JPH0145502B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a metal coating composition, and more particularly to a metal coating composition that can be coated relatively thickly for the purpose of corrosion resistance, water resistance, impact resistance, electrical insulation, etc. Conventionally, asphalt, fiber-reinforced asphalt, coal tar enamel, and the like have been used as coating materials for this type of coating composition. However, these materials are inferior in physical properties such as impact resistance, flexibility, and adhesion at low temperatures. Furthermore, when applying these materials, they must be heated and melted, and the application process requires skill. Furthermore, there are other problems such as the generation of irritating gases, odors, and the risk of ignition. Tar epoxy resin paint is also used, but
Curing is slow, workability after painting is poor, and therefore painting efficiency is extremely poor. Polyethylene fusion bonding is also used, but it requires large-scale equipment and is not suitable for coating small quantities, and cannot be applied to welded parts or irregularly shaped parts of steel pipes on-site. The present inventors are already applying for a metal coating composition that eliminates these drawbacks and has excellent corrosion resistance, water resistance, impact resistance, insulation properties, etc. However, under certain conditions, such as painting welded parts on site, repairing paint film defects, and painting irregularly shaped parts, the painted steel pipe surface may "sag" and the paint film may become uneven, resulting in corrosion resistance. , there may be problems with water resistance, impact resistance, insulation resistance, etc. In order to eliminate these drawbacks, the present inventors have conducted extensive research and have now provided the present invention. That is, (a) a polymer polyol whose main chain is formed only of carbon atoms and hydrogen atoms, has two or more hydroxyl groups in the molecule, and has a hydroxyl value of 120 mgKOH/g or less [hereinafter referred to as (a) polyol] ] and (b) polyols with a hydroxyl value of 120 mgKOH/g or less [however, (a) polyols are excluded. (hereinafter referred to as (b) polyol); and (c) a compound that has two or more hydroxyl groups and/or amino groups in the molecule and has a hydroxyl value and/or amine value higher than 120 mgKOH/g [hereinafter referred to as (c) compound. ], (d) an organic polyisocyanate compound [hereinafter referred to as (d) compound], and if necessary, (e) a catalyst, and (f) a plasticizer, and the blending ratio of each component is (a) the polyol is 100-X parts by weight, (b) polyol is X parts by weight (X is 0 to 50 parts by weight), (c) compound is 0 to 300 parts by weight, (d) compound is (a) polyol + (b) polyol + (c) For all hydroxyl groups and amino groups of the compound
A metal consisting of a polyurethane resin synthesized by reacting each component with an amount such that the ratio of NCO/(OH + NH ₂ ) is 0.85 to 1.5, a catalyst of 0 to 100 parts by weight, and a plasticizer of 0 to 100 parts by weight. In the coating composition,
The polyurethane resin contains a filler A = [specific surface area of filler] x [parts by weight of filler] ÷ [total parts by weight of various components used in polyurethane resin synthesis] (However, in the formula, the specific surface area of filler is m ² /g (The total parts by weight of various components used in polyurethane resin synthesis do not include parts by weight of fillers.) A metal coating composition containing an amount such that the value of A in the formula is 3.5 or more. be. The polyol (a) used in the present invention has a molecular main chain formed only of carbon atoms and hydrogen atoms, has two or more hydroxyl groups in the molecule, and has a hydroxyl value of 120 mg.
KOH/g or less, but examples include those that are mainly composed of 1,4-bonds and have a hydroxyl value of 20 to 20.
120mgKOH/g of hydroxyl-terminated liquid polybutadiene. These are Poly bd R-45HT,
Poly bd R-45M, Poly bd CS-15 (both
It is commercially available under product names such as ARCO (manufactured by ARCO). Furthermore, as a well-known production method, the hydrogen peroxide method
-22048), an azobisisonitrile compound having a hydroxyl group (Japanese Patent Publication No. 38-5993), a peroxide compound having a hydroxyl group (Japanese Patent Publication No. 14747-1977), etc. were used as initiators. 1, produced by a radical polymerization method,
There is a hydroxyl group-terminated polyol mainly composed of a 4-conjugated diene polymer. (a) When polybutadiene polyol is used as the polyol, it is preferable to use a polybutadiene polyol containing 60% or more of 1,4-bonds. 1,2-bonds cause a crosslinking and curing reaction due to oxygen in the air, which tends to cause brittleness in the resin. Therefore, when exposed to air for a long period of time, especially under conditions of exposure to heat, ultraviolet rays, etc., intermolecular crosslinking occurs, causing deterioration in flatness tests and impact tests. Furthermore, polybutadiene polyol mainly composed of 1,2-bonds has a high viscosity and tends to cause poor mixing. (b) Examples of the polyol include polyoxyalkylene polyol, polytetramethylene ether glycol, polyester polyol, and the like, and those having a hydroxyl value of 120 mgKOH/g or less. (c) Compounds include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, hexanediol, octanediol, hydroquinone, bisphenol A, trimethylolpropane, glycerin, triethanolamine, bis(2-hydroxypropyl)aniline and compounds having two or more hydroxyl groups such as alkylene oxide adducts of these, diaminodiphenylmethane, methylenebis(orthochloroaniline) (hereinafter referred to as MOCA), phenylenediamine, tolylenediamine,
Amino groups such as compounds having two or more amino groups such as ethylenediamine and piperazine, and compounds in which alkylene oxide is added to a part of the amino group of monoethanolamine, aminoethylethanolamine, and the above compounds having two or more amino groups. and compounds having two or more hydroxyl groups. (c) The hydroxyl value and/or amine value of the compound is higher than 120 mgKOH/g, preferably 250 to 900 mg
KOH/g is good. (d) Compounds include tolylene diisocyanate (hereinafter referred to as TDI), crude diphenylmethane diisocyanate (hereinafter referred to as crude MDI), and liquid diphenylmethane diisocyanate (hereinafter referred to as liquid MDI).
), hexamethylene diisocyanate,
Examples include isophorone diisocyanate and xylylene diisocyanate. Next, as a catalyst to be used as necessary, dibutyltin dilaurate, stannath octoate, dibutyltin diacetate, lead octylate,
Examples include organometallic compounds such as lead naphthenate. Examples of the plasticizer that may be used as necessary include coal tar, process oil, liquid petroleum resin, dibutyl phthalate, dioctyl phthalate, and chlorinated paraffin. In the metal coating composition of the present invention, the blending ratio of (a) polyol and (b) polyol is such that (a) polyol is
(b) polyol should be used in an amount of 100 to 50 parts by weight, and (b) polyol should be used in an amount of 0 to 50 parts by weight, and the total amount of both should be 100 parts by weight. In metal coating compositions intended for corrosion prevention and insulation, the water absorption rate, hydrolysis resistance, and electrical insulation properties of the resin are important. (a) Polyurethane resins using polyols have excellent properties. Therefore, in order to achieve the purpose as a metal coating composition, (a) polyol should be an essential component when synthesizing a polyurethane resin. (b) Since polyols have ether bonds or ester bonds in their molecules, they not only have high water absorption and water permeability when formed into a coating, but also have low insulation resistance, which is an indicator of anticorrosion performance. On the other hand, polyol (a) does not have bonds in its molecules that reduce anticorrosion performance, such as ether bonds or ester bonds, so the water absorption rate and water permeability of the coating film are low, and the insulation resistance is also high. However, as the molecular weight of (a) polyol increases, in other words, as the hydroxyl value decreases, the viscosity increases. It is effective to use (a) a polyol, especially a polyoxyalkylene polyol, in order to lower the viscosity of the coating solution and improve workability during coating. (b) To improve workability, even if polyol is added, the anticorrosive effect must not be reduced (a)
There should be at least 50 parts by weight of polyol and less than 50 parts by weight of (b) polyol. (a) When the amount of polyol is less than 50 parts by weight, the water absorption rate of the coating film increases, and the insulation resistance decreases accordingly. Further, when a polyester polyol is used as the (b) polyol, if the (a) polyol is less than 50 parts by weight, the coating film deteriorates due to hydrolysis. The amount of the compound (c) to be used can be 0 to 300 parts by weight based on the total of 100 parts by weight of the (a) polyol and (b) polyol. Furthermore, the compound (c) should be adjusted so that the average hydroxyl value of (a) polyol + (b) polyol + (c) compound, or the sum of it and the average amine value (hereinafter referred to as average hydroxyl value), is 100 to 300 mgKOH/g. should be used for As in the present invention, by combining a polyol with a high hydroxyl value ((c) compound) and a polyol with a low hydroxyl value ((a) polyol and (b) polyol), the average hydroxyl value is 100 to 300 mg.
When expressed as KOH/g, the hydroxyl value is 100 to 300.
The resulting polyurethane resin has higher elasticity than when mgKOH/g polyol is used alone, and the coating film has excellent properties such as mechanical strength, impact strength, and abrasion resistance. Polyurethane resins obtained by reacting only (a) polyol and (b) polyol with compound (d) tend to be flexible but tend to have low mechanical strength. The compound (c) is used to improve the mechanical strength of the polyurethane resin coating obtained by reaction.
(c) Compounds should be used in amounts of 0 to 300 parts by weight. (c)
If the amount of the compound is 300 parts by weight or more, the mechanical strength will be high, but the coating will be hard, resulting in low cold resistance, low elongation of the coating at low temperatures, and low impact strength. Therefore, the amount of compound (c) should be limited to 300 parts by weight or less. When the average hydroxyl value is less than 100 mgKOH/g, the resulting coating film has excellent flexibility and cold resistance, but has too low mechanical strength. Conversely, if the average hydroxyl value is greater than 300 mgKOH/g, the mechanical strength will be high, but the flexibility and cold resistance will be poor, and the impact strength at low temperatures will be low. Therefore,
The above (a) polyol, (b) polyol, and (c) compound should be mixed in a limited proportion, and the average hydroxyl value should be 100 to 300 mgKOH/g. The hydroxyl value of (a) polyol and (b) polyol is
When it is larger than 120 mgKOH/g, the hydroxyl values of (a) polyol, (b) polyol, and (c) compound become close in order to set the average hydroxyl value to 100 to 300 mgKOH/g. Therefore, the performance of the above-mentioned coating film is deteriorated, so the hydroxyl value of polyol (a) and polyol (b) should be 120 mgKOH/g or less.
Note that a polyol that has the same structure as the (a) polyol and (b) polyol but has a hydroxyl value greater than 120 mgKOH/g should be considered as the (c) compound. Generally, as the average hydroxyl value decreases, mechanical strength decreases, but cold resistance improves. When the hydroxyl value increases in the reaction, mechanical strength is improved, but cold resistance is inferior. Furthermore, as the hydroxyl value increases, the resin becomes brittle. (d) The compound is (a) polyol + (b) polyol + (c)
NCO/ for hydroxyl and amino groups of compounds
A ratio of (OH+ _NH2 ) in the range 0.85 to 1.5 should be used. If this ratio is less than 0.85, curing will be insufficient and tackiness will remain. On the other hand, if this ratio exceeds 1.5, the free isocyanate groups react with moisture in the air, which tends to cause blisters in the coating layer.
The catalyst used as needed should be used in an amount of 0 to 10 parts by weight, and the plasticizer should be used in an amount of 0 to 100 parts by weight.
The catalyst is used to accelerate the curing reaction of the urethane resin, but after the reaction is completed, it is not incorporated into the molecule, so it acts as a plasticizer. Furthermore, if 10 parts by weight or more of the catalyst is used, the initial curing becomes too fast, making coating impossible. Therefore, the amount of catalyst used should be limited to 0 to 10 parts by weight, if necessary. Further, since the plasticizer is not incorporated into the polyurethane molecules, it has the effect of improving workability and imparting flexibility to the resin, but causes a decrease in mechanical strength, impact resistance, etc. Therefore, the amount of plasticizer used, if necessary, should be limited to 0 to 100 parts by weight. Next, examples of the filler of the present invention include talc, surface-treated calcium carbonate, silicates, asbestos, and the like. The amount of filler is A = [Specific surface area of filler] x [Parts by weight of filler] ÷ [Total parts by weight of each component used in polyurethane resin synthesis] (However, in the formula, the specific surface area of filler is m ² / The total weight part of each component used in polyurethane resin synthesis does not include the weight part of the filler.) In the formula, A is 3.5 or more, preferably
The amount is 5.0 or more and 30 or less. The value of A is
If it is smaller than 3.5, there is no sag prevention effect,
A: Sagging of the paint film occurs and the thickness of the paint film becomes uneven
If the value is greater than 30, the liquid with the filler added will be too hard and difficult to mix with the other liquid.
Actual use is often difficult. Therefore, the value of A is 3.5 or more, preferably 5.0 or more, and
The amount is preferably 30 or less. In the formula, the specific surface area of the filler is determined as the surface area per gram of powder based on the amount of nitrogen gas adsorbed by the BET method. A filler with a large specific surface area is effective when blended in a small amount, whereas a filler with a small specific surface area requires a large amount to be blended. When two or more types of fillers are used together, the arithmetic mean value of the specific surface area may be calculated as the specific surface area of the mixed filler. In the formula, the molecule [specific surface area of filler]×[parts by weight of filler] represents the total surface area of the filler. The denominator [total parts by weight of each component used in polyurethane resin synthesis] represents the total weight of the liquid components. The formula therefore represents the surface area of filler per liquid component. As the total surface area of the filler increases, the amount of liquid it can adsorb increases, making dripping less likely. Conversely, as the total surface area decreases, the amount of liquid adsorbed decreases, making the mixture highly fluid and prone to dripping. Next, the total weight of each component used in polyurethane resin synthesis is (a) polyol, (b) polyol, (c) compound, and (d) compound, as well as catalysts, plasticizers, and other additives used as necessary. is the total amount used (parts by weight). The total parts by weight do not include the amount of filler used (parts by weight). The filler-containing polyurethane resin of the present invention, that is, the metal coating composition, can be obtained by the following method. (1) A first liquid in which predetermined amounts of (a) polyol, (b) polyol, (c) compound, filler, catalyst used as necessary, plasticizer, etc. are uniformly mixed in advance, and (d) compound. Mix it with the second liquid and apply it to metal etc. (one shot method). (2) A first liquid (prepolymer) obtained by reacting a part of each of (a) polyol, (b) polyol, and (c) compound with all of (d) compound, and (a) polyol, (b) ) Polyol, the remainder of the compound (c), a filler, a catalyst used as necessary, a plasticizer, etc. are uniformly mixed together and the second liquid is stored separately, and when used, the first liquid and the second liquid are mixed together. Mix and apply to metal etc. (prepolymer method). In these methods, when applying to metal etc., it is preferable to perform cleaning treatment such as blasting treatment in advance, and then apply a primer thereon to improve adhesion. Further, as a method for coating metal etc., the following various methods can be used, for example. (1) A method in which the first and second liquids are accurately weighed into a suitable container such as a vat, mixed thoroughly with a drill mixer, etc., and then applied with a trowel, etc. (2) Spray painting method using a two-component mixed spray paint machine. Next, metals of the present invention include steel pipe sheet piles, steel plates, H
Examples include shaped steel. As described above, according to the present invention, it is possible to provide a metal coating composition that has excellent properties such as water absorption, water resistance, impact resistance, insulation resistance, and corrosion resistance, and does not cause "sag" during coating. The present invention will be explained below with reference to Examples. In the examples, "parts" are by weight. Examples 1 and 2 Prepolymer production; Predetermined (a) polyol and (b) polyol were placed in 24 reaction vessels, and (d) compound was added and reacted at 80°C for 1 hour to form the first liquid. did. Production of curing agent; Predetermined amount of (a) polyol, (b) remainder of polyol and
(c) The compound, catalyst, plasticizer, and filler were uniformly mixed to form a second liquid. After the first liquid and the second liquid were mixed in a vat, they were coated on the surface of a vertically erected steel pipe with a diameter of 1000 mm and a length of 1200 mm using a trowel. The results are shown in Table 1. Comparative Examples 1, 4, and 5 were also conducted in the same manner. In Examples 1 and 2, no sagging occurred and a uniform coating film was obtained. In addition, the water absorption rate, volume resistivity, and anticorrosion performance of the coating film were also good. Since Comparative Example 1 did not use the filler of the present invention, the coating film sagged. Pinholes occurred in the thin areas of the coating during the impact test. The appearance of the paint was poor because a lot of sagging occurred. In addition, as a result of applying the coating film of Comparative Example 1 to a horizontally placed steel plate, the anticorrosion performance as a metal coating composition was good. Therefore, in actual use, the filler of the present invention should be added as shown in Examples 1 and 2. Comparative Example 4 does not use polyol (a), which is an essential component of the present invention, and uses only polypropylene polyol as the polyol component, so the water absorption rate is high and the volume resistivity of the coating film is low. Because it is too strong, it cannot be used as a metal coating composition. In addition, since the filler of the present invention is used in the amount of the present invention, sagging is less likely to occur. Comparative Example 5 also did not use polyol (a), which is an essential component of the present invention, and only used polyester polyol. Therefore, the water absorption rate is high,
The volume resistivity of the coating film becomes lower. Furthermore, when the coating film was immersed in saline for a long period of time, the ester bond was hydrolyzed, causing the coating film to soften. For these reasons, although Comparative Example 5 has little sag, it cannot be used as a metal coating composition.

【table】

[Table] The same applies to the following examples. Examples 3 and 4 A first liquid in which (a) polyol, (b) polyol, (c) compound, catalyst, plasticizer, and filler are uniformly mixed and a second liquid (d) compound in a two-liquid mixing airless The same vertical steel pipe as in Example 1 was coated with a spray paint machine. The results are shown in Table 2. Comparative Examples 2 and 3 were also carried out in the same manner. In Examples 3 and 4, the value of A was within the range of the present invention, so no sagging was observed in the coating film, and variations in film thickness were tolerable considering that the coating was sprayed. In Comparative Example 2, the same amount of filler was used as in the Example, but since the specific surface area of the filler was small, the value of A was outside the range of the present invention, so 0.3 mm was used in one coating.
It can only be painted to a certain extent. When the coating was applied in the same manner as in the example, sagging occurred in the coating film. Due to sagging, the thickest part of the paint film was 10.2mm, and the thinnest part was 0.5mm. When performing an impact test, pinholes appear in the thin parts of the paint film. For this reason, it cannot be used as a metal coating composition for the purpose of corrosion prevention. In addition, when the composition of Comparative Example 2 was applied to a horizontally placed steel plate and tested, it showed good performance as a metal coating composition. In Comparative Example 3, the specific surface area of the filler is within the range of the present invention, but the value of A is outside the range of the present invention because the amount added is too small. Similar to Comparative Example 2, when the coating was applied in the same manner as in Example 3, sagging occurred. When an impact test was performed, pinholes were found in thin areas of the coating. In this case, no sagging occurred up to 0.3 mm with one coating, so tests were also conducted on coated steel pipes coated 12 times with 0.3 mm each, and the composition showed good performance as a metal coating composition. In addition, Example 3
In the case of , the painting was completed in 5 minutes, but in order to apply uniformly with this method, the paint must be allowed to harden for 10 minutes after each application, so it took 2 hours to complete the painting. It cost. It was difficult to use this coating method practically because of its poor coating workability.

【table】

[Table] Example 5 (c) 220 parts of compound polyhardener UD-503,
(c) Amount of surface-treated calcium carbonate with a specific surface area of 26 m ² /g added to a mixture of 50 parts of the compound castor oil, 30 parts of the plasticizer DOP (dioctyl phthalate), and 0.1 part of the catalyst lead octylate. A second solution was prepared in which the amount was varied from 0 to 100 parts. The prepolymer of Example 1 in Table 1 was used as the first liquid. After mixing the first and second liquids at the specified ratio,
It was painted with a trowel to a thickness of 3 mm on a vertical steel plate. After curing, the film thickness of each part was measured using an electromagnetic film thickness meter. The results are shown in Figure 1. If the value of A is less than 3.5, sagging is likely to occur, the maximum and minimum film thicknesses are greatly different, and the appearance of the coating is poor. Even when the value of A is 5 or more, there is a difference between the maximum and minimum film thicknesses, but this is due to variations in film thickness during coating, and no sagging was observed in the coating film.

[Brief explanation of drawings]

FIG. 1 shows the value of A and the thickness of the coating film when the amount of surface-treated calcium carbonate added was changed.

Claims (1)

[Claims] 1 (a) The main chain of the molecule is formed only of carbon atoms and hydrogen atoms, and the molecule has two or more hydroxyl groups,
A polymer polyol with a hydroxyl value of 120 mgKOH/g or less [hereinafter referred to as (a) polyol], and (b) a polyol with a hydroxyl value of 120 mgKOH/g or less [however, (a) polyol is excluded. (hereinafter referred to as (b) polyol); and (c) a compound that has two or more hydroxyl groups and/or amino groups in the molecule and has a hydroxyl value and/or amine value higher than 120 mgKOH/g [hereinafter referred to as (c) compound. ], (d) an organic polyisocyanate compound [hereinafter referred to as (d) compound], and if necessary, (e) a catalyst, and (f) a plasticizer, and the blending ratio of each component is (a) the polyol is 100-X parts by weight, (b) polyol is X parts by weight (X is 0 to 50 parts by weight), (c) compound is 0 to 300 parts by weight, (d) compound is (a) polyol + (b) polyol + (c) For all hydroxyl groups and amino groups of the compound
A metal consisting of a polyurethane resin synthesized by reacting each component in an amount such that the ratio of NCO/(OH + NH ₂ ) is 0.85 to 1.5, the catalyst is 0 to 10 parts by weight, and the plasticizer is 0 to 100 parts by weight. In the coating composition,
The polyurethane resin contains a filler A = [specific surface area of filler] x [parts by weight of filler] ÷ [total parts by weight of various components used in polyurethane resin synthesis] (However, in the formula, the specific surface area of filler is m ² /g (The total parts by weight of various components used in polyurethane resin synthesis do not include parts by weight of fillers.) A metal coating composition containing an amount such that the value of A in the formula is 3.5 or more. 2. The metal coating composition according to claim 1, which uses talc, surface-treated calcium carbonate, silicate, or asbestos as a filler.