JPS61230771A - Method for forming coating film to hollow container - Google Patents

Abstract

PURPOSE:To obtain a beautiful and strong coating film by preventing air bubbles generated in the coating film, by applying a liquid containing a resin to one surface side of a hollow container while the container is simultaneously heated from the other surface side thereof. CONSTITUTION:When the spray coating of a liquid paint is applied onto the surface of a matter such as a non-plastic hollow container, the liquid paint applied to one surface side 11f of plate shaped matter 11 by spraying is adhered to said surface to form a coating layer P2. Simultaneously with this coating work, the matter 11 is heated as shown by a character Hb from the side of the surface 11b opposite to the coated surface. The temp. of the matter 11 is raised by this heating and the heat of the matter 11 is further conducted to the coating layer P2 from the coated surface 11f to heat the liquid paint and the liquid contained in the liquid paint is evaporated by said heat to form air bubbles in the coating layer P2 but these air bubbles are gradually pushed to the surface side by the solidification action of the paint successively moved and advanced to the surface side and expelled to the open air at last and the presence of air bubbles in the coating layer P2 is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a coating film of a resin-containing liquid on a hollow container.

The present invention utilizes the method for forming a coating film in Patent Application No. 1 filed on March 30, 1985 by the present applicant for a hollow container.

Now, to briefly describe the gist of the above-mentioned 1 coating film forming method, when a liquid containing resin is spread on one side of an object that has two sides, the opposite side of the coated side is heated. This is a method of drying the applied layer.

In addition, the hollow containers to which the present invention is directed refer to hollow containers made of various materials other than plastics, such as paper, metal, and ceramics. It applies a liquid containing plastic, ie synthetic or natural resin. In addition to general liquid paints, the term resin-containing liquids refers to water-soluble systems, water-dispersed systems, powder slurries, and the like.

Hereinafter, the liquid containing resin will be abbreviated as liquid paint or the like.

Conventionally, when coating the outer or inner surface of a hollow container, etc. with a liquid paint, etc., first, as shown in FIG. Then, as shown in Figure 1B, the coated surface is heated with hot air (Hf) from the same outer surface.
It was heated and dried by spraying.

Now, in the above-mentioned drying process, the following troublesome phenomenon actually occurred. Please refer to FIG. 1C, which is an enlarged view of part A in FIG. The liquid component on the surface of the coating layer P evaporates and dries. That is, it solidifies to form a hard skin Pf. In other words, the inside of the skin is in an undried liquid state. The heat that is supplied later is conducted through the epidermis and is further transmitted to the liquid part on the inner side of the epidermis.
Naturally, the liquid evaporates and generates gas. They gather to form bubbles Vf. When this phenomenon occurs on the surface of the above-mentioned coating layer, the vaporized gas is dissipated into the atmosphere, but when this phenomenon occurs inside, the surface of the liquid is covered with the above-mentioned hard skin. Therefore, the generated air bubbles Vf have no place to escape, that is, they end up being trapped in the dried and solidified paint. In this manner, the drying and solidification of the coating layer progresses, and when the entire solidification is completed, the generated air bubbles remain inside the solidified coating film. In this way, many air bubbles are scattered in the coating film, which not only spoils the aesthetic appearance of the coating but also reduces the strength of the serum, which has been a problem in the industry for many years. In order to prevent these problems, manufacturers are trying to make the drying film thinner than safe, lowering the drying temperature and lengthening the drying time, and selecting and blending other solvents, resins, additives, etc. A lot of consideration and extraordinary efforts have been made.

The motivation for the present invention was to solve the above problems.

The purpose of the present invention is to prevent foaming from occurring in the paint film during painting work on the inside or outside surface of a hollow container, and to create a complete vehicle coating that is beautiful and has high adhesion strength. It is in the formation.

The gist of the present invention is to utilize the method for forming a cloth film in patent application 1''' dated March 30, 1985 for hollow containers, etc.; When coating one side of the surface with a liquid containing resin, heat must be applied from the opposite side of the coated surface.k
Therefore, it is a drying method. The following three methods can be cited as the timing for heating from the opposite side.

That is, heat is applied at the same time as or after the application of the - side. ■After completing the heating work in the previous section (■), heat the coated side more. ■-face! After finishing the cloth, heat both sides at the same time.

The functions and effects of the above-mentioned patent application dated March 1985 entitled "Coating film forming method JK" are as follows.

See Figure 2B.

This figure is an enlarged view of a cross section when a Kg body paint or the like is sprayed on the surface of an object that has two sides. The liquid paint applied by spraying is applied to one surface of the plate-shaped object 11, that is, the surface 11f, to form a coating layer P2. Simultaneously with the above coating process, heat (H
b) Do. The heating causes the temperature of the stolen property 11 to rise, and the heat is further conducted to the opposite side 11f and reaches the coating surface 11f. The heat is then conducted to the coating layer P2 that is in contact with the coating surface, and heats the liquid paint that is glue-coated.

The heat causes the liquid contained in the liquid paint to vaporize, creating bubbles Vfs within the coating layer. At the same time, the vaporized portion of the liquid becomes only the resin containing no liquid and solidifies. Due to the solidifying action, the bubbles Vfs are still unsolidified, i.e., the surface If of the coating layer P2.
Pushed to i111J. In this way, the vaporized bubbles Vfl of the liquid in the liquid paint inside the coating layer are gradually pushed toward the surface of the coating layer by the solidifying action of the paint, which progresses. It is finally expelled into the atmosphere. Therefore, no air bubbles exist in the solidified coating layer. That is, as shown in FIG. 2C, a completely flawless coating film P3 without any air bubbles can be obtained.

Although the above-mentioned application method is a spray method, this refers to both a near spray method and an airless spray method, and also includes a roll coat method, a dipping method, a kiss coat method, and the like.

The above is the basis of the patent application "Coating film forming method" dated March 30, 1985, and various methods can be considered for the timing of heating the opposite side. That is, the heating may be performed simultaneously with the coating on one side of the hollow container, after the coating is completed, or on both sides. Each item of these methods will be explained below.

Law 1. See Figure 2A. The outer surface of the hollow container
This method involves applying a liquid paint or the like by spraying, and simultaneously heating the inner surface by blowing hot air. The spray nozzle N and hot air blowing mouth Hm are also fixed, and only the hollow container that is the object to be coated is rotating.

FIG. 3 shows a method in which the inner surface is coated with a liquid paint by spraying and the outer surface is heated by far infrared rays or the like. In this method, spray nozzle N! , the heater Hu, and the object to be coated 21 may all be fixed. The simultaneous heating with the above-mentioned coating operation may be performed after the coating is completed. This method is the basis of the present invention and can be applied to all cases, but in terms of time,
Depending on the conditions, each of the first-order methods can be applied if there is a sense of reducing the drying time by 30%.

Second law. Apply liquid paint, etc. to the outer or inner surface of the hollow container, and at the same time or after coating, heat the opposite inner or outer surface (method 1), and then,
Furthermore, this is a method in which the coated side is also heated, and one both sides are sequentially heated.

In this method, after heating in the first method above, the surface of the coating layer is heated and dried at the point when the evaporation of the liquid is approximately completed, that is, when no bubbling phenomenon occurs even if the coating surface is heated. It is. The key here is the timing, and if the timing is appropriate, the drying time can be significantly shortened.

Third law. This is a method in which the outer or inner surface of a hollow container is coated with a liquid paint or the like, and after the coating operation is completed, both sides, the side toward which the coating is applied and the side opposite thereto, are simultaneously heated and dried. In this method, half of the heat is applied from the surface of the coating layer, which is the same as in the conventional method, and there is a risk that air bubbles may be trapped. However, even with conventional methods, there are cases where relatively few bubbles remain due to various conditions, such as the characteristics of the solvent and resin, the thickness of the coating layer, the heating temperature, the shape of the object to be coated, and the know-how of the contractor. There was also. In such cases, in addition to the conventional heating from the front side, if heating is applied from the back side, it will be possible to dry the product perfectly and in a much shorter time. .

As described above, in the application of a liquid containing resin to a hollow container according to the present invention, by heating the side opposite to the application surface, air bubbles that are generated are prevented from being trapped in the paint film, and the drying time is shortened. Moreover, it is possible to obtain a coating film that is beautiful and has high adhesion strength.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. On the entire outside (11f) or inside of the hollow container 11 or an object similar in shape to it,
A hollow mold characterized in that a liquid containing a resin is coated, and at the same time or thereafter, the opposite side (11b) to the coated surface is heated, thereby drying the coated coating layer P_2. A method for forming a paint film on a container. 2. Applying a resin-containing liquid to the entire outside or inside of a hollow container or an object similar in shape to it, and at the same time or after that, apply the coating to the opposite side 1. A method for forming a paint film on a hollow container, which comprises heating, and then heating the coating surface side as well, thereby drying the coating layer. 3. Applying a resin-containing liquid to the entire outside or inside of a hollow container or an object similar in shape to it, and then coating the coated surface and the opposite surface. A method for forming a paint film on a hollow container, characterized by simultaneously heating and drying the coated layer.