Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/22—Roughening, e.g. by etching
  • C23C18/24—Roughening, e.g. by etching using acid aqueous solutions
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/04—Electroplating: Baths therefor from solutions of chromium
  • C25D3/06—Electroplating: Baths therefor from solutions of chromium from solutions of trivalent chromium
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/10—Electroplating with more than one layer of the same or of different metals
  • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
  • C25D5/14—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium two or more layers being of nickel or chromium, e.g. duplex or triplex layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/54—Electroplating of non-metallic surfaces
  • C25D5/56—Electroplating of non-metallic surfaces of plastics
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/605—Surface topography of the layers, e.g. rough, dendritic or nodular layers
  • C25D5/611—Smooth layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/627—Electroplating characterised by the visual appearance of the layers, e.g. colour, brightness or mat appearance

Definitions

• the present invention relates to a method for producing a plated molded product having a thin portion.
• the present invention also relates to a method for plating a surface of a coinjection molded product having a resin molded product and an elastic layer incorporated on a rear side thereof.
• the present invention relates to a method for plating surfaces of electrical or electronic components (e.g., switches, and key tops for controlling a personal computer), OA equipment (e.g., personal computers and telephones), and communication equipment (e.g. , DVDs and MDs) , and more particularly to a method for producing operation buttons (keys) for cellular phones.
• electrical or electronic components e.g., switches, and key tops for controlling a personal computer
• OA equipment e.g., personal computers and telephones
• communication equipment e.g. , DVDs and MDs
• buttons (keys) attached thereto need to be as thin as possible.
• operation buttons are molded from ABS resin ( crylonitrile • butadiene • styrene copolymer) which is easy to plate.
• ABS resin has poor adhesiveness to the body of a cellular phone.
• an operation button may have a portion which is not plated for decoration purposes.
• coinjection molding may be performed using resin other than ABS resin, such as PC (polycarbonate) resin.
• a bright surface and a deluster surface may be provided on a surface of an operation button for decoration purposes .
• buttons for cellular phones are produced by inmolding
• the resultant operation buttons exhibit a lack of sharpness and bright impression.
• the surface of a molded product is plated after coinjection molding as described above.
• a molding method in which a cavity and a core are reversed is typically used other than commonly used methods.
• a metal plating layer is formed on a surface of a molded product by electroless plating; a nickel layer is formed on a surface of the electroless plating layer by electroplating; and a chromium or chromium alloy layer is formed on a surface of the nickel layer by electroplating.
• Such plating easily comes off in a cross-out adhesion test, a heat shock test. etc ,
• Operation buttons for cellular phones may be provided with an elastic layer which is incorporated into a coinjection molded product in order to provide a cushion on a rear surface of the molded product. Further, a surface of the coinjection molded product may be subjected to plating.
• the plating of the surface of such a molded product is typically conducted by electroless plating, in which an etching step, a washing step, a catalyst step, and an accelerator step are successively performed, followed by electroplating.
• a molded product is immersed in a chromic acid mixture of chromic acid and sulfuric acid.
• the elastic layer tends to be easily dissolved in the chromic acid mixture.
• the dissolved components may agglomerate in the subsequent washing step etc. and are diffused in the further subsequent steps so that the small foreign particles are attached to a plated surface of the molded product, resulting in a defective product .
• the concentration of the chromic acid mixture is lowered to a point that the elastic layer resists being dissolved.
• a plating layer plated on the molded product surface has poor adhesiveness.
• chromium plating solution used employs a bath composition containing hexavalent chromium, and hexavalent chromium is ionized and deposited on a surface of a subject product by electrophoresis to form a metal chromium coating.
• hexavalent or trivalent ions or the like are not present in the metal chromium coating, there is a need to consider the adverse influence of the coating on the skin of a human.
• metal chromium corrosion leads to a reduction to hexavalent chromium which remains in nature, causing a problem.
• buttons for cellular phones which are coinjection molded products
• a newly introduced trivalent chromium plating bath if plating conditions are set within standard control values defined by the manufacturer, some problems arise so that the specification which a user desires cannot be well controlled, and changes in the standard control values and equipment are required.
• minute ridges and protrusions may be formed on a surface of a plated product.
• the cause is considered to be that dust entering the solution or impurities generated in electrolysis are captured in the plating coat. Further, the throwing power is poor.
• the cause is speculated to be that current cannot flow at a standard current density when a plated product has a very rough surface.
• a surface of a molded product having a thin portion obtained by high-speed injection molding of resin is subjected to plating.
• the method comprises the steps of:
• the "high-speed" of the high-speed injection molding means a level of speed at which the orientation of the butadiene molecules in ABS resin is changed.
• the butadiene molecules are substantially circularly oriented at a conventional injection speed.
• the butadiene molecules are ellipti ⁇ ally oriented. Therefore, conventional plating easily comes off the surface of a molded product .
• the copper plating is conducted under the following conditions: the molded product is immersed in a copper sulfate bath containing copper sulfate having a concentration of
• a bright surface and a rough surface are provided on the surface of the molded product .
• the plated molded product of the present invention is produced by any of the above-described methods.
• the molded product is a button for operating a cellular phone.
• the metal plating layer formed by the electroless plating is a nickel layer, a copper layer, or the like.
• a plating which resists removal can be obtained. Further, even when a plating is formed on a satin-finished surface, the plating can reproduce the satin-finished surface.
• the function of the present invention is the following.
• a metal plating layer such as a nickel layer or a copper layer
• a copper plating layer is formed on the surface of the electroless plating layer.
• a nickel layer and a chromium or chromium alloy layer is formed on the surface of the copper plating layer by electroplating. Therefore, even for a molded product having a thin portion, a metal plating layer can be securely adhered to the underlying surface (the molded product) and resists in coming off. Further, the plating can reproduce the luster surface and the satin-finished surface of the molded product .
• a cross-out adhesion test 1 mm by 1 mm cross-cut Heat shock test : Repetition of cycles of 85°C • 1 hour and -35°C • 1 hour. The plating needs to be still intact after 6 cycles or more. Conventional plating are destroyed after 3 cycles .
• a surface of a molded product obtained by integrally molding an elastic layer as a secondary molded product on at least a portion of a surface of a primary molded product is treated by plating.
• the method comprises the step of etching the surface of the molded product by immersing the molded product in a mixture of chromic acid and sulfuric acid, wherein the etching step is conducted under the following conditions:
• the chromic acid concentration of the mixture is 370 g/1 to 390 g/1;
• the sulfuric acid concentration of the mixture is 190 g/1 to 230 g/1.
• the method further comprises a washing step, a catalyst step, and an accelerator step in this order after the etching step.
• the accelerator step comprises the steps of immersing the molded product in an acidic solution having a pH closer to the neutral than the pH of an acidic solution used in the catalyst step and causing the acidic solution to be in contact with activated charcoal so that impurities contained in the acidic solution were adsorbed, and thereafter washing the molded product.
• the washing step comprises the step of providing a nozzle on a bottom side of a water tank. the nozzle blowing minute air bubbles, and blowing the air bubbles toward the molded product.
• the elastic layer consists of thermoplastic polyurethane elastomer.
• the plated molded product of the present invention is obtained by any of the above-described methods.
• the plated molded product is a button for a cellular phone.
• plating can be provided on the surface of a coinjection molded product comprising a resin molded product and an elastic layer integrally molded to the rear surface of the resin molded product without fine roughness.
• the function of the present invention is the following.
• plating can be provided on the surface of the molded product with good adhesion while inhibiting dissolution of the elastic layer as much as possible.
• the adhesion of the plating is insufficient, leading to less durability.
• etching is excessively conducted, the elastic layer is dissolved, leading to degradation of the surf ce condition of the molded product . As a result, the incidence of defective products is increased.
• a surface of a molded product obtained by coinjection molding is treated by trivalent chromium plating.
• the method comprises the step of plating under the following conditions : (a) the trivalent chromium concentration of a plating bath is 6 to 10 g/1;
• the amount of overall impurities in the plating bath is 60 ppm or less;
• bathing temperature is 40 to 50°C;
• pH of the plating bath is 3.2 to 3.6;
• cathode current density is 3 to 5 A/dm 2 ;
• anode/cathode ratio is 1.5 to 2 : 1.
• the plating conditions further includes:
• (g) rectifier one that has an ability to rectify an amount of current which is three times or more as much as the total current amount
• the molded product is a silver button for operating a cellular phone.
• a surface of a molded product obtained by coinjection molding is treated by trivalent chromium plating.
• the method comprises the step of plating under the following conditions :
• the trivalent chromium concentration of a plating bath is 5 to 10 g/1;
• the amount of overall impurities in the plating bath is 60 ppm or less;
• (c) bathing temperature is 53 to 63°C;
• anode/cathode ratio is 1.5 to 2 : 1.
• the plating conditions further includes : (g) rectifier: one that has an ability to rectify an amount of current which is three times or more as much as the total current amount; and
• the molded product is a black button for operating a cellular phone.
• Plated molded products are produced with any one of the above-described methods.
• a chemically converted coat having excellent resistance to corrosion can be formed by surface treatment using a treatment solution without hexavalent chromium.
• the function of the present invention is the following.
• plating conditions are changed as follows with respect to the following items.
• Filtering performance in a plating bath is improved, and the impurity control value of the bath is changed, resulting in an improvement in the uniformity of particles in liquid (an improvement in filtering precision) and a reduction in attached foreign matters.
• the metal concentration of the bath is adjusted to be high as compared to conventional methods, thereby improving the throwing power. Further, the reaction rate is improved, thereby improving the throwing power. Furthermore, the pH is set to be higher, thereby increasing the reaction rate.
• Figure 1 is a cross-sectional view of an exemplary plated molded product obtained by a production method according to the present invention.
• Figure 2 is a cross-sectional view of another exemplary plated molded product obtained by a production method according to the present invention.
• a thin molded product 14 comprises a thin portion 13 produced by coinjection molding. Further, the thin molded product 14 comprises a primary molded product 11 formed of ABS resin, and a secondary molded product 12 molded at an inner side of the primary molded product 11 by coinjection molding.
• the secondary molded product 12 can be formed of transparent resin, such as PC.
• This dish-like injection-molded product 14 has a thin portion typically having a thickness of 0.35 mm or less and preferably 0.15-0.30 mm.
• the molded product can be molded by coinjection molding where a cavity and a core are reversed. Since the thin portion is provided, the injection speed is faster than conventional.
• the thus-obtained molded product having the thin portion is subjected to plating to plate a surface of the molded product by the following steps .
• a metal plating layer is formed on the surface of the molded product by electroless nickel plating (chemical plating) or electroless copper plating (chemical plating).
• the electroless plating can be conducted in the following manner.
• Etching step the molded product is immersed in an aqueous solution containing chromic anhydride and sulfuric acid at a predetermined temperature, followed by washing, and the surface of the molded product is roughened.
• Catalyst (catalyzer) step the molded product is immersed in an aqueous solution containing palladium chloride, stannous chloride and hydrochloric acid, followed by washing, so that palladium is absorbed to the surface of the molded product .
• Accelerator step the molded product is immersed in an aqueous hydrochloric acid solution, followed by washing, so that tin which has been absorbed along with palladium in the catalyst step is dissolved and detached with the hydrochloric acid solution.
• Electroless nickel plating or electroless copper plating (chemical plating): the molded product is immersed in a mixture of nickel or copper, formalin, Rochelle salt , sodium hydroxide, water, sodium hypophosphite, ammonia, etc., followed by washing, so that nickel (copper) is deposited on the palladium due to a reduction reaction of formalin and sodium hypophosphite .
• electroplating is conducted on the electroless plating layer in the following manner.
• a copper plating layer is formed on a surface of the electroless plating layer by electroplating.
• a thickness of the copper plating layer is typically 5 ⁇ m to 15 ⁇ m.
• Conditions for copper plating may be the following.
• the molded product is immersed in copper sulfate bath having a copper sulfate concentration of 70-90 g/1 and a sulfuric acid concentration of 170-210 g/1 at 10-30°C (more preferably 20°C) , and plating is conducted at a cathode current density of 1-4 A/dm 2 .
• non-leveling copper sulfate is employed. Since copper sulfate has an excellent followingness, a portion of the original surface of the molded product subjected to blasting (grain) becomes ridges and protrusions of blast pattern (grains) as they are. Moreover, a flat portion (bright surface) can exhibit brightness impression as is conventionally obtained.
• a nickel layer is formed on a surface of the copper plating layer by electroplating.
• the molded product is immersed in a mixture of nickel sulfate, nickel chloride, boric acid, and brightener, and treated under predetermined conditions of voltage and current , followed by washing, whereby a nickel coat is formed on the surface of the molded product.
• a chromium or chromium alloy layer is formed on a surface of the nickel layer by electroplating.
• the molded product comprises portions (15, 16) of different resin materials . Therefore, a portion of the surface of the molded product may be transparent. Alternatively, the plating is scratched away from a portion of the surface of the molded product via which the molded product is securely attached with an adhesive to a silicone rubber sheet of a cellular phone body, for example .
• conventional copper sulfate for decoration provides plating having a high leveling ability.
• the non-leveling copper sulfate can provide plating having excellent followingness. Therefore, the coat layer can follow and maintain the ridge-and-protuberance pattern of the blasted portion (grain) of the underlying layer.
• the smooth portion (bright surface) of the underlying layer is conventionally caused to have a brightness impression.
• a molded product 24 according to the present invention such as operation buttons of a cellular phone, is obtained by coinjection molding as shown in Figure 2.
• the molded product 24 comprises a primary molded product 21 formed of a molded resin, and an elastic layer 22 as a secondary molded product which is molded on the rear side of the primary molded product 21 by coinjection molding.
• the primary molded product 21 can be made of ABS resin, polypropylene, vinyl chloride resin, polystyrene. polycarbonate, methacryl resin, polysulfone, polyester, polya ⁇ etal, polyamide, etc. ABS resin is particularly preferable.
• the secondary molded product (elastic layer) 22 is made of rubber, elastomer, etc.
• the elastic layer 22 confers cushioning to operation buttons.
• the hardness of the elastic layer 22 is preferably 80 or more in Shore A, and particularly about 85 to 92.
• the elastic layer 22 can confer button cushioning, leading to an improvement in the operability of the buttons, and can absorb the impact when an instrument, such as a cellular phone, is dropped, thereby preventing damage.
• the elastic layer 22 can be particularly made of thermoplastic polyurethane elastomer.
• Thermoplastic polyurethane elastomer is commercially available.
• a surface of the thus-obtained molded product 24 is subjected to the following plating treatment to provide a plating 23.
• the electroless plating can be conducted as follows .
• the molded product is immersed in a mixture (chromic acid mixture) of chromic anhydride and sulfuric acid at predetermined temperature for a predetermined time. followed by washing, so that the surface of the molded product is roughened.
• the temperature of the chromic acid mixture used is preferably 65 to 69°C, and more preferably 66 to 68°C.
• the chromic acid concentration of the chromic acid mixture is preferably 370 g/1 to 390 g/1.
• the sulfuric acid concentration thereof is preferably 190 g/1 to 230 g/1.
• the processing time of the etching step is typically 8 to
• the elastic layer 22 is disadvantageously melted and impurities are dissolved into the mixture.
• the sulfuric acid concentration is excessively higher than the above-described range, a crystal is developed, inhibiting continuous production. The reason is considered to be that high sulfuric acid concentration causes the chromic acid in the chromic acid mixture to be saturated.
• a preliminary etching step may be conducted before the above-described etching step.
• conditions for the etching are the following.
• Preliminary etching step The temperature of the chromic acid mixture used is preferably 66 to 68°C.
• the chromic acid concentration of the chromic acid mixture is preferably 135 g/1 to 165 g/1.
• the sulfuric acid concentration is preferably 180 g/1 to 220 g/1.
• the processing time of the etching step is typically 2 to 4 minutes.
• washing step is conducted.
• the washing step can be conducted by showering the molded product with water. Further, after the washing, if necessary, neutralization is conducted and washing is then conducted again.
• Catalyst (catalyzer) step The above-described molded product is immersed in an aqueous solution of palladium chloride, stannous chloride, and hydrochloric acid, followed by washing, whereby palladium is absorbed to the surface of the molded product surface.
• the immersion is conducted under the following conditions .
• the washing can be conducted by showering.
• the molded product is immersed in an aqueous solution of hydrochloric acid, followed by washing, whereby tin which has been absorbed along with palladium in the catalyst step is dissolved and detached with the hydrochloric acid.
• Preferable immersion conditions in the accelerator step are the following.
• the pH of the acidic solution used in the catalyst step (typically, pH 1) is rapidly reduced toward the neutral, so that impurities such as hydroxide are generated and are likely to be attached to the surface of the molded product.
• the pH of the acidic solution is about 1.5 and the acidic solution is passed through activated charcoal so that the impurities are absorbed.
• a nozzle which blows out minute air bubbles is provided at the bottom of a water tank so that the elastic layer 22 is washed.
• the air bubbles strike the surface of the molded product (particularly, the elastic layer 22) so that the impurities and residual drug attached on the surface of the molded product can be effectively removed.
• the molded product is immersed in a mixture of nickel or copper, formalin, Rochelle salt, sodium hydroxide, sodium hypophosphite, ammonia, water, etc.,' followed by washing.
• nickel (copper) is deposited on palladium due to a reducing reaction of formalin and sodium hypophosphite.
• electroplating is conducted on the electroless plating layer as follows.
• nickel electroplating after the nickel or copper plating, nickel electroplating, chromium plating, chromium alloy plating, gold plating, or other alloy plating are conducted.
• Trivalent chromium plating is conducted on the surface of the above-described molded product having a thin portion by the following steps .
• a metal plating layer is formed on the surface of the molded product by electroless nickel plating (chemical plating) or electroless copper plating.
• the electroless plating can be conducted as follows .
• Etching step the molded product is immersed in an aqueous solution containing chromic anhydride and sulfuric acid at a predetermined temperature, followed by washing, and the surface of the molded product is roughened.
• Catalyst (catalyzer) step the molded product is immersed in an aqueous solution containing palladium chloride, stannous chloride and hydrochloric acid, followed by washing, so that palladium is absorbed to the surface of the molded product .
• Accelerator step the molded product is immersed in an aqueous hydrochloric acid solution, followed by washing, so that tin which has been absorbed along with palladium in the catalyst step is dissolved and detached with the hydrochloric acid solution.
• Electroless nickel plating or electroless copper plating (chemical plating): the molded product is immersed in a mixture of nickel or copper, formalin, Rochelle salt, sodium hydroxide, sodium hypophosphite, ammonia, water, etc., followed by washing, so that nickel (copper) is deposited on the palladium due to a reduction reaction of formalin and sodium hypophosphite.
• electroplating is conducted on the electroless plating layer in the following manner.
• a copper plating layer is formed on the surface of the electroless plating layer by electroplating.
• a thickness of the copper plating layer is typically 5 ⁇ m to 15 ⁇ m.
• Conditions for copper plating may be the following.
• the molded product is immersed in copper sulfate bath having a copper sulfate concentration of 70-90 g/1 and a sulfuric acid concentration of 170-210 g/1 at 10-30°C (more preferably 20°C) , and plating is conducted at a cathode current density of 1-4 A/dm 2 .
• a nickel layer is formed on a surface of the copper plating layer by electroplating.
• the molded product is immersed in a mixture of nickel sulfate, nickel chloride, boric acid, and brightener, and treated under predetermined conditions of voltage and current, followed by washing, whereby a nickel coat is formed on the surface of the molded product .
• water is preferably given vibration by means of a particular device, so that liquid penetrating the gaps or the like between the primary and secondary molded products 1 and 2 of the coinjection molded product can be completely removed.
• a chromium or chromium alloy layer is formed on the surface of the nickel layer by electroplating.
• trivalent chromium plating is conducted.
• the composition of a plating solution is, for example, chromium sulfate (trivalent), chromium acetate (trivalent), chromium nitrate (trivalent), chromium chloride (trivalent), or biphosphate chrome (trivalent) (see Japanese Laid-Open Publication No. 2000-54157).
• conditions for silver color plating are the following.
• Bathing temperature 40 to 50°C (preferably 47 to 49°C)
• Rectifier one that has an ability to rectify an amount of current which is three times or more as much as the total current amount .
• (h) Filtering ability the entire bathing solution is passed through a filter seven times or more per hour. This filtering is continuously conducted. Specifically, whereas the amount of the circulating bathing solution is conventionally about two time per hour, that is 7 to 10 times per hour in the present invention.
• the filter used (filter cloth) preferably has a mesh size of 5 ⁇ m to 10 ⁇ m (conventionally about 50 to 100 ⁇ m) .
• the above-described current is preferably always applied to the plating bath.
• the chromium concentration and the liquid temperature is increased by about 2%, the pH is decreased by about 0.2, and the filtering ability is increased by a factor of 2.5 or more with respect to the standard plating conditions recommended by the manufacturer, thereby making it possible to reduce impurities.
• a primary molded product made of ABS resin and a secondary molded product made of thermoplastic polyurethane elastomer were molded together by coinjection molding to obtain a molded button product for a cellular phone.
• This molded product was etched under the following conditions. After the etching, the molded product was washed with water two times. Each washing water was passed through a membrane filter (#2), and residues adsorbed by the filter paper were visually observed and evaluated (its factor ranges from the worst, 50, to the best, 0) . Further, the washed molded product was plated with a conventional method and the plating of the molded product was visually observed.
• thermoplastic polyurethane elastomer was dissolved, and solidified by the washing or the like, and the solidified elastomer is dispersed in the subsequent steps, so that defective products are produced. Whether the cause is the chromic acid or the sulfuric acid of the chromic acid mixture was studied.
• Chromic acid mixtures are prepared by combining the three levels of chromic acid concentrations (350 to 410 g/1 in 30 g/1 steps) and the three levels of sulfuric acid concentration (180 to 240 g/1 in 30 g/1 steps).
• n represents the total number of tests
• p represents the number of defective products
• % represents the percentage of defective products. The size and area of a bump was visually measured.
• a molded product treated by nickel plating was subjected to trivalent chromium plating under the following conditions to obtain a silver button for a cellular phone.
• Rectifier one that has an ability to rectify an amount of current which is three times as much as the total current amount.
• Example 3 A molded product treated by nickel plating was subjected to trivalent chromium plating under the following conditions to obtain a black button for a cellular phone.
• Rectifier one that has an ability to rectify an amount of current which is three times as much as the total current amount.
• a molded product treated by nickel plating was subjected to trivalent chromium plating under the following conditions to obtain a silver button for a cellular phone.
• Rectifier one that has an ability to rectify an amount of current which is one times as much as the total current amount.
• Filtering ability the entire bathing solution is passed through a filter continuously two times per hour.
• Rectifier one that has an ability to rectify an amount of current which is two times as much as the total current amount.
• the judgment of surface roughness was conducted as follows: attached foreign matters, flaws, etc. were visually observed from a distance of 30 cm or more, and a product having a foreign matter having a size of 0.2 mm or more was judged as a reject.
• the judgment of throwing power was conducted as follows : whether or not the plating is uniform and the presence or absence of discoloration, tarnishing, etc. were visually observed, and a product having discoloration, tarnishing, etc. was judged as a reject.
• the first invention even for a molded product having a thin portion obtained by high-speed injection molding, a plating which resists removal can be obtained. Further, even when a plating is formed on a satin-finished surface, the plating can reproduce the satin-finished surface.
• a plating having good adhesion can be provided on a coinjection molded product by etching the surface of the molded product while the elastic layer is prevented from being dissolved as much as possible. Therefore, it is possible to prevent the development of bumps on the surface of the molded product, thereby reducing the incidence of defective products.
• a metal coating having excellent corrosion resistance can be provided by surface treatment using a treatment solution which does not contain hexavalent chromium. Further, the chromium concentration and the liquid temperature is increased by about 2% , the pH is decreased by about 0.2, and the filtering ability is increased by a factor of 2.5 or more with respect to the standard plating conditions recommended by the manufacturer, thereby making it possible to reduce impurities .

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