JPH0751693B2 - Coating resin composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel coating resin composition, and more particularly, it has improved thick film coating suitability and corrosion resistance particularly suitable for cathodic electrodeposition coating. And a coating resin composition.

[Prior Art] As a resin composition for a cathodic electrodeposition coating, an epoxy-polyamine obtained by reacting an epoxy group-containing resin with a polyamine, as disclosed in, for example, JP-A-54-93024. A resin composition in which a resin and a polyisocyanate curing agent blocked with alcohols are combined is common. As the epoxy group-containing resin, from the viewpoint of anticorrosion, a resin obtained by polymerizing bisphenol A diglycidyl ether into a high molecular weight using bisphenol A is usually used. Further, a partially soft polyester, polyether, or epoxy resin, A plasticizer obtained by introducing a plastic modifier such as polyamide, polybutadiene, or butadiene-acrylonitrile copolymer has been put into practical use.

[Problems to be Solved by the Invention] Recently, in the field of electro-deposition coating of automobile bodies and under parts, development of paints having suitability for thick film coating and high anticorrosion property from the viewpoint of aesthetics and coating performance. The demand for is increasing.

In order to meet these requirements, the conventional plasticity modifier of the epoxy resin is increased in order to impart suitability for thick film coating in cathodic electrodeposition coating, a component with weak corrosion resistance is introduced into the resin, and sufficient corrosion resistance is obtained. On the other hand, if the amount of the plasticity modifier is reduced to try to reinforce the anticorrosion property, there is a problem that the suitability for thick film coating cannot be obtained.

[Means for Solving Problems] The inventors of the present invention have conducted earnest studies for the purpose of obtaining a resin composition having suitability for thick film coating and high anticorrosion property, and as a result, have 3 to 4 carbon atoms. The inventors have found that the above object can be achieved by using an epoxy resin into which a specific amount of individual alkylene oxides has been introduced, and completed the present invention.

Therefore, according to the present invention, (a) the following general formula (I) In the formula, R represents CH ₃ or CH ₂ CH ₃ , and m + n is an integer of 1 to 6, a diepoxide compound represented by: (b) bisphenols and, if necessary, (c) bisphenol diglycidyl There is provided a coating resin composition comprising an epoxy-polyamine resin obtained by adding (d) an amine compound having active hydrogen to an epoxy resin obtained by reacting ether as a main component.

The diepoxide compound (a) represented by the general formula (I) used in the present invention contains bisphenol A having 3 to 3 carbon atoms.
It is obtained by adding four 1,2-alkylene oxides and then epoxidizing it with epichlorohydrin,
The diepoxide compound thus obtained has an alkyleneoxy structure, which is a plastic component, and a hard bisphenol A structure which forms a repeating structure at relatively short intervals. Therefore, the diepoxide compound has suitability for thick film coating and high corrosion resistance. Is considered to indicate.

When ethylene oxide is used as the alkylene oxide to be added to bisphenol A, such an advantage is not obtained, and 1,2-alkylene oxide having 3 to 4 carbon atoms, that is, 1,2-propylene oxide or 1,2
-For the first time by using butylene oxide,
It has been found in the present invention that the above performance can be satisfied. When ethylene oxide is used as the alkylene oxide, the resulting diepoxide compound has low hydrophobicity and poor corrosion resistance, while alkylene oxides having 5 or more carbon atoms are generally difficult to obtain and have many carbon atoms. The use of alkylene oxide is not preferable because the obtained resin tends to be softened and the corrosion resistance tends to deteriorate.

The total number (m + n) of the repeating units m and n of the alkyleneoxy group in the formula (I) diepoxy compound is 1
It is an integer in the range of ˜6, preferably in the range of 1 to 3. If the total number of repeating units (m + n) exceeds 6, the obtained resin tends to be soft and the anticorrosive property tends to deteriorate, which is not preferable.

In the present invention, the diepoxide compound (a) represented by the above formula (I) is reacted with a bisphenol (b) and, if necessary, a bisphenol diglycidyl ether (c), and an amine compound having an active hydrogen ( d)
To give an epoxy-polyamine resin.

Examples of reaction modes for obtaining the epoxy-polyamine resin include the following.

(I) A method in which the diepoxide compound (a) is reacted with less than an equivalent amount of bisphenols (b) and the amine compound (d) is added to the terminal oxirane group of the resulting epoxy resin; (ii) the diepoxide compound (a) And the bisphenols (b) in excess of the equivalent amount are reacted with the terminal hydroxyl groups of the resin to be reacted with bisphenol diglycidyl ether (c) in excess of the equivalent amount, and the terminal oxirane group of the resulting epoxy resin is converted into the amine compound (d ) Is added; (iii) An amount of bisphenols that is less than the equivalent amount of hydroxyl groups with respect to the total oxirane groups of diepoxide compound (a), bisphenol diglycidyl epoxy (c) and (a) + (c). Amine compound (d) is added to the terminal oxirane group of the epoxy resin obtained by simultaneously reacting with (b).
How to add.

In the above methods (i), (ii) and (iii), the addition of the amine compound (d) can be carried out at the same time when the epoxy resin has a high molecular weight. Among the above reaction methods (i), (ii) and (iii), the method (ii) is particularly preferable in terms of resin design and control.

Representative examples of the bisphenols (b) used in the above reaction include bis (4-hydroxyphenyl) -2,2-propane, bis (4-hydroxyphenyl) -1,1-ethane,
Bis (4-hydroxyphenyl) -methane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, bis (4-hydroxyphenyl)
-1,1-isobutane, bis (4-hydroxy-3-t-
Butylphenyl) -2,2-propane and the like.

The bisphenol diglycidyl ether (c) has a number average molecular weight of at least about 320, preferably about 340.
-2000 and an epoxy equivalent of at least about 160,
Suitably bisphenol diglycidyl ethers in the range of about 170 to 1000 are suitable, in particular The bisphenol A-type diglycidyl ether represented by is particularly preferable in terms of price and corrosion resistance.

When an epoxy resin is produced by reacting the diepoxide compound (a), the bisphenol (b), and optionally (c) bisphenol diglycidyl ether,
The amount of the diepoxide compound (a) used is (a),
It is preferably 10% by weight or more based on the total amount of the components (b) and (c). If the amount of diepoxide compound (a) used is less than 10% by weight, suitability for thick film coating tends to be unobtainable.

The obtained epoxy resin preferably has a number average molecular weight within the range of 1000 to 5000 from the viewpoint of corrosion resistance and suitability for thick film coating.

The reaction of the oxirane group and the hydroxyl group to obtain the epoxy resin can be carried out by a method known per se,
For example, it can be carried out by heating at a temperature of about 50 ° C to about 200 ° C for about 1 to about 15 hours in the presence of a catalyst such as a basic amino compound such as dimethylbenzylamine, tributylamine, triethylamine and the like.

The epoxy resin obtained as described above can be made into an epoxy-polyamine resin by subsequently adding an amine compound (d) having active hydrogen. The active hydrogen-containing amine compound (d) reacts with an oxirane group such as an aliphatic, alicyclic or aromatic-aliphatic primary or secondary amine, an alkanolamine or a tertiary amine salt. And amine compounds capable of introducing an amino group or a quaternary ammonium salt into the epoxy resin having active hydrogen. The following can be mentioned as typical examples of these amine compounds having active hydrogen.

(1) A primary amino group of an amine compound containing one secondary amino group such as diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, and methylaminopropylamine and one or more primary amino groups, a ketone, With aldehydes or carboxylic acids, for example
A compound modified by heating to a temperature of about 100 to 230 ° C to give an aldimine, ketimine, oxazoline or imidazoline; (2) diethylamine, diethanolamine, di-n
-Or-secondary iso-propanolamine, N-methylethanolamine, N-ethylethanolamine, etc.
Secondary monoamine; (3) secondary amine-containing compound obtained by adding monoalkanolamine such as monoethanolamine and dialkyl (meth) acrylamide by Michael addition reaction; (4) monoethanolamine, neopentanol A compound obtained by modifying the primary amino group of an alkanolamine such as amine, 2-aminopropanol, 3-aminopropanol, 2-hydroxy-2 '(aminopropoxy) ethyl ether into ketimine; (5) dimethylethanolamine, triethylamine, trimethylamine , Salts of tertiary amines such as triisopropylamine and methyldiethanolamine with organic acids such as acetic acid and lactic acid.

An epoxy-polyamine resin can be obtained by reacting these active hydrogen-containing amine compounds with the oxirane groups in the epoxy resin at a temperature of about 30 to about 160 ° C. for about 1 to about 5 hours. . Further, the addition of the amine compound into the epoxy resin can be carried out simultaneously with the increase in the molecular weight of the epoxy resin, as described above.

The amount of these amine compounds having active hydrogen used is such that the amine value of the epoxy-polyamine resin of the present invention is 15 to 100.
The amount is preferably within the range. When the amine value is less than 15, it becomes difficult to disperse the resin in water, and the amine value is 10 or less.
If it exceeds 0, the water resistance of the resulting coating film tends to deteriorate.

The above epoxy-polyamine resin is also reacted with a reaction agent such as, for example, a tertiary amine salt, a monocarboxylic acid, a secondary sulfide salt, a monophenol or a monoalcohol to control the water dispersibility and the smoothness of the coating film. Can be improved.

Further, a block isocyanate group, a β-hydroxycarbamic acid ester group, in an epoxy-polyamine resin,
Internal crosslinkability can be imparted by introducing a crosslinkable functional group such as α, β-unsaturated carbonyl group and N-methylol group.

The reaction with the above reaction reagent and the introduction of the crosslinkable functional group are
It may be performed before the addition of the amine compound having active hydrogen to the epoxy resin.

The epoxy-polyamine resin obtained as described above can be used in combination with an external crosslinking agent. As the external cross-linking agent which can be used in combination, a compound having two or more cross-linkable groups in one molecule, for example, block polyisocyanate, β-hydroxycarbamic acid ester of polyamine, malonic acid ester derivative, methylolated melamine, methylolated urea, etc. Can be mentioned. The compounding ratio (solid content ratio) of the epoxy-polyamine resin and these external crosslinking agents is
The range of 100/0 to 60/40 is preferable.

In order to make the above epoxy-polyamine resin water-soluble or water-dispersible, the amino group may be protonated with a water-soluble organic acid such as formic acid, acetic acid, lactic acid, and dissolved or dispersed in water.

The amount of acid used for protonation (neutralization value) cannot be strictly specified, but generally it is about 5 to 40 per 1 g of resin solid content.
From the viewpoint of electrodeposition characteristics, it is preferable that the number of KO mg is within the range of 10 to 20 KOH mg. The aqueous solution or aqueous dispersion thus obtained is particularly suitable for cathodic electrodeposition coating, and in this case, a pigment, a solvent, a curing catalyst, a surfactant and the like can be added and used if necessary.

As a method and apparatus for performing electrodeposition coating on an object to be coated using the above aqueous solution or aqueous dispersion, known methods and apparatuses conventionally used in cathodic electrodeposition coating can be used. At this time, it is desirable to use the object to be coated as a cathode and the stainless steel or carbon plate as the anode. The electrodeposition coating conditions that can be used are not particularly limited, but generally, bath temperature: 20 to 30 ° C, voltage: 100
~ 400V (preferably 200-300V), current density: 0.01-3A / d
m ^2, the energizing time: 1-5 min, electrode area ratio (A / C): 2 / 1~1 / 2, interelectrode distance: 10 to 100 cm, it is desirable to electrodeposited under stirring.

The coating deposited on the cathode coating is about 140
It can be baked and cured at temperatures between 180 ° C and about 180 ° C.

Hereinafter, the present invention will be described more specifically by way of examples.
In the following, "parts" and "%" indicate "parts by weight" and "% by weight", respectively.

Production Example 1 A reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas inlet was blown with nitrogen gas and propylene oxide-modified bisphenol A diglycidyl ether ^{(Note 1)} 52
5 parts, 342 parts of bisphenol A and 36 parts of a methylisobutylketone solution of ketimine of 80% active ingredient monoethanolamine and methylisobutylketone were charged and reacted at 160 ° C. until the epoxy groups disappeared.

Further, to this was added 665 parts of bisphenol diglycidyl ether having an epoxy equivalent of about 190 and 232 parts of a methylisobutylketone solution of ketimine of 80% monoethanolamine and methylisobutylketone at 140 ° C.
The reaction was carried out until the epoxy group concentration reached 0.27 mmol / g. As a result, an epoxy resin liquid having a number average molecular weight of about 1500 was obtained. Then, dilute and cool with 365 parts of ethylene glycol monobutyl ether, and when 100 ° C is reached, the active ingredient
Add 80 parts of 80% diethylenetriamine methyl isobutyl ketone diketimine methyl isobutyl ketone solution and react at 100 ° C until the increase in viscosity stops.
% Epoxy-polyamine resin solution was obtained. This product was mixed with ethylene glycol monobutyl ether to a solid concentration of 50
The Gardner viscosity (25 ° C.) was W when adjusted to be%.

(Note 1) Propylene oxide-modified bisphenol A diglycidyl ether [manufactured by Sanyo Chemical Co., Ltd., trade name: Glyciere BPP-350, epoxy equivalent of about 340, m + n = 2 to 3 in formula (I)].

Production Example 2 Propylene oxide-modified bisphenol A diglycidyl ether was introduced into a reactor similar to that of Production Example 1 under nitrogen gas blowing.
^{(Note 1)} 840 parts, bisphenol A with an epoicy equivalent of about 190
608 parts of diglycidyl ether, 410 parts of bisphenol A and 1.9 parts of dimethylbenzylamine were mixed and reacted at 160 ° C. until the epoxy group concentration became 1.1 mmol / g.
As a result, an epoxy resin liquid having a number average molecular weight of about 1900 was obtained. Then ethylene glycol monobutyl ether
Dilute and cool with 420 parts, charge 147 parts of diethanolamine when it reaches 100 ° C, raise the temperature to 120 ° C, react at the same temperature until the epoxy group concentration becomes 0.4 mmol / g, and then cool to 100 ° C. , 109 parts of an adduct of 80% N, N-dimethylaminopropylacrylamide with monoethanolamine (ethylene glycol monobutyl ether solution) was charged, and reacted at 100 ° C until the viscosity did not rise, and an epoxy with 82% solid content was added. A polyamine resin solution was obtained.

The Gardner viscosity (25 ° C.) when this product was adjusted to a solid content concentration of 50% with ethylene glycol monobutyl ether was Y.

Production Example 3 476 parts of polypropylene glycol diglycidyl ether having an epoxy equivalent of about 317, 342 parts of bisphenol A, and 80% of active ingredient were introduced into a reactor similar to that of Production Example 1 under nitrogen gas blowing.
Charge 36 parts of the methylisobutylketone solution of ketimine with monoethanolamine and methylisobutylketone,
The reaction was carried out at 160 ° C until the epoxy groups disappeared.

Furthermore, to this was charged 665 parts of bisphenol A diglycidyl ether having an epoxy equivalent of about 190 and 232 parts of a methylisobutylketone solution of ketimine of monoethanolamine and methylisobutylketone containing 80% of the active ingredient, 1
The reaction was carried out at 40 ° C. until the epoxy group concentration reached 0.28 mmol / g.

As a result, an epoxy resin liquid having a number average molecular weight of about 1500 was obtained. Dilute and cool this product with 365 parts of ethylene glycol monobutyl ether, and when it reaches 100 ° C, add 100 parts of a solution of 80% diethylenetriamine in methylisobutylketone diketimine in methylisobutylketone and stop increasing the viscosity at 100 ° C. Solid content 81
% Epoxy-polyamine resin solution was obtained.

The Gardner viscosity (25 ° C.) when this product was adjusted to a solid content concentration of 50% with ethylene glycol monobutyl ether was V.

Production Example 4 In a reactor similar to that of Production Example 1, under nitrogen gas blowing, an ethylene oxide-modified bisphenol A diglycidyl ether ^{(Note 2)} 450 parts with an epoxy equivalent of about 300 and bisphenol A were prepared.
342 parts and 36 parts of methylisobutylketone ketimine (methylisobutylketone solution) of monoethanolamine containing 80% of active ingredient were charged and reacted at 160 ° C. until the epoxy group disappeared.

Furthermore, to this was charged 665 parts of bisphenol A diglycidyl ether having an epoxy equivalent of about 190 and 232 parts of a methylisobutylketone solution of ketimine of monoethanolamine and methylisobutylketone containing 80% of the active ingredient, 1
The reaction was carried out at 40 ° C until the epoxy group concentration reached 0.29 mmol / g. As a result, an epoxy resin liquid having a number average molecular weight of about 1500 was obtained. Next, this product was diluted with 350 parts of ethylene glycol monobutyl ether and cooled, and when it reached 100 ° C, 100 parts of a solution of 80% diethylenetriamine in methylisobutylketone diketimine in methylisobutylketone was added. The reaction was continued until stopped, and an epoxy-polyamine resin solution having a solid content of 81% was obtained.
The Gardner viscosity (25 ° C.) when this product was adjusted to a solid content concentration of 50% with ethylene glycol monobutyl ether was Y.

(Note 2) Ethylene oxide modified bisphenol A diglycidyl ether [manufactured by Sanyo Chemical Co., Ltd., trade name: Glyciere BPE-300, epoxy equivalent of about 300] Examples 1 and 2 and Comparative Examples 1 and 2 Methyl ethyl ketoxime block isophorone diisocyanate was added to each of the four resin solutions so that the block isocyanate group was equivalent to the total amount of the primary hydroxyl group and primary amino group in the epoxy-polyamine resin.

Further, polypropylene glycol (manufactured by Sanyo Kasei Co., Ltd., based on 100 parts by weight of the solid content of the resin composition compounded as described above,
1 part of Sannix PP4000), 0.96 part of acetic acid and 1 part of lead acetate are added, and deionized water is gradually added with stirring to a temperature of up to 60 ° C to disperse the water to obtain an emulsion with a resin solid content of 30% and good stability. Got

3 parts of basic lead silicate, 13 parts of titanium white, 0.3 part of carbon black, 3 parts of clay, 2 parts of dibutyltin oxide and 2 parts of nonionic surfactant per 100 parts by weight of the resin solid content of the emulsion thus obtained. Name: Neugen 142B, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. (1 part) was added, and the pigment was dispersed in a ball mill until the particle size became 10 μm or less, and then diluted with deionized water to a resin solid content of 15%.

The bath temperature of the four diluted paints obtained as described above 28
Cation electrodeposition coating was performed on the untreated steel sheet and the Bt-3080 (zinc phosphate) treated steel sheet at a voltage of 250 V for 3 minutes. After these electrodeposition coated plates were baked at 160 ° C. for 20 minutes, a corrosion resistance test was conducted.

The resin composition and test results are shown in Table 1 below.

The anticorrosion test in Table 1 was performed according to the following method.

(Note 4) Salt spray resistance The electrodeposited film is cross-cut with a knife to reach the substrate, and the test is performed according to JIS Z2371 to measure rust from knife scratches and blistering width. The test time was 480 hours for the untreated steel sheet and 1000 hours and 1500 hours for the Bt-3080 treated steel sheet.

(Note 5) Saltwater immersion resistance The electrodeposition coated plate was immersed in a 5% NaCl aqueous solution, and changes in the flat surface portion were observed. Immersion time is 480 when uncoated steel sheet
Time, 800 hours for Bt-3080 treated steel sheet.

The evaluation criteria are as follows.

⊚: Almost no change.

◯: There is a change in the coated surface, but blistering and peeling are less than 5%.

Δ: Blisters and peeling are 10% to less than 50%.

×: 50% or more of blisters and peeling.

[Effects of the Invention] The coating composition of the present invention comprising an epoxy-polyamine resin having a diepoxide compound represented by the above formula (I) introduced into a bisphenol type epoxy resin skeleton as a main component is suitable for cathodic electrodeposition coating. By using it, under normal electrodeposition coating conditions (voltage 200 to 300 V, energizing time 1 to 5 minutes), a film thickness of 35 μm or more and no coating surface abnormality, it has excellent suitability for thick film coating and excellent corrosion resistance. A coating film can be obtained.

Claims (3)

[Claims] 1. (a) The following general formula (I): In the formula, R represents CH ₃ or CH ₂ CH ₃ , and m + n is an integer of 1 to 6, a (b) bisphenol compound, and, if necessary, (c) bisphenol di compound. A coating resin composition comprising an epoxy-polyamine resin obtained by adding (d) an amine compound having active hydrogen to an epoxy resin obtained by reacting glycidyl ether as a main component. 2. A diepoxide compound represented by the general formula (I) comprises bisphenol A and 1,2-C3-4 carbon atoms.
The coating resin composition according to claim 1, which is obtained by reacting an adduct with an alkylene oxide with epichlorohydrin. 3. An epoxy resin is reacted with a diepoxide compound represented by the general formula (I) and an amount of bisphenols which is a hydroxyl group in an amount exceeding the equivalent amount to the oxirane group in the diepoxide compound, The coating resin composition according to claim 1, which is obtained by reacting bisphenol glycidyl ether.