JPH0684486B2 - Paint composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coating composition which is applied to a metal surface having a rust layer to form a film excellent in long-term rust prevention. More specifically, it relates to a coating composition comprising a low molecular weight compound having an isocyanate group, a main agent containing a terminal isocyanate addition type polymer, and a curing agent containing a low molecular weight epoxy resin and a high molecular weight epoxy resin.

PRIOR ART AND ITS PROBLEMS The process by which iron and steel rust is complex and is not well understood, but rust is a permanent problem, especially in moist environments. The heavy-duty anticorrosion coating applied to iron products used under severe conditions has a good balance of quick-drying properties, recoatability including adhesion and adhesion, and long-term rust resistance to rusty substrates. There is a demand for a paint or coating system that can be removed, but it is difficult to find a paint or coating system that is currently well balanced in the required properties. And a huge amount of money is lost annually through the damage caused by rust.

Epoxy resin paints, polyurethane paints, chlorinated rubber paints, vinyl chloride resin paints, etc. have been conventionally used for long-term corrosion protection of steel materials and steel structures. Among these paints, epoxy resin paints are used in a wide range of fields as metal anticorrosion paints because of their excellent anticorrosion performance. However, rust prevention itself is not only determined by the type of paint, film thickness, etc., but it is largely dependent on the surface treatment before painting, mainly on the extent of rust removal, and the paint is applied to the surface after sufficient rust removal. Then, it is well known that the adhesion between the base material of the steel material and the paint is improved, and the rust preventive effect as the paint is exhibited. Therefore, before painting, it is necessary to apply enough so-called base treatment on the surface to be coated with a power tool or power brush, or to completely remove rust by sandblasting, etc. There is a drawback in that the adhesion of the resin coating material to the metal base is deteriorated and the anticorrosion performance is remarkably lowered. Especially when painting a rusted steel plate during use, such as on a repair ship, the surface treatment requires man-hours two to three times as much as a new steel plate, and even if some rust remains on the treated steel plate, the conventional paint will paint. Adhesion between the steel sheet and the steel sheet is reduced, and long-term durability is deteriorated. Thus, there is a great inconvenience when it is used for repairing an existing structure or an old coating film. Furthermore, when subjecting the metal to be coated to an undercoat, the generation of powder dust, noise, etc. is unavoidable, and the occurrence of these is not preferable from the viewpoint of environmental hygiene, etc., and therefore an anticorrosion coating method in which the undercoat of the metal is omitted, That is, there is a strong demand for the development of an anticorrosion paint that provides excellent anticorrosion performance even when it is directly applied to a metal surface having a rust layer.

Various methods have been proposed to prevent corrosion by directly coating a paint on rust without such a base treatment. For example, a method of improving the adhesion to a bad ground such as a low-keren surface by mixing a petroleum resin with an epoxy resin is generally performed, but in this case, the primary adhesion to the bad ground is certainly Although it is improved, there is a drawback that excellent corrosion resistance cannot be maintained for a long period of time because the petroleum resin is mixed.

Further, there is a method of using a processing drying oil, an alkyd resin, a phenolic resin, etc. alone or a mixture of these as a main coating film-forming element, and using a paint prepared by adding an anticorrosive pigment thereto. This product has inadequate water resistance and anticorrosion properties, and since it has poor solvent resistance, it is coated with a topcoat paint with excellent anticorrosion properties such as epoxy resin-based, urethane resin-based, vinyl resin-based, etc. There is a drawback that you cannot do it. There is also a method of applying a paint using a moisture-curable isocyanate resin to the rust surface, but this paint generates carbon dioxide gas during the curing reaction, so many pinholes are generated in the paint film, which is useful for long-term corrosion protection. It has a shortcoming. More recently, it has been proposed to use a paint composed of a precondensate of an epoxy resin and a phenol resin and a polyamine or polyamide curing agent. When this paint is used, the water contained in the rust layer is sealed by the coating film and remains as it is, so the growth of rust under the coating film continues to progress and eventually forms blister rust or spot rust. There are drawbacks. On the other hand, compounding the chelate-bonding ability into the paint,
After application, chelate reaction with the iron surface of the base material,
Attempts have been made for a long time to improve its performance. For example, there is a primer that is intended to penetrate the rust surface and react with iron ions on the surface of the steel material to make the rust insoluble and stable, at the same time prevent the progress of rust and improve the adhesion of the paint. , The composition of these primers is orthophosphoric acid, potassium ferrocyanide, pyridine derivative,
Since it is difficult to fix rust to each other because it consists of an aqueous solution of salicylic acid derivative, tannic acid, etc., its strength is extremely weak. Therefore, even if a rust-preventive paint is applied to the surface treated with these primers, it will cause a slight impact. For example, it has a drawback that it is easily peeled off in the rust layer due to the reasons such as the above, and aside from the extremely lightly corroded surface, the above-mentioned rust removal is still required for the corroded surface or more. In other words, in addition to the rust prevention treatment, a coating treatment process is required, which is not a process advantage. As mentioned above, when painting a steel plate that has been contaminated with conventional oil and rust, after removing oil with a cleaning agent, a method for completely removing rust by sandblasting must be applied, which requires a large amount of cost. Since it is not economical, a power worker such as a disk sander removes rust to reduce the construction cost, but it is difficult to remove rust and oil, so the adhesion of the paint is poor and a satisfactory coating can be obtained. Absent. As a result, coating defects such as "blister", "peeling" and "rusting" occur early after coating, so that the purpose of coating cannot be achieved. As a result of earnest studies to solve the above problems, the present inventors have found that the low molecular weight 2
A coating composition having a terminal isocyanate-addition type polymer containing a compound containing at least one isocyanate group as a main agent and an epoxy resin containing a low molecular weight epoxy resin as a curing agent penetrates deep into the rust layer and has excellent suppression. The present invention has been completed by finding that a coating film having rust property can be provided.

As is clear from the above description, the object of the present invention is to apply a rough sandy metal surface such as a disk sander, a power brush, or a low grade blast to a rough metal surface that has been pretreated or a rough metal surface that has not been grounded. The present invention is to provide a coating composition capable of obtaining an anticorrosion coating equivalent to that subjected to high-grade sandblast treatment.

(Means for Solving Problems) A base agent containing a terminal isocyanate addition type polymer having an average molecular weight of 1000 or more and a compound having two or more isocyanate groups having an average molecular weight of less than 1000, and an average molecular weight of 80.
A coating composition comprising 0 or more epoxy resin and a curing agent containing an epoxy resin having an average molecular weight of less than 800.

The average molecular weight used in the present invention is 1000 or more terminal isocyanate addition type polymer, a polyol, a polyhydroxy compound such as polyester or a compound having active hydrogen such as polyamine, tolylene diisocyanate,
Hexamethylene diisocyanate, metaxylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, lysine diisocyanate derivative, etc., or a terminal obtained by excessively reacting a dimer or trimer of these It is a prepolymer composed of an isocyanate adduct, and the isocyanate group may be one end, both ends, or a mixture of both, but a both end isocyanate addition type polymer is preferable. The average molecular weight of the terminal isocyanate addition type polymer is 1000 or more, preferably 2000 or more 5000
It is 0 or less. Examples of compounds having two or more isocyanate groups having an average molecular weight of less than 1000 (hereinafter abbreviated as isocyanate compounds) include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol. , Neopentyl glycol,
Pentadiol, hexanediol, octanediol, 2-ethyl-1,3-hexanediol, 1,4-butynediol, bisphenol A, diethylene glycol,
Low molecular weight glycols such as triethylene glycol and dipropylene glycol, a molecular weight less than 1000 obtained by reacting with a large excess of an aromatic or aliphatic polyisocyanate compound to remove the excess polyisocyanate compound, preferably 150 or more. There may be mentioned up to 800 prepolymers. Examples of the aromatic or aliphatic polyisocyanate compound include 1,5-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, di- and tetraalkyldiphenylmethane diisocyanate, 4, 4'-dibenzyl isocyanate, 1,3-
Phenylene diisocyanate, toluene diisocyanate, chlorinated isocyanates, brominated isocyanates, phosphorus-containing isocyanates, butane-1,4-diisocyanate, hexane-1,6-diisocyanate, dicyclohexylmethane diisocyanate, cyclohexane-
1,4-diisocyanate, xylene diisocyanate,
Lysine diisocyanate, 1-methylbenzol-2,4,
Examples thereof include 6-triisocyanate, bisphenyl-2,4,4'-triisocyanate and triphenylmethane triisocyanate. These can be mixed and used.

The main ingredient of the present invention is that the weight ratio of the isocyanate compound to the terminal isocyanate addition type polymer is 99: 1.
To 1:99, preferably 75:25 to 25:75, and preferably a solvent. If the latter is less than 99: 1, the permeability will be poor and sufficient adhesion will not be obtained, and if it is more than 1:99, the rust prevention and rust resistance will be poor.

Examples of the epoxy resin used in the present invention include known epoxy resins described in Chapter 2 of "Epoxy Resin" by Kuniyuki Hashimoto, published by Nikkan Kogyo Shimbun in 1969. Examples of more suitable epoxy resins include epoxy resins having an average molecular weight of 800 or more and less than 800 obtained by reacting a polyhydric alcohol, a polyhydric phenol or the like with an excess of epichlorohydrin or alkylene oxide. Examples of polyhydric alcohols are ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, glycerin, neopentyl glycol, butylene glycol, hexanediol, trimethylolethyne, trimethylolpropane,
Pentaerythritol, diglycerol, sorbitol, and the like, and polyphenols such as 2,2-bis (4-
Hydroxyphenyl) propane (commonly referred to as bisphenol A), halogenated bisphenol A, 4,
4'-dihydroxyphenylmethane (generally referred to as bisphenol F), tris (4-hydroxyphenyl) propane, resorcin, tetrahydroxyphenylethane, nopolak type polyhydric phenol, cresol type polyhydric phenol and the like. Other examples of epoxy resins that can be used in the present invention are 1,2,3-tris (2,3-
Epoxypropoxy) propane, glycidyl adduct of aniline or aniline derivative (eg orthotoluidine), glycidyl esters such as phthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, epoxidized soybean oil And so on.

The curing agent in the present invention is an epoxy resin having an average molecular weight of 800 or more and an average molecular weight of less than 800, preferably a weight ratio of the epoxy resin of 500 or less is 99: 1 to 1:99, preferably
It is prepared by adding 75:25 to 25:75 and adding a solvent. The addition amount of epoxy resin having an average molecular weight of less than 800 is 99:
If it is less than 1, the penetrability is poor and sufficient adhesion performance cannot be obtained, and if it exceeds 1:99, the coating film strength is reduced and the rust preventive property, rust preventive property and rust preventive property are deteriorated.

When a solvent is contained as a thinner in the main agent and the curing agent of the present invention, the solvent is used to dilute and disperse a trace amount of the adhered oil component on the metal surface to be coated, and the resin component in the coating material easily penetrates into the rust, which is preferable. Examples of the solvent include aromatic hydrocarbons such as toluene and xylene, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and diisobutyl ketone, esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, cellosolve and cellosolve acetate. Usual solvent for paints may be mentioned. The amount used can be appropriately added depending on the working conditions when the urethane resin as the main ingredient and the epoxy resin as the curing agent are mixed, but it is usually 20 to 70% by weight in the total composition. In addition to the above-mentioned components, conventionally used pigments, additives, plasticizers and the like can be appropriately added to the curing agent.

As a method for coating the coating composition of the present invention, a conventionally known coating means such as spray coating or brush coating is used. The metal surface of the object to be coated has a rust layer for the purpose of the present invention, and it is not necessary to remove the floating rust during coating.

The mixing ratio of the main agent and the curing agent of the coating composition is not particularly limited, but is usually 0.5 to 10 parts by weight of the main agent with respect to 1 part by weight of the curing agent. However, since it is necessary to remove the water contained in the rust layer by the chemical action of the isocyanate group, it is preferable to mix them so that the amount of the isocyanate group in the main agent is larger than that of the curing agent. Although the coating amount is not particularly limited, it is generally about 3 μ to about 380 μ, preferably about 20 μ to about 150 μ in dry film thickness.

(Examples) Hereinafter, the present invention will be described more specifically with reference to Examples.

The type and properties of the terminal isocyanate addition type polymer and the isocyanate compound used in each example and comparative example are described below.
The epoxy resin is shown in Table 2 and the epoxy resin is shown in Table 2.

Example 1 1700 parts by weight of urethane resin M54-80A (solid content 80%) as a terminal isocyanate addition type polymer having an average molecular weight of 1000 or more, 1000 parts by weight of hexamethylene diisocyanate, 123 parts by weight of toluene, 123 parts by weight of acetic acid as an isocyanate compound. A base agent was prepared by adding parts by weight. Next, 350 parts by weight of the epoxy resin (G) and 150 parts by weight of toluene were added to 350 parts by weight of the epoxy resin (F), azeotropically dehydrated, and then 150 parts by weight of methyl ethyl ketone was added to prepare a curing agent. A coating material prepared by mixing 100 parts by weight of a curing agent with 350 parts by weight of the main component was shot sprayed on a shot blasted steel sheet, and the shot blasted steel sheet was sprayed with 5% salt water for 1 week in advance to generate rust, and after washing, The product dried at room temperature for 1 day was brushed. The coating film performance test results of the obtained coated plate are shown in Table 4 below.

Example 2 1700 parts by weight of the same urethane resin M54-80A (solid content 80%) used in Example 1 was added as an isocyanate compound.
A coating material was prepared according to Example 1 except that 1000 parts by weight of NP1000 (solid content: 75%), 123 parts by weight of toluene, and 123 parts by weight of ethyl acetate were added to prepare a coating material, and the coating material was applied. The coating film performance test of the obtained coated plate is shown in Table 4 below.

Example 3 1700 parts by weight of the same urethane resin M54-80A (solid content 80%) used in Example 1 was added as an isocyanate compound.
A coating material was prepared in accordance with Example 1 except that 1000 parts by weight of 4,4'-diphenylmethane diisocyanate, 123 parts by weight of toluene, and 123 parts by weight of ethyl acetate were added to prepare the base material, and the coating material was applied. The coating film performance test of the obtained coated plate is shown in Table 4 below.

Example 4 1700 parts by weight of urethane resin M54-80A (solid content 80%) was mixed with isophorone diisocyanate as an isocyanate compound.
A coating material was prepared in accordance with Example 1 except that 1000 parts by weight, 123 parts by weight of toluene, and 123 parts by weight of ethyl acetate were added to prepare the main component, and the coating material was applied. The coating film performance test of the obtained coated plate is shown in Table 4 below.

Examples 5 to 8 Example 1 except that urethane resin M54-80A (solid content 80%), hexamethyldiisocyanate, epoxy resin (F) and epoxy resin (G) were used in the compositions shown in Table 3.
A coating material was prepared in accordance with the above and used for coating. The coating film performance test of the obtained coated plate is shown in Table 4 below.

Comparative Example 1 A paint was prepared and applied in accordance with Example 1 except that 123 parts by weight of toluene and 123 parts by weight of ethyl acetate were added to 1700 parts by weight of a urethane resin M54-80A (solid content 80%) to prepare a base compound. I served. The coating film performance test of the obtained coated plate is shown in Table 4 below.

Comparative Examples 2 to 3 Comparative Example 2 is based on Example 1 except that the epoxy resin (F) is not used, and Comparative Example 3 is based on Example 1 except that the epoxy resin (G) is not used. It was prepared and provided for painting. The coating film performance test of the obtained coated plate is shown in Table 4 below.

(Effect of the invention) As is clear from the above test results, when the coating composition of the present invention is applied to a poor surface, both the terminal isocyanate addition type polymer and the epoxy resin penetrate into the rust, and at this time, the terminal isocyanate addition occurs. The type polymer solidifies while chemically reacting with the hydroxyl groups of water and the epoxy resin hydroxyl groups that make up the rust molecule, while also recording the evaporation of the solvent, and strengthens the rust with a small amount of oil adhered inside. Stick to. On the other hand, the hydroxyl group of the epoxy resin forms a hydrogen bond with an oxygen atom of rust and strongly adheres to rust or a metal substrate, so that the coating composition of the present invention has good penetration into a rust layer, adsorption, and a rust surface. The cured coating has excellent adhesion and exhibits excellent corrosion resistance on the rust surface.

Claims (1)

[Claims] 1. A base material comprising a terminal isocyanate addition type polymer having an average molecular weight of 1000 or more and a compound having two or more isocyanate groups having an average molecular weight of less than 1000.
A coating composition comprising an epoxy resin having an average molecular weight of 800 or more and a curing agent containing an epoxy resin having an average molecular weight of less than 800.