Silicone-modified epoxy resin, coating composition, and article coated with said coating composition

Abstract

Provided are a silicone-modified epoxy resin and a coating composition containing said resin, from which a cured product exhibiting high heat resistance can be obtained. Specifically provided is a silicone-modified epoxy resin having an epoxy equivalent weight in the range of 1,000-3,000 g / equivalent weight, and having an alkyl group with 10 or more carbon atoms.

Description

Silicone-modified epoxy resin, coating composition, and article coated with said coating composition

[0001] The present invention relates to a silicone-modified epoxy resin, a coating composition, and an article coated with the coating composition.

[0002] Coating the surfaces of metal components with a protective resin is widely used as a method for imparting heat resistance and corrosion resistance (weather resistance) to industrial metal components such as steel sheets for automobiles, steel pipes for gas pipelines, and metal building materials, as well as household metal components such as frying pans and barbecue grills.

[0003] In particular, motorcycle mufflers and steel pipes for gas pipelines, which require high heat resistance and corrosion resistance, are generally coated with epoxy resin for protection.

[0004] As the epoxy resin, a silicone-modified epoxy resin, which is modified with silicone, is known (for example, Patent Document 1). The silicone-modified epoxy resin has enhanced heat resistance by introducing a siloxane bond, which has high bond strength, into the epoxy resin.

[0005] Special Publication No. 2020-521020

[0006] The epoxy resin in Patent Document 1 is a silicone-modified epoxy resin obtained by modifying an epoxy resin with a reactive organosilane, but its heat resistance does not reach 500° C., and its performance cannot be said to be sufficient.

[0007] High cross-linking can improve the heat resistance of epoxy resins themselves, but increasing the epoxy equivalent to achieve high cross-linking also increases viscosity, posing the problem of significantly reducing compatibility with pigments that impart various functions to coatings, such as extender pigments and anti-rust pigments. If compatibility between the epoxy resin and pigment cannot be ensured, voids will form in the resulting coating, impairing the coating's heat resistance. For this reason, there is naturally an upper limit to the epoxy equivalent of epoxy resins for coatings.

[0008] The problem to be solved by the present invention is to provide a silicone-modified epoxy resin that can produce a cured product exhibiting high heat resistance, and a coating composition containing said resin.

[0009] As a result of extensive research to solve the above problems, the present inventors discovered that by introducing an alkyl group having 10 or more carbon atoms into a silicone-modified epoxy resin, it is possible to prevent the resin from becoming too viscous and also ensure compatibility with pigments, and thus completed the present invention.

[0010] That is, the present invention relates to the following silicone-modified epoxy resins, etc.: 1. A silicone-modified epoxy resin having an epoxy equivalent in the range of 1,000 to 3,000 g / equivalent and having an alkyl group having 10 or more carbon atoms. 2. The silicone-modified epoxy resin according to 1, which has a bisphenol structure. 3. The silicone-modified epoxy resin according to 1 or 2, which has an acid value in the range of 1 to 10 mgKOH / g. 4. The silicone-modified epoxy resin according to any one of 1 to 3, which has as reaction components an epoxy resin having a hydroxyl group, a silicone compound having a silanol group, and a fatty acid. 5. The silicone-modified epoxy resin according to 4, wherein the epoxy resin having a hydroxyl group is a bisphenol-type epoxy resin having a hydroxyl group. 6. The silicone-modified epoxy resin according to 4, wherein the silicone compound having a silanol group is a bisphenol-type epoxy resin having a hydroxyl group. ３ SiO １／２ Units (M units), SiO ４／２ Unit (Q unit), R ２ SiO ２／２ Units (D units) and RSiO ３／２The silicone-modified epoxy resin according to 4 or 5, which is a silicone compound having one or more siloxy units selected from units (T units) (R is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, or a hydroxyl group), has two or more silanol groups, and the proportion of phenyl groups in R in the siloxy units is 50 mol % or more. 7. The silicone-modified epoxy resin according to any of 4 to 6, wherein the fatty acid is a saturated fatty acid having 11 to 22 carbon atoms. 8. The silicone-modified epoxy resin according to any of 4 to 7, wherein, in the reaction components, the epoxy resin is in the range of 30 to 60 parts by mass, the silicone compound having a silanol group is in the range of 20 to 50 parts by mass, and the fatty acid is in the range of 1 to 5 parts by mass. 9. A coating composition containing the silicone-modified epoxy resin according to any of 1 to 8 and a pigment. 10. A cured product of the coating composition according to 9. 11. An article coated with the cured product of the coating composition according to 9. 12. A metal member coated with the cured product of the coating composition according to 9.

[0011] The present invention provides a silicone-modified epoxy resin that exhibits high heat resistance, and a coating composition that can yield a coating that exhibits high heat resistance.

[0012] An embodiment of the present invention will be described below. The present invention is not limited to the following embodiment, and can be carried out by making appropriate modifications within the scope that does not impair the effects of the present invention. The compounds in this specification may be derived from fossil resources or biological resources.

[0013] [Silicone-Modified Epoxy Resin] The silicone-modified epoxy resin of the present invention has an epoxy equivalent in the range of 1,000 to 3,000 g / equivalent and has an alkyl group having 10 or more carbon atoms. Despite the high epoxy equivalent, the silicone-modified epoxy resin of the present invention can be prevented from becoming highly viscous by introducing an alkyl group having 10 or more carbon atoms. Furthermore, by introducing an alkyl group having 10 or more carbon atoms, compatibility with pigments, which will be described later, can be ensured.

[0014] In the present invention, "having an alkyl group having 10 or more carbon atoms" means that the silicone-modified epoxy resin has at least one alkyl group having 10 or more carbon atoms. In the present invention, at least one of the terminal epoxy groups of the silicone-modified epoxy resin is preferably substituted with an alkyl group having 10 or more carbon atoms. In other words, the silicone-modified epoxy resin of the present invention preferably has an alkyl group having 10 or more carbon atoms at at least one terminal.

[0015] The alkyl group having 10 or more carbon atoms contained in the silicone-modified epoxy resin of the present invention is preferably an alkyl group having 12 to 22 carbon atoms, and more preferably an alkyl group having 12 to 18 carbon atoms. The alkyl group having 10 or more carbon atoms contained in the silicone-modified epoxy resin of the present invention may be either a branched alkyl group or a linear alkyl group, but is preferably a linear alkyl group.

[0016] The silicone-modified epoxy resin of the present invention may have an epoxy equivalent in the range of 1,000 to 3,000 g / equivalent, preferably in the range of 1,000 to 2,500 g / equivalent, and more preferably in the range of 1,000 to 2,200 g / equivalent. The epoxy equivalent of the silicone-modified epoxy resin of the present invention is evaluated by the method described in the examples.

[0017] The acid value of the silicone-modified epoxy resin of the present invention is, for example, in the range of 1 to 10 mgKOH / g, preferably in the range of 1 to 8 mgKOH / g, more preferably in the range of 1 to 7 mgKOH / g, and even more preferably in the range of 1 to 6 mgKOH / g. The acid value of the silicone-modified epoxy resin of the present invention is evaluated by the method described in the Examples.

[0018] The number average molecular weight of the silicone-modified epoxy resin of the present invention is not particularly limited, but is, for example, in the range of 500 to 10,000, preferably 1,000 to 8,000, and more preferably 1,000 to 6,000. The weight average molecular weight of the silicone-modified epoxy resin of the present invention is not particularly limited, but is, for example, in the range of 10,000 to 50,000, and preferably 20,000 to 40,000. The number average molecular weight and weight average molecular weight of the silicone-modified epoxy resin of the present invention are evaluated by the methods described in the examples.

[0019] The silicone-modified epoxy resin of the present invention preferably comprises an epoxy resin having a hydroxyl group, a silicone compound having a silanol group, and a fatty acid as reaction components. Here, "reaction components" refers to components that constitute the structure of the silicone-modified epoxy resin, and does not include solvents or catalysts that do not constitute the structure of the silicone-modified epoxy resin. Each component will be explained below.

[0020] (Epoxy Resin Having Hydroxyl Group) An epoxy resin is a resin having at least one epoxy group in the molecule, and examples thereof include bisphenol-type epoxy resins such as bisphenol A type, bisphenol F type, bisphenol E type, bisphenol B type, bisphenol S type, bisphenol AD ​​type, bisphenol AP type, and bisphenol BP type; novolac-type epoxy resins such as phenol novolac type and cresol novolac type; resorcinol-type epoxy resins; aromatic epoxy resins such as trisphenolmethane triglycidyl ether; naphthalene-type epoxy resins; fluorene-type epoxy resins; and biphenyl-type epoxy resins. The epoxy resin having a hydroxyl group of the present invention is, for example, the above-mentioned epoxy resin, further having a hydroxyl group.

[0021] The epoxy resin having a hydroxyl group is preferably a bisphenol A type epoxy resin having a hydroxyl group, and more preferably a compound represented by the following general formula (A-1).

[0022] (In the general formula (A-1), X is a bisphenol structure represented by the following general formula (A-2), and n is the number of repeating units.)

[0023] (In the general formula (A-2), R １ and R ２ are each independently an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, n1 and n2 are each independently an integer ranging from 0 to 4, L is a single bond, an alkylene group having 1 to 6 carbon atoms, an ether bond (—O—), a ketone bond (—C(═O)—), an ester bond (—C(═O)O—, a sulfide bond (—S—), or a sulfonyl bond (—SO ２ -) is.)

[0024] In general formula (A-2), R １ If there are multiple R １ may be the same or different. ２ If there are multiple R ２ may be the same as or different from each other.

[0025] When the epoxy resin having a hydroxyl group is, for example, a compound represented by the general formula (A-1), the epoxy group of the compound represented by the general formula (A-1) reacts with a fatty acid to introduce an alkyl group at the terminal.

[0026] The epoxy equivalent of the hydroxyl group-containing epoxy resin is preferably in the range of 300 to 3,000 g / equivalent, more preferably 450 to 3,000 g / equivalent, and even more preferably 600 to 3,000 g / equivalent. The epoxy equivalent is the weight of the epoxy resin required to obtain 1 mol of epoxy groups, and is measured by the method described in the Examples.

[0027] In the present invention, the epoxy resins having hydroxyl groups used should be used so that their average epoxy equivalent falls within the range of 1,000 to 3,000 g / equivalent. For example, when two types of epoxy resins having hydroxyl groups are used, they should be used so that their average epoxy equivalent, calculated as (total weight of epoxy resins) / {(amount of epoxy resin 1 used / epoxy equivalent of epoxy resin 1)+(amount of epoxy resin 2 used / epoxy equivalent of epoxy resin 2), falls within the range of 1,000 to 3,000.

[0028] The epoxy resin having a hydroxyl group may be a commercially available product, and examples of such commercially available products include EPICLON 1055, EPICLON 3040, EPICLON 3050, EPICLON 4050, EPICLON 7050 (all manufactured by DIC Corporation), LAPOX P-62, LAPOX P-5 (all manufactured by ATUL INDIA), E-20 (epoxy equivalent: 455 to 555 g / Eq), E-21 (epoxy equivalent: 480 to 580 g / Eq), E-42 (epoxy equivalent: 230 to 280 g / Eq), E-44 (epoxy equivalent: 210 to 240 g / Eq), and E-51 (epoxy equivalent: 184 to 194 g / Eq) (all manufactured by Sinopec Corporation).

[0029] (Silanol Group-Containing Silicone Compound) The silanol group of the silicone compound having a silanol group can react with the hydroxyl group of the epoxy resin to form a crosslinked structure that crosslinks epoxy resins together.

[0030] The silicone compound having a silanol group is preferably a silicone compound having two or more silanol groups, and more preferably R ３ SiO １／２ Units (M units), SiO ４／２ Unit (Q unit), R ２ SiO ２／２ Units (D units) and RSiO ３／２ The silicone compound has one or more siloxy units selected from units (T units) (R is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, or a hydroxyl group), and has two or more silanol groups.

[0031] The silicone compound having a silanol group is R ３ SiO １／２ Units (M units), SiO ４／２ Unit (Q unit), R ２ SiO ２／２ Units (D units) and RSiO ３／２ In the case of a silicone compound having one or more siloxy units selected from units (T units) (R is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, or a hydroxyl group) and having two or more silanol groups, the proportion of the phenyl groups in R in the siloxy units is preferably 50 mol % or more.

[0032] Heat resistance can be improved by setting the proportion of phenyl groups in R in the siloxy units to 50 mol % or more. The proportion of phenyl groups in the siloxy units can be confirmed by Fourier transform infrared spectroscopy (FTIR), and the upper limit of the proportion of phenyl groups in the siloxy units is, for example, 80 mol %.

[0033] The silicone compound having a silanol group can be a commercially available product, and examples of such commercially available products include DOWSIL RSN-6018, DOWSIL RSN-0220, and DOWSIL 3040 (all manufactured by The Dow Chemical Company). The proportion of phenyl groups in R in the siloxy units of the commercially available products is 73 mol % for DOWSIL RSN-6018, 67 mol % for DOWSIL RSN-0220, and 50 mol % for DOWSIL 3040.

[0034] (Fatty Acid) The fatty acid is preferably a saturated fatty acid having 11 to 22 carbon atoms, more preferably a straight-chain saturated fatty acid having 11 to 22 carbon atoms, and even more preferably a straight-chain saturated fatty acid having 11 to 18 carbon atoms.

[0035] The fatty acids may be used alone or in combination of two or more.

[0036] Specific examples of fatty acids include undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, heneicosylic acid, and behenic acid.

[0037] Oils containing fatty acids may be used as reaction components. Examples of such fats include hydrogenated coconut oil fatty acids, hydrogenated palm kernel oil fatty acids, hydrogenated palm oil fatty acids, hydrogenated olive oil fatty acids, hydrogenated castor oil fatty acids, and hydrogenated rapeseed oil fatty acids. These are obtained by hydrolyzing and hydrogenating oils obtained from coconut, palm kernel, palm, olive, castor, and rapeseed, respectively, and all are mixtures of two or more long-chain aliphatic monocarboxylic acids.

[0038] The silicone-modified epoxy resin of the present invention preferably contains an epoxy resin having hydroxyl groups, a silicone compound having silanol groups, and a fatty acid as reaction components, and may further contain components other than these as long as the effects of the present invention are not impaired. The silicone-modified epoxy resin of the present invention is preferably a reaction product of an epoxy resin having hydroxyl groups, a silicone compound having silanol groups, and a fatty acid.

[0039] The blending ratio of the silicone compound having a silanol group is, for example, in the range of 50 to 100 parts by mass, preferably in the range of 60 to 90 parts by mass, and more preferably in the range of 70 to 85 parts by mass, per 100 parts by mass of the epoxy resin having a hydroxyl group.

[0040] The mixing ratio of the fatty acid is, for example, in the range of 1 to 10 parts by mass, preferably in the range of 1 to 7 parts by mass, more preferably in the range of 1 to 5 parts by mass, and even more preferably in the range of 3 to 4 parts by mass, relative to 100 parts by mass of the epoxy resin having a hydroxyl group.

[0041] The proportions of the respective components in the reaction components are preferably in the range of 30 to 60 parts by mass of the hydroxyl group-containing epoxy resin, 20 to 50 parts by mass of the silanol-modified silicone compound, and 1 to 5 parts by mass of the fatty acid.

[0042] The reaction of an epoxy resin having a hydroxyl group, a silicone compound having a silanol group, and a fatty acid can be carried out by a known method, and for example, the silicone-modified epoxy resin of the present invention can be prepared by heating a reaction system containing an epoxy resin having a hydroxyl group, a silicone compound having a silanol group, and a fatty acid. Alternatively, the silicone-modified epoxy resin of the present invention can be prepared by reacting an epoxy resin having a hydroxyl group with a silicone compound having a silanol group to form a silicone-modified epoxy resin, and then reacting the resulting resin with a fatty acid.

[0043] [Coating Composition] The coating composition of the present invention contains the silicone-modified epoxy resin of the present invention and a pigment, and is used, for example, by dissolving it in a solvent.

[0044] Examples of the solvent for the coating composition of the present invention include alcohol solvents such as methanol, ethanol, propanol, n-butanol, iso-butanol, tert-butanol, and 3-methoxybutanol; glycol solvents such as ethylene glycol and propylene glycol; glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol dimethyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol dimethyl ether; glycol ester solvents such as ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, and tetrahydrofuran. The solvent may be used alone or in combination of two or more kinds.

[0045] In the coating composition of the present invention, the solvent is used so that the solid content concentration is, for example, 10 to 80 mass %, and preferably 50 to 70 mass %.

[0046] The coating composition of the present invention can ensure sufficient pigment compatibility. The pigments include, for example, those called "extender pigments" and those called "anti-rust pigments." Extender pigments are pigments that are blended with resin compositions to improve their properties (weight increase, colorability, drying properties, etc.), while anti-rust pigments are pigments that are blended with resin compositions to improve their corrosion resistance.

[0047] Specific examples of extender pigments include barium sulfate, barium carbonate, calcium carbonate, magnesium oxide, magnesium carbonate, magnesium hydroxide, barium titanate, calcium hydroxide, calcium sulfite, calcium sulfate, calcium oxide, calcium silicate, titanium oxide, silica, zeolite, and talc.

[0048] Specific examples of the rust-preventive pigment include phosphates, hydrogen phosphates, phosphosilicates, borosilicates, borates, metaborates, molybdates, chromates, polyphosphates, and the like of one or more metals selected from the group consisting of calcium, strontium, barium, zinc, aluminum, and magnesium.

[0049] The coating composition of the present invention may contain at least one of an extender pigment and an anti-rust pigment. The coating composition may contain one or more types of extender pigments. Similarly, the coating composition may contain one or more types of anti-rust pigments.

[0050] When the coating composition of the present invention contains an extender pigment and / or an anti-rust pigment, the total content of the extender pigment and the anti-rust pigment (pigment content) is, for example, in the range of 20 to 80 parts by mass, and preferably in the range of 30 to 70 parts by mass, per 100 parts by mass of the silicone-modified epoxy resin of the present invention.

[0051] (Other Components) The coating composition of the present invention may be in the form of a one-component paint that does not use a curing agent, or in the form of a multi-component paint that does use a curing agent.

[0052] Examples of the curing agent include polyisocyanate compounds, melamine compounds, epoxy compounds, oxazoline compounds, and carbodiimide compounds.

[0053] The coating composition of the present invention may further contain, as necessary, various additives such as a metal drier (which plays a role in promoting oxidative polymerization of carbon-carbon double bonds in the resin), wax, surfactant, stabilizer, flow modifier, dye, leveling agent, rheology control agent, ultraviolet absorber, antioxidant, plasticizer, antistatic agent, defoaming agent, viscosity modifier, light resistance stabilizer, weather resistance stabilizer, heat resistance stabilizer, pigment dispersant, thermosetting resin, thermoplastic resin, etc. Known additives can be used for these.

[0054] The coating composition of the present invention may be applied directly to the article to be coated, or a primer coating material suitable for the article to be coated may be applied first, and then the coating composition of the present invention may be applied.

[0055] Examples of materials for the article to be coated include various metals such as iron, copper, zinc, aluminum, magnesium, etc., and alloys of these metals; plastic substrates such as polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS), PC-ABS polymer alloy, polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyamide (PA), polypropylene (PP), fiber reinforced plastic (FRP) containing fillers such as glass fiber and carbon fiber; and glass.

[0056] As a method for applying the coating composition of the present invention, known methods can be used, and the method varies depending on the article to be coated. Examples include methods using a gravure coater, roll coater, comma coater, knife coater, air knife coater, curtain coater, kiss coater, shower coater, wheeler coater, spin coater, dipping, screen printing, spraying, applicator, bar coater, brush, roller, etc.

[0057] The coating composition of the present invention can also be cured by a known method after application. The conditions are adjusted appropriately depending on the presence or absence of a curing agent, the desired film thickness, etc., but for example, a method of heating and curing for a certain period of time at a temperature in the range of about 120 to 350°C can be used.

[0058] Examples of articles having a cured coating film of the coating composition of the present invention include housings and internal parts of home appliances such as televisions, refrigerators, washing machines, and air conditioners; housings and internal parts of electronic devices such as smartphones, mobile phones, tablet devices, personal computers, digital cameras, and game consoles; housings of office equipment such as printers and facsimiles; leisure and sporting goods; interior and exterior materials for various vehicles such as automobiles, ships, and railway cars; industrial machinery; interior and exterior materials for buildings such as exterior walls, roofs, glass, and decorative panels; and civil engineering materials such as soundproof walls and drainage ditches.

[0059] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0060] In the examples of the present application, the acid value, hydroxyl value, and epoxy equivalent values ​​were evaluated by the following methods. [Method for measuring acid value] Measured by a method conforming to JIS K0070-1992. [Method for measuring hydroxyl value] Measured by a method conforming to JIS K0070-1992. [Method for measuring epoxy equivalent] Measured by a method conforming to JIS K7236-2009.

[0061] In the examples of the present application, the number average molecular weight and weight average molecular weight of the epoxy resin are values ​​calculated as polystyrene based on GPC measurement, and the measurement conditions are as follows. [GPC measurement conditions] Measurement apparatus: High-speed GPC apparatus "HLC-8320GPC" manufactured by Tosoh Corporation Column: "TSK GURADCOLUMN SuperHZ-L" manufactured by Tosoh Corporation + "TSK gel SuperHZM-M" manufactured by Tosoh Corporation + "TSK gel SuperHZM-M" manufactured by Tosoh Corporation + "TSK gel SuperHZ-2000" manufactured by Tosoh Corporation + "TSK gel SuperHZ-2000" manufactured by Tosoh Corporation Detector: RI (differential refractometer) Data processing: "EcoSEC Data Analysis Version 1.07" manufactured by Tosoh Corporation Column temperature: 40°C Developing solvent: tetrahydrofuran Flow rate: 0.35 mL / min Measurement sample: 7.5 mg of sample was dissolved in 10 ml of tetrahydrofuran, and the resulting solution was filtered through a microfilter to prepare the measurement sample. Sample injection amount: 20 μl Standard sample: The following monodisperse polystyrene with known molecular weight was used in accordance with the measurement manual for the "HLC-8320GPC".

[0062] (Monodisperse polystyrene) "A-300" manufactured by Tosoh Corporation "A-500" manufactured by Tosoh Corporation "A-1000" manufactured by Tosoh Corporation "A-2500" manufactured by Tosoh Corporation "A-5000" manufactured by Tosoh Corporation "F-1" manufactured by Tosoh Corporation "F-2" manufactured by Tosoh Corporation "F-4" manufactured by Tosoh Corporation "F-10" manufactured by Tosoh Corporation "F-20" manufactured by Tosoh Corporation "F-40" manufactured by Tosoh Corporation "F-80" manufactured by Tosoh Corporation "F-128" manufactured by Tosoh Corporation "F-288" manufactured by Tosoh Corporation

[0063] Synthesis Example 1: Preparation of Alkyl-Containing Silicone-Modified Epoxy Resin A-1 A four-neck flask equipped with a stirrer, thermometer, temperature controller, and nitrogen inlet tube was charged with 17.0 parts by mass of bisphenol A-type epoxy resin "EPICLON 3050" (DIC Corporation, epoxy equivalent: 740-860 g / Eq), 11.0 parts by mass of bisphenol A-type epoxy resin "EPICLON 7050" (DIC Corporation, epoxy equivalent: 1750-2100 g / Eq), 1.0 part by mass of lauric acid (Kao Corporation), 23.0 parts by mass of silanol-modified silicone compound "DOWSIL RSN 6018" (Dow Corning Corporation), and 16.0 parts by mass of ortho-xylene as a solvent. These were melted and heated to 130-140°C with stirring, and then allowed to react for 3-4 hours while maintaining the same temperature and dehydrating. After the reaction was completed, the ortho-xylene was distilled off under reduced pressure, and the resulting mixture was diluted with methoxypropyl acetate to obtain a silicone-modified epoxy resin A-1 (non-volatile content 51% by mass) having alkyl groups at the terminals.

[0064] The physical properties of the obtained silicone-modified epoxy resin A-1 were as follows: Acid value: 4.9 mg KOH / g Epoxy equivalent: 2,000 g / Eq Number average molecular weight: 5,000 Weight average molecular weight: 35,000 Decomposition temperature: 420°C

[0065] Comparative Synthesis Example 1: Preparation of Silicone-Modified Epoxy Resin B-1 A four-neck flask equipped with a stirrer, thermometer, temperature controller, and nitrogen inlet tube was charged with 15.0 parts by mass of bisphenol A epoxy resin "EPICLON 1055" (DIC Corporation, epoxy equivalent: 450-500 g / Eq), 25.0 parts by mass of silanol-modified silicone compound "DOWSIL RSN 6018" (Dow Corning Corporation), and 25.0 parts by mass of a cyclohexanone / butyl acetate mixed solvent (cyclohexanone:butyl acetate = 50:50 (by mass)) as a solvent. These were melted and heated to 75°C with stirring, and 0.05 g of zinc naphthenate was added as a catalyst. The mixture was heated to 125°C and allowed to react for 5 hours while maintaining the same temperature and dehydrating, to obtain a silicone-modified epoxy resin B-1 (non-volatile content: 50% by mass).

[0066] The physical properties of the obtained silicone-modified epoxy resin B-1 were as follows: Epoxy equivalent: 475 g / Eq Number average molecular weight: 1,200 Weight average molecular weight: 15,000 Decomposition temperature: 360°C

[0067] (Synthesis Comparative Example 2: Preparation of Silicone-Modified Epoxy Resin B-2) A four-neck flask equipped with a stirrer, thermometer, temperature controller, and nitrogen inlet tube was charged with 17.0 parts by mass of bisphenol A-type epoxy resin (DIC Corporation's "EPICLON 3050"), 11.0 parts by mass of bisphenol A-type epoxy resin (DIC Corporation's "EPICLON 7050"), 24.0 parts by mass of a silanol-modified silicone compound (Dow Corning Corporation's "DOWSIL RSN 6018"), and 16.0 parts by mass of ortho-xylene as a solvent. These were melted and heated to 130-140°C with stirring, and reacted for 3-4 hours while maintaining the same temperature and dehydrating. After completion of the reaction, the pressure was reduced to distill off the ortho-xylene, and the mixture was diluted with methoxypropyl acetate to obtain silicone-modified epoxy resin B-2 (non-volatile content 50% by mass).

[0068] The physical properties of the resulting silicone-modified epoxy resin B-2 were as follows: Epoxy equivalent: 1,996 g / Eq Number average molecular weight: 2,500 Weight average molecular weight: 10,000 Decomposition temperature: 300°C

[0069] (Example 1 and Comparative Examples 1-2: Preparation of coating compositions, formation of coating films and evaluation) Coatings were prepared using the produced silicone-modified epoxy resins according to the formulations shown in Tables 1 and 2, and the prepared coating compositions were applied to the substrates shown in Tables 1 and 2 to form coating films. The resulting coating films were evaluated as follows. The results are shown in Tables 1 and 2.

[0070] Specifically, the coating film was formed by applying the coating composition to a substrate with a bar coater to a film thickness of 20 μm, followed by baking and heat treatment at 270° C. for 10 minutes. The coating film was evaluated after being left to stand at room temperature of 25° C. for 1 day.

[0071] (Formulation Pattern I) 28.26 parts by mass of the silicone-modified epoxy resin shown in Tables 1 and 2, 28.26 parts by mass of titanium oxide ("Ti-Pure R-960" manufactured by Chemours), and 14.79 parts by mass of propylene glycol monomethyl ether acetate as a solvent were mixed and milled in a paint shaker for 90 minutes to obtain a milled base. 28.26 parts by mass of the silicone-modified epoxy resin shown in Tables 1 and 2, 0.43 parts by mass of a silicone leveling agent ("Modaflow 2100" manufactured by ALLNEX), and 14.79 parts by mass of propylene glycol monomethyl ether acetate were further added to the obtained milled base and mixed to prepare a coating composition with a non-volatile content of 57% by mass and a pigment mass concentration of 50% by mass.

[0072] (Mixture Pattern II) 28.22 parts by mass of the silicone-modified epoxy resin shown in Tables 1 and 2, 28.22 parts by mass of titanium oxide (Chemours' "Ti-Pure R-960"), carbon black (Mitsubishi Chemical Corporation's "Carbon Black 1000"), and 14.77 parts by mass of propylene glycol monomethyl ether acetate as a solvent were mixed and milled in a paint shaker for 90 minutes to obtain a milled base. 28.22 parts by mass of the silicone-modified epoxy resin shown in Tables 1 and 2, 0.43 parts by mass of a silicone leveling agent (ALLNEX's "Modaflow 2100"), and 14.79 parts by mass of propylene glycol monomethyl ether acetate were further added and mixed to the obtained milled base to prepare a coating composition with a non-volatile content of 57% by mass and a pigment mass concentration of 50% by mass.

[0073] (Storage stability) The prepared coating compositions were stored for 3 months at room temperature of 25°C, and a coating film was formed using the stored coating composition by the above method. The resulting coating film was visually evaluated according to the following criteria: A: No blisters (bubble swelling) or discoloration (yellowing, etc.) were observed on the coating film surface. B: Blisters (bubble swelling) and / or discoloration (yellowing, etc.) were observed on the coating film surface. C: The coating film did not adhere to the substrate.

[0074] (Gloss Value) The gloss of the coating film formed on the substrate was measured at any five points at an incident angle of 60° and a reflection angle of 60° using a gloss meter Micro-Tri-Gloss (manufactured by BYK), and the measured values ​​were taken as the gloss value. The gloss value is an index of pigment dispersion, and a higher value indicates better pigment dispersion.

[0075] (Substrate Adhesion) The substrate adhesion of the coating film formed on the substrate was evaluated in accordance with JIS K-5400:1990. Specifically, 1 mm wide cuts were made on the coating film with a cutter to form 100 grids, and cellophane tape was applied so as to cover all of the grids, which were then quickly peeled off. The number of grids remaining in adhesion after the test was expressed as a percentage. In terms of substrate adhesion, 100% means that no coating film peeled off, and 0% means that the entire coating film peeled off. Adhesion of 95% or more can be considered to be acceptable for practical use.

[0076] (Koenig Hardness) The Koenig hardness of the coating film formed on the substrate was measured in accordance with ISO1522.

[0077] (Pencil Hardness) The pencil hardness of the coating film formed on the substrate was measured in accordance with EN13523-4.

[0078] (Heat resistance) The coated substrate was placed in a ceramic oven and heated at 600°C for 10 minutes. After heating, the heated coated substrate was immersed in water at room temperature. This process was repeated five times. After five cycles, the coating surface of the coated substrate was visually inspected and evaluated according to the following criteria: A: No scratches, discoloration, or blisters on the coating surface B: At least one of scratches, discoloration, and blisters on the coating surface C: The coating was completely damaged

[0079] (Adhesion to Substrate After Heating) For those samples that were rated "A (no scratches, discoloration or blisters on the coating surface)" in the heat resistance evaluation, the above-mentioned substrate adhesion evaluation was carried out again.

[0080]

[0081]

[0082] Tables 1 and 2 show that high heat resistance is obtained with coating films prepared using a coating composition containing a silicone-modified epoxy resin A-1 having an alkyl group. On the other hand, sufficient heat resistance is not obtained with coating films prepared using a coating composition containing a silicone-modified epoxy resin B-1 (having no alkyl group). In coating films prepared using a coating composition containing a silicone-modified epoxy resin B-2 (having no alkyl group), the high epoxy equivalent of the silicone-modified epoxy resin B-2 results in insufficient compatibility with the pigment, resulting in a loss of gloss in the coating film. Furthermore, insufficient pigment dispersion is expected to result in the formation of voids in the coating film, and heat resistance is also not achieved.

Claims

1. A silicone-modified epoxy resin having as reaction components an epoxy resin having a hydroxyl group, a silicone compound having a silanol group, and a fatty acid, A silicone-modified epoxy resin having an epoxy equivalent in the range of 1,000 to 3,000 g / equivalent and an alkyl group having 10 or more carbon atoms.

2. 2. The silicone-modified epoxy resin according to claim 1, which has a bisphenol structure.

3. 3. The silicone-modified epoxy resin according to claim 1, having an acid value in the range of 1 to 10 mgKOH / g.

4. 3. The silicone-modified epoxy resin according to claim 1, wherein the epoxy resin having a hydroxyl group is a bisphenol-type epoxy resin having a hydroxyl group.

5. The silicone compound having a silanol group is R ３ SiO １／２ Units (M units), SiO ４／２ Unit (Q unit), R ２ SiO ２／２ Units (D units) and RSiO ３／２ 3. The silicone-modified epoxy resin according to claim 1 or 2, which is a silicone compound having one or more siloxy units selected from units (T units) (R is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, or a hydroxyl group), has two or more silanol groups, and the proportion of phenyl groups in R in the siloxy units is 50 mol % or more.

6. 3. The silicone-modified epoxy resin according to claim 1, wherein the fatty acid is a saturated fatty acid having 11 to 22 carbon atoms.

7. 3. The silicone-modified epoxy resin according to claim 1, wherein, in the reaction components, the epoxy resin is in a range of 30 to 60 parts by mass, the silicone compound having a silanol group is in a range of 20 to 50 parts by mass, and the fatty acid is in a range of 1 to 5 parts by mass.

8. A coating composition comprising the silicone-modified epoxy resin according to claim 1 or 2 and a pigment.

9. A cured product of the coating composition according to claim 8.

10. An article coated with the cured coating composition according to claim 8.

11. A metal member coated with the cured product of the coating composition according to claim 8.