Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
1999-06-30
2001-08-14
Zirker, Daniel (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S3550EN, C428S356000, C428S516000, C428S517000
Reexamination Certificate
active
06274235
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pressure-sensitive adhesive sheet for surface protection and an adhesive composition therefor, and more particularly to a pressure-sensitive adhesive sheet for surface protection for protecting coats which is excellent in strength at low temperature and high-speed removal property, and an adhesive composition therefor which is excellent in low temperature adhesive property to coats and high-speed removal property.
BACKGROUND ART
Conventional methods for protecting surfaces of top coats formed as finish coatings on the surfaces of vehicles include coating thinly with paraffin wax. However, this method involves a problem that it does not exhibit sufficient protecting function and it costs much time and labor when the paraffin wax coating is to be removed, in addition that the effluent, which occurs at the time of the removal, causes environmental pollution, etc.
Meanwhile, there is a method for applying directly a pressure-sensitive adhesive sheet for surface protection to surfaces of coats, such as shown in Japanese Provisional Patent Publication Nos. 73352/1994 and 3420/1997, and however, these adhesive sheets are poor in adhesive property, particularly at low temperature, to coats having hardly adhesive property which is excellent in water repellency and stain resistance, and, since the tear strength and the tensile elongation are small, it has problems that the surface protective adhesive sheets have entirely peeled off at the time of wheels transport in winter season or it has partially peeled because of partial tear or cut.
On the other hand, as a pressure-sensitive adhesive sheet for protecting coats which has good low-temperature properties, proposed is a pressure-sensitive adhesive sheet for surface protection having an adhesive layer in which the main component is a hydrogenated random copolymer of styrene and diene series hydrocarbon (Japanese Provisional Patent Publication No. 149631/1994). Further, proposed is a pressure-sensitive adhesive sheet for protecting coats in which an adhesive containing as main component at least one of a polyisobutylene, a butyl rubber and a polybutene has been applied on a substrate (Japanese Provisional Patent Publication No. 143829/1996). However, although such sheets never peel at the time of wheels transport, there are problems that they are easily cut or torn because of high removal strength at the time of high-speed removal. Alternatively, since it must be removed at low-speed, there are problems that it makes the removal workability worse and it has left stains on surfaces of coats through the influence of tackifier.
The purpose of the present invention is to provide a pressure-sensitive adhesive sheet for surface protection which exhibits good applicability to adhesive-retarded coats having high water repellency and stain resistance, which never peels due to partial tear or cut even at low temperature, which is excellent in protection properties within a broad temperature range, and also which can be easily removed at high-speed without tear or cut at the time of removing.
Further, the purpose of the invention is to provide an adhesive for a pressure-sensitive adhesive sheet for surface protection at low temperature, which is excellent in adhesive property, particularly at low temperature, to adhesive-retarded coats having high water repellency and stain resistance, and which can easily be removed at high-speed without contaminating surfaces of adherends or leaving stains thereon at the time of the removal.
DISCLOSURE OF THE INVENTION
The present invention is to provide to a pressure-sensitive adhesive sheet for surface protection, which has a substrate containing an ethylene/propylene copolymer and an ethylene/1-butene copolymer at 60:40 to 90:10 (in terms of weight ratio).
Further, the present invention is to provide a pressure-sensitive adhesive sheet for surface protection, wherein the tensile strength at −20° C., the tensile elongation at −20° C. and the Elmendorf tear strength at 5° C. in the crosswise and the lengthwise directions are 1.5 N/mm or more, 100% or more and 0.5 N or more, respectively, and the elastic modulus at 23° C. in the lengthwise direction is 300 to 500 N/mm
2
.
Furthermore, the present invention is to provide the pressure-sensitive adhesive sheet for surface protection, wherein the light transmittance of the substrate at 200 to 400 nm is 0.5% or less.
Further, the present invention is to provide an adhesive composition for pressure-sensitive adhesive sheets for surface protection, which contains 5 to 30 parts by weight of a rosin resin tackifier based on 100 parts by weight of a blend comprising 50 to 100% by weight of a polyisobutylene and/or a butyl rubber and 50 to 0% by weight of a polybutene.
BEST MODE FOR CARRYING OUT THE INVENTION
The substrate layer of the pressure-sensitive adhesive sheet for surface protection of the present invention contains an ethylene/propylene copolymer and an ethylene/1-butene copolymer at a weight ratio of 60:40 to 90:10, preferably 75:25 to 85:15. When the amount of the ethylene/1-butene copolymer is more than 40% by weight, the application workability and the removal workability make worse. On the other hand, when the amount of the ethylene/1-butene copolymer is less than 10% by weight, it tends to be easily torn or cut since the tear strength and the elongation at low temperature falls down, and the protection function becomes worse because of partial peel at the time of low temperature transport, and the removal workability becomes worse. In addition, the fittability on uneven portions and curved portions of adherends also becomes worse.
The ethylene/propylene copolymer to be used in the present invention is a block copolymer or a random copolymer and is in general called “block polypropylene” or “random polypropylene” which contains ethylene from the polymerization step. Such ethylene/propylene copolymer may preferably be such a polymer that a melt flow rate (measured according to ASTM D1238, hereinafter abbreviated to “MER”) is 0.5 to 5 g/10 min. at 230° C. under a load of 2.16 kg. Commercially available products of the ethylene/propylene copolymer employable for the present invention include, for example, NOBLEN BJS-M (TM, available from Grand Polymer Co., Ltd.), GRANDPOLYPRO J702L (TM, available from Grand Polymer Co., Ltd.).
The ethylene/1-butene copolymer to be used for the present invention may preferably be such a polymer that MFR (determined in accordance with JIS K-7201) is 0.1 to 20 g/10 min. at 190° C. under a load of 2.16 kg. The weight ratio of ethylene and 1-butene includes, for example, 75:25 to 85:15. Commercially available products of the ethylene/1-butene copolymer employable for the present invention include, for example, JSR EBM 2011P (TM, available from Japan Synthetic Rubber Co., Ltd.), EXCELEN N0391 (TM, available from Sumitomo Chemical Co., Ltd.).
Further, the substrate layer of the pressure-sensitive adhesive sheet for surface protection of the present invention may preferably be such a layer that the light transmittance at 200 to 400 nm is 0.5% or less, from the viewpoint of weathering resistance. In order to adjust the light transmittance at 200 to 400 nm to 0.5% or less, a method of adding titanium oxide, an ultraviolet light absorber, an ultraviolet light stabilizer, etc., to the layer may be exemplified.
In the case of adding titanium oxide to the substrate layer, it may be preferable to add 3 to 15 parts by weight of titanium oxide to 100 parts by weight of the total amounts of an ethylene/propylene copolymer and an ethylene/1-butene copolymer.
In the case of adding an ultraviolet light absorber or an ultraviolet light stabilizer to the substrate layer, a benzotriazole type-, hindered amine type-, benzoate type-compounds, etc., may be exemplified as its type. These ultraviolet light absorber or ultraviolet light stabilizer may preferably be added in an amount of 0.3 parts by weight based on 100 parts by weight of the ethylene/propylene copolymer and the ethylene/1-butene
Endo Mikihiro
Hino Kinnosuke
Ichimura Syuji
Kono Kazuhiro
Tsuzuki Yoshinaga
Conlin David G.
Dike, Bronstein, Roberts & Cushman Intellectual Property Group
Nichiban Company Limited
Zirker Daniel
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