JPH0626697B2 - Cleaning method for paint transfer pipe - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating material that remains adhered in a coating material transfer pipe used in a coating line for vehicles, electric appliances, various devices, and the like.
The present invention relates to a method for cleaning the inside of the pipe by effectively removing contaminants such as pigments, rust and dust.

2. Description of the Related Art In a coating line for vehicles, electric appliances, various devices, etc., paint is delivered from a paint mixing room (mixing room) to a branch pipe in a paint booth through a paint transfer pipe (circulation pipe). It is applied to an object to be coated such as a vehicle body through an automatic painting machine or a painting gun connected to the branch pipe, and excess paint is returned to the paint preparation room.

In this case, not only rusting occurs with time in the paint transfer pipe, but also paints, pigments, fiber scraps, and dust-rich contaminants adhere and remain. Such paint solids, pigments,
Rust and contaminants are entrained by the paint flowing in the pipe and are deposited on the surface of the object to be coated, resulting in a coating failure. Therefore, a regular cleaning process in the pipe and / or a cleaning process before feeding a newly prepared paint. Is a process that cannot be omitted.

A conventional mainstream cleaning method is a circulation co-cleaning method in which a cleaning thinner is normally circulated in a paint transfer pipe for about 0.5 months to 1 month, but paints, pigments, rust, etc. adhered to the inner wall of the pipe. Can hardly be removed.

In addition, the high-pressure water washing method and the pig washing method are also used in some parts, but the paint transfer pipe has a small diameter (1 /
8 to 2 inches), long (50 to 1000 m), has many bent portions, and has low pressure resistance, so that the range of application of such a cleaning method is narrow and a satisfactory cleaning effect cannot be obtained.

Further, a cleaning method using a solvent type paint remover or an inorganic acid has been proposed, but it is not expected to sufficiently remove the complex stain-adhering residue consisting of paint, pigment, rust and other impurities.

As described above, the conventional cleaning method cannot sufficiently remove the paint, pigment, rust, and other contaminants that stick and remain in the paint transfer pipe. For this reason, in the past, in order to repair coating defects due to such complex contamination adhesion residue, the coated object is subjected to sandpaper scrubbing and repainting treatment, but such repair treatment requires a large amount of extra work. Need a cost.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention has been made to provide a method for effectively removing from the paint transfer pipe the above-mentioned complex stain-adhering residue that causes a paint failure requiring a repair treatment. It is a thing.

Means for Solving the Problems That is, in the present invention, in cleaning the inside of the paint transfer pipe, the inside of the pipe is first treated with a paint remover, and then treated with an acid, and then a flushing treatment is performed. Further, the present invention relates to a method for cleaning the inside of a paint transfer pipe, which is characterized by performing a water replacement process.

As the paint remover used in the present invention, a conventionally known solvent type, for example, a chlorine-based solvent (e.g., methylene chloride, trichlene, 1,1,1-trichloroethane, tetrachloroethylene, etc.) in monoethanolamine, diethanolamine, Triethanolamine, phenol, formic acid,
A paint remover containing oxalic acid, acetic acid, sulfuric acid, nitric acid, hydrofluoric acid, paraffin wax, a surfactant, a thickener, etc. may be used, but is it difficult to remove the paint adhered to the pipe wall? Alternatively, since the adhered coating material is swollen and peeled off, the subsequent filtration treatment becomes difficult, and the coating film of the coating material in the coating factory shrinks due to the chlorine-based solvent vapor, which is not very practical.

The most preferable paint remover used in the present invention is an aqueous solution of an alkali that does not bring about these problems, that is, an alkali such as sodium hydroxide or potassium hydroxide is a water-soluble solvent, for example, methanol, ethanol or diethylene glycol. It is a solution dissolved in monomethyl ether or ethylene glycol monomethyl ether.

The above solution can be prepared by dissolving an alkali in an appropriate amount of water and diluting this with a water-soluble solvent. The alkali concentration in the paint remover is preferably 5 to 50% by weight, and the water-soluble solvent therein is preferably 10 to 40% by weight.

The concentration of such a water-soluble alkali solution used depends on the degree of contamination of the pipe to be treated and the type of paint adhered to the pipe wall, and is not particularly limited, but the alkali concentration in the paint remover is, for example, 25 At 5% by weight, the paint remover is usually about 5
It is used by diluting with 100%, preferably about 40 to 60% with water.

If desired, a chelating agent (eg, EDTA, NTA, sodium citrate, etc.) may be added to the aqueous solution of alkali in a solvent.
Additives such as a peeling accelerator (for example, monoethanolamine, diethanolamine, triethanolamine, etc.), a rust preventive (for example, sodium nitrite, sodium phosphate, sodium borate, organic acid salt, etc.) may be appropriately blended. .

The paint removing agent is circulated in the paint transfer pipe by using a circulation device. As the circulation device, any one known per se may be used, and the capacity and material of the circulation device are appropriately selected in consideration of the diameter and length of the paint transfer pipe and the type of paint remover. In addition, from the standpoint of avoiding the time and economic loss associated with the on-site assembly work of circulation equipment and ensuring a certain cleaning grade and work safety by standardizing cleaning work, tanks, pumps, filtration equipment, etc. are integrated. It is preferable to use a unit circulation device incorporated in the.

The circulating temperature, circulating time, and circulating speed of the paint remover may be appropriately selected according to the type and concentration of the paint remover and the degree of contamination in the pipe to be treated, etc., but are not particularly limited, but usually from room temperature to about 90 ° C, about 0.5-8 hours and about 0.5-3 m / sec.

By the treatment process using the above paint remover, the adhered paint on the inner wall of the pipe is almost completely dissolved and removed. After this treatment step is completed, the treatment agent containing the dissolved coating material is discharged to the outside of the system, the inside of the pipe is washed with water, and the process proceeds to the next acid treatment step.

The acid treatment step is mainly performed to remove the pigment and rust that are not removed by the above paint remover but remain on the pipe wall.

The most suitable acid is an inorganic acid such as hydrochloric acid, sulfuric acid, hydrofluoric acid, phosphoric acid, sulfamic acid, etc., but when the amount of pigment or rust deposited on the pipe wall is small, organic acids such as citric acid or tartaric acid are used. Acids can also be used.

The concentration of the acid used depends on the type of the acid, the residual amount of pigment, rust, etc. deposited, and is not particularly limited.
%, Preferably about 5-20%.

If desired, the acid treating agent may be a corrosion inhibitor such as thiourea,
Diethyl thiourea, mercaptan, sulfide, oxalic acid, sodium hexametaphosphate and the like may be appropriately mixed.

The acid treatment agent is circulated in the paint transfer pipe by using the above circulation device. The circulation temperature, circulation time and circulation speed of the acid treating agent may be appropriately selected depending on the type and concentration of the acid and the residual amount of deposit such as pigment and rust.
60 ° C., about 0.5-4 hours and about 0.5-3 m / sec.

By the above acid treatment step, the pigment and rust remaining on the inner wall of the paint transfer pipe are almost completely removed. After this acid treatment step is completed, the acid treatment agent containing pigment and rust is discharged out of the system, the inside of the pipe is washed with water, and the pair of flushing treatment steps is performed. A flushing process is performed in order to remove other contaminants such as paint residues, rust pieces, and dust remaining on the inner wall of the pipe even after the treatment process using the paint removing agent and the subsequent treatment process using an acid.

Although only water may be used as the flushing agent, it is preferable to use an aqueous solution of the rust preventive agent (usually about 0.5 to 10%) to prevent rusting of the inner wall of the pipe cleaned by the above-mentioned treatment step. .

As rust preventive agents, sodium nitrite, sodium phosphate,
Examples include monoethanolamine, diethanolamine, triethanolamine, boron compounds, amine salts of organic acids, etc., and amine salts of organic acids that are soluble in the water displacing agent used in the subsequent water displacing step are preferable.

The flushing agent is also circulated in the paint transfer pipe by using the above-mentioned circulation device, and other contaminants such as paint residues, rust pieces and dust that are conveyed are captured by the filtration device, and the filter is appropriately replaced.

The circulation temperature, circulation time and circulation speed of the flushing agent are not particularly limited, but usually about 0 to 50 ° C.,
It is about 5 to 24 hours and about 0.5 m / sec or more (preferably about 1.5 to 7.0 m / sec). Especially the flow velocity is 0.5m
If the flow rate is less than 1 / sec, the flushing effect is weak, and if it is more than 7 m / sec, there are problems in terms of load on the joint portion of the paint transfer pipe, pressure resistance, and economical efficiency.

However, if the pipe can withstand, it is also possible to perform the flushing by increasing the transfer pressure.

By the above-mentioned flushing process step, contaminants such as paint residue, rust pieces, and dust remaining in the paint transfer pipe are almost completely removed. After this treatment process is completed, the flushing agent is discharged to the outside of the system, and the process proceeds to the next water replacement process.

The water replacement is carried out in order to remove the water remaining in the paint transfer pipe after the above-mentioned treatment process. Moisture mixed in the paint is one of the causes of coating film failure, and the water replacement process in the pipe is performed so that the water content is usually about 0.5% or less.

Suitable as the water displacing agent is a water-soluble low-boiling organic solvent,
For example, methanol, ethanol, isopropyl alcohol, acetone and the like.

Water replacement is carried out by circulating such a water displacing agent in the paint transfer pipe using the above-mentioned circulation device. The circulation rate, circulation time, and circulation rate of the water displacing agent are not particularly limited, but usually about 0 to 40 ° C. and about 0.5, respectively.
~ 2 hours and about 0.5-3 m / sec.

After the completion of the water replacement step, the water replacement agent in the pipe is discharged to the outside of the system to complete the method for cleaning the paint transfer pipe in the present invention.

Hereinafter, the present invention will be described with reference to examples.

Example Example 1 Paint transfer pipe for automobile coating line (melamine resin-based paint feed operation days: 1 year, material: STPG, pipe inner diameter:
First, the paint remover is circulated using a unit circulation device that integrally incorporates a tank, a pump, a filtration device, etc. (1 inch, total length of pipe: 400 m) (paint remover composition: potassium hydroxide, diethylene glycol monoethyl ether). , Monoethanolamine, organic acid salt, circulation temperature: 50
C., circulation time: 3 hours, circulation speed: 1.7 m / sec), after the removal agent was discharged out of the system, the inside of the pipe was washed with water, and then the acid treatment agent was circulated (acid treatment agent composition: phosphorus Acid, thiourea, sodium hexametaphosphate), circulation temperature: 45 ° C., circulation time: 1 hour, circulation speed: 1.7 m / sec), after the acid treatment agent is discharged out of the system, the inside of the pipe is washed with water. did. Subsequently, the flushing agent was circulated (composition of flushing agent: monoethanolamine, pt-butyl benzoic acid, circulation temperature: 35 ° C., circulation time: 16 hours, circulation speed: 3.1 m
/ Sec), the flushing agent was discharged to the outside of the system, and then the water in the pipe was replaced (water displacement agent: isopropyl alcohol, circulation temperature: 26 ° C., circulation time: 0.5 hour, circulation speed 1 0.7 m / sec), and a clean inner wall surface of the pipe appeared. When the number of dust in the contamination kit was examined for the final washing solution, it was as follows: 50 μm or more dust ... 0 40-50 μ dust ... 0 30-40 μ dust ... 2 10 to 20μ of dust ... 5 10μ or less of dust ... 2 A car body that uses paint transfer piping that has been subjected to the above cleaning treatment was painted with melamine resin-based paint, and a paint filter (300 mesh) Was not clogged at all. Moreover, when the foreign substances on the painted surface were examined with the naked eye,
Only a few points were observed, and no other paint defects were observed.

Comparative Example 1 A paint thinner was used at room temperature in the same manner as in Example 1 in a paint transfer pipe that had passed the same paint feeding operation days as in Example 1.
It was circulated for a day (circulation speed: 3.1 m / sec), but no clean inner wall of the pipe appeared.

The number of dust in the contamination kit of the final washing solution was examined and the results were as follows. : 50μ or more dust ... 1 40-50μ dust ... 4 30-40μ dust ... 20 10-20μ dust ... 36 10μ or less dust ... innumerable this thinner cleaning treatment When the car body was painted with melamine resin-based paint using the paint transfer pipe attached to
Paint filter (300 mesh) is 1 for clogging
I had to replace it once a day. Moreover, when foreign substances on the coated surface were examined with the naked eye, about 40 to 60 points were observed.

EFFECTS OF THE INVENTION According to the cleaning method of the present invention, it is possible to effectively remove contaminants such as paints, pigments, rust, and dust that cause coating defects from the paint transfer pipe. Even if it is reused, the paint filter does not become clogged, and there is no need for a repair process after painting due to the accumulation of foreign substances on the surface of the coated product.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taketaro Katayama 1-27-17 Hamamatsucho, Minato-ku, Tokyo Within Neos Co., Ltd. (56) Reference JP-A-1-109873 (JP, A)

Claims (5)

[Claims] 1. When cleaning the inside of a paint transfer pipe, the inside of the pipe is first treated with a paint remover, then treated with an acid, and then flushed and then replaced with water. A method for cleaning the inside of a paint transfer pipe, which is characterized by: 2. The method according to claim 1, wherein the paint removing agent is a solution of an alkali in an aqueous solvent. 3. The method according to claim 1, wherein the acid is an inorganic acid. 4. The method according to claim 1, wherein the flushing treatment is performed using an aqueous solution of a rust preventive agent. 5. The method according to claim 1, wherein the water replacement treatment is carried out using a water-soluble low boiling point organic solvent.