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
  • B05D7/06—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 wood
• • 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
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
  • B05D3/0209—Multistage baking
• • 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
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
  • B05D3/0254—After-treatment
  • B05D3/0263—After-treatment with IR heaters
• • 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
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/04—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to gases
  • B05D3/0406—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to gases the gas being air
  • B05D3/0413—Heating with air

Definitions

• the invention relates to a method for powder coating of wood substrates according to the preamble of claim 1 and an apparatus for performing the method according to the preamble of claim 7.
• the powder coating of metal parts is already well known.
• the furniture industry is eager to use wood substrates that are powder coated. This was due to the poor electrical conductivity of wood initially the problem of applying the paint powder evenly on the wood substrates. This problem seems largely solved.
• the powder layer must be fused and crosslinked. On the one hand, the wood substrate should not get too hot otherwise vapor bubbles will form, which can destroy the powder coating.
• High temperature MDF boards can damage the glue parts and thus significantly reduce the stability of the boards.
• wood substrate there are defined parts containing wood, e.g. Solid wood, plywood or wood fibers.
• the wood substrate is present in particular in the form of plates.
• No. 6,596,347 B2 describes a multi-stage process for applying two powder layers to substrates made of metal or plastic.
• the layers are cross-linked one after another, with infrared radiation and hot air treatment taking place simultaneously.
• the air velocity is 0.5 to 13 m / s.
• the temperature of the substrate reached 125 ° to 200 0 C.
• the process is not suitable for the treatment of wood substrates, because the temperature of the substrate is too high.
• An object of the invention is to provide a process for the powder coating of wood substrates, in which the paint layer is largely crosslinked. Another object is to provide an apparatus for carrying out the method.
• the problem is solved by claim 1.
• the freshly sprayed wood substrates are pretreated by means of a short-term infrared radiation, so that the paint powder just so adheres to the wood substrates and the surface of the powder layer is precrosslinked. In this case, most of the paint powder melts, so that the paint powder parts stick together and with the substrate surface. Only then is the subsequent hot air treatment possible.
• This is done according to the invention intensive, that is short and with very high air velocities. This causes heat to be transferred very quickly to the surfaces of the wood substrates, thus achieving the required temperature in the powder layer within a very short time, and therefore crosslinking.
• the short treatment time causes the heat does not penetrate far into the plate and therefore it is heated only relatively little. Due to the very high air velocity, not only the main surfaces of plates, for example, are treated intensively, but also, for example, end faces and / or undercut surfaces. This eliminates special treatments for such areas. Due to the short treatment times required, productivity is high.
• the wooden substrates despite the high air speed, are kept sufficiently quiet during transport - that is, without oscillating so that they abut.
• the temperature of the hot air of 120 ° to 200 0 C ensures a largely networking of the paint layer, without the wood substrate is too hot.
• the treatment time of the hot air treatment from 100 s to 300 s is adapted to the temperature of the hot air. In the treatment time of the pretreatment of 30 s to 90 s, a melting of the surface of the powder layer is achieved, which allows the subsequent intensive hot air treatment.
• the arrangement of a plurality of nozzle boxes in succession allows optimal coordination between the transport speed of the wood substrates and the treatment time in the hot air treatment.
• variable adjustability of the distance of opposite nozzle boxes allows an optimal adjustment of the distance of the nozzle boxes to the surface of the wooden substrates.
• the flow can be adapted to the wooden substrates according to their design.
• the fischgrat shame arrangement of radiators in the pretreatment causes also other than the main surfaces of the wood substrates are reached by the rays. This virtually all surfaces of the powder coating are melted.
• FIG. 1 shows a side view of a device according to the invention for powder coating wood substrates
• FIG. 3 shows a view of an arrangement of a nozzle box with an opposite further nozzle box in the transport direction
• FIG. 4 shows a horizontal section according to FIG. 3
• FIG. 5 shows a nozzle with zigzag-shaped nozzle bottom
• FIG. 6 shows another nozzle with zigzag-shaped nozzle bottom.
• a device for powder coating comprises a transport device 1, on which wood substrates 2 with a general transport direction according to arrow 3 can be suspended at a loading station.
• the transport device 1 is e.g. as an endless loop.
• successive means for spraying 4 of the paint powder means for preheating 5 the freshly applied powder layer by means of infrared rays and means for fusing and crosslinking 6 of the preheated powder layer.
• the transport device 1 is, for example, a suspension conveyor with a rail 7, in which a circulating chain is guided. Hooks 8 can be hooked into the chain (selectable according to the size of the wood substrates).
• the means for spraying 4 of the paint powder are known and are supplied for example by the company Wagner (CH Alt Zhaon) or Nordson (DE Erkrath). They will not be described here.
• the means for preheating 5 the freshly sprayed coating powder are particularly well visible in Figure 2 and comprise two with their front sides parallel opposite support frames 9. Their mutual distance is variable over e.g. a handwheel adjustable.
• Each support frame 9 is on five sides of a first housing
• the infrared radiators 1 1 are tubular carbon radiators, which are fixed like a fishbone on the front plane.
• the infrared radiator 11 are hereby arranged in two columns, wherein they extend at an angle of approximately 45 ° from the bottom to the top to the center of the front side. Down from the center and top of the sides of the front side starting infrared emitters 11 lesser (half effective here) length attached to keep the area as low as possible without infrared emitters. From the envelope of the entirety of the infrared radiators 11, an effective area of the means for preheating 5 results for each side.
• the carbon radiators e.g.
• Type CRS 2300 G from Heraeus are coated on their housing-facing side with an infrared ray-reflecting material, e.g. steamed with gold.
• the infrared radiators 11 can be installed in a twisted manner such that the emission direction is alternated by e.g. 45 ° upwards and downwards. To protect the infrared radiator 11 from overheating, they are assigned a forced ventilation.
• each nozzle box 12 faces another at a predetermined distance, and each panel 6a has two opposed nozzle boxes 12.
• the distance between two opposite front sides of the nozzle boxes 12 is variably adjustable.
• Each nozzle box 12 is mounted in a machine frame 13.
• Each nozzle box 12 is associated with a pressure box 14 which is connected via channels 15 with that.
• a fan 16 is arranged at a suction opening, which is driven by a motor and stored in the machine frame 13.
• each nozzle box 12 a plurality of here eight parallel, vertically aligned nozzles 17 is attached.
• Each nozzle 17 has a plane nozzle plane with in a pattern arranged nozzle openings and is connected by a pressure line 18 to the nozzle box 12. Between opposite nozzle levels, a treatment room is formed.
• a burner 19 is arranged so that the hot gases leaving it reach the suction chamber of the fan 16.
• the fusing and crosslinking means 6 are surrounded by a heat-insulating casing except for a slot 20 for passing the hooks 8 and the wood substrates 2.
• the machine frame 13 is integrated. All or individual partitions between two panels 6a may be insulated.
• individual or all of the nozzles 17 described above with a plane nozzle plane are replaced by nozzles 17 with a specific nozzle plane. Two examples of this can be seen in FIGS. 5 and 6.
• the nozzle planes are here in each case zigzag-shaped, wherein the zigzag shape in the example of FIG. 5 is formed in cross section and in the example of FIG. 6 in longitudinal section of the nozzle plane.
• the effective height of the means for preheating 5 and the means for fusing and crosslinking 6 corresponds at least to the largest height of the wood substrates 2 to be treated, the latter height being related to a state suspended in the transport device 1.
• the effective height here is about 2 m.
• the wood substrates 2 to be processed in the device preferably have a moisture content of 7% by weight. For this they are before the powder coating e.g. stored in a climatic chamber at 50% relative humidity and a temperature of 20 ° C.
• the provided wood substrates 2 are mounted by machine or by hand in the hook 8 of the transport device 1 and continuously conveyed in the direction of the arrow 3 through the device.
• the wood substrates 2 first pass into the spraying means 4, where all surfaces are sprayed with a suitable paint powder in a uniform thickness; so that the paint powder sufficiently adheres to the wood substrates 2, they are electrostatically charged.
• the freshly sprayed with the paint powder wood substrates 2 are then transported into the preheating means 5.
• all infrared radiators 11 are normally switched on.
• the powder layer is heated so that it at least softens and glued to the wood substrate 2 and the individual particles with each other. Due to the special arrangement of the infrared radiator 11 and the secondary surfaces (top, bottom, front and rear sides) of the wood substrates 2 are sufficiently heated.
• the wood substrates 2 enter the means for fusing and crosslinking 6.
• the fans 16 operate and blow hot air from the nozzles 17 onto the surfaces of the wood substrates 2;
• the air here has a temperature of 130 ° to 200 0 C and an impact velocity of 20 to 35 m / s.
• the previously molten powder layer melts completely and within a short time is largely crosslinked (sintered).
• the result is a closed paint surface of the powder layer with a certain smoothness, which has a high chemical and mechanical stability.
• each fan 16 sucks the air from an upper and a lower part of the treatment space and pushes them back into the treatment space on the wood substrates 2 via the pressure box 14, the air channels 15, the nozzle box 12, the pressure lines 18 and the nozzles 17.
• the air flow emerging from the nozzles 17 is substantially perpendicular to the main surfaces of the wood substrates 2.
• the air is heated by the burner 19 to the desired temperature of 130 ° to 200 ° C and kept constant by a corresponding control.
• the burners 19 of the last panel 6a are out of operation and the fans 16 suck in ambient air as cooling air. For this purpose, corresponding flaps are opened. The heated cooling air is discharged.
• the finished coated wood substrates 2 are unmounted by hand or by machine from the transport device 1 and removed or stored.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)

Applications Claiming Priority (2)

Publications (4)

Family

ID=38690110

Family Applications (1)

Country Status (6)

Families Citing this family (4)

Family Cites Families (6)

• 2006
  • 2006-09-22 DE DE102006044959A patent/DE102006044959B4/de not_active Expired - Fee Related
• 2007
  • 2007-08-14 DE DE502007004513T patent/DE502007004513D1/de active Active
  • 2007-08-14 EP EP07786677.0A patent/EP2066456B2/fr not_active Not-in-force
  • 2007-08-14 CA CA002663876A patent/CA2663876A1/fr not_active Abandoned
  • 2007-08-14 US US12/441,923 patent/US20090181181A1/en not_active Abandoned
  • 2007-08-14 WO PCT/EP2007/007162 patent/WO2008034497A1/fr active Application Filing
  • 2007-08-14 AT AT07786677T patent/ATE474673T1/de active

Non-Patent Citations (1)

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