JPH02152577A - Painting method - Google Patents

Abstract

PURPOSE:To execute painting of automobiles, etc., with which horizontal and vertical parts coexist with a single paint and to finish the coated surfaces which are excellent in smoothness, distinctness and brightness and are good in appearance by mixing an org. solvent with the paint to adjust the flowability and painting the horizontal parts before the vertical parts are spray painted. CONSTITUTION:The org. solvent is mixed with the paint to previously adjust the flowability before the vertical parts are spray painted by using the paint for painting the vertical parts. The above-mentioned org. solvent mixture is ejected in the arbitrary part of the route communicating with a painting machine for painting the horizontal parts (exclusive of the route communicating with a painting machine for the vertical parts based on the press feeding direction of the paint) or at the front end of the painting machine, by which the horizontal parts are painted. Xylene; 2-ethyl hexyl alcohol, etc., are used as the org. solvent. The mixing ratio of the solvent with the paint is 1 to 50wt.%, more particularly preferably 5 to 20wt.%. This method is highly effectual for paining of external plates of metal fabricated products, etc., without requiring the large change of the existing equipment and with less damage in the event of the contingent stop of the line.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating method for a workpiece having both a horizontal part and a vertical part, and more specifically, the present invention relates to a method of painting a workpiece having both a horizontal part and a vertical part. The present invention relates to a coating method capable of finishing a painted surface with a particularly good finished appearance.

When painting exterior panels (mainly metal, plastic, etc.) of automobiles (including buses, trucks, and motorcycles), household metal products, and processed metal products, there is a strong demand for excellent finished appearance. However, these exterior panels have a horizontal part and a vertical part, and it was difficult to spray paint both parts with a single paint to the same degree and with a good finished appearance. In other words, in general, the applied paint on vertical parts tends to partially flow down (sag) during setting and baking, resulting in thin areas or accumulations on the entire surface, which tends to deteriorate the finished appearance, especially the smoothness. In order to prevent these, anti-sagging agents are added or the viscosity is increased, but if you paint horizontal areas with a paint that has adjusted fluidity in this way, it will suppress the fluidity and cause minute irregularities. Surfaces tend to form, making it difficult to achieve a smooth finish.On the other hand, paints that have been adjusted to give a good finish on horizontal areas tend to flow, and when painted on vertical areas, the above-mentioned defects occur. In other words, there is currently no established method for finishing horizontal and vertical areas to the same degree and with excellent finished appearance using a single coating.

It is also known to apply a single coat of paint to the horizontal and vertical parts while rotating the object, but this requires large equipment to rotate the object, and the coating line is also large. If it suddenly stops, it has defects such as the risk of deteriorating the finished appearance of most of the objects to be coated that exist in the line from the middle of painting to just before the coating film hardens.

Furthermore, it is possible to paint the vertical and horizontal parts separately with two or more types of paint that are compatible with each other, but this would require preparation of paint of 2f1 or more, the painting process would be complicated, and problems such as circulation etc. This is undesirable due to high equipment costs and difficult maintenance.

The purpose of the present invention is to eliminate the above-mentioned various defects, and its characteristics include: (1) painting horizontal and vertical parts with a single paint; and (2) painting a good finish when applied to vertical parts. 1) The paint is also used for painting horizontal areas, and the fluidity is adjusted in advance by mixing the paint with an organic solvent before spraying. As a result, the above objectives were fully achieved and the present invention was completed.

That is, the present invention is a method for painting an object having a horizontal portion and a vertical portion. The present invention relates to a coating method characterized in that fluidity is adjusted in advance by mixing with an organic solvent.

Objects that can be coated by the method of the present invention are objects that have both vertical and horizontal parts, and specific examples include the exterior panels of the aforementioned automobiles, home appliances, office equipment, etc., and in particular the finished appearance. For example, it is preferable to apply the method to automobile exterior panels where it is important to finish the painted surface with excellent smoothness, sharpness, gloss, etc., where:
The vertical part refers to the angle between the extension line of the surface of the object to be coated and the horizontal plane when the object is placed or suspended from the painting process to the drying (baking) process of the coating film.
As a general rule, it should be within the range of degrees. If this angle is 90 degrees, the surface to be coated will be perpendicular to the horizontal plane.
The surface to be coated with an angle outside the above range is considered to be a horizontal portion.

In addition, in the case of a curved surface to be coated, if the angle between the tangent and the horizontal plane is within the range of 50 to 130 degrees, it is considered to be a vertical portion, and outside this range, it is generally considered to be a horizontal portion. The object to be coated may have both a flat part and a curved part.

The paint used in the present invention 1 is a known organic solvent-based liquid paint that can form a film with excellent smoothness, sharpness, and gloss on the vertical portion of the object to be coated. Preferably, the form is a solution type or a non-aqueous dispersion type, and any of a clear paint, a colored paint, or a metallic paint may be used.

The main components of this paint are a base resin and an organic solvent.
Furthermore, if necessary, a curing agent, a colored pigment, a metallic pigment, an extender pigment, a fluidity regulator, an anti-settling agent, a surface regulator, an ultraviolet absorber, etc. are appropriately blended. As the base resin,
For example, acrylic resins, polyester resins, alkyd resins, or modified resins thereof are preferably used, and the curing agent is preferably an amino resin or a block polyisocyanate compound, but is not limited to these.

What is particularly important about this paint is that it has the ability to form a coating film with an excellent finished appearance when applied to vertical areas. It is preferable to control the fluidity of the applied coating liquid, for example, the yield stress of the applied coating liquid is 0 or 2.
It is preferable to adjust it to dyne/cm" or more.

These adjustments can be made, for example, by adding a fluidity regulator to the paint, or by controlling the balance of organic solvent components in the paint, but are not limited to these. As a regulator, JP-A-53
Those described in Japanese Patent No. 67733 are preferably used, and include aliphatic, cycloaliphatic and aromatic diisocyanates (for example, hexamethylene-1,6-diisocyanate, tolylene diisocyanate, etc.) and 1 to 5 diisocyanates. Reaction products with carbon-containing monoamines or hydroxymonoamines (e.g. benzylamine, propylamine, tertiary butylamine, 2-amylethanol) (
In addition, regarding the balance of organic solvents in the paint, organic solvents with different evaporation rates as indicated by boiling point and vapor pressure are used to ensure good coating workability and to maintain the balance of organic solvents in the paint. It is determined as appropriate so that the liquid has the above-described appropriate viscosity range (yield value).

In the method of the present invention, both the vertical and horizontal parts of the object to be coated are coated with the above paint. For painting, conventionally known spray coating methods can be used, such as air spray, airless spray, electrostatic air spray, electrostatic airless spray,
Paint using an electrostatic rotary atomizer, etc. The viscosity of the paint at the time of coating is preferably in the range of 10 to 45 seconds at 20 DEG C. and 4 Ford cup teeth.

When vertical and horizontal areas are spray-painted with this paint, it is possible to finish the vertical areas with excellent paint surfaces such as clarity, smoothness, and gloss, but the fluidity of the applied paint is low. The finished appearance of the horizontal parts is not satisfactory. Therefore, in the present invention, when painting the horizontal parts, it is necessary to mix the above-mentioned paint with an organic solvent to adjust the fluidity in advance before spraying. That is, before spraying
The above paint is mixed with an organic solvent and its fluidity is adjusted so that a coating film with an excellent finished appearance is formed on the horizontal areas, and then the mixture is sprayed to paint the horizontal areas.

The organic solvent to be mixed with the paint before spraying has excellent compatibility with the paint and has a boiling point of 120°C or higher, preferably 130°C or higher, and more preferably 140°C.
Examples of such organic solvents, which are preferably composed mainly of the above-mentioned organic solvents, include Swazol #310. Swazol #1000. Swazol #1500. Swazol #1800 (all of the above are Cosmo Oil (…product name,
Hydrocarbon solvents), xylene, ethylene glycol monoisopropyl ether (isopropyl cellosolve), ethylene glycol motsubutyl ether (butyl cellosolve), 3-methoxybutyl acetate, diethylene glycol monoethyl ether (calpitol), diethylene glycol motsubutyl ether (butyl calpitol) ), acetic acid diethylene glycol monoethyl ether (carpitol acetate), 2-ethylhexyl alcohol, methylcyclohexanol, etc., and these can be used alone or in combination of two or more kinds.

The organic solvent may contain other 81 solvents that have insufficient compatibility with the paint or have a boiling point of 120°C or lower, n-butanol, iso-butanol, etc. within a range that does not impede the achievement of the purpose of the present invention. It may be contained in

The mixing ratio of the paint and the organic solvent is arbitrarily selected depending on the purpose, but is 1 to 50% by weight, preferably 3 to 30% by weight, more preferably 5 to 30% by weight, based on the above paint.
A range of 20% by weight is suitable.

The paint and the organic solvent are mixed in a part that is within the path for pumping the paint to the horizontal part and is not in communication with the vertical part coating machine in the paint pumping direction, for example,
As long as the route is connected only to the horizontal section sprayer, mixing may be done at any point from the paint supply source to the sprayer, or if the route is connected to the horizontal section sprayer and the vertical section sprayer. In the case of a system in which the coating is carried out, any part from the branch point to the horizontal partial coating machine may be used, and mixing of the two in this route can be easily carried out using a static mixer or the like.

Furthermore, as a method of mixing the paint and the organic solvent, in addition to the method described above, mixing can also be carried out at the tip of the coating machine. Then,
In an electrostatic rotary atomizer, the paint is pumped to the surface of the rotating cup and the solvent is also supplied to the surface of the cup at the same time, thereby making it possible to mix and spray the two almost simultaneously.

The coating of the object having vertical and horizontal parts according to the present invention is preferably carried out as follows.

First, the vertical portions are spray-coated with the above-mentioned paint using the above-mentioned coating machine in a known manner, and it is possible to finish the coated surface with excellent image clarity, smoothness, and gloss.

On the other hand, the same paint is also used for painting horizontal areas, but it is different from painting vertical areas in that it is sprayed after being mixed with an organic solvent or at the same time as mixing. That is,
Organic solvents may be mixed in any part of the path leading to the spray machine for painting horizontal areas (excluding the route leading to the spray machine for painting vertical areas, based on the direction of paint pumping) or at the tip of the spray machine. Paint horizontal areas by spraying or while mixing.

Therefore, even if the organic solvent is sprayed before or after the paint is sprayed, it is difficult to uniformly mix the two, and the object of the present invention cannot be achieved.

By the method of the present invention, it has become possible to finish a coated object having both vertical and horizontal parts with a single paint to a coated surface with excellent image clarity, smoothness, and gloss. . Moreover, in adopting this method, there is no need to make major changes to existing equipment, and furthermore, even if the painting line suddenly stops, damage can be minimized.

Examples and Comparative Examples A metal box-shaped container (cube with all angles of 90 degrees) coated with electrodeposited brimer and intermediate paint is placed on a stand, and a metallic layer is applied to the horizontal and vertical parts of the outer surface. Apply paint (Note 1) using an electrostatic air spray gun (REA gun,
(manufactured by Nippon Landsburg Co., Ltd.), 15±2 based on the cured coating.
It was coated to a thickness of μ. After leaving it at room temperature for 3 minutes, clear paint was applied to the vertical and horizontal parts using the method of the present invention.

That is, clear paints (I) to (III) are applied to the vertical portions.
) (Note 2) was coated with an electrostatic spray coating machine (Mini Bell, manufactured by Nippon Landsparg Co., Ltd.) to a thickness of 40±3μ based on the cured coating. On the other hand, for the horizontal part, we used a spray coating machine (Mini Bell) similar to the one above, but with piping installed on the cup surface of the rotating part so that both clear paint and organic solvent could be pumped at the same time. The solvent was supplied at the same time, and the horizontal portions were painted while mixing the two. The coating thickness is 40±3μ based on the cured coating.
Both coatings were then cured by heating at 140° C. for 30 minutes.

The composition of the organic solvent used in painting the horizontal portion, the ratio of the solvent to the clear paint during spray painting, and the condition of the finished paint film are shown in Table 2.

In the formulation of paints, etc., all parts and percentages are based on weight.

(Note 1) Metallic base paint 50% acrylic resin liquid A (medium) 11110 parts 60% Kneepan 20 S E-60 (*-2142 parts 45% acrylic resin non-aqueous dispersion fl-3144 parts Aluminum paste (I- 4120 parts Bentone #27K-511 parts The above mixture was mixed with a mixed solvent consisting of 30 parts toluene, 30 parts ethyl acetate, 10 parts isobutyl alcohol, and 30 parts Swasol #1OO0 to a viscosity of 13 seconds (Ford Cup No., 4/20°C). ) was adjusted.

(Medium-1) 50% Acrylic Jugetsuji A Methyl methacrylate 30 parts, Ethyl acrylate
35 parts, n-butyl acrylate 24 parts, bitroxyethyl acrylate 10 parts, acrylic acid 1 part using a polymerization initiator α,α'-azobisisobutyronitrile in a mixed solvent of xylene/n-bucnol 80/20. Acrylic resin liquid 1* with a weight average molecular weight of J130.000 and a resin solid content of 50% - 2160% Kneepan 20SE-60, trade name manufactured by Mitsui Toatsu Chemical Co., Ltd., butanol-modified melamine formaldehyde resin liquid I - 3145% acrylic resin non-aqueous dispersion In an n-hebutane solution of an adduct of poly-12-hydroxystearic acid (6* form) and glycidyl methacrylate, 98 parts of methyl methacrylate, 1 part of glycidyl methacrylate, and 1 part of methacrylic acid were added. Milky white acrylic resin non-aqueous dispersion obtained by heterogeneous polymerization and then cross-linking the particle portion by adding dimethylaminoethanol (Book-4) Aluminum Paste Manufactured by Toyo Aluminum Co., Ltd., Aluminum Paste #55-519 (*-5 ) Benton #27 Manufactured by NL Chemical Co., thixotropy imparting agent (Note 2) Clear paint (1) to (II+) 50% acrylic resin liquid B
(*-61l OO part 60% knee pants 20 S E
-60 [+-2150 parts 1% Raybo No. 3 (umbrella -8
The clear paint obtained by stirring 10.3 parts was diluted with the diluting solvent shown in Table 1.

(i6) 50% acrylic resin liquid B styrene 10 parts, inbutyl methacrylate 30 parts,
Weight average molecule IL1 obtained by the same method as above in a xylene solution of 12 parts of n-butyl methacrylate, 25 parts of 2-ethylhexyl methacrylate, 20 parts of 2-hydroxyethyl methacrylate, and 3 parts of methacrylic acid.
0.000, acrylic resin liquid with resin content of 50% (Umbrella-7) 50% diurea type thixotropy obtained by reacting hexamethylene diisocyanate and benzylamine, a diurea xotropy imparting agent, in the above 50% acrylic resin liquid B Imparting agent (*-811% Rainbow No.
3 Composition (parts) of silicone additives Table 1 clear paints (1) to (II+) manufactured by Reibo Ichi Chemical Co., Ltd.

(Middle-101 organic solvent (A): Swasol #1500 (B): Swasol #1500/Carpitol acetate = 80/20 (C): Xylene (*-111 organic solvent spray N Number of parts relative to clear paint spray Jul 00 parts f*-
121P G D value rJcRI-GGD-166 type Gd manufactured by Japan Color Research Institute
It was measured using a meter.

(◆-1311cM value Measurement was carried out using "Image Clarity Measuring Machine" manufactured by Suga Test Instruments ■.

Claims (1)

[Claims] A method for painting an object having a horizontal part and a vertical part, in which both parts are spray-painted with a paint for painting the vertical part, and the paint on the horizontal part is mixed with an organic solvent before spraying the paint. A coating method characterized by adjusting fluidity in advance.