A painting method with excellent coating efficiency.

Abstract

The objective is to provide a non-electrostatic air atomization coating method using an automatic paint gun that achieves a coating efficiency of 80% or more, has good reproducibility of coating efficiency, can produce a superior coating film appearance, and reduces noise during painting. [Solution] In a non-electrostatic air atomization painting method using an automatic paint gun, the following requirements (1) and (2): (1) Coating efficiency of 80% or more, (2) Gun distance is 20mm to 90mm, Satisfying the conditions, Furthermore, the following requirements (3a) and / or (3b): (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. The present invention provides a painting method that satisfies the above conditions.

Description

Technical Field

[0001] The present invention relates to a coating method excellent in coating efficiency. Specifically, the present invention relates to a coating method having a coating efficiency of 80% or more, preferably 85% or more. Background Art

[0002] Coating can dramatically extend the service life (life cycle) of products by preventing product deterioration caused by rust and ultraviolet rays, and can further add added value to products by improving design properties, functions and the like. In industrial coating, for example, at coating sites for plastic products, spray coating in which liquid paint is atomized and applied is adopted from the viewpoints of finished quality of the coating film and workability. On the other hand, paints used for coating are mainly petrochemical products, and CO2 generation from production to disposal has become a major social problem. As a solution for reducing and suppressing CO2 in coating, improving coating efficiency is an extremely important approach. If the coating efficiency can be improved and the amount of paint that is wasted without being applied can be reduced, the generation of paint (material) waste such as booth sludge and VOC (volatile organic compounds) can be suppressed, and CO2 emissions can also be suppressed, which is advantageous from an environmental point of view. Furthermore, it is also possible to reduce raw material costs. However, conventional spray coating has a coating efficiency of only about 60% at the highest, and improvement of coating efficiency has been an issue.

[0003] As prior art related to improvement of coating efficiency, for example, the following Patent Documents 1 to 3 can be mentioned. Patent Document 1 describes a coating method excellent in coating efficiency for coating a substrate having irregularities on a surface, in which after coating using a sponge roll wrapped with cloth, air is blown to the recesses of the substrate to scatter the paint accumulated in the recesses.

[0004] Patent Document 2 discloses a liquid spraying method that can be applied to an object with high coating efficiency, comprising the steps of: discharging at least one liquid from a liquid discharge port; ejecting a first compressed gas from a first compressed gas outlet provided around the liquid discharge port to atomize the liquid discharged from the liquid discharge port and create a particle ejection flow; and ejecting a second compressed gas from a plurality of second compressed gas outlets toward the liquid particle ejection flow, causing at least a portion of the second compressed gas to collide with the liquid particle ejection flow, thereby causing the liquid particle ejection flow to swirl and atomize it into fine particles.

[0005] Patent Document 3 discloses a method for applying metallic paint in an automobile topcoat base coating process, which involves using a bell-type coating apparatus and supplying shaping air to the bell-type coating apparatus at an air pressure of 196 to 294 kPa and an air flow rate of 500 to 700 NL / min to apply the paint, thereby forming a coating film that provides substrate concealment and a metallic feel, and has high coating efficiency. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2005-111314 [Patent Document 2] Japanese Patent Publication No. 2004-089976 [Patent Document 3] Japanese Patent Application Publication No. 11-300239 [Overview of the project] [Problems that the invention aims to solve]

[0007] The coating method described in Patent Document 1 is a roll coating method, which makes it difficult to form a coating film with a high visual appearance, and therefore cannot be applied to coating methods other than roll coating. The painting method described in Patent Document 2 involves a complex apparatus and complex control system. The painting method described in Patent Document 3 is a technology specific to bell-type painting apparatus and cannot be applied to painting methods that do not use bell-type painting apparatus.

[0008] In industrial painting, significantly increasing coating efficiency is necessary to reduce and control CO2 emissions. Therefore, it is necessary to establish advanced coating technologies that offer superior coating efficiency, such as "electrostatic atomization" or "hydraulic spraying," or to establish coating technologies that solve the problem of splashing in "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 in the painting of plastic parts, spray painting, which atomizes liquid paint for application, is widely adopted from the standpoint of paint finish quality and workability. Among the atomization methods for liquid paint, the most common conventional method is air atomization, which atomizes the liquid paint by discharging high-pressure compressed air along with the paint from the tip of the nozzle, thereby forming a homogeneous paint film with a high level of appearance evaluation. While air atomization can form a high-quality paint film and offers good workability, it has low coating efficiency, high paint loss, a large environmental impact, and noise problems, so improvements have been desired.

[0010] The problem that this invention aims to solve is to provide a non-electrostatic air atomization coating method using an automatic paint gun that has a coating efficiency of 80% or more, good reproducibility of coating efficiency, can produce a superior coating film appearance, and reduces noise during coating. [Means for solving the problem]

[0011] The inventors of this invention conducted diligent research to solve the above problems. We then discovered that the above problems could be solved by adopting specific painting conditions. Specifically, it is as follows:

[0012] [Section 1] In a non-electrostatic air atomization painting method using an automatic paint gun, the following requirements (1) and (2): (1) Coating efficiency of 80% or more, (2) Gun distance is 20mm to 90mm, Satisfying the conditions, Furthermore, the following requirements (3a) and / or (3b): (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. The painting method that satisfies the requirements. [Section 2] Furthermore, the following requirements (4)~(7): (4) The paint supply rate is 7 mL / min to 55 mL / min. (5) The viscosity of the paint used for painting, according to the Iwata cup method, is between 5 seconds and 13 seconds. (6) The paint contains one or more organic solvents, including ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, wherein the evaporation rate of the organic solvent is 140 or more and 1100 or less, with the value of butyl acetate set to 100. (7) The paint contains one or more organic solvents, including ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, the organic solvent having a boiling point of 150°C or higher at a pressure of 0.1 MPa. A painting method as described in item 1, which satisfies one or more of the following requirements. [Section 3] Painting method described in item 1 or 2, which involves applying multiple coats of paint. [Section 4] A painting method described in any one of items 1 to 3, in which multiple coats are applied so that the center position of the paint is different. [Effects of the Invention]

[0013] According to the present invention, there is provided a non-electrostatic air atomization coating method using an automatic coating gun, which has a coating efficiency of 80% or more, good reproducibility of coating efficiency, can provide an excellent coating film appearance, and has reduced noise during coating. [BRIEF DESCRIPTION OF THE DRAWINGS]

[0014] [Figure 1] Schematic configuration diagram according to one embodiment of a coating system used in the coating method of the present invention. [Figure 2] Schematic configuration diagram according to one 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 coating gun of the present invention. [Figure 4] Schematic diagram of a No.1 round air cap attached to the automatic coating gun of the present invention. [Figure 5] Diagram showing the film thickness distribution of a coated article obtained by the coating method of Example D1 of the present invention. [MODE FOR CARRYING OUT 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 is 80% or more, (2) Gun distance is 20 mm to 90 mm, which is satisfied, further satisfies the following requirement (3a) and / or (3b): (3a) Atomization air pressure is 0.013 MPa to 0.070 MPa, and pattern air pressure is 0.020 MPa to 0.100 MPa, (3b) Atomization air flow rate is 5 L / min to 25 L / min, and pattern air flow rate is 2 L / min to 35 L / min, which is a coating method that satisfies the above.

[0016] The coating method of the present invention further satisfies the following requirements (4) to (7): (4) Paint supply amount is 7 mL / min to 55 mL / min, (5) The viscosity of the paint used for painting, according to the Iwata cup method, is between 5 seconds and 13 seconds. (6) The paint contains one or more organic solvents, including ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, wherein the evaporation rate of the organic solvent is 140 or more and 1100 or less, with the value of butyl acetate set to 100. (7) The paint contains one or more organic solvents, including ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, the organic solvent having a boiling point of 150°C or higher at a pressure of 0.1 MPa. A painting method that satisfies one or more of the following requirements may also be used.

[0017] The painting method of the present invention may involve applying multiple coats. The painting method of the present invention may also involve applying multiple coats so that the center position of the paint is different from that of the previous coat.

[0018] The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments and examples, and can be implemented with appropriate modifications.

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

number

[0020] In equation (I), the mass W (g) of the applied dry coating 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 was formed.

[0021] In equation (I), the paint spray volume F(g) can be calculated, for example, by using a flow meter installed in the paint flow path, first determining a conversion factor using the integrated value of the instantaneous paint flow rate measured by the flow meter and the actually measured paint flow rate, then calculating the flow rate by multiplying the integrated value of the instantaneous paint flow rate during painting by the conversion factor, and finally calculating the paint spray volume F(g) using the specific gravity of the paint. Alternatively, the paint spray volume F(g) in equation (I) can also be calculated by determining the total amount W1(g) of paint in the paint tank 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 then using the specific gravity of the paint to calculate the paint spray volume F(g).

[0022] The solid content NV (%) of the paint can be determined using the paint's catalog value, or it can be calculated from the difference between the mass (g) of the test panel immediately after applying a specified amount (ml) of paint and the mass (g) of the test panel after drying and forming the paint film.

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

[0024] [(2) Gun range] In the painting method of the present invention, (B) gun distance is the distance from the paint discharge port of the automatic paint gun to the object to be painted. In the painting 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, the paint can be reliably applied to the object being coated, splashing back from the object can be prevented, and coating efficiency can be improved. Until now, in painting using automatic paint guns, the gun distance has been set at 100 mm or more (see, for example, the website of Meiji Machine Works Co., Ltd. https: / / www.meijiair.co.jp / product / gun / detail / 73). The painting method of the present invention enables improvement in coating efficiency from a completely different technical perspective than before.

[0026] [(3a) Atomizing air pressure and pattern air pressure] In the painting method of the present invention, the atomizing air pressure in the automatic paint gun can be set to 0.013 MPa to 0.070 MPa, and the pattern air pressure in the automatic paint gun can be set to 0.020 MPa to 0.100 MPa.

[0027] If the atomizing air pressure in an automatic paint gun is less than 0.013 MPa, the paint workability may decrease, and it may become impossible to properly spray the paint. If the atomizing air pressure in an automatic paint gun exceeds 0.070 MPa, the sprayed paint may bounce back, reducing the coating efficiency, and it may become impossible to properly spray the paint.

[0028] If the pattern air pressure in an automatic paint gun is less than 0.020 MPa, it may become difficult to achieve an appropriate spray shape for the paint ejected from the automatic paint gun, potentially resulting in improper paint ejection. If the pattern air pressure in an automatic paint gun exceeds 0.100 MPa, it may become difficult to achieve an appropriate spray shape for the paint ejected from the automatic paint gun, potentially causing the ejected paint to bounce back and reducing the coating efficiency, potentially resulting in improper paint ejection.

[0029] The lower limit of the atomizing air pressure in an automatic paint gun can preferably be 0.010 MPa or higher, more preferably 0.011 MPa or higher, and even more preferably 0.012 MPa or higher, and the upper limit of the atomizing air pressure in an automatic paint gun can preferably be 0.065 MPa or lower, more preferably 0.060 MPa or lower, and even more preferably 0.055 MPa or lower.

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

[0031] In the painting method of the present invention, both the atomizing air pressure and the pattern air pressure are pressures in the automatic paint gun. The atomizing air pressure and pattern air pressure in the automatic paint gun can be confirmed by installing pressure gauges near the automatic paint gun in the atomizing air piping and pattern air piping. Specifically, the pressure gauges can be installed in a position that is not affected by pressure loss in the atomizing air piping and pattern air piping. Alternatively, the atomizing air pressure and pattern air pressure in the automatic paint gun may be calculated by pre-acquiring the relationship between the pressure adjustment mechanism and the automatic paint gun and the pressure loss occurring between them. When the atomizing air piping and pattern air piping become long, and the distance between the automatic paint gun and the automatic paint gun controller increases, pressure loss can cause errors in the atomizing air pressure and pattern air pressure in the automatic paint gun controller and the atomizing air pressure and pattern air pressure in the automatic paint gun, which may prevent accurate control of the painting process.

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

[0033] If the atomizing air flow rate supplied to the automatic paint gun is less than 5 L / min, painting workability may decrease, and it may become impossible to spray the paint properly. If the atomizing air flow rate supplied to the automatic paint gun exceeds 25 L / min, the sprayed paint may bounce back, reducing the coating efficiency, and it may become 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 become difficult to achieve an appropriate spray shape for the paint ejected from the automatic paint gun, potentially resulting in improper paint ejection. If the pattern air flow rate supplied to the automatic paint gun exceeds 35 L / min, it may become difficult to achieve an appropriate spray shape for the paint ejected from the automatic paint gun, potentially causing the ejected paint to bounce back and reducing the coating efficiency, potentially resulting in improper paint ejection.

[0035] The lower limit of the atomizing air flow rate can preferably be 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 painting gun can preferably be 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 can preferably be 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 pattern air flow rate in the automatic paint gun can preferably be 32 L / min or less, more preferably 30 L / min or less, and even more preferably 28 L / min or less.

[0037] In the painting method of the present invention, the atomizing air flow rate and pattern air flow rate supplied to the automatic paint 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 become very long, the atomizing air flow rate and pattern air flow rate at any point in the piping remain constant. Therefore, when using the atomizing air flow rate and pattern air flow rate to control an automatic paint gun, painting can be accurately controlled without considering the effects of pressure loss.

[0038] [(4) Paint supply amount] In the painting method of the present invention, the amount of paint supplied to the automatic paint 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 painting workability may decrease, and it may become impossible to spray the paint properly. If the paint supply rate to the automatic paint gun exceeds 55 mL / min, it may become difficult to maintain an appropriate spray shape for the paint sprayed from the automatic paint gun, the sprayed paint may bounce back, reducing the coating efficiency, and it may become impossible to spray the paint properly.

[0040] The lower limit of the paint supply rate can preferably be 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 can preferably be 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 painting method of the present invention, the paint used for painting is a paint whose viscosity, measured by the Iwata Cup method, is between 5 seconds and 13 seconds. In the painting method of the present invention, the viscosity of the paint used for painting is the viscosity at the time the paint is prepared for painting and is measured using the Iwata Cup.

[0042] If the viscosity of the paint used for painting is less than 5 seconds according to the Iwata Cup method, the dried paint film may become smudged or runny, potentially reducing the workability of the paint. If the viscosity of the paint used for painting is more than 13 seconds according to the Iwata Cup method, the dried paint film may develop an orange peel texture or other appearance defects.

[0043] In the painting method of the present invention, the viscosity measured by the Iwata cup method is the viscosity measured using the NK-2 viscosity cup manufactured by Anest Iwata Corporation, and is the viscosity at the temperature and pressure of the painting environment. Viscosity is measured by submerging a viscosity cup in the paint, then lifting the cup out of the paint, and measuring the time (in seconds) from the moment the viscosity cup is lifted until the flow of paint from the viscosity cup stops. For reactive paints, the measurement is performed within 5 minutes of paint preparation.

[0044] [(6) Evaporation rate of organic solvents contained in paint] In the coating method of the present invention, the paint used for coating may contain one or more organic solvents from among ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, wherein the evaporation rate value is 140 to 1100 when the value of butyl acetate is set to 100.

[0045] When paints used for painting contain one or more organic solvents from the following categories: ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, the likelihood of adverse effects on the environment and worker health is low, making them advantageous in terms of safety and other factors. When the paint used for coating contains an organic solvent whose evaporation rate is between 140 and 1100 (with butyl acetate set to 100), the drying rate of the coating film can be made appropriate, and a coating film with an excellent appearance can be formed.

[0046] The paint used for coating preferably contains one or more ketone-based organic solvents and ester-based organic solvents.

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

[0048] One or more organic solvents from the categories of ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, with an evaporation rate of 140 to 1100 when the value of butyl acetate is set to 100, include, for example, acetone (evaporation rate 720), methyl ethyl ketone (evaporation rate 465), methyl isobutyl ketone (evaporation rate 165), methyl alcohol (evaporation rate 370), ethyl alcohol (evaporation rate 203), isopropyl alcohol (evaporation rate 205), methyl acetate (evaporation rate 1040), ethyl acetate (evaporation rate 525), isobutyl acetate (evaporation rate 145), ethyl tert-butyl ether (evaporation rate 717), diisopropyl ether (evaporation rate 662), methyl tert-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 paint used for coating may contain one or more organic solvents, including 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 with a boiling point of 150°C or higher at a pressure of 0.1 MPa.

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

[0051] The paint used for coating preferably contains one or more ether-based organic solvents and ester-based organic solvents.

[0052] One or more organic solvents from the ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, with a boiling point of 150°C or higher at a pressure of 0.1 MPa, include, for example, ketone-based organic solvents such as diisobutyl ketone, cyclohexanone, diacetone alcohol, and γ-butyrolactone; and 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, 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 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 mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol dimethyl ether, tripropylene glycol mono-n-propyl ether, tripropylene glycol mono-n-butyl ether, etc.Examples of ester-based organic solvents include 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, nonyl acetate, and other similar ester-based organic solvents; and one or more such solvents.

[0053] [Layering paint] In the painting method of the present invention, multiple coats may be applied. Multiple coats can be applied by painting the object to be painted two or more times. When applying multiple coats, a drying step may be included in between, or the process may be performed wet on wet without a drying step, or a combination of these methods may be used. The painting method of the present invention may involve applying multiple coats of paint so that the center position of the paint is different from that of the previous coat, applying multiple coats so that the center position of the paint is the same as that of the previous coat, or a combination of these methods. In the painting 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 the coats so that the center position of the paint differs from that of the previous coat, the width of the paint ejection pattern from the automatic paint gun can be overlapped to some extent, and a paint film with a uniform thickness can be formed. When applying multiple coats, it is preferable to ensure that any excess paint particles from the overspray adhere to the previously painted surface and prevent it from causing surface roughness.

[0054] [paint] The paint used in the painting method of the present invention is not particularly limited. Commercially available paints may be used, or newly formulated paints may be used. The paint used in the painting method of the present invention contains at least a resin component, and optionally a hardening agent component, pigment, solvent, and other additive components. The paint used in the painting method of the invention may be any of the following: solvent-based paint, emulsion (dispersion) type paint, solvent-free paint, one-component paint, or two-component paint.

[0055] The resin component is a component that functions as a coating film-forming element. Conventional resin components known as paint components can be used as the resin component. Examples of resin components include one or more acrylic resins, polyester resins, alkyd resins, fluororesins, epoxy resins, polyurethane resins, polyether resins, olefin resins, epoxy resins, vinyl chloride resins, silicone resins, and alkoxysilane condensates.

[0056] Examples of curing agent components include curing agent components that react with the reactive groups in the resin component. The curing agent component can be selected according to the reactive groups in the resin component. For example, one or more of the following can be selected: polyisocyanate compounds, amino resins, polyamine compounds, polycarboxylic acid compounds, polyol compounds, melamine compounds, epoxy compounds, aldehyde compounds, aziridine compounds, carbodiimide compounds, hydrazine compounds, etc., which may be blocked by a blocking agent.

[0057] Examples of pigments include coloring pigments for coloring paints and filler pigments. Examples of coloring pigments include one or more 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 extender pigments such as calcium carbonate, talc, mica, and silica, and rust-preventive pigments.

[0058] As a solvent, conventionally known solvents that constitute paints can be used. As a solvent, for example, those listed as solvents that satisfy requirement (6) or requirement (7) above can be used. Specifically, 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, 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, propylene glycol monoethyl ether acetate; diethyl ether, propylene glycol monomethyl ether, ethylene glycol Examples include one or more of the following: ether-based organic solvents such as chloroform monoethyl ether, dioxane, and tetrahydrofuran (THF); amide-based organic solvents such as formamide, N-methylformamide, dimethylformamide (DMF), dimethylacetamide, dimethyl sulfoxide (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 resin components, hardening agents, pigments, and solvents, paints may contain one or more of the following components: dispersants, film-forming aids, antifreezes, crosslinking accelerators, hardening agents, leveling agents, surface modifiers, defoamers, plasticizers, preservatives, fungicides, and UV stabilizers.

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

[0061] In the painting method of the present invention, the shape of the object to be painted is not particularly limited. Examples include plate-shaped, film-shaped, rod-shaped, and various molded products. Examples include vehicle parts, building interior materials, household goods, and electrical equipment parts.

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

[0063] [Painting System] Figures 1 and 2 are schematic diagrams of a painting system suitable for carrying out the painting method of the present invention. Hereinafter, embodiments of a painting system suitable for carrying out the painting 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, it is possible to make appropriate modifications without departing from the scope in which the effects of the present invention are achieved. Note that the use of the same reference numeral in different drawings indicates similar or identical items or features.

[0064] Figure 1 is a schematic diagram showing one embodiment of a painting system suitable for carrying out the painting method of the present invention using a general-purpose automatic paint gun. In Figure 1, G is an automatic paint gun, and S is the paint pattern sprayed from the automatic paint gun. The automatic paint gun G is connected to a needle valve operating air pipe 12, an atomizing air pipe 13, and a pattern air pipe 14, which are supplied with air from a compressor 11. The automatic paint gun G is also connected to 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 needed.

[0065] The atomizing air piping 13 is equipped with an atomizing air pressure adjustment mechanism 15a, a first atomizing air flow rate / pressure sensor 16a located near the automatic paint gun G side of the atomizing air pressure adjustment mechanism 15a, and a second atomizing air flow rate / pressure sensor 17a located near the automatic paint gun G. 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 by the measurement value of the first atomizing air flow rate / pressure sensor 16a. In addition, the pressure and / or flow rate of the atomizing air supplied to the automatic paint gun G is measured by the second atomizing air flow rate / pressure sensor 17a. Note that the atomizing air pressure adjustment mechanism 15a may be part of the control mechanism of the painting apparatus (automatic paint gun).

[0066] The atomizing air pressure adjustment mechanism 15a can be controlled by a computer or the like, if necessary. Furthermore, the operating data and measured values ​​of the atomizing air pressure adjustment mechanism 15a, the first atomizing air flow rate / pressure sensor 16a, and the second atomizing air flow rate / pressure sensor 17a may be sent to a controller or storage means (not shown) for control or recording, if necessary, for controlling the atomizing air pressure / flow rate, pattern air pressure / flow rate, paint flow rate, etc.

[0067] The pattern air piping 14 is equipped 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 by the measurement value of the first pattern air flow rate / pressure sensor 16b. In addition, the pressure and / or flow rate of the pattern air supplied to the automatic paint gun G is measured by the second pattern air flow rate / pressure sensor 17b. The pattern air pressure adjustment mechanism 15b may be part of the control mechanism of the painting apparatus (automatic paint gun).

[0068] The pattern air pressure adjustment mechanism 15b can be controlled by a computer or the like, if necessary. Furthermore, the operating data and measured values ​​of the pattern air pressure adjustment mechanism 15b, the first pattern air flow rate / pressure sensor 16b, and the second pattern air flow rate / pressure sensor 17b can be recorded by transmitting them via wired or wireless connection to a recording device or control means (not shown). The pattern air-related data measured by the first pattern air flow rate / pressure sensor 16b and the second pattern air flow rate / pressure sensor 17b may be sent, if necessary, to a controller or storage means (neither shown) that controls atomizing air pressure / flow rate, pattern air pressure / flow rate, paint flow rate, etc., for control or recording.

[0069] The paint piping 25 is equipped with a pump 24 and a valve 26. The paint 21 in the paint tank 22, which is sucked in by the pump 24 and enters the paint piping, is controlled by the valve 26 to be supplied to the automatic paint gun G when painting is in progress 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 G to measure the flow rate of the paint supplied to the automatic paint gun G. The paint flow rate data measured by the paint flow rate sensor 27 may be sent, if necessary, to a controller or storage means (not shown) that controls atomizing air pressure and flow rate, pattern air pressure and flow rate, paint flow rate, etc., for control and recording.

[0070] Figure 2 is a schematic diagram showing one embodiment of a painting system suitable for implementing the painting method of the present invention using an automatic paint gun with improved needle valve responsiveness. The painting system shown in Figure 2 is provided with an internal switching valve operating air piping 18 for the automatic paint gun body that controls a switching valve that switches the communication between the needle valve control air chamber and the exhaust port, which are located inside the automatic paint gun G, ON (connected: when not painting) or OFF (not connected: when painting). By providing a switching valve inside the automatic paint gun G, the responsiveness (paint shutdown performance) when switching from painting to non-painting can be improved.

[0071] [Automatic paint gun] The automatic paint gun used in the painting method of the present invention is not particularly limited, as long as it is an automatic paint gun capable of atomizing paint into fine particles with atomizing air and forming a pattern with pattern air. In the painting method of the present invention, an automatic paint gun is preferred in which the nozzle tip is tapered, and by increasing the flow velocity in the atomization region, the atomizing air comes into contact with the paint at supersonic speed, thereby atomizing the paint. 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 Machine Works Co., Ltd., can be used. For example, the air caps used to attach to the automatic paint gun can be the M-type air cap shown in Figure 3 or the round 1-type air cap shown in Figure 4. The painting method of the present invention can reliably achieve a coating efficiency of 80% or more, even when using a general-purpose automatic paint gun.

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

[0073] <Thickness of the coating film> The thickness of the coating film (dry film thickness) formed by the coating method of the present invention is not particularly limited and can be adjusted as appropriate according to the application. 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 painting method of the present invention, the spraying angle of the paint from the automatic paint gun is not particularly limited. For example, it can be 90° (the painted surface of the object to be painted is perpendicular to the discharge direction). In the painting method of the present invention, the orientation of the painted surface of the object to be painted is not particularly limited. For example, it can be a horizontal plane (perpendicular to the direction of gravity). In the coating method of the present invention, after applying the paint to the object to be coated, the coating film may be dried and cured at room temperature or by heating to form the coated object. When heating, the temperature can 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. Furthermore, if an active energy ray curing type paint is used, curing can be performed by energy rays such as ultraviolet rays or heat. From the viewpoint of finish quality, the object may be set (left to stand) at room temperature beforehand before drying or curing.

[0075] <Noise> In the painting method of the present invention, it is preferable that the noise level during painting with an automatic paint gun is 75 dB or less. Compared to conventional painting methods using automatic paint guns, the painting method of the present invention has lower atomizing air pressure and pattern air pressure, and a shorter gun distance (the distance from the paint discharge port of the automatic paint gun to the object to be painted), so the noise level during painting can be suppressed to 75 dB or less. [Examples]

[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 following paints were used. All are two-component acrylic urethane paints. The diluents all contain a ketone-based organic solvent with an evaporation rate of 140 to 1100 when butyl acetate is set to 100, and an ester-based organic solvent with an evaporation rate of 140 to 1100 when butyl acetate is set to 100. Paint 1: Main component (Musashi Paint Co., Ltd. "EC-P79- Eco High-Ulex P MATT BLACK GT") + Hardener (Musashi Paint Co., Ltd. "Z-EC-H-800") + Thinner (Musashi Paint Co., Ltd. "Z-EC-K775") Paint 2: Main component (Musashi Paint Co., Ltd. "EC-P79- Eco High-Ulex P MATT BLACK GT") + Hardener (Musashi Paint Co., Ltd. "Z-EC-H-800") + Thinner (Musashi Paint Co., Ltd. "Z-EC-K781") Paint 3: Main component (Musashi Paint Co., Ltd. "EC-P79- Eco High-Ulex P MATT BLACK GT") + Hardener (Musashi Paint Co., Ltd. "Z-EC-H-800") + Thinner (Musashi Paint Co., Ltd. "Z-EC-K060") Paint 4: Main component (Musashi Paint Co., Ltd. "EC-P79- Eco High Urex P MATT BLACK GT") + Hardener (Musashi Paint Co., Ltd. "Z-EC-H-800") + Diluent (Musashi Paint Co., Ltd. "Z-EC-K060" and a high-boiling point organic solvent containing diethylene glycol mono-n-butyl ether) Paint 5: Main component (Musashi Paint Co., Ltd. "EC-MH62- Eco Sunshine Super MH Piano Black") + Hardener (Musashi Paint Co., Ltd. "Z-EC-H-760") + Thinner (Musashi Paint Co., Ltd. "Z-EC-K657") Paint 6: Main component (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 paint guns and air caps used in the examples and comparative examples are as follows: Paint gun 1: Meiji Machine Works Co., Ltd. "AJ-P55-P-GO" (Air cap M) Paint gun 2: Meiji Machine Works Co., Ltd. "AJ-P55-P-GO" (round air cap 1) Paint gun 3: Meiji Machine Works Co., Ltd. "AJ-P55-P-GO-1" (Air cap M) Paint gun 4: Meiji Machine Works Co., Ltd. "AJ-P55-P-GO-1" (Air cap round 1) Paint gun 5: Meiji Machine Works Co., Ltd. "AJ-P13P"

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

[0080] <Paint viscosity> Viscosity measurements were taken using an NK-2 viscosity cup manufactured by Anest Iwata Corporation, under the temperature and pressure conditions of the painting environment.

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

[0082] <Atomizing air pressure> The pressure value of the pressure adjustment mechanism in the control device was set to atomizing air pressure 1. The pressure measured by a pressure gauge located more than 10 meters away from the pressure adjustment mechanism and near the automatic paint gun was defined 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 located more than 10 meters away from the pressure adjustment mechanism and near the automatic paint gun was defined as pattern air pressure 2.

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

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

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

[0087] <Coating efficiency> It was calculated using the method described in [(1) Coating Efficiency] above. The paint spray volume F(g) used in equation (I) was calculated by first determining a conversion factor using the integrated value of the instantaneous paint flow rate measured in advance with a flow meter installed in the paint flow path, and the measured paint flow rate. 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 volume F(g) was calculated using the specific gravity of the paint.

[0088] <Appearance of the coating film> The appearance of the painted products obtained in the examples and comparative examples was observed visually and evaluated according to the following criteria. A rating of 5 or 4 is considered acceptable, while a rating of 3 or lower is considered unacceptable. Rating 5: No visible defects in the appearance of the paint film, such as buildup or unevenness, were observed. Rating 4: Fine defects in the appearance of the coating, such as minute accumulations and minute unevenness, can be observed upon close inspection. Rating 3: Visual defects such as buildup and unevenness are observed. Evaluation 2: Visual defects such as buildup and unevenness are clearly observed. Evaluation 1: Unable to form a coating film. "Pouring" refers to a situation where paint pools form due to problems with paint flow during application and film formation, and these pools are observed in the paint film.

[0089] <Noise Evaluation> A sound level meter was placed 5 meters away from the automatic paint gun, and noise levels were measured.

[0090] [Examples A1-A77, Comparative Examples A1-A5] Painting conditions were set as shown in Tables 1 and 2, and painting was performed on an aluminum plate on a horizontal surface using an automatic paint gun. The spray angle was 90° (the painted surface of the object being painted was perpendicular to the spray direction). The results are shown in Tables 1 and 2. In Tables 1 and 2, the numbers in the "Recoating" column represent the number of coats.

[0091] [Table 1]

[0092] [Table 2]

[0093] [Examples B1-B35, Comparative Examples B1-B5] The painting conditions were as shown in Tables 3 and 4, and painting was performed on an aluminum plate on a horizontal surface using an automatic paint gun. The spray angle was 90° (the painted surface of the object being painted was perpendicular to the spray direction). The results are shown in Tables 3 and 4. In Tables 3 and 4, the numbers in the "Recoating" column represent the number of coats.

[0094] [Table 3]

[0095] [Table 4]

[0096] [Examples C1-C8, Comparative Examples C1-C2] Painting conditions were set as shown in Table 5, and painting was performed on a plastic plate on a horizontal surface using an automatic paint gun. The spraying angle was set to 90° (the painted surface of the object was perpendicular to the spray direction). The appearance of the paint film on the obtained painted objects was also evaluated. The results are shown in Table 5. In Table 5, the number in the "Recoating" column represents the number of coats.

[0097] [Table 5]

[0098] [Example D1] A paint gun 4 was used as an automatic spray gun to paint 2 on a horizontal plastic film and plastic sheet. The paint gun speed was 200 mm / s, the spray gun distance was 50 mm, the paint supply rate was 11 mL / min, the atomizing air pressure 1 was 0.040 MPa, the atomizing air pressure 2 was 0.034 MPa, the pattern air pressure 1 was 0.090 MPa, and the pattern air pressure 2 was 0.068 MPa. The paint was applied in 10 coats to obtain the painted object. The 10 coats were performed by shifting the painting center by 20 mm each time, making 2.5 back-and-forth motions for 5 coats, and then applying another 5 coats along the same trajectory. The spray angle was 90° (the painted surface of the object to be painted was perpendicular to the discharge direction). After drying, the appearance of the painted coating on the plastic sheet was evaluated and received a rating of 5. After drying, the film thickness of the coating on the plastic film was measured using a digital micrometer (manufactured by Shinwa Measuring Instruments Co., Ltd.). The results are shown in Figure 5. The coating obtained in Example D1 was a uniform coating with a thickness of 18 μm over an effective pattern of 60 mm.

[0099] [Noise measurement] The noise level during painting in Example C3 was measured to be 73 dB. On the other hand, when paint 2 was applied to an aluminum plate using paint gun 5 as an automatic spray gun 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 discharge rate) 310 mL / min), the noise level was measured to be 90 dB.

[0100] Although the present invention has been described in detail above, various modifications can be made to the above configuration without departing from the scope of the invention. Therefore, all matters included in the above description or shown in the accompanying drawings should be construed as illustrative. [Explanation of Symbols]

[0101] G: Automatic paint gun S: Atomized paint 11: Compressor 12: Needle valve operating air piping 13: Atomizing 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: Automatic paint gun internal switching valve operation air piping 21:Paint 22:Paint tank 23: Mass measuring device 24: Pump 25: Paint piping 26: Valve 27: Paint flow sensor

Claims

1. In a non-electrostatic air atomization painting method using an automatic paint gun, the following requirements (1) and (2): (1) Coating efficiency of 80% or more, (2) Gun distance is 20mm to 90mm, Satisfying the conditions, Furthermore, the following requirements (3a) and / or (3b): (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. The painting method that satisfies the requirements.

2. Furthermore, 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, according to the Iwata Cup method, is between 5 seconds and 13 seconds. (6) The paint contains one or more organic solvents, including ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, wherein the evaporation rate of the organic solvent is 140 or more and 1100 or less, with the value of butyl acetate set to 100. (7) The paint contains one or more organic solvents, which are ketone-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, ether-based organic solvents, and aliphatic hydrocarbon-based organic solvents, and which have a boiling point of 150°C or higher at a pressure of 0.1 MPa. The painting method according to claim 1, which satisfies one or more of the following requirements.

3. The painting method according to claim 1 or 2, wherein multiple coats are applied.

4. The painting method according to claim 1 or 2, wherein multiple coats are applied so that the center positions of the paints are different.

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