JPS63256163A - Method for cleaning inside of paint transfer piping - Google Patents

Abstract

PURPOSE:To effectively remove composite solid contaminating residues from the inside of a paint transfer piping by treating the inside of the paint transfer piping with a paint removing agent first, then treating the same with an acid and subjecting the inside of the piping to a flashing treatment and further to a water replacement treatment. CONSTITUTION:The inside of the paint transfer piping is first treated with the paint removing agent consisting of a water soluble alkaline solvent soln. The inside of the piping is then treated with the inorg. acid and is thereafter subjected to the flashing treatment with the aq. soln. of a rest inhibitor such as sodium nitrite. The inside of the piping is further subjected to the water replacement treatment with a water soluble low boiling point org. solvent such as methanol. As a result, extraneous materials such as paints, pigments, rust and dust which are the cause for defective painting are effectively removed from the paint transfer piping. Clogging of a paint filter is thereby obviated even if the paint transfer piping after the cleaning is reused; in addition, there is no need for a post-painting repair treatment by deposition of the extraneous materials on the surface of the painted articles.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applied to paints, pigments, rust, dust, and other contaminants that remain in paint transfer pipes used in painting lines for vehicles, electrical products, various types of equipment, etc. The present invention relates to a method of cleaning the inside of the pipe by effectively removing substances.

Conventional technology In painting lines for vehicles, electrical products, various equipment, etc., paint is sent from the paint preparation room (mixing room) through the paint transfer pipe (circulation vibe) to the branch pipe in the paint booth. The object to be coated, such as a car body, is coated via an automatic paint machine or a paint gun connected to the branch pipe, and excess paint is returned to the paint preparation room.

In this case, not only rust develops over time in the paint transfer pipe, but also paint, pigment, and foreign matter such as fiber waste and dust remain firmly attached to the pipe. Such paint solidified products, pigments,
Rust and foreign substances are carried by the paint flowing in the pipes and deposited on the surface of the object to be coated, resulting in poor coating, so cleaning the pipes at regular intervals and/or before supplying a newly formulated paint is necessary. is a process that cannot be omitted.

The mainstream cleaning method in the past is a circulating coprecipitation method in which cleaning thinner is circulated within the paint transfer piping for typically 0.5 to 1 month. It is almost impossible to remove paint, pigments, rust, etc. that are stuck to the inner walls of pipes.

In addition, high-pressure water washing methods and pig washing methods are also used in some cases, but the diameter of the paint transfer piping is small (l
/8 to 2 inches), long (50 to 10,100 degrees), has many bent parts, and has low pressure resistance, so the range of application of this cleaning method is narrow and a satisfactory cleaning effect cannot be obtained.

Additionally, cleaning methods using solvent-based paint removers or inorganic acids have been proposed, but these methods cannot be expected to sufficiently remove complex contaminant-fixed residues consisting of paint, pigments, rust, and other contaminants.

As described above, conventional cleaning methods cannot sufficiently remove paint, pigments, rust, and other impurities that remain stuck in the paint transfer pipe.

For this reason, conventionally, painted objects are sandpapered and repainted to repair paint defects caused by such complex contamination and fixed residues, but such repair processing requires a great deal of extra time and effort. Requires cost.

PROBLEMS TO BE SOLVED BY THE INVENTION The present invention provides a method for effectively removing from paint transfer piping the complex contaminant-fixed residue described in item 1- above, which causes coating defects requiring repair treatment. It has been done.

Means for solving the problem, that is, the present invention, when cleaning the inside of the paint transfer pipe, first treats the inside of the pipe with a paint remover, then with an acid, and then performs a flushing process, The present invention further relates to a method for cleaning the inside of a paint transfer pipe, which is characterized by carrying out a water displacement process.

The paint remover used in the present invention is a conventionally known solvent type, such as chlorinated solvents (e.g., methylene chloride, trichlene, 1,1.1-)lychloroethane, tetrachlorethylene, etc.), monoethanolamine, jetanol, etc. Paint removers containing amines, triethanolamine, phenol, formic acid, oxalic acid, acetic acid, sulfuric acid, nitric acid, hydrofluoric acid, paraffin wax, surfactants, thickeners, etc. may be used; The problem is that the removability of adhered paint is poor, or that the adhered paint swells and peels off, making subsequent filtration processing difficult.Furthermore, chlorinated solvent vapor causes the problem of shrinkage of the paint film of painted objects in the paint factory. Not very practical.

The most suitable paint remover for use in the present invention is an aqueous solution of an alkali that does not cause these problems, i.e., an alkali such as sodium hydroxide or potassium hydroxide is mixed with a water-soluble solvent such as methanol, ethanol, diethylene glycol, etc. This is a solution dissolved in monomethyl ether or ethylene glycol monomethyl ether.

The concentration of such an aqueous alkaline solvent solution depends on the degree of contamination of the pipe to be treated, the type of paint stuck to the pipe wall, etc., and is not particularly limited, but is usually about 5 to 100%, preferably It is about 40-60%.

The alkaline aqueous solvent solution optionally contains a chelating agent (for example, EDTA, NTA, sodium citrate, etc.),
Additives such as release accelerators (e.g. monoethanolamine, jetanolamine, triethanolamine, etc.) and rust preventive agents (e.g. sodium nitrite, sodium phosphate, sodium borate, organic acid salts, etc.) are appropriately added. Good too.

The above paint remover is circulated within the paint transfer pipe using a circulation device. Any known circulation device 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, the type of paint remover, etc. In addition, from the viewpoint of avoiding time and economic losses associated with on-site assembly of circulation equipment and ensuring a certain level of cleanliness and work safety by standardizing cleaning work, tanks, pumps, filtration equipment, etc. Preferably, an integrally integrated unit circulation device is used.

The circulation temperature, circulation time, and circulation speed of the paint remover may be appropriately selected depending on the type and concentration of the paint remover, the degree of contamination in the pipes to be treated, etc., and are not particularly limited. 90° C. for about 0.5 to 8 hours and about 0.5 to 3 IIl/sec.

By the treatment process using the above-mentioned 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 paint is discharged from the system, the inside of the piping is washed with water, and the next acid treatment step is started.

The acid treatment process mainly removes pigments that are not removed by the paint remover mentioned above and remain deposited on the pipe wall soil. This is done to remove +'t.

The most suitable acids are inorganic acids such as hydrochloric acid, sulfuric acid, hydrofluoric acid, phosphoric acid, and sulfamic acid, but if there is a small amount of pigment or rust deposited on the pipe wall, organic acids such as citric acid or tartaric acid are most suitable. You can also use acid.

The concentration of acid used depends on the type of acid and the amount of deposited residual pigment and rust, etc., and is not particularly limited, but is usually about 1 to 50%.
, preferably about 5-20%.

The acid treatment agent may optionally contain a corrosion inhibitor such as thiourea,
Diethylthiourea, mercaptan, sulfide, sikolic acid, sodium hexametaphosphate, etc. may be blended as appropriate.

The acid treatment agent is circulated within the paint transfer pipe using the above circulation device. The circulation temperature, circulation time, and circulation speed of the acid treatment agent may be appropriately selected depending on the type and concentration of the acid and the amount of deposited residual pigments, rust, etc.
60° C. for about 0.5 to 4 hours and about 0.5 to 3 m/sec.

By the above acid treatment step, the pigment and rust deposited and remaining on the inner wall t of the paint transfer pipe are almost completely removed. After this acid treatment step is completed, the acid treatment agent containing pigments and insects is discharged from the system, the inside of the piping is washed with water, and the next flushing treatment step is started. A flushing process is performed to remove paint residue, debris, dust, and other impurities that remain on the inner wall of the piping even after the treatment process using the paint remover and the subsequent treatment process using an acid.

Although water alone may be used as the flushing agent, it is preferable to use an aqueous solution of a rust preventive agent (usually about 0.5% to 10%) to prevent rust from forming on the inner walls of the pipes cleaned by the above treatment process. .

Rust inhibitors include sodium nitrite, sodium phosphate,
Examples include monoethanolamine, noethanolamine, triethanolamine, boron compounds, amine salts of organic acids, etc., and amine salts of organic acids that dissolve in the water displacement agent used in the subsequent water displacement step are preferred. be.

The flushing agent is also circulated through the paint transfer piping using the above-mentioned circulation device, and other impurities such as paint residue, scraps, and dust are captured by the filtration device, and the filter is replaced as appropriate.

The circulation temperature, circulation time and circulation speed of the flushing agent are also not particularly limited, and are usually about 0 to 50°C, respectively.
1 about 5 to 24 hours and about 0.5 m7 seconds or more (preferably about 1.5 to 7.0 m/sec).

In particular, the flanging effect is weak when the flow velocity is less than 05 m/s.
If it exceeds 7 m/sec, it is not preferable because it causes problems in terms of load on the joints of the paint transfer piping, pressure resistance, economic efficiency, etc.

By the above flushing treatment process, impurities such as paint residue, end pieces, and dust remaining in the paint transfer pipe are almost completely removed. After this treatment step is completed, the flushing agent is discharged from the system and the next water replacement step is started.

Water replacement is performed to remove moisture remaining in the paint transfer pipe after the above-mentioned treatment process is completed. Moisture mixed into paint is one of the causes of paint film defects, and water replacement treatment in piping is usually performed to reduce the water content to about 0.5% or less.

Suitable water displacing agents include water-soluble low-boiling organic solvents;
Examples include methanol, ethanol, isopropyl alcohol and acetone.

Water replacement is performed by circulating such a water replacement agent through the paint transfer pipe using the above-mentioned circulation device. Although the circulation temperature, circulation time, and circulation speed of the water displacing agent are not particularly limited, they are usually about 0 to 40°C.
5-2 hours and approximately 0°5-3 m/sec.

After the water displacement step is completed, the water displacement agent in the pipe is discharged to the outside of the system, thereby completing the cleaning method for the paint transfer pipe according to the present invention.

Hereinafter, the present invention will be explained by examples.

Example: Paint transfer piping for the painting line of a parking garage at Hitake (delivery of melamine resin paint. Operation days: 1 year, material: 5TPO, inner diameter of 1 pipe.
1 inch, total length of pipe: 400 m), the paint remover is first circulated using a unit circulation system that integrally incorporates a tank, pump, filtration device, etc. (paint remover composition: potassium hydroxide, diethylene glycol monoethyl ether) , monoethanolamine, (T-acid salt, circulation temperature = 5
0°C, circulation time = 3 hours, circulation speed + 1.7 m/s),
After discharging the removal agent out of the system, the inside of the piping was washed with water, and then the acid treatment agent was circulated (acid treatment agent composition: diphosphoric acid, thiourea, sodium hexametaphosphate), circulation temperature: 45 ° C., circulation time. : 1 hour, circulation speed: 1.7 m/sec) After the acid treatment agent was discharged from the system, the inside of the piping was washed with water.

Continue to circulate the flushing agent (flushing agent composition: monoethanolamine, pt, butylbenzoic acid,
Circulation temperature: 35℃, circulation time: 16 hours, circulation speed: 3
, 1 m7 seconds), after discharging the flushing agent out of the system, the water in the piping was replaced (water replacement agent:
Isopropyl alcohol, circulation temperature: 26°C, circulation time 20.5 hours, circulation rate = 1°71 Tl/sec), clean inner wall surface of the pipe was cleaned.

In addition, when we investigated the number of dust in the contamination kit for the final cleaning solution, it was as follows;
...0 Dust of 40-50μ...0 Dust of 30-40μ...2 Dust of 10-20μ...5 Dust of 10μ or less...2 Paint transfer piping that has been subjected to more than one cleaning treatment When the body of a car using melamine paint was painted with melamine resin paint, no clogging of the paint filter (300 mesh) was observed. In addition, when we visually inspected the foreign matter on the painted surface, we found that
Only a few points were observed, and no other paint defects were observed.

Comparative Example 1 In the same way as in Example 1, cleaning thinner was applied at room temperature for 30 minutes to a paint transfer pipe that had been in operation for the same number of days as in Example 1.
Although the pipe was circulated for days (circulation speed: 3°, 1 m/sec), the inner wall of the pipe was not clean.

In addition, when the number of dust in the contamination kit for the final cleaning solution was investigated, it was as follows. : Dust of 50μ or more...1 Dust of 40-50μ...4 Dust of 30-40μ...20 Dust of 10-20μ...36 Dust of 10μ or less...Countless This thinner cleaning process When the car body was painted with melamine resin paint using the paint transfer pipe attached to the
The paint filter (300 mesh) had to be replaced once a day due to clogging. Further, when the foreign matter on the painted surface was visually inspected, approximately 40 to 60 foreign matters were observed.

Effects of the Invention According to the cleaning method of the present invention, impurities such as paint, pigments, rust, and dust that cause painting defects can be effectively removed from the paint transfer pipe, so that the paint transfer pipe can be cleaned after cleaning. Even if it is reused, the paint filter will not become clogged, and there is no need for post-painting repair treatment due to the accumulation of foreign matter on the surface of the painted product.

Patent applicant NEOS Co., Ltd. Agent Patent attorney Maeda Sao and 2 other procedural amendments (
Mr. White Commissioner of the Patent Office December 3, 1986 2
Name of the invention Method for cleaning inside paint transfer pipes 3 Relationship with the case of the person making the amendment Name of the patent applicant Name of the patent applicant Mashishikikaifu Neos 4 Agent Address 2-1-61, Higashi-ku-mi, Osaka City, Osaka Prefecture, 540
No. 6, Subject of amendment Column 7 of "Detailed Description of the Invention" of the specification, Contents of amendment (1) Specification, page 5, line 14, "..."
After , add the following statement on a new line.

"The above solution can be prepared by dissolving an alkali in an appropriate amount of water and diluting it with a water-soluble solvent.The alkali concentration in the paint remover is 5 to 50% by weight, and the water-soluble solvent in it is is preferably 10 to 40% by weight.'' (2) Same, page 5, lines 17 to 19, ``Usually...
・It is. "When the alkali concentration in the paint remover is, for example, 25% by weight, the paint remover is usually
It is used after being diluted with water to a concentration of ~100%, preferably approximately 40-60%. ” he corrected.

that's all

Claims (1)

[Claims] 1. When cleaning the inside of the paint transfer pipe, the inside of the pipe is first treated with a paint remover, then treated with an acid, followed by a flushing treatment, and then a water displacement treatment. A method for cleaning the inside of a paint transfer pipe, characterized by performing the following steps. 2. The first method in which the paint remover is an alkaline water-soluble solvent solution
The method described in section. 3. The method according to item 1, wherein the acid is an inorganic acid. 4. The method according to item 1, wherein the flushing treatment is performed using an aqueous rust preventive solution. 5. The method according to item 1, wherein the water displacement treatment is performed using a water-soluble, low-boiling organic solvent.