JP3518384B2 - Painted steel plate with excellent durability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD [0001] The present invention is intended to provide excellent workability.
At the same time, it is hard to be scratched.
Excellent durability, such as less rusting
Especially for indoor and outdoor building materials and home appliances
Regarding the board. [0002] 2. Description of the Related Art A coated steel sheet is pre-painted,
Painted steel plate that does not require painting after construction (pre-coated steel plate)
Has been widely used for indoor and outdoor building materials.
You. Typical painted steel sheet for building materials is used for painting.
Classified by the type of resin used, and
Riester type, fluorine type with high weather resistance, thick film
Examples thereof include vinyl chloride based materials having excellent corrosion resistance and durability.
Epoxy is used as a primer (primer) for these paints.
Si coatings are generally used. [0003] Polyester-coated steel sheet has a molecular weight of 3,000 to
About 5000 paints mainly composed of polyester resin
It was painted with a coating thickness of about 15 μm. Inexpensive
However, due to the small thickness of the coating film, scratches
Corrosion resistance, especially in the processed part, is insufficient.
It is. Further, the workability is not satisfactory. [0004] A typical fluorine-coated steel sheet is polyfluoride.
Paint with vinylidene and acrylic resin as main components
It is something. This painted steel sheet has excellent weather resistance
But the coating thickness is undercoat (primer) + overcoat (top
(Coat) is about 25μm, so the same as above
Rust is easily generated from scratches. Fluorine paint is expensive.
It is economically disadvantageous because it is expensive. [0005] A polyvinyl chloride coating which is abbreviated as a PVC steel sheet
The coated steel sheet is made of polyvinyl chloride (PVC) sol paint (Plastic
Sol) to a thickness of about 150 to 300 μm.
You. Paint film compared to polyester or fluorine coated steel sheet
The thickness is so large that even if it is damaged,
And excellent corrosion resistance. Also, the coating film
Made of thermoplastic resin and containing a plasticizer,
Excellent workability, for example, close contact when bending
Bending (OT) is also possible, so it is widely used for building materials.
Have been. [0006] However, in recent years, polysalts have been developed.
The use of vinyl chloride resin is becoming more difficult,
The situation is the same. One reason is that polyvinyl chloride
Concerns about dioxin emissions during the disposal of
You. If the disposal takes place at high temperatures, the resin is completely decomposed
Is considered to be no problem, but the incinerator temperature is low.
Hazardous substances may occur. Another reason is that in polyvinyl chloride resin
Environmental contamination by plasticizers contained in Poly
Vinyl chloride resin is generally plasticized to improve processability.
The agent has been added. A common plasticizer is dioctyl phthalate
Typ (DOP), dibutyl phthalate (DBP), etc.
It is a boiling point solvent, but these gradually evaporate from the coating film
Conceivable. The shadow of the plasticizer thus volatilized on the human body
Hibiki is not clear at present, but such substances
Unnecessary painted steel sheets are required in the market
ing. [0008] The present invention relates to the thickness of a vinyl chloride coated steel sheet.
It can be made into a film, has high corrosion resistance, and has excellent workability
Durable, with the advantage of no environmental pollution
An object of the present invention is to provide a coated steel sheet having excellent properties. [0009] [Means for Solving the Problems] A precoat that can be thickened
As a steel sheet, JP-A-10-130572 discloses a specific alicyclic ring.
Formula diamine and specific polyisocyanate
With a blocked isocyanate blocked by
Resin as base coat and used as top coat
Is a polyester resin component and a specific block isocyanate
And a blocked isocyanate component containing
A coated steel sheet using a urethane resin has been proposed. [0010] The undercoat paint is a resin containing a urea bond.
Layer, and the top coating is a resin layer containing urethane bonds.
So that the lower layer of the above coated steel sheet is a urea resin,
Painted steel with a two-layer coating consisting of polyurethane resin on the upper layer
It is a board. Undercoat paint can be thickened up to 50μm thickness
Therefore, it is possible to manufacture thick-film coated steel sheets,
Workability is also good. However, we tested
However, with this primer, the corrosion resistance of the coated steel sheet obtained
Is still not enough, especially if the damage reaches the base material or
Rust generation on the surface cannot be prevented. [0011] Corrosion resistance of paint film when anti-rust pigment is added to paint
Can be increased. A common antirust pigment is chromic acid
Chromic acid, including strontium and zinc chromate
It is a salt-based rust-preventive pigment. These are strong in rust prevention, but hexavalent
Since it is a chromium compound, use it as much as possible.
desirable. However, conventional coated steel sheets maintain workability
To improve corrosion resistance while adding a relatively small amount of
I have to use chromate rust preventive pigments that can improve the corrosion
I didn't get it. The present inventors have made it possible to increase the film thickness,
In particular, coated steel sheets with high corrosion resistance and excellent workability
As a result of repeated examinations for development, JP-A-10-130572
Specific non-chrome
(Non-chromate) -based rust-preventive pigments
Corrosion resistance is significantly improved with the addition amount that does not deteriorate the corrosion resistance
And found that the above problems could be solved
Was. Here, the present invention is characterized in that a pre-coating treatment is performed.
One or both sides of zinc or aluminum plated steel sheet
On the surface, the reaction product of polyamine and polyisocyanate
10-50wt% in urea resin consisting ofContains anti-rust pigment,
The rust preventive pigment isChoose from phosphate and phosphite
One or two or moreConsists ofThickness 10 ~
80 μm first coating layer and polyester formed on it
Thickness 15 ~
Having a second coating layer of 40 μm,processing
Sex andIt is a coated steel sheet with excellent durability. The coated steel sheet of the present invention is subjected to a pre-coating treatment.
Polyamide or aluminum-based coated steel sheet
Containing styrene, blocked isocyanate, and the above rust preventive pigment
And the content of the rust-preventive pigment is 10 to 10
After applying and baking 50% by weight paint, polyester
To apply and bake with polyurethane or polyurethane paint
Can be manufactured more. In the present invention, the base resin for the undercoat paint is used as the base resin.
Urea resin as described in JP-A-10-130572
And combine this resin with a non-chromate rust preventive pigment.
Thick film coated steel sheet that does not contain hexavalent chromium
Can be realized. Other base resin for undercoat paint
For the resin types, the proportion of non-chromate rust-preventive pigments
The desired corrosion resistance cannot be obtained
However, the workability of the coated steel sheet deteriorates significantly
It becomes difficult to use. That is, non-chromate rust-preventive pigments
When used, other resin types have both corrosion resistance and workability.
Can not stand. [0016] BEST MODE FOR CARRYING OUT THE INVENTION In the coated steel sheet of the present invention,
Zinc and aluminum plated steel with excellent corrosion resistance
Use a board. What is galvanized steel sheet?
It is meant to include zinc alloy plated steel sheets,
Aluminum-plated steel sheet and aluminum-coated steel sheet
Alloyed steel sheet. As a specific example of such a plated steel sheet,
Electrogalvanized steel, including but not limited to
Sheet, hot-dip galvanized steel sheet, alloyed hot-dip galvanized steel sheet,
Electric zinc-nickel alloy plated steel sheet, hot-dip 5% Al-Zn alloy
Gold-plated steel sheet, 55% Al-Zn alloy plated steel sheet, hot-dip
A luminium-plated steel plate is exemplified. [0018] The plated steel sheet of the base metal has corrosion resistance and coating film adhesion.
In order to improve the quality of the paint,
Processing). As this pre-painting treatment, for example,
Phosphate treatment (typically zinc phosphate treatment) is an example.
You. The pre-painting treatment can be performed in the same manner as before,
The amount of application may be the same as the conventional one. As a guide, zinc phosphate treatment
0.3 ~ 1.2 g / m^TwoIt is about. As the undercoat paint, a thick film can be formed.
Therefore, block isocyanates and polyamines are
Use a paint that has a good resin component. Of polyisocyanate
The isocyanate group is blocked by reacting with a blocking agent.
The use of blocked isocyanate requires only one liquid
This is to make it a type. When heated, the coating dissociates the blocking agent.
The isocyanate group (-NCO) is regenerated, and this is
Amine group in the amine (-NH_Two) To react with the urea bond (-NHCON
It polymerizes by forming H-). Therefore, for baking
The resin in the coating film formed from polyamine and polyisocyanate
It is a urea resin consisting of a reaction product with anate. Only
The urea resin coating alone ensures sufficient corrosion resistance
It is not possible to prevent rust on the scratches and edges that have reached the base material.
I can't do that. Therefore, in the present invention, this undercoat paint
Further contain a rust-preventive pigment. In the present invention, the block isoform used in the undercoat paint
Cyanate was developed as a one-pack type polyurethane paint.
A suitable blocking agent
And obtained by reacting Polyisocyanate
Are roughly divided into aromatics and aliphatics.
Excellent, aliphatic is excellent in weather resistance and hard to yellow. That
Therefore, in general, polyurethane paints have excellent weather resistance.
Aliphatic polyisocyanates including alicyclic compounds capable of forming a film
Acrylates are mainly used.
Block is obtained by reacting a lysocyanate with a blocking agent.
Socyanates are the mainstream. However, in the present invention, the paint used for the undercoat paint is used.
Since rock isocyanate does not require weather resistance,
Aliphatic resins may be used, but aromatic
Liisocyanate can form a coating film with better adhesion
More preferred. Ports suitable for use in the present invention
As the isocyanate, tolylene diisocyanate
G, diphenylmethane diisocyanate, polymethylene
Polyphenyl polyisocyanate, naphthalene diisocyanate
Aromatic resins such as anate and tolidine diisocyanate
Illustrated are lysocyanates. Above all, tolylene diiso
Cyanates are preferred for performance and economy. Polyisocyanates are not monomers, but
Repolymer, adduct (with trimethylolpropane, etc.
Addition), isocyanurate form and biuret form
Other derivatives can also be used. In addition, two or more polyisomers
Anate or a derivative thereof may be used in combination.
No. As a blocking agent for polyisocyanate
From block isocyanate to enable thick film
The dissociation temperature at which the blocking agent dissociates is 150 ° C or higher
Are preferred. Blocks with a dissociation temperature below 150 ° C
Agent (e.g., cresol with a dissociation temperature of 120 ° C, dissociation temperature of 140 ° C
Methyl ethyl ketone oxime)
Socyanate generates foam (bubbles) during baking after painting.
Because it is easy to produce, thick film coating may be difficult.
If the dissociation temperature is too high, the baking temperature will be very high
Or the baking time needs to be extended, so dissociation
The temperature should be below 200 ° C, especially below 180 ° C. Good
A preferred example of a blocking agent is ε- having a dissociation temperature of 170 ° C.
Caprolactam, but has a dissociation temperature of 150-200 ° C.
Other blocking agents having a temperature between 160 and 180 ° C can also be used. Reaction of polyisocyanate with blocking agent
Can be the same as in the past.
Reaction of an equivalent or slightly excess blocking agent to the plate under heating
This is done by letting Blocked isocyanates
Those having a number average molecular weight in the range of 1,000 to 4,000 are preferred.
Various products are commercially available for blocked isocyanates
Use appropriate commercial products
Can be. Polyamines used in undercoats are also aliphatic.
 (Including alicyclic) system and aromatic system may be used.
Preferred are cycloaliphatic polyamines. Alicyclic polyamine
Are used, for example, as curing agents for epoxy resins
Can be used. As a specific example, 1-
Cyclohexylamino-3-aminopropane, diamino
Cyclohexanes, bis (4-aminocyclohexyl)
Tan, bis (4-aminocyclohexyl) sulfone, 3,3 '
-Dimethyl-4,4'-diaminodicyclohexylmethane,
And isophorone diamine. Most preferred is 3,3 '
-With dimethyl-4,4'-diaminodicyclohexylmethane
is there. One or more polyamines can be used. Block isocyanate in undercoat paint
The mixing ratio of the isocyanate group / polyamine is
The molar ratio of the amino groups should be in the range of 0.6 to 2.0
Is preferred. This molar ratio is more preferably 0.8 to 1.
2 Block isocyanate and polyamine
The paint contained can be applied to a coated steel plate because thick film coating is possible.
It is suitable, but it alone does not provide sufficient corrosion resistance on the end face etc.
It is enough. Therefore, in the present invention, this paint is further added.
Add a rust-preventive pigment and apply this paint to the primer (primer
ー) Non-chromate pigments as rust preventive pigments,
Specifically, phosphate-based and phosphite-based rust preventive pigments
Use one or more selected from these. like this
Specific examples of rust preventive pigments include aluminum phosphate and phosphorus.
Zinc acid, zinc phosphite, calcium phosphite, phosphorous acid
Strontium, zinc calcium phosphite, phosphite
Lead strontium and the like are exemplified. In the present invention, it is possible to thicken the undercoat paint,
Since a resin system with good processability was selected,
Even non-chromate rust preventive pigments with lower rust resistance
Sufficient corrosion resistance is provided at a content that does not reduce workability.
Can be given. Amount of this non-chromate rust preventive pigment
Is the total amount of non-volatiles in the coating (blocked isocyanate
(The blocking agent part is not included in the non-volatile content)
It is in the range of 10 to 50% by weight, preferably 20 to 40% by weight. Ten
If the amount is less than 50%, the corrosion resistance of the cut end face cannot be secured, and 50%
If the amount is larger, the processability decreases, and the secondary adhesion of the coating film (long term
(Adhesion) also decreases. [0031] Such non-chromate rust preventive pigments are
Rust prevention ability due to less elution than romate rust prevention pigments
Is weak, and it is conventionally desired not to add more than the above.
New corrosion resistance could not be imparted to painted steel sheets
Therefore, a remarkable decrease in workability was inevitable. In the present invention
Is capable of thickening the undercoat paint and has excellent workability.
Non-chromate rust prevention in a range that does not cause a decrease in workability
Desirable corrosion resistance can be given by pigment content
It becomes. The base coat is prepared by adding a block solvent to a suitable solvent.
In the resin solution in which cyanate and polyamine are dissolved, add the above
Add a non-chromate rust preventive pigment to disperse it evenly.
And can be prepared by: Solvents are generally organic solvents
Used, for example, hydrocarbons such as toluene and xylene
Base, ester such as ethyl acetate and butyl acetate, cello
Ethers such as sorbs, and methyl isobutyl
Ketone, methyl ethyl ketone, isophorone, cyclohexene
Examples thereof include ketone solvents such as sanone. Optional paints which may optionally be added to this paint
Ingredients are used to adjust coating film properties and reduce costs.
Extender (e.g., silica, alumina, tal
, Calcium carbonate, titania, etc.). Extender pigment
When adding, the amount of addition is 20 wt.
%, Especially 10 wt% or less.
preferable. In addition to the undercoat, defoamers, pigment dispersants,
Anti-sagging agent, leveling agent, silane coupling agent, etc.
Various additives, and polyisocyanates and polyamides
A small amount of catalyst (e.g., organotin compound)
May be added. This undercoat was subjected to a pre-coating treatment.
Paint on plated base steel. Painting is a roll coat,
Any suitable such as curtain flow coat, spray painting
In a simple way. A place for continuous painting on coiled steel plates
In such a case, a roll coat is generally used. Painting is 10 ~ 80μm
Is performed so as to obtain a coating film thickness of The coating thickness is 10μm
If it is too small, it will not be possible to prevent rusting due to scratching,
If the film thickness is larger than 80 μm, the workability is reduced. This coating thickness
The thickness is preferably 20 to 60 μm. Undercoat used in the present invention
Paint can form a coating film of the above thickness in one application.
However, it may be painted two or more times. Baking after applying undercoat paint reaches the highest
It is preferable to carry out at a temperature of 180 to 240 ° C for 30 to 70 seconds.
No. By this baking, the block isocyanate in the coating film
When the blocking agent dissociates from the
The anate reacts with the polyamine to form a urea resin. Follow
The formed undercoat film (first layer film) is made of urea resin
It has a structure in which non-chromate rust preventive pigments are dispersed.
The content of the non-chromate rust preventive pigment in the coating film is 10 to 50.
wt% range. A top coat is applied on the undercoat.
And baking to form a top coat (second layer coat)
To achieve. Polyester or polyester
Use a urethane-based paint. Thereby, the undercoat film
Is a thick film containing a considerable amount of rust-preventive pigment
Regardless, it is possible to obtain coated steel sheets with excellent workability.
it can. Polyurethane coating used as a top coating
Paint is a coating containing a polyisocyanate and a polyol.
And use commercially available or known methods.
It may be made. Polyurethane used as topcoat
Paints also react polyisocyanates with blocking agents
One-part coating containing
It is preferable to use the material. As a polyisocyanate for a topcoat paint
Is excellent in weather resistance and can form a coating film that is not easily yellowed.
Aliphatic polyisocyanates including cyclic ones are preferred.
Examples of such an aliphatic polyisocyanate include:
Hexamethylene diisocyanate, isophorone diisocyanate
Anate, xylylene diisocyanate, hydrogenated diph
And phenylmethane diisocyanate. Poly
Isocyanates include prepolymers, adducts, isocyanates
Nurate body, biuret body and the like may be used. Particularly preferred polyisocyanates are processed
Hydrogenated diphenylmethane that can form a coating film with excellent properties
Diisocyanate. However, this polyisocyanate
Since the salt is quite expensive, other polyisocyanates
May be used in combination. In that case, in the polyisocyanate
At least 20% by weight of hydrogenated diphenylmethane diisocyanate
By using anate, it is possible to obtain a coating film with excellent processability.
Wear. Polyol component used for polyurethane paint
Polyester and polyether (e.g.,
Ethylene oxide or polyhydric alcohol as initiator
Ring-opening polymerization of propylene oxide)
In the present invention, one or more of them are used.
Can be used. The preferred polyol component is a polyester
is there. As this polyester, a high molecular weight saturated poly
Preferably, an ester resin is used. This polyes
Ter resin is one or more saturated fats
(Including alicyclic) or aromatic dicarboxylic acids and glycos
Is a linear polyester obtained by polycondensing
No. Examples of suitable dicarboxylic acids are succinic acid, glutar
Acid, adipic acid, azelaic acid, sebacic acid, dodecane
Diacid, phthalic acid, isophthalic acid, terephthalic acid, naphthalic acid
Phthalenedicarboxylic acid, diphenyldicarboxylic acid, 1,4
-Cyclohexanedicarboxylic acid and the like;
Examples are ethylene glycol, propylene glycol,
Tylene glycol, 1,5-pentanediol, neopen
Tyl glycol, 1,6-hexanediol, diethylene
Glycol, triethylene glycol, 1,4-cyclohexane
Xandimethanol, hydroquinone and the like. Saturated poly
The ester resin may also be used in addition to the above-mentioned reaction components.
Carboxylic acids (eg, trimellitic acid, etc.) and / or
Trihydric or higher alcohols (eg, glycerin, trimethylol
(Lupropane, pentaerythritol, sorbitol, etc.)
May be used as a branched polyester. As a polyol component of a polyurethane paint
Polyester resin used is preferably a weight average molecule.
The amount is 5000-20,000, more preferably 8,000-15,000,
Hydroxyl content is 1.0 to 4.0 wt%, more preferably 2.0 to 4.0 wt%
3.0 wt%, with a glass transition temperature of -30 ° C to 0 ° C
You. As a result, both weather resistance and workability are excellent.
A coated polyurethane coating is formed. Preferred polyurethane paints are hydrogenated
Diphenylmethane diisocyanate is a suitable blocking agent
At least 20 blocked isocyanates blocked with
wt% or more of blocked isocyanate
The preferred molecular weight, hydroxyl content and
And a polyester resin having a glass transition temperature.
To do. Isocyanates in polyurethane coatings
The molar ratio of nate groups / hydroxyl groups is 0.6-2.0, especially 0.8-1.
It is preferably within the range of 2. The top coating is a polyester coating.
There may be. Polyester suitable for use in the present invention
Paint is the polyol component of the polyurethane paint
Polyester resin as described as melamine tree
Crosslinking with fats, especially alcohol-modified melamine resins
Kind of thing. Polyester paint is polyurethane
Although a slight decrease in workability is seen compared to
It is more economically advantageous than polyurethane paint. [0045] Glass fiber, alumina fiber
Inorganic fillers such as fibers and boron nitride, and thermoplastic resin
(E.g., acrylic resin or nylon beads, average particle size
Is preferably 1 to 50 μm).
It may be contained in the following amounts. As a result, the coating surface becomes concave
Protrudes to improve the abrasion resistance of the coating, making it less likely to be scratched
You. Also, especially in the case of resin beads, the appearance is low gloss
As a result, the design is imparted. The top coating is usually a color pigment other than the above.
It contains. Solvents and other ingredients (e.g., extenders, other
(Fat, various additives)
The same may be applied. The top coat is prepared in the same manner as the undercoat.
Can be painted. For coating, the coating thickness is preferably 15 to 40 μm, preferably
Is performed so as to be 20 to 25 μm. Topcoat is too thin
In this case, the hue is not stable, and the corrosion resistance and weather resistance become insufficient.
If this coating is too thick, the processability will decrease. Baking after painting
The maximum temperature is 200-240 ° C, preferably 220-24
It is preferable to perform the drying at a temperature of 0 ° C for 40 to 90 seconds.
Good. The coated steel sheet of the present invention thus obtained is
Place zinc or aluminum on the plate in order from the bottom.
Coating layer, undercoating layer (pre-coating layer), non-chrome
A first coating layer made of a urea resin containing a rust preventive pigment,
And polyurethane or polyester resin
A second coating layer, which is a structure having four coating layers.
You. The resin coating layer is the same as the first coating layer.
It is not limited to two layers of the second coating layer. 3 paintings
If it is acceptable to do the above,
Further, another coating layer may be formed below. However, the best
The layer is the second coating layer described above. For example, traditionally painted steel
Epoxy resin coating that has been used as a primer for boards
As a bottom coat under the urea resin coat, or
Form an intermediate coating on the urea resin coating and apply the coating
It may have a three-layer structure. In that case, non-chromate
Rust-preventive pigments, epoxy resin
It is also possible to add it to the system coating film. The at least two resin-based coatings described above
Although it may be formed on both sides of the base metal plated steel sheet,
Form only on the surface. In that case, the opposite side should be plated
As it is, as it is, or as other base resin
Painting may be applied. The coated steel sheet of the present invention has a thick undercoat
So it is hard to be scratched.
The corrosion resistance of the cut end surface is excellent due to the
Even if there is a scratch reaching the base material, rust hardly occurs. further,
The upper and lower coating films are excellent in workability, so they can be bent tightly
Excellent workability is also ensured. Therefore, this coated steel sheet
Various building materials especially used indoors (eg, partitions)
And home appliances (e.g. personal computer, audio or
Not only is it useful for exterior panels such as video
(E.g. roofing materials, wall materials, shutters) and home appliances outdoors
(E.g., outdoor units for air conditioners and vending machines)
Can be used. Of course, other uses other than building materials and home appliances
It is also applicable to [0052] [Example] [Example 1] Hot-dip galvanized steel sheet (sheet thickness 0.6 m
m, plating weight is 90 g / m on one side^Two) As the base material,
After degreasing, use zinc phosphate on both sides with a commercially available treatment solution.
Treatment (Adhesion amount is 1g / m on one side^Two). The undercoat was made of polyamine (BASF Laromi).
3,3'-dimethyl-4,4'-diaminodicyclohexyl
Methane) and blocked isocyanate (Sumitomo Bayer Ure
Tan Death Module BL1100, ε-capacitor with a dissociation temperature of 170 ° C
Tolylene diisocyanate blocked with prolactam
G) with a molar ratio of amino group to isocyanate group of 1:
Dissolved in the solvent cyclohexanone at a ratio of 1.2
Then, the obtained resin liquid was added to the total amount of nonvolatile components shown in Table 1.
Of the non-chromate rust-preventive pigment
Aluminum phosphate, zinc phosphate, or phosphite
Rontium or, for comparison, chromate-based rust-preventive pigment
Strontium chromate, 5 wt% extender silica
And disperse it uniformly by appropriate means.
Prepared. A piece of the pre-treated hot-dip galvanized steel sheet
The undercoat was coated on the surface with a bar coater as shown in Table 1.
Apply to the thickness of the coating film,
Baking was performed for 60 seconds to form an undercoat film. On this undercoat film, as a topcoat paint
Polyurethane-based paint has a coating thickness of 20μ using a bar coater
m at a maximum temperature of 230 ° C for about 60 seconds
Baking to form a top coat, and
A sample was prepared. The polyurethane paint used was Polyester.
Ter resin (Sumitomo Bayer Urethane Alkinol 2013,
Weight average molecular weight 8,000, hydroxyl content 3wt%, glass inversion
Linear saturated polyester resin with a transfer temperature of -20 ° C) and hydrogenation
Addition of diphenylmethane diisocyanate to ε-caprolact
Tom blocked isocyanate (Sumitomo Buy
El urethane Sumidule 2117) and solid content weight ratio
1: 0.2 (molar ratio of isocyanate group / hydroxyl group = 1.2)
Mixed in proportions, and as a white extender, titanium oxide
 (Ishihara CR97) at the same weight as the resin solids.
And dilute appropriately with the solvent (cyclohexanone)
Prepared by The following performances were obtained for the obtained coated steel sheet.
The evaluation was performed, and the test results are also shown in Table 1. Comparison
For commercial PVC steel sheets (thickness: about 180 μm)
Tested similarly. (1) Workability Bend 180 ° at 23 ° C with the painted side outside
Observe the cracks in the area with a 10x loupe,
The minimum number of sandwiched plates where no rack is recognized (T, 0T
(Bending). 2T or less is good. (2) Corrosion resistance The salt spray test specified in JIS Z 2371 was used. test
Do you put a cross cut on the piece to reach the coated steel base
And spray it with salt water for 200 hours,
The blister width (maximum value) was measured. This swollen width is 2mm or less
If it is, the corrosion resistance is good. (3) Wet resistance Specimen with cross cut reaching plated steel base
Was exposed to a humid atmosphere of 50 ° C-RH 98% or more for 500 hours.
After that, the swelling width of the coating film swollen due to rust generation in the cross cut part
(Maximum value) was measured. If this swollen width is 2mm or less
The wet resistance is good. (4) Scratch resistance Using a diamond needle, scratch the coating surface of the test piece
Was evaluated. Load of diamond needle
The needle is moved at a speed of about 1 cm / s
At the limit load at which the plated steel base is exposed when separated.
Was. The larger the load, the stronger the coating film is
And If this load is 100g or more, scratch resistance
Good. [0062] [Table 1]As can be seen from Table 1, non-chromate protection
In undercoat paints using rust pigments, chromate-based rust-preventive pigments
Compared to the undercoat paint using
At the same film thickness, film swelling in corrosion and wet resistance
The width is large, but if the coating thickness is increased,
Absolute amount is large and sufficient while maintaining good processability
In addition, corrosion resistance and scratch resistance can be improved. However, if the thickness of the undercoat film is too large,
Workability decreases little by little. In addition, uniform by the occurrence of armpit
It is difficult to form a proper undercoat film. Example 2 Hot-dip galvanized steel sheet (sheet thickness 0.6
mm, plating weight 120 g / m on one side^Two) As base material
After degreasing, phosphoric acid is applied to both surfaces using a commercially available treatment solution.
Zinc treatment (Adhesion amount is 1g / m on one side^Two). The undercoat paint is composed of a non-chromate rust preventive pigment and
And prepared in the same manner as in Example 1 using aluminum phosphate.
This is a piece of pre-treated hot-dip galvanized steel sheet
Using a bar coater on the surface so that the coating film thickness shown in Table 2
And baked in the same manner as in Example 1,
A film was formed. On this undercoat film, a topcoat paint
20μ of polyester coating with bar coater
m at a maximum temperature of 230 ° C for about 60 seconds
Baking to form a top coat, and
A sample was prepared. The polyester paint used was Polyester
Ter Resin (Sumitomo Bayer Urethane Alkinol 2013)
100 parts by weight of melamine resin as a crosslinking agent
20 parts by weight of Anamid Cymel 303) and a catalyst
White was added to the resin solution obtained by mixing 0.5 parts by weight of ruenesulfonic acid.
Titanium oxide (CR97, manufactured by Ishihara Sangyo) as a color extender
The same weight as the fat solids is added and dispersed, and the solvent (cyclohexane)
(Xanone). Workability, corrosion resistance and moisture resistance of the obtained coated steel sheet
The wettability and scratch resistance were evaluated in the same manner as in Example 1.
The results are also shown in Table 2. As can be seen from Table 2, the topcoat
Even if the paint is polyester resin, processability is impaired.
Good corrosion resistance, wet resistance and scratch resistance
be able to. [0070] [Table 2][0071] According to the present invention, it is possible to increase the thickness of the coated steel sheet.
Block isocyanate and polyamine as base resin
Non-chromate rust-preventive pigments
Non-chromate rust preventive pigments with low rust resistance to form
Sufficient corrosion resistance due to thick film despite using
Can be given. Therefore, the coating film is damaged during construction.
Even if scratches occur, the damage reaches the base metal or plating
Is less likely to cause rust from scratches,
When steel plate or plated surface is reached,
Food habits are also secured. Therefore, compared to conventional coated steel sheets,
The durability is remarkably excellent. Further, a top coat film is formed with high workability and
Polyurethane paint or polish with good adhesion to the paint film
Undercoat film by forming from ester paint
Is a thick film coating containing a large amount of non-chromate rust preventive pigments.
Despite the excellent workability of 0-2T
You. Both undercoat and topcoat films are vinyl chloride
It is not based and does not contain chromate-based rust preventive pigments
So there are no environmental concerns. The conventional coated steel sheet is compared with the chromate type steel sheet.
Non-chromate rust preventive pigments with low rust prevention
In order to impart food quality, a large amount of addition that reduces workability is necessary.
It couldn't be used in practice
However, in the present invention, an undercoat paint that can be made thick and has good workability.
By incorporating a non-chromate rust preventive pigment into the
It is possible to obtain sufficient corrosion resistance while maintaining workability
The use of non-chromate rust preventive pigments
Durable complete with excellent workability and scratch resistance
Or almost completely chromate-free coated steel sheet
That was successful.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C09D 167/00 C09D 167/00 175/02 175/02 175/04 175/04 (72) Inventor Akito Yoshioka Chuo-ku, Osaka-shi 4-5-33 Kitahama Sumitomo Metal Industries Co., Ltd. (72) Inventor Hiroshi Kumagai 4-5-33 Kitahama, Chuo-ku, Osaka City Sumitomo Metal Industries Co., Ltd. (72) Inventor Sachio Matsuo Dejima Nishimachi, Sakai City, Osaka Prefecture No. 2 Sumitomo Metal Building Materials Co., Ltd. Sakai Works (72) Inventor Shigeyoshi No. 2 Sumitomo Metal Building Materials Co., Ltd. Sakai Works (72) Inventor Kenichiro Kobayashi 2 Dejima Nishimachi, Sakai City, Osaka Address Sumitomo Metal Building Materials Co., Ltd. Sakai Works (56) References JP-A-7-51620 (JP, A) JP-A-10-130572 (JP, A) JP-A-55-99971 (JP, A) (58 ) Surveyed fields (Int. Cl. ⁷ , DB name) B05D 1/00-7/26 B32B 15/08 C09D 5/08 C09D 167/00 C09D 175/02 C09D 175/04

Claims (1)

(57) [Claims 1] A urea resin comprising a reaction product of polyamine and polyisocyanate is coated on one or both surfaces of a zinc-based or aluminum-based plated steel sheet which has been subjected to a coating pretreatment. containing 50 wt% of the anticorrosive pigment, thickness the anticorrosive pigment is made of one or two or more species selected from Li <br/> phosphate salt and phosphite-based 10~80μm Excellent in processability and durability, characterized in that it has a first coating layer having a thickness of 15 to 40 μm and a second coating layer having a thickness of 15 to 40 μm formed from a polyester-based or polyurethane-based coating formed thereon. Painted steel plate.