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
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
  • B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field
  • B05D1/045—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field on non-conductive substrates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/08—Plant for applying liquids or other fluent materials to objects
• • 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
  • B05D2201/00—Polymeric substrate or laminate
  • B05D2201/02—Polymeric substrate

Definitions

• This invention relates to articles which are suitable for electrostatic application of a coating, more particularly a muffle coating, and to the use of a fibrous web for manufacturing such articles.
• a coating more particularly a muffle coating
• plastics are also used increasingly in the manufacture of housings for various machines.
• One of the ongoing problems associated with the use of plastics is finishing the surface, in particular if this is to be done through a coating.
• Muffling further involves the problem of poor conductivity of the plastics, so that electrostatic coating, which is most desirable from an environmental point of view, is not properly possible, if at all.
• the object of the present invention is to provide a system in which the disadvantages of the prior art are not encountered.
• This invention accordingly relates to the use of a conducting fibrous web incorporated in a plastics article at or below the surface of the article for providing conduction for electrostatic application of a coating to said surface.
• the fibrous web is preferably a web of metallized fibres, more particularly metallized plastics fibres.
• Suitable fibres are plastics fibres, preferably acrylic or polyester fibres, or glass fibres, which fibres have been metallized with nickel, copper or silver, or with alloys based on one.or more of these metals. It has been found that metallized fibres are appreciably more suitable for the present use than metal fibres, as metallized fibres yield an appreciably better conduction upon incorporation into the article. Moreover, metal fibres have the disadvantage that in the course of time the bond in the article deteriorates. Accordingly, although metal fibres can also be used, the use of metallized fibres is preferred.
• the conducting fibrous web may consist of conducting fibres only, but it is also possible to use a combination of conducting and non-conducting fibres in the web. In that case, for obtaining good conduction, the length of the conducting fibres is preferably 40-60 mm.
• the web can be bonded thermically, chemically or mechanically.
• a woven fabric can be used.
• a combination is used of a web of metallized fibres which is in contact with a net of metal wires, for instance copper wires of a diameter of 0.05- 0.5 mm, which net can be relatively coarse, having for instance a mesh of 0.5-10 cm.
• the present invention further relates to an article made from a plastics, suitable for electrostatic application of a coating, in particular a muffle coating, in which article an electrically conducting fibrous web has been incorporated at or below at least one of the surfaces thereof.
• the article according to the invention can comprise the above-described web at or just below its surface. If the web is located at the surface, the metallized fibres partly project through the plastics, so that the surface also has antistatic properties.
• the surface resistivity of the article can be low, for instance not more than 100, preferably not more than 10, more particularly not more than 1 Ohm #. This is very favourable for obtaining a surface to be coated electrostatically.
• the advantage of a conducting surface is that the potential can be applied in a simple manner by means of a conducting tape which is provided on the surface, for instance adjacent or on the edge.
• the article can be made from a thermoplastic or a thermosetting plastics.
• ther osetting plastics are phenolic resins, epoxy resins, polyester resins and polyurethane resins.
• Thermoplastics that can be used include the various "engineering plastics" such as polypropylene, ABS and related styrene polymers, polycarbonate, polyetherimide, polyphenylene oxide, polyphenylene sulfide and mixtures of such plastics. These plastics may also be reinforced with fibres. Known applications in this field are for instance articles made of fibre-reinforced polyester resin.
• the fibres to be used for the conducting fibrous web, and also for optional fibre reinforcement of the plastics are, in particular, acrylic fibres, polyester fibres, glass fibres, carbon fibres and aramid fibres. Naturally, the choice of the fibres is partly determined by the temperatures the materials must be able to resist during manufacture and use.
• the articles according to the invention can be made in different ways, depending on the materials to be used. Generally, in such systems a closed mould is used.
• the conducting fibrous web is introduced into a mould, optionally in combination with a fibrous web that can serve as a reinforcement of the plastics, for instance for the manufacture of a fibre-reinforced laminate.
• Suitable methods for manufacturing the articles according to the invention are SMC and RTM techniques.
• SMC Sheet Moulding Compounds
• a so-called prepreg is introduced into the mould, whereupon the mould is closed and under the influence of pressure and temperature, the prepreg runs.
• the conducting web is already present in the mould and is subsequently impregnated with the prepreg.
• thermosetting polyester resin a fluid resin, such as a thermosetting polyester resin
• RTM Resin Transfer Moulding
• the fibrous webs to be used are provided with humidifiers and/or deaerators so as to improve the quality of the surface of the material. In this manner, a smooth plastics surface free of air-bubbles can be obtained.
• the article with a conducting fibrous web at or below t?- surface is particularly suitable for electrostatic applicat._. n of a powdered coating, more particularly a muffle coating.
• Suitable powders are the conventional sinterable powders on a nylon, polyester, polyurethane or epoxy base. After the electrostatic application of the powdered coating, the lacquer is baked in a known manner.
• the invention is illustrated in and by the following examples which are not intended to limit the invention.
• the web so obtained had a density of 0.48 g/cm 3 measured at a pressure of 40 g/cm 2 and a surface resistivity measured over a length of 10 m of ⁇ 0.1 Ohm #.
• the web was pressed as a surface web with SMC (on the basis of unsaturated polyester resin) to form a product of high surface smoothness and low porosity.
• the product was electrostatically coated with a polyester powdered coating.
• the coated product was hardened at 180°C. A homogeneous and smooth surface was obtained.
• 40 g nickeled acrylic fibre was needled on a random polyacrylic needle web of 60 g/m 2 with interposition of a fabric of about 10 g/m 2 having per 5 cm diagonally applied copper wires of a diameter of 0.1 mm.
• the needle web so obtained had an elongation at break of more than 80% and a surface resistivity of ⁇ l Ohm #.
• the web was used as a surface web in the RTM process (on the basis of unsaturated polyester resin) . After hardening of the product and applying a potential difference between the conducting layer and the powder to be applied, the surface could be coated electrostatically.

Landscapes

• Laminated Bodies (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=19857711

Family Applications (1)

Country Status (4)

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• 1990
  • 1990-09-21 NL NL9002073A patent/NL9002073A/nl not_active Application Discontinuation
• 1991
  • 1991-09-23 EP EP91919322A patent/EP0549728B1/de not_active Expired - Lifetime
  • 1991-09-23 DE DE69105741T patent/DE69105741T2/de not_active Expired - Fee Related
  • 1991-09-23 WO PCT/NL1991/000184 patent/WO1992004985A1/en active IP Right Grant

Non-Patent Citations (1)

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