JPH0426914B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a method for producing a polyphenylene sulfide resin thick film coated body having excellent coating film smoothness and density and improved hot water resistance. (Prior Art and Its Disadvantages) Conventionally, in order to form a coating film of the above-mentioned polyphenylene sulfide resin (hereinafter abbreviated as PPS resin in the present invention), for example, as disclosed in Japanese Patent Publication No. 56-9151, A method has been adopted in which a coating film is formed by fusing PPS resin powder to objects to be coated such as pipes and fittings, then rapidly cooling the resin to solidify it, and then reheating it to crosslink the resin. There is. The use of PPS resin as a rust-preventing and anti-corrosion material for metal surfaces has been rapidly increasing due to its excellent heat resistance and chemical resistance, and the resin has come to be widely used as a paint for metal surfaces. It's on. However, the glass transition temperature of this resin is as low as approximately 85°C, and the coating film of this resin also has high water permeability to hot water and becomes a relatively flexible coating film at high temperatures, so it is difficult to coat metal surfaces. For example, if a coating film with a thickness of 200μ or less is exposed to hot water for a long time, it will deteriorate its adhesion to metal, and even cause blisters (blister).
The problem was that the coating film's function was impaired and its hot water resistance was poor. As a result of extensive studies as a means of improving the hot water resistance of the resin, it was found that increasing the coating thickness of the resin to 500 μm or more or increasing the heating temperature after fusion is effective. However, even if such improvement measures are simply applied to the coating method disclosed in the above-mentioned Japanese Patent Publication No. 56-9151, the heating process may be affected by the fluidity of the PPS resin used under heating conditions, the shape of the object to be coated, etc. In some cases, sagging may occur and a uniform thick film may not be obtained. For example, when painting non-axisymmetric pipes, fittings, etc., the object to be painted cannot be rotated, so the paint sag downwards.
In addition, when thickening the film, it is necessary to raise the heating temperature to ensure heat-resistant physical properties, but if the heating temperature is raised, foaming or sagging may occur on the surface or inside of the paint film, causing damage to the paint film. There was a drawback that smoothness and denseness were impaired. (Purpose) In view of the above-mentioned drawbacks, the present invention aims to obtain a thick film coated body with excellent coating film smoothness and density and improved hot water resistance even for non-axisymmetric pipes, joints, etc. The purpose of this invention is to provide a manufacturing method that enables the following. (Structure) The gist of the present invention is to provide a method for manufacturing a thick film coated body by fusing powder coating mainly composed of polyphenylene sulfide resin to a body to be coated in multiple times. Fusion is performed multiple times so that the thickness of the fusion is 200 μ or less, and the previously fused coating layer is heated at 350 to 390°C for 20 to 60 minutes to semi-cure. The present invention relates to a method for producing a polyphenylene sulfide resin thick film coated body, which comprises fusing a coating layer to be next formed thereon. The powder coating used in the present invention is a powder coating mainly composed of PPS resin. And what is PPS resin?

A compound containing a repeating unit of the formula and which may be partially oxidized or branched or crosslinked. Additives such as silica powder and alumina powder may be added to the powder coating used in the present invention. The objects to be coated used in the present invention include:
It is not particularly limited as long as it is made of a metal material, an inorganic material, etc., and may be a plate-shaped body, a tubular body, or a joint, and it does not matter whether it is axially symmetrical or asymmetrical. In the present invention, the powder coating mainly composed of PPS resin is fused to the object to be painted in multiple steps, but as a method for fusing the powder resin, for example, the object to be painted is made of a metal material. If so, there are methods such as attaching resin powder to the metal surface using electrostatic coating method and then heating and melting it, or heating the object to be coated in advance and attaching and melting the resin powder by spraying, suction, dipping, etc. However, it is not limited to these methods, and any powder coating method can be applied. In the present invention, the powder resin is fused multiple times so that the thickness of each fusion is 200 μm or less. This is because if the thickness per fusion exceeds 200 μm, sagging occurs during heating and melting, impairing the smoothness of the coating film. On the other hand, if the welding thickness is too small, the number of times of welding will increase, which will reduce production efficiency and become uneconomical, so in the present invention, it is preferable that the thickness is 100 μm or more. Next, in the present invention, the previously fused coating layer is heated and semi-cured before the next coating layer formed on the coating layer is fused. . Here, semi-curing means partially causing intermolecular crosslinking in the PPS resin to control the fluidity of the fused PPS resin. In the present invention, the temperature is 20 to 60 at 350 to 390℃.
Heat for a minute. If the heating temperature is less than 350℃,
The rate of introduction of partial crosslinking into PPS resin is slow, and as a result, it is not possible to control the fluidity of the coating film due to heating, and it is not sufficient to prevent the coating film from sagging. If the temperature exceeds ℃, heating for a short time will
This is because although partial crosslinking may occur in the PPS resin, foaming occurs on the surface or inside the coating layer, making it difficult to obtain a dense coating film with a smooth surface. In addition, if the heating time is less than 20 minutes, crosslinking will not be sufficient and sagging will occur when the coating layers are fused together. If the coating thickness is 200μ or less and the heating temperature is 350℃ or higher, heating for 60 minutes will sufficiently cause crosslinking and no sagging will occur, and further heating will only reduce work efficiency. be. Then, as mentioned above, the powder coating mainly made of PPS resin is applied to the object to be coated to a thickness of 200 μm each time.
After repeating fusing and semi-curing in multiple steps as shown below, a thick coated body is produced by firing at 350 to 450°C. In the present invention, a powder coating material mainly composed of PPS resin may be fused after a primer for PPS resin is applied to the object to be coated. As described above, the method of the present invention is structured so that when producing a PPS resin thick film coated body, the fusion thickness is first determined.
20~20~20~20~20~200~200~200μ
After semi-curing by heating at 350-390℃ for 60 minutes, the next coating layer is fused on top of it by repeating the same process multiple times for 20-60 minutes. By semi-curing, the fluidity of the PPS resin is controlled and cross-linking occurs in some parts of the coating film, so even if the coating layers are repeatedly fused in sequence, the coating film will not sag or pinholes will occur. A smooth paint film with no pinholes can be obtained. This is particularly effective for non-axially symmetrical pipes, fittings, etc., and even for axially symmetrical pipes, fittings, etc., there is no need to rotate them, and the apparatus can be simplified. Therefore, the PPS resin thick film coated body obtained by the method of the present invention has excellent hot water resistance under high temperature conditions such as hot water.

Claims (1)

[Claims] 1. In a method of manufacturing a thick film coated body by fusing a powder coating mainly composed of polyphenylene sulfide resin to the object to be coated in multiple steps, the thickness of each fusion is 200μ or less. In this way, the fusion is performed multiple times, and the previously fused coating layer is
A polyphenylene sulfide resin thick film coated body characterized by semi-curing by heating at 350 to 390°C for ~60 minutes, and then fusing the next coating layer thereon. manufacturing method.