阅读说明：本技术 阳离子电沉积涂料组合物和固化电沉积涂膜的形成方法 (Cationic electrodeposition coating composition and method for forming cured electrodeposition coating film ) 是由 小谷诚之 长谷川祐子 古谷康幸 小幡桂悟 筒井启介 新井弘树 山崎浩美 于 2019-12-12 设计创作，主要内容包括：本发明提供兼顾具备良好的防缩孔性与良好的涂膜外观的阳离子电沉积涂料组合物。阳离子电沉积涂料组合物,其含有SP值大于10.5且为15.0以下的有机硅化合物(A)、和涂膜形成树脂(B),相对于前述涂膜形成树脂(B)的树脂固体成分100质量份,含有0.01质量份以上4.5质量份以下的前述有机硅化合物(A)。例如,有机硅化合物(A)为选自聚醚改性有机硅化合物(A-1)、聚酯改性有机硅化合物(A-2)和聚丙烯酸改性有机硅化合物(A-3)中的至少一种。(The invention provides a cationic electrodeposition coating composition having both good anti-cratering properties and good coating film appearance. A cationic electrodeposition coating composition comprising an organosilicon compound (A) having an SP value of more than 10.5 and not more than 15.0 and a coating film-forming resin (B), wherein the organosilicon compound (A) is contained in an amount of 0.01 to 4.5 parts by mass per 100 parts by mass of the resin solid content of the coating film-forming resin (B). For example, the organosilicon compound (A) is at least one selected from the group consisting of a polyether-modified organosilicon compound (A-1), a polyester-modified organosilicon compound (A-2), and a polyacrylic acid-modified organosilicon compound (A-3).)

1. Cationic electrodeposition coating composition containing

An organosilicon compound (A) having an SP value of more than 10.5 and not more than 15.0, and

a coating film-forming resin (B),

the organic silicon compound (A) is contained in an amount of 0.01 to 4.5 parts by mass based on 100 parts by mass of the resin solid content of the coating film forming resin (B).

2. The cationic electrodeposition coating composition according to claim 1, wherein the SP value of the organosilicon compound (a) is 12.0 to 15.0.

3. The cationic electrodeposition coating composition according to claim 1 or 2, wherein the aforementioned organosilicon compound (a) is at least one selected from a polyether-modified organosilicon compound (a-1), a polyester-modified organosilicon compound (a-2), and a polyacrylic acid-modified organosilicon compound (a-3).

4. The cationic electrodeposition coating composition according to any one of claims 1 to 3, wherein the organosilicon compound (A) is contained in an amount of 0.04 parts by mass or more and 4.5 parts by mass or less based on 100 parts by mass of a resin solid content of the coating film forming resin (B).

5. The cationic electrodeposition coating composition according to any one of claims 1 to 4, wherein the organosilicon compound (A) is soluble or dispersible in an aqueous solvent.

6. A method for forming a cured electrodeposition coating film, comprising:

dipping a substrate in the cationic electrodeposition coating composition according to any one of claims 1 to 5, performing electrodeposition coating to form an uncured electrodeposition coating film, and

the uncured electrodeposition coating film is cured by heating to form a cured electrodeposition coating film on the object to be coated.

Technical Field

The present disclosure relates to a cationic electrodeposition coating composition and a method for forming a cured electrodeposition coating film.

Background

In the cationic electrodeposition coating composition, the generation of craters due to the incorporation of contaminants is problematic.

Patent document 1 discloses a pigment dispersion paste for electrodeposition paint containing a pigment dispersion resin, cellulose, an extender pigment and water. According to patent document 1, an attempt is made to improve the shrinkage resistance by containing a predetermined amount of a predetermined extender pigment.

[ Prior art documents ]

[ patent document ]

[ patent document 1 ] Japanese patent laid-open No. 2012 and 092293.

Disclosure of Invention

Problems to be solved by the invention

In recent years, cationic electrodeposition coating compositions have been required to have both good anti-cratering properties and good coating film appearance. However, the invention according to patent document 1 aims to improve the anti-cratering property (also referred to as cratering resistance), and therefore, the smoothness of the coating film is poor, and the appearance of the coating film is likely to be poor, such as uneven coating.

In addition, patent document 1 discloses an attempt to improve the shrinkage-preventing property by using a gelled particulate polymer having a predetermined structure. However, the gelled particulate polymer described in patent document 1 is a polymer formed by intraparticle crosslinking, and therefore, deterioration in coating film appearance such as reduction in coating film smoothness can occur.

As described above, in general, when the anti-cratering property of the cationic electrodeposition coating composition is improved, the smoothness of the coating film tends to be poor, and the appearance of the coating film tends to be poor, such as uneven coating. On the other hand, in order to obtain a good coating film appearance such as good coating film smoothness and no occurrence of coating unevenness, the anti-cratering property tends to be poor.

Therefore, good anti-cratering properties are inversely related to good coating film appearance such as good coating film smoothness and no occurrence of coating unevenness, and there is a demand for a cationic electrodeposition coating composition which can provide both good anti-cratering properties and such good coating film appearance.

In view of the above problems, an object of the present disclosure is to provide a cationic electrodeposition coating composition that can provide a good coating film appearance in which good anti-cratering property, good coating film smoothness, no occurrence of coating unevenness, and the like are compatible. In addition, the present disclosure provides a method for forming a cured electrodeposition coating film using the specified cationic electrodeposition coating composition.

Means for solving the problems

In order to solve the above problem, the present disclosure provides the following aspects.

[1] The cationic electrodeposition coating composition of the present disclosure contains:

an organosilicon compound (A) having an SP value of more than 10.5 and not more than 15.0, and

a coating film-forming resin (B),

the organic silicon compound (A) is contained in an amount of 0.01 to 4.5 parts by mass per 100 parts by mass of the resin solid content of the coating film-forming resin (B).

[2] In some embodiments, the SP value of the organosilicon compound (a) in the cationic electrodeposition coating composition is 12.0 or more and 15.0 or less.

[3] In certain modes, the organosilicon compound (A) in the cationic electrodeposition coating composition is at least one selected from the group consisting of a polyether-modified organosilicon compound (A-1), a polyester-modified organosilicon compound (A-2), and a polyacrylic acid-modified organosilicon compound (A-3).

[4] In some embodiments, the cationic electrodeposition coating composition contains the organosilicon compound (a) in an amount of 0.04 to 4.5 parts by mass based on 100 parts by mass of the resin solid content of the coating film forming resin (B).

[5] In some embodiments, the organosilicon compound (a) in the cationic electrodeposition coating composition may be dissolved or dispersed in an aqueous solvent.

[6] In another aspect, the present disclosure provides a method for forming a cured electrodeposition coating film, including:

impregnating a substrate with the above cationic electrodeposition coating composition, carrying out electrodeposition coating to form an uncured electrodeposition coating film, and

the uncured electrodeposition coating film is cured by heating to form a cured electrodeposition coating film on the substrate.

ADVANTAGEOUS EFFECTS OF INVENTION

The cationic electrodeposition coating composition according to the present disclosure can form a coating film having both good anti-cratering properties and good coating film appearance. Further, according to the method for forming a cured electrodeposition coating film, a cured electrodeposition coating film having both good anti-cratering property and good coating film appearance can be formed.

Detailed Description

The passage of the cationic electrodeposition coating composition until the completion of the present disclosure is explained.

For example, when a coating film is formed using a cationic electrodeposition coating composition, cratering of the coating film due to oil that may remain on a steel sheet or the like as a coated object, cratering of the coating film due to oil that may be present in coating equipment, a drying furnace, or the like may occur.

For example, a shrinkage-preventing agent containing an acrylic resin is used as the main component in order to prevent shrinkage. After an electrodeposition coating film is formed from an electrodeposition coating composition containing such a shrinkage-preventing agent, a coating composition such as a top-coat coating composition may be further applied to form a top-coat coating film.

However, coating compositions applied on electrodeposition coating films, such as topcoat coating compositions, are often modified and may contain various ingredients. Therefore, the electrodeposition coating composition is required to have both good anti-cratering property and good appearance of the coating film, and to improve adhesion to the coating film formed of the novel coating composition applied to the electrodeposition coating film.

However, in the case of an electrodeposition coating composition using a crater inhibitor containing an acrylic resin, there is still a need to improve the crater inhibition property and adhesion.

Furthermore, it is necessary to reduce the amount of solvent used and reduce the load on the environment.

The present inventors have made extensive studies to solve the problems of the prior art described above, and as a result, have completed the present invention, in which a coating film having good anti-cratering properties, good coating film smoothness, good coating film appearance without causing coating unevenness, and good adhesion to various coating compositions can be formed.

(cationic electrodeposition coating composition)

The present disclosure relates to a cationic electrodeposition coating composition comprising:

an organosilicon compound (A) having an SP value of more than 10.5 and not more than 15.0, and

a coating film-forming resin (B),

the organic silicon compound (A) is contained in an amount of 0.01 to 4.5 parts by mass based on 100 parts by mass of the resin solid content of the coating film forming resin (B).

Hereinafter, each composition will be described.

(organic silicon Compound (A))

The organosilicon compound (A) according to the present disclosure has an SP value of more than 10.5 and an SP value of 15.0 or less. The cationic electrodeposition coating composition according to the present disclosure contains the organosilicon compound (a) in an amount of 0.01 to 4.5 parts by mass based on 100 parts by mass of the resin solid content of the coating film forming resin (B).

By containing such a predetermined amount of the predetermined organosilicon compound, the electrodeposition coating composition of the present disclosure can form a coating film having good shrink-hole resistance, good coating film smoothness, and good coating film appearance without causing coating unevenness. Further, it is possible to exhibit good coating stability, for example, good filterability, suppression of generation of pockmarks, and the like.

Without being limited to a specific theory for explanation, it is considered that by containing the specific organosilicon compound (a) related to the present disclosure in a specific amount, the cationic electrodeposition coating composition of the present disclosure can be stably present in an aqueous system with good coating stability.

More specifically, the electrodeposition coating composition of the present disclosure can exhibit good anti-cratering properties even when the mechanism of the presence of oil is different, as shown in the following evaluation of the formation of craters by containing a predetermined amount of a predetermined organosilicon compound (a).

Therefore, for example, even oil derived from an apparatus usable in a drying or curing process such as an indirect furnace or a drying furnace, that is, oil that may be mixed after coating or before curing, can exhibit good anti-cratering properties. For example, oil components that may be mixed after coating and before curing may be mixed in at a high temperature such as near the baking temperature.

Further, when an oil component is mixed in the coating composition, the coating film can exhibit good anti-cratering property even if the coating film is formed under such a condition that the oil component can remain on the object to be coated.

The obtained electrodeposition coating film can exhibit good appearance, and for example, generation of pockmarks (small protruded impurities) can be suppressed. Further, the coating film may have a uniform coating film surface and a good coating film appearance such as no coating unevenness.

In addition, the electrodeposition coating composition of the present disclosure has good coating stability, for example, stability in an aqueous system. Furthermore, in the production of a cationic coating composition, if the organosilicon compound (a) according to the present disclosure is used, it can be dispersed in an aqueous solvent without being diluted with a solvent, and thus the load on the environment can be reduced.

Further, when a known coating composition, for example, a top coat coating composition is applied to an electrodeposition coating film formed from the cationic electrodeposition coating composition of the present disclosure and cured, the electrodeposition coating film and the top coat coating film can exhibit good adhesion.

Such an effect can be obtained even in the following numerical value range.

The organosilicon compound (A) according to the present disclosure has an SP value of more than 10.5 and an SP value of 15.0 or less. In some embodiments, the SP value of the organosilicon compound (a) is 11.0 to 15.0, for example 12.0 to 15.0. In another embodiment, the SP value of the organosilicon compound (a) is 12.3 or more and less than 15.0, for example, the SP value is 12.5 or more and less than 15.0.

When the SP value of the organosilicon compound (a) is within such a range, the coating film obtained has good anti-cratering properties even under various conditions of the entry route of oil components without impairing the appearance.

Further, for example, the coating composition can exhibit good adhesion to a top coat coating film or the like.

When the SP value of the organosilicon compound (a) is within such a range, the shrinkage resistance can be satisfactorily ensured, and the coating composition having a predetermined composition according to the present disclosure can exhibit coating stability.

Furthermore, the cationic electrodeposition coating composition of the present invention contains the organosilicon compound (a) having a predetermined SP value, and therefore has excellent stability in an aqueous system. In addition, the filter has good filterability and can inhibit pockmark generation.

While not being bound to a particular theory, it is considered that when the SP value of the organosilicon compound (a) is in such a range, good anti-cratering property and appearance can be achieved at a high level without impairing the coating stability.

The SP value is a shorthand for solubility parameter, which is a measure of solubility. The larger the value of the SP value, the higher the display polarity, and conversely, the smaller the value, the lower the display polarity.

For example, the SP value can be actually determined by the following method [ reference: SUH, CLARKE, J.P.S.A-1, 5, 1671 ~ 1681 (1967) ].

As a sample, the following samples obtained as follows were used: 0.5g of an organic solvent was weighed in a 100ml beaker, 10ml of acetone was added using a graduated pipette, and the resulting sample was dissolved by a magnetic stirrer. For this sample, a poor solvent was dropped using a 50ml burette at a measurement temperature of 20 ℃ to set the point of turbidity as a drop amount. The cloud point measurement was performed using ion-exchanged water as the high SP poor solvent and n-hexane as the low SP poor solvent. The SP value of the organic solvent is given by the following calculation formula.

＝（V_ml ^1/2 _ml＋V_mh ^1/2 _mh）/（V_ml ^1/2＋V_mh ^1/2）

V_m＝V₁V₂/（φ₁V₂＋φ₂V₁）

_m＝φ_{1 1}＋φ_{2 2}

And Vi: molecular volume of solvent (ml/mol)

Phi i: volume fraction of each solvent at cloud point

i: SP value of solvent

ml: low SP poor solvent mixed system

mh: high SP poor solvent mixed system.

When the organosilicon compound (a) contains a plurality of organosilicon compounds (a), the SP value of the organosilicon compound (a) can be determined by calculating an average value based on the mass ratio of the solid components in the organosilicon compound (a) component using the SP values of the respective compounds.

The cationic electrodeposition coating composition according to the present disclosure contains the organosilicon compound (a) in an amount of 0.01 to 4.5 parts by mass based on 100 parts by mass of the resin solid content of the coating film forming resin (B). In some embodiments, the cationic electrodeposition coating composition contains the organosilicon compound (a) in an amount of 0.04 to 4.5 parts by mass, for example, 0.04 to 4.0 parts by mass, based on 100 parts by mass of the resin solid content of the coating film forming resin (B).

In some embodiments, the cationic electrodeposition coating composition contains the organosilicon compound (a) in an amount of 0.04 parts by mass or more and 3.0 parts by mass or less, for example, 0.04 parts by mass or more and 2.5 parts by mass or less, and in some embodiments, 0.05 parts by mass or more and 2.0 parts by mass or less, based on 100 parts by mass of the resin solid content of the coating film forming resin (B).

When the amount of the organosilicon compound (a) is within such a range, the obtained coating film does not deteriorate in appearance, and has excellent anti-cratering properties even for various craters having different mechanisms which can be generated in the evaluation of the presence of oil craters, the evaluation of bumping oil craters, and the like. Further, for example, the coating composition can exhibit good adhesion to various coating films such as a top coating film.

The cationic electrodeposition coating composition of the present invention is excellent in stability in an aqueous system, has good filterability, and can suppress the generation of pockmarks.

In the present specification, the 100 mass of the resin solid content of the coating film forming resin (B) refers to the total mass of the solid content of the resin component forming the coating film by the curing reaction after the electrodeposition coating.

For example, when the coating film-forming resin (B) contains a plurality of resins, 100 parts by mass of the resin solid content contained in the coating film-forming resin (B) means 100 parts by mass in total of the plurality of resin solid contents forming the coating film after curing.

In some embodiments, in the case where the coating film-forming resin (B) contains the aminated resin (B-1) and the curing agent (B-2), 100 parts by mass of the resin solid content of the coating film-forming resin (B) means that the total of the resin solid content of the aminated resin (B-1) and the resin solid content of the curing agent (B-2) is 100 parts by mass.

For example, the specific organosilicon compound (a) according to the present disclosure may be dissolved or dispersed in an aqueous solvent. In certain aspects, the present disclosure relates to specific organosilicon compounds (a) that are readily dispersible in water as a single ingredient.

While not being bound to a particular theory of explanation, it is believed that the specific organosilicon compound (a) according to the present disclosure can exist stably in an aqueous system because it has a predetermined SP value, can be dissolved or dispersed in an aqueous solvent, and can be easily dispersed in water as a single component.

In the present specification, the organosilicon compound (a) is soluble or dispersible in an aqueous solvent, and this means that the organosilicon compound (a) according to the present disclosure can be easily dissolved or uniformly dispersed when mixed with an aqueous solvent at normal temperature in a predetermined amount as shown in the present disclosure. Further, the organosilicon compound (a) can be easily dispersed in water as a single component, which means that the organosilicon compound (a) can be uniformly dispersed in an aqueous solvent at room temperature without using a dispersant, a surfactant, or the like.

By providing the organosilicon compound (a) with such properties, it is possible to provide a coating material having good stability, for example, stability in an aqueous system. Further, in the production of the cationic coating composition, the organosilicon compound (a) can be dispersed in an aqueous solvent without being diluted with a solvent, and therefore, the load on the environment can be reduced.

In certain embodiments, the organosilicon compound (a) has a polysiloxane on the main backbone. For example, the polysiloxane has 3 to 20 Si atoms, for example 3 to 10, in the molecule. In certain embodiments, the organosilicon compound (a) has polydimethylsiloxane in the main skeleton.

In certain modes, the organosilicon compound (A) is at least one selected from the group consisting of a polyether-modified organosilicon compound (A-1), a polyester-modified organosilicon compound (A-2), and a polyacrylic acid-modified organosilicon compound (A-3). The cationic electrodeposition coating composition of the present disclosure may contain these modified organosilicon compounds alone or in combination.

By containing such an organosilicon compound (a), the cationic electrodeposition coating composition of the present disclosure can have both of a better anti-cratering property and a better coating film appearance, and can exhibit a better coating stability.

In certain modes, the organosilicon compound (A) comprises at least 1 selected from the group consisting of a polyester-modified organosilicon compound (A-2) and a polyacrylic acid-modified organosilicon compound (A-3), and a polyether-modified organosilicon compound (A-1).

By containing such a combination, the organosilicon compound (a) can have more stable hydration properties.

In addition, the cationic electrodeposition coating composition of the present disclosure having such an organosilicon compound (a) may have excellent anti-cratering properties. In addition, better stability of the coating can be exhibited. Further, the electrodeposition coating film formed from the cationic electrodeposition coating composition of the present disclosure can be made more excellent in adhesion to a top coat coating film and the like.

Examples of the polyether-modified organosilicon compound (A-1) include compounds having a polyether chain introduced into the terminal and/or side chain of a polysiloxane. For example, the polysiloxane may further have a substituent other than a polyether chain.

In some embodiments, the polyether-modified organosilicon compound (A-1) is a compound having a polyether chain introduced into a side chain of polysiloxane, for example, polydimethylsiloxane.

By containing the polyether-modified organosilicon compound (a-1), the cationic electrodeposition coating composition of the present disclosure can exhibit effects such as more excellent anti-cratering properties, more excellent coating film appearance, e.g., good coating film smoothness, and no occurrence of coating unevenness. In addition, better stability of the coating can be exhibited.

Further, the electrodeposition coating film formed from the cationic electrodeposition coating composition of the present disclosure can be made more excellent in adhesion to a top coat coating film and the like.

Examples of the polyester-modified organosilicon compound (A-2) include compounds obtained by introducing a polyester chain into a terminal and/or a side chain of a polysiloxane. For example, the polysiloxane may further have a substituent other than the polyester chain.

In some embodiments, the polyester-modified organosilicon compound (A-2) is a compound having a polyester chain introduced into a side chain of a polysiloxane, for example, polydimethylsiloxane.

By containing the polyester-modified organosilicon compound (a-2), the cationic electrodeposition coating composition of the present disclosure can exhibit more excellent anti-cratering properties and coating film appearance. In addition, better stability of the coating can be exhibited. Further, the electrodeposition coating film formed from the cationic electrodeposition coating composition of the present disclosure can be made more excellent in adhesion to a top coat coating film and the like.

Examples of the polyacrylic acid-modified organosilicon compound (a-3) include compounds having a polyacrylic acid chain introduced into the terminal and/or side chain of the polysiloxane. For example, the polysiloxane may further have a substituent other than the polyacrylic acid chain.

In some embodiments, the polyacrylic acid-modified organosilicon compound (A-3) is a compound having a polyacrylic acid chain introduced into a side chain of polysiloxane, for example, polydimethylsiloxane.

By containing the polyacrylic acid-modified organosilicon compound (a-3), the cationic electrodeposition coating composition of the present disclosure can exhibit more excellent anti-cratering properties and coating film appearance. In addition, better stability of the coating can be exhibited. Further, the electrodeposition coating film formed from the cationic electrodeposition coating composition of the present disclosure can be made more excellent in adhesion to a top coat coating film and the like.

(coating film-forming resin (B))

The coating film-forming resin (B) according to the present disclosure is not particularly limited, and may contain a coating film-forming resin (B) generally used in a cationic electrodeposition coating composition. For example, the coating film-forming resin (B) contains an aminated resin (B-1) and a curing agent (B-2).

In some embodiments, in the case where the coating film-forming resin (B) contains the aminated resin (B-1) and the curing agent (B-2), 100 parts by mass of the resin solid content of the coating film-forming resin (B) means 100 parts by mass in total of these resin solid contents. In addition to this example, when the coating film-forming resin (B) contains a plurality of resins, 100 parts by mass of the resin solid content contained in the coating film-forming resin (B) means 100 parts by mass of the total of the plurality of resin solid contents.

(aminated resin (B-1))

The aminated resin (B-1) is contained in the coating film-forming resin (B) constituting the electrodeposition coating film.

The aminated resin (B-1) may be an amine-modified epoxy resin obtained by modifying an oxirane ring in an epoxy resin skeleton with an amine compound. Generally, an amine-modified epoxy resin is prepared by reacting an oxirane ring in a molecule of a starting material resin with an amine compound such as a primary amine, a secondary amine, or a tertiary amine and/or an acid salt thereof to open a ring. Typical examples of the starting material resin are bisphenol A, bisphenol F, bisphenol S, phenol novolak（フェノールノホ゛ラック), cresol novolac（クレソ゛ールノホ゛ラック) with epichlorohydrin, and the like. Examples of other starting material resins include oxazolidone ring-containing epoxy resins described in Japanese patent application laid-open No. 5-306327. These epoxy resins can be prepared by reacting a diisocyanate compound or by reacting the isocyanate group of a diisocyanate compound with methanol or ethyleneA biscarbamate compound obtained by end-capping a lower alcohol such as an alcohol with epichlorohydrin.

For example, the aminated resin (B-1) may be selected for the chipping resistance.

The above-mentioned starting material resin can be used by chain-extending a 2-functional polyester polyol, polyether polyol, bisphenol, dicarboxylic acid, or the like, before the ring-opening reaction of the oxirane ring by the amine compound.

In addition, a monohydroxy compound such as 2-ethylhexanol, nonylphenol, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-n-butyl ether, and propylene glycol mono-2-ethylhexyl ether, or a monocarboxylic acid compound such as octanoic acid may be added to a part of the ethylene oxide ring before the ring-opening reaction of the ethylene oxide ring by the amine compound for the purpose of adjusting the molecular weight or the amine equivalent, improving the thermal fluidity, and the like.

The amine-modified epoxy resin can be obtained by reacting the oxirane ring of the epoxy resin with an amine compound. As the amine compound to be reacted with the oxirane ring, primary and secondary amines are listed. When the epoxy resin is reacted with a secondary amine, an amine-modified epoxy resin having a tertiary amino group can be obtained. In addition, when the epoxy resin is reacted with a primary amine, an amine-modified epoxy resin having a secondary amino group can be obtained. Further, by using a secondary amine having a blocked primary amine, an amine-modified epoxy resin having a primary amino group can be prepared. For example, in the preparation of an amine-modified epoxy resin having a primary amino group and a secondary amino group, a ketimine may be prepared by capping the primary amino group with a ketone before the reaction with the epoxy resin, and then introducing the ketimine into the epoxy resin and then deblocking the ketimine. As the amine to be reacted with the oxirane ring, a tertiary amine may be used in combination as necessary.

The primary amine, secondary amine, and tertiary amine may be the amines described above. Specific examples of the secondary amine having a blocked primary amine include ketimine of aminoethylethanolamine and diketimine of diethylenetriamine. Specific examples of the tertiary amine which can be used as needed include triethylamine, N-dimethylbenzylamine, and N, N-dimethylethanolamine. These amines may be used alone in 1 kind, or in combination of 2 or more kinds.

The amine compound that reacts with the oxirane ring of the epoxy resin preferably contains a secondary amine in an amount of 50 to 95 mass%, a secondary amine having a blocked primary amine in an amount of 0 to 30 mass%, and a primary amine in an amount of 0 to 20 mass%.

The number average molecular weight of the aminated resin (B-1) is preferably in the range of 1,000 to 5,000. When the number average molecular weight is 1,000 or more, the cured electrodeposition coating film obtained has good physical properties such as solvent resistance and corrosion resistance. On the other hand, the aminated resin (B-1) can be easily adjusted in viscosity by the number average molecular weight of 5,000 or less, and can be synthesized smoothly, and the treatment for emulsifying and dispersing the aminated resin (B-1) obtained becomes easy. More preferably, the number average molecular weight of the aminated resin (B-1) is in the range of 2,000 to 3,500.

In the present specification, the number average molecular weight is a polystyrene-equivalent number average molecular weight measured by Gel Permeation Chromatography (GPC).

The amine value of the aminated resin (B-1) is preferably in the range of 20 to 100 mgKOH/g. By setting the amine value of the aminated resin (B-1) to 20mgKOH/g or more, the aminated resin (B-1) in the electrodeposition coating composition has good emulsion dispersion stability. On the other hand, when the amine value is 100mgKOH/g or less, the amount of amino groups in the cured electrodeposition coating film is appropriate, and there is no fear that the water resistance of the coating film is lowered. The amine value of the aminated resin (B-1) is more preferably in the range of 20 to 80 mgKOH/g.

The hydroxyl value of the aminated resin (B-1) is preferably in the range of 150 to 650 mgKOH/g. When the hydroxyl value is 150mgKOH/g or more, curing becomes good and the appearance of the coating film is improved in the case of curing the electrodeposition coating film. On the other hand, when the hydroxyl value is 650mgKOH/g or less, the amount of hydroxyl groups remaining in the cured electrodeposition coating film is appropriate, and there is no fear that the water resistance of the coating film is lowered. The hydroxyl value of the aminated resin (B-1) is more preferably in the range of 180 to 300 mgKOH/g.

The electrodeposition coating composition of the present invention can provide a coated object with more excellent corrosion resistance by using the aminated resin (B-1) having a number average molecular weight in the range of 1,000 to 5,000, an amine value of 20 to 100mgKOH/g, and a hydroxyl value of 150 to 650 mgKOH/g.

As the aminated resin (B-1), aminated resins (B-1) having different amine values and/or hydroxyl values can be used in combination as required. When 2 or more aminated resins (B-1) having different amine values and hydroxyl values are used in combination, the average amine value and average hydroxyl value calculated based on the mass ratio of the aminated resin (B-1) used are preferably within the above-mentioned numerical ranges. Further, as the aminated resin (B-1) to be used in combination, it is preferable to use an aminated resin (B-1) having an amine value of 20 to 50mgKOH/g and a hydroxyl value of 50 to 300mgKOH/g in combination with an aminated resin (B-1) having an amine value of 50 to 200mgKOH/g and a hydroxyl value of 200 to 500 mgKOH/g. When such a combination is used, there is an advantage that the core portion of the emulsion becomes more hydrophobic and the shell portion becomes hydrophilic, so that excellent corrosion resistance can be imparted.

The aminated resin (B-1) may contain, for example, an amino group-containing acrylic resin, an amino group-containing polyester resin or the like.

(curing agent (B-2))

The coating film-forming resin (B) according to the present disclosure may contain a curing agent (B-2). The curing agent (B-2) undergoes a curing reaction with the aminated resin (B-1) under heating to form a coating film. As the curing agent (B-2), a melamine resin or a blocked isocyanate curing agent can be suitably used. Blocked isocyanate curing agents which can be suitably used as the curing agent (B-2) can be prepared by blocking a polyisocyanate with a blocking agent.

Examples of the polyisocyanate include aliphatic diisocyanates such as hexamethylene diisocyanate (including trimer), tetramethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and 4, 4' -methylenebis (cyclohexyl isocyanate); aromatic diisocyanates such as 4, 4' -diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate; modified products of these diisocyanates (urethane, carbodiimide, Uretdione, uretonimine, biuret and/or isocyanurate modified products, etc.).

Examples of the blocking agent include monohydric alkyl (or aromatic) alcohols such as n-butanol, n-hexanol, 2-ethylhexanol, lauryl alcohol, phenol methanol (phenol carbinol) and methyl phenyl methanol; cellosolves such as ethylene glycol monohexyl ether and ethylene glycol mono 2-ethylhexyl ether; polyether type double-end-capped glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol phenol and the like; polyester type double-capped polyols obtained from diols such as ethylene glycol, propylene glycol and 1, 4-butanediol and dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid and sebacic acid; phenols such as p-tert-butylphenol and cresol; oximes such as dimethyl ketoxime, methyl ethyl ketoxime, methyl isobutyl ketoxime, methyl amyl ketoxime and cyclohexanone oxime; and lactams typified by-caprolactam and γ -butyrolactam.

The blocking rate of the blocked isocyanate curing agent is preferably 100%. This has the advantage of good storage stability of the electrodeposition coating composition.

The blocked isocyanate curing agent is preferably used in combination with a curing agent prepared by blocking an aliphatic diisocyanate with a blocking agent and a curing agent prepared by blocking an aromatic diisocyanate with a blocking agent.

The blocked isocyanate curing agent is preferentially reacted with the primary amine of the aminated resin (B-1), and further reacted with a hydroxyl group to cure.

Examples of the melamine resin include a partially or completely methylolated melamine resin obtained by reacting melamine with formaldehyde, a partially or completely alkyl ether type melamine resin obtained by partially or completely etherifying methylol groups of a methylolated melamine resin with an alcohol component, an imino group-containing type melamine resin, and a mixed type melamine resin thereof. Among them, examples of the alkyl ether type melamine resin include methylated melamine resin, butylated melamine resin, and methyl/butyl mixed alkyl type melamine resin.

As the curing agent (B-2), at least one curing agent selected from organic curing agents such as melamine resins and phenol resins, silane coupling agents, and metal curing agents may be used in combination with the blocked isocyanate curing agent.

In the preparation of the cationic electrodeposition coating composition according to the present disclosure, it is preferable, for example, to prepare a resin emulsion by separately dissolving the aminated resin (B-1) and the curing agent (B-2) in an organic solvent to prepare solutions, mixing the solutions, and then neutralizing with a neutralizing acid.

Examples of the neutralizing acid include organic acids such as methanesulfonic acid, sulfamic acid, lactic acid, dimethylolpropionic acid, formic acid, and acetic acid. In the present disclosure, for example, it is more preferable to neutralize the resin emulsion containing the aminated resin (B-1) and the curing agent (B-2) with one or more acids selected from formic acid, acetic acid, and lactic acid.

The neutralizing acid is used more preferably in an amount such that the ratio of the neutralizing acid equivalent to the amino equivalent of the aminated resin (B-1) is 10 to 100%, and still more preferably 20 to 70%. In the present specification, the ratio of the neutralization acid equivalent to the amino equivalent possessed by the aminated resin (B-1) is referred to as neutralization ratio. By setting the neutralization rate to 10% or more, the affinity with water is ensured and the water dispersibility is good.

The content of the curing agent (B-2) needs to be an amount sufficient for reacting with an active hydrogen-containing functional group such as a primary amino group, a secondary amino group or a hydroxyl group in the aminated resin (B-1) at the time of curing to provide a good cured coating film. The content of the curing agent (B-2) is preferably 90/10 to 50/50, more preferably 80/20 to 65/35, in terms of the solid content mass ratio of the aminated resin (B-1) to the curing agent (B-2) (aminated resin (B-1)/curing agent (B-2)). By adjusting the solid content mass ratio of the aminated resin (B-1) to the curing agent (B-2), the fluidity and curing speed of the coating film (precipitated film) during film formation are improved, and the coating appearance is improved.

(pigment dispersing paste)

The cationic electrodeposition coating composition according to the present disclosure may contain a pigment dispersion paste as needed. The pigment-dispersion paste generally contains a pigment-dispersion resin and a pigment.

(pigment dispersing resin)

The pigment dispersion resin is a resin for dispersing a pigment, and is used, for example, by being dispersed in an aqueous medium. As the pigment-dispersing resin, a pigment-dispersing resin having a cationic group such as a modified epoxy resin having at least 1 or more selected from quaternary ammonium groups, tertiary sulfonium groups and primary amino groups can be used. As the aqueous solvent, ion-exchanged water, water containing a small amount of alcohol, or the like can be used.

(pigment)

The pigment is a pigment commonly used in electrodeposition coating compositions. Examples of the pigment include inorganic pigments and organic pigments which are generally used, and for example, colored pigments such as titanium white (titanium dioxide), carbon black, and iron oxide red; filler pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay; and rust preventive pigments such as iron phosphate, aluminum phosphate, calcium phosphate, aluminum tripolyphosphate, and aluminum phosphomolybdate, aluminum zinc phosphomolybdate, and the like.

(other additives)

The cationic electrodeposition coating composition of the present invention may further contain additives commonly used in the coating field. The cationic electrodeposition coating composition of the present invention, particularly the additive(s) may be contained in a range not to impair the effects of the specified organosilicon compound (a) according to the present disclosure.

The additives include, for example, organic solvents such as ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethylhexyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and propylene glycol monophenyl ether, anti-drying agents, surfactants such as antifoaming agents, viscosity modifiers such as acrylic resin fine particles, known anti-cratering agents, and inorganic rust inhibitors such as vanadium salts, copper, iron, manganese, magnesium, and calcium salts, as necessary. In addition, other than these, known auxiliary complexing agents, buffers, smoothing agents, stress moderators, gloss agents, semi-gloss agents, antioxidants, ultraviolet absorbers, and the like may be blended according to the purpose. These additives may be added at the time of mixing at the 2 nd stage of the production of the resin emulsion, may be added at the time of the production of the pigment dispersion paste, or may be added at the time of or after mixing of the resin emulsion and the pigment dispersion paste.

(electrodeposition coating and method for Forming cured electrodeposition coating film)

In another aspect, the present disclosure provides a method for forming a cured electrodeposition coating film, comprising: impregnating a substrate with a prescribed cationic electrodeposition coating composition according to the present disclosure, conducting electrodeposition coating to form an uncured electrodeposition coating film, and

the uncured electrodeposition coating film is cured by heating to form a cured electrodeposition coating film on the substrate.

Thus, the cationic electrodeposition coating composition of the present invention can be used for electrodeposition coating of a substrate and formation of a cured electrodeposition coating film.

According to the method for forming a cured electrodeposition coating film of the present disclosure, since electrodeposition coating is performed on a substrate using the cationic electrodeposition coating composition of the present invention containing a specific amount of a specific organosilicon compound, and a cured electrodeposition coating film is formed, a coating film can be formed which exhibits good anti-cratering properties, and which has good coating film appearance such as good coating film smoothness and no occurrence of coating unevenness.

Further, even when the mechanism of the presence of oil is different, a coating film exhibiting good anti-cratering properties can be formed.

Therefore, according to the method for forming a cured electrodeposition coating film of the present disclosure, a coating film exhibiting good anti-cratering properties can be formed even with respect to oil components originating from apparatuses used in drying and curing processes such as an indirect oven and a drying oven, i.e., oil components that can be mixed after coating and before curing. Further, for example, oil mixed after coating and before curing may be mixed in at a high temperature such as near baking temperature, and even with such oil, a coating film exhibiting good anti-cratering properties can be formed.

In addition, according to the method for forming a cured electrodeposition coating film of the present disclosure, when an oil component is mixed in a coating composition, a coating film exhibiting good anti-cratering properties can be formed even if the coating film is formed under such a condition that the oil component can remain on a substrate.

Further, according to the method for forming a cured electrodeposition coating film of the present disclosure, the cationic electrodeposition coating composition used has good coating stability, for example, stability in an aqueous system. In addition, if the specific organosilicon compound (a) according to the present disclosure is used, it can be dispersed in an aqueous solvent without being diluted with a solvent, and thus the load on the environment can be reduced.

In electrodeposition coating using the cationic electrodeposition coating composition of the present disclosure, a substrate is immersed in the cationic electrodeposition coating composition, the substrate is used as a cathode, and a voltage is applied between the substrate and the anode (electrodeposition coating step). Thereby, an electrodeposition coating film (uncured electrodeposition coating film) is deposited on the substrate.

In the electrodeposition coating step, after the object to be coated is immersed in the electrodeposition coating composition, electrodeposition coating is performed by applying a voltage of 50 to 450V. When the applied voltage is less than 50V, electrodeposition may become insufficient, and when it exceeds 450V, the coating film may be broken to form an abnormal appearance. During electrodeposition coating, the bath temperature of the coating composition is usually adjusted to 10 to 45 ℃.

The time for applying the voltage varies depending on the electrodeposition conditions, and may be set to 2 to 5 minutes in general.

The thickness of the electrodeposition coating film is preferably 5 to 40 μm, more preferably 10 to 25 μm, based on the thickness of the cured electrodeposition coating film finally obtained by heat curing. When the thickness of the electrodeposition coating film is less than 5 μm, the corrosion resistance may be poor. On the other hand, if it exceeds 40 μm, the coating composition is wasted.

The cured electrodeposition coating film obtained in this way (uncured electrodeposition coating film) can be formed by heating the electrodeposition coating film obtained in this way at 120 to 260 ℃, preferably 140 to 220 ℃ for 10 to 30 minutes after the electrodeposition process is completed, directly or after washing with water.

In some embodiments, the coating composition of the present disclosure can form a coating film in which the arithmetic average roughness (Ra (2.5)) of the electrodeposition coating film cured by heating, that is, the (Ra) for cutting off the wavelength of 2.5mm or more is 0.1 to 0.3, for example, 0.15 to 0.25. According to the coating composition of the present disclosure, a coating film having an arithmetic average roughness (Ra (2.5)) in such a range can be formed, and a coating film having good smoothness and excellent appearance can be formed. For example, the arithmetic average roughness (Ra) can be measured in accordance with JIS-B0601.

(substrate)

Various substrates that can be energized can be used as the substrate to which the electrodeposition coating composition of the present invention is applied. Examples of the applicable object include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel, electrogalvanized steel sheets, hot-dip galvanized steel sheets, zinc-aluminum alloy-based plated steel sheets, zinc-iron alloy-based plated steel sheets, zinc-magnesium alloy-based plated steel sheets, zinc-aluminum-magnesium alloy-based plated steel sheets, aluminum-silicon alloy-based plated steel sheets, and tin-based plated steel sheets.

These substrates may be substrates subjected to a known blood activating surface treatment or the like.