CS265488B1 - Primer for paint removal - Google Patents

Abstract

The solution relates to a base layer for removing coatings applied thereto, in particular on covers of painted surfaces, which contains 1.0 to 45.0% of a gas-generating modifier initiated from the outside.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a primer layer for removing paints, in particular from painted surface covers.

Paint finishes (painting, dipping or spraying) are the most widespread working process in the field of surface treatment of materials. Brush coatings are universally applicable, even in mechanical engineering, where certain parts of the painted component must remain unpainted. These are in particular screw threads, pressing surfaces, adhesive surfaces and functional parts, which are further modified in a different way.

In mass production, however, more progressive painting methods are used, by dipping or spraying, where surfaces that have been omitted when brushing must now be protected by the covers of the painted surfaces. These metal covers are attached to the workpiece in various ways, for example mechanically by means of different springs, springs or magnetically. For dipping or spraying, these covers are removed and reused to protect the unpainted surfaces of other panels.

After repeated use, the coatings are so thick that the covers no longer work. In fact, the overlap of the coating coating also covers those areas which must be painted and the coating formed on the panel joins with the coating on the cover, so that when the cover is removed, the painted surfaces are damaged. The resulting build-up of paints is usually removed by tanning and mechanical finishing. This method of cleaning the covers of painted surfaces has a number of disadvantages. Handling a burning paint is dangerous, developing toxic fumes that worsen the working environment and often deform the covers of the painted surfaces due to heat. Final manual cleaning is unhygienic, laborious and significantly increases the overall labor intensity.

Another method of removing paint layers from painted surface covers utilizes the solubility of coatings formed as a backing layer on painted surface covers. A 20% solution of polyvinyl alcohol in water is most commonly used. The covers are soaked in this solution and dried to form the above-described undercoat. After a certain number of coatings have been made, the coating is removed by treating the painted surfaces with water and performing steps to disrupt at least one point on the cover so that water reaches the underlying water-soluble layer. Mechanical methods are used, such as tumbling in drums, etc. The water then dissolves the base layer over the entire surface of the cover and a jet of water is sufficient to peel off the coating.

The disadvantage, however, is that the coating must be laboriously disturbed to allow water to reach the undercoat. Disturbance is only possible mechanically in light coatings of two or three coats. Thicker coatings cause considerable problems and the use of a soluble backing layer is no longer appropriate economically.

It is an object of the present invention to overcome these disadvantages of the prior art methods of removing paint deposits from painted surface covers.

It is an object of the invention to provide a base undercoat which, on the external impulse, causes a partial destruction of the coating deposited thereon so that water can have good access thereto.

The surrounding is solved by a base layer for removing paint from the covers of lacquered surfaces, the essence of the invention is that it contains 1.0 to 45.0% of a gas generating modifier.

Further features of the undercoat according to the invention result from the description thereof.

Example 1

Undercoat for synthetic firing coating system

A 20% solution of polyvinyl alcohol in water, which is modified with 10% azodicarbonamide, is used to form the undercoat. When the paint is fired (80 ° C to 100 ° C depending on the type of varnish), the modifier is stable and does not react. If paint coatings need to be removed from the painted surface cover, they are heated to 200 ° C to 220 ° C to decompose the modifier according to the scheme:

Η ₂ Ν-ς-Ν = Ν-ς-ΝΗ ₂ -x ------> n ₂ t + co ₂ f + cot + nh ₂ conh ₂

The released gases lift the coating to be removed and the base coat itself foams strongly. Another activity is to immerse the covers in warm water, where there is possibly a wetting agent. The water reaches the base underlay which dissolves through cracked and raised paint. Dissolution proceeds rapidly because of the large surface and sponginess of the underlayer caused by the modifier. After this substrate has dissolved, the cleaning is completed by rinsing with water.

Example 2

Undercoat for nitrocellulose coating system

A 20% solution of polyvinyl alcohol in water, modified with 45% finely divided ammonium carbonate, was used to form the undercoat. In the case of paint removal, the workpiece is immersed in hot water, where the modifier reacts in the base layer:

(NH ₄ ) ₂ CO ₃ ------> 2NH ₃ f + CO ₂ f + H ₂ O

The released gases lift the coating and accelerate the dissolution of the undercoat. The covers are then cleaned by rinsing with water.

Example 3

Undercoat for two-component coating system

A release lacquer, for example based on a polymer resin, modified with 20% finely divided ammonium carbonate, is used to form the undercoat. In order to remove the coating, the lacquer cover is heated to 80 ° C to 100 ° C, when the reaction described in Example 2 occurs. The loose and raised coating is easily removed mechanically. In more difficult cases it is possible to use eg tumbling in a drum etc.

Example 4

Undercoat for electrostatically applied powder coatings

A 5% aqueous carboxymethylcellulose solution is used to form the undercoat and 3% toluenesulfonylsemicarbazide is admixed. After the powder coating has been applied and fired, the coating surfaces are exposed to a temperature of 225 ° C, where the toluenesulfonyl semicarbazide decomposes to form gaseous components, namely hydrogen, nitrogen and carbon monoxide. With such a disturbed coating, the covers are soaked in water with the addition of detergent, thereby cleaning them.

Example 5

Undercoating for dipping coatings

A 5% aqueous carboxymethylcellulose solution was used to form the undercoat.

into which 1% ammonium carbonate is admixed. This undercoat is removed after each individual soaking of the cover member together with the application of hot water.

Claims (1)

OBJECT OF THE INVENTION Substrate for removing paints, in particular from painted surface covers, characterized in that it contains 1.0 to 45.0% of a gas generating modifier.