Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2002-02-15
2004-11-02
Zirker, Daniel (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S343000, C428S353000, C428S515000, C428S516000, C428S517000
Reexamination Certificate
active
06811869
ABSTRACT:
The invention relates to a self-adhesive sheet for temporarily protecting fresh paint surfaces of vehicles such as automobiles and freshly painted vehicle parts against soiling and damage during assembly, transit, and storage, and to its use on vehicles, especially on automobiles.
The preservation and protection of motor vehicles in transit from manufacturer to dealer has long been common practice. A known method of preserving automobiles is to apply paraffin waxes in a thickness of from 5 to 20 &mgr;m. It has been found, however, that, especially on horizontal areas of the vehicles, such a thin and usually nonuniform coat does not afford adequate protection against external influences, such as the corrosive effect of bird droppings, for example. A considerable disadvantage of sealing with paraffin wax is, furthermore, the need to remove the preservative using a steam jet, surfactants or solvents. Environmentally sound recovery and disposal of the residues entail considerable deployment of apparatus and also very high costs.
A current development in the field of automobile transit protection is the use of covers which go over the entire vehicle and are shrunk on to fit by exposure to heat. Cover solutions of this kind are very costly and involve a great deal of effort in applying the cover, effecting shrinkage, and especially for entry to the masked vehicle. For that particular purpose, zipper openings are provided, whose necessary opening and reclosing is time-consuming. Visibility when maneuvering the vehicle is severely impaired, moreover, and the enclosed dirt and unavoidable scuffing result in instances of dulling on the finish in certain areas. The widespread establishment of this solution has not so far been possible.
Self-adhesive surface protection sheets for motor vehicles have likewise been known for some time. In the majority of cases, they comprise permanently adhesive and decorative sheets, such as an anti-stonechip sheet, for example. These self-adhesive sheets remain permanently on the vehicle following their application.
In recent years, increased use has been made of temporary self-adhesive surface protection sheets. These reversibly adhesive protective sheets are specially intended for mechanical and chemical protection of freshly painted motor vehicles and vehicle parts during transit and storage, have a much better protective effect than the waxes, and have the advantage over the covers of being more favorably priced and much quicker to apply. One essential requirement made of a temporary surface protection sheet is its weathering stability and light stability over a period of several months. Accordingly, even after six months of intense sunlight exposure and fluctuating climatic conditions, a sheet of this kind must be able to be removed without residue.
The quality of absence of residues must likewise be ensured for the removal of the protective sheet at elevated temperatures of at least 50° C., since it can be assumed that, especially in the summer months and in southerly regions, the surfaces of the vehicle will become hot, and it cannot be assumed that the person removing the surface protection sheets will wait for the vehicles to cool down.
The final bond strength on the finish, referred to by the skilled worker as peel increase, must not be too high, since otherwise a large amount of force or even tearing of the sheet will accompany the unmasking of the paint surfaces. Moreover, the surface protection sheet is required to possess a sufficiently high initial tack, in order to ensure sufficiently reliable bonding even in difficult surface geometries.
Reversibly adhering surface protection sheets available to date have had considerable deficiencies in respect of bonding reliability, peel increase or aging stability.
Essential qualities of a surface protection sheet are:
effective protection for the paint against chemical and mechanical influences.
Weathering stability over the entire duration of the transit chain from plant to dealer, which depending on distance may amount to several months. Even after long and intense sunlight exposure, therefore, such a sheet must be able to be removed in one piece and must not leave residues of adhesive on the paint.
Adequate initial tack, in order to prevent premature self-induced detachment in difficult bonding geometries.
Balanced final bond strength, in order that the sheet, firstly, adheres securely (even in a strong slipstream or heavy rain) but on the other hand can be removed without great force or even tearing. Ideally, the desired bond strength should be present right from the start. In practice, however, the adhesion is weaker to start with and then increases over time and particularly under the influence of temperature. This is referred to in the art as “peel increase”.
Paint compatibility, which means that the paint surface should not exhibit any adverse effects whatsoever, in the form of deposits or deformation, after the adhesive tape has been removed. Deformations are impressions in the paint which show up, firstly, as contours of the film edge, included air bubbles and folds, and secondly as areas of dulling over the entire area where the sheet was stuck.
In accordance with the prior art, the film materials used for temporary surface protection generally comprise polyolefins or mixtures thereof, blended customarily with light stabilizers and titanium dioxide (DE 199 23 780 A1, DE 196 35 704 A1).
Self-adhesive compositions used include polar and nonpolar polymers. In principle, all known polar self-adhesive compositions, such as those based, for example, on EVA and polyacrylate, exhibit considerable paint incompatibility in testing, i.e., following application to painted metal panels and subsequent storage under alternating climatic conditions. Incompatibility with the paint results in high bond strength, referred to as peel increase by the skilled worker, and also in paint deformation following weather storage.
The adhesive sheet described in DE 195 32 220 A1, with polar polyethylene-vinyl acetate (EVAc) adhesive compositions, is superior in adhesion properties to the systems described above.
This system achieves good bond values after just a short time, and ensures a high level of bonding reliability toward unwanted self-induced detachment during transit. On the other hand, following application, owing to the use of the polar polyethylene-vinyl acetate adhesive, severe peel increase of the surface protection sheet, and also considerable deformations of the paint surface, are observed.
Deformations are visually perceptible, irreversible changes to the paint surface which come about if the fresh paint, not yet fully cured, is covered with an unsuitable protective film. The skilled worker will therefore avoid polar adhesive systems for temporary surface protection.
The majority of known nonpolar, noncrosslinked self-adhesive compositions, on the other hand, exhibit low cohesion, which leads to residues of adhesive when the protective film is removed following use.
WO 96/37568 A1 describes the use of polyhexene and/or polyoctene for a nonpolar pressure sensitive adhesive. Although the peel increase of the polymers described in the examples is low from paint surfaces, the low molecular weight of commercial polymers of this kind nevertheless means that these polymers, too, lead to considerable residues on the paint surface following use. Even by adding what are referred to as “cold flow restricting agents”, it is impossible to avoid these residues. Where, however, these adhesive compositions are crosslinked chemically or by radiation before use for the purpose of increasing the cohesion, unwanted deformation of the paint surface is observed.
An exception is formed only by self-adhesive compositions based on natural rubber, which can be removed residuelessly with little paint deformation. These compositions, however, are not stable to aging under UV radiation. A consequence of this are severe residues, which are greasy or have undergone paintlike hardening, on the painted metal following extreme climatic
Böhm Nicolai
Lühmann Bernd
Müssig Bernhard
Neubert Ingo
Schütz Ingolf
Norris & McLaughlin & Marcus
tesa AG
Zirker Daniel
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