JPH02263879A - Metal-coating composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition having excellent initial bond strength, cathode peel resistance, water-resistant adhesivity and corrosion proofing property by adding a specific amount of calcium sulfate to a thermosetting polyurethane resin. CONSTITUTION:The objective composition is produced by adding (A) 50-300 pts.wt. of preferably anhydrous calcium sulfate to (B) 100 pts.wt. of a thermosetting polyurethane resin (preferably a polyurethane derived from a polyol component such as epoxymodified polyol, a polyol produced by adding an alkylene oxide to bisphenols, etc., and a polyisocyanate component such as diphenylmethane diisocyanate or polymethylene polyphenylene polyisocyanate).

Description

Detailed Description of the Invention The present invention relates to a metal coating composition, and more specifically to a metal coating composition that has excellent water resistance, cathodic peeling resistance, adhesion, and corrosion resistance. It is related to.

Steel, the most common metal material, has the disadvantage of being easily corroded, so it is usually subjected to various anti-corrosion treatments before or during use. For anti-corrosion treatment of steel,
For example, a method using anticorrosive coating or a method using a plastic coating material such as polyethylene is used. The method of using anti-corrosion coating is widely used because it can be applied relatively easily regardless of the form of the steel material.

In particular, polyurethane heavy-duty anti-corrosion paints not only have good low-temperature curing properties and are excellent in winter paintability, but also have good flexibility and impact resistance, and have excellent long-term durability, so they can last for a long time. The demand for this product is increasing significantly because it is expected to have a maintenance-free anti-corrosion effect. Polyurethane heavy-duty anti-corrosion paints have the excellent features mentioned above, but if a primer is not used, the water-resistant adhesion and cathodic peeling resistance may be somewhat low.

However, in the past, epoxy resin-based or polyurethane-based brimers have been used to improve water-resistant adhesion and cathode peeling resistance.Some epoxy resin-based brimers have poor water-resistant adhesion , has excellent cathode peeling resistance. For example, JP-A-57-159866, JP-A-58-91
No. 778, JP-A-58-217573, JP-A-59-
No. 71374, JP-A-59-222275, JP-A-5
No. 9-232160, JP-A No. 60-258277, and JP-A No. 60-258278 describe adhesives for laminating polyolefins and metals with excellent cathodic peeling resistance and water-resistant adhesion. However, careful painting management is required to ensure the adhesion between the epoxy brusher, which is a different material, and the polyurethane resin topcoat.

On the other hand, polyurethane resin-based brimers have good adhesion to the polyurethane resin top coat, but have a problem in that they have somewhat poor cathode peeling resistance.

The present invention is a metal coating composition that solves the above-mentioned drawbacks.
The purpose is to provide a brimer that improves water-resistant adhesion and cathodic peeling resistance when used as a brimer for heavy polyurethane anti-corrosion coatings, and that also ensures adhesion even when used under conditions where sufficient coating control is not possible. That is.

The invention of this invention, which is intended to improve the performance of the invention, was made by paying attention to such conventional problems. That is, it is a metal coating composition made by adding 50 to 300 parts by weight of calcium sulfate to 100 parts by weight of a thermosetting polyurethane resin.

The metal coating composition of the present invention has thermosetting polyurethane resin 1
50 to 300 parts by weight of calcium sulfate is added to 00 parts by weight, but the calcium sulfate used in the present invention is in powder form, and its average particle size is 0.1 to 20 mμ.
It is preferable to use In addition, calcium sulfate generally has anhydrous, hemihydrate, and dihydrate forms, but
Preference is given to using anhydrides.

The amount of calcium sulfate added is 1 part of thermosetting polyurethane resin.
Add 50 to 300 parts by weight per 00 parts by weight. If the amount added is less than 50 parts by weight, the cathode peeling resistance will decrease, making it impossible to achieve the object of the present invention. Addition amount is 300
When the amount is more than 1 part by weight, the strength of the brimer coating film decreases, causing a decrease in initial adhesion and water-resistant adhesion. When adding powdered pigments other than calcium sulfate for the purpose of coloring, etc., the total amount of pigments added should not exceed 300 parts by weight.

Next, the thermosetting polyurethane resin used in the present invention is obtained by reacting a compound having two or more hydroxyl groups (hereinafter referred to as a polyol) with a compound having two or more isocyanate groups (hereinafter referred to as a polyisocyanate compound). As the polyol, epoxy modified polyol, polyether polyol, polyester polyol, polybutadiene polyol, polycarbonate polyol, etc. can be used. Among these polyols, polyester polyols are not preferred because they easily undergo hydrolysis due to the ester bond, while epoxy-modified polyols and polyols with alkylene oxide added to bisphenols have phenyl groups in their molecular skeletons. Adhesiveness,
The molecular weight of these polyols, which are excellent in water resistance and are preferable for obtaining the thermosetting polyurethane resin of the present invention, is preferably 100 to 500 per hydroxyl group.

If the molecular weight per hydroxyl group is less than 100, the resulting resin will be too hard and will likely crack in the brimer layer during an impact test.

On the other hand, if the molecular weight per hydroxyl group is greater than 500, the brimer layer becomes soft, which may cause problems in adhesion and water-resistant adhesion. Therefore, the molecular weight per hydroxyl group of the polyol is preferably 100 to 500.

Examples of polyisocyanate compounds include tolylene diisocyanate, diphenylmethane diisocyanate (hereinafter referred to as MDI), polymethylene polyphenylene polyisocyanate (hereinafter referred to as crude MDI), liquid MDI, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, and these polyisocyanates. A terminal isocyanate prepolymer obtained by reacting with the polyol in a state containing an excess of isocyanate groups can be used. Among these polyisocyanates, MDI and crude MDI are particularly excellent in performance such as curability, adhesion, and water-resistant adhesion.

The thermosetting polyurethane resin can be obtained by mixing a polyol and a polyisocyanate compound immediately before coating, or by applying the isocyanate-terminated prepolymer and hardening it with moisture in the air.

There are several methods of converting the data, and any of these methods can be used.

Calcium sulfate is normally mixed uniformly with a polyol before storage and preferably mixed with a polyisocyanate compound immediately before painting.

It is optional to use a solvent when applying the metal coating composition of the present invention. If the viscosity of the blend of resin and calcium sulfate is high, a solvent should be added to adjust the viscosity. use? Agents include aromatic solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, ketone solvents such as acetone and methyl ethyl ketone, and halogen solvents such as methylene chloride and trichloroethane, either alone or in combination. It can be used as Alcohol solvents such as ethanol, methanol, and isopropanol are not preferred because they react with the polyisocyanate compound.

Additionally, catalysts, antioxidants, and
Addition of auxiliary agents such as stabilizers is optional.

Methods for applying the metal coating composition of the present invention include brushing,
It can be applied using the same methods as regular paints, such as painting with a roller, spraying with air spray, airless spray, etc.

When the metal coating composition of the present invention is used as a primer for heavy-duty anticorrosive coating, it is usually preferable to apply the coating so that the dry film thickness is 5 to 100 μm, but there is no particular limitation.

The metals to be coated with the metal coating composition of the present invention include iron, steel, copper, aluminum, etc., and iron and steel are particularly useful. Its forms include steel pipes, iron pipes, steel sheet piles, and HY3.
Applicable to steel, steel plates, belts, etc., and structures made from these.

Disaster Management The present invention will be explained in more detail with reference to Examples below. In addition, in Examples and Comparative Examples, "parts" and "%" are based on weight.

Example 1 Polyether polyol (propylene oxide added to bisphenol A to give a molecular weight of 400) 1
After adding 120 parts of anhydrous calcium sulfate to 00 parts and kneading with three rolls, 40 parts of toluene was added. 260 parts of this solution and 75 parts of liquid MDI were mixed and applied to a grid-blasted steel plate using air spray so that the dry film thickness was 30 μm. After drying for one day, a heavy polyurethane anticorrosion paint was applied to a thickness of 2.5 mm.

The test results are shown in Table 1.

Comparative Example 1 A similar test was conducted using calcium carbonate instead of calcium sulfate in Example 1, and the results are shown in Table 1.

Example 2 100 parts of polypropylene glycol having a molecular weight of 400 and 1140 parts of crude MD were mixed in the presence of 240 parts of toluene at 90%
The reaction was carried out at °C for 2 hours to obtain a polyurethane prepolymer solution with a solid content of 50%. 50 parts of calcium sulfate was mixed with 100 parts of this solution using a high-speed disperser, and the mixture was coated on a grid-blasted steel plate so that the film thickness when dried was 30 μm. After drying at room temperature for one day, a heavy polyurethane anticorrosion paint was applied. The test results are shown in Table 1.

Comparative Example 2 Aluminum silicate was used in place of calcium sulfate in Example 2. The results are shown in Table 1.

Comparative Example 3 A test was conducted in the same manner as in Example 2 except that the calcium sulfate of Example 2 was not used and only the polyurethane prepolymer was used. The results are shown in Table 1.

Comparative Example 4 250 parts of calcium sulfate was added to 100 parts of the polyurethane prepolymer solution of Example 2, and the same test as in Example 2 was conducted. The results are shown in Table 1.

(Left below) As is clear from the Examples, the metal coating composition of the present invention can be used as a primer for heavy-duty anti-corrosion paints to produce polyurethane with excellent initial adhesion strength, cathodic peeling and water-resistant adhesion strength. A highly anti-corrosion coating is obtained.

On the other hand, in the case of a brimer using an inorganic filler outside the range of the present invention as in Comparative Example 1.2, the cathodic peeling resistance becomes poor. When no inorganic filler is used as in Comparative Example 3, the cathode peeling resistance and water resistant adhesion deteriorate. Furthermore, even if the inorganic filler of the present invention is used as in Comparative Example 4, if the amount used is too large, the strength of the brimer coating film will be low, and the initial adhesion strength will be low.

As described above, by using the metal coating composition of the present invention as a brimer, not only the initial adhesion strength but also
Cathodic peeling resistance and water resistant adhesion can be significantly improved.

Claims (1)

[Claims] A metal coating composition comprising 50 to 300 parts by weight of calcium sulfate added to 100 parts by weight of a thermosetting polyurethane resin.