Aromatic functionalization of polysiloxanes via free radical addition reaction

Abstract

A process for grafting an aryl functionality onto a polysiloxane includes the following steps: (a) combining a vinyl-functional polysiloxane and an aryl-methyl compound to form an initial reactant mixture; (b) adding a solvent to form a liquid solution, but if already a liquid solution adding a solvent is optional; (c) mixing and purging the liquid solution with an inert gas to form a purged liquid solution; (d) adding a radical generator to the purged liquid solution to form a reaction mixture; (e) triggering the radical generator; (f) ceasing triggering of the radical generator; and (g) removing non-grafted components from the reaction mixture to obtain an aryl-functional polysiloxane; wherein the aryl-methyl compound is free of: (i) groups containing four atoms or more that are ortho to the methyl group of the aryl-methyl compound; and (ii) amine and / or carboxylic acid functionality containing groups para to the methyl group of the aryl-methyl compound.

Description

[0001] AROMATIC FUNCTIONALIZATION OF POLYSILOXANES VIA FREE RADICAL ADDITION REACTION

[0002] FIELD

[0003] The present invention relates to a process for grafting an aryl functionality onto a polysiloxane by free radical addition to produce an aryl functional polysiloxane having an aryl pendant group attached to a polysiloxane backbone with a three -carbon chain between the silicon atom of the polysiloxane backbone and the closest carbon of the aryl aromatic ring.

[0004] INTRODUCTION

[0005] Aryl-functional polysiloxanes are useful in silicone fields due to their thermal stability and compatibility with chemical environments that are otherwise typically not miscible with silicones. The aryl functionality can increase thermal stability and miscibility of a polysiloxane, both of which can be desirable. However, preparing aryl-functional polysiloxanes can be challenging, expensive, and generally suffer from poor reaction selectivity. It can be challenging to prepare polysiloxanes with a controlled number of aryl functionalities per molecule, especially if it is desirable to only have one or two aryl groups per molecule. It can further be challenging to prepared aryl-functional polysiloxanes with aryl functionality in specific desired locations on the polysiloxane.

[0006] US 12234327 discloses a method for preparing anhydride and aromatic functionalized polyorganosiloxanes. The method uses a free radical reaction to combine an unsaturated anhydride functionality with an alkenyl-functional polyorganosiloxane in such a way that results in a pendant group with an anhydride functionality between the polysiloxane and the aryl functionality. While the unsaturated anhydride functionality is required in the process of US 12234327 and necessarily results in an anhydride between a polysiloxane and aryl group in the product of US 12234327, anhydride functionality is not always desirable in an aryl-functional polysiloxane especially between the polysiloxane backbone and aryl functionality in a pendant group.

[0007] It is desirable to identify a controlled way to introduce an aryl functionality onto a polysiloxane without requiring an anhydride functionality between the polysiloxane and aryl group. It is desirable to be able to control the process so as to introduce a single aryl functionality onto a specific location of a polysiloxane chain. It is further desirable if the process allows for additional functionalities to be unaffected by the addition reaction and remain on the aryl-functional polysiloxane addition product as future reaction sites.SUMMARY

[0008] The present invention provides a process for adding in a controlled way to an aromatic functionality onto a polysiloxane without requiring an anhydride functionality between the polysiloxane and the aryl group. The process of the present invention achieves provides the ability to add a single aryl functionality onto a specific location of a polysiloxane chain.

[0009] Moreover, the present invention allows functionalities such as epoxy functionalities and succinic anhydride functionalities to remain unaffected during the aryl addition to a polysiloxane thereby allowing formation of aryl-functional polysiloxanes that have other functional groups suitable as future reaction sites.

[0010] The present invention is a result of discovering a way to do a free radical addition reaction (grafting reaction) using certain aryl-methyl compounds (such as methyl benzene compounds) and vinyl-functional polysiloxanes wherein the methyl group of the aryl-methyl compound forms a radical that undergoes an addition reaction with the vinyl group on the polysiloxane. Such a grafting reaction allows addition of a single aryl group onto a specific location on the polysiloxane where there is a vinyl group on the polysiloxane. Unlike free radical polymerization reactions, the present addition reaction is essentially a terminal addition with only one free radical reaction occurring with the aryl-containing reactant. A characteristic of the product of the process of the present invention is that there are three carbon atoms between the aryl group and the silicon of the polysiloxane functionalized by the aryl group.

[0011] It has been discovered in developing the present invention that not all aryl-methyl compounds will successfully participate in the free radical addition reaction to a vinyl group a polysiloxane. The aryl-methyl compounds must be free of amine or carboxylic acid containing pendant group ortho or para to the methyl group of the aryl-methyl compound. The aryl-methyl compound must also be free of pendant groups on the aryl group having more than 4 atoms that are ortho to the methyl group of the aryl-methyl compound.

[0012] In a first aspect, the present invention is a process for grafting an aryl functionality onto a polysiloxane, the process comprising the following steps: (a) providing and combining a vinylfunctional polysiloxane and an aryl-methyl compound to form an initial reactant mixture; (b) if the initial reactant mixture is not already a liquid solution, then combining the initial reactant mixture with a solvent to form a liquid solution, but if the initial reactant mixture is already a liquid solution combining with solvent is optional; (c) mixing and purging the liquid solution with an inert gas to form a purged liquid solution; (d) adding a radical generator to the purged liquid solution and mixing form a reaction mixture; (e) triggering the radical generator to facilitate a grafting reaction between the vinyl-functional polysiloxane and aryl-methylcompound, where triggering of thermally triggered free radical initiators occurs by heating the reaction mixture and triggering of photoinitiators occurs by irradiated with light of a frequency that triggers the photoinitiator; (f) ceasing triggering of the radical generator by cooling reaction mixtures containing a thermally triggered free radical initiator to 30 degrees Celsius or lower and / or ceasing active irradiation of reaction mixtures containing photoinitiator; and (g) optionally, removing non-grafted components from the reaction mixture to obtain a reaction product, where the reaction product is an aryl-functional polysiloxane; wherein the aryl-methyl compound is characterized by being free of: (i) groups containing four atoms or more that are ortho to the methyl group of the aryl-methyl compound; and (ii) amine and / or carboxylic acid functionality containing groups para to the methyl group of the aryl-methyl compound.

[0013] In a second aspect, the present invention is an aryl-functional polysiloxane, wherein the aryl-functional polysiloxane has an aryl pendant group attached to a polysiloxane backbone with a three-carbon chain between a silicon atom of the polysiloxane backbone and the closest carbon of the aryl aromatic ring.

[0014] The process of the present invention is useful for preparing the aryl -functional polysiloxanes of the second aspect of the present invention.

[0015] DETAILED DESCRIPTION

[0016] Products identified by their tradename refer to the compositions available under those tradenames on the priority date of this document.

[0017] “Multiple” means two or more. “And / or” means “and, or as an alternative”. All ranges include endpoints unless otherwise indicated.

[0018] Polysiloxane refers to a polymer containing multiple siloxane (Si-O-Si) bond linkages. Polysiloxane, silicone, and siloxane all have the same meaning herein.

[0019] In a first aspect, the present invention is a process for carrying out an addition reaction, which is a grafting reaction. An addition reaction is a reaction where a first reactant combines with only one second reactant. The second reactant can conceivably have multiple reactive sites at which different first reactants can attach through addition reactions, but a first reactant only reacts once during the reaction. This is distinct from a polymerization reaction or crosslinking reaction in which each reactant reacts with two or more other reactants. In a polymerization, an addition reaction can occur as a capping reaction that terminates polymerization.

[0020] The process is a process for grafting an aryl functionality to a polysiloxane. The process adds an aryl functionality to a polysiloxane backbone by a radical grafting reaction between a vinyl-functional polysiloxane and an aryl-methyl compound using a radical generator. The process comprises the following steps (a)-(g).Step (a): Forming an initial reaction mixture. Form an initial reaction mixture by providing and combining a vinyl-functional polysiloxane and an aryl-methyl compound.

[0021] Vinyl-Functional Polysiloxan e

[0022] The vinyl-functional polysiloxane is a siloxane comprising on average one or more than vinyl group per molecule bound to a silicon atom. The vinyl-functional polysiloxane can contain additional functional groups or be free of additional functional groups. Functional groups typically are groups other than saturated organic groups and include groups such as epoxy functional groups and alkoxy functional groups. In the broadest scope of the invention, the vinyl-functional polysiloxane can be any one or any combination of more than one linear, branched, or resinous vinyl-functional polysiloxane.

[0023] The vinyl-functional polysiloxane can be selected from polysiloxanes having the average chemical formula (I):

[0024] [AaVibR(3-a-b)SiO][R2SiO]d[R’RSiO]d'[AaVibR(3-a-b)Si] (I) where:

[0025] A in each occurrence is independently selected from functional groups other than a vinyl group. A can be, for example, selected from a group consisting of epoxycontaining groups and alkoxy groups. Particularly desirable epoxy-containing groups include:

[0026] -(CH)(CH2)2OCH2CHOCH2.

[0027] Examples of suitable alkoxy groups include methoxy, ethoxy, propoxy, and butoxy.

[0028] Subscript a refers to the average number of A groups with the subscript “a” and that are bound to the silicon atom associated with the A group. Subscript a is in each occurrence independently selected from a value of 0, 1, 2 or 3 provided that the sum of subscripts a and b is 3 or less.

[0029] Vi refers to a vinyl group. Subscript b refers to the number of vinyl groups with the subscript b and that are bound to the silicon. Subscript b is selected from 1 and 0.

[0030] R independently in each occurrence refers to a hydrocarbyl group that contains 6 or fewer carbon atoms. Desirably, R is independently in each occurrence selected from methyl, ethyl, and propyl groups.

[0031] Subscript d refers to the average number of [R2SiO] siloxane units per molecule. Typically, the value of d is in a range of 0 to 200 and can be 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 20 or more, 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, 80 ormore, 90 or more, 100 or more, 110 or more, 120 or more, 130 or more, 140 or more, even 150 or more, while at the same time is typically 200 or less, and can be 180 or less, 160 or less, 150 or less, 120 or less, 100 or less, 80 or less, 60 or less, 40 or less, 20 or less, 10 or less, 5 or less, even 4 or less.

[0032] Subscript d’ refers to the average number of [R’RSiO] siloxane units per molecule. Typically, the value of d’ is in a range of 0 to 10 and can be 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, even 9 or more, while at the same time is typically 9 or fewer, 8 or fewer, 7 or fewer, 6 or fewer, 5 or fewer, 4 or fewer, 3 or fewer, 2 or fewer, or even 1 or fewer.

[0033] Examples of suitable vinyl-functional siloxanes include those having the following chemical structures (la)-(Id), were “Me” refers to a methyl group and “Vi” refers to a vinyl group:

[0034] Me3SiO-ViMeSiO-SiMe3(la) ViMe2SiO-[Me2SiO]i5o-SiMe2Vi (lb) ViMe2SiO-[ViMeSiO]3-[Me2SiO]i47-SiMe2Vi (Ic) A1(MeO)2SiO-[ViMeSiO] i.9-[Me2SiO]3.4-Si(MeO)2A1(Id) where A1refers to a -(CH)(CH2)2OCH2CHOCH2group.

[0035] The concentration of vinyl-functional polysiloxane is typically 5 weight-percent (wt%) or more, and can be 6 wt% or more, 7 wt% or more, 8 wt% or more, 9 wt% or more, even 10 wt% or more, while at the same time is typically 15 wt% or less, and can be 14 wt% or less, 13 wt% or less, 12 wt% or less, 11 wt% or less, 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, even 6 wt% or less based on the combined weight of vinyl-functional polysiloxane, arylmethyl compound, radical generator and solvent.

[0036] Aryl-Methyl Compound

[0037] The aryl-methyl compound has a methyl group bound directly to a carbon of an aromatic ring forming the aryl group. The aryl group can be, in the broadest scope of the invention, any type of aryl group. Preferably, the aryl group is selected from phenyl and naphthyl groups, and most preferably the aryl group is a phenyl group.

[0038] The aryl-methyl group can be free of additional substitution on the aryl ring besides the methyl group. Alternatively, and desirably , the aryl-methyl group does include additional substituent groups on the aryl ring in addition to a methyl group. Such additional substituent groups are groups bound to the aryl ring in place of a hydrogen atom and can include, for example, any one or combination of more than one selected from a group consisting of ethercontaining groups, epoxy containing groups, and succinic anhydride groups . However, the arylmethyl compound is characterized by being free of: (i) groups containing four atoms or more that are ortho to the methyl group of the aryl-methyl compound; and (ii) amine and / or carboxylic acid containing groups para to the methyl group of the aryl-methyl compound. The aryl-methyl compound can be free of amine and / or carboxylic acid containing groups in any position on the aryl ring. The aryl-methyl compound can also be free of vinyl functionality.

[0039] Some aryl-methyl compounds are liquid and can eliminate need for additional solvent in the reaction mixture. If the aryl-methyl compound is liquid it can act as both a reactant and a carrier fluid / diluent for the other components of the reaction mixture, allowing formation of a reaction mixture that is a liquid solution without need for additional solvent. When that is the case, additional solvent beyond the liquid aryl-methyl compound is an optional component in the reaction mixture.

[0040] Examples of suitable aryl-methyl compounds include any one or combination or more than one selected from: 4-tert-butyltoluene; 3-methylanisole: 4-methylanisole: 2-methylanisol; 3-(4-methylbenzyl)dihydrofuran-2, 5-dione; and 2-p-tolyloxymethyl-oxirane.

[0041] The concentration of aryl-methyl compound is typically 5 wt% or more, and can be 7 wt% or more, 10 wt% or more, 15 wt% or more, 20 wt% or more, 25 wt% or more, 30 wt% or more, 40 wt% or more, 50 wt% or more, 60 wt% or more, 70 wt% or more, even 80 wt% or more, while at the same time is typically 90 wt% or less, and can be 80 wt% or less, 70 wt% or less, 60 wt% or less, 50 wt% or less, 40 wt% or less, 30 wt% or less, 20 wt% or less, even 10 wt% or less, where wt% is relative to the combined weight of vinyl-functional polysiloxane, aryl-methyl compound, radical generator and solvent. It is desirable to use an excess of the aryl-methyl compound relative to the vinyl-functional polysiloxane to reduce gelation during the grafting reaction, with greater excess of the aryl-methyl compound typically corresponding to a lower chance of gelation. This is particularly true when the aryl-methyl compound is used as a carrier instead of a solvent.

[0042] It is desirable that the molar ratio of aryl-bound methyl groups on the aryl-methyl compound to vinyl groups on the vinyl-functional polysiloxane is greater than 20, and can be 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, 73 or more, 75 or more, 80 or more, even 90 or more, while at the same time is typically 95 or less, and can be 90 or less, 80 or less, 75 or less, 70 or less, even 60 or less.

[0043] Step (b): Adding Solvent if Necessary. If the initial reactant mixture is not already a liquid solution, then combine the initial reactant mixture with a solvent to form a liquid solution. If the initial reactant mixture is already a liquid solution combining with solvent is optional.Add sufficient solvent to form a liquid solution. Forming a liquid solution is desirable to both facilitate mixing of reactants and to dilute the reactants to inhibit gelling during the grafting reaction. The aryl-methyl compound can be a liquid component and can be present in an excess relative to vinyl-functional siloxane to form a liquid solution without requiring solvent. In that case, addition of solvent is optional. However, if the aryl-methyl compound is not a liquid, it is generally desirable to add a solvent to form a liquid solution. If the concentration of aryl-methyl compound is similar to the concentration of vinyl-functional siloxane then solvent can be desirable to dilute the reactants even if the aryl-methyl compound is a liquid. Adding solvent can occur during step (a), that is as part of combining the vinyl-functional polysiloxane and aryl-methyl compound, or after combining the vinyl-functional polysiloxane and aryl-methyl compound in step (a).

[0044] Solvent

[0045] Suitable solvent is desirably an aromatic solvent for compatibility with the vinylfunctional polysiloxane and aryl-methyl compound. The solvent can be reactive or non-reactive. A reactive solvent can participate in the free radical reaction while a non-reactive solvent does not participate in the free radical reaction. Liquid aryl-methyl compounds are examples are suitable reactive solvents. Examples of suitable solvent include any one or any combination of more than one selected from a group consisting of chlorobenzene, toluene, ethylbenzene, 1,2-dimethylbenzene (o-xylene), 1,3-dimethylbenzene (m-xylene), 1,4-dimethylbenzene (p-xylene), 1,2,4-trimethylbenzene, 1, 3, 5 -trimethylbenzene, 1,2,3-trimethylbenzene, and substituted versions of any of these compounds.

[0046] The concentration of solvent is typically zero wt% or more, and can be 5 wt% or more, 10 wt% or more, 15 wt% or more, 20 wt% or more 25 wt% or more, 30 wt% or more, 35 wt% or more, 40 wt% or more, 45 wt% or more, 50 wt% or more 55 wt% or more, 60 wt% or more, 65 wt% or more, 70 wt% or more, even 80 wt% or more, while at the same time is typically 85 wt% or less, and can be 80 wt% or less, 75 wt% or less, 70 wt% or less, 65 wt% or less, 60 wt% or less, 55 wt% or less, 50 wt% or less, 45 wt% or less, 40 wt% or less, 35 wt% or less, 30 wt% or less, 25 wt% or less, 20 wt% or less, 15 wt% or less, 10 wt% or less, even 5 wt% or less, with wt% relative to the combined weight of vinyl-functional polysiloxane, aryl-methyl compound, radical generator and solvent.

[0047] Step (c): Purging and Mixing Step. The purging and mixing step comprises mixing the liquid solution under an inert atmosphere to form a purged liquid solution. The objective of the mixing step is to increase homogeneity of the liquid solution as possible while purging the liquid solution with an inert gas to remove oxygen and form a purged liquid solution. Suitable meansfor mixing include stirring or flowing through a static mixer. Purging with inert gas can occur by bubbling the inert gas through the liquid solution, especially while mixing. The inert gas is desirably one or more gas selected from a group consisting of nitrogen, helium, neon, argon, krypton, xenon, or any combination thereof.

[0048] Step (d): Adding Radical Generator. Add a radical generator to the purged liquid solution and mix to form a reaction mixture. Mix by any method suitable for dispersing the radical generator in the purged liquid solution. Suitable means include stirring or pumping through a static mixer. The objective of mixing is to disperse the radical generator throughout the purged liquid solution. The radical generator can be one or any combination of thermally triggered free radical initiator, photoinitiator, and chemically triggered free radical initiator. The radical generator can be free of any one or any combination of types of radical generators provided there is at least one type of radical generator present. Thermally triggered free radical initiators generally generate a free radical upon heating. Photoinitiators can generate a free radical upon exposure to or irradiation with light of an appropriate frequency. Chemically triggered free radical initiators generally create a free radical by means of a redox reaction. The free radical that forms from the radical generator can initiate a grafting reaction between reactants.

[0049] Suitable thermally triggered free radical initiators can be, for example, any one or combination of more than one component selected from a group consisting of benzoyl peroxide, tert-butyl peroxide, dicumyl peroxide, lauroyl peroxide, peracetic acid, cyclohexanone peroxide, cumene hydroperoxide, tert-butyl peroxide, tert-butyl hydroperoxide, 2,2’-azobisisobutyronitril (AIBN), 2,2’-azodi(2-methylbutyronitrile) (AMBN), tert-amyl peroxybenzoate, tert-butyl peracetate, tert-butyl peroxybenzoate, tert-butylperoxy isopropyl carbonate, cumene hydroperoxide and potassium persulfate.

[0050] Suitable photoinitators include, for example, any one or any combination of more than one component selected from a group consisting of onium salts, nitrobenzyl sulfonate esters, diaryliodonium salts of sulfonic acids, triarylsulfonium salts of sulfonic acids, diaryliodonium salts of boronic acids, tri arylsulfonium salts of boronic acids, bis-diaryl iodonium salts (such as bis(dodecyl phenyl) iodonium hexafluoroarsenate and bis(dodecylphenyl) iodonium hexafluoroantimonate), dialkylphenyl iodonium hexafluoroantimonate, diaryliodonium salts of sulfonic acids, triarylsulfonium salts of sulfonic acids, diaryliodonium salts of boronic acids, and triarylsulfonium salts of boronic acids. Preferred diaryioadonium salts of sulfonic acid are selected from diaryliodonium salts of perfluoroalkylsulfonic acids and diaryliodonium salts of aryl sulfonic acids. Preferred diaryliodonium salts of perfluoroalkylsulfonic acids includediaryliodonium salts of perfluorobutanesulfonic acid, diaryliodonium salts of perfluoroethanesulfonic acid, diaryliodonium salts of perfluoro-octanesulfonic acid, and diaryliodonium salts of trifluoromethane sulfonic acid. Preferred diaryliodonium salts of aryl sulfonic acids include diaryliodonium salts of para-toluene sulfonic acid, diaryliodonium salts of dodecylbenzene sulfonic acid, diaryliodonium salts of benzene sulfonic acid, and diaryliodonium salts of 3 -nitrobenzene sulfonic acid. Preferred tri aryl sulfonium salts of sulfonic acid are selected from triarylsulfonium salts of perfluoroalkylsulfonic acids or triarylsulfonium salts of aryl sulfonic acids. Preferred triarylsulfonium salts of perfluoroalkylsulfonic acids include triarylsulfonium salts of perfluorobutanesulfonic acid, triarylsulfonium salts of perfluoroethanesulfonic acid, triarylsulfonium salts of perfluoro-octanesulfonic acid, and triarylsulfonium salts of trifluoromethane sulfonic acid. Preferred triarylsulfonium salts of aryl sulfonic acids include triarylsulfonium salts of para-toluene sulfonic acid, triarylsulfonium salts of dodecylbenzene sulfonic acid, triarylsulfonium salts of benzene sulfonic acid, and triarylsulfonium salts of 3 -nitrobenzene sulfonic acid. Preferred diaryliodonium salts of boronic acids include diaryliodonium salts of perhaloarylboronic acids and preferred triarylsulfonium salts of boronic acids are the triarylsulfonium salts of perhaloarylboronic acid.

[0051] Chemically triggered free radical initiators include tertiary amine compounds such as dimethyl p-toluidine and trimethylaniline as well as redox metal compounds of Mn(III), Ce(IV), V(V), Co(III), Cr(VI) and Fe(III).

[0052] The concentration of radial generator is typically 0.1 wt% or more, and can be 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, 1.0 wt% or more, 1.2 wt% or more, 1.4 wt% or more, 1.6 wt% or more, 1.8 wt% or more, 2.0 wt% or more, 2.2 wt% or more, even 1.4 wt% or more, while at the same time is typically 2.5 wt% or less, 2.3 wt% or less, 2.1 wt% or less, 2.0 wt% or less, 1.8 wt% or less, 1.6 wt% or less, 1.4 wt% or less, 1.2 wt% or less, 1.0 wt% or less, 0.8 wt% or less, 0.6 wt% or less, 0.4 wt% or less, even 0.2 wt% or less, with wt% relative to the combined weight of vinyl-functional polysiloxane, aryl-methyl compound, radical generator and solvent.

[0053] Step (e): Triggering the Radical Generator. Trigger the radical generator in the reaction mixture to initiate the graft reaction between the vinyl-functional polysiloxane and the aryl-methyl compound. Triggering a radical generator means to cause or enhance the formation of radicals with the radical generator.

[0054] Typically, trigger thermally triggered free radical initiators in a reaction mixture by heating the reaction mixture. To trigger thermally triggered free radical initiators in a reactionmixture it is desirable to heat the reaction mixture to a temperature of 100 degrees Celsius (°C) or higher, 110 °C or higher, 120 °C or higher, 130 °C or higher, 140 °C or higher, 150 °C or higher, 160 °C or higher, 170 °C or higher, 180 °C or higher, even 190 °C or higher. At the same time, it is common to heat the reaction mixture to a temperature of 200 °C or less, 190 °C or less, 180 °C or less, 170 °C or less, 160 °C or less, 150 °C or less, 140 °C or less, 130 °C or less, even 120 °C or less. Heat the reaction mixture long enough to achieve a desirable extent of grafting, typically as long as needed to no longer achieve further grafting in the reaction mixture. For example, it can be useful to heat the reaction mixture containing thermally triggered free radical initiators for one minute or more, 5 minutes or more, 10 minutes or more, 20 minutes or more, 30 minutes or more, 45 minutes or more, one hour or more, 1.5 hours or more, 2 hours or more, 3 hours or more, 4 hours or more, 5 hours or more, 6 hours or more, even 7 hours or more, while at the same time it is typical to heat a reaction mixture containing a thermally triggered free radical initiator for 8 hours or less, 7 hours or less, 6 hours or less, 5 hours or less, 4 hours or less, 3 hours or less, 2 hours or less, one hour or less, 45 minutes or less, even 30 minutes or less.

[0055] Trigger photoinitiators in a reaction mixture by exposing the reaction mixture to light of a frequency that triggers the photoinitiator. Usually, ultraviolet (UV) light triggers photoinitiators commonly used in these reactions. It is common to expose a reaction mixture containing a photoinitiator to light that triggers the photoinitiator for as long as necessary to achieve a desirable extent of grafting reaction, typically as long as is needed to no longer achieve further grafting product.

[0056] Step (f): Ceasing Triggering of Radical Generator. Once the grafting reaction has progressed to a desirable extent, typically to a point where no additional grafting product is being produced, cease triggering of the radical generator. Cease triggering a thermally triggered free radical initiator in a reaction mixture by cooling the reaction mixture, typically to a temperature of 30 °C or lower. Cease triggering a photoinitiator in a reaction mixture by ceasing active irradiation for the purpose of initiating the grafting reaction with light of a frequency for triggering the photoinitiator in the reaction mixture.

[0057] Step (g): Optionally, Removing Non-Grafted Components. This step is an optional step, but desirable step, which occurs after and / or during step (f) and serves to remove unreacted vinyl-functional polysiloxane, aryl-methyl components, and solvent from the reaction mixture in order to obtain remove unreacted components and by-products to provide a cleaner reaction product. Remove non-grafted components from the reaction mixture by any suitable means. For example, evaporation; roto-evaporating (rotovapping), preferably under vacuum; or distilling offnon-grafted components are often suitable means. Removing non-grafted components can also involve washing and / or filtering of solid products. The resulting reaction product is a polysiloxane with an aryl functionality grafted onto the polysiloxane, which is an aryl-functional polysiloxane. The aryl-functional polysiloxane reaction product is characterized by having an aryl pendant group attached to a polysiloxane backbone with a three-carbon chain between a silicon atom of the polysiloxane backbone and the closes carbon of the aryl aromatic ring. The three-carbon chain between the poly siloxane and aryl group forms when the methyl of the arylmethyl component grafts onto a vinyl group on the vinyl-functional polysiloxane.

[0058] In a second aspect, the present invention is an aryl-functional polysiloxane characterized by having an aryl pendant group attached to a polysiloxane backbone with a three-carbon chain between a silicon atom of the polysiloxane backbone and the closes carbon of the aryl aromatic ring, which is characteristic of an aryl-functional polysiloxane made by the process of the present invention. The aryl-functional polysiloxane can be made by the process of the present invention. The aryl of the aryl pendant group can be a phenyl group.

[0059] The aryl of the aryl pendant group can comprise substituted aromatic ring provided that the substituted aromatic ring is free of: (i) groups containing four atoms or more that ortho to the three carbon chain connecting the aryl group to a silicone atom of the polysiloxane; and (ii) amine and / or carboxylic acid functionality containing groups para to the three-carbon chain connecting the aryl group to a silicon of the poly siloxane.

[0060] EXAMPLES

[0061] Table 1 discloses materials for use in preparing the samples that follow. “Me” refers to a methyl group. “Vi” refers to a vinyl group. “A” refers to a -(CH)(CH2)2OCH2CHOCH2 group.Table 1

[0062]

[0063] Synthesis of VS-3

[0064] Obtain the a,co-dimetliylvinylsiloxy-terininated random copolymer of polydimethylsiloxane and polymetliylvinylsiloxane by base-catalyzed (KOH) ring opening equilibrium polymerization of octamethyltetracyclosiloxane (D4) and tetramethyltetravinyltetracylcosiloxane with divinyl tetramethyldisiloxane that is subsequently neutralized, filtered and stripped of volatile dimethylsiloxanes and volatile methyl-vinylsiloxane containing species.

[0065] Synthesis of VS-4

[0066] Reaction product of 3-glycidoxypropyltrimethoxysilane and an oligomeric random copolymer diol of poly(methylvinylsiloxane-dimethylsiloxane) having a zero shear' viscosity of 15 mPa-s at 25 °C and vinyl content of 6 wt% Vi. Produce according to the method in US4033924.

[0067] Synthesis of AM- 5

[0068] Prepare AM-5 according to the teachings in JP06247955.

[0069] Grafting Reactions

[0070] Tables 2 and 3 provide components in a reaction composition for comparative and inventive attempts at grafting an aryl-methyl compound onto a vinyl -functional siloxane. Values for each component are in wt% relative to the combined weight of all components.

[0071] Carry out the grafting reactions as follows. Fit a 3-neck round bottom flask with a stir bar, condenser, nitrogen inlet and thermocouple. Add to the flask the vinyl-functional siloxane (VS) component and the aryl-methyl compound (AM) component. If Sol 1 is present in the formulation, also add that to the flask. Mix using the stirring bar. Purge the contents of the flask thoroughly with nitrogen. Add the Cat 1 component rapidly to the purged contents of tire flask while mixing. Heat the contents ofthe flask to a temperature of 135 to 137 °C and maintain at a temperature in that range while stirring for 6 to 8 hours to ensure complete reaction. Allow tire flask contents to cool to a temperature of 30 °C or lower. Remove an aliquot of the flask contents for analysis and then remove non-grafted components from the contents of the flask under vacuum using a rotary evaporator at 50 °C and under vacuum to 7500 pascals to obtain final grafted reaction product.

[0072] Analyze the aliquot removed for analysis by gas chromatography with mass spectroscopy (GC-MS) using a Thermo Trace 1310 Gas Chromatograph, Agilent 19191 S column, 20 °C injector temperature, a thermal gradient of 150 °C for 0.5 minutes with a ramp to 300 °C at 15 °C per minute followed by a 2 minute hold, an injection volume of 1 microliter with a split ratio of 20: 1 and a column flow of 1.5 milliliters per minute. From the resulting GC data calculate a percent yield of aryl grafted polysiloxane product.

[0073] Carbon-13 (13C) and proton (1H) nuclear magnetic resonance (NMR) spectroscopy analysis is useful to confinn the structure of components in the GC-MS aliquot and in tire final product.

[0074] Results

[0075] Table 2 presents reaction compositions that result in successful graft reactions. Table 3 presents reaction compositions that do not result in successful graft reactions. Yield percent for reaction product for the reaction compositions are included with the reaction compositions in Table 2 and Table 3. Ar-Me / Vi molar ratio refers the molar ratio of aryl-bound methyl groups from the aryl-methyl compound to vinyl groups from the vinyl-functional siloxane.

[0076] Table 2 reveals that when the aryl-methyl compound is in scope of the presently claimed invention, then it is able to graft with multiple different vinyl-functional polysiloxanes. In contrast, Table 3 reveals the inability for AM-7 to AM- 13 to graft onto even the simplest of the vinyl-functional polysiloxanes. AM-7 to AM- 13 each fall outside the scope of the aryl-methyl compound requirements for the present invention by either failing to have a methyl group attached to an aryl ring, or by having a functional group with 4 or more atoms ortho to the methyl group attached to the aryl ring or by having an amine and / or a carboxylic acid functionality containing group para to the methyl group of the aryl-methyl compound.Table 2

[0077]

[0078] Table 3

[0079]

Claims

CLAIMS:

1. A process for grafting an aryl functionality onto a polysiloxane, the process comprising the following steps:(a) providing and combining a vinyl-functional polysiloxane and an aryl-methyl compound to form an initial reactant mixture;(b) if the initial reactant mixture is not already a liquid solution, then combining the initial reactant mixture with a solvent to form a liquid solution, but if the initial reactant mixture is already a liquid solution combining with solvent is optional; (c) mixing and purging the liquid solution with an inert gas to form a purged liquid solution;(d) adding a radical generator to the purged liquid solution and mixing form a reaction mixture;(e) triggering the radical generator to facilitate a grafting reaction between the vinylfunctional polysiloxane and aryl-methyl compound, where triggering of thermally triggered free radical initiators occurs by heating the reaction mixture and triggering of photoinitiators occurs by irradiated with light of a frequency that triggers the photoinitiator;(f) ceasing triggering of the radical generator by cooling reaction mixtures containing a thermally triggered free radical initiator to 30 degrees Celsius or lower and / or ceasing active irradiation of reaction mixtures containing photoinitiator; and(g) optionally, removing non-grafted components from the reaction mixture to obtain a reaction product, where the reaction product is an aryl-functional polysiloxane; wherein the aryl-methyl compound is characterized by being free of: (i) groups containing four atoms or more that are ortho to the methyl group of the aryl-methyl compound; and (ii) amine and / or carboxylic acid functionality containing groups para to the methyl group of the aryl-methyl compound.

2. The process of claim 1, wherein the reaction mixture comprises the following components at the following concentrations:(a) 5-11 weight-percent vinyl-functional poly siloxane;(b) 7-90 weight-percent aryl-methyl compound;(c) 0.1-2.5 weight-percent radical generator; and(d) zero to 85 weight-percent solvent;where weight-percent values are relative to combined weight of components (a)-(d).

3. The process of claim 1 or claim 2, wherein the vinyl-functional polysiloxane is a linear polysiloxane.

4. The process of any one previous claim, wherein the aryl-methyl compound is a methylphenyl compound.

5. The process of any one previous claim, wherein the solvent is selected from aromatic organic solvents.

6. The process of any one previous claim, wherein the aryl-methyl compound is free of vinyl functionality.

7. The process of any one previous claim, wherein the molar ratio of aryl methyl groups from the aryl-methyl compound to vinyl groups on the vinyl-functional polysiloxane is greater than 20.

8. An aryl-functional polysiloxane, wherein the aryl-functional poly siloxane has an aryl pendant group attached to a polysiloxane backbone with a three-carbon chain between a silicon atom of the polysiloxane backbone and the closest carbon of the aryl aromatic ring.

9. The aryl-functional polysiloxane of claim 8, wherein the aryl of the aryl pendant group is a phenyl group.

10. The aryl-functional poly siloxane of any one of claim 8 or claim 9, wherein the aryl group comprises a substituted aromatic ring provided that the substituted aromatic ring is free of: (i) groups containing four atoms or more that are ortho to the three carbon chain connecting the aryl group to a silicon atom of the polysiloxane; and (ii) amine and / or carboxylic acid functionality containing groups para to the three-carbon chain connecting the aryl group to a silicon of the polysiloxane.

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