JPS5859813A - Method and device for fixing coating of plastic material onto article - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for fixing a lining of plastics material to the cylindrical inner surface of a hollow metal article, and to an apparatus for carrying out the method.

The present invention particularly relates to, but is not limited to, hollow articles used as pipes for the transportation of gases, viscous liquids or solids. It is not something that will be done.

In many applications, at least the interior of the hollow initial article must be clean to improve slippage and corrosion resistant to delay replacement of the hollow article. For this purpose, the inner surface of the hollow article is coated with 7, for example polyamide "ILl".
It is well known to deposit a plastic material such as ``Niha Commercial SR Rilsan'', etc., and this layer has good uniformity and can be thickened, so it is necessary to prevent wear. It is possible to protect the material against geometrical accuracy and wear.

Since before fixation the plastic material is generally in the form of very fine particles, for example 20 to 200 microns, the flow of the particles throughout is particularly fluid-like.

A variety of bonding methods are currently in use for applying and coating the inner surface of pretreated pipes with a layer of brimer material.

The first method consists in first heating the metal article to be coated in a furnace and then placing it in a powder of plastic material contained in a tank, which powder is kept in suspension by air. There is. This powder melts and adheres on contact with heated metal surfaces. The thickness of this layer is 250 ~
It has a thickness of 500 microns. This thickness depends on the temperature of the article and the time it remains in the powder.

A second fixing method involves placing the pipe in an air stream containing the powder and then heating the pipe with an induction coil. In this case as well, the powder melts on contact with the heating pipe to create a thickness of 150-250 microns.

In a third method, the powder is suspended in water and the solution is applied into the cylinder with two spray sprayers, around which the pipe force is applied at a rate such that the desired thickness is achieved. be rotated.

The pipe is then heated first slowly to remove the water, then rapidly to melt it, and finally cooled to form a 50-300 micron thick film of plastic material.

While the thicknesses produced by these three methods are sufficient for certain applications, they are insufficient for applications such as solid fluid transport conduits, which require a service life of about 20 years.

That is, the thickness of the coating must be at least 6 mm to withstand wear in this case. To achieve this, a method using gravity rotomolding was implemented. In this method, the pipe to be coated is rotated on its own axis by a support C1.
1, and the roller is rotated at a slow circumferential speed of, for example, 4 m/min.

The amount of powder required to achieve the coating thickness is introduced into a cold pipe, but due to its fluid properties the powder is heated by heating means such as a gas lamp (or multiple gas lamps for large diameter pipes). It collects on a part of the inner surface of the pipe where it is exposed.

When the heating is stopped, the melted powder has a constant thickness at the point where it contacts the heated pipe, and the melted plastic material and the solid material are combined by gravity to form a part of the cylindrical inner surface. Even if you rotate the pipe, it will still collect.

Therefore, no plastic material other than the adhesively anchored film will flow on the inner wall of the pipe during this time.

The coverage of this film is not good, it cannot reach a thickness of a few millimeters, and the surface condition is irregular.

The results obtained according to the invention are that the coating of plastic material fixed on the cylindrical inner surface of the hollow metal article has a uniform and geometrically perfectly accurate surface condition and has a very large thickness. have.

Therefore, the present invention is characterized in that in the above-mentioned method, centrifugal forces of the following three phases are continuously applied to the hollow article. That is, in the first phase, centrifugal force is applied cold to distribute the material in a concentric uniform layer in the solid state, and in the second phase, in addition to the centrifugal force, a heating means is activated to cool the hollow article. The temperature is raised uniformly to create a complete melting of all the plastic materials distributed in the above phases, regardless of their thickness, and in the last phase the heating is stopped but the centrifugal force continues to be applied. All plastic material melted in the above phase is cooled and hardened.

The present invention further provides an apparatus for carrying out the above method.
BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood from the following examples, which are explained with reference to the accompanying drawings. However, the present invention is not limited thereto.

As in the known method, the hollow article 1 to be treated first passes through a surface treatment station 2 for degreasing and mechanical removal of surface oxides. The surface treatment station 2 is followed by a station 3 for applying, depending on the properties of the plastic material to be coated, a so-called "primary" layer for reinforcing the anchoring effect of the coating.

Then, in station 5, solid particles of mackerel powder or granular plastic material necessary to obtain the desired coating are introduced into the unheated hollow article 4 which has been treated as described above. The solid particle profile is precalculated so that the powder can be uniformly dispersed over the entire length of the hollow article by a doctor.

One feature of the invention is that the hollow article 7 (pretreated and loaded with powder as described above) is sent to a centrifugal custition consisting of a series of three phases 9, 10° 11, in which centrifugal force is applied in succession. At the point. In this first phase 9, a centrifugal force is applied cold, which causes the still solid coating material to be distributed concentrically in a uniform layer.

At the end of this first phase 9 a heating action 12 is started. That is, the second phase 10 begins.

During this second phase of centrifugation, the temperature of the hollow body is raised uniformly so that all the plastic material distributed in said phase is completely melted at any thickness.

Since the plastic material is uniformly distributed over the inner circumferential surface of the tube, the thickness of the plastic material may be thinner than if it were concentrated on a portion of the inner cylindrical surface. Therefore, the heating state is reliable.

When this happens, the heating action is discontinued (in phase 13 the molten plastic material hardens and solidifies, and when this phase ends, the operation of applying the coating 15 to the hollow object 14 ends).

The above plastic material fixing method of the present invention has many advantages over conventional simple rotary molding and gravity molding as follows.

1) There are no defects such as bubble generation.

2) Coating density is improved.

3) A perfectly smooth surface is obtained.

4) Even if a defect occurs during centrifugal casting of a hollow article, it is automatically compensated for.

5) Very thick coatings, for example of the order of l1m, can be fixed.

The centrifugal speed 1N in revolutions per minute is equal to the inner diameter r of the coating in meters, the outer diameter [R-1] and the pressure in pearls exerted on the plastic material by the centrifugal force 1". It is a function of PJ and can be expressed by the following known formula.

P=N(R-r·d) 2g Here, y indicates the density of the plastic material used, and y indicates the gravitational acceleration.

The heating temperature is determined depending on the characteristics of the plastic material, but is above the melting point of the material and below the temperature at which the molten plastic material becomes unstable.

The apparatus for carrying out the invention comprises a heating source 17, a centrifugal speed regulator 18, heating start and stop as well as intensity regulating means 19.
It consists of a centrifugal stand equipped with

For example, this device consists of a table 20 having a pair of rollers 21, 22, ie a rotating body;
, 22 on which the hollow article 7 is placed. This hollow article 7 is a starting hollow article 1 loaded with powder 6. The hollow article 7 is held on the rollers 21, 22 by at least one rotating body or a series of rollers 23. This roller 23 is movable forward and backward for attaching and detaching the hollow article 7.

At least one of the support rollers 21, 22 and/or the pressure roller 23 is brought into contact with the hollow article 7 and driven to rotate, thereby causing the hollow article to rotate. For this purpose, a motor 25 incorporating a transmission 26 is supported on the machine base 24 combined with the table 20, and an output shaft 27 of the transmission 26 is connected to the shaft 28 of the roller, that is, the rotating body 22, and any known A rotational connection is provided via a transmission 29.

Any known type of heating can be used.

In the embodiment, the hollow article between the support rollers 21 and 22 is heated from below by gas lamps 30, and the number of gas lamps can be increased to 30 or 31 depending on the diameter of the hollow article.

The above assembly is covered with a movable shield 32. The inner surface of the movable shield 32 is preferably covered with a heat insulating material 33 such as asbestos in order to retain heat during heating and to protect the surrounding area from swelling.

A chamber 34 surrounded by the shield 32 and the table 20 is provided with a temperature control detector 35 and means for forcibly cooling the hollow body in the final phase.

[Brief explanation of drawings]

Figure 1 is a conceptual block diagram of the method of the present invention. FIG. 2 is a sectional view of a hollow article and an apparatus for carrying out the above method. 1-.Hollow parts 6..Plastic material 8..
Centrifugal castration 9...First phase 10...Second phase 11...Third phase 12...Start of heating 13...
Heating stop 17...Heating source 18...Centrifugal speed adjusting device 19-al1 node means

Claims (2)

[Claims] (1) A method for adhering a coating of thermofusible plastic material onto the previously pretreated cylindrical inner surface of a hollow metal article, the hollow article being cold and below the temperature at which the plastic material melts. The material is introduced into a hollow article in the form of solid particles in the amount necessary to obtain a coating of the desired thickness at a temperature of These centrifugal forces occur one after the other in succession, further distributing the material (6) in a uniform layer in one phase (9) in the solid state; A centrifugal force is applied cold to the material still in the solid particle state to provide flowability for concentric distribution of the material in the particulate form, and heating means are applied α2 during the molten phase α value. to uniformly raise the temperature of the article (1), thereby heating the article (1) to a temperature sufficient to completely melt the plastic material with said distribution for any thickness of the plastic material, followed by a cooling phase. A method characterized in that the heating action is interrupted in the above-mentioned phase and the centrifugal force is continued until the plastic material melted in the above phase is cooled, that is, hardened and solidified. (2) An apparatus for fixing a coating of hot-melt plastic material on a previously pretreated cylindrical inner surface of a hollow metal article, comprising a heating source, a centrifugal speed regulating means aJI and a cold A device characterized in that it is constituted by a means for starting the action of a heating source αη on the distributed powder material and then stopping said action on the melting diameter of this material.