Photoinitiator and curable composition comprising the same

Abstract

This invention provides a photoinitiator prepared by a ring-opening reaction of an epoxidized vegetable oil with one or more Norrish type II photoinitiators having carboxylic acid groups, hydroxyl groups, thiol groups, and / or amine groups, and one or more acrylic compounds. This invention also provides a photocurable composition comprising this photoinitiator. The photoinitiator of this invention has advantages such as low migration rate, non-toxicity, low volatility, thermal stability, and easy solubility in organic solvents.

Description

[Technical Field]

[0001] This invention relates to a photoinitiator and a photocurable composition comprising the same. [Previous Technology]

[0002] Since the 1990s, with the advent of photoinitiators such as isopropylthioxanthone (ITX), 2,4,6-trimethylbenzoyldiphenyl phosphine oxide (TPO), and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (also known as photoinitiator 819), ultraviolet (UV) curing has seen substantial development. UV-curable coatings refer to coatings in which liquid resin monomers in the coating composition undergo a polymerization reaction at room temperature and transform into a solid film upon exposure to ultraviolet light. Compared to traditional thermosetting coatings, UV-curable coatings offer advantages such as faster curing speed, room temperature curing, energy saving, space saving, environmental friendliness, improved product performance, and suitability for high-speed automated production.

[0003] Currently, commercially available photoinitiators mainly include benzophenone (BP), ITX, TPO, and other series of photoinitiators. However, these photoinitiators often have an odor and are prone to migrating from printed materials to the surface, posing a health hazard. One way to overcome these problems is to modify the photoinitiator by increasing its molecular weight to reduce migration.

[0004] On the other hand, epoxidized vegetable oil is a widely available biomass raw material that is inexpensive and has certain chemical reactivity, and can be used as a structural basis for the preparation of polymer materials. For example, epoxidized soybean oil (ESBO) is an epoxidized vegetable oil product obtained by epoxidizing soybean oil.

[0005] Currently, photoinitiators have been introduced into epoxidized soybean oil (ESBO) for modification to increase its molecular weight. For example, Chinese Invention Patent Publication No. CN101705044B discloses a soybean oil methylpropiophenone photoinitiator, which utilizes the reaction of 2-hydroxy-2-methylpropiophenone and epoxidized soybean oil (ESBO) to form a soybean oil photoinitiator. In addition, a journal article published in 2012 by Jie Yin et al. (Aifang Luo, Xuesong Jiang, Jie Yin, "Thioxanthone-containing renewable vegetable oil as photoinitiators", Polymer. 2012, 53, 2183–2189) discloses a soybean oil thioxanthone photoinitiator, which utilizes soybean oil to react with thioxanthone compounds (2-acetic thioxanthone, ATX) as photoinitiators and 4-dimethylaminobenzoic acid (DBA) as amine synergist to prepare soybean oil thioxanthone photoinitiator (ESBO-ATX-DBA).

[0006] However, the reactivity of these photoinitiators is still insufficient, and a considerable amount of these photoinitiators is usually required to achieve the desired curing speed. Furthermore, using too much photoinitiator will prevent the formation of a hardened solid and will increase its viscosity, easily leading to an increase in migration rate.

[0007] Therefore, the industry still needs a modified photoinitiator with low mobility and high reactivity to facilitate subsequent industrial applications. [Summary of the Invention]

[0008] One object of the present invention is to provide a photoinitiator, which is prepared by ring-opening reaction of epoxidized vegetable oil with one or more Norrish type II photoinitiators having carboxylic acid groups, hydroxyl groups, thiol groups and / or amine groups and one or more acrylic compounds.

[0009] Another object of the present invention is to provide a photoinitiator prepared by ring-opening reaction of an epoxidized vegetable oil with one or more acrylic compounds and one or more compounds of formula (II), wherein (II) R2 and R3 are independently selected from C1-6 alkyl, C1-6 alkoxy, hydroxyl, halogen, -COO-C1-6 alkyl, C6-10 aryl, or -NR4R4; or R2 and R3 together form -S-, -O-, -CO- or -C=C-; m is 0, 1, 2, 3 or 4; n is 0, 1, 2 or 3; R6 is selected from -COOH, -OH, -SH, -NR4R4, -COR5OH or -OR5-COOH; R4 is independently selected from H or C1-6 alkyl; and R5 is selected from unsubstituted or substituted with one or more hydroxyl, halogen, C1-6 alkoxy, or acetoxy C1-20 alkyl or C2-20 alkylene. If m is greater than 1, then the R3 group can be part of a ring structure. If n is greater than 1, then the R2 group can be part of a ring structure. Ideally, n and m should both be 0.

[0010] Another object of the present invention is to provide a photoinitiator according to an idealized formula (III): (III), wherein RA1, RB1, RA2, RB2, RA3, RB3, RA4, RB4, RA5, RB5, RA6 and RB6 are independently selected from , and , provided that (1) the total amount of and is 4 to 6; (2) the total amount of is 1 to 5; (3) the total amount of is 1 to 5; (4) for each i, where i is 1 to 6: if RAi is or , then the corresponding RBi is; and (5) for each i, where i is 1 to 6: if RBi is or , then the corresponding RAi is.

[0011] Another object of the present invention is to provide a photocurable composition comprising an olefinic unsaturated curable compound and a photoinitiator as described above.

[0012] This invention effectively solves the above-mentioned problems by preparing photoinitiators using epoxidized vegetable oils, and develops products with more diverse applications. This invention prepares photoinitiators with higher molecular weights by reacting epoxidized vegetable oils with Norrish type II photoinitiators such as benzophenone and acrylic compounds such as acrylic acid. Compared with traditional photoinitiators, these photoinitiators have the advantages of high reactivity, low migration, biomass units, non-toxicity, and low volatility, and also offer higher efficiency.

Implementation Method

[0013] The present invention will be described in conjunction with the following embodiments. In addition to the following embodiments, the present invention may be carried out by other methods that do not depart from the spirit of the invention; the scope of the present invention should not be interpreted or limited solely based on the disclosure of the specification.

[0014] To facilitate understanding of the disclosure herein, several terms are defined below. The terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting of the invention. Unless otherwise expressly stated, the singular form is intended to also include the plural form. Further understanding: When the terms "comprising," "having," or "including" are used in this specification, they indicate the presence of the stated feature, number, step, component, or combination thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0015] All figures for expression content, proportion, physical characteristics, etc., used in this specification and the claims should be understood to be modified by the term "about" in all cases. Herein, the term "about" means the acceptable error of a particular value as determined by a person of ordinary skill in the art, depending in part on how the value is measured or determined.

[0016] The present invention provides a photoinitiator, which is prepared by ring-opening reaction of epoxidized vegetable oil with one or more Norrish type II photoinitiators having carboxylic acid groups, hydroxyl groups, thiol groups and / or amine groups and one or more acrylic compounds.

[0017] As used herein, epoxidized vegetable oil can be any product obtained by epoxidizing unsaturated vegetable oil, which may include, but is not limited to, epoxidized soybean oil, cottonseed oil, rapeseed oil, corn oil, peanut oil, sunflower oil, and / or safflower oil. In one specific embodiment of the invention, the epoxidized vegetable oil is epoxidized soybean oil.

[0018] As used herein, Norrish type II photoinitiators are well known in the art, and aromatic ketones are preferred. Suitable examples of aromatic ketones include, but are not limited to, benzophenone and its derivatives.

[0019] As used herein, the term "alkyl" can refer to a straight-chain or branched saturated hydrocarbon group having 1 to 20 carbon atoms, or in some embodiments 1 to 12, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Alkyl groups further include cycloalkyl groups. Examples of straight-chain alkyl groups include those having 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, and n-octyl groups. Examples of branched alkyl groups include (but are not limited to) isopropyl, isobutyl, dibutyl, tributyl, neopentyl, isopentyl, and 2,2-dimethylpropyl groups. Additionally, alkyl groups may be substituted, as appropriate.

[0020] The term "alkenyl" can be a straight-chain or branched group having 2 to 20 carbon atoms, or in some embodiments 2 to 12, 2 to 8, 2 to 6, or 2 to 4 carbon atoms, containing at least one C=C bond. Additionally, the alkenyl group can be substituted, as appropriate.

[0021] As used herein, the terms "alkyl" and "alkenyl" refer to divalent groups derived from their corresponding monovalent groups by further extraction of hydrogen atoms. For example, alkyl groups are derived from alkyl groups.

[0022] As used herein, the term "alkoxy" refers to the -O-alkyl group. Examples include methoxy, ethoxy, propoxy, isopropoxy, cyclopropoxy, cyclohexyloxy, and similar groups.

[0023] The term "acetylated group" as used herein refers to the R(C=O)O- group, wherein "R" may be alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, aryl, cyclohexyl, heteroaryl, or heterocycloalkyl. The acetylated group is attached to the parent molecule structure via an oxygen functional group.

[0024] The term "alkynyl" refers to a straight-chain or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms, containing at least one triple bond, and having 2 to 10 carbon atoms (i.e., C2-C10 alkynyl). The alkynyl group is connected to the parent molecule structure by a single bond, for example, ethynyl, propynyl, butynyl, pentyynyl, hexynyl and similar groups.

[0025] As used herein, the terms “heteroalkyl”, “heteroalken” and “heteroynyl” respectively include alkyl, alken and ynyl groups having one or more skeletal chain atoms selected from carbon (e.g., oxygen, nitrogen, sulfur, phosphorus or combinations thereof).

[0026] As used herein, the term "aryl" refers to a cyclic aromatic hydrocarbon that does not contain heteroatoms. Aryl groups include monocyclic, bicyclic, and polycyclic ring systems. Thus, aryl groups include (but are not limited to) phenyl, azulel, cycloheptatrienyl, cyclophenyl, dicyclopentadienylphenyl, fluorenyl, phenanthrene, benzophenanthrene, pyrene, fused tetraphenyl, chrysenyl, biphenyl, anthracene, indene, indanyl, cyclopentadienyl, and naphthyl groups. In some embodiments, the aryl group contains 6-14 carbons, and in other cases, 6 to 12 or even 6-10 carbon atoms in the ring portion of the group. The phrase "aryl group" includes groups containing fused rings, such as fused aromatic-aliphatic ring systems (e.g., indene, tetrahydronaphthyl, and similar groups). Aryl groups can be substituted or unsubstituted.

[0027] As used herein, the term "heteroaryl" refers to a group having a 5-18 member monocyclic or polycyclic (e.g., bicyclic or tricyclic) aromatic ring system (e.g., having 6, 10 or 14 π electrons shared in a cyclic array), having a cyclic carbon atom and 1-6 cyclic heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen, phosphorus and sulfur ("5-18 member heteroaryl").

[0028] As used herein, the terms "heterocyclic group," "heterocyclic alkyl group," or "heterocyclic carbocyclic group" each refer to any 3 to 18 non-aryl monocyclic or polycyclic moiety containing at least one heteroatom selected from nitrogen, oxygen, phosphorus, and sulfur. Heterocyclic groups can be monocyclic, bicyclic, tricyclic, or tetracyclic systems, wherein polycyclic systems can be fused, bridged, or spirocyclic systems. Heterocyclic polycyclic systems may include one or more heteroatoms in one or two rings. Heterocyclic groups can be saturated or partially unsaturated. If a heterocyclic group contains at least one double bond, a partially unsaturated heterocyclic alkyl group may be referred to as a "heterocyclic alkenyl group," or if a heterocyclic group contains at least one triple bond, a partially unsaturated heterocyclic alkyl group may be referred to as a "heterocyclic ynyl group."

[0029] As used herein, the term "substituted" means that one or more hydrogen atoms are substituted by groups that are not hydrogen or carbon atoms. Substituents include, but are not limited to, halogens, hydroxyl groups, alkoxy groups, -CN groups, alkenyl groups, carboxyl groups, C6-C14 aryl groups, heterocyclic groups, etc.

[0030] As used herein, the term "acrylic compound" refers to acrylic acid or its derivatives having a carboxylic acid group, including but not limited to acrylic acid, methacrylic acid, 2-carboxyethyl acrylate, itaconic acid, maleic acid, and fumaric acid, which may be used alone or in combination of two or more. The acrylic compound can undergo a ring-opening reaction with the epoxy groups of an epoxidized vegetable oil, thereby grafting it onto the epoxidized vegetable oil. (Meth)acrylic acid and / or 2-carboxyethyl acrylate are preferred. Acrylic acid and / or 2-carboxyethyl acrylate are even more preferred. Even more preferably, acrylic acid is used. The symbol

[0031] indicates a connection point.

[0032] According to one embodiment of the present invention, the total molar equivalent of the Norrish type II photoinitiator and the acrylic compound is 1 molar equivalent, based on the epoxy groups in 1 molar equivalent of the epoxidized vegetable oil. The ratio of the molar equivalent of the Norrish type II photoinitiator to the molar equivalent of the acrylic compound is preferably 5:1 to 1:5, more preferably 3:1 to 1:3.

[0033] According to one embodiment of the invention, a polymerization inhibitor is further used in the ring-opening reaction. Suitable polymerization inhibitors can be selected from phenols such as hydroquinone, hydroquinone monomethyl ether, mono-tert-butylhydroquinone, catechol, p-tert-butylcatechol, 2,6-di-tert-butyl-m-cresol, 2,6-di-tert-butyl-4-methylphenol, pyrogallol, and β-naphthol; quinones such as benzoquinone, 2,5-diphenyl-p-benzoquinone, methyl-p-benzoquinone, and p-dimethylquinone; nitro compounds or nitroso compounds such as nitrobenzene, m-dinitrobenzene, 2-methyl-2-nitrosopropane, α-phenyl-tert-butylnitrone, and 5,5-dimethyl-1-pyrroline-1-oxide; amines such as tetrachlorobenzoquinone-amine, diphenylamine, diphenylpicrylhydrazine, phenyl-α-naphthylamine, pyridine, and phenothiazine; and sulfides such as dithiobenzoyl sulfide and dibenzyltetrasulfide. These polymerization inhibitors can be used alone or in combination.

[0034] According to one embodiment of the present invention, the photoinitiator of the present invention has a structural unit of formula (I): (I) wherein R1 is selected from -COO-, -O-, -S-, -NR4-, -COR5-O- or -OR5-COO-; R2 and R3 are independently selected from C1-6 alkyl, C1-6 alkoxy, hydroxyl, halogen, -COO-C1-6 alkyl, C6-10 aryl or -NR4R4; or R2 and R3 together form -S-, -O-, -CO- or -C=C-; m is 0, 1, 2, 3 or 4; n is 0, 1, 2 or 3; R4 is independently selected from H or C1-6 alkyl; and R5 is selected from unsubstituted or substituted with one or more hydroxyl, halogen, C1-6 alkoxy, or acetoxy groups of C1-20 alkyl or C2-20 alkylene. If m is greater than 1, the R3 group may be part of a ring structure. If n is greater than 1, then the R2 group can be part of a ring structure. n and m are preferably 0. The present invention also provides a photoinitiator prepared by a ring-opening reaction of an epoxidized vegetable oil with one or more acrylic compounds and one or more compounds of formula (II), wherein R2, R3, R6, m, and n are as previously defined.

[0035] According to one embodiment of the present invention, a polymerization inhibitor, such as hydroquinone monomethyl ether, may be further added to the aforementioned ring-opening reaction.

[0036] The photoinitiator described above can be prepared by reacting according to the steps shown in the following illustrative process, wherein the epoxidized vegetable oil is exemplified by epoxidized soybean oil with the representative chemical formula shown on the left side of the reactants; the Norrish II type photoinitiator is exemplified by the representative chemical formula shown on the upper right side of the reactants, and acrylic acid is further used as a reactant: wherein R is the Norrish II type photoinitiator or the residue after the ring-opening reaction of acrylic acid with an epoxy group. In a specific embodiment of the present invention, the epoxidized soybean oil photoinitiator of the above process product is prepared by the following steps: In a reaction vessel, 1 molar equivalent of epoxidized soybean oil, and 6 molar equivalents of photoinitiator (e.g., benzophenone acid, BPA) and acrylic acid (the proportion can be adjusted arbitrarily, the total amount is 6 molar equivalents) are added, and the mixture is heated to 100°C under normal pressure and protected from light for 12 hours to obtain the epoxidized soybean oil photoinitiator (ESBO-ABPA).

[0037] According to one embodiment of the present invention, in the method for preparing the photoinitiator, the total molar equivalent of the Norrish type II photoinitiator and acrylic acid is approximately the total epoxy molar equivalent of the epoxy vegetable oil, based on the total molar equivalent of the epoxy vegetable oil. In one embodiment of the present invention, epoxidized soybean oil is used as the raw material for the epoxidized vegetable oil, and the total molar equivalent of the Norrish type II photoinitiator and acrylic acid is approximately 6 molar equivalents, based on 1 molar equivalent of the epoxidized soybean oil. The preferred range for the molar amount of the Norrish type II photoinitiator relative to the total molar amount of the Norrish type II photoinitiator is from 5% to 95%, more preferably from 30% to 70%, and most preferably from 40% to 60%.

[0038] Since the exact composition of vegetable oils is variable (depending on factors such as soil conditions, climate, and plant variety), the exact composition of epoxidized vegetable oils is also variable. Therefore, it is difficult to give a precise structure of the photoinitiator according to the present invention. An idealized structure is depicted in formula (III).

[0039] The photoinitiator is preferably based on formula (III): (III), wherein RA1, RB1, RA2, RB2, RA3, RB3, RA4, RB4, RA5, RB5, RA6 and RB6 are independently selected from , and, wherein the conditions are: (1) the total amount of and is 4 to 6, preferably 5 or 6, more preferably 6; (2) the total amount of is 1 to 5, preferably 2 or 3; (3) the total amount of is 1 to 5, preferably 2, 3 or 4, more preferably 3 or 4; (4) for each i, where i is 1 to 6: if RAi is or, then the corresponding RBi is; and (5) for each i, where i is 1 to 6: if RBi is or, then the corresponding RAi is. Therefore, in this preferred embodiment of the present invention, when RA1, RA2, RA3, RA4, RA5 or RA6 are respectively OR, then RB1, RB2, RB3, RB4, RB5 or RB6 are respectively OR; and when RB1, RB2, RB3, RB4, RB5 or RB6 are respectively OR, then RA1, RA2, RA3, RA4, RA5 or RA6 are respectively OR.

[0040] The photoinitiator of the present invention (e.g., ESBO-BPA) based on epoxy vegetable oil can photopolymerize commonly used industrial UV-curable resins (e.g., olefinic unsaturated curable compounds) under short-wavelength light irradiation (200 to 400 nm) to form a cured coating. These coatings can then be applied industrially, for example, as fiber optic coatings, inks, varnishes, or floor coatings. In low-mobility tests using a 500 MHz nuclear magnetic resonance (NMR) spectrometer, the inventors unexpectedly discovered that when the polymeric photoinitiator of the present invention (e.g., ESBO-BPA) is used to photopolymerize resin monomers, the polymeric photoinitiator of the present invention exhibits excellent low mobility and high conversion efficiency. Due to the excellent low mobility, the present invention can effectively reduce the possibility of human health hazards caused by the photoinitiator in the coating in industrial applications, especially in applications involving indirect food contact.

[0041] The present invention further provides a photoinitiator of formula (III): (III), wherein RA1, RB1, RA2, RB2, RA3, RB3, RA4, RB4, RA5, RB5, RA6 and RB6 are independently selected from , and, wherein the conditions are: (1) the total amount of and is 4 to 6, preferably 5 or 6, more preferably 6; (2) the total amount of is 1 to 5, preferably 2 or 3; (3) the total amount of is 1 to 5, preferably 2, 3 or 4, more preferably 3 or 4; (4) for each i, where i is 1 to 6: if RAi is or, then the corresponding RBi is; and (5) for each i, where i is 1 to 6: if RBi is or, then the corresponding RAi is. Therefore, if RA1, RA2, RA3, RA4, RA5 or RA6 are respectively OR, then RB1, RB2, RB3, RB4, RB5 or RB6 are respectively OR; and if RB1, RB2, RB3, RB4, RB5 or RB6 are respectively OR, then RA1, RA2, RA3, RA4, RA5 or RA6 are respectively OR.

[0042] The present invention further provides a photocurable composition comprising an olefinic unsaturated curable compound and a photoinitiator as described above.

[0043] As used herein, the term "olefinic unsaturated curable compound" means a compound containing a polymerizable carbon-carbon double bond. A polymerizable carbon-carbon double bond is a carbon-carbon double bond that can react with another carbon-carbon double bond in a polymerization reaction. Polymerizable carbon-carbon double bonds are generally selected from the group consisting of: acrylates (including cyanoacrylates), methacrylates, acrylamide, methacrylamide, styrene, maleic acid esters, trans-butenedioic acid esters, itconic acid esters, allyl, propenyl, vinyl, and combinations thereof.

[0044] According to one embodiment of the invention, the olefinic unsaturated curable compound may be selected from (meth)acrylate-functionalized monomers, (meth)acrylate-functionalized oligomers, amine-modified acrylates, and mixtures thereof. As used herein, the term "(meth)acrylate-functionalized monomer" means a monomer containing a (meth)acrylate group, particularly an acrylate group. The term "(meth)acrylate-functionalized oligomer" means an oligomer containing a (meth)acrylate group, particularly an acrylate group. The term "(meth)acrylate group" encompasses acrylate groups (-O-CO-CH=CH2) and methacrylate groups (-O-CO-C(CH3)=CH2).

[0045] The light-curable composition preferably comprises an oligomer and a reactive diluent. The oligomer is preferably a UV-curable oligomer, preferably selected from urethane (meth)acrylate, polyether urethane (meth)acrylate, polyester urethane (meth)acrylate, epoxy (meth)acrylate polyether acrylate, and polyester (meth)acrylate.

[0046] Due to viscosity considerations, the use of reactive diluents in this photocurable composition is generally beneficial. A reactive diluent is a compound that can reduce the viscosity of the formulation and can be copolymerized on a free radical basis. Various acrylic, methacrylic, or vinyl functional monomers can be used as reactive diluents. Suitable examples include diacrylates or dimethacrylates of diols or polyether glycols, such as propoxylated neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), diethylene glycol diacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, neopentyl glycol diacrylate, 1,4-butanediol diacrylate (e.g., SR213), alkyl oxidized aliphatic diacrylates (e.g., SR9209A), alkyl oxidized hexanediol diacrylates (e.g., Sartomer Co., Inc.'s SR561, SR562, SR563, SR564), polyethylene glycol (200) diacrylate (SR259), polyether glycol 200-diacrylate, PEG300 - Diacrylates, polypropylene glycol diacrylates, ethoxylated (3) bisphenol A-diacrylates, BDDA butanediol diacrylates, BDDMA butanediol dimethacrylates, or higher functional acrylates, such as trimethylolpropane triacrylate (TMPTA), ethoxylated trimethylolpropane triacrylate, TMP3EOTA ethoxylated (3) trimethylolpropane triacrylate, TMP6EOTA ethoxylated (6) trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol (4)-propoxylated triacrylate, pentaerythritol tetraacrylate, ethoxylated or propoxylated neopentyl glycol, propoxylated (4) glycerol triacrylate, trifunctional monomers, such as BASF's Laromer type or Allnex's Ebecryl 2047 or Ebecryl 12. Di-trimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate (Di-PEPA), dipentaerythritol hexaacrylate (DPHA). Examples of vinyl compounds are butanediol divinyl ether or the monofunctional compound N-vinylcaprolactam. Although monofunctional (meth)acrylates, such as lauryl (meth)acrylate and phenoxyethyl (meth)acrylate, are permitted, reactive diluents having at least two free radical curable vinyl unsaturated groups are preferred for low migration. Mixtures may also be used. The reactive diluent is preferably selected from the group consisting of mono-, di-, tri-, tetra-, penta-, and hexa-(meth)acrylates with a molecular weight of less than 800 g / mol, and any combination thereof.Relative to the total weight of the photocurable composition, the photocurable composition of the present invention may contain from 10% to 80% by weight, particularly from 15% to 75% by weight, and even more particularly from 20% to 70% by weight of (meth)acrylate functionalized oligomers. Relative to the total weight of the photocurable composition, the one or more reactive diluents having one or more, preferably two or more, free radical curable vinyl unsaturated groups may be present in the photocurable composition in an amount of at least 1% by weight, or at least 5% by weight, or at least 10% by weight, and in an amount of at most 85% by weight, or at most 80% by weight, or at most 75% by weight, or at most 70% by weight.

[0047] In a specific embodiment of the invention, the photocurable composition of the invention may further comprise an amine synergist. The amine synergist is introduced into the photocurable composition of the invention to synergize with the photoinitiator and / or reduce oxygen inhibition. The amine synergist is typically a tertiary amine. When used in conjunction with the photoinitiator, the tertiary amine provides an active hydrogen donor site for the excited triplet state of the photoinitiator, thus generating a reactive alkyl-amine radical, which can subsequently initiate polymerization. The tertiary amine is also capable of converting non-reactive peroxide species formed by the reaction between oxygen and the radical into reactive alkyl-amine radicals, thus reducing the effect of oxygen on curing.

[0048] The reaction mechanism of benzophenone and amine synergist to generate free radicals at 200~400nm can be shown in the following process.

[0049] Examples of suitable amine synergists include low molecular weight tertiary amines (i.e., those with a molecular weight less than 200 g / mol), such as triethanolamine and N-methyldiethanolamine (MDEA). Other types of amine synergists are aminobenzoic acid esters. Examples of aminobenzoic acid esters include ethyl 4-(dimethylamino)benzoate (EDB), amyl 4-(dimethylamino)benzoate, 2-ethylhexyl 4-(dimethylamino)benzoate, and 2-butoxyethyl 4-(dimethylamino)benzoate (BEDB). In addition to these amine synergists, acrylated amine synergists, such as AgiSyn™002, AgiSyn™003, and / or AgiSyn™008, may be used appropriately. In addition to these amine synergists, oligomeric amine synergists, such as AgiSyn™701 and / or AgiSyn™703, may be used. An example of an oligomeric dimethylaminobenzoate is Omnipol ASA. Amine synergists can also be incorporated into the photoinitiator according to the invention. In particular, when acid-functionalized amine synergists such as dimethylaminobenzoic acid are used, they can be readily incorporated during the synthesis of the photoinitiator. Therefore, according to one embodiment of the invention, the photoinitiator may comprise Norrish type II groups, acrylic compounds, and amine synergist groups.

[0050] According to one embodiment of the present invention, in a photocurable composition, the photoinitiator may be in the range of about 0.01 to about 0.1 molar equivalents (e.g., about 0.05 molar equivalents) based on the total amount of the olefinic unsaturated curable compound being 1 molar equivalent; and the amine synergist may be in the range of about 0.03 to about 0.3 molar equivalents (e.g., about 0.15 molar equivalents).

[0051] The examples disclosed herein illustrate embodiments of the present invention and explain its technical features, but are not intended to limit the scope of protection of the present invention. Any changes or equivalent arrangements that can be easily made by a person skilled in the art to which this invention pertains are within the scope of protection claimed by the present invention, and the scope of protection of the present invention shall be determined by the scope of the patent application. Comparative Experiment 1: Preparation of ESBO-BPA

[0052] Weigh 1 gram (1.025 mmol) of epoxidized soybean oil and 1.392 gram (6.154 mmol) of 2-benzoylbenzoic acid and add them to a 100 ml single-necked round-bottom flask. Heat to 100°C and react under normal pressure in the dark for 12 hours to obtain the epoxidized soybean oil photoinitiator (ESBO-BPA, which may contain structural components illustrated by the following chemical formulas). Comparative Experiment 2: Preparation of BP acrylate (BPHEA)

[0053] Under nitrogen atmosphere and at 0°C, a solution of 0.912 g of dicyclohexylcarbodiimide in CH₂Cl was slowly added to a stirred mixture of 0.512 g hydroxyethyl acrylate, 1.0 g 2-benzoylbenzoic acid, and 0.054 g 4-dimethylaminopyridine in CH₂Cl₂. After the addition was complete, the temperature was raised to room temperature and the reaction mixture was stirred overnight. Next, the reaction mixture was filtered and washed with 1 mol / L NaHCO₃ aqueous solution, saturated NaCl solution, and distilled water. After evaporating the solvent, the product was purified by silica gel column chromatography (ethyl acetate / hexane = 1:15) to obtain BPHEA. Example 1: Preparation of ESBO-ABPA

[0054] Weigh 1 gram (1.025 mmol) of epoxidized soybean oil, 0.696 gram (3.078 mmol) of 2-benzoic acid, 0.222 gram (3.078 mmol) of acrylic acid, and 0.002 gram of the polymerization inhibitor monomethyl ether of hydroquinone (MEHQ) and add them to a 100 ml single-necked round-bottom flask. React at 100°C and atmospheric pressure in the dark for 12 hours to obtain epoxidized soybean oil acrylate photoinitiator (ESBO-ABPA, which may contain structural components illustrated by the following chemical formula). Structural identification using a 500 MHz nuclear magnetic resonance (NMR) instrument confirmed the successful preparation of the aforementioned epoxidized soybean oil photoinitiator (ESBO-BPA) and epoxidized soybean oil acrylate photoinitiator (ESBO-ABPA).

[0055] The glass transition temperature (Tg) of the polymeric photoinitiator was measured using differential scanning calorimetry (DSC). The tests revealed that the glass transition temperatures of the epoxidized soybean oil photoinitiator (ESBO-BPA) and the epoxidized soybean oil acrylate photoinitiator (ESBO-ABPA) were -1.84℃ and -21.46℃, respectively. Example 2: Synthesis of Thin Film Polymers

[0056] Tripropylene glycol diacrylate (TPGDA), 2-hydroxyethyl acrylate (HEA), and lauryl acrylate (LA) monomers were photopolymerized within 5 seconds under short-wavelength light irradiation (365 nm) with 1 molar equivalent of a photoinitiator (i.e., the aforementioned ESBO-BPA or ESBO-ABPA) and 0.15 molar equivalent of N-methyldiethanolamine as an amine synergist. This yielded a thin-film polymer of the monomer. Example 3: Conversion Rate Test

[0057] The monomer conversion rate was tested using Fourier-transform infrared spectroscopy (FTIR). The conversion rate was tested as follows: Tripropylene glycol diacrylate was used as the monomer, and its Fourier-transform infrared spectra before and after curing were measured. The conversion rate could be calculated from the ratio of carbonyl to propylene groups. After testing, the conversion rates of both epoxidized soybean oil photoinitiator (ESBO-BPA) and epoxidized soybean oil acrylate photoinitiator (ESBO-ABPA) were 99.9%. Data shows that this photoinitiator can achieve a high reactivity effect. Example 4: Mobility Test

[0058] Using the obtained tripropylene glycol diacrylate resin as the test resin, the cured resin film was immersed in acetonitrile (ACN) and stirred at room temperature for 4 hours. After filtering the sample, mesitylene was added to the liquid as an internal standard. The migration rate could be calculated by the integral ratio of mesitylene to photoinitiator using nuclear magnetic resonance. After testing, the migration rates of epoxidized soybean oil photoinitiator (ESBO-BPA) and epoxidized soybean oil acrylate photoinitiator (ESBO-ABPA) were 8.7% and 0.8%, respectively, while the migration rates of conventional benzophenone (BP) and BPHEA were 87% and 19%, respectively. The results are shown in Table 1. Table 1 Photoinitiator Migration rate (%) Migration reduction factor during acrylate esterification Example 1 ESBO-ABPA 0.8 10.9 times Comp 1 ESBO-BPA 8.7 Comp 2 BPHEA 19 4.6 times Comp 3 BP 87

[0059] Experimental results show that significantly low migration levels, down to 0.8%, can be achieved using the epoxidized soybean oil-acrylate photoinitiator of the present invention. This finding is particularly noteworthy when considering the comparative effect of benzophenone acrylate esterification: acrylate esterification of the epoxidized soybean oil (ESBO) photoinitiator resulted in a migration reduction factor of nearly 11-fold, despite the already low initial migration value of the ESBO photoinitiator. In contrast, acrylate esterification of the benzophenone photoinitiator produced a migration reduction factor of 4.6-fold (or nearly 5-fold). This significant difference in migration reduction factor (11-fold vs. 5-fold) indicates an unexpected synergistic effect from the combination of ESBO and acrylate esterification for obtaining a low-migration photoinitiator.

Claims

1. A photoinitiator prepared by ring-opening reaction of epoxidized vegetable oil with one or more Norrish type II photoinitiators having carboxylic acid groups, hydroxyl groups, thiol groups and / or amine groups and one or more acrylic compounds.

2. The photoinitiator of claim 1, wherein the epoxidized vegetable oil is epoxidized soybean oil.

3. The photoinitiator of claim 1 or 2, wherein the sum of the molar equivalents of the Norrish type II photoinitiator and the acrylic compound is 1 molar equivalent, with the epoxy group in the epoxy vegetable oil being 1 molar equivalent.

4. The photoinitiator of claim 1 or 2, wherein the molar equivalent ratio of the Norrish II type photoinitiator to the molar equivalent ratio of the acrylic compound is 5:1 to 1:

5.

5. The photoinitiator of claim 1 or 2, having a structural unit of formula (I): (I) wherein R1 is selected from -COO-, -O-, -S-, -NR4-, -COR5-O- or -OR5-COO-; R2 and R3 are independently selected from C1-6 alkyl, C1-6 alkoxy, hydroxyl, halogen, -COO-C1-6 alkyl, C6-10 aryl or -NR4R4; or R2 and R3 together form -S-, -O-, -CO- or -C=C-; m is 0, 1, 2, 3 or 4; n is 0, 1, 2 or 3; R4 is independently selected from H or C1-6 alkyl; and R5 is selected from unsubstituted or substituted with one or more hydroxyl, halogen, C1-6 alkoxy, or acetoxy C1-20 alkyl or C2-20 alkenyl, The conditions are that if m is greater than 1, then the R3 group can be part of the ring structure, and / or if n is greater than 1, then the R2 group can be part of the ring structure.

6. The photoinitiator of claim 5, wherein the total molar equivalent of the Norrish type II photoinitiator and the acrylic compound is 1 molar equivalent, with the epoxy group in the epoxy vegetable oil being 1 molar equivalent, and the ratio of the molar equivalent of the Norrish type II photoinitiator to the molar equivalent of the acrylic compound is 5:1 to 1:

5.

7. The photoinitiator as requested in item 5, where n and m are 0.

8. A photoinitiator prepared by ring-opening reaction of an epoxidized vegetable oil with one or more acrylic compounds and one or more compounds of formula (II), wherein (II) R2 and R3 are independently selected from C1-6 alkyl, C1-6 alkoxy, hydroxyl, halogen, -COO-C1-6 alkyl, C6-10 aryl or -NR4R4; or R2 and R3 together form -S-, -O-, -CO- or -C=C-; m is 0, 1, 2, 3 or 4; n is 0, 1, 2 or 3; R6 is selected from -OH, -SH, -NR4R4, -COOH, -COR5OH or -OR5COOH, wherein R4 is independently selected from H or C1-6 alkyl; and R5 is selected from unsubstituted or substituted with one or more hydroxyl, halogen, C1-6 alkoxy, or acetoxy groups of C1-20 alkyl or C2-20 alkylene. The conditions are that if m is greater than 1, then the R3 group can be part of the ring structure, and / or if n is greater than 1, then the R2 group can be part of the ring structure.

9. The photoinitiator as requested in item 8, where n and m are 0.

10. The photoinitiator of any one of claims 1, 2 and 8, wherein a polymerization inhibitor is further added in the ring-opening reaction.

11. A photoinitiator as claimed in any of claims 1, 2 and 8, wherein the one or more acrylic compounds are selected from the group consisting of methacrylic acid, acrylic acid and 2-carboxyethyl acrylate.

12. The photoinitiator of any one of claims 1, 2 and 8, wherein the acrylic compound is acrylic acid.

13. The photoinitiator of any of claims 1, 2 and 8, wherein the amine synergist is incorporated into the photoinitiator.

14. A photoinitiator as claimed in any of claims 1, 2 and 8, wherein the photoinitiator has formula (III): (III), wherein RA1, RB1, RA2, RB2, RA3, RB3, RA4, RB4, RA5, RB5, RA6 and RB6 are independently selected from , and , provided that (1) the total of and is 4 to 6; (2) the total of is 1 to 5; (3) the total of is 1 to 5; (4) for each i, where i is 1 to 6: if RAi is or , then the corresponding RBi is; and (5) for each i, where i is 1 to 6: if RBi is or , then the corresponding RAi is; wherein R1 is selected from -COO-, -O-, -S-, -NR4-, -COR5-O- or -OR5-COO-; R2 and R3 are independently selected from C1-6 alkyl, C1-6 alkoxy, hydroxy, halogen, -COO-C1-6 alkyl, C6-10 aryl or -NR4R4; or R2 and R3 together form -S-, -O-, -CO- or -C=C-; m is 0, 1, 2, 3 or 4.

15. The photoinitiator of claim 14, wherein (1) the total amount of and is 5 or 6; (2) the total amount of is 2 or 3; and (3) the total amount of is 2, 3 or 4.

16. The photoinitiator of claim 14, wherein the total amount of (1) and is 6; the total amount of (2) is 2 or 3; and the total amount of (3) is 3 or 4.

17. A photocurable composition comprising an olefinic unsaturated curable compound and a photoinitiator as claimed in any one of claims 1 to 16.

18. The light-curable composition of claim 17, wherein the light-curable composition comprises (meth)acrylate-functionalized oligomers and (meth)acrylate-functionalized monomers.