JPH04161471A - Coating composition for precoat steel plate and primer composition - Google Patents

Abstract

PURPOSE:To obtain a coating composition for precoat steel plate containing a specific epoxy resin, a curing agent and an organic solvent and having excellent workability, heat stability, rust proofing property, adhesion with steel plate, stain resistance, etc. CONSTITUTION:The objective composition containing (A) an epoxy resin obtained by reacting (i) an epoxy resin having one or more adjacent epoxy groups per molecule with (ii) a phenol compound having one or more hydroxyl groups per molecule and (iii) a polyamidedicarboxylic acid obtained by reacting polymerized fatty acid based on a dimmer acid with a diamine and having <=20 amine value and 20-200 acid value at an amount ratio of the component (iii) of 0.1-50wt.% based on the total amount of these components i, ii and iii and having 500-10000 epoxy equivalent weight, 1000-100000 weight-average molecular weight and <=5 acid value, (B) a curing agent and (C) an organic solvent.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a coating composition and a primer composition for pre-coated steel sheets, and more specifically, after curing, the present invention relates to coating compositions and primer compositions for pre-coated steel sheets. The present invention relates to a coating composition for a good pre-coated steel plate and a primer composition for a steel plate having excellent secondary adhesion.

[Prior Art] Conventionally, steel plates used as materials for home appliances such as washing machines, furniture such as lockers, and vending machines used outdoors have been processed into steel plates in an unpainted state based on their respective uses. It was processed, molded, and finally painted. However, in recent years,
With the aim of increasing productivity, improving quality, diversifying designs, improving the work environment, saving space, etc., there is a lot of research into pre-coated panels, which are sheared, processed, and formed after painting a flat steel plate. .

Here, regarding the paint used for pre-coated steel sheets,
The coating film is required to have workability that can withstand shearing and processing, adhesion to the steel plate, and rust prevention and thermal stability after forming. However, since the color of the copper plate adversely affects the color of the top coat, such paints are usually applied via a white primer. In this case, secondary adhesion is required for the primer.

Conventionally, acrylic L polyester resin has been used as a top coat and epoxy resin as a primer for painting home appliances and the like. Such epoxy resins include D, E, R664; D, E, R.

General purpose bisphenol A type epoxy resins such as 667i D, E, R, 669 (all trademarks of The Dow Chemical Company) were used.

Acrylic resin paints have been used because they have excellent hardness and stain resistance, but it is difficult to obtain processability that satisfies use on pre-coated copper plates. Regarding polyester resin, currently,
Although it has been put into practical use as a paint for pre-coated steel sheets, it maintains a good balance between the contradictory properties of workability and rust prevention.
It is difficult to say that it has properties that fully satisfy market demands.

In addition, conventional epoxy resins have excellent rust prevention properties but poor weather resistance, so they are used as the back coating of pre-coated copper plates or as primers, and other epoxy resins such as polyester are used as top coats. Resin-based paint is used. However, at present, paints and primers with properties that are fully satisfactory for applications such as home appliances that require high workability and excellent secondary adhesion have not yet been obtained.

[Problems to be Solved by the Invention] The present invention was developed in view of the problems of the prior art described above, and its purpose is to have rust prevention properties comparable or improved to those of conventional epoxy resins, and to have processability. Another object of the present invention is to provide a coating composition for pre-coated steel plates that has excellent thermal stability and adhesion, and a primer composition for steel plates that has excellent secondary adhesion.

[Means for Solving the Problem] According to the present invention, in order to achieve the above object, (a-1
) Epoxy resins with an average of more than one vicinal epoxy group per molecule; (a-2) average II per molecule! a phenol compound having more hydroxyl groups; and (a-3) an amine value of 20 or less obtained by reacting a polymerized fatty acid mainly based on dimer acid and a diamine at a molar ratio of 2:1.0 to 1.9. and 20-200
Polyamide dicarboxylic acid having an acid value of
) in a quantitative ratio of 0.1 to 50% by weight, which has an epoxy equivalent of 500 to 10.000, a weight average molecular weight of 1.000 to 100,000, and an acid value of 5 or less. A coating composition for a precoated steel plate and a primer composition for a steel plate are provided, each comprising an epoxy resin; (b) at least one curing agent; and (c) at least one organic solvent.

In the present invention, a known epoxy resin is used as the epoxy resin used as component (a-1).

The preferred epoxy resin used here has an epoxy equivalent of 170 to 3.5 QO1, more preferably 175 to 1,
000, and the weight average molecular weight is 340-18,00
0.

More preferably, it is 340 to 3,000. As the epoxy resin of component (a-1), for example, JP-A-1
- Publication No. 153715, especially page 5, top left, second line ~
The epoxy resins listed on the bottom right of the question page - line 8 can be used.

More specifically, epoxy resins having an average of more than 1 and less than 3 adjacent epoxy groups per molecule are suitable, such as bisphenol A, bisphenol, bisphenol F, bisphenol S1 and suphenol AD.
and diglycidyl ethers of mixtures thereof. The most preferred epoxy resin is diglycidyl ether of bisphenol A.

Examples of commercially available epoxy resins include D, E, and R.

331L; D, E, R, 383 D, E, R, 66
1; D, E, R, 664; D, E, R, 667; D
, E, R, 669 (all commercial products of The Dow Chemical Company, WA), etc. can be used.

In the present invention, as the phenol compound used as component (a-2), those known as raw materials for epoxy resins are used. As the phenol compound of component (a-2), for example, JP-A No. 1-153715,
In particular, those described in the 7th line of the upper left column of the 6th page to the 3rd line of the lower right column of the same page can be used. More specifically, phenolic compounds having an average of more than 1 and less than 3 hydroxyl groups per molecule are suitable, such as bisphenol A, bisphenol K, bisphenol F, bisphenol S
, bisphenol AD and mixtures thereof. The most preferred phenolic compound is bisphenol A
It is.

The weight ratio of component (a-1) and component (a-2) is preferably 60:40 to 99:1, more preferably 6140 to 99:1.
90:10, preferably 60:40-8
They are mixed at a ratio of 0:20. Here, component (a-2) is 40
If the weight percentage is exceeded, the OH groups of the phenolic compound will be in excess of the epoxy groups, and the resulting product will have fewer epoxy groups, thereby losing the good performance characteristic of epoxy resins. In addition, when component (a-2) is 1% by weight ungrooved, the product mainly obtained is a polymerization reaction between the epoxy resin as component (a-1) and the polyamide dicarboxylic acid as component (a-3). This product does not have sufficient crosslinking density in the reaction with the curing agent, and the resulting coating film is inferior in processability and hardness.

Component (a-3) used in the present invention mainly consists of a polymerized fatty acid based on dimer acid and a diamine in a ratio of 2:1.
．． 2 obtained by reacting at a molar ratio of 0 to 1.9.
0, preferably 10 or less, and 20 to 200
More preferably, it is a polyamide dicarboxylic acid having an acid value of 80 to 100.

The polymerized fatty acid used here preferably contains a dimer of unsaturated fatty acid (dimer acid) in an amount of 70% by weight, more preferably 95% by weight or more, and the remaining amount includes a monomer or a trimer. The unsaturated fatty acid is preferably a carboxylic acid compound having 12 to 24 carbon atoms (including the carbon atoms of the carboxyl group) and having one or more unsaturated bonds in one molecule. Examples of fatty acids with one unsaturated bond include oleic acid, elaidic acid, and cetoleic acid; examples of fatty acids with two unsaturated bonds include sorbic acid, linoleic acid, etc. Examples of the above fatty acids include liluic acid and aragidonic acid.

In the present invention, a commercially available polymerized fatty acid, for example, Hallidimer 300. Haridimer 200 (both manufactured by Layatsu Kasei Kogyo Co., Ltd.), Persadime 288 (manufactured by Henkel Hakusuisha)
etc. can be used.

In the present invention, the diamine includes ethylenediamine, 4,4-methylene dianiline, H-oleyl-
Known diamines such as 1,3-propanediamine can be used.

The reaction between polymerized fatty acids and diamines is 2F1.0-1.9
At a molar ratio of , while removing water as a by-product,
This can be carried out based on known polymerization methods.

If the molar ratio of diamine is less than 1.0, the concentration of carboxyl groups will be higher than the concentration of amide groups, and the resulting resin will have poor processability. When the molar ratio of 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, if the amine value exceeds 20, the viscosity of the resulting paint or primer becomes too high, which adversely affects workability. Regarding the acid value, if it is less than 20, the molecular weight of the resulting resin will be too large (eg, weight average molecular weight io, ooo or more) and the solubility in organic solvents will be insufficient. Acid value is 20
It is difficult to synthesize one with a value exceeding 0, considering the acid value of the polymerized fatty acid that is the raw material.

The component (a-3) obtained as described above is 0.1 to 50% by weight based on the total solid content (total amount of components (a-1), (a-2) and (a-3)), Preferably, it can be blended in an amount of 1 to 20% by weight.

When the proportion of component (a-3) exceeds 50% by weight,
It becomes impossible to obtain sufficient hardness as a paint or primer for pre-coated steel sheets. Furthermore, when the proportion of component (a-3) is less than 0.1% by weight, the properties of the resulting paint or primer are no different from those of conventionally used epoxy resins.

In the present invention, the above components (a), (b) and (c)
The polyamide epoxy ester resin obtained by reacting has an epoxy equivalent of 500 to 10,000, preferably 1.000 to 5,000, and an acid value of 5 or less, preferably 2 or less. This polyamide epoxy ester resin has a molecular weight of 1.000 to 100,000, preferably 10.
000~so,oo.

It has a weight average molecular weight of Its epoxy equivalent is 500
If it is less than that, the concentration of secondary hydroxyl groups, which are said to contribute to adhesion and adhesion, becomes too low, making it impossible to obtain sufficient adhesion, processability, and stain resistance. Epoxy equivalent is 10,0
When it exceeds 00, wettability deteriorates.

Furthermore, if the acid value exceeds 5, high processability, which is one of the characteristics of the present invention, cannot be achieved due to the carboxylic acid present at the molecular chain ends. Therefore, the closer the acid value is to O, the more desirable it is.

The polyamide epoxy ester resin used in the present invention can be prepared by appropriately reacting the above components (a), (b) and (c). For example, except for adjusting the blending ratio of each component to a range suitable for the steel plate of the present invention, the specification of Japanese Patent Application No. 1-107,799, page 9, line 11 to
It can be manufactured by referring to the method described on page 16, line 12.

In the present invention, when producing a high molecular weight polyamide epoxy ester resin, it is possible to introduce an organic solvent into the reaction system in order to prevent the polymerization reaction system from becoming non-uniform due to its high viscosity. Solvents that can be used in the polymerization reaction system include those that have high solubility in the epoxy resin and have a boiling point of 1.
An inert organic solvent having a temperature of 20°C or higher, preferably 140°C or higher is desirable. Examples of such organic solvents include glycol-based solvents such as ethylene glycol and propylene glycol:
Glycol monoether solvents such as Dowanol EB, Dowanol PnB (both trademarks of The Dow Chemical Company); butyl acetate, Dowanol PMA (both trademarks of The Dow Chemical Company);
Acetate solvents such as Dow Chemical Company (trademark); Alcohol solvents such as amyl alcohol and cyclohexanol; Ketone solvents such as cyclohexanone and diisobutyl ketone; Aromatic solvents such as xylene and Trupetz 100 (manufactured by Esso Standard) Solvents can be used. Among these, acetate solvents and aromatic solvents are particularly desirable. These solvents can be used alone or in combination of two or more, but if a solvent containing a hydroxyl group is used at a high concentration, an esterification reaction will occur between the carboxyl group and the hydroxyl group in the reaction system, resulting in the formation of oligomers. Because the amount increases, solvents containing hydroxyl groups account for 5% of the total solids.
It is preferable that it is less than % by weight.

The polyamide epoxy ester resin used in the present invention can be used in combination with commonly used epoxy resins to the extent that its properties are not impaired.

In the present invention, a coating composition or a primer composition can be prepared by blending a curing agent, an organic solvent, etc. with the polyamide epoxy ester resin obtained as described above.

The composition of the present invention preferably has a weight ratio of the polyamide epoxy ester resin to curing agent of 70:30 to 9.
8:2, preferably 80:20 to 95:5, and the organic solvent is 700 parts by weight per 100 parts by weight of solid content (total weight of polyamide epoxy ester resin and curing agent) in the composition. ~100 parts by weight, preferably 5
00 to 150 parts by weight.

Examples of curing agents that can be incorporated into the composition of the present invention include amino resins such as melamine/formaldehyde and urea/formaldehyde; alkyl etherified amino resins obtained by etherifying the amino resin with lower alcohols such as methanol and ethanol; isophorone diisocyanate; (2) Polyisocyanates such as xylene diisocyanate; Blocked isocyanates in which a blocking agent such as an alcohol such as methanol or a phenol such as cresol is introduced into the polyisocyanate; and alkyl etherified phenol resins such as allyl ether monomethylol phenol.

As the organic solvent to be added to the composition of the present invention, the aforementioned glycol-based, glycol monoether-based, alcohol-based, ketone-based and aromatic organic solvents can be used.

In addition, appropriate amounts of pigments, plasticizers, colorants, flow control agents, and catalysts for accelerating curing may be added to the composition of the present invention, if necessary.

The coating composition or primer composition obtained by the above method can be applied to a ferrous steel plate such as a galvanized steel plate or a non-ferrous steel plate such as aluminum by a known method such as spray coating or roll coating.

The coating composition of the present invention is excellent in processability, thermal stability, rust prevention, etc., and is particularly suitable for use in coating the back surface of pre-coated steel sheets.

Further, since the composition of the present invention has good secondary adhesion as a primer, it can be suitably used as a primer composition for steel plates. In this case, an ordinary paint is roughly applied as a top coat onto the primer film provided on the steel plate. Examples of such paints include alkyd resin paints, polyester resin paints, thermosetting acrylic resin paints, vinyl resin paints, and silicone resin paints. Among these, polyester resin paints have particularly good adhesion to the primer of the present invention;
Suitably used.

[Examples and Comparative Examples] Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to these Examples.

In addition, in the following examples, unless otherwise specified, parts and percentages are based on weight. Moreover, the epoxy equivalent in the examples was measured based on JIS 7236.

Polyamide dicarbonate C36-dimer a! ! (Haridimer 300 [manufactured by Harimaro Kasei Kogyo Co., Ltd. 1; monomer 1%, dimer 97%, trimer 2%, acid value 195] 950 parts and 53 parts of ethylenediamine were placed in a reaction chamber, under a nitrogen stream, without catalyst, at 60°C.
The mixture was heated for 30 minutes, then heated to 240°C over 2 hours, maintained at that temperature for 3 hours, and then left to cool to room temperature.

The obtained polyamide carboxylic acid A had an amine value of 1 and an acid value of 91.

Examples 1 to 5 (4 sets of coating) Bisphenol A type liquid epoxy resin (D, E, R.

331Li (trademark of The Dow Chemical Company),
Bisphenol A and polyamide dicarboxylic acid A prepared as described above were blended in the amounts shown in Table 1, and 200 parts of Zurpetz 100 (propylene glycol monomethyl ether acetate) as an organic solvent and ethyl triphenyl as a catalyst were added. 0.7 part of carbonium acetate (70% solution) was added, and the resulting mixture was placed in a reaction vessel, heated to 160° C. under a nitrogen stream, and reacted for about 3 hours.

1st Table, E, R, 331 Bis A Polyamitracarlinic acid--Tatehoshi>W discharge-1 engineer and m-1 Example 1 496 276 28 Example 2 494 278 28 Example 3
510 250 40 Example 4 48
5 259 56 Examples 5 480
264 56 Next, add the above solvent and cool it,
A polyamide epoxy ester resin having the properties shown in Table 2 was obtained. Note that the amination and acid value of the obtained resin were both approximately O.

Table 2 Epoxy equivalent Weight average weight Example 1 3,500 35.000 Example 2 3,800 40.000 Example 3 2.200 20.000 Example 4 2, 900 28, 000 Example 5 3, 800 40.000 Using the thus obtained resin, coating compositions A-E (Examples 1 to 5) having the following composition 1 were prepared.

JLJL-1, epoxy resin solid content of each example -1-95 parts 2
, Cymel 303 (methylated melamine; manufactured by Mitsui Cyanamid Co., Ltd.) solid content -1-5 parts 3, Tsurpets 100 (
(manufactured by Esso Standard Company) ---130 parts 4, Dauanol PMA (manufactured by The Dow Chemical Company) ---130 parts 5, cyclohexanone -130 parts 1 and 2 Instead of polyamide epoxy ester resin, Each, E, R, 667, and E, Ii! Coating compositions F and G (Comparative Examples 1 to 2) having the above composition 1 were prepared in the same manner, except that .

Baa! -5- The coating compositions A to G of each of the above Examples and Comparative Examples were formed into a coating film as described below, and the processability and thermal stability of the obtained coating film were evaluated.

(Workability test) Coating compositions A-G were applied to a 0.6 mm thick galvanized steel plate using a percoater so that the dry film thickness was 5 μ■.
It was baked at 210°C for 1 minute.

Bend the obtained test piece so that the primer side faces outward, and place a 0.6mm thick spacer between the bent parts.
After inserting the sheet and pressing it with a vise, damage to the processed portion was observed using a 15x magnifying glass. The same operation was carried out by increasing the number of spacers one by one, and workability was evaluated based on the minimum number (T) of spacers in which no damage was observed. The results are shown in Table 3.

(Thermal stability test) The test piece obtained as described above was subjected to TGA (Thermo Stability Test).
40 from room temperature using Gravimetric Analyzer)
The temperature was raised to 0° C., and the percent weight loss of the coating film at that time was measured. The results are shown in Table 3.

Table 3 Examples Paint Processability Thermal Stability No. Composition Uni Ura L-Real I A I
T 8 real 2 B 2T 9 real 3
C3T 9 Real 4 D 2T 9 Real 5
E IT 7 ratio I F
>47 >20 ratio 2 G 3T
19 From the results shown in Table 3, it was found that the coating films formed by the coating compositions according to the present invention (Examples 1 to 5) had excellent processability and thermal stability.

Examples 6 to 10 (primer composition) Using the polyamide epoxy resins obtained in Examples 1 to 5, a primer composition H- having the following composition 2 was prepared.
L was prepared.

庙-盈-λ 1, Epoxy resin solid content of each example --- 85 parts 2
, MG to 110(2) (Blocked isocyanate; manufactured by Mitsubishi Kasei Corporation) Solid content -1-15 parts 3, Tsurpets 1
00 (manufactured by Etsuso Standard) ---190 copies 4
, Downol PMA (manufactured by The Dow Chemical Company) ---190 parts 5, cyclohexanone-m-190 parts 3 and 4 D in place of polyamide epoxy ester resin.

A primer composition having the above composition 2 was prepared in the same manner as in Examples 6 to 10, except that E, R, 667, and E, R, 669 (all trademarks of The Dow Chemical Company) were used. Monoma and N were prepared.

Nu1-N2 The primer compositions H to N of each Example and each Comparative Example were formed into a coating film as described below, and the resulting coating film was evaluated for rust prevention properties and adhesion to a copper plate. In general, physical properties such as secondary adhesion when a top coat was applied on top were evaluated.

(Rust prevention test and adhesion test) Primer composition H-N was applied to a galvanized steel plate with a thickness of 0.8 to 1 using a bar coater so that the dry film thickness was 3μI, and was heated at 150°C for 1 minute. Burnt it.

After cross-cutting the obtained test piece based on JIS K5400, it was tested using a salt spray tester (manufactured by Suga Test Instruments Co., Ltd.).
After 300 hours, the width of the bulge from the cross-cut portion was measured. The results are shown in Table 4.

In addition, JISK5 was added to the test piece obtained as described above.
Based on 400, 1+s 鳳X 1+*+i (100
? (7) Goblin stitches were created using an NT cutter, and a tape peeling test was conducted using Nichiban tape. The results are shown in Table 4.

On the primer surface of the test piece obtained as described above (before cross-cutting), a top coat paint having the following composition was roughly applied using a bar coater so that the total dry film thickness was 20 μ■. It was baked at 230°C for 1 minute.

Composition of top coat 1, Pylon 300 (copolymerized polyester; manufactured by Toyobo Co., Ltd.) ---80 parts 2, Seitul 303 (methylated melamine; manufactured by Mitsui Cyanamid Co., Ltd.) Solid content -m-20 parts 3, Titanium white
-1-30 parts 3, Turupetz 150 (manufactured by Esso Standard) ---200 parts 4, Dauanol PMA (manufactured by The Dow Chemical Company) ---200 parts 5, cyclohexanone ---200 parts (Secondary adhesion test) The thus obtained test piece was immersed in boiling water for 2 hours, and the peeling M of the coating film was visually observed to evaluate the secondary adhesion. The results are shown in Table 4. In the table, those in which peeling could not be visually observed were marked as 'OJ', and those in which peeling could be observed were marked as "x".

Table 4 Examples Primer rust prevention properties Secondary bonding with copper plate
Niho Tsume 1 (an) Adhesion Adhesion Fruit 6 8
1.5 10 0 fruit? I
1.1 10 0 real 8 J
1.5 10 0 actual 9 K 1.8
100 real 10L 1.5
10 0 ratio 3 M 3.0 1
0 X ratio 4 N 2.0 1
From the results shown in Table 4, Examples 6 to 1
It was found that the primer made of the primer composition of the present invention according to No. 0 was excellent in all of rust prevention, adhesion to steel plate, and secondary adhesion.

[Effects of the Invention] As is clear from the above description, according to the present invention, a coating composition for pre-coated steel sheets with excellent workability, thermal stability, rust prevention, adhesion to steel sheets, etc. can be provided. Further, according to the present invention, a primer composition for steel sheets is provided that is excellent in all of the properties necessary for a primer, such as workability, thermal stability, rust prevention, adhesion to top coat and steel sheet, and secondary adhesion. provided.

Claims (1)

[Scope of Claims] 1. (a-1) An epoxy resin having an average of more than one adjacent epoxy group per molecule; (a-2) A phenol compound having an average of more than one hydroxyl group per molecule; and (a- 3) Amine value of 20 or less and 20 to 200 obtained by reacting a polymerized fatty acid mainly based on dimer acid and a diamine at a molar ratio of 2:1.0 to 1.9.
Polyamide dicarboxylic acid having an acid value of
) in a quantitative ratio of 0.1 to 50% by weight, which has an epoxy equivalent of 500 to 10,000, a weight average molecular weight of 1,000 to 100,000, and an acid value of 5 or less. A coating composition for a precoated steel sheet, comprising: an epoxy resin; (b) at least one curing agent; and (c) at least one organic solvent. 2. The coating composition according to claim 1, wherein the component (a-1
) is selected from diglycidyl ethers of bisphenol A, bisphenol K, bisphenol F, bisphenol S, bisphenol AD and mixtures thereof. 3. In the coating composition according to claim 1, the component (a-2
) is selected from diglycidyl ethers of bisphenol A, bisphenol K, bisphenol F, bisphenol S, bisphenol AD and mixtures thereof. 4. The coating composition according to claim 1, wherein the component (a-3
), wherein the polymerized fatty acid is a dimer of fatty acids selected from oleic acid, elaidic acid, cetoleic acid, sorbic acid, linoleic acid, linoleic acid, and aragidonic acid. 5. The coating composition according to claim 1, wherein the component (a-3
A coating composition in which the diamine of ) is selected from ethylene diamine, 4,4-methylene dianiline, N-oleyl-1,3-propanediamine and mixtures thereof. 6. (a-1) Epoxy resins having an average of more than one adjacent epoxy group per molecule; (a-2) Phenolic compounds having an average of more than one hydroxyl group per molecule; and (a-3) mainly containing dimer acids. An amine value of 20 or less and 20 to 200 obtained by reacting a polymerized fatty acid and a diamine at a molar ratio of 2:1.0 to 1.9.
Polyamide dicarboxylic acid having an acid value of
) in a quantitative ratio of 0.1 to 50% by weight, which has an epoxy equivalent of 500 to 10,000, a weight average molecular weight of 1,000 to 100,000, and an acid value of 5 or less. A primer composition for a steel sheet, comprising: an epoxy resin; (b) at least one curing agent; and (c) at least one organic solvent.