2 ~ ~
COMPOSITION AND PROCESS FOR ENHANCED DRAINAGE OF RESIDUAL
AQUEOUS RINSE ON THE EXTERNAL SURFACES OF PLASTIC PARTS
FIELD OF THE INVENTION
-The present ;nvention relates to compositions and processes for rinsing plastic parts. Aqueous solutions of an ethylene oxide-propylene oxide block copolymer and an ethylene oxide-propylene oxide random copolymer are effective at enhancing the drainage of residual rinse water from the surfaces of the plastic parts.
BACKGROUND OF THE INVENTION
Plastic ;s painted for both cosmetic and funct~onal reasons. These reasons include protection against weathering and fading, shielding electronic parts from electromagnetic and radio frequency interferences and achieving a smooth finish.
In the automotive industry, the formed plastic parts (fascia) used are often painted. This is to provide a smooth, oftentimes metal-like finish. The paint covers molding and other substrate imperfections. Decorative effects such as mirror finishes, texturing and color match of differently processed parts are also achieved by painting. I
Most plastics need to be cleaned before painting them.
The most common contaminants that must be removed before pa;nting are mold release agents, shop soil, material handling soil, machining soils, fingerprints and plastic sanding dust. These contaminants are removed by chemical means such as detergents.
The process of cleaning plastic parts generally entails a wash stage, a rinse stage and a final rinse stage with deionized water. The plastic part can be either spray washed or immersed in the detergen~. The most common processes are either an acidic detergent wash stage followed by two rinse stages, or an alkaline detergent stage, followed by a rinse stage, an acidic detergent wash stage, and two rinse stages.
When the plastic part is to be painted, the cleaning operation is performed in a production line with the freshly cleaned part sequentially conveyed into the paint booth.
Problems can occur however, when the freshly cleaned part is not fully dry. This can lead to "spotting" when painted and will result in an imperfect paint job. This will require skripping of the part and/or an additional painting procedure.
Removing the aqueous rinse water from the surface of the plastic requires a drainage enhancing solution which will effec-tively aid in drying the plastic part to be painted. The present inventors have discovered an aqueous solution which will aid in reducing spotting on the external surface of plastic parts.
2~32~8 SUMMARY OF T~E INYENTION
The present invention provides for a composition and process for enhancing the drainage of residual aqueous rinse from the external surfaces of plastic parts comprising an ethylene oxide-propylene oxide block copolymer and an ethylene oxide-propy-lene oxide random copolymer.
The present invention effectively reduces the amount of water on the external surfaces of plastic parts prior to their being painted. Any water left on the external surfaces can lead to spots or imperfections in the final paint finish. This invention is particularly effective at aiding in the drainage oF an aqueous rinse from the external surfaces of virgin and rework plastic used in the automotive industry.
- DESCRIPTION OF THE RELATED ART
15 United States Patent ~,S60,493, Scharf et al., December 1985, discloses a composition and method for reducing the liquid residue remaining on a metal surface consisting of octane-1-phos-phonic acid or water soluble salt thereof.
United States Patent 3,082,172, Temple et al., March 1963, discloses a polyoxyalkylene glycol mixture which is useful as a rinse additive composition in machine dishwashing. The composition comprises a conventional rinse additive formulation, organic poly-ethenoxy nonionic surface active agent, and a polyoxyalkylene 2~327~
glycol mixture consisting of alternating hydrophobic and hydro-philic polyoxyalkylene chains.
BASF/Wyandotte Technical Bulletin, "The Wonderful World of Pluronic Polyols", United States Library of Congress No. 70-150738 (1971), discloses various uses for ethylene oxide/propylene oxide block copolymers.
BASF Technical Bulletin, "Performance Chemicals for Rinse Aid Formulations", discloses various rinse aid components such as surfactants and hydrotropes.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides for a composition and process for enhancing the drainage of residual aqueous rinse from the external surfaces of plastic parts comprising an ethylene oxide-propylene oxide block copolymer and an ethylene oxide-propylene oxide random copolymer.
The preferred materials in accordance with this invention include ethylene oxide-propylene oxide (EO-PO) block copolymers with less than about 40% ethylene oxide. These are available from BASF/Wyandotte as Pluronic ~L-43, Pluroni ~ L-61, Pluronic~
31R1 and Pluroni ~ 17R4.
The ethylene oxide-propylene oxide randGm copolymer is an alkoxylated polyether and is the butyl ether of an ethyl~ne oxide-propylene oxide random copolymer with about 50% ethylene oxide.
It is available from Union Carbide ~orporat;on as UC0 ~ 50-HB-5100 and from BASF/Wyandotte as Pluroco ~ W5100.
This alkyl terminated ethylene oxide-propylene oxide random copolymer is the product of the reaction of ethylene oxide and propylene oxide with an alkyl alcohol such as butanol.
The E0-P0 block copolymer and the E0-P0 random copolymer are preferably blended together in an aqueous medium, such as deionized water, to form a concentrate. The copolymers may be present in the concentrate up to and preferably at 7.5% by weight each. Higher concentrations are achievable provided that the copolymer combination remains water soluble. In the aqueous rinse, the individual copolymers may be present at a concentration from about 7.5 parts per million to about 7S0 parts per million.
A microbiological growth inhibitor such as methylene bis-thiocyanate or fluoride compound may also be added in small ~uantities to inhibit the growth of microorganisms during skorage of the blended product.
The f`luoride compound is added to the drainage enhancing solution for several reasons. Fluoride ion may combine with and remove ions causing hardness, such as calcium and magnesium ions, which may be objectionable under a paint film. The fluoride ion may be used ~o track addition rates of the drainage enhancing solution through the use of an ion specific electrode.
2~63278 The blended product is employed as a rinse aid from abou-t 25 ppm to about 150 ppm active. Higher concentrations could be used but may give diminishing returns.
The aqueous solution designated treatment A in accordance with the present invention comprises:
7-.5% by weight E0-P0 block copolymer 7.5% by weight E0-P0 random copolymer 85.0% by weight deionized water The process of contacting the diluted solution to the plastic part may be either by spraying the plastic part or by immersing the plastic part in -the diluted solution.
Most plastics are pain-table with the appropriate choice of paint. However, some plastics will not accept paint (poor "wet-out" or adhesion) regardless of the cleanliness of their surfaces~
Examples of plastics that are paintable and used in the automotive industry include polycarbonate/polybutylene terephthalate, polyphenylene oxide/nylon 66, polyphenyleneoxide/polybutylene terephthalate, polyether-polyester copolymer/polybutylene terephthalate, polycarbonate (both unfilled and glass filled), polyphenyleneoxide (both unfilled and filled) and a resin/glass material.
The invention will now be further described with reference to a number of specific examples which are to be regarded solely as illustrative, and not as restricting the scope of thelinvention.
Automotive grade plastic in the form of virgin and rework parts were cleaned in the following sequence:
~9~ Treatment Step 1 3% Kleen 132 alkaline wash 1 minute spray at 140F
2 Tap water rinse 3 1% Permatreat 325 acidic wash 30 second spray at 130F
4 Tap water rinse Deionized water rinse Kleen 132 and Permatreat 325 are trade names of Betz Laboratories, Inc.
To evaluate the efficacy of the inventive concentrate as a rinse enhancer, dilute solutions of the concentrate were used in place of the deionized water spray rinse in stage 5. The results are reported in Table I. The concentrate evaluated was Treatment A.
Concentration Observations Delonized Water Heavy beading on virgin plastic -some sheeting on rework plastic 0.03% v/v No beading but sheeting on virgin plastic Few beads on rework plastic Q.1% v/v Same observations as O.G3% v/v From these observations, it can be seen that the inventive treatment is effective at enhancing the drainage of rinse water from the surfaces of plastic parts.
~3278 Quantitative tests were also performed to determine the efficacy of the inventive treatment. A 4 inch by 3 inch plastic piece (trade name, Xenoy, available from General Electric) underwent the following processing:
Staqe Treatment Step 1 3h Kleen 13? alkaline wash 1 minute spray at 140F
2 Tap water rinse 3 1% Permatreat 302 acidic wash 30 second spray at 135F
4 Tap water rinse Deionized water rinse Permatreat 302 is a trade name of Betz Laboratories, Inc.
To evaluate the inventive treatment, dilute solutions in deionized water were used in place of deionized water in Stage 5.
The plastic part was weighed, processed as per the above sequence, allowed to drain 1 minute, then reweighed. The results for Treatment A are reported in Table II.
Average % Water Weight of Retained Reduction Compared Test Solution Water Grams per part to Deionized Wa~er Deionized Water 1.2059 0.8885 I.1573 0.9322 0.03% 0.5970 41.0%
TABLE II (Cont'd) Average % Water Weight of Retained Reduction Compared Test Solution Water Grams_per part to Delonlzed Water 0.10% 0.4618 51.0%
0.5679 These results clearly showed improved drainage with use o~ -the inventive composition.
While this invention has been described with respect to particular embodiments thereof~ it is apparent that numerous other forms and modifications will be obvious to those skilled in the art.