octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), or dodecamethylcyclohexasiloxane (D6) in amounts less than 2000 ppm, less than 1800 ppm, less than 1500 ppm, less than 1250 ppm, less than 1000 ppm, less than 750 ppm, less than 500 ppm, less than 250 ppm, and even less than 100 ppm. In one embodiment, the pressure-sensitive adhesive contains D4, D5, or D6 cyclic siloxane in amounts less than 2000 ppm, less than 1800 ppm, less than 1500 ppm, less than 1250 ppm, less than 1000 ppm, less than 750 ppm, less than 500 ppm, less than 250 ppm, and even less than 100 ppm.

[0087] This technology has been described in the above detailed description with reference to various embodiments and models. This technology can be further understood by referring to the following examples. These examples are intended to further illustrate embodiments and models of this technology, but are not necessarily limited to such embodiments or models.

[0088] Examples

[0089] MQ Silicone Resin

[0090] The solid MQ silicone resins used to prepare the pressure-sensitive adhesives had silanol content ranging from 95,473 ppm to 47,746 ppm. The MQ resins used were referred to as MQ1 resin (silanol content 95,473 ppm), MQ2 resin (silanol content 47,746 ppm), and MQ3 resin (silanol content 56,642 ppm).

[0091] Silicone rubber

[0092] Examples 1-6

[0093] Examples 1-6 describe the silicone rubbers used in the examples and their properties, such as weight-average molecular weight (MW) and cyclic content. Weight-average molecular weight was determined by gel permeation chromatography (GPC) calibrated using polystyrene standards in chloroform solvent. Solution viscosity of the materials was determined using a Brookfield (DV1) viscometer at 25°C with spindles #2 to #6. Cyclic siloxane concentration was quantified using gas chromatography.

[0094] The silicone rubbers used in Examples 1-6 are listed in Table 1 below: [Table 1]

[0095] Preparation of silicone PSA

[0096] Examples 7-18

[0097] Example 7

[0098] In a 3-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), the silicone rubber of Example 1 (287.23 g) and Example 2 (95.74 g) was added, followed by the addition of MQ1 resin (517.02 g), or in the reverse order. The temperature of the reactor was set to 125–130°C under a positive nitrogen stream. The above mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 1–4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 7.5 g of tetramethylammonium siloxanolate (CAS number 68440-88-0) was added, and the reaction was continued for a further 3 hours. Finally, the temperature of the reactor was raised to 150°C and maintained under N2 for 2–3 hours. After this step, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts ethyl acetate (~600 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 33500 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0099] Example 8

[0100] In a 3-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), the silicone rubber of Example 1 (287.23 g) and Example 2 (95.74 g) was added, followed by the addition of MQ1 resin (517.02 g), or in the reverse order. The temperature of the reactor was set to 125–130°C under a positive nitrogen stream. The above mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 1–4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 7.5 g of tetramethylammonium siloxanolate (CAS number 68440-88-0) was added, and the reaction was continued for a further 3 hours. Finally, the temperature of the reactor was raised to 150°C and maintained under N2 for 2–3 hours. After this step, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts heptane (~600 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 15900 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0101] Example 9

[0102] In a 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), 80 grams of silicone rubber from Example 3 were added, followed by 100 grams of MQ1 resin, or in the reverse order. The reactor temperature was set to 125–130°C under a positive nitrogen flow. The mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 1–4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 1.2 grams of tetramethylammonium siloxanolate (CAS number 68440-88-0) was added, and the reaction was continued for a further 3 hours. Finally, the reactor temperature was raised to 150°C and maintained under N2 for 2–3 hours. After this step, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts heptane (~120 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 13120 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0103] Example 10

[0104] In a 3-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), the silicone rubber of Example 1 (287.23 g) and Example 2 (95.74 g) was added, followed by the addition of MQ1 resin (100 g), or in the reverse order. The temperature of the reactor was set to 125–130°C under a positive nitrogen flow. The above mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 1–4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 25% tetraethylammonium hydroxide (CAS No. 77-98-5) in 10.50 g methanol was added, and the reaction was continued for a further 3 hours. Finally, the temperature of the reactor was raised to 150°C and maintained under N2 for 2–3 hours. After this step, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts heptane (~600 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 10800 cPs at 25°C, and the GPC showed multimode resin and polymer peaks.

[0105] Example 11

[0106] In a 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), 127.34 grams of silicone rubber from Example 4 were added, followed by 172.65 grams of MQ2 resin, or in the reverse order. The reactor temperature was set to 125–130°C under a positive nitrogen stream. The mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 1–4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 2.0 grams of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (CAS No. 5505-72-6) were added, and the reaction was continued for a further 3 hours. Finally, the reactor temperature was raised to 150°C and maintained under N2 for 2–3 hours. After this process, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts ethyl acetate (~200 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 780 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0107] Example 12

[0108] In a 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), 133.33 grams of silicone rubber from Example 5 were added, followed by 166.66 grams of MQ2 resin, or in the reverse order. The reactor temperature was set to 125–130°C under a positive nitrogen stream. The mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 1–4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 2.0 grams of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (CAS No. 5505-72-6) were added, and the reaction was continued for a further 3 hours. Finally, the reactor temperature was raised to 150°C and maintained under N2 for 2–3 hours. After this step, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts ethyl acetate (~200 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 1100 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0109] Example 13

[0110] In a 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), 133.33 grams of silicone rubber from Example 5 were added, followed by 166.66 grams of MQ2 resin, or in the reverse order. The reactor temperature was set to 125–130°C under a positive nitrogen stream. The mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 1–4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 2.0 grams of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (CAS No. 5505-72-6) were added, and the reaction was continued for a further 3 hours. Finally, the reactor temperature was raised to 150°C and maintained under N2 for 2–3 hours. After this step, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts heptane (~200 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 1060 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0111] Example 14

[0112] In a 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), 120 grams of silicone rubber from Example 4 were added, followed by 180 grams of MQ2 resin, or in the reverse order. The temperature of the reactor was set to 125–130°C under a positive nitrogen stream. The mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 1–4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 2.0 grams of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (CAS No. 5505-72-6) were added, and the reaction was continued for a further 3 hours. Finally, the temperature of the reactor was raised to 150°C and maintained under N2 for 2–3 hours. After this step, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts ethyl acetate (~200 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 380 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0113] Example 15

[0114] In a 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), 120 grams of silicone rubber from Example 5 were added, followed by 180 grams of MQ2 resin, or in the reverse order. The temperature of the reactor was set to 125–130°C under a positive nitrogen flow. The mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 1–4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 2.0 grams of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (CAS No. 5505-72-6) were added, and the reaction was continued for a further 3 hours. Finally, the temperature of the reactor was raised to 150°C and maintained under N2 for 2–3 hours. After this process, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts ethyl acetate (~200 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 530 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0115] Example 16

[0116] In a 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), 105.26 grams of silicone rubber from Example 4 were added, followed by 194.73 grams of MQ3 resin, or in the reverse order. The reactor temperature was set to 125–130°C under a positive nitrogen stream. The mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 1–4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 2.0 grams of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (CAS No. 5505-72-6) were added, and the reaction was continued for a further 3 hours. Finally, the reactor temperature was raised to 150°C and maintained under N2 for 2–3 hours. After this step, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts ethyl acetate (~200 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 240 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0117] Example 17

[0118] In a 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), 45.28 grams of silicone rubber from Example 6 were added, followed by 74.71 grams of MQ3 resin, or in the reverse order. The reactor temperature was set to 55°C under a positive nitrogen flow. The mixture was stirred at 125–130°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 6–8 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 0.3 grams of allylamine (CAS No. 107-11-9) was added, and the reaction was continued for a further 3 hours. Finally, the reactor temperature was raised to 55°C and maintained under N2 for 1 hour. After this condensation step, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts ethyl acetate (~80 grams) at 50°C to adjust the solid content to 60%. The viscosity of the PSA was 310 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0119] Example 18

[0120] In a 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 sparging), the rubbers of Example 6 (22.64 g) and Example 5 (22.64 g) were added, followed by the addition of MQ3 resin (74.71 g), or in the reverse order. The temperature of the reactor was set to 90°C under a positive nitrogen flow. The above mixture was stirred at 90°C until a completely homogeneous solution / dispersion was obtained. This mixing process was continued for 4 hours until the MQ resin was completely dissolved or dispersed in the rubber mixture. 0.3 g of allylamine (CAS No. 107-11-9) was added, and the reaction was continued for 1 hour. After the condensation step, the reactor was cooled. The resulting high-viscosity mass was then dissolved in 40 parts heptane (~80 g) at 50°C to adjust the solids content to 60%. The viscosity of the PSA was 1170 cPs at 25°C, and the GPC showed multimode resin and polymer peaks.

[0121] Example 19

[0122] 200.0 g of the rubber from Example 5 was added to a Ross 2-pint planetary mixer equipped with a rectangular blade, heating device, thermocouple, and sparge tube (for N2 sparging), followed by the addition of MQ2 resin (250.0 g) in three portions. The reactor temperature was set to 150°C under a positive nitrogen flow. The mixture was stirred at 150°C until a completely homogeneous solution / dispersion was obtained. The nitrogen sparge tube was then replaced with a vacuum tube, and the mixing process was continued under vacuum for 2 to 3 hours. 0.30 g of dimethylbis(isopropylamino)silane (CAS No. 6026-42-2) was added, and the reaction was continued for 1 to 2 hours. After the condensation step, the reactor was cooled. Approximately 1.5 g of the solid product was placed on a 10-inch x 10-inch 25 μm PET film placed on a hot press preheated to 100°C. After the product was softened over 10 minutes, it was covered with Housewell's FL167 fluorosilicone release liner and compressed at low pressure with a spacer to form a thin film. The resulting film was used to measure its tackiness and release properties.

[0123] Example 20

[0124] 160.0 g of the rubber from Example 6 was added to a Ross 2-pint planetary mixer equipped with a rectangular blade, heating device, thermocouple, and sparge tube (for N2 sparging), followed by the addition of MQ2 resin (200.0 g) in three portions. The reactor temperature was set to 150°C under a positive nitrogen flow. The mixture was stirred at 150°C until a completely homogeneous solution / dispersion was obtained. The nitrogen sparge tube was then replaced with a vacuum tube, and the mixing process was continued under vacuum for 2 to 3 hours. 0.35 g of dimethylbis(isopropylamino)silane (CAS No. 6026-42-2) was added, and the reaction was continued for 1 to 2 hours. After the condensation step, the reactor was cooled. Approximately 1.5 g of the solid product was placed on a 10-inch x 10-inch 25 μm PET film placed on a hot press preheated to 100°C. After the product was softened over 10 minutes, it was covered with Housewell's FL167 fluorosilicone release liner and compressed at low pressure with a spacer to form a thin film. The resulting film was used to measure its tackiness and release properties.

[0125] Example 21

[0126] 160.0 g of the rubber from Example 5 was added to a Ross 2-pint planetary mixer equipped with a rectangular blade, heating device, thermocouple, and sparge tube (for N2 sparging), followed by the addition of MQ2 resin (200.0 g) in three portions. The reactor temperature was set to 150°C under a positive nitrogen flow. The mixture was stirred at 150°C until a completely homogeneous solution / dispersion was obtained. The nitrogen sparge tube was then replaced with a vacuum tube, and the mixing process was continued under vacuum for 2 to 3 hours. 1.0 g of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (CAS No. 5505-72-6) was added, and the reaction was continued for 1 to 2 hours. After the condensation step, the reactor was cooled. Approximately 1.5 g of the solid product was placed on a 10-inch x 10-inch 25 μm PET film placed on a hot press preheated to 100°C. After the product was softened over 10 minutes, it was covered with Housewell's FL167 fluorosilicone release liner and compressed at low pressure with a spacer to form a thin film. The resulting film was used to measure its tackiness and release properties.

[0127] Example 22

[0128] 160.0 g of the rubber from Example 6 was added to a Ross 2-pint planetary mixer equipped with a rectangular blade, heating device, thermocouple, and sparge tube (for N2 sparging), followed by the addition of MQ2 resin (200.0 g) in three portions. The reactor temperature was set to 150°C under a positive nitrogen flow. The mixture was stirred at 150°C until a completely homogeneous solution / dispersion was obtained. The nitrogen sparge tube was then replaced with a vacuum tube, and the mixing process was continued under vacuum for 2 to 3 hours. 2.0 g of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (CAS No. 5505-72-6) was added, and the reaction was continued for 1 to 2 hours. After the condensation step, the reactor was cooled. Approximately 1.5 g of the solid product was placed on a 10-inch x 10-inch 25 μm PET film placed on a hot press preheated to 100°C. After the product was softened over 10 minutes, it was covered with Housewell's FL167 fluorosilicone release liner and compressed at low pressure with a spacer to form a thin film. The resulting film was used to measure its tackiness and release properties.

[0129] Comparative Examples 1-4

[0130] Comparative Example 1

[0131] A 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 purging), as well as a Dean-Stark water trap filled with heptane, contained solutions of Example 1 (76.59 g) and Example 2 (25.53 g) and MQ3 resin (229.78 g) in heptane (68.1 g). The mixture was homogenously mixed under a positive nitrogen stream at 90°C for 3 hours. 1.5 g of 1% lithium hydroxide solution was added, and the reaction was continued for 3 hours. The reaction temperature was raised to 110°C, and the mixture was refluxed until the last traces of water were observed. A neutralization step was carried out at 70°C using 1% phosphoric acid in IPA. The viscosity of the PSA was 9700 cP at 25°C, and the GPC showed multimode resin and polymer peaks.

[0132] Comparative Example 2

[0133] A solution of Example 6 (45.28 g) and MQ3 resin (74.71 g) in heptane (80 g) was added to a 1-liter planetary mixer equipped with a helical blade, heating device, thermocouple, and sparge tube (for N2 purging), as well as a Dean-Stark water trap filled with heptane. The mixture was homogenously mixed under a positive nitrogen stream at 90°C for 3 hours. 0.3 g of allylamine (CAS No. 107-11-9) was added. The reaction was allowed to continue for a further 8 hours as the viscosity of the reaction mixture did not increase rapidly. A gel was formed after 6 hours. No further characterization was performed.

[0134] Comparative Example 3

[0135] A 1-liter planetary mixer equipped with a spiral blade, heating device, thermocouple, and sparge tube (for N2 purging), as well as a Dean-Stark water trap filled with heptane, contained a solution of Example 4 (125 g) and MQ2 resin (175 g) in heptane (200 g). The mixture was homogenously mixed under a positive nitrogen stream at 80°C for 3 hours. 2.0 g of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane (CAS No. 5505-72-6) was added, and the reaction was continued for a further 3 hours. The reactor was cooled after the viscosity increased. The solids content was then adjusted to 60% and the mixture was contained. The viscosity of the PSA was 230 cPs at 25°C. The material gelled within one week of storage. No further characterization of the PSA was performed.

[0136] Comparative Example 4

[0137] Momentive Performance Materials' commercially available product, PSA610.

[0138] Testing of PSA samples

[0139] PSA was formulated using 2 wt% benzoyl peroxide (BPO) in a 10 wt% toluene solution, or without the addition of benzoyl peroxide, and its tackiness and adhesion were measured at a thickness of 25–35 micrometers. This adhesive formulation was applied to a polyimide substrate, dried at 90°C for 2 minutes, and then cured in a forced-circulation oven at 180°C for 2 minutes. Tackiness tests were performed according to FINAT FTM9 for measuring tackiness in grams. Peel adhesion tests were performed according to ASTM D3330 / D3330M, measuring adhesion to mirror-finish stainless steel (SS) at a peel angle of 180 degrees. The peel adhesion test results were recorded as peel strength N / inch from stainless steel at a peel rate of 12 inches per minute for a 1-inch test strip. SAFT tests were performed according to FINAT FTM8 standards. The results are shown in Table 2. The solution viscosity of the materials was determined using a Brookfield (DV1) viscometer at 25°C with spindles #2 to #6. [Table 2]

[0140] Estimation of cyclic substances

[0141] Cyclic substances present in PSA were quantified using gas chromatography. The sample was extracted over 24 hours as described below.

[0142] Experimental method: Approximately 0.5 g of the sample was weighed into a 20 mL vial. The weight of the sample was accurately recorded. The sample was extracted for 24 hours in 10 mL of working solution prepared using acetone as the solvent and toluene and dodecane as internal standards (0.05 mg / mL). Calibration plots for D4, D5, and D6 were generated by preparing various standards at concentrations ranging from 0.005 to 0.1 mg / mL in acetone. Peak areas were normalized by dividing by the peak area for dodecane and plotted against concentration. Cyclic substances present in the sample were calculated using the normalized peak areas of the sample in the GC chromatogram and the calibration curve.

[0143] GC conditions

[0144] Equipment: Agilent 7890A GC

[0145] Detector: FID (Flame Ionization Detector) 350℃; H2: 30 mL / min, Air: 300 mL / min, Makeup flow: 25.4 mL / min

[0146] Sample introduction: Split injection / 225°C / 50:1 split ratio

[0147] Injection volume: 2 μL (Agilent 7693 autosampler)

[0148] Carrier gas: Nitrogen (1.4 mL / min, constant flow mode)

[0149] Capillary column: Agilent HP-5 (30m x 0.32mm x 0.25μm)

[0150] Temperature program: From 50°C (5 minutes) to 200°C at a rate of 15°C / minute, then to 315°C (20 minutes) [Table 3]

[0151] Estimation of silanol content

[0152] The silanol content is, 29 This was determined using Si nuclear magnetic resonance technology.

[0153] Experimental method: The sample was prepared by adding approximately 2 g of the sample to 3 mL of CDCl3. 30 mg of chromium(III) acetylacetonate was added as a relaxing agent. 2.5 mL of the sample solution was transferred to a 10 mm Teflon tube. 29 Si spectra were obtained. Integrating all peaks in the NMR spectrum gives a molar percentage, which is converted to a weight percentage by multiplying by the weight of the corresponding repeating unit of the species. The sample was quantified on a Bruker 400 MHz NMR spectrometer. 29 Analysis was performed using SiNMR spectroscopy. Experimental parameters:

[0154] System: Bruker 400MHz

[0155] Probe: 10mm 29 Siprobe

[0156] Pulse program: ZGIG45

[0157] Recycling delay: 5 seconds

[0158] Decoupling method: with reverse gate

[0159] Decoupling sequence: WALTZ16

[0160] Scan count: 9472 [Table 4]

[0161] Viscoelastic properties

[0162] The viscoelastic properties of silicone PSA prepared by a novel process were evaluated using a dynamic spectrometer (DHR3 rheometer, TA Instruments). The silicone adhesive was dried at 150°C for 1 hour, then transferred from the release liner to a 25 mm diameter parallel plate and piled up to a thickness of approximately 1.0 mm. The silicone adhesive was characterized by angular vibration frequencies swept from 0.1 to 100 rad / s at 30°C and equivalent or less than 0.01% strain.

[0163] The following viscoelastic parameters, such as the storage modulus (G''), loss modulus (G''), and kinematic viscosity, were evaluated as functions of frequency: 1. Storage modulus (G', dyne / cm²) 2 ) 2. Loss modulus (G'', dyne / cm²) 2 ) 3. Kinematic viscosity (Poise) [Table 5]

[0164] The above descriptions include examples provided herein. Naturally, it is impossible to describe all recognizable combinations of components or methods for the purposes of this specification, but those skilled in the art will recognize that many other combinations and substitutions are possible herein. Thus, this specification is intended to encompass all such changes, modifications, and variations that are included within the idea and scope of the claims. Furthermore, where the term “includes” is used in the detailed description of the invention or in the claims, the term is intended to be inclusive in a manner similar to how the term “includes” is interpreted when it is used as a substitute in the claims.

[0165] The above description identifies various non-limiting embodiments of methods for producing silicone pressure-sensitive adhesives and pressure-sensitive adhesives produced by such methods. Modifications can be envisioned by those skilled in the art and those who create and use the present invention. The disclosed embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention or the specifics described in the claims.

Claims

1. A process for producing pressure-sensitive adhesive: A process in which MQ silicone resin is reacted with at least one polydiorganosiloxane, where the MQ silicone resin is a solid, solvent-free resin, and the reaction is carried out in the absence of a solvent.

2. The process of claim 1, wherein, based on the total weight of the silicone resin and the polydiorganosiloxane, the MQ silicone resin is present in an amount of 40% to 70% by weight, and the polydiorganosiloxane is present in an amount of 60% to 30% by weight.

3. The process according to claim 1 or 2, wherein the reaction is carried out at a temperature of 25°C to 200°C.

4. The process according to any one of claims 1 to 3, wherein the reaction is carried out at a temperature of 50°C to 150°C.

5. The process according to any one of claims 1 to 4, wherein the reaction is carried out in the presence of a catalyst, a chain extender, or a combination thereof.

6. The process of claim 5, wherein the catalyst is selected from hydrochloric acid, phosphoric acid, polyphosphate, carboxylic acid, metal carboxylate salt, alkali metal oxide, alkali metal alkoxide, alkali metal hydroxide, alkali metal silanolate, alkali metal siloxanolate, alkali metal amide, alkyl metal, ammonia, amine, ammonium hydroxide, quaternary phosphonium hydroxide, or two or more combinations thereof.

7. The process of claim 5 or 6, wherein the reaction is carried out in the presence of at least one chain extender selected from silazane, metal silanolate, metal siloxanolate, bis(alkylamino)dialkylsilane, bis(alkylamino)dialkenylsilane, or two or more combinations thereof.

8. The process of claim 7, wherein the silazane is selected from disilazane, trisilazane, tetrasilazane, or a combination of two or more of these.

9. The process of claim 7 or 8, wherein the silazane is selected from alkyl or alkenyl-substituted cyclosilazanes, linear alkyl or polyalkyl-substituted polysilazanes, or combinations of two or more thereof, having a ring size of 6 or 8.

10. The silazane is selected from 2,2,5,5-tetramethyl-2,5-disila-1-azacyclopentane, 2,2,6,6-tetramethyl-2,6-disila-1-azacyclohexane, hexamethyldisilazane, 2,2,4,4,6,6-hexamethylcyclotrisilazane, 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane, 2,2,4,4,6,6,8,8-octamethylcyclotetrasilazane, 1,1,3,3-tetramethyldisilazane, 1,3-diethyl-1,1,3,3-tetramethyldisilazane, or any combination of two or more of these, according to any process of claims 7 to 9.

11. The process of any one of claims 7 to 10, wherein the metal siloxanolate is selected from potassium siloxanolate, lithium siloxanolate, sodium siloxanolate, or a combination of two or more of these.

12. Bis(alkylamino)dialkylsilane or bis(alkylamino)dialkenylsilane includes bis(methylamino)dimethylsilane, bis(methylamino)diethylsilane, bis(methylamino)divinylsilane, bis(methylamino)di-n-propylsilane, bis(methylamino)diisopropylsilane, bis(methylamino)di-n-butylsilane, bis(methylamino)diisobutylsilane, bis(methylamino)di-sec-butylsilane, bis(methylamino)di-t-butylsilane, and bis(methylamino)di-n-neopentyl Silane, bis(methylamino)dicyclopentylsilane, bis(methylamino)dicyclohexylsilane, bis(methylamino)di-4-methoxyphenylsilane, bis(methylamino)methylethylsilane, bis(methylamino)methyl-t-butylsilane, bis(methylamino)methylphenylsilane, bis(methylamino)ethyl-t-butylsilane, bis(methylamino)sec-butylmethylsilane, bis(methylamino)sec-butylethylsilane, bis(methylamino)methylcyclopentylsilane, bis(methylamino)ethyl Cyclopentylsilane, bis(methylamino)cyclopentylcyclohexylsilane, bis(methylamino)methylcyclohexylsilane, bis(methylamino)didecahydronaphthylsilane, bis(methylamino)texylmethylsilane, bis(ethylamino)dimethylsilane, bis(ethylamino)diethylsilane, bis(ethylamino)divinylsilane, bis(ethylamino)di-n-propylsilane, bis(ethylamino)diisopropylsilane, bis(ethylamino)di-n-butylsilane, bis(ethylamino)diisobutylsilane, Bis(ethylamino)di-sec-butylsilane, bis(ethylamino)di-t-butylsilane, bis(ethylamino)dicyclopentylsilane, bis(ethylamino)dicyclohexylsilane, bis(ethylamino)didecahydronaphthylsilane, bis(ethylamino)methylethylsilane, bis(ethylamino)methyl-t-butylsilane, bis(ethylamino)methylphenylsilane, bis(ethylamino)ethyl-t-butylsilane, bis(ethylamino)sec-butylmethylsilane, bis(ethylamino)sec-butylethylsilane,Bis(ethylamino)methylcyclopentylsilane, bis(ethylamino)cyclopentylcyclohexylsilane, bis(ethylamino)methylcyclohexylsilane, bis(ethylamino)t-butylisobutylsilane, bis(ethylamino)cyclohexyltexylsilane, bis(n-propylamino)dimethylsilane, bis(n-propylamino)diethylsilane, bis(n-propylamino)divinylsilane, bis(n-propylamino)di-n-propylsilane, bis(n-propylamino)diisopropylsilane, bis(n-propylamino)di-n-butylsilane, bis(n-propylamino)diisobutylsilane, bis(n-propylamino)di-sec-butylsilane, bis(n-propylamino)di-t-butylsilane, bis(n-propylamino)di-n-neopentylsilane, bis(n-propylamino) A process according to any one of claims 7 to 11, selected from mino)dicyclopentylsilane, bis(n-propylamino)dicyclohexylsilane, bis(isopropylamino)dimethylsilane, bis(isopropylamino)diethylsilane, bis(isopropylamino)divin-propylsilane, bis(isopropylamino)diisopropylsilane, bis(isopropylamino)di-n-butylsilane, bis(isopropylamino)diisobutylsilane, bis(isopropylamino)di-sec-butylsilane, bis(isopropylamino)di-t-butylsilane, bis(isopropylamino)dineopentylsilane, bis(isopropylamino)dicyclopentylsilane, bis(isopropylamino)dicyclohexylsilane, or any combination of two or more of these.

13. A process any one of claims 5 to 12, further comprising heating to a temperature sufficient to decompose the catalyst or, if a chain extender is used, to remove ammonia by-products, amine by-products, or combinations thereof.

14. Polydiorganosiloxane is given by the formula: 【Transformation 3】 It has R in the formula ４ Each of these is independently selected from alkyl, alkenyl, aromatic, arylalkyl, and fluoroalkyl, R ５ The process according to any one of claims 1 to 13, wherein is -OH and n+m is 50 or greater, and the polydiorganosiloxane has a viscosity from 500 cPs to 200,000,000 cPs.

15. The process according to any one of claims 1 to 14, wherein the polydiorganosiloxane has a viscosity of 20,000 cPs to 200,000,000 cPs.

16. The process according to any one of claims 1 to 15, wherein the polydiorganosiloxane has a viscosity from 25,000 cPs to 150,000,000 cPs.

17. The process according to any one of claims 1 to 16, wherein the polydiorganosiloxane comprises a mixture of two or more polydiorganosiloxanes.

18. The process of claim 17, wherein a mixture of two or more polydiorganosiloxanes comprises a first polydiorganosiloxane having a first viscosity of 100,000 cPs to 450,000 cPs and a second polydiorganosiloxane having a second viscosity of 300,000 cPs to 750,000 cPs, where the second polydiorganosiloxane has a higher viscosity than the first polydiorganosiloxane.

19. MQ silicone resin has a density of 0.3 to 0.9 g / cm³. ３ A process having a density in the range of any one of claims 1 to 18.

20. The process according to any one of claims 1 to 19, wherein the MQ silicone resin has a ratio of M units to Q units of 0.2:1 to 1.7:

1.

21. The process according to any one of claims 1 to 20, wherein the MQ resin contains 2% to 12% free Si-OH functional groups.

22. A process of any one of claims 1 to 21, comprising treating the reaction by nitrogen sparging.

23. The process according to any one of claims 1 to 22, wherein the reaction is carried out under vacuum for a predetermined time.

24. A process comprising dissolving a pressure-sensitive adhesive in a non-aromatic solvent, any one of claims 1 to 23.

25. The process according to any one of claims 1 to 24, wherein the pressure-sensitive adhesive produced by this process has a cyclic siloxane content of 2000 ppm or less.

26. The process according to any one of claims 1 to 25, wherein the pressure-sensitive adhesive produced by the process has an octamethylcyclotetrasiloxane content of 2000 ppm or less; a decamethylcyclopentasiloxane content of 2000 ppm or less; and / or a dodecamethylcyclohexasiloxane content of 2000 ppm or less.

27. The process according to any one of claims 1 to 26, wherein the pressure-sensitive adhesive produced by the process has an octamethylcyclotetrasiloxane content of 1,000 ppm or less; a decamethylcyclopentasiloxane content of 1,000 ppm or less; and / or a dodecamethylcyclohexasiloxane content of 1,000 ppm or less.

28. The process according to any one of claims 1 to 27, wherein the pressure-sensitive adhesive produced by the process has an octamethylcyclotetrasiloxane content of 500 ppm or less; a decamethylcyclopentasiloxane content of 500 ppm or less; and / or a dodecamethylcyclohexasiloxane content of 500 ppm or less.

29. The process according to any one of claims 1 to 22, wherein the pressure-sensitive adhesive produced by the process has an octamethylcyclotetrasiloxane content of 250 ppm or less; a decamethylcyclopentasiloxane content of 250 ppm or less; and / or a dodecamethylcyclohexasiloxane content of 250 ppm.

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