JPH0689290B2 - Paint composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a coating composition which is soluble in mineral spirits and which gives a coating film excellent in corrosion resistance, adhesion, flexibility and the like.

<Prior Art and Problems to be Solved> Epoxy resins have been widely used as resins for anticorrosion paints because of their excellent corrosion resistance, adhesion, chemical resistance and the like. When such an epoxy resin is used as a paint, it is generally used by dissolving it in an organic solvent, but the organic solvent that dissolves the epoxy resin is usually a low flammability typified by toluene, xylene, methyl ethyl ketone, ethyl acetate, etc. point,
It was a solvent with a low boiling point and high toxicity. Therefore the painting environment,
There is a problem in coating workability, and when it is applied on an old paint film as a paint for repairing the old paint film, there is a problem that the old paint film is dissolved or swelled and a film defect such as lifting occurs.

Therefore, it is conceivable to use mineral spirit or the like, which has a high flash point, a high boiling point and low pollution, as an organic solvent which does not have the above-mentioned problems.

However, conventional epoxy resins for paints are hardly soluble in mineral spirits.

The present inventors have arrived at the present invention as a result of earnestly studying to develop an epoxy resin for paints that is soluble in mineral spirits in view of such a situation.

<Means for Solving the Problems> That is, the present invention relates to a coating composition containing a modified epoxy resin, a curing agent for the modified epoxy resin, and an organic solvent, wherein the modified epoxy resin is (a) in one molecule. An epoxy resin having two or more epoxy groups and having an average epoxy equivalent of about 250 or less, and (b) an aliphatic monocarboxylic acid are used, when the equivalent ratio of the carboxyl group of the carboxylic acid and the epoxy group of the epoxy resin is (1: The reaction product (i) obtained by reacting the diisocyanate compound (ii) at a ratio of 1.8 to 2.5) has an equivalent ratio of the hydroxyl group of the reaction product to the isocyanate group of the diisocyanate compound (1:
The coating composition is a modified epoxy resin obtained by reacting at a ratio of 0.8 to 1.2), and the organic solvent is mineral spirit or an organic solvent containing mineral spirit as a main component.

Since the modified epoxy resin used in the present invention is soluble in mineral spirits, the paint combined with the mineral spirits and the curing agent has good coating environment and painting workability, and even if it is applied over the old coating, Without dissolving or swelling, a coating film defect such as lifting can be prevented from occurring, and a coating film having good corrosion resistance, adhesion and flexibility can be obtained.

Hereinafter, the present invention will be described in detail.

The epoxy resin (a) used in the present invention has 2 in one molecule.
Has more than one epoxy group and has an average epoxy equivalent of about 25
It is an epoxy resin of 0 or less. If the average epoxy equivalent exceeds 250, the solubility of the resulting modified epoxy resin in mineral spirits decreases, which is not preferable.

Examples of such epoxy resin (a) include Epotote YD-128, YD-134, YD-011, and YD manufactured by Tohto Kasei Co., Ltd.
Bisphenol A marketed under the trade name such as -014
Epichlorohydrin type; Bisphenol F / epichlorohydrin type marketed under the trade name of Epichron 830 manufactured by Dainippon Ink and Chemicals; EPOM manufactured by Mitsui Petrochemical
Typical examples are AD type epoxy resins marketed under the trade names of IK R-710 and the like, but the present invention is not limited thereto.

The epoxy resin (a) is said to have an average epoxy equivalent of about 250 or less. However, for example, a mixture of epoxy resins having an average epoxy equivalent of 250 or less even if an epoxy resin having an epoxy equivalent of about 500 is used together. If so, it can be used.

The aliphatic monocarboxylic acid (b) used in the present invention is a dry oil fatty acid or a semi-dry oil fatty acid, and specifically, tall oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, dehydrated castor oil fatty acid, cottonseed oil fatty acid, Typical examples include safflower oil fatty acid, tung oil fatty acid, palm oil fatty acid, palm oil fatty acid, and the like, and saturated fatty acids such as octylic acid and neodecanoic acid and petroleum-based synthetic acids can also be used in combination.

Typical examples of the diisocyanate compound used in the present invention include tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and tetramethylene diisocyanate.

Next, a typical method for producing the modified epoxy resin used in the present invention will be described.

First, the epoxy resin (a) and the aliphatic monocarboxylic acid (b) are heated in a mineral spirit in the presence or absence of a catalyst to about 100 to 200 ° C. to obtain an acid value of 2 mgK.
React until OH / g or less. Examples of the catalyst include alkali catalysts such as sodium mercuride, potassium mercuride and lithium mercurate; amines such as triethylamine and tripropylamine or amine salt catalysts thereof; tetramethylammonium bromide, tetramethylammonium chloride, tetraethylammonium bromide. A quaternary ammonium salt catalyst such as tetraethylammonium chloride can be used as a typical one.

The reaction between the two must be carried out at a ratio such that the equivalent ratio of the carboxyl group of the monocarboxylic acid (b) and the epoxy group of the epoxy resin (a) is (1: 1.8 to 2.5). When the epoxy group equivalent is smaller than the above range, the original coating film performance of the epoxy resin cannot be exhibited, and the corrosion resistance and the like decrease.
On the other hand, if it is too large, the solubility in mineral spirits decreases, making it impossible to achieve the object of the present invention.

In the reaction product (i) thus obtained, a hydroxyl group is generated by ring opening of the epoxy group, and the diisocyanate compound (ii) is reacted with the hydroxyl group. That is, the reaction product (i) solution is heated to 40 to 80 ° C., the diisocyanate compound (ii) is dropped therein, and both are reacted to produce a modified epoxy resin.

The reaction between the two must be carried out at a ratio such that the equivalent ratio of the hydroxyl group of the reaction product (i) and the isocyanate group of the diisocyanate compound (ii) is (1: 0.8 to 1.2). If the isocyanate group equivalent is less than the above range, it is difficult to be a polymer resin, the coating performance is deteriorated, while if it is too large, the viscosity of the varnish increases, the stability deteriorates, and the solubility in mineral spirits decreases, All of them are not preferable because the coating material aimed at by the present invention cannot be obtained.

The coating composition of the present invention is a modified epoxy resin produced by the above-described method, an organic solvent containing mineral spirit or a main component thereof, a curing agent, and if necessary, a coloring pigment, an extender pigment, a rust preventive pigment, It is a mixture of high quality resin and additives.

As the organic solvent, mineral spirits may be used alone, and if necessary, a small amount of organic solvents such as solvent naphtha, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, etc. which have been commonly used from the past may be used in combination. Is also possible.

As the curing agent, those conventionally used as a curing agent for epoxy resins can be used without particular limitation, for example, triethylenetetramine, metaxylenediamine,
Representative examples include amines such as diaminodiphenylmethane and isophoronediamine, and polyamide resins.

<Effects of the Invention> Since the coating composition of the present invention uses a modified epoxy resin soluble in mineral spirits, which has a high flash point, a high boiling point, and low pollution, it can be made into a coating by the solvent, and therefore Good coating environment and coating workability, and even if it is applied repeatedly for repairing the old coating film, it does not dissolve or swell the old coating film, and a coating film excellent in corrosion resistance, adhesion, flexibility, etc. is obtained, It can exhibit various excellent coating film performance that could not be achieved with conventional epoxy resin paints.

Hereinafter, the present invention will be described in more detail with reference to Examples. In the examples, "part" and "%" are based on weight.

Examples 1 to 5 and Comparative Examples 1 to 5 In a reactor equipped with a thermometer, a stirrer and a reflux condenser, mineral spirits (amount of 70% as nonvolatile content), epoxy resin and aliphatic monocarboxylic acid were added first. Charge at the ratio shown in the table, raise the temperature to about 110 ° C, add 0.01% of potassium hydroxide to the total resin amount with stirring, and then add 150 ° C.
The temperature is increased to 2 hours and kept at the same temperature for 3 hours.
After confirming the following, the temperature was cooled to 40 ° C. At the same temperature, the diisocyanate compound was added dropwise at the ratio shown in Table 1,
A modified epoxy resin (70% mineral spirit solution) varnish was produced by reacting until no absorption of -NCO was observed with an infrared spectrophotometer.

The properties of the resulting modified epoxy resin are shown in Table 1.

As is clear from Table 1, Examples 1 to 5 which are varnishes of the modified epoxy resin used in the present invention have good transparency,
It had good storage stability (that is, it was well dissolved in mineral spirits).

On the other hand, the equivalent ratio (epoxy group / carboxyl group) is 2.5 / 1
Comparative Example 1 using a reaction product (i) exceeding 50%, Comparative Example 3 using a modified epoxy resin having an epoxy equivalent exceeding 250, and a modified epoxy resin composition having an equivalent ratio (hydroxyl group / isocyanate group) of less than 1 / 1.2. Comparative Example 5 was turbid and had poor storage stability and could not be practically used as a varnish for paint.

Next, the varnishes obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were subjected to a performance test as a paint.

Reference Examples A to E and Reference Comparative Examples F to J The varnishes obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were blended with the components shown in Table 2 to prepare coating materials.

The paint, the adhesion and the corrosion resistance of the obtained coating were tested, and the results are shown in the lower column of Table 2.

As is clear from Table 2, all of Reference Examples A to E, which are coating compositions of the present invention, had good coating stability, and the coating films obtained were excellent in adhesion and corrosion resistance.

On the other hand, Reference Comparative Examples F, H, and J, which are paints using the turbid modified epoxy resin of Comparative Examples 1, 3, and 5, were not suitable as practical paints because the varnish separated.

The equivalent ratio (epoxy group / carboxyl group) is 1.8 / 1.
Reference comparative example G, which is a paint using a modified epoxy resin of less than 0, and the equivalent ratio (hydroxyl group / isocyanate group) is 1 / 0.8
Reference Comparative Example 1, which is a coating material using a modified epoxy resin having a viscosity of more than 1, was inferior in corrosion resistance.

In addition, the coating materials of Reference Examples A to E were salt rubber-based old coating films (exposed for one year outdoors) and alkyd resin-based old coating films (1
For 5 years and then exposed for 5 years and observed 5 hours later, no abnormality was observed.

Similarly, when a commercially available epoxy resin paint using a strong solvent was applied, all the old coating films were lifted.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Yamada 37-3 Aobadai, Izumi City, Osaka Prefecture (72) Inventor Takashi Fujii 5-2-22 Kasuga, Ibaraki City, Osaka Prefecture (56) Reference JP-A-51-41737 (JP, A) JP 58-201857 (JP, A)

Claims (1)

[Claims] 1. A coating composition containing a modified epoxy resin, a curing agent for the modified epoxy resin, and an organic solvent, wherein the modified epoxy resin has (a) two or more epoxy groups in one molecule, and An epoxy resin having an average epoxy equivalent of about 250 or less, (b) an aliphatic monocarboxylic acid, and an equivalent ratio of a carboxyl group of the carboxylic acid and an epoxy group of the epoxy resin are (1: 1.8 to 2.5). The reaction product (i) obtained by reacting the diisocyanate compound (ii) at a ratio such that the equivalent ratio of the hydroxyl group of the reaction product to the isocyanate group of the diisocyanate compound is (1: 0.8 to 1.2). Is a modified epoxy resin obtained by reacting with, and the organic solvent is mineral spirit or an organic solvent containing mineral spirit as a main component. Charge composition.