Method for preparing haplotype photoinitiators

Abstract

The present disclosure provides a process for the preparation of a compound of formula (V) wherein n of the groups R6'to R9 'is-RbOC (O) C (R13) = CH2, and further wherein R13 is H or C1 alkyl, n is an integer from 1 to 3, and for each of the n groups, Rb is independently selected from a covalent bond, a C2-C12 alkylene, a C3-C18 cycloalkylene, or a C6-C18 arylene. In a first process step i), a disulfide compound of formula (I) is reacted with a hydroxy-functional compound of formula (II) in an acidic medium having a pH < = 4 to produce a compound of formula (III) wherein: R2 to R5 are independently selected from H or C1-C6 alkyl, R6 to R9 correspond to the substituents R6'to R9 'and are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C1-C12 alkoxyalkyl, SR12, COOR12 and N (R12) 2; r10 and R11 are H; and each R12 is independently selected from C1-C6 alkyl or C6-C18 aryl, with the proviso that n of the groups R6 to R9 are Rb (OH), and for each of the n groups, Rb is independently selected as defined above. In a second step ii) the compound of formula (III) is reacted in an inert aprotic solvent with a (meth) acrylating agent of formula (IV) to produce the compound of formula (V) wherein: in formula (IV), X is a halide or-OC (O) C (R13) = CH2; and the number of moles of (meth) acrylate groups provided by the compound of formula (IV) is at least equal to the number of moles of hydroxyl groups provided by the compound of formula (III). # imgabs0 #

Description

Technical Field

[0001] The present disclosure relates to a method for preparing a compound having an ethylenically unsaturated group and a moiety that can decompose upon photoirradiation to form radicals. The compound can be used in the preparation of copolymers having photoreactive side groups. Background Art

[0002] The preparation of compositions that can be cured upon photoirradiation and in particular upon ultraviolet light irradiation - such as but not limited to reactive hot melt compositions - is known in the art. Broadly, photocuring provides flexibility as a crosslinking method, since the user can determine where and when the light radiation occurs and can moderate the exposure of the curable composition to the radiation.

[0003] Photocurable compositions generally contain one or more photoinitiators. The term "photoinitiator" as used herein refers to a compound that can be activated by irradiation with an energy-bearing activation beam - such as electromagnetic radiation. The present disclosure relates to "radical photoinitiators", which are herein defined as photoreactive compounds that generate radicals.

[0004] Radical photoinitiators are generally classified into Norrish type I and Norrish type II photoinitiators. When exposed to actinic radiation, Norrish type I radical photoinitiators undergo a Norrish type I reaction: the reaction is defined by IUPAC as the α-cleavage of an excited carbonyl compound, resulting in an acyl-alkyl radical pair (from an acyclic carbonyl compound) or an acyl-alkyl biradical (from a cyclic carbonyl compound) as the main photoproduct. When exposed to actinic radiation, Norrish type II radical photoinitiators undergo a Norrish type II reaction: the reaction is defined by IUPAC as the photochemical abstraction of a γ-hydrogen by an excited carbonyl compound to produce a 1,4-biradical as the main photoproduct.

[0005] During the curing process, unreacted low-molecular-weight photoinitiators, which have a molecular weight of, for example, less than 1000 daltons, can diffusively move within the cured film. This migration of photoinitiators is called migration and can be detrimental to most applications of the cured film. This is especially true for food packaging applications, where the allowable levels of migration of low-molecular-weight compounds, such as the photoinitiator and its degradation products, but also including especially unreacted monomers, photosensitizers, stabilizers, and scavengers, from the packaging film and related printed products into food are the subject of legislative control. For example, EU regulations 1935 / 2004 and 2020 / 1245 specify in detail that the specific migration value (SML) of non-genotoxic low-molecular-weight compounds from articles intended to come into contact with food is 10 micrograms per kilogram of food.

[0006] The tendency of Norrish type II (hydrogen abstraction) photoinitiators to migrate or extract from cured poly(meth)acrylate films is theoretically higher than that of Norrish type I (cleavage) photoinitiators. Norrish type I photoinitiators generate two highly reactive free radicals, which tend to be incorporated into the cured film by reacting with acrylate groups. Norrish type II hydrogen abstraction photoinitiators also generate two free radicals in a bimolecular reaction with an amine synergist. Among these free radicals, the aminoalkyl radical is highly reactive and is incorporated into the cured film by reacting with acrylate groups, but the carbonyl radical has low reactivity towards acrylate bonds and undergoes termination reactions or oxidizes back to the ketone. Solvent extraction of the cured film never recovers all of the Norrish type II photoinitiators.

[0007] In some cases, the migration of Norrish type II photoinitiators in the art has been reduced by using multifunctional initiators that can be incorporated within the cured film rather than monofunctional initiators. Minimizing the initial concentration of the photoinitiator in the curable composition is an alternative strategy but is a strategy that depends on the efficiency of the photoinitiator converting the energy of the radiation source. As another alternative, copolymers with photoreactive side groups have been developed in the art.

[0008] WO2021 / 225778A1 (Henkel IP and Holding GmbH) describes a photo-crosslinking agent responsive to ultraviolet light having a wavelength of 365 nm or higher, the photo-crosslinking agent having a structure defined in the following formula (I):

[0009]

[0010] Wherein: R is H, C1-C 30 alkyl, C1-C 30 alkoxy, C1-C 30acyloxy, C3-C 30 aryloxy, halogen or C1-C 30 thioether;

[0011] R 1 is H or CH3; and

[0012] X is optionally present, and when X is absent, R is not H.

[0013] There is also disclosed a hot melt pressure-sensitive adhesive comprising a (meth)acrylate polymer incorporating a photo-crosslinking agent according to formula (I).

[0014] EP-A-0 017 364 (Rohm & Haas) describes copolymers which can be used especially in adhesives and sealants and which contain 0.1 to 10% by weight of allyl benzoylbenzoate as a copolymerized photoinitiator. Although these materials can be crosslinked using UV radiation, they are considered to be too low in reactivity towards such radiation, resulting in low curing efficiency, especially at deeper points in the material layer. In addition, for certain adhesive applications, the layers produced from the copolymers are not considered to be tacky enough.

[0015] The low reactivity and low efficiency of crosslinked copolymers containing 0.01 to 5% by weight of copolymerizable 2-alkoxy-2-phenyl-2-benzoylethyl acrylate are also considered to be disadvantages taught by US Patent No. 4,144,157 (Beiersdorf AG).

[0016] In practice, the low curing efficiency of copolymers containing copolymerizable photoinitiators can be mitigated by increasing the dose of the radiation applied. Unfortunately, however, the low curing efficiency contributes to the continued use of mercury-based UV systems for the photoirradiation of crosslinked polymers: mercury lamps provide a broadband spectral distribution such that the shorter wavelength light promotes surface curing of the applied composition, while the longer wavelength light effects deeper curing.

[0017] However, these solutions may not be desirable or actually feasible in certain applications. In particular, in accordance with the 2013 Minamata Convention on Mercury, the manufacture, import, or export of mercury lamps became illegal in January 2020. Thus, there is a need in the art to economically provide a copolymer comprising a copolymerizable photoinitiator that responds to an alternative UV irradiation source to a mercury lamp in terms of both a viable coating weight and an applied irradiation dose. Of course, it is advantageous to economically provide a copolymer comprising a copolymerizable photoinitiator that can be cured using a UV light-emitting diode (UV-LED), given that such systems particularly have the following advantages: small size; lack of fragility; temperature-independent output; and absence of a warm-up or preheating time.

[0018] Thioxanthone and its derivatives have been identified as potentially valuable photoinitiators based on the fact that they exhibit two absorption peaks in the ultraviolet region of the electromagnetic spectrum. For example, CN200410093977 (Jiuri Chemical Co., Ltd) and WO2012 / 003644A1 (Tianjin Jiuri Chemical Co., Ltd) describe thioxanthone-4-carboxylates, their preparation methods, and their use in photoinitiator compositions. In addition, U.S. Patent No. 7,354,957 (Herlihy) discloses a compound of formula (I) that can be used as a photoinitiator:

[0019]

[0020] wherein n is a number from 1 to 6; R 3 is hydrogen, methyl, or ethyl; A represents a group of the formula -[O(CHR 2 CHR 1 ) a y -, -[O(CH2) b CO)] y -, -O(CH2) b CO)] y or -[O(CHR 2 CHR 1 )a]-, wherein one of R' and R 2 is hydrogen and the other is hydrogen, methyl, or ethyl; a is 1 or 2; b is 4 or 5; y is from 3 to 10; Q is the residue of a polyhydroxy compound having 2 to 6 hydroxyl groups; and X is greater than 1.

[0021] U.S. Patent No. 5,248,805 (Boettcher et al.) describes thioxanthone derivatives having a spacer group such as a carbonate group to link the thioxanthone sensitizer to an ethylenically unsaturated group.​

[0022] The inventors of the present invention have recognized a need in the art to develop a viable method for economically and efficiently providing thioxanthone derivatives that can copolymerize with ethylenically unsaturated monomers to form copolymers. SUMMARY OF THE INVENTION

[0023] According to a first aspect of the present disclosure, there is provided a method for preparing a compound of formula (V):

[0024]

[0025] wherein: R 6' to R 9' are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C1-C 12 alkoxyalkyl, SR 12 , COOR 12 and N(R 12 )2; and

[0026] each R 12 is independently selected from C1-C6 alkyl or C6-C 18 aryl,

[0027] provided that n of the groups R 6’ to R 9’ are -R b OC(O)C(R 13 )=CH2, wherein:

[0028] R 13 is H or C1 alkyl;

[0029] n is an integer from 1 to 3, preferably 1 or 2; and

[0030] for each of the n groups, R b is independently selected from a covalent bond, C2-C 12 alkylene, C3-C 18 cycloalkylene or C6-C 18 arylene,

[0031] The method comprises the following steps:

[0032] i) reacting a disulfide compound of formula (I) with a hydroxy-functional compound of formula (II) to produce a compound of formula (III)

[0033]

[0034] wherein: the reaction is carried out in an acidic medium having a pH equal to or lower than 4.0;

[0035] R 2to R 5 independently selected from H or C1-C6 alkyl;

[0036] R 6 to R 9 corresponding to said substituent R 6’ to R 9’ and independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C1-C 12 alkoxyalkyl, SR 12 , COOR 12 and N(R 12 )2;

[0037] R 10 and R 11 are H; and

[0038] each R 12 independently selected from C1-C6 alkyl or C6-C 18 aryl,

[0039] provided that n of the groups R 6 to R 9 are R b (OH), where for each of said n groups, R b is independently selected from a covalent bond, C2-C 12 alkylene, C3-C 18 cycloalkylene or C6-C 18 arylene; and

[0040] ii) reacting the compound of formula (III) with a compound of formula (IV) in an inert aprotic solvent to produce the compound of formula (V)

[0041]

[0042] wherein: X is a halide or -OC(O)C(R 13 )=CH2; and

[0043] the number of moles of (meth)acrylate groups provided by the compound of formula (IV) is at least equimolar to the number of moles of hydroxyl groups provided by the compound of formula (III).

[0044] Regarding formula (I), preferably R 2 to R 5 are independently selected from H or C1-C4 alkyl. For example, R 2 to R 5 can be independently selected from H or C1-C2 alkyl, and in some embodiments, R 2 to R 5 are each H.

[0045] Regarding the formula (II), preferably R 6 to R 9 are independently selected from H, C1-C4 alkyl, C1-C4 alkoxy, C1-C8 alkoxyalkyl, COOR 12 and N(R 12 )2; R 10 and R 11 are H; and each R 12 is independently selected from C1-C4 alkyl or C6-C 18 aryl, provided that n of the groups R 6 to R 9 are -OH, where n is an integer of 1 or 2.

[0046] In certain embodiments, step i) of the method can be carried out in an acidic medium with a pH equal to or lower than 3.5, for example equal to or lower than 3.0. As an alternative or supplement to this statement of pH conditions, step ii) should desirably be carried out at a temperature below the boiling point of the acidic medium: subject to meeting this requirement, step i) can be carried out at a temperature of 20°C to 120°C - for example 40°C to 120°C or 60°C to 100°C.

[0047] In step ii), the molar ratio of the (meth)acrylate group provided by the compound of formula (IV) to the hydroxyl group provided by the compound of formula (III) should typically be from 1:1 to 2:1, preferably from 1.1:1 to 1.5:1, more preferably from 1.1:1 to 1.4:1. Independent of or as a supplement to these preferred molar ratio statements, step ii) should be carried out at a temperature of -40 to 20°C, preferably -20 to 20°C.

[0048] Regarding the formula (IV), it is desired that X is a halide, and preferably X is chloride. When X is a halide, the reaction of step ii) should be carried out in the presence of a base - such as but not limited to a tertiary amine. For example, the tertiary amine base can be selected from: tris(C1-C 12 )alkylamine; bis(C1-C 12 )alkyl(C3-C8)cycloalkylamine; tris(C1-C 10 )alkenylamine; and mixtures thereof. And exemplary tris(C1-C12)alkylamines that can be included alone or in combination include: trimethylamine; ethyldimethylamine; diethylmethylamine; triethylamine; triisopropylamine; tri-n-propylamine; tri-n-butylamine; diisobutylpentylamine; n-butyl-octyl-sec-butylamine; tripentylamine; trihexylamine; and mixtures thereof.

[0049] According to a second aspect of the present disclosure, there is provided the use of a compound of formula (V) obtained by the method defined above and in the appended claims as a monomer in radical polymerization.

[0050] The present disclosure also provides a copolymer obtained by radical polymerization, wherein, based on the total weight of the monomers, the copolymer comprises: 0.1 to 10% by weight of a) at least one compound of formula (V) obtained by the method defined above and in the appended claims; and 90 to 99.9% by weight of b) at least one ethylenically unsaturated nonionic monomer that does not have an epoxy group or a moiety that can decompose upon photoirradiation to form radicals. Detailed embodiments

[0051] Definitions

[0052] As used herein, the singular forms "a", "an", "the", and "said" include plural referents unless the context clearly dictates otherwise.

[0053] The terms "comprising", "including", and "consisting of" used herein are synonymous with "containing" or "having", and are inclusive or open-ended and do not exclude additional, unrecited members, elements, or method steps.

[0054] As used herein, the term "consisting of" excludes any element, ingredient, member, or method step not specified. For completeness, the term "including" encompasses "consisting of".

[0055] When equivalents, concentrations, dimensions, and other parameters are expressed in ranges, preferred ranges, upper limit values, lower limit values, or preferred upper limit values and upper limit values, it should be understood that any range obtained by combining any upper limit value or preferred upper limit value with any lower limit value or preferred lower limit value is also specifically disclosed, regardless of whether the obtained range is explicitly mentioned in the context.

[0056] In addition, according to standard understanding, a weight range expressed as "0 to x" specifically includes 0% by weight: the component defined by the range may not be present in the material, or may be present in the material in an amount not exceeding x% by weight.

[0057] The words "preferred", "preferably", "desirably", and "particularly" are often used herein to refer to embodiments of the present disclosure that can provide certain benefits in certain circumstances. However, the listing of one or more preferred, preferred, desirable, or particular embodiments does not mean that other embodiments are not available, and is not intended to exclude those other embodiments from the scope of the present disclosure.

[0058] The term "exemplary" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, the use of the term exemplary is intended to present concepts in a concrete fashion.

[0059] As used throughout this application, the word "may" is used in a permissive sense - which means possible - rather than in a mandatory sense.

[0060] As used herein, room temperature is 23°C ± 2°C.

[0061] The molecular weights mentioned in this specification can be measured by gel permeation chromatography (GPC) using polystyrene calibration standards, for example, in accordance with ASTM 3536.

[0062] The term "aprotic solvent" as used herein refers to a solvent that does not produce or accept protons. In contrast, "protic solvents" are those solvents that are capable of producing or accepting protons. The "polar solvents" as used herein refer to solvents having a dielectric constant (ε) greater than 5 measured at 25°C: this term includes both aprotic solvents and protic solvents. The determination of the dielectric constant (ε) is well known in the art and within the knowledge of those skilled in the art: mention may be made of the measurement voltage used across a parallel plate capacitor in such determination.

[0063] As used herein, the term "radical initiator" refers to any chemical substance that, upon exposure to sufficient energy - such as in the form of light or heat - decomposes into two moieties that are electrically neutral but each have at least one unpaired electron. Thus, a thermal radical initiator produces radicals upon exposure to heat. And known thermal radical initiators include, but are not limited to, peroxide compounds, azo compounds, and persulfate compounds.

[0064] As used herein, the term "monomer" refers to a substance that can undergo a polymerization reaction to contribute a structural unit to the chemical structure of a polymer. The term "monofunctional" as used herein refers to having one polymerizable moiety. The term "polyfunctional" as used herein refers to having more than one polymerizable moiety.

[0065] As used herein, the term "water" is intended to encompass tap water, spring water, purified water, deionized water, softened water, and distilled water.

[0066] As used herein, a "solvent" is a substance capable of dissolving another substance to form a homogeneous solution; during dissolution, neither the solvent nor the dissolved substance undergoes a chemical change. A solvent can be either polar or nonpolar.

[0067] As used herein, the term "disulfide group" refers to a functional group having the structure R-S-S-R'. In the case where a compound is referred to as a disulfide, the compound must have an -S-S- bond.

[0068] As used herein, "(meth)acryloyl" is a shorthand term for "acryloyl" and / or "methacryloyl". Thus, the term "(meth)acrylamide" refers to the collective term for acrylamide and methacrylamide.

[0069] As used herein, "C1-C n alkyl" group refers to a monovalent group containing from 1 to n carbon atoms, which is a group of an alkane and includes straight-chain and branched-chain organic groups. Thus, "C1-C 18 alkyl" group refers to a monovalent group containing from 1 to 18 carbon atoms, which is a group of an alkane and includes straight-chain and branched-chain organic groups. Generally, it should be noted that alkyl groups containing 1 to 12 carbon atoms (C1-C 12 alkyl) are preferred, such as alkyl groups containing 1 to 8 carbon atoms (C1-C8 alkyl). Examples of alkyl groups include, but are not limited to: methyl; ethyl; propyl; isopropyl; n-butyl; isobutyl; sec-butyl; tert-butyl; n-pentyl; n-hexyl; n-heptyl; and 2-ethylhexyl. In the present invention, such alkyl groups may be unsubstituted or may be substituted by one or more halogens. In cases where it is applicable to a given moiety (R), one or more non-halogen substituents will be indicated as being permissible in the alkyl group in this specification.

[0070] The term "C1-C 18 hydroxyalkyl" as used herein refers to a HO-(alkyl) group having from 1 to 18 carbon atoms, wherein the point of attachment of the substituent is through an oxygen atom, and the alkyl group is as defined above.

[0071] "Alkoxy" refers to a monovalent group represented by -OA, where A is an alkyl group: non-limiting examples thereof are methoxy, ethoxy, and isopropoxy. The term "C1-C 18 alkoxyalkyl" as used herein refers to an alkyl group having an alkoxy substituent as defined above, and wherein the moiety (alkyl-O-alkyl) in total contains from 1 to 18 carbon atoms: such groups include methoxymethyl (-CH2OCH3), 2-methoxyethyl (-CH2CH2OCH3), and 2-ethoxyethyl. Similarly, the term "C7-C 18 alkoxyaryl" as used herein refers to an aryl group having an alkoxy substituent as defined above, and wherein the moiety (aryl-O-alkyl) in total has from 7 to 18 carbon atoms.

[0072] As used herein, the term "C2-C4 alkylene" is defined as a saturated divalent hydrocarbon group having 2 to 4 carbon atoms. Generally in the present disclosure, such an alkylene group may be unsubstituted or may be substituted by one or more halogens.

[0073] The term "C3-C 18 cycloalkyl" should be understood to mean a saturated, monocyclic or polycyclic hydrocarbon group having 3 to 18 carbon atoms. In the present invention, such a cycloalkyl group may be unsubstituted or may be substituted by one or more halogens. Where applicable to a given moiety (R), it will be indicated in the present specification that one or more non-halogen substituents are permitted in the cycloalkyl group. Examples of cycloalkyl groups include: cyclopropyl; cyclobutyl; cyclopentyl; cyclohexyl; cycloheptyl; cyclooctyl; adamantane; and norbornane.

[0074] As used herein, "C3-C 18 subcycloalkyl" refers to a divalent group formed by removing two hydrogen atoms from one or more rings of a cycloalkyl group having 3 to 18 carbon atoms. Generally in the present disclosure, such a subcycloalkyl group may be unsubstituted or may be substituted by one or more halogens.

[0075] As used herein, "C6-C 18 aryl" - as in "arylalkyl" - refers to monocyclic, bicyclic and tricyclic systems, where the monocyclic system is aromatic or at least one of the bicyclic or tricyclic systems is aromatic. Bicyclic and tricyclic systems include benzo-fused 2- to 3-membered carbocycles. In the present invention, such an aryl group may be unsubstituted or may be substituted by one or more halogens. Where applicable to a given moiety (R), it will be indicated in the present specification that one or more non-halogen substituents are permitted in the aryl group. Exemplary aryl groups include: phenyl; (C1-C4)alkylphenyl, such as tolyl and ethylphenyl; indenyl; naphthyl, tetrahydronaphthyl, tetrahydroindenyl; tetrahydroanthracenyl; and anthracenyl. And it may be noted that phenyl is preferred.

[0076] As used herein, "C6-C 18 arylene" refers to a divalent group formed by removing two hydrogen atoms from one or more rings of a cycloalkyl group having 3 to 18 carbon atoms. Generally in the present disclosure, such an arylene group may be unsubstituted or may be substituted by one or more halogens.

[0077] As used herein, "C2-C 20"Alkenyl" means a hydrocarbon group having 2 to 20 carbon atoms and at least one ethylenic unsaturated unit. The alkenyl group can be straight-chain, branched-chain or cyclic, and can optionally be substituted by one or more halogens. Where applicable to a given moiety (R), it will be indicated in this specification that one or more non-halogen substituents are permitted in the alkenyl group. The term "alkenyl" also includes groups having "cis" and "trans" configurations, or "E" and "Z" configurations, as understood by those of ordinary skill in the art. However, generally, it should be noted that preference is given to unsubstituted alkenyl groups containing 2 to 10 (C 2-10 ) or 2 to 8 (C 2-8 ) carbon atoms. Examples of the C2-C 12 alkenyl group include, but are not limited to: -CH=CH2; -CH=CHCH3; -CH2CH=CH2; -C(=CH2)(CH3); -CH=CHCH2CH3; -CH2CH=CHCH3; -CH2CH2CH=CH2; -CH=C(CH3)2; -CH2C(=CH2)(CH3); -C(=CH2)CH2CH3; -C(CH3)=CHCH3; -C(CH3)CH=CH2; -CH=CHCH2CH2CH3; -CH2CH=CHCH2CH3; -CH2CH2CH=CHCH3; -CH2CH2CH2CH=CH2; -C(=CH2)CH2CH2CH3; -C(CH3)=CHCH2CH3; -CH(CH3)CH=CHCH; -CH(CH3)CH2CH=CH2; -CH2CH=C(CH3)2; 1-cyclopent-1-enyl; 1-cyclopent-2-enyl; 1-cyclopent-3-enyl; 1-cyclohex-1-enyl; 1-cyclohex-2-enyl; and 1-cyclohex-3-enyl.

[0078] As used herein, "alkylaryl" means an aryl group substituted with an alkyl group, where both groups are defined as above. In addition, as used herein, "arylalkyl" means an alkyl group substituted with an aryl group as defined above.

[0079] The term "hetero" as used herein means a group or moiety containing one or more heteroatoms (such as N, O, Si, and S). Thus, for example, "heterocyclic" means a cyclic group having, for example, N, O, Si, or S as part of the ring structure. "Heteroalkyl", "heterocycloalkyl", and "heteroaryl" moieties are alkyl, cycloalkyl, and aryl groups as defined above, respectively, containing N, O, Si, or S as part of their structure.

[0080] The materials and compositions of the present invention may be defined herein as "substantially free" of certain compounds, elements, ions, or other similar components. The term "substantially free" is intended to mean that the compound, element, ion, or other similar component is not intentionally added to the material or composition and is present at most only in trace amounts that do not (adversely) affect the desired properties of the material or composition. Exemplary trace amounts are less than 1000 ppm by weight of the material or composition. The term "substantially free" encompasses those embodiments in which the specified compound, element, ion, or other similar component is completely absent from the material or composition or is not present in any amount measurable by techniques commonly used in the art.

[0081] As used herein, the term "anhydrous" is equivalent to the term "substantially free of water". Water is not intentionally added to a given composition and is present at most only in trace amounts that do not (adversely) affect the desired properties of the composition.

[0082] Two steps of the method of the present disclosure are illustrated in the appended Figure 1 herein.

[0083] Step i)

[0084] The first stage of the present disclosure comprises providing a disulfide compound according to formula (I) below as a reactant:

[0085]

[0086] wherein: R 2 to R 5 are independently selected from H or C1-C6 alkyl.

[0087] Preferably, R 2 to R 5 are independently selected from H or C1-C4 alkyl, more preferably R 2 to R 5 are independently selected from H or C1-C2 alkyl. In an important embodiment, R 2 to R 5 are each H, whereby the reactant according to formula (I) is 2,2'-dithiobenzoic acid.

[0088] The first stage of the present disclosure further comprises providing a hydroxy-functional reactant according to formula (II) below:

[0089]

[0090] wherein: R 6 to R 9 are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C1-C 12 alkoxyalkyl, SR 12 、COOR12 and N(R 12 )2;

[0091] R 10 and R 11 is H; and

[0092] each R 12 is independently selected from C1-C6 alkyl or C6-C 18 aryl,

[0093] provided that n of the groups R 6 to R 9 are R b (OH), where n is an integer from 1 to 3, and for each of said n groups, R b is independently selected from a covalent bond, C2-C 12 alkylene, C3-C 18 cycloalkylene or C6-C 18 arylene.

[0094] Regarding formula (II), preferably:

[0095] R 6 to R 9 are independently selected from H, C1-C4 alkyl, C1-C4 alkoxy, C1-C8 alkoxyalkyl, COOR 12 and N(R 12 )2;

[0096] R 10 and R 11 are H; and

[0097] each R 12 is independently selected from C1-C4 alkyl or C6-C 18 aryl,

[0098] provided that n of the groups R 6 to R 9 are R b OH, where n is an integer of 1 or 2.

[0099] In this first stage (i)), the disulfide compound of formula (I) is reacted with the hydroxy-functional compound of formula (II) to produce a hydroxy-functional compound according to formula (III).

[0100]

[0101] For completeness, within the compound of formula (III) depicted above and Figure 1 in, the substituents R 2 to R 9 have the meanings consistent with those above.

[0102] The reaction of this step is carried out in an acidic medium with a pH equal to or lower than 4.0. In certain embodiments, the acidic medium may have a pH equal to or lower than 3.5 or equal to or lower than 3.0. Exemplary acidic media that can be used include: concentrated sulfuric acid; a concentrated mixture of sulfuric acid and acetic acid; concentrated hydrochloric acid; concentrated phosphoric acid (H3PO4); acetic acid; and a mixture of acetic acid and acetic anhydride. In forming the acidic reaction medium, the number of moles of the acid should typically be at least ten times the number of moles of reactant compound (I).

[0103] The reaction temperature should be lower than the boiling point of the acidic medium and is typically selected to be in the range of 20 °C to 120 °C, such as 40 °C to 120 °C or 60 °C to 100 °C. In certain embodiments, the reaction can be carried out under a multi-stage regime with respect to temperature. For example, the reactant and the acid in the medium can be initially mixed at room temperature, and then the temperature of the mixture - with continuous stirring - is slowly raised to the range of 40 to 120 °C for a first duration (e.g., 1 to 5 hours). While maintaining stirring, the temperature of the mixture can then be returned to room temperature, and the reaction is continued for a second duration (e.g., 2 to 12 hours).

[0104] Provided that the acidic medium should not boil, the process pressure is not critical: thus, the reaction can be carried out under a pressure lower than atmospheric pressure, equal to atmospheric pressure, or higher than atmospheric pressure, but is preferably carried out under a pressure equal to or slightly higher than atmospheric pressure. Pressures in the range of 50 to 200 kPa, such as 100 to 200 kPa, can be mentioned in this regard.

[0105] The progress of the above reaction step i) can be monitored by known techniques, which can include 1 1H NMR, Fourier transform infrared spectroscopy, ultra-high performance liquid chromatography (UPLC), or thin layer chromatography (TLC). After the reaction is completed, the compound of formula (III) precipitates from the product mixture, which is typically achieved by introducing the mixture into boiling water. The precipitate can then be separated and washed, usually with water.

[0106] The obtained solid crude product can subsequently be purified by methods known in the art, including but not limited to solvent extraction, filtration, evaporation, distillation, (re)crystallization, and chromatography. Recrystallization of the product from a C1-C4 alkanol (such as methanol) can be particularly mentioned.

[0107] Step ii)

[0108] In this step, a compound of formula (III) is reacted with a (meth)acrylic acid esterifying agent selected from (meth)acryloyl halides and (meth)acrylic anhydrides in an inert aprotic solvent. More particularly, the (meth)acrylic acid esterifying agent has the following formula (IV):

[0109]

[0110] wherein: X is a halide or -OC(O)C(R 13 )=CH2; and

[0111] R 13 is H or a C1 alkyl group.

[0112] In a preferred embodiment, X is a halide. Exemplary (meth)acryloyl halides include: acryloyl fluoride; acryloyl chloride; acryloyl bromide; acryloyl iodide; methacryloyl chloride; and methacryloyl bromide. Particular mention may be made of the use of (meth)acryloyl chloride as the (meth)acrylic acid esterifying agent.

[0113] The reaction of step ii) is depicted below:

[0114]

[0115] For completeness, within the depicted compound of formula (V), the substituents R 2 to R 5 have the meanings as defined above. Except for the conversion of n hydroxyl groups into (meth)acrylate groups, R 6' to R 9' correspond to R 6 to R 9 . Thus in formula (V):

[0116] R 6' to R 9' are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C1-C 12 alkoxyalkyl, SR 12 , COOR 12 and N(R 12 )2; and

[0117] each R 12 is independently selected from C1-C6 alkyl or C6-C 18 aryl,[[]]END]]

[0118] provided that n of the groups R 6' to R 9' are independently selected from -R b OC(O)C(R 13 )=CH2, wherein:

[0119] R 13is H or a C1 alkyl group;

[0120] n is an integer from 1 to 3, preferably 1 or 2; and

[0121] For each of the n groups, R b is independently selected from a covalent bond, C2-C 12 alkylene, C3-C 18 cycloalkylene or C6-C 18 arylene.

[0122] (Meth)acrylate esterifying agent should be used in an amount such that the number of moles of (meth)acrylate groups provided by the (meth)acrylate esterifying agent is at least equimolar to the number of moles of hydroxyl groups provided by the compound of formula (III). In some embodiments, the molar ratio of (meth)acrylate groups provided by the (meth)acrylate esterifying agent to hydroxyl groups provided by the compound of formula (III) is preferably from 1:1 to 2:1, such as from 1.1:1 to 1.5:1 or from 1.1:1 to 1.4:1. Providing a stoichiometric excess of (meth)acrylate groups can promote the complete reaction of hydroxyl groups and can compensate for the reaction of the (meth)acrylate groups with any water entrained in the inert aprotic solvent.

[0123] When the (meth)acrylate esterifying agent is (meth)acryloyl halide, the reaction is desirably carried out in the presence of a base that acts as a hydrogen halide trap. The base is conventionally used in an amount that is superstoichiometric with respect to the reactant (meth)acryloyl halide. Exemplary bases include, but are not limited to: alkali metal hydroxides; alkali metal alkoxides, especially C1-C4 aliphatic alkoxides of lithium, sodium or potassium; alkaline earth metal hydroxides; and tertiary amines.

[0124] In this regard, it is preferred to use one or more tertiary amines. Without wishing to limit the present disclosure, the tertiary amine used should be liquid under the reaction conditions. Alternatively or additionally, it is preferred that the tertiary amine or each tertiary amine is selected from tri(C1-C 12 )alkylamines, di(C1-C 12 )alkyl(C3-C8)cycloalkylamines or tri(C1-C 10 )alkenylamines. It may be mentioned that it is particularly preferred to use tri(C1-C 12 )alkylamines, examples of which include, but are not limited to: trimethylamine; ethyldimethylamine; diethylmethylamine; triethylamine; triisopropylamine; tri-n-propylamine; tri-n-butylamine; diisobutylamine; n-butyl-octyl-sec-butylamine; tripentylamine; and trihexylamine.

[0125] This step is further carried out in the presence of an inert aprotic solvent. Examples of suitable aprotic solvents that can be used alone or in combination include, but are not limited to: pentane; hexane; heptane; cyclopentane; cyclohexane; cycloheptane; dimethyl ether; chloroform; dimethyl carbonate; methyl ethyl carbonate; diethyl carbonate; toluene; o-xylene; m-xylene; p-xylene; ethylbenzene; 2-propylbenzene (cumene); 2-isopropyltoluene (o-cymene); 3-isopropyltoluene (m-cymene); 4-isopropyltoluene (p-cymene); 1,3,5-trimethylbenzene (mesitylene); acetonitrile; N,N-bis(C1-C4)alkylamides, such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc); hexamethylphosphoramide; N-methylpyrrolidone; pyridine; esters, such as (C1-C8)alkyl acetates, ethoxydiethylene glycol acetate, dimethyl glutarate, dimethyl maleate, dipropyl oxalate, ethyl lactate, benzyl benzoate, butyloctyl benzoate, and ethylhexyl benzoate; ketones, such as acetone, ethyl ketone, methyl ethyl ketone (2-butanone), and methyl isobutyl ketone; ethers, such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), and 1,2-dimethoxyethane; 1,3-dioxolane; dimethyl sulfoxide (DMSO); and dichloromethane (DCM).

[0126] Although not critical, it is preferred that the reaction of this step be carried out under anhydrous conditions. If necessary, exposure to atmospheric moisture can be avoided by providing an inert dry gas blanket to the reaction vessel. Although dry nitrogen, helium, and argon can be used as the blanket gas, precautions should be taken when using ordinary nitrogen as the blanket because this nitrogen may not be dry enough due to its tendency to entrain moisture; nitrogen may require an additional drying step before being used herein.

[0127] The process pressure is not critical: thus, the reaction can be carried out at a pressure below atmospheric pressure, equal to atmospheric pressure, or above atmospheric pressure, but a pressure equal to or slightly above atmospheric pressure is preferred. Pressures in the range of 50 to 200 kPa - such as 100 to 200 kPa - can be mentioned in this regard.

[0128] The reaction temperature is generally from -40 to 20 °C, such as -20 to 20 °C. Since the reaction is generally exothermic, some cooling may be required as it proceeds.

[0129] In certain embodiments, the reaction stage can be carried out in the presence of a polymerization inhibitor or a polymerization retarder. A polymerization inhibitor inhibits the occurrence of a polymerization reaction, and exemplary compounds that can be used as inhibitors herein include: N,N'-dialkylbenzene diamines; N,N'-diarylbenzene diamines; N-aryl-N'-alkylbenzene diamines; and quinone diimides. Although a polymerization retarder slows down the rate of the polymerization reaction, in this case, the polymerization retarder is less effective than the polymerization inhibitor, but on the contrary, it is consumed more slowly. Exemplary polymerization retarders include quinomethide compounds, as disclosed especially in U.S. Patent No. 4,003,800, U.S. Patent No. 5,583,247, and U.S. Patent No. 7,045,647. The combination of a polymerization inhibitor and a polymerization retarder is disclosed in US20200017610 A1 (Masere et al.).

[0130] The progress of the reaction in step ii) can be monitored by known techniques, which may include 1 1H NMR, Fourier transform infrared spectroscopy, ultra-high performance liquid chromatography (UPLC), or thin layer chromatography (TLC). After the reaction is completed, the reaction mixture is washed with water, and the organic product phase is separated from the aqueous phase. Then, the aprotic solvent can be removed completely or partially from the organic phase: this should be achieved under reduced pressure and without raising the temperature of the solution to significantly higher than room temperature (preferably not exceeding 40 °C or even 35 °C). Thus, the solid crude product can be obtained either after complete removal of the solvent or can be formed by subsequent cooling of the concentrated organic phase.

[0131] The obtained solid crude product can subsequently be purified by methods known in the art, including but not limited to solvent extraction, filtration, evaporation, distillation, (re)crystallization, and chromatography.

[0132] Exemplary illustrative embodiments of the method

[0133] According to an exemplary illustrative embodiment of the present disclosure, a method for preparing a compound of formula (VA) is provided:

[0134]

[0135] wherein: R 6' to R 9' are independently selected from H, C1-C4 alkyl, C1-C4 alkoxy, C1-C8 alkoxyalkyl, COOR 12 and N(R 12 )2; and

[0136] each R 12 is independently selected from C1-C4 alkyl or C6-C 18 aryl,

[0137] The prerequisite is that the group R 6' to R 9' in which n are -OC(O)C(R 13 )=CH2, where R 13 is H or C1 alkyl, and further where n is an integer of 1 or 2,

[0138] The method comprises the following steps:

[0139] i) Reacting a disulfide compound of formula (IA) with a hydroxy-functional compound of formula (II) to produce a compound of formula (IIIA)

[0140]

[0141] wherein: The reaction is carried out in an acidic medium with a pH equal to or lower than 3.0;

[0142] The reaction is carried out at a temperature below the boiling point of the acidic medium and in the range of 40 to 120 °C;

[0143] R 6 to R 9 correspond to the substituents R 6’ to R 9’ and are independently selected from H, C1-C4 alkyl, C1-C4 alkoxy, C1-C8 alkoxyalkyl, COOR 12 and N(R 12 )2;

[0144] R 10 and R 11 are H; and

[0145] each R 12 is independently selected from C1-C4 alkyl or C6-C 18 aryl,

[0146] The prerequisite is that the group R 6 to R 9 in which n are -OH, where n is an integer of 1 or 2;

[0147] iv) Reacting the compound of formula (IIIA) with a compound of formula (IV) in an inert aprotic solvent to produce the compound of formula (VA)

[0148]

[0149] wherein: X is chloride;

[0150] The molar ratio of the (meth)acrylate group provided by the compound of formula (IV) to the hydroxyl group provided by the compound of formula (IIIA) is from 1.1:1 to 1.5:1; and

[0151] The reaction of step ii) is carried out in the presence of a base selected from: tris(C1-C 12 )alkylamine; bis(C1-C 12 )alkyl(C3-C8)cycloalkylamine; tris(C1-C 10 )alkenylamine; and mixtures thereof.

[0152] A copolymer is formed by radical polymerization

[0153] The present disclosure also provides a polymer obtained by radical polymerization of a compound of formula (V), wherein the compound of formula (VA) is an example of the compound of formula (V). In particular, the present disclosure provides a copolymer obtained by radical polymerization, wherein, based on the total weight of the monomers, the copolymer comprises: 0.1 to 10% by weight of a) at least one compound according to formula (V); and 90 to 99.9% by weight of b) at least one ethylenically unsaturated nonionic monomer that does not have an epoxy group or a moiety that can decompose under light radiation to form free radicals.

[0154] The copolymers of the present disclosure are prepared by radical polymerization. As will be appreciated by those skilled in the art, radical polymerization consists of three stages: initiation, in which the decomposition of an initiator generates reactive free radicals that have unpaired electrons and react with the monomers present to produce initiating radical chains; propagation, in which the formed initiating radical chains attack second monomer molecules, thereby transferring their active centers to the attacked molecules, and repeating the process to grow the polymer chains; and termination, in which the growth of the macromolecular chains stops and the polymerization terminates by disabling the active centers. The two most common termination mechanisms in radical polymerization are combination and deprotonation.

[0155] Radical polymerization can be carried out in bulk, in emulsion, in suspension or in solution. Without limiting the specific intent of the present disclosure, the copolymer is preferably prepared by radical solution polymerization: by this is meant that a solution of the monomers in a solvent (which is also capable of dissolving the copolymer) is polymerized by radical polymerization, i.e., in the presence of a polymerization initiator. The concentration of the monomers in the solution can vary, but the weight ratio of the monomers to the solvent is generally in the range of 1:20 to 2:1, for example 1:2 to 1.5:1.

[0156] The free radical solution polymerization should desirably be carried out in the presence of a polar solvent having a boiling point of at least 20 °C, such as at least 30 °C or at least 40 °C, where the boiling point is measured at 1 atmosphere (1.01325 bar). Examples of such polar solvents that can be used alone or in combination include, but are not limited to: water; C1-C8 alkanols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, and isobutanol; acetonitrile; N,N-di(C1-C4)alkylamides such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc); hexamethylphosphoramide; N-methylpyrrolidone; pyridine; esters such as (C1-C8)alkyl acetates, ethoxydiethylene glycol acetate, dimethyl glutarate, dimethyl maleate, dipropyl oxalate, ethyl lactate, benzyl benzoate, butyloctyl benzoate, and ethylhexyl benzoate; ketones such as acetone, ethyl ketone, methyl ethyl ketone (2-butanone), and methyl isobutyl ketone; ethers such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), and 1,2-dimethoxyethane; 1,3-dioxolane; dimethyl sulfoxide (DMSO); and dichloromethane (DCM). In one exemplary embodiment, the polymerization is carried out in the presence of a (C1-C8)alkyl acetate, particularly ethyl acetate.

[0157] As noted above, the free radical polymerization will be triggered by at least one free radical-generating thermal initiator. As will be understood by those skilled in the art, a thermal initiator is a compound that can be activated by heat energy to generate its free radicals, for example, when heated or irradiated in the infrared or microwave wavelength regions. Based on the total weight of the polymerizable monomers, the polymerization composition should conventionally contain 0.1 to 1 wt%, such as 0.1 to 0.5 wt%, of the at least one free radical-generating thermal initiator.

[0158] Without intending to limit the invention, one exemplary class of free radical-generating thermal initiators suitable for use herein is organic peroxides, which are selected from, for example: cyclic peroxides; diacyl peroxides; dialkyl peroxides; hydroperoxides; peroxycarbonates; diperoxycarbonates; peroxyesters; and peroxyketals.

[0159] While certain peroxides, such as dialkyl peroxides, have been disclosed as available initiators, particularly in U.S. Patent No. 3,419,512 (Lees) and U.S. Patent No. 3,479,246 (Stapleton), and can in fact be used herein, hydroperoxides represent the preferred class of initiators for the present invention. Further, while hydrogen peroxide itself can be used, the most desirable polymerization initiators are organic hydroperoxides. For completeness, materials that decompose or hydrolyze to form an organic hydroperoxide in situ, such as organic peroxides or organic peresters, are included within the definition of hydroperoxides: examples of such peroxides and peresters are cyclohexyl and hydroxycyclohexyl peroxides and tert-butyl perbenzoate, respectively.

[0160] In one embodiment of the present invention, the free-radical generating thermal initiator comprises at least one hydroperoxide compound represented by the following formula or consisting thereof:

[0161] R p OOH

[0162] wherein: R p is an aliphatic or aromatic group containing no more than 18 carbon atoms, and preferably wherein: R p is a C1-C 12 alkyl, C6-C 18 aryl or C7-C 18 aralkyl.

[0163] As exemplary peroxide initiators that can be used alone or in combination, mention may be made of: cumene hydroperoxide (CHP); p-menthane hydroperoxide; tert-butyl hydroperoxide (TBH); tert-butyl perbenzoate; tert-butyl perpivalate; di-tert-butyl peroxide; tert-butyl peracetate; tert-butyl per-2-hexanoate; tert-amyl hydroperoxide; 1,2,3,4-tetramethylbutyl hydroperoxide; benzoyl peroxide; dibenzoyl peroxide; 1,3-bis(tert-butylperoxyisopropyl)benzene; diacetyl peroxide; butyl 4,4-bis(tert-butylperoxy)valerate; p-chlorobenzoyl peroxide; tert-butyl cumyl peroxide; di-tert-butyl peroxide; di-cumyl peroxide; 2,5-dimethyl-2,5-di-tert-butylperoxyhexane; 2,5-dimethyl-2,5-di-tert-butyl-peroxyhex-3-yne; and 4-methyl-2,2-di-tert-butylperoxypentane.

[0164] Without wishing to limit the present invention, another class of exemplary free-radical generating thermal initiators suitable for use herein are azo polymerization initiators, which are for example selected from: azo nitriles; azo esters; azo amides; azo amidines; azo imidazolines; and macromolecular azo initiators.

[0165] As representative examples of suitable azo polymerization initiators, mention may be made of: 2,2'-azobis(2-methylbutyronitrile); 2,2'-azobis(isobutyronitrile); 2,2'-azobis(2,4-dimethylvaleronitrile); 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile); 1,1'-azobis(cyclohexane-1-carbonitrile); 4,4'-azobis(4-cyanovaleric acid); dimethyl 2,2'-azobis(2-methylpropionate); 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide]; 2,2'-azobis(N-butyl-2-methylpropionamide); 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride; 2,2'-azobis[2-(2-imidazolin-2-yl)propane]; 2,2'-azobis(2-methylpropamidine) dihydrochloride; 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropamidine] tetrahydrate; a polymer of 4,4-azobis(4-cyanovaleric acid) and α,ω-bis(3-aminopropyl)polydimethylsiloxane (VPS-1001, available from Wako Pure Chemical Industries, Ltd.); and a 4,4'-azobis(4-cyanovaleric acid)·polyethylene glycol polymer (VPE-0201, available from Wako Pure Chemical Industries, Ltd.).

[0166] Redox initiators are a combination of an oxidizing agent and a reducing agent and can also be used in the present invention. Suitable oxidizing agents may be selected from cyclic peroxides, diacyl peroxides, dialkyl peroxides, hydroperoxides, peroxycarbonates, diperoxycarbonates, peroxyesters, and peroxyketals. Corresponding reducing agents may be selected from: alkali metal sulfites; alkali metal bisulfites; alkali metal pyrosulfites; formaldehyde sulfoxylates; alkali metal salts of aliphatic sulfinic acids; alkali metal hydrosulfides; salts of polyvalent metals, especially Co(II) salts and Fe(II) salts, such as iron(II) sulfate, iron(II) ammonium sulfate, or iron(II) phosphate; dihydroxymaleic acid; benzoin; ascorbic acid; and reducing sugars, such as sorbose, glucose, fructose, and / or dihydroxyacetone.

[0167] In addition to initiators, radical polymerization is considered to be possible in the presence of a chain transfer agent, which is used to transfer radicals and reduce the molecular weight of the resulting polymer and / or control chain growth in the polymerization. When added, the chain transfer agent should be in the range of 0.01 to 1% by weight based on the total weight of the polymerizable monomers.

[0168] The method for preparing the copolymer is preferably carried out in such a way that the copolymer has a number-average molecular weight (Mn) of from 50,000 to 500,000 daltons, such as from 75,000 to 300,000 daltons or from 100,000 to 250,000 daltons. The amounts of the polymerization initiator and any chain transfer agent present will determine the number-average molecular weight of the copolymer, although the choice of solvent may also be important.

[0169] Without wishing to limit the present invention, conventional polymerization conditions include temperatures in the range from 0 to 175 °C, such as from 25 to 125 °C or from 50 to 100 °C. The polymerization pressure is generally not critical and thus the polymerization can be carried out at a pressure below atmospheric pressure, equal to atmospheric pressure or above atmospheric pressure. In addition to the pressure, the polymerization can, if necessary, be carried out under exclusion of oxygen: the reaction vessel can be provided with an inert, dry gas blanket, such as an inert, dry gas blanket of nitrogen, helium and argon.

[0170] For the sake of completeness, it is considered that the polymerization according to the present invention can be carried out as a batch or semi-batch procedure or as a continuous procedure. As will be appreciated by those skilled in the art, in a batch procedure, the monomers to be polymerized and optionally the solvent used in the polymerization procedure are charged to the reaction vessel, while most or all of the polymerization initiator is added to the reaction vessel during the polymerization. In a semi-batch procedure, at least a part, not more than and including the total amount, of the polymerization initiator and the solvent are first charged to the reaction vessel: a small part of the monomers can also be charged in this way, but most of the monomers to be polymerized are added to the reaction vessel during the polymerization. In a continuous process, the monomers, the polymerization initiator and optionally the solvent are continuously added to the reaction vessel and the polymer obtained is continuously discharged from the polymerization vessel.

[0171] For the implementation of the polymerization according to the present invention, a semi-batch procedure is preferably mentioned. In particular, at least 75% by weight of the total weight of the monomers to be polymerized should be added to the reaction vessel during the polymerization reaction.

[0172] Without particularly wishing to limit the timing of introducing the different functional monomers of the copolymer, parts a) and b), into the polymerization procedure. The monomers can be provided to the polymerization vessel in a fixed molar ratio either at the start of the polymerization (for a batch method) or during the entire polymerization method (for semi-batch and continuous methods). In an alternative, the molar ratio of the monomer types can vary during the polymerization: this is intended to cover the embodiment in which only the monomers of part a) or, conversely, only the monomers of part b) are added to the polymerization vessel during the polymerization. Those skilled in the art can determine the appropriate molar ratio based on the desired form or randomness of the copolymer and the reactivity ratios of the monomers.

[0173] The copolymer reaction product can be separated and purified using methods known in the art, where extraction, evaporation, crystallization, distillation, and chromatography may be mentioned as suitable techniques. In the case of carrying out free radical solution polymerization, it is most convenient to separate the copolymer by distilling off the solvent and any unreacted starting materials under reduced pressure. In the case where the (optionally purified) copolymer is intended to be stored during production, the polymer should be placed in a container with an airtight and moisture-proof seal. The storage container should not allow the penetration of light radiation.

[0174] The following examples are illustrative of the invention and are not intended to limit the scope of the invention in any way.

[0175] Examples

[0176] The following commercially available compounds were used in the examples:

[0177] Example 1 : Synthesis of 2-hydroxy-3-(propan-2-yl)-9H-thioxanthen-9-one

[0178]

[0179] Note: "H2SO4 conc." refers to concentrated H2SO4.

[0180] 5.0 g (16.33 mmol) of 2,2'-dithiobenzoic acid was suspended in 50 ml of concentrated (95%) sulfuric acid. 13 g (95.5 mmol) of 2-(propan-2-yl)phenol was added to the suspension within 10 minutes: during this time, the mixture was heated to about 50 °C. The reaction mixture was then heated to 80 °C and this temperature was maintained for 3 hours. Thereafter, the mixture was cooled to room temperature and stirred overnight. The resulting mixture was added dropwise to 500 ml of boiling deionized water. The resulting precipitate was filtered out and washed once with 50 ml of boiling water and once with 100 ml of cold water. The resulting product was dried under vacuum. Product: green powder; approximately 50% yield.

[0181] Example 2 : Synthesis of 9-oxo-3-(propan-2-yl)-9H-thioxanthen-2-yl prop-2-enoate

[0182]

[0183] Dissolve 5 g (18.5 mmol) of 2-hydroxy-3-(propan-2-yl)-9H-thioxanthen-9-one in 200 ml of anhydrous dichloromethane. After adding 4 g (39.5 mmol) of triethylamine, cool the reaction mixture to 0 °C under stirring and a nitrogen atmosphere. Add 2 ml (24.5 mmol) of acryloyl chloride dropwise through a septum. After stirring at 0 °C for 4 h, stir the reaction mixture further overnight at room temperature. Wash the resulting mixture carefully twice with 50 ml of deionized water. Concentrate the organic phase on a rotary evaporator to a volume of about 15 ml while not exceeding 40 °C. After cooling to 0 °C, filter off the precipitate and wash it with methanol. Recrystallize the filtered product from methanol and dry it under vacuum. Product: yellow powder; about 50% yield.

[0184] Example 3 : Synthesis of 2-hydroxy-1,3-dimethyl-9H-thioxanthen-9-one

[0185]

[0186] Note: "H2SO4 conc." refers to concentrated H2SO4.

[0187] Suspend 5.0 g (16.33 mmol) of 2,2'-dithiobenzoic acid in 50 ml of concentrated (95%) sulfuric acid. Add 95.5 mmol of 2,6-dimethylphenol to the suspension within 10 min: during this time, heat the mixture to about 50 °C. Then heat the reaction mixture to 80 °C and maintain this temperature for 3 h. Thereafter, cool the mixture to room temperature and stir overnight. Add the resulting mixture dropwise to 500 ml of boiling deionized water. Filter off the resulting precipitate and wash it once with 50 ml of boiling water and once with 100 ml of cold water. Dry the resulting product under vacuum. Product: green powder; about 50% yield.

[0188] React the obtained 2-hydroxy-1,3-dimethyl-9H-thioxanthen-9-one with acryloyl chloride according to the procedure of Example 2.

[0189] Example 4 : Synthesis of 1-hydroxy-4-(2-methoxyethyl)-9H-thioxanthen-9-one

[0190]

[0191] Note: "H2SO4 conc." refers to concentrated H2SO4.

[0192] Suspend 5.0 g (16.33 mmol) of 2,2'-dithiobenzoic acid in 50 ml of concentrated (95%) sulfuric acid. Add 95.5 mmol of 4-(2-methoxyethyl)phenol to the suspension within 10 minutes: during this time, heat the mixture to about 50 °C. Then heat the reaction mixture to 80 °C and maintain this temperature for 3 hours. Thereafter, cool the mixture to room temperature and stir overnight. Add the resulting mixture dropwise to 500 ml of boiling deionized water. Filter off the resulting precipitate and wash it once with 50 ml of boiling water and once with 100 ml of cold water. Dry the resulting product under vacuum. Product: green powder; about 50% yield.

[0193] React the obtained 1-hydroxy-4-(2-methoxyethyl)-9H-thioxanthen-9-one with acryloyl chloride according to the procedure of Example 2.

[0194] Example 5 : 3-acetyl-2-hydroxy-9H-thioxanthen-9-one

[0195]

[0196] Note: "H2SO4 conc." refers to concentrated H2SO4.

[0197] Suspend 5.0 g (16.33 mmol) of 2,2'-dithiobenzoic acid in 50 ml of concentrated (95%) sulfuric acid. Add 95.5 mmol of 1-(2-hydroxyphenyl)ethan-1-one to the suspension within 10 minutes: during this time, heat the mixture to about 50 °C. Then heat the reaction mixture to 80 °C and maintain this temperature for 3 hours. Thereafter, cool the mixture to room temperature and stir overnight. Add the resulting mixture dropwise to 500 ml of boiling deionized water. Filter off the resulting precipitate and wash it once with 50 ml of boiling water and once with 100 ml of cold water. Dry the resulting product under vacuum. Product: green powder; about 50% yield.

[0198] React the obtained 3-acetyl-2-hydroxy-9H-thioxanthen-9-one with acryloyl chloride according to the procedure of Example 2.

[0199] Example 6 : Synthesis of 3-(dimethylamino)-1-hydroxy-9H-thioxanthen-9-one

[0200]

[0201] Note: "H2SO4 conc." refers to concentrated H2SO4.

[0202] Suspend 5.0 g (16.33 mmol) of 2,2'-dithiobenzoic acid in 50 ml of concentrated (95%) sulfuric acid. Add 95.5 mmol of 3-(dimethylamino)phenol to the suspension within 10 minutes: during this time, heat the mixture to about 50 °C. Then heat the reaction mixture to 80 °C and maintain this temperature for 3 hours. Thereafter, cool the mixture to room temperature and stir overnight. Add the resulting mixture dropwise to 500 ml of boiling deionized water. Filter out the resulting precipitate and wash it once with 50 ml of boiling water and once with 100 ml of cold water. Dry the resulting product under vacuum. Product: green powder; approximately 50% yield.

[0203] According to the procedure of Example 2, react the obtained 3-(dimethylamino)-1-hydroxy-9H-thioxanthen-9-one with acryloyl chloride.

[0204] Example 7 : 2-Hydroxy-9-oxo-9H-thioxanthene-3-carboxylate

[0205]

[0206] Note: "H2SO4 conc." refers to concentrated H2SO4.

[0207] Suspend 5.0 g (16.33 mmol) of 2,2'-dithiobenzoic acid in 50 ml of concentrated (95%) sulfuric acid. Add 95.5 mmol of 2-hydroxybenzoate to the suspension within 10 minutes: during this time, heat the mixture to about 50 °C. Then heat the reaction mixture to 80 °C and maintain this temperature for 3 hours. Thereafter, cool the mixture to room temperature and stir overnight. Add the resulting mixture dropwise to 500 ml of boiling deionized water. Filter out the resulting precipitate and wash it once with 50 ml of boiling water and once with 100 ml of cold water. Dry the resulting product under vacuum. Product: green powder; approximately 50% yield.

[0208] React the obtained 2-hydroxy-9-oxo-9H-thioxanthene-3-carboxylate with acryloyl chloride according to the procedure of Example 2.

[0209] Example 8 : Synthesis of 3-Ethoxy-2-hydroxy-9H-thioxanthen-9-one

[0210]

[0211] Note: "H2SO4 conc." refers to concentrated H2SO4.

[0212] 5.0 g (16.33 mmol) of 2,2'-dithiobenzoic acid was suspended in 50 ml of concentrated (95%) sulfuric acid. 95.5 mmol of 2-ethoxyphenol was added to the suspension within 10 minutes: during this time, the mixture was heated to about 50 °C. The reaction mixture was then heated to 80 °C and this temperature was maintained for 3 hours. Thereafter, the mixture was cooled to room temperature and stirred overnight. The resulting mixture was added dropwise to 500 ml of boiling deionized water. The resulting precipitate was filtered off and washed once with 50 ml of boiling water and once with 100 ml of cold water. The resulting product was dried under vacuum. Product: green powder; ~50% yield.

[0213] The obtained 3-ethoxy-2-hydroxy-9H-thioxanthen-9-one was reacted with acryloyl chloride according to the procedure of Example 2.

[0214] In view of the foregoing description and examples, it will be apparent to those skilled in the art that equivalent modifications can be made thereto without departing from the scope of the claims.

Claims

1. A method for preparing a compound of formula (V): Wherein: R 6' to R 9' are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C1-C 12 alkoxyalkyl, SR 12 , COOR 12 and N(R 12 )2; and Each R 12 is independently selected from C1-C6 alkyl or C6-C 18 aryl, The prerequisite is that the group R 6’ to R 9’ in which n are -R b OC(O)C(R 13 )=CH2, where: R 13 is H or a C1 alkyl group; n is an integer from 1 to 3, preferably 1 or 2; and For each of the n groups, R b is independently selected from a covalent bond, C2-C 12 alkylene, C3-C 18 cycloalkylene or C6-C 18 arylene, The method comprises the following steps: iii) Reacting a disulfide compound of formula (I) with a hydroxy-functional compound of formula (II) to produce a compound of formula (III) wherein: The reaction is carried out in an acidic medium with a pH equal to or lower than 4.0; R 2 to R 5 are independently selected from H or C1-C6 alkyl; R 6 to R 9 corresponding to the substituent R 6’ to R 9’ and independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C1-C 12 alkoxyalkyl, SR 12 , COOR 12 and N(R 12 )2; R 10 and R 11 is H; and Each R 12 is independently selected from C1-C6 alkyl or C6-C 18 aryl, The prerequisite is that the group R 6 to R 9 in which n are R b (OH), where for each of the n groups, R b is independently selected from a covalent bond, C2-C 12 alkylene, C3-C 18 cycloalkylene or C6-C 18 arylene; and iv) Reacting the compound of formula (III) with a compound of formula (IV) in an inert aprotic solvent to produce the compound of formula (V) wherein: X is a halide or -OC(O)C(R 13 )=CH2; and The number of moles of the (meth)acrylate group provided by the compound of formula (IV) is at least equimolar to the number of moles of the hydroxyl group provided by the compound of formula (III).

2. The method according to claim 1, wherein R 2 to R 5 are independently selected from H or C1-C4 alkyl.

3. The method according to claim 2, wherein R 2 to R 5 are independently selected from H or C1-C2 alkyl.

4. The method according to claim 3, wherein R 2 to R 5 are each H.

5. The method according to any one of claims 1 to 4, wherein in formula (II): R 6 to R 9 are independently selected from H, C1-C4 alkyl, C1-C4 alkoxy, C1-C8 alkoxyalkyl, COOR 12 and N(R 12 )2; R 10 and R 11 is H; and Each R 12 is independently selected from C1-C4 alkyl or C6-C 18 aryl, The prerequisite is that n of the groups R 6 to R 9 are -OH, where n is an integer of 1 or 2.

6. The method according to any one of claims 1 to 5, wherein the pH of the acidic medium in step i) is equal to or lower than 3.5, preferably equal to or lower than 3.

0.

7. The method according to any one of claims 1 to 6, wherein step i) is carried out at a temperature lower than the boiling point of the acidic medium.

8. The method according to any one of claims 1 to 7, wherein step i) is carried out at a temperature of 20 °C to 120 °C, preferably 40 to 120 °C and more preferably 60 to 100 °C.

9. The method according to any one of claims 1 to 8, wherein in step ii), the molar ratio of the (meth)acrylate group provided by the compound of formula (IV) to the hydroxyl group provided by the compound of formula (III) is 1:1 to 2:1, preferably 1.1:1 to 1.5:1, and more preferably 1.1:1 to 1.4:

1.

10. The method according to any one of claims 1 to 9, wherein X is a halide, and preferably wherein X is chloride.

11. The method according to claim 10, wherein the reaction in step ii) is carried out in the presence of a base.

12. The method according to claim 11, wherein the base is selected from: tris(C1-C 12 )alkylamine; di(C1-C 12 )alkyl(C3-C8)cycloalkylamine; tris(C1-C 10 )alkenylamine; and mixtures thereof.

13. The method according to claim 11, wherein the base is selected from: trimethylamine; ethyldimethylamine; diethylmethylamine; triethylamine; triisopropylamine; tri-n-propylamine; tri-n-butylamine; diisobutylpentylamine; n-butyl-octyl-sec-butylamine; tripentylamine; trihexylamine; and mixtures thereof.

14. The method according to any one of claims 1 to 13, wherein step ii) is carried out at a temperature of -40 °C to 20 °C, preferably -20 to 20 °C.

15. The method according to claim 1, which is a method for preparing a compound of formula (VA): Wherein: R 6' to R 9' are independently selected from H, C1-C4 alkyl, C1-C4 alkoxy, C1-C8 alkoxyalkyl, COOR 12 and N(R 12 )2; and Each R 12 is independently selected from C1-C4 alkyl or C6-C 18 aryl, The prerequisite is that the group R 6’ to R 9’ in which n of them are -OC(O)C(R 13 )=CH2, where R 13 is H or C1 alkyl, and further where n is an integer of 1 or 2, The method comprises the following steps: iii) Reacting a disulfide compound of formula (IA) with a hydroxy-functional compound of formula (II) to produce a compound of formula (IIIA) wherein: The reaction is carried out in an acidic medium with a pH equal to or lower than 3.0; The reaction is carried out at a temperature lower than the boiling point of the acidic medium and in the range of 40 to 120 °C; R 6 to R 9 corresponding to the substituent R 6’ to R 9’ and independently selected from H, C1-C4 alkyl, C1-C4 alkoxy, C1-C8 alkoxyalkyl, COOR 12 and N(R 12 )2; R 10 and R 11 is H; and Each R 12 is independently selected from C1-C4 alkyl or C6-C 18 aryl, The prerequisite is that n of the groups R 6 to R 9 are -OH, where n is an integer of 1 or 2; iv) Reacting the compound of formula (IIIA) with a compound of formula (IV) in an inert aprotic solvent to produce the compound of formula (VA) wherein: X is chloride; The molar ratio of the (meth)acrylate group provided by the compound of formula (IV) to the hydroxyl group provided by the compound of formula (IIIA) is from 1.1:1 to 1.5:1; and The reaction of step (ii) is carried out in the presence of a base selected from: tris(C1-C 12 )alkylamine; bis(C1-C 12 )alkyl(C3-C8)cycloalkylamine; tris(C1-C 10 )alkenylamine; and mixtures thereof. Use of a compound of formula (V) obtained by the process according to any one of claims 1 to 15 as a monomer in radical polymerization.

17. A copolymer obtained by radical polymerization, wherein, based on the total weight of the monomers, the copolymer comprises: 0.1 to 10% by weight of a) at least one compound of formula (V) obtained by the process according to any one of claims 1 to 15; and 90 to 99.9% by weight of b) at least one ethylenically unsaturated nonionic monomer which does not carry an epoxy group or a moiety which can be decomposed under light irradiation to form radicals.

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