Water-based paint compositions, coatings, and machinery

Abstract

To provide an aqueous coating composition whose coating layer exhibits improved resistance to cutting oil or lubricating oil when coating.SOLUTION: An aqueous coating composition contains a hydroxy group-containing resin (A), an isocyanate compound (B) containing an isocyanate group or a blocked isocyanate group, a polycondensate of an epoxy group-containing silane compound (C), and an epoxy group-containing silane compound (D).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to aqueous coating compositions, coating films, and machinery. [Background technology]

[0002] Water-based paint compositions use water as a solvent or dispersant, and generally contain less volatile organic compounds (VOCs) compared to solvent-based paint compositions. Therefore, there is a growing demand for water-based paint compositions from an environmental perspective.

[0003] For example, Patent Document 1 describes a composition for repair primers containing an acrylic emulsion (A) containing a specific acrylic resin, a water-dispersible polyisocyanate (B), and a hydrolysate (C) of an epoxy group-containing alkoxysilane. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2009-249491 [Overview of the project] [Problems that the invention aims to solve]

[0005] It is conceivable to use a water-based paint composition to coat the surfaces of machine tools (machines that perform processes such as cutting, drilling, grinding, polishing, rolling, forging, and bending on materials such as metal) and other machinery. However, according to the inventors' findings, conventional water-based paint compositions have a problem in that the coating film is prone to peeling or deterioration when it comes into contact with cutting oil used during the use of machine tools or lubricating oil used during the use of other machinery. In other words, conventional water-based paint compositions had room for improvement in terms of resistance to cutting oil or lubricating oil.

[0006] This invention has been made in view of these circumstances. The object of this invention is to provide an aqueous coating composition that has improved resistance to cutting oil or lubricating oil when applied as a coating film. [Means for solving the problem]

[0007] According to the present invention, the following aqueous coating compositions, coating films, and machines are provided. [1] Hydroxyl group-containing resin (A), An isocyanate compound (B) having an isocyanate group or a blocked isocyanate group, Polycondensate of epoxy group-containing silane compounds (C), Epoxy group-containing silane compound (D), A water-based paint composition containing [the specified ingredient]. [2] The aqueous paint composition described in [1] above, An aqueous paint composition in which the mass ratio ((D) / (C)) of the above polycondensate (C) to the above epoxy group-containing silane compound (D) is 0.1 or more and 10 or less. [3] The aqueous paint composition described in [1] or [2] above, An aqueous coating composition in which the content of the polycondensate (C) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate (C), and the epoxy group-containing silane compound (D) is 0.1% by mass or more and 10% by mass or less. [4] A water-based paint composition according to any of the above [1] to [3], An aqueous coating composition in which the content of the epoxy group-containing silane compound (D) is 1% by mass or more and 50% by mass or less, relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate (C), and the epoxy group-containing silane compound (D). [5] A water-based paint composition according to any of the above [1] to [4], In the polycondensate (C) of the epoxy group-containing silane compound described above, An aqueous paint composition in which the content of epoxy groups per 1 mol of Si atoms is 0.05 mol or more. [6] The aqueous paint composition according to any one of [1] to [5] above, An aqueous paint composition in which the hydroxyl value of the above-mentioned hydroxyl group-containing resin (A) is 50 mgKOH / g or more and 200 mgKOH / g or less. [7] The aqueous paint composition according to any one of [1] to [6] above, An aqueous paint composition further containing a pigment. [8] The aqueous paint composition according to any one of [1] to [7] above, An aqueous paint composition used for painting a machine using cutting oil or lubricating oil. [9] A coating film formed from the aqueous paint composition according to any one of [1] to [8] above.

[10] A machine using cutting oil or lubricating oil, comprising the coating film according to [9] above.

Advantages of the Invention

[0008] According to the present invention, there is provided an aqueous paint composition having improved resistance to cutting oil or lubricating oil when formed into a coating film.

Modes for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described based on embodiments.

[0010] In the present embodiment, "A to B" indicating a numerical range represents A or more and B or less unless otherwise specified.

[0011] The solid content in the present embodiment refers to the components obtained by excluding water and organic solvents from the aqueous resin composition. That is, it is the components remaining on the base material when the aqueous paint composition is applied to the base material to form a coating film.

[0012] In the notation of groups (atomic groups) in this embodiment, notations that do not specify whether they are substituted or unsubstituted include both unsubstituted and substituted groups. For example, "alkyl group" includes not only unsubstituted alkyl groups but also substituted alkyl groups.

[0013] In this embodiment, the term "(meth)acrylic" represents a concept that encompasses both acrylic and methacrylic. The same applies to similar terms such as "(meth)acrylate."

[0014] [Water-based paint composition] The aqueous paint composition of this embodiment is Hydroxyl group-containing resin (A), An isocyanate compound (B) having an isocyanate group or a blocked isocyanate group, Polycondensate of epoxy group-containing silane compounds (C), Epoxy group-containing silane compound (D), It contains.

[0015] The aqueous coating composition of this embodiment can form a coating film with improved resistance to cutting oil or lubricating oil. The mechanism by which this effect is achieved is not clear, but it is presumed to be due to the synergistic effect of the above-mentioned components (A) to (D).

[0016] Furthermore, our studies have revealed that the polycondensate of epoxy group-containing silane compounds (C) and epoxy group-containing silane compound (D) are in a polycondensate-monomer relationship, and that the above effects cannot be obtained if only one of them is included. From this, it is presumed that the synergistic effect of these components is important for the above effects to be exhibited.

[0017] The following describes in detail each component contained in the aqueous coating composition of this embodiment.

[0018] <Hydroxy group-containing resin (A)> In this embodiment, the hydroxyl group-containing resin (A) refers to a resin containing hydroxyl groups. The coating film hardens when the hydroxyl groups of the hydroxyl group-containing resin (A) react with the isocyanate groups of the isocyanate compound (B) described later.

[0019] The following describes a suitable numerical range for the hydroxyl value of the hydroxyl group-containing resin (A). However, if the hydroxyl group-containing resin (A) is obtained in the form of a solution or dispersion, the hydroxyl value of the hydroxyl group-containing resin (A) shall be the hydroxyl value per unit of solids in the solution or dispersion.

[0020] The hydroxyl value of the above-mentioned hydroxyl group-containing resin (A) is preferably 50 mg KOH / g or more, more preferably 60 mg KOH / g or more, and even more preferably 70 mg KOH / g or more. This increases the crosslinking density of the coating film formed from the aqueous coating composition, further improving the mechanical properties of the coating film.

[0021] The hydroxyl value of the above hydroxyl group-containing resin (A) is preferably 200 mg KOH / g or less, more preferably 190 mg KOH / g or less, and even more preferably 180 mg KOH / g or less. This reduces the amount of residual hydroxyl groups that remain without being used for crosslinking in the coating film formed from the aqueous paint composition, thereby further improving the water resistance of the coating film.

[0022] The hydroxyl value of the above hydroxyl group-containing resin (A) is preferably 50 mg KOH / g or more and 200 mg KOH / g or less, more preferably 60 mg KOH / g or more and 190 mg KOH / g or less, and even more preferably 70 mg KOH / g or more and 180 mg KOH / g or less. This further improves the balance between the mechanical properties and water resistance of the coating film.

[0023] The hydroxyl value can typically be determined according to the provisions of JIS K 0070.

[0024] The usable hydroxyl group-containing resin (A) is not particularly limited and can be used without any particular restriction as long as it can react with at least the isocyanate compound (B) when the paint composition is heated.

[0025] Examples of hydroxyl group-containing resins (A) include polyol resins, alkyd resins, phenolic resins, (meth)acrylic resins, polyester resins, polyamide resins, epoxy resins, nitrocellulose resins, rosin-modified resins, maleic acid resins, urethane resins, vinyl chloride resins, vinyl acetate resins, and vinyl chloride-vinyl acetate copolymers, all of which contain hydroxyl groups.

[0026] The hydroxyl group-containing resin (A) preferably contains a hydroxyl group-containing (meth)acrylic resin.

[0027] The dosage form of the hydroxyl group-containing resin (A) is not particularly limited, but from the viewpoint of ease of preparing the aqueous coating composition, it is preferably an aqueous dispersion.

[0028] The hydroxyl group-containing resin (A) preferably contains a hydroxyl group-containing (meth)acrylic resin and is an aqueous dispersion. Examples of commercially available aqueous dispersions containing such hydroxyl group-containing (meth)acrylic resins include the Barnock® series from DIC Corporation and the MACRYNAL® series from Daicel Ornex Co., Ltd.

[0029] The aqueous coating composition of this embodiment may contain only one type of hydroxyl group-containing resin (A), or it may contain two or more types.

[0030] The content of the hydroxyl group-containing resin (A) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate product of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more.

[0031] The content of the hydroxyl group-containing resin (A) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate product of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0032] The content of the hydroxyl group-containing resin (A) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate product of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 1% by mass or more and 90% by mass or less, more preferably 5% by mass or more and 85% by mass or less, and still more preferably 10% by mass or more and 80% by mass or less.

[0033] <Isocyanate compound (B)> In this embodiment, the isocyanate compound (B) refers to a compound having an isocyanate group or a blocked isocyanate group.

[0034] The usable isocyanate compound (B) is not particularly limited and can be used without any particular restriction as long as it can react with at least the polyester resin (A) when the paint composition is heated.

[0035] Specific examples of isocyanate compounds (B) include the following:

[0036] Aliphatic diisocyanate compounds: hexamethylene diisocyanate, trimethylene diisocyanate, 1,4-tetramethylene diisocyanate, pentamethylene diisocyanate, lysine diisocyanate, 1,3-butylene diisocyanate, etc.

[0037] Alicyclic diisocyanate compounds: isophorone diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), methylcyclohexane-2,4-(or-2,6-)diisocyanate, 1,3-(or 1,4-)di(isocyanatomethyl)cyclohexane, 1,4-cyclohexanediisocyanate, 1,3-cyclopentanediisocyanate, 1,2-cyclohexanediisocyanate, etc.

[0038] Aromatic diisocyanate compounds: xylylene diisocyanate, metaxylylene diisocyanate, tetramethylxylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, (m- or p-)phenylene diisocyanate, etc.

[0039] Other polyisocyanates: Polyisocyanate compounds having three or more isocyanate groups, such as triphenylmethane-4,4',4''-triisocyanate; adducts obtained by reacting polyols such as ethylene glycol, propylene glycol, 1,4-butylene glycol, polyalkylene glycol, trimethylolpropane, and hexanetriol with an excess amount of polyisocyanate compounds relative to the hydroxyl groups; biuret-type adducts such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and 4,4'-methylenebis(cyclohexyl isocyanate); isocyanuric ring-type adducts, etc.

[0040] Examples of commercially available isocyanate compounds (B) include Covestro's Bayhydur® series, DIC Corporation's Barnock® series, and Evonik's VESTAGON® series.

[0041] Furthermore, blocked isocyanate compounds in which some or all of the isocyanate groups of the above-mentioned isocyanate compounds are blocked by a blocking agent can also be mentioned. More specifically, blocked isocyanate compounds in which the isocyanate groups are blocked by blocking agents such as alcohols, phenols, lactams, and oximes can also be used as curing agents.

[0042] Furthermore, phenol-based, lactam-based, or oxime-based blocking agents are preferred as blocking agents. Examples of phenolic blocking agents include phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, hydroxydiphenyl, t-butylphenol, and methyl hydroxybenzoate. Examples of lactam-based blocking agents include ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam. Examples of oxime-based blocking agents include acetaldehyde, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, and cyclohexane oxime.

[0043] The amount of isocyanate groups in isocyanate compound (B) can be expressed as the mass ratio of isocyanate groups to the total isocyanate compound. The mass ratio of isocyanate groups to the total isocyanate compound (B) (hereinafter referred to as the NCO amount) is preferably 5 to 50%, more preferably 5 to 30%, and even more preferably 10 to 25%. This further improves the mechanical properties of the coating film.

[0044] The amount of NCO can typically be determined according to the provisions of JIS K 6806.

[0045] The ratio (NCO / OH) of the number of moles of isocyanate groups in the isocyanate compound (B) to the number of moles of hydroxyl groups in the hydroxyl group-containing resin (A) is preferably 0.5 to 1.5, and more preferably 0.8 to 1.2. This further improves the mechanical properties of the coating film.

[0046] The aqueous coating composition of this embodiment may contain only one isocyanate compound (B), or it may contain two or more isocyanate compounds (B).

[0047] The content of the isocyanate compound (B) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate product of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more.

[0048] The content of the isocyanate compound (B) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate product of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0049] The content of the isocyanate compound (B) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate product of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 45% by mass or less, and still more preferably 10% by mass or more and 40% by mass or less.

[0050] <Polycondensate of epoxy group-containing silane compounds (C)> In this embodiment, any polycondensate (C) of an epoxy group-containing silane compound can be used as long as it is obtained by polycondensing an epoxy group-containing silane compound.

[0051] Specific examples of epoxy group-containing silane compounds that serve as raw materials for the polycondensation of the polycondensate (C) of epoxy group-containing silane compounds include 3-glycidoxytrialkoxysilanes such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 3-glycidoxypropyltrippropoxysilane; 3-glycidoxyalkyldialkoxysilanes such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropylmethyldipropoxysilane; and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0052] Polycondensate (C) of epoxy group-containing silane compounds can be obtained by polycondensation reaction of epoxy group-containing silane compounds. For example, when polycondensing methoxysilane, the polycondensate (C) can be obtained by carrying out the polymerization reaction while removing methanol by hydrolysis.

[0053] Polycondensation reactions can be carried out under any conditions, but from the viewpoint of reaction efficiency, it is preferable to carry them out at room temperature or above, more preferable at 50°C or above, even preferable at 60°C or above, and even preferable at 70°C or above. Furthermore, from the viewpoint of preventing decomposition of the polycondensate, polycondensation reactions are usually carried out at 300°C or below.

[0054] During polycondensation reactions, the pH may be adjusted to accelerate the reaction. For example, the pH may be lowered using an acid such as hydrochloric acid or sulfuric acid, or it may be raised using a base such as sodium bicarbonate, sodium carbonate, or sodium hydroxide.

[0055] Alternatively, the polycondensation reaction may be carried out under reduced pressure. Carrying the polycondensation reaction under reduced pressure can accelerate the reaction. For example, when polycondensing methoxysilane, the reaction proceeds while methanol is removed by hydrolysis. However, the polycondensation reaction can be accelerated by removing methanol under reduced pressure.

[0056] As mentioned above, polycondensate (C) of epoxy group-containing silane compounds can be obtained by polycondensation of epoxy group-containing silane compounds, but in this process, some epoxy groups may undergo ring-opening.

[0057] As an indicator of the amount of epoxy groups remaining without ring opening, the content of epoxy groups (moles) per mole of Si atoms can be used. Since this value indicates the amount of epoxy relative to silane in the polycondensate (C), the larger the amount of epoxy groups remaining without ring opening, the higher this value will be.

[0058] The content of epoxy groups (moles) per 1 mol of Si atoms was determined by referring to the method described in paragraphs

[0039] to

[0041] of Japanese Patent Publication No. 2020-050858. 1 It can be obtained by 1H-NMR analysis.

[0059] Specifically, the polycondensate (C) of epoxy group-containing silane compounds 1 H NMR was measured, and the hydrogen atoms H on the epoxy group a The peak area and the hydrogen atom H on the carbon atom adjacent to the silicon atom. b The peak area is obtained, and the ratio of the obtained peak areas ([hydrogen atom H a [Peak area of ​​hydrogen atom H] / [H] b The peak area of ​​the peak can be expressed as the content of epoxy groups (moles) per 1 mol of Si atoms. Hydrogen atom H a and hydrogen atom H b The position is as shown in the general formula (1) below.

[0060] [ka]

[0061] In the general formula (1), n is an arbitrary number greater than 0, and R 1 is an arbitrary organic group, and R 2 is an arbitrary organic group or a hydroxy group. Examples of the organic group include an alkyl group, an alkoxy group, a thioalkyl group, etc.

[0062] In the polycondensate (C) of the epoxy group-containing silane compound according to this embodiment, the content (mol) of the epoxy group per 1 mol of Si atoms is preferably 0.01 mol or more, more preferably 0.05 mol or more, and still more preferably 0.10 mol or more. By being within the above numerical range or more, a certain amount or more of the epoxy group can be ensured. Thereby, the water resistance of the coating film formed from the aqueous coating composition is further improved.

[0063] In the polycondensate (C) of the epoxy group-containing silane compound according to this embodiment, the content (mol) of the epoxy group per 1 mol of Si atoms is preferably 0.99 mol or less, more preferably 0.98 mol or less, still more preferably 0.97 mol or less, and even more preferably 0.96 mol or less. By being within the above numerical range or less, a certain amount of the hydroxy group generated by the ring-opening of the epoxy group can be ensured, and a certain amount of the cross-linked structure formed by the reaction of the hydroxy group with the isocyanate compound (B) etc. can also be ensured. Thereby, the mechanical properties of the coating film formed from the aqueous coating composition are further improved. Also, thereby, the cutting oil resistance of the coating film formed from the aqueous coating composition is further improved.

[0064] In the polycondensate (C) of the epoxy group-containing silane compound according to this embodiment, the content (mol) of the epoxy group per 1 mol of Si atoms is preferably 0.01 mol or more and 0.99 mol or less, more preferably 0.05 mol or more and 0.98 mol or less, and still more preferably 0.10 mol or more and 0.97 mol or less. This further improves the balance between the mechanical properties and water resistance of the coating film formed from the water-based paint composition.

[0065] Furthermore, epoxy equivalent can be used to indicate the amount of epoxy groups in the polycondensate (C) of the epoxy group-containing silane compound according to this embodiment. The epoxy equivalent can be measured in accordance with JIS K7236:2001.

[0066] The epoxy equivalent of the polycondensate (C) of the epoxy group-containing silane compound according to this embodiment is preferably 100 or more, more preferably 150 or more, and even more preferably 200 or more.

[0067] The epoxy equivalent of the polycondensate (C) of the epoxy group-containing silane compound according to this embodiment is preferably 4000 or less, more preferably 3000 or less, and even more preferably 2500 or less.

[0068] The aqueous coating composition of this embodiment may contain only one type of polycondensate (C) of epoxy group-containing silane compounds, or it may contain two or more types.

[0069] The content of the polycondensate of the epoxy group-containing silane compound (C) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more.

[0070] The content of the polycondensate of the epoxy group-containing silane compound (C) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 10% by mass or less, more preferably 7.5% by mass or less, and even more preferably 5.0% by mass or less.

[0071] The content of the polycondensate of the epoxy group-containing silane compound (C) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 7.5% by mass or less, and still preferably 1.0% by mass or more and 5.0% by mass or less.

[0072] <Epoxy group-containing silane compound (D)> In this embodiment, any silane compound containing an epoxy group can be used as the epoxy group-containing silane compound (D).

[0073] Specific examples of epoxy group-containing silane compounds (D) include those described above, which serve as raw materials for the polycondensation of the epoxy group-containing silane compound polycondensate (C).

[0074] The aqueous coating composition of this embodiment may contain only one epoxy group-containing silane compound (D), or it may contain two or more.

[0075] The epoxy equivalent of the epoxy group-containing silane compound (D) in this embodiment is preferably 160 or more, more preferably 200 or more, and even more preferably 220 or more.

[0076] The epoxy equivalent of the epoxy group-containing silane compound (D) in this embodiment is preferably 400 or less, more preferably 350 or less, and even more preferably 300 or less.

[0077] The epoxy equivalent can be measured in accordance with JIS K7236:2001.

[0078] The content of the epoxy group-containing silane compound (D) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more.

[0079] The content of the epoxy group-containing silane compound (D) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate product of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0080] The content of the epoxy group-containing silane compound (D) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is preferably 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 45% by mass or less, and still more preferably 10% by mass or more and 40% by mass or less.

[0081] The mass ratio ((D) / (C)) of the polycondensate (C) of the epoxy group-containing silane compound described above to the epoxy group-containing silane compound described above is preferably 0.1 or higher, more preferably 0.2 or higher, and even more preferably 0.3 or higher. This further improves the cutting oil resistance of the coating film formed from the aqueous coating composition.

[0082] The mass ratio ((D) / (C)) of the polycondensate (C) of the epoxy group-containing silane compound described above to the epoxy group-containing silane compound described above is preferably 10 or less, more preferably 9 or less, and even more preferably 8 or less. This further improves the cutting oil resistance of the coating film formed from the aqueous coating composition.

[0083] The mass ratio ((D) / (C)) of the polycondensate (C) of the epoxy group-containing silane compound described above to the epoxy group-containing silane compound described above is preferably 0.1 to 10, more preferably 0.1 to 9, and even more preferably 0.2 to 8. This further improves the cutting oil resistance of the coating film formed from the aqueous coating composition.

[0084] <Optional ingredients> The aqueous paint composition of this embodiment may contain any other components as needed.

[0085] The aqueous paint composition of this embodiment preferably further contains a pigment. This makes it possible to give the paint film a desired color and enhance the aesthetic appeal of the paint film.

[0086] The pigments that can be used are not particularly limited. For example, known inorganic pigments and organic pigments can be used. Specifically, white pigments such as titanium dioxide (titanium white), zinc oxide, 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 pyrite (yellow iron oxide); and orange pigments such as chrome orange, chrome vermilion, and permanent orange. Examples of pigments include, but are not limited to, brown pigments such as iron oxide and amber; red pigments such as red iron oxide, red lead, permanent red, quinacridone-based red pigments, and diketopyrrolopyrrole-based red pigments; purple pigments such as cobalt purple, fast violet, and methyl violet lake; blue pigments such as ultramarine, Prussian blue, cobalt blue, phthalocyanine blue, and indigo; and green pigments such as chrome green, pigment green B, and phthalocyanine green.

[0087] The amount of pigment in the aqueous coating composition of this embodiment is not particularly limited and can be adjusted as appropriate in consideration of the desired color and other performance characteristics. As an example, the pigment content is typically 50 to 150 parts by mass, preferably 70 to 100 parts by mass, when the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate of the epoxy group-containing silane compound (C), and the epoxy group-containing silane compound (D) is 100 parts by mass.

[0088] The aqueous paint composition of this embodiment may contain additive components that enhance the smoothness of the paint film surface. Examples of such components include surface modifiers, defoamers (components that break air trapped during painting), plasticizers, silicone compounds, waxes, leveling agents, and anti-blooming agents, all of which are known in the paint field. Examples of surface modifiers and defoamers include the BYK series manufactured by BYK Corporation.

[0089] Furthermore, as other optional components, the aqueous coating composition of this embodiment may also contain resin components other than the hydroxyl group-containing resin (A), a curing catalyst, a coupling agent, a pigment dispersant, an ultraviolet absorber, a light stabilizer, an antioxidant, a magnetic powder, a charge control agent, and the like. Furthermore, the aqueous paint composition of this embodiment may also contain an aqueous solvent such as DPDM (dipropylene glycol dimethyl ether).

[0090] You may use only one optional component, or you may use multiple components in combination.

[0091] <Application> The applications of the aqueous coating composition of this embodiment are not particularly limited, but it is preferably used to paint machinery that uses cutting oil or lubricating oil.

[0092] Cutting oils and lubricants can be broadly classified into two types: oil-based oils, whose main component is mineral oil and / or fatty oil, and water-soluble oils, which are used after being diluted with water.

[0093] To add some information about the classification of water-soluble cutting fluids, according to JIS standards, water-soluble cutting fluids are further classified into A1 type: milky white (emulsion), A2 type: semi-transparent to transparent (soluble), or A3 type: transparent (solution).

[0094] In recent years, cutting fluids containing synthetic lubricants as lubricating components have also been used. Such cutting fluids are sometimes called "oil-free" because they do not contain natural components (mainly mineral oil), or "synthetic" because they use chemically synthesized lubricating components (synthetic lubricants).

[0095] The aqueous coating composition of this embodiment can provide a coating film with improved resistance to cutting oil or lubricating oil, and is therefore suitable for coating machinery that uses cutting oil or lubricating oil as described above.

[0096] The material of the machine using cutting oil or lubricating oil is typically metal, preferably iron (steel), but is not limited to this. Furthermore, the shape of the machine is not particularly limited. Furthermore, the surface of the machine to which the aqueous paint composition of this embodiment is applied may be pre-treated in some way from the viewpoint of rust prevention and adhesion. Examples of pre-treatment include, but are not limited to, washing, degreasing, blasting, primer coating, pre-heating, drying, and film formation (e.g., zinc phosphate treatment).

[0097] [coating film] The coating film in this embodiment is formed using the above-described aqueous coating composition.

[0098] The coating film of this embodiment can be formed by applying the above-described aqueous coating composition to the surface of a substrate. The application method is not particularly limited and can be applied by any means such as a spray, brush, or roller.

[0099] The material of the substrate on which the coating film is formed in this embodiment is not particularly limited and may be any material such as metal, resin, stone, wood, or paper.

[0100] The coating film of this embodiment may be cured. The curing method is not limited; it may be cured at room temperature or by heat treatment. The temperature and time of the heat treatment should be set appropriately within a range that does not cause deformation of the substrate layer. For example, the temperature can be 30 to 140°C, and the time can be 1 minute to 24 hours. Specific methods of heat treatment include using hot air or a drying oven (dryer) of a known coating machine.

[0101] [machine] The machine of this embodiment is equipped with the above-mentioned coating.

[0102] The type of machine in this embodiment is not particularly limited, but it is preferable that it is used with cutting oil or lubricating oil.

[0103] Machines that use cutting oil or lubricating oil during operation include machine tools, that is, machines that perform processing on materials such as metals, such as cutting, drilling, grinding, polishing, rolling, forging, and bending. More specifically, machine tools include lathes, drilling machines, boring machines, milling machines, grinding machines, gear cutting machines, machining centers, turning centers, and the like. More specifically, examples of machines that use lubricating oil include internal combustion engines, transmissions, differentials, pumps, and bearings.

[0104] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0105] Embodiments of the present invention will be described in detail based on examples and comparative examples. However, the present invention is not limited to these examples.

[0106] [Epoxy group content per 1 mol of Si atoms (mol)] With reference to the method described in paragraphs

[0039] to

[0041] of Japanese Patent Publication No. 2020-050858, 1 The content of epoxy groups (moles) per mole of Si atoms was obtained by 1H-NMR analysis.

[0107] First, under the following conditions, the polycondensate (C-1) of the epoxy group-containing silane compound obtained was 1 1H-NMR was measured. • Frequency: 400MHz • Number of scans: 64 • Solvent: Deuterated chloroform Standard: Tetramethylsilane

[0108] Next, the hydrogen atom H on the epoxy group a The peak area and the hydrogen atom H on the carbon atom adjacent to the silicon atom. b The peak area is obtained, and the ratio of the obtained peak areas ([hydrogen atom H a [Peak area of ​​hydrogen atom H] / [H] b The peak area of ​​the peak was defined as the content of epoxy groups (moles) per 1 mol of Si atoms. Note that hydrogen atom H a and hydrogen atom H b The position is as shown in the general formula (1) below.

[0109] [ka]

[0110] In general formula (1), n ​​is any number greater than 0, and R 1 is any organic group, and R 2 is any organic group or hydroxyl group. Examples of organic groups include alkyl groups, alkoxy groups, thioalkyl groups, etc.

[0111] [Synthesis of polycondensates (C) of epoxy group-containing silane compounds] <Synthesis of polycondensate (C-1) of epoxy group-containing silane compounds> In a reaction vessel equipped with a stirrer, thermometer, dropping funnel, condenser, and air inlet, 100 parts by mass of Dynasylan® GLYMO (3-glycidoxypropyltrimethoxysilane, manufactured by Evonik) was charged under a nitrogen atmosphere. Next, a mixture of 40 parts by mass of methanol and 10 parts by mass of 1 N hydrochloric acid was charged and stirred. While continuing to stir, the temperature inside the reaction vessel was raised to 60°C, and stirring was continued for a further 4 hours to obtain the reaction mixture. The resulting reaction mixture was mixed with 0.1 N hydrochloric acid to adjust the pH to 3.0. The resulting reaction product was filtered, and water was added to adjust the solid content to 40.0% to obtain the polycondensate (C-1) of the epoxy group-containing silane compound.

[0112] The epoxy group content (moles) per mol of Si atoms in the polycondensate (C-1) of the epoxy group-containing silane compound obtained by the above method was 0.50 mol.

[0113] <Synthesis of polycondensates (C-2) of epoxy group-containing silane compounds> 100 parts by mass of Dynasylan® GLYMO were charged into a reaction vessel equipped with a stirrer, thermometer, dropping funnel, condenser, and air inlet under a nitrogen atmosphere. Next, a mixture of 9.2 parts by mass of water, 5.3 parts by mass of methanol, and 0.01 parts by mass of sodium bicarbonate was charged and stirred. While continuing to stir, the temperature inside the reaction vessel was raised to 70°C, and stirring was continued for a further 2 hours to obtain the reaction mixture. The resulting reaction mixture was cooled to 60°C, and 0.1 N hydrochloric acid was added to adjust the pH to 5.6. The reaction mixture, with the pH adjusted to 5.6, was stirred at 100°C for 1 hour under reduced pressure of 10 mbar or less to obtain the reaction product. The obtained reaction product was filtered, and water was added to adjust the solid content to 40.0% to obtain the polycondensate (C-2) of the epoxy group-containing silane compound.

[0114] The epoxy group content (moles) per mol of Si atoms in the polycondensate (C-2) of the epoxy group-containing silane compound obtained by the above method was 0.95 mol.

[0115] [Preparation of water-based paint compositions] Details of each component shown in Table 1 are as follows.

[0116] <Hydroxy group-containing resin (A)> • Barnock (registered trademark) WD-566: Aqueous dispersion of hydroxyl group-containing acrylic resin, hydroxyl value per solid content 100 mg KOH / g, solid content 43% by mass, manufactured by DIC Corporation. • MACRYNAL (registered trademark) VSM 6299w / 42WAB: Aqueous dispersion of hydroxyl group-containing acrylic resin, hydroxyl value per solid content 135 mgKOH / g, solid content 42%, manufactured by Daicel Ornex.

[0117] <Isocyanate compounds having an isocyanate group or a blocked isocyanate group (B)> • Bayhydur® 3100: Polyisocyanate, NCO content 17.4%, manufactured by Covestro. • Barnock (registered trademark) DNW-5500: Polyisocyanate, NCO content 13.5%, manufactured by DIC Corporation.

[0118] <Polycondensate of epoxy group-containing silane compounds (C)> • Polycondensate of epoxy group-containing silane compounds (C-1) obtained in the above [Synthesis of polycondensate of epoxy group-containing silane compounds (C)] • Polycondensate of epoxy group-containing silane compounds (C-2) obtained in the above [Synthesis of polycondensate of epoxy group-containing silane compounds (C)]

[0119] <Epoxy group-containing silane compound (D)> • Dynasylan® GLYMO: 3-Glycidoxypropyltrimethoxysilane, manufactured by Evonik.

[0120] <Other ingredients> • Defoaming agent BYK-025: Polysiloxane-based defoaming agent, manufactured by BYK. • Surface modifier BYK-347: Polyethersiloxane-based surfactant, manufactured by BYK. • Solvent: DPDM (Dipropylene Glycol Dimethyl Ether), manufactured by Sankyo Chemical Co., Ltd. ·water • Pigment CR-95: Titanium dioxide, manufactured by Ishihara Sangyo Co., Ltd.

[0121] <Preparation of aqueous paint composition> (Example 1) According to the component names and proportions listed in Table 1, a hydroxyl group-containing resin (A), solvent, water, and pigment were prepared and mixed to obtain a mixed solution. The resulting mixture was placed in a polyethylene container with titania beads and shaken for 2 hours using a paint shaker (manufactured by Asada Iron Works Co., Ltd.). After that, the titania beads were filtered out to obtain a dispersion. To the obtained dispersion, an isocyanate compound (B), a polycondensate of an epoxy group-containing silane compound (C), an epoxy group-containing silane compound (D), an antifoaming agent, and a surface modifier were added according to the component names and amounts listed in Table 1, and the mixture was mixed to obtain an aqueous resin composition.

[0122] (Examples 2-9, Comparative Examples 1-2) An aqueous resin composition was obtained in the same manner as in Example 1, according to the amounts of each component listed in Table 1.

[0123] [Preparation of test coated panels] A commercially available cold-rolled steel sheet (manufactured by Nippon Test Panel Co., Ltd., SPCC-SD: 75mm wide x 150mm long x 0.8mm thick) was used as the base material, and the aqueous resin composition obtained in the above [Preparation of Aqueous Paint Composition] was applied to it by air spraying to a dry film thickness of approximately 50 μm. The aqueous resin composition was diluted with thinner as appropriate before air spraying. The painted substrate was dried at room temperature for 7 days to obtain a test coated plate on which a coating film had formed on the substrate surface.

[0124] [Physical property testing] The following tests were performed using the obtained test coated panels.

[0125] <Adhesion> Using the test coating plates obtained in the above [Preparation of test coating plates], tests were conducted based on JIS K5600-5-6 (1999) "Mechanical properties of coating films - Adhesion (cross-cut method)". The adhesion of the coating film to the substrate was then evaluated based on the following evaluation criteria. The results are shown in Table 1.

[0126] 5: The edges of the cuts are perfectly smooth, and there is no peeling in any of the grid lines. 4: There is small peeling of the paint film at the intersection of the cuts, and the area of ​​the peeled area is less than 5%. 3: The area of ​​the peeled portion is 5% or more but less than 15%. 2: The area of ​​the peeled portion is 15% or more but less than 35%. 1: The area of ​​the peeled portion is 35% or more.

[0127] <Hot water resistance> First, on the coating film of the test coating panel obtained in the above [Preparation of Test Coating Panel], eleven parallel lines were drawn at 2 mm intervals, reaching the substrate, using a cutter knife with the cutting blade held at a 30-degree angle. Then, eleven parallel lines perpendicular to these lines were drawn at 2 mm intervals, forming 100 grid patterns on the coating film. After immersing the test coated panels, which had formed a grid pattern, in 40°C hot water for 240 hours, each test coated panel was visually inspected to check for appearance abnormalities such as blister formation and peeling of the coating film, and evaluated based on the following criteria. The results are shown in Table 1.

[0128] 5: There is no peeling in any of the grid lines, and no visible abnormalities are found. 4: There is no delamination in any of the grid lines, but there are cosmetic abnormalities such as blistering. 3: There is peeling in fewer than 50 grid squares. 2: There is peeling in more than 50 grid squares. 1: The entire coating has peeled off the substrate.

[0129] <Resistant to water-based cutting fluids> The following four types of water-based cutting fluids were prepared. • Syntylo 9954 (manufactured by Castrol) • Yushiroken Synthetic #663 (manufactured by Yushiro Chemical Industry Co., Ltd.) • Yushiroken EC50T3 (manufactured by Yushiro Chemical Industry Co., Ltd.) • BrasoCut 4000 Strong (Brother Swisslube)

[0130] A test coated plate with a grid pattern was obtained using the method described above, and this plate was immersed in a 5% aqueous solution of each of the above-mentioned water-soluble cutting oils at 50°C for 240 hours (10 days). After 240 hours, the test plates were removed from each aqueous solution and visually inspected for any abnormalities in appearance and any peeling of the coating. The time taken for the appearance abnormalities, such as blistering, or peeling in one or more grid patterns, was then evaluated based on the following criteria. The results are shown in Table 1.

[0131] After 5:240 hours, no abnormalities in appearance or paint peeling occurred. 4. Between 200 hours and less than 240 hours. 3. Between 150 hours and less than 200 hours. 2: Between 100 hours and less than 150 hours. Less than 1:100 hours.

[0132] <Resistant to oily cutting fluids> The following oil-based cutting fluids were prepared: • ReliaCut TG30 (manufactured by ENEOS Corporation)

[0133] A test coated plate with a grid pattern was obtained using the method described above, and this plate was immersed in the above-mentioned oily cutting fluid at 50°C for 240 hours (10 days). After 240 hours, the test plates were removed from the oil-based cutting fluid and visually inspected for any abnormalities in the appearance of the test coated plates and any peeling of the coating film. The results were then evaluated based on the criteria described in the section on <Resistance to Water-Based Cutting Fluids>. The results are shown in Table 1.

[0134] <Impact Resistance> The test was performed using a DuPont impact resistance tester under conditions of 23°C and 50% relative humidity. Specifically, impact tests were conducted on the coating surface of the test coating plates obtained using the method described above, under the conditions of a weight of 500g, a striking die tip diameter of 1 / 2 inch, and a drop height of 10-50cm, and the maximum height (cm) at which the coating did not crack was measured. The results are shown in Table 1.

[0135] <Bending resistance> A bending test was performed in accordance with JIS K5600-5-1 (1999) "Mechanical properties of coatings - Bending resistance (cylindrical mandrel method)" to deform each test plate obtained in the above <Formation of coating> section. The condition of the coating after the test was visually observed and evaluated according to the following criteria. The test was performed using a Type 1 test apparatus with a cylindrical mandrel with a diameter of 3 mm. The results are shown in Table 1.

[0136] 4: No cracks in the paint film. 3: There are very slight cracks in the paint film, but no peeling of the paint film. 2: Cracks appear in the paint film, but there is no peeling of the paint film. 1: Cracks appear and the paint film peels off.

[0137] [Table 1]

[0138] As shown in Table 1, the coating films formed from the aqueous coating composition of this embodiment (Examples 1-9) exhibited superior resistance to cutting oil compared to the coating film of Comparative Example 1, which was formed from an aqueous coating composition that did not contain the polycondensate (C) of the epoxy group-containing silane compound, and the coating film of Comparative Example 2, which was formed from an aqueous coating composition that did not contain the epoxy group-containing silane compound (D). In other words, it was demonstrated that the aqueous coating composition of this embodiment can form a coating film with improved resistance to cutting oil.

[0139] Furthermore, a comparison of Examples 2 and 9 suggests that a relatively low content of epoxy groups per mole of Si atoms in the polycondensate (C) of the epoxy group-containing silane compound tends to result in better flexibility and cutting oil resistance of the coating film formed from the aqueous coating composition.

Claims

1. Hydroxyl group-containing resin (A), An isocyanate compound (B) having an isocyanate group or a blocked isocyanate group, Polycondensate of epoxy group-containing silane compounds (C), Epoxy group-containing silane compound (D), It contains, The mass ratio ((D) / (C)) of the polycondensate (C) to the epoxy group-containing silane compound (D) is 0.1 or more and 10 or less. The content of the hydroxyl group-containing resin (A) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate (C), and the epoxy group-containing silane compound (D) is 10% by mass or more and 80% by mass or less. The content of the isocyanate compound (B) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate (C), and the epoxy group-containing silane compound (D) is 10% by mass or more and 40% by mass or less. The content of the polycondensate (C) relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate (C), and the epoxy group-containing silane compound (D) is 0.1% by mass or more and 10% by mass or less. An aqueous coating composition in which the content of the epoxy group-containing silane compound (D) is 1% by mass or more and 50% by mass or less, relative to the total amount of the hydroxyl group-containing resin (A), the isocyanate compound (B), the polycondensate (C), and the epoxy group-containing silane compound (D).

2. The aqueous paint composition according to claim 1, In the polycondensate (C) of the epoxy group-containing silane compound, A water-based paint composition having an epoxy group content of 0.05 mol or more per mol of Si atoms.

3. An aqueous paint composition according to claim 1 or 2, An aqueous coating composition wherein the hydroxyl value of the hydroxyl group-containing resin (A) is 50 mg KOH / g or more and 200 mg KOH / g or less.

4. An aqueous paint composition according to claim 1 or 2, Furthermore, a water-based paint composition containing pigments.

5. An aqueous paint composition according to claim 1 or 2, A water-based paint composition used for coating machinery that uses cutting oil or lubricating oil.

6. A coating film formed by the aqueous coating composition according to claim 1 or 2.

7. A machine that uses cutting oil or lubricating oil, comprising the coating film described in claim 6.

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