Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
  • B05D7/146—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies to metallic pipes or tubes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/002—Processes for applying liquids or other fluent materials the substrate being rotated
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2507/00—Polyolefins
  • B05D2507/01—Polyethylene

Definitions

• the coating of metal pipes with polyethylene powder is known, the z. B. is applied by trickling, spin coating or starting on the preheated tube to 300 to 360 ° C.
• the polyethylene types used in this process have melt indexes (190 ° C / 2.16 kg) of 1.2 to 1.7 g / 10 min.
• the melt index must be higher than in the first-mentioned process, because easier melting is essential here.
• the coating time for powder coating processes is generally about 5 minutes.
• this method has the disadvantage that relatively high preheating temperatures and thus a high energy expenditure are required to melt the polyethylene, because the melt index should not be too low for reasons of adequate corrosion protection.
• Another publication describes a composite pipe made of a polyethylene welded onto a steel pipe powder layer and a welded to this polyethylene layer, the z. B. was wound in the form of a polyethylene film emerging from an extruder onto the hot sintered polyethylene powder layer.
• the steel tube is z. B. preheated to 150 ° C. At this temperature, however, it is not possible to produce a smooth, coherent layer in a desired required minimum layer thickness of 1.5 to 4 mm.
• a polyethylene layer is applied to a steel pipe, firstly a 0.05 mm thick first layer of an adhesion promoter at a tube temperature about 100 ° C. above the solidification temperature of the adhesion promoter and then the second layer of the adhesion promoter at 20 to Pipe temperature 50 ° C above the solidification temperature, e.g. B. is applied at 140 ° C.
• the adhesion promoter of the first layer can be applied in powder form or by wrapping it with a film.
• the second layer can be applied by pre-extrusion in the form of a double tube or a double wrapping film.
• the temperature of 140 ° C. is not sufficient for the purposes desired according to the present invention, that is to say for the required minimum layer thickness.
• Another document also discloses coating a steel tube surface with a high melt index polyethylene, e.g. B. 1 to 1.5 g / 10 min (ASTM-D 12 38-53 T).
• the invention relates to a method for coating metal pipes by applying polyethylene powder to preheated pipes, wherein first a polyethylene with a melt index of over 1 g / 10 min is applied to a heated metal pipe and then a polyethylene with a low melt index is applied, which is characterized in that is d ate a polyethylene with a melt index of 1.2 to 70, preferably 15 to 70, in particular 17 to 25 g / 10 min (190 ° C / 2.16 kg) on the metal tube, which has a temperature of at least 200 ° C has applied, then the coating is allowed to cool to a temperature of about 110 to 170 ° C, preferably 110 to 150, in particular up to 120 ° C, and that in a third stage a self-supporting film of polyethylene with a melt index of 0 is then applied , 1 to 7 g / 10 min at this temperature so that the total coating has a minimum layer thickness between 1.5 and 4 mm.
• Another possible embodiment of the invention provides that first a polyethylene powder with a melt index of about 1.2 to 1.7 g / 10 min or a strip of polyethylene emerging directly from an extruder. with a melt index of maximum 1.7 g / 10 min (190 ° C / 2.16 kg) on a metal tube that has a temperature of at least 300 ° C in the case of powder coating and a maximum of 250 ° C in the case of coating by the extruder , applying thereon the coating to a temperature of about 110 to 170, preferably, can be 110 to cool to 150 ° C and then a self-supporting light-stabilized in the third stage, bright color ig en film made of polyethylene having a melt index of 0.4 to 1.1 g / 10 min at this temperature.
• compounds of the benzotriazole type are suitable as light stabilizers for the light-colored polyethylene film.
• the minimum layer thickness of 1.5 to 4 mm is required for adequate corrosion protection. In some cases, the layer thickness can also be more than 4 mm.
• the process according to the invention has the advantage that, compared with the known processes, it surprisingly results in high energy savings and nevertheless a considerably higher working speed with at least equally good product properties.
• the light-colored cover layer provides good protection for the pipes against excessive heating when stored outdoors for long periods under the influence of heat, for example due to sunshine or by laying in strongly heated floor layers.
• the coating of the extruder is also very simple and time-saving without additional equipment.
• the strip emerging from the extruder advantageously has a melt index of at least 0.4 g / 10 min.
• the polyethylene in the powder coating expediently has a particle size of 1 to 600 ⁇ m, preferably 100 to 400 ⁇ m.
• the self-supporting polylithylene film is advantageously in the form of a polyethylene tape, for. B. made of polyethylene with a melt index of 0.1 to 1.2 g / 10 min, applied. It can be applied to a rotating tube. This has the advantage that the tape can be wound automatically. The bandwidth can be varied as desired. It is z. B. at least 20 mm, expediently 10 to 1500 mm. A range of up to about 1 m is generally used. When applying, make sure that the individual turns overlap or that there is a mutual connection of the individual turns at the same time takes place in order to achieve perfect corrosion protection.
• the layer thickness of the tapes is usually 100 to 400 ⁇ m, preferably 100 to 200 ⁇ m.
• the light colored bands are preferably white. However, another color can also be selected as desired, e.g. B. the warning color yellow, but also light orange, light blue, light green or the like. If necessary, the light-colored tapes can also be used to identify the pipes.
• the speed of the coating can vary within wide limits. It depends on the desired layer thickness and the pipe diameter.
• the outer tube diameter is 50 to 2000 mm.
• the coating of a pipe with a diameter of 400 mm and a layer thickness of 1.5 mm (this is the minimum thickness for adequate corrosion protection) generally requires about 8 to 20, usually about 15 minutes for a 12 m long coating.
• an additional resin in the form of a polymer, e.g. As polyvinyl acetate, ethylene-vinyl acetate copolymer, ethylene-acrylic acid and / or acrylic ester-C opolymerisat, optionally with further comonomers, or other polymers, advantageously in a proportion of 5 to 15, 5 to 10 wt .- worzugêt%, based on the polyethylene powder.
• a polymer e.g. As polyvinyl acetate, ethylene-vinyl acetate copolymer, ethylene-acrylic acid and / or acrylic ester-C opolymerisat, optionally with further comonomers, or other polymers, advantageously in a proportion of 5 to 15, 5 to 10 wt .- worzugêt%, based on the polyethylene powder.
• this coating can according to the usual coating ver drive, by spraying, but preferably by powder coating.
• the same additional resins can also be contained in the poly
• the tubes coated by the method according to the invention are used in a variety of ways. Because of their surface protection, they are particularly suitable for laid pipes, e.g. B. in pipelines for the extraction of petroleum, but also of other gaseous, liquid or highly viscous substances, for example natural gas, water, sewage sludge, concrete, waste water, slurries or the like.
• Example 2 The same tube as in Example 1 is used, but with a preheating temperature of 310 ° C.
• the tube is coated with polyethylene powder with a melt index of 1.2 to 1.7 g / 10 min with a layer thickness of 2 mm. After 10 minutes the coating has melted smoothly and has reached a temperature of 180 ° C. The cooling time to 60 ° C simply by leaving it lying there is 50 minutes.
• Example 2 The same tube as in Example 2 is used, but with a preheating temperature of 360 ° C.
• the tube is coated at this temperature with polyethylene powder with a melt index of 1.2 to 1.7 1 1/2 minutes with a layer thickness of 2 mm.
• the coating melted in the course of 4 minutes and at the same time cooled to 310 ° C. Lattschmelzen to G, however, a post-heating is required. Therefore, after these 4 minutes, the pipe is reheated for one minute. The coating is smooth after this additional minute.
• the cooling time to 60 ° C from the start of the powder coating and without additional cooling is 42 minutes.
• the energy expenditure ie the preheating temperature and at the same time the cooling time, is significantly less in the examples according to the invention than in the comparative I examples.
• Example 3 The procedure is as in Example 1, but instead of the polyethylene powder, a powder is now applied in the form of a mixture of polyethylene with 10% by weight, based on polyethylene, of a vinyl acetate homopolymer. A coating is obtained with the same properties as in Example 1 and with a perfect smooth surface.
• Example 4 The procedure is as in Example 2, but instead of the polyethylene tape, a tape made from a mixture of polyethylene and 3.5% by weight, based on polyethylene, of a vinyl acetate homopolymer is now used. A smooth and flawless coating with the same properties as in Example 2 is obtained.
• An iron tube (outer diameter 108 mm, wall thickness 10 mm) is preheated to 310 ° C and then coated for 2 minutes with polyethylene powder (melt index 1.2 to 1.7 g / 10 min) with a layer thickness of 2 mm. After 20 minutes the coating has melted and the tube temperature has dropped to 160 ° C. Starting at this tube temperature, a 200 ⁇ m thick, 50 mm wide polyethylene tape with a melt index of 0.4 g / 10 min is applied in a layer thickness of 200 ⁇ m at 160 ° C. Then the tube is allowed to cool to room temperature either simply by leaving it lying there or by passing a cooling medium through it. Immediately after the tape has been applied, a perfect and smooth fusion of both coating layers occurs. After 40 minutes from the start of the powder coating, the tube has cooled to 60 ° C without being cooled.
• An iron pipe (outer diameter 90 mm, wall thickness 4.5 mm), is preheated to 360 ° C and then 1 1/2 minutes with polyethylene p ulver (melt index 1.2 to 1.7 g / 10 min) with a layer thickness covered by 2 mm. After a maximum of 8 minutes the coating melted smoothly and after 12 minutes it cooled to 150 ° C. At this tube temperature, a 40 mm wide polyethylene tape with a melt index of 0.4 g / 10 min is applied in a layer thickness of 200 ⁇ m and the tube is then cooled to room temperature. The tape is applied by wrapping the tube rotating around its axis, the spool being moved along the tube. Immediately after the tape has been applied, it fuses perfectly with the first polyethylene layer. After 30 minutes from the start of the pipe coating, the pipe has cooled to 60 ° C without being cooled.
• An iron tube (outer diameter 500 mm, wall thickness 6 mm) is preheated to 250 ° C. and coated with an ethylene-acrylic acid copolymer in powder form as an adhesive primer with a layer thickness of approximately 100 ⁇ m.
• a polyethylene tape emerging directly from an extruder with a melt index of 1.2 g / 10 min and a layer thickness of 250 ⁇ m is applied to these tubes, which are still warm. This winding process is continued until the desired layer thickness of 4 mm is reached.
• the tube is cooled to about 140 ° C by simply leaving it there. At this temperature, a yellow polyethylene tape with a melt index of 0.7 g / 10 min, a width of 300 mm and a layer thickness of 200 ⁇ m is applied.
• a perfect and smooth fusion of the two polyethylene coating layers occurs. After 30 minutes from the start of the extruder coating, the tube has cooled to 60 ° C without any additional cooling.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Laminated Bodies (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Lining Or Joining Of Plastics Or The Like (AREA)
• Protection Of Pipes Against Damage, Friction, And Corrosion (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (2)

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Family Applications (1)

Country Status (5)

Cited By (2)

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Citations (7)

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• 1980
  • 1980-09-30 EP EP80105906A patent/EP0026906B1/fr not_active Expired
  • 1980-09-30 DE DE8080105906T patent/DE3064429D1/de not_active Expired
  • 1980-09-30 ES ES495475A patent/ES8106418A1/es not_active Expired
  • 1980-10-03 CA CA000361493A patent/CA1151017A/fr not_active Expired
• 1982
  • 1982-09-16 US US06/419,035 patent/USRE31354E/en not_active Expired - Lifetime

Patent Citations (7)

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