Ultraviolet absorbers and resin compositions containing the same

Abstract

The objective of this invention is to provide an ultraviolet absorber with excellent ultraviolet absorption properties and biodegradability, as well as a resin composition incorporating the ultraviolet absorber. The solution is an ultraviolet absorber containing flavonoids represented by the following general formula (1). General formula (1) [In the formula, R1 to R4 independently represent hydrogen atom, halogen atom, alkyl group with 1 to 8 carbon atoms (the alkyl chain may have more than one substituent other than alkyl), hydroxyl group, alkyloxy group with 1 to 8 carbon atoms (the alkyl chain may have more than one substituent other than alkyl, and the alkyl chain may also have more than one ether bond, but does not have a cyclic structure), formyloxy group, alkylcarbonyloxy group with 1 to 7 carbon atoms (the alkyl chain may have more than one substituent other than alkyl), amino group, monoalkylamino group with 1 to 4 carbon atoms, dialkylamino group with a total number of 2 to 8 carbon atoms of each alkyl group, nitro group, carboxyl group, or alkyloxycarbonyl group with 1 to 8 carbon atoms (the alkyl chain may have more than one substituent other than alkyl), R5 represents hydrogen atom or hydroxyl group, bond M represents single bond or double bond, R6 represents hydrogen atom or hydroxyl group when bond M represents single bond, and R6 does not exist when bond M represents double bond].

Description

Technical Field

[0001] This invention relates to novel ultraviolet absorbers containing flavonoids, and also to ultraviolet absorbers using the aforementioned flavonoids that possess both excellent ultraviolet absorption and biodegradability, as well as resin compositions containing the aforementioned flavonoids. Background Technology

[0002] It is well known that resins deteriorate under the influence of ultraviolet (UV) radiation from natural light, resulting in softening, embrittlement, discoloration, and a significant reduction in mechanical strength. UV absorbers have historically been added to resin processing to prevent UV-induced degradation and are used in various fields, including automotive parts, building materials, electronic materials, medical materials, containers, packaging materials, and agricultural and fishery supplies. Known UV absorbers for resins include various organic compounds such as benzophenone, benzotriazole, and triazine compounds.

[0003] However, the UV absorbers currently used in resins are not easily biodegradable, thus remaining in soil, rivers, and oceans, raising concerns about their potential ingestion by fish and other organisms. Furthermore, there are concerns about the potential adverse effects on human health due to the toxicity and bioaccumulation of these UV absorbers. Therefore, there is a need to develop safe UV absorbers that are biodegradable in the natural environment.

[0004] On the other hand, biodegradable resins, which are biodegradable in natural environments, decompose into water and carbon dioxide in soil, rivers, and oceans, thus leaving no environmental residue. As resins with low environmental impact, they have been used in recent years for agricultural and fishery materials, containers, and medical supplies. However, to prevent the degradation of biodegradable resins due to ultraviolet radiation, benzophenone-based, benzotriazole-based, or triazine-based UV absorbers, which are not easily biodegradable, are used. Although the biodegradable resins can be biodegraded, the UV absorbers remain in the environment, thus failing to fundamentally solve environmental pollution. Therefore, there is a need to develop UV absorbers that can be biodegraded along with the biodegradable resins in the natural environment.

[0005] Patent document 1 proposes a lignocellulose membrane incorporating biodegradable lignin as a UV absorber. However, it is known that lignin generates free radicals upon absorbing UV light, leading to photo-oxidation, which causes yellowing or decomposition into low-molecular-weight compounds, altering its absorption properties. Consequently, it has unsatisfactory properties as a UV absorber, limiting its applications.

[0006] Patent documents 2 and 3 proposed using flavonoid glycosides, such as α-glucose-based osmin or senna-based glycosides, which incorporate cyclic sugars into flavonoids as ultraviolet absorbers. However, these glycosides are considered to have very high water solubility due to the influence of cyclic sugars, making them difficult to be compatible with plastics. Furthermore, due to the influence of cyclic sugars, they have large molecular weights and low absorbance per unit weight. Therefore, they have undesirable properties as ultraviolet absorbers for use in plastics, limiting their applications.

[0007] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 4-33986 Patent Document 2: Japanese Patent Application Publication No. 2001-158796 Patent Document 3: Japanese Patent Application Publication No. 2001-200238 Summary of the Invention

[0008] The problem that the invention aims to solve Under such circumstances, the objective of the present invention is to provide an ultraviolet absorber with excellent ultraviolet absorption and biodegradability, and a resin composition incorporating the ultraviolet absorber.

[0009] Technical solutions for solving the problem In this invention, the main solution to the above problem is to use flavonoids represented by the following general formula (1) as ultraviolet absorbers and resin compositions. General formula (1) [In the formula, R1 to R4 independently represent hydrogen atom, halogen atom, alkyl group with 1 to 8 carbon atoms (the alkyl chain may have more than one substituent other than alkyl), hydroxyl group, alkyloxy group with 1 to 8 carbon atoms (the alkyl chain may have more than one substituent other than alkyl, and the alkyl chain may also have more than one ether bond, but not a cyclic structure), formyloxy group, alkylcarbonyloxy group with 1 to 7 carbon atoms (the alkyl chain may have more than one substituent other than alkyl), amino group, monoalkylamino group with 1 to 4 carbon atoms, dialkylamino group with a total number of carbon atoms of each alkyl group of 2 to 8, nitro group, carboxyl group, or alkyloxycarbonyl group with 1 to 8 carbon atoms (the alkyl chain may have more than one substituent other than alkyl), R5 represents hydrogen atom or hydroxyl group, bond M represents single bond or double bond, when bond M represents single bond R6 represents hydrogen atom or hydroxyl group, when bond M represents double bond R6 does not exist]

[0010] Further preferred are R1 to R4 in the above general formula (1) as hydrogen atom, hydroxyl group, alkyloxy group with 1 to 8 carbon atoms, formyloxy group, or alkyl carbonyloxy group with 1 to 7 carbon atoms, respectively.

[0011] Invention Effects The ultraviolet absorber of the present invention possesses both excellent ultraviolet absorption and biodegradability, thus preventing resin degradation caused by ultraviolet radiation and being biodegradable without residue in the natural environment. Therefore, the ultraviolet absorber and resin composition of the present invention are useful as ultraviolet absorber and resin compositions capable of solving the problems of the prior art. Attached Figure Description

[0012] Figure 1 The UV-Vis absorption spectrum of the polycarbonate film of compound (a) is shown.

[0013] Figure 2 The UV-Vis absorption spectrum of the polylactic acid film of compound (a) is shown.

[0014] Figure 3 The UV-Vis absorption spectrum of the polylactic acid film of compound (b) is shown.

[0015] Figure 4 It is the ultraviolet-visible absorption spectrum of the polylactic acid film of compound (c).

[0016] Figure 5 It is the UV-Vis absorption spectrum of the polylactic acid film of compound (d).

[0017] Figure 6 It is the ultraviolet-visible absorption spectrum of the polylactic acid film of compound (e).

[0018] Figure 7 The UV-Vis absorption spectrum of the polyvinyl alcohol film of compound (e) is shown.

[0019] Figure 8 The UV-Vis absorption spectrum of the polyvinyl alcohol film of compound (f) is shown.

[0020] Figure 9 It is the ultraviolet-visible absorption spectrum of the polyvinyl alcohol film of compound (g).

[0021] Figure 10 It is the ultraviolet-visible absorption spectrum of the polyvinyl alcohol film of compound (h). Detailed Implementation

[0022] The present invention will now be described in detail. The present invention is an ultraviolet absorber containing a flavonoid as shown in the following general formula (1) and a resin composition incorporating the ultraviolet absorber. Hereinafter, the flavonoid as shown in the following general formula (1) will be described. General formula (1) In general formula (1), R1 to R4 independently represent hydrogen atoms; halogen atoms; alkyl groups with 1 to 8 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl, 2-ethylhexyl, 2-hydroxyethyl, 8-hydroxyoctyl, and 2-aminoethyl (the alkyl chain may have more than one substituent other than an alkyl group); hydroxyl groups; alkyloxy groups with 1 to 8 carbon atoms, such as methoxy, ethoxy, propoxy, butoxy, octyloxy, and 2-(2-hydroxyethoxy)ethoxy (the alkyl chain may have more than one substituent other than an alkyl group, and the alkyl chain may also have more than one ether bond, but does not have a cyclic structure); formyloxy; methyl carbonyloxy, ethyl carbonyloxy, propyl carbonyloxy, and heptyl carbonyl. Alkyl carbonyloxy groups with 1 to 7 alkyl carbon atoms, such as oxy-oxygen group, 2-hydroxyethyl carbonyloxy group, etc. (the alkyl chain may have more than one substituent other than an alkyl group); amino group; monoalkylamino group with 1 to 4 alkyl carbon atoms, such as N-methylamino group, N-butylamino group, etc.; dialkylamino group with a total of 2 to 8 alkyl carbon atoms, such as N,N-dimethylamino group, N,N-dibutylamino group, etc.; nitro group; carboxyl group; or alkyloxycarbonyl group with 1 to 8 alkyl carbon atoms, such as methoxycarbonyl group, octoxycarbonyl group, 4-hydroxybutyloxycarbonyl group, etc. (the alkyl chain may have more than one substituent other than an alkyl group), R5 represents a hydrogen atom or a hydroxyl group, bond M represents a single bond or a double bond, when bond M represents a single bond R6 represents a hydrogen atom or a hydroxyl group, when bond M represents a double bond R6 does not exist.

[0023] Preferably, the flavonoids in the above general formula (1) are flavonoids in which R1 to R4 independently represent hydrogen atoms, hydroxyl groups, alkyloxy groups with 1 to 8 carbon atoms, formyloxy groups, or alkyl carbonyloxy groups with 1 to 7 alkyl carbon atoms.

[0024] Specific examples of flavonoids represented by the above general formula (1) include the following substances: 5-hydroxyflavanone, 5,7-dihydroxyflavanone, 5-hydroxy-7-octoxyflavanone, 7-acetoxy-5-hydroxyflavanone, 4',5,7-trihydroxyflavanone, 3',4',5,7-tetrahydroxyflavanone, 3',5,7-trihydroxy-4'-methoxyflavanone, 3',5-dihydroxy-4',7-dimethoxyflavanone, 4',5-dihydroxy-3',7-dimethoxyflavanone, 5-hydroxy-3',4',7-trimethoxyflavanone, 5-hydroxyflavone, 5,7-dihydroxyflavone, 5-hydroxy-7-octoxyflavanone, 7-acetoxy-5-hydroxyflavanone, 5-hydroxy-7-methylflavanone, 7-aminoflavanone, etc. 5-hydroxy-5-hydroxyflavone, 5-hydroxy-7-methylaminoflavone, 5-hydroxy-7-dimethylaminoflavone, 5-hydroxy-7-nitroflavone, 7-carboxy-5-hydroxyflavone, 5-hydroxy-7-methoxycarbonylflavone, 5,6,7-trihydroxyflavone, 3',4',5,7-tetrahydroxyflavone, 3',5,7-trihydroxy-4'-methoxyflavone, 3',5-dihydroxy-4',7-dimethoxyflavone, 4',5-dihydroxy-3',7-dimethoxyflavone, 5-hydroxy-3',4',7-trimethoxyflavone, 2',3,4',5,7-pentahydroxyflavone, 3,3',4',5,7-pentahydroxyflavone, etc.

[0025] Among the flavonoids exemplified herein, 5-hydroxyflavanone, 5,7-dihydroxyflavanone, 5-hydroxy-7-octyloxyflavanone, 7-acetoxy-5-hydroxyflavanone, 4',5,7-trihydroxyflavanone, 3',4',5,7-tetrahydroxyflavanone, 3',5,7-trihydroxy-4'-methoxyflavanone, 3',5-dihydroxy-4',7-dimethoxyflavanone, 4',5-dihydroxy-3',7-dimethoxyflavanone, 5-hydroxy-3',4',7-trimethoxyflavanone, 5- Hydroxyflavonoids, 5,7-dihydroxyflavonoids, 5-hydroxy-7-octoxyflavonoids, 7-acetoxy-5-hydroxyflavonoids, 5,6,7-trihydroxyflavonoids, 3',4',5,7-tetrahydroxyflavonoids, 3',5,7-trihydroxy-4'-methoxyflavonoids, 3',5-dihydroxy-4',7-dimethoxyflavonoids, 4',5-dihydroxy-3',7-dimethoxyflavonoids, 5-hydroxy-3',4',7-trimethoxyflavonoids, 2',3,4',5,7-pentahydroxyflavonoids, 3,3',4',5,7-pentahydroxyflavonoids.

[0026] The method for synthesizing the flavonoids in general formula (1) of the present invention is not particularly limited, and existing well-known reaction principles can be widely used, for example, the synthesis can be carried out by the reaction shown in reaction formula 1 or reaction formula 2 below. As the flavonoid-containing ultraviolet absorber of the present invention, it is possible to use only the flavonoids of the present invention, or to use them in combination with other ultraviolet absorbers. As for other ultraviolet absorbers used in combination, there are no particular limitations as long as they are commercially available products that can absorb ultraviolet rays. For example, ultraviolet absorbers such as benzophenone-based, benzotriazole-based, and triazine-based absorbers can be used. Only one of them can be used, or two or more can be appropriately mixed.

[0027] When the flavonoid-containing ultraviolet absorber of the present invention is incorporated into a resin material, examples of resin materials include: α-olefin polymers such as polyethylene, polypropylene, polybutene, polypentene, poly-3-methylbutene, and polymethylpentene; polyolefins such as ethylene-vinyl acetate copolymers and ethylene-propylene copolymers; polyvinyl chloride; polybrominated polyethylene; polyfluorinated polyethylene; chlorinated polypropylene; brominated polyethylene; chlorinated rubber; vinyl chloride-vinyl acetate copolymers; vinyl chloride-ethylene copolymers; vinyl chloride-propylene copolymers; vinyl chloride-styrene copolymers; and vinyl chloride-isocyanate copolymers. Butene copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-styrene-maleic anhydride terpolymers, vinyl chloride-styrene-acrylonitrile terpolymers, vinyl chloride-butadiene copolymers, vinyl chloride-isobutylene copolymers, vinyl chloride-propylene chloride copolymers, vinyl chloride-vinylidene chloride-vinyl acetate terpolymers, vinyl chloride-acrylate copolymers, vinyl chloride-maleic acid ester copolymers, vinyl chloride-methacrylate copolymers, vinyl chloride-acrylonitrile copolymers, halogenated synthetic resins of internally plasticized polyvinyl chloride, petroleum resins, coumarone resins, polystyrene, and styrene and its derivatives. Copolymers of monomers (maleic anhydride, butadiene, acrylonitrile, etc.), acrylonitrile-butadiene-styrene resins, acrylate-butadiene-styrene resins, methacrylate-butadiene-styrene resins, etc., styrene-based resins, polyvinyl acetate, polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, acrylic resins, methacrylic resins, polyacrylonitrile, polyphenylene ether, polycarbonate, modified polyphenylene ether, polyacetal, phenolic resins, urea resins, melamine resins, epoxy resins, silicone resins, polyethylene terephthalate, reinforced polyethylene terephthalate, and polyethylene terephthalate... Non-biodegradable resins such as butylene formate, polysulfone resins, polyethersulfone, polyphenylene sulfide, polyetherketone, polyetherimide, polyoxybenzoyl, polyimide, polymaleimide, polyamideimide, alkyd resins, amino resins, vinyl resins, water-soluble resins, powder coating resins, polyamide resins, polyurethane resins, and unsaturated polyester resins can also be listed.

[0028] The flavonoid-containing ultraviolet absorber of the present invention preferably contains 0.01 to 20% relative to the above-mentioned resin material, and more preferably 0.1 to 10%.

[0029] In the resin composition of the present invention containing flavonoids, resin additives other than ultraviolet absorbers can be used. Examples include antioxidants, light stabilizers, plasticizers, antistatic agents, flame retardants, colorants, lubricants, foaming agents, etc.

[0030] The flavonoid-containing resin composition of the present invention can be molded using conventional resin molding methods such as injection molding, blow molding, and extrusion molding. Furthermore, when molding into films or sheets, in addition to the methods described above, solution casting or casting methods can also be used.

[0031] Example The following examples illustrate the synthesis method of the flavonoids of the present invention, and the characteristics of the flavonoid and resin composition are described in detail by way of examples, but the present invention is not limited to these methods.

[0032] (Synthesis example 1) [Synthesis of compound (a); 5-hydroxy-3',4',7-trimethoxyflavonoid] A spherical condenser, thermometer, and stirrer were installed in a 300 ml four-necked flask. 6.43 g (0.021 mol) of 3',5,7-trihydroxy-4'-methoxyflavone (manufactured by Tokyo Chemical Industry Co., Ltd.), 63 ml of N,N-dimethylformamide, and 51.03 g (0.48 mol) of soda ash were added. 60.74 g (0.48 mol) of dimethyl sulfate was added dropwise over 20 minutes at 10 °C, and the mixture was stirred at 50 °C for 3 hours. Then, 150 ml of ethyl acetate and 400 ml of water were added, and the lower layer was removed at 55 °C. 100 ml of water and 10 ml of acetic acid were added, and the lower layer was removed at 55 °C. The organic solvent was removed by distillation under reduced pressure. Next, 60 ml of 2-propanol was added, the mixture was heated to 70 °C, cooled to 15 °C, filtered, washed with 2-propanol, and dried to obtain the crude product of 5-hydroxy-3',4',7-trimethoxyflavone. A spherical condenser, thermometer, and stirrer were installed in a 300 ml four-necked flask. The crude product, 50 ml of toluene, and 2 ml of N,N-dimethylformamide were added. The mixture was heated to 70 °C and then cooled to 20 °C. The mixture was filtered, washed with toluene, and dried to obtain 2.35 g of 5-hydroxy-3',4',7-trimethoxyflavone (yield 34%) as a yellow powder. The melting point was 168 °C.

[0033] In addition, the purity of compound (a) was determined by HPLC analysis.

[0034] <HPLC determination conditions> Device: Chromaster-5110 (Hitachi High Technology Co., Ltd.) Column: SUMIPAX ODS A-212 6×150mm 5μm Column temperature: 40℃ Mobile phase: Methanol / water = 8 / 2 (phosphoric acid 3 ml / L) Flow rate: 1.0 ml / min <Measurement Results> HPLC area percentage purity: 98.1% In addition, compounds (c) and (d) were also analyzed by HPLC under the same determination conditions as compound (a).

[0035] In addition, the ultraviolet-visible absorption spectrum of compound (a) was measured, and the maximum absorption wavelength λmax was 338 nm, at which point the molar absorptivity ε was 23500. The spectral measurement conditions are as follows.

[0036] <Measurement Conditions> Device: UV-1850 (manufactured by Shimadzu Corporation) Measurement wavelength: 250–450 nm Solvent: Chloroform Concentration: 10 ppm Cuvette: 1cm quartz In addition, the UV-Vis absorption spectra of compounds (b) to (d) were also measured under the same conditions as those of compound (a).

[0037] Furthermore, the NMR analysis of compound (a) yielded results supporting the aforementioned structure. The determination conditions are as follows.

[0038] <Measurement Conditions> Device: ECX-500 (II) (manufactured by Nippon Electronics Co., Ltd.) Resonance frequency: 500MHz (1H-NMR) Solvent: Chloroform-d Tetramethylsilane was used as the internal standard for 1H-NMR, with chemical shift values ​​expressed as δ (ppm) and coupling constants as Hertz. Additionally, s stands for singlet, d for doublet, dd for double doublet, t for triplet, and m for multiplet. Furthermore, compounds (b) to (d) were measured under the same conditions as compound (a). The obtained 1H-NMR spectra are shown below.

[0039] δ 12.80 (s, 1H, OH), 7.53 (dd, J=8.4, 1.5Hz, 1H, Flavone-H), 7.34 (d, J=2.3Hz, 1H, Flavone-H), 6.98 (d, J=8.4Hz, 1H, Flavone-H), 6.59 (s, 1H, Flavone-H), 6.50 (d, J=2.3Hz, 1H, Flavone-H), 6.37 (d, J=2.3Hz, 1H, Flavone-H), 3.99 (s, 3H, Methoxy-H), 3.97 (s, 3H, Methoxy-H), 3.89 (s, 3H, Methoxy-H). (Synthesis example 2) [Synthesis of compound (b); 5-hydroxy-7-octyloxyflavone] A spherical condenser, thermometer, and stirrer were installed in a 300 ml four-necked flask. 7.00 g (0.028 mol) of 5,7-dihydroxyflavone (manufactured by Tokyo Chemical Industry Co., Ltd.), 21 ml of N,N-dimethylformamide, 2.33 g (0.022 mol) of soda ash, 4.62 g (0.031 mol) of 1-chlorooctane, 1.35 g of polyethylene glycol 400, and 0.12 g of potassium iodide were added and mixed. The mixture was stirred at 80–95 °C for 16 hours. Then, 60 ml of toluene and 60 ml of water were added, and the lower layer was removed at 80 °C. Another 60 ml of water was added, and the lower water layer was removed at 80 °C. The organic solvent was removed by distillation under reduced pressure. Next, 50 ml of methanol was added, and the mixture was heated to 60 °C and then cooled to 5 °C. The crystals were filtered, washed with methanol, and dried to obtain 9.50 g (94% yield) of 5-hydroxy-7-octoxyflavone as a pale yellow powder. Its melting point is 102℃.

[0040] In addition, the purity of compound (b) was determined by HPLC analysis.

[0041] <HPLC determination conditions> Device: Chromaster-5110 (Hitachi High Technology Co., Ltd.) Column: SUMIPAX ODS A-212 6×150mm 5μm Column temperature: 40℃ Mobile phase: Methanol / water = 95 / 5 (phosphoric acid 3 ml / L) Flow rate: 1.0 ml / min <Measurement Results> HPLC area percentage purity: 99.5% In addition, the ultraviolet-visible absorption spectrum of compound (b) was measured, and the maximum absorption wavelength λmax was 271 nm, at which the molar absorptivity ε was 31100.

[0042] In addition, the NMR analysis of compound (b) yielded results that supported the above structure.

[0043] δ 12.71 (s, 1H, OH), 7.90-7.88 (m, 2H, Flavone-H), 7.57-7.51 (m, 3H, Flavone-H), 6.67 ( s, 1H, Flavone-H), 6.50 (d, J=2.3Hz, 1H, Flavone-H), 6.37 (d, J=2.3Hz, 1H, Flavone-H ), 4.03 (t, J=6.9Hz, 2H, Methylene-H), 1.85-1.79 (m, 2H, Methylene-H), 1.49-1.44 (m, 2H, Methylene-H), 1.38-1.30 (m, 8H, Methylene-H), 0.90 (t, J=6.9Hz, 3H, Methyl-H). (Synthesis example 3) [Synthesis of compound (c); 7-acetoxy-5-hydroxy-flavonoid] A 300 ml four-necked flask equipped with a spherical condenser, thermometer, and stirrer was used to add 7.00 g (0.028 mol) of 5,7-dihydroxyflavone (manufactured by Tokyo Chemical Industry Co., Ltd.), 28 ml of acetic acid, 3.37 g (0.033 mol) of anhydrous acetic acid, and 0.1 ml of 95% sulfuric acid. The mixture was stirred at 80–90 °C for 3.5 hours. Then, 30 ml of water was added, and the mixture was cooled to 20 °C. The crystals were filtered, washed with water, and dried to obtain crude 5-hydroxy-7-acetoxyflavone. A 300 ml four-necked flask equipped with a spherical condenser, thermometer, and stirrer was used to add the obtained crude product and 23 ml of acetic acid. The mixture was heated to 78 °C, cooled to 20 °C, filtered, washed with acetic acid and 2-propanol, and dried to obtain 5.18 g (63% yield) of 5-hydroxy-7-acetoxyflavone as a yellow powder. The melting point is 171℃, and the HPLC area percentage purity is 99.5%.

[0044] In addition, the ultraviolet-visible absorption spectrum of compound (c) was measured, and the maximum absorption wavelength λmax was 271 nm, at which the molar absorptivity ε was 29700.

[0045] Furthermore, the NMR analysis of compound (c) yielded results supporting the aforementioned structure. The obtained 1H-NMR spectrum is as follows.

[0046] δ 12.74 (s, 1H, OH), 7.90-7.88 (m, 2H, Flavone-H), 7.59-7.52 (m, 3H, Flavone-H) , 6.87 (d, J=2.3Hz, 1H, Flavone-H), 6.74 (s, 1H, Flavone-H), 6.58 (d, J=2.3Hz, 1H, Flavone-H), 2.35 (s, 3H, Acetyl-H). (Synthesis example 4) [Synthesis of compound (d); 5-hydroxy-3',4',7-trimethoxyflavanone] A stir bar was placed in a 30 ml flask, and 0.60 g (1.98 mmol) of 3',5,7-trihydroxy-4'-methoxyflavanone (manufactured by Tokyo Chemical Industry Co., Ltd.), 7 ml of 4-methyl-2-pentanone, and 5.20 g (49.0 mmol) of soda ash were added. Dimethyl sulfate 6.50 g (51.5 mmol) was added dropwise over 10 minutes at 50 °C, and the mixture was stirred at 50 °C for 16 hours. Next, 15 ml of water was added, and the lower layer was removed at 70 °C. Then, 10 ml of water and 0.5 ml of acetic acid were added, and the lower layer was removed at 70 °C. Another 10 ml of water was added, and the lower layer was removed at 70 °C. The organic solvent was removed by distillation under reduced pressure. Then, 10 ml of methanol was added, the mixture was heated to 65 °C, cooled to 20 °C, filtered, washed with methanol, and dried to obtain the crude product of 5-hydroxy-3',4',7-trimethoxyflavanone. A stir bar was added to a 30 ml gaiwan flask, along with the crude product, 3 ml of methanol, and 3 ml of 2-propanol. The mixture was heated to 65 °C, then cooled to 20 °C, filtered, washed with methanol and 2-propanol, and dried to obtain 0.15 g (25% yield) of 5-hydroxy-3',4',7-trimethoxyflavanone as a white powder. The melting point was 135 °C, and the HPLC area percentage purity was 95.6%.

[0047] In addition, the ultraviolet-visible absorption spectrum of compound (d) was measured, and the maximum absorption wavelength λmax was 288 nm, at which point the molar absorptivity ε was 21400.

[0048] Furthermore, the NMR analysis of compound (d) yielded results supporting the aforementioned structure. The obtained 1H-NMR spectrum is as follows.

[0049] δ 12.04 (s, 1H, OH), 6.99 (dd, J=6.1, 1.5Hz, 2H, Flavanone-H), 6.91 (m, 1H, Flavanone-H), 6.07 (dd, J=8.4, 2.3Hz, 2H, Flavanone-H), 5.37 (dd, J=13.0, 3.1Hz, 1H , Flavanone-H), 3.93 (s, 3H, Methoxy-H), 3.91 (s, 3H, Methoxy-H), 3.82 (s, 3H, Methoxy-H), 3.09-3.15 (m, 1H, Flavanone-H), 2.79-2.83 (m, 1H, Flavanone-H). (Example 1) [Preparation of polycarbonate resin composition] 5 g of polycarbonate resin granules (TARFLON IR2200, manufactured by FORMOSA IDEMITSUPETROCHEMICAL CORPORATION) were added to each 100 ml volumetric flask. Compound (a) obtained in Synthesis Example 1 and conventional UV absorber compound (i) as a comparative example were also added; 0.01 g of 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole was added. The mixture was brought to volume with dichloromethane and allowed to stand for 24 hours to obtain solutions of polycarbonate resin compositions containing UV absorbers. 20 ml of each solution of the obtained polycarbonate resin compositions containing UV absorbers was transferred to a 12 cm diameter petri dish and dried at 25 °C for 48 hours. The solvent was removed to obtain a 0.05 mm thick membrane containing 0.2% UV absorber from the polycarbonate resin composition.

[0050] [Preparation of polylactic acid resin composition] 5g of polylactic acid resin granules (standard / general grade, manufactured by Standard-Testpiece Co., Ltd.) as a biodegradable resin was added to each 100ml threaded tube. Compounds (a), (b), (c), (d), and (e) obtained in Synthetic Examples 1-4 were added; 4',5,7-trihydroxyflavanone (manufactured by Tokyo Chemical Industry Co., Ltd.); and the aforementioned compound (i) as a comparative example, compound (j) as a conventional UV absorber; and 0.005g of 2,4-dihydroxybenzophenone were also added. 100ml of dichloromethane was added, and the mixture was allowed to stand for 24 hours to obtain a solution of polylactic acid resin composition containing a UV absorber. 40ml of each solution of polylactic acid resin composition containing a UV absorber was added to a 12.5×10.0cm fluoropolymer-coated SUS plate, and the mixture was dried at 25°C for 24 hours. The solvent was removed to obtain a film with a thickness of 0.1mm containing 0.1% UV absorber from the polylactic acid resin composition.

[0051] [Preparation of Polyvinyl Alcohol Resin Composition] 80 g of polyvinyl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.: n = approximately 2000, saponification degree approximately 80 mol%) and 1520 g of pure water, used as a biodegradable resin, were added to a 2 L four-necked flask. The mixture was stirred at 25 °C for 48 hours to prepare 1600 g of polyvinyl alcohol aqueous solution. 200 g of the prepared polyvinyl alcohol aqueous solution was transferred to different PP containers, and 0.002 g of the above-mentioned compounds (e), (f); 5,6,7-trihydroxyflavone (manufactured by Tokyo Chemical Industry Co., Ltd.), compound (g); 3',4',5,7-tetrahydroxyflavone (manufactured by Tokyo Chemical Industry Co., Ltd.), compound (h); 3,3',4',5,7-pentahydroxyflavone hydrate (manufactured by Tokyo Chemical Industry Co., Ltd.) and the above-mentioned compounds (i) and (j) as comparative examples were added. The mixture was stirred at 25 °C for 3 hours to disperse the compounds. 100g of the prepared dispersion was added to a 12.5×10.0cm fluoropolymer-coated SUS plate and dried at 40°C and normal pressure for 40 hours, and then dried under vacuum for 3 hours to obtain a film of polyvinyl alcohol resin composition with a thickness of 0.3mm and dispersed with 0.02% ultraviolet absorber.

[0052] [Determination of ultraviolet-visible absorption spectra] The UV-Vis absorption spectra of the films of the above-obtained polycarbonate, polylactic acid, and polyvinyl alcohol resin compositions were measured under the following conditions. The absorbance at the maximum absorption wavelength is shown in Table 1 below. The spectrum of the polycarbonate film of compound (a) is shown in Table 1 below. Figure 1 The spectra of polylactic acid films containing compounds (a) to (e) are represented in... Figures 2-6 The spectra of polyvinyl alcohol films containing compounds (e) to (h) are represented as follows: Figures 7-10 .

[0053] <Measurement Conditions> Device: UV-1850 (manufactured by Shimadzu Corporation) Measurement wavelength: 300–450 nm for polycarbonate film Polylactic acid film and polyvinyl alcohol film 250-450nm [Table 1] [Determination of Biochemical Oxygen Demand] Aqueous solutions containing 5 ppm of compounds (e), (f), (g), and (h), and compounds (i) and (j) as comparative examples were prepared, and biochemical oxygen demand (BOD) was determined according to JIS K 0102 (2019) 21 and 32.3. The BOD determination results are presented in Table 2 below.

[0054] [Table 2] As shown in Table 1, the UV absorber of the present invention strongly absorbs ultraviolet light in each resin, exhibiting essentially the same UV absorption properties as existing UV absorbers. Furthermore, as shown in Table 2, the UV absorber of the present invention has a higher BOD value compared to existing UV absorbers, making it more readily biodegradable by microorganisms and thus possessing the property of being degraded in the natural environment without easily remaining. Therefore, it can be seen that the UV absorber of the present invention and the resin composition containing it exhibit the same UV absorption properties as existing products, while also being highly safe and achieving a reduction in environmental impact.

[0055] Industrial availability The ultraviolet absorber of this invention strongly absorbs ultraviolet light in the resin region, exhibiting the same ultraviolet absorption properties as existing ultraviolet absorbers. Furthermore, because the ultraviolet absorber of this invention is more readily biodegradable than existing ultraviolet absorbers, it possesses the property of being degradable in the natural environment and not easily retained. Therefore, it offers high safety and reduces environmental impact, thus addressing environmental issues. Consequently, it is suitable for use in various resins, particularly biodegradable resins.

Claims

1. An ultraviolet absorber comprising flavonoids represented by the following general formula (1): In the formula, R1 to R4 independently represent hydrogen atoms, halogen atoms, alkyl groups with 1 to 8 carbon atoms, hydroxyl groups, alkyloxy groups with 1 to 8 carbon atoms, formyloxy groups, alkyl carbonyloxy groups with 1 to 7 carbon atoms, amino groups, monoalkylamino groups with 1 to 4 carbon atoms, dialkylamino groups with a total of 2 to 8 carbon atoms in each alkyl group, nitro groups, carboxyl groups, or alkyloxycarbonyl groups with 1 to 8 carbon atoms. The alkyl group having 1 to 8 carbon atoms may have one or more substituents other than alkyl in the alkyl chain; the alkyloxy group having 1 to 8 carbon atoms may have one or more substituents other than alkyl in the alkyl chain, and may also have one or more ether bonds in the alkyl chain, but does not have a cyclic structure; the alkylcarbonyloxy group having 1 to 7 carbon atoms may have one or more substituents other than alkyl in the alkyl chain; the alkyloxycarbonyl group having 1 to 8 carbon atoms may have one or more substituents other than alkyl in the alkyl chain, R5 represents a hydrogen atom or a hydroxyl group, bond M represents a single bond or a double bond, when bond M represents a single bond R6 represents a hydrogen atom or a hydroxyl group, and when bond M represents a double bond R6 is not present.

2. The ultraviolet absorber containing flavonoids as described in claim 1, characterized in that: In the general formula (1), R1 to R4 are independently hydrogen atoms, hydroxyl groups, alkyloxy groups with 1 to 8 carbon atoms, formyloxy groups, or alkyl carbonyloxy groups with 1 to 7 carbon atoms.

3. A resin composition, characterized in that: The resin material contains the ultraviolet absorber as described in claim 1 or 2.

4. A biodegradable resin composition, characterized in that: The biodegradable resin material contains the ultraviolet absorber as described in claim 1 or 2.

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