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Publication numberUS3911178 A
Publication typeGrant
Publication dateOct 7, 1975
Filing dateFeb 19, 1974
Priority dateFeb 19, 1974
Publication numberUS 3911178 A, US 3911178A, US-A-3911178, US3911178 A, US3911178A
InventorsFloyd E Mcdowell, Michael J Williams
Original AssigneeMccord Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Painting of a molded urethane part
US 3911178 A
Abstract
Molded urethane automobile parts containing an internal waxy mold release agent that normally causes "fisheying" in urethane paints used to topcoat such parts are effectively painted by first applying a thin clear coat of the thermosetting vehicle of a urethane-type paint free of pigment, at least partially curing the clear coating to bind the lubricant or mold release agent, followed by application of the pigmented final color coat of a urethane paint and fully curing both coats.
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United States Patent 1191 McDowell et al. Oct. 7, 1975 [5 1 PAINTING OF A MOLDED URETHANE 3,516,957 6/1970 Gray et a1. 264/300 x PART 3,639,147 2/1972 Benefiel et a1. 1 17/72 X 3,698,927 10/1972 Sawyer ll7/l38.8 D X [75] Inventors: Floyd E. McDowell, Exeter; Michael 3 752,695 8/1973 Fin 1|i 117/138 8 D X J. Williams, Somersworth, both of 3,817,774 6/1974 Kuzmik 117/47 A N.l-l.

[73] Assignee: McCord Corporation, Detroit, Primary ExaminerRalph Husack Mich Attorney, Agent, or FirmMcGlynn and Milton [22] Filed: Feb. 19, 1974 21 App]. No.: 443,319

[52] US. Cl. 427/316; 427/307; 427/322; 427/379; 427/385; 427/407; 428/425 [51] Int. C1. B32B 27/40; BOSD 1/38 [58] Field of Search 117/72, 138.8 D, 47 A, 117/47 l-l; 161/190; 264/300, DIG. 77; 427/316, 307, 322, 379, 385, 407

[56] References Cited UNITED STATES PATENTS 3,442,837 5/1969 Brotz et al. 264/300 X Molded urethane automobile parts containing an internal waxy mold release agent that normally causes fisheying in urethane paints used to topcoat such parts are effectively painted by first applying a thin clear coat of the thermosetting vehicle of a urethanetype paint free of pigment, at least partially curing the clear coating to bind the lubricant or mold release agent, followed by application of the pigmented final color coat of a urethane paint and fully curing both coats.

ABSTRACT 4 Claims, 1 Drawing Figure Mold Urethane Part with Internal Mold Release Agent Apply CI of Urethane Vehicle ear Coat l2 1 Partially Cure ClearCoat I Apply Color Coat of Vehicle Pl us Pigment Fully Cure Both Films Mold Urerhane Parr IO with Internal Mold W Release Agent ll Clean Surface Apply Clear Coal l2 of Urethane Vehicle l Partially Cure Clear Coal Apply Color Coal of 4 Vehicle Plus Pigment ll Fully Cure Bolh Films flw 1 x PAINTING OF A MOLDED URETI-IANE PART INTRODUCTION Certain automobile interior and exterior parts are now made from molded urethanes such as the so-called thermoplastic urethanes and the self-skinning urethane foams. Such parts after molding are painted to color match the color of the automobile.

Internal mold release agents are customarily used in the manufacture of such parts, such as waxes added to the molding formulations which migrate, bleed or bloom to the surface during molding and aid in release of the part during demolding. When a paint comprising a vehicle and a pigment is applied to such a molded surface the mold release agent can be absorbed by the paint film and effect the forces that hold the pigment in dispersion in the paint such that fisheying or crawling will occur in the paint film, i.e., the pigment in the paint tends to separate in areas where the mold release agent or lubricant is present on the surface of the part such that pigment pockets or voids result.

The mold release agents that are preferred are usually esters or amides of C C fatty acids. Once they have migrated to the surface and served their mold release function, they are quite difficult to remove. Reasonably cleaning with solvents or detergents will often not reliably do so.

THIS INVENTION It has now been found that when such molded parts are to be painted with a urethane type paint that contains a dispersed pigment, the deleterious effect of the mold release agent on the surface can be blocked by first applying a clear coat of only the urethane vehicle of the paint and at least partially heat curing the clear coat following which the part can be painted in the normal manner. It has been found that the lubricant on the surface of the part does not prevent wetting and uniform film formation by the urethane vehicle and that once the clear film is at least partially cured this seems to lock the lubricant in and prevent further migration of any significant amount thereof that would be harmful to the subsequently applied paint film.

In one situation where Chevrolet 8" and Cadillac bumper end fillers were being manufactured, rejects because of unsatisfactory paint film formation were reduced from an average of 10 to 12 per cent to under 3 per cent by the use of the barrier coat technique of this invention.

Full curing of the clear barrier coat prior to the application of the final topcoat does not appear to be required. Heating of the film to a true film temperature in a range of 180 to 260F appears to adequately bind the lubricant while leaving the barrier coat film sufficiently uncured to bind well with the topcoat when it is applied. The barrier when partially cured in this manner will not normally pass the xylene rubbing test although in some cases it may be sufficiently cured to do so. Too hard a cure of the clear barrier coat may prevent the topcoat from effectively bonding with it. After the topcoat is applied both films are fully cured by heating them to a temperature above 225F.

The clear barrier coat film while continuous need not have a thickness of greater than 0.5 mil as film thick nesses in the order of 0.2 to 0.4 mil seems to lock adequately the mold release lubricant in against migration. Thicker films may contribute to cold flex cracking. The

top pigment-containing paint film can have the customary thickness, usually about one mil or more.

Generally it is desirable to remove as much as possible of the mold release agent by solvent degreasing, detergent washing or the like so as to minimize the chance of strike through.

Because both the barrier coat and the paint contain a solvent, it is preferred to heat the part to a temperature greater than 130F prior to their application and to allow the part to air flash after the application of the barrier coat and after the application of the paint.

While the paints used in the present inventions are referred to as urethane paints or urethane lacquers, they are more properly identified as urethanepolyester-extended melamine lacquers the vehicles of which are cross-linkable or heatcurable.

DRAWING Attached to and forming a part hereof is a drawing which schematically illustrates the significant steps of the process of this invention and is self-explanatory.

In the drawing the first block, block 10, is labeled Mold Urethane Part with Internal Mold Release Agent. Block 11 is labeled Clean Surface and block 12 is labeled Apply Clear Coat of Urethane Vehicle. Block 13 is labeled Partially Cure Clear Coat." Block 14 is labeled Apply Color Coat of Vehicle Plus Pigment and block 15 is labeled Fully Cure Both Films.

EXAMPLE Test blocks 8 inches X 8 inches X Aa inch are prepared by injection molding of a thermoplastic urethane, Roylar E-2B sold by Uniroyal Chemical, Naugatuck, Connecticut, 60770, to which 0.3 weight percent of ethylene-bis-stearamide is added as a mold release agent. Advawax 280 F sold by Cincinnati Milacron Chemicals, Inc. Reading, Ohio 45215 could as well be used. The surface of the test blocks are cleaned by washing with a xylene soaked rag.

The clear lacquer used is Durathane applied by an air gun as supplied by the manufacture, Pittsburgh Plate and Glass Chemical Company. The color coat used is Durathane lOO dark metallic green (WV-4517) also applied by air gun as supplied.

The test blocks are preheated to F prior to application of the first coat and are allowed to air flash for about 5 minutes after the first coat is applied.

One block is coated with the color coat after the solvent washing and after the air flash it may be noticed that unacceptable fisheying has occurred.

The 8 inch X 8 inch surface of another preheated block is first coated with a 0.3 mil film (dry) of the clear Durathane 100, air flashed and baked 30 minutes at 200F. After allowing some cooling but while the part is still warm the surface is sprayed with a one mil film (dry) of the color coat, air flashed for a few minutes then baked at 240F for 30 minutes. Paint film formation will be noticed to be good and the sample will pass all of the usual tests such as flex cracking, aging, weathering, and the like.

We claim:

1. In the painting with a paint of a molded urethane part made from a moldable urethane formulation containing a wax of a type and in an amount sufficient to serve as a mold release agent, said paint comprising a urethane lacquer vehicle with a pigment dispersed therein, the improvement comprising:

A. cleaning a surface of said part to at least in part remove said wax therefrom:

B. applying a clear continuous barrier coat to said surface of said vehicle free of pigment as a film having a thickness under 0.5 mil, dry;

C. at least partially curing said barrier coat by heating to a film temperature in the range of l80260F, and

D. applying said paint as a film and curing said film by baking at a film temperature in excess of 225F.

2. The process of claim 1 wherein said barrier coat lene-bis-stearamide.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3442837 *Dec 1, 1965May 6, 1969Elisabeth HertleinTransparent polyvinyl chloride containing high density polyethylene as a lubricant
US3516957 *Apr 29, 1968Jun 23, 1970Eastman Kodak CoThermoplastic polyester composition containing organic ester mold release agent
US3639147 *Feb 3, 1970Feb 1, 1972Celanese Coatings CoArticle having multilayer coating and process for producing same
US3698927 *Oct 28, 1970Oct 17, 1972Goodyear Tire & RubberFoam structure with protective overcoat
US3752695 *Sep 23, 1970Aug 14, 1973Goodyear Tire & RubberCoated polyurethane foam having an integral skin
US3817774 *Jul 24, 1972Jun 18, 1974Macdermid IncPreparation of plastic substrates for electroless plating
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4163072 *Jun 7, 1977Jul 31, 1979Bell Telephone Laboratories, IncorporatedEncapsulation of circuits
US4191796 *Oct 23, 1978Mar 4, 1980Eckhoff Paul SMethod of preventing peel of old paint
US4282285 *May 15, 1980Aug 4, 1981International Telephone & Telegraph CorporationProcess for preparing polyurethane molded part
US4292354 *Sep 21, 1978Sep 29, 1981Inoue Gomu Kogyo Kabushiki KaishaMoldings for automobiles
US4407871 *Oct 8, 1981Oct 4, 1983Ex-Cell-O CorporationVacuum metallized dielectric substrates and method of making same
US4421827 *Jan 18, 1982Dec 20, 1983Scott Bader Company LimitedComposites and methods for providing metal clad articles and articles produced
US4431711 *Oct 8, 1981Feb 14, 1984Ex-Cell-O CorporationVacuum metallizing a dielectric substrate with indium and products thereof
US4431763 *Aug 31, 1982Feb 14, 1984Minnesota Mining And Manufacturing CompanyFlexible solvent barrier coating
US4477533 *Oct 5, 1982Oct 16, 1984Scott Bader Company LimitedLaminates containing inorganic structural materials
US4668535 *Sep 4, 1984May 26, 1987Goodyear Aerospace CorporationProcess for preparing a fuel tank of polyurethane laminate having contiguous contrasting layers
US5654037 *Mar 24, 1995Aug 5, 1997Apx InternationalMethod of minimizing defects in painted composite material products
US5733494 *Dec 30, 1996Mar 31, 1998Apx InternationalMethods of making preforms for resin transfer molding
US5736472 *Mar 29, 1995Apr 7, 1998Specialty Adhesive Film Co.Marking SBR and natural rubber products
US5869168 *Jan 10, 1997Feb 9, 1999Mahn, Jr.; JohnReflective heat activated transfer
US6099899 *Feb 12, 1999Aug 8, 2000Basf CorporationMethod for a multilayer coating
USRE31960 *Oct 5, 1984Jul 30, 1985Scott Bader Company LimitedComposites and methods for providing metal clad articles and articles produced
EP0104779A2 *Aug 26, 1983Apr 4, 1984Minnesota Mining And Manufacturing CompanyFlexible solvent barrier coating
EP0104779A3 *Aug 26, 1983Sep 18, 1985Minnesota Mining And Manufacturing CompanyFlexible solvent barrier coating
Classifications
U.S. Classification427/316, 428/31, 427/393.5, 428/425.9, 427/307, 428/423.3, 427/379, 427/322, 427/412.1
International ClassificationC08J7/04, B05D7/02, B05D3/02
Cooperative ClassificationB05D7/02, C08J7/04, C08J2375/04, B05D7/546
European ClassificationC08J7/04, B05D7/02, B05D7/546
Legal Events
DateCodeEventDescription
Mar 12, 1986ASAssignment
Owner name: DAVIDSON RUBBER COMPANY, INC., DOVER, N.H., A CORP
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:MCCORD CORPORATION BY NAME CHANGE NOW MCCORD GASKET CORPORATION;REEL/FRAME:004521/0943
Effective date: 19860305