Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2002-02-15
2004-10-26
Watkins, III, William P. (Department: 1772)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C428S3550BL, C428S344000, C428S343000, C428S354000, C428S219000, C428S213000, C428S137000, C428S138000, C428S304400, C442S315000, C442S304000, C442S151000, C442S149000
Reexamination Certificate
active
06808587
ABSTRACT:
The invention relates to a self-adhesive article for the in-transit protection of painted automobile parts such as, in particular, bumpers, which are subject to high mechanical stress.
The painting of plastic automobile parts such as bumpers or mirror housings the same color as the car is nowadays standard in the contemporary visual design of modern motor vehicles. Consequently, these parts are very sensitive to scratching. The bumpers and mirrors in particular are exposed auto parts which can very easily be grazed. The response of automakers to the increased level of quality awareness among customers must therefore be to provide these parts with effective protection as they travel through the operations of painting via assembly in the car plant through to delivery to the customer, in order to prevent complaints from the outset.
In recent years, therefore, attempts have been made to transfer the method successfully employed for freshly painted sheet metal parts, namely that of masking the parts with special, paint-compatible transit protection films, as described for example in DE 195 32 220 A1 or in EP 0 827 526 A1, to bumpers.
This was found difficult with bumpers on account of the fact that in the course of maneuvering the automobiles, said films were no match for the frequent severe stresses occurring as a result of scrapes along the bumper and minor collisions, and did not give an adequate protective effect. Moreover, on the highly curved bonding geometries of the bumpers and mirror housings, the relatively rigid films can be adhered only with a great deal of creasing, leading in many cases, and particularly when promoted by any gradual outgassing of solvents from the bumper plastic, to irreversible impressions of the creasing on the sensitive paint.
An improved protective effect against impact loads is possessed, however, by foam cushions bonded adhesively to the bumpers. On scraping collision, against concrete pillars, for example, the mechanical resistance offered by foams is low, however.
The main problem, though, is with secure adhesive bonding. Experience has shown that in many cases simply in rain the cushions fall off, and so firstly no longer provide any protective effect and secondly contaminate the environment. More securely bonding adhesives generally prove to be incompatible with the paint, with the inevitable consequence of deformations.
DE 197 16 712 A1 discloses for bumper protection a masking material based on woven fabric which is provided with a self-adhesive polyisobutylene composition. Although such a tape has a good mechanical protective effect, an open weave offers no protection against harmful chemical effects as exerted by service fluids such as gasoline, battery acid or brake fluid. Additionally, such a fabric may become full of water and, over a period of time, can cause incipient swelling of the sensitive paint. The most serious effect, however, is that of the fabric structure, which is transferred to the thin film of adhesive and, in the case of particularly fresh and sensitive paints, can result in irreversible impressions of the fabric pattern.
EP 0 959 119 A1 describes a self-adhesive protective article which is composed of a film
onwoven laminate. An article of this kind does offer a good protective effect against frictional loads and an effective seal against liquid contaminants. Nonwovens as specified therein, however, are generally not very stretchy, and so a laminate stressed in this way can be applied only with severe creasing and, as a result, is highly incompatible with the paint.
It is an object of the invention to provide a transit protection article for bumpers and other painted plastic mounted parts for automobiles which does not exhibit the disadvantages of the prior art, or not to the same extent. In particular, the article ought first to be highly conforming to curved surfaces and secondly to be impervious to water and automotive service media (such as gasoline, diesel, brake fluid) while possessing a high degree of abrasion resistance, and therefore combining outstanding mechanical protection with excellent paint compatibility on the particularly sensitive paint on such parts.
This object is achieved by means of a self-adhesive article as specified in the main claim. The subclaims relate to advantageous developments of the protective article and to particular application options.
The invention accordingly provides a paint-compatible self-adhesive article for mechanical protection of painted plastic mounted parts of automobiles, comprising a backing material in film form whose outer side is laminated with a layer of knitted fabric and whose inner side is pressure-sensitively adhesive as a result of application of a self-adhesive composition.
In one preferred embodiment, the protective article is composed of a UV-stabilized unoriented polyolefin film backing material, said film having a Young's modulus of less than 300 N/mm
2
, preferably less than 150 N/mm
2
, and a thickness of from 10 to 150 &mgr;m, preferably from 40 to 100 &mgr;m.
The top of the film of the invention is laminated with a knitted fabric which advantageously has a basis weight of from 10 to 200 g/m
2
, preferably from 20 to 80 g/m
2
.
With further preference, the underside of the film is coated with from 10 to 80 g/m
2
, preferably from 15 to 40 g/m
2
, of a self-adhesive composition.
Suitable materials for the backing film are, in principle, all polymeric substances from which it is possible to produce films having a low Young's modulus, such as polyolefins, polyurethanes or plasticized PVC.
It is possible with preference to use low density polyolefins with which the inventive Young's modulus range can be obtained. Suitable for this purpose are a wide variety of copolymers of ethylene with &agr;-olefins such as, typically, propylene, 1-butene, 1-hexene or 1-octene (predominantly LLDPE, VLDPE, ULDPE), but also ethylene-styrene copolymers and copolymers of propylene with ethylene and &agr;-olefins, thus including EPDM and EPM rubbers. Likewise highly suitable are saturated synthetic rubbers such as polyethylene-vinyl acetate (EVM), hydrogenated nitrile rubbers, and synthetic styrenic rubbers such as SEBS and SEPS, since unlike the unsaturated variants, including natural rubber, these have a good weathering stability. It is also possible for halogenated polymers such as chlorinated polyethylene or chloroprene to find application.
Preference is given to using mixtures of different suitable polyolefins in order to allow optimum setting of the mechanical and thermal properties and also qualities such as processability, anchoring of the adhesive, etc.
In order to increase further the softness of a suitable material and the impact damping effects, the film may also be foamed.
In order to give the backing film the requisite weathering stability, the addition of light stabilizers is preferred. Their function lies primarily in preventing the embrittlement of the backing film.
Light stabilizers of this kind are described in Gaechter und Müller, Taschenbuch der Kunststoff-Additive, Munich 1979, in Kirk-Othmer (3rd) 23, 615-627, in Encycl. Polym. Sci. Technol. 14, 125-148, and in Ullmann (4th) 8, 21; 15, 529, 676. HALS stabilizers in particular are suitable for the protective film of the invention.
The amount of light stabilizer should be at least 0.15% by weight, preferably at least 0.30% by weight, based on the backing film.
An additional improvement in the light stability of the backing film is also possible through the addition of titanium dioxide. Advantageous in respect of the mechanical properties and the homogeneity of the whiteness are additions of from 5 to 15% by weight of titanium dioxide. As a result of the interaction of light stabilizers and pigments, the UV transmittance of the protective film in the region from 290 to 360 nm is preferably below about 1%, more preferably below about 0.1%.
For optical reasons, the film may also be color pigmented.
In the case of painted plastic parts having a high residual paint solvent content, as a resul
Böhm Nicolai
Klemp Jobst-Waldemar
Schütz Ingolf
Wappler Ulrike
Norris McLaughlin & Marcus PA
tesa AG
Watkins III William P.
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