JPS62132972A - Coating composition - Google Patents

Abstract

PURPOSE:To provide a coating composition enabling the life of the coating film to be extended even coated with reduced substrate on steel construction, comprising a polyhydroxyl compound, polyisocyanate aromatic oligomer and flaky pigment in specified proportion. CONSTITUTION:The objective composition essentially comprising (A) 100pts.wt. of a polyhydroxyl compound (a resin with at least two hydrooyl groups, e.g. polyether polyol), (B) 50-100pts.wt. of a polyisocyanate (e.g. m-phenylene diisocyanate), (C) 50-100pts.wt. of an aromatic oligomer (pref. with a number- average molecular weight 300-600, viscosity (at 25 deg.C) 5-20cps and nonvolatiles >=50%; e.g. low-viscosity xylene resin) and (D) 50-150pts.wt. of flaky pigment (e.g. flaky mica).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a coating composition that makes it possible to extend the life of the coating film even when coating steel structures with reduced surface treatment.

(Prior art) Conventionally, corrosion protection by painting of general environmental steel structures involves forming a coating film through a surface treatment, painting, and soft wire process.

It becomes an anti-corrosion coating. Blasting is the base treatment.

Power tool treatment, hand tool treatment, etc. are performed, and the painting specifications include one coat of oil-based anti-rust paint, two to three coats of long-oil alkyd resin paint, three to four coats, and a film thickness of 80 to 100.
μ is usually implemented. As is clear from the curing and drying mechanism of such oxidative polymerization type paints, the film thickness achieved with one coat is 20 to 30μ, and it is necessary to apply three or four coats to obtain anticorrosion performance. . In addition to the alkyd resins, urethane resins, epoxy resins, polyester resins, phenol resins, vinyl chloride resins, chlorinated rubber resins, and the like are used as anticorrosive paint vehicles for steel structures.

In particular, epoxy resins and urethane resins are widely used as anticorrosive paint vehicles for steel structures because they provide coating films with excellent physical properties and anticorrosion properties.

However, in order to exhibit its excellent physical properties and anti-corrosion properties, careful surface treatment is required, and if this surface treatment is insufficient, the physical properties and anti-corrosion properties will be significantly reduced.

On the other hand, research on paints for rough surfaces such as rusted surfaces is being carried out intensively, and methods for stabilizing rust include adding a penetrant, iron chelate conversion method, magnetite conversion method, etc., and none of them are commercially available. Although there are many paints available, they do not have a stable effect and the unit price of the paint is high, so paints for surfaces made of bad materials are not widely used.

As well-known examples similar to the present invention, Japanese Patent Publication No. 58-25348 and Japanese Patent Publication No. 5B-46134 describe coating compositions in which aromatic oligomers are blended with urethane resin paints, but scaly pigments are Although there is a description that this paint composition has good coating workability, there is no description that it can reduce the need for surface treatment.

On the other hand5. Coating compositions containing scaly pigments are well known, and there is no need to list the literature;
Publication No. 733 (scaly aluminum), JP-A-54-1136
Publication No. 32 (Glass flakes)/Japanese Patent Application Laid-open No. 47-2723
Publication No. 1 (scaly aluminum), JP-A-47-3073'i
' publication (mica), Japanese Patent Application Laid-Open No. 47-34529 (
Mica flakes), JP-A-53-31744 (scaly diatomaceous earth), Painting technique Vol. 16. Na3.25
Page (1981), Table 5 (MIO-based paints), etc.

However, there is no known coating composition that combines this scaly pigment, the urethane resin coating, and an aromatic oligomer, and there is no description of the combined effect that this coating composition can reduce the need for surface treatment during painting. Nor.

(Problems to be Solved by the Invention) The purpose of the present invention is to have excellent adhesion and anti-corrosion properties even when directly applied to a steel plate with reduced surface treatment such as remaining mill scale or a rusted steel plate, and to have a long lifespan of the coating film. The object of the present invention is to provide a coating composition that can extend the period of time.

Many studies have been reported regarding pernicious surface paints.

For example, defects that tend to occur in paint films painted on rusted surfaces include rust formation in a short period of time and blistering of the paint film. There are methods to improve this, such as adding penetrants to the paint, but they often have shortcomings in compatibility with the vehicle resin, or it is difficult to achieve the desired anti-corrosion performance of the paint film. Another disadvantage was that the unit price of paint was extremely high.

(Means for Solving the Problems) The present inventors have focused on the above-mentioned actual situation, and have conducted extensive research into a paint composition that reduces the need for surface treatment, reduces construction costs, and improves anti-corrosion performance. As a result, (A) (B
) (C) By combining (D), it was discovered that this objective could be achieved as a result of the combination, and the present invention was achieved.

That is, the present invention contains (A) 100 parts by weight of a polyhydroxy compound and (B) 50 to 1 part of a polyisocyanate as essential components.
00 parts by weight, (C) 50 to 100 parts by weight of aromatic oligomer (D) 50 to 150 parts by weight of kA flaky pigment, and by using the coating composition,
We have discovered that it is possible to improve anticorrosion performance while reducing surface treatment and reducing construction costs.

The present invention will be explained in detail below.

The polyhydroxy compound used in the present invention is a resin containing two or more hydroxyl groups, which is generally called a polyol resin, and includes polyether polyol, polyester polyol,
Examples include acrylic polyols and epoxy polyols, but epoxy polyols obtained by modifying epoxy resins with alkanolamines are superior in terms of adhesion to the substrate.

Polyincyanate is a prepolymer component having free incyanate groups, such as m-phenylene diinocyanate, p-phenylene diisocyanate, 4-4'-diphenyl diisocyanate, 4-4'
-diphenylmethane diincyanate, 2.4- or 2.6-dolylene diisocyanate or mixtures thereof, 4.4'-) luidine isocyanate, 1,3 or 1
, 4-xylene diisocyanate, or a mixture thereof; and aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene quisocyanate.

These can be used alone or as a mixture of two or more. Alternatively, a prepolymer obtained by reacting a polyhydric alcohol with an excess of the diisocyanate described above may be used.

If the amount of polyinsyanate exceeds 100 parts by weight with respect to 100 parts by weight of the polyhydroxy compound, the formed coating film becomes brittle and the desired object of the present invention cannot be achieved.
If the amount is less than 1 part by weight, the coating film will be too soft and the desired purpose cannot be achieved.

This polyisocyanate not only reacts with the polyhydroxy compound, but also reacts with moisture in the rust layer, and has the effect of improving adhesion to rough surfaces such as rust surfaces.

Next, aromatic oligomers have a number average molecular weight of 300~
600, 5-20 centivoise (25℃)
An aromatic low polymer or a modified product thereof having a viscosity of 50% or more and a non-volatile content of 50% or more. Specifically, there are low-viscosity xylene resins, liquid coumaron resins, low-molecular petroleum resins, liquid low polymers of isopropenyltoluene, or copolymers of isopropenyltoluene and α-methylstyrene.

If the amount exceeds 100 parts by weight based on 100 parts by weight of the polyhydroxy compound, the drying and curing time of the coating film becomes long, making it impossible to achieve the desired object of the present invention.

If the amount is still less than 50 parts by weight, the ability of the paint to penetrate into the substrate will be poor, and the desired purpose will not be achieved. This aromatic oligomer exhibits a permeability function and can also serve as a main element in forming a coating film even if the object to be coated is a rusted surface or other rough surface.

Furthermore, good compatibility with the polyhydroxy compound and polyisocyanate is an essential condition.

Next, the scaly pigment is a flaky inorganic pigment, and specific examples include mica, MIO (mica-like iron oxide), glass flakes, and flaky aluminum. These are layered in the coating film, and by blocking corrosion-causing substances such as water, steam, and oxygen, they not only have the effect of improving anticorrosion performance, but also have the bonding effect described below. Polyhydroxy compound 1
If the amount of the flaky pigment exceeds 150 parts by weight, the viscosity of the paint will become high, causing problems in coating, and if it is less than 50 parts by weight, the coating film will not exhibit its environmental barrier effect.

In addition to the above-mentioned components, extender pigments such as talc, clay, and pallite, which are used as ordinary paint components, coloring pigments such as titanium white, Bengara, and carbon black, solvents without active hydrogen, and thixotropy imparting agents can also be used. Various additives such as these can also be added as appropriate.

The paint is a two-component type, and immediately before use, a polyisocyanate component as a curing agent is uniformly mixed with a main component mainly composed of a polyhydroxy compound, and then used for painting.

Painting methods include no-ke, airless spray, and low 2.
It can be painted using simple methods such as -.

The objects to be coated include steel structures and members, new construction,
The coating composition of the present invention can be applied to any existing facility.

(Function) The four essential components of the coating composition of the present invention, namely (A) polyhydroxy compound (B) polyincyanate (C) aromatic oligomer (D) g flaky pigment needles, exhibit their respective effects and at the same time , exerts the following effects as a combined effect.

In order for a paint film to firmly adhere to a rusted surface, it is necessary for the paint to sufficiently penetrate into the surface inside the rust.
The main force behind this penetrating power is the polyhydroxy compound and the aromatic oligomer that is compatible with the polyisocyanate. The permeability of this oligomer is greatly demonstrated when there is a large amount of solvent in the paint.In other words, by blending the scaly pigment with the polyhydroxy compound or polyisocyanate, the scaly pigment suppresses the evaporation rate of the solvent. In other words, it exerts the effect of maintaining an appropriate balance between the time for the paint to penetrate into the base surface and the time for the paint to harden.

In addition, the aromatic oligomer functions as a wetting agent and a dispersant for the scale pigment and the aromatic oligomer. Therefore, it is desirable to disperse and knead the scaly pigment and aromatic oligomer in advance during paint production. In this way, only by the presence of at least four components (A) polyhydroxy compound (B) polyisocyanate) (C) aromatic oligomer (D) scaly pigment,
Therefore, the object of the present invention can be achieved.

(Example) (1) Example 1 A rusted steel plate of 70 x 150 x 3.2 mm (a steel plate exposed outdoors for 6 months) and a power brushed steel plate were treated with the following composition so that the dry film thickness was 75μ. The paint was applied using an airless sprayer.

(Main component) 30 parts by weight of epoxy polyol
5 parts by weight titanium oxide
5 parts by weight toluene
16 parts by weight MEK
2 parts by weight total 100 parts by weight (
Curing agent component) Trimethylolpropane adduct of 2.4 or 2.6-drilene diisocyanate (NGO Chini 13%) 900 parts by weight Total 100 parts by weight Main agent/curing agent = 1
00/20 (2) Example 2 The same steel plate as in Example 1 was coated with a paint having the following composition using an airless sprayer so that the dry film thickness was 75 μm.

(Main component) Epoxy polyol (Asahi Denka Kogyo product BPX-55.OH value 140) 40 parts by weight Liquid coumaron resin (Nippon Steel Chemicals L-20) 25 parts by weight Mica (Wakita Kogyo product A-300) 20 parts by weight Talc 5 parts by weight Titanium oxide 5 parts by weight Toluene
2 parts by weight
100 parts by weight (curing agent component) 4.4'-diisocyanate diphenylmethane trimethylolpropane adduct (N00%: 11%)
90 parts by weight main agent/curing agent = 1O
O/33 (3) Comparative Example 1 (An example in which the main resin was different, no aromatic oligomer was mixed, and MIO was insufficient) The same steel plate as in Example 1 was coated three times so that the dry film thickness was 75μ. The paint having the following formulation was applied using an airless sprayer (at intervals of 24 hours).

Long oil alkyd resin (Dainippon Ink Chemical Products Pesocosol P-470-70) 40 parts by weight MIO (Japan Inorganic Chemical Products NF) 10 parts by weight Talc
10 parts by weight Titanium oxide 20 parts by weight Cobalt naphthenate (Co: 6%) 1 part by weight Lead naphthenate (
pb: 15%) 1 part by weight toluene
lO0 parts by weight
100 parts by weight (4) Comparative Example 2 (An example where the main resin is different and no aromatic oligomer is blended) A paint with the following formulation was airlessly sprayed onto the same steel plate as in Example 1 so that the dry film thickness was 75μ. Painted at.

(Main component) Epoxy resin (synthetic resin product AER661) 30 parts by weight Mica (Wakita Sewing Products A-300) 20 parts by weight Talc 10 parts by weight Titanium oxide 18 parts by weight Toluene 16 parts by weight MEK
6 parts by weight
100 parts by weight (curing agent component) Polyamide resin (Dainippon Ink Chemical Products Laccamite T
D-973) 40 parts by weight talc
40 parts by weight xylene
20 parts by weight Total 100 parts by weight Main agent/curing agent = 100150 (5) Comparative Example 3 (Example where the petroleum resin was not the oligomer of the present invention and MIO was insufficient) A steel plate similar to Example 1 was coated with a dry film thickness of 75 μm. Paint with the following composition was applied using an airless sprayer.

(Main component) Epoxy polyol 30 parts by weight Dicyclopentadiene petroleum resin (Nippon Zeon, Quinton 1700 = 80% toluene solution) 24 parts by weight MIO (Nippon Inorganic Chemical Industry Products NF) lo parts by weight Talc 10 parts by weight Toluene
14 parts by weight MIBK
6 parts by weight titanium oxide
5 parts by weight
100 parts by weight (curing agent component) Trimethylolpropane adduct of 2.4- or 2.6-) lylene diisocyanate (N00%:13%) 90 parts by weight Toluene 10 parts by weight Total
100 parts by weight Main agent/curing agent: lOO
/20 or higher coated steel sheets were dried for 7 days at a temperature of 20° C. and a humidity of 75° C. and then subjected to a salt spray test.

The test results are shown in Table 1.

〔Effect of the invention〕

By applying the coating composition of the present invention to bad surfaces such as rusted surfaces, no surface treatment is performed, but even if the surface treatment is reduced, the rusting and blistering of the paint film will be reduced as if the surface treatment had been completely performed. It is possible to suppress the occurrence of cracking, and the adhesion is also extremely good. It is possible to apply a strong anti-corrosion coating to a steel plate with a reduced surface treatment using a paint that costs almost the same as a regular paint without using an expensive bad surface paint, and the economic effect is great.

Claims (2)

[Claims] (1) As essential components (A) polyhydroxy compound 100 parts by weight (B) polyisocyanate 50 to 100 parts by weight (C) aromatic oligomer 50 to 100 parts by weight (D) scaly pigment 50 parts by weight
A coating composition containing ~150 parts by weight. (2) Aromatic oligomer has a number average molecular weight of 300 to 60
0. The coating composition according to claim 1, wherein the coating composition is 0.