What problems are often encountered in the use of color coated steel plate coating

Color coated plate is a kind of composite material formed by baking one or more layers of organic coating on a metal substrate, which is used in home appliances and construction industries because of its good corrosion resistance and aesthetics. Since Baosteel established its first color coating unit in the late 1980s, after 30 years, Baosteel has 3 modern color coating units with an annual output of nearly 600,000 tons. The variety of products produced has increased from the original four paint categories of 16 colors to more than a dozen paint types involving construction, home appliances and other industries and uses.

There are often some technical problems in the use of color coated plate coating, this paper selects a few common problems for brief introduction.

1: Glitter paint visual error problem

Color coating layer paint is divided into two categories, namely "plain paint" and "flash paint", (flash paint is also divided into "metal paint" and "pearl paint"). Unlike plain paint, which produces color through the selective absorption and diffuse reflection of light by pigment particles, metal and pearlescent sheet pigments are distributed in layers and arranged parallel to the paint film in the same orientation. When light hits the surface of the paint film, part of the light is almost not absorbed due to the direct reflection of aluminum powder, and part of the light is particularly bright, giving people a very dazzling feeling. Part of the light is reflected by the aluminum powder many times, and the light is dark. Therefore, it gives people different visual effects when viewed from different angles.

As shown in the light reflection diagram of flash paint pigment, the light generated by the same incident light source increases with the reflection, the light darkens, and the effect seen at the observation Angle A and observation Angle B will be different due to the brightness and darkness of the light, so the visual effect of flash paint will vary with the Angle of light incident (corresponding to changes in nature, such as dawn and dusk) and the observation position of the observer. Therefore, the color difference of flash paint is more difficult to control, and users sometimes reflect visual color difference in use.

On the one hand, steel mills should choose the same paint supplier and the same batch of paint in the same user contract in the production control to concentrate production at the same time to avoid the difference between different paints and processes, and use a multi-angle color difference meter that is closer to the human eye measurement effect for color difference comparison. On the other hand, the user is guided to help it avoid the color difference problem caused by different directions of material installation.

2: Coating bonding problem

When the color coated board is used as a sandwich board, a problem often faced is poor bonding or foaming. Because the coating is used to make the sandwich board, the coating must be effectively combined with the blowing agent to ensure the overall integrity of the sandwich board. Generally speaking, the more poor bonding problems encountered by users mainly include "not sticking" and "surface holes".

2.1 "Not Sticky"

Color coated plate back coating bonding poor picture. The main reasons for such problems are as follows:

(1) glue reaction time: The length of the user's glue reaction time during processing affects the foaming effect, and the foaming effect will not be ideal if the time is too long or too short. .

(2) Coating quality: The type of coating determines the surface activity of the coating after curing, which will affect the foaming effect of the color coating plate and blowing agent. If the coating active group is less, the foaming property will be affected. It is a poor foaming model of coating with less active groups.

(3) Glue quality: foaming glue is generally composed of black glue and white glue, white glue is a polyether polyol with hydroxyl, and black glue is a product with cyanate ester, and the two are mixed in a certain proportion to form polyurethane, that is, foaming material. The active ingredients in the glue seriously affect the foaming effect of the product. If other substances are added to the white glue to reduce the cost or polyether polyols are replaced by polyester polyols with lower prices, poor foaming is likely to occur.

(4) Others: foaming process, production environment, etc., are also important factors affecting the quality of sandwich board finished products.