WO2000076834A1

WO2000076834A1 - Exterior vehicle component with moldable thermoplastic composition and ultraviolet stabilized color concentrate

Info

Publication number: WO2000076834A1
Application number: PCT/US2000/008191
Authority: WO
Inventors: Willem Tekelenburg, Jr.; Thomas Salley
Original assignee: Plastech Engineered Products, Inc.
Priority date: 1999-06-10
Filing date: 2000-03-28
Publication date: 2000-12-21

Abstract

An exterior vehicle component which is provided for exterior appearance purposes. The component comprises a substrate of a moldable thermoplastic, such as a copolymer polypropylene composition which defines the shape of the component and includes pigmentation distributed therein for defining the color of the exterior surface. The composition also has an ultraviolet radiation deterioration preventing agent.

Description

EXTERIOR VEHICLE COMPONENT WITH

MOLDABLE THERMOPLASTIC COMPOSITION AND

ULTRAVIOLET STABILIZED COLOR CONCENTRATE

TECHNICAL FIELD

This invention relates to vehicles and, more particularly, to exterior components of automotive vehicles which are either provided for appearance purposes or are of such size as to make a contribution to the exterior appearance of the vehicle, wherein the exterior component is formed from a moldable thermoplastic composition, such as a copolymer polypropylene, and a color concentrate containing an ultraviolet stabilizing agent.

BACKGROUND ART

It is said that materials account for about 30-50% of the costs of most manufactured products. New materials that can save the costs of production while enhancing performance can yield a competitive edge in many industries, including automobile, aircraft, industrial machinery and other industries.

Dramatic advances in structural materials have been made. Certain materials exhibit favorable relationships between high temperature strength, high stiffness, and low density, compared with traditional materials such as aluminum and steel. Further, the materials themselves can have characteristics which can be tailored to have the properties demanded by a given environment. Ideally, the use of designed materials may lead to higher fuel efficiencies, lower assembly costs, and longer life for many manufactured products. Included among such advanced materials are polymers. Chief among the advantage of polymers is their light weight coupled with high stiffness and strength. Other desirable properties include enhanced resistance to corrosion and fatigue. However, one generic limitation of polymers in the past has been temperature. Automobiles and industrial equipment are major users of advanced polymers. Such materials currently are in limited production, primarily in interior components. An advantage of polymers is the potential for parts consolidation, which results in lower assembly costs. Polymers can also accommodate styling changes with lower retooling costs than would be possible with metals.

In the automobile industry, plastic components which have been used in the past are made of injection molded thermoplastic polyolefins ("TPOs"). Conventional practices have called for painting the exterior surface of the molded component in a color which is compatible with the appearance of the automobile. This may be a color similar to the body or a contrasting neutral color. Thereafter, a clear coat final coating is often sprayed on the paint to give it a desired luster, mar resistance and ultraviolet protection. It has been necessary to prepare the exterior surfaces of the molded component or substrate either by applying a primer or by other means to promote adhesion of the paint to the surface of the molded substrate. Often, the color of the component derives from the pigmentation in an intermediate paint layer. The final coating which is thereafter applied enhances the luster. Formulations have been proposed for the substrate which promote paint adhesion to the point that a primer and/or adhesion promoter coat can be eliminated.

Automotive vehicles may include exterior plastic components such as a bumper fascia formed as a molded product in the condition which it comes out of the mold. In this case, the plastic which is used to injection mold the component may be loaded with pigmentation so that the desired color appears not only on the surface but throughout the molded substrate which forms the component. The surface which is provided by the molded bumper fascia while initially presenting a desirable color often lacks luster and, in fact, presents a surface which can be easily scratched and marred to further detract from its lackluster. Further, it tends to discolor upon prolonged exposure to sunlight.

The characteristics which are desirable in an exterior vehicular component are several. First, the component must maintain its form without becoming too soft in very hot weather or too brittle in extreme cold weather. Moreover, the product must resist deterioration from exposure to the ultraviolet rays of the sun. Particularly in the case of a bumper fascia, the plastic part must be flexible without permanently denting or deforming. Any coating should have elastomeric properties that prevent flaking and scaling which would adversely affect the appearance. In all such components, surface appearance is important. It is also desirable that the surface appearance has a long-lasting luster. Thus, elastomeric coatings must likewise be strongly adherent. To produce an uncoated plastic bumper fascia which is pigmented in the mold is less costly than molding the same non-color matched component, applying a primer or otherwise treating the surface for adhesion promotion, applying a coating of paint and then applying a clear coat on top of the paint. The final coat is provided solely for appearance and to impart a lustrous finish which can be achieved through the multiple coatings provided.

An elusive characteristic with which to imbue these products is resistance to ultraviolet deterioration. A problem with UV stabilizers is that, when they are added to TPO in a sufficient quantity to effectively protect against UV deterioration of the substrate, they may weaken adhesion of the paint to the TPO. After the substrate is painted, the paint itself may include opacity and UV screeners which provide the protection against UV deterioration. On the other hand, where the substrate itself is pigmented, the UV protection for the resin must be embodied in the TPO as an additive. Such pigmented TPO products have been utilized without any subsequent coating. If these existing products were treated with a clear coat, the coating may not adhere. Consequently, there exists a need for a product which can achieve both the advantages of a painted substrate and a pigmented, unstabilized substrate without the disadvantages thereof.

Illustrative of conventional practices are U.S. Patent Nos. 5,037,680 and 5,750,580 which are incorporated herein by reference.

DISCLOSURE OF INVENTION

An object of the present invention is to provide an economically advantageous process which allows the use of resins combined with highly ultraviolet stabilized color concentrates to mold exterior grade automotive parts. Such products have the characteristics of resistance to discoloration under the combined action of light and oxygen, and are suitable, for example, for exterior automotive applications without additional lacquer coating.

Thus, it is an object of the present invention to provide an exterior vehicle component having an exterior appearance, the color of which can be predetermined by selection of a suitable pigment that is added in-process before solidification, together with an ultraviolet stabilizing agent, such that the color of the component does not change upon exposure to sunlight, air, or oxygen. The component is formed from a substrate of a polymer polypropylene. The composition has pigmentation therein to define the exterior color of the exterior surfaces. No coating of clear material is required to be applied on the exterior surfaces to imbue the exterior color and configurational appearance with an enhanced luster. The quantity of ultraviolet radiation screening agent provides a level of resistance to UV deterioration that is acceptable in the exterior vehicular environment of the component. Lacking an exterior coating, tenacity of adherence of the coating to the substrate is not a factor in the manufacturing process.

Another object of the present invention is to provide an exterior vehicle component which is straightforward in construction, economical to manufacture, and meets operational requirements.

These and other objects of the present invention will become more apparent in the following detailed description and claims.

The invention may best be understood with reference to the accompanying drawings wherein an illustrative embodiment is shown.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a process flow diagram illustrating the major steps in practicing the disclosed invention. BEST MODE FOR CARRYING OUT THE INVENTION

The major process steps that are depicted in Figure 1 include: preparing the copolymer polypropylene resin (step A); adding a colorant(s) (step B); and adding an ultraviolet protectorant(s) (Step C). It should be noted that these process steps can be performed in a sequence other than that specifically depicted.

The automotive vehicle exemplifies the type of vehicles to which the present invention is applicable. It will be understood that all other types of automotive vehicles, such as sedans, sports cars, station wagons, limousines, trucks and the like, are also within the ambit of the present invention, as are non- automotive vehicles, such as watercraft, aircraft, and the like. The invention, with the construction of a component or components of, relates to such vehicles. Consider as a non-limiting example a component, such as a bumper fascia, which is provided for exterior appearance purposes. As mentioned, while a bumper fascia presents one illustration of the invention, the invention is also applicable to other exterior components of vehicles which have in the past been made of thermoplastic materials, specifically poly olefins, also known as TPOs. The invention has particular applicability to large components, such as door sides, wheel covers, and trunk lids where plastic components have historically been utilized.

In the present invention, the bumper fascia is formed of a substrate of a moldable thermoplastic, preferably a copolymer polypropylene composition which defines the shape of the bumper fascia. The substrate is a molded component having exterior surfaces which define the configurational appearance of the bumper fascia. The composition of the substrate will be more particularly described. It contains pigmentation for defining the color of the exterior surfaces of the substrate and an ultraviolet protectant. The color pigmented thermoplastic substrate forming the component or bumper fascia of the present invention comprises a copolymer polypropylene resin, color producing pigments and additives, ultraviolet stabilizers, and other additives. The color imparted to the substrate formed from the resin composition can be accomplished by ingredients and techniques known in the art. The color pigmentation of the resin is carried out to produce a desired value on a particular color chart. Typically, coloration is provided to the resin substrate by incorporating such agents as titanium dioxide, blue tone phthalocyanine green, yellow tone phthalocyanine green, green tone phthalocyanine blue, lamp black or carbon black, and combinations thereof. The amounts of color additives and the particular combinations used to achieve the desired color of the thermoplastic resin are known to those skilled in the art. For example, black molded articles which typically comprise an interior vehicle component generally contain about OJ-5.0% by weight of carbon black, which performs the dual purposes of imparting color and as absorbing UV radiation. Such colorants are available from Uniform Color Company, Holland, Michigan.

Ultraviolet radiation deterioration preventing agents that can be used in the resin substrate include carbon black, white pigments, and other pigments that absorb and/or reflect ultraviolet radiation, organic ultraviolet stabilizers such as hindered amine light stabilizers (HALS) , hydroxybenzophenones, hydroxyphenylbenzotnazoles, alpha-cyanoacrylates, oxanilides, salicylates, hindered amines, and the like, and mixtures thereof. Such materials are available from Ciba- Geigy Corp.

The amount of stabilizer present in the molded polyolefinic thermoplastic resin composition can range from about zero to about 10 percent by weight of the thermoplastic composition depending upon the desired color pigmentation of the resin composition. For example, resin compositions that are color pigmented with carbon black may present sufficient resistance to UV deterioration without the need for an additional organic UV stabilizer because carbon black itself is a suitable UV absorber. Preferably, however, an additional organic UV stabilizer is desirable even where the pigment has UV stabilizer characteristics. Also, organic UV stabilizers may not be needed in resin compositions that are color pigmented with a white pigment since they reflect and absorb ultraviolet radiation. Nevertheless, it may be desirable to include some additional organic UV stabilizer. Moldable resin compositions that are color pigmented with other color pigments and additives, e.g. blues, greens, reds, etc. , may require some quantity of a UV stabilizer which generally ranges from about 0.02 to about 5.00 weight percent of the resin composition. It is preferred to use a hindered amine, especially oligomeric hindered amines as the ultraviolet radiation stabilizer at about 0.02-5.0 weight percent level.

Examples of other components which can be added to the resin composition include various stabilizers such as antioxidants, weatherability improvers, thermal degradation inhibitors, antistatic agents, and lubricants or plasticizers. As indicated earlier, the moldable resin or composition, is preferably a moldable thermoplastic composition, i.e. a thermoplastic polyolefin. Examples include polyethylene and polypropylene, homopolymers, copolymers, alloys, blends and terpolymers. Also suitable may be copolymers of ethylene and propylene; ethylene and 1-butene; ethylene and 1-hexene, ethylene and 1-octene, and the like; and copolymers of propylene with 1-butene, 1-hexene, 1-octene, and the like. Other polymers including the aforementioned olefins and other polymarizable monomers such as the (meth) acrylates, styrene, vinyltoluene, vinylchloride, vinylidene chloride, and the like may also be used. Poly vinylchloride (PVC), thermoplastic ployurethane (TPU), thermoplastic polyester, and other moldable or thermoformable polymer are also suitable.

The thermoplastic resin compositions of this invention can be prepared, for example, by kneading the above components by means of a mixing device such as a single screw extruder, a twin screw extruder, a Banbury mixer, a molding machine, a roll or a Brabender plastogram and cooling and solidifying the mixture. Products may also be produced by polymerization reaction.

The shaped substrates can be produced by a conventional shaping process, for example an injection molding process, from the copolymer polypropylene resin compositions of the invention. The resulting shaped substrates exhibit excellent rigidity, resistance to impact at a low temperature, resistance to thermal deformation, and the retention of appearance following exposure to sunlight.

Thus, according to the invention, by deploying UV screeners within the plastic substrate, the substrate will not absorb as much UV light which will extend its life. By screening the light, the invention improves color and property retention. Also, a wider selection of pigments may be available because automotive manufacturers allow some color shift over time. By screening light, pigments which previously failed may now pass.

Example 1- Mechanical Properties

Example 2 - Typical Exterior Applications:

Bumper Step Pads Air Dams Wheel Liners Claddings Rub Strips Box Top Rails Bed Liners Mesh Grills ► Delete Covers

► Fascias

Example 3 - The Preferred Resin*

*Avaιlable Irom Exxon Chemical as ESCORENE^® polypropylene (PP8114), this preferred material is an unfilled, reactor grade, natural resin Example 4 - Testing of Disclosed Invention

The following summarizes tests to which the disclosed invention was subjected as embodied in a Ford Explorer step pad. Testing was performed on ESCORENE^® PP8114 and ESCORENE^® PP8154-E7 with uniform color (Med. Platinum). a) Heat Resistance b) Environmental Cycling c) Accelerated Weathering d) Florida Exposure

Low Temperature Impact - As received

- After 1600 hours Weather ometer

- After 12 months exposure e) Other Testing

Medium platinum step pads that were injection molded at Plastech (the assignee of this invention) in Bryan, Ohio were tested as received.

a) Heat Resistance

Two unassembled step pads (Part Nos. 541, 542) were placed on the floor of a preheated Envirotronics walk-in chamber maintained at 121 °C. After 30 minutes, the two parts were removed from the chamber and cooled to room temperature (23 °C + 2°C).

Before and after the exposure, each part was measured in three locations with a 1M Mitutoyo digital caliper.

There was no evidence of wrinkling, blistering, or excessive part warpage.

40- b) Accelerated Weathering

Two pieces of a step pad were subjected to accelerated weathering testing. Six 4 in. x 4 in. specimens were tested in a Sunshine Carbon Arc Weatherometer and examined after 1600 hours of exposure with satisfactory results.

There was no unacceptable change in appearance, color, or configuration following accelerated weathering.

c) Florida Exposure

Three step pads were sent to South Florida Test Service for an extended Florida exposure with satisfactory results.

After such exposure, though the material exhibited slight chalking and dulling, no cracking was evident. Neither was there any blistering or other evidence of degradation.

d) Low Temperature Impact Resistance

The As Received Low Temperature Impact Resistance was tested with no failures reported.

e) Other Testing

Five specimens were cut from one step pad and 2 specimens cut from another Xenon Arc Weatherometer exposure according to SAE J1960. Prior to the exposure Lab color readings were taken on a Macbeth Spectrophotometer and 60° gloss readings were taken on a Sheen Glossmeter.

The specimens have been exposed for 2500 kJ/m² without showing any visible evidence of color or gloss change.

Claims

WHAT IS CLAIMED IS:

1. An exterior vehicle component which is provided for exterior appearance purposes comprising: a substrate of a moldable thermoplastic composition for defining the shape of the component, the substrate having an exterior surface, the composition having pigmentation distributed therein for defining the color of the exterior surface, the composition also having an ultraviolet radiation screening agent distributed therein.

2. A component as defined in claim 1 wherein said ultraviolet radiation deterioration preventing agent present in said composition is selected from the group consisting of carbon black, white pigments, and other pigments that absorb and/or reflect ultraviolet radiation, organic ultraviolet stabilizers such as hindered am i ne l i g ht s tab i l iz e r s (H A L S ) , hy d r o x y b e nz o p h e n o ne s , hydroxyphenylbenzotriazoles, alpha-cyanoacrylates, oxanilides, salicylates, hindered amines, and the like, and mixtures thereof.

3. A component as defined in claim 2 wherein the amount of ultraviolet radiation screening agent ranges from about 0.02 to about 5.00 percent by weight.

4. A component as defined in claim 1 wherein said ultraviolet radiation deterioration preventing agent in said composition is a hindered amine and is present in amounts ranging up to about 5.00 percent by weight of the composition.

5. A component as defined in claim 2 wherein said composition additionally contains an organic ultraviolet stabilizer.

6. A component as defined in claim 5 wherein said organic stabilizer is a hindered amine.

7. A component as defined in claim 1 wherein the pigmentation is selected from the group consisting of titanium dioxide, blue tone phthalocyanine green, yellow tone phthalocyanine green, green tone phthalocyanine blue, lamp black or carbon black, and combinations thereof.

8. A component as defined in claim 1 wherein the moldable thermoplastic composition is selected from the group consisting of a thermoplastic polyolefin, polymers, and copolymers of propylene.

9. A component as defined in claim 1 wherein the composition having pigmentation comprises, at least partially, the composition having an ultraviolet radiation screening agent.