Light base

Abstract

The present invention relates to the use of a triphenylphosphonium carboxylate of the following formula (I) as a photobase generator in a photopolymerizable composition comprising at least one monomer for the preparation of a photopolymer by curing the composition by irradiation with light of a suitable wavelength: wherein R1 and R2 are each independently selected from-H and-OCH3, at least one of R1 and R2 represents-OCH3, and wherein R3 is selected from the group consisting of-H and-CH3 and X is absent or selected from the group consisting of chemical bonds:-CH2-,-O-CH2-,-CH2-O-,-C (= O)-,-O-, and-S-; and the corresponding novel triphenylphosphonium carboxylate salts of formula (I).

Description

[0001] This invention relates to the use of novel carboxylates as photoalkalizing agents in photopolymerizable compositions. Existing technology

[0002] The concept of organic photo-basin generators (PBGs) was first proposed in 1990 by Cameron and Frechet, who used photo-instantaneous carbamate groups to generate basic amines (J. C. Cameron, J. M. J. Frechet, J. Org. Chem. 55, 5919-5922 (1990)). Subsequent reports described the photoinduced release of primary, secondary, or tertiary amines, but these amines were weakly basic and therefore less efficient in activating anionic polymerization. The use of salts for basin generation first appeared in a 1998 report in the form of quaternary ammonium salts (Sarker et al., J. Phys. Chem. A102, 5375-5382 (1998)), which significantly improved the storage stability of formulations. In recent years, many carboxylates have been described as counterions of the base in the salts used as PBGs. For example, one article discloses several salts, including 2-(3-benzoylphenyl)propionate or 2-(3-benzoylphenyl)acetate, 2-(xanthonone-2-yl)propionate or 2-(xanthonone-2-yl)acetate, and 2-(thioxanthonone-2-yl)propionate or 2-(thioxanthonone-2-yl)acetate, as carboxylate-functionalized chromophores of PBG. These salts are characterized by absorption maxima at short wavelengths below 400 nm, thus making them suitable for curing formulations by UV irradiation. As cations of the salts, fully alkylated guanidines and phosphononitriles are particularly mentioned (Zivic et al., Angew. Chem. Int. Ed. 58(31), 10410-10422(2019)).

[0003] Recently, triarylphosphine was also disclosed as a nucleophilic catalyst for oxa-Michael addition, specifically investigating the catalytic effects of triphenylphosphine, monomethoxylated triphenylphosphine, and trimethoxylated triphenylphosphine on 16 different Michael donor and acceptor combinations. The use of tri(4-methoxyphenyl)phosphine tended to yield the best conversion, but in almost half of the experiments, there was little difference between the three catalysts (Fischer et al., Beilstein J. Org. Chem. 17, 1689-1697 (2021)).

[0004] Against this backdrop, the object of the present invention is to prepare novel carboxylates and their use as photoalkali-generating agents in photopolymerizable compositions.

[0005] Invention Disclosure

[0006] In a first aspect, the present invention achieves this objective by providing a novel photopolymerization method, namely, the use of a triphenylphosphonic acid salt of formula (I) as a photoalkalizing agent in a photopolymerizable composition comprising at least one monomer for preparing a photopolymer by curing the composition with light of a suitable wavelength:

[0007]

[0008] Where R 1 and R 2 Each is independently selected from -H and -OCH3, wherein on each of the three phenyl groups, R 1 and R 2 At least one of them represents -OCH3, and where R 3 Selected from -H and -CH3 and X is absent or selected from chemical bonds: -CH2-, -O-CH2-, -CH2-O-, -C(=O)-, -O- and -S-.

[0009] In fact, the inventors have discovered that salts composed of the triphenylphosphonium cation as defined above and anions of phenylacetic acid or phenylpropionic acid derivatives (all of which were first prepared by the inventors) are sometimes very suitable as photoalkalizing agents, as clearly demonstrated in the examples below. However, most surprisingly, salts formed from the same triphenylphosphonium cation but with other anions, or from the same carbonate anion but with other cations, sometimes prove completely unsuitable under the same photopolymerization conditions, or even fail to induce any conversion of the reactants.

[0010] According to the present invention, the conversion has been achieved even using only monomethoxylated phenyl groups, wherein the methoxy group is located at the ortho position (i.e., -OCH3 as R). 1 ) compared to the position located at the para (i.e., -OCH3 as R) 2 This provides slightly better results. However, the triphenylphosphonium cation with polymethoxylated phenyl groups is significantly superior. Therefore, in the preferred embodiment, at least one R group is present on each of the three phenyl groups. 1 Represented by -OCH3, more preferably two R 1 Represents -OCH3, especially R 1 and R 2 Both represent -OCH3. That is to say, the phosphonium cation of the salt is preferably tris(2-methoxyphenyl)phosphonium cation, more preferably tris(2,6-dimethoxyphenyl)phosphonium cation, and especially tris(2,4,6-trimethoxyphenyl)phosphonium cation.

[0011] Regarding the carboxylate anion, X is absent or selected from the chemical bonds -O- and -S- in the preferred embodiment. More preferably, it is the anion of one of the following carboxylic acids: 2-(3-benzoylphenyl)propionic acid (ketoprofen) or 2-(3-benzoylphenyl)acetic acid, 2-(xanthonone-2-yl)propionic acid or 2-(xanthonone-2-yl)acetic acid, or 2-(thioxanthonone-2-yl)propionic acid or 2-(thioxanthonone-2-yl)acetic acid. In particular, the photoalkali-generating agents are selected from the following triphenylphosphonic carboxylates: tris(2,6-dimethoxyphenyl)phosphon-2-(3-benzoylphenyl)propionate, tris(2,4,6-trimethoxyphenyl)phosphon-2-(3-benzoylphenyl)propionate, tris(2,6-dimethoxyphenyl)phosphon-2-(xanthonone-2-yl)acetate, tris(2,4,6-trimethoxyphenyl)phosphon-2-(xanthonone-2-yl)acetate, tris(2,6-dimethoxyphenyl)phosphon-2-(thioxanthonone-2-yl)acetate, or tris(2,4,6-trimethoxyphenyl)phosphon-2-(thioxanthonone-2-yl)acetate, and excellent results have been obtained using them.

[0012] There are no particular limitations on the type of curing of the photopolymer composition. However, in a preferred embodiment, the photopolymer composition can be coated onto a substrate and cured by irradiation to form a coating, or cured layer by layer by irradiation in an additive manufacturing process to form a three-dimensional object. In both cases, curing can be carried out under heat, so that the resulting photopolymer can be subjected to thermal post-treatment to optimize mechanical properties.

[0013] In this case, as an additive manufacturing process, thermolithography is preferably performed at a temperature of at least 50°C, at least 70°C, or at least 80°C, where a high conversion rate can be achieved in a particularly short time.

[0014] The application of the invention is not limited to Michael addition-based polymerization, but in a preferred embodiment, at least two monomers polymerizable by Michael addition reaction are used in the photopolymerizable composition. These monomers are more preferably polymerizable by oxa-en-addition, oxa-in-addition, or C-C addition reactions of CH-active compounds, particularly by oxa-en-addition polymerization. Particularly preferred examples of monomers are combinations of (meth)acrylates or (meth)acrylamides and alcohols, especially with respect to additive manufacturing processes, preferably converted in solvent-free bulk form in the presence of a photoalkali-generating agent.

[0015] In addition, the photopolymerizable composition may also contain at least one photosensitizer (preferably 9,10-dibutoxyanthracene) and / or at least one free radical scavenger (preferably 2,6-di-tert-butyl-p-cresol (butyl hydroxytoluene, BHT)) to improve the reaction rate and conversion and enhance the storage stability of the composition.

[0016] In a second aspect, the present invention also provides a photopolymer that can be obtained by curing the photopolymerizable composition as described above.

[0017] In a third aspect, the present invention also relates to a novel salt, namely a triphenylphosphonic carboxylate of formula (I), which is prepared for the first time by the inventors and can be used as a photoalkali-generating agent in the method according to the invention.

[0018]

[0019] Where R 1 and R 2 Each is independently selected from -H and -OCH3, and R is selected from R. 3 The salt is selected from -H and -CH3 and X is absent or selected from -O- and -S-, wherein the salt is specifically selected from the following group:

[0020] Tris(4-methoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (1):

[0021]

[0022] Tris(2-methoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (2):

[0023]

[0024] Tris(2,6-dimethoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (3):

[0025]

[0026] Tris(2,4,6-trimethoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (4):

[0027]

[0028] Tris(2,4,6-trimethoxyphenyl)phosphonium-2-(xanthone-2-yl)acetate (5):

[0029]

[0030] Tris(2,4,6-trimethoxyphenyl)phosphonium-2-(thioxanone-2-yl)acetate (6):

[0031]

[0032] Finally, the present invention also relates to the use of one of these novel triphenylphosphonic acid salts as a photoalkali-generating agent in a photopolymerizable composition for the preparation of photopolymers. Brief description of the attached diagram

[0034] The invention will now be described in more detail with reference to specific examples and accompanying drawings, which show:

[0035] Figure 1 This is a diagram illustrating the reaction conversion rates achieved at different reaction temperatures in Example 14.

[0036] Figure 2 This is a photodynamic DSC diagram of photopolymerization performed in Example 16.

[0037] Figure 3 A- Figure 3 C Figure 4 A- Figure 4 B Figure 5 A- Figure 5 B and Figure 6 A- Figure 6 B is a photograph of four three-dimensional objects prepared by thermolithography in Example 22.

[0038] Example

[0039] Synthesis Examples – Examples 1 to 6, Comparison Examples 1 to 5

[0040] To prepare the new phosphonocarboxylate salts, commercially available reagents were primarily used, namely the corresponding triphenylphosphine (or BINAP in Comparative Example 2, i.e., 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) and the corresponding carboxylic acid (or triethylammonium tetraphenylborate in Comparative Example 3). These reagents were dried under high vacuum and used to form the salts without further purification. For Comparative Examples 3, 5, and 6, the corresponding anionic acids (i.e., triethylammonium tetraphenylborate, 9-oxo-9H-xanthen-2-acetic acid) were provided. Or 9-oxo-9H-thioxanthen-2-acetic acid (9-Oxo-9H-thioxanthen-2- Preparation, purification, and drying were carried out according to the literature.

[0041] In each case, the salt is formed by adding a solution or suspension of acid to anhydrous THF (abs. THF), adding an equimolar amount of base (or half the molar amount of the bisphosphine ligand BINAP for Comparative Example 2), stirring for 1 hour, removing the solvent under high vacuum, washing the residue with anhydrous solvent, and drying the salt under high vacuum. For the examples according to the invention, quantitative conversion (>99% of the theoretical value, “quantitative”) is achieved in most cases. In each case, characterization is performed by NMR spectroscopy.

[0042] Compare Example 1 (V1)

[0043] Unsubstituted triphenylphosphine reacts with 2-(3-benzoylphenyl)propionic acid to yield triphenylphosphine-2-(3-benzoylphenyl)propionate (V1):

[0044]

[0045]

[0046] 2-(3-benzoylphenyl)propionic acid (1 equivalent, 2 mmol, 0.509 g) and triphenylphosphine (1 equivalent, 2 mmol, 0.525 g) were dissolved in anhydrous THF (6 ml). After solvent removal, a viscous solid residue was obtained. The residue was washed with petroleum ether and dried to give a white solid (yield: 0.896 g, 87% of theoretical value).

[0047] 1 H-NMR (600MHz, C6D6) δ: 7.85 (t, 1H), 7.70 (dd, 2H), 7.54 (dt, 1H), 7.47-7.33 (m, 6H), 7.2 3(dt,1H), 7.14-7.09(m,1H), 7.08-7.00(m,11H), 6.98(t,1H), 3.40(q,1H), 1.22(d,3H).

[0048] 13 C-NMR (151MHz, C6D6) δ: 195.31,180.22,140.21,138.26,137.73,137.63,133.91,133.78,131 .96,131.07,129.99,129.42,128.98,128.54,128.51,128.46,128.42,128.08,45.04,17.74.

[0049] 31 P-NMR (243MHz, C6D6) δ: -5.41.

[0050] Example 1

[0051] Tris(4-methoxyphenyl)phosphine reacts with 2-(3-benzoylphenyl)propionic acid to yield tris(4-methoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (1):

[0052]

[0053] 2-(3-benzoylphenyl)propionic acid (1 equivalent, 1.8 mmol, 0.458 g) and tris(4-methoxyphenyl)phosphine (1 equivalent, 1.8 mmol, 0.634 g) were dissolved in anhydrous THF (7 ml). After solvent removal, a white solid residue was obtained. The residue was washed with THF and dried to obtain a white solid (yield: 1.092 g, quantitative).

[0054] 1 H-NMR (600MHz, C6D6) δ: 7.85 (s, 1H), 7.70 (dd, 2H), 7.53 (dt, 1H), 7.41 (dd, 5H), 7.23 (dt, 1H), 7.13-7 .07(m,1H),7.05-7.00(m,4H),6.96(t,1H),6.76-6.71(m,5H),3.38(q,1H),3.23(s,9H),1.21(d,3H).

[0055] 13 C-NMR (151MHz, C6D6) δ: 194.42, 178.94, 159.48, 139.46, 137.39, 136.89, 134.40, 134.26, 131.08 ,130.21,129.11,128.75,128.58,128.09,127.55,127.19,113.43,113.38,53.49,44.17,16.93.

[0056] 31 P-NMR (243MHz, C6D6) δ: -10.32.

[0057] Example 2

[0058] Tris(2-methoxyphenyl)phosphine reacts with 2-(3-benzoylphenyl)propionic acid to yield tris(2-methoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (2):

[0059]

[0060] 2-(3-benzoylphenyl)propionic acid (1 equivalent, 1.8 mmol, 0.458 g) and tris(2-methoxyphenyl)phosphine (1 equivalent, 1.8 mmol, 0.634 g) were dissolved in anhydrous THF (7 ml). After solvent removal, a viscous solid residue was obtained. The residue was washed with ether and dried to give a white solid (yield: 0.900 g, 82% of theoretical value).

[0061] 1H-NMR (600MHz, C6D6) δ: 7.85 (s, 1H), 7.72-7.67 (m, 2H), 7.53 (dt, 2H), 7.23 (dt, 1H), 7.12-7.07 (m, 6H ),7.06-7.00(m,2H),6.97(t,1H),6.76(td,3H),6.51(m,3H),3.39(q,1H),3.17(s,9H),1.21(d,3H).

[0062] 13 C-NMR (151MHz, C6D6) δ: 195.29, 179.91, 161.85, 161.73, 140.28, 138.26, 137.74, 134.05, 131.96, 13 1.08,129.95,129.77,128.96,128.42,128.08,125.54,125.43,120.94,110.06,54.76,45.03,17.77.

[0063] 31 P-NMR (243MHz, C6D6) δ: -37.31.

[0064] Example 3

[0065] Tris(2,6-dimethoxyphenyl)phosphine reacts with 2-(3-benzoylphenyl)propionic acid to yield tris(2,6-dimethoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (3):

[0066]

[0067] 2-(3-benzoylphenyl)propionic acid (1 equivalent, 1.5 mmol, 0.381 g) and tris(2,6-dimethoxyphenyl)phosphine (1 equivalent, 1.5 mmol, 0.664 g) were dissolved in anhydrous THF (7 ml). After solvent removal, a white solid residue was obtained. The residue was washed with THF and dried to obtain a white solid (yield: 1.045 g, quantitative).

[0068] 1 H-NMR (600MHz, C6D6) δ: 7.92 (d, 1H), 7.74-7.70 (m, 2H), 7.55 (dt, 1H), 7.38 (dt, 1H), 7.15-7.10 (tt,3H),7.03(m,3H),7.10-7.02(t,1H),6.31(dd,6H),3.58(q,1H),3.22(s,18H),1.32(d,3H).

[0069] 13 C-NMR (151MHz, C6D6) δ: 195.44, 178.09, 162.73, 162.67, 141.32, 138.10, 137.84, 131.89, 13 1.41,129.98,129.49,128.64,128.59,128.33,128.03,127.97,104.35,55.42,45.40,18.25.

[0070] 31 P-NMR (243MHz, C6D6) δ: -37.31.

[0071] Example 4

[0072] Tris(2,4,6-trimethoxyphenyl)phosphine reacts with 2-(3-benzoylphenyl)propionic acid to yield tris(2,4,6-trimethoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (4):

[0073]

[0074] 2-(3-benzoylphenyl)propionic acid (1 equivalent, 2.38 mmol, 0.605 g) and tris(2,4,6-trimethoxyphenyl)phosphine (1 equivalent, 2.38 mmol, 1.266 g) were dissolved in anhydrous THF (9 ml). After solvent removal, a beige viscous solid residue was obtained. The residue was washed with diethyl ether and dried to give a light beige solid (yield: 1.252 g, 67% of theoretical value).

[0075] 1 H-NMR (600MHz, C6D6) δ: 8.05 (t, 1H), 7.79-7.74 (m, 2H), 7.64 (dt, 1H), 7.57 (dt, 1H), 7.16-7.1 0(m,3H),7.10-7.03(m,3H),6.11(d,6H),3.88(q,1H),3.42(s,9H),3.28(s,18H),1.48(d,3H).

[0076] 13 C-NMR (151MHz, C6D6) δ: 195.82, 177.51, 163.72, 163.67, 143.51, 138.07, 137.69, 132.09, 131. 73,130.07,129.71,129.20,128.10,127.94,91.49,55.60,55.48,55.23,54.62,46.70,19.12.

[0077] 31 P-NMR (243MHz, C6D6) δ: -64.88.

[0078] Comparison Example 2

[0079] 2,2'-bis(diphenylphosphino)-1,1'-binaphthylene reacts with 2-(3-benzoylphenyl)propionic acid to yield 2,2'-bis(diphenylphosphono)-1,1'-binaphthylene-bis[2-(3-benzoylphenyl)propionate](V2):

[0080]

[0081] 2-(3-benzoylphenyl)propionic acid (2 equivalents, 1.6 mmol, 0.4068 g) and 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (1 equivalent, 0.8 mmol, 0.498 g) were dissolved in anhydrous THF (5 ml). After solvent removal, a white solid residue was obtained. The residue was washed with THF and dried to give a white solid (yield: 0.690 g, 76% of theoretical value).

[0082] 1 H-NMR(400MHz,C6D6)δ:7.95(t,2H),7.89-7.70(m,7H),7.70-7.43(m,11H),7.41-6.93(m,25H),6.78(m,2H),3.48(q,2H),1.31(d,6H).

[0083] 13 C-NMR (101MHz, C6D6) δ: 195.24, 180.07, 140.20, 138.29, 137.75, 134.56, 134.34, 133.08, 132.98 ,132.88,131.92,131.03,129.94,129.39,128.96,128.39,128.06,126.35,125.72,45.01,17.18.

[0084] 31 P-NMR (162MHz, C6D6) δ: -15.04.

[0085] Comparison Example 3

[0086] Tris(2,4,6-trimethoxyphenyl)phosphine reacts with triethylammonium tetraphenylborate to yield tris(2,4,6-trimethoxyphenyl)phosphonium tetraphenylborate (V3):

[0087]

[0088]

[0089] According to the literature (Faulkner et al., J. Am. Chem. Soc. 137(22), 7224-7230(2015)), triethylammonium tetraphenylborate (1 equivalent, 1.0 mmol, 0.421 g) and tris(2,4,6-trimethoxyphenyl)phosphine (1 equivalent, 1.0 mmol, 0.535 g) were prepared and dissolved in anhydrous THF (7 ml). After solvent removal, a white solid residue was obtained. The residue was washed with ethane and dried to obtain a white solid (yield: 0.464 g, 54% of theoretical value).

[0090] 1 ¹H-NMR (600MHz, acetone-d6) δ: 7.35 (m, 8H), 6.94 (t, 8H), 6.79 (tt, 4H), 6.38 (d, 6H), 3.91 (s, 9H), 3.77 (s, 18H).

[0091] 13 C-NMR (151MHz, C6D6) δ: 205.32, 164.26, 136.16, 125.09, 121.36, 91.45, 91.40, 56.11, 55.40.

[0092] 31 P-NMR (243MHz, acetone-d6) δ: -52.03.

[0093] Comparison Example 4

[0094] Tris(2,4,6-trimethoxyphenyl)phosphine reacts with benzoylcarboxylic acid to yield tris(2,4,6-trimethoxyphenyl)phosphonium phenylacetoxylate (V4):

[0095]

[0096] Benzoyl carboxylic acid (1 equivalent, 1.0 mmol, 0.150 g) and tris(2,4,6-trimethoxyphenyl)phosphine (1 equivalent, 1.0 mmol, 0.533 g) were dissolved in anhydrous THF (3 ml). After solvent removal, a beige viscous solid residue was obtained. The residue was washed with THF and dried to obtain a light beige viscous solid (yield: 0.683 g, quantitative).

[0097] 1¹H-NMR (400MHz, acetone-d6) δ: 7.90–7.83 (m, 2H), 7.46–7.38 (m, 1H), 7.32 (tt, 2H), 6.15 (d, 2H), 3.71 (d, 9H), 3.53 (s, 18H).

[0098] 13 C-NMR (101MHz, acetone-d6) δ: 170.08, 163.19, 132.52, 129.39, 128.19, 91.35, 91.30, 55.79, 55.41, 55.08.

[0099] Comparison Example 5

[0100] Tris(2,4,6-trimethoxyphenyl)phosphine reacts with phthalimide acetate to yield tris(2,4,6-trimethoxyphenyl)phosphine phthalimide acetate (V5):

[0101]

[0102] N-phthaloylglycine (1 equivalent, 1.0 mmol, 0.205 g) and tris(2,4,6-trimethoxyphenyl)phosphine (1 equivalent, 1.0 mmol, 0.533 g) were dissolved in anhydrous THF (3 ml). After solvent removal, a beige solid residue was obtained. The residue was washed with THF and dried to obtain a light beige solid (yield: 0.738 g, quantitative).

[0103] 1 ¹H-NMR (400MHz, acetone-d6) δ: 7.89–7.81 (m, 4H), 6.25–6.14 (m, 6H), 4.34 (s, 2H), 3.83 (s, 9H), 3.59 (s, 18H).

[0104] 13 C-NMR (101MHz, acetone-d6) δ: 168.74, 167.56, 163.54, 163.47, 133.99, 122.83, 91.18, 91.16, 55.46, 54.73, 40.96.

[0105] Example 5

[0106] Tris(2,4,6-trimethoxyphenyl)phosphine reacts with 2-(xanthonone-2-yl)acetic acid to yield tris(2,4,6-trimethoxyphenyl)phosphonium-2-(xanthonone-2-yl)acetate (5):

[0107]

[0108] According to the literature (Blake et al., Org Lett. 8(6), 1057-1060 (2006), except that K2CO3 was used instead of Cs2CO3), 9-oxo-9H-xanthon-2-acetic acid (1 equivalent, 0.2 mmol, 51 mg) and tris(2,4,6-trimethoxyphenyl)phosphine (1 equivalent, 0.2 mmol, 107 mg) were dissolved in anhydrous THF (0.6 ml). After removing the solvent, a beige solid residue was obtained. The residue was washed with THF and dried to obtain a light beige solid (yield: 158 mg, quantitative).

[0109] 1 ¹H-NMR (400 MHz, acetone-d6) δ: 8.13 (dd, 1H), 8.06 (d, 1H), 7.77–7.66 (m, 2H), 7.51–7.40 (m, 2H), 7.38–7.29 (m, 1H), 6.03 (s, 6H), 3.66 (s, 9H), 3.61 (s, 2H), 3.39 (s, 18H).

[0110] 13 C-NMR (101 MHz, acetone-d6) δ: 171.64, 163.39, 136.66, 135.07, 126.60, 126.21, 124.05, 118.10, 117.98, 91.11, 55.32, 54.59, 39.67.

[0111] Example 6

[0112] Tris(2,4,6-trimethoxyphenyl)phosphine reacts with 2-(thioxanthone-2-yl)acetic acid to yield tris(2,4,6-trimethoxyphenyl)phosphonium-2-(thioxanthone-2-yl)acetate (6):

[0113]

[0114] According to the literature (Yilmaz et al., Macromol. Rapid Commun. 37(13), 1046-1051(2016)), 9-oxo-9H-thioxanthroline-2-acetic acid (1 equivalent, 0.15 mmol, 41 mg) and tris(2,4,6-trimethoxyphenyl)phosphine (1 equivalent, 0.15 mmol, 80 mg) were dissolved in anhydrous THF (0.5 ml). After solvent removal, a light green solid residue was obtained. The residue was washed with THF and dried to obtain a light green solid (yield: 121 mg, quantitative).

[0115] 1¹H-NMR (400MHz, acetone-d6) δ: 8.42–8.29 (m, 2H), 7.63–7.54 (m, 4H), 7.49–7.35 (m, 1H), 5.97 (d, 6H), 3.84 (s, 0.3H), 3.69 (s, 1.7H), 3.64 (s, 9H), 3.37 (s, 18H).

[0116] 13 C-NMR (101MHz, acetone-d6) δ: 163.25, 134.28, 132.58, 129.95, 129.35, 126.43, 126.31, 126.19, 91.06, 55.22, 54.48, 40.28.

[0117] Examples 7 to 12, compared to Examples 6 to 10 - photocatalytic "oxaenes"

[0118] The novel compounds (1) to (6) and the compounds of comparative examples (V1) to (V5) prepared as described above according to the present invention were first examined for their suitability as photoalkalizing agents in a photoinitiated model reaction. The reaction progress was monitored by Photo-DSC (model: Netzsch DSC 204F1 Phonenix), and then based on the respective reaction mixtures dissolved in CDCl3. 1 H-NMR spectroscopy determined the achieved conversion rate. As a model reaction, the oxa-Michael addition between an alcohol and an acrylate was chosen, specifically the oxa-Michael addition between benzyl alcohol as the Michael donor and benzyl acrylate as the Michael acceptor, as follows:

[0119]

[0120] To determine the conversion rate, the chemical shifts of the two hydrogen atoms in the methylene group of benzyl alcohol (as highlighted in the diagram above) were used. These resulted in... 1 Each exhibits a single peak in the H-NMR spectrum. The peak for benzyl alcohol, which is present as a reactant in the reaction mixture, appears at 4.63 ppm. After successful addition to the acrylate double bond, the peak shifts to a lower field at 4.43 ppm (while the peak for the methylene group of benzyl alcohol, which is an ester bond, is above 5 ppm in each case).

[0121] Therefore, the conversion rate percentage is calculated using the following formula:

[0122] U(%)=I P / (I P +I E )x 100

[0123] Where I PThe integral representing the singlet in the product (i.e., at 4.43 ppm) and I E The integral of the peak in the reactant (at 4.63 ppm).

[0124] The reactants for the model reaction (expressed in molar amounts) were: 1 equivalent of benzyl alcohol, 1 equivalent of benzyl acrylate, 2 mol% of a potential photo-alkalizing agent, 0.02 mol% of 9,10-dibutoxyanthracene (BAnt) as a photosensitizer, and 2 mol% of 2,6-di-tert-butyl-p-cresol (butylhydroxytoluene, BHT) as a free radical scavenger. In each case, 10 to 15 mg of the mixed formulation at room temperature was introduced into an aluminum DSC crucible and covered with a quartz glass cover. The reaction mixture was then heated to 80°C and then subjected to light at that temperature using a medium-pressure mercury lamp in the DSC apparatus with wavelengths between 320 nm and 500 nm (133 mW / cm²). 2 Irradiate for 50 seconds, then maintain the temperature for 850 seconds, and repeat this process for each subsequent 50-second irradiation and 850-second maintenance (i.e., the reaction duration is 2 × 15 minutes). Then, briefly cool the reaction mixture and dissolve it in CDCl3, subsequently recording the results. 1 H-NMR spectrum.

[0125] The conversion rates calculated using the above formula are shown in Table 1 below.

[0126] Table 1

[0127] Example compound Conversion rate (%) Comparison Example 6 (V1) 0 Example 7 (1) 6 Example 8 (2) 10 Example 9 (3) 58 Example 10 (4) 69 Example 11 (5) 81 Example 12 (6) 84 Compare Example 7 (V2) 0 Comparison Example 8 (V3) 0 Comparison Example 9 (V4) 0 Comparison Example 10 (V5) 0

[0128] It is clear that none of the comparative substances can undergo transformation, i.e., cleavage under irradiation and initiation of a Michael addition reaction. In other words, unsubstituted triphenylphosphonium cations or BINAP cations combined with anions according to the invention, and tri(2,4,6-trimethoxyphenyl)phosphonium cations combined with substituted anions according to the invention, are unsuitable as photoalkalizing agents.

[0129] In the combination of the methoxy-substituted triphenylphosphonium cation and the anion of phenylacetic acid or phenylpropionic acid derivative according to the present invention, on the one hand, it has been found that the number and position of the substituents significantly affect reactivity: with respect to the para position of compound (1) (where the substituent R is present), 2 Compared to compound (2), the ortho position of the methoxy group on the phenyl group (i.e., as a substituent R) is different. 1 () is more preferred. However, by increasing the number of substituents to two or three, the conversion rate that could only be obtained by 10% or 6% can be increased several times: the compound (3) substituted with dimethoxy and the compound (4) substituted with trimethoxy achieved conversion rates of 58% and 69%, respectively.

[0130] On the other hand, it can also be seen that the cyclization between the two phenyl groups in the aromatic anion further improves the applicability of the salt as a photoalkalizing agent: when combined with tris(2,4,6-trimethoxyphenyl)phosphonium cation, the 2-(xanthonone-2-yl)acetate anion achieves an 81% conversion rate for compound (5), while the 2-(thioxanthonone-2-yl)acetate anion achieves an 84% conversion rate for compound (6). Therefore, the inventors believe that if the chemical bond: -CH2-, -O-CH2, -CH2-O- or -C(=O)- is used as the substituent X in the molecular formula (I) or a longer-chain alkyl group (e.g., ethyl or propyl) is used as the substituent R. 3 Similar results can be expected. However, increasing the molecular weight of the photo-alkali-producing agent is not preferred unless significantly better results are obtained.

[0131] Example 13, compared to Example 11 - photocatalysis "CC"

[0132] According to the invention, the novel compound (4) and the known CC Michael addition catalyst, namely CGI1193 (from BASF), are used:

[0133]

[0134] In similar optical DSC experiments, the transformation achievable in a model reaction using diethyl malonate as the Michael donor and benzyl acrylate as the Michael acceptor was investigated, as follows:

[0135]

[0136] To determine the conversion rate, the chemical shifts of the two hydrogen atoms of the benzylmethylene group of benzyl acrylate in the reactants and products (as highlighted in the figure above) were used.

[0137] In this case, the reaction ingredients were: 1 equivalent of diethyl malonate, 2 equivalents of benzyl acrylate, 2 mol% of compound (4) or CGI 1193, 0.02 mol% of BAnt as a photosensitizer, and 2 mol% of BHT as a free radical scavenger. The reaction conditions in Example 13 were the same as before (80°C, 2 × 50 seconds of light exposure, followed by 850 seconds of temperature maintenance after each light exposure). Those from... 1 The conversion rates calculated by H-NMR spectroscopy are shown in Table 2 below.

[0138] Table 2

[0139] Example compound Conversion rate (%) Compare Example 11 CGI 1193 45 Example 13 (4) 79

[0140] Therefore, the new compound (4) according to the present invention exceeds the known compounds as photo-alkali-producing agents by 75% in terms of reaction conversion, which also demonstrates its excellent suitability as a CC-Michael addition catalyst.

[0141] Example 14 - Reaction Temperature

[0142] Given that it can be assumed that the conversion rate can be further improved by increasing the concentration of the photoalkali-producing agent, the sensitizer, or the reaction temperature, the inventors conducted further photo-DSC experiments on compound (4), which had previously achieved a conversion rate of 69% in the oxaene experiment.

[0143] In this case, the concentration of the photoalkali-producing agent increased from 2 mol% to 5 mol%, and the concentration of the sensitizer increased from 0.02 mol% to 1 mol%, with each ingredient starting at room temperature (25°C) and gradually increasing to 150°C in increments of 25°C. Again, as described above, from their respective... 1 The conversion rates calculated by H-NMR spectroscopy are shown in Table 3 below, and... Figure 1 It is represented graphically.

[0144] Table 3

[0145] Temperature (°C) Conversion rate (%) 25 20 50 52 75 87 100 83 125 74 150 48

[0146] These results suggest that the optimal reaction temperature for the reaction mixture should be between 80°C and 90°C. Furthermore, the experimental results indicate that the reaction conversion rate can be significantly increased by more than 25% compared to the 69% obtained with compound (4) in Example 10, particularly by increasing the concentration of the photo-alkali-producing agent.

[0147] It can also be concluded that even compounds (1) and (2) with only methoxy monosubstituted morphology, which give relatively poor results under the reaction conditions described above in Examples 7 and 8, can be used industrially as photoalkalizing agents after parameter optimization. This certainly also applies to ortho / para-disubstituted variants that have not yet been tested, especially in combination with the cycloanion of formula (I).

[0148] Example 15 – Storage Stability

[0149] To investigate the storage stability of the formulation, the model formulation previously studied in Example 10 was used again, which contained: 1 equivalent of benzyl alcohol, 1 equivalent of benzyl acrylate, 2 mol% of compound (4), 2 mol% of BHT as a free radical scavenger, and BAnt as a photosensitizer, wherein in this example, only the amount of the photosensitizer was increased from 0.02 mol% to 0.1 mol%. Several of the ingredients were stored at room temperature (RT) or 60°C in the dark for up to 14 days, after which they were again subjected to [further testing / inspection]. 1Its composition was studied by H-NMR, and any conversion rates were calculated as previously described. The results obtained are given in Table 4 below.

[0150] Table 4

[0151]

[0152]

[0153] This clearly demonstrates that no reaction occurred at room temperature for 14 days. Even at 60°C, a low conversion rate was observed after only 4 days, and even after 14 days, only 7% of the reactant reacted at this high temperature. Overall, this demonstrates that the formulation according to the invention exhibits very satisfactory storage stability.

[0154] Example 16 - Photopolymerization

[0155] To verify the applicability of the photoalkali-generating agent according to the invention for the preparation of photopolymers, another photo-DSC experiment was first conducted using a multifunctional monomer. Specifically, a reaction mixture consisting of 1 equivalent of trimethylolpropane (TMP), 1 equivalent of trimethylolpropane triacrylate (TMPTA), 5 mol% of compound (4), 2 mol% of BHT as a free radical scavenger, and BAnt as a photosensitizer, but the amount of photosensitizer was now reduced again to 0.02 mol%.

[0156] On the other hand, the reaction temperature is increased to 100°C.

[0157]

[0158] like Figure 2 As shown, a strong exothermic reaction was observed within seconds of the onset of illumination, and the exothermic reaction completely subsided after a little over a minute, indicating that the reactants were completely converted. Therefore, the corresponding photopolymers can be prepared in a very short time using the photoalkali-producing agent (4) according to the present invention.

[0159] Example 17 - Photopolymerization for Coating Preparation

[0160] The reaction mixture consisting of the following components was applied to a glass plate in a 100 μm thick layer using a scraper: 1 equivalent of TMP, 1 equivalent of TMPTA, 2 mol% of compound (4), 2 mol% of BHT as a free radical scavenger, and 0.02 mol% of BAnt as a photosensitizer.

[0161] The reaction mixture was heated to 80°C in an INTELLI-RAY 600 UV oven from Uvitron International and irradiated with UV light at 320nm-500nm using the oven's broadband UV mercury lamp. After only one minute of irradiation, a hard, transparent coating was obtained on the glass plate.

[0162] Examples 18 to 21, compare with Examples 12 and 13

[0163] To further determine the reaction parameters of the above photopolymerization reaction, another photo-DSC test was conducted using a reaction mixture similar to that in Example 17, consisting of 1 equivalent of TMP, 1 equivalent of TMPTA, 2 mol% of the corresponding photoalkalizing agent, 2 mol% of BHT as a free radical scavenger, and 0.02 mol% of BAnt as a photosensitizer.

[0164] The properties of compounds (1) to (4) according to the invention, namely tri(methoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate substituted with different positions or different amounts of methoxy groups, and compounds from comparative examples 3 and 4 with different anions, namely tri(2,4,6-trimethoxyphenyl)phosphoniumtetraphenylborate (V3) and tri(2,4,6-trimethoxyphenyl)phosphoniumphenylacetoxyate (V4), were investigated.

[0165] Based on the corresponding optical-DSC plot, the following terms were determined: peak area (J / g) as a measure of the obtained conversion rate, peak height (mW / mg) as a measure of the polymerization rate, and the time t to reach 95% conversion. 95 (s) is used as a measure of the overall reaction rate. The results are given in Table 5 below.

[0166] Table 5

[0167] Example compound Area (J / g) Altitude (mW / mg) <![CDATA[t 95 (s)]]> Compare Example 12 (V3) 233 10.3 48.2 Compare Example 13 (V4) 155 5.3 52.5 Example 18 (1) 328 19.3 40.1 Example 19 (2) 299 18.3 38.6 Example 20 (3) 311 18.7 39.0 Example 21 (4) 326 20.7 38.7

[0168] At first glance, it can be seen that the two comparative substances, which failed to produce any conversion in the Michael addition of benzyl alcohol and benzyl acrylate between the above comparative examples 8 and 9, now also exhibit activity as photo-alkali-producing agents. However, the four compounds according to the invention significantly surpass them in all respects. The peak area of ​​the four compounds according to the invention is about 1.5 to 2 times larger, the peak height is about 2 to 4 times larger, and the t 95 Shortening the time by about 20% indicates that they are able to generate significantly higher conversion rates in a shorter time period.

[0169] Compared with the above results of the photo-DSC experiment between benzyl alcohol and benzyl acrylate, it is surprising that not only do (V3) and (V4) now also act as photoalkalizing agents, but also that all four compounds according to the invention in Examples 18 to 21 give comparable results: although the conversion achieved in the preceding Examples 7 to 10 varied greatly (6%, 10%, 58%, or 69% conversion), the four compounds differed by no more than 10% in all three parameters.

[0170] While not wishing to be confined to a single theory, the inventors believe both can be attributed to the Tromsdorff effect, or gel effect, under which the reaction rate increases with increasing conversion during polymerization because the heat of reaction becomes increasingly difficult to dissipate as the viscosity of the reaction mixture increases, thus causing an increase in temperature in exothermic polymerization. This effect is primarily observed in bulk polymerization, i.e., in the absence of solvent dilution.

[0171] In any case, these results also demonstrate that the combination of formula (I) of the methoxy-substituted triphenylphosphonium cation and the defined phenylacetic acid or phenylpropionic acid derivative anion according to the invention is superior to other similar salts that do not correspond to the definition according to the invention.

[0172] Example 22 - Thermolithography

[0173] Since the controlled reaction mixtures require relatively high reaction temperatures or are preferably at relatively high reaction temperatures, they are well-suited for 3D printing via thermolithography, which involves irradiating liquid mixtures layer by layer with a laser while heating them to high temperatures to prepare three-dimensional photopolymers with predetermined shapes and structures.

[0174] For this purpose, four experiments were conducted, each using the same reaction mixture as in Example 16, namely 1 equivalent of TMP, 1 equivalent of TMPTA, 2 mol% of compound (4), 2 mol% of BHT, and 0.02 mol% of BAnt. The first three experiments were conducted in a Cubicure Caligma The thermolithography system was heated to 80°C and solidified layer by layer (50 μm thickness) using a 375 nm laser (60 mW) at a scanning rate of 200 mm / s to form a three-dimensional object. The resulting image is shown in [the image / photograph]. Figure 3 and 4 middle.

[0175] First, a complete regular square pyramid was prepared. Figure 3 A), and then a hollow cube was prepared ( Figure 3 B). Subsequently, hollow pyramids were constructed. Figure 3C and Figure 4 As can be seen, among them Figure 4 A marks the area of ​​one of the four pillars. Figure 4 Figure B shows an enlarged view of the area, from which it can be seen that the layers that harden sequentially and individually in 3D printing are even visible to the naked eye.

[0176] Finally, using something similar to Cubicure Caligma The system, Blue Printer 10, includes an Ikarus II light engine from IN-VISION with a wavelength of 385nm and a pixel pitch of 50μm, thus enabling DLP thermolithography and 3D printing using the same reaction mixture as described above. Figure 5 A and Figure 5 A more complex cube shape is shown in B (slightly larger).

[0177] Printing was performed again at 80°C, with a light exposure time of 18 seconds and an intensity of 75 mW / cm². 2 In this case, however, digital light processing, or DLP for short, is used, in which a projector or beamer is used instead of a laser, and light is deflected onto the reaction mixture to be cured using reflective micromirrors.

[0178] exist Figure 6 In A and 6B, optical microscope images of this complex hollow cube at different magnifications can be seen, highlighting the high resolution of this 3D printing method.

[0179] All four experiments—and other examples—clearly demonstrate the suitability of the triphenylphosphonic carboxylate according to formula (I) as a photoalkali-generating agent.

Claims

1. The use of a triphenylphosphonic acid salt of formula (I) as a photoalkalizing agent in a photopolymerizable composition containing at least one monomer, for the preparation of a photopolymer by curing the composition with light of a suitable wavelength: Where R 1 and R 2 Each is independently selected from -H and -OCH3, wherein on each of the three phenyl groups, R 1 and R 2 At least one of them represents -OCH3, and where R 3 Selected from -H and -CH3 and X is absent or selected from chemical bonds: -CH2-, -O-CH2-, -CH2-O-, -C(=O)-, -O- and -S-.

2. The use according to claim 1, characterized in that, At least one R on each of the three phenyl groups 1 Represents -OCH3.

3. The use according to claim 2, characterized in that, The phosphonium cation of the salt is one of the following triphenylphosphine cations: tris(2-methoxyphenyl)phosphine, tris(2,6-dimethoxyphenyl)phosphine, or tris(2,4,6-trimethoxyphenyl)phosphine.

4. The use according to any one of claims 1 to 3, characterized in that, X is absent or selected from chemical bonds: -O- and -S-.

5. The use according to claim 4, characterized in that, The carboxylate anion of the salt is an anion of one of the following carboxylic acids: 2-(3-benzoylphenyl)propionic acid or 2-(3-benzoylphenyl)acetic acid, 2-(xanthonone-2-yl)propionic acid or 2-(xanthonone-2-yl)acetic acid, or 2-(thioxanthonone-2-yl)propionic acid or 2-(thioxanthonone-2-yl)acetic acid.

6. The use according to claim 5, characterized in that, The photoalkali-producing agent is selected from the following triphenylphosphonic carboxylates: tris(2,6-dimethoxyphenyl)phosphon-2-(3-benzoylphenyl)propionate, tris(2,4,6-trimethoxyphenyl)phosphon-2-(3-benzoylphenyl)propionate, tris(2,6-dimethoxyphenyl)phosphon-2-(xanthonone-2-yl)acetate, tris(2,4,6-trimethoxyphenyl)phosphon-2-(xanthonone-2-yl)acetate, tris(2,6-dimethoxyphenyl)phosphon-2-(thioxanthonone-2-yl)acetate and tris(2,4,6-trimethoxyphenyl)phosphon-2-(thioxanthonone-2-yl)acetate.

7. The use according to any one of claims 1 to 6, characterized in that, The photopolymerizable composition is coated onto a substrate and cured by irradiation to form a coating, or cured layer by layer by irradiation in an additive manufacturing process to form a three-dimensional object, wherein the curing is performed by heating if necessary in each case, and wherein the resulting photopolymer is subjected to thermal post-treatment if necessary.

8. The use according to claim 7, characterized in that, As an additive manufacturing process, thermolithography is performed at a temperature of at least 50°C, at least 70°C, or at least 80°C.

9. The use according to any one of claims 1 to 8, characterized in that, The photopolymerizable composition uses at least two monomers that can be polymerized via Michael addition reaction.

10. The use according to claim 9, characterized in that, The monomer can be polymerized via oxaene addition, oxayne addition, or C-C addition reactions of CH active compounds, preferably via oxaene addition polymerization.

11. The use according to claim 10, characterized in that, Combining (meth)acrylates or (meth)acrylamides with alcohols as monomers is preferred, and the mixture is used in a solvent-free bulk form.

12. The use according to any one of claims 1 to 11, characterized in that, The photopolymerizable composition further comprises at least one photosensitizer and / or at least one free radical scavenger, wherein the at least one photosensitizer is preferably 9,10-dibutoxyanthracene and the at least one free radical scavenger is preferably 2,6-di-tert-butyl-p-cresol (butyl hydroxytoluene, BHT).

13. A photopolymer that can be obtained by curing a photopolymerizable composition according to any one of claims 1 to 12.

14. A triphenylphosphonium carboxylate of formula (I), Where R 1 and R 2 Each is independently selected from -H and -OCH3, and R is selected from R. 3 Selected from -H and -CH3 and X is absent or selected from -O- and -S-. in, The salt is selected from the group consisting of: Tris(4-methoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (1): Tris(2-methoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (2): Tris(2,6-dimethoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (3): Tris(2,4,6-trimethoxyphenyl)phosphonium-2-(3-benzoylphenyl)propionate (4): Tris(2,4,6-trimethoxyphenyl)phosphonium-2-(xanthone-2-yl)acetate (5): Tris(2,4,6-trimethoxyphenyl)phosphonium-2-(thioxanone-2-yl)acetate (6):

15. The use of the triphenylphosphonic acid salt according to claim 14 as a photoalkali-generating agent in a photopolymerizable composition for the preparation of photopolymers.

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