JPS591574A - Coating composition for zinc substrate - Google Patents

Abstract

PURPOSE:To provide the titled compsn. excellent in adhesion to zinc substrates, by incorporating a particular phthalate resin and calcium plumbate. CONSTITUTION:Polybasic acids consisting mainly of phthalic anhydride and contg. 1-20wt% straight-chain dibasic acid of formula (wherein n is 4-17), polyols (e.g., ethylene glycol), and oils (e.g., soybean oil) or fatty acids are polycondensed by dehydrating at 200-260 deg.C for 5-20hr to yield a phthalate resin having an oil length of 30-65%, a hydroxyl value of 20-50, and an acid value of 20 or below. Then, 0.5-65wt% calcium plumbate, solvents (e.g., toluene), driers (e.g., cobalt drier), etc. are incorporated with 30-95wt% said phthalate resin. EFFECT:It is possible to obtain films excellent in durability, gloss retention, adhesion, water resistance, and anti-corrosion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating composition for zinc substrates such as galvanized steel sheets or substrates having zinc-rich paint coatings.

Phthalic acid resin paints have been widely used since they have excellent durability, gloss retention, and are inexpensive.

By the way, what about steel structures such as bridges, steel towers, and tanks?

Galvanization is applied to these base materials to prevent corrosion.
Or it has been preserved with a zinc-rich paint.

However, in such a zinc base material, white rust was generated up to that point, which caused aesthetic problems. Therefore, the conventional method has been to apply the above-mentioned phthalic acid resin paint to the surface to prevent white rust from forming on the zinc-light surface and maintain its aesthetic appearance.

However, the zinc on the substrate surface is chemically very active and reacts with the free acids in phthalate paints to form zinc soaps, which reduce the adhesion of the paint film and are therefore often Defects such as peeling were observed.

The present invention takes advantage of the characteristics of the phthalic acid resin paint, while
Moreover, the present invention provides a coating material with excellent adhesion to zinc base materials.

That is, the present invention uses a linear dibasic acid represented by the general formula HOOC-(cH2-)-nCOOH [where n is an integer of G~/7] among all polybasic acids/~-~ The present invention relates to a coating composition for a zinc base material, which contains as essential components a phthalic acid resin obtained from a polybasic acid containing phthalic anhydride as a main component, a polyhydric alcohol, and an oil or fatty acid, and calcium leadate.

The coating composition of the present invention has greatly improved adhesion to zinc substrates compared to conventional phthalic acid resin coatings, and can prevent zinc consumption. The reason is not clear, but
By using the linear dibasic acid as a part of the polybasic acid that is a component of the phthalic acid resin, a strong ester bond is formed.

Therefore, the free acid that reacts with zinc on the surface of the base material does not dissociate,
This is thought to be due to the fact that the formation of zinc soap, which has an adverse effect on adhesion, can be prevented, and the phthalic acid resin has sufficient elasticity to cope with the expansion and contraction of the object to be coated. In addition, by using calcium leadate, which is alkaline,
This is thought to be due to the fact that the activity of zinc is reduced, thereby suppressing the reaction between zinc and free acid.

The phthalic acid resin used as a binder in the present invention is obtained by reacting a polybasic acid containing phthalic anhydride as a main component, a polyhydric alcohol, and an oil or fatty acid.

In the present invention, the polybasic acid has the general formula HOOC (
It is characterized by the fact that the linear dibasic acid represented by '-CH÷C0OH (where n is an integer from 1 to /) is blended in a weight-predominant manner.

In the present invention, the linear dibasic acid is 7-. 20-layer It
Mix the width. This greatly improves adhesion to zinc substrates. In the above range, if the linear dibasic acid is less than 30% by weight, the adhesion will not improve much.
If it exceeds heavy-it's, drying properties and water resistance will deteriorate.

Representative examples of the 1α-chain dibasic acids include anopic acid, pimelic acid, superric acid, azelaic acid, and sebacic acid. These may be used alone or in combination.

In addition, in the above general formula of the linear dibasic acid, it is not preferable that the n value is 3 or less because adhesion is poor.

Further, the upper limit of the n value is about 77, and in particular from the viewpoint of water resistance, etc., a value of g or less is suitable.

Phthalic anhydride is used as the remainder of the polybasic acid constituting the phthalic acid resin. In some cases, it is desirable to use benzoic acid as a molecular weight regulator in an amount of /θ to 30% by weight.

When benzoic acid is used in this way, the amount of the linear dibasic acid to be blended is as follows.

Based on the total weight of benzoic acid and polybasic acid, the weight should be 20% by weight.

The polyhydric alcohols that make up phthalic acid resin include ethylene glycol and propylene glycol.

Typical examples include dihydric alcohols such as neopentyl glycol; trihydric alcohols such as glycerin, trimethylolethane, and trimethylolethane; and tetrahydric alcohols such as pentaerythritol.

Further, as the oil or fatty acid constituting the phthalic acid resin, semi-drying oils, drying oils, or their fatty acids having an iodine value of /θ0 or less are preferable. Specifically, soybean oil, linseed oil, dehydrated castor oil, tung oil, safflower oil, or any of these fats can be typically used.

The phthalic acid resin used in the present invention is synthesized by a conventional dehydration condensation polymerization reaction. For example, the dehydration condensation polymerization reaction is carried out at a reaction temperature of about 200 DEG C. and a 2AO0C1 reaction time of about 5 to 20 hours.

The above-mentioned phthalic acid resin has an oil length of 3[theta] to 6"1 hydroxyl value 0-1 acid value 0 or less.

If the oil length is less than 30, the coating performance such as adhesion will decrease,
On the other hand, if it exceeds 63, the drying properties will deteriorate, so it is not preferable.

Furthermore, if the hydroxyl value is less than 20, the adhesion will decrease,
On the other hand, if jθ is exceeded, adhesion and water resistance deteriorate, which is not preferable.

Further, if the acid value exceeds 20, adhesion and water resistance deteriorate, which is not preferable.

The coating composition of the present invention uses the phthalic acid resin as an ingredient, further contains calcium leadate in at least a part of it as a pigment, and also contains a solvent and a drying agent similar to ordinary room temperature drying phthalic acid resin coatings. etc. and, if necessary, various additives such as a suspending agent, and an extender paint such as calcium carbonate.

Typical examples of the solvent that can be used include hydrocarbon solvents such as toluene, xylene, and mineral spirits; ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone; and ester solvents such as methyl cellosolve acetate and ethyl acetate.

Examples of desiccants include cobalt, manganese, lead,
A metal salt desiccant such as nickel can typically be used.

In the coating composition of the present invention, it is appropriate that the phthalic acid resin is blended in a proportion of 30-9 ta weight i based on the total solid content of the coating.

In addition, the calcium leadate is θ, S ~ 6 in the total paint solid content.
．． ．． It is appropriate to mix them at a ratio of S' heavy weight. Note that if the amount of calcium leadate is less than the O15 weight ratio, it will not contribute to improving adhesion. On the other hand, if the weight exceeds 6 twA', the physical and chemical properties of the coating film will deteriorate, which is undesirable.

The coating composition of the present invention can be applied onto a zinc substrate by a conventional method such as spraying or brushing, and is dryable at room temperature.

Thus, the coating film obtained using the coating composition of the present invention has not only durability and gloss retention but also excellent adhesion.

Shows excellent properties such as water resistance and corrosion resistance.

The present invention will be explained below with reference to examples.

Note that [part J and r%J are expressed on a weight basis.

Example/ 70.0 parts of soybean oil, 6 parts of pentaerythritol/Hiroshi,
After heating and reacting 3.0 parts of glycerin and 0.7 parts of sodium formate at Utah θ°C for 7 hours, 3.0 parts of phthalic anhydride, 6.0 parts of adipic acid, and 10 parts of benzoic acid were added. θ parts, 7.0 parts of ethylene glycol were added, and 23 parts were heated and reacted at ℃ for 6 hours to determine the oil length θ ratio, hydroxyl value 1IO1 acid value/θ
phthalic acid resin was produced.

Non-volatile content S made by adding xylene to the generated phthalic acid resin
Phthalic acid in O group (for printing durability varnish Sθ part, 10 parts of calcium leadate, 30 parts of calcium carbonate, xylene/, !r parts,
75 eulead dryer 1/part, S4 cobalt dryer θ,
7 parts and 1/part of tS manganese dryer O were added to prepare a paint.

Example A paint was prepared in the same manner as in Example 1, except that 70 parts of calcium leadate was used instead of 10 parts of calcium leadate and 30 parts of calcium carbonate.

Example 3 A paint was prepared in the same manner as in Example 1, except that calcium leadate/part and calcium carbonate 39 parts were used instead of 10 parts calcium leadate and 3θ parts calcium carbonate.

3g of soybean oil fatty acid in place of the phthalic acid resin in Example/Example/3
Part, Pentaerythritol/F, Part A, Glycerin 7.2 parts, Phthalic anhydride 3θ, θ part, Adipic acid 6. θ
parts, benzoic acid 10. θ part, ethylene glycol3. θ
A coating material was prepared in the same manner except that a phthalic acid resin having an oil length of 4 to, a hydroxyl value of 4 to, and an acid value of /θ obtained by reacting the phthalic acid resin for 6 hours at 23θ was used.

Examples 5 to IO and Comparative Examples / to 3 A phthalate resin was produced in the same manner as in Example / using the components shown in Table 1 instead of the phthalate resin in Example /,
A paint was prepared.

A paint was prepared in the same manner as in Comparative Example/Example, except that 70 parts of calcium carbonate was used instead of 70 parts of calcium leadate and 30 parts of calcium carbonate.

The paints obtained in Examples/~10 and Comparative Examples/~ were applied to a hot-dip galvanized steel plate...ke/, 4'Ji'/dm2
After coating and drying for one week, adhesion, water resistance, and salt spray resistance were tested, and each paint was roughly tested for drying properties.

The results are shown in Table 1.

Table λ Note 7) Seven years after the outdoor argument, I took the Gopan eyes test.

○: 100/100~g//100Δ:gθ
/ 100-37 / /θθ, ×:! fθ//θ0Note 2) The appearance of the coating film was observed after being immersed in tap water for several months.

○: No abnormality, △D Some blisters, ×: Blisters occur on the entire surface Note 3) The appearance of the coating film was observed after 300 hours of salt spray test.

○: No abnormality, ∆ some blistering, ×: Fully blistering Note) - 〇〇〇, Paint was applied under the same conditions as above in a 7% RH environment, and after a period of time, there was no trampling or footprints. Cases with no markings were designated as O1 and cases with markings were designated as X.

As is clear from Table 1, the coating film obtained from the coating composition of the present invention had excellent coating performance. However, the coating films obtained from Comparative Example 30, which used a small amount of adipic acid, and Comparative Example 30, which used glutaric acid [n value of the above general formula is 3], had poor adhesion and also had an excessive amount of adipic acid. The coating film obtained from the composition of Comparative Example - had poor water resistance and drying properties, and the coating film obtained from the composition of Comparative Example D, which did not contain calcium leadate, had poor adhesion, water resistance, The results showed poor salt spray resistance.

565-

Claims (2)

[Claims] (1) Contains a linear dibasic acid represented by the general formula % formula % [where n is an integer of Hiroshi ~/7] in a proportion of 20 to 20 times in all polybasic acids, and A coating composition for a zinc base material containing a phthalic acid resin obtained from a polybasic acid containing phthalic anhydride as a main component, a polyhydric alcohol, and an oil or fatty acid, and calcium leadate as essential components. (2) Phthalic acid resin has an oil length of 30-4! The coating composition according to claim 1, wherein the coating composition has a hydroxyl value of -0 to 0 and an acid value of 0 or less.