JPH09216311A - Method for manufacturing coated metal material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technology for manufacturing polyolefin-coated metal material which makes it possible to conduct an overcoating without large difference from normal polyolefin-coated metal material. SOLUTION: The overcoating paintable polyolefin-coated metal material is obtained by the method for manufacturing it comprising the steps of bringing the powder of modified polyolefin resin having adhesive properties into contact with the surface of a melted layer of polyolefin resin and fusion bonding it to be added in the steps of coating with normal polyolefin of forming the melted layer of the resin on the surface of a metal material and cooling to solidify it, thereby forming an adhesive medium layer on the surface of the polyolefin resin-coated layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for advantageously producing a polyolefin resin-coated metal material having an overcoating property or an overcoating adhesive property.

[0002]

2. Description of the Related Art As a long-term anticorrosive measure for metal materials such as steel pipes, a heat-melting type thick film coating with a thermoplastic polyolefin resin such as polyethylene or polypropylene has become mainstream.

Polyolefin resin absorbs water extremely
It is hard to permeate, and it can prevent corrosion for several tens of years with a film thickness of 0.5 mm or more.It also has high toughness and is not easily damaged by external damage.Furthermore, a molten layer of polyolefin resin is formed on the surface of metal material Since it may be cooled and solidified, it has a feature that it can be manufactured inexpensively and without using an organic solvent.

On the other hand, since polyolefin resin has a property of being easily decomposed and deteriorated by ultraviolet rays, carbon black is usually used as a coating for outdoor long-term anticorrosion applications.
Measures have been taken to prevent the ingress of ultraviolet rays by blending 0.5 to 3%, and the coating is often black.

However, in recent years, structures such as bridge piers and revetments, and various pipelines installed outdoors have tended to be in harmony with the landscape, and there has been a demand for toning polyolefin coatings. There is. In addition, whitening of the coating may be required to avoid the temperature rise of the structure (up to 80 ° C) due to sunlight in hot areas. In addition, with regard to line pipes of various plants, it is often necessary to adjust the colors in order to identify the inner transportation items.

In order to meet the above requirements, the polyolefin coating is subjected to surface modification treatment such as flame treatment, strong oxidant treatment, corona discharge, arc discharge, etc. to polarize the surface of the non-polar polyolefin and top coat or Techniques have been taken to enable film adhesion.

However, the above surface modification treatment requires not only the skill of a worker or complicated equipment and treatment operation, but it is difficult and uniform to treat uniformly the coated surface of various shapes, and is unstable. Further, since the treatment effect is difficult to last, it is necessary to perform the treatment immediately before the overcoating, so that it cannot be carried out efficiently.

In order to solve the above-mentioned problems, a technique has been developed in which an adhesion mediating layer made of a modified polyolefin resin having adhesiveness is provided on the surface of polyethylene so as to impart top coatability and the like, and JP-A-63-87230. Is disclosed in. Regarding this technique, a primer solution using the modified polyolefin resin as an organic solvent solution has already been marketed, and the solution is applied to the surface of the polyolefin, and after drying, transient heating is performed from the surface to melt the coating layer. It can be used for general purposes in the form of being adhered to the base polyolefin. The top coatability and the like imparted by this technique will not disappear with time.

That is, it becomes easy to color paint a polyolefin-coated metal material, and it is also possible to manufacture and supply a polyolefin-coated metal material which is provided with the above-mentioned adhesion mediating layer and is given a top coatability in advance. The solution coating / heating and melting method described above is a method in which a coated metal material is once manufactured and then a separate process is performed, and a liquid using an organic solvent which is not absolutely necessary for the polyolefin coating construction. Since it is done by painting, the number of man-hours increases, a separate coating facility, a heat treatment facility for primer-melting, etc. are required, the cost related to the facility increases, and work environment measures etc. are required, The problem remains that the characteristic of the polyolefin-coated metal material that can be provided at low cost is diminished.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is a method for producing a polyolefin-coated metal material that can be overcoated or adhered without causing a large increase in cost. The purpose is to provide.

[0011]

Means for Solving the Problems The main object of the present invention, which has been made to achieve the above object, is to provide a main coating layer made of a polyolefin resin for imparting a top coat paintability or a top-coating adhesive property to a polyolefin resin-coated metal material. A method for producing a coated metal material in which an adhesion mediating layer made of a modified polyolefin resin is provided on the surface of a polyolefin resin, which is formed by forming a molten layer of polyolefin resin on the surface of the metal material and cooling and solidifying the molten layer. In the process, on the surface of the molten layer of the polyolefin resin, a modified polyolefin resin powder is contacted and fused to form a coating layer of the modified polyolefin resin, and the coating layer is the molten layer of the polyolefin resin. It is characterized in that the adhesion mediating layer is provided by cooling and solidifying together.

As described above, the present invention is characterized in that the adhesion mediating layer is formed in the course of a series of operations usually performed for applying a polyolefin resin coating to a metal material.

Here, the material and thickness of the main coating layer made of the above-mentioned polyolefin resin may be as specified according to the original purpose of use such as long-term corrosion protection. Carbon black, antioxidants, stabilizers, etc., which have been conventionally blended, are preferable from the viewpoint of ensuring light resistance with respect to the above-mentioned adhesion mediating layer and the main coating layer shielded from light by the overcoating. ,
Depending on the degree of shading by the upper layer, the amount of the above composition may be reduced or omitted.

Next, as the modified polyolefin resin used in the adhesion mediating layer, acid modified products such as maleinized modified products of polyolefin, ethylene-vinyl acetate copolymer (EVA), saponified products or acid modified products of EVA, etc. From the polyolefin modified products having polarities or the compounds containing these as the main components, those capable of adhering the paint to be overcoated or the adhesive to be used for overcoating are appropriately selected.

Further, it is necessary to have a hot melt adhesive property with the polyolefin resin used for the main coating layer, but a solution of the modified polyolefin resin is applied to the surface of the once solidified polyolefin resin coating layer, and it is temporarily heated. Unlike the conventional method in which the coating layer is mainly melted and adhered, that is, B is unilaterally fused to A in the solid phase, in the method of the present invention, melting is performed with a large heat capacity including the base metal material. The modified polyolefin resin is fused to the surface of the polyolefin resin layer, that is, the fused material can be sufficiently melted, and a system in which both resin layers are in close contact with each other in a molten state before solidification is realized, Because of the progress of cooling and solidification of this system, that is, because A and B are fused together evenly after going through the process of being in the molten phase, they are easily adhered, and the material selection from the viewpoint of the above heat fusion adhesiveness is performed. The degree of freedom is increasing. In addition, the strength and durability of the adhesive are naturally improved.

The method of the present invention is carried out in the usual manufacturing process of a polyolefin resin-coated metal material,
The thickness of the main coating layer made of the above resin is often 0.5 to 5 m.
It is in the range of m. On the other hand, the thickness of the adhesion medium layer applied on this layer is 30 to 100 μm, which can cover the main coating layer, because the pinholes do not exist in a concentrated manner in view of functional requirements. Is enough. However, there is no problem even if a thick film of, for example, about 300 μm is formed due to circumstances in toning design or manufacturing.

It is desirable to add an appropriate amount of carbon black, an antioxidant and a stabilizer to the above-mentioned adhesion mediating layer, depending on the light-shielding performance by the overcoating or the like applied thereon. In addition, a light-colored pigment may be blended for the purpose of distinguishing it from the main coating layer at the time of construction and use, or for assisting toning such as overcoating.

In the method of the present invention, the formation of the adhesion mediation layer for imparting the top coat paintability to the polyolefin resin-coated metal material is performed by the connection mediation in the conventional coating process for producing the polyolefin-coated metal material. Since it can be done by a simple means such as adding the operation of supplying the resin powder for forming the layer to the target surface, it is possible to give the top coatability while keeping the cost increase to almost only the material cost. Is.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The coating of a metal material on which the method of the present invention is carried out with a polyolefin resin is usually carried out by a powder coating method or an extrusion coating method.

The polyethylene resin coating by the powder coating method will be described as an example. Depending on the heat capacity of the metal material (it varies depending on the wall thickness, etc.), or the heating and melting characteristics of the coating material and the heat fusion property to the base material. A molten layer of the coating material, which is made by contacting and melting the powder of polyethylene coating material having a typical particle size of 100 to 200 μm on the surface of a metal material heated to 200 to 300 ° C by fluidized dipping method or powder projection method. Is formed, the molten layer is cooled and solidified, and coating is performed.

In the method of the present invention, a powder of a modified polyethylene resin such as maleated EVA is formed in the same manner in the above process in order to form the adhesion mediating layer on the surface of the molten layer. It can be carried out by performing an operation of bringing them into contact with each other and melting and adhering them by the retained heat of the molten layer. As the particle size of the modified polyethylene resin powder, a typical particle size of about 100 to 200 μm is suitable because the fluidized dipping operation or the powder blasting operation can be performed stably.

The melting point of the modified polyethylene resin is generally
It is around 100 ° C, and when the powder of the resin is brought into contact with the surface of the molten layer of the polyethylene resin (usually around 200 ° C), it is melted and adhered with almost no interval, and the modified polyethylene resin is coated. A layer is formed. Since it suffices that the pinholes are not concentrated on the coating layer, it is more important that the coating molten layer covers the underlying molten layer evenly than the thickness. Therefore, as described above, it is preferable to make it easy to distinguish from the base molten layer by adding a light color pigment and to apply thinly and uniformly.

The polyethylene resin and the modified polyethylene resin formed as described above, which are in close contact with each other in a molten state, are cooled to a temperature of about 80 ° C. or lower to solidify them, and An adhesion mediating layer is formed which is firmly integrated with the coating layer.

Even when the polyolefin resin coating is applied by the extrusion coating method, the temperature of the molten layer of the polyolefin resin is slightly lower than that of the powder coating method (150 to 200 ° C. in the case of polyethylene). The method of the present invention can be carried out in substantially the same manner as in the case of the coating method.

[0025]

EXAMPLE A carbon steel pipe (JIS SGP400A, length 6 m) was coated with polyethylene having a top coatability by the conventional method and the method of the present invention. <Comparative example> Density of 0.93 g / cm3 mixed with carbon black
The black polyethylene of No. ³ was coated by the usual powder coating method to prepare a polyethylene-coated steel pipe with a film thickness of about 1.5 mm. Then, a commercially available adhesive modified polyethylene solution was applied to the coated steel pipe (“Thermo-Tac E30” manufactured by China Paint Co., Ltd.).
0 ") was applied at room temperature by an airless spray and dried to form a coating film of about 15 μm. Thereafter, the coating film was irradiated with far-infrared radiation to heat-bond to the undercoating layer to form an adhesion mediating layer, thereby obtaining a top-coating polyethylene-coated steel pipe. An additional input of about 4 hours was required to form the adhesion medium layer.

<Example of the present invention> [0026] A polyethylene pipe is coated on a steel pipe with the same specifications as in the comparative example, and a polyethylene powder is brought into contact with the heated steel pipe to fuse them to form a molten layer. While rotating, the surface of the molten layer was sprinkled with powder of modified polyethylene (a material having the same composition as the nonvolatile content of Thermotac, crushed; gray color) to apply the fusion coating, and then the usual polyethylene coating was applied. The same cooling as in construction was carried out and solidification was performed to obtain a top coatable polyethylene-coated steel pipe having an adhesion medium layer of about 30 μm. In the above-mentioned examples of the present invention, it took only about 20 minutes additional time to form the adhesion medium layer.

[0027]

As described above, according to the method of the present invention,
A modified polyolefin having an adhesive property on the surface of a molten layer of a polyolefin resin formed on the surface of a metal material in the production process of a polyolefin-coated metal material having an overcoating property or an adhesive property for overcoating in a normal polyolefin coating construction process. It can be performed at low cost simply by adding the operation of bringing the resin powder into contact with each other and fusing them.

That is, it is possible to provide a polyolefin-coated metal material that can be toned by top-coating or the like without diminishing the feature of the polyolefin-coated metal material that can be provided at low cost. Since the polyolefin-coated metal material is usually black, and the conventional method is costly toning, there is a tendency that the application is restricted in terms of harmony with the landscape. The restrictions have been dispelled.

Claims (1)

[Claims] 1. A coated metal material comprising a polyolefin resin-coated metal material having an adhesion mediating layer formed on a surface of a main coating layer made of a polyolefin resin, for the purpose of imparting an overcoating property or an adhesive property for overcoating. A method of manufacturing, wherein a molten layer of a polyolefin resin is formed on the surface of a metal material, and this is performed by cooling and solidifying the molten layer. In the process of coating the polyolefin resin, the surface of the molten layer of the polyolefin resin is a modified polyolefin resin. A coating layer of modified polyolefin resin is formed by contacting and fusing the powder of 1. above, and the adhesive layer is provided by cooling and solidifying the coating layer together with the molten layer of the polyolefin resin. Manufacturing method of metal material.