Intermediate coating composition, article using same, and method for manufacturing article

Abstract

Provided is a intermediate-coat coating material composition which can form a intermediate-coat coating film having high adhesion to layers of a multilayer coating film, can form a multilayer coating film having high adhesion to an object to be coated, and furthermore can form a multilayer coating film having an excellent coating film appearance.　The present invention provides a intermediate-coat coating material composition which contains a coating film-forming resin (A), a coating film-forming resin (B) and a coating film-forming resin (C). The coating film-forming resin (B) and the coating film-forming resin (C) are acrylic resins. The glass transition temperature Tg (A), the glass transition temperature Tg (B) and the glass transition temperature Tg (C) satisfy the relationship Tg (A) < Tg (B) < Tg (C). The glass transition temperature Tg (I) of the intermediate-coat coating material composition is 25-60ºC. The coating film-forming resins (A), (B) and (C) are contained under specific conditions relative to 100 parts by mass in terms of resin solid content of the intermediate-coat coating material composition.

Description

[Technical field]

[0001] The present invention relates to an intermediate coating composition, an article using the same, and a method for producing an article. [Background technology]

[0002] Multilayer coating films having multiple coating films with different functions that are disposed on a substrate are used in various fields. For example, multilayer coating films are sometimes provided on vehicle exterior members.

[0003] JP 2018-8205 A (Patent Document 1) discloses a multilayer coating film obtained by forming an uncured coating film of a primer coating composition on a substrate and applying a topcoat coating composition on the uncured coating film using a wet-on-wet coating method, the primer coating composition containing an epoxy resin (a1), and a topcoat coating composition (B) containing an acrylic resin (b1) and an active methylene-blocked polyisocyanate compound (b2), the acrylic resin (b1) being 60 to 80 parts by mass and the active methylene-blocked polyisocyanate compound (b2) being 20 to 40 parts by mass based on 100 parts by mass of the total solid content of the acrylic resin (b1) and the active methylene-blocked polyisocyanate compound (b2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-8205 A Summary of the Invention [Problem to be solved by the invention]

[0005] A multi-layer coating film must satisfy performance requirements according to its application. For example, multi-layer coating films used for vehicles are required to have various physical properties. Furthermore, in order to improve the function and appearance of the multi-layer coating film, the provision of a coating film that functions as a clear coating film has also been considered. As a multi-layer coating film having such a function, for example, a multi-layer coating film having an undercoat coating film disposed on the substrate, an intermediate coating film disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film has been considered.

[0006] On the other hand, Patent Document 1 discloses a multi-layer coating film for vehicle use, which has two coating layers. Compared with the two-layer structure of the multi-layer coating film shown in Patent Document 1, a multi-layer coating film having at least three coating layers, which further has a layer that functions as a clear coating film, has more coating layers. Therefore, the number of layer interfaces also increases, and it is necessary to more effectively prevent peeling between coating films (coating film interfaces). Therefore, there is a need to improve the adhesion between each coating film in order to prevent peeling at the coating interface in a multi-layer coating film having at least three coating films, and further, the multi-layer coating film is also required to have high adhesion to the substrate.

[0007] The present disclosure is to solve the above-mentioned conventional problems, and its object is to provide an intermediate coating composition for forming an intermediate coating film capable of improving the adhesion between the coating films constituting the multi-layer coating film on a substrate, including a topcoat coating film, an intermediate coating film, and an undercoat coating film, and between the multi-layer coating film and the substrate. Furthermore, the present disclosure provides an exterior vehicle part using the intermediate coating composition and a method for producing the same. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following aspects. [1] A multi-layer coating film having an undercoat coating film disposed on a substrate, an intermediate coating film disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film, comprising an intermediate coating composition for forming the intermediate coating film, The intermediate coating composition comprises: The composition includes a film-forming resin (A), a film-forming resin (B), and a film-forming resin (C), The film-forming resin (B) and the film-forming resin (C) are acrylic resins, The glass transition temperature of the film-forming resin (A) is Tg(A), the glass transition temperature of the film-forming resin (B) is Tg(B), and the glass transition temperature of the film-forming resin (C) is Tg(C). Tg(A) <Tg(B)<Tg(C) Satisfying the relationship, the glass transition temperature Tg(I) of the mixture of the film-forming resin (A), the film-forming resin (B) and the film-forming resin (C) contained in the intermediate coating composition is 25° C. or higher and 60° C. or lower; In a total of 100 mass% of the film-forming resin (A), the film-forming resin (B), and the film-forming resin (C), The film-forming resin (A) is 20% by mass or more and 40% by mass or less, The film-forming resin (B) is 20% by mass or more and 75% by mass or less, and The coating film-forming resin (C) is 5 parts by mass or more and 45% by mass or less. Intermediate coating composition. [2] The intermediate coating composition according to [1], wherein the film-forming resin (A) has a weight average molecular weight of 9,000 or more and 90,000 or less, a hydroxyl value of 50 mgKOH / g or more and 150 mgKOH / g or less, and a glass transition temperature Tg(A) of -25°C or more and 5°C or less. [3] The intermediate coating composition according to [1] or [2], wherein the film-forming resin (B) has a weight average molecular weight of 5,000 or more and 30,000 or less, a hydroxyl value of 20 mgKOH / g or more and 100 mgKOH / g or less, and a glass transition temperature Tg(B) of 20°C or more and 80°C or less. [4] The intermediate coating composition according to any one of [1] to [3], wherein the film-forming resin (C) has a weight average molecular weight of 5,000 or more and 60,000 or less, a hydroxyl value of 0 mgKOH / g or more and 35 mgKOH / g or less, and a glass transition temperature Tg(C) of 40°C or more and 100°C or less. [5] The intermediate coating composition according to any one of [1] to [4], wherein the coating film-forming resin (B) comprises a polymer of a monomer comprising at least one selected from the group consisting of (meth)acrylic acid, hydroxyethyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate. [6] The intermediate coating composition according to any one of [1] to [5], wherein the coating film-forming resin (C) comprises a polymer of a monomer comprising at least one selected from the group consisting of (meth)acrylic acid, hydroxyethyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate. [7] The intermediate coating composition according to any one of [1] to [6], which is used for coating a substrate including a resin member. [8] The intermediate coating composition according to [7], which is for coating a substrate containing a polyolefin resin. [9] The intermediate coating composition according to any one of [1] to [8], which is used for painting vehicle exterior members.

[10] The intermediate coating paint composition according to [9], which is used for painting vehicle exterior components including resin components.

[11] A multi-layer coating film having a substrate, an undercoat coating film disposed on the substrate, an intermediate coating film disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film; An article comprising: The intermediate coating film is formed from an intermediate coating composition according to any one of [1] to [6], The thickness of the undercoat coating is 3 μm or more and 15 μm or less, The thickness of the intermediate coating film is 10 μm or more and 30 μm or less, The thickness of the above topcoat coating is 20 μm or more and 40 μm or less. Goods.

[12] The article according to

[11] , wherein the substrate comprises a resin member.

[13] The article according to

[12] , wherein the resin member contains a polyolefin resin.

[14] The substrate is a resin member containing a polyolefin resin, and the peel strength T(P) [N / m] of the undercoat coating film from the substrate and the peel strength T(L) [N / m] of the multilayer coating film from the substrate are 0.49<(T(L)-T(P))<4.9 The article according to

[12] or

[13] , which satisfies the relationship:

[15] The article according to any one of

[11] to

[14] , wherein the substrate is an exterior component for a vehicle.

[16] The article according to

[15] , wherein the substrate comprises a resin member.

[17] The object to be coated, and A multi-layer coating film having an undercoat coating film disposed on a substrate, an intermediate coating film disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film. A method of manufacturing an article comprising: A step of applying an undercoat coating composition onto the substrate to form an uncured undercoat coating film; A step of applying an intermediate coating composition according to any one of [1] to [7] onto the uncured undercoat coating film to form an uncured intermediate coating film; A step of applying a topcoat coating composition onto the uncured intermediate coating film to form an uncured topcoat coating film; and A step of simultaneously baking and curing the uncured undercoat coating film, the uncured intermediate coating film, and the uncured topcoat coating film at a temperature of 60°C or higher and 100°C or lower. A method for manufacturing an article comprising the steps of:

[18] The object to be coated, and A multi-layer coating film having an undercoat coating film disposed on a substrate, an intermediate coating film disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film. A method of manufacturing an article comprising: A step of applying an undercoat coating composition onto the substrate to form an uncured undercoat coating film, and baking and curing the uncured undercoat coating film at a temperature of 60° C. or higher and 100° C. or lower to form an undercoat coating film; A step of applying an intermediate coating composition according to any one of [1] to [7] onto the undercoat coating film to form an uncured intermediate coating film, and baking and curing the uncured intermediate coating film at a temperature of 60° C. or higher and 100° C. or lower to form an intermediate coating film; a step of applying a topcoat coating composition onto the intermediate coating film to form an uncured topcoat coating film, and baking and curing the uncured topcoat coating film at 60° C. or higher and 100° C. or lower to form a topcoat coating film; A method for manufacturing an article, comprising:

[19] The method for producing an article according to

[17] or

[18] , wherein the substrate comprises a resin member.

[20] The method for producing an article according to

[19] , wherein the resin member contains a polyolefin resin. [twenty one] The method for producing an article according to any one of

[17] to

[20] , wherein the substrate is an exterior component for a vehicle. Effect of the Invention

[0009] The intermediate coating composition according to the present disclosure is capable of forming an intermediate coating film that can enhance adhesion between the individual coating films that make up the multilayer coating film on a substrate, including a topcoat coating film, an intermediate coating film, and an undercoat coating film, and between the multilayer coating film and the substrate. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram showing a peel strength test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The circumstances under which the present invention was completed will be described below. In order to solve the above-mentioned problems, the present inventors have conducted various investigations. For example, there is a demand for further weight reduction in exterior vehicle parts. In addition, there is a demand for high designability, and the number of exterior vehicle parts having complex shapes is increasing. From this viewpoint, in recent years, the use of resin members that are lightweight and easy to mold as such exterior vehicle parts has been considered.

[0012] On the other hand, when a substrate containing a resin member is used as the substrate, the baking temperature of the multilayer coating film must be set within a range that does not adversely affect the substrate, which is the resin member. For example, when the substrate is a substrate containing a resin member, it is preferable to set the baking temperature of the multilayer coating film lower than when the substrate is a member composed only of metal. However, when the baking temperature of the multilayer coating film is set low, the formation (curing) of the multilayer coating film becomes insufficient, and the adhesion between each coating film constituting the multiple coating films and the adhesion between the multilayer coating film and the substrate (hereinafter, these may be collectively referred to as "adhesion") may be poor.

[0013] From this perspective, the inventors have focused on an intermediate coating composition that forms an intermediate coating film for a multilayer coating film having an undercoat coating film, an intermediate coating film, and a topcoat coating film, in order to form a multilayer coating film having good adhesion even when the substrate contains a resin, and have completed the present invention.

[0014] The intermediate coating composition according to the present disclosure comprises: An intermediate coating composition for forming an intermediate coating film in a multi-layer coating film having an undercoat coating film arranged on a substrate, an intermediate coating film arranged on the undercoat coating film, and a topcoat coating film arranged on the intermediate coating film, The intermediate coating composition is The composition includes a film-forming resin (A), a film-forming resin (B), and a film-forming resin (C), The film-forming resin (B) and the film-forming resin (C) are acrylic resins, The glass transition temperature Tg(A) of the film-forming resin (A), the glass transition temperature Tg(B) of the film-forming resin (B), and the glass transition temperature Tg(C) of the film-forming resin (C) are Tg(A) <Tg(B)<Tg(C) Satisfying the relationship, The glass transition temperature Tg(I) of the intermediate coating composition is 25°C or higher and 60°C or lower, Of the total of film-forming resin (A), film-forming resin (B), and film-forming resin (C) being 100% by mass, The film-forming resin (A) is 20% by mass or more and 40% by mass or less, The film-forming resin (B) is 20% by mass or more and 75% by mass or less, and The coating film-forming resin (C) is contained in an amount of 5% by mass or more and 45% by mass or less.

[0015] With the above-mentioned configuration, the intermediate coating composition according to the present disclosure can form an intermediate coating film that can improve the adhesion between each coating film constituting the multiple coating films and the adhesion between the multilayer coating film and the substrate, regardless of the type of topcoat coating film and undercoat coating film. Furthermore, the multilayer coating film obtained using the intermediate coating composition according to the present disclosure has better adhesion to the substrate than the multilayer coating film using the conventional intermediate coating film, even in a hot water resistance test in an exterior application quality evaluation.

[0016] Furthermore, the intermediate coating composition according to the present disclosure can provide a multilayer coating film with good conformability, and can therefore be used on components with complex shapes and high design quality, and can provide a multilayer coating film with good appearance. Furthermore, with the intermediate coating composition according to the present disclosure, even in an embodiment in which the substrate is a resin, a multilayer coating film with good adhesion can be formed without impairing the properties of the substrate, and the baking temperature can be significantly reduced compared to an embodiment in which the substrate is a metal.

[0017] The intermediate coating composition according to the present disclosure will be described in more detail below.

[0018] (Intermediate coating composition, intermediate coating film) The intermediate coating composition according to the present disclosure is a coating composition that forms an intermediate coating in a multilayer coating film having an undercoat coating film placed on a coated article, an intermediate coating film placed on this undercoat coating film, and a topcoat coating film placed on this intermediate coating film, and the intermediate coating film mainly serves as a base layer that adjusts the hue.

[0019] The intermediate coating composition according to the present disclosure comprises a film-forming resin (A), a film-forming resin (B), and a film-forming resin (C), The film-forming resin (B) and the film-forming resin (C) are acrylic resins, The glass transition temperature Tg(A) of the film-forming resin (A), the glass transition temperature Tg(B) of the film-forming resin (B), and the glass transition temperature Tg(C) of the film-forming resin (C) are Tg(A) <Tg(B)<Tg(C) Satisfying the relationship, The glass transition temperature Tg(I) of the intermediate coating composition is 25°C or higher and 60°C or lower. The film-forming resin (A), film-forming resin (B), and film-forming resin (C) contained in the intermediate coating composition according to the present disclosure, and the glass transition temperature of the intermediate coating composition, satisfy the above relationship, thereby making it possible to form an intermediate coating film that exhibits high adhesion to each coating film of the multilayer coating film. Furthermore, the intermediate coating composition according to the present disclosure can form a multilayer coating film that exhibits high adhesion to the substrate, and can also form a multilayer coating film that has excellent coating film appearance.

[0020] In one embodiment, the substrate includes a resin member. The substrate may be, for example, a vehicle exterior member, and the vehicle exterior member may include a resin part. The substrate may be, for example, a vehicle exterior member composed of a resin member. In such an embodiment, the undercoat coating film disposed on the substrate needs to exhibit high adhesion to the resin member. On the other hand, in this embodiment, the intermediate coating composition according to the present disclosure can form an intermediate coating film that exhibits high adhesion to the undercoat coating film, and can also exhibit high adhesion to the topcoat coating film provided on the intermediate coating film. Therefore, with the intermediate coating paint composition according to the present disclosure, when the substrate includes a resin component, for example, in an embodiment in which the substrate is a resin component for the exterior of a vehicle, high adhesion can be maintained between the substrate and the multilayer coating film, and further, adhesion between the coating films in the multilayer coating film (adhesion at the interface between each coating film) can be improved. Furthermore, the multilayer coating film obtained using the intermediate coating composition according to the present disclosure can exhibit such high adhesion and excellent coating film conformality even when the substrate is a resin member for the exterior of a vehicle, and can therefore be used for components with a high level of design.

[0021] In one embodiment, the glass transition temperature Tg(I) of the intermediate coating composition may be, for example, 30°C or more and 60°C or less, or 32°C or more and 58°C or less, for example, 35°C or more and 58°C or less. When the glass transition temperature of the intermediate coating composition satisfies the above-mentioned conditions, the intermediate coating composition according to the present disclosure can more easily form an intermediate coating film that exhibits high adhesion to each layer of a multilayer coating film. Furthermore, a multi-layer coating film in which each coating film is less likely to peel off can more easily exhibit high adhesion to the substrate, and a multi-layer coating film with excellent coating appearance can be more easily formed.

[0022] The glass transition temperatures Tg(A) to Tg(C) of the coating film-forming resins (A) to (C) and the glass transition temperature Tg(I) of the intermediate coating composition can be measured by detecting the thermal change accompanying the glass transition of the resin using a differential scanning calorimeter. An example of the differential scanning calorimeter is the "X-DSC7000" manufactured by SII NanoTechnology Co., Ltd. The glass transition temperature can be determined, for example, from the tangent at the baseline and the inflection point of the DSC curve obtained using the differential scanning calorimeter.

[0023] The intermediate coating composition according to the present disclosure has a glass transition temperature Tg(A) of the film-forming resin (A), a glass transition temperature Tg(B) of the film-forming resin (B), and a glass transition temperature Tg(C) of the film-forming resin (C), Tg(A) <Tg(B)<Tg(C) the glass transition temperature Tg(I) of the mixture of the film-forming resin (A), the film-forming resin (B) and the film-forming resin (C) contained in the intermediate coating composition is 25°C or higher and 60°C or lower; and In a total of 100 mass% of the film-forming resin (A), the film-forming resin (B), and the film-forming resin (C), The coating composition contains a coating film-forming resin (A) in an amount of 20% by mass or more and 40% by mass or less, The coating composition contains a coating film-forming resin (B) in an amount of 20 parts by mass or more and 75% by mass or less, The coating film forming resin (C) is contained in an amount of 5 parts by mass or more and 45% by mass or less. By containing the film-forming resins (A), (B) and (C) in such ratios, an intermediate coating film that exhibits high adhesion to each layer of the multilayer coating film can be formed, and a multilayer coating film that is less likely to peel at the coating film interface can be formed. Furthermore, the intermediate coating composition according to the present disclosure can form a multilayer coating film that exhibits high adhesion to the substrate, and can also form a multilayer coating film that has excellent coating film appearance.

[0024] In one embodiment, the intermediate coating composition according to the present disclosure comprises, based on a total of 100 mass% of the film-forming resin (A), the film-forming resin (B), and the film-forming resin (C), The coating composition contains a coating film-forming resin (A) in an amount of 20% by mass or more and 40% by mass or less, The coating composition contains a film-forming resin (B) in an amount of 20% by mass or more and 75% by mass or less, The coating composition contains a film-forming resin (C) in an amount of 5% by mass or more and 45% by mass or less, Furthermore, the content of the film-forming resin (A), the content of the film-forming resin (B), and the content of the film-forming resin (C) are Content of film-forming resin (A) < Content of film-forming resin (C), and / or Content of film-forming resin (B) < Content of film-forming resin (C) It is preferable to satisfy the following relationship. By having the film-forming resins (A), (B) and (C) in such a relationship, it is possible to more easily form an intermediate coating film that exhibits high adhesion to each layer of the multilayer coating film, and it is possible to more easily form a multilayer coating film that is less likely to peel at the coating film interface. Also, the intermediate coating composition according to the present disclosure can more easily form a multilayer coating film that exhibits high adhesion to the substrate, and moreover, it can more easily form a multilayer coating film that has excellent coating film appearance.

[0025] [Coating film forming resin (A)] In one embodiment, the film-forming resin (A) preferably has a weight average molecular weight of 9,000 or more and 90,000 or less, and may be, for example, 9,000 or more and 80,000 or less. The weight average molecular weight can be calculated from the measurement results of gel permeation chromatography (GPC) using polystyrene as a standard.

[0026] In one embodiment, the coating film-forming resin (A) has a hydroxyl value of 50 mgKOH / g or more and 150 mgKOH / g or less, for example, 70 mgKOH / g or more and 130 mgKOH / g or less, for example, 70 mgKOH / g or more and 120 mgKOH / g or less. The hydroxyl value is expressed as a value converted into a solid content, and is a value measured by a method according to JIS K 0070.

[0027] In one embodiment, the film-forming resin (A) has a glass transition temperature Tg(A) of −25° C. or more and 5° C. or less, for example, −20° C. or more and 5° C. or less. The method for measuring the glass transition temperature is as described above. Although not intended to be limited to any particular theory, it is believed that by having the glass transition temperature Tg(A) of the coating film-forming resin (A) within the above range, cohesive failure of the coating film can be suppressed and, further, excellent coating color design can be achieved.

[0028] In one embodiment, the coating film-forming resin (A) preferably has a weight average molecular weight of 9,000 to 90,000, a hydroxyl value of 50 to 150 mgKOH / g, and a glass transition temperature Tg(A) of -25°C to 5°C. Because the film-forming resin (A) has such properties, the intermediate coating composition according to the present disclosure can more easily form an intermediate coating film that exhibits high adhesion to each layer of the multilayer coating film. Furthermore, the intermediate coating composition according to the present disclosure can more easily form a multilayer coating film that exhibits high adhesion to the substrate, and can also more easily form a multilayer coating film that has excellent coating film appearance. In one embodiment, the weight average molecular weight, hydroxyl value, and glass transition temperature Tg(A) of the coating film-forming resin (A) can be appropriately selected within the ranges of the present disclosure.

[0029] In one embodiment, the film-forming resin (A) comprises at least one selected from the group consisting of acrylic resins, polyester resins, alkyd resins, polyether resins, polyolefin resins, urethane resins, epoxy resins, and melamine resins. For example, the film-forming resin (A) may comprise at least one selected from acrylic resins, urethane resins, and polyester resins.

[0030] In one embodiment, the film-forming resin (A) comprises an acrylic resin. By comprising an acrylic resin, the film-forming resin (A) can be mixed with the film-forming resin (B) and the film-forming resin (C) more homogeneously, and the strength of the coating film can be increased. In addition, by comprising an acrylic resin, a multi-layer coating film that exhibits high adhesion to the substrate can be more easily formed, and a multi-layer coating film that has excellent coating appearance can be more easily formed.

[0031] Examples of monomer components constituting the acrylic resin include aromatic vinyl monomers such as styrene, vinyl toluene, 2-methylstyrene, t-butylstyrene, and chlorostyrene; butyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and n-, i-, or t-butyl (meth)acrylate; carbonyl compounds of (meth)acrylic acid such as hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, and cyclohexyl (meth)acrylate. Examples of the alkyl ester or cycloalkyl ester having a prime number of 1 to 18 include: hydroxyalkyl esters of (meth)acrylic acid having 2 to 8 carbon atoms, such as hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc.; N-substituted (meth)acrylamide monomers, such as N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-methoxymethyl (meth)acrylamide, etc.; (meth)acrylic acid, glycidyl (meth)acrylate, etc., or a mixture of two or more selected from the group consisting of glycidyl (meth)acrylate, glycidyl (meth)acrylate, and the like. In this specification, "(meth)acrylic" means both acrylic and methacrylic.

[0032] The polymer can be produced by polymerizing the monomers by a conventional method such as solution polymerization or bulk polymerization. For example, the polymerization of the monomers can be carried out by radical polymerization using a polymerization initiator. The polymerization initiator is not particularly limited, and examples of the polymerization initiator that can be used include persulfates such as potassium persulfate and ammonium persulfate, and azo compounds such as azobiscyanovaleric acid and azobisisobutyronitrile.

[0033] The acrylic resin may comprise a polymer of a monomer including at least one selected from the group consisting of (meth)acrylic acid, hydroxyethyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate.

[0034] In one embodiment, the coating film-forming resin (A) contains both an acrylic resin and a urethane resin. In this case, the amount of the acrylic resin contained in the coating film-forming resin (A) may be within the range of 25 to 99% by mass, and the amount of the urethane resin may be within the range of 1 to 75% by mass. When using a plurality of acrylic resins, the total of the parts by mass of each acrylic resin may be within the above range, and when using a plurality of urethane resins, the total of the parts by mass of each urethane resin may be appropriately adjusted to be within the above range.

[0035] [Coating film forming resin (B)] In one embodiment, the film-forming resin (B) may have a weight average molecular weight of 5,000 or more and 30,000 or less, for example, 7,000 or more and 25,000 or less.

[0036] In one embodiment, the film-forming resin (B) has a hydroxyl value of 20 mgKOH / g or more and 100 mgKOH / g or less, for example, 30 mgKOH / g or more and 100 mgKOH / g or less.

[0037] In one embodiment, the film-forming resin (B) has a glass transition temperature Tg(B) of 20°C or more and 80°C or less, such as 30°C or more and 80°C or less, such as 30°C or more and 75°C or less. Although not intended to be limited to any particular theory, when the glass transition temperature Tg(B) of the coating film-forming resin (B) is within the above range, excellent coating color design can be achieved and furthermore, coating film strength can be increased.

[0038] In one embodiment, the film-forming resin (B) may have a weight average molecular weight of 5,000 to 30,000, a hydroxyl value of 20 to 100 mgKOH / g, and a glass transition temperature Tg(B) of 20°C to 80°C. Because the film-forming resin (B) has such properties, the intermediate coating composition according to the present disclosure can more easily form an intermediate coating film that exhibits high adhesion to each layer of the multilayer coating film. Furthermore, the intermediate coating composition according to the present disclosure can more easily form a multilayer coating film that exhibits high adhesion to the substrate, and can also more easily form a multilayer coating film that has excellent coating film appearance. In one embodiment, the weight average molecular weight, hydroxyl value, and glass transition temperature Tg(B) of the coating film-forming resin (B) can be appropriately selected within the ranges of the present disclosure.

[0039] The acid value of the coating film-forming resin (B) may be, for example, 2.7 mgKOH / g or more and 4.7 mgKOH / g or less. The acid value is expressed as a value converted into a solid content, and is a value measured by a method according to JIS K 0070. The solubility parameter Sp value of the coating film-forming resin (B) may be, for example, from 9.0 to 10.0. The Sp value can be determined by actual measurement or calculation using a known method.

[0040] The film-forming resin (B) is an acrylic resin. Since the film-forming resin (B) is an acrylic resin, the intermediate coating film has high coating strength, and further has the advantage of providing high adhesion to each layer of the multi-layer coating film.

[0041] Examples of monomer components constituting the acrylic resin that is the coating film-forming resin (B) include aromatic vinyl monomers such as styrene, vinyl toluene, 2-methylstyrene, t-butylstyrene, and chlorostyrene; butyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and n-, i-, or t-butyl (meth)acrylate; and (meth)acrylates such as hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, and cyclohexyl (meth)acrylate. Examples of the monomer include one or a mixture of two or more selected from alkyl esters or cycloalkyl esters of acrylic acid having 1 to 18 carbon atoms; hydroxyalkyl esters of (meth)acrylic acid having 2 to 8 carbon atoms, such as hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; N-substituted (meth)acrylamide monomers, such as N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and N-methoxymethyl (meth)acrylamide; (meth)acrylic acid, glycidyl (meth)acrylate, and the like.

[0042] The polymer can be produced by polymerizing the monomers by a conventional method such as solution polymerization or bulk polymerization. For example, the polymerization of the monomers can be carried out by radical polymerization using a polymerization initiator. The polymerization initiator is not particularly limited, and examples of the polymerization initiator that can be used include persulfates such as potassium persulfate and ammonium persulfate, and azo compounds such as azobiscyanovaleric acid and azobisisobutyronitrile.

[0043] For example, the acrylic resin that is the coating film-forming resin (B) may be a polymer of a monomer containing at least one selected from the group consisting of (meth)acrylic acid, hydroxyethyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate. In one embodiment, in preparing the acrylic resin in the coating film-forming resin (B), a preferred embodiment is a polymer of a monomer mixture that contains hydroxylethyl (meth)acrylate among the various monomers described above. By including such an acrylic resin in the coating film-forming resin (B), the intermediate coating composition of the present disclosure can form an intermediate coating film that exhibits high adhesion to each layer of the multilayer coating film according to the present disclosure. Furthermore, the intermediate coating composition of the present disclosure can form a multilayer coating film that exhibits high adhesion to the substrate, and can also form a multilayer coating film that has excellent coating film appearance.

[0044] For example, the polymerization of the monomers can be carried out by radical polymerization using a polymerization initiator. The polymerization initiator is not particularly limited, and examples of the polymerization initiator that can be used include persulfates such as potassium persulfate and ammonium persulfate, and azo compounds such as azobiscyanovaleric acid and azobisisobutyronitrile.

[0045] [Coating film forming resin (C)] In one embodiment, the film-forming resin (C) may have a weight average molecular weight of 5,000 or more and 60,000 or less, such as 9,000 or more and 60,000 or less.

[0046] In one embodiment, the film-forming resin (C) has a hydroxyl number of from 0 mgKOH / g to 35 mgKOH / g, such as from 0 mgKOH / g to 20 mgKOH / g.

[0047] In one embodiment, the film-forming resin (C) has a glass transition temperature Tg(C) of 40°C or more and 100°C or less, for example, 50°C or more and 100°C or less. Although not intended to be limited to any particular theory, when the glass transition temperature Tg(C) of the coating film-forming resin (C) is within the above range, an intermediate coating film having excellent coating film strength and hardness can be formed.

[0048] In one embodiment, the coating film-forming resin (C) preferably has a weight average molecular weight of 5,000 to 60,000, a hydroxyl value of 0 to 35 mgKOH / g, and a glass transition temperature Tg(C) of 40°C to 100°C. Because the film-forming resin (C) has such properties, the intermediate coating composition according to the present disclosure can more easily form an intermediate coating film that exhibits high adhesion to each layer of the multilayer coating film. Furthermore, the intermediate coating composition according to the present disclosure can more easily form a multilayer coating film that exhibits high adhesion to the substrate, and can also more easily form a multilayer coating film that has excellent coating film appearance. In one embodiment, the weight average molecular weight, hydroxyl value, and glass transition temperature Tg(C) of the coating film-forming resin (C) can be appropriately selected within the ranges of the present disclosure.

[0049] Since the coating film-forming resin (C) is an acrylic resin, the intermediate coating film has high coating film strength and, further, high adhesion to each layer of the multi-layer coating film.

[0050] Examples of monomer components constituting the acrylic resin that is the coating film-forming resin (C) include aromatic vinyl monomers such as styrene, vinyl toluene, 2-methylstyrene, t-butylstyrene, and chlorostyrene; butyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and n-, i-, or t-butyl (meth)acrylate; and (meth)acrylates such as hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, and cyclohexyl (meth)acrylate. Examples of the monomer include one or a mixture of two or more selected from alkyl esters or cycloalkyl esters of acrylic acid having 1 to 18 carbon atoms; hydroxyalkyl esters of (meth)acrylic acid having 2 to 8 carbon atoms, such as hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; N-substituted (meth)acrylamide monomers, such as N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and N-methoxymethyl (meth)acrylamide; (meth)acrylic acid, glycidyl (meth)acrylate, and the like.

[0051] The polymer can be produced by polymerizing the monomers by a conventional method such as solution polymerization or bulk polymerization. For example, the polymerization of the monomers can be carried out by radical polymerization using a polymerization initiator. The polymerization initiator is not particularly limited, and examples of the polymerization initiator that can be used include persulfates such as potassium persulfate and ammonium persulfate, and azo compounds such as azobiscyanovaleric acid and azobisisobutyronitrile.

[0052] For example, the acrylic resin that is the coating film-forming resin (C) may be a polymer of a monomer containing at least one selected from the group consisting of (meth)acrylic acid, hydroxyethyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate. In one embodiment, the acrylic resin in the coating film-forming resin (C) is preferably a polymer of a monomer mixture that contains ethyl (meth)acrylate among the various monomers mentioned above. By including such an acrylic resin in the film-forming resin (C), it is possible to suitably prepare a film-forming resin (C) having the above-mentioned properties, which has the advantage of being able to form an intermediate coating film that exhibits high adhesion to each layer of a multi-layer coating film.

[0053] [Hardening agent] In one embodiment, the intermediate coating composition may contain a curing agent that appropriately corresponds to the type of curable functional group possessed by the film-forming resin (A), the film-forming resin (B) and / or the film-forming resin (C). The curing agent may be a conventionally known one, such as an amino resin, a blocked isocyanate resin, an epoxy compound, an aziridine compound, a carbodiimide compound, an oxazoline compound, etc. In terms of the performance of the resulting coating film and the cost, an amino resin and / or a blocked isocyanate resin is generally used.

[0054] The amino resin in the curing agent is not particularly limited, and a water-soluble melamine resin and / or a water-insoluble melamine resin can be used.

[0055] Blocked isocyanate resins can be prepared by adding a blocking agent having active hydrogen to a polyisocyanate such as trimethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, etc. In such blocked isocyanate resins, the blocking agent is dissociated by heating to generate isocyanate groups, which react with functional groups in the resin component to cure.

[0056] The amount of the curing agent may be, for example, 2 to 50 parts by mass, and preferably 3 to 40 parts by mass, per 100 parts by mass of the total of the film-forming resin (A), the film-forming resin (B), the film-forming resin (C), and the curing agent. By using an amount of the curing agent within this range, an intermediate coating film having sufficient curability can be more easily formed, and the intermediate coating film can be more effectively prevented from becoming too hard or brittle.

[0057] [solvent] In one embodiment, the intermediate coating composition according to the present disclosure is a solvent-based coating composition. Examples of organic solvents that can be used in solvent-based coating compositions include hydrocarbon solvents, ester solvents, ketone solvents, alcohol solvents, ether solvents, aromatic petroleum solvents, etc. The intermediate coating composition according to the present disclosure is a solvent-based coating composition, and therefore the bake-curing temperature of the multi-layer coating film can be within the range of 60° C. to 100° C. Therefore, even in an embodiment in which the substrate is a resin member, the multi-layer coating film can be formed without impairing the properties of the resin member.

[0058] [Other additives] The intermediate coating composition according to the present disclosure may contain, as necessary, pigments, surface conditioners (antifoaming agents, leveling agents, etc.), pigment dispersants, plasticizers, film-forming aids, ultraviolet absorbers, antioxidants, flame retardants, antistatic agents, electrostatic aids, heat stabilizers, light stabilizers, solvents (water, organic solvents), and other additives.

[0059] When the intermediate coating composition contains a pigment, the pigment content may be within a range that is usually set depending on the application. For example, the ratio of the pigment content to the total content of the components that form the coating layer, such as the coating film-forming resins (A) to (C), the curing agent, and the pigment, [mass %] (PWC: Pigment Weight Concentration) is preferably 0.1 to 50 mass %.

[0060] In one embodiment, the intermediate coating composition according to the present disclosure may contain, in addition to the film-forming resins (A), (B), and (C), a film-forming resin such as a polyester-based resin, an alkyd-based resin, a polyether-based resin, a polyolefin-based resin, a urethane-based resin, or a melamine-based resin.

[0061] (Undercoat paint composition, undercoat paint film) The undercoat coating film is disposed on the substrate. The undercoat coating film is formed, for example, from an undercoat paint composition described below. As described below, the substrate is not particularly limited, and may be, for example, a substrate including a resin member, a substrate including a metal member, or a substrate including both a resin member and a metal member.

[0062] The undercoat paint composition may contain an acid anhydride-modified chlorinated polyolefin resin and an acrylic-modified alkyd resin. By combining these resins, the undercoat paint film has better adhesion to, for example, resin members containing polyolefin resin, and is often used as a primer layer for, for example, resin members for vehicle exteriors containing polyolefin resin, and can exhibit better resistance to high-pressure car washing and better resistance to gasohol.

[0063] In one embodiment, the basecoat coating composition comprises an anhydride-modified chlorinated polyolefin and an acrylic-modified alkyd resin.

[0064] The mass ratio of the acid anhydride-modified chlorinated polyolefin and the acrylic-modified alkyd resin may be 80:20 to 20:80. By containing the acid anhydride-modified chlorinated polyolefin and the acrylic-modified alkyd resin at this ratio, for example, an undercoat coating film having better resistance to high-pressure car washing can be formed, and further, for example, the undercoat coating film can exhibit better adhesion to a resin member containing a polyolefin resin. Furthermore, such an undercoat coating film can also exhibit better adhesion to an intermediate coating film formed from the intermediate coating composition according to the present disclosure. As a result, it can contribute to improving the adhesion between a resin member containing a polyolefin resin and a multi-layer coating film.

[0065] [Acid anhydride modified chlorinated polyolefin] For example, the acid anhydride-modified chlorinated polyolefin may be a propylene-α-olefin copolymer containing 50 mol % or more and 99 mol % or less of a propylene component and at least one α-olefin having a carbon number of 2 or 4 to 6. The chlorine content may be 15 mass % or more and 24 mass % or less, the amount of acid anhydride modification may be 0.6 mass % or more and 2.0 mass %, and the weight average molecular weight may be selected within the range of 40,000 or more and 120,000 or less.

[0066] In one embodiment, the copolymerization rate of α-olefin in the propylene-α-olefin copolymer is in the range of 1 mol% to 50 mol%, preferably 5 mol% to 30 mol%.By this copolymerization rate being in the above range, it is possible to obtain an undercoat paint composition with better storage stability.Furthermore, the obtained coating film shows better adhesion to, for example, resin members containing polyolefin resin, and shows better resistance to high-pressure car washing to, for example, resin members for vehicle exteriors containing polyolefin resin. The range of the weight average molecular weight of the propylene-α-olefin copolymer is, for example, 40,000 or more and 120,000 or less, and preferably 50,000 or more and 100,000 or less.

[0067] Chlorination of the propylene-α-olefin copolymer can be carried out by conventional techniques. For example, chlorination can be easily achieved by blowing chlorine gas into a chloroform solution of polyolefin at high temperature. In the present disclosure, the chlorination rate is preferably in the range of 15% by mass or more and 24% by mass or less, more preferably 18% by mass or more and 21% by mass or less. By having the chlorination rate within the above range, it is possible to obtain an undercoat paint composition with better storage stability. In addition, the resulting coating film can have better gasohol resistance.

[0068] The acid anhydride-modified chlorinated polyolefin can be obtained by copolymerizing an acid anhydride such as maleic anhydride or itaconic anhydride with the polyolefin. As the copolymerization method, a known method of copolymerizing an acid anhydride at high temperature in the presence of a radical generator can be used. The copolymerization amount of the acid anhydride is preferably 0.6% by mass or more and 2.0% by mass or less, more preferably 1.0% by mass or more and 1.6% by mass or less. By the copolymerization amount of the anhydride being within the above range, the undercoat coating film can exhibit better gasohol resistance. In addition, a coating film with excellent moisture resistance can be formed. Thus, the chlorination step of the polyolefin resin and the acid anhydride copolymerization step in producing the acid anhydride-modified chlorinated polyolefin of the present invention are both known techniques, and either one may be carried out first.

[0069] [Acrylic modified alkyd resin] For example, the acrylic modified alkyd resin may be composed of an alkyd resin polymerized portion and an acrylic resin polymerized portion.

[0070] The fats and oils of the alkyd resin are preferably fats and oils having an iodine value of 80 or more, such as castor oil, soybean oil, dehydrated castor oil, and linseed oil. The polybasic acid is not particularly limited, but may be one or more selected from the group consisting of dicarboxylic acids such as orthophthalic acid, phthalic anhydride, tetrahydroorthophthalic acid, and tetrahydrosophthalic anhydride, or acid anhydrides thereof. The polyhydric alcohol is not particularly limited, but may be one or more selected from dihydric or higher alcohols such as pentaerythritol, glycerin, and neopentyl glycol.

[0071] A known method can be used to produce the alkyd resin. For example, fats and oils are transesterified with polyhydric alcohols under inert gas at 200°C to 250°C using lithium hydroxide as a catalyst, and then subjected to an alcoholysis reaction. The alcoholysis reaction is then terminated by methanol tolerance, and then esterified with a polybasic acid. If necessary, a polyhydric alcohol may also be blended to adjust the OH value of the alkyd resin. In this case, the oil length is set to 35% to 70%, preferably 50% to 60%.

[0072] The acrylic modification can be carried out by a known method using the alkyd resin described above. For example, the acrylic resin can be modified by heating the alkyd resin to 120° C. under an inert gas, dropping a mixed solution of an acrylic monomer and a peroxide at a constant rate, adding the remaining peroxide, and then keeping the temperature for a certain period of time.

[0073] The glass transition temperature of the acrylic resin polymerized portion is preferably 50° C. or higher, and more preferably 60° C. or higher. When the glass transition temperature is 50° C. or higher, the undercoat coating film can have better resistance to high-pressure car washing. Examples of the acrylic monomer include acrylic acid ester monomers such as methyl acrylate, methyl methacrylate, butyl methacrylate, and 2-hydroxyethyl acrylate, as well as styrene, vinyl toluene, and α-methylstyrene. For example, an acrylic resin polymerized portion may be obtained by polymerizing at least one monomer selected from the group consisting of these monomers so that the glass transition temperature is 50° C. or higher.

[0074] The mass ratio of the alkyd resin polymerized portion to the acrylic resin polymerized portion may be, for example, 25:75 to 75:25, and preferably 40:60 to 60:40. By having the mass ratio within the above range, it is possible to form an undercoat film having better gasohol resistance and better resistance to high-pressure car washing. The weight average molecular weight of the acrylic modified alkyd resin may be, for example, 10,000 or more and 100,000 or less, and preferably 15,000 or more and 60,000 or less. By having the weight average molecular weight within such a range, the coating film strength can be further increased. Furthermore, by having the weight average molecular weight within the above range, the undercoat coating film can exhibit better resistance to high-pressure car washing and better resistance to gasohol, and furthermore, can exhibit a good coating film appearance. Furthermore, by having the weight average molecular weight within the above range, compatibility with the acid anhydride-modified chlorinated polyolefin can be maintained well, and the coating composition can exhibit better storage stability.

[0075] The undercoat coating composition may contain, in addition to the acid anhydride-modified chlorinated polyolefin and the acrylic-modified alkyd resin, as necessary, resin components such as acrylic resin, polyester resin, epoxy resin, acrylic-modified chlorinated polyolefin resin, cellulose resin, melamine resin, blocked isocyanate resin, etc. In such an embodiment, the other resin is blended in an amount of more than 0 parts by mass and not more than 90 parts by mass per 100 parts by mass of the total of the acid anhydride-modified chlorinated polyolefin and the acrylic-modified alkyd resin, and the paint can be made using mainly aromatic hydrocarbon solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, and ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone. These organic solvents can be blended in an amount of 200 parts by mass or more and not more than 500 parts by mass per 100 parts by mass of the total of the acid anhydride-modified chlorinated polyolefin and the acrylic-modified alkyd resin.

[0076] The undercoat paint composition can be colored to improve workability by blending pigments such as titanium oxide, carbon black, conductive carbon black, extender pigments such as talc, clay, barium sulfate, or various organic pigments, and can also be used for electrostatic painting by making it conductive. In such an embodiment, the pigment is blended in an amount of more than 0 part by mass and not more than 100 parts by mass per 100 parts by mass of the total of the acid anhydride-modified chlorinated polyolefin and the acrylic-modified alkyd resin.

[0077] (Topcoat paint composition, topcoat paint film) In the multi-layer coating film, the topcoat coating film is disposed on the intermediate coating film. The topcoat coating film is formed, for example, from a topcoat paint composition described below. The topcoat coating film may also have a protective function as a clear coating film.

[0078] The topcoat coating composition may be a solvent-based or water-based type. The topcoat coating composition is preferably a two-liquid type topcoat coating composition. The two-liquid type topcoat coating composition may be a two-liquid type topcoat coating composition consisting of a base material containing a hydroxyl group-containing acrylic resin and a polycarbonate diol compound, and a curing agent containing a polyisocyanate compound.

[0079] [Hydroxyl-containing acrylic resin] In one embodiment, the hydroxyl group-containing acrylic resin in the topcoat paint composition has a hydroxyl group value in the range of 80 mgKOH / g to 200 mgKOH / g, preferably 90 mgKOH / g to 190 mgKOH / g, more preferably 100 mgKOH / g to 180 mgKOH / g. By having the hydroxyl group value of the hydroxyl group-containing acrylic resin in the above range, the resulting coating film can have better physical properties.

[0080] In one embodiment, the hydroxyl-containing acrylic resin in the topcoat paint composition has an acid value of 1 mgKOH / g or more and 20 mgKOH / g or less, preferably 3 mgKOH / g or more and 18 mgKOH / g or less, more preferably 5 mgKOH / g or more and 10 mgKOH / g or less. By having the acid value of the hydroxyl-containing acrylic resin within the above range, the reactivity with the polyisocyanate compound can be controlled to a more appropriate range, and the resulting multilayer coating film can have a better coating film appearance and physical properties of the coating film.

[0081] In the topcoat paint composition, the hydroxyl-containing acrylic resin is a solution polymer of a monomer mixture containing a (meth)acrylic acid hydroxyl-containing alkyl ester monomer, and the number of carbon atoms in the hydroxyl-containing alkyl moiety of the (meth)acrylic acid hydroxyl-containing alkyl ester monomer in the topcoat paint composition is, for example, 3 or less.

[0082] By including in the monomer mixture a (meth)acrylic acid hydroxyl group-containing alkyl ester monomer having a hydroxyl group-containing alkyl moiety with 3 or less carbon atoms, the reactivity with the polyisocyanate compound can be adjusted to a more appropriate range, thereby improving the coating appearance of the resulting multilayer coating film.

[0083] Specific examples of (meth)acrylic acid hydroxyl group-containing alkyl ester monomers in which the hydroxyl group-containing alkyl moiety has 3 or less carbon atoms include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate.

[0084] The amount of the (meth)acrylic hydroxyl group-containing alkyl ester monomer, in which the hydroxyl group-containing alkyl moiety has 3 or less carbon atoms, contained in the monomer mixture is preferably in the range of 20 parts by mass or more and 60 parts by mass or less, and more preferably in the range of 30 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the monomer mixture.

[0085] The monomer mixture may contain a hydroxyl group-containing (meth)acrylic monomer as necessary other than the (meth)acrylic acid hydroxyl group-containing alkyl ester monomer in which the carbon number of the hydroxyl group-containing alkyl moiety is 3 or less. Examples of such monomers include hydroxyalkyl (meth)acrylates such as 4-hydroxybutyl (meth)acrylate and 2-hydroxybutyl (meth)acrylate; PLACCEL FM-1 (trade name, an adduct of 2-hydroxyethyl (meth)acrylate and polycaprolactone, manufactured by Daicel Chemical Industries, Ltd.); polyalkylene glycol mono(meth)acrylates, and the like.

[0086] The monomer mixture preferably contains other ethylenically unsaturated group-containing monomers in addition to the (meth)acrylic acid hydroxyl group-containing alkyl ester monomers in which the carbon number of the hydroxyl group-containing alkyl moiety is 3 or less. The other ethylenically unsaturated group-containing monomers are not particularly limited, and examples thereof include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, and Examples of the monomers include acid group-containing monomers such as fumaric acid, aromatic vinyl monomers such as styrene and vinyl toluene, epoxy group-containing monomers such as glycidyl (meth)acrylate, amino group-containing monomers such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate, acrylamide monomers such as (meth)acrylamide, N-ethyl (meth)acrylamide, N,N-butoxymethyl (meth)acrylamide and N-methylacrylamide, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, etc. These may be used alone or in combination of two or more.

[0087] The hydroxyl-containing acrylic resin can be prepared by solution polymerization of a monomer mixture under conditions generally used in the art.

[0088] The weight-average molecular weight of the hydroxyl-containing acrylic resin is preferably from 3000 to 50000. Having a weight-average molecular weight within the above range has the advantage that good workability and curability of the resulting topcoat paint composition can be more easily ensured.

[0089] [Polyisocyanate compounds] The topcoat paint composition may contain a polyisocyanate compound. The polyisocyanate compound of the topcoat paint composition is preferably contained in the curing agent in the two-liquid topcoat paint composition. The polyisocyanate compound is not particularly limited. Representative polyisocyanate compounds include aliphatic polyisocyanates (particularly aliphatic diisocyanates) such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (HDI), and trimethylhexamethylene diisocyanate; 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 1,2-cyclohexane diisocyanate, and isophorone diisocyanate. alicyclic polyisocyanates (particularly alicyclic diisocyanates) such as norbornane diisocyanate methyl (IPDI) and norbornane diisocyanate methyl; aromatic polyisocyanates such as xylylene diisocyanate (XDI), 2,4-tolylene diisocyanate (TDI) and 2,6-tolylene diisocyanate; and isocyanurate compounds, uretdione compounds, urethane compounds, allophanate compounds, biuret compounds, and adducts with trimethylolpropane derived therefrom.

[0090] The polyisocyanate compound is preferably at least one selected from the group consisting of aliphatic diisocyanates, alicyclic diisocyanates, and the nurate and uretdione derivatives of these diisocyanates. The use of a polyisocyanate compound has the advantage that a topcoat film having better weather resistance can be formed and the reaction rate with the hydroxyl group-containing acrylic resin can be better controlled.

[0091] In the topcoat paint composition, the molar ratio of the isocyanate functional group of the polyisocyanate compound to the hydroxyl functional group of the hydroxyl-containing acrylic resin (molar number of isocyanate functional group / molar number of hydroxyl functional group) is, for example, in the range of 1.15 to 1.35. By using a topcoat paint composition in which the molar ratio of the isocyanate functional group to the hydroxyl functional group is within the above range, a coating film having good coating film appearance and coating film strength can be formed when a multilayer coating film is formed.

[0092] [Polycarbonate diol compound] The topcoat paint composition may contain a polycarbonate diol compound. For example, the polycarbonate diol (A) is preferably one represented by the following general formula:

[0093] [ka]

[0094] In the formula, the structure of R is determined by the diol component used in the production of the polycarbonate diol. The diol component can be a dihydric alcohol having 2 to 10 carbon atoms, preferably 4 to 8 carbon atoms. Specifically, for example, aliphatic diols such as 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-ethyl-1,6-hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and neopentyl glycol; alicyclic diols such as 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol; aromatic diols such as p-xylenediol and p-tetrachloroxylenediol; and diethylene glycol and dipropylene glycol. These diols can be used alone or in combination of two or more. The polycarbonate diol can be obtained by reacting the diol with a carbonylating agent such as phosgene.

[0095] In the polycarbonate diol compound, R in the above general formula is preferably a linear alkylene group (linear alkanediyl group). In this case, R in the general formula is more preferably a linear alkylene group (linear alkanediyl group) having 2 to 40 carbon atoms.

[0096] In addition, the polycarbonate diol compound is more preferably a polymer of a diol component containing 1,6-hexanediol and a carbonylating agent. By using such a polycarbonate diol compound (C), there is an advantage that it is possible to obtain better scratch resistance while more easily maintaining durability and hardness.

[0097] Particularly preferred are polycarbonate diol compounds obtained by polycondensing a diol component, such as a combination of 1,6-hexanediol and 1,5-pentanediol, a combination of 1,6-hexanediol and 1,4-butanediol, or a combination of 1,6-hexanediol and 1,4-dimethylolcyclohexane, with a carbonylating agent, using two or more diol components in combination, with 1,6-hexanediol as an essential diol component.

[0098] Among these, a combination of 1,6-hexanediol and 1,5-pentanediol in a molar ratio of 1,6-hexanediol to 1,5-pentanediol of 80:20 to 20:80 is preferred. Such a combination of two types or a combination of three or more types is preferred in terms of better abrasion resistance.

[0099] As the carbonylating agent, for example, one or a combination of two or more of commonly used alkylene carbonates, dialkyl carbonates, diallyl carbonates, phosgene, etc. can be used. Among these, preferred ones include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, and diphenyl carbonate.

[0100] The polycarbonate diol compound preferably has a hydroxyl equivalent of 320 g / eq or more and 2000 g / eq or less, more preferably 350 g / eq or more and 1000 g / eq or less. By having the hydroxyl equivalent within the above range, there is an advantage that abrasion resistance, stain resistance, water resistance, etc. can be maintained better.

[0101] The polycarbonate diol compound more preferably has a number average molecular weight in the range of 500 to 6,000.

[0102] Commercially available polycarbonate diols can be used. Examples of commercially available polycarbonate diols include Asahi Kasei's Duranol T-5650J, T-5650E, T-5651, and T-5652 (diol components: 1,6-hexanediol and 1,5-pentanediol), and T-4671 (diol components: 1,6-hexanediol and 1,4-butanediol), and Ube Industries' ETERNACOLL UM-90 (1 / 1,1 / 3) (diol components: 1,6-hexanediol and 1,4-dimethylolcyclohexane).

[0103] By including a hydroxyl-containing acrylic resin and a polycarbonate diol compound in the topcoat paint composition, particularly by including a hydroxyl-containing acrylic resin and a polycarbonate diol compound as the main components of a two-component topcoat paint composition, there is an advantage in that the topcoat paint film can acquire a self-repairing function that absorbs external forces and repairs scratches.

[0104] The content of the polycarbonate diol compound is preferably in the range of 0 to 40 parts by mass, more preferably in the range of 5 to 20 parts by mass, per 100 parts by mass of the resin solid content of the hydroxyl group-containing acrylic resin (A).

[0105] The topcoat paint composition may further contain a viscosity control agent. By including a viscosity control agent, the coating workability can be improved. The viscosity control agent can generally be one that exhibits thixotropy, and for example, those already described in the aqueous base paint composition can be used. If necessary, the topcoat paint composition may also contain a curing catalyst, a surface conditioner, etc. The topcoat paint composition may further contain a known ultraviolet absorber, a light stabilizer, an antioxidant, etc. In addition, the topcoat paint composition may contain a known rheology control agent, other surface conditioners, etc., and solvents such as alcohol-based solvents, aromatic hydrocarbon-based solvents, ester-based solvents, and ketone-based solvents can also be used for the purpose of viscosity adjustment, etc. These additives can be included in the base agent and / or the curing agent.

[0106] When the topcoat paint composition is a two-liquid topcoat paint composition, the base agent and the curing agent may be mixed before use and applied by a normal painting method. Alternatively, the two liquids may be delivered to a two-liquid mixing gun and mixed at the tip of the gun.

[0107] Multilayer coating film and method for manufacturing article A multi-layer coating film can be formed by applying the intermediate coating composition, the undercoat coating composition, and the topcoat coating composition to a substrate. The multi-layer coating film has an undercoat coating film disposed on the substrate, an intermediate coating film disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film.

[0108] (subject to be coated) The substrate is not particularly limited, and may include, for example, a resin member or a metal member. The substrate may also include both a resin member and a metal member. Examples of metal members include metals such as iron, steel, copper, aluminum, tin, and zinc, and alloys containing these metals. The metal substrate may be subjected to a chemical conversion treatment (e.g., zinc phosphate chemical conversion treatment, zirconium chemical conversion treatment, etc.) as necessary before the formation of the electrodeposition coating film. The resin member may contain, for example, polyolefin resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, polyamide resin, etc. When the substrate is a resin member, the undercoat coating film is required to be a coating film having excellent adhesion to the resin member. For such an undercoat coating film having excellent adhesion to the resin member, an undercoat coating film formed from the undercoat paint composition according to the present disclosure can exhibit good adhesion to the undercoat coating film. In terms of physical properties such as strength and mass, the resin member preferably contains a polyolefin resin.

[0109] The substrate may be an exterior vehicle component. The vehicle is not particularly limited, and examples thereof include automobiles, motorcycles, heavy machinery vehicles, etc. The substrate may be, for example, an automobile body provided with an electrodeposition coating, and in this case, the automobile body includes a metal component.

[0110] In one embodiment, the substrate is a resin component for vehicle exterior use, and may be, for example, a resin component for vehicle exterior use containing a polyolefin resin.

[0111] In one embodiment, the substrate is an automobile exterior resin part, for example, an automobile exterior resin part containing a polyolefin resin.

[0112] (Substrates and articles including multi-layer coatings) The article according to the present disclosure comprises: The object to be coated, and A multi-layer coating film having an undercoat coating film disposed on a substrate, an intermediate coating film formed from an intermediate coating composition according to the present disclosure disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film. Includes. The substrate, undercoat and topcoat may be those described above.

[0113] Since the multilayer coating film has an intermediate coating film formed from the intermediate coating composition according to the present disclosure, the multilayer coating film can exhibit high adhesion between the respective coating films, and peeling of the coating films can be suppressed. Furthermore, the intermediate coating composition according to the present disclosure can form a multilayer coating film that exhibits high adhesion to the substrate, and can also form a multilayer coating film that has excellent coating film appearance. Furthermore, the multi-layer coating film can conform to complex shapes and has high adhesion to the substrate, making the article according to the present disclosure suitable for use in articles with high design quality.

[0114] In one embodiment, the multi-layer coating film has a thickness of the undercoat coating film of 3 μm or more and 15 μm or less, a thickness of the intermediate coating film of 10 μm or more and 30 μm or less, and a thickness of the topcoat coating film of 20 μm or more and 40 μm or less.

[0115] In addition, since the multi-layer coating film has a coating film formed from the intermediate coating composition according to the present disclosure, in an embodiment in which the substrate is a resin member, for example, a resin member containing a polyolefin resin, a coating film having the above-mentioned various properties can be formed without impairing the properties of the substrate. Furthermore, compared to an embodiment in which the substrate is a metal, the baking temperature can be significantly reduced.

[0116] In one embodiment, the peel strength of the undercoat coating film from a substrate that is a resin member containing a polyolefin resin (hereinafter sometimes referred to as the "peel strength of the undercoat coating film") T(P) [N / m], and the peel strength of the multilayer coating film from the substrate (hereinafter sometimes referred to as the "peel strength of the multilayer coating film") T(L) [N / m], 0.49<(T(L)-T(P))<4.9 Satisfy the relationship.

[0117] By satisfying such a relationship between the peel strength T(P) of the undercoat coating film and the peel strength T(L) of the multi-layer coating film, a higher adhesion can be obtained between the substrate and the multi-layer coating film. Furthermore, a higher adhesion can be obtained between each coating film in the multi-layer coating film, and interfacial peeling in the multi-layer coating film can be further suppressed. Moreover, a multi-layer coating film with a better coating film appearance can be formed. Furthermore, even in an embodiment in which the object to be coated has a complex shape, the multi-layer coating film can have higher adhesion, and can provide articles with high design quality, such as vehicle exterior parts.

[0118] In one embodiment, the peel strength T(P) of the undercoat coating and the peel strength T(L) of the multi-layer coating are 0.55<(T(L)-T(P))<4.5 For example, 0.60<(T(L)-T(P))<4.0 Satisfy the relationship. By satisfying such a relationship between the peel strength T(P) of the undercoat coating film and the peel strength T(L) of the multi-layer coating film, it is possible to obtain even higher adhesion between the substrate and the multi-layer coating film. Also, even higher adhesion can be exhibited between each coating film in the multi-layer coating film, and interfacial peeling in the multi-layer coating film can be more effectively suppressed.

[0119] In one embodiment, it is preferred that the multilayer coating film on the substrate shows no abnormality when visually evaluated for appearance even when exposed to conditions of 95% relative humidity and 50° C. for 240 hours.

[0120] The method for producing the article according to the present disclosure is not particularly limited. The substrate, undercoat film, and topcoat film may be those described above.

[0121] In one embodiment, an article including a substrate and a multi-layer coating film can be produced by a wet-on-wet method. That is, in one embodiment, the article according to the present disclosure is A step of applying an undercoat coating composition onto a substrate to form an uncured undercoat coating film; A step of applying an intermediate coating composition according to the present disclosure onto an uncured undercoat coating film to form an uncured intermediate coating film; A step of applying a topcoat coating composition onto the uncured intermediate coating film to form an uncured topcoat coating film; and A process in which an uncured undercoat film, an uncured middle coat film, and an uncured top coat film are simultaneously baked and cured at temperatures between 60°C and 100°C. The composition can be produced by a production method including the steps of:

[0122] In another embodiment, the article according to the present disclosure comprises: A step of applying an undercoat coating composition onto a substrate to form an uncured undercoat coating film, and baking and curing the uncured undercoat coating film at 60°C or higher and 100°C or lower to form an undercoat coating film; A step of applying an intermediate coating composition according to the present disclosure onto an undercoat coating film to form an uncured intermediate coating film, and baking and curing the uncured intermediate coating film at 60° C. or higher and 100° C. or lower to form an intermediate coating film; A process of applying a topcoat paint composition onto the intermediate coating film to form an uncured topcoat coating film, and baking and curing the uncured topcoat coating film at 60°C or higher and 100°C or lower to form a topcoat coating film. The composition can be produced by a production method including the steps of:

[0123] In these embodiments, the intermediate coating composition according to the present disclosure can be used to bake and cure each coating film at a low temperature of 60° C. to 100° C. Therefore, even when the substrate is sensitive to heat, for example, a resin member, a coating film having the above-mentioned various properties can be formed without impairing the properties of the substrate. By forming a multi-layer coating film using the intermediate coating composition according to the present disclosure, even when the coating film is baked and cured at a low temperature of, for example, 60°C or higher and 100°C or lower, a higher adhesion can be obtained between the substrate and the multi-layer coating film. Furthermore, a higher adhesion can be exhibited between each coating film in the multi-layer coating film, and interfacial peeling in the multi-layer coating film can be further suppressed. In addition, a multi-layer coating film having a better coating film appearance can be formed. Furthermore, even in the case where the object to be coated has a complex shape, the multi-layer coating film can have higher adhesion, and it is possible to provide parts with high design quality, such as vehicle exterior parts.

[0124] The undercoat coating composition may be applied onto the substrate so that the dried thickness of the undercoat coating film is 3 μm to 15 μm. Furthermore, before applying the intermediate coating composition, the undercoat coating film may be dried at room temperature or under heated conditions (e.g., 60° C. to 90° C.) as necessary.

[0125] The intermediate coating composition according to the present disclosure may be applied onto the undercoat coating so that the dried thickness of the intermediate coating film is 10 μm or more and 30 μm or less. The intermediate coating film may be dried at room temperature or by heating before applying the topcoat coating composition.

[0126] The topcoat paint composition may be applied onto the intermediate coat so that the dry thickness of the topcoat coat is 20 μm or more and 40 μm or less.

[0127] A multi-layer coating film can be formed on the substrate by simultaneously baking and curing the uncured undercoat coating film, the uncured intermediate coating film, and the uncured topcoat coating film obtained as described above at a temperature of 60°C or higher and 100°C or lower.

[0128] In another embodiment, the undercoat coating composition, intermediate coating composition, and topcoat coating composition may be applied, and bake curing may be performed each time. For example, the undercoat coating composition may be applied on a substrate to form an uncured undercoat coating film, the uncured undercoat coating film obtained is baked and cured at 60°C to 100°C to form an undercoat coating film, the intermediate coating composition may be applied on the undercoat coating film to form an uncured intermediate coating film, the uncured intermediate coating film obtained is baked and cured at 60°C to 100°C to form an intermediate coating film, and the topcoat coating composition may be applied on the intermediate coating film to form an uncured topcoat coating film, and the uncured topcoat coating film obtained is baked and cured at 60°C to 100°C to form a topcoat coating film. EXAMPLES

[0129] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0130] Production Example 1 Preparation of Undercoat Paint Composition (Acid anhydride modified chlorinated polyolefin) The acid anhydride-modified chlorinated polyolefin used had the following characteristics: Propylene / ethylene molar ratio: 90 / 10 Maleic anhydride content (%): 1.3 Weight average molecular weight: 80,000

[0131] (Preparation of Acrylic Modified Alkyd Resin) An alkyd resin polymerized portion was prepared using 50.5 parts by mass of dehydrated castor oil, 27.1 parts by mass of phthalic anhydride, 14.5 parts by mass of pentaerythritol, and 7.9 parts by mass of neopentyl glycol. Also, an acrylic resin polymerized portion was prepared using 61.0 parts by mass of methyl methacrylate, 20.0 parts by mass of styrene, 18.4 parts by mass of n-butyl acrylate, and 0.6 parts by mass of methacrylic acid. The obtained alkyd resin polymerized portion was reacted with the acrylic resin polymerized portion to prepare an acrylic-modified alkyd resin.

[0132] The above-mentioned acid anhydride-modified chlorinated polyolefin (7 parts (solid content), acrylic-modified alkyd resin (7 parts (solid content), pigment (Titanium R-820, Ishihara Sangyo Kaisha, Ltd.)) and 72 parts of toluene were mixed to prepare an undercoat paint composition (polyolefin primer composition).

[0133] Production Example 2 Preparation of topcoat paint composition (Preparation of Hydroxyl-Containing Acrylic Resin) A vessel equipped with a stirrer, a temperature control device, and a reflux condenser was charged with 30 g of butyl acetate and heated to 120 ° C. Next, a monomer mixture of the following composition (styrene 20 parts, n-butyl acrylate 15.8 parts, n-butyl methacrylate 21.8 parts, 2-hydroxypropyl methacrylate 41.1 parts, acrylic acid 1.3 parts), and then Kayaester O 12 parts and butyl acetate 6 parts were dropped simultaneously over 3 hours, and then left for 30 minutes, a solution of Kayaester O 0.5 parts and butyl acetate 4 parts was dropped over 30 minutes, the reaction solution was stirred for 1 hour to increase the conversion rate to resin, and the reaction was terminated to obtain a hydroxyl group-containing acrylic resin with a solid content of 70 mass%, a number average molecular weight of 3800, a hydroxyl value of 160 mg KOH / g (including 100% secondary hydroxyl group), and an acid value of 10 mg KOH / g.

[0134] (Preparation of the base material in the topcoat paint composition) To a 1 L metal container, 245.3 parts of the above hydroxyl group-containing acrylic resin, 19.0 parts of Asahi Kasei's Duranol T-5650E, 5.6 parts of Ciba-Geigy's ultraviolet absorber "Tinuvin 384", 5.6 parts of Ciba-Geigy's light stabilizer "Tinuvin 123", 5.6 parts of an acrylic surface conditioner, 37.0 parts of toluene, and 37.0 parts of xylene were added in that order, and thoroughly stirred with a disperser to obtain the main component of a two-component clear coating composition.

[0135] (Preparation of hardener in topcoat paint composition) Into another metal container, 100.0 parts of Dismodur N-3300 (NCO active ingredient 22%) manufactured by Sumitomo Bayer Urethane Co., Ltd. and 30 parts of 2-ethylethoxypropanol were added in that order and thoroughly stirred to obtain a hardener for a two-liquid clear coating composition.

[0136] Production Example 3 Preparation of each component contained in the intermediate coating composition The components contained in the intermediate coating composition were prepared or obtained as follows.

[0137] [Table 1]

[0138] [Table 2]

[0139] [Table 3]

[0140] The glass transition temperatures of the above coating film-forming resins (A) to (C) were determined from the tangent line at the baseline and the inflection point of the DSC curve obtained using a differential scanning calorimeter. The specific measurement procedure is as follows.

[0141] The glass transition temperature was measured using an X-DSC7000 manufactured by SII NanoTechnology Inc. To measure the glass transition temperature, test specimens for measurement were prepared by coating each of the film-forming resins and then drying. In order to remove the solvent from the resin solution, a pretreatment was carried out according to the following procedure. Most of the solvent was removed from the test pieces by drying (in a dryer) at normal pressure at 60°C for 1 hour, and then the test pieces were further dried at 25°C at a reduced pressure of 760mmHg for 4 hours (in a vacuum dryer). The dryer used was SPHH-100 (Tabaiespec), and the vacuum dryer was EYLA VOS-450SD (Tokyo Rikakikai). Next, to prepare the test specimen, the mass of the test specimen was taken at about 10 mg and measured to the nearest 0.1 mg. The required amount was poured evenly and uniformly into a container (aluminum pan) so that there were no gaps, and the container lid was placed on and fixed. The containers were attached in the following manner: a container filled with test pieces was attached to one of the container holders, and an empty container with a lid was attached to the other container holder. The flow rate of nitrogen gas was set at 20 m per minute, and the flow was continued without changing the flow rate until the end of the test. The container filled with the test pieces was placed in a DSC apparatus, and in order to match the thermal history, (1) the temperature was raised at 20°C per minute to a temperature approximately 40°C higher than the end of the glass transition and held there for 10 minutes, then the temperature was lowered at 10°C per minute to a temperature approximately 50°C lower than the glass transition temperature and held there for 3 minutes, and then the temperature was raised at 10°C per minute to a temperature approximately 30°C higher than the end of the transition, and a DSC curve was created. Next, in the measurement of the glass transition temperature, the difference in the vertical axis direction of the step-like change was adjusted to be at least 10% of the full scale of the recording paper. For the obtained DSC curve, the temperature of the intersection of a straight line extending the low-temperature base line to the high-temperature side and a tangent drawn at the point where the gradient of the curve of the step-like change of the glass transition is maximum was calculated. The temperature was calculated to one decimal place and rounded off. The above procedure was repeated three times for the same material, and the glass transition temperature was determined by calculating the average of the temperatures obtained.

[0142] The weight average molecular weight of the coating film-forming resins (A) to (C) was calculated from the results of gel permeation chromatography (GPC) using polystyrene as a standard. The hydroxyl value of the coating film-forming resins (A) to (C) is a value calculated as a solid content, and is a value measured by a method according to JIS K 0070.

[0143] Example 1 Preparation of intermediate coating composition The coating film-forming resins (A) to (C) shown in the table below were placed in a stirring bag and stirred, and then 10 parts by weight of Disparlon Paste (Kusumoto Chemicals, polyamide wax) as a viscosity agent was added and stirred. Next, 4 parts by weight of Duranate MF-K60X (Asahi Chemicals, blocked isocyanate) as a hardener and 6 parts by weight of aluminum paste (Toyo Aluminum, aluminum pigment) as a lustrous agent were added, and 18 parts by weight of butyl acetate, xylene, ethyl acetate, and a silicon-based additive (Tenkazai 5648, Toray Industries, Inc.) as an additive were added in sequence and stirred. The absence of aggregates was visually confirmed, and an intermediate coating paint composition was obtained.

[0144] Multi-layer coating The substrate used was a polypropylene substrate, BK-211S / FT-28 (3 mm thick) manufactured by Mitsubishi Chemical. As a pretreatment, the substrate surface was wiped with a cloth coated with IPA (isopropyl alcohol). The undercoat paint composition obtained above was applied onto a substrate to a thickness of 9 μm to form an undercoat paint film. Next, the intermediate coating composition obtained above was applied onto the resulting undercoat coating film to a thickness of 18 μm to form an intermediate coating film. The above-obtained topcoat paint composition was applied to a thickness of 34 μm on the obtained intermediate coating film. The obtained uncured undercoat coating film, intermediate coating film and topcoat coating film were cured at 80° C. for 0.75 hours to form a multi-layer coating film on the substrate.

[0145] Examples 2 to 5 Intermediate coating compositions were prepared in the same manner as in Example 1, except that in the film-forming resins (A), (B), and (C) used in Example 1, the types and / or blending amounts of the components were changed as shown in the table below. Using the intermediate coating compositions obtained, multi-layer coating films were formed on substrates in the same manner as in Example 1.

[0146] Comparative Examples 1 to 5 Intermediate coating compositions were prepared in the same manner as in Example 1, except that in the film-forming resins (A), (B), and (C) used in Example 1, the types and / or blending amounts of the components were changed as shown in the table below. Using the intermediate coating compositions obtained, multi-layer coating films were formed on substrates in the same manner as in Example 1.

[0147] The following evaluations were carried out using the intermediate coating compositions obtained in the above Examples and Comparative Examples. The various evaluation conditions and evaluation results are shown in the following table.

[0148] [Peel strength measurement] Coated panels for evaluation were prepared in the following manner. A masking tape with a width of 3 cm was attached to the edge of the polypropylene (PP) substrate. Then, the undercoat paint composition was applied to a film thickness of 9 μm. After applying the undercoat paint composition, the undercoat paint composition was left for 5 minutes, and the masking tape was peeled off to create a portion without the undercoat paint film. Next, the intermediate paint composition was applied to a film thickness of 18 μm. After applying the intermediate paint composition, the undercoat paint composition was left for 5 minutes, and then the clear paint composition, which is the topcoat paint composition, was applied to a film thickness of 32 μm and left to stand at room temperature for 5 minutes. The obtained uncured undercoat paint film, intermediate paint film, and topcoat paint film were baked in an oven at 80° C. for 20 minutes to form a multi-layer paint film. After curing for 48 hours at room temperature, a 100-120 μm thick auxiliary coating for measurement at the time of peel strength measurement (a mixture of 100% Nippon Paint R-278 040MG and 40% hardener R-271) was laminated and cured at room temperature. The resulting coated plate was aged at room temperature to obtain a coated plate for evaluation. The resulting coated plate for evaluation was cut at 10 mm width intervals using a cutter, and the film length was extended with reinforcing tape so as to extend onto the substrate. FIG. 1 is a diagram showing a schematic diagram of a peel strength test. The measurement test machine used was an AG-IS manufactured by Shimadzu Corporation. As shown in Figure 1, the coated plate to be evaluated was clamped with one of a pair of chucks, and the reinforcing tape was clamped with the other chuck, and the peel strength between the substrate and the undercoat film was measured at a peel angle of 180°, peel speed of 20 mm / min, and peel length of 15 mm. The tensile test conditions were: pull speed: 50 mm / min, peel width: 10 mm, peel angle: 180°, and measurement temperature: 20°C. The measurement was performed three times, and the average value was taken as the peel strength.

[0149] Moisture resistance test A humidity chamber (model CT-3, manufactured by Suga Test Instruments) was used to hang the test piece in the humidity chamber and slowly rotate it to examine the change in the state of the coating. A hole with a diameter of about 5 mm was drilled in the corner of a test piece (50 x 50 mm or more) having a multi-layer coating film prepared according to the procedure of each Example and Comparative Example, so that it could be hung. Two test pieces were prepared for each Example and Comparative Example. One test piece was tested, and the remaining one was stored as a comparison plate. The test was carried out according to the standard for inspection using a humid box (humidity conditions: 49°C ± 1°C, relative humidity: 95% or more, air flow rate: about 3 times the volume of the humid box per hour, water: deionized water, speed of the rotating ring: about 1 / 3 revolutions per minute). The test pieces were hung from the rotating ring using a fishing tackle for 240 hours, with a gap of 5mm or more between each piece so that the painted surfaces of the test pieces did not overlap. After that, the test pieces were taken out, the adhering water was wiped off, and the test pieces were lined up in the room so that the painted surfaces did not overlap. The test piece was then taken out and left at room temperature for 24 hours, after which the adhesion evaluation was carried out. The adhesion evaluation procedure was as follows.

[0150] [About adhesion evaluation] An adhesion test was carried out in accordance with JIS K5400. Using a cutter knife, cross cuts were made so that 100 1 mm2 cuts (grids) were made. Next, cellophane adhesive tape was completely attached onto the created grids, and one end of the tape was lifted and peeled upward. This peeling operation was carried out three times at the same location. After that, the number of peeled grids was judged according to the criteria described below. A score of 8 or more on the following evaluation criteria was considered to be a pass. 10: No peeling 8: Peeling is within 5 stitches 6: Peeling is more than 5 stitches but not exceeding 15 stitches 4: Peeling is more than 15 stitches but not exceeding 35 stitches 2: Peeling is more than 35 stitches but not exceeding 65 stitches 0: Peeling is more than 65 meshes but less than 100 meshes

[0151] Hot water resistance test evaluation Test pieces having multi-layer coating films prepared by the procedures of each of the Examples and Comparative Examples were immersed in a thermostatic water bath adjusted to 40° C. for 10 days (240 hours) or 20 days (500 hours). The test piece was then taken out and left at room temperature for 24 hours, after which the adhesion evaluation was carried out. The adhesion evaluation procedure was as follows.

[0152] [About adhesion evaluation] An adhesion test was carried out in accordance with JIS K5400. Using a cutter knife, cross cuts were made so that 100 1 mm2 cuts (grids) were made. Next, cellophane adhesive tape was completely attached onto the created grids, and one end of the tape was lifted and peeled upward. This peeling operation was carried out three times at the same location. After that, the number of peeled grids was judged according to the criteria described below. A score of 8 or more on the following evaluation criteria was considered to be a pass. 10: No peeling 8: Peeling is within 5 stitches 6: Peeling is more than 5 stitches but not exceeding 15 stitches 4: Peeling is more than 15 stitches but not exceeding 35 stitches 2: Peeling is more than 35 stitches but not exceeding 65 stitches 0: Peeling is more than 65 meshes but less than 100 meshes

[0153] [Table 4]

[0154] According to the results of the examples, when an intermediate coating film is formed using the intermediate coating composition according to the present disclosure, the intermediate coating composition according to the present disclosure can form an intermediate coating film that exhibits high adhesion to each layer of a multi-layer coating film. Furthermore, the intermediate coating composition according to the present disclosure can form a multi-layer coating film that exhibits high adhesion to the substrate. The resulting multi-layer coating film has good moisture resistance. The multi-layer coating film further has an excellent coating appearance and is capable of conforming to complex shapes. Therefore, the multi-layer coating film obtained using the intermediate coating composition according to the present disclosure can be used for parts with high design quality. Moreover, the multi-layer coating film obtained using the intermediate coating composition according to the present disclosure can satisfy high adhesion between the substrate and the multi-layer coating film. Furthermore, the intermediate coating composition according to the present disclosure maintains adhesion to materials that can be used for exteriors, etc., and has better adhesion than conventional undercoat coating films. Therefore, the intermediate coating composition according to the present disclosure has the advantage of being able to ensure improved adhesion to coating films other than those such as primer coating films and / or clear coating films (e.g., steel plate substrates, etc.).

[0155] In addition, the intermediate coating composition according to the present disclosure can form a coating film having the above-mentioned various properties without impairing the properties of the substrate, even in an embodiment in which the substrate contains a resin. Furthermore, in an embodiment in which the substrate contains a resin, the intermediate coating composition according to the present disclosure can perform baking (curing of the coating film) at a lower temperature than in an embodiment in which the substrate is metal. And the multi-layer coating film formed using the intermediate coating composition according to the present disclosure has the advantage of having good adhesion to the substrate, even when baking and curing are performed at a low temperature.

[0156] On the other hand, Comparative Examples 1 to 3 did not contain any one of the coating film-forming resins (A) to (C), and therefore had insufficient hot water resistance. In Comparative Examples 4 and 5, the glass transition temperature Tg(I) of the mixture of film-forming resins (A) to (C) contained in the intermediate coating composition was outside the range of the present invention. In these cases, the hot water resistance and other properties were also insufficient. [Industrial Applicability]

[0157] The intermediate coating composition according to the present disclosure can form an intermediate coating film that exhibits high adhesion to each layer of the multilayer coating film. Furthermore, the intermediate coating composition according to the present disclosure has the advantage that it can form a multilayer coating film that exhibits high adhesion to the substrate, and further, can form a multilayer coating film that has excellent coating film appearance.

Claims

1. A multi-layer coating film having an undercoat coating film disposed on a substrate, an intermediate coating film disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film, comprising an intermediate coating composition for forming the intermediate coating film, The intermediate coating composition comprises: The composition includes a film-forming resin (A), a film-forming resin (B), and a film-forming resin (C), The film-forming resin (B) and the film-forming resin (C) are acrylic resins, The glass transition temperature of the film-forming resin (A) is Tg(A), the glass transition temperature of the film-forming resin (B) is Tg(B), and the glass transition temperature of the film-forming resin (C) is Tg(C). Tg(A)<Tg(B)<Tg(C) Satisfying the relationship, the glass transition temperature Tg(I) of the mixture of the film-forming resin (A), the film-forming resin (B) and the film-forming resin (C) contained in the intermediate coating composition is 25° C. or higher and 60° C. or lower; In a total of 100% by mass of the film-forming resin (A), the film-forming resin (B), and the film-forming resin (C), The coating film-forming resin (A) is 20% by weight or more and 40% by weight or less, The coating film-forming resin (B) is 20% by weight or more and 75% by weight or less, and The coating film-forming resin (C) is 5 parts by mass or more and 45% by mass or less; Intermediate coating composition.

2. 2. The intermediate coating composition according to claim 1, wherein the film-forming resin (A) has a weight average molecular weight of 9,000 or more and 90,000 or less, a hydroxyl value of 50 mg KOH / g or more and 150 mg KOH / g or less, and a glass transition temperature Tg(A) of -25°C or more and 5°C or less.

3. 3. The intermediate coating composition according to claim 1, wherein the film-forming resin (B) has a weight average molecular weight of 5,000 or more and 30,000 or less, a hydroxyl value of 20 mg KOH / g or more and 100 mg KOH / g or less, and a glass transition temperature Tg(B) of 20° C. or more and 80° C. or less.

4. The intermediate coating composition according to any one of claims 1 to 3, wherein the film-forming resin (C) has a weight average molecular weight of 5,000 to 60,000, a hydroxyl value of 0 to 35 mgKOH / g, and a glass transition temperature Tg(C) of 40 to 100°C.

5. The intermediate coating composition according to any one of claims 1 to 4, wherein the coating film-forming resin (B) comprises a polymer of a monomer comprising at least one selected from the group consisting of (meth)acrylic acid, hydroxyethyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate.

6. The intermediate coating composition according to any one of claims 1 to 5, wherein the coating film-forming resin (C) comprises a polymer of a monomer comprising at least one selected from the group consisting of (meth)acrylic acid, hydroxyethyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate.

7. The intermediate coating composition according to any one of claims 1 to 6, which is used for coating a substrate containing a resin member.

8. 8. The intermediate coating composition according to claim 7, which is used for coating an object containing a polyolefin resin.

9. The intermediate coating composition according to any one of claims 1 to 8, which is used for coating vehicle exterior members.

10. The intermediate coating composition according to claim 9, which is used for coating vehicle exterior members containing resin members.

11. A multi-layer coating film having a substrate, an undercoat coating film disposed on the substrate, an intermediate coating film disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film; An article comprising: The intermediate coating film is formed from the intermediate coating composition according to any one of claims 1 to 6, The thickness of the undercoat coating film is 3 μm or more and 15 μm or less, The thickness of the intermediate coating film is 10 μm or more and 30 μm or less, The thickness of the topcoat coating film is 20 μm or more and 40 μm or less. Goods.

12. The article according to claim 11 , wherein the substrate comprises a resin member.

13. The article according to claim 12 , wherein the resin member comprises a polyolefin resin.

14. The substrate is a resin member containing a polyolefin resin, and the peel strength T(P) [N / m] of the undercoat coating film from the substrate and the peel strength T(L) [N / m] of the multilayer coating film from the substrate are 0.49<(T(L)-T(P))<4.9 The article according to claim 12 or 13, which satisfies the following relationship:

15. The article according to any one of claims 11 to 14, wherein the substrate is an exterior vehicle member.

16. The article according to claim 15 , wherein the substrate comprises a resin member.

17. The object to be coated, and A multi-layer coating film having an undercoat coating film disposed on a substrate, an intermediate coating film disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film. A method of manufacturing an article comprising: A step of applying an undercoat coating composition onto the substrate to form an uncured undercoat coating film; A step of applying an intermediate coating composition according to any one of claims 1 to 7 onto the uncured undercoat coating film to form an uncured intermediate coating film; A step of applying a topcoat coating composition onto the uncured intermediate coating film to form an uncured topcoat coating film; and A step of simultaneously baking and curing the uncured undercoat coating film, the uncured intermediate coating film, and the uncured topcoat coating film at a temperature of 60° C. or higher and 100° C. or lower. A method for manufacturing an article comprising the steps of:

18. The object to be coated, and A multi-layer coating film having an undercoat coating film disposed on a substrate, an intermediate coating film disposed on the undercoat coating film, and a topcoat coating film disposed on the intermediate coating film. A method of manufacturing an article comprising: A step of applying an undercoat coating composition onto the substrate to form an uncured undercoat coating film, and baking and curing the uncured undercoat coating film at a temperature of 60° C. or higher and 100° C. or lower to form an undercoat coating film; A step of applying an intermediate coating composition according to any one of claims 1 to 7 onto the undercoat coating film to form an uncured intermediate coating film, and baking and curing the uncured intermediate coating film at 60°C or higher and 100°C or lower to form an intermediate coating film; A step of applying a topcoat coating composition onto the intermediate coating film to form an uncured topcoat coating film, and baking and curing the uncured topcoat coating film at 60° C. or higher and 100° C. or lower to form a topcoat coating film; A method for manufacturing an article, comprising:

19. The method for manufacturing an article according to claim 17 or 18, wherein the substrate comprises a resin member.

20. The method for manufacturing an article according to claim 19 , wherein the resin member comprises a polyolefin resin.

21. The method for producing an article according to any one of claims 17 to 20, wherein the substrate is an exterior vehicle member.

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