JPH02157067A - Method for peeling coating film - Google Patents

Abstract

PURPOSE:To peel off even a strong crosslinking film efficiently, securely and stably by applying to a material with a coating film the treatment of peeling solution containing amine salt having 2 - 16 carbon numbers of fluoric acid, and more adequately heat treatment. CONSTITUTION:A material with a coating film is treated with peeling solution containing amine salt having 2 - 16 carbon atoms of fluoric acid and the coating film is peeled off. As the suitable examples of amine, trimethylamine, triethylamine, butylamine and the like are used, and 0.1 - 20wt.% amine salt is preferably used. Methylene chloride, fluorinated solvent and the like are the suitable examples of organic solvents for prepating a peeling solution. Peeling can be increased in the peeling solution by heat treatment, and the heat treatment at the temperature of boiling point or under of the solvent to be used is suitable.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for removing paint films.

(Prior Art) Painting is indispensable as a means for protecting, anticorrosion, and beautifying aluminum-based, iron-based, and other various metal products, as well as other material products. Cross-linked coatings are superior in terms of adhesion to the substrate and cohesive force between molecules, but
If a defect occurs due to some reason such as a defect in the paint itself or the painting process, or if an old paint film is to be replaced with a new one, it is necessary to remove the paint film from the metal material for repainting. However, crosslinked coatings are strong because their molecules are three-dimensionally bonded. A known method for removing such paint films is to treat them with a solvent-based solution consisting mainly of methylene chloride and a small amount of formic acid or ammonium fluoride; however, formic acid or ammonium fluoride is water-soluble. Because of its chemical properties, it has poor compatibility with water-insoluble methylene chloride, and as a result, there is no synergistic effect between the two, and each acts independently, resulting in long peeling times and poor stability of the peeling effect. However, there is a strong demand for its improvement.

The present invention was devised to solve the above-mentioned problems, and its purpose is to provide a coating film of this type that can efficiently, reliably and stably remove even strong cross-linked coatings. The object of the present invention is to provide a peeling method.

(Means for solving the problem) In order to achieve the above object, the present invention treats a material such as a metal having a coating film with a stripping solution containing a C2 to C16 amine salt of hydrofluoric acid, in particular heat treatment. This allows the paint film to be peeled off.

Specifically, the feature of the present invention is that C2 to C of hydrofluoric acid
16 amine salts are used. C2 of this hydrofluoric acid
The ~C16 amine salt has good compatibility with organic solvents, and when used together, it swells the crosslinked coating film and quickly penetrates into the coating film, forming coating molecules in a three-dimensionally bonded state. Since it destroys the metal and etches the base material such as metal, the coating film can be removed extremely easily and reliably, and the stability of the remover is also increased.

For this purpose, a C2 to C16 amine salt of hydrofluoric acid is essential. If it is less than C1, the above effect will not be achieved because the compatibility with the organic solvent will be poor, and if it exceeds C16, the reaction with hydrofluoric acid will be slow, which is inappropriate.

Typical C2-C16 amine salts of hydrofluoric acid include trimethylamine, triethylamine, diethylamine, butylamine, hexylamine, octylamine, and laurylamine.

Note that the C2 to C16 amine includes alkanolamine, and examples thereof include diethanolamine, triethanolamine, and the like.

The amount of the C2 to C16 amine acid in the hydrofluoric acid is preferably about 0.1% to 20% by weight. If the amount is less than 0.1%, no peeling effect can be expected, and if it exceeds 20%, the peeling effect will be greater, but the etching property for materials such as metals will also be greater, which is not preferable.

The organic solvent is preferably one that easily swells the coating film, and methylene chloride, trichloroethylene, perchloroethylene, fluorine solvents, ketone solvents, anone solvents, benzol, toluol, etc. are common, but methylene chloride swells the coating film easily. gender is highly representative.

However, in the present invention, other organic solvents can be used since by heating the stripping solution, stripping can be significantly increased with the aid of this heating. The heating temperature is suitably below the boiling point of the stripping solution, especially the solvent used.

When using a stripping solution, evaporation of the solvent in the solution is unavoidable. Especially when heated, this tendency becomes even more pronounced. For this purpose, solvent must be replenished.

As a countermeasure to this problem, a method is used to seal the liquid surface by adding a small amount of paraffin.

However, some of the paraffin attached to materials such as metals from which the paint film has peeled off, mixed with the electrodeposited paint, floated on the paint, and adhered to the paint film after painting, causing paint film defects and causing problems. .

So, when we sealed it with a water layer instead of paraffin,
Although the paint film defect caused by paraffin disappears, the water layer absorbs the water-soluble formic acid and ammonium fluoride in the stripping solution, leaving only water-insoluble methylene chloride.
The removability became extremely weak and it became unusable.

The present invention also solves this problem by using hydrofluoric acid as a C2-C
Even if the amine salt of No. 16 and a water-insoluble organic solvent with a specific gravity heavier than water, such as methylene chloride, trichloroethylene, perchloroethylene, or fluorine-based solvent, are used, a water layer is formed on top of the organic solvent, and the sealing is performed. , C2-C16 amine salts of hydrofluoric acid are well compatible with organic solvents, so the problem of absorption into the water layer is significantly improved, the amount of organic solvent used is greatly reduced, and the peelability is no longer weakened. .

In particular, heating significantly increases the releasability.

It is appropriate that the heating be carried out at a temperature below the boiling point of the solvent used and below the boiling point of water.

If a portion of a polymerization catalyst soluble in the solvent, such as besozoyl peroxide, lauryl peroxide, azobisisobutyronitrile, t-butyl peroxide, etc. is added to the solvent, the releasability will be further enhanced.

Note that formic acid is not an essential component of the present invention. However, this does not preclude its use, and the stripping solution of the present invention increases the compatibility of formic acid with organic solvents, resulting in greater stripping properties. The appropriate amount to add is approximately 0.1 to 20%.

The above-mentioned treatment method using the stripping solution may be carried out in the same manner as known methods, such as filling a container with the stripping solution and immersing a material such as metal having a coating film therein.

The material is generally metal, but it can also be applied to ceramics, a material from which only the paint film is substantially removed when removed with the stripping solution of the present invention.

(Effects of the Invention) According to the present invention, it is possible to reliably remove a strong crosslinked coating film in a significantly shorter time than with conventional methods, and there is little deterioration in performance even with long-term treatment, resulting in stable The excellent effect of being able to exhibit excellent peeling performance can be obtained.

Example 1 Water was added to a stripping solution consisting of 6 parts of octylamine salt of hydrofluoric acid and 94 parts of methylene chloride to form a water layer of about 5 cm.
Create a composite layer consisting of an upper layer of water and a lower layer of stripping liquid. Heat this to about 35°.

Next, an alumite sash having an electrodeposited acrylic melamine resin coating film with a thickness of about 10 microns as a crosslinked coating film was immersed in the stripping solution, and then washed with water to clean it. The painted product was completely peeled off in 2 minutes.

Next, the above conditions were maintained for 5 days, and water was added as appropriate to maintain a water layer of about 5 cm.

Then, as described above, the coated product was immersed, and it was completely peeled off in 2 minutes.

Similarly, after leaving it for 5 days and peeling it off for the third time,
It was completely peeled off in 2 minutes.

For comparison, tests were conducted under the same conditions except that ammonium fluoride or formic acid was used instead of the octylamine salt of hydrofluoric acid and the liquid temperature was 25°C.

In both cases, it completely peeled off in about 5 minutes, but almost no peeling occurred even after 30 minutes of immersion the second time.

The third time, it did not peel off at all.

Therefore, the method of the present invention is extremely superior to the conventional method,
It wasn't a problem.

Example 2 Tributylamine salt of hydrofluoric acid 5 parts methylene chloride 90
A stripping solution consisting of 5 parts trichlorethylene is prepared.

Next, an alumite sash having an electrodeposited acrylic melamine resin coating with a thickness of about 10 microns as a crosslinked coating was immersed, and it was completely peeled off in 2 minutes.

This peeling operation was repeated for 24 hours, but there was no difference in the processing time required for peeling between the start and end of the operation.

For comparison, the same test was conducted except that formic acid was used instead of tributylamine in hydrofluoric acid.

The results showed that 35 minutes of immersion was required at the beginning of the 24-hour peeling, and 38 minutes of immersion was required at the end of the 24-hour peeling.

The decrease in stripping solution during operation was controlled by adding a solvent.

Therefore, it can be seen that according to the present invention, the peeling performance is 18 times higher than that of the conventional row.

Claims (1)

[Scope of Claims] 1. A method for removing a coating film, which comprises treating a material having a coating film with a stripping solution containing an amine salt of C_2 to C_1_6 of hydrofluoric acid, particularly heat-treating the material. 2. The material with the coating film is immersed in a composite solution consisting of a C_2 to C_1_6 amine salt of hydrofluoric acid and a solvent with a higher specific gravity than water, with an aqueous layer on top, and in particular heat treatment. Characteristic paint film removal method.