CA1093394A - Metallized flexible plastic automobile trim component - Google Patents

Abstract

A B S T R A C T
A metallized flexible plastic automobile trim com-ponent, such as a fender extension, is made by applying a series of four coatings to an polymeric substrate of the desired configuration, preferably of a molded thermoplastic urethane. The coatings comprise:
1) a primer coat of a baked pigmented urethane lacquer or enamel, the urethane being preferably an inherently light stable aliphatic urethane, 2) a leveling base coat of a thermosetting resin, e.g. a baked melamine-formaldehyde and more preferably a blend of an aliphatic urethane with an anhydride cured epoxy, 3) a vacuum deposited layer of stainless steel or chromium, or of aluminum when the part is to be used in an interior application, and 4) a top coat of a tough abuse-resistant acrylic and/or urethane lacquer and most preferably one com-prising a blend of an aliphatic urethane, acrylic and melamine resins.

Description

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~35/536 BAC~GROUND AND PRIOfl APT
Vacuum metallizing of plastic sur~aces has been practiced for some time. F'or exarnple, see U. S~ Paten-ts Nos.
3,201,271; 3,740,254; 2,~3,806; and 3,783,012. More recently, attempts have been made to manu~acture automobile exterior trim components such as bumpers, bumper sections or ~ender ex-tensions of a tough bu-t ~lexible, abuse-resistant plastic hav-ing a bright metal-like surface. Generally speaklng, such metallized surfaces have not had the low-temperature ~lex-J.-bility~ the resistance agalnst impact ~rom gravel, the corro-sion resistance, the chrome-plated appearance, and tne like required for automotive use. An article in the December 1974 issue o~ Modern Plastics, "Restoring the Luster to Metallized ~larkets", pp. 42-46, by C. Otis Post presents a good summary.
In that article it is noted with regard to making metallized coatings environmentally acceptable that:
"The relationships among plastic substrate, base coat, metallized coating, and top coat are so intricate that changing any one member usually means reformulating one or more o~ the others."

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Accordingly the invention provides a metallized plastic automobile trim component comprising:
(a) a molded flexible elastomeric polyurethane sub-strate having an extensibility greater than 30%, ~ b) a light-blocking primer coat of a pigmented resin on and immediately contiguous to the surface of said substrate, (c) a clear base coat directly over said primer coat of a thermosetting resin, (d) a -~acuum deposited reflective layer directly on said base coat of a metal said layer being in the range of 200 to 1000 A thick, and (e) a moisture impervious well-adhered flexible film thereover of a non-opaque lacquer comprising a blend of acrylic, aliphatic urethane and melamine resins, the whole of said trim component having been heat treated to cure said lacquer and sufficient to develop light pervious microfissures in said vacuum deposited layer.
Thus, the present invention is a metallized flexible plastic article having a composite coating which is built up in a specific manner from certain select films or ingredients.
The metallizing involves the use of vacuum deposited chromium or stainless steel such as a "ferrous-chrome" containing 13% to 30%
chromium when the part is designed for exterior use on an auto-mobile. Such a stainless steel or chromium coated part can also be used in the interior of an automobile such as for trim for an instrument cluster. One may prefer to use aluminum instead of stainless steel where weathering and abuse resistance are not too important as aluminum gives a more pleasing chromium plated-like appearance, i.e. it more nearly duplicates the appearance of conventional electroplated chrome parts. ~lowever, when a thin layer of aluminum oxidizes it becomes transparent or trans-333~3~L

lucen-t and the metallic luster is lost. In an exterior appli~
cation such as a bumper section, if there is a break or blemish caused by a stone nick or the like, an aluminum layer disappears at the break or blemish point in a short period of time and then will continue to oxidize and disappear until the entire aluminum layer is gone.
The base plastic from which the part is made is a tough but flexible elastomer, preferably an injection molding grade thermoplastic polyurethane (TPU). By "flexible elastomer" is meant a natural or synthetic thermoplastic or therrnoset plastic or polymer having an extensibility of greater than approximately 30 percent, as compared to a "rigid" plastic which may be con-sidered to have an extensibility of less than 10 percent. While it is preferred to use a molded -thermoplastic urethane because of its other properties, such a urethane is more deleteriously affected by sunlight than many other plastics, that is, it is light sensitive.

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~ ~3 3 An article o~ t~l~ desired shape Irlade from the elastolner, a~ter sur~ace cleaning if required, is ~uccess~vely coated in accordance with the present invention with preferab]y four well~bon~ed layers or ~llms to prodllce the final lustrous metallic ~ppe~rance desired.
The cleaned plastic part is first prime coated with a pigmented ~nd thus light-blocking urethane lacquer havin~ a dry film thickness of o.8 to 1.2 mils~ which is air flashed and baked. While aromatic urethanes have been used, the urethane is preferably an aliphatic one which is inherently more light stable. This is ~ollowed by a base coat of a melamine formaldenyde resin or preferably, a urethane-epoxy resin having a dry film thickness of about o.8 to 1.2 mils.
The base coat is also baked, and if it were applied directly to the plastic substrate, it would not adhere well. On the other hand, the pigmented urethane lacquer prime coat will not flow readily and form the level, sheeny and smooth uni-~orm surface required for the vacuum deposited metal.
Desirably, the base coat should also be light stable.
Depending on the appearance desired in the final part, the base coat can be applied to be sheeny or to be matte appearing It is preferred to apply the base coat "wet-on-wet" directly onto the air~flashed but not completely baked primer as be-tter intercoat adhesion is obtained.
The metal is then vacuum deposited onto the base coat using pre~erably the resistance method. Electron beam and sputtering vacuum deposlting can also be used. Sputtering gives a deposit tha-t is brighter appearing than the others, ~u-t a lacquer top coating thereover tends to microcrack in the metal layer. Resistance coating is favored as the re-quired lnvestment in equipment is substantially less.
:- B The metal c~ating i5 ~e~e~eb~y about 200-lOOO A
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thick -- thick enough ~o develop the proper metallic color.
The chromium content of the stainless steel is essen~ial, but the steel can a~so have incorporated therein rni.lor amounts of nickel and/or magnesium and/or other metals. The use of essentially pure chromium is lncluded within the ambit of this invention because, contrary to what some believed3 it was found that chromium could be successfully vacuum deposited for this application. Essen-tially pure aluminum gives the more pleasing appearance and most closely matches that o~
traditional electrodeposited chromium on metal parts. Chromium deposited by resistance vacuum metallizing iæ the next most effective in matching electrodeposited chromium.
The thin metal coating is not, o~ course, resistant to mechanical abuse and to long-term weathering and needs to be protected. While various ~lexible abuse-resistan-~ non-opaque top coats, such as an acrylic lacquer might be usedg it has been found that a clear lacquer derived from a blend o~
acrlyic, aliphatic urethane and melamine resin has de~inite advantages and is to be preferred. This particular top coat can also be used in other applications such as for the pro-tection of painted parts.
The film thickness of the top coat is preferably in the range of o.8 to 1.2 mils, dry basis, and it is pre~erably thoroughly baked, e.g. at 250F, but too high a temperature may cause some yellowing and/or iridescence. The top coat is ~ormu~
lated to adhere to the metal layer as well as ~o the base plastic. By deliberately overlapping the top coat~ the metal coat and the two underlying layers can be "encapsulated"
between it and the base plastic, eliminating edge delamina-tlon.
The development work on this invention turned up an inter&sting ~inding, Viz: that 1ight may penetrate the :

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metal coatinU and base coa-t film and reach the sur~ace o:~ the underlylng primer coat, causing degradation thereo~ and inter-facial loss of adhesion between the base coat and the primer coat. That light penetrates the metal film, which appears to the eye to be con-tinuous and opaque, is surprising. This was found to be so as ~ollows: When a metallized layer de-posited on a film of the base coat supported on a glass plate is exposed to visible light, including ultraviolet light rays, the light will not pass through. When, however, the acrylic top coat is applied thereover and baked, some of the light will pass through. It is believed that this is because mlnute, microscopic cracks or fissures through the metal film were ~ormed which allowed the light to pass. Apparently the solvents normally used in the top coat material and the di~ference in thermal expansion o~ the metal and resin films during baking cause these minute cracks to appear.
As the light does pass through the metal layer, as the base coat is not pigmented, and as the thermoplastic urethane base part is quite light sensitive, the skilled in the art will appreciate that it is quite desirable to make the primer coat light opaque and to use a resin therein that is, preferably, inherently light stable, such as an aliph~tic urethane. Long term outdoor, e.g. Florida sunshine ~or one yea weatherin~ tests have conclusively established that interfacial adhesion loss will occur between the base coat and the primer coat before it will occur at the interfaces of the other layers. Use o~ a properly formulated, pi~-mented and applied primer coat will offset this interfacial adhesion loss.
There is little question that this ~inding o~ light penetration and effect is an important one that lends con-siderable merit to the present claim for inventiveness for , .

~.q~3.3~3 the described mul~i-layerec1 metallir~ed produet. ~nd, o~
course, as the metal film is in a sense deliberately micro-crazed or minutely cracked in a controlled regulated mznnerg this permits later flexing and b~nding o~ the product without appreciable or too objectionable change in ~ts appearance.
Moreover, llght is reflected back through these microscopic cracks to some extent3 and this characteristic can be used to esthetic advantage. A white or tinted light blocking pigmented primer coat can be e~fectively employed to ad-vantageously change the appearanc~ of the metal layer andenhance the overall appearance o~ the multi-layered metallized plastic article.
m E DRAWING
The drawing i5 a greatly enlarged schematic cross-sec~ional view of a metallized surface made according to this invention~ in which the number designatin~ the layers are:
l) Injection molded thermoplastic urethane.

2) Baked urethane lacquer.

3) Baked melamine formaldehyde resin.

4) 800 A vacuum deposited ferrous-chrome-20 stainle~s steel.

5) Clear acrylic lacquer.
EXAMPLE I
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~-~ The sample part mada was a ~975 Cadillac1 Fender ~; 25 Extension, part numbsr Xl605647.
An elastomeric thermoplastic urethane was "in house"
manufactured from a gra~ted poly (oxypropylene) diol (Union Carbide Company's NIAX1D-432, 270 Park Avenue, New ~ork, New York 10017), lOO parts by weight; polytetramethylene ether glycol (Quaker Oats Company Polymeg1lOO, Merchandise Mar~ Plazag Chicago, Illinols 60654), 28 p~rts; 4', 4' di-phenylmethane di:isocyanateg 86 parts; and 13 4 butanediol, -~ rr~ ks ~ -6- ~

lUr333 26 parts. This the~oplastic urethane is fully des~ribed in UOS. Patent ~io. 3,933,938. Commercially availa~le Uniroyal thermoplastic urethane de~ignated E-2A could also be used (Uniroyal, Inc., 1230 Avenue of the Americas, Mew York~ ~lew Yor~ 10020). The nature of -the flexible urethane substrate does not appreciably af~ect the performance of the applied coating. The urethane cannot be so sti~f or rigid that it will not serve its intended function as a flexible trim component nor can it be too flexible or elastomeric. The present coating system can, of course, be applied and used with a ~ubstantially more rigid substrate, but other methods of bright trin~ling such as platiny may be rnore economical to use on fi~n or hard surfaces.
The urethane lacquer pximer was a standard productio~
item supplied by PPG Industries, 3800 West 143rd Street, Cleveland, Ohio, under the code designation DEL-600-32906. ~ny equivalent light-blocking primer that adheres well to the molded thermoplastic uretllane can be used. The one used was a thermoplastic and was not cunsidered too stable to ultraviolet lights as ik was an aromatic urethane. It was picJmented to a gray color with black and white pigments. The prirner was sprayed as supplied by the manufacturer in three or four passes onto the properly cleaned surface at room temperature to a thickness of 1.0 + 0.2 mils (dry basis).
The applied coating requires an air flash for 10 minutes or so, but it was not baked at this point. One of the findings made during the development of this i~ventioll was that the subsequent base coat could be applied "wet-on~wet"
with improved intercoat adhe~ion and the consequent saving coming from the elimination of the primer baking ~tep.
The base coat applied over the primer also was a cor.~ercially available tough melamine formaldehyde resin, ' ' ' :

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diluted to spray viscosity of 3~ + 2 seconds (~lo. 1 Zahn Cup~.
The base coat was SM~1240-6, supplied by Red Spot Paint &
Varnish Co., Inc., 100 Main Street, Evansville, IndianaO It was applied to a ~hickness of 1.0 ~ 0.2 mils. The coatiny was air flashed Eor 15 mlnutes, and then the two coatin~s were baked for 45 minutes at 250F ~ 5F (oven air temperature).
After cooliny to room temperature, the parts were vacuum metallized using an Airco Temescal electron beam metallizer. The metal used was a ferrous-chrome~20 stainless steel supplied by Airco Temescal~ 2850 Seventh Street, BerkPley, California 94710, and it was applied to a ~hic]cness of 800 A + 200 A. The procedure used was as follows:
1) Metallizer was broucJht up to and maintained at steady state condition as per manufacturer' 5 in-structions.
2) Samples were loaded into the interlock ch~er.
3) Chamber was sealed and brought down to proper vacuum.
4) Samples were moved into the me-tallizing chamber, throuyh the metal vapor cloud and back to the interlock chamb~r.
5~ Interlock chamber was pressurized and the ~amples wexe removed.
The top coat was a solvent based acrylic lacquer spray applied by conventional methods. The base material is supplied by Pan Chemical Corp., 1 Washing~on Avenue, Hawthorne, ; New Jersey, as 68-189A or 68-202A. The coating was applied ~o a thickness of 1~3 to 1.6 mils (dry basis) followed by air flashing for 15 minutss and bak~ng at 150F 2F (oven air temperature) for 60 minutes~

Thermoplastic urethan~ (TPU) Cadillac Fender Ex-~ensio~s made with the "in house" material and metallized and ~U~33~3~L

P-535~536 coated as above-dascribed were subject ~o various test~ with the results as given in tlle following Table.
TEST RESULTS
Test Results 5 200 Weatherometer Hours (33 Sliyht dulliny and water spottiny Water Immersion (3) Pass Tape Adhesion (3) Pass Thermal Cycle Pass 10 C.A.S.S. Test (1) Pass Cold Flex (3) Substrate Pass Finish Cracked Gravelometer (SAE Test J--400) Pass Salt Spray (2) Pass 15 Gravelometer plus C.A~S.S. (3) Pas.s Gravelometer plus Salt Spray ~3) Pass Car Wash (3) at 1/2% Pass at 5~ Pass 20 (1) General ~otors Test 4476-P
(2) General ~otors Test 4298-P
(3) Accordin~ ~o Cadillac Bright Trim Specifications _ g _ , ~ .

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EXAM~IE II
The coating of Exam~le I is applied to an instru-ment gau~e rim with the only diff`erence being that an aluminum is used in place Or -the stainless steel. The aluminum is a 99.9~% high purity aluminum supplied by R. H. Cheney Inc. of `
Attleboro, Massachusetts 02703~ and is applied to a thickness of 800 A ~ 200 A. This part is suitable for use in the in-terior of an automobile.
For critical exterior use, PPG Industries Dure~
thanel300 is preferably used as the primer. This is a pig-mented enamel instead of a lacquer and is based in a thermo-setting resin. The resin is an aliphatic urethane which is more light stable than the aromatic urethane of the DEL-600-32306. Durethane 300 is weatherable, flexible at low tempera-tures and possesses good adhesion a~fin~ty ~or the moldedthermoplastic urethane surface.
Durethane 300 is white color and it has been found that this underlying white coat material enhances the pleas-ing metallic appearance of the product, i.e. the metal film is usually thin enough such that the color of the primer coat can be seen through the metal ~ilm. Obviously, ln some in-stances it may be desirable to tint the primer coat to irn-prove the appearance of the part. Also, the use of a white primer coat has the additional advan~age that if the metal ~ilm is scratched or scored9 the white shows through, i.e.
one sees the white which is cornplimentary to the metal and not some disfi~uring color such as black or gray.
The following formulation has been found to work exceptionally well as a base coat formula-tion in place of the previously described Red Coat7SM 1240-6.
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~ ght Aliphatic urethane ~l (40~ solids) 50,0 Epoxy resln (l) 3.0 H~P~ (2) 3.
Catalyst sollltion (3) 4.0 Cellosolve~acetate (4) 46.o Methyl-ethyl ketone . 50.0 156.0 (l) 3, 4 epoxy cylcohexylmethyl - 3,4 epoxy cycloh~xane car-boxylate (2) hexahydrophthalic anhydride (3) ~ive parts by weight uranyl nitrate3 balance Cellosolve - acetate (4) Union Carbide trade name ~or 2, ethyloxyethyl acetate The aliphatic urethane solution ~l was based on re-acting epsilon caprolactone polyester diols and triols with cyclohexyl diisocyatate (CHDI) at 50~ solids in toluene, ~ollowed by dilution to the 40~ solids level with additional toluene. The polyesters were Union Carbide Corporation's 20 NIAX PCP-0200 (the diol) and NIAX PCP-0300 (the triol) and - ~ were reacted as follows:
Parts by weight PCP-0300 14.698 PCP-0200 . 3.4~8 25 CHDI (l) 21.799 Toluene 59.994.
: Catalyst (2) OoOll 100 . 000 (l) Hylene1~W--E.I. duPont de Nemours & Co., 1007 Market Street~
Wilmington, Delaware l9808.
(2) dibutyl tin dilurate r~ S

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As can be seerl, -this base coat formulation ls com-posed o~ an ali~hatic amine blencled with an anhydride cured epoxy, with the curing being catalyzed by the uranyl nitrate.
This blend was formulated to optimumize flexi.bility versus hardness and to provide the excel.lent metal adhesion that the epoxies are noted ~or. The weight ratio of urethane resin to cured epoxy resin in the above is about 3 to 1 but this can vary ~rom 1 to 1 to 1 to 2.
The following ~ormulation has been found to work better as a top coat formulation than the previously described Pan Chemical's 68-202A:
Par-ts by weight ~liphatic urethane ~2 (40~ solids)30 0 Acrylic (1) 16~0 15 Melamine (2) 3-Catalyst (3) 0.3 Methyl-ethyl ketone 50.0 Cellosolve acetate (4) 60.0 Toluene 40.0 199.3 (1) Cyanamid XC-4011 (carboxyl ~unctional acrylic)-~American Cyanamid Co., South Cherry Street, Walling~ord, Gon-necticut 06492 (2) Cyanamid 303 (hexa.methoxymethyl melamine) (3) Cyanamid 4040 (acid catalyst) (4) Union Carbide trade name ~or 2, ethyloxyethyl acetate : The aliphatic urethane solution #2 was based on re-acting epsilon ca~rolactone polyester triol (NIAX PCP--0300) and 1~ 6 hexane adipate diol. with cyclohexyl diisocyanate (CHDI) at 40~ solids level as ~ollows:

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53.~/53 CHDI (1) 20.092 Cataly~st (2) 0.011 13.495 1, 6 Hexane ad~pate diol (3) 6 . 1~o7 Toluene 100.000 (1) Hylene W
(2) Dibutyl tin dilaurate (3) Age~lex1 6-1000--Witco Che~ical Co., 277 Park Avenue, New York, New York 10017 The wei.ght ratlos o~ the resins in this top coat are such that the aliphatic urethane and acrylic resins are used in about equal amounts, although up to 5 times as much ure-thane as acrylic can be used. The melamine will usually amountto 5 to 20 weight percent o~ the acrylic resi.ns.
TPU Cadillac fender extensions made with this metal-lized bright trim system give the ~ollowing test results: ~r * ~ ~,a~k :;
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T15ST I~SULTS
Test Results 500 WeatheroMeter llours (3) Slight dulling and water spottlng 5 Water I~ersion (3) Pass Tape Adhesion (3) Pass Thermal Cycle Pass C.A.S.S. Test (1) Pass Cold Flex (3) Substrate Pass Finish Pass Gravelometer (S~E Test J~400) Pass Salt Spray (2) Pass Gravelometer plus C.A.S.S. (3) Pass Gravelom~er plus Salt Spray (3) Pass 15 Car Wash (3) at 1/2% Pass at 5% Pass (1) General Motors Test 4476-P
(2) General Motors Test 429g-P
(3) According to Cadillac ~right Trim Specifications Reference i5 directed under Rule 43 to our copending application Serial No. 26g,147, filed December 17, 1976.

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Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A metallized plastic automobile trim component compris-ing:
(a) a molded flexible elastomeric polyurethane sub-strate having an extensibility greater than 30%, (b) a light-blocking primer coat of a pigmented resin on and immediately contiguous to the surface of said substrate, (c) a clear base coat directly over said primer coat of a thermosetting resin, (d) a vacuum deposited reflective layer directly on said base coat of a metal said layer being in the range of 200 to 1000 .ANG. thick, and (e) a moisture impervious well-adhered flexible film thereover of a non-opaque lacquer comprising a blend of acrylic, aliphatic urethane and melamine resins;
the whole of said trim component having been heat treated to cure said lacquer and sufficient to develop light pervious microfissures in said vacuum deposited layer.

2. The component of claim 1, wherein in said blend (e) the weight ratio of said aliphatic urethane resin to said acrylic resin is in the range of 1/1 to 5/1 and said melamine resin is in the range of 5% to 20% by weight of the acrylic resin.

3. The component of claim 1 or 2 in which the vacuum de-posited layer (d) is a metal selected from chromium, chromium stainless steel, aluminum, and alloys thereof.