TECHNICAL DATA SHEET GROWCLEAR PLUS

Transcription

1 TECHNICAL DATA SHEET GROWCLEAR PLUS CATHODIC ELECTROPHORETIC CLEAR / TINTED LACQUERING PROCESS Introduction Growclear Plus is an advanced version of the earlier popular electrophoretic Clearlyte lacquer. It is a water-based lacquer which gives a clear protective coating on metal articles. Growclear Plus is cathodically electrodeposited. After curing the deposit with excellent gloss and image clarity is obtained. Components can be transferred directly from the final electroplating process stage through rinses to Growclear Plus without the need for an intermediate drying stage. Growclear Plus shows an excellent throwing to recess area and gives uniform deposit thickness. No runs and tears are observed and high corrosion and chemical resistance are obtained. GIVES : Better Gloss Better Throwing Power Higher concentration (50% solids) Can be used for low-build deposits of 6 to 8 microns as also for higher thickness upto 20 microns Imparts a richer gold shade (Similar to 24 Karat Gold Finish) when used in conjunction with Clearlyte Gold dye. Process Sequence : A typical process sequence is below: *Growclear Prepas 4V 1 min. water rinse Demineralised water rinse, twice. Pre-dip in demineralised water with 20ml/ltr. Growclear Plus bath solution or ultrafiltrate permeate rinse. Lacquer coat - Post rinse in pure ultrafiltrate (permeate). - Demineralised water rinse, alongwith 1 ml/ltr. Growclear RA, twice. - Air dry (60 70ºC, approx. 10 min.). - Cure ( ºC, approx. 25 min.). GROWCLEAR PLUS 1

2 The purpose of the demineralised rinses is to prevent the lacquer solution from being contaminated. The pre-dip in dilute lacquer permeate dip is considered essential in order to prevent film defect caused by gassing. The post-rinse is used to remove the lacquer solution from the coated object. Although a separate pre and post-rinse is recommended, it is possible to use the pre-rinse also as post-rinse in running ultrafiltrate permeate rinse. PROCESS EQUIPMENT : A full range of specially developed equipment is available from Growel. All tanks in contact with lacquer solution should be suitable plastic construction or of steel with acid and solvent resistant lining such as polypropylene. TANK : The Growclear Plus working tank should be fitted with : An overflow compartment. A circulating pump with circulation capacity of at least 5 times tank volumes per hour. A filter, preferably equipped with a bypass system for optimum circulation, with a 1-3 micron cartridge. A low energy heater (quartz) whenever required, especially in the north during winter season in India. A cooling coil or Teflon or stainless steel 316 grade protected from direct current is necessary to maintain temperature at the optimum level. Stainless steel anodes are used grade 316. ULTRAFILTRATION The use of an ultrafiltration unit has proven to be an integral part of successfully operating Growclear Plus baths. Every installation should have a UF unit. The use of ultrafiltration helps to minimize the effect of metallic contamination and stabilizes the ph of the solution. OVEN Recirculatory hot air ovens or tunnel should be used. A gradual increase in temperature up to 140ºC for a partial curing and 150ºC to 180ºC for a fully cross linked cure is ideal. An excellent system is a conveyor oven with temperature zoning in which the parts are heated slowly to the curing temperature. It is very important to maintain a clean working atmosphere in the shop. Any dust or floating shop soils will settle on Growclear Plus bath and will deteriorate the final finish. It is certainly advisable to install Growclear Plus plant in cool and dust-free room. PROCESS MAKE-UP All demineralised rinses should be filled with demineralised water with a conductivity of less than 5ms. The pre-rinse is pre-rinse is prepared by adding 20ml/ltr. Growclear Plus bath solution to demineralised water. Ensure that the ph of the pre-rinse is the same as the Growclear Ultra bath. The pre and post-rinse can be replaced with clean demineralised water or ultrafilter permeate which will be gradually contaminated with the solution from the Growclear Plus bath, specially post-dip. working solution : The Growclear Plus concentrate as supplied should be diluted with demineralised water in the ratio of 1 part concentrate to 4 parts of demineralised water by volume. This gives a solid content (non-volatiles) of 8-10 % by weight. In case of Growclear Plus tinted dyes, select the dye and add 10 to 12 ml/l in concentrate Growclear Plus resin and dilute with demineralised water up to resin make-up. The recommended procedure is to add the water to the concentrate with constant mixing. The demineralised water should have a conductivity of less than 5 ms. A low speed electric stirrer is the ideal equipment for thorough mixing. The new bath must be circulated and / or stirred to 48 to 72 hours before use. GROWCLEAR PLUS 2

3 This ageing must be carried out with the cover off the tank all the time and with a bath temperature of 25 to 28ºC. Watch the solution level in the weir compartment. The use of an ultrafiltration unit will speed the ageing of the solution. It is not advised to measure the ph immediately after make-up of the new solution, but after the first 48-72hrs. of stabilization. No alkali must be added to the Growclear Plus solution. OPERATING CONDITIONS Solution Solid Content % ph (Electrometric) Conductivity ms. at 25 o C MEQ (Add Growclear ES 1 ml/l to increase 10 MEQ.) Voltage volts, Cathode current density - Average A/dm. sq. Surge A/dm sq. (do not exceed 0.5 A/dm 2 ) Anode :Cathode area - Max. 1 : 1 Deposition rate - Deposition is fast, during first few seconds, and then slows down, giving typically 8 microns in the first 30 seconds. Process Time - Variable between 10 and 120 seconds. Allow a dwell time of 10 to 15 seconds before switching on the current. Curing - GW CLEARLYTE PLUS will be fully cured by stoving at a metal temperature of 155 o C. for 20 minutes. It is essential that the metal components are at the curing temperature for the full 20 minutes. Temperature range is 150 o C to 180 o C. Temperature o C., Optimum 28 o C. Temperature may be allowed to fall to 15ºC. during long closed down periods. *Dyes - Variety of Colour Shades are available for process in tank dyes in Growclear Plus resin. *Consult G & W local TSD for your specific dye requirement. PROCESS MAINTENANCE : Demineralised Rinse : The demineralised rinses before lacquering, serve to minimize drag-in of hard water salts and pre-treatment chemical into the Growclear Plus solution and thereby prevent it from being contaminated. After lacquering, it serves as a clean final rinse. The rinse should be dumped when the conductivity exceeds 25μs. Post-rinse : This solution gradually becomes contaminated by drag-in from the Growclear Plus bath. It should be replaced periodically or when the solids content reaches 1.5% by weight. GROWCLEAR PLUS 3

4 Solution Level : Water is lost by evaporation; the level in the overflow section should be restored regularly by adding demineralised water. Watch the solution level in the weir compartment; do not let the pump suck air. Do not use the post-rinse solution for topping up. Solid Content : A freshly prepared Growclear Plus bath contains 8-10% by weight solids. The concentration will need to be increased up to 10-12% after the first working days. Growclear Plus concentrate should be used to obtain and maintain this solid content. The best method of addition is to premix the required amount of concentrate with the working solution in a separate container. Never add the concentrate directly to the bath. Preferably additions are done at eh end of production day. Consumption is dependent on drag-out and film thickness. Normally the solids content should be determined once or twice a week. Solvent Content : Solvent is lost by evaporation and drag-out. Normally the solvent level is maintained by the addition of Growclear Plus concentrate. If solvent additions are necessary, following long idle periods for example, they should be made in increments of 0.5% through the weir. It takes about one to two hours of solution circulation before the effect becomes apparent. Solvent level should be determined once a week. ph : the ph of the bath should be lie between Growclear Plus as supplied has a ph value within this range so that a freshly prepared bath has the correct ph. It is good practice to check the ph once or twice a week. It is not advised to use ph paper for ph measurements. Ionic Contamination : Avoid contamination of the Growclear Plus bath by soluble salts. They will decrease the efficiency, leading to bad deposits. Only with ultrafiltration can the ionic contamination be removed (slowly) by discarding the permeate. Adequate circulation and filtration will keep the lacquer in a fit condition. Filter cartridge will be clogged up with use. They should be cleaned or changed periodically. The circulation pump should not suck air; any air getting into the circulation system will cause pitting. It is recommended to carry out a batch filtration, followed by tank cleaning every one or two months. During prolonged idle periods tank circulation can be stopped, the cover of the tank must be closed. Alternatively, the bath solution can be stored in closed containers. Ultra filter equipment and filters should be flushed out with demineralised water and left filled with demineralised water. GROWCLEAR STIRIPPER : For defective elctrophoretic lacquer coated component can be stripped in Growclear Stripper without affecting the under-coat. This is ready to use product. After stripping with this product, normal cleaning activation cycle and applied before recoating in electrophoretic lacquer. ANALYTICAL PROECEDURES : 1. Solids content determination : a) By weight Method : - Weight a clean watch glass or aluminium foil. - Add 10 ml of Growclear Plus solution. - Stove in the oven for 2 hours at 165ºC - Cool and re-weight. - Calculate the % solids content by weight difference. GROWCLEAR PLUS 4

5 b) By Refractrometer Method : - On daily basis at shop floor level a quick determination of solid content can be made on a basis of refractrometer reading. % solids (by weight) = 0.64 x Reading (O Brix). - The solid content should be maintained at optimum level by regular addition of Growclear Plus. 2. Solvent lever determination. For each analysis of the solvent level contact Growel. 3. ph measurement : - calibrate ph meter - Rinse electrodes in demineralised water, dry and immerse in Growclear Plus. - After measuring, thoroughly rinse electrodes in Growclear Plus solvent and finally rinse in demineralised water again. WASTE DISPOSAL solution Increase ph of the solution 7 8 with alkali. The solids will precipitate out in the settlement tank. Supernatant liquid will contain about 4% by volume solvent and lactic acid. This liquid should be further diluted before discharge to meet local authority laws. For more details see MSDS. Issued on Supersedes all earlier GROWCLEAR PLUS 5