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
  • B05D7/02—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 macromolecular substances, e.g. rubber
• • 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
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2350/00—Pretreatment of the substrate
  • B05D2350/60—Adding a layer before coating
  • B05D2350/65—Adding a layer before coating metal layer

Definitions

• the present invention concerns a method for coating a resin molded product that is capable of simultaneously endowing the resin molded product with good coating adhesion and with the conductivity needed for electrostatic coating.
• Electrostatic coating is often utilized in the coating of molded resin products.
• undercoating materials referred to as "conductive primers" have generally been applied as a pretreatment to attain the objective of good adhesion to the overcoat and to obtain good throwing power in the electrostatic coating.
• a conductive filler is added to the material in this primer, or a conductive additive such as a surfactant is added to it.
• conductive fillers which can be used include nonmetallic fillers such as carbon black and graphite, metallic fillers such as silver, copper, nickel, tin, zinc, titanium, palladium, and aluminum, and composite fillers obtained by plating fine particles of materials such as glass, mica, plastic, and carbon with materials such as copper or silver.
• the coating must be applied to a sufficient thickness, leading to the problem of increases in the overall processing costs.
• the electrostatic coating must include a grounding treatment to ensure a specified potential difference between the object to be coated and the coating material, a ground connection must be formed on the back surface.
• Such treatment is difficult to carry out with devices such as automatic electrostatic coating devices, human labor must be used, leading to a further increase in the coating costs.
• the present invention concerns a method for coating a molded resin product that solves such problems in the prior art as described above, simultaneously provides sufficient material throwing power and material adhesion in the electrostatic coating of molded resin products, and imparts a good coating appearance.
• the above objectives are achieved by a method for coating a molded resin product in which a metal film is applied to the surface of a molded resin product for the purpose of obtaining a specified surface resistance, after which electrostatic coating is carried out without applying a conductive primer.
• the process for applying the metal component be an electroless plating method.
• the surface resistance of the molded resin product possessing a film of metal component formed in the aforementioned manner be on the order of 1 ⁇ cm or above and 107 ⁇ cm or less.
• a surface resistance suitable for electrostatic coating is achieved by applying a metal component film of a suitable variety and thickness to the surface of the resin product. As a result, good coating adhesion is obtained, and good throwing power is imparted to the material at the same time.
• the present invention has been conceived upon noting that the surface resistance which is necessary and adequate in practical terms for electrostatic coating is obtained according to the state of the applied film of metal component, in consideration of the fact that, when sufficient surface resistance is obtained by applying a sufficient amount of metal film to the surface of the resin, the coating process is easily performed, but the coating adhesion is reduced by the complete metallization, as well as the fact that, if an insufficient amount of metal component is applied, when the surface resistance is high, the electrical field formed on the side to which the coating has been applied loses uniformity, and the electrostatic coating cannot be carried out evenly.
• the application of the metal in the present invention can be implemented by any appropriate means, it is possible to form the film by electroless plating.
• the electroless plating film can be obtained by various known methods depending on the variety of the resin, but is not limited thereto.
• a washing process, a surface roughening process (chemical etching), a catalyst addition process needed for the initial deposition of the electroless plating, and an electroless plating process are carried out; however, the processes are not limited to this particular sequence.
• a catalytic layer containing a material such as Pd, Ag, Au, or Pt is selected at this time, Pd is often used in the interests of economy.
• examples of the type of metal used in the electroless plating film include nickel, copper, gold, silver, and tin, but are not limited to these.
• Each of these processes can include, or have performed before and after it, a process such as washing. Moreover, they can also contain processes such as drying.
• Examples of the type of resin used include various polymer materials, such as ABS, PA6, PA66, PBT, PET, PC, PA6/PPE alloy, PA6/noncrystalline PP alloy, noncrystalline PA, and/or fillers that are suitable in these resins. However, they are not limited thereto.
• the aforementioned type of electroless plating film is ordinarily necessary in performing electroless plating of nonconductive materials, it is held to be indispensable in the plating of plastic surfaces.
• a surface resistance of 1 ⁇ cm or less is necessary. It is indicated that when the surface resistance of the pertinent material is higher than this, the application of the metal plating layer becomes nonuniform, and its adhesion strength also decreases.
• an electroless plating film that gives a resistance in the range of 1 ⁇ cm or above and 107 ⁇ cm or less is suitable as the surface resistance of the molded resin product.
• an electroless plating film providing the above desired surface resistances is formed on the surface of the molded resin product, after which electrostatic coating is carried out without applying a conductive primer.
• the coating material for carrying out the electrostatic coating any material can be used, e.g., melamine-crosslinked polyester polyol resin coating materials and acrylic urethane coating materials.
• the coating material is not limited to these.
• the coating method pertaining to the present invention is implemented, in comparison to situations where a conductive primer is applied, the desired conductivity is obtained by electroless plating.
• the application of an electroless plating as a pretreatment for electrostatic coating makes it easy to obtain the uniform electrical field needed for electrostatic coating.
• the grounding treatment needed in the-electrostatic coating process for rendering the back surface conductive is also facilitated. Accordingly, the costs relating to the coating material and the coating operation can be reduced.
• test pieces used in the application examples were obtained using Noryl GTX6006 (a trademark; product of GE Plastics Japan, Inc.; a resin composition containing polyphenylene ether resin and polyamide resin).
• test pieces were subjected to the following type of etching treatment for surface roughening with an etching treatment solution and water washing.
• the treatment temperature and treatment time were 10 min [treatment temperature omitted].
• Electroless nickel plating solution EP Naico GL Solution A 100 mL/L (trademark; product of Kizai Corp.)
• the specimen obtained by the above-mentioned application example was dried at 120°C for 10 min with hot air.
• test samples obtained in the aforementioned application example were subjected to the following kind of test to confirm the effect of the present invention.
• test pieces were measured in accordance with JIS K 6911, "General Test Method for Thermosetting Plastics.”
• test pieces that had been subjected to electroless plating treatment were subjected to a treatment of repeated baking in a 160°C hot blast oven, and the surface resistance at each baking was measured.
• the results were as shown in Table I.
• Haiepico [transliteration] No. 100 (trademark; product of Nihon Yushi K.K., intermediate coat) was applied as the coating material by means of electrostatic coating, and the test pieces were allowed to stand for 10 min, after which they were baked for 30 min in a 140°C hot blast oven. They were then removed and allowed to stand for 30 min. Subsequently, Neoamilac [transliteration] (trademark; product of Kansei Paint K.K., overcoat) was applied by electrostatic coating, and the test pieces were allowed to stand for 10 min. They were then baked for 30 min at 140°C and removed, after which they were allowed to stand for 24 h at room temperature, and subjected to the following evaluation.
• Neoamilac [transliteration] (trademark; product of Kansei Paint K.K., overcoat) was applied by electrostatic coating, and the test pieces were allowed to stand for 10 min. They were then baked for 30 min at 140°C and removed, after which they were allowed to stand for 24 h at room temperature, and
• Tape peeling was carried out in a condition conforming to a checkerboard test (using 100 1-mm squares) according to JIS K 5400, and the number of coating films remaining from the 100 was measured.
• test pieces were immersed in 40°C warm water for ten days, after which they were tested in the same manner as in the aforementioned initial adhesion test.
• the appearance of the coating surface was evaluated visually.
• the cross section of the coating film was observed by electron microscope, and the film thickness was measured.
• Application Example 2 was carried out in the same manner as in Application Example 1, with the exception that an electroless copper plating film was formed in place of the nickel in the electroless plating.
• the test pieces used were formed from Noryl GTX6006 (trademark; product of GE Plastics Japan; resin composition containing polyphenylene ether resin and polyamide resin) in the same manner as in Application Example 1.
• test pieces were subjected to the following type of etching treatment for surface roughening with an etching treatment solution and water washing.
• the treatment temperature and treatment time were 40°C and 10 min.
• the aforementioned etched test pieces were washed with water and subjected to a neutralizing treatment, after which they were subjected to a 3 min, 40°C sensitizing treatment process for the purpose of adding a catalyst.
• test pieces obtained in Application Example 3 as shown above were subjected to the same tests as in Application Example 1 for the purpose of confirming the effect of the present invention.
• a ground is required in implementing electrostatic coating; conventionally, it has normally been necessary to spray a grounding coating material onto the back surface of the molded product to form a conductive area for use as a ground.
• electroless plating the formation of an electroless plating film on the entire back surface of the molded product eliminates the need to subject the molded resin product that is coated to a special treatment.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Chemically Coating (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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Cited By (1)

Citations (3)

• 1992
  • 1992-12-24 JP JP35743192A patent/JPH06190333A/ja active Pending
• 1993
  • 1993-12-17 EP EP93310218A patent/EP0604132A3/en not_active Withdrawn

Patent Citations (3)

Non-Patent Citations (1)

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