JP2000290544A - Washing coating line for aqueous paint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow washing and removal of adhering aqueous paint for a short time and increase coating efficiency by washing and removing the aqueous paint adhering to a pipe for transporting the paint and a coating machine with an aqueous solution containing water and an hydrophilic organic solvent and having pH adjusted in a specific range. SOLUTION: In a process of continuously coating an item with two kinds of colored aqueous paints by turns in the same line, the aqueous paint A goes from a paint tank to a color changer via a circulation pipe and a valve is opened to send the paint under a pressure to a coating machine by which the paint is sprayed on an item to be coated with. When the coating is finished, the valve is closed and a valve for washing is opened to wash and remove the paint remaining in the coating machine, the inner side of the pipe and the like and 10 to 30 seconds later a paint B is sent under a pressure to the coating machine and is sprayed on the item to be coated with. The washing solution is a mixture of 50 to 99% by weight of water and 1 to 50% by weight of a hydrophilic organic solvent such as isopropyl alcohol and pH of the washing solution is adjusted at 9 to 13 by adding a pH adjusting agent such as 2- aminopropanol or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a coating line capable of easily cleaning and removing a water-based paint adhering to a paint transport pipe or a coating machine in a water-based paint coating line.

[0002]

2. Description of the Related Art A coating line for water-based paint usually comprises a paint tank, a circulation pipe, a color changer, a coating machine and the like. The circulation pipe is of a circulation type so that the aqueous paint in the paint tank returns to the original paint tank via the color changer.

[0003] An outline in which two types of water-based paints a and b are successively applied to separate workpieces in one coating line will be described. A dedicated paint tank and a circulation pipe for each of the paint a and the paint b are provided, and these two suction pipes are connected to one color changer. First, paint a
The paint tank reaches the color changer through a circulation pipe, where the valve a is opened and the hose is pumped through a hose to a coating machine (for example, a bell type electrostatic coating machine), where the spray is sprayed. The object to be coated a is painted. afterwards,
The valve a is closed, the valve s for the cleaning liquid connected to the color changer is opened, and the paint a remaining on the inside of the hose from the valve a to the coating machine and at the tip of the coating machine is removed. After that, from the paint tank,
The paint b sent to the color changer through the suction pipe is opened by opening the valve b and fed to the coating machine through the hose, where the paint b is sprayed to coat the workpiece b.

[0004] In such a coating line, the object to be coated is continuously carried in. Therefore, after the coating of the coating material a is completed,
The interval from the start of the coating of the paint b is usually very short, about 10 to 30 seconds. During that time, the valve s for the cleaning liquid is opened as described above, and -It is necessary to wash and remove the paint a remaining in the inside of the coating and at the tip of the coating machine.

Until now, this cleaning solution has been used in the form of water 80 to 9
A mixture of 0% by weight and 20 to 10% by weight of a hydrophilic organic solvent (eg, isopropyl alcohol or butyl cellosolve) has been used. However, the solubility of the remaining paint is not sufficient, and It is difficult to remove by washing, and it is often recognized that the finished appearance, coating efficiency and the like are reduced, and improvement of washing efficiency is strongly desired.

[0006]

SUMMARY OF THE INVENTION According to the present invention, when two or more water-based paints are successively applied in the above-mentioned coating line, the water-based paints previously applied and remaining are quickly and quickly cleaned. The purpose is to improve the coating efficiency, which can be removed. As a result of diligent research, it contains water and a hydrophilic organic solvent as a cleaning solution, and has a pH of 10 to 10.
It has been found that the object can be achieved by using an aqueous liquid adjusted within the range of 13, and the present invention has been completed.

That is, according to the present invention, in a water-based paint coating line, a water-based paint adhered to a paint transport pipe, a coating machine, or the like, contains water and a hydrophilic organic solvent and has a pH of 10 to 13. The present invention provides a method for cleaning a coating line for a water-based paint, which is characterized by washing and removing with an aqueous liquid adjusted to fall within the range.

[0008] The method for cleaning a coating line of a water-based paint according to the present invention will be described below in more detail.

The water-based paint applicable in the method of the present invention is a liquid paint containing water as a main dispersion medium or solvent, and may contain an organic solvent. Specifically, it is a room temperature drying type or a heat curing type containing a coating resin, and includes a solid color type, a metallic type, a clear type, an undercoating, an intermediate coating and an overcoating. The solid content of these paints is suitably in the range of 20 to 80% by weight, and the viscosity at the time of painting can be arbitrarily selected depending on the painting equipment and the like. In this method, using two or more water-based paints,
It is preferable to use these in the step of painting on the same painting line. The coating line may be any as long as a plurality of water-based paints are sequentially applied to different objects to be coated on the same line.
For example, after the water-based paint a is applied to the object a on the same line, then the water-based paint b is applied to the object b. Specifically, there is a known coating line composed of a paint tank, a circulation pipe, a color changer, and a coating machine. The paint tank stores the water-based paint to be used for painting, and is provided in the same number or more as the paint used. The circulation pipes are circulation pipes which return from the respective paint tanks to the original paint tanks again via the color changer, and are provided with the same number or more as the number of paints to be used. In principle, one color changer is used in one coating line. Each color changer communicates with an individual suction pipe and is provided with a valve for discharging each paint.

As a specific example, an outline of a coating line will be described based on a process of successively and alternately applying two types of colored water-based paints a and b on the same coating line. A water-based paint a flows from a paint tank through a circulation pipe to form a color.
After reaching the changer, the valve a attached thereto is opened, and the coating machine (for example, a bell type electrostatic coating machine) is opened through a hose.
, Where it is spray-coated on the object a. After that, the valve a is closed, the valve s for the cleaning liquid connected to the color changer is opened, and the valve a is left inside the hose from the valve a to the coating machine and at the tip of the coating machine. After the paint a is removed by washing, the paint b sent from the paint tank to the color changer through the circulation pipe is opened by opening the valve b, and fed to the coating machine via the hose. The object b is sprayed and painted. In this coating line, since the objects to be coated are continuously carried in, the interval from the end of the coating of the coating a to the start of the coating of the coating b is usually very short, about 10 to 30 seconds. In the meantime, it is necessary to wash and remove the paint a remaining in the hose and the tip of the coating machine.

The feature of the present invention is that, for example, a washing liquid for washing and removing the paint a remaining in the hose and at the tip of the coating machine contains "water and a hydrophilic organic solvent, Aqueous solution adjusted to a range of 10 to 13 ", which has excellent solubility of the remaining paint, enables all to be washed and removed in a short time, and gives a finished appearance and The coating efficiency was improved, and the above demand was satisfied.

The washing liquid used in the present invention is an aqueous liquid containing water and a hydrophilic organic solvent and having a pH adjusted within the range of 10 to 13, and includes water, a hydrophilic organic solvent and p
It is an aqueous solution comprising an H adjuster.

The water is preferably deionized water, and the hydrophilic organic solvent is an organic solvent which dissolves in water at 20 ° C. without any limitation, for example, chlorinated carbon such as ethylene chlorohydrin and propylene chlorohydrin. Hydrogen-based;
Diethyl glycol monomethyl ether, diethyl glycol monoethyl ether, methoxy triglycol acetate, methyl lactate, methyl lactate, dioxolan,
Dioxane, ethylene glycol monomethyl ether,
Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether
Ether systems such as ter, diethylene glycol diethyl ether, and diethylene glycol monobutyl ether;
Methyl alcohol, ethyl alcohol, allyl alcohol
, N-propyl alcohol, isopropyl alcohol
And alcohols such as tert-butyl alcohol and ethylene glycol; and ketones such as acetone and diacetone alcohol. Of these, isopropyl alcohol and ethylene glycol monobutyl ether (butyl cellosolve) are particularly preferred. As the pH adjuster, an alkaline compound can be used. For example, hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide; ammonia; ethylamine , Propylamine, butylamine, benzylamine,
Monoethanolamine, neopentanolamine, 2-
Primary monoamines such as aminopropanol, 3-aminopropanol and 2-aminomethylpropanol; diethylamine, diethanolamine, di-n- or di-is
Secondary monoamines such as o-propanolamine, N-methylethanolamine and N-ethylethanolamine; tertiary monoamines such as dimethylethanolamine, trimethylamine, methyldiethanolamine and dimethylaminoethanol; diethylenetriamine, hydroxy And polyamines such as ethylaminoethylamine.

In the washing liquid used in the present invention, the ratio of water to the hydrophilic organic solvent is based on the total weight of both components.
Water is preferably in the range of 50 to 99%, particularly 75 to 98%, and the hydrophilic organic solvent is preferably in the range of 50 to 1%, especially 25 to 2%.
The H adjusting agent has a pH of the washing solution of 10 to 13, particularly 11 to 1
A degree within the range of 2.5 is suitable. Cleaning solution pH
However, if the amount deviates from this range, the cleaning properties of the remaining paint are reduced, and the object of the present invention cannot be achieved.

[0015] The method of the present invention is, for example, a method in which a water-based paint a is applied to an object a continuously on the same line, and then the water-based paint b is applied to the object b. a reaches the color changer through the circulation pipe from the paint tank, is fed to the coating machine through the valve a, and is spray-coated with the object a. Then, the valve a is closed and the color changer is closed. The cleaning liquid valve s is opened to allow the cleaning liquid to flow out, and a valve from the valve a to the coating machine is opened.
After the paint a remaining in the interior of the coating machine and at the tip of the coating machine is removed by washing, the coating b sent to the color changer is similarly opened to the coating machine through the hose by opening the valve b. An aqueous liquid containing the above-mentioned water and a hydrophilic organic solvent and having a pH adjusted within a range of 10 to 13 is used as a cleaning liquid in a coating line in which the object to be coated b is sprayed under pressure and sprayed. I do.

[0016]

As described above, the use of the above-mentioned specific liquid as a cleaning liquid has excellent solubility in the residual water-based paint, and remains in the interior of the hose from the valve to the coating machine and at the tip of the coating machine. It was possible to easily and easily remove the paint in a short time, improve the finished appearance and coating efficiency, etc., and satisfied the demand.

[0017]

EXAMPLES Examples and comparative examples according to the present invention will be described below. All parts and percentages are by weight.

Example 1 A water-based paint (Note 1) was applied to a tin plate by spraying so as to have a film thickness (uncured coating film) of about 100 μm.
The coated test plate dried for 4 hours was immersed in a stationary washing solution (Note 2) at 20 ° C. for 3 minutes and 5 minutes, and the removability of the coating film was observed. Further, the coated test plate was immersed in a cleaning liquid (Note 2) at 20 ° C., and immediately after the coated test plate was manually shaken in the liquid for 20 seconds, the coated surface was observed. The results are shown in Table 1. In Table 1, .largecircle. Indicates that the film could be completely removed by washing, .largecircle. Indicates that a small amount of the coating remained on the tin plate, and x indicates that most of the coating remained on the tin plate.

Example 2 A water-based paint (Note 1) was applied to a tin plate by spraying so as to have a film thickness (uncured coating film) of about 100 μm.
The test plate dried for 4 hours was immersed for 3 minutes and 5 minutes in a stationary washing solution (Note 3) at 20 ° C., and the removability of the coating film was observed. Further, the coated test plate was immersed in a washing solution (Note 3) at 20 ° C., and immediately after the coated test plate was manually shaken in the liquid for 20 seconds, the coated surface was observed. The results are shown in Table 1.

Example 3 A water-based paint (Note 1) was applied to a tin plate by spraying so as to have a film thickness (uncured coating film) of about 100 μm.
The test plate dried for 4 hours was immersed in a stationary washing solution (Note 4) at 20 ° C. for 3 minutes and 5 minutes, and the removability of the coating film was observed. Further, the coated test plate was immersed in a washing liquid (Note 4) at 20 ° C., and immediately after the coated test plate was shaken by hand in the liquid for 20 seconds, the coated surface was observed. The results are shown in Table 1.

COMPARATIVE EXAMPLE 1 An aqueous paint (Note 1) was applied to a tin plate by spraying so as to have a film thickness (uncured coating film) of about 100 μm.
The test plate dried for 4 hours was immersed in a stationary washing solution (Note 5) at 20 ° C. for 3 minutes and 5 minutes, and the removability of the coating film was observed. Further, the coated test plate was immersed in a washing liquid (Note 5) at 20 ° C., and immediately after the coated test plate was manually shaken in the liquid for 20 seconds, the coated surface was observed. The results are shown in Table 1.

(Note 1) Aqueous paint: A white paint containing a polyester resin and a melamine resin, and has a solid content of 50% when applied by spraying.

(Note 2) Washing solution: 2-aminomethylpropanol was added to a mixture of 90% deionized water, 5% isopropyl alcohol and 5% butyl cellosolve at a pH of 1
Liquid added to 1.9.

(Note 3) Washing solution: 2-aminomethylpropanol was added to a mixture of 90% deionized water, 5% isopropyl alcohol and 5% butyl cellosolve at a pH of 1%.
2. Liquid added to be 2.1.

(Note 4) Washing solution: 2-aminomethylpropanol having a pH of 1 was added to a mixture of 90% deionized water, 5% isopropyl alcohol, and 5% butyl cellosolve.
Liquid added to 2.3.

(Note 5) Washing solution: a mixed solution (pH 5.3) consisting of 90% of deionized water, 5% of isopropyl alcohol, and 5% of butyl cellosolve.

[0027]

[Table 1]

Claims (1)

[Claims] In a water-based paint coating line, a water-based paint attached to a paint transport pipe, a coating machine, or the like is adjusted to contain water and a hydrophilic organic solvent and to have a pH within a range of 9 to 13. A method for cleaning a water-based paint coating line, characterized by washing and removing with an aqueous liquid.