Method for producing alkyd resin, and coating composition containing alkyd resin obtained by said production method

Abstract

Provided is a method for producing an alkyd resin with which it is possible to increase the amount of polyethylene terephthalate used. Specifically, provided is a method for producing an alkyd resin, which comprises: a step in which a polyhydric alcohol and a fatty acid are added to polyethylene terephthalate and a transesterification reaction is performed to produce a resin intermediate; and a step for adding a polycarboxylic acid to the resin intermediate to perform an esterification reaction, wherein the alkyd resin contains 20 mass% or more of a structure derived from polyethylene terephthalate.

Description

Technical Field

[0001] The present invention relates to a method for producing an alkyd resin and a coating composition containing the alkyd resin obtained by the method. Background Art

[0002] Polyethylene terephthalate is used in large quantities as a material for, for example, beverage bottles, and conventionally, used polyethylene terephthalate has been collected and reused.

[0003] The recycled polyethylene terephthalate is mainly used as a material for beverage bottles, food packaging such as egg packaging and fruit and vegetable trays, and fiberized to be used as clothing fibers.

[0004] In order to improve sustainability, there is an active trend to expand the reuse applications of recycled polyethylene terephthalate. For example, it has been proposed to use recycled polyethylene terephthalate as a raw material for coating resins (for example, Patent Documents 1 and 2).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2002-136021

[0008] Patent Document 2: Japanese Patent Application Publication No. 2004-83695 Summary of the invention

[0009] Problems to be solved by the invention

[0010] In the coating resins of Patent Documents 1 and 2, the amount of polyethylene terephthalate actually used is extremely small, and there is a problem that the polyethylene terephthalate cannot be fully recycled.

[0011] An object of the present invention is to provide a method for producing an alkyd resin capable of increasing the amount of polyethylene terephthalate used.

[0012] Another problem to be solved by the present invention is to provide a coating composition containing an alkyd resin in which a large amount of polyethylene terephthalate is used.

[0013] Means for solving problems

[0014] The present invention relates to a method for producing an alkyd resin, etc.

[0015] 1. A method for producing an alkyd resin, comprising:

[0016] A step of adding a polyol and a fatty acid to polyethylene terephthalate to perform an ester exchange reaction to prepare a resin intermediate; and

[0017] a step of adding a polycarboxylic acid to the above-mentioned resin intermediate to carry out an esterification reaction,

[0018] The alkyd resin contains 20% by mass or more of a structure derived from polyethylene terephthalate.

[0019] 2. The method for producing an alkyd resin according to 1, wherein the polyethylene terephthalate is recycled polyethylene terephthalate.

[0020] 3. The method for producing an alkyd resin according to 1 or 2, wherein the polyol is pentaerythritol and / or glycerin.

[0021] 4. The method for producing an alkyd resin according to any one of 1 to 3, wherein the fatty acid is a vegetable oil fatty acid.

[0022] 5. The method for producing an alkyd resin according to any one of 1 to 4, wherein the polycarboxylic acid is at least one selected from the group consisting of sebacic acid, succinic acid, and phthalic acid.

[0023] 6. The method for producing an alkyd resin according to any one of 1 to 5, wherein the oil content of the resin intermediate is less than 60%.

[0024] 7. The method for producing an alkyd resin according to any one of 1 to 6, wherein in the step of preparing the resin intermediate, the amount of polyethylene terephthalate is 20 parts by mass or more, based on 100 parts by mass of the total of the polyethylene terephthalate, the polyol and the fatty acid.

[0025] 8. The method for producing an alkyd resin according to any one of 1 to 7, wherein in the step of preparing the resin intermediate, the transesterification reaction is carried out without adding a catalyst of a metal compound.

[0026] 9. The method for producing an alkyd resin according to any one of 1 to 8, wherein the alkyd resin has an oil content of less than 60%.

[0027] 10. A coating composition comprising an alkyd resin obtained by the production method according to any one of 1 to 9.

[0028] 11. The coating composition according to 10, which is a coating composition.

[0029] 12. A coated substrate coated with the coating composition described in 11.

[0030] Effects of the Invention

[0031] According to the present invention, an alkyd resin capable of increasing the amount of polyethylene terephthalate used can be provided.

[0032] According to the present invention, there is provided a coating composition containing an alkyd resin in which a large amount of polyethylene terephthalate is used. DETAILED DESCRIPTION

[0033] Hereinafter, an embodiment of the present invention will be described. The present invention is not limited to the following embodiment, and can be implemented with appropriate modifications within a range that does not impair the effects of the present invention.

[0034] It should be noted that the compounds in this specification may be derived from fossil resources or biological resources.

[0035] [Method for producing alkyd resin]

[0036] The method for producing an alkyd resin of the present invention comprises: a step (1) of adding a polyol and a fatty acid to polyethylene terephthalate to carry out an ester exchange reaction to prepare a resin intermediate; and a step (2) of adding a polycarboxylic acid to the resin intermediate to carry out an esterification reaction.

[0037] According to the method for producing an alkyd resin of the present invention, an alkyd resin containing 20% ​​by mass or more of a structure derived from polyethylene terephthalate can be produced.

[0038] Hereinafter, the above steps (1) and (2) will be described.

[0039] (Process (1))

[0040] In step (1), a polyol and a fatty acid are added to polyethylene terephthalate to carry out an ester exchange reaction to prepare a resin intermediate.

[0041] The polyethylene terephthalate used in step (1) is preferably recycled polyethylene terephthalate (hereinafter sometimes referred to as "recycled PET"). Recycled PET is polyethylene terephthalate obtained by washing, drying, crushing, remelting, etc., of PET molded after use as food packaging such as beverage bottles, to obtain flakes or pellets.

[0042] The number average molecular weight of recycled PET is generally in the range of about 10,000 to about 30,000.

[0043] Examples of the polyol used in step (1) include glycerol, ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, tetraethylene glycol, trimethylolethane, trimethylolpropane, trimethylolhexane, triethylolpropane, 1,2,4-butanetriol, and pentaerythritol.

[0044] The polyol used may be a single type or two or more types may be used in combination.

[0045] The above-mentioned polyol is preferably pentaerythritol and / or glycerol.

[0046] Among these, the presence of a biomass-derived polyol can increase the biomass content of the obtained alkyd resin.

[0047] The fatty acid used in step (1) is preferably a vegetable oil fatty acid, more preferably at least one vegetable oil fatty acid selected from castor oil fatty acid, tall oil fatty acid, palm oil fatty acid, coconut oil fatty acid, soybean oil fatty acid, cocoa fatty acid, corn oil fatty acid, linseed oil fatty acid, cottonseed oil fatty acid, rapeseed oil fatty acid and rice bran fatty acid.

[0048] In step (1), an oil containing a fatty acid may be used instead of the fatty acid.

[0049] When oil is used as the fatty acid in step (1), the oil is preferably a vegetable oil, more preferably at least one vegetable oil selected from castor oil, tall oil, palm oil, coconut oil, soybean oil, cocoa butter, corn oil, linseed oil, cottonseed oil, rapeseed oil and rice oil.

[0050] The above-mentioned vegetable oil is a glyceride formed by ester bonding of fatty acid and glycerol. The vegetable oil can be used in the form of a mixture of fatty acid and polyol.

[0051] In step (1), the feed ratio of polyethylene terephthalate, polyol and fatty acid is preferably adjusted so that the oil content of the obtained resin intermediate is less than 60%. Specifically, when the total amount of polyethylene terephthalate, polyol and fatty acid is 100 parts by mass, the feed amount of fatty acid in terms of oil conversion is less than 60 parts by mass.

[0052] The oil content of the resin intermediate obtained in step (1) is preferably 55% or less, 50% or less, and 40% or less in this order. The lower limit of the oil content of the resin intermediate is not particularly limited, and is, for example, 20%.

[0053] The oil content of the resin intermediate corresponds to the ratio of the input amount of the fatty acid in terms of oil, based on 100 parts by mass of the total of the polyethylene terephthalate, the polyol, and the fatty acid.

[0054] In step (1), the amount of polyethylene terephthalate charged is preferably 20 parts by mass or more, preferably 25 parts by mass or more, and more preferably 30 parts by mass or more, based on 100 parts by mass of the total of polyethylene terephthalate, the polyol and the fatty acid.

[0055] In addition, the upper limit of the charging amount of polyethylene terephthalate is not particularly limited, and is, for example, 60 parts by mass.

[0056] In step (1), the amount of the polyol added is preferably 10 to 30 parts by mass, more preferably 14 to 26 parts by mass, based on 100 parts by mass of the total of polyethylene terephthalate, the polyol and the fatty acid.

[0057] The reaction conditions for the transesterification reaction in step (1) may be known reaction conditions, and for example, the reaction temperature may be set to 100 to 400° C. (preferably 200° C. or higher and lower than 280° C.) and the reaction time may be set to 1 to 20 hours.

[0058] It is known that in transesterification reactions, oxides, hydroxides, inorganic acid salts, organic acid salts (such as carboxylates), halides, sulfides, etc. of metals (such as lithium, zinc, calcium, lead, barium, manganese, cobalt, zirconium, germanium, antimony, titanium, and tin) are generally used as catalysts.

[0059] However, in step (1) of the present invention, it is preferred not to add a catalyst that is a metal compound. In the present invention, alcoholysis based on polyols and acidolysis based on fatty acids are used together, and the transesterification effect of the ester compound obtained by the reaction of polyols and fatty acids allows sufficient reaction even when a large amount of polyethylene terephthalate is used. By not adding a metal compound catalyst, the amount of rare metals used can be reduced, which can also contribute to sustainability.

[0060] The number average molecular weight of the resin intermediate obtained in step (1) is, for example, in the range of 100 to 5,000, preferably in the range of 500 to 3,000, and more preferably in the range of 500 to 2,000.

[0061] The weight average molecular weight of the resin intermediate obtained in step (1) is, for example, in the range of 500 to 30,000, preferably in the range of 1,000 to 20,000, and more preferably in the range of 1,000 to 12,000.

[0062] The molecular weight of each resin intermediate was confirmed by the method described in Examples.

[0063] The acid value of the resin intermediate obtained in step (1) is, for example, in the range of 10 or less.

[0064] The acid value of the resin intermediate was confirmed by the method described in Examples.

[0065] (Process (2))

[0066] In step (2), a polyvalent carboxylic acid is added to the resin intermediate produced in step (1) to carry out an esterification reaction.

[0067] Examples of the polycarboxylic acid used in step (2) include phthalic acid, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, hexahydrophthalic acid, maleic acid, fumaric acid, succinic acid, adipic acid, sebacic acid, azelaic acid, trimellitic acid, and pyromellitic acid.

[0068] As the polycarboxylic acid, a polycarboxylic acid derivative such as an acid anhydride may be used. In addition, the polycarboxylic acid used may be a single type or two or more types may be used in combination.

[0069] The polycarboxylic acid is preferably at least one selected from succinic acid, sebacic acid, and phthalic acid (including phthalic anhydride).

[0070] Among these, the presence of a biomass-derived polycarboxylic acid can increase the biomass content of the obtained alkyd resin.

[0071] In step (2), the charging ratio of the resin intermediate to the polycarboxylic acid is, for example, resin intermediate: polycarboxylic acid (mass ratio) = 60:40 to 100:0, preferably resin intermediate: polycarboxylic acid (mass ratio) = 60:40 to 95:5, and more preferably resin intermediate: polycarboxylic acid (mass ratio) = 70:30 to 90:10.

[0072] The reaction conditions for the esterification reaction in step (2) may be known reaction conditions, and may be set, for example, within the range of a reaction temperature of 100 to 300° C. and a reaction time of 1 to 10 hours.

[0073] In the esterification reaction, a solvent that can azeotropically distill water generated during the esterification reaction and remove water to the outside of the reaction system can be used, and for example, xylene can be used.

[0074] The alkyd resin obtained by the production method of the present invention (hereinafter, sometimes referred to as "the alkyd resin of the present invention") contains 20% by mass or more of a structure derived from polyethylene terephthalate. Here, "containing 20% ​​by mass or more of a structure derived from polyethylene terephthalate" means that when the total amount of the reaction raw materials (polyethylene terephthalate, polyol, fatty acid, polycarboxylic acid, etc.) used in the production of the alkyd resin is 100 parts by mass, the amount of polyethylene terephthalate is 20 parts by mass or more. The content of the structure derived from polyethylene terephthalate in the alkyd resin of the present invention is preferably 25% by mass or more, and more preferably 30% by mass or more.

[0075] It should be noted that the "reaction raw materials" in the present invention means raw materials that constitute the structure of the alkyd resin, and does not include solvents, catalysts, etc. that do not constitute the structure of the alkyd resin.

[0076] It should be noted that the structure containing 20% ​​by mass or more of polyethylene terephthalate can also be obtained by using 1 H-NMR spectrum or 13 The alkyd resin was analyzed by C-NMR for confirmation.

[0077] The upper limit of the structure derived from polyethylene terephthalate in the alkyd resin of the present invention is not particularly limited, but is, for example, 60 mass % or less, preferably 50 mass % or less, and more preferably 45 mass % or less.

[0078] The number average molecular weight of the alkyd resin of the present invention is, for example, in the range of 1,000 to 10,000, preferably in the range of 1,000 to 5,000, and more preferably in the range of 1,000 to 4,000.

[0079] The weight average molecular weight of the alkyd resin of the present invention is, for example, in the range of 1,000 to 100,000, preferably in the range of 1,000 to 100,000, and more preferably in the range of 8,000 to 100,000.

[0080] The molecular weight of each alkyd resin was confirmed by the method described in Examples.

[0081] The acid value of the alkyd resin of the present invention is, for example, in the range of 20 mgKOH / g or less.

[0082] The acid value of the alkyd resin is confirmed by the method described in Examples.

[0083] The hydroxyl value of the alkyd resin of the present invention is, for example, in the range of 50 to 300 mgKOH / g.

[0084] The hydroxyl value of the alkyd resin is confirmed by the method described in Examples.

[0085] The oil content of the alkyd resin of the present invention is, for example, less than 60%, preferably less than 55%, more preferably less than 50%, and further preferably less than 45%. The lower limit of the oil content of the alkyd resin of the present invention is, for example, 20% or more.

[0086] The oil content of the alkyd resin refers to the ratio of the amount of the fatty acid charged in terms of oil relative to the total mass of the reaction components used in the production of the alkyd resin, expressed as a mass percentage.

[0087] The alkyd resin of the present invention is an alkyd resin containing 20% ​​by mass or more of a structure derived from polyethylene terephthalate, and can promote the reuse of recycled polyethylene terephthalate. In addition, when the polyol is pentaerythritol and / or glycerol, the fatty acid is a vegetable oil fatty acid, and the polycarboxylic acid is sebacic acid and / or succinic acid, the reaction raw materials of the alkyd resin can be set to only components derived from recycled raw materials (recycled polyethylene terephthalate) and components derived from biomass raw materials (polyol, fatty acid and polycarboxylic acid), which can greatly contribute to sustainability.

[0088] [Coating composition]

[0089] The alkyd resin of the present invention can be used, for example, as a binder resin for a coating composition, preferably as a binder resin for a paint composition.

[0090] (Curing agent)

[0091] When the coating composition of the present invention is used as a coating composition, the coating composition of the present invention contains the alkyd resin of the present invention and a curing agent. As the curing agent, a known curing agent can be used, for example, melamine resin, epoxy compound, etc. can be used.

[0092] The melamine resin as the curing agent is preferably a melamine resin having a structure derived from a melamine compound having a hydroxymethyl group and / or an alkoxymethyl group.

[0093] As the melamine resin serving as the curing agent, a commercially available product can be used. Examples of the commercially available product include CYMEL 300, CYMEL 301, CYMEL 303LF, CYMEL 350, CYMEL 370N, CYMEL 771, CYMEL 325, CYMEL 327, CYMEL 703, CYMEL 712, CYMEL 701, CYMEL 266, CYMEL 267, CYMEL 285, CYMEL 232, CYMEL 235, CYMEL 236, CYMEL 238, CYMEL 272, CYMEL 212, CYMEL 253, CYMEL 254, CYMEL 202, CYMEL 207, and MYCOAT 506 (all manufactured by Allnex Japan); Nikalac MW-30M, Nikalac MW-30, Nikalac MW-30HM, Nikalac MW-390, Nikalac MW-100LM, Nikalac MX-750LM, Nikalac MW-22, Nikalac MS-21, Nikalac MS-11, Nikalac MW-24X, Nikalac MS-001, Nikalac MX-002, Nikalac MX-730, Nikalac MX-750, Nikalac MX-708, Nikalac MX-706, Nikalac MX-042, Nikalac MX-035, Nikalac MX-45, Nikalac MX-43, Nikalac MX-417, Nikalac MX-410 (the above are made by SANWA CHEMICAL); U-VAN 20SB, U-VAN 20SE60, U-VAN 21R, U-VAN 22R, U-VAN122, U-VAN 125, U-VAN 220, U-VAN 225, U-VAN 228, U-VAN 2020 (all manufactured by Mitsui Chemicals); AMIDIR J-820-60, AMIDIR L-109-65, AMIDIR L-117-60, AMIDIR L-127-60, AMIDIR 13-548, AMIDIR G-821-60, AMIDIR L-110-60, AMIDIR L-125-60, AMIDIR L-166-60B (all manufactured by DIC Corporation), etc.

[0094] The epoxy compound as the curing agent is preferably an epoxy compound having two or more epoxy groups in one molecule.

[0095] Specific examples of epoxy compounds used as curing agents include cresol novolac epoxy resins, phenol novolac epoxy resins, biphenyl epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, naphthalene epoxy resins, dicyclopentadiene epoxy resins, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, and the like.

[0096] As the curing agent, in addition to melamine resin and epoxy compound, a drying agent such as isocyanate compound and metal soap can be used. The isocyanate compound as the curing agent is preferably a polyfunctional isocyanate compound, more preferably a polyfunctional isocyanate compound having 2 to 6 reactive isocyanate groups per molecule.

[0097] The curing agent contained in the coating composition may be used alone or in combination of two or more.

[0098] The content of the curing agent in the coating composition is, for example, 3 to 40 parts by mass, preferably 10 to 35 parts by mass, and more preferably 20 to 30 parts by mass, based on 100 parts by mass of the total nonvolatile components in the coating composition.

[0099] (Pigment particles)

[0100] The coating composition of the present invention preferably contains pigment particles.

[0101] Specific examples of the pigment particles include white pigments such as titanium oxide (titanium white), zinc oxide (zinc white), lead white, basic lead sulfate, lead sulfate, lithopone, zinc sulfide, and antimony white; black pigments such as carbon black, acetylene black, lamp black, graphite, iron black (black iron oxide), and aniline black; yellow pigments such as naphthol yellow S, Hansa yellow, pigment yellow L, benzidine yellow, permanent yellow, and yellow iron (yellow iron oxide); orange pigments such as chrome orange, chrome vermilion, and permanent orange; brown pigments such as iron oxide and umber; red pigments such as red iron oxide (red iron oxide), red lead, permanent red, quinacridone red pigments, and diketopyrrolopyrrole red pigments; violet pigments such as cobalt violet, fast violet, and methyl violet lake; blue pigments such as ultramarine, Prussian blue, cobalt blue, phthalocyanine blue, and indigo; green pigments such as chrome green, pigment green B, and phthalocyanine green; and the like.

[0102] The pigment particles may include an extender pigment.

[0103] Specific examples of the extender pigment include barium oxide powder, barium sulfate, barium carbonate, calcium carbonate, gypsum, clay, silica, white carbon, diatomaceous earth, talc, magnesium carbonate, hydrous magnesium silicate, alumina white, glossy white, and mica powder.

[0104] The size (particle diameter, etc.) of the pigment particles is not particularly limited. The size may be appropriately set according to various purposes. The average particle diameter of the pigment particles is preferably 0.1 to 10 μm, more preferably 0.1 to 7 μm.

[0105] The pigment particles contained in the coating composition may be used alone or in combination of two or more.

[0106] When the total amount of nonvolatile components in the coating composition is 100 parts by mass, the content of the pigment particles in the coating composition is, for example, in the range of 10 to 70 parts by mass, or preferably in the range of 30 to 60 parts by mass.

[0107] (Solvent)

[0108] The coating composition of the present invention is usually used after being diluted with a solvent.

[0109] Specific examples of the solvent include aromatic hydrocarbon solvents such as toluene and xylene; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, isobutanol, tert-butanol (2-methyl-2-propanol), tert-amyl alcohol, and diacetone alcohol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as dimethyl carbonate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, butyl cellosolve, and PGMAC; and hydrocarbon solvents such as T-SOL-100FLUID, T-SOL-150FLUID, and Pegasol 3040.

[0110] The coating composition of the present invention may further contain a curing accelerator (curing catalyst, etc.), a surfactant, a leveling agent, a thixotropy regulator, an ultraviolet absorber, a light stabilizer, a dispersant, etc. in addition to the above.

[0111] The form of the coating composition of the present invention may be either a one-component type or a two-component type, and may be appropriately set according to the purpose and application.

[0112] An article having a coating film can be produced by applying the coating composition of the present invention to a substrate, drying the solvent, and further thermally curing the coating composition.

[0113] The coating method is not particularly limited, and may be spraying, brushing, rolling, etc. A coating device or a printing device may be used for coating.

[0114] The temperature and time of heat curing may be appropriately set within a range where there is no deformation of the substrate. The temperature is, for example, room temperature to 180° C., and the time is, for example, 10 minutes to 24 hours. Examples of heat curing methods include hot air and a drying oven (dryer) provided in a coating machine.

[0115] The amount of the coating composition applied is not particularly limited, and may be appropriately adjusted so that the thickness of the coating film falls within a range of, for example, 10 to 1,000 μm.

[0116] Example

[0117] Hereinafter, the present invention will be specifically described by way of Examples and Comparative Examples.

[0118] It should be noted that the present invention is not limited to the following examples.

[0119] In the examples of the present application, the acid value and the hydroxyl value are values ​​evaluated by the following methods.

[0120] [Measurement method of acid value]

[0121] The measurement was conducted by a method in accordance with JIS K0070-1992.

[0122] [Method for determination of hydroxyl value]

[0123] The measurement was conducted by a method in accordance with JIS K0070-1992.

[0124] In the examples of the present application, the number average molecular weight of the alkyd resin is a value obtained by GPC measurement and polystyrene conversion, and the measurement conditions are as follows.

[0125] [GPC measurement conditions]

[0126] Measuring device: HLC-8320GPC manufactured by Tosoh Corporation

[0127] Column: TSK-GUARDCOLUMN HXL-H manufactured by Tosoh Corporation

[0128] + TSK-GEL G5000HXL made by Tosoh Corporation

[0129] + TSK-GEL G4000HXL made by Tosoh Corporation

[0130] + TSK-GEL G3000HXL manufactured by Tosoh Corporation

[0131] + TSK-GEL G2000HXL manufactured by Tosoh Corporation

[0132] Detector: RI (differential refractometer)

[0133] Data processing: HLC-8320GPC EcoSEC-Work Station manufactured by Tosoh Corporation

[0134] Determination conditions: column temperature 40°C

[0135] Eluent: tetrahydrofuran

[0136] Flow rate: 1.0mL / min

[0137] Measurement sample: A tetrahydrofuran solution containing 0.5% by mass in terms of resin solid content filtered through a microfilter

[0138] Sample injection volume: 100μl

[0139] Standard sample: Based on the measurement manual of the above-mentioned "HLC-8320GPC", the following monodisperse polystyrene having a known molecular weight was used.

[0140] Standard: A calibration curve was prepared using monodisperse polystyrene (A-500, F-2, F-20, F-80, F-288, A-2500, F-10, F-40, F-128, and F-380 manufactured by Tosoh Corporation).

[0141] (Example 1: Production of alkyd resin and preparation and evaluation of coating composition)

[0142] 106.4 parts by mass of rice bran fatty acid, 75.6 parts by mass of tall oil fatty acid, 161.2 parts by mass of polyethylene terephthalate, and 90.8 parts by mass of pentaerythritol (derived from biomass) were charged into a 4-mouth reaction vessel and reacted at 250° C. for 3 hours to produce a resin intermediate.

[0143] The obtained resin intermediate had an acid value of 2 mgKOH / g, an oil content of 47%, and a number average molecular weight of 800.

[0144] In addition, the polyethylene terephthalate used in Example 1 was recycled PET (produced by FPCO Co., Ltd.).

[0145] The reaction system containing the above-mentioned resin intermediate was temporarily cooled to 160°C, and 65.3 parts by mass of sebacic acid was further added, and the reaction was carried out at 180°C for 10 hours. The process analysis was carried out using an alkyd resin / xylene = 50 / 50 (mass ratio) solution, and the reaction was terminated when the acid value reached 6 mgKOH / g or less. The obtained alkyd resin was diluted with butyl acetate to prepare an alkyd resin solution (non-volatile content 65% by mass).

[0146] The obtained alkyd resin had an oil content of 38%, an acid value of 8, and a number average molecular weight of 2,100.

[0147] In the resulting alkyd resin solution, melamine resin (DIC Corporation's "AMIDIR L-109-65") as a curing agent was added such that the ratio of alkyd resin to melamine resin (by mass) was 75:25. Further, titanium oxide (Chemours Company's "Ti-Pure R-960") was added to prepare an enamel paint (Japanese: エナメル塗料) (non-volatile content: 71% by mass, pigment mass concentration: 60%).

[0148] On a hot-dip galvanized chromate-treated steel sheet with a thickness of 0.5 mm, the resulting enamel paint was applied with a spreader to form an enamel coating film with a film thickness of 76 μm. The steel sheet with the enamel coating film formed thereon was heated in an oven at 130 °C for 20 minutes, thereby obtaining a steel sheet with a topcoat having a dry film thickness of 26 μm.

[0149] The resulting painted steel sheet was evaluated as follows. The results are shown in Table 1.

[0150] (Gloss value)

[0151] For the resulting painted steel sheet, the 60-degree specular reflectance was measured.

[0152] (Substrate adhesion)

[0153] For the resulting painted steel sheet, the substrate adhesion was evaluated based on JIS K-5600. Specifically, on the coating film, incisions 1 mm wide were made with a cutter and the number of checkerboard squares was set to 100. A transparent tape was attached so as to cover all the checkerboard squares and then quickly peeled off. The number of checkerboard squares that remained adhered after the test was expressed as a percentage.

[0154] For substrate adhesion, 100% means that there is no peeling part of the coating film, and 0% means that the entire coating film has peeled off. If adhesion of 95% or more is confirmed, it can be regarded as a performance with no practical problems.

[0155] (Pencil hardness)

[0156] For the painted surface of the steel sheet, the pencil hardness of the painted part of the painted steel sheet was measured in accordance with JISK-5600.

[0157] (DuPont impact)

[0158] Based on JISK5600, an impact die with a hemispherical tip having a radius of 6.3 mm was placed statically on the painted surface of the resulting painted steel sheet, and a weight with a load of 500 g was dropped from heights of 30 cm, 35 cm, 40 cm, 45 cm, and 50 cm onto the above impact die. The height at which cracks occurred is shown in Table 1. It should be noted that in the case where no sheet cracks occurred even when dropped from 50 cm, it was recorded as >50 cm.

[0159] (Example 2: Production of alkyd resin and preparation and evaluation of coating composition)

[0160] 106.4 parts by mass of rice bran fatty acid, 75.6 parts by mass of tall oil fatty acid, 161.2 parts by mass of recycled PET, and 96.5 parts by mass of pentaerythritol (derived from biomass) were placed in a 4-mouth reaction vessel and reacted at 250° C. for 3 hours to produce a resin intermediate.

[0161] The obtained resin intermediate had an acid value of 3 mgKOH / g, an oil content of 45%, and a number average molecular weight of 700.

[0162] The reaction system containing the above-mentioned resin intermediate was temporarily cooled to 160°C, and 80.8 parts by mass of phthalic anhydride was further added, and the reaction was carried out at 180°C for 10 hours. The process analysis was carried out using an alkyd resin / xylene = 50 / 50 (mass ratio) solution, and the reaction was terminated at the time when the acid value of the alkyd resin became 6 mgKOH / g or less. The obtained alkyd resin was diluted with xylene to prepare an alkyd resin solution (non-volatile content 65% by mass).

[0163] The obtained alkyd resin had an oil content of 40%, an acid value of 9 mgKOH / g, and a number average molecular weight of 1,700.

[0164] In addition, the polyethylene terephthalate used in Example 2 was recycled PET (produced by Utsumire Cycle Systems Co., Ltd.).

[0165] The obtained alkyd resin was used to prepare an enamel paint in the same manner as in Example 1, and a coated steel plate was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0166] (Comparative Example 1: Production of alkyd resin and preparation and evaluation of coating composition)

[0167] 106.4 parts by mass of rice bran fatty acid, 67.7 parts by mass of tall oil fatty acid, 120.6 parts by mass of glycerol, 7.7 parts by mass of pentaerythritol (derived from biomass) and 189.7 parts by mass of phthalic anhydride were placed in a 4-mouth reaction vessel and reacted at 210°C for 6 hours. The process analysis was performed using an alkyd resin / xylene = 50 / 50 (mass ratio) solution, and the reaction was terminated when the acid value of the alkyd resin became 3 mgKOH / g or less. The obtained alkyd resin was diluted with xylene to prepare an alkyd resin solution (non-volatile content 60% by mass).

[0168] The obtained alkyd resin had an oil content of 40%, an acid value of 4 mgKOH / g, and a number average molecular weight of 2,400.

[0169] The obtained alkyd resin was used to prepare an enamel paint in the same manner as in Example 1, and a coated steel plate was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0170] [Table 1]

[0171]

[0172] The results in Table 1 show that, although the alkyd resins in the coatings of Examples 1 and 2 contain a high proportion of structures derived from PET, practical performance comparable to that of Comparative Example 1 using an alkyd resin containing no structures derived from PET is obtained.

[0173] In particular, the reaction components of the alkyd resin of Example 1 consist only of components derived from biomass and components derived from recycling, and thus the alkyd resin has excellent sustainability.

Claims

1. A method for producing an alkyd resin, comprising: A step of adding a polyol and a fatty acid to polyethylene terephthalate to perform an ester exchange reaction to prepare a resin intermediate; as well as a step of adding a polycarboxylic acid to the resin intermediate to carry out an esterification reaction, The alkyd resin contains 20% by mass or more of a structure derived from polyethylene terephthalate.

2. The method for producing an alkyd resin according to claim 1, wherein The polyethylene terephthalate is recycled polyethylene terephthalate.

3. The method for producing an alkyd resin according to claim 1 or 2, wherein: The polyol is pentaerythritol and / or glycerol.

4. The method for producing an alkyd resin according to claim 1 or 2, wherein: The fatty acid is vegetable oil fatty acid.

5. The method for producing an alkyd resin according to claim 1 or 2, wherein: The polycarboxylic acid is at least one selected from the group consisting of sebacic acid, succinic acid, and phthalic acid.

6. The method for producing an alkyd resin according to claim 1 or 2, wherein: The oil content of the resin intermediate is less than 60%.

7. The method for producing an alkyd resin according to claim 1 or 2, wherein: In the step of preparing the resin intermediate, the amount of polyethylene terephthalate is 20 parts by mass or more, based on 100 parts by mass of the total of the polyethylene terephthalate, the polyol, and the fatty acid.

8. The method for producing an alkyd resin according to claim 1 or 2, wherein: In the step of preparing the resin intermediate, the transesterification reaction is performed without adding a catalyst as a metal compound.

9. The method for producing an alkyd resin according to claim 1 or 2, wherein: The oil content of the alkyd resin is less than 60%. 10 . A coating composition comprising an alkyd resin obtained by the production method according to claim 1 or 2 .

11. The coating composition according to claim 10, which is a coating composition.

12. A coated substrate coated with the coating composition of claim 11.

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