JPH0659458B2 - Manufacturing method of contact type thick film lining by rotational molding method of fluororesin powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to, for example, a reaction tower, a storage tank, a stirring tank, and their peripheral equipment mainly used in plants related to the chemical industry.
The present invention relates to a method for producing a contact type thick film lining by a rotational molding method of a fluororesin powder, which protects from corrosion caused by erosion or permeation by gas or chemical under conditions of high temperature, high pressure, negative pressure and the like.

[Prior Art] Conventional fluororesin linings for corrosion resistance are generally manufactured by the following method.

(1) Electrostatic powder coating method In this method, a fine powder of fluororesin is kneaded with a fine carbon powder having an electrostatic property, and a pre-charged base material which is a material to be lined is sprayed with a spray gun. This is a method in which this is heated and sintered while still standing. With this method, since the coating film only attracts carbon and the base material due to static electricity, a film thickness of 50μ to 100μ can be obtained in one step, and even with multiple coatings.
The limit is 800μ.

In this method, since the fluororesin contains impurities such as carbon, it is liable to elute into the content liquid, or due to overcoating, delamination occurs, and there is a drawback that it is mixed into the content liquid.

(2) Sheet lining method This is a method in which a plate of fluororesin having a thickness of 1 to 2 mm is attached with an adhesive along the surface of the base material at room temperature or while being softened by heating.

In this method, in the case of a complicated shape, the attachment work takes time and there is a problem in the adhesiveness by the adhesive. Further, all the seams between the plates have to be welded, and the residual stress easily causes phenomena such as peeling and cracking at the site of use.

(3) Loose lining method This is a method that is mainly applied to the inner surface of a straight pipe.First, a separately made fluororesin pipe is inserted into the inside of a metallic pipe, and both ends are flared (expanded). ) To finish. The same applies to the case of construction on a curved pipe.

In this method, since there is no adhesiveness between the fluororesin and the base material, it is weak against a negative pressure and cannot be used under a negative pressure, and the base material is limited to a simple shape.

The above is the known lining method.

[Problems to be Solved by the Invention]

However, the conventional processing method suffers from processing restrictions due to poor moldability of the fluororesin itself, and also has the following problems at the site of use.

(1) It is penetration of gas and chemicals that determines the life of the lining layer. Since the permeation is proportional to the film thickness, the thicker it is, the more effective it is. However, with the conventional processing method, it was impossible to form a seamless thick film layer (1 to 10 mm) regardless of the base material.

(2) Further, the strength of the adhesion between the base material and the fluororesin layer has a great relation to the life and application of the lining layer. If the adhesion is weak, peeling, cracking, deformation, etc. occur early depending on the conditions of use on site. Therefore, in order to prevent these and extend the life, it is necessary to strengthen the adhesive interface between the base material and the lining resin layer as much as possible.

(3) Furthermore, the shape of the base material is also restricted. Conventionally, most of the steps are manual work, so it has been impossible to lining complicated shapes, inaccessible places, invisible hidden places, and the like.

(4) Furthermore, mechanization is required to reduce the number of skilled workers and reduce costs. However, mechanization of conventional processing methods has been almost impossible due to the nature of processing.

The present invention was made in view of the above problems and was devised to solve the problems, and the object thereof is to provide an arbitrary film thickness on the inner surface of the hollow base material in only one step. Is fired, and even if it is a base material with a complicated shape, an integral type thick film lining layer with a uniform film thickness is formed seamlessly, and this can be machined to eliminate the need for skilled workers. To provide a method for manufacturing a contact-type thick film lining by a rotational molding method of a fluororesin powder, which can be processed in time and can prevent residual bubbles from being formed in a lining layer formed by welding on the inner surface of a hollow base material. It is in.

[Means for Solving the Problems]

In order to achieve the above object, the present invention is to put a thermoplastic fluororesin powder inside a metallic or ceramic hollow base material and heat it for a certain period of time while rotating and / or rocking, After rapidly raising the small allowable temperature and heating for a certain period of time to form a lining layer by welding to the inner surface of the hollow base material, gradually lowering the small allowable temperature to continue heating to eliminate bubbles contained in the lining layer, Then, it is cooled to form a seamless coating layer on the inner surface of the hollow base material.

Here, when the fluororesin powder put in the front is in a molten state, the rotation and / or the oscillation are temporarily stopped and a new fluororesin powder is partially added to a desired position of the hollow base material, and A method of partially thickening the lining layer may be included in the above invention.

In addition, a method of partially performing heat treatment on a desired portion of the hollow base material before welding of the fluororesin powder to partially reduce the thickness of the lining layer at the desired location of the hollow base material may be included in the above invention. .

[Action]

In this way, a stable and ideal close contact type thick film lining layer can be obtained. For that reason, the following elements act more effectively.

(1) In order to increase the adhesion strength between the hollow base material and the fluororesin layer, first, pretreatment depending on the type of hollow base material is important.
Next, electric ions are generated on the inner surface of the hollow base material to activate the surface and form an appropriate oxide film. Also, a special jig is required to create a uniform surface condition, and if the temperature range most suitable for the resin used is set and baked,
Effective in improving adhesion strength.

(2) When the fluororesin is dissolved, countless bubbles are generated in the sintered layer. This is because air is entrapped between the resin particles and the decomposition gas of the resin is generated, and all of these must be defoamed. Therefore, it is important to set the temperature suitable for defoaming. This is determined by the type of resin, film thickness, base material conditions, and the like. Further, at this time, by enclosing active gas or the like, it reacts with the decomposition gas to bring about a neutralizing effect and effectively act to promote defoaming.

(3) Further, in order to make the film thickness uniform, the rotation method and the rotation speed at the time of firing the hollow base material are the most important factors. First, depending on the size and shape of the hollow base material, the swing rotation method or the biaxial rotation method is determined. Next, the rotation speed is determined according to the film thickness and the type of fluororesin. At this time, it is important not to follow the same locus when the fluororesin powder on the inner surface of the hollow base material moves by rotation. In addition, heating and heat removal by a special jig also have a great effect on preventing uneven thickness.

〔Example〕

Hereinafter, the present invention will be described more specifically based on the embodiments illustrated in the drawings.

-Example 1- Here, FIG. 1 is a cross-sectional view of a hollow base material.

ETFE is used as the fluororesin powder, and the amount used is 0.7 kg.

The hollow base material 1 has a cylindrical shape as shown in FIG. This cylindrical shape has a closed bottom surface and an open top surface, and a flange is formed around the open top surface. The dimensions of the hollow base material are as follows.

The inner diameter is l ₁ = 160 mm, the height is h = 250 mm, the body thickness is t ₁ = 3 mm, the flange thickness is t ₂ = 5 mm, and the hollow base material is iron.

The work of forming the lining layer 2 on the inner surface of the hollow base material 1 is performed in the following steps.

That is, 0.7 kg of fluororesin powder (ETFE) is put into a cylindrical hollow base material 1, a lid 3 is attached, and this is attached to the rotating part of a rotary molding machine a that rotates in two axial directions. And
The rotary forming machine a to which the hollow base material 1 is attached is put in a heating furnace, and the rotary forming machine a is driven to rotate the hollow base material 1 only in one axial direction. The rotary molding machine a rotates in two axial directions based on the principle shown in FIG.

The number of revolutions is 20 revolutions per minute, and the hollow base material 1 is heated and heated while rotating. After raising the temperature to 320 ° C. over 30 hours, the welding process is started.

In the welding process, the rotation of the hollow base material 1 is switched from uniaxial rotation to biaxial rotation, and the rotation speed of the biaxial is changed from 20 rpm to 30 rpm.
Raise to rpm and increase the temperature rapidly from 320 ° C to 325 ° C. Then continue under these conditions for 15 minutes.

During this welding step, the fluororesin powder (ETFE) is uniformly welded to the entire inner surface of the cylindrical hollow base material 1 to form the lining layer 2. In the welding process, the rotation direction of the biaxial rotation is gradually changed at intervals of 2 minutes, and each rotation is rotated in the forward and reverse directions so that the fluororesin powder (ETFE) is evenly distributed throughout the hollow base material. To

After the welding process is completed, the defoaming process is started. The defoaming step is a step for eliminating bubbles contained in the lining layer 2. In the defoaming step, the temperature is gradually lowered from 325 ° C to 310 ° C over 20 minutes to eliminate the bubbles contained in the lining layer 2. At this time, the respective rotational speeds in the two axis directions remain unchanged and do not change.

After the defoaming process is completed, the final cooling process is started. Although there are three types of cooling methods, natural cooling is adopted in this first embodiment. In this cooling step, the rotary molding machine a to which the hollow base material 1 is attached is taken out from the heating furnace and cooled in a natural state.

Then, after the hollow base material 1 was completely cooled through the cooling step, the lid 3 was removed, and a lining layer 2 having a thickness of 2 mm was formed in close contact with the inner surface of the hollow base material 1.

-Example 2- Here, FIG. 2 is a cross-sectional view of a hollow base material.

ETFE is used as the fluororesin powder, and the amount used is 14 kg.

The shape of the hollow base material 1 is a cylindrical shape as shown in FIG. 2, and a small diameter cylindrical shape is formed to project on the left and right side surfaces and the bottom surface, of which the bottom surface cylindrical shape is bent at 90 degrees. Has been done. The upper surface of this cylindrical shape is open, a thick flange is formed on the peripheral edge of the open upper surface, and a flange is also formed on the peripheral edge of another small-diameter cylindrical opening. Its dimensions are as follows.

The inner diameter of the main body is l ₁ = 500 mm, the height is h = 500 mm, and the thickness of the upper flange is t ₂ = 20 mm. Also, the inner diameter of the cylinder on the left side is l ₂ = 200 mm, the inner diameter of the cylinder on the right and bottom is l ₃ = 50 mm, and the thickness of the body and other flanges is t ₁ =
It is 6 mm, and the material of the hollow base material is stainless steel.

This hollow base material 1 has a plate thickness difference of 6 mm to 20 mm, and there is a possibility of uneven thickness. Therefore, a special jig for heat treatment is attached to such a part, and the lining layer is partially formed. Prevents 3 from becoming thick.

That is, the heat insulating material 4 as a special jig for heat treatment is attached to the lower surface of the thick flange on the upper surface, and the curved cylindrical shape of the bottom surface is used as a special jig for heat treatment. The heat radiation plate 5 is temporarily attached.

The work of forming the lining layer 2 on the inner surface of the hollow base material 1 is performed in the following steps.

That is, 10 kg of fluororesin powder (ETFE) is put in a relatively complicated cylindrical hollow base material 1, a lid (not shown) is attached to each opening, and the lid is rotated in a biaxial direction. Attach it to the rotating part. Then, the rotary molding machine a to which the hollow base material 1 is attached is put into a heating furnace, and the rotary molding machine a is driven to rotate the hollow base material 1 only in one axial direction. The rotary molding machine a rotates in two axial directions based on the principle shown in FIG.

The number of revolutions is about 8 revolutions per minute, the hollow base material 1 is rotated and heated to raise the temperature, and the temperature is raised to 320 ° C. over 40 minutes, and then the welding step is started.

In the welding process, the rotation of the hollow base material 1 is switched from uniaxial rotation to biaxial rotation, and the rotation speed is changed from 8 rpm to 13 rpm.
The temperature is rapidly raised from 320 ° C to 330 ° C. Then continue under these conditions for 25 minutes.

In this welding process, at the same time, a heat removal treatment for preventing uneven thickness is performed by using a special jig attached to the uneven thickness dangerous portion. This heat removal treatment is performed at a curved cylindrical portion on the bottom surface where the heat dissipation plate 5 is temporarily attached.

In the heat removal treatment, cooling air is blown to the rotating heat radiating plate 5 to cool the heat radiating plate 5, and the inner surface of the curved cylindrical shape to which the heat radiating plate 5 is temporarily attached is heated through the heat radiating plate 5. To prevent the uneven thickness of the lining layer 2 which is partially formed thick. The cooling jet pipe for jetting cooling air is integrally attached to the rotary molding machine.

Note that there is also a simple method for removing heat treatment by simply attaching the heat insulating material 4 and not requiring any other treatment.

During this welding step, the fluororesin powder (ETFE) is uniformly welded to the entire inner surface of the cylindrical hollow base material 1 to form the lining layer 2. In the welding process, in the welding process,
The rotation direction of the biaxial rotation is gradually changed at intervals of 2 minutes, and each rotation is rotated in the forward and reverse directions to obtain fluororesin powder (ETF).
E) is distributed evenly throughout the hollow base material 1.

After the welding process is completed, the defoaming process is started. The defoaming step is a step for eliminating bubbles contained in the lining layer 2. In the defoaming step, the temperature is gradually lowered from 330 ° C. to 310 ° C. over 25 minutes to eliminate the bubbles contained in the lining layer 2. At this time, the respective rotational speeds in the two axis directions remain unchanged and do not change.

After the defoaming process is completed, the final cooling process is started. There are three types of cooling methods, but in this second embodiment, forced rapid cooling in which water atomized is sprayed is adopted. In this cooling step, the rotary molding machine a to which the hollow base material 1 is attached is taken out of the heating furnace, and a mist of water is sprayed on it for 10 minutes.

The cooling process is completed in 10 minutes, and after that, when the hollow base material 1 is removed from the rotary molding machine a and all lids (not shown) are removed,
A uniform lining layer 2 having a thickness of 5 mm was formed on the inner surface of the hollow base material 1 at both thick and thin portions.

-Example 3-Here, FIG. 3 is a cross-sectional view of a hollow base material.

PFA is used as the fluororesin powder, and the amount used is 10 kg.

The shape of the hollow base material 1 is a rectangular shape as shown in FIG.
The prism has a closed bottom surface and an open top surface. A flange is formed on the periphery of the open upper surface. Further, two protrusion pieces 6 are formed on the inner bottom surface of the prism. Its dimensions are as follows.

The inner diameter of the main body is l ₁ = 500 mm x 500 mm, and the height is h = 3
50 mm, the thickness of the body and the flange is t ₁ = 9 mm, the height of the protruding piece 6 is h ₁ = 50 mm, the thickness is t ₂ = 6 mm,
The material of the hollow base material is iron.

In this hollow base material 1, the plate thickness of the body portion is 9 mm, and the plate thickness of the protruding piece 6 is 6 mm. In this case, if it is processed as it is, the layer thickness of the lining layer 2 is different between the root of the protrusion 6 and the tip side. That is, the lining layer 2 is thinner on the tip end side of the projection piece 6 having a plate thickness of 6 mm than in the body portion having a plate thickness of 9 mm. Therefore, a special jig is attached to the hollow base material 1 to partially increase the thickness Need to do.

For this reason, two heat storage plates 7 as special jigs are temporarily attached to the outside of the portion where the protruding piece 6 is formed.

The work of forming the lining layer 2 on the inner surface of the hollow base material 1 is performed in the following steps.

That is, 10 kg of fluororesin powder (PFA) is put into the rectangular hollow base material 1, a lid (not shown) is attached, and the rotary part of the swing rotary molding machine b swings while rotating in a uniaxial direction. Install on. Then, the rocking rotary molding machine b to which the hollow base material 1 is attached is placed in a heating furnace, and the rocking rotary molding machine b is driven to rotate the hollow base material 1 only in one axial direction. The oscillating rotation molding machine b rotates in the uniaxial direction while oscillating on the principle as shown in FIG.

The number of revolutions is about 10 revolutions per minute to heat and raise the temperature of the hollow base material 1 while rotating it, and the temperature is raised to 350 ° C. over 30 minutes, and then the welding step is started.

In the welding process, the rotation of the hollow base material 1 was switched to the state in which the oscillating operation was added to the uniaxial rotation, the rotation speed was increased from 10 rpm to 15 rpm, and the temperature was changed from 350 ° C to 370 ° C. Sharply raise. The rocking operation is 10 reciprocations per minute, and the rocking angle is 40 degrees for each depression angle and elevation angle. Then continue under these conditions for 15 minutes.

In the welding step, at the same time, the heat storage plate 7 of the special jig attached to the location of the protruding piece 6 is used to supply sufficient heat to the tip side of the protruding piece 6. Then, 15 minutes after the welding process is started, the hollow base material 1 is once stopped from rotating and rocking.
With the temperature kept unchanged, powder of fluororesin powder (PFA) is evenly sprinkled on the surface of the protrusion, and thereafter, shaking and rotation are restarted and this is continued for 7 minutes.

An important point in this step is to uniformly sprinkle the second raw material on the surface of the projection when the first raw material is melted. When the second raw material is added in the molten state, the first and second raw materials are fused to form the lining layer 2 as one layer. As a result, the originally thin lining layer 2 of the protrusion 6 is so-called thickened, and the lining layer 2 having the same thickness as the other portions is formed.

During this welding step, the fluororesin powder (ETFE) is uniformly welded to the entire inner surface of the cylindrical hollow base material 1 to form the lining layer 2. In the welding process, the fluororesin powder (EFTE) is swung and rotated forward and backward so that the fluororesin powder (EFTE) is evenly distributed throughout the hollow base material 1.

After the welding process is completed, the defoaming process is started. The defoaming step is a step for eliminating bubbles contained in the lining layer 2. In the defoaming step, the temperature is gradually lowered from 370 ° C to 345 ° C over 20 minutes to eliminate the bubbles contained in the lining layer 2. At this time, the swing operation is 1
10 reciprocations in a minute, and the number of rotations is 15r.pm and it remains the same and does not change.

After the defoaming process is completed, the final cooling process is started. There are three types of cooling methods, but in this third embodiment, forced cooling by blowing cold air is adopted. In this cooling step, the rocking rotary molding machine b to which the hollow base material 1 is attached is taken out from the heating furnace,
Spray cold air evenly over this for 20 minutes.

The cooling process is completed in 20 minutes, and after the completion, the hollow base material 1 is removed from the rocking rotary molding machine b, and the lid (not shown) is removed. Had a uniform lining layer 2 with a thickness of 3 mm.

Through the working steps described above, the molding conditions and the special jig for the hollow base material are appropriately devised from the size, shape, material of the hollow base material 1, the kind of the raw material of the fluororesin powder, the film thickness, and the like. By using the same, it is possible to form a uniform lining layer 2 on any hollow base material 1.

The present invention is not limited to the above embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

〔The invention's effect〕

As is clear from the above description, according to the method of manufacturing the adhesion type thick film lining by the rotational molding method of the fluororesin powder according to the present invention, the following excellent effects are exhibited.

All conventional lining processing methods are applied by hand. This requires long experience and skill, and it is said that cost reduction is difficult. In particular, the number of skilled workers has decreased and there is a shortage, so there is a demand for machine lining.

The present invention is an improvement from the conventional manual processing method to the mechanical processing method, and has the effect that no skilled worker is required and that even an amateur can easily perform lining processing of stable quality in a short time. Although the construction time varies depending on the shape and size of the base metal, it can be greatly reduced to 1/5 to 1/30 of that of the conventional method.

Moreover, since it is an advanced coating that solves the problems of conventional processing methods, it is possible to bring out 100% of the excellent properties originally possessed by fluororesin, which greatly improves the service life of equipment at the site of use. be able to.

Combined with the above effects, after forming a lining layer by welding to the inner surface of the hollow base material, before entering the cooling step,
By continuing the heating while gradually lowering the allowable temperature, it is possible to eliminate bubbles contained in the lining layer and prevent residual formation of bubbles in the lining layer. As a result, it is possible to avoid that air bubbles remain in the lining layer and thus fail to function as the coating layer.

Further, according to the method of the invention described in claim 2, the thickness of the lining layer can be partially increased. For this reason, in particular, for a portion where the lining layer is partially thinned due to the plate thickness or shape of the hollow base material, by using this method, the lining having the same thickness as other portions can be obtained. A layer can be formed, and it becomes possible to form a lining layer having a uniform thickness as a whole.

Furthermore, according to the method of the invention described in claim 3, the thickness of the lining layer can be partially reduced. For this reason, in particular, in the part where the lining layer is partially formed thick due to the plate thickness and shape of the hollow base material, by using this method, the lining having the same thickness as other parts can be obtained. A layer can be formed, and it becomes possible to form a lining layer having a uniform thickness as a whole.

As described above, according to the method of the present invention, the reliability as a corrosion-resistant material in the industrial world is enhanced, and the life and safety of the lining equipment is extended, so that the effect of safety and economy is great, and the method is expected to be used in the future. It can be expected to expand.

[Brief description of drawings]

The drawings show an embodiment of a method for manufacturing a contact type thick film lining by a rotational molding method of a fluororesin powder according to the present invention, and FIGS. 1 to 3 are sectional views of hollow base materials used in each embodiment, FIG. 4 is a schematic principle diagram of the rotary molding machine, and FIG. 5 is a schematic principle diagram of the swing rotary molding machine. [Explanation of Codes] 1: Hollow base material, 2: Lining layer 3: Lid, 4: Heat insulating material 5: Heat dissipation plate, 6: Projection piece 7: Heat storage plate a: Rotational molding machine, b: Oscillating rotation molding machine

Claims (3)

[Claims] 1. A thermoplastic fluororesin powder is placed inside a metallic or ceramic hollow base material, which is heated for a certain period of time while rotating and / or oscillating, and the temperature is rapidly raised to a constant value. After heating for a period of time to fuse it to the inner surface of the hollow base material to form a lining layer, gradually lower the temperature while continuing to heat to eliminate the air bubbles contained in the lining layer, and then cool to provide a seamless coating. A method for producing a contact type thick film lining by a rotational molding method of fluororesin powder, wherein a layer is formed on the inner surface of a hollow base material. 2. When the fluororesin powder put in the front is in a molten state, rotation and / or rocking is temporarily stopped and new fluororesin powder is partially added to a desired portion of the hollow base material to obtain a desired hollow base material. The method for producing a contact type thick film lining by the rotational molding method of a fluororesin powder according to claim 1, wherein the lining layer at the location is partially thickened. 3. The fluororesin according to claim 1, wherein a desired portion of the hollow base material is partially heat-treated before welding the fluororesin powder to partially reduce the thickness of the lining layer at the desired portion of the hollow base material. A method for manufacturing a contact type thick film lining by a powder rotational molding method.