JP4871649B2 - Resin powder coating method for metal rope - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a metal rope coating method, and more particularly to a powder resin baking method for manufacturing a coating rope having good corrosion resistance and excellent landscape.

Steel wire ropes are commonly used as metal ropes, but when used in places exposed to seawater or sea breeze, or in severe corrosive environments such as saltwater inflow rivers or acidic environments in volcanic areas, the corrosion resistance is impaired and the strength, There was a problem that the flexibility was lowered, the service life was shortened, and the landscape was damaged by rust.
As a countermeasure, it is effective to coat or paint with resin, and conventionally, a method of obtaining strands and ropes by twisting together after resin coating on each of the strands has been adopted, It takes a lot of time and labor to paint each strand of resin one by one, and there is a problem that the quality is likely to deteriorate due to peeling or damage of the coating when twisting.

As a countermeasure against this, it is advantageous to apply resin coating to the rope itself, but no practical and appropriate baking coating method has been found in the past. That is, in order to directly apply resin to the rope, (1) the rope is heated in advance to a temperature equal to or higher than the melting point of the resin powder and immersed in the fluidized resin powder, or (2) A method in which resin powder is adhered and melted and baked with an electrostatic coating apparatus is conceivable.
However, in the method of (1) dipping in the fluidized powder, unlike the strands, the rope in which a large number of strands are twisted has large irregularities on the surface, so the powder adheres to a uniform thickness. There is a problem that the powder is clogged between adjacent strands and between adjacent strands, resulting in a form close to a round bar as a whole, and as a result, there is a drawback that flexibility is greatly reduced.

In the electrostatic coating method (2), since the rope is preheated to a high temperature equal to or higher than the melting temperature of the resin, the sprayed powder is melted one after another from the surface between adjacent strands or strands. . For this reason, it becomes difficult for the resin powder to enter the narrow gap, and a pinhole is generated. Furthermore, if it is going to fill this pinhole, the resin powder spray time will become long, and as a result, it will have to become a very thick coating film about 300 micrometers or more like FIG. In FIG. 6, C is a buried pinhole.
In any of the above methods, the object to be coated is heated in advance to a temperature equal to or higher than the melting point of the resin powder, and the resin powder is adhered and melted on the object, and the resin powder contacts the object to be coated. At the same time, the heating starts, so that the powder melts one after another, eventually resulting in a thick coating, and the inherent flexibility of the rope is impaired.
In other words, a rope made by twisting a large number of strands, unlike a round bar, is slippery between adjacent strands and strands when bent, so it is flexible and flexible. Since the slip between each other is suppressed by the coating film which is in close contact with each other and between the strands, the flexibility of the rope is lowered. And as the coating film becomes thicker, the flexibility is lowered, and cracking is likely to occur in the coating film by bending.

  Moreover, in the case of a very long piece of wire having a length of 1000 m or more such as a wire rope, the processing time becomes remarkably long unless continuous rapid heating baking is performed, and practical production cannot be performed. When high-speed processing is performed by an atmospheric heating method such as a hot air furnace, the atmospheric temperature needs to be significantly higher than the melting point of the resin powder. In this case, from the surface of the resin powder adhering to the rope surface Since it is first heated and directly exposed to a high atmospheric temperature, the melting point of the resin powder is greatly exceeded, the coating resin deteriorates or burns, and stable quality baking cannot be performed. Therefore, when baking with atmospheric heating, the resin powder must be baked at a relatively low temperature above the melting point of the powder so that the resin powder does not deteriorate. Processing is required.

From the above points, in order to perform rapid baking, rapid heating from the surface of the rope under the adhered resin powder is required. For this reason, it is conceivable to use a high-frequency heating device. According to this, since the temperature rises rapidly from the rope surface under the adhered resin powder layer, the surface temperature is increased to an appropriate temperature that does not cause deterioration of the resin powder. Appropriate baking is possible if heated.
However, in a metal rope in which a number of strands are twisted together, the cross-sectional shape is significantly more complicated than that of a round wire, and is far from the circular shape. When this is heated in the coil of the high-frequency heating device, the temperature rise is delayed in the valley portion compared to the mountain portion of the rope, so that a temperature difference occurs and heating unevenness occurs. This heating unevenness becomes more prominent as the rope diameter increases. Therefore, at the peak portion of the rope, the temperature becomes too high and the resin powder is likely to be deteriorated or burnt. On the other hand, in the valley portion, the heating is insufficient, and a stable uniform coating cannot be performed.

  The present invention was made in order to solve the above-mentioned problems, and its purpose is excellent in rust prevention effect and weather resistance, and durability that does not cause cracks on the coating film surface even when bent. An object of the present invention is to provide a method capable of efficiently producing a good resin-coated rope.

In order to achieve the above object, the coating method of the present invention preheats a metal rope having a diameter of 6 mm or more obtained by twisting a plurality of strands obtained by twisting three or more strands to a temperature below the melting point of the resin powder. Then, after the preheating , the resin powder is continuously adhered by an electrostatic coating apparatus, and after the adhesion, the resin powder is heated and baked by the high frequency heating apparatus to a temperature higher than the melting point of the resin powder, and then cooled.

  In the present invention, the resin powder is not attached in a state where the rope is heated to a temperature equal to or higher than the melting point of the resin powder. The body is attached, and then the resin powder is heated rapidly above the melting point with a high-frequency heating device, and the powder is baked. Thus, for example, when the length of the dent in the coating thickness between adjacent strands on the outermost surface is L and the strand diameter is d, (L / d) × 100 (%) A uniform thin film coating of 6% or more can be applied, and a durable rope that does not crack on the coating surface even when bent can be mass-produced at low cost.

This preheating step may be performed using either a high-frequency heat treatment apparatus or an atmospheric heating apparatus such as a hot stove, and thereafter, the powder is adhered by an electrostatic coating apparatus, and then the main heating in the high-frequency overheating apparatus. Two-stage heating is performed.

  When the temperature is raised from room temperature to the baking temperature all at once, the temperature difference between the crest and trough of the rope becomes remarkably large. Can be reduced. That is, by preheating to a predetermined temperature by this preheating, the temperature difference between the peak and trough of the rope is reduced before the main heating is performed. Since the temperature is raised to the heating temperature, the temperature rise width in the main heating is smaller than in the case without preheating, and as a result, heating unevenness can be suppressed. This aspect is effective when the object to be coated is a rope having a large diameter, for example, 6 mm or more.

  Further, another preferred aspect of the present invention is that the resin powder is attached in series in the electrostatic coating apparatus without preheating the metal rope before the resin powder is attached in the electrostatic coating apparatus. Baking is carried out by heating above the melting point of the resin powder by two or more high-frequency heating devices arranged apart from each other.

  In the same manner as the above method, preheating is not performed before the resin powder is adhered, and after the powder is adhered in the electrostatic coating apparatus, it is preheated up to a predetermined temperature at the upstream of the high frequency heating apparatus disposed apart from each other. The temperature difference between the peak and trough of the rope can be reduced before entering the next heating device. Can also be suppressed. Note that two or more high-frequency heating devices may be used to sequentially increase the heating temperature.

Preferably, as the resin powder, a saturated polyester-based synthetic resin containing 8 to 20 mol% of isophthalic acid and having an intrinsic viscosity of 0.7 to 1.0 is used.
According to this, since the viscosity becomes close to water when the resin reaches the melting temperature, fine unevenness and gaps between the twisted strands are well wetted and solidified. In addition, the coating film is tough and, for example, the coating does not peel off from the rope surface even with a strong impact at the time of breakage in a tensile test. Further, the elongation is 30% or more and the adhesion is excellent, and the adhesion strength is 3% of epoxy resin. Since it reaches up to 5 times, cracks are not generated on the painted surface even when the rope is bent, and the durability is excellent. In addition, the coating film obtained has excellent outdoor durability, dielectric strength, impact resistance, cold resistance, adhesive strength, acid resistance, water resistance, and gas barrier properties, and has excellent adhesion to the rope surface compared to other resins. Even if scratched, it is optimal because it can suppress the spread of corrosion from that area to a small extent, and it is less likely to deteriorate during long-term outdoor use.

The present invention will be described below with reference to the accompanying drawings. FIG. 1 and FIG. 2 show an example of a resin-coated metal rope obtained by the present invention, 1 is a rope body, and a plurality of strands 1a are arranged. A plurality of twisted strands 1b are twisted to form a 3 × 7 structure in this example, and a valley 3 is formed between the strands. The diameter of the rope is usually 8 mm or more.
The material of the strand 1a is required to have corrosion resistance and is usually made of iron or steel. Preferably, the surface of the element wire 1a is plated with zinc, zinc aluminum alloy, brass or the like.

  Reference numeral 2 denotes a resin powder baking coating film applied to the surface of the rope body 1. This resin may be either thermoplastic or thermosetting, but must have excellent outdoor durability, dielectric strength, impact resistance, cold resistance, adhesive strength, acid resistance, water resistance, and gas barrier properties. Among various resins, polyester resins are particularly excellent in weather resistance, have little deterioration in long-term outdoor use, and have high adhesion to the plating layer. It is recommended because of its low corrosion spread and excellent corrosion resistance.

A typical example of the polyester-based resin is a modified saturated polyester resin, and in particular, a crystalline isolephthalic acid copolymer containing 8 to 20 mol% of an isophthalaleic acid component and having an intrinsic viscosity of 0.7 to 1.0. Saturated polyester (polyester polymer made of polyethylene isoterephthalate copolymer) is preferred.
Here, the reason for limiting the isophthalaleic acid component is that if less than 8%, the adhesion is impaired, and if it exceeds 20%, the crystallinity decreases and the elongation decreases, and the viscosity is limited. This is because a high molecular weight polymer is required to cover the surface of the plating layer with good fluidity while suppressing the progress of the conversion.
When the modified saturated polyester resin resin reaches a certain temperature, the viscosity is remarkably lowered to a so-called shabu-shabu state like water. For this reason, it enters into a minute gap and wets and solidifies the solid there to form a film. In addition, the adhesiveness is very good and the adhesive strength reaches 150 kg / cm ² .

The resin powder baked coating film 2 is a thin film that can visually confirm irregularities on the rope surface, and the dots in FIG. 1 represent a coating film and are not scattered with powder. As can be seen from FIGS. 1 and 2, the resin powder baking coating film 2 is applied so that the peaks and valleys of the adjacent strands 1a and 1a are clearly visible. That is, as shown in FIGS. 2 (a) and 2 (b), the V-shaped film 20 is formed in the valley between adjacent strands 1a and 1a, and this is also formed in the valley between the strands 1b. The film is formed along the outer contour of the adjacent strand. The film is continuous along the contour of the cross section and is a uniform thin film without pinholes.
Specifically, the thickness of the coating film is 40 to 170 μm. The reason why the lower limit of the thickness is set to 40 μm is that when the thickness is reduced to 40 μm or less due to the particle size of the resin, an open pore-shaped pinhole is generated from the rope surface to the coating surface, and the upper limit is set to 170 μm. This is because if the thickness is greater than this, the rope becomes stiff and difficult to bend, resulting in poor handling and a risk of partial cracking when bent at a small bending radius.

Then, as shown in FIG. 2 (b), if the length of the coating thickness dent between adjacent strands 1a and 1a on the outermost surface is L and the strand diameter is d, (L / d) × 100 ( %) To 6% or more. This is an index created by the present inventor for making the coating thickness thin and uniform everywhere on the rope cross section, and uniform corrosion resistance and ease of bending of the rope are maintained by satisfying this condition. If L / d is less than 6%, the irregularities of the strands are invisible, and the groove between the adjacent strands 1a and 1a is almost filled with a resin film, that is, in a rod shape, and the rope is difficult to bend. . When the dent condition of the coating film between the strands is satisfied, since the coating film has a thin, uniform and sharp outline, the rope slips when the rope is used, for example, when the ropes are crossed and clamped Therefore, it is possible to securely fix them in an orthogonal shape.

FIG. 3 shows an example of another rope obtained by the present invention. (A) is a 7 × 19 structure rope body 1 with a resin powder baking coating film 2, (b) is a 7 × 7 structure rope body 1 with a resin powder baking coating film 2. Each is shown, and is painted uniformly so that the outline of the strands can be clearly seen without filling the valley 3. Since other configurations are the same as described, the description is incorporated.

  The first aspect of the manufacturing method of the present invention will be described. After the rope body 1 is manufactured by a normal method, continuous processing is performed in a process in which equipment as shown in FIG. 4 is arranged. In the manufacture of ropes, oils for lubrication are basically not used. This is because if the oil remains on the rope surface, the adhesion between the coating resin and the rope surface is impaired. When oil is used, the degreasing treatment is performed before this step or at the beginning of this step.

  In FIG. 4, reference numeral 4 denotes a supply device that retracts the rope body 1, and 5 denotes a constant speed winding device. Between the supply device 4 and the winding device 5, a brake device 6, a preheating heating device 7 </ b> A, The shot blasting device 8, the electrostatic coating device 9, the main heating high-frequency heating device 7B, the cooling device 10 and the drying device 11 are arranged in this order from upstream to downstream. Note that the preheating heating device 7 </ b> A may be disposed downstream of the shot blasting device 8.

  The rope body 1 drawn out from the supply device 4 is first preheated by the preheating heating device 7A. A high-frequency heating device is used as the preheating heating device 7A from the viewpoint of shortening the heating time, but it may be an atmospheric heating device. In the former case, a high frequency is applied to the rope by a high frequency coil while the rope is running, and heat is diffused from the surface of the rope to the inside to achieve a uniform heating state. The latter is performed by blowing hot air into a tunnel through which a rope passes, using a hot air furnace or the like. In any case, the heating temperature is controlled so that the rope surface temperature measured at the position immediately before the electrostatic coating apparatus 9 does not exceed the melting point of the resin powder.

The rope body 1 preheated in this way is introduced into the shot blasting device 8, and the shot material is sprayed to the entire circumference of the rope surface while passing through it, so that the surface is processed into a satin finish made up of fine irregularities.
This treatment is for obtaining strong adhesion between the rope surface (plating layer) and a resin described later, and is performed by causing a hard shot material such as alumina to collide with compressed air as a medium. That is, while moving the rope body 1 in the passage of the closed cross section, the abrasive is air-blasted from the nozzle attached to the passage wall of the closed cross section at a position obtained by dividing the circumference into three or five equal parts.

The rope body 1 thus preheated and with fine irregularities on the surface is guided to the electrostatic coating device 9 in this state, where resin powder is sprayed onto the rope surface for electrodeposition.
In this step, in order to make it easier to enter the gap between adjacent strands and the gap between strands, the particle size of the resin powder is, for example, that passed through a fine sieve of 80 mesh pass or less, preferably 120 mesh pass or less. Is preferred.
This electrostatic coating process is performed by using an electrostatic flow method such as electrostatic spraying, charging resin powder, and spraying it on the rope surface with an air gun. As a result, the resin powder is subjected to air shot blasting and is electrically attached to the rope surface on which numerous irregularities are scattered.

In this way, the entire surface of the rope body 1 is covered with resin powder particles while passing through the electrostatic coating device 9, and the resin powder is melted from the rope surface while passing through the high-frequency heating device 7B in this state. Rapid heating to a predetermined temperature higher than the temperature. For example, a high frequency is applied so that the rope surface temperature becomes the resin melting point + (20 to 60 ° C.). However, if the temperature is higher than that, the resin deteriorates due to thermal decomposition.
The resin powder melts from the lower layer in contact with the rope surface, flows into innumerable irregularities by shot blasting, bites in and adheres like a rust, and forms a uniform film on the surface of the strand and the surface of the strand. When the resin powder is melted, the temperature difference between the peak and valley portions of the rope can be reduced because the two-step heating is performed in which the preliminary heating is applied before the main heating as described above. The non-uniformity of the film thickness at the peaks and valleys is suppressed, and a uniform thin film without pinholes as a whole can be obtained.

  When this melting has progressed, it is immersed in a cooling device 10 such as a water tank to solidify and adhere the molten resin to the rope surface. Then, it is made to dry through the drying apparatus 11, and is finally wound up with the constant speed winding apparatus 5. FIG. In this way, the painted ropes of FIGS. 2 and 3 are obtained.

Next, the second aspect of the present invention will be described. As shown in FIG. 5, from upstream to downstream, the supply device 4 → the brake device 6 → the shot blast device 8 → the electrostatic coating device 9 → the plurality of high-frequency heating devices 7A and 7B → The cooling device 10 → the drying device 11 → the constant speed winding device 5 is arranged. The plurality of high-frequency heating devices 7A and 7B are arranged at an appropriate distance from each other.
In this embodiment, before the electrostatic coating, the rope is not preheated, the electrostatic coating is performed at room temperature, and then the rope is heated by the high-frequency heating device 7A on the upstream side. The heating temperature at this time is below the melting point of resin, for example, it heats so that rope surface temperature may become about resin melting point- (50-80 degreeC). And it heats to the temperature more than the melting point of resin with the high frequency heating apparatus 7B of a downstream side.

By such two-stage heating, a temperature difference (heating unevenness) due to a delay in the temperature rise in the valley portion is suppressed as compared to the mountain portion of the rope, and the rope surface is heated up by the first stage heating. Resin that comes into contact with or approaches is softened, and by the second stage heating, complete melting proceeds uniformly and smoothly from the semi-molten state where the melting starts and gradually propagates. Therefore, it becomes the continuous resin film 2 which has uniform coating-film quality, few uneven thickness, and no pinholes.

Any aspect is not a metal rope that is resin-coated and twisted one by one on each strand of wire, but is a method of coating thinly directly on a twisted metal rope, so that the coating is not damaged by the twisting process, and the above conditions Thus, the coating film has a thin thickness of 40 to 170 μm where irregularities on the rope surface can be clearly confirmed from the appearance, and the dent length of the coating film thickness between adjacent strands on the outermost surface is L, and the strand diameter is d. (L / d) × 100 (%) 6% or more can be secured, and a uniform thin film coating without pinholes can be obtained. The coating thickness can be freely adjusted by selecting electrostatic coating conditions.

The coated metal rope shown in FIG. 2 was manufactured by applying the present invention. The rope main body is a wire rope having a diameter of 18 mm and a 3 × 7 structure in which three strands obtained by twisting seven strands each galvanized are twisted.
This rope was painted at a speed of 5 m / min in the above-described process. After passing through the brake device, preheat the surface temperature to about 120 ° C at the position just before electrostatic coating with a high-frequency heating device, then make the entire surface satin by shot blasting, and then a particle size of 120 mesh pass Saturated polyester resin powder (isoterephthalic acid copolymerized saturated polyester containing 8 to 20 mol% isophthalic acid and having an intrinsic viscosity of 0.7 to 1.0), coating voltage and discharge amount of powder from gun Etc. were controlled to apply electrostatic powder. After that, the main powder was heated to about 300 ° C. using a high-frequency heating device to melt the resin powder, and then was immersed in cooling water to be solidified and adhered.
Through the above steps, a very uniform thin coating without pinholes having an average coating thickness of 120 μm was applied, and (L / d) × 100 = 8.2 (%). The coating does not peel even when subjected to a strong impact at the time of tensile fracture, has good adhesion, and it is confirmed that peeling and cracking do not occur even when wound on a drum with a diameter of 540 mm used for winding a normal non-painted rope It was done. Even after 5000 hours passed through a salt spray tester, no rust or cracks were generated.

Using a wire rope having a diameter of 16 mm and a 7 × 7 structure in which six strands are twisted around one strand obtained by twisting seven strands shown in FIG. The modified saturated polyester resin powder was baked in the same process as in No. 1.
As a result, a thin coating having a uniform coating thickness of 102 μm on average and without pinholes was obtained, and (L / d) × 100 = 7.2 (%). It is confirmed that the coating does not peel off even when subjected to a strong impact at the time of tensile breakage, has good adhesion, and does not peel off or crack even when wound on a drum with a diameter of 540 mm used for winding a normal non-painted rope. It was. Even after 5000 hours passed through a salt spray tester, no rust or cracks were generated.

A wire of 7 × 19 structure with a diameter of 6 mm, in which 7 strands of 19 strands shown in FIG. 3A are twisted and 1 strand in the center and 6 strands around the strand are twisted The modified saturated polyester resin powder was baked using a rope in the same manner as in Examples 1 and 2.
In this way, a thin coating having a uniform coating thickness of 90 μm on average and without pinholes was obtained, and (L / d) × 100 = 7.9 (%). It is confirmed that the coating does not peel off even when subjected to a strong impact at the time of tensile break, has good adhesion, and does not peel off or crack even when wound on a drum with a diameter of 280 mm, which is used for winding ordinary non-painted ropes. It was. Even after 5000 hours passed through a salt spray tester, no rust or cracks were generated.

The same resin powder was applied in the next step using a 3 × 7 rope having the same diameter of 18 mm as in Example 1 at a speed of 5 m / min.
The rope fed out from the supply device was passed through the brake device, then passed through a shot blasting device to make the surface a satin finish, and then the powder was adhered by an electrostatic coating device. Subsequently, the rope surface temperature is heated to about 200 ° C. by the first high-frequency heating device, and the main surface is heated to about 300 ° C. by the second high-frequency heating device disposed about 1 m away from the device, and the powder is heated. Was melted. Then, it cooled with water, it was made to solidify and adhere, and it wound up with the winding device through the drying apparatus.
In this way, a thin coating without a very uniform pinhole with an average coating thickness of 124 μm was obtained, and (L / d) × 100 = 7.8 (%). About the characteristic of the coating film, it was confirmed that it is the same as that of Example 1.

It is a side view of the resin powder coating metal rope obtained by this invention. (A) is an expanded sectional view which shows an example of this invention rope, (b) is the partially expanded view. (A) And (b) is an expanded sectional view which shows the other example of this invention rope. It is process drawing which shows the 1st aspect of this invention. It is process drawing which shows the 2nd aspect of this invention. It is a partial expanded sectional view of the conventional painting rope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rope main body 1a Wire 1b Strand 2 Resin powder baking coating film 7A Preheating heating device
7B Heating device for heating
9 Electrostatic coating device 10 Cooling device

Claims (3)

A metal rope having a diameter of 6 mm or more obtained by twisting a plurality of strands in which three or more strands are twisted together is preheated to a temperature below the melting point of the resin powder , and continuously after that preheating with an electrostatic coating apparatus. A resin powder coating method for a metal rope, characterized in that a resin powder is adhered, and after the adhesion, the resin powder is heated and baked by a high-frequency heating device above the melting point of the resin powder and then cooled. Before the powder resin is attached to the electrostatic coating device, a preheated metal rope is introduced into the shot blast device, and while passing through this, the shot material is sprayed around the metal rope surface, 2. The method of coating a metal rope with resin powder according to claim 1, wherein the metal rope is processed into a satin finish having fine irregularities .   The resin powder according to any one of claims 1 to 2, wherein the polyester resin is a saturated polyester-based synthetic resin containing 8 to 20 mol% of isophthalate and having an intrinsic year of 0.7 to 1.0. The resin powder coating method of the metal rope of description.

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