JP2014098105A - Ethylated melamine resin, method for producing the same, curing agent for coating, resin composition, coating film, and laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkyl-etherified melamine resin capable of providing a cured product excellent in hardness and water resistance in a good balance.SOLUTION: In an ethylated melamine resin, at least some of methylol groups in a melamine resin are ethyl-etherified, and a ratio of A to B (A/B) is in a range of 0.1 to 1.1 assuming that in IR measurement, the intensity of the O-H stretching vibration of a hydroxyl group at around 3350 cmis A and the intensity of the C-H stretching vibration of an ethyl group at around 2980 cmis B.

Description

  The present invention relates to an ethylated melamine resin, a method for producing the same, a curing agent and a resin composition for a coating containing the ethylated melamine resin, a coating film obtained from the composition, and a laminate including the coating film.

  Conventionally, a melamine resin has been known as a curing agent for thermosetting paints, and in order to stabilize the melamine resin, it is common to alkylate the methylol group of the melamine resin with an alcohol. Has been done.

  As the alcohol, methanol, butanol and isopropanol are used. In particular, methylated melamine resins and butylated melamine resins have been studied and manufactured as alkyl etherified melamine resins.

  In addition, there is a document that discloses an ethylated melamine resin, such as Japanese Patent Application Laid-Open No. 47-1224.

JP 47-1224 A

However, according to the study by the present inventors, when a methyl etherified resin is used, the obtained cured product has excellent hardness but is not sufficient in terms of water resistance, and uses a butyl etherified resin. In such a case, it has been found that the obtained cured product is excellent in water resistance, but has insufficient hardness.
Furthermore, it has been found that when an isopropyl etherified resin is used, the hardness of the resulting cured product is similar to that when a butyl etherified resin is used.

  Further, according to the study by the present inventors, even when using a resin etherified according to Examples and Reference Examples of Patent Document 1, good results were not obtained.

  Accordingly, an object of the present invention is to provide an alkyl etherified melamine resin capable of obtaining a cured product having a good balance between hardness and water resistance.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by using a specific ethylated melamine resin, and have completed the present invention.
The configuration of the present invention is as follows.

[1] At least a part of the methylol group of the melamine resin is ethyl etherified, and the IR intensity of the hydroxyl group in the vicinity of 3350 cm ⁻¹ of the OH stretching vibration of the hydroxyl group is represented by A and the C—H stretching vibration of the ethyl group. An ethylated melamine resin having a ratio of A to B (A / B) in the range of 0.1 to 1.1 when the strength in the vicinity of 2980 cm ⁻¹ is B.

  [2] The ethylated melamine resin according to [1], wherein the alkali metal content is 100 mass ppm or less per ethylated melamine resin.

[3] The ethylated melamine resin according to [1] or [2], which is obtained by condensing melamine, formaldehyde, and ethanol in the presence of an acid catalyst.
[4] It is obtained by condensing melamine, formaldehyde and ethanol in the presence of an acid catalyst, and then neutralizing the obtained product with a basic compound containing no alkali metal. [1] The ethylated melamine resin according to any one of to [3].

[5] Obtained using melamine, formaldehyde and ethanol,
The ethylation according to any one of [1] to [4], wherein the amount of formaldehyde used is 3 to 7 mol and the amount of ethanol used is 3 to 20 mol when the amount of melamine used is 1 mol. Melamine resin.

  [6] The ethylated melamine resin according to any one of [1] to [5], wherein a polystyrene-reduced weight average molecular weight measured by GPC (gel permeation chromatography) is 800 to 15000.

[7] The method for producing an ethylated melamine resin according to any one of [1] to [6], comprising a step of condensing melamine, formaldehyde and ethanol in the presence of an acid catalyst.
[8] The method for producing an ethylated melamine resin according to [7], comprising a step of neutralizing a product obtained by further condensation using a basic compound not containing an alkali metal.

  [9] A curing agent for paint, comprising the ethylated melamine resin according to any one of [1] to [6].

[10] A resin composition comprising the ethylated melamine resin according to any one of [1] to [6] and a resin having a hydroxyl group.
[11] The resin having a hydroxyl group is at least one resin selected from the group consisting of an acrylic resin having a hydroxyl group, a polyester resin having a hydroxyl group, an epoxy resin having a hydroxyl group, a urethane resin having a hydroxyl group, and polyvinyl alcohol. [10] The resin composition according to [10].

  [12] The resin composition according to [10] or [11], which is for paints.

[13] A coating film obtained by curing the resin composition according to any one of [10] to [12].
[14] The coating film according to [13], which is for a metal substrate.

[15] A laminate comprising a substrate and the coating film according to [13] or [14].
[16] The laminate according to [15], wherein the substrate is a metal.

  According to the ethylated melamine resin of the present invention, a cured product having a good balance between hardness and water resistance can be obtained.

≪Ethylated melamine resin≫
The ethylated melamine resin of the present invention is a resin in which at least a part of the methylol group of a melamine resin (the melamine resin refers to a thermosetting resin obtained from melamine and formaldehyde) is ethyl etherified. The ratio of A to B when A is the intensity around 3350 cm ⁻¹ of the O—H stretching vibration of a hydroxyl group and B is the intensity around 2980 cm ⁻¹ of the C—H stretching vibration of an ethyl group by IR measurement (A / B) is in the range of 0.1 to 1.1.

  That A / B is in the above range means that the ethylated melamine resin of the present invention has a relatively high proportion of the methylol group of the resin being ethyl etherified. Hereinafter, the fact that A / B is in the above range may be referred to as “showing a specific IR spectrum”.

The ratio of A to B (A / B) is preferably 0.5 to 1.1, more preferably 0.7 to 1.1, and still more preferably 0.9 to 1.1. .
By using an ethylated melamine resin having A / B in the above range, it is surprisingly possible to obtain a cured product having excellent hardness and water resistance at the same time. Such an ethylated melamine resin is excellent in curability.
On the other hand, if A / B is less than 0.1, the curability tends to be poor, and if it exceeds 1.1, it tends to be difficult to obtain a cured product having a good balance between hardness and water resistance.
The strengths A and B can be measured by the methods described in the following examples.

Such an ethylated melamine resin exhibiting a specific IR spectrum can be obtained by the following method for producing an ethylated melamine resin, preferably by condensing melamine, formaldehyde and ethanol in the presence of an acid catalyst.
Moreover, the value of the intensity ratio A / B can be adjusted by adjusting the amount of formaldehyde or ethanol used.

In the present invention, it can be confirmed by using, for example, ¹ HNMR that at least a part of the methylol group of the melamine resin is etherified.

The ethylated melamine resin of the present invention preferably has an alkali metal content of 100 mass ppm or less, more preferably 20 mass ppm or less, per the resin. Further, the ethylated melamine resin of the present invention preferably contains substantially no alkali metal, and the lower limit of the alkali metal content contained per resin may be 0 mass ppm.
By using a resin having an alkali metal content in the above range, a cured product having excellent transparency can be obtained. For this reason, when using the obtained hardened | cured material for the use as which transparency is calculated | required, it is preferable to use resin which has an alkali metal content in the said range.
The alkali metal content contained in the resin can be measured by the method described in the following examples.

  Such an ethylated melamine resin having an alkali metal content in a specific range is preferably obtained by condensing melamine, formaldehyde and ethanol in the presence of an acid catalyst by the following method for synthesizing an ethylated melamine resin. The obtained product can be obtained by neutralizing with a basic compound not containing an alkali metal.

The ethylated melamine resin of the present invention has a polystyrene equivalent weight average molecular weight measured by GPC (gel permeation chromatography) of preferably 800 to 15000, more preferably 1000 to 7000, and further preferably 1100. 5000.
When the weight average molecular weight is in the above range, a resin composition having an appropriate viscosity can be obtained, and a cured product having excellent mechanical properties, smoothness, appearance, and the like can be obtained.

  The ethylated melamine resin of the present invention preferably does not contain an amino compound having an acid functional group or a group derived from an amide compound having an acid functional group from the viewpoint of cost.

≪Method for producing ethylated melamine resin≫
The method for producing an ethylated melamine resin of the present invention is not particularly limited as long as the ethylated melamine resin exhibiting the specific IR spectrum can be obtained, but the step 1 of condensing melamine, formaldehyde and ethanol in the presence of an acid catalyst. It is preferable that the method includes:

<Step 1>
The step 1 is preferably a step of first carrying out a methylolation reaction using melamine and formaldehyde followed by an ethyl etherification reaction. The reaction vessel is charged with melamine, formaldehyde and ethanol and heated to the reflux temperature. After that, it is more preferable to perform the above three-component condensation reaction using an acid as a catalyst.
According to the method including the step 1, an ethylated melamine resin exhibiting the specific IR spectrum can be produced.

〔melamine〕
The melamine is not particularly limited and may be synthesized by a conventionally known method or may be a commercially available product.

[Formaldehyde]
The formaldehyde may be an aqueous solution or solid paraformaldehyde. Paraformaldehyde having a formalin concentration of 80% or more is preferred from the economical viewpoint.

  The amount of formaldehyde used is preferably 3 to 7 mol, more preferably 4 to 6.7 mol, when the melamine used is 1 mol. When the amount of formaldehyde used is in the above range, the ethylated melamine resin of the present invention can be efficiently produced.

〔ethanol〕
In the said process 1, an ethylated melamine resin can be manufactured by using ethanol. In this case, the terminal of the obtained melamine resin is considered to be —CH ₂ OH or —CH ₂ OCH ₂ CH ₃ and the proportion of —CH ₂ OCH ₂ CH ₃ is relatively high. According to such an ethylated melamine resin, the reason why an excellent cured product having a good balance between hardness and water resistance can be obtained is not clear, but following the reaction of —CH ₂ OH during curing, — It is considered that CH ₂ OCH ₂ CH ₃ reacts. Therefore, the curing reaction proceeds uniformly throughout the resin, and it is considered that the cured product is excellent in balance between hardness and water resistance.

Here, if methanol is used, a methylated melamine resin can be obtained. In this case, because the functional group is —CH ₂ OCH ₃ group or —CH ₂ OH group, physical properties of the cured product and curing It is thought that the balance with the water resistance of a thing is inferior.
In addition, if butanol is used, a butylated melamine resin can be obtained. In this case, the terminal of the obtained melamine resin is considered to be —CH ₂ OH or —CH ₂ OCH ₂ CH ₂ CH ₂ CH _3. It is done. Since such a butylated melamine resin has a slow reaction, it is considered that the hardness of the obtained cured product tends to decrease.

  The amount of ethanol used is preferably 3 to 20 mol, more preferably 5 to 9 mol, when the melamine used is 1 mol. When the amount of ethanol used is in the above range, the ethylated melamine resin of the present invention can be produced efficiently and inexpensively. Moreover, when manufacturing ethylated melamine resin, even if the usage-amount of ethanol is the said range by using an acid catalyst, ethylated melamine resin can be manufactured efficiently.

In the step 1, substantially ethanol alone may be used, but ethanol and a small amount of C _n H _{2n + 1} OH (n is 1 or an integer of 3 to 8) as long as the object of the present invention is not impaired. Mixtures with other alcohols represented by
From the viewpoint of economy and coating film performance, n is preferably 1, 3 or 4.

[Acid catalyst]
In the present invention, by using an acid catalyst, an ethylated melamine resin exhibiting the specific IR spectrum can be obtained easily and inexpensively.
As the acid catalyst, either an organic acid or an inorganic acid can be used. Examples of the organic acid include formic acid, oxalic acid, and paratoluenesulfonic acid. Examples of the inorganic acid include phosphoric acid, hydrochloric acid, sulfuric acid, and nitric acid. . Among these, organic acids are preferable, and paratoluenesulfonic acid is more preferable.

  The amount of the acid catalyst used is preferably 0.01 mmol to 10 mmol, more preferably 0.1 mmol to 3 mmol, when the melamine used is 1 mol. When the usage-amount of an acid catalyst exists in the said range, the ethylated melamine resin of this invention can be manufactured efficiently.

〔solvent〕
Examples of the solvent used as necessary include ethanol, but are not limited thereto.

<Process 2>
In the method for producing the ethylated melamine resin, it is preferable to include a step 2 of neutralizing the obtained product with a basic compound not containing an alkali metal after the step 1. Since the ethylated melamine resin undergoes a self-crosslinking reaction under acidic conditions, and the self-crosslinked ethylated melamine resin has low storage stability, it is preferable to neutralize the product obtained in Step 1 above.
In Step 2, by using a compound containing no alkali metal as the basic compound, an ethylated melamine resin having an alkali metal content in a specific range can be produced, and a cured product having excellent transparency can be obtained. Can do.

[Basic compounds without alkali metals]
The compound not containing an alkali metal refers to a compound not containing an alkali metal as a constituent element when the compound is expressed by a chemical formula.

The basic compound is not particularly limited, and any of an inorganic base and an organic base can be used.
Examples of the inorganic base include ammonia, and examples of the organic base include alkanolamines such as monoethanolamine, dimethylethanolamine, and triethanolamine, and alkylamines such as diethylamine, triethylamine, and tributylamine, Although other amines, such as amine morpholine, etc. are mentioned, it is not limited to these. Among these, alkanolamines are preferable.

The amount of the basic compound used is preferably 0.01 mmol to 20 mmol, more preferably 0.1 mmol to 6 mmol, when the melamine used is 1 mol. When the usage-amount of a basic compound exists in the said range, the ethylated melamine resin of this invention can be manufactured efficiently.
In the neutralization, in addition to the basic compound not containing an alkali metal, a basic compound containing an alkali metal may be used in a very small amount, for example, 20 wtppm or less as an alkali metal with respect to an ethylated melamine resin. However, it is more preferable not to use it.

After the step 2, it is preferable to remove water, ethanol remaining unreacted, and the like from the reaction solution by distillation, if necessary.
The distillation operation may be vacuum distillation or azeotropic distillation in the presence of a nonpolar solvent such as xylene.

≪Curing agent for paints≫
The coating curing agent of the present invention only needs to contain the ethylated melamine resin, and may substantially consist of only the ethylated melamine resin. However, depending on the desired application, the effect of the present invention is impaired. To the extent not included, ethylated melamine resin is mixed with other components such as solvents, pigments, dyes, leveling agents, stability improvers, foam inhibitors, weather resistance improvers, anti-waxing agents and antioxidants. There may be.
As the paint, a thermosetting paint is preferable, and the curing agent contains the ethylated melamine resin of the present invention, and therefore has excellent performance for curing the paint when used in the thermosetting paint.
The “paint” in the present invention may be a solvent-based paint or an aqueous paint.

The resin that can be cured with the curing agent for paint is preferably a thermosetting resin that undergoes a crosslinking reaction with the ethylated melamine resin, and more preferably a thermosetting resin having a hydroxyl group.
Specific examples include a hydroxyl group-containing polyester resin, a hydroxyl group-containing acrylic resin, a hydroxyl group-containing epoxy resin, a hydroxyl group-containing urethane resin, polyvinyl alcohol, and the like, or a mixed resin composed of these resins.

  The dosage form of the curing agent is not particularly limited and may be appropriately selected according to a desired application, and examples thereof include powder and solution.

≪Resin composition≫
The resin composition of the present invention contains the ethylated melamine resin and a resin having a hydroxyl group.
Since the resin composition contains the ethylated melamine resin, it is excellent in storage stability and curability. Furthermore, the ethylated melamine resin tends to be hardened even at a low temperature, and the resin composition of the present invention is considered to be easily hardened at a low temperature. For this reason, the resin composition of this invention can be used suitably as a coating material, and it is thought that the resin composition of this invention is applicable also to the base material inferior to heat resistance, such as a plastics.

  The resin having a hydroxyl group is not particularly limited as long as it has a hydroxyl group, but is a single component selected from a polyester resin having a hydroxyl group, an acrylic resin having a hydroxyl group, an epoxy resin having a hydroxyl group, a urethane resin having a hydroxyl group, polyvinyl alcohol, and the like. Or the mixed resin etc. which consist of these resin are preferable.

  The ratio of the ethylated melamine resin to the resin having a hydroxyl group (ethylated melamine resin / resin having a hydroxyl group) is preferably 0.5 / 9.5 to 8/2 (weight ratio). More preferably, it is desirable to blend in the resin composition so as to be 2/8 to 5/5 (weight ratio). When the blended amount of the ethylated melamine resin is within the above range, a composition having excellent storage stability and curability can be obtained.

The resin composition may be added with a diluent such as a solvent or a dispersion medium, various additives, and the like within a range not impairing the effects of the present invention, depending on a desired application. Examples of the diluent and various additives include the other components.
For example, in order to improve the storage stability of the resin composition, the above-mentioned basic compound, particularly an organic base is added, or when the resin composition is used as a paint, a solvent is used to improve the paintability. Any known coating workability and coating film improvement method such as adding various diluents for the purpose of improving the smoothness of the coating film surface or preventing foaming, etc. Can be applied.

  As the diluent, those usually used as a solvent or a dispersion medium can be used. The solubility of the ethylated melamine resin of the present invention contained in the coating material, the coating method and coating environment of the coating material, and the drying of the coating film It is desirable to determine the type of diluent, the amount added, etc. in consideration of conditions and the like.

≪Coating film≫
The coating film of the present invention is formed by curing the resin composition.
Since the resin composition contains the ethylated melamine resin of the present invention, the coating film is excellent in balance between hardness and water resistance, and further has solvent resistance, adhesion to a substrate, weather resistance, machine Excellent characteristics.

The coating film is preferably a coating film obtained by applying the resin composition on a substrate and then curing the resin composition.
The coating film obtained by such a method may be peeled off from the base material, and depending on the base material, it may not be peeled off from the base material and may be used as it is as a laminate of the base material and the coating film. Good.

Although it does not restrict | limit especially as said base material, The plastic substrate etc. which consist of metal substrates, such as a steel plate and an iron plate, a polypropylene, etc. are mentioned.
Since the resin composition has a tendency to be relatively easily cured even at a low temperature, it is possible to obtain a coating film by heating and curing at a relatively low temperature using a plastic substrate having poor heat resistance as a base material. Since the effects of the present invention can be more exhibited, the substrate is preferably a metal substrate.
When a metal substrate is used as the base material, the coating of the metal substrate can prevent the corrosion of the metal substrate such as rust, and the coating film of the present invention is particularly excellent in water resistance. Therefore, the metal substrate can be better protected.

The base material may be a surface of a metal substrate or plastic substrate, a primer coated on the metal substrate or plastic substrate, or a functional film formed on the metal substrate or plastic substrate. There may be.
Since the resin composition can be cured at a low temperature, various base materials can be selected according to a desired application such as a base material having poor heat resistance.

  The method for applying the resin composition on the substrate is not particularly limited, and examples thereof include a roll coating method, a gravure coating method, a spin coating method, and a method using a bar coater or a doctor blade.

Although it does not restrict | limit especially as a method of hardening the said resin composition, For example, the method of heating a resin composition is mentioned.
The heating conditions may be appropriately determined according to the base material and the resin having a hydroxyl group. For example, the heating temperature is preferably 90 to 180 ° C, more preferably 100 to 130 ° C. The heating time is preferably 20 minutes to 30 minutes. Note that heating may be performed in two or more stages.
Further, the curing may be performed under reduced pressure or in an inert gas atmosphere.

  Although the thickness of the said coating film is not specifically limited, What is necessary is just to select suitably according to a desired use, Preferably it is 10-60 micrometers, More preferably, it is 20-40 micrometers.

The pencil hardness of the coating film is preferably F or more, more preferably H or more.
The pencil hardness can be measured by the method described in the following examples.

  The present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples. In the following examples, “parts” means parts by weight unless otherwise specified.

<Appearance>
The external appearance of the resin solution was evaluated by visually observing the resin solutions obtained in Examples 1 and 2 and Comparative Examples 1 and 2 below. The results are shown in Table 1.

<Nonvolatile content>
Nonvolatile content in the resin solutions obtained in the following Examples 1 and 2 and Comparative Examples 1 and 2 was measured based on JIS K5601-1-2. The results are shown in Table 1.
<Viscosity>
The viscosity (bubble viscosity) of the resin solutions obtained in the following Examples 1 and 2 and Comparative Examples 1 and 2 was measured based on JIS K5600-2-2. The results are shown in Table 1.

<Weight average molecular weight>
The weight average molecular weights of the resins obtained in the following Examples 1 and 2 and Comparative Examples 1 and 2 were measured by GPC under the following conditions. The results are shown in Table 1.
Apparatus: Showa Denko Co., Ltd. Shodex GPC-101
Detector: RI-71S
Column: Showa Denko Co., Ltd. GPC KF804L (Φ8.0 mm × 300 mm) × 3 Measurement temperature: 40 ° C.
Eluent: THF (tetrahydrofuran)
Flow rate: 1.0 ml / min

<IR intensity ratio>
The FT-IR spectra of the resins obtained in the following Examples 1 and 2 and Comparative Examples 1 and 2 were obtained by using an infrared-visible spectroscopy (FT-IR) apparatus (“FT / IR-4100”, manufactured by JASCO Corporation). It measured using. Specifically, after applying the following resin solution (sample) to an infrared transmitting material (NaCl plate), the solvent was volatilized to form a thin film and analyzed with an IR apparatus.
In the obtained IR spectrum, the ratio of A to B when the intensity around 3350 cm ⁻¹ of the OH stretching vibration of the hydroxyl group is A and the intensity around 2980 cm ⁻¹ of the CH stretching vibration of the ethyl group is B. (A / B) was determined. The results are shown in Table 1.

Note that the absorbance around 4000 cm ^-1 in the range of 90% to 100%, so that the vicinity of 1550 cm ^-1 most absorbance decreases of 30% to 20%, and adjusting the thickness of the sample on the plate. Then, a tangent is drawn from the vicinity of 3900cm ^-1 in the vicinity of 2300 cm ^-1, was 3350 cm ^-1 vicinity of the peak height intensity A, the strength of the height of the peak around 2980cm ^-1 by the tangent B from the tangent.

<Alkali metal content>
The alkali metal contents of the resins obtained in the following Examples 1 and 2 and Comparative Examples 1 and 2 were measured based on the metal analysis ICP method. The obtained resin was added to sulfuric acid for ashing, and then the solution obtained by dissolving the ashed product in nitric acid was used for analysis by the ICP-AES method.
The quantification was performed by preparing a calibration curve with an element standard solution with a known concentration in advance and using the calibration curve method. The results are shown in Table 1.

[Example 1]
Preparation of ethylated melamine resin solution 1 In a four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen introduction tube, 126 g (1 mol) of melamine, 163 g (5 mol) of paraformaldehyde having a formalin concentration of 92% and ethanol 368 g (8 mol) was charged and the temperature was raised to the reflux temperature. After carrying out methylolation reaction at reflux temperature for 1 hour, 0.2 g (1.2 mmol) of paratoluenesulfonic acid was added, and alkyl etherification reaction was carried out at reflux for 3 hours. Thereafter, the reaction product is neutralized with triethanolamine, and then ethanol is distilled off under reduced pressure. Then, the ethylated melamine resin solution 1 is diluted with xylene until the nonvolatile content becomes 60% by weight. Obtained. The viscosity of the obtained resin solution 1 was Z1 (Gardner No./25° C.).

[Example 2]
Production of ethylated melamine resin solution 2 In Example 1, the ethylated melamine resin solution 2 was prepared in the same manner as in Example 1 except that the amount of paraformaldehyde having a formalin concentration of 92% was changed as shown in Table 1 below. Manufactured. The non-volatile content in the obtained resin solution 2 was 60%, and the viscosity was Z2 (Gardner No./25° C.).

[Comparative Examples 1 and 2]
Preparation of ethylated melamine resin solutions 3 and 4 In Example 1, Example 1 was used except that paratoluenesulfonic acid was not used and the amount of 92% paraformaldehyde and / or ethanol was changed as shown in Table 1 below. In the same manner, ethylated melamine resin solutions 3 and 4 were produced.

<Appearance of coating film>
The appearance of the coating film was evaluated by visually observing the coating films obtained in Examples 3 and 4 and Comparative Examples 3 to 6 below. The results are shown in Table 2.
In addition, it was set as "(circle)" when the coating film was transparent without white turbidity, and the surface was smooth.

<Adhesion>
Using the test plate with a coating film obtained in Examples 3 and 4 and Comparative Examples 3 to 6 below, based on JIS K5600-5-6, the adhesion between the steel plate and the coating film in the number of adhesion sites after tape peeling. Sex was evaluated. The results are shown in Table 2.
In addition, in 100 squares, the case where there is no part which peeled is described as 100/100, and the case where all peeled is described as 0/100.

<Water resistance>
The change in the coating film was visually observed after the test plates with the coating films obtained in Examples 3 and 4 and Comparative Examples 3 to 6 were immersed in water at 60 ° C. for 1 week. The results are shown in Table 2.
In addition, it is the same as the state of the coating film before being immersed in water, it is transparent without white turbidity, the case where the surface is smooth is `` ○ '', changed from the state of the coating film before being immersed in water, becomes cloudy, The case where the surface state changed was indicated as “x”.

<Pencil hardness>
The pencil hardness of the coating films obtained in the following Examples 3 and 4 and Comparative Examples 3 to 6 was measured based on JIS K5600-5-4. The results are shown in Table 2.

<MEK rubbing>
The coating film surfaces obtained in the following Examples 3 and 4 and Comparative Examples 3 to 6 were rubbed with gauze soaked with methyl ethyl ketone (MEK), and the coating film changes were visually observed when reciprocating 50 times. The results are shown in Table 2.
In addition, the case where the coating film did not change is indicated as “◯”, the case where the coating film is slightly glossy is indicated as “△”, the coating film changes, becomes cloudy, the surface condition changes, The case where it was shaved was defined as “×”.

<Storage stability>
30 g of the resin composition obtained in the following Examples 3 and 4 and Comparative Examples 3 to 6 was weighed into a 50 ml glass tube, and the appearance change after standing at 40 ° C. for 60 hours was visually evaluated. The results are shown in Table 2.
In addition, the case where the external appearance of the resin composition did not change was set as “◯”, and the case where the external appearance of the resin composition changed and became cloudy or precipitated was expressed as “X”.

[Example 3]
50 parts of the resin solution 1 obtained in Example 1 above, 116 parts of a polyester resin Almatex P646 having a hydroxyl group (trade name, 60% nonvolatile content (manufactured by Mitsui Chemicals)), and a diluent solvent (xylene) / N-butanol / propylene glycol monomethyl ether acetate = 2/1/2) was mixed to prepare a resin composition 1.
The obtained resin composition 1 was coated on a zinc phosphate-treated steel plate (150 mm × 70 mm × 0.8 mm thickness) using a bar coater so that the cured dry film thickness was 15 μm, and then the composition was 120 A test plate with a coating film was prepared by curing and drying at 30 ° C. for 30 minutes.

[Example 4]
In Example 3, Resin Composition 2 was prepared in the same manner as Example 3 except that Resin Solution 2 was used instead of Resin Solution 1.
A test plate with a coating film was prepared in the same manner as in Example 3 except that the obtained resin composition 2 was used.

[Comparative Example 3]
In Example 3, a resin composition 3 was prepared in the same manner as in Example 3 except that the resin solution 3 was used instead of the resin solution 1.
A test plate with a coating film was prepared in the same manner as in Example 3 except that the obtained resin composition 3 was used.

[Comparative Example 4]
In Example 3, a resin composition 4 was prepared in the same manner as in Example 3 except that the resin solution 4 was used instead of the resin solution 1.
A test plate with a coating film was prepared in the same manner as in Example 3 except that the obtained resin composition 4 was used.

[Comparative Example 5]
In Example 3, instead of the resin solution 1, a methylated melamine resin solution (trade name, Cymel 325: Nihon Cytec Industries, Ltd., non-volatile content 80 wt%) was used in the same manner as in Example 3. Resin composition 5 was prepared.
A test plate with a coating film was prepared in the same manner as in Example 3 except that the obtained resin composition 5 was used.

[Comparative Example 6]
In Example 3, instead of the resin solution 1, a butylated melamine resin solution (trade name, Uban 20SE60: manufactured by Mitsui Chemicals, Inc., nonvolatile content 60%) was used in the same manner as in Example 3, Resin composition 6 was prepared.
A test plate with a coating film was prepared in the same manner as in Example 3 except that the obtained resin composition 6 was used.

Claims (16)

At least a portion of the methylol groups of the melamine resin are ethyl etherification, by IR measurement, the intensity around 3350 cm ^-1 of O-H stretching vibration of hydroxyl group A, the C-H stretching vibration of an ethyl group 2980Cm ^-1 An ethylated melamine resin having a ratio of A to B (A / B) in the range of 0.1 to 1.1 when the strength in the vicinity is B.   The ethylated melamine resin according to claim 1 whose alkali metal content is 100 mass ppm or less per ethylated melamine resin.   The ethylated melamine resin according to claim 1 or 2, which is obtained by condensing melamine, formaldehyde and ethanol in the presence of an acid catalyst.   The melamine, formaldehyde and ethanol are obtained by condensing in the presence of an acid catalyst and then neutralizing the resulting product with a basic compound containing no alkali metal. The ethylated melamine resin according to any one of the above. Obtained using melamine, formaldehyde and ethanol,
The ethylation according to any one of claims 1 to 4, wherein when the amount of melamine used is 1 mol, the amount of formaldehyde used is 3 to 7 mol and the amount of ethanol used is 3 to 20 mol. Melamine resin.   The ethylated melamine resin according to any one of claims 1 to 5, wherein the polystyrene-reduced weight average molecular weight measured by GPC (gel permeation chromatography) is 800 to 15000.   The method for producing an ethylated melamine resin according to any one of claims 1 to 6, comprising a step of condensing melamine, formaldehyde and ethanol in the presence of an acid catalyst.   Furthermore, the manufacturing method of the ethylated melamine resin of Claim 7 including the process of neutralizing the product obtained by condensing using the basic compound which does not contain an alkali metal.   The hardening | curing agent for coating materials containing the ethylated melamine resin of any one of Claims 1-6.   A resin composition comprising the ethylated melamine resin according to any one of claims 1 to 6 and a resin having a hydroxyl group.   The resin having a hydroxyl group is at least one resin selected from the group consisting of an acrylic resin having a hydroxyl group, a polyester resin having a hydroxyl group, an epoxy resin having a hydroxyl group, a urethane resin having a hydroxyl group, and polyvinyl alcohol. The resin composition described in 1.   The resin composition according to claim 10 or 11, which is used for a paint.   The coating film formed by hardening | curing the resin composition of any one of Claims 10-12.   The coating film of Claim 13 which is an object for metal substrates.   The laminated body containing a base material and the coating film of Claim 13 or 14.   The laminate according to claim 15, wherein the substrate is a metal.