JPH08318216A - Coated material with excellent resistance to dirt attaching property and its production - Google Patents

Abstract

PURPOSE: To provide a coated material with excellent resistance to dirt attaching property by setting a paint film surface, so that the surface layer part of the paint film provided on the surface of a material to be coated is removed and the paint film has a surface shape in which both surface length rate shown by the ratio of in-plane rectilinear distance to a bath surface distance and 10 points average roughness have a specific value respectively. CONSTITUTION: For example, in the case of continuously coating a coil-shaped metal plate, the metal plate under cooling or after cooling is polished by a buff roll, a brush roll, a grindstone, etc. Further, in the case of a coated molded form such as an external wall panel and an existing coated material, a paint film after cooling is polished by a rotary polisher. At this time, a paint film surface having large surface free energy is formed. In this case, the paint film surface is set up, so that paint film has surface shape in which surface length rate S1 shown by the ratio of in-plane rectilinear distance L1 to a bath surface distance L2 exceeds 100.04% and 10 points average roughness Rz is >=0.25. Thereby, a coated material is obtained in which hydrophilicity of a paint film surface is increased and resistance to dirt attaching property is excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roof, an outer wall, etc. of a building having improved stain resistance and a coating plate used therefor and a method for producing the same.

[0002]

2. Description of the Related Art Painted plates such as painted steel plates are used for exterior walls of buildings and houses, decorative panels for overpasses, and the like. For paint finishing of plate materials used for this type of application, urethane paints, acrylic paints, polyester paints, silicone paints, fluorine paints, etc., which have excellent weather resistance in consideration of outdoor durability, are sprayed, roll coaters. Etc., then dried at room temperature or dried and baked in a heating furnace. Although the obtained coated surface has excellent weather resistance,
As the air pollution caused by soot and the like from the factory becomes more severe, dirt easily attaches, and the dirt becomes noticeable in a relatively short time. As a method for preventing the deterioration of appearance due to adhesion of dirt, a resin containing a hydroxyl group (Japanese Patent Laid-Open No. 26402/1994) is used.
No. 0), a resin containing a group having a salt structure (Japanese Patent Laid-Open No. 6-1
79790), a water-soluble resin (JP-A-5-2715).
It is known that the surface of the coating film is made hydrophilic by adding (for example, No. 72) to the coating material. On the surface of the hydrophilic coating film, stains such as lipophilic carbon are less likely to be attached, and the attached stains are easily washed away by rainwater.

[0003]

However, the method by modifying the coating does not improve the stain resistance to a satisfactory degree. That is, even if a resin containing a hydroxyl group or a group having a salt structure is added to the paint, the polar groups do not orient well on the coating surface when the paint is dried and baked, and most polar groups are inside the coating. It gets in. for that reason,
The surface of the coating film is not sufficiently hydrophilized and the stain resistance is not sufficiently improved. The method of using a coating material to which a water-soluble resin is added can make the surface of the coating film relatively hydrophilic, but the effect is not durable and the durability is poor. Therefore, Japanese Patent Laid-Open No. 7-
In Japanese Patent No. 18209, the stain resistance is improved by forming a continuous uneven shape on the coating film surface. The continuous uneven shape is formed by applying a coating material containing a powdery additive or by spraying the powdery additive before the coating film solidifies. However, in order to do so, a special paint or process is required, and the management of operating conditions becomes troublesome in order to form a predetermined continuous uneven shape. The present invention has been devised to solve such a problem, by adjusting the surface roughness of the coating film surface by a simple method of removing the surface layer portion of the cured coating film, stain resistance And to obtain a coated article having excellent durability.

[0004]

In order to achieve the object, the coated object of the present invention has the surface layer portion of the coating film provided on the surface of the object to be coated removed and the ratio of the creepage distance to the in-plane linear distance is removed. The surface length ratio S _l represented by is more than 100% and has a 10-point average roughness R _z 0.25 or more. This coated object has a surface length ratio S represented by the ratio of the creepage distance to the in-plane linear distance after the coating material is applied to the surface of the coating object and dried or baked to form a coating film.
It is produced by removing the surface layer portion of the coating film so that _l exceeds 100% and the 10-point average roughness R _{z is} 0.25 or more. The surface layer portion of the coating film is removed by polishing the surface of the coating film while the baking-cured coating film is being cooled or after being cooled.

The object to be coated according to the present invention is not particularly limited by the material, but for example, a metal plate such as an aluminum plate, a cold rolled steel plate, a Zn plated steel plate, an aluminum plated steel plate, a stainless steel plate, or the like, Inorganic boards such as concrete boards and particle boards, or board materials such as natural wood and synthetic wood can be used. Furthermore, it is also possible to target an existing concrete wall or the like. In order to improve the adhesion of the coating material, it is preferable that the surface of these objects to be coated is previously subjected to chemical treatment such as dirt and oil removal by degreasing treatment, roughening by sandblasting, chromate treatment and the like. The paint used in the present invention is not particularly limited in its type, and specifically, there are urethane paint, acrylic paint, polyester paint, silicone paint, fluorine paint and the like. However, the effect of the removal of the surface layer of the coating film on the improvement of the stain resistance is different depending on the type of paint, and a resin system having a larger polarity has a larger effect of improving the stain resistance. In this respect, it is effective to newly synthesize a highly polar resin or to add a highly polar resin and a filler to a conventional paint.

These paints affect the stain resistance as a top coat. At this time, by applying a primer selected according to the application, the adhesion between the article to be coated and the top coating film and the corrosion resistance are improved. As the coating method, an appropriate method is adopted according to the type and application of the coating material. For example, when coating a coil-shaped metal plate continuously, roll coating, die coating, curtain coating, etc. are preferable. Further, when coating a molded body such as an outer wall panel or an existing material, spray coating, powder coating, etc. are preferable. The coating material applied to the object to be coated is dried and baked and cured by an appropriate method according to the type of coating material. For bake-curable paint, drying / baking using a hot air oven, infrared oven, induction heating oven, etc. is adopted. The dried and baked coated article is cooled by an appropriate method such as water cooling or air cooling. The room temperature dry paint is naturally dried in the air after painting.

Only the surface layer portion of the coating film cured by drying and baking is removed by means such as polishing. The removal of the surface layer part is intended to remove the molecular layer oriented on the surface of the coating film so that the surface free energy of the coating film becomes small due to the influence of the atmosphere or the atmosphere in the furnace during drying or baking.
Therefore, the surface of the coating film having a large surface free energy is exposed only by removing the extreme surface layer of about several μm or less of the coating film. The coating film surface having a large surface free energy is formed by polishing the metal plate during or after cooling with a buff roll, a brush roll, a grindstone roll, or the like, for example, when a coil-shaped metal plate is continuously coated. In addition, in the case of coating a molded product such as an outer wall panel or an existing product, when the coating film after cooling is polished by a rotary polisher or the like, a coating film surface having large surface free energy is formed. In any case, polishing with an abrasive can be performed. In order to increase the free energy on the surface of the coating film, it is sufficient to remove the pole surface layer of about several μm or less. Even if the coating film is removed by several μm or more, not only the effect of improving the stain resistance is saturated, but also the coating film thickness becomes thin, which may deteriorate the weather resistance and corrosion resistance originally required for the coating film. There is.

The surface portion of the coating film is removed by setting the surface length ratio S _l represented by the ratio of the creepage distance to the in-plane linear distance to 100.0.
It exceeds 4% and the 10-point average roughness R _z is set so that the coating film has a surface shape of 0.25 or more. 10 points average roughness R
_z represents the height of the unevenness, and the surface length ratio _Sl is related to the height of the unevenness and the number of the unevenness in the unit surface. Therefore, the surface shape can be expressed by measuring the 10-point average roughness R _z and the surface length ratio S _l . The numerical values representing these surface shapes show different values depending on the difference in the measuring means of the contact type roughness meter and the non-contact type roughness meter using a laser or the like. However, as shown in Examples described later, when the surface length ratio S _l > 100.04% and R _z ≧ 0.25, a coating film surface excellent in stain resistance is obtained.

[0009]

[Examples] Preparation of test piece Test piece 1: After performing chemical conversion treatment and primer coating on the hot-dip galvanized steel strip in a continuous coating line, a polyester white paint (KP manufactured by Kansai Paint Co., Ltd.) was applied using a roll coater.
−1573) was applied so that the dry film thickness would be 15 μm. Then, after baking for 40 seconds at the maximum attainable temperature of 220 ° C., it was cooled in a shower-type water cooling tank. At this time, the surface of the coating film was polished at the same time as cooling by a baffle roll placed in a water cooling tank. Test piece 2: A coated steel sheet was produced in the same manner as in test piece 1 except that polishing was not performed during cooling. Test piece 3: hot-dip galvanized steel sheet is formed into a panel,
Degreased and primed. And the dry film thickness is 30
Fluorine white paint (New Germet # 300 manufactured by Toupe Co., Ltd.) is spray-coated so that the thickness becomes μm, and 170
It was baked for 20 minutes in a hot air oven set to 0 ° C. and allowed to cool in air. After cooling, a polishing liquid containing an abrasive having a particle size of 1 μm was dropped on the coating surface of the coated panel, polished with a rotary polisher, and washed with water. Specimen 4: A coated panel obtained in the same manner as Specimen 3 was polished except that a polishing liquid containing an abrasive having a particle size of 5 μm was used. Test piece 5: A painted panel that was not polished was prepared as a test piece of test piece 5.

Investigation of surface shape The surface shape of a test piece cut out from each coated steel plate and each coated panel was measured by a laser type and a contact type roughness meter, and JI
In addition to the center line average roughness R _a and 10-point average roughness R _z as defined in S, it was determined surface length ratio S _1. Surface length ratio S _l
Is expressed by the creepage distance L ₂ with respect to the linear distance L ₁ on the surface of the test piece as illustrated in FIG. 1.

Evaluation test of hydrophilicity and stain resistance : Hydrophilicity investigation: 4 cm × 7 cm test pieces cut out from each coated steel plate and each coated panel were immersed in water at 20 ° C. for 1 minute and then tested from water. The piece was pulled vertically. Then, measure the time until the water on the entire surface of the test piece repels,
The hydrophilicity was evaluated by the length of this time. Investigation of stain resistance: 10 cm × 20 cm test pieces were cut out from each coated steel plate and each coated panel. The test pieces were mounted vertically on an exposure test stand having a roof on which the coating film surface of each test piece was made to flow rainwater, and an outdoor exposure test was conducted in Ichikawa City for 3 months. After the lapse of 3 months, the degree of adhesion of rain streak stains on the surface of the test piece was evaluated by the L value by a spectrophotometer. In general, rain streak stains appear as blackish stains, and the more rain streak stains adhere, the smaller the L value becomes.

[0012] Findings Test Results As seen in Table 1 showing the test piece was polished removed coating surface portion 1, 3 and 4 a surface length ratio S _l and 10 points were measured with a contact-type roughness meter Average roughness R _z is 10 each
It exceeded 0.04% and 0.25, and showed high values in comparison with the surface length ratio S ₁ and the 10-point average roughness R _z of the test pieces 2 and 5. Along with this, the test pieces 1, 3 and 4 were remarkably excellent in water wettability as compared with the test pieces 2 and 5 in which the surface layer portion was not removed, and the stain resistance was improved.

[0013]

[Table 1]

Further, the surface shape of the test pieces to which various coatings were applied was measured by a contact type roughness meter, and the relationship between the surface shape and the water wetting time was investigated. As a result, as shown in Table 2, surface length ratio S _l > 100.04 and 10-point average roughness R _z ≧ 0.25.
When the coating film surface satisfied the above condition, all exhibited excellent water wettability and excellent stain resistance. On the other hand, in the case where the degree of polishing was small or the polishing treatment was not performed, the hydrophilicity was not sufficiently imparted, and the stain resistance was inferior.

[0015]

[Table 2]

[0016]

As described above, according to the present invention, the hydrophilicity of the coating film surface is increased by a simple means for removing only the surface layer portion of the coating film applied to the object to be coated, and the stain resistance is improved. It has an excellent coated product. The coated article exhibits excellent stain resistance over a long period of time when placed outdoors. Further, even if dirt adheres, the adhered dirt is washed away with rainwater, so that a beautiful surface is maintained.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the surface length ratio S _l.

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[Procedure amendment]

[Submission date] July 4, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

In order to achieve the object, the coated object of the present invention has the surface layer portion of the coating film provided on the surface of the object to be coated removed and the ratio of the creepage distance to the in-plane linear distance is removed. The surface length ratio S ₁ represented by exceeds 100.04%,
The 10-point average roughness R _z has a surface roughness of 0.25 or more. This coated object has a surface length ratio S ₁ represented by the ratio of the creepage distance to the in-plane linear distance of 100. More than 04%, 10-point average roughness R
It is produced by removing the surface layer portion of the coating film so that _z is 0.25 or more. The surface layer portion of the coating film is removed by polishing the surface of the coating film while the baking-cured coating film is being cooled or after being cooled.

Claims (2)

[Claims] 1. A surface layer portion of a coating film provided on a surface of an object to be coated is removed, and a surface length ratio S ₁ represented by a ratio of a creepage distance to an in-plane linear distance exceeds 100.04%, 10-point average roughness R _z A coated article having a surface profile of 0.25 or more and having excellent stain resistance. 2. A surface length ratio S ₁ represented by the ratio of the creepage distance to the in-plane linear distance is 10 after the coating material is applied to the surface of the object to be coated and dried or baked to form a coating film.
A method for producing a coated article having excellent stain resistance, which comprises removing the surface layer portion of the coating film so as to have a 10-point average roughness R _{z of} 0.25 or more in excess of 0.04%.