Coating composition and aluminum-coated can

Abstract

To provide a coating composition and an aluminum-coated can, enabling the formation of a coating film with high blister resistance even when used with two-component hair dyes.SOLUTION: A coating composition comprises: a hydroxyl group-containing base agent in an amount of 25 mass% or more and 92 mass% or less on a solids basis; a novolac-type curing agent in an amount of 8 mass% or more and 75 mass% or less on a solids basis; and a phosphoric acid catalyst in an amount of 0.02 mass% or more and 2 mass% or less on a solids basis. An aluminum-coated can comprises an aluminum can at least coated with the coating composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to coating compositions and coated aluminum cans. [Background technology]

[0002] In Japanese Patent Laid-Open No. 61-217353 (Patent Document 1), the paint on the inside of a can has a viscosity of 1×10 6 dyne / cm 2 Young's modulus and 100kg / cm 2 This paper discloses an aerosol can for heat sterilization, the inside of which is coated with an epoxy resin curing paint having the following coating shrinkage stress. Also, JP 2003-191935 A (Patent Document 2) discloses a metal container, the inside of which is entirely coated with a first layer of epoxy-phenolic resin paint having high processing resistance provided at least on the part of the inside that is highly processed, and a second layer of epoxy-phenolic resin paint having high corrosion resistance provided at least on the part of the inside that is less processed. Furthermore, JP 2008-189364 A (Patent Document 3) discloses a metal tube for hair dye, the inside paint of which is the innermost layer composed of a heat-drying resin paint mainly composed of polyvinylidene fluoride resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 61-217353 [Patent Document 2] JP 2003-191935 A [Patent Document 3] JP 2008-189364 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, with the demand for shorter hair dyeing times, problems have arisen such as deterioration of the inner paint film of the container (such as an aerosol can) that stores the hair dye due to an increase in the amount of oxidizing components, mainly hydrogen peroxide, contained in the two-component hair dye. Specifically, there was a problem that it was difficult to prevent deterioration and blistering of the inner paint film of the container for storing the two-component hair dye with the epoxy resin curing paint disclosed in Patent Document 1 or the two types of epoxy-phenol resin paint disclosed in Patent Document 2. In addition, there was a problem that the paint mainly composed of polyvinylidene fluoride resin disclosed in Patent Document 3 had sufficient blister resistance against one-component hair dye, but insufficient blister resistance against two-component hair dye.

[0005] Therefore, an object of the present disclosure is to solve the above problems and provide a coating composition and a coated aluminum can that form a coating film with high blister resistance even when used with a two-component hair dye. [Means for solving the problem]

[0006] [1] A coating composition according to one embodiment of the present disclosure includes a hydroxyl group-containing base agent having a solid content of 25% by mass or more and 92% by mass or less, a novolac-based curing agent having a solid content of 8% by mass or more and 75% by mass or less, and a phosphoric acid-based catalyst having a solid content of 0.02% by mass or more and 2% by mass or less.

[0007] [2] In the coating composition according to [1] above, the novolac-based curing agent may have a mass average molecular weight of 800 or more and 8,000 or less.

[0008] [3] A coated aluminum can according to another embodiment of the present disclosure has at least the inner surface of an aluminum can coated with the coating composition according to [1] or [2] above.

[0009] [4] In the coated aluminum can according to the above item [3], the coating composition applied to at least the inner surface of the aluminum can may be in the form of a single layer. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a coating composition and a coated aluminum can that form a coating film with high blister resistance even when used with a two-component hair dye. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Embodiment 1: Coating composition] The coating composition according to an embodiment of the present disclosure includes a hydroxyl-containing base agent having a solid content of 25% to 92% by mass, a novolac-based curing agent having a solid content of 8% to 75% by mass, and a phosphoric acid-based catalyst having a solid content of 0.02% to 2% by mass. The coating composition according to the present embodiment forms a coating film having high blister resistance against two-component hair dyes, particularly against oxidizing components mainly composed of hydrogen peroxide.

[0012] (Hydroxyl-containing base agent) The hydroxyl group-containing main agent contained in the coating composition of the present embodiment is not particularly limited as long as it contains a hydroxyl group and reacts with a novolac-based curing agent in the presence of a phosphoric acid-based catalyst to form a coating film, and examples thereof include epoxy resins, acrylic resins, polyester resins, PVC-based resins, and butyral (polyvinyl alcohol) resins. From the viewpoint of high adhesion and processability, the hydroxyl group-containing main agent is preferably an epoxy resin or an acrylic resin. From the viewpoint of having high processability such as neck processing, the content of the hydroxyl group-containing main agent is 25% by mass or more, preferably 40% by mass or more, and more preferably 60% by mass or more, in terms of solid content. In addition, from the viewpoint of not impairing curability, the content of the hydroxyl group-containing main agent is 92% by mass or less, preferably 91% by mass or less, and more preferably 90% by mass or less, in terms of solid content.

[0013] (Novolac hardener) The novolac-based curing agent contained in the coating composition of this embodiment is not particularly limited as long as it contains a novolac resin and reacts with the hydroxyl-containing main agent in the presence of a phosphoric acid catalyst to form a coating film. Here, the novolac resin refers to an oligomer (novolac) formed mainly by methylene bonds, which is obtained by subjecting phenols and aldehydes to an addition condensation reaction with an excess of phenols using an acid catalyst (e.g., sulfuric acid, hydrochloric acid, phosphoric acid, oxalic acid, etc.). In addition, phenols are a general term for compounds having a hydroxyl group on an aromatic substituent in the molecule, and include phenol, cresol, rosin, etc. Aldehydes are a general term for compounds having an aldehyde group in the molecule, and include formaldehyde, acetaldehyde, etc. Among novolac resins, those obtained by subjecting phenols to an addition condensation reaction with formaldehyde are called novolac-type phenolic resins.

[0014] In addition, oligomers (resoles) formed with methylene bonds and / or dimethyl ether bonds and rich in oxymethyl groups, which are produced by addition condensation reaction of phenols and aldehydes with an excess of aldehydes using an alkaline catalyst (such as alkali metal hydroxide, ammonia, amine, etc.), are called resole resins, not novolac resins. Among resole resins, those produced by addition condensation of phenol and formaldehyde are called resole-type phenolic resins.

[0015] The content of the novolac-based hardener is 8% by mass or more, preferably 9% by mass or more, more preferably 10% by mass or more, in terms of solid content, from the viewpoint of ensuring sufficient hydrogen peroxide resistance without impairing hardening properties. Also, the content of the novolac-based hardener is 75% by mass or less, preferably 55% by mass or less, more preferably 40% by mass or less, in terms of solid content, from the viewpoint of improving processability, compatibility with the hydroxyl group-containing base agent, and smoothness of the coating film.

[0016] The mass average molecular weight of the novolac-based curing agent is preferably 800 or more, more preferably 1500 or more, from the viewpoint of not damaging the curing agent, and is preferably 8000 or less, more preferably 4000 or less, from the viewpoint of improving compatibility with the hydroxyl group-containing main agent.

[0017] (Phosphoric acid catalyst) The phosphoric acid catalyst contained in the coating composition of this embodiment is not particularly limited as long as it contains a phosphoric acid compound as a main component (meaning a component that is 50% by mass or more in terms of solid content relative to the solid content of the catalyst, the same applies below) and has catalytic activity to form a coating film by curing the hydroxyl group-containing main agent and the novolac curing agent. There are water-soluble and oil-soluble phosphoric acid compounds. Examples of water-soluble phosphoric acid compounds include phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid (diphosphoric acid), triphosphoric acid, and tetraphosphoric acid, as well as salts thereof, and phosphonic acid and salts thereof. Examples of oil-soluble phosphoric acid compounds include those in which some or all of the hydroxyl groups are blocked with metals, amines, or alcohols, such as CYCAT (registered trademark)-XK-406-N (manufactured by Allnex), Amidea P-198 (manufactured by DIC), and Nacure-4167 (manufactured by KING INDUSTRIES).

[0018] The content of the phosphoric acid catalyst is 0.02% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, based on the solid content, from the viewpoint of increasing the curability and hydrogen peroxide resistance, and 3% by mass or less, preferably 2% by mass or less, more preferably 1% by mass or less, based on the solid content, from the viewpoint of suppressing an increase in the viscosity of the coating composition.

[0019] (others) The coating composition of this embodiment may contain other components in addition to the hydroxyl-containing base agent, the novolac-based curing agent, and the phosphoric acid-based catalyst, so long as they do not impair the application and curing of the coating composition and the physical properties of the formed coating film. Suitable examples of other components include resol-based curing agents, amino resins, fillers, pigments, lubricating waxes, etc. Here, the resol-based curing agent refers to a curing agent that contains a resol resin and reacts with the hydroxyl-containing base agent in the presence of a phosphoric acid-based catalyst to form a coating film.

[0020] [Embodiment 2: Aluminum Coated Can] A coated aluminum can according to another embodiment of the present disclosure has at least the inner surface of the aluminum can coated with the coating composition of embodiment 1. The coated aluminum can of this embodiment has at least the inner surface a coating film that has high blister resistance against two-component hair dyes, particularly oxidizing components mainly composed of hydrogen peroxide.

[0021] In the coated aluminum can of this embodiment, the coating composition may be one layer. Here, one layer refers to a layer in which the coating composition has the same composition. In other words, it means that even if a coating composition of the same composition is applied twice or more, it is still one layer. One layer of coating film is formed from such one layer of coating composition, and even if it is a single layer, such coating film has high blister resistance against two-component hair dyes, especially against oxidizing components mainly composed of hydrogen peroxide. EXAMPLES

[0022] 1. Preparation of hydroxyl-containing base agent (1) Epoxy A Epoxy A (epoxy resin with a solid content of 50% by mass) was obtained by dissolving 100 parts by mass of a bisphenol A type epoxy resin (E1009 manufactured by Mitsubishi Chemical Corporation) in 100 parts by mass of a mixed solvent consisting of 50 parts by mass of butyl cellosolve and 50 parts by mass of xylene.

[0023] (2) Acrylic A In advance, 30 parts by mass of methyl methacrylate, 25 parts by mass of 2-hydroxyethyl methacrylate, 25 parts by mass of styrene, 20 parts by mass of butyl cellosolve, and 0.8 parts by mass of benzoyl peroxide were prepared in a dropping tank by stirring. 61 parts by mass of butyl cellosolve was charged in a flask equipped with a thermometer, a stirrer, a gas inlet tube, a cooling tube, and a dropping tank inlet, and after nitrogen replacement, the temperature was raised to 90°C by heating. While maintaining the temperature in the flask at 90°C, the above stirred mixture was dropped from the dropping tank over 3 hours to perform polymerization. 30 minutes after the end of the dropping, 0.2 parts by mass of benzoyl peroxide was added. After 30 minutes, the temperature in the flask was raised to 115°C and maintained at the same temperature for 1.5 hours to obtain acrylic A (acrylic resin with a solid content of 50% by mass).

[0024] 2. Preparation of Curing Agent (1) NP1 100 parts by mass of Super Beccasite 3011 manufactured by DIC Corporation was dissolved in 100 parts by mass of cyclohexanone to obtain NP1 (a first novolak resin (specifically, a novolak-type phenolic resin) having a solid content of 50% by mass).

[0025] (2) NP2 100 parts by mass of R-70 manufactured by Lignite Corporation was dissolved in 100 parts by mass of cyclohexane to obtain NP2 (a second novolak resin (specifically, a novolak-type phenolic resin) having a solid content of 50% by mass).

[0026] (3)RP 100 parts by mass of Shownol CKM-1634 manufactured by Aica Kogyo Co., Ltd. was dissolved in 100 parts by mass of cyclohexane to obtain RP (a resol resin having a solid content of 50% by mass (specifically, a resol-type phenolic resin)).

[0027] 3. Catalyst Preparation (1) Phosphoric acid catalyst As the phosphoric acid-based catalyst, phosphoric acid with a solid content of 85% by mass was used.

[0028] (2) Catalysts other than phosphoric acid As a catalyst other than phosphoric acid, a sulfonic acid catalyst, Nacure-2500 (p-toluenesulfonic acid) manufactured by KING INDUSTRIES, with a solid content of 25 mass % was used.

[0029] 4. Preparation of Coating Composition For Examples 1 to 5 and Comparative Examples 1 to 4, a hydroxyl-containing base agent, a curing agent, and a catalyst were mixed in the composition shown in Table 1, and a mixed solvent of cyclohexanone and xylene in a mass ratio of 1:1 was further added and mixed until the solid content reached 30 mass%, to obtain each coating composition.

[0030] 5. Sample Preparation In each of Examples 1 to 5 and Comparative Examples 1 to 4, the coating composition obtained above was applied to an aluminum plate having a thickness of 0.23 mm so that the dry coating thickness was 10 μm, and then cured at 230° C. for 10 minutes to prepare six samples having coating films.

[0031] 6.Evaluation of coating properties (1) Blister resistance Of the above samples, 10 μL (microliters) of 5% by mass hydrogen peroxide was dropped onto each of three samples, which were then dried in an oven at 180°C for two minutes, after which the surface condition of the coating film (particularly the presence or absence of blisters (swelling)) was observed. Samples that were free of abnormalities were rated as excellent, samples that showed no blisters but showed signs of blistering in at least one sample were rated as good, samples that showed very slight blisters in at least one sample were rated as acceptable, and samples that showed clear blisters in at least one sample were rated as unacceptable. The results are summarized in Table 1.

[0032] (2) Bendability Each of the three samples was folded 180° in the direction that the coating film was on the outside, and an aluminum plate with a thickness of 0.23 mm was sandwiched between the folded plates, and a rectangular weight of 3 kg was dropped from a height of 30 cm onto the folded part to completely fold it. The presence or absence of cracks and / or peeling of the coating film that occurred at the folded part was observed. The reason for folding in the direction in which the coating film was on the outside, i.e., in the direction in which the coating film was subjected to tensile stress more than the aluminum plate, is that this is a condition in which cracks and / or peeling are more likely to occur in the coating film than bending in the opposite direction. Samples that had no cracks in all samples were evaluated as good, samples that had no cracks but showed signs of cracking were evaluated as good, samples that had slight cracks in at least one sample were evaluated as acceptable, and samples that had clear cracks and / or peeling in at least one sample were evaluated as unacceptable. The results are summarized in Table 1.

[0033] [Table 1]

[0034] With reference to Table 1, it was confirmed that a coating composition containing a hydroxyl-containing base agent having a solid content of 25% to 92% by mass, a novolac-based curing agent having a solid content of 8% to 75% by mass, and a phosphoric acid-based catalyst having a solid content of 0.02% to 2% by mass forms a coating film having high blister resistance and high bending ability. It was also found that a coated aluminum can in which the coating composition is applied to at least the inner surface of the aluminum can has a coating film having high blister resistance and high bending ability.

[0035] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is indicated by the claims, not by the embodiments and examples described above, and is intended to include the meaning equivalent to the claims and all modifications within the scope.

Claims

1. A coating composition comprising: a hydroxyl group-containing base agent having a solid content of 25% by mass or more and 92% by mass or less; a novolac-based curing agent having a solid content of 8% by mass or more and 75% by mass or less; and a phosphoric acid-based catalyst having a solid content of 0.02% by mass or more and 2% by mass or less.

2. The coating composition according to claim 1 , wherein the novolac-based curing agent has a mass average molecular weight of 800 or more and 8,000 or less.

3. 3. A coated aluminum can, at least the inner surface of which is coated with the coating composition according to claim 1 or 2.

4. 4. The coated aluminum can according to claim 3, wherein the coating composition applied to at least the inner surface of the aluminum can is one layer.

Images