JPH0316191B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a plastic powder thermal spray coating method in which plastic powder is thermally sprayed onto a substrate to be coated without preheating. [Conventional technology] Thermal spraying technology for ceramics and metals is now widely used, but its history is long, and 60 years have already passed since metal spraying technology was introduced in 1921. However, when polyethylene is coated by thermal spraying, the problem of cracks occurring due to deterioration of the polyethylene and the problem of peeling of the film once coated has not been solved, and it has been several years since the technology was introduced. Industrialization was halted. Very recently, EVA powder and epoxy powder that does not require post-heating have been used, for example, in JP-A-54
-Disclosed in Publication No. 95643. [Problems to be Solved by the Invention] As described above, although improvements in plastic materials and thermal spraying machines have been made successively as technology advances, no progress has been made in plastic thermal spraying technology. One reason for this is that small objects can now be coated with plastic powder using the fluidized dipping method, and medium-sized objects can be coated with plastic powder using the electrostatic coating method. Furthermore, the biggest problem with conventional plastic powder spray coating methods is that the substrate to be coated must be preheated to near the melting point of the plastic to be sprayed. A major reason for this is that it is almost impossible to preheat, even partially, bridges, tanks, rigs, ships, large steel structures, etc., for example. Due to these circumstances, although the plastic powder spray coating method is a method for producing high-performance plastic coatings and is capable of producing a thick film of 1 mm or more in a single operation, Its advantages were not fully exploited. Thermal spraying of plastic powders, such as polyethylene, nylon, and EVA, is generally done by bringing the particles to a nearly molten state in a gas flame mixed with acetylene gas, propane gas, oxygen, or air, and then spraying them onto a preheated substrate. It adheres one after another and becomes a complete melt due to the thermal energy of preheating and the thermal energy of the flame. Therefore, if the base material is not preheated at this time, when the nearly molten plastic particles reach the base material, they will absorb heat from the base material and become solid, resulting in incomplete adhesion to the base material. Cracks may appear in the sprayed coating or it may fall off from the substrate. The present invention was made to solve the above-mentioned problems in thermal spray coating of plastic powder, and it is possible to use polyethylene, nylon,
Plastic powders such as epoxy, saponified ethylene vinyl acetate copolymer, polybutene, polyamide, polytetrafluoroethylene, polyethylene tetrafluoroethylene, polyfluoroethylene propylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride, etc. The object of the present invention is to provide a plastic powder spray coating method that does not require preheating of the substrate. [Means for Solving the Problems] The present invention provides a liquid adhesive having at least one double bond and one or more side chains imparting polarity to a base material that has not been preheated at room temperature. A primer layer of polyethylene, nylon, epoxy, saponified ethylene vinyl acetate copolymer, polybutene, polyamide, polytetrafluoroethylene, etc. is applied on the primer layer.
This is a plastic powder spray coating method characterized by spraying plastic powder such as polyethylenetetrafluoroethylene, polyfluoroethylenepropylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride, etc. In addition, the adhesive primer may be an acrylic ester resin, a polychloroprene resin, a polyamide amine-curing epoxy resin, an acid amide amine-curing epoxy resin, a polychloroprene resin, an aromatic polyamine-curing epoxy resin, a vinyl acetate resin, a polyolefin resin, or a urethane resin. This is the above-mentioned plastic powder spray coating method using one type selected from epoxy phenol resins. [Function] In the present invention, when the plastic powder to be thermally sprayed is rapidly cooled and solidified on the substrate surface, that is, when the substrate is not preheated, sufficient adhesion can be obtained as long as the wetting with the substrate surface is sufficient. Based on this basic idea, we conducted various studies to develop an organic polymer material that has sufficient wettability and adhesion to the base material, and also has sufficient bonding with the plastic particles to be thermally sprayed. This was developed with a focus on providing an adhesive layer. For this purpose, an adhesive primer that meets this purpose must first satisfy the following conditions. Adhesive primers must have good wettability and strong adhesion with the base material. The base material is generally subjected to a pretreatment such as shot blasting or sandblasting, so the adhesive primer used here has an excellent anchoring effect that sufficiently wets the blasted surface. For this purpose, it is preferable to have appropriate viscosity and to form a small contact angle (approximately 40° or less, preferably 30° or less) with the substrate. Further, primers containing many polar groups, such as polychloroprene resin, acrylic acid ester resin, polyamide amine curing type epoxy resin, etc., are particularly preferable because they exhibit good adhesion to the base material. Adhesive primers must have good wettability and high adhesion with thermally sprayed plastic particles. Preferably, the adhesive primer surface becomes chemically active due to the flame at the start of thermal spraying and chemically bonds with the sprayed plastic particles.
The adhesive primer used for this purpose has at least one double bond in its polymer and one or more side chains to impart polarity to the polymer, such as polychloroprene resin, acrylic ester resin, etc. , polyamide amine curing type epoxy resin, etc. are preferable. It should not exhibit tackiness after adhering to the thermal spray coating. If tackiness still remains after the coating has adhered, this is undesirable since it impairs the scratch resistance and heat resistance of the coating. However, it is possible to make some adjustment by reducing the film thickness of the primer to about 200 μm or less. The adhesive force of the thermal sprayed plastic coating and the cohesive force of the thermal sprayed plastic coating should be well balanced. The cohesive force of plastic (high molecular polymer) when forming a film is generally quite high, so if it is not balanced with the adhesive force with the adhesive primer, it may peel off from the substrate, crack the sprayed plastic film, or cause damage to the primer surface. A peeling phenomenon (referred to as phase peeling) occurs between the two. In particular, the adhesion force at the interface between the adhesive primer and the thermally sprayed plastic coating must be strong. Do not deteriorate or separate due to flame during thermal spraying. During thermal spraying, the primer is exposed to flame for a short period of time, so if deterioration or decomposition occurs at this time, it will result in non-uniform adhesion. Therefore, the adhesive primer must have excellent heat resistance and be flame retardant. Emulsion-based primers, such as acrylic resin emulsions, are not very satisfactory in terms of heat resistance, and primers containing aromatic rings, such as copolymerized phenol resins, such as epoxyphenol resins, or aromatic polyamine-cured epoxy resins, etc. It is best to use a polymer blend of these materials. Adhesive properties should remain the same even after being left for several hours or several days after application of the adhesive primer. In actual field work, thermal spraying work is often carried out several hours to several days after application of the primer. Therefore, it is necessary that the adhesive behavior does not change significantly within that period. Even if the primer is apparently dry, it may be activated by the heat at the start of thermal spraying, such as a polyamide amine-curing epoxy resin that has a sulfon group or halogen in the side chain of the polymer in the primer. Preferred are acid amide amine-curing epoxy resins, polychloroprene resins, and the like. Adhesive strength does not decrease over a long period of time, corrosion resistance,
Excellent performance such as heat resistance and scratch resistance. Since it comes into contact with the base material, it is particularly desirable that it have excellent anti-corrosion properties. For this purpose, it is preferable to mix anti-rust pigments such as zinc dust, red lead, barium chromate, etc. in the primer. It has a long pot life (the usable time after mixing and adjustment) and can be spray painted. Naturally, a long pot life is desired. Particularly from the viewpoint of application to large steel structures intended by the present invention, it contains a small amount of a solvent with a slow evaporation rate (for example, isophorone, diacetone alcohol, methyl isobutyl ketone, DMF, etc.). It is preferable. For applying adhesive primers to large substrates, it is preferable to use a sprayer (air spray or airless spray), which requires a solution with a viscosity of less than 500 cp (20°). is desirable. When adjusting the solution viscosity, it is also a good method to dilute with a solvent with excellent solubility, such as xylene or toluene, or to impart thixotropy by adding a thixotropic agent. It goes without saying that if all of the above conditions are met, a nearly perfect adhesive primer can be obtained, but they do not necessarily have to be met. As a result of selecting an adhesive primer that meets the above conditions, we found that it is sufficient for plastic resin powders such as polyethylene resin, nylon resin, saponified ethylene vinyl acetate copolymer resin, epoxy resin, polybutene resin, and polyamide resin. Furthermore, it has become possible to thermal spray coating plastic powder, which also enables adhesion of fluorine-containing resin powder, which has been difficult to adhere to in the past. An example of an adhesive primer used for thermal spray coating of fluorine-containing resin powder is one based on polychloroprene resin, with a blending ratio of phenolic resin of 5 to 5 to increase heat resistance, cohesive force, and melting point. Examples include those containing 30%. Note that the content thereof is characterized by being contained in a larger amount than in general adhesives. [Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples. The surface of the 20 mm thick SS steel material was sandblasted to SIS (Sweden Standard) Sa2.5 (remaining rust area 5% or less), and a polychloroprene adhesive primer [Yokohama Rubber Co., Ltd.] Made by
Product name Hamatite Y-395-K, solid content 26±1%,
[Viscosity 150-350cp/20℃] by air spray [Iwata Painting Equipment Co., Ltd., Wider spray gun, W-77]
-3G], air pressure 3.5Kg/cm ² , spraying distance
Sprayed at 250mm. At this time, the coating amount is 600g/m ² and 1200g/m ²
Two types of coating films were prepared. Polyvinylidene fluoride powder [manufactured by Kureha Chemical Industry Co., Ltd., KF
Polymer] with a mixed gas consisting of 1 part propane and 2 parts air using a powder spraying device (manufactured by Sciori, ZB-2 type)
It was supplied and sprayed. The powder discharge rate is 100g/min, and the gun distance is
It was set to 400mm. After thermal spraying, as shown in the table below, JISK5400
Paint tests were conducted for each item specified in the above conditions. The results are shown in the table. As is clear from the table, the characteristics did not change even when the amount of primer applied and the number of days before thermal spraying were changed, and both showed good results. In addition, the phenol content is higher than that of the hamatite Y-
I tried using Hamatite A-862-B, which is said to have a lower content than 395-K, but it was found to have almost the same effect. The present invention is not limited to fluorine-containing plastic powders such as polyvinylidene fluoride powder used in this example, but also applies to other plastic powders such as common polyethylene, nylon, epoxy, saponified ethylene vinyl acetate copolymer. A similar effect can be obtained even when applied to plastic powder such as coalescent.

[Table] [Effects of the Invention] As described above, according to the plastic powder spray coating method of the present invention, polyethylene, nylon, epoxy, and saponified ethylene vinyl acetate copolymers can be coated by applying a liquid adhesive primer. , polybutene, polyamide, polytetrafluoroethylene, polyethylene tetrafluoroethylene, polyfluoroethylene propylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinylidene fluoride, and preheating plastic powder of high performance polymer materials. It can be thermally sprayed without any heat, and the coating is made of high-performance polymer material that has excellent chemical resistance, heat resistance, light (weather) resistance, corrosive gas resistance, as well as impact resistance and abrasion resistance. can be formed.

Claims (1)

[Claims] 1. At room temperature, at least 1.
A liquid adhesive primer containing one or more double bonds and one or more side chains imparting polarity is applied to form a primer layer, and then polyethylene, nylon, epoxy, saponified ethylene, etc. are applied on the primer layer. One type of plastic powder selected from vinyl acetate copolymer, polybutene, polyamide, polytetrafluoroethylene, polyethylenetetrafluoroethylene, polyfluoroethylenepropylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and polyvinylidene fluoride. A plastic powder spray coating method characterized by thermal spray coating. 2 The adhesive primer is an acrylic ester resin, a polychloroprene resin, a polyamide amine curable epoxy resin, an acid amide amine curable epoxy resin, a polychloroprene resin, an aromatic polyamine curable epoxy resin, a vinyl acetate resin, a polyolefin resin, a urethane resin. 2. The plastic powder thermal spray coating method according to claim 1, wherein the coating material is one selected from the group consisting of epoxyphenol resins and epoxyphenol resins. 3. The plastic powder according to claim 1 or 2, characterized in that the adhesive primer is blended with one type of rust preventive pigment selected from zinc dust, red lead, and barium chromate. Body spray painting method. 4 In preparing the adhesive primer, isophorone, diacetone alcohol, methyl isobutyl ketone, DMF, xylene,
The plastic powder spray coating method according to any one of claims 1 to 3, characterized in that one selected from toluene is used or a thixotropic agent is blended.