Patent Application
20070270553
Described below are the adhesive tapes with which masking was performed.
An adhesive composed of 50 parts of Kraton FG 1901 (SEBS, no diblock, with 30 per cent by weight (referred to below only as “%”) styrene content and, in grafted form, about 2% of maleic anhydride, product of the company Kraton), 50 parts of Kraton FG 1924 (SEBS with about 40% diblock, 13% block polystyrene and about 1% maleic anhydride, from Kraton), 90 parts of Regalite R 1100 (hydrogenated hydrocarbon resin with a softening point of about 110° C., from Eastman) and 20 parts of Regalite R 1010 (hydrogenated liquid hydrocarbon resin from Eastman) and 2 parts of aluminium acetylacetonate was dissolved in a mixture of toluene and isopropanol in a ratio of 9 to 1 and the solution was coated directly onto a 100 μm PET film, using a coating bar, in such a way that drying resulted in an adhesive coatweight of 25 g/m2. Prior to its use, the specimen was lined with a siliconized release paper.
As Example 1, but using an adhesive with a composition of 50 parts Kraton FG 1901, 50 parts Kraton FG 1924, 120 parts Pentalyn H (hydrogenated rosin ester from Eastman), 15 parts Ondina G 41 (white oil with low naphthenic fraction, from Shell) and 2 parts titanyl acetylacetonate.
As Example 1, but using an adhesive with a composition of 50 parts Kraton FG 1901, 50 parts Kraton FG 1924, 70 parts Dercolyte A 115 (α-pinene resin with a softening point of about 115° C., from DRT), 40 parts Wingtack 10 (liquid hydrocarbon resin from Goodyear) and 2 parts acetylacetonate.
As Example 1, but using an adhesive composed of 50 parts Kraton G 1650 (SEBS, no diblock, with 30% styrene content, no maleic anhydride, product of the company Kraton), 50 parts Kraton G 1657 (SEBS with about 40% diblock, 13% block polystyrene, no maleic anhydride, from Kraton), 90 parts Regalite R 1100 and 20 parts Regalite R 1010.
As Example 1, but using an adhesive with a composition of 50 parts Kraton G 1650, 50 parts Kraton G 1657, 120 parts Pentalyn H and 15 parts Ondina G 41.
As Example 1, but carrying out priming with a solution of 2 parts of natural rubber in toluene, which had been mixed with 1 part of diphenylmethane diisocyanate, with a coatweight of 0.3 g/m2. In a downstream operation this primer was coated with a natural rubber self-adhesive composition. The self-adhesive composition consisted of 100 parts natural rubber, 10 parts zinc oxide, 20 parts Pentalyn H, 10 parts Vulkaresen PA 510 (reactive alkylphenol resin from Schenectady), 50 parts Regalite R 1100 and 5 parts Ondina G 41.
As Example 1, but carrying out priming with a solution of polyvinylidene chloride in toluene. In a downstream operation an acrylic ester copolymer as self-adhesive composition was coated onto this primer. The self-adhesive composition consisted of 40 parts butyl acrylate, 40 parts 2-ethylhexyl acrylate, 12 parts vinyl acetate, 5 parts methyl acrylate and 3 parts acrylic acid.
Decisive test criteria considered important, and thus employed, for the present addressed problem were as follows:
Adhesive Residues
Strips 15 mm wide were cut as test strips from the coated specimens. These test strips were adhered, as far as possible without creases, and with a radius of 200 mm, to a metal panel coated with cathodic electrocoat (Cathoguard 500 from BASF) and baked according to manufacturer instructions, this adhering was possible only with slight stretching of the backing.
Subsequently the panel thus bonded was placed in a heating cabinet which had been preheated to 170° C., and left there for an hour. After the panel had cooled, the external radius of the test strip was assessed for adhesive residues.
The evaluation criteria were as follows:
Strips 15 mm wide were cut as test strips from the coated specimens. These test strips were adhered in a straight line without creases to a metal panel coated with cathodic electrocoat (Cathoguard 500) and baked according to manufacturer instructions.
The panel thus bonded was subsequently placed in a heating cabinet, which had been preheated to 170° C., and left there for an hour and forty minutes. After the panel had cooled, the test strip was removed, and a reactive one-component PU window adhesive (Sikaflex DM2 from Sika), which for the purpose of improved processing had been preheated to 50° C., was applied, in the form of a triangular bead with a width of about 1 cm and a height of 1 cm, to the site of former bonding. The triangular profile, whose base lay on the cathodic electrocoat, was pressed flat, using a polyethylene plate, so that the bead subsequently had a height of about 0.5 cm and a width of about 1.2 cm.
The metal panel was stored for ten days at 23° C.±1° C. and at a relative humidity of 50%±1% for the adhesive to cure.
After curing had taken place, the bead of adhesive was raised at one prepared end and peeled from the metal panel at an angle of approximately 90°.
If bonding has been effective, exclusively cohesion failure occurs within the adhesive bead—that is, no adhesion failure to the cathodic electrocoat. Continued peeling of the bead is then achieved by making incisions with a knife into the cohesively fracturing bead residue down to the electrocoat.
In the case of adhesion failure, the bead of adhesive can be peeled from the electrocoat without substantial residues. If the proportion of adhesion fraction is more than 10%, the test is classed as failed.
The evaluation criteria used were as follows:
The results of the masking solutions are summarized in the following table.
It is apparent that the masking solutions of the invention meet both important criteria simultaneously, whereas the prior-art counterexamples each meet only one, and are therefore unsuitable.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 023 936.9 | May 2006 | DE | national |
