Note: Descriptions are shown in the official language in which they were submitted.
2 ~ ~
M-695
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
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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.
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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
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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.
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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.
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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.
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EXAMPLES
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.
TABLE I
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.
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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.
TAB~E 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%
0.6~22
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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.
