A coating method with excellent coating efficiency

Abstract

The object of the present invention is to provide a non-electrostatic air atomization coating method using an automatic coating gun, which has a coating efficiency of 80% or more, good reproducibility of the coating efficiency, excellent coating appearance, and reduced noise during coating. (1) Coating efficiency of 80% or more, (2) Gun distance: 20mm to 90mm Fulfilling Additionally, the following requirements (3a) and / or (3b): (3a) The atomizing air pressure is 0.013 MPa·s to 0.070 MPa·s, and the pattern air pressure is 0.020 MPa·s to 0.100 MPa·s; (3b) Atomization air flow rate is 5L / min to 25L / min, and pattern air flow rate is 2L / min to 35L / min; The coating method satisfies the above requirements.

Description

[Technical Field]

[0001] The present invention relates to a coating method with excellent coating efficiency, specifically to a coating method with a coating efficiency of 80% or more, preferably 85% or more. [Background technology]

[0002] Painting can dramatically extend a product's life cycle by preventing deterioration due to rust and ultraviolet rays, and can also add value to products by improving their design and functionality. In industrial painting, for example, at painting sites for plastic products, spray painting, which atomizes and applies liquid paint, is used from the perspective of the finished quality of the paint film and ease of work. However, the paints used in painting are mainly petrochemical products, and CO2 emissions from production to disposal have become a major social issue. Improving transfer efficiency is an extremely important approach to solving the problem of reducing and controlling CO2 emissions in painting. If transfer efficiency can be improved and the amount of paint that is not applied and is wasted can be reduced, it will be possible to reduce the generation of paint (material) waste such as booth sludge and VOCs (volatile organic compounds), as well as CO2 emissions, which is beneficial from an environmental perspective. It will also be possible to reduce raw material costs. However, with conventional spray painting, the transfer efficiency was only around 60% at best, so improving transfer efficiency has been a challenge.

[0003] Prior art relating to improving coating efficiency includes, for example, the following Patent Documents 1 to 3. Patent Document 1 describes a coating method with excellent coating efficiency when coating a substrate having an uneven surface, in which coating is performed using a sponge roll wrapped with cloth, and then air is blown into the recesses of the substrate to scatter the paint that has accumulated in the recesses.

[0004] Patent Document 2 discloses a method for spraying a liquid onto a substrate with high coating efficiency, comprising the steps of: discharging at least one liquid from a liquid outlet; ejecting a first compressed gas from a first compressed gas outlet provided around the liquid outlet and atomizing the liquid discharged from the liquid outlet to create a particle jet; and ejecting a second compressed gas from a plurality of second compressed gas outlets toward the liquid particle jet, causing at least a portion of the second compressed gas to collide with the liquid particle jet, causing the liquid particle jet to swirl and atomize.

[0005] Patent Document 3 discloses a metallic paint application method with high coating efficiency in an automotive topcoat base painting process, in which a bell-type coating device is used and shaping air is supplied to the bell-type coating device at an air pressure of 196 to 294 kPa and an air flow rate of 500 to 700 NL / min, thereby forming a coating film that can hide the base and has a metallic finish. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-111314 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-089976 [Patent Document 3] Japanese Patent Application Publication No. 11-300239 Summary of the Invention [Problem to be solved by the invention]

[0007] The coating method described in Patent Document 1 is a roll coating method, and therefore it is difficult to form a coating film that has a high appearance rating, and it cannot be applied to coating methods other than roll coating. The coating method described in Patent Document 2 requires a complicated device and its control is also complicated. The coating method described in Patent Document 3 is a technique specific to a bell-type coating device, and cannot be applied to coating methods that do not use a bell-type coating device.

[0008] In industrial painting, in order to reduce and control CO2 emissions, it is necessary to significantly improve coating efficiency. To achieve this, it is necessary to establish a coating technology that utilizes advanced "electrostatic atomization" or "hydraulic spraying" to achieve excellent coating efficiency, or to establish a coating technology that solves the problem of rebounding air atomization while maintaining appearance quality. However, electrostatic atomization cannot be applied to non-conductive substrates, and hydraulic spraying is difficult to apply to large-area painting.

[0009] In industrial painting, particularly at painting sites for plastic parts, spray painting, which atomizes and applies liquid paint, is widely adopted from the perspective of paint finish quality and workability. The most common method of atomizing liquid paint is the air atomization method, which atomizes the liquid paint by ejecting high-pressure compressed air from the tip of a nozzle along with the paint, resulting in a uniform coating that meets high standards for appearance evaluation. While the air atomization method can produce high-quality coatings and is easy to work with, it suffers from low coating transfer efficiency, high paint waste, a significant environmental impact, and noise issues, leaving room for improvement.

[0010] The problem to be solved by the present invention is to provide a non-electrostatic air atomization coating method using an automatic coating gun, which has a coating efficiency of 80% or more, good reproducibility of the coating efficiency, excellent coating appearance, and reduced noise during coating. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to solve the above problems. The inventors have found that the above problems can be solved by adopting specific coating conditions. Specifically, it is as follows:

[0012] [Section 1] In a non-electrostatic air atomization coating method using an automatic coating gun, the following requirements (1) and (2) are met: (1) Coating efficiency of 80% or more, (2) Gun distance: 20mm to 90mm 、 Fulfilling Additionally, the following requirements (3a) and / or (3b): (3a) Atomization air pressure is 0.013MP a~ 0.070MP In a Yes, pattern air pressure is 0.020MP a~ 0.100MP a、 (3b) Atomization air flow rate is 5L / min to 25L / min, and pattern air flow rate is 2L / min to 35L / min; The coating method satisfies the above. [Section 2] In addition, the following requirements (4) to (7): (4) The paint supply rate is 7 mL / min to 55 mL / min. (5) The viscosity of the paint used for painting is 5 to 13 seconds according to the Iwata Cup method. (6) The paint contains one or more organic solvents selected from the group consisting of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, and the evaporation rate of which is 140 or more and 1100 or less, when the value of butyl acetate is taken as 100. (7) The paint contains one or more organic solvents selected from the group consisting of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, and the organic solvent has a boiling point of 150°C or higher at a pressure of 0.1 MPa. The coating method according to item 1, which satisfies one or more of the following requirements. [Section 3] Item 3. The coating method according to item 1 or 2, wherein recoating is performed. [Section 4] 4. The coating method according to any one of items 1 to 3, wherein the coating is applied in layers so that the center positions of the coatings differ. [Effects of the Invention]

[0013] The present invention provides a non-electrostatic air atomization coating method using an automatic coating gun, which has a coating efficiency of 80% or more, good reproducibility of the coating efficiency, excellent coating film appearance, and reduced noise during coating. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing an embodiment of a coating system used in the coating method of the present invention. [Figure 2] 1 is a schematic diagram showing an embodiment of a coating system used in the coating method of the present invention. [Figure 3] Schematic diagram of an M-type air cap attached to the automatic spray gun of the present invention. [Figure 4] Schematic diagram of a round type 1 air cap attached to the automatic spray gun of the present invention. [Figure 5] FIG. 2 is a diagram showing the film thickness distribution of a coated object obtained by the coating method of Example D1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The coating method of the present invention is a non-electrostatic air atomization coating method using an automatic coating gun, which satisfies the following requirements (1) and (2): (1) Coating efficiency of 80% or more, (2) Gun distance: 20mm to 90mm 、 Fulfilling Additionally, the following requirements (3a) and / or (3b): (3a) Atomization air pressure is 0.013MP a~ 0.070MP In a Yes, pattern air pressure is 0.020MP a~ 0.100MP a、 (3b) Atomization air flow rate is 5L / min to 25L / min, and pattern air flow rate is 2L / min to 35L / min; This is a painting method that satisfies the above.

[0016] The coating method of the present invention further satisfies the following requirements (4) to (7): (4) The paint supply rate is 7 mL / min to 55 mL / min. (5) The viscosity of the paint used for painting is 5 to 13 seconds according to the Iwata Cup method. (6) The paint contains one or more organic solvents selected from the group consisting of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, and the evaporation rate of which is 140 or more and 1100 or less, when the value of butyl acetate is taken as 100. (7) The paint contains one or more organic solvents selected from the group consisting of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, and the organic solvent has a boiling point of 150°C or higher at a pressure of 0.1 MPa. The coating method may satisfy one or more of the above requirements.

[0017] The coating method of the present invention may be used to apply multiple coats of paint. The coating method of the present invention may be used to apply multiple coats of paint so that the center position of the paint applied is different from that of the previous coat.

[0018] Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments and implementations, and can be carried out with appropriate modifications.

[0019] [(1) Coating Efficiency] In the coating method of the present invention, the coating efficiency is the ratio, expressed as a percentage (%), of the amount of solid matter in the coating used for coating to the amount of solid matter in the coating applied to the product. The coating efficiency is calculated using the following formula (I): where E (%) is the coating efficiency, W (g) is the mass of the applied dry coating film, F (g) is the sprayed amount of paint, and NV (%) is the solid content of the paint:

number

[0020] In formula (I), the mass W (g) of the applied dry coating film can be calculated by subtracting the mass (g) of the substrate before coating from the mass (g) of the substrate on which the dry coating film is formed.

[0021] The paint spray amount F(g) in formula (I) can be calculated, for example, by using a flow meter installed in the paint flow path, and first calculating a conversion factor using the integrated value of the instantaneous paint flow rate measured by the flow meter and the actual measured paint flow rate, and then multiplying the integrated value of the instantaneous paint flow rate during painting by the conversion factor to calculate the flow rate, and then using the specific gravity of the paint to calculate the paint spray amount F(g). In addition, the paint spray amount F(g) in formula (I) can also be calculated by determining the total amount W1(g) of paint in the paint tank that contains the paint to be supplied to the automatic paint gun before painting, the total amount W2(g) of paint in the paint tank after painting, and the total amount W3(g) of paint remaining in the painting system (in the paint gun) after painting, and using the specific gravity of the paint.

[0022] The solid content (NV) of paint can be calculated using the value in the paint's catalogue, or by calculating the difference between the mass (g) of the test plate immediately after applying a specified amount (ml) of paint and the mass (g) of the test plate on which the paint film has been formed after drying.

[0023] In the coating method of the present invention, the coating efficiency is 80% or higher, preferably 82% or higher, and more preferably 85% or higher. The upper limit of the coating efficiency is theoretically 100%, and is usually 97% or lower.

[0024] [(2) Gun distance] In the coating method of the present invention, (B) gun distance is the distance from the paint discharge port of the automatic coating gun to the object to be coated. In the coating method of the present invention, the gun distance is 20 mm to 90 mm. The lower limit of the gun distance can be 20 mm or more, preferably 25 mm or more, more preferably 30 mm or more, and even more preferably 40 mm or more, and the upper limit of the gun distance can be 90 mm or less, preferably 80 mm or less, more preferably 75 mm or less, and even more preferably 70 mm or less.

[0025] By setting the gun distance to 20mm to 90mm or less, the paint can be applied reliably to the object to be coated, splashing off the object can be prevented, and coating efficiency can be improved. Until now, when painting using an automatic paint gun, the gun distance has been set to 100 mm or more (see, for example, the website of Meiji Machinery Manufacturing Co., Ltd., https: / / www.meijiair.co.jp / product / gun / detail / 73). The painting method of the present invention makes it possible to improve coating efficiency from a completely different technical perspective than before.

[0026] [(3a) Atomization air pressure and pattern air pressure] In the coating method of the present invention, the atomizing air pressure in the automatic coating gun is set to 0.013 MP. a~ 0.070MP a and At the same time, the pattern air pressure in the automatic paint gun was reduced to 0.020MP. a~ 0.100MP a and It is possible.

[0027] Atomizing air pressure for automatic paint gun is 0.013MP a If the pressure is less than 0.070MP, the paint workability may be reduced and the paint may not be sprayed properly. a If it exceeds this limit, the sprayed paint may bounce back, reducing the coating efficiency and making it impossible to spray the paint properly.

[0028] Pattern air pressure for automatic paint gun is 0.020MP a If the pattern air pressure in the automatic spray gun is less than 0.070MP, it may be difficult to achieve the proper spray shape of the paint sprayed from the automatic spray gun, and the paint may not be sprayed properly. aIf it exceeds this limit, it may be difficult to spray the paint from the automatic paint gun in the appropriate shape, the sprayed paint may bounce back, reducing the coating efficiency and making it impossible to spray the paint properly.

[0029] The lower limit of atomizing air pressure for automatic paint guns is: 0.013 The upper limit of the atomizing air pressure in an automatic coating gun can be set to preferably 0.065 MPa or less, more preferably 0.060 MPa or less, and even more preferably 0.055 MPa or less.

[0030] The lower limit of the pattern air pressure in the automatic coating gun can be preferably 0.022 MPa or more, more preferably 0.025 MPa or more, and the upper limit of the pattern air pressure in the automatic coating gun can be preferably 0.095 MPa or less, more preferably 0.090 MPa or less.

[0031] In the coating method of the present invention, the atomizing air pressure and the pattern air pressure are both pressures in the automatic coating gun. The atomizing air pressure and the pattern air pressure in the automatic coating gun can be confirmed by providing a pressure gauge in the atomizing air pipe and the pattern air pipe near the automatic coating gun. Specifically, the pressure gauge can be provided in a position that is not affected by pressure loss in the atomizing air pipe and the pattern air pipe. Furthermore, the atomizing air pressure and pattern air pressure at the automatic coating gun may be calculated by previously acquiring the relationship of the pressure loss occurring between the pressure adjustment mechanism and the automatic coating gun. If the atomizing air piping and pattern air piping become long and the distance between the automatic coating gun and the automatic coating gun controller becomes long, pressure loss can cause errors to occur between the atomizing air pressure and pattern air pressure in the automatic coating gun controller and the atomizing air pressure and pattern air pressure in the automatic coating gun, which can make it difficult to control coating accurately.

[0032] [(3b) Atomization air flow rate and pattern air flow rate] In the coating method of the present invention, the atomizing air flow rate supplied to the automatic coating gun can be set to 5 L / min to 25 L / min, and the pattern air flow rate supplied to the automatic coating gun can be set to 2 L / min to 35 L / min.

[0033] If the atomizing air flow rate supplied to an automatic spray gun is less than 5 L / min, the paint workability may be reduced and the paint may not be sprayed properly.If the atomizing air flow rate supplied to an automatic spray gun is more than 25 L / min, the sprayed paint may bounce back, reducing the coating efficiency and making it impossible to spray the paint properly.

[0034] If the pattern air flow rate supplied to the automatic paint gun is less than 5 L / min, it may be difficult to ensure the appropriate spray shape of the paint sprayed from the automatic paint gun, and the paint may not be sprayed properly.If the pattern air flow rate supplied to the automatic paint gun is more than 35 L / min, it may be difficult to ensure the appropriate spray shape of the paint sprayed from the automatic paint gun, and the sprayed paint may rebound, reducing coating efficiency and preventing the paint from being sprayed properly.

[0035] The lower limit of the atomizing air flow rate is preferably 7 L / min or more, more preferably 10 L / min or more, and even more preferably 12 L / min or more, and the upper limit of the atomizing air pressure in the automatic coating gun is preferably 22 L / min or less, more preferably 20 L / min or less, and even more preferably 18 L / min or less.

[0036] The lower limit of the pattern air flow rate is preferably 3 L / min or more, more preferably 4 L / min or more, and even more preferably 5 L / min or more, and the upper limit of the atomizing air pressure in the automatic coating gun is preferably 32 L / min or less, more preferably 30 L / min or less, and even more preferably 28 L / min or less.

[0037] In the coating method of the present invention, the atomizing air flow rate and pattern air flow rate supplied to the automatic coating gun can be confirmed by providing flow meters in the atomizing air piping and pattern air piping. Even if the atomizing air piping and pattern air piping are long, the atomizing air flow rate and pattern air flow rate at any point in the piping remain constant. Therefore, when controlling an automatic coating gun using the atomizing air flow rate and pattern air flow rate, coating can be accurately controlled without considering the effects of pressure loss.

[0038] [(4) Paint supply amount] In the coating method of the present invention, the amount of paint supplied to the automatic coating gun can be set to 7 mL / min to 55 mL / min.

[0039] If the paint supply rate to the automatic paint gun is less than 7 mL / min, the paint workability may be reduced and the paint may not be sprayed properly.If the paint supply rate to the automatic paint gun is more than 55 mL / min, it may be difficult to spray the paint in the correct shape from the automatic paint gun, the sprayed paint may bounce back, reducing the coating efficiency and making it impossible to spray the paint properly.

[0040] The lower limit of the paint supply rate is preferably 8 mL / min or more, more preferably 10 mL / min or more, and even more preferably 12 mL / min or more, and the upper limit of the paint supply rate is preferably 45 mL / min or less, more preferably 42 mL / min or less, and even more preferably 40 mL / min or less.

[0041] [(5) Paint viscosity] In the coating method of the present invention, the paint used for coating has a viscosity of 5 to 13 seconds as measured by the Iwata cup method. In the coating method of the present invention, the viscosity of the paint used for coating is the viscosity at the time when the paint is prepared to be used for coating, and is the viscosity measured using the Iwata cup.

[0042] If the viscosity of the paint used for painting is less than 5 seconds as measured by the Iwata Cup method, the dried paint film may become smeared or sagged, reducing paint workability.If the viscosity of the paint used for painting is more than 13 seconds as measured by the Iwata Cup method, the dried paint film may become orange peel-like or have poor appearance.

[0043] In the coating method of the present invention, the viscosity according to the Iwata Cup method is the viscosity measured using a viscosity cup NK-2 manufactured by Anest Iwata Corporation, and is the viscosity at the temperature and pressure of the coating environment. Viscosity is measured by submerging a viscosity cup in the paint, then lifting it out of the paint, and measuring the time (seconds) from when the viscosity cup is lifted until the paint stops flowing out of the viscosity cup. For reactive paints, measurements are taken within 5 minutes of preparing the paint.

[0044] [(6) Evaporation rate of organic solvents contained in paint] In the coating method of the present invention, the coating material used for coating may contain one or more organic solvents selected from the group consisting of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, and may contain an organic solvent whose evaporation rate is 140 to 1100, where the evaporation rate of butyl acetate is taken as 100.

[0045] When the paint used for painting contains one or more organic solvents selected from the group consisting of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, it is less likely to have adverse effects on the environment or the health of workers, and is therefore advantageous in terms of safety, etc. When the paint used for painting contains an organic solvent with an evaporation rate of 140 to 1100, where the value of butyl acetate is 100, the drying rate of the paint film can be made appropriate, and a paint film with excellent appearance can be formed.

[0046] The paint used for painting preferably contains at least one of a ketone-based organic solvent and an ester-based organic solvent.

[0047] When the value of butyl acetate, an organic solvent contained in the paint used for painting, is taken as 100, the lower limit of the evaporation rate can be preferably 150 or more, more preferably 200 or more, and even more preferably 350 or more. When the value of butyl acetate, an organic solvent contained in the paint used for painting, is taken as 100, the upper limit of the evaporation rate can be preferably 1000 or less, more preferably 900 or less, and even more preferably 800 or less.

[0048] Examples of the organic solvents that are one or more of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents and have an evaporation rate of 140 to 1100, where the evaporation rate of butyl acetate is taken as 100, include one or more of acetone (evaporation rate 720), methyl ethyl ketone (evaporation rate 465), methyl isobutyl ketone (evaporation rate 165), methyl alcohol (evaporation rate 370), ethyl alcohol (203), isopropyl alcohol (205), methyl acetate (evaporation rate 1040), ethyl acetate (evaporation rate 525), isobutyl acetate (evaporation rate 145), ethyl tertiary butyl ether (evaporation rate 717), diisopropyl ether (evaporation rate 662), methyl tertiary butyl ether (evaporation rate 1167), 2-methylfuran (evaporation rate 488), methylcyclohexane (evaporation rate 320), and ethylcyclohexane (evaporation rate 145).

[0049] [(7) Boiling point of organic solvents contained in paint] In the coating method of the present invention, the coating material used for coating may contain one or more organic solvents selected from the group consisting of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, and may contain an organic solvent having a boiling point of 150°C or higher at a pressure of 0.1 MPa.

[0050] When the paint used for painting contains one or more organic solvents selected from the group consisting of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, and the organic solvent has a boiling point of 150°C or higher at a pressure of 0.1 MPa, the orientation of the pigment in the paint, for example, flake pigments, can be adjusted, the drying speed of the paint film can be made appropriate, and a paint film with excellent appearance can be formed.

[0051] The paint used for painting preferably contains at least one of an ether-based organic solvent and an ester-based organic solvent.

[0052] The organic solvent is one or more of a ketone-based organic solvent, an alcohol-based organic solvent, an ester-based organic solvent, an ether-based organic solvent, and an aliphatic hydrocarbon-based organic solvent, and has a boiling point of 150°C or higher at a pressure of 0.1 MPa. Examples of the organic solvent include ketone-based organic solvents such as diisobutyl ketone, cyclohexanone, diacetone alcohol, and γ-butyrolactone; 1-octanol, 2-ethylhexanol, 1-nonanol, 1-decanol, 1-undecanol, ethylene glycol, 1,2-propylene glycol, and 1,3-butylene glycol. Alcohol-based organic solvents such as 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, 2,4-heptanediol, 2-ethyl-1,3-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, and glycerin; monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monoethyl ether ether-based organic solvents such as ethylene glycol ether, diethylene glycol monoisopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol monomethyl ether, triethylene glycol-n-butyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, tripropylene glycol mono-n-propyl ether, and tripropylene glycol mono-n-butyl ether;Examples of suitable organic solvents include esters such as ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, triacetin, propylene glycol diacetate, dipropylene glycol methyl-n-propyl ether, dipropylene glycol methyl ether acetate, 1,4-butanediol diacetate, 1,3-butylene glycol diacetate, 1,6-hexanediol diacetate, triethylene glycol diacetate, methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, dihexyl malonate, diethyl succinate, dipropyl succinate, dibutyl succinate, dihexyl succinate, dimethyl adipate, diethyl adipate, dibutyl adipate, ethyl lactate, and nonyl acetate.

[0053] [Overpainting] In the coating method of the present invention, multiple coats may be applied. Multiple coats can be applied by applying two or more coats to the substrate. When applying two or more coats, a drying step may be added between coats, or the coating may be wet-on-wet without an intermediate drying step, or a combination of these may be used. In the coating method of the present invention, recoating may be performed so that the center position of the coating is different from that of the previous coating, or so that the center position of the coating is the same as that of the previous coating, or a combination of these may be used. In the coating method of the present invention, it is preferable to apply multiple coats to improve uniform film thickness and finish. When applying multiple coats, by applying coats so that the center position of the coat differs from that of the previous coat, it is possible to overlap the width of the paint spray pattern from the automatic coating gun to some extent, thereby forming a coating film of uniform film thickness. When recoating, it is preferable to prevent oversprayed paint particles from adhering to the previously coated surface and causing roughness.

[0054] [paint] The paint used in the coating method of the present invention is not particularly limited, and may be a commercially available paint or a newly prepared paint. The coating material used in the coating method of the present invention contains at least a resin component, and may contain a curing agent component, a pigment, a solvent, and other additive components as required. The paint used in the coating method of the invention may be any of solvent-based paint, emulsion (dispersion)-based paint, solventless paint, one-component paint, and two-component paint.

[0055] The resin component functions as a film-forming element. As the resin component, any resin component known in the art for use in paints can be used. Examples of the resin component include one or more of acrylic resin, polyester resin, alkyd resin, fluororesin, epoxy resin, polyurethane resin, polyether resin, olefin resin, epoxy resin, vinyl chloride resin, silicone resin, and alkoxysilane condensate.

[0056] The curing agent component may be a curing agent component that reacts with the reactive groups in the resin component. The curing agent component may be selected depending on the reactive groups in the resin component. For example, one or more of polyisocyanate compounds, which may be blocked with a blocking agent, amino resins, polyamine compounds, polycarboxylic acid compounds, polyol compounds, melamine compounds, epoxy compounds, aldehyde compounds, aziridine compounds, carbodiimide compounds, and hydrazine compounds may be used.

[0057] Examples of pigments include color pigments for coloring paints, filler pigments, etc. Examples of color pigments include one or more of inorganic pigments such as titanium dioxide, red iron oxide, and carbon black, organic pigments such as phthalocyanine blue, dyes, and fluorescent pigments. Examples of filler pigments include one or more of extender pigments such as calcium carbonate, talc, mica, and silica, and anti-rust pigments.

[0058] As the solvent, a conventionally known solvent for constituting a paint can be used. For example, the solvents listed as those satisfying the above requirement (6) or (7) can be used. Specific examples of the solvent include alcohol-based organic solvents such as methanol, ethanol, 2-propanol, 1-butanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butylene glycol, pentamethylene glycol, and 1,3-octylene glycol; ester-based organic solvents such as ethyl acetate, butyl acetate, isobutyl acetate, ethyl propionate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; diethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether, and ethylene glycol. Examples of suitable organic solvents include ether-based organic solvents such as ethanol monoethyl ether, dioxane, and tetrahydrofuran (THF); amide-based organic solvents such as formamide, N-methylformamide, dimethylformamide (DMF), dimethylacetamide, dimethylsulfoxide (DMSO), and N-methylpyrrolidone (NMP); ketone-based organic solvents such as acetone, methyl ethyl ketone (MEK), methyl propyl ketone, methyl isobutyl ketone, acetylacetone, and cyclohexanone; aliphatic hydrocarbons such as mineral spirits and kerosene; aromatic hydrocarbons such as toluene, xylene, mesitylene, and dodecylbenzene; and halogenated organic solvents such as chloroform and dichloromethylene.

[0059] In addition to the resin component, hardener component, pigment, and solvent, the paint may contain one or more of the following components: dispersant, film-forming aid, antifreeze agent, crosslinking accelerator, hardener, leveling agent, surface conditioner, antifoaming agent, plasticizer, preservative, mildew inhibitor, and UV stabilizer.

[0060] [Subject to be coated] In the coating method of the present invention, the material constituting the substrate to which the coating material is applied is not particularly limited. Examples include various plastics, metals such as iron and aluminum, glass, ceramics, concrete, paper, and wood, and composite materials such as laminates and compositions composed of one or more of these materials. The coating method of the present invention can be suitably used for coating plastics, metals, glass, wood, and composite materials made from one or more of these materials.

[0061] In the coating method of the present invention, the shape of the substrate to which the coating material is applied is not particularly limited. Examples include plates, films, rods, and various molded products. Examples include vehicle parts, building interior materials, household goods, and electrical equipment parts.

[0062] If the surface of the substrate is contaminated with oil or other contaminants, it can be degreased and cleaned with alcohol, etc. In addition, the substrate may be subjected to surface treatments such as roughening, plasma treatment, flame treatment, and primer treatment to improve the adhesion of the coating film and the corrosion resistance of the coated object.

[0063] [Painting system] 1 and 2 are schematic diagrams of a coating system suitable for carrying out the coating method of the present invention. Hereinafter, embodiments of a coating system suitable for carrying out the coating method of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. Furthermore, appropriate modifications can be made within the scope of the effects of the present invention. The use of the same reference numerals in different drawings indicates similar or identical items or features.

[0064] FIG. 1 is a schematic diagram showing one embodiment of a coating system suitable for carrying out the coating method of the present invention using a general automatic coating gun. In Figure 1, G1 is an automatic paint gun, and S is a paint pattern sprayed from the automatic paint gun. Connected to the automatic paint gun G1 are a needle valve operating air pipe 12 to which air is supplied from a compressor 11, an atomizing air pipe 13, and a pattern air pipe 14. Also connected to the automatic paint gun G1 is a paint pipe 25 that supplies paint 21 from a paint tank 22. Furthermore, although not shown, a controller is provided to control the air in each air pipe and the paint in the paint pipe, and a three-way valve or the like is provided as necessary.

[0065] The atomizing air piping 13 is provided with an atomizing air pressure adjustment mechanism 15a, a first atomizing air flow rate / pressure sensor 16a located near the automatic coating gun G1 side of the atomizing air pressure adjustment mechanism 15a, and a second atomizing air flow rate / pressure sensor 17a located near the automatic coating gun G1. The pressure of the air from the compressor 11 is adjusted by the atomizing air pressure adjustment mechanism 15a, and the operation of the atomizing air pressure adjustment mechanism 15a is controlled based on the measurement value of the first atomizing air flow rate / pressure sensor 16a. The second atomizing air flow rate / pressure sensor 17a measures the pressure and / or flow rate of the atomizing air supplied to the automatic coating gun G. The atomizing air pressure adjustment mechanism 15a may be included in the control mechanism of the coating device (automatic coating gun).

[0066] Control of atomizing air pressure adjustment mechanism 15a can be performed by a computer, etc., as necessary. Furthermore, the operating data and measurements of atomizing air pressure adjustment mechanism 15a, first atomizing air flow rate / pressure sensor 16a, and second atomizing air flow rate / pressure sensor 17a may be sent to a controller or memory means (none of which are shown) that controls the atomizing air pressure / flow rate, pattern air pressure / flow rate, and paint flow rate, etc., as necessary, and may be configured to be controlled and recorded.

[0067] The pattern air piping 14 is provided with a pattern air pressure adjustment mechanism 15b, a first pattern air flow rate / pressure sensor 16b located near the automatic paint gun G side of the pattern air pressure adjustment mechanism 15b, and a second pattern air flow rate / pressure sensor 17b located near the automatic paint gun G. The pressure of the air from the compressor 11 is adjusted by the pattern air pressure adjustment mechanism 15b, and the operation of the pattern air pressure adjustment mechanism 15b is controlled based on the measurement value of the first pattern air flow rate / pressure sensor 16b. The second pattern air flow rate / pressure sensor 17a measures the pressure and / or flow rate of the pattern air supplied to the automatic paint gun G1. The pattern air pressure adjustment mechanism 15b may be included in the control mechanism of the painting device (automatic paint gun).

[0068] Pattern air pressure adjustment mechanism 15b can be controlled by a computer or the like as needed. Furthermore, the operational data and measurements of pattern air pressure adjustment mechanism 15b, first pattern air flow rate / pressure sensor 16b, and second pattern air flow rate / pressure sensor 17a can be recorded by being transmitted via wire or wirelessly to a recording device or control means (not shown). Pattern air-related data measured by first pattern air flow rate / pressure sensor 16b and second pattern air flow rate / pressure sensor 17a may be sent to a controller or storage means (none of which are shown) that controls the atomization air pressure / flow rate, pattern air pressure / flow rate, and paint flow rate, as needed, for control or recording.

[0069] The paint pipe 25 is provided with a pump 24 and a valve 26, and the paint 21 in the paint tank 22 that is sucked into the paint pipe by the pump 24 is controlled by the valve 26 so that it is supplied to the automatic paint gun G1 during painting and returned to the paint tank 22 when not painting. A paint flow rate sensor 27 is provided between the valve 26 and the automatic paint gun G1 to measure the flow rate of paint supplied to the automatic paint gun G1. The paint flow rate data measured by the paint flow rate sensor 27 may be sent to a controller or memory means (not shown) that controls the atomizing air pressure and flow rate, pattern air pressure and flow rate, and paint flow rate, as necessary, for control and recording.

[0070] Figure 2 is a schematic diagram showing one embodiment of a coating system suitable for carrying out the coating method of the present invention using an automatic coating gun with improved needle valve responsiveness. The coating system shown in Figure 2 differs from the coating system shown in Figure 1 in that it is equipped with an internal switching valve operating air pipe 18 for controlling a switching valve that turns on (connected: when not coating) or off (not connected: when coating) the communication between the needle valve control air chamber and the exhaust port provided inside the automatic coating gun G2. The provision of a switching valve inside the automatic coating gun G improves responsiveness (paint shutdown capability) when switching from coating to non-coating mode.

[0071] [Automatic paint gun] The automatic coating gun used in the coating method of the present invention is not particularly limited as long as it can atomize the paint with atomizing air and form a pattern with pattern air. In the coating method of the present invention, an automatic coating gun having a tapered nozzle tip and capable of atomizing the paint by increasing the flow rate in the atomization region so that the atomizing air contacts the paint at supersonic speed is preferred. For example, the A110 series, A210 series, FA110 series, FA210 series, SA110 series, JA110 series, A55 series, AJ-P series, AJ55-P series, AJ55-PR series, A110L series, etc. manufactured by Meiji Machinery Works, Ltd. can be used. As the air cap to be attached to the automatic coating gun, for example, an M-type air cap shown in FIG. 3 or a round 1-type air cap shown in FIG. 4 can be used. The coating method of the present invention can achieve coating with a coating efficiency of 80% or more with good reproducibility, even when using a general-purpose automatic coating gun.

[0072] [Other painting conditions, etc.] <Paint gun speed> In the coating method of the present invention, the scanning speed of the automatic coating gun during coating is not particularly limited and can be, for example, 10 mm / s or more, preferably 50 mm / s or more, more preferably 100 mm / s or more, and can be, for example, 1000 mm / s or less, preferably 700 mm / s or less, more preferably 500 mm / s or less. If the spray gun speed is slow, the paint workability may decrease, the paint film thickness may become uneven, and the paint film appearance may be poor.If the spray gun speed is fast, the paint film thickness may become thin, and the paint film appearance may be poor.

[0073] <Coating film thickness> The thickness (dry film thickness) of the coating film formed by the coating method of the present invention is not particularly limited and can be adjusted appropriately depending on the application, etc. For example, the dry film thickness can be 0.1 μm or more, preferably 1 μm or more, and can be, for example, 1000 μm or less, preferably 300 μm or less.

[0074] <Coating film formation conditions> In the coating method of the present invention, the spray angle of the paint from the automatic coating gun is not particularly limited, and can be, for example, 90° (the coated surface of the object to be coated is at a right angle to the spray direction). In the coating method of the present invention, the orientation of the coated surface of the object to be coated is not particularly limited. For example, it can be in a horizontal plane (perpendicular to the direction of gravity). In the coating method of the present invention, after applying the paint to the substrate, the coating film may be dried and cured at room temperature or by heating to form a coated object. When heating, the temperature may be raised above room temperature, for example, to 50°C or higher, by heating in a heating furnace or by blowing hot air. The heating time is not particularly limited. When an active energy ray-curable paint is used, curing can be carried out by energy rays such as ultraviolet rays or heat. From the viewpoint of finish quality, the paint may be allowed to set (stand still) at room temperature before drying and curing.

[0075] <Noise> In the coating method of the present invention, the noise level during coating using the automatic coating gun is preferably 75 dB or less. Compared to conventional coating methods using automatic coating guns, the coating method of the present invention has lower atomizing air pressure and pattern air pressure, and a shorter gun distance (the distance from the coating nozzle of the automatic coating gun to the workpiece), so that the noise level during coating can be kept to 75 dB or less. [Example]

[0076] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0077] [paint] The paints used in the examples and comparative examples are as follows. The paints used were the following. All were two-component acrylic urethane paints. The diluents all contained a ketone-based organic solvent with an evaporation rate of 140 to 1100, where butyl acetate is taken as 100, and an ester-based organic solvent with an evaporation rate of 140 to 1100, where butyl acetate is taken as 100. Paint 1: Base agent (Musashi Paint Co., Ltd. "EC-P79- Eco High Urex P MATT BLACK GT") + Hardener (Musashi Paint Co., Ltd. "Z-EC-H-800") + Thinner (Musashi Paint Co., Ltd. "Z-EC-K775") Paint 2: Base agent (Musashi Paint Co., Ltd. "EC-P79- Eco High Urex P MATT BLACK GT") + Hardener (Musashi Paint Co., Ltd. "Z-EC-H-800") + Thinner (Musashi Paint Co., Ltd. "Z-EC-K781") Paint 3: Base agent (Musashi Paint Co., Ltd. "EC-P79- Eco High Urex P MATT BLACK GT") + Hardener (Musashi Paint Co., Ltd. "Z-EC-H-800") + Thinner (Musashi Paint Co., Ltd. "Z-EC-K060") Paint 4: Base agent (Musashi Paint Co., Ltd.'s "EC-P79- Eco Hi-Ulex P MATT BLACK GT") + Hardener (Musashi Paint Co., Ltd.'s "Z-EC-H-800") + Diluent (Musashi Paint Co., Ltd.'s "Z-EC-K060" and diethylene glycol mono-n-butyl ether-containing high-boiling organic solvent) Paint 5: Base agent (Musashi Paint Co., Ltd. "EC-MH62- Eco Sanshan Super MH Piano Black") + Hardener (Musashi Paint Co., Ltd. "Z-EC-H-760") + Thinner (Musashi Paint Co., Ltd. "Z-EC-K657") Paint 6: Musashi Paint Co., Ltd. "EC-GPX79- Eco High Urex P Grande Bonheur Metallic Silver" + hardener (Musashi Paint Co., Ltd. "Z-EC-H-250") + thinner (Musashi Paint Co., Ltd. "Z-EC-K775")

[0078] [Automatic paint gun] The automatic coating guns and air caps used in the examples and comparative examples are as follows: Paint gun 1: Meiji Machinery Manufacturing Co., Ltd. "AJ-P55-P-GO" (air cap M) Paint gun 2: Meiji Machinery Manufacturing Co., Ltd. "AJ-P55-P-GO" (1 round air cap) Paint gun 3: Meiji Machinery Manufacturing Co., Ltd. "AJ-P55-P-GO-1" (air cap M) Paint gun 4: Meiji Machinery Manufacturing Co., Ltd. "AJ-P55-P-GO-1" (air cap round 1) Paint gun 5: Meiji Machinery Manufacturing Co., Ltd. "AJ-P13P"

[0079] [Measurement method] In the examples and comparative examples, the viscosity, paint supply amount, atomizing air pressure, pattern air pressure, atomizing air flow rate and pattern air flow rate were measured as follows.

[0080] <Viscosity> The viscosity was measured using Anest Iwata's viscosity cup NK-2 at the temperature and pressure of the painting environment.

[0081] <Paint supply amount> The flow rate was measured using a flow meter installed in the paint supply pipe.

[0082] <Atomization air pressure> The pressure value of the pressure adjustment mechanism in the control device was set to atomization air pressure 1. The pressure measured by a pressure gauge installed near the automatic coating gun, more than 10 m away from the pressure adjustment mechanism, was taken as atomizing air pressure 2.

[0083] <Pattern air pressure> The pressure value of the pressure adjustment mechanism in the control device was set to pattern air pressure 1. The pressure measured by a pressure gauge installed near the automatic coating gun, more than 10 m away from the pressure adjustment mechanism, was taken as pattern air pressure 2.

[0084] <Atomization air flow rate> The measurement was performed using a flow meter installed in the atomizing air supply pipe.

[0085] <Pattern air flow rate> The flow rate was measured using a flow meter installed in the pattern air supply pipe.

[0086] [Calculation / Evaluation] In the examples and comparative examples, the calculation of the coating efficiency, the evaluation of the appearance of the coating film, and the evaluation of noise were carried out as follows.

[0087] <Coating efficiency> It was calculated by the method described above in [(1) Coating Efficiency]. The paint spray amount F(g) used in formula (I) was calculated using a flow meter installed in the paint flow path. A conversion factor was calculated in advance using the integrated value of the instantaneous paint flow rate measured by the flow meter and the actually measured paint flow rate, and then the flow rate was calculated by multiplying the integrated value of the instantaneous paint flow rate during painting by the conversion factor, and the paint spray amount F(g) was calculated using the specific gravity of the paint.

[0088] <Coating film appearance> The appearance of the coated articles obtained in the examples and comparative examples was visually observed and rated according to the following criteria: 5 and 4 are acceptable, and 3 or less is unacceptable. Rating 5: No poor appearance of the coating film such as pooling or unevenness is visually observed. Rating 4: Minor defects in the appearance of the coating film, such as minute pools and minute unevenness, are observed by careful observation. Rating 3: Poor appearance such as accumulation and unevenness is visually observed. Rating 2: Poor appearance such as accumulation and unevenness is clearly observed visually. Rating 1: No coating film can be formed. The term "pooling" refers to a situation in which problems with the flow of paint occur during paint application and paint film formation, resulting in the formation of paint pools, which are observed in the paint film.

[0089] <Noise evaluation> A sound level meter was placed 5 m away from the automatic paint gun to measure noise.

[0090] [Examples A1 to A77, Comparative Examples A1 to A5] The coating conditions were as shown in Tables 1 and 2, and coating was carried out on a horizontally placed aluminum plate using an automatic spray gun. The spray angle was 90° (the coated surface of the substrate was perpendicular to the spray direction). The results are shown in Tables 1 and 2. In Tables 1 and 2, the numbers in the recoat column indicate the number of coats applied.

[0091] [Table 1]

[0092] [Table 2]

[0093] [Examples B1 to B35, Comparative Examples B1 to B5] The coating conditions were as shown in Tables 3 and 4, and coating was carried out on a horizontally placed aluminum plate using an automatic spray gun. The spray angle was 90° (the coated surface of the substrate was perpendicular to the spray direction). The results are shown in Tables 3 and 4. In Tables 3 and 4, the numbers in the recoat column indicate the number of coats applied.

[0094] [Table 3]

[0095] [Table 4]

[0096] [Examples C1 to C8, Comparative Examples C1 to C2] The coating conditions are shown in Table 5, and coating was carried out on a horizontally placed plastic plate using an automatic spray gun. The spray angle was 90° (the coated surface of the substrate was perpendicular to the spray direction). The appearance of the coating film on the resulting coated object was also evaluated. The results are shown in Table 5. In Table 5, the numbers in the recoat column indicate the number of coats applied.

[0097] [Table 5]

[0098] [Example D1] A plastic film and a plastic plate placed on a horizontal surface were sprayed 10 times using automatic spray gun 4 with paint 2 at a spray gun speed of 200 mm / s, a spray gun distance of 50 mm, a paint supply rate of 11 mL / min, atomizing air pressure 1 of 0.040 MPa, atomizing air pressure 2 of 0.034 MPa, pattern air pressure 1 of 0.090 MPa, and atomizing air pressure 2 of 0.068 MPa. The 10 coats were obtained by applying five coats of paint in 2.5 round trips, shifting the center of the coating by 20 mm each time, followed by five coats of paint in the same trajectory. The spray angle was 90° (the coated surface of the substrate was perpendicular to the spray direction). After drying, the appearance of the coating film on the plastic plate was evaluated and given a rating of 5. After drying, the thickness of the coating film on the plastic film was measured using a digital micrometer (manufactured by Shinwa Measurement Co., Ltd.) The results are shown in Figure 5. The coating film obtained in Example D1 was a uniform coating film having a thickness of 18 μm in an effective pattern of 60 mm.

[0099] [Noise measurement] The noise generated during painting in Example C3 was measured to be 73 dB. On the other hand, when using paint gun 5 as an automatic spray gun and applying paint 2 to an aluminum plate under the standard painting conditions of paint gun 5 (atomizing air pressure 0.25 MPa, pattern air pressure 0.25 MPa, gun distance (spraying distance) 200 mm, paint supply rate (paint spray rate) 310 mL / min), the noise was measured and was found to be 90 dB.

[0100] Although the present invention has been described in detail above, various changes can be made in the above configuration without departing from the scope of the present invention. Accordingly, all matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative only. [Explanation of symbols]

[0101] G: Automatic paint gun S: Atomized paint 11: Compressor 12: Needle valve operating air piping 13: Atomization air piping 14: Pattern air piping 15a: Atomization air pressure adjustment mechanism 15b: Pattern air pressure adjustment mechanism 16a: First atomizing air flow rate / pressure sensor 16b: Second pattern air flow / pressure sensor 17a: Second atomizing air flow rate / pressure sensor 17b: Second pattern air flow / pressure sensor 18: Air piping for operating the switching valve inside the automatic coating gun body 21:Paint 22:Paint tank 23: Weight measuring device 24: Pump 25: Paint piping 26: Valve 27: Paint flow sensor

Claims

1. In a non-electrostatic air atomization coating method using an automatic coating gun, the following requirements (1) and (2) are met: (1) Coating efficiency is 80% or more; (2) Gun distance is 20mm to 90mm, Fulfilling Furthermore, the following requirements (3a) and / or (3b) are satisfied: (3a) The atomizing air pressure is 0.013 MPa to 0.070 MPa, and the pattern air pressure is 0.020 MPa to 0.100 MPa; (3b) The atomizing air flow rate is 5 L / min to 25 L / min, and the pattern air flow rate is 2 L / min to 35 L / min; Fulfilling The automatic coating gun is an automatic coating gun that atomizes paint with atomizing air and forms a pattern with pattern air, and has a tapered nozzle tip, The viscosity of the paint used in the coating method is 5 to 13 seconds according to the Iwata Cup method. The coating method.

2. Furthermore, the following requirements (4), (6) to (7): (4) The paint supply amount is 7 mL / min to 55 mL / min. (6) The coating material contains one or more organic solvents selected from the group consisting of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, and the evaporation rate of the organic solvent is 140 to 1100, where the evaporation rate of butyl acetate is 100. (7) The coating material contains one or more organic solvents selected from the group consisting of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, and the organic solvent has a boiling point of 150°C or higher at a pressure of 0.1 MPa. The coating method according to claim 1, which satisfies one or more of the following requirements.

3. The coating method according to claim 1 or 2, wherein recoating is performed.

4. 3. The coating method according to claim 1, wherein the coating is applied in layers so that the center positions of the coatings are different.

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