Adhesive masking tape

p0001The invention relates to a self-adhesive protective film preferably used for protecting the finish of cars against undesired contamination and damage during installation and transportation.

p0002The preservation and protection of motor vehicles in transit from manufacturer to dealer has been practiced for some time. It is known that to preserve cars, paraffin waxes are applied in the thickness of 5 to 20 microns. It has been found that, especially on horizontal areas of the vehicles, a thin and usually nonuniform layer against external influences, such as the corrosive effect of bird droppings, does not offer enough protection. A considerable disadvantage of sealing with paraffin wax is the need to remove the preservative using a steam jet, surfactants or solvents. The environmentally friendly Rückgewinnug and disposal of the residues entail considerable apparatus and also very high costs.

p0003Self-protective films for motor vehicles have also been known for some time. In most cases, these are permanently adhesive protective and decorative films, such as a stone chip protection film. These self-adhesive films remain permanently on the vehicle following their application.

p0004Reversibly self adhesive films for protecting the car during transportation have so far found only in a few cases without much success using.

p0005Thus, in 1977 a self-adhesive film from Beiersdorf AG, which uses a PVC film having a crosslinked self-adhesive composition of polyacrylate and isocyanate, to protect the paint on the front of the vehicle against stone chipping and fouling by colliding insects during Einfahnvorgangs the automobile. However, the application was found to be problematic because the polyacrylate composition had to be very highly crosslinked to not to interact with the vehicle paint. This led to application problems due to insufficient adhesive strength of the film.

p0006Also known are polyacrylate compositions which are crosslinked and after 16 hours at 80 ° C a good compatibility with paint surfaces show, but they are so soft that they left when the film is ground residues in the primer. Once these materials are chemically or radiation-crosslinked, they can be removed without residue but then give rise to permanent deformations on the paint surface.

p0007From Japanese patent application JP 02199184 a radiation-crosslinkable pressure is known, in which for protective use on coats of paint, a low glass transition temperature must be set to prevent permanent deformations of the paint layer. There are problems owing to inadequate bond strength of the self-adhesive film on motor vehicles during transportation and outdoor storage.

p0008European Patent Application EP 0519278 discloses the protection of automobiles, a film consisting of a carrier with an adhesive rubber-based adhesive, the dynamic elastic modulus of 2 x 10⁵ to 7 x 10⁶ dyne / cm², Corresponding in SI units to a value of 2 x 10⁴ to 70 x 10⁴ Pa, at 60 ° C, is coated. The adhesive can moreover, be blended with a silicone oil or a low molecular weight acrylic polymer. Performance tests with a self-adhesive foil exhibit a relatively good compatibility with paint surfaces. However, the adhesive strength after alternating climatic conditions on the automotive industry common paints is so low that the required in practice is not always attained. Particularly in wet conditions on the film, the adhesive strength is often reduced so that the film during transportation of the vehicle it is protecting becomes detached so that no protection exists. Moreover, said elastic modulus range is not a sufficient criterion for a serviceable pressure-sensitive adhesive.

p0009The object of the invention was to remedy this situation, in particular to provide a self-adhesive protective film, which at least does not have or not to the extent the disadvantages of the prior art.

p0010This object is achieved by a self-adhesive protective film as characterized in more detail in the patent claims.

p0011The protective film of the invention is a self-adhesive protective film which has a film as support, with a self-adhesive composition of polyethylene - depending on the type and compounding - with a loss angle tan δ from 0.6 to 1.0, measured at a temperature of 60 ° C and a frequency of 10^-2 Hz, and is from 0.4 to 0.7, measured at a temperature of 60 ° C and a frequency of 10 Hz, coated. The protective film has a thickness of 50 to 200 microns, preferably 65 to 80 microns.

p0012The film preferably consists of polypropylene, polyethylene or a mixture of the two components. The film has a thickness of 10 to 100 microns, preferably 50 to 60 .mu.m. Furthermore, the film in a preferred embodiment is free of halogen. To improve the unrolling properties from a large roll, the film can be provided on its reverse side with a release coating.

p0013To optimize the properties of the self-adhesive composition may be blended with one or more additives such as rosin esters, hydrocarbon resins, paraffin oils, anti-aging agents or elastomers and, furthermore, be halogen-free.

p0014To improve the anchoring of the adhesive to the film, the use of a primer is possible.

p0015For self-adhesive protective films use different adhesive compositions is possible. Most, however, have serious disadvantages which severely restrict their use.

p0016Ultimate Evolution size for a self-adhesive system that meets the conditions under which use of such protectors conditions, the rheological behavior of the compounded self-adhesive system. So the glass transition point, characterized by a tan δ maximum, are at temperatures from -5 ° to -25 ° C. and the maximum nearly frequency constant values ​​should take up a maximum of 1.0. This ensures an excellent repositioning due to a very low initial. At temperatures above 10 to 30 ° C, preferably 20 ° C, an increase in the tan δ is a function of the temperature required. It should at 60 ° C the tan δ at 10^-2 Hz minimal amount 0.6 to decay at 10 Hz on minimal 0.4. This ensures the marked rise in bond strength even within the first 30 minutes after bonding.

p0017Known non-polar self-adhesive compositions, comprising polyacrylate and polyurethane show in the test, in which they are applied for 16 hours at 80 ° C on painted sheets, better paint compatibility than polar compositions. However, on the other hand they are too soft and residues of composition when the film is removed. If the masses are radiation- or chemically crosslinked, they lead to unwanted paint-film deformation.

p0018Self-adhesive compositions based on natural rubber resin can be removed without residue and only minimally resist deformation. These compositions are not stable to aging under the influence of UV radiation.

p0019A self-adhesive polyisobutylene with the loss modulus G '' G '' = 1.29 x 10⁶ dyne / cm², Corresponding in SI units to a value of G '' = 12.9 x 10⁴ Pa, and a loss angle tan δ of 0.2 (both values ​​measured at a temperature of 60 ° C and a frequency of 1 Hz) shows only very slight paint deformations. However, the peel strength of the paint surface is very low by alternating climatic conditions and thus not properly set.

p0020Those skilled Unforeseeably a smeared on a polypropylene / polyethylene film self-adhesive composition of polyethylene vinyl acetate with a loss angle tan δ from 0.6 to 1.0, measured at a temperature of 60 ° C and a frequency of 10^-2 Hz, and from 0.4 to 0.7, measured at a temperature of 60 ° C and a frequency of 10 Hz, the desired self-creation. In particular, on a 50 micron thick polypropylene / polyethylene film, in which the two polymers in a ratio of 9: 1 to 1: 9, preferably 4: 6 are used and which comprises a pre-coat of polyethylene vinyl acetate, the self-adhesive composition according to the invention shows on with polyurethane paint lacquered and at 130 ° C the dried sheets after storage for 16 hours at 80 ° C no deformation lacquer.

p0021The peel force of the protective film of the invention of various adhesion reasons is practical 2 to 5 N / cm. Even exposure of the protective film with UV light, for example, with a 500 W strong UV lamp with a sunlight spectrum over 5 days, resulting in no detectable deterioration in the properties of the protective film. It occurs no embrittlement, and the self-adhesive composition causes neither paint deformations still residues of composition occur to peel off the protective film.

p0022In addition, the protective film of the invention is characterized in that it is be applied in a large width over the hood, roof and trunk of the automobile and to plan and slightly spherically shaped surfaces adapts very well due to their flexibility. In order to protect the most vulnerable to pollution horizontal surfaces is possible. However, even narrow areas such as projection of the door below the windows can be easily covered. Protection of the vertical surfaces on the vehicle is particularly appropriate during its assembly.

p0023The self-adhesive composition has on one side at different common in the automotive industry baking finishes a good adhesion to, even under moisture or humidity influence, so that the protective film even under wind exposure not detach from the vehicle, on the other hand it is reversible due to very low initial adhesive adhesive, so that during application a correction of the position of the protective film on the vehicle is possible. In addition, the self-adhesive composition shows a distinct rise in bond strength even with low initial adhesive power and within the first 30 minutes after bonding.

p0024The protective film is resistant to sunlight, moisture, heat and cold, with weathering stability is given up to six months.

p0025After application of the protective film and by the self-adhesive composition after storage for 16 hours at 80 ° C and under influence of the weather on any deformation of the underlying paint layer. Moreover, the uniform overall thickness of the protective film guarantees in comparison to preservation with wax, flawless protection against soiling and damage of the entire vehicle.

p0026After use, the protective film can be removed in spite of the required good adhesion without leaving any residue and without tearing the backing film. Since the protective film is halogen-free, material recycling or energy recovery is the same problem.

p0027The invention will be explained with reference to examples, without, however, intended to limit it so unnecessary.

Examples

example 1

p0028A self-adhesive composition of polyethylene, which is dissolved in toluene in a proportion of 15%, with a vinyl acetate content of 45 wt .-% and a loss angle tan δ of 0.8, at a temperature of 60 ° C and a frequency of 10^-2 Hz is measured, is in a coating unit with coating bar and drying tunnel on a 50 .mu.m thick, 1450 mm wide, both sides corona-pretreated, is provided with Carbamatlack and with EVA primer white foil with 15 g / m² applied, wherein the film comprises 90% polypropylene and 10% polyethylene. The drying temperature is 60 to 100 ° C with a residence time of 3 minutes. On channel end the coated backing web is cut at the edges and wound into rods of 66 m in length and 1400 mm width.

p0029The self-adhesive film produced can be wrinkle-free handle, applied without problems and removed again after use without defects when used to protect cars.

p0030The material is characterized by the following physical properties: <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Overall thickness of protective film:</entry><entry namest="col2" nameend="col2" align="left">65 microns</entry></row><row><entry namest="col1" nameend="col1" align="left">Peel strength from the PU varnish after storage for 16 hours at 80 ° C, a peel angle of less than 90 ° and a peel rate of 300 mm / min:</entry><entry namest="col2" nameend="col2" align="left">3.8 N / cm</entry></row><row><entry namest="col1" nameend="col1" align="left">Peel force from the reverse side at a peel angle of less than 90 ° and a peel rate of 300 mm / min:</entry><entry namest="col2" nameend="col2" align="left">0.5 N / cm</entry></row></tbody></tgroup></table></tables>

p0031The measurements were carried out using an instrument from Rheometric Scientific under deformation-constant conditions.

example 2

p0032Referring to Example 1, first 90 wt .-% polyethylene-be with a vinyl acetate content of 45 wt .-% and a loss angle tan δ of 0.78 (60 ° C and 10^-2 Hz) and 10 wt .-% rosin mixed with a softening point of 85 ° C, dissolved in toluene in a proportion of 15%, and according to Example 1 to a film consisting of 80% polypropylene and 20% polyethylene, with 12 g / m² coated.

p0033The material is characterized by the following physical properties work: <tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Overall thickness of protective film:</entry><entry namest="col2" nameend="col2" align="left">63 microns</entry></row><row><entry namest="col1" nameend="col1" align="left">Peel strength from the PU varnish after storage for 16 hours at 80 ° C, a peel angle of less than 90 ° and a peel rate of 300 mm / min:</entry><entry namest="col2" nameend="col2" align="left">3.1 N / cm</entry></row><row><entry namest="col1" nameend="col1" align="left">Peel force from the reverse side at a peel angle of less than 90 ° and an offtake velocity of 300 mm / min:</entry><entry namest="col2" nameend="col2" align="left">0.4 N / cm</entry></row></tbody></tgroup></table></tables>

example 3

p0034A self-adhesive composition of polyethylene vinyl acetate with a vinyl acetate content of 45 wt .-% and a loss angle tan δ of 0.6 (60 ° C and 10 Hz) is in an extruder with a slot die in coextrusion at 160 to 170 ° C with a layer of from Example 1 known film extruded in the width of 1700 mm, the self-adhesive composition having 15 g / m² is applied. The film receives a thickness of 52 microns. Then it is cut into rolls of 66 m length and 1500 mm width.

p0035The material is characterized by the following physical properties: <tables id="tabl0003" num="0003"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Overall thickness of protective film:</entry><entry namest="col2" nameend="col2" align="left">67 microns</entry></row><row><entry namest="col1" nameend="col1" align="left">Peel strength from the PU varnish after storage for 16 hours at 80 ° C, a peel angle of less than 90 ° and a peel rate of 300 mm / min:</entry><entry namest="col2" nameend="col2" align="left">3.2 N / cm</entry></row><row><entry namest="col1" nameend="col1" align="left">Peel force from the reverse side at a peel angle of less than 90 ° and a peel rate of 300 mm / min:</entry><entry namest="col2" nameend="col2" align="left">0.5 N / cm </entry></row></tbody></tgroup></table></tables>

example 4

p0036Referring to Example 3 wt .-% polyethylene vinyl acetate first 90 are with a vinyl acetate content of 45 wt .-% and a loss angle tan δ of 0.58 (60 ° C and 10 Hz) and 10 wt .-% rosin ester having a softening point of 85 ° C., and according to example 3 with the known from example 1 coextruded a film, the self-adhesive composition having 19 g / m² is applied. The film receives a thickness of 61 microns.

p0037The material is characterized by the following physical properties: <tables id="tabl0004" num="0004"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Overall thickness of protective film:</entry><entry namest="col2" nameend="col2" align="left">80 microns</entry></row><row><entry namest="col1" nameend="col1" align="left">Peel strength from the PU varnish after storage for 16 hours at 80 ° C, a peel angle of less than 90 ° and a peel rate of 300 mm / min:</entry><entry namest="col2" nameend="col2" align="left">2.8 N / cm</entry></row><row><entry namest="col1" nameend="col1" align="left">Peel force from the reverse side at a peel angle of less than 90 ° and a peel rate of 300 mm / min:</entry><entry namest="col2" nameend="col2" align="left">0.8 N / cm</entry></row></tbody></tgroup></table></tables>