JPS581702B2 - Zinkritchi Paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel inorganic zinc-rich paint that eliminates the need for a mist coat during topcoating.

Conventionally, zinc-rich paint containing a high concentration of zinc powder has been used as an anticorrosive paint for ships, bridges, steel structures, etc.

As such zinc-rich paints, organic zinc-rich paints using epoxy resins, polystyrene, etc. as binders, and inorganic zinc-rich paints using water glass, alkyl silicate, etc. as binders are known.

However, organic zinc-rich paints have inferior paint film durability compared to those using inorganic binders.On the other hand, among inorganic binders, water glass has a short pot life, poor coating workability, and poor paint film durability. Alkyl silicate-based zinc-rich paints are the mainstream.

However, such alkyl silicate-based zinc-rich paints contain 85-9% zinc dust in the total solid content of the paint.
By incorporating zinc at a high concentration of 5% by weight, excellent anticorrosion performance is exhibited due to the electrochemical action of zinc.

By the way, in order to expect the above-mentioned electrochemical corrosion prevention effect, contact between zinc particles in the coating film is essential.
It was therefore common for pigment volume concentrations to typically exceed 80%.

However, a paint film with a very high pigment volume concentration like this is extremely porous, and if a top coat is applied directly on top of it, foaming will occur in the top coat, which will not only deteriorate the performance of the paint film but also affect its aesthetic appearance. I don't like the top either.

Therefore, in the past, the top coat of paint was generally applied with thinner on top of the alkyl silicate-based zinc chloride paint film.
Apply a so-called mist coat diluted to about 0.00%,
After drying for a day, a top coat of paint was applied.

However, the application of the mist coat added one day to the painting process, and in addition, even the application of the mist coat could not completely prevent foaming of the top coat film.

On the other hand, for the purpose of improving the coating workability and coating film performance of conventional alkyl silicate-based zinc-rich paints, it has been proposed to add and mix polyvinyl butyral resin and the like.

(For example, Japanese Patent Application Laid-open No. 1634/1983) However,
Since the above-mentioned proposal is aimed at improving coating film performance, it is natural that the proportion of zinc powder in the total solid content is very high, and the pigment volume concentration is also very large. It was completely useless in preventing foaming and required mist coating.

As a result of intensive research on preventing foaming of the top coat paint film on alkyl silicate-based zinc-rich paint, the present inventors have found that it is possible to prevent the foaming of the top coat paint film on alkyl silicate-based zinc-rich paint without impairing the excellent anti-corrosion performance inherent in zinc-rich paint, and without any mist coating. This led to the invention of an inorganic zinc-rich paint that does not require mist (hereinafter referred to as non-mist).

That is, the present invention comprises (a) a tetraalkyl silicate initial condensate and a polyvinyl butyral resin, and the ratio of SiO2 in the tetraalkyl silicate initial condensate/polyvinyl butyral resin = 7/3 to 2/8 (weight ratio); Contains a binder consisting of 12 to 25% by weight of the total solid content of the paint, (mouth)
Contains 75 to 85% by weight of zinc powder in the total solid content of the paint,
e.) Contains 0.1 to 10% by weight of carbon black and/or graphite in the total solid content of the paint, (d) the remainder is an extender pigment and/or a colored pigment, and (e) the pigment volume concentration is 40%. -60% zinc-rich paint.

The tetraalkyl silicate initial condensate used in the present invention is an initial condensate of a partial hydrolyzate, such as tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, tetrapentyl orthosilicate. , and initial condensates of partial hydrolysates such as tetrahexyl orthosilicate.

Among the above, the most preferred is an initial condensate of a partial hydrolyzate of tetraethyl orthosilicate.

Also, polyvinyl butyral used in the present invention? The fat is
It is a commercially available resin with an average weight of about 200-2000.

The tetraalkyl silicate precondensate and polyvinyl butyral resin act as a binder in the zinc-rich paint of the present invention.

In the present invention, the tetraalkyl silicate initial condensate and polyvinyl butyral resin are such that SiO content in the tetraalkyl silicate initial condensate/polyvinyl butyral resin=7/3 to 2/8 (solid content weight ratio), preferably 6/ Use at a ratio of 4 to 4/6.

In the above range, if the amount of Sin in the tetraalkyl silicate initial condensate is higher than 7/3, the film forming property will be poor and cracks will easily appear in the coating, and the non-mist property will be lost. If the amount of resin is large, the non-mist property will be improved, but lifting will easily occur when the top coat is applied, so either case is not preferable.

In the zinc-rich paint of the present invention, the binder is used in an amount of 12 to 25% by weight based on the total solid content of the paint.

In this range, if the binder content is less than 12% by weight, the pigment volume concentration will inevitably increase, and the non-mist property, which is one of the important effects of the present invention, cannot be expected.On the other hand, if the binder content exceeds 25% by weight, the coating This is not preferable because the anticorrosion properties of the film decrease.

Furthermore, the concentration of zinc dust in the zinc-rich paint of the present invention is 75 to 85% by weight based on the total solid content of the paint.

In this range, if the zinc dust concentration is less than 75% by weight, the electrochemical corrosion protection effect due to contact between zinc dust particles in the paint film will decrease, and conversely, if the zinc dust concentration exceeds 85% by weight, the electrochemical corrosion prevention effect will decrease in the paint film. The pigment volume concentration becomes high, and as a result, the non-mist property decreases.

Further, carbon black and/or graphite in the zinc-rich paint of the present invention are present between the zinc dust particles and are used to facilitate electrical contact between the zinc dust particles.

Therefore, the electrochemical corrosion protection effect of the coating film can be maintained even with a small amount of zinc powder.

The carbon black and/or graphite are used in an amount of 0.1 to 10% by weight based on the solid content of the paint.

In this range, if carbon black and/or graphite is less than 0.1% by weight, the effect of promoting electrical contact between zinc dust particles cannot be expected, whereas if it exceeds 10% by weight, the pigment volume concentration becomes large. Both are undesirable because foaming occurs during the application of the top coat, zinc is significantly consumed, and the durability of the anticorrosion potential becomes poor.

In the present invention, extender pigments and/or coloring pigments are used in addition to the above-mentioned components.

The amount thereof is 13% by weight or less in the total solid content of the paint.

What is more important in the present invention is the pigment volume concentration range in the zinc-rich paint of the present invention.

The concentration range should be 40-60%.

In the above, if the pigment volume concentration is less than 40%, sufficient contact between the zinc dust particles will not occur, resulting in a decrease in the anticorrosion properties of the coating, while on the other hand, if the pigment volume concentration exceeds 60%, the non-mist property will decrease. However, this is not preferable because it can hardly be expected and foaming etc. will occur in the top coat film.

Needless to say, in the present invention, the term "pigment volume concentration" includes the concentration of volume pigments other than zinc dust when used in conjunction with the zinc-rich paint.

The solid content composition of the zinc-rich paint of the present invention is as described above, but in addition, alcohol-based, aliphatic hydrocarbon-based, aromatic hydrocarbon-based, etc. Requires normal solvent.

Furthermore, the zinc-rich paint of the present invention may optionally include:
It is possible to add other additives, such as anti-settling agents, stabilizers and the like.

The zinc-rich paint of the present invention thus obtained is applied onto a steel plate or steel material by a conventional coating method such as brushing or spraying, and is formed into a film by drying at room temperature or by forced drying at a low temperature.

As already explained, the zinc-rich paint of the present invention is characterized by having the raw material composition ratios as described above.

In other words, by using a combination of tetraalkyl silicate, which has a relatively high specific gravity, and polyvinyl butyral resin, which has a low specific gravity, within a certain weight range, and by specifying the pigment volume concentration and zinc dust concentration, it is possible to create a pigment that is lower than that of conventional zinc-rich paints. It is possible to maintain a relatively high volume concentration of zinc dust.

Furthermore, by using carbon black and/or graphite, these fine particles can be inserted between the zinc particles to help electrical contact between the zinc dust particles.

Therefore, it is possible to provide a zinc-rich paint that does not require a mist coat and does not impair its corrosion resistance, which is the most important feature of conventional zinc-rich paint coatings.

Therefore, there is no doubt that the painting process can be significantly shortened and that it is extremely effective industrially.

The details of the present invention will be explained below with reference to Examples.

"Parts" or "%" are expressed as "parts by weight" or "% by weight" unless otherwise specified.

Examples and Comparative Examples A zinc-rich paint was prepared according to the formulation shown in Table 1, and a JIS-G-3141 sandblasting plate (1
．． 6 x 70 x 1 50 mm) by air spray and dried at room temperature for 4 days to obtain a coating film with a dry film thickness of 90 ± 10 μm.

Next, an epoxy resin paint (trade name: Eponics 73HB Primer, manufactured by Inunippon Paint Co., Ltd.) was applied onto the above coating film using an airless sprayer to a dry film thickness of 100±10 μm, dried, and subjected to a comparative test.

The test results are shown in Table-2.

(1) Observe the condition of the painted surface 24 hours after applying the top coat.

○: No foaming × Two foams (2) A scratch reaching the substrate was made on the test piece prepared in (1), and after salt water was sprayed for 48 hours, the state of rust on the scratched portion was observed.

○: No rust observed ×: Rust developed (3) After 7 days of immersion in 3% saline solution, reference electrode (TOA HS-205C)
The potential was measured based on .

(4) A painted board with an unpainted area of 3 degrees in diameter was prepared, and after drying at room temperature for 4 days, the rusting status of the unpainted area was examined after being immersed in a 3% saline solution for 48 hours.

○: No rust observed ×: Rust formed As is clear from the above test result table, no abnormalities such as foaming occurred even when the top coat was directly applied on the coating film obtained from the zinc chloride paint of the present invention. There was no need for a mist coat at all, and the inherent corrosion resistance of the zinc-rich paint was not impaired in any way.

On the other hand, even if the ratio of SiO2/polyvinyl butyral resin in the alkyl silicate initial condensate is within the range of the present invention, if the zinc dust content is higher than the present invention and the pigment volume concentration is high (Comparative Example 1) Although the corrosion resistance was good, foaming occurred in the top coat.

Similarly, even if the ratio of SiO2/polyvinyl butyral resin in the alkyl silicate initial condensate is within the range of the present invention, when no carbon black is used and the pigment volume concentration is low (Comparative Example 2), the corrosion resistance is significantly lower. It was inferior.

Furthermore, in the ratio of SiO2/polyvinyl butyral resin in the alkyl silicate initial condensate, when the amount of polyvinyl butyral resin is large and the amount of carbon black used is large (Comparative Example 3), lifting occurs in the top coat. At the same time, the corrosion resistance was also extremely poor.

Claims (1)

[Scope of Claims] 1 (a) A binder consisting of a tetraalkyl silicate initial condensate and a polyvinyl butyral resin, with a ratio of Si02 in the tetraalkyl silicate initial condensate/polyvinyl butyral resin 7/3 to 2/8. is 12 to 25% by weight of the total solid content of the paint. (1) Zinc powder is 75 to 85% by weight of the total solid content of the paint. (c) Carbon black and/or graphite is 0.1 to 10% of the total solid content of the paint. A zinc-rich paint characterized in that (d) the remainder is an extender pigment and/or a colored pigment, and (v) the pigment volume concentration is from 40 to 60% by weight. 2. The zinc-rich paint according to claim 1, wherein an initial condensate of a partial hydrolyzate of tetraethyl orne silicate is used as the initial condensate of tetraalkyl silicate.