JP2000327989A - Paint composition and lubricated metal sheet - Google Patents

Abstract

[PROBLEMS] To provide a paint composition having improved alkali film removal properties, coating film drying properties, blocking resistance, rust prevention properties, paint stability, and press workability, and a lubricated metal sheet using the same. Offer. A coating composition containing an acrylic resin and a neutralizing agent, wherein the acrylic resin has methacrylic acid ester composed of methacrylic acid and an alcohol having 2 or more carbon atoms, styrene, and a carboxyl group. The composition comprises a copolymer (a) with a monomer and a polymer (b) of a polymerizable compound having an ether bond.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition and a lubricated metal sheet having a coating film formed by applying the coating composition to the surface, and more particularly to a galvannealed steel sheet, Rolled steel sheet, cold rolled steel sheet, plated steel sheet,
When applied to stainless steel plates and aluminum plates, presses with powdering resistance and mold galling resistance while maintaining alkali film removal, chemical conversion, rust prevention, coating drying and blocking resistance The present invention relates to a coating composition capable of improving moldability and a lubricated metal plate obtained by applying the same to various metal plates.

[0002]

2. Description of the Related Art Conventionally, galvanized steel sheets (electroplated steel sheets and galvannealed steel sheets) have been used for automobile structural materials and parts that require high rust resistance. In recent years, the use of alloyed hot-dip galvanized steel sheets has been increasing from the viewpoint of cost reduction as a substitute for parts employing electric galvanized steel sheets. However, conventionally, the galvannealed steel sheet has a large dynamic friction coefficient and is inferior in press formability as compared with the electroplated steel sheet. there were.

That is, the range in which press molding can be performed is narrowed. Peeling of the plating layer, that is, powdering, occurs at the sliding portion between the mold and the steel plate. In the worst case, mold seizure occurs, and the mold is contaminated and damaged, so that the frequency of repairing the mold increases, and at the same time, the quality of the molded product deteriorates. Therefore, in order to use an alloyed hot-dip galvanized steel sheet, it is necessary to improve press formability including powdering resistance and mold galling resistance. Further, with respect to hot-rolled steel sheets, cold-rolled steel sheets, electrogalvanized steel sheets, and electrogalvanized-nickel-plated steel sheets, studies are being made on further improving press formability by improving lubrication characteristics (dynamic friction coefficient). However, it is difficult to achieve this by using rust preventive oil or press oil.

[0004] On the other hand, demand for aluminum sheets is expected to increase in the current trend of reducing the weight of automobile bodies. However, at present, aluminum sheets are inherently small in elongation, and therefore, applicable parts are limited. Have been. Further, the stainless steel sheet is often used after being subjected to deep drawing, such as a bathtub or a washing tub of a washing machine. At present, a polyvinyl chloride film is attached to the die side of the steel plate before molding to prevent mold galling due to contact with the mold.However, it is necessary to peel off the vinyl chloride film from the molded product after press molding. In addition, there is a problem that environmental pollution is caused depending on a disposal method of the peeled film. Therefore, in order to improve the press formability of each metal plate, it has been proposed to apply an organic resin coating to improve the lubricity of the metal plate.

These organic resin-coated metal sheets are press-formed by a customer, then the organic resin coating film is removed by alkali washing, that is, alkali-removed, and then a chemical conversion coating is formed by phosphoric acid treatment or the like. After that, it is coated by electrodeposition coating or spray coating. Through such a surface treatment step, the adhesion between the exterior coating film and the metal plate is ensured. Further, rusting during the storage period until the consumer uses the organic resin-coated metal plate also poses a problem. In recent years, from the viewpoint of cost reduction emphasis, the organic resin coating film has a low temperature and
It is desired to be formed by baking for a short time, and a coating film drying property has been required. The organic resin-coated metal plate is often stored in a state where a large load is applied, with the coating surfaces being in contact with each other in a band or plate shape immediately after the formation of the coating,
In this case, it must be avoided that it cannot be peeled off during use. That is, blocking resistance is also required.

[0006] In order to satisfy the above characteristics, there have been many proposals for forming a coating film such as an organic film composition of an alkali delamination type on a steel sheet surface, for example, Japanese Patent Publication No. 53-37817.
JP-A-6-84193, JP-A-3-2193
03996, JP-A-5-194988 and the like. JP-A-5-194983 discloses an organic resin coating composition containing two types of esterified products obtained by esterifying a specific styrene-maleic acid copolymer with a hydroxyl group-containing compound having an alkyl group or an alkenyl group. Attempts have been made to solve the above problem by applying an object. However, since this copolymer has a low molecular weight, the breaking strength of the coating film is small and the press formability is poor. In particular, when the temperature of the mold rises, there is a problem that the press formability is significantly reduced.

Further, Japanese Patent Publication No. 53-37817, Japanese Patent Application Laid-Open No. 62-84193 and Japanese Patent Application Laid-Open No. 3-203996 disclose that an organic resin is specified to improve press moldability, and that a carboxyl group in the organic resin is improved. There has been proposed a technique for ensuring the alkali film-removing property by its existence and further by defining this acid value. For example, Japanese Patent Publication No. 53-37
The organic resin described in Japanese Patent No. 817 is a water-soluble copolymer composed of an acrylate ester, methyl methacrylate, styrene and a carboxyl group-containing monomer, having a weight average molecular weight of 15,000 to 50,000 and a glass transition. Point Tg is 60 to 90
° C. However, the formation of crystals of the chemical conversion coating film after alkali washing in these techniques is insufficient, and there is also a problem in press formability, particularly in press formability in a warm state.

[0008]

The problems of the prior art described above are summarized as follows, and it is an object of the present invention to solve these problems. <Press formability (powdering resistance and galling resistance)> At the time of continuous press of hundreds to thousands of times or remarkable deep drawing at a demand destination, at least the mold temperature is reduced due to frictional heat and deformation resistance. It is said that the temperature rises to 40 ° C. and sometimes 100 ° C. In order to alleviate this temperature rise, press molding is generally performed while applying oil to a mold. However, as the number of presses increases, the cooling effect of the oil decreases and the mold temperature increases. As a result, the conventional technique has a problem that the organic resin coating film is softened, the lubricating effect is reduced, and press cracking, powdering, and mold galling occur.

<Alkali film-removing property (alkali film-removing property / chemical conversion property)> At the demand side, after press molding, alkali cleaning treatment and chemical conversion treatment are performed to form a chemical conversion film, and then electrodeposition coating. It is necessary to secure the adhesion between the coating film of the exterior paint and the metal plate by electrostatic coating or the like. In order to form a chemical conversion coating, the organic resin coating must be removed, and it is important to remove the organic resin coating by alkali washing before the chemical conversion treatment (alkali removal).

Particularly, in a galvanized steel sheet, the ionic bond between the zinc in the plating layer and the carboxyl group contained in the organic resin significantly reduces the alkali film-removing property, making it difficult to completely remove the organic resin coating film. For this reason, even if the water wettability after the alkali washing is sufficient, the problem of the shape of the chemical conversion treatment film crystal and the shortage of the adhesion amount occur. Such a problem commonly exists in the above-mentioned prior art.

<Rust prevention> In order to ensure alkali film removal,
When the carboxyl group is left in the organic resin coating film as in the prior art, the problem is that the coating film absorbs moisture in the atmosphere and rusts from shipment of the metal plate to use by the customer. was there.

The present invention is concerned with the problems that have been left in a metal plate having an organic resin coating film (lubricated coating film) on the metal plate surface, namely, alkali film removal properties, chemical conversion treatment properties, press moldability (powder resistance). A coating composition capable of remarkably improving the ring resistance, mold galling resistance), rust prevention, and even coating drying and blocking resistance, and lubrication having an organic resin coating formed by applying the coating composition to the surface of a metal plate. It is an object to provide a treated metal plate together.

[0013]

The above object is easily solved by the following means. That is, the present invention provides a coating composition containing an acrylic resin and a neutralizing agent,
The acrylic resin is a methacrylic acid ester composed of methacrylic acid and an alcohol having 2 or more carbon atoms, a copolymer (a) of styrene and a monomer having a carboxyl group, and a polymerizable compound having an ether bond. A coating composition comprising the polymer (b).

Further, the present invention provides a coating composition containing an acrylic resin and a neutralizing agent, wherein the acrylic resin is a methacrylic acid ester comprising methacrylic acid and an alcohol having 2 or more carbon atoms, styrene, and an ether bond. A coating composition comprising a copolymer (c) with a polymerizable compound having the formula (I) and a monomer having a carboxyl group.

Further, the present invention is a lubricated metal plate having a coating film formed by applying any one of the above-mentioned coating compositions to the surface.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the coating composition and lubricated metal sheet of the present invention will be described in detail. The present invention relates to a coating composition containing an acrylic resin and a neutralizing agent. The metal sheet to be improved has press formability (powdering resistance, mold galling resistance), rust prevention and blocking resistance. The study was conducted with emphasis on enhancing the performance of a copolymer in which methacrylic acid ester and styrene were introduced into the base of an acrylic resin.

On the other hand, in order to improve the alkali film-removing property, chemical conversion property and coating film drying property, it is necessary to introduce or contain a polymer of a polymerizable compound having an ether bond as a component constituting the copolymer. We considered with emphasis on. Further, the coating composition of the present invention contains a neutralizing agent which is a base such as ammonia and amines to neutralize the acrylic resin. Therefore, the coating composition of the present invention may contain one or more kinds of additives, rust preventives, lubricants, coloring agents and the like which are usually added to coatings.

Acrylic Copolymer (a) The present inventors have studied acrylic resins from the viewpoint of press moldability. As a result, the copolymer of methacrylic acid ester, styrene and a monomer having a carboxyl group is It has been found that it is possible to maintain the breaking energy of the organic resin coating film at a high level, which is effective for improving the press formability. It has also been found that limiting the alcohol to be esterified with methacrylic acid to alcohols having 2 or more carbon atoms is effective in ensuring rust prevention. In the case of a methyl group having 1 carbon atom, rust prevention is extremely reduced.

It is presumed that this is because the polarization of the ester group is increased by the methyl group, and as a result, the interaction with water is increased. As an alcohol having 2 or more carbon atoms,
Aliphatic monohydric alcohols are practical, and as the methacrylic acid ester of the present invention, ethyl methacrylate (abbreviation: E
MA: Tg = 65 ° C.), isopropyl methacrylate (abbreviated as iso-PMA: Tg = 81 ° C.), methacrylic acid-n
-Butyl (abbreviation: n-BMA: Tg = 20 ° C.), isobutyl methacrylate (abbreviation: iso-BMA: Tg = 67 ° C.)
And the like.

The acrylic ester usually has a glass transition point Tg of less than 0 ° C., and tends to have poor press moldability. In the present invention, a methacrylic acid ester is indispensable, and a methacrylic acid ester having a Tg of 0 ° C. or more is preferable because it has excellent press moldability. Generally, actual press forming by a customer is continuous and at a high speed, and the temperature of a metal plate or a mold may reach 100 ° C. due to frictional heat or heat due to deformation resistance of a metal plate. Therefore, when the copolymer containing a methacrylic acid ester having a Tg of less than 0 ° C. is contained, the soft component is separated from the metal plate or melted by heat, thereby lowering the lubricating performance of the entire coating film. . The methacrylate preferably has a Tg of 1
It is in the range of 0 ° C to 90 ° C.

Styrene, which is the second copolymer component of the copolymer (a), has high moisture resistance and a high glass transition point Tg.
It is essential for achieving both rust prevention and press formability. The copolymerization ratio of the methacrylate and styrene is preferably from 10:90 to 90:10 by weight. In the total amount of the two, when the ratio of the methacrylic acid ester is less than 10% by weight, the content ratio of styrene increases, so that the press formability and the rust prevention property are improved.
Even when the acid value is set to a predetermined value described below, the alkali film-removing property tends to decrease, and the storage stability of the paint tends to decrease. Conversely, when the ratio of the methacrylic acid ester exceeds 90% by weight, the rupture strength of the coating film decreases, the press moldability decreases, and at the same time, the hydrophobicity of the coating film decreases. A more preferred weight ratio of the methacrylate: styrene copolymerization ratio is from 30:70 to 85:15, and still more preferably from 50:50 to 80:20.

The third copolymer component of the copolymer (a) is a monomer having a carboxyl group, for example, ethylene having one or two carboxyl groups such as acrylic acid, methacrylic acid, maleic acid and itaconic acid. Unsaturated carboxylic acids. As a result, the copolymer has a carboxyl group in the molecule, and can be made water-soluble by neutralizing with a base such as ammonia or amine.
As a result, the copolymer (a) has an alkali film-removing property, which is one of the important properties of the paint.

The copolymer (a) has an acid value before neutralization of 20 to
It is preferable to adjust so as to be 300 mg-KOH / g. When the acid value is less than 20 mg-KOH / g, the alkali film-removing property of the coating film with an alkaline cleaning liquid is extremely reduced. In addition, the water solubility of the copolymer (a) itself is low, and it is difficult to form a coating by making the copolymer water-soluble. On the other hand, the acid value is 300m
If it exceeds g-KOH / g, the rust-preventing property of the coating film is extremely reduced, and the effects of styrene and other rust-preventing agents are not exhibited. More preferred acid value is 25 to 250 mg-K
OH / g, and further 100 to 230 mg-KOH / g
It is. In order to secure the above-mentioned preferable acid value, for example, in the case of methacrylic acid, methacrylic acid may be 4 to 50 parts by weight based on 100 parts by weight of the copolymer (a) of methacrylic acid, styrene and methacrylic acid ester. .

The preferred molecular weight of the copolymer (a) is
It is 10,000 to 60,000 in weight average molecular weight. Within this range, the lubricating effect of the coating film is effectively exhibited, which is preferable for press moldability. Further, in the copolymer (a), the carboxyl group is made water-soluble by a neutralizing agent which is a base such as ammonia or amine. Therefore, it is not necessary to use a surfactant used for emulsification or the like. Therefore, the surfactant remains in the dried coating film, and there is no problem of lowering the rust prevention property and press moldability of the coating film. In addition, as an essence of the emulsion paint containing a surfactant, it is necessary to set the drying baking temperature to (Tg + 20 ° C.) or more, and a film can be formed only by drying at a higher temperature. This means that when the surfactant is contained, the drying property of the coating film is inferior. In the case of the copolymer (a), this problem is also avoided.

The copolymer (a) can be obtained by known copolymerization in an aqueous solvent. For example, under a nitrogen atmosphere, methacrylic acid ester and styrene are adjusted in an aqueous solvent (for example, butyl cellosolve) adjusted to 80 to 140 ° C., and the weight ratio of methacrylic acid ester: styrene is preferably adjusted to 10:90 to 90:10. And a monomer having a carboxyl group, preferably having an acid value of 3
Copolymerization is carried out dropwise over 4 to 5 hours together with the polymerization initiator so as to be 0 to 200 mg-KOH / g, and further, the mixture is heated and stirred at the same temperature for 2 to 8 hours to complete the copolymerization. A combination (a) is obtained. Thereafter, the solution was
The solution is cooled to 、 60 ° C., neutralized with a base such as ammonia or amine, and made water-soluble.

Preferred Neutralizing Agent When the metal sheet to which the coating composition is applied is an alloyed hot-dip galvanized steel sheet, as described above, the interaction between zinc in the plating layer and the carboxyl group of the coating composition. , There is a tendency for the alkali film-removing property to decrease. In the coating composition, from the viewpoint of improving the rust resistance of metal plates and press formability,
It is required to improve the breaking strength of the organic resin coating film. Therefore, when the Tg and the molecular weight of the copolymer (a) are increased, the alkali film-removing property of the organic resin coating film is reduced. This can be improved by specifying a neutralizing agent and adding a polymer (b) of a compound having an ether bond.

When the alkali washing in the consumer is performed at a temperature lower than the Tg of the copolymer (a) and for a relatively short time, no matter how much the carboxyl groups not neutralized by the neutralizing agent are increased. In addition, the alkali film removal property becomes poor. Therefore, if the carboxyl group can be maintained in a neutralized state even after coating with the organic resin, the alkali film-removing property can be improved. Therefore, by neutralizing a part of the carboxyl groups in the organic resin coating with a base that does not easily evaporate during the coating of the organic resin, that is, an amine or hydroxide having a high boiling point, the hydrophilic substance is contained in the organic resin coating. It is preferable because it can be increased. The use of these neutralizing agents assists the penetration of alkali into the organic resin coating film during alkali cleaning, and enables alkali removal at a low temperature in a short time.

When the boiling point of the amine as a neutralizing agent is less than 30 ° C., the amine is volatilized even when the organic resin coating film is dried at room temperature, and the alkali film-removing property is deteriorated. More preferred is an amine having a boiling point of 100 ° C. or higher, and more preferred is 160 or more.
It is an amine of not less than ° C. As amines having a boiling point of 30 ° C. or higher, isopropylamine (boiling point 32 ° C.), diethylamine (boiling point 56 ° C.), N, N-dimethylethanolamine (boiling point 130 ° C.), monoethanolamine (boiling point 170 ° C.)
℃), triisopropanolamine (boiling point 305 ℃),
Examples thereof include triethanolamine (boiling point: 360 ° C.), and alkanolamine and alkylamine are particularly preferable. Examples of the hydroxide include sodium hydroxide and potassium hydroxide.

The neutralizing agent is added in an amount of 0.1 equivalent of ammonia to 1 equivalent of the acid contained in the resin solid content of the copolymer (a).
It is preferable that the amine or hydroxide having 6 to 4.0 equivalents and a boiling point of 30 ° C. or higher is 0.05 to 0.5 equivalents. When the amount of the amine or hydroxide having a boiling point of 30 ° C. or more is 0.0
If the amount is less than 5 equivalents, it is difficult to secure the alkali film-removing property under a short alkali washing, and if it exceeds 0.5 equivalents, the breaking strength of the coating film is reduced, and the press formability is reduced. And productivity decreases. Further, the blocking resistance is also reduced. A more preferable addition amount of the amine or hydroxide having a boiling point of 30 ° C. or more is 0.1 to 0.4 equivalent. On the other hand, if the amount of ammonia is less than 0.6 equivalent, it is difficult to make water soluble by neutralization, while if it exceeds 4.0 equivalent, the breaking strength of the coating film is deteriorated and lubricity tends to be impaired. Become.

Polymer (b) of a polymerizable compound having an ether bond In the present invention, a polymer (b) of a polymerizable compound having an ether bond is contained in addition to the copolymer (a). Provides alkali film removal properties. Copolymer (a)
, Neutralization is broken by baking of the coating film and subsequent leaving,
Carboxyl groups tend to increase, and the alkali film-removing property decreases accordingly. Unlike the copolymer (a), the polymer (b) of the polymerizable compound having an ether bond can ensure water solubility regardless of neutralization or non-neutralization. ) Can prevent a decrease in alkali delamination property due to carboxylation. The polymer (b) of the polymerizable compound having an ether bond is mixed with the copolymer (a) to form a composition.

Unlike the copolymer (a), the polymer (b) of the polymerizable compound having an ether bond has good compatibility with water even if it is not neutralized with a base. The coating composition containing b) is effective for alkali film removal. As the polymerizable compound having an ether bond, an unsaturated carboxylic acid ester having the following structural formula is typical, and a polyalkylene (C2 to C3) glycol monoalkyl (C2) of an ethylenically unsaturated carboxylic acid is used. 1-3) It is preferably an ester of ether.

[0032]

Embedded image

Examples of the ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid and the like. To this, 1 to 20 moles of an alkylene (2 or more carbon atoms) oxide is added, and the terminal is an alkyl (1 to 3 carbon atoms) ether. The polymerization degree (m) of the polyalkylene glycol is preferably from 1 to 20. If the degree of polymerization exceeds 20, the rust-preventive properties deteriorate.

The polymer (b) of the polymerizable compound having an ether bond coexists with the copolymer (a) to form a composition, thereby exhibiting a suitable effect. In the polymer (b) of the polymerizable compound having an ether bond, the terminal group of the ester of the polyalkylene glycol ether is generally a hydroxyl group. Components may cause a dehydration reaction, resulting in three-dimensional formation and gelation. On the other hand, it is possible to secure the paint stability during long-term storage by etherifying the terminal hydroxyl groups with alcohols (alkyl alcohols such as methyl alcohol and ethyl alcohol) or esterifying them with aliphatic carboxylic acids. it can.

The copolymer (a) and the polymer (b) each have a copolymer (a) content of 95 to 70% by weight, preferably 100 to 100% by weight, preferably 100 to 100% by weight. 9
The polymer (b) is used in a proportion of 5 to 30% by weight, preferably 5 to 20% by weight, in a proportion of 5 to 80% by weight. When the amount of the copolymer (a) exceeds 95% by weight, the alkali film-removing property tends to decrease, and when the amount is less than 70% by weight, the rustproofing property tends to decrease. When the amount of the polymer (b) is less than 5% by weight, sufficient alkali film-removing property cannot be obtained, and when the amount exceeds 30% by weight, rust prevention tends to decrease.

The coating composition of the present invention is prepared, for example, as follows. The copolymer (a) and the polymer (b) are
It is dispersed in a predetermined amount of water, heated to 60 to 70 ° C, and neutralized by adding a predetermined amount of ammonia. Further, if necessary, a high-boiling amine, for example, triethanolamine is added to neutralize. Further, if necessary, in addition to a solid lubricant, wax, fatty acid such as lauric acid, phosphoric acid, and metal soap, an organic phosphoric acid as an anti-settling agent described later is added.

In the present invention, it is sufficient that the copolymer (a) and the polymer (b) are simply mixed to form a composition, but it is sufficient that the above composition ratio is maintained and the copolymer ( a)
And a polymerizable compound having an ether bond are copolymerized to obtain an integrated copolymer (c), which is used in place of the copolymer (a) and the polymer (b). You can also. By copolymerizing a polymerizable compound having an ether bond, low molecular weight components in the coating composition are reduced, and press moldability is further improved.

A copolymer of a component constituting the copolymer (a) and a polymerizable compound having an ether bond, that is, a methacrylic acid ester composed of methacrylic acid and an alcohol having 2 or more carbon atoms, styrene, and a carboxyl group The copolymer (c) of the monomer having the compound and the polymerizable compound having an ether bond is produced, for example, by the following method.

In the case of the solution polymerization method, for example, 23 parts by weight of styrene, 24 parts by weight of n-butyl methacrylate, 23 parts by weight of methacrylic acid are added to a water-soluble solvent such as butyl cellosolve heated to 80 to 140 ° C. under a nitrogen atmosphere. Parts, and 10 parts by weight of polyethylene glycol monomethyl ether ester of methacrylic acid, and after premixing,
A method is possible in which the copolymerization is carried out while dropping over 4 to 5 hours together with the polymerization initiator to complete the copolymerization.

The obtained coating composition was extracted with chloroform, and filtered through a filter having a pore size of 0.45 μm.
Was measured. The spectrum had one peak, and it was confirmed that this was a copolymer. In this case, the ratio of the component constituting the copolymer (a) to the component constituting the polymer (b) is 90:10. Then, 5
Cool to 5 to 60 ° C., add 0.5 equivalent of ammonia or 0.1 to 0.5 equivalent of a high-boiling amine or hydroxide to 1 equivalent of the acid contained in the copolymer, and neutralize, Solubilization was performed.

When the coating composition of the present invention is a copolymer (c) obtained by copolymerizing a component constituting the copolymer (a) and a polymerizable compound having an ether bond, the acid value is as follows: The acid value of the copolymer (c) before neutralization.

The acid value of the coating composition is from 20 to 300 mg-
It is preferable to adjust so as to be KOH / g. More preferably, it is 25 to 250 mg-KOH / g, and more preferably 100 to 230 mg-KOH / g. For example, when the acid value of the copolymer (c) is less than 20 mg-KOH / g, the alkali film-removing property is extremely reduced. When the acid value of the copolymer (c) exceeds 300 mg-KOH / g, the rust-preventing property is extremely reduced, and the effects of styrene and other rust-preventing agents added are not exhibited.

The weight average molecular weight of the coating composition is 10,0
It is preferably from 100 to 70,000, and 10,000
More preferably, it is ~ 50,000. 10,000
If it is less than 70, press moldability will deteriorate, and if it exceeds 70,000, the viscosity of the coating composition will increase, and coating tends to be difficult.

The glass transition point Tg of the coating composition is 0
It is preferable that the temperature is not less than ° C. When the temperature is less than 0 ° C., the coating formed by applying the coating composition on the surface of the metal plate is released or melted from the metal plate due to heat generation during press molding,
This is because the lubrication performance of the coating film is reduced. Preferred Tg
Is 30 to 100 ° C.

Preferred Additives It is preferable that a lubricant, a rust preventive, a colorant, and the like are added to the acrylic resin for the purpose of further improving rust prevention and press moldability. Preferred lubricants include:
Metal soaps, which are salts of higher fatty acids such as lauric acid, palmitic acid, stearic acid and oleic acid with alkaline earth metals such as calcium and barium; and zinc, calcium or ammonium salts of phosphoric acid and molybdic acid. The preferred amount of the rust inhibitor is 3 to 30% by weight, preferably 5 to 20% by weight, based on the total resin solid content of the coating composition. Within this range, the rust resistance is excellent without extremely impairing the stability of the paint.

The coating composition may further contain a solid lubricant or wax as a lubricant. Examples of the solid lubricant include graphite, molybdenum disulfide, talc, a fluorine-containing resin, boron nitride, and carbonate. Calcium, melamine, isocyanuric acid adducts and the like can be mentioned.

Examples of the wax include polyethylene wax, petroleum paraffin wax, animal and vegetable fats and oils, higher fatty acids, higher alcohols, esters of higher fatty acids and higher alcohols, higher fatty acid amides, amine salts of higher fatty acids, and the like. For this reason, it is preferable to use one having a melting point of 45 ° C. or higher. To increase the melting point, there is a method of eliminating double bonds by hydrogenation. The preferred amount of the lubricant is 3 to the total resin solid content of the coating composition.
-50% by weight, preferably 5-30% by weight. Within this range, the alkali film-removing property is not impaired, the press formability is excellent, the stability of the coating material is not extremely impaired, and the rust prevention is also excellent.

In particular, when a metal soap or a zinc, calcium or ammonium salt of phosphoric acid and molybdic acid is used as an additive, their specific gravities are larger than that of the solvent, and the sedimentation is liable to occur. Therefore, it also functions as an antisettling agent. It is preferable to blend the following alkyl phosphonic acid monoalkyl ester (phosphorus organic substance A) and alkyl phosphonic acid dialkyl ester (phosphorus organic substance B). For example, the phosphorus-based organic substance is preferably in a weight ratio of 1:99 to 20: 8 with respect to the total resin solid content of the coating composition.
0, more preferably from 5:95 to 15:85. If the content of the phosphorus-based organic substance is less than 1% by weight, the effect of preventing sedimentation is not exhibited, and if it exceeds 20% by weight, the cohesive strength of the coating film is reduced, and the coating film is peeled off during processing, so-called powdering is likely to occur.

When a mixture of phosphorus-based organic substances is used, the weight ratio of the phosphorus-based organic substance A (monoalkyl alkylphosphonic acid ester) to the phosphorus-based organic substance B (dialkyl alkylphosphonic acid ester) is 10:90 to 90:10. If there is, the effect is remarkable. 10% by weight of phosphorus organic substance A
When the amount is less than 90%, the paint stability is remarkably deteriorated. When the amount exceeds 90% by weight, the amount of hydroxyl groups adsorbed on the surface of the steel sheet is increased, so that the alkali film removing property is deteriorated.

[0050]

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Here, R ₁ is a saturated hydrocarbon group or an unsaturated hydrocarbon group having 10 to 50 carbon atoms, which may be linear or branched, and specifically, α 1 having 40 carbon atoms.
-Olefins are exemplified. R ₂ is a saturated or unsaturated hydrocarbon group having 1 to 8 carbon atoms,
₃ , C ₃ H ₇ , C ₅ H ₁₁ and C ₈ H ₁₇ , and are preferably α-olefins having 5 or 8 carbon atoms. When there are two R _{2 s} , they may be the same or different.

In addition to the above components, solvents such as hydrocarbons, coloring agents, pigments, dyes, etc. may be added to the coating composition. An additive that is added to the coating composition of (1) can also be added.

When the coating composition is applied to a metal plate such as a hot-rolled steel plate, a cold-rolled steel plate, a stainless steel plate, various surface-treated steel plates, and an aluminum plate, the adhesion amount is 0.5 to 5 g / dry weight per one side. m ² is preferable. 0.
If it is less than 5 g / m ^2, it is not possible to fill the irregularities on the surface of the metal plate, and the effect of the present coating film on press formability and rust resistance is not exhibited. If it exceeds 5 g / m ² , powdering occurs during press molding. A more preferred range is 0.5 to 3 g / m ^2.

The coating can be performed by a known method such as roll coating, spray coating, dip coating, and brush coating. Drying conditions are a temperature of 40 ° C to 200 ° C and a drying time of about 1 to 90 seconds. In addition, the metal plate in the present invention includes a metal band that is a band-shaped metal plate, and is not particularly limited, but a hot-dip galvanized steel sheet, an alloyed hot-dip galvanized steel sheet,
Hot rolled steel sheet, cold rolled steel sheet, galvanized steel sheet, electric Zn-
Examples include a Ni-plated steel plate, an aluminum plate, and a stainless steel plate.

[0055]

The present invention will be described more specifically below with reference to examples and comparative examples. (Examples 1 to 20, Comparative Examples 21 to 26) <Test piece preparation method> The following acrylic copolymers A to G were applied to the surfaces of the following metal bands A to G degreased by alkali washing.
Table 1 was prepared by adding the following neutralizing agents A to G and the following additives to G (component composition and physical properties are shown in Table 1).
The coating composition shown in Table 1
g / m ² , and dried using a hot air drier so that the reached plate temperature after 10 seconds would be 60 ° C.
Then, rust-preventive oil (16.0 cSt / 40) was applied on both surfaces.
C) was applied so as to be 0.5 to 1.0 g / m ² to obtain a test piece.

Metal plate A: Alloyed hot-dip galvanized steel sheet (Zn adhesion amount per side:
60 g / m ² ) B: Hot-rolled steel sheet C: Cold-rolled steel sheet D: Stainless steel sheet E: Aluminum sheet F: Electrogalvanized steel sheet (Zn adhesion amount per side: 40 g)
/ M ² ) G: Hot-dip galvanized steel sheet (Zn adhesion amount per side: 60 g)
/ M ² )

Acrylic resin A: Mixture of (a) and (b) Copolymer (a): Ethyl methacrylate-styrene-methacrylic acid copolymer Polymer (b): Ester of acrylic acid and polyethylene glycol monomethyl ether Polymer B: Mixture of (a) and (b) Copolymer (a): Isopropyl methacrylate-styrene-itaconic acid copolymer Polymer (b): Esterified product of acrylic acid and polyethylene glycol monomethyl ether Polymer

C: mixture of (a) and (b) Copolymer (a): n-butyl methacrylate-styrene-methacrylic acid polymer Polymer (b): weight of esterified product of acrylic acid and polyethylene glycol Combined D: mixture of (a) and (b) Copolymer (a): isobutyl methacrylate-styrene-
Acrylic acid copolymer Polymer (b): Polymer of esterified product of methacrylic acid and polyethylene glycol

E: (c) homopolymer (c): copolymer of esterified product of methacrylic acid-n-butyl-styrene-acrylic acid-methacrylic acid and polyethylene glycol monopropyl ether F: (c) homopolymer Polymer (c): Copolymer of esterified product of methacrylic acid-n-butyl-styrene-methacrylic acid-acrylic acid and polyethylene glycol G: (c) homopolymer (c): Isopropyl methacrylate-styrene-methacrylic Copolymer of acid-methacrylic acid and esterified product of polyethylene glycol

Additives (% by weight based on the total resin solid content of the coating composition) Calcium stearate 5% Zinc phosphate 5% Polyethylene wax 10% Phosphorus organic substance A: In the formula, R ₁ is an α-olefin having 40 carbon atoms. Organic substance B: wherein R ₂ is an α-olefin having 5 carbon atoms

Neutralizer A: Ammonia (boiling point -33 ° C.) B: Isopropylamine (boiling point 32 ° C.) C: Diethylamine (boiling point 56 ° C.) D: N, N-dimethylethanolamine (boiling point 130)
C) E: Monoethanolamine (boiling point 170 ° C) F: Triisopropanolamine (boiling point 305 ° C) G: Triethanolamine (boiling point 360 ° C)

The test pieces thus obtained were examined for press formability, rust prevention, alkali film removal, chemical conversion treatment, blocking resistance, coating film drying property, and paint stability. Table 1 shows the results. In addition, the evaluation of each characteristic of the test piece was performed as follows.

<Evaluation method> (1) Press formability Room temperature press formability (limit wrinkle holding load, galling resistance, powdering resistance) Using an Erichsen cup drawing tester, under the following press conditions and in a mold: While maintaining the temperature at room temperature (25 ° C.), cylindrical deep drawing was performed to obtain a test piece. Punch diameter 33mmφ (Cylinder, beaded cylinder) Drawing die shoulder curvature 2mmR Blank diameter Cylinder 68mmφ, Cylinder with bead 68mmφ Limit wrinkle holding load Evaluated by the maximum number of t that can be formed without breaking

(Evaluation standard for mold galling resistance) The side wall of the test piece was observed, and the presence or absence of mold galling was evaluated in four steps. ◎ = No mold seizure 〇 = Slight mold seizure △ = Slightly large seizure × = Many seizure

(Criteria for Evaluation of Powdering Resistance) The side walls of the test pieces were observed, and the presence or absence of powdering was evaluated on a four-point scale. ◎ = No powdering occurred 〇 = Some powdering occurred △ = Somewhat powdering occurred × = Many powdering occurred

Warm press formability (critical wrinkle holding load, galling resistance, and powdering resistance) Using an Erichsen cup drawing tester, under the following pressing conditions and keeping the mold temperature at 80 ° C, Draw-forming was performed to obtain a test piece. Punch diameter 33mmφ (cylinder) Draw die shoulder curvature 2mmR Blank diameter cylinder 68mmφ Draw speed 60mm / sec Limit wrinkle holding load Evaluated by the maximum t number that can be formed without breaking

(Evaluation Criteria for Galling Resistance) The side walls of the test pieces were observed, and the presence or absence of mold galling was evaluated on a four-point scale. ◎ = No mold seizure 〇 = Slight mold seizure △ = Slightly large seizure × = Many seizure

(Criteria for Evaluation of Powdering Resistance) The side walls of the test pieces were observed, and the presence or absence of powdering was evaluated on a four-point scale. ◎ = No powdering occurred 〇 = Some powdering occurred △ = Somewhat powdering occurred × = Many powdering occurred

(2) Rust prevention properties The test pieces were further coated with 2 g / m ^{2 of} rust prevention oil ("Non-last" Z5: manufactured by Idemitsu Kosan Co., Ltd.), and JIS Z2371 was applied.
According to the above, spray 3% by weight of salt solution and spray white rust after 17 hours (Red rust for cold rolled steel sheet and hot rolled steel sheet)
Was evaluated as the area ratio.

(3) Alkali film-removing property A test piece was sprayed with an alkali cleaning solution (degreaser: Fine Cleaner 4460, manufactured by Nippon Parkerizing Co., Ltd.) adjusted to a concentration of 3% by weight and a liquid temperature of 40 ° C. at a spray pressure of 1 kg / cm. ^Two
Degreased by spraying for 10 seconds, the degreased test piece was immersed in water, and the water-wetted area after pulling up was visually observed, and the alkali delamination property was evaluated in three steps based on the following criteria. 〇 = Wet site: 100% of the surface area of the metal plate △ = Water site: 95% or more of the surface area of the metal plate × = Water site: Less than 95% of the surface area of the metal plate

(4) Chemical conversion property A test piece was sprayed with an alkali cleaning solution (degreaser: Fine Cleaner 4460: manufactured by Nippon Parkerizing Co., Ltd.) adjusted to a concentration of 3% by weight and a liquid temperature of 40 ° C. at a spray pressure of 1 kg / cm ^2.
And then degreased by spraying for 30 seconds, then immersed in a chemical conversion solution (PB-L3020M: manufactured by Nippon Parkerizing Co., Ltd.) adjusted to 43 ° C. for 120 seconds to perform a chemical conversion treatment, and then using a scanning electron microscope (× 1000). The crystal morphology of the chemical conversion treatment film was observed. Each metal plate coated with a coating composition other than the coating composition of the present invention was subjected to a chemical conversion treatment under the same conditions as a chemical conversion coating film. 〇 = A good chemical conversion coating that is no different from a chemical conversion coating on an unpainted steel sheet. △ = A chemical conversion coating with a slight reduction in crystal size and coarseness compared to a chemical conversion coating on an unpainted steel sheet. Generates almost no

(5) Blocking Resistance Two test pieces superimposed with the coating surfaces facing each other
While being tightened with a torque of 0 kg · cm, it was left in a thermostat at 60 ° C. for 6 hours. Thereafter, the stacked test pieces were peeled off, and the blocking resistance was evaluated on a four-point scale according to the adhesion state at the time of peeling off. ◎ = No stickiness 〇 = Some sticky △ = Stuck × = Large sticky

(6) Drying of Coating Film The coating film of the present invention was immediately applied and baked, and at the same time, the coating film was checked for tackiness by finger touch, and at the same time, the coating surfaces immediately after coating and baking were placed inside each other. 30 pieces of two test pieces
It was left at room temperature for 6 hours while being tightened with a torque of 0 kg · cm. Thereafter, the peeling state and the change in appearance when the torque was released were evaluated in four steps. ◎ = No stickiness / peeled off by its own weight when releasing the torque of stacked test pieces, no change in appearance ○ = No sticky / peeling off by its own weight when releasing the torque of stacked test pieces, appearance changed △ = Slightly sticky・ Does not peel by its own weight when releasing the torque of stacked test pieces. × = There is stickiness. ・ Does not peel by its own weight when releasing the torque of stacked test pieces.

(7) Paint stability The paint composition of the present invention placed in a 200 ml graduated cylinder was opened for one month during opening at 50 ° C., and the state of paint separation after the standing was visually observed, and the viscosity was measured. And the viscosity before standing was evaluated on a 4-point scale. The solid content in the coating composition was 20% by weight. ◎ = No separation of the coating composition and no change in viscosity ○ = No separation of the coating composition, but there is a tendency to increase the viscosity △ = Some sediment or suspended matter and increased viscosity × = Sediment or suspended matter Significantly generated and viscosity increased

[0075]

[Table 1]

[0076]

[Table 2]

[0077]

[Table 3]

[0078]

[Table 4]

[0079]

[Table 5]

[0080]

[Table 6]

[0081]

[Table 7]

[0082]

[Table 8]

[0083]

The lubricated metal sheet having the coating composition of the present invention and the coating film formed by applying the coating composition of the present invention to the surface has alkali film-removing properties, chemical conversion properties,
Excellent in rust prevention, coating dryness, blocking resistance, paint stability, and press formability including mold galling resistance and powdering resistance are remarkably improved. INDUSTRIAL APPLICABILITY According to the present invention, difficult-to-form press molding, which has conventionally been a problem, becomes possible, and is suitably used as a material for automobile parts and the like.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Ogata 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Corporation (72) Inventor Shigeru Umino 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki (72) Inventor Kazuo Wakasa 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture F-term (reference) 4D075 CA03 CA08 CA23 DB02 DB04 DB07 EB22 4F100 AB01B AH03A AH03H AK12A AK25A AL01A AL06A AT00B BA02 CA14A CA14H GB32 JB02 JK16 4J038 CC021 CG031 CG061 CG071 CG141 CG142 CH031 CH041 CH142 GA06 PC02

Claims (3)

[Claims] 1. A coating composition containing an acrylic resin and a neutralizing agent, wherein the acrylic resin is a monomer having methacrylic acid ester composed of methacrylic acid and an alcohol having 2 or more carbon atoms, styrene and a carboxyl group. A coating composition comprising a copolymer (a) with a polymer and a polymer (b) of a polymerizable compound having an ether bond. 2. A coating composition containing an acrylic resin and a neutralizing agent, wherein the acrylic resin has methacrylic acid ester composed of methacrylic acid and an alcohol having 2 or more carbon atoms, styrene, and a polymerizable polymer having an ether bond. A coating composition comprising a copolymer (c) of a compound and a monomer having a carboxyl group. 3. A lubricated metal plate having a coating film formed by applying the coating composition according to claim 1 or 2 to the surface.