Epoxy resin coating composition

Abstract

To provide an epoxy resin coating composition capable of surely suppressing poor appearance of a coated film regardless of use environment.SOLUTION: An epoxy resin coating composition contains a main agent having an epoxy resin, and an amine-based curing agent, where a content of a solvent having a boiling point of lower than 200°C is 1-15 mass%, and 50 mass% or more of the solvent is lower alcohol having 1 to 5 carbon atoms.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an epoxy resin coating composition containing a main agent having an epoxy resin and an amine-based curing agent. Specifically, it relates to a high-solid epoxy resin coating with a low solvent content, and an epoxy resin coating composition that is less likely to cause appearance abnormalities when applied.

Background Art

[0002] In a two-component curing type paint formed by the reaction of an epoxy resin as the main agent and an amine-based compound as the curing agent, appearance abnormalities such as stickiness and cracks in the cured paint film in a low-temperature environment, and whitening due to water wetting often occur in high-solid paints with a low solvent content.

[0003] Reducing volatile organic solvents generated from paints is one of the major goals of the paint industry from the viewpoints of environmental protection and reducing the burden on workers. High-solid paints are a solution to this problem, but the above-mentioned problems with paint film quality are major challenges in their widespread use.

[0004] The cause of stickiness and appearance abnormalities in the paint film is thought to be that the reaction rate of the amine-based compound with moisture and carbon dioxide in the environmental atmosphere is faster than the curing reaction rate of the epoxy resin and the amine-based compound, resulting in a large amount of carbamate being generated in the epoxy resin paint film. In particular, when the temperature (air temperature) in the environment where the paint film is applied is low, the reaction rate of the epoxy resin and the amine-based compound slows down, making such appearance abnormalities more likely to occur.

[0005] Generally, in paints with low solvent content, epoxy resins and amine compounds with relatively small molecular weights are used. In particular, amine compounds commonly used in two-component curing paints, such as 1,3-bis(aminomethyl)cyclohexane, 4,4'-methylenebis(cyclohexylamine), xylylenediamine, and isophoronediamine, tend to appear on the surface of the paint film due to the influence of surface tension, and the reactions of the amine compounds mentioned above can cause abnormal appearances such as whitening.

[0006] For this reason, in the past, methods to prevent poor appearance have been used, such as modifying amine compounds to suppress reactivity or increasing molecular weight to suppress bleeding onto the coating surface.Specific examples include (i) modification by the Mannich reaction with phenolic compounds and aldehyde compounds, (ii) adduct modification by reaction with epoxy resins, (iii) modification by reaction with compounds containing carboxyl groups, and (iv) modification by the Michael reaction with acrylic compounds.

[0007] However, these modifications increase the viscosity of the amine-based compound. This ultimately requires an increase in the amount of dilution solvent, making it difficult to develop a high-solids paint with a low solvent content. Non-reactive diluents (plasticizers) can also be used instead of dilution solvents, but this can impair the corrosion resistance that is important for paints.

[0008] Therefore, epoxy resin coating compositions containing a polyamine compound such as 1,3-bis(aminomethyl)cyclohexane, xylylenediamine, or a modified product thereof, and an alkylamine compound have been known (see Patent Documents 1 to 3). By incorporating an alkylamine compound into the polyamine compound that has been conventionally used, such epoxy resin coating compositions can eliminate the tackiness of the coating film surface and prevent stickiness, and can also prevent whitening that occurs when water droplets adhere to the coating film. [Prior art documents] [Patent documents]

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] The epoxy resin coating compositions according to Patent Documents 1 to 3 as described above have been relatively widely used so far, and an effect of suppressing appearance defects such as stickiness and whitening has been recognized.

[0011] However, although these effects are effective under a certain environment, in an inappropriate environment, specifically in a high-humidity environment, the effects are limited. This is because when an amine-based compound appears on the coating film surface and reacts with carbon dioxide in the air, water acts like a catalyst, so it is difficult to prevent the reaction between the amine-based compound and carbon dioxide in a high-humidity environment. Moreover, by blending an alkylamine compound, the appearance of the coating film may be deteriorated instead.

[0012] Therefore, as a result of intensive studies on the above problems by the present inventors, surprisingly, by using a lower alcohol, which has not been adopted so far, as a solvent in the epoxy resin coating composition, it is possible to suppress appearance defects such as stickiness, cracks, and whitening of the coating film even in a low-temperature environment and a high-humidity environment, and the present invention has been completed.

[0013] Therefore, an object of the present invention is to provide an epoxy resin coating composition capable of reliably suppressing appearance defects of a coating film regardless of the use environment.

Means for Solving the Problems

[0014] That is, the present invention is an epoxy resin coating composition containing a base agent having an epoxy resin and an amine-based curing agent, characterized in that the content of a solvent having a boiling point of less than 200°C is 1 to 15 mass %, and 50 mass % or more of the solvent is a lower alcohol having 1 to 5 carbon atoms.

[0015] In the present invention, the solvent used in the epoxy resin coating composition is a lower alcohol having 1 to 5 carbon atoms, with the proportion of the solvent being 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more. The reason for using such a lower alcohol is to promote compatibility of the amine curing agent with the epoxy resin, particularly to achieve good compatibility with the cyclic aliphatic polyamine preferably used in the present invention, as described below. This prevents bleeding of the amine curing agent in the epoxy resin coating composition of the present invention without being affected by the environment.

[0016] The lower alcohol having 1 to 5 carbon atoms is not particularly limited, but examples thereof include primary alcohols such as methanol, ethanol, propan-1-ol, butan-1-ol, and pentan-1-ol, and secondary alcohols such as propan-2-ol, butan-2-ol, pentan-2-ol, and 1-methoxy-2-propanol, and one or more of these can be used. Of these, primary alcohols are preferred.

[0017] Furthermore, in the present invention, solvents other than lower alcohols having 1 to 5 carbon atoms can be included as long as the above-mentioned quantitative restrictions are satisfied. There are no particular restrictions on these other solvents, except that they must have a boiling point of less than 200°C. However, since lower alcohols are relatively poor solvents for epoxy resins, the following solvents are preferred: ketone-based organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester-based organic solvents such as methyl acetate, ethyl acetate, and butyl acetate; and hydrocarbon solvents such as toluene and xylene.

[0018] The present invention is a two-component epoxy resin coating composition containing a main agent having an epoxy resin and an amine-based curing agent. Considering general usage modes as a coating, solvents with a boiling point of less than 200 °C are targeted. In particular, the epoxy resin coating composition in the present invention is premised on being a high-solid coating, and the solvent content in the epoxy resin coating composition is 1 to 15% by mass. This solvent content is preferably 1 to 10% by mass, and more preferably 1 to 5% by mass. Although generally, coatings with a solvent content of 30 or less may be called high-solid coatings according to the definition, the present invention is an epoxy resin coating composition with an even lower solvent content.

[0019] There are no particular restrictions on the amine-based curing agent in the epoxy resin coating composition of the present invention, and any amine-based compound of aliphatic amine or aromatic amine generally used as an amine-based curing agent can be used. Among them, due to the ability to ensure excellent corrosion resistance and workability, etc., it is preferably an amine-based curing agent containing an amine-based compound composed of a cycloaliphatic polyamine or an aliphatic polyamine having two or more amino groups, or preferably an amine-based curing agent containing both of these amine-based compounds.

[0020] Among these, specific examples of the cycloaliphatic polyamine include 1,3-bis(aminomethyl)cyclohexane, 4,4'-methylenebis(cyclohexylamine), xylylenediamine, isophoronediamine, etc., and one or more of them can be used. Specific examples of the aliphatic polyamine include polyoxypropylene diamine, tetraethylene pentamine, etc., and one or more of them can be used. As long as the viscosity of the coating is within a paintable range, the amine-based compound used as the amine-based curing agent may be a modified product. Among them, considering the curing reaction rate and the properties of the resulting coating film, etc., those modified with phenolic compounds, aldehyde-based compounds, epoxy resins, acrylic compounds, etc. can be used.

[0021] Furthermore, the above-mentioned amine-based curing agent may contain a plasticizer component for the purpose of adjusting viscosity, etc. As the plasticizer component, a non-reactive diluent such as benzyl alcohol or a high-boiling-point hydrocarbon is generally used.

[0022] On the other hand, the epoxy resin constituting the main component of the epoxy resin coating composition of the present invention can be any epoxy resin that has two or more epoxy groups per molecule and can react with an amine-based curing agent to form a crosslinked coating film. Examples include bisphenol-type epoxy resins such as bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol AD epoxy resin, as well as special epoxy resins such as chelate-modified epoxy resin, dimer acid-modified epoxy resin, propylene oxide-modified epoxy resin, and sulfide-containing epoxy resin. These epoxy resins can be used alone or in combination of two or more. Representative examples of commercially available epoxy resins include the YD series manufactured by Nippon Steel Chemical & Material Co., Ltd. and the jER series manufactured by Mitsubishi Chemical Corporation.

[0023] In particular, in the present invention, the main solvent is a lower alcohol that is not a good solvent for epoxy resins, so in consideration of the solubility, it is preferable to use an epoxy resin with an epoxy equivalent of 100 to 1000. More preferably, it is an epoxy resin with an epoxy equivalent of 100 to 300. Additionally, from the viewpoint of the corrosion resistance and workability of the coating film, the weight-average molecular weight of the epoxy resin is preferably 200 to 4000, more preferably 300 to 2000.

[0024] There are no particular restrictions on the ratio of the main agent to the amine-based curing agent in the epoxy resin coating composition of the present invention, and it can be made to be about the same as the formulation in a general epoxy resin coating composition. As a rough guide, the amount of the amine-based curing agent used is preferably such that the ratio of the amount of active hydrogen in the amine-based compound to the epoxy groups in the epoxy resin is in the range of 0.3 to 1.5, and preferably, from the viewpoint of coating film performance, the ratio is in the range of 0.5 to 1.0. As will be described later, when the epoxy resin coating composition of the present invention contains an aliphatic monoamine, it is advisable to consider the ratio of the amount of active hydrogen in the amine-based compound to the epoxy groups in the epoxy resin, including the amount of active hydrogen in this aliphatic monoamine.

[0025] Further, the epoxy resin coating composition of the present invention may contain an aliphatic monoamine having 10 to 20 carbon atoms. This aliphatic monoamine is desirably a monofunctional amine compound, and specifically, it is a compound having a primary amine such as stearylamine or tallow alkylamine. By blending such an aliphatic monoamine, the effect of suppressing abnormal appearance can be supplemented. However, if an excessive amount of aliphatic monoamine is blended in the epoxy resin coating composition, the interlayer adhesion when the paint is applied in multiple layers may deteriorate. Therefore, when blending an aliphatic monoamine, it is preferably made to be 2% by mass or less, preferably 1% by mass or less, and more preferably 0.5% by mass or less in the epoxy resin composition. Also, in order to supplement the effect of suppressing abnormal appearance, it is advisable to blend 0.01% by mass or more of the aliphatic monoamine in the epoxy resin composition. Paint composition so that it is 2% by mass or less, preferably 1% by mass or less, and more preferably 0.5% by mass or less. Also, in order to supplement the effect of suppressing abnormal appearance, Paint it is advisable to blend 0.01% by mass or more of the aliphatic monoamine in the epoxy resin

[0026] The epoxy resin coating composition of the present invention may contain a pigment. As the pigment, various extender pigments, coloring pigments, rust preventive pigments, etc. commonly used in paints can be used. Typically, as extender pigments, calcium carbonate, barium sulfate, talc, silica, etc. can be mentioned. As coloring pigments, titanium oxide, red iron oxide, yellow iron oxide, carbon black, etc. can be mentioned. As rust preventive pigments, zinc chromate, strontium chromate, zinc phosphate, zinc phosphomolybdate, aluminum phosphate, etc. can be mentioned. However, it is desirable to use phosphate-based defensive pigments considering safety rather than rust preventive pigments containing heavy metals harmful to health such as chromium and lead. The content of these pigments is preferably 50 to 200 parts by mass, more preferably 60 to 150 parts by mass, based on 100 parts by mass of the total resin components of the epoxy resin and the amine compound, from the viewpoints of corrosion resistance of the coating film and pot life of the paint.

[0027] In addition, various additives can be blended into the epoxy resin coating composition of the present invention for the purpose of improving coating performance, etc. Representative examples of such additives include commonly used silane coupling agents, pigment dispersants, anti-settling agents, defoamers, etc.

[0028] The epoxy resin coating composition in the present invention eliminates appearance abnormalities such as stickiness, crack generation, and whitening of the coating film, which were the drawbacks of amine-based curing agents using alicyclic polyamines such as 1,3-bis(aminomethyl)cyclohexane, 4,4'-methylenebis(cyclohexylamine), xylylenediamine, and isophoronediamine, and an epoxy resin coating film excellent in water resistance can be obtained. The use of this epoxy resin coating composition is not particularly limited, and for example, it can be used as a paint for coating the roofs and wall surfaces of steel structures, indoor steel frames of structures, etc., or as a coating material for corrosion prevention of metals and concrete in floor materials, etc. In particular, it is particularly effective in applications for outdoor painting that are easily exposed to low-temperature environments and high-humidity environments.

Advantages of the Invention

[0029] The epoxy resin coating composition of the present invention can reliably prevent poor appearance of the coating film regardless of the environment in which it is used. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be described below based on examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" are based on mass unless otherwise specified. [Example]

[0031] (Preparation of epoxy resin coating composition) The base agent and amine-based curing agent were prepared in the mass proportions shown in Table 1, and mixed at the respective mixing ratios to prepare the epoxy resin coating compositions according to Examples 1 to 7 and Comparative Examples 1 to 7. Details of the components used are as follows:

[0032] Epoxy resin: Epotohto YDF-170 (product name of Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent weight 170) Talc: Talc PS-85 (product name, manufactured by Fukuoka Talc Kogyo Co., Ltd., oil absorption capacity 50 ml / 100 g, average particle size 4.5 μm) Titanium oxide: TITONE R-5N (product name, manufactured by Sakai Chemical Industry Co., Ltd., average particle size 0.26 μm) Carbon black: MA-100 (product name of Mitsubishi Chemical Corporation) Solvents (methanol, ethanol, propylene glycol monomethyl ether, 1-hexanol, benzyl alcohol, toluene) Amine compound A: a mixture of epoxy-modified isophorone diamine, isophorone diamine, and 1,6-hexanediamine, 2,2,4-trimethyl (trade name: Sanmaid IM-544, manufactured by Evonik Japan Co., Ltd., active hydrogen equivalent: 100) Amine compound B: A mixture of 4,4'-methylenebis(cyclohexylamine) and modified 4,4'-methylenebis(cyclohexylamine) (trade name: Ancamine 2143, manufactured by Evonik Japan Co., Ltd., active hydrogen equivalent: 118) Amine compound C: Stearylamine (active hydrogen equivalent: 135)

[0033] In preparing these, as the main agent, after adding a specified amount of epoxy resin, solvent, various pigments, and various additives and dispersing for 60 minutes, a product with the pigments sufficiently dispersed was prepared. On the other hand, for the amine-based curing agent, stearylamine, which is amine-based compound C, was added to either amine-based compound A or B, and it was well stirred until they were uniformly dissolved to prepare a product. The charging amount of the prepared amine-based curing agent into the main agent was adjusted while ensuring that the ratio of the equivalent of NH groups (active hydrogen) in the amine-based compound (including amine-based compound C) to the epoxy equivalent in the main agent (active hydrogen / epoxy equivalent) was 0.8 - 1.0, and the main agent and the curing agent were thoroughly mixed at the mass ratio shown in Table 1 to obtain an epoxy resin coating composition.

[0034]

Table 1

[0035] (Observation of Coating Film Appearance) The main agent colored gray was thoroughly mixed with the curing agent, coated on a tin plate using an applicator with a 600 μm gap, and cured for 4 days in a thermo-hygrostat at 10°C and 30% RH, 10°C and 80% RH, and 23°C and 30% RH. Then, visual appearance observation was used to conduct a three-level evaluation. Each judgment criterion is as follows, and the results are summarized in Table 1. ○: No abnormality. (There is no appearance abnormality such as cracks or quality abnormality such as stickiness.) △: Slight abnormality. (There is an appearance abnormality such as orange peel or slight cracks or a slight quality abnormality such as stickiness.) ×: Abnormality. (There is an appearance abnormality such as wrinkles or cracks or a quality abnormality such as stickiness.)

[0036] As can be seen from the results shown in Table 1, in the epoxy resin coating compositions of Comparative Examples 1 to 7 using 1-hexanol, benzyl alcohol, or toluene as the main solvent, the appearance of the coating film was not a problem under room temperature and low humidity environments. However, when the temperature became lower or the humidity became higher, appearance abnormalities were confirmed. On the other hand, in the epoxy resin coating compositions of Examples 1 to 7 using lower alcohols as the main solvent, appearance abnormalities could be suppressed compared to the case of the comparative examples. That is, it was possible to obtain an epoxy resin coating composition that reduced appearance defects and was resistant to environmental changes.

Claims

1. An epoxy resin coating composition containing a main agent having an epoxy resin, an amine-based curing agent, and a pigment, wherein the solvent content is 1 to 15% by mass, the boiling point of the solvent is less than 200°C, and 50% by mass or more of the solvent is a lower alcohol having 1 to 5 carbon atoms. The amine-based curing agent contains an amine-based compound composed of an alicyclic polyamine and / or an aliphatic polyamine and an aliphatic monoamine having 10 to 20 carbon atoms, and contains 0.01% by mass or more and 2% by mass or less of the aliphatic monoamine. An epoxy resin coating composition characterized by the above.

2. The epoxy resin coating composition according to Claim 1, wherein the epoxy equivalent of the epoxy resin is 100 to 1000.

3. The epoxy resin coating composition according to Claim 1 or 2, wherein the lower alcohol is any one or two or more selected from the group consisting of methanol, ethanol, propan-1-ol, butan-1-ol, pentan-1-ol, propan-2-ol, butan-2-ol, pentan-2-ol, and 1-methoxy-2-propanol.

4. The epoxy resin coating composition according to any one of Claims 1 to 3, which is for outdoor coating applications.

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