Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-07-13
2001-11-20
Zirker, Daniel (Department: 1771)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C428S3550EN, C428S353000, C428S354000, C428S343000, C428S515000, C428S517000
Reexamination Certificate
active
06319353
ABSTRACT:
The invention relates to a self-adhesive protective film for protecting the fresh paint finish of vehicles such as cars and for protecting freshly painted vehicle components against soiling and damage during assembly, transportation and storage, and to its use on vehicles, especially on cars.
The preservation and protection of motor vehicles in the course of transportation from manufacturer to dealer has long been common practice.
It is known that, in order to preserve cars, paraffin waxes are applied in a thickness of from 5 to 20 &mgr;m. However, it has been found that, especially on horizontal areas of the vehicles, a thin and usually non-uniform layer of this nature does not afford adequate protection against external influences such as, for example, the corrosive action of bird droppings.
A considerable disadvantage of sealing with paraffin wax is the need to remove the preservative using a steam jet, surfactants or solvents. Environmentally sound recovery and disposal of the residues are the cause of great complexity in terms of apparatus, and very high costs.
Self-adhesive surface protective films for motor vehicles have also been known for some time. In most cases these are permanently adhesive films for protection and decoration, for example a stone-chip protective film. These self-adhesive films remain permanently on the vehicle following their application.
Reversibly adhering self-adhesive films for protecting the car during transportation have so far been used only in a few special cases and without great success. The object of the invention was to remedy this situation and, in particular, to provide a self-adhesive protective film which does not have the disadvantages of the prior art, or at least not to the same extent. This object is achieved by a self-adhesive protective film as characterized in more detail in the patent claims.
The adhesive film of the invention is a protective film for use on painted vehicles, especially cars, having an adhesive comprising a polymer of at least two different &agr;-olefin monomers with a number of in each case from 2 to 12 carbon atoms, and at least one further comonomer, where no &agr;-olefin should have a proportion of 75 mol-% or more, and having a bond strength of from 0.2 to 2.8 N/cm, preferably from 0.3 to 1.5 N/cm on steel (AFERA Method 4001 corresponding to DIN EN 1939). The number of carbon atoms of the &agr;-olefins is between 2 and 12. Examples are linear alkenes, such as ethylene, propene, 1-butene, 1-hexene and 1-octene, and isoalkenes, such as 4-methyl-1-pentene; the proportion of the further comonomers (third and any other comonomers) should be below 30 mol-% if they are non-olefinic comonomers. These latter may be polar, such as vinyl acetate, esters of acrylic or methacrylic acid, vinyl chloride, vinyl ethers or acrylonitrile, or apolar, such as isobutene, styrene or an &agr;-olefin, for example.
Too high a proportion of polar non-olefinic monomers, however, increases the sticking force to painted metal vehicle panels following storage under alternating climatic conditions. It is therefore advantageous to keep the proportion of polar comonomers below 20 mol-% and, in particular, to omit them entirely; in this case, the copolymer comprises at least three apolar monomers.
The proportion of each of the &agr;-olefinic monomers should be below 75 mol-%; more favourable is a proportion of not more than 65 mol-%. The most suitable are terpolymers comprising three &agr;-olefins, whose proportion of &agr;-olefinic monomers is in each case between 5 and 60 mol-%. Limiting the proportion of individual monomers avoids increased sticking forces following storage under alternating climatic conditions, poor tack on application, and deformation of the paintwork. Deformation comprises visually perceptible, irreversible changes to the painted surface, which result when the fresh, not yet fully cured paint has been covered with an inappropriate protective film.
In order to optimize its properties, especially its adhesive behaviour on specific paints, the self-adhesive composition employed can be blended with one or more additives, such as resins, plasticizers, for example diesters or polyesters of phthalic acid, trimellitic acid or adipic acid, liquid oligomers of 1-butene and/or isobutene, mineral oils, fillers, pigments, UV absorbers, light stabilizers or anti-ageing agents, or elastomers. Examples of such elastomers are polyisobutylene, butyl rubber, hydrogenated block copolymers of styrene and dienes, or acrylate copolymers. Suitable resins are rosin esters (especially hydrogenated types), hydrocarbon resins, terpene resins or liquid tackifier resins. For some paint systems it is advantageous to add constituents of the paints to the adhesive in order to reduce the migration of paint constituents (e.g. fatty acid esters) from the paint into the adhesive composition. Paint constituents of this kind are described in more detail in EP 0 763 584 and U.S. Pat. No. 5,612,135.
It is advantageous, moreover, for recycling and energy recovery if the adhesive, in particular the entire protective film, is free from halogen.
The backing for the adhesive comprises thermo-plastic films, preferably polyolefin films. These may consist, for example, of polyethylene, polypropylene and mixtures or copolymers thereof (e.g. random copolymers). Appropriate thicknesses for the backing films are from 20 to 80 &mgr;m (including, if appropriate, the adhesion promoter layer). The softness of the backing film is relevant to the flexibility of the protective film during application; the force at 10% extension should not exceed 25 N/115 mm, preferably 16 N/15 mm, either in the lengthwise or transverse direction. On account of their stability to shrinkage under hot conditions and their good flexibility, propylene copolymers are particularly suitable. For improving the adhesion between film and adhesive it is advantageous, although not absolutely necessary, to use an adhesion promoter layer; in that case the backing film consists of the base layer and the adhesion promoter layer. The latter consists preferably of polymers comprising predominantly olefinic monomers and/or components of base layer and/or adhesive. With particular preference the adhesion promoter comprises at least one polymer of which at least 50 mol-% consists of one or more &agr;-olefins. Examples of such polymers are ionomers based on ethylene-(meth)acrylic acid copolymer, or maleic anhydride-modified polyolefins.
In order to provide the backing film with weathering stability, it is sensible to add light stabilizers—in the case of polyolefins, this is generally vital. In the context of application to the protective film, their function is primarily to avoid embrittlement of the backing film. In the case of a multilayer backing film the protection relates in particular to the base layer. Light stabilizers of this kind are described in Gaechter and Müller, Taschenbuch der Kunststoff-Additive [Pocketbook of plastics additives], Munich 1979, in Kirk-Othmer (3.) 23, 615-627, in Encycl. Polym. Sci. Technol. 14, 125-148 and in Ullmann (4.) 8, 21; 15, 529, 676. HALS light stabilizers in particular, such as CAS Nos. 106990-43-6, 65447-77-0, 70624-18-9 or 52829-07-9, for example, are suitable for the protective film of the invention. The amount of light stabilizer should be at least 0.15, preferably at least 0.30, % by weight, based on the backing film. The use of antioxidants for the film (e.g. Irganox 1010, Ciba, or trisnonylphenyl phosphite) is advantageous but not absolutely necessary.
The light stabilizers mentioned for the film can also be employed for the adhesive composition. Such an addition raises the ageing stability of the adhesive composition, especially under UV exposure of more than 100 kLy (kilolangleys), but is generally dispensable for applications entailing up to 6 months of outdoor weathering. In the case of the polyisobutylene homopolymer adhesives or butyl rubber adhesives which are not in accordance with the invention, such an addition is vital to prevent residues of
Beiersdorf AG
Norris & McLaughlin & Marcus
Zirker Daniel
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