JP2002012820A - Primer coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosetting primer coating composition applicable to various metal raw materials, excellent in processability, hardness and scratch, water, corrosion and chemical resistances, especially excellent in corrosion resistance of a cut end face part in the case applied on aluminum-zinc alloy- plated steel plate which is predicted to prospectively become a main current of a raw material for precoating steel plate. SOLUTION: This primer coating composition comprises, as a nonvolatile component, (a) 2-40 wt.% epoxy resin, (b) 2-40 wt.% epoxy resin modified with an alkanolamine compound and/or an isocyanate compound, (c) 2-30 wt.% blocked isocyanate compound, (d) 2-30 wt.% rustproof pigment, (e) 2-40 wt.% pigment other than the component (d) and/or a filler and (f) 0.01-5 wt.% curing catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting primer coating composition which is excellent in corrosion resistance and workability and is particularly useful for precoated steel sheets.

[0002]

2. Description of the Related Art In recent years, with respect to painted metal plates used for building exteriors and wall materials, with respect to performance such as weather resistance, workability, hardness, scratch resistance, water resistance, corrosion resistance, stain resistance, chemical resistance, etc. The required quality of the market is getting higher.
In particular, high workability and durability such as long-term weather resistance and corrosion resistance including the processed part are essential. Therefore, in addition to the paint used, in addition to the conventional hot-dip galvanized steel sheet, aluminum-zinc alloy-plated steel sheet, which is a durability improving material, has been developed in addition to the conventional hot-dip galvanized steel sheet. Further, in order to improve corrosion resistance and adhesion to a coating film, various types of plated steel sheets are subjected to a chemical conversion treatment such as a phosphate-based or chromate-based treatment to improve workability and durability. On the other hand, for the paint used,
Workability and durability are reciprocal characteristics, and it has been difficult to achieve both characteristics. That is, if the formed coating film is hard, the durability is high, but a soft coating film is desirable in order to improve workability. In addition, what is commonly needed to improve workability and durability is adhesion between the coating film and the steel plate, and toughness of the coating film. In order to satisfy these properties, pre-coated steel sheets generally have multiple layers of coatings, and depending on the application, the primer used as the lower layer imparts adhesion, workability and corrosion resistance to the steel sheet, and the upper layer has durability and appearance. Has the function of giving

[0003] Conventionally, in a pre-coated steel plate coating material, a polyester resin, an acrylic resin, a vinyl chloride resin, a fluorine resin, or a polyurethane resin is used as a top coat as an upper layer depending on purposes such as weather resistance and workability. System paints are generally used. Epoxy resin paints have been used as primers for the lower layer mainly for many years due to their toughness. However, in recent years, as materials have been upgraded, aluminum-zinc alloy-plated steel sheets are frequently used as described above. However, compared to conventional hot-dip galvanized steel sheets, the materials themselves have good corrosion resistance. There is
When used as a coated metal plate, there is a drawback that the corrosion resistance of the cut end surface is inferior. To overcome this drawback,
Japanese Patent No. 148461 discloses that a linear polyester resin can be used in place of a conventional epoxy resin-based paint as a primer to compensate for the drawback. However, although the workability and the corrosion resistance are excellent because of the soft resin, the scratch resistance or the chemical resistance is inferior to the epoxy resin. On the other hand, Japanese Patent Publication No. 4-63109,
Japanese Patent Publication No. 75941/1995 and Japanese Patent Publication No. 7-74321 disclose a mixed resin system of a lactone-modified urethane epoxy resin and a resol-type phenol resin as a primer resin applicable to various metal materials. I have. This denatures the epoxy resin,
The workability, wet adhesion resistance and the like are improved by using a phenol resin having good adhesion, but when used for an aluminum zinc alloy plated steel sheet, the corrosion resistance of the cut end face is not sufficient.

[0004]

The present invention can be applied to various metal materials, and has workability, hardness, scratch resistance, water resistance,
Thermosetting primer coating composition with excellent corrosion resistance and chemical resistance, especially excellent corrosion resistance at the cut end face when applied to aluminum zinc alloy plated steel sheet, which is expected to become the mainstream material for pre-coated steel sheet in the future The purpose is to provide things.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above problems, and as a result, have found that epoxy resins, epoxy resins modified with alkanolamine compounds and / or isocyanate compounds, lactones Primer coating composition capable of producing a coated metal plate free from the above-mentioned defects by combining a blocked isocyanate compound having a polyurethane skeleton modified with a compound, an amino resin, an antirust pigment, other pigments and / or a filler and a curing agent Was obtained, and the present invention was completed. That is, in the present invention, the nonvolatile component
(A) 2 to 40% by weight of epoxy resin, (b) 2 to 40% by weight of epoxy resin modified with alkanolamine compound and / or isocyanate compound, (c) 2 to 30% by weight of blocked isocyanate compound, (d) protection 2 to 30% by weight of rust pigment, pigments other than components (e) and (d) and / or
Or a primer coating composition comprising 2 to 40% by weight of a filler and (f) 0.01 to 5% by weight of a curing catalyst. Further, (g) a polyester resin is further added to the primer coating composition (a) to
(F) The primer coating composition containing 30% by weight or less based on the total amount of the components.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The primer coating composition of the present invention has a nonvolatile component of (a) 2 to 40% by weight of an epoxy resin, and (b) epoxy resin 2 to 2 which is modified with an alkanolamine compound and / or an isocyanate compound. 40% by weight, (c) 2 to 30% by weight of blocked isocyanate compound, (d) 2 to 30% by weight of rust preventive pigment, (e) 2 to 40% by weight of pigment and / or filler other than component (d), and (F) The curing catalyst is characterized by comprising 0.01 to 5% by weight. The epoxy resin (a) of the present invention is a polyepoxide compound having two or more epoxy groups in one molecule. Such epoxy resins include, for example, bisphenol A type epoxy resin, bisphenol F
Epoxy resins such as epoxy resin, hydrogenated bisphenol A epoxy resin, and brominated bisphenol A epoxy resin; phenol or alkyl phenol such as phenol novolak epoxy resin, orthocresol novolak epoxy resin, bisphenol A novolak epoxy resin Novolak type epoxy resin which is a polyglycidyl ether of novolak resin; ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl Ether, polyglycidyl ether of alkylene glycol such as pentaerythritol tetraglycidyl ether Luylene glycol type epoxy resin; diglycidyl orthophthalate, diglycidyl isophthalate, diglycidyl terephthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, diglycidyl succinate, diglycidyl adipate Examples include glycidyl ester type epoxy resins such as esters, diglycidyl sebacate and diglycidyl dimer, and glycidylamine type epoxy resins such as triglycidyl isocyanurate and tetraglycidyl diaminodiphenylmethane. Among them, a bisphenol A type epoxy resin is preferred because of its excellent adhesion to a metal substrate and strength of a cured coating film.

The molecular weight of the epoxy resin (a) used in the present invention is not particularly limited, but the number average molecular weight is 400.
~ 8000, more preferably 400 ~ 70.
00. If it is less than 400, the curability will be poor, and the hardness, workability and corrosion resistance of the coating film will be significantly reduced. If it exceeds 8,000, an excessive diluting solvent is required because of high viscosity,
It is not preferable because the workability of coating with a roll coater or the like is inferior, and the ratio of solid content in the coating material is reduced so that an appropriate coating film cannot be obtained.

The amount of the epoxy resin (a) is 2 to 40% by weight, preferably 5 to 30% by weight in the nonvolatile component of the primer coating composition. If it is less than 2% by weight, the hardness, scratch resistance, corrosion resistance, water resistance and chemical resistance of the coating film will be reduced. If it exceeds 40% by weight, the viscosity will be high and the coating workability will be poor, and the workability will be reduced. is there.

As the modified epoxy resin used as the component (b) of the present invention, one or both of an alkanolamine compound and an epoxy resin modified with an isocyanate compound are used. The epoxy resin modified with the alkanolamine compound is obtained by adding an amino group contained in the alkanolamine compound to the epoxy group of the epoxy resin used as the component (a). In this case, the epoxy resin used as the component (a) and the epoxy resin used as the component (b) need not be the same at the same time. As such an alkanolamine compound, any of the usual primary or secondary alkanolamines can be used. For example, monoethanolamine, N-methylethanolamine, N-methylisopropanolamine, N-benzylethanolamine and the like can be used. Monoalkanolamines or dialkanolamines such as diethanolamine, diisopropanolamine, aminodibenzyl alcohol and the like can be used.

The amount of modification with the alkanolamine compound is 0.8 to 1.8 for the amino group with respect to one chemical equivalent of the epoxy group contained in the epoxy resin (a).
The ratio is preferably 0.9 to 1.0 chemical equivalent.
As a method for obtaining an epoxy resin modified with an alkanolamine compound, the epoxy resin and the alkanolamine compound can be mixed at the above ratio and allowed to react slowly at room temperature without a catalyst. ~ 15
It can be easily obtained by heating at 0 ° C. in the presence or absence of a catalyst and a solvent.

The epoxy resin modified with an isocyanate compound is obtained by reacting a hydroxyl group contained in the epoxy resin (a) with an isocyanate group contained in the isocyanate compound. As the isocyanate compound, any of ordinary diisocyanate compounds can be used, for example, aliphatic diisocyanate such as hexamethylene diisocyanate, alicyclic diisocyanate such as isophorone diisocyanate; xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate and the like. And the like can be used.

The amount of modification with the isocyanate compound is 0.5 to 20 in terms of the weight ratio of the isocyanate compound used in all the raw materials used in the production of the component (b) (all the raw materials including the isocyanate compound excluding the solvent). % By weight. If the amount of modification is less than 0.5% by weight, the processability decreases, while if the amount of modification exceeds 20% by weight, the viscosity becomes high and the coating workability is inferior. In order to obtain an epoxy resin modified with an isocyanate compound, the epoxy resin and the isocyanate compound can be mixed in the above ratio and stirred at a temperature of 80 ° C. for about 3 hours.

(B) alkanolamine compounds and / or
Alternatively, the amount of the epoxy resin modified with the isocyanate compound is 2 to 40% by weight, preferably 5 to 30% by weight in the nonvolatile component of the primer coating composition.
If it is less than 2% by weight, workability and corrosion resistance are reduced, while 40%
Exceeding the weight% is not preferred because the hardness, scratch resistance and chemical resistance of the coating film are lowered, and the viscosity becomes high, resulting in poor coating workability.

The (c) blocked isocyanate compound used in the present invention is obtained by blocking an isocyanate group of a polyisocyanate compound with a blocking agent. Examples of the isocyanate compound include aliphatic diisocyanates such as hexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate; xylylene diisocyanate, tolylene diisocyanate,
Aromatic diisocyanates such as 4'-diphenylmethane diisocyanate; and polyisocyanate compounds such as multimers of these diisocyanates or adducts with polyhydric alcohols. These include phenols, alcohols, lactams, oximes, amines, A compound blocked with a blocking agent such as a methylene compound can be used. These blocked isocyanate compounds can be used as they are or as modified products.

The (c) blocked isocyanate compound of the present invention is preferably a compound having a polyurethane skeleton modified with a lactone compound. The blocked isocyanate compound modified with a lactone compound is obtained by preliminarily subjecting the hydroxyl group of the polyhydric alcohol to ring-opening addition of the lactone compound, and then adding the above isocyanate compound under the condition that the isocyanate group is excessive relative to the hydroxyl group. It is obtained by removing the isocyanate compound and then blocking with the above blocking agent. Here, examples of the polyhydric alcohol used for the blocked isocyanate compound include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, Butyl-2-ethyl-1,3-propanediol, glycerin, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol and the like. As the lactone compound, a lactone having 5 or more ring carbon atoms, for example,
Examples include δ-valerolactone, ε-caprolactone and alkyl-substituted products thereof, for example, β-methyl-δ-valerolactone, and among them, ε-caprolactone is particularly preferred.

The amount of modification with the lactone compound is as follows:
The weight ratio of the lactone compound used in all the raw materials (all the raw materials including the lactone compound excluding the solvent) used in the production of the component (c) is 10 to 80% by weight. 10% by weight
If it is less than 80%, the workability and the corrosion resistance at the end face are reduced. If it exceeds 80% by weight, the hardness, scratch resistance and water resistance of the coating film are undesirably reduced.

The amount of the blocked isocyanate compound (c) is 2 to 30% by weight, preferably 5 to 20% by weight in the nonvolatile component of the primer coating composition. If the amount is less than 2% by weight, the processability and the corrosion resistance of the end face of the coating film are reduced. If the amount exceeds 30% by weight, the hardness, scratch resistance and water resistance of the coating film are undesirably reduced.

The rust preventive pigment of the component (d) of the present invention includes
For example, chromate-based rust preventive pigments such as strontium chromate, zinc chromate, barium chromate, and calcium chromate or phosphate-based rust preventive pigments such as aluminum phosphate and zinc phosphate can be used.

The compounding amount of the rust preventive pigment of the component (d) is as follows.
2 to 30 as a ratio in the non-volatile component of the primer coating composition
% By weight. If it is less than 2% by weight, the corrosion resistance cannot be sufficiently obtained, and if it exceeds 30% by weight, the effect of the present invention is not hindered, but the improvement of the rust prevention effect commensurate with the amount added in terms of efficiency cannot be obtained. .

The pigments and / or fillers other than the component (d) which is the component (e) of the present invention include, for example, calcium carbonate, kaolin, clay, talc, silica, benton, titanium oxide, and the like, depending on the purpose and use. Various additives such as barium sulfate, other coloring pigments, fillers, and other additives such as an antifoaming agent, a dispersant, and an antisettling agent can be appropriately compounded.

The compounding amount of the component (e) is 2 to 40% by weight in the non-volatile component of the primer coating composition. If the content is less than 2% by weight, sufficient scratch resistance cannot be obtained, while if it exceeds 40% by weight, the workability is undesirably reduced.

The curing catalyst of component (f) used in the present invention comprises:
(C) used as a catalyst for the blocked isocyanate compound of the component, using an organic metal compound such as dibutyltin dilaurate, a quaternary ammonium salt or a quaternary phosphonium salt such as tetrabutylammonium bromide or tetraethylammonium carboxylate; Can be.

The primer coating composition of the present invention may optionally use an amino resin as a curing agent. As the amino resin, an amino resin which is usually used as a curing agent for a coating material can be used without limitation.For example, a resin obtained by reacting urea, melamine, benzoguanamine or the like with formaldehyde, and a resin obtained by methanol, butanol or the like Alkyl ethers with lower alcohols can be used. Specific examples include a methylated urea resin, an n-butylated urea resin, a methylated melamine resin, an n-butylated melamine resin, an iso-butylated melamine resin, and an n-butylated benzoguanamine resin.

The amount of the amino resin is from 0 to 30% by weight in the nonvolatile component of the primer coating composition.
Preferably it is 2 to 20% by weight. If it exceeds 30% by weight, the crosslink density becomes too high and the flexibility of the coating film is lost, so that the processability is lowered and the end face corrosion resistance is deteriorated. As a curing catalyst for amino resin,
If necessary, hydrochloric acid, monoalkyl phosphate, p-
Acids such as toluenesulfonic acid or salts of these acids with tertiary amine or secondary amine compounds can also be used. The compounding amount of the curing catalyst of the component (f) is 0.01 to 5% by weight in the nonvolatile component of the primer coating composition. If the amount is less than 0.01% by weight, curing is insufficient, and the hardness, scratch resistance and water resistance of the coating film are reduced.

The primer coating composition of the present invention may contain a polyester resin as the component (g) in order to further improve the processability and the end face corrosion resistance. Examples of the polybasic acid as a component of the polyester resin include, for example, generally used polyester resins such as phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, adipic acid, and sebacic acid. Polybasic acids can be used. In addition, fatty acids having 8 to 18 carbon atoms, dimer acids, and the like can be used.

Examples of the polyhydric alcohol as another component of the polyester resin include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, neopentyl glycol, hexylene glycol, 1,4 -Butanediol, 1,5-
Pentanediol, 1,6-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 3,3
Dihydric alcohols such as -diethyl-1,5-pentanediol can be used. In addition, it is an important component in maintaining the balance between workability and hardness of the coating film,
As the trivalent or higher polyol which is an essential component of the polyester resin, for example, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol and the like can be used.

In addition, the polyester resin may have a chain extended by reacting a hydroxyl group contained in the polyester resin with a lactone compound and / or an isocyanate compound in some cases. These polyester resins can be used alone or in combination of two or more. Using these raw materials, a polyester resin can be produced by a conventional method.

The polyester resin thus produced is not particularly limited as long as it has a number average molecular weight of 2,000 to 10,000, but the preferable range of the number average molecular weight is 3,000 to 8,000. If the number average molecular weight of the polyester resin is less than 2,000, workability and end face corrosion resistance decrease, while if the number average molecular weight exceeds 10,000, the viscosity becomes high and coating workability is poor, which is not preferable. The hydroxyl value of the polyester resin is 30 to 150.
It is preferably mgKOH / g. Hydroxyl value is 30m
If the amount is less than gKOH / g, the crosslinking density becomes insufficient and the hardness of the coating film decreases. On the other hand, if the hydroxyl value exceeds 150 mgKOH / g, the water resistance decreases, which is not preferable. The blending amount of the polyester resin is 0 to 30% by weight based on the total amount of the components (a) to (f). If the blending amount of the polyester resin exceeds 30% by weight, compatibility with other resin components,
It is not preferable because hardness, scratch resistance, water resistance and chemical resistance of the coating film are reduced.

In preparing and using the primer coating composition of the present invention, an organic solvent is used. The organic solvent used is not limited at all, for example,
Alcohols such as butanol, cyclohexanol and 2-ethylhexanol, 2-methoxypropyl acetate, ethyl acetate, butyl acetate, amyl acetate, acetic acid esters such as hexyl acetate, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, etc. Ketones, toluene, xylene, ethylethoxypropionate, Solvesso 100 (manufactured by Exxon Chemical Co., Ltd.) and the like.

The primer coating composition of the present invention can be produced by using a dispersion mixer such as a sand grind mill and a disper.

The primer coating composition of the present invention is applied to a material for a precoated steel sheet such as a hot-dip galvanized steel sheet or an aluminum-zinc alloy-plated steel sheet which has been subjected to a chemical conversion treatment such as a phosphate or a chromate. Is possible. At that time, aesthetic appearance is attached, weather resistance, workability, chemical resistance,
In order to enhance various performances required for pre-coated steel sheets such as stain resistance, water resistance and corrosion resistance, it is necessary to apply a top coat on the primer. As the top coat, for example, a polyester resin paint, a silicone polyester resin paint, a polyurethane resin paint, an acrylic resin paint, a fluororesin paint, or the like can be appropriately selected and used. As a method such as a chemical conversion treatment or a top coat coating, a conventionally known method generally used can be applied.

The coating method of the primer coating composition of the present invention is not limited at all, and examples thereof include coating with a generally used high-speed roll coater and heating and curing in a hot-air drying furnace. At this time, the film thickness is 1 to 10 μm.
m, reached metal temperature of 150 to 300 during heat curing
For example, a condition of about 15 ° C. for about 15 to 150 seconds can be exemplified.

[0033]

The present invention will be described below in detail with reference to examples. In the following, “parts” means “parts by weight”. Production Example 1 (Synthesis of Epoxy Resin Solution A Modified with Alkanolamine Compound) In a flask equipped with a stirrer, a condenser and a thermometer, Epicoat 1009 (manufactured by Yuka Shell Epoxy Co., Ltd., bisphenol A type epoxy resin, epoxy Equivalent = 2400g
/ Eq, molecular weight = 3750｝ 38.3 parts, diethanolamine 1.7 parts, cyclohexanone 40.0 parts were charged, heated and stirred at 100 ° C., and reacted for 5 hours. Xylene 20.0 parts was added, and diethanolamine was added. Thus, an epoxy resin solution A modified by was obtained. The nonvolatile content is 40% by weight, and the varnish viscosity (Gardner method, 25 ° C.) is Z3 to Z4.
Met.

Production Examples 2 to 4 (Synthesis of Epoxy Resin Solutions B to D Modified with Alkanolamine Compound) Based on the formulations shown in Table 1, epoxy resins BD to D modified with the alkanolamine compound were prepared as in Production Example 1. Synthesized in a similar manner. Table 1 shows the characteristic values of the obtained resin solution.

[0035]

[Table 1]

Production Example 5 (Synthesis of Epoxy Resin Solution E Modified with Isocyanate Compound) In a flask equipped with a stirrer, a cooling tube and a thermometer, add Epicoat 1004 (manufactured by Yuka Shell Epoxy Co., Ltd., bisphenol A type epoxy resin). , Epoxy equivalent = 900 g /
eq, molecular weight = 1600｝ 38.0 parts, hexamethylene diisocyanate 2.0 parts, cyclohexanone 40.0
The mixture was heated at 80 ° C., stirred and reacted for 3 hours, and then 20.0 parts of xylene was added to obtain an epoxy resin solution E modified with hexamethylene diisocyanate.
Non-volatile content is 40% by weight, varnish viscosity (Gardner method, 2
5 ° C.) was U-W.

Production Example 6 (Synthesis of Epoxy Resin Solution F Modified with Isocyanate Compound) Based on the formulation shown in Table 2, an epoxy resin F modified with an isocyanate compound was synthesized in the same manner as in Production Example 5. Table 2 shows the characteristic values of the obtained resin solution.

[0038]

[Table 2]

Production Example 7 (Synthesis of Modified Block Isocyanate Compound A Modified with Lactone Compound) As a first step reaction, 29.0 parts of trimethylolpropane and ε were placed in a flask equipped with a stirrer, a condenser and a thermometer.
147.8 parts of caprolactone, 5.0 parts of octylic acid,
70.8 parts of methyl amyl ketone was charged, heated to 160 ° C., stirred and reacted for 4 hours to obtain a lactone compound-modified polyol solution. Next, as a second-stage reaction, 544.5 parts of hexamethylene diisocyanate was charged into a flask equipped with a stirrer, a condenser, a dropping funnel, and a thermometer, and heated to 80 ° C. under a nitrogen gas atmosphere. 252.5 parts of the solution was added dropwise over 2 hours, stirred, and allowed to react for another 4 hours. Unreacted hydroxyl groups were traced by infrared absorption spectrum measurement by sampling over time, and the reaction was terminated when the hydroxyl groups disappeared. Then, the pressure in the flask was reduced to 80 ° C. and 10 mmHg for 4 hours to distill off methyl amyl ketone, octylic acid and unreacted hexamethylene diisocyanate, thereby obtaining an isocyanate compound modified with a lactone compound. Further, as a third-stage reaction, 285.7 parts of the isocyanate compound modified with the lactone compound and toluene 143.2 were placed in a flask equipped with a stirrer, a condenser, a dropping funnel and a thermometer.
8 parts were charged, the temperature was raised to 80 ° C. in a nitrogen gas stream, and 59.2 parts of methyl ethyl ketone oxime was added dropwise over 1 hour.
The mixture was further reacted for 3 hours while stirring, and the unreacted isocyanate group was traced by infrared absorption spectrum measurement by sampling over time. When the isocyanate group disappeared, the reaction was terminated, and the lactone compound-modified modified blocked isocyanate compound solution A was obtained. 70% non-volatile content,
The varnish viscosity (Gardner method, 25 ° C.) was R. Table 3 shows the composition and characteristic values of the obtained resin solution.

Production Example 8 (Synthesis of Modified Block Isocyanate Compound B Modified with Lactone Compound) As the first step reaction, 17.8 parts of trimethylolpropane was placed in a flask equipped with a stirrer, a condenser and a thermometer.
15.7 parts of 1,6-hexanediol, 169.8 parts of ε-caprolactone, 7.4 parts of octylic acid, and 79.7 parts of methyl amyl ketone were charged, and heated and stirred at 160 ° C.
The reaction was carried out for an hour to obtain a lactone compound-modified polyol solution. Next, as a second stage reaction, 558.5 parts of hexamethylene diisocyanate was charged into a flask equipped with a stirrer, a condenser, a dropping funnel, and a thermometer, and heated to 80 ° C. under a nitrogen gas atmosphere to obtain the lactone compound-modified polyol. 290.4 parts of the solution was added dropwise over 2 hours and stirred.
Unreacted hydroxyl groups were tracked by infrared absorption spectrum measurement by sampling over time, and the reaction was terminated when the hydroxyl groups disappeared. Next, 80
The pressure was reduced at 10 mmHg for 4 hours to remove methyl amyl ketone, octylic acid and unreacted hexamethylene diisocyanate to obtain an isocyanate compound modified with a lactone compound. Further, as a third step reaction, 315.0 parts of the isocyanate compound modified with the lactone compound and 90.3 parts of toluene were charged into a flask equipped with a stirrer, a condenser, a dropping funnel, and a thermometer. C., 60.7 parts of methyl ethyl ketone oxime was added dropwise over 1 hour, and the mixture was further reacted for 3 hours with stirring. Unreacted isocyanate groups were traced by infrared absorption spectrum measurement by sampling over time. When disappeared, the reaction was terminated, and a modified blocked isocyanate compound solution B modified with a lactone compound was obtained. The nonvolatile content was 80%, and the varnish viscosity (Gardner method, 25 ° C.) was XY. Table 3 shows the composition and characteristic values of the obtained resin solution.

Production Example 9 (Production of Modified Polyester Resin Solution A) An ε-caprolactone modified polyester resin solution having a urethane bond was produced by the following method. As a first-stage reaction, 235 parts of isophthalic acid, 135 parts of adipic acid, 55 parts of trimethylolpropane, 55 parts of 1,6-hexanediol 276 were placed in a flask equipped with a stirrer, a rectification column, a water separator, a condenser, and a thermometer. The mixture was heated and stirred, and the condensed water generated was distilled off to the outside of the system.
The temperature was raised to a constant rate over 4 hours. Temperature 230
When the temperature was raised to 15 ° C., 15 parts of xylene was gradually added, and the temperature was maintained at 230 ° C. to continue the condensation reaction. Acid value is 5m
The reaction was terminated when gKOH / g or less, and a polyester prepolymer was obtained. Next, as a second step reaction, after cooling the polyester prepolymer solution to 100 ° C. and recovering xylene under reduced pressure, 266 parts of ε-caprolactone and 0.2 part of dibutyltin dilaurate were added, and the reaction was carried out at a temperature of 150 ° C. Continued. When the solid content became 98% or more, the mixture was cooled to 100 ° C., and 180 parts of xylene and 180 parts of methyl ethyl ketone were added. Further, as a third step reaction, 29 parts of hexamethylene diisocyanate was added dropwise at 80 ° C. in a nitrogen gas stream to continue the reaction. Unreacted isocyanate groups are tracked by IR over time by sampling,
At the time of disappearance, 250 parts of toluene was added to obtain an ε-caprolactone-modified polyester resin solution A having a urethane bond. The nonvolatile content is 59.4%, the varnish viscosity (Gardner tube, 25 ° C.) is U, and the resin acid value is 3.5 m.
gKOH / g, the number average molecular weight of the resin was 5,000, and the hydroxyl value was 55 mgKOH / g.

[0042]

[Table 3]

Examples 1 to 11 (Preparation of a primer coating composition) In a suitable amount of a mixed organic solvent (solvesso 100 / cyclohexanone / n-butanol = 55/27/18), the primer coating composition shown in Table 4 was prepared. According to the solid content composition, (a) a commercially available epoxy resin, (b) an epoxy resin modified with an alkanolamine compound and / or an isocyanate compound obtained in Production Example, (g) an appropriate amount of a polyester resin and a pigment component (D) and (e) were mixed with the entire amount and dispersed by a sand grind mill until the particle size became 15 to 20 μm. Further, after mixing the remaining component (c) or amino resin obtained in the commercially available or production example, a mixed organic solvent was added, and the mixture was stirred with a disper under the condition of a liquid temperature of 40 ° C. or less. From the viewpoint of the workability of coating, the viscosity of the paint was measured using Ford Cup No. 4, the temperature was adjusted to 130 ± 10 seconds (25 ° C.), and the primer coating compositions P1 to P1
1 was obtained. Further, from the viewpoint of the workability of coating, the viscosity of the paint was set to the value of Ford Cup No. The temperature was adjusted to 100 ± 10 seconds (25 ° C.) in Step 4, and the specimen was prepared. Table 4 shows the formulation of the primer coating composition.

[0044]

[Table 4]

Notes to Table 4 (* 1) Epicoat 834: epichlorohydrin / bisphenol A type epoxy resin, trade name of Yuka Shell Epoxy Co., Ltd. (* 2) Epicoat 1001: epichlorohydrin / bisphenol A type epoxy resin, oily Shell Epoxy Co., Ltd., (* 3) Epicoat 1009: epichlorohydrin / bisphenol A type epoxy resin, Yuka Shell Epoxy Co., Ltd., (* 4) Coronate 2507: hexamethylene diisocyanate MEK oxime block resin solution , NCO = 1
1.6%, solid content = 80%, trade name, manufactured by Nippon Polyurethane Industry Co., Ltd., (* 5) Desmodur TPLS2217: 4,4'-
Active methylene block resin of diphenylmethane diisocyanate, NCO = 9.1%, solid content = 80%, trade name, manufactured by Sumitomo Bayer Urethane Co., Ltd. (* 6) Uban 10S60: Butylated urea resin, solid content = 60%, Mitsui (* 7) Cymel 303: methylated melamine resin, solid content = 100%, trade name, manufactured by Mitsui Cytec Co., Ltd., (* 8) Titanium oxide / kaolin / silica / bentonite = 18 / 51/30/1 (weight ratio). Titanium oxide: JR
-602, trade name, manufactured by Teica Co., Ltd., kaolin: NN kaolin clay, trade name, manufactured by Tsuchiya Kaolin Industry Co., Ltd., silica: Cycilia 446, trade name, manufactured by Fuji Silysia Chemical Ltd., bentonite: Benton 34, National Red Product name.

The method of preparing the test piece is as follows. (Preparation of Test Piece) Using the obtained primer coating composition, a test piece was prepared by the following method. That is, the thickness
A chromic acid-based treatment liquid ZN-R1 is applied to the surface of a 0.6 mm aluminum zinc alloy plated steel sheet (basis weight AZ-150).
415A (manufactured by Nippon Parker Rising) was roll-coated so that the coating amount became 20 to 80 mg / m ² (dry state) in terms of the amount of chromium, and dried at 90 ° C. to obtain a chemically treated steel sheet. The primer coating composition prepared above was applied thereon with a bar coater so as to have a dry film thickness of 5 μm, and baked in a hot air drier at a maximum temperature of 200 ° C. for 40 seconds. Furthermore, as a top coat, a regular polyester resin-based top coat (hereinafter referred to as a polyester paint) [manufactured by NOF Corporation, Precolor HD0030 Brown color, gloss 5, registered trademark], or a polyvinylidene fluoride resin-based top coat Paint (hereinafter referred to as fluorine paint) [Precolor No.
8800 gray color, gloss 30, registered trademark] was applied with a bar coater so that the polyester paint had a thickness of 15 μm and the fluorine paint had a thickness of 20 μm. It was baked in a hot air drier at 250 ° C. for 50 seconds to obtain a total of 15 types of test pieces.

(Method for Testing and Evaluating Coating Film Performance) Bending workability Insert a test piece with a steel plate of the same thickness
It was folded at 80 degrees. It is 0T processing to bend a steel plate without sandwiching it, and 2 when two steel plates are sandwiched.
It is called T processing. When the top coat is polyester paint, 2T and 3T processing which is a standard of practical performance level,
In the case of a fluorine paint, 0T processing was respectively performed. The top portion after bending was subjected to a peeling test using Cellotape (registered trademark), and the peeling area of the coating film was evaluated by the following five-point method. 5 points; no peeling, 4 points; 1 to 10% peeling, 3 points; 11 to 30% peeling, 2 points; 31 to 50% peeling, 1 point; 51% or more peeling.

2. Pencil hardness A pencil for hardness measurement (Mitsubishi Uni) is pressed in with a certain force, and the breaking strength of the coating film is represented by the hardness of the core. The judgment 3H indicates that the coating film is broken in the case of 4H, but not broken in the case of 3H. It can be said that 2H or more is a practical level.

3. Scratchability The coating film was scratched at a constant force on the outer periphery of a 10-yen coin (with no jagged outer periphery), and the damage of the coating film was evaluated according to the following criteria. ；: Sufficient scratch resistance, little appearance of primer surface, △: Some degree of scratch resistance, but part of primer peeled, ×: Scratch resistance small, whole film peeled The base is exposed.

4. A test piece cut into a boiling water of 6 × 20 cm was immersed in boiling water for 5 hours (10 hours if the top coat was a fluorine coating), allowed to stand at room temperature for 1 hour, and then adhered by the following two methods. Tested. (1) Cross section Eriksen Cross section (1 mm width, 10 × 10
This cell was extruded 6 mm from the back side with an Erichsen tester. The extruded portion was peeled off with a cellophane tape, and evaluated by the number of strips on a grid. (2) Bending process The test was performed according to a test method and an evaluation method for bending workability.

5. Corrosion resistance (1) Processed part A test piece subjected to 4T processing (2T processing when the top coat is a fluorine paint) is subjected to a salt spray tester [JIS K-54].
00], a test was conducted for 1000 hours (2000 hours when the overcoat was a fluorine paint), and the swelling and rusting of the processed portion were observed. The evaluation was performed as follows. 5 points: no abnormality, 4 points: slight white rust but no swelling, 3 points: small amount of white rust occurred and slight swelling, 2 points: white rust generated and small amount of swelling 1 point: white rust is generated on the entire surface and there are many blisters. 4 points or more can be said to be a practical level.

(2) End face Three cut surfaces (cut so that burrs appear on the coating film side of the test piece)
And a test piece sealed on the back side with a polyester tape was tested with a salt spray tester [JIS-K-5400].
The swollen width and white rust width of the coating film from the unsealed end face were observed. The evaluation was performed as follows. 5 points; both swelling and white rust are less than 0 to 1 mm; 4 points; both swelling and white rust are less than 1 to 2 mm; 3 points; both swelling and white rust are less than 2 to 5 mm. 2 points; both swelling and white rust are 5 to 8 mm. Less than 1 point: Both swelling and white rust are 8 mm or more, and 4 points or more are practical levels.

6. Chemical resistance A 5 cm × 5 cm test piece was placed in each chemical test solution (5% NaOH
Aqueous solution, 5% H ₂ SO ₄ aqueous solution, and 5% HCl aqueous solution) for 72 hours.
-Evaluated according to D714-56. When there was no abnormality, it was set to 10.

Table 5 shows the evaluation results of the coating films obtained by the above methods.

[0055]

[Table 5]

Notes on Table 5 (* 1) In the table, a circle indicates that the following paint was used for coating. Precolor HD0030 Brown color: Regular polyester resin top coat, manufactured by NOF Corporation, Gl
oss = 5, (* 2) The circle in the table indicates that the following paint was used for painting. Precolor No. 8800 gray color: Polyvinylidene fluoride resin top coat, Glo
ss = 30,

Comparative Examples 1 to 7 Primer coating compositions PH1 to PH were prepared in the same manner as in Examples.
H5 was manufactured, and a test piece was prepared using this to evaluate. The composition of the primer coating composition is shown in Table 6, and the evaluation results of the coating film are shown in Table 7.

[0058]

[Table 6]

[0059]

[Table 7]

From the results in Tables 5 and 7, Comparative Example 1 shows (a)
Of the epoxy resin is less than 2% by weight in the nonvolatile component of the primer coating composition, and in particular, the pencil hardness and scratch resistance are poor, and the chemical resistance is also poor. Comparative Example 2
Is the case where the compounding amount of the epoxy resin modified with the alkanolamine compound and / or isocyanate compound (b) is less than 2% by weight in the nonvolatile component of the primer coating composition, and particularly, the processability is remarkably inferior. . In Comparative Example 3, the content of the blocked isocyanate compound (c) was 2% by weight in the nonvolatile component of the primer coating composition.
And the workability and especially the corrosion resistance are inferior. Comparative Example 4 does not contain the component (c), and the amino resin exceeds 30% by weight in the nonvolatile component of the primer coating composition. The pencil hardness is increased, but the processability and the corrosion resistance are extremely poor. . Comparative Example 5 is a case where the compounding amount of the (d) rust preventive pigment is less than 2% in the nonvolatile component of the primer coating composition, and (e) the pigment and / or the filler other than the component (d). If the agent exceeds 40% by weight,
It can be seen that the workability and corrosion resistance are significantly inferior. On the other hand, Examples 1 to 8 of the present invention are the conventional ones in which excellent workability, corrosion resistance of end faces and processed parts, practical level of hardness, scratch resistance, and chemical resistance, which were problems to be solved conventionally, have been achieved. It shows that this is a primer coating composition that enables the production of excellent and unpainted metal sheets.

[0061]

EFFECT OF THE INVENTION By using the primer coating composition of the present invention, an excellent unprecedented coating which achieves both workability, corrosion resistance of end faces and processed parts, hardness of practical level, scratch resistance and chemical resistance. Enables production of metal plates.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J038 DB001 DB002 DB031 DB032 DB061 DB062 DB071 DB072 DB091 DB092 DB391 DB392 DD002 DG302 HA166 HA206 HA246 HA446 HA526 HA536 KA04 KA05 KA08 MA14 NA03 NA04 NA05 NA11 PB05 PC02

Claims (3)

[Claims] 1. The method according to claim 1, wherein the non-volatile component is (a) an epoxy resin 2 to 4
0% by weight, (b) epoxy resin 2 modified with alkanolamine compound and / or isocyanate compound
40% by weight, (c) blocked isocyanate compound 2
30% by weight, (d) 2 to 30% by weight of rust preventive pigment, (e)
A primer coating composition comprising 2 to 40% by weight of a pigment and / or a filler other than the component (d) and (F) 0.01 to 5% by weight of a curing catalyst. 2. The primer coating composition according to claim 1, wherein the blocked isocyanate compound (c) has a polyurethane skeleton modified with a lactone compound. 3. The polyester resin (g) further comprises (a)
3. The primer coating composition according to claim 1, comprising 30% by weight or less based on the total amount of the components (f) to (f).