WO2013068536A1

WO2013068536A1 - Vehicle light bezels

Info

Publication number: WO2013068536A1
Application number: PCT/EP2012/072274
Authority: WO
Inventors: Richard Jacques Theodoor Frissen; Godefridus Bernardus Wilhelmus Leonardus LIGTHART
Original assignee: Dsm Ip Assets B.V.
Priority date: 2011-11-10
Filing date: 2012-11-09
Publication date: 2013-05-16
Also published as: EP2776509A1

Abstract

The invention relates to a vehicle light bezel produced from a polymer composition comprising at least 30 wt% of polyamide-410 with respect to the total composition. Preferably, the vehicle light bezel is produced from a polymer composition further comprising a thermal conductive additive.

Description

VEHICLE LIGHT BEZELS

This invention relates to vehicle light bezels, also referred herein as bezel. Bezels are known and are usually made from polycarbonate or polyesters, such as poly(butylene terephtalate) (PBT). US2010/00227182, for example, describes a bezel comprising a thermoplastic polyester. As bezels are near a light source, such as headlights, rear lights, fog lamps, daytime running lights (DRL) and interior lights, it is required that they can withstand heat. Withstanding heat implies that the heat deflection temperature (HDT) of a bezel has to be sufficient, as well as low outgassing is necessary. Outgassing is also referred to as fogging and is in the context of this application understood to be the deposition of volatile compounds, originating from the plastic composition of a bezel and volatilized by heating of the lamp and/or LED units under operating condition, on cold spots such as the lens and reflector, or other areas affecting the visual appearance or headlamp illumination performance. Measures applied to reduce fogging include, for example, exclusion of solvents in the

composition; thinner designs for the moulded parts, thus reducing the amount of material contributing to fogging; and insulating the part by applying a coating. Another solution relates to special designs of the moulded part, or of the mirror optic system as a whole, as a result of which an internal air flow is induced when the vehicle is moving and the material contributing to fogging is guided away from the critical part, thus resulting in reduced deposition of the material contributing to fogging on that part.

Moreover, as bezels are visible parts in the automotive industry, the surface quality has to be high. Outgassing is not desired as it deteriorates the surface quality, reduces light transmission of lenses and increases light reflection losses of light reflecting area's, such as reflectors. Bezels are parts that are usually relatively heavy, such as for example between 200 and 300 g per bezel. Weight reduction has a positive influence on fuel consumption in cars, and thus it is desirable to have less heavy bezels. However, as the parts are also quite large, it is usually necessary to prepare bezels with relatively large thickness, as otherwise the mould is not completely filled, due to flowing properties of the material used.

It is thus an object of the present invention to provide vehicle light bezels that combine both dimensional stability, low outgassing properties, while being lighter in weight than those known in the prior art.

It has now surprisingly been found that a vehicle light bezel produced from a polymer composition comprising at least 30 wt% of polyamide-410 with respect to the total composition, combines the properties of dimensional stability and allowing for less wall thickness, which allows bezels to be much lighter in weight. This has been exemplified in the examples below.

An advantage of a bezel according to the invention is that the surface quality is high, as well as high dimensional stability. Moreover, bezels with lower wall thickness can be prepared, which allows for less heavy bezels. Also less orange peel is observed on the surface of a bezel according to the invention. Another advantage is that the outgassing limit, i.e. the temperature at which no outgassing is observed, of the bezel according to the invention is high.

Polyamide-410

Polyamide-410 is here understood to be a polyamide containing monomer units derived from a dicarboxylic acid with 10 carbon atoms and a diamine with 4 carbon atoms. Preferably as the dicarboxylic acid 1 ,10 decandioic acid is used. As the diamine preferably 1 ,4-butanediamine is used. PA-410 may comprise up to 30 wt. % of further monomeric units, for example dicarboxylic acids with more or less than 10 carbon atoms or diamines with more or less than 4 carbon atoms, with respect to the total amount of polyamide. Preferably the PA-410 used in the bezel according to the invention comprises at least 80 wt. % with respect to the total amount of polyamide of monomer units derived from dicarboxylic acid with 10 carbon atoms and a diamine with 4 carbon atoms, more preferably at least 90 wt. % with respect to the total amount of polyamide, even more preferably at least 95 wt. % with respect to the total amount of polyamide, even more preferably at least 99 wt. %, most preferably at least 99.9 wt. %, with respect to the total amount of polyamide.

The bezel according to the invention preferably is produced from a polymer composition comprising at least 40 wt% of polyamide-410 with respect to the total composition, more preferably at least 50 wt % of polyamide-410, and most preferred at least 60 wt% of polyamide-410.

The bezel according to the invention can also comprise a further polymer in the polymer composition, such as polyamides and/or polyphtalamides. The further polymer is for example chosen from the group of polyamide-610, polyamide-6, polyamide-66, polyamide-46 and aromatic copolyamides. Polyamide-610 as further polymer has the advantage that the surface quality remains high. Polyamide-6 or polyamide-66 as further polymer have the advantage that these are readily available. Even more preferred is a further polymer being a copolyamide, based on monomeric units of adipic acid, terephtalic acid, hexamethylene diamine and diaminobutane. This has the advantage that the temperature resistance is improved, as well as moisture uptake is decreased. The amount of a further polymer may be for example at least 5 wt%, preferably at least 10 wt% with respect to the total amount of polymer

composition. The amount may be preferably at most 50 wt%, more preferably at most 40 wt% with respect to the total amount of polymer composition. Polyamide-410 can be prepared as for example described in

WO00/09586. Bezel

The bezel according to the invention can be prepared by injection molding, which is a technique known in the art. The bezel according to the invention may have a shiny surface, as well as a matt surface. Surface class A has been observed for bezels according to the invention. Surface class A surfaces is a term used in automotive design to describe a set of freeform surfaces of high efficiency and quality.

The bezel according to the invention may also be treated by for example metallization to at least one surface, to provide a metal look. Metallization is usually vacuum metallization either via direct or indirect metallization. This results in a bezel comprising at least one surface having a metal layer. This has the advantage that the bezel can also serve as a reflector for the light source. The metal layer may be selected from the group of aluminum, chrome, and stainless steel.

The bezel according to the invention may also comprise other materials in the polymer composition, such as heat-stabilizers, mold-release agents, pigments, thermal conductive materials, electrical conductive materials and fillers. Fillers include for example minerals, glass fibers and carbon fibers. Typical amount of fillers are for example amounts between 10 to 30 wt%, with respect to the total composition. Preferably, the filler is glass fiber in an amount between 10 to 30 wt% with respect to the total composition.

Heat-stabilizers may be copper compounds and a salt containing a halogenide acid group, for example an iodide or a bromide salt. Good examples of suitable copper compounds include copper (I) halogenides, preferably copper iodide (Cul) and further copper salts like for instance copper acetate, copper sulfate and cupper stearate. As the salt containing an halogenide acid group preferably potassium bromide (KBr) of potassium iodide (Kl) are used. Most preferably a combination of copper iodide and potassium iodide (Cul/KI) is used. The copper compound and the salt suitably are present in the polymer composition for the bezel according to the invention in a molar ratio of Cu : halogenide = 1 : 5 - 15. The amount of Cu preferably is between 10 - 500 ppm, based on the total of the composition, more preferably between 1 - 100 ppm, even more preferably 10 - 70 ppm.

Thermal conductive materials include for example, aluminium, aluminium oxide, copper, magnesium, magnesium oxide, brass, carbon, silicon nitride, aluminium nitride, boron nitride, zinc oxide, graphite, ceramic fibre and the like.

Mixtures of such thermally conductive materials are also suitable. The thermally conductive material may be in the form of granular powder, particles, whiskers, short fibres, flake, platelet, rice, strand, or spherical-like shapes or any other suitable form. The thermal conductive material is preferably present in an amount between 1 to 10 wt% with respect to the total polymer composition, more preferably between 2 and 7 wt% with respect to the total polymer composition.

Preferably, the thermal conductive material are expanded graphite platelets, or PITCH-based carbon fibres, as these are also electrical conductive. For example, PITCH-based carbon fibre having an aspect ratio of about 50:1 can be used. PITCH-based carbon fibres contribute significantly to the heat conductivity. The presence of expanded graphite platelets as thermal conductive material in the present invention results in lower outgassing behaviour of the bezel during use, better performance and makes the bezel anti-static, which is beneficial against dust accumulation. Most preferred, expanded graphite platelets are present in an amount between 2 and 7 wt%, as this keeps the dielectrical strength high and thus leaves the bezel insulating. This amount also reduces the risk for electrical charge and discharge and consequent damage brought to LED electronics systems and/or other electronic parts.

As electrical conductive materials PITCH-based carbon fibres, PAN- based carbon fibres as well as carbon black may be employed. Electrical conductive materials have the advantage that dust accumulation is reduced. PAN-based carbon fibres have a larger contribution to the mechanical strength.

Pigments include for example carbon black and nigrosine.

Preferably the polymer composition of the bezel according to the present invention contains less than 1 wt. % more preferably less than 0.5 wt. %, even more preferably less than 0.3 wt. %, even more preferably less than 0.2 wt. %, even more preferably less than 0.1 wt. % of a mold release agent, with respect to the total composition. A mold release agent is a chemical compound that facilitates the release of a part from a mold, preferably by creating a slip effect between the surface of the part and the surface of the mold cavity. Examples of mold release agents include fatty acids, fatty acid metals salts, fatty acid esters, fatty acid amides, fatty acid soaps, (modified) paraffin waxes, (modified) polyolefin waxes. Preferably, the mold release agents are chosen from the group of fatty acids, such as for example metal salts of stearates especially sodium, zinc or calcium stearate or montanate, and polyetheylene wax and an fatty acid amide such as ethylen-bis-stearamide or combinations thereof. Most preferably the polymer composition does not contain any mold release agent at all. With the low amount or even with the total absence of the mold release agent, the bezel according to the invention, produced from the polymer composition comprising PA-410, still show very good mold release characteristics, but also have a very good surface quality. A low amount or even with the total absence of the mold release agent, the outgassing limit also remains high, as the presence of a mold release agent is disadvantageous for outgassing.

Another important improvement is that the bezel according to the invention is no longer fully based on fossil carbon, since polyamide-410 may be at least partly based on renewable resources. This is especially an advantage, even if the polymer composition of the bezel only contains a fraction of polyamide-410 and also a further polymer. A bezel is a relatively heavy part of a vehicle and therefore these products contribute strongly to the production of green house gases. Employing PA410 in bezels which is at least partly based on monomers originating from natural resources already provides an important decrease in the production of green house gases for bezels and vehicles in general. Moreover, the bezel according to the invention allows for recycling as it has a high thermal stability, and shows very high outgassing limit compared to other bio-based materials.

The minimum thickness required for a bezel is usually determined by the choice of material. Good flowing material allows for thinner parts, which is beneficial for weight reduction. State of the art bezels made from polycarbonate for example usually have a thickness around 2.5 mm when pressures around 150 bar are used to fill the mold. The bezel according to the present invention surprisingly shows that thicknesses of less than 2 mm can be used, while still obtaining sufficient filling of the mold. This allows for substantial weight reduction per bezel.

Examples

Heat deflection temperature under load (0.45 MPa) was measured according to ISO 7501/-2. Water absorption was measured according to ISO 62 at 100% relative humidity. Outgassing limits were measured on injection molded plates of 80x80x2mm. A plate was inserted in a thermally isolated clean oven. Within 10 cm above the plate, a mirror of 70x70mm was placed. The mirror was cooled to 60 °C by air in a controlled manner. The plate was heated for 4 hours at a constant temperature in a controlled manner. Each test was performed on a new specimen and several temperatures were measured. The maximum temperature at which no deposit was visible on the mirror is denoted as the outgassing limit. The experiments were performed in duplo. The results are shown in Table 1.

Table 1 Outgassing limit

Table 1 clearly shows that the material comprising polyamide-410 combines a high HDT, which is a measure for heat resistance, together with high outgassing limit and low moisture absorption.

Claims

Vehicle light bezel produced from a polymer composition comprising at least

30 wt% of polyamide-410 with respect to the total composition.

Vehicle light bezel according to claim 1 in which the polymer composition comprises at least 40 wt% of polyamide-410 with respect to the total composition.

Vehicle light bezel according to claim 1 or 2, in which the polymer composition comprises at most 1 wt% of a mold release agent, with respect to the total composition.

Vehicle light bezel according to any of the claims above, in which the polymer composition comprises a further polymer.

Vehicle light bezel according to claim 4, in which the further polymer is chosen from the group of polyamide-6, polyamide-66 and polyamide-610.

Vehicle light bezel according to any of the claims above, in which the polymer composition comprises a heat stabilizer.

Vehicle light bezel according to any of the claims above, in which the polymer composition further comprises 10 to 30 wt% glass fibers, with respect to the total composition.

Vehicle light bezel according to any of the claims above, in which the polymer composition further comprises a thermal conductive additive in an amount of between 1 to 10 wt% with respect to the total composition.

Vehicle light bezel according to claim 8, in which the thermal conductive additive is expanded graphite platelet.

Vehicle light bezel according to any of the claims above, further comprising at least one surface having a metal layer. Vehicle light bezel according to claim 9, in which the metal layer is selected from the group of aluminum, chrome, and stainless steel.