JPH05301940A - Polyamide-modified epoxy resin and coating composition containing the same - Google Patents

Abstract

PURPOSE:To provide the subject resin giving cured products good in the flexibil ity, hardness, chemical resistance and corrosion resistance and useful for coatings, etc., by reacting a specifinc epoxy resin with a polyamidedicarboxylic acid produced by reacting a polymeric fatty acid with a diamine having a cyclic skeleton. CONSTITUTION:(A) An epoxy resin having on the average > one adjacent epoxy group per molecule and comprising the glycidyl ether of bisphenol A, bisphenol K, bisphenol F, bisphenol S, bisphenol S, and their mixture is reacted with (B) a polyamidedicarboxylic acid having an amine value of 0-20 and an acid value of 20-200 and produced by reacting a polymeric fatty acid (e.g. oleic acid) with a diamine having a cyclic skeleton (e.g. metaxylylenq diamine) in a molar ratio of 2:1 to 1.9, the amount of the component Bbeing 0.1-50 wt.% based on the total amount of the components A and B, to provide the objective polyamide-modified epoxy resin having an acid value of 0-5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide-modified epoxy resin and its coating composition, and more specifically, it has improved workability due to its low viscosity, and its cured product has flexibility,
The present invention relates to a polyamide-modified epoxy resin excellent in hardness, chemical resistance, rust resistance, etc. and a coating composition thereof.

[0002]

BACKGROUND OF THE INVENTION Epoxy resins are widely used in various applications including the coating field because of their excellent rust resistance, stain resistance, adhesion and flexibility. ..

Conventionally, steel sheets used as materials for home electric appliances such as washing machines, furniture such as lockers, and vending machines used outdoors are sheared, worked and formed in an unpainted state according to their respective uses. It was applied by the method called so-called post coating, which is applied at the end. However, in recent years, for the purpose of improving productivity, improving quality, diversifying designs, improving working environment, saving space, etc., the present invention relates to a pre-coated steel sheet obtained by performing a shearing and forming after coating a flat steel sheet. Research is active.

In the precoated steel sheet, the epoxy resin is inferior in weather resistance and is therefore used as a primer or a back surface coating. However, a resin having sufficiently satisfactory properties has not been obtained for applications such as home electric appliances that require excellent balance between workability and rust prevention.

Japanese Unexamined Patent Publication No. 2-286709 discloses an epoxy resin having excellent adhesion, flexibility and stain resistance. However, the epoxy resin disclosed in the publication exhibits extremely excellent characteristics with a fairly high molecular weight, but may exhibit unsatisfactory characteristics with a low molecular weight depending on the application. High molecular weight resins are generally highly viscous and require the use of large amounts of organic solvents to improve handling. However, it is not preferable to use a large amount of organic solvent because of problems such as environmental pollution and deterioration of working environment. Further, an epoxy resin having improved rust prevention and flexibility is also desired.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and balances the physical properties such as flexibility, hardness, chemical resistance, and rust resistance of the cured product. It is an object of the present invention to provide an epoxy resin and a coating composition thereof which are improved in workability and improved in workability by lowering the viscosity, and as a result, the organic solvent content can be reduced.

[0007]

According to the present invention, in order to achieve the above object, (a) an epoxy resin having an average of more than one adjacent epoxy group per molecule; and (b) a polymerized fatty acid and a cyclic group. 2: 1.0 with a diamine having a skeleton
0-2 obtained by reacting at a molar ratio of ~ 1.9.
A polyamide dicarboxylic acid having an amine value of 0 and an acid value of 20 to 200 is reacted in an amount ratio of 0.1 to 50% by weight of component (b) with respect to the total amount of components (a) and (b). A polyamide-modified epoxy resin having an acid value of 0 to 5 thus obtained is provided. In the present invention,
When a low molecular weight epoxy resin is used as the component (a), a phenol compound having an average of more than one hydroxyl group per molecule is added as the third component (component (c)) for increasing the molecular weight of the final resin. You can also

Further, according to another aspect of the present invention, there is provided a coating composition containing the above polyamide-modified epoxy resin and at least one curing agent and / or at least one organic solvent.

The present invention will be described in detail below.

As the epoxy resin of the component (a) used in the present invention, a known epoxy resin having an average of more than one adjacent epoxy groups per molecule is used (for example, JP-A-1-153715, particularly See page 5, upper left column, line 2 to same page, lower right column, line 8). The preferred epoxy resin used here has an epoxy equivalent of 170 to 5,500, more preferably 175 to 3,0.
And a weight average molecular weight of 340 to 50,000,
More preferably, it is 340 to 20,000.

As the epoxy resin of component (a), more specifically, an epoxy resin having an average of two adjacent epoxy groups per molecule is suitable, and examples thereof include bisphenol A, bisphenol K, bisphenol F, bisphenol S, Included are glycidyl ethers of bisphenol AD and mixtures thereof. The most preferred epoxy resin is glycidyl ether of bisphenol A.

Examples of commercially available epoxy resins include D.I.
ER 331L; DER 383J; DER661; DER 664; D.
ER 667; DER 669E (both are trademarks of The Dow Chemical Company) can be used.

In the present invention, when the phenol compound of the component (c) is used, an epoxy resin having a relatively low epoxy equivalent of 170 to 340 is preferably used as the epoxy resin of the component (a). Ingredient (c)
As the phenol compound of (1), those known as a raw material of epoxy resin can be used (for example, JP-A No. 1-15).
3715, particularly page 6, upper left column, line 7 to same lower right column, line 3). More specifically, a phenol compound having two hydroxyl groups per molecule is suitable, and examples thereof include bisphenol A, bisphenol K, bisphenol F, bisphenol S, bisphenol AD, and mixtures thereof. The most preferred phenolic compound is bisphenol A.

In this case, the epoxy resin as the component (a) and the phenol compound as the component (c) are in a weight ratio of preferably 60:40 to 90:10, more preferably 60:40 to.
It is blended at 80:20. Where the phenolic resin is 4
When it exceeds 0% by weight, the hydroxyl group of the phenol compound becomes excessive with respect to the epoxy group, and the resulting product has a small number of epoxy groups, so that the good performance peculiar to the epoxy resin is lost.

The component (b) used in the present invention is
2: 1.0-
An amine value of 20 or less, preferably 5 or less, obtained by reacting at a molar ratio of 1.9, preferably 2: 1.0 to 1.2, and 20 to 200, more preferably 60 to 1
It is a polyamide dicarboxylic acid having an acid value of 10.

The "polymerized fatty acid" used herein is preferably a dimer of unsaturated fatty acid or a dimer of the unsaturated fatty acid saturated by hydrogenation, preferably 70% by weight, more preferably 95% by weight. % Or more and the remaining amount contains monomers, trimers, etc. The unsaturated fatty acid preferably has 12 to 24 carbon atoms (including carbon atoms of the carboxyl group), more preferably 15 to 22 carbon atoms. As a fatty acid having one unsaturated bond in one molecule,
For example, there are oleic acid, elaidic acid, cetoleic acid, etc., and fatty acids having two unsaturated bonds include, for example, sorbic acid, linoleic acid, etc., and fatty acids having three or more unsaturated bonds include, for example, linoleic acid, Examples include arachidonic acid.

In the present invention, commercially available polymerized fatty acids such as Haridimer 300, Haridimer 250 (all manufactured by Harima Kasei Co., Ltd.), Versadim 288 (manufactured by Henkel Hakusui Co., Ltd.) and Pripol 1004 (manufactured by Unichema International Co., Ltd.) are used. Can be used.

A feature of the present invention is that a diamine having a cyclic skeleton is used as the diamine constituting the component (b). The diamine preferably used in the present invention is 1
Is a diamine having 3 to 3 alicyclic structures, 1 to 3 aromatic rings, or a mixed cyclic skeleton thereof. Such preferred amines include, but are not limited to,
Diamines represented by the following general formulas (1) to (4) can be used.

[0019]

[Chemical 1]

[0020]

[Chemical 2]

[0021]

[Chemical 3]

[0022]

[Chemical 4]

[0023]

[Chemical 5]

In the above general formulas (1) to (4), A is independently a divalent chemical bond or a divalent hydrocarbon group having 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms (for example, an alkylene group). , Alkenylene group, etc.), and X independently represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a halogen atom. In the general formula (2), an oxygen atom may be bonded to the cyclohexenylene ring.

The diamines particularly preferably used in the present invention include those having an alicyclic skeleton such as menthenediamine, isophoronediamine, diaminocyclohexylmethane and diaminodicyclohexylmethane, metaphenylenediamine, metaxylenediamine and diaminodiphenylmethane. Examples thereof include diamines having an aromatic ring skeleton.

The reaction between polymerized fatty acid and diamine is 2:
With a molar ratio of 1.0 to 1.9, it can be carried out based on a known polymerization method while removing water as a by-product. When the molar ratio of the diamine is less than 1.0, the concentration of the carboxyl group becomes higher than the concentration of the amide group, and the obtained resin has poor processability. When the molar ratio of the diamine is larger than 1.9, it becomes difficult to synthesize a polyamide dicarboxylic acid having an amine value of 20 or less and an acid value of 20 or more. At this time,
When the amine value exceeds 20, the viscosity of the obtained coating material becomes too high, which adversely affects workability. For acid value,
When it is less than 20, the molecular weight of the obtained resin becomes too large (for example, the weight average molecular weight is 100,000 or more), and the solubility in an organic solvent becomes insufficient. It is difficult to synthesize those having an acid value of more than 200, considering the acid value of the polymerized fatty acid as a raw material.

The component (b) obtained above is the total solid content (components (a) and (b), or component (a),
The total amount of (b) and (c) is 0.1 to 50% by weight, preferably 1 to 20% by weight. Ingredient (a
When the proportion of -2) is less than 0.1% by weight, the properties of the obtained resin are no different from those of the epoxy resin used conventionally. The ratio of component (c) is 50
When the content is more than 10% by weight, the resulting coating film has poor corrosion resistance.

The polyamide-modified epoxy resin according to the present invention can be manufactured by, for example, but not limited to, the following method. (1) Component (a) (for example, a bisphenol type solid epoxy resin having an epoxy equivalent of 500 to 5,000 and a weight average molecular weight of 1,000 to 40,000) and component (b) of 70 to 100%. A method comprising polymerizing at a solids concentration, if desired in the presence of a catalyst, at a temperature of 120-200 ° C. (2) Component (a) and component (b) at a solids concentration of 80 to 100%, if desired in the presence of a catalyst, 120
The reaction is carried out at a temperature of ˜200 ° C., whereby 5
The following acid number, epoxy equivalent of 180-300 and 500
A semi-solid or liquid polyamide-modified epoxy resin having a weight average molecular weight of ˜3,000 is obtained, the component (c) is further added to the obtained resin, and the solid content concentration is 70 to 100% in the presence of a catalyst. A method comprising polymerizing at a temperature of 120 to 200 ° C. (3) The component (b) and the component (c) are condensed at a solid content concentration of 80 to 100% at a temperature of 120 to 200 ° C., and an acid value of 5 or less and a value of 500 to 500 obtained by the condensation are thereby obtained.
70-100% of a component (a) and a polyamide bisphenol ester resin having a weight average molecular weight of 3,000
At a solids concentration of 120 to 20 in the presence of a catalyst.
A method comprising polymerizing at a temperature of 0 ° C. (4) The components (a), (b) and the component (c) are simultaneously added to 70
At a solids concentration of -100%, optionally in the presence of a catalyst, at a temperature of 120-200 ° C.

In the above methods (1) to (4), the reaction conditions such as reaction time, reaction temperature, solid content concentration, kind of catalyst and addition amount are appropriately selected by those skilled in the art. The reaction time varies depending on other conditions, but is generally 1 to 15 hours. The reaction temperature is appropriately determined in consideration of the catalyst activity and the like. The reaction can be carried out either under normal pressure or under pressure, or in air, but is preferably carried out under an inert gas atmosphere, for example under a nitrogen atmosphere. Further, in the above method (3), since water is by-produced by the condensation reaction, it is preferable to carry out the reaction using a reactor equipped with a device capable of removing water.

When a high molecular weight polyamide-modified epoxy resin is produced in the above production method, a uniform reaction can be carried out by using an organic solvent to reduce the viscosity in the reaction system and increase the stirring efficiency. As the organic solvent used at this time, an organic solvent having a high solubility in an epoxy resin and a boiling point of 110 ° C., preferably 140 ° C. or higher is desirable. Examples of such organic solvents include glycol solvents such as ethylene glycol and propylene glycol, glycol monoether solvents such as Dowanol EB, Dowanol DB, Dowanol PnB (all are trademarks of The Dow Chemical Company); butyl acetate, Dowanol P
Acetate solvents such as MA (trademark of The Dow Chemical Company); n-butanol, amyl alcohol,
Alcoholic solvents such as cyclohexanol; xylene,
Aromatic solvents such as Solvesso 100 (manufactured by Esso Standard); ester solvents such as ethyl 3-ethoxypropionate can be used. The solid content concentration of the diluted reaction system is preferably 70 to 100%, and the amount of organic solvent tends to be regulated. Therefore, the higher the solid content concentration is, the more preferable it is in the allowable viscosity range.

In the present invention, the polyamide modified epoxy resin obtained by reacting the components (a) and (b) or the components (a), (b) and (c) preferably has an epoxy equivalent of 170-. It is 10,000, more preferably 500 to 5,000, and the acid value is preferably 5 or less, more preferably 2 or less. The polyamide modified epoxy resin preferably has a weight average molecular weight of 340 to 100,000, more preferably 5,000 to 50,000. When the epoxy equivalent is less than 170,
In some cases, the concentration of the secondary hydroxyl group, which is said to contribute to the adhesiveness and the adhesiveness, becomes too low and sufficient adhesiveness, processability and stain resistance cannot be obtained. If the epoxy equivalent exceeds 10,000, the wettability will deteriorate. When the acid value exceeds 5, the carboxylic acid existing at the terminal of the molecular chain may not be able to obtain the high flexibility, which is one of the characteristics of the present invention.
Therefore, it is desirable that the acid value be close to zero.

In the present invention, as the catalyst, a known catalyst as shown on page 7, left column, lines 26 to 44 of Japanese Patent Publication No. 2-11613 can be used. -Imidazoles such as methylimidazole; tertiary amines such as triethylamine, tripropylamine, tributylamine; phosphonium salts such as ethyltriphenylphosphonium phosphate, ethyltriphenylphosphonium acetate acetic acid complex, ethyltritolylphosphonium phosphate; benzyltrimethyl Examples thereof include ammonium salts such as ammonium chloride and benzyltrimethylammonium hydroxide. In the present invention, an acidic catalyst is preferable. The amount of the catalyst used is 0.001 to 1% by weight, more preferably 0.01 to 0.3% by weight, based on the total amount of the reaction mixture.

In the present invention, the polyamide-modified epoxy resin obtained as described above may be mixed with a curing agent, an organic solvent and the like to prepare a coating composition.

The composition of the present invention preferably has a weight ratio of the polyamide-modified epoxy resin to the curing agent of 70:30.
To 98: 2, particularly preferably 80:20 to 95: 5, and an organic solvent is added to 100 parts by weight of non-volatile components (total weight of polyamide-modified epoxy resin and curing agent) in the composition. It is preferably 700 to 100 parts by weight, more preferably 500 to 150 parts by weight.

As the curing agent to be added to the composition of the present invention, amino resins such as melamine formaldehyde, urea formaldehyde and the like;
Alkyl etherified amino resins etherified with lower alcohols such as ethanol; polyisocyanates such as isophorone diisocyanate and m-xylene diisocyanate; blocks obtained by introducing blocking agents such as alcohols such as methanol and phenols such as cresol into the polyisocyanates. Isocyanates; alkyl etherified phenolic resins such as allyl ether monomethylol phenol.

As the organic solvent to be added to the composition of the present invention, the above-mentioned glycol-based, glycol ether-based, acetate-based, alcohol-based, ketone-based, aromatic-based organic solvents and the like can be used.

Further, in the coating composition of the present invention, a pigment, a plasticizer, a colorant, a flow control agent, a curing accelerating catalyst, a foam suppressor, a thixotropic agent, an ultraviolet stabilizer, a filler, a surface may be added, if necessary. An appropriate amount of activator or the like can be added.

As the pigment to be added to the coating composition of the present invention, known inorganic and organic pigments can be used. Examples thereof include metal oxides such as titanium oxide, zinc oxide and iron oxide; metals such as aluminum flakes. Flake; carbon black and the like can be mentioned.

The coating composition obtained by the above method is
It can be applied to iron-based steel sheets such as galvanized steel sheets and non-ferrous steel sheets such as aluminum by a known method such as spray coating or roll coating. The coating composition of the present invention can be particularly preferably used as a coating for coating a precoated steel sheet.
It can also be used for applications other than coating such as composite materials and sealants.

When the coating composition of the present invention is used as a steel sheet primer, the topcoat is coated with a conventional coating composition. Examples of such paints include alkyd resin paints, polyester resin paints, thermosetting acrylic resin paints, vinyl resin paints, and silicone resin paints.

The coating composition of the present invention can also be used for can coating, especially for coating the inner surface of a can, as long as the diamine used is legally permitted.

[0042]

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following examples, "parts" and "%" are based on weight unless otherwise specified.

Synthesis Example of Polyamide Dicarboxylic Acid The dimer acid shown in Table 1 and the diamine having a cyclic skeleton were placed in a reaction vessel at the compounding ratio shown in Table 1, and heated under a nitrogen stream at 100 ° C. for 1 hour, 2 hours after 1 hour
The temperature was raised to 40 ° C., and the reaction was carried out at that temperature for 3 hours. The obtained polyamide dicarboxylic acid was diluted with an aromatic solvent (Solvesso 100; manufactured by Esso Standard Co., Ltd.) so that the nonvolatile content was 50%.

The properties of the obtained polyamide dicarboxylic acid are shown in Table 1. The amine value and the acid value are shown in terms of solid content.

Table 1 Synthesis example Polyamide Polymerized fatty acid Diamine Amine value Acid value Dicarboxylic acid (parts) (parts) mgKOH / g mgKOH / g 1 A halidimer 300 isophorone diamine 0.1 or less 92 (870) (130) 2 B halidimer 300 metaxylene diamine 0.1 or less 90 (894) (106) 3 C polyphenol 1004 Isophorone diamine 0.1 or less 73 (889) (111) 4 D Halidemer 300 Ethylene diamine 0.1 or less 91 (950) (50)

Examples 1 to 12 (Preparation of polyamide modified epoxy resin)
In a reaction vessel equipped with a condenser, diglycidyl ether of bisphenol A (DER 331L; trademark of The Dow Chemical Company), bisphenol A, polyamide dicarboxylic acid A obtained in the above synthesis example, Solvesso 100, Dowanol PMA and 70% of ethyltriphenylphosphonium acetate acetic acid complex as a catalyst
A methanol solution was introduced at the composition ratio shown in Table 1 and reacted at 160 ° C. under a nitrogen stream. After that, Dowanol PMA
/ Solvesso 100 / cyclohexanone (final weight ratio 1: 1: 1) is added to give a nonvolatile concentration of 35
%, Weight average molecular weight of about 30,000 (Examples 1, 4, 7
And 10), 35,000 (Examples 2, 5, 8 and 1)
1) 40,000 (Examples 3, 6, 9 and 12) polyamide-modified epoxy resin solutions were obtained.

Table 2 shows the composition ratios of the raw materials used in Examples 1 to 12.

Table 2 (unit: part) Example DER331L Bisphenol A Polyamido Solveso 100 Dawanol PMA Carboxylic Acid A 1-3 495 277 56 72 100 4-6 499 273 56 72 100 7-9 485 259 112 44 100 10-12 473 247 160 20 100

Comparative Examples 1 to 12 In the same manner as in Example 1 except that polyamidedicarboxylic acid D (ethylenediamine was used as the diamine) was used, the nonvolatile component concentration was 35%, and the weight average molecular weight was about 3.
50,000 (Comparative Examples 1, 4, 7 and 10), about 35,0
00 (Comparative Examples 2, 5, 8 and 11), about 40,000
A polyamide-modified epoxy resin solution containing a diamine having no cyclic skeleton of (Comparative Examples 3, 6, 9 and 12) was obtained.

Table 3 shows the viscosities of the polyamide-modified epoxy resin solutions obtained in Examples 1 to 12 and Comparative Examples 1 to 12 at 25 ° C.

Table 3 (unit: cst) Examples-Weight average molecular weight Weight average molecular weight Weight average molecular weight Comparative example 30,000 35,000 40,000 Examples 1-3 3,800 5,000 6,400 Examples 4-6 2,800 3,300 4, 100 Examples 7-9 2,300 2,700 3,100 Examples 10-12 2,100 2,300 2,700 Comparative Examples 1-3 6,800 8,700 11,000 Comparative Examples 4-6 2, 900 3,800 4,700 Comparative Examples 7-9 3,500 4,600 6,200 Comparative Examples 10-12 11,000 30,000 84,000

As is clear from the results shown in Table 3, the polyamide-modified epoxy resin prepared by using the diamine having a cyclic skeleton has a diamine having no cyclic skeleton when compared with those having the same molecular weight. It was found that the viscosity was remarkably lower than that of the polyamide-modified epoxy resin prepared by using. Therefore, the epoxy resin of the present invention can significantly reduce the amount of the organic solvent used as compared with the conventional case.

Examples 13-17 and Comparative Examples 13-14
(Preparation of coating composition) Using the raw materials shown in Table 4, a polyamide-modified epoxy resin was prepared in the same manner as in Example 1, and the obtained resin was used to prepare a coating composition having the following composition. did. Paint composition -Epoxy resin non-volatile components of Examples and Comparative Examples 118.7 parts-Cymel 303 (manufactured by Mitsui Cyanamid Co., Ltd.) 6.3 parts-Catalyst 6000 (manufactured by Mitsui Toatsu Chemicals, Inc.) 0.6 part-Titanium White ( CR-95, Ishihara Sangyo Co., Ltd.) 125.0 parts-Solvesso 100 250.0 parts-Dowanol PMA 250.0 parts-Cyclohexanone 250.0 parts

Table 4 Example, raw materials of type and amount Comparative Example DER331L bisphenol A port Riamito Bu Shi Bu Soruhe Bu Tsu source data Bu Wanoru Karubonsan 100 PMA Example 13 495 277 A: 56 72 100 Example 14 485 259 A: 112 44 100 Example 15 495 277 B: 56 72 100 Example 16 499 273 B: 56 72 100 Example 17 493 279 C: 56 72 100 Comparative Example 13 495 277 D: 56 72 100 Comparative Example 14 485 259 D: 112 44 100

Physical Properties Test The coating compositions obtained in Examples 13 to 17 and Comparative Examples 13 to 14 were applied to a 0.7 mm thick galvanized steel sheet with a bar coater so that the dry film thickness was 5 μm, and the coated steel sheet was coated. A sample was prepared by baking so that the temperature was heated from room temperature to 210 ° C. in 60 seconds. Using the samples thus obtained, the following flexibility test, pencil hardness test, solvent resistance test and corrosion resistance test were performed.

(Flexibility test) The obtained test piece was bent so that the coated surface was on the outside, and a plurality of 0.7 mm-thick spacers were sandwiched between the bent parts and pressed, and then 15
The damage of the processed part was observed with a magnifying glass. After sequentially reducing the spacers one by one, the same operation was repeated, and the flexibility was evaluated by the minimum number (T) of the spacers in which no damage was observed in the coating film.

(Pencil hardness test) The hardness of the coating film is measured according to JIS K.
It was measured based on 5401.

(Solvent resistance) A gauze of a rubbing tester to which a load of 2 pounds (906 g) was soaked with xylene was rubbed with the coating film, and the number of times until the surface of the steel sheet was exposed was measured. The solvent resistance was evaluated by a three-level evaluation. ◎: 150 times or more ○: 100 times or more X: Less than 100 times

(Corrosion resistance) 4 test pieces were placed in a salt spray tester.
After standing for 80 hours, the ratio (%) of the area where rust occurred to the entire area was measured, and the corrosion resistance was evaluated by the following three-stage evaluation. ◎: Less than 5% ○: Less than 10% X; 10% or more

Table 5 shows the above test results.

Table 5 Epoxy equivalent Flexibility Pencil hardness Solvent resistance Rust resistance Example 13 4,400 3T 5H ◎ ○ Example 14 3,400 3T 4H ○ ◎ Example 15 4,300 4T 6H ◎ ○ Example 16 3,300 4T 6H ◎ ◎ Example 17 4,700 2T 4H ○ ◎ Comparative Example 13 4,500 4T 4H ○ X Comparative Example 14 3,500 4T 4H XX

As is clear from the results shown in Table 5, coating compositions containing a polyamide-modified epoxy resin prepared by using a diamine having a cyclic skeleton (Examples 13 to 17)
The coating film made of was superior to the coating film made of the coating composition (Comparative Examples 13 and 14) containing the polyamide-modified epoxy resin prepared using a diamine having no cyclic skeleton, in terms of flexibility, hardness and resistance. It was found that both solvent resistance and corrosion resistance were remarkably improved.

[0063]

As described above, the coating composition of the present invention can provide a coating film having improved physical properties such as flexibility, rust resistance, hardness and chemical resistance in a well-balanced manner. is there. Further, since the epoxy resin of the present invention has a low viscosity as compared with the conventional polyamide-modified epoxy resin, it brings about an improvement in workability and also meets the requirement for environmental improvement of high solidification of the coating, It is extremely useful industrially.

Claims (7)

[Claims] 1. An epoxy resin having (a) an average of more than one adjacent epoxy groups per molecule; and (b) a polymerized fatty acid and a diamine having a cyclic skeleton,
A polyamide dicarboxylic acid having an amine value of 0 to 20 and an acid value of 20 to 200, which is obtained by reacting at a molar ratio of 2: 1.0 to 1.9, is added to all components (a) and (b). On the other hand, a polyamide-modified epoxy resin having an acid value of 0 to 5, which is obtained by reacting the component (b) in an amount ratio of 0.1 to 50% by weight. 2. The polyamide-modified epoxy according to claim 1, which is obtained by reacting, in addition to the components (a) and (b), a phenol compound having an average of more than one hydroxyl group per molecule as the component (c). resin. 3. The polyamide-modified epoxy resin according to claim 1, wherein the component (a) is selected from glycidyl ethers of bisphenol A, bisphenol K, bisphenol F, bisphenol S, bisphenol AD and mixtures thereof. 4. The polymerized fatty acid of component (b) is oleic acid,
The polyamide-modified epoxy resin according to claim 1, which is selected from elaidic acid, cetoleic acid, sorbic acid, linoleic acid, linoleic acid and arachidonic acid. 5. The diamine of component (b) is menthenediamine, metaxylenediamine, isophoronediamine, diaminocyclohexylmethane, metaphenylenediamine,
The polyamide-modified epoxy resin according to claim 1, which is a diamine having at least one cyclic skeleton selected from diaminodiphenylmethane. 6. A coating composition containing the resin according to claim 1 and at least one curing agent. 7. The coating composition according to claim 6, further comprising at least one organic solvent.