Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1991-03-01
1993-10-19
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
525240, C08L 2320
Patent
active
052546128
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INDUSTRIAL APPLICATION
This invention relates to strippable protective films of polyolefin which are applied temporarily to the surface of manufactured articles such as metal component, plastics product and rubber product for the purposes of preventing them from scratch, contamination or corrosion when they are processed, transported or stored, and which, after fulfilling the above-mentioned purposes, are capable of being stripped therefrom readily and integrally, and to compositions therefor.
TECHNOLOGICAL BACKGROUND
Strippable protective films are applied temporarily to such a manufactured article as metal components, plastics products or rubber products for the purposes of preventing it from scratch, contamination or corrosion at the time when it is processed, transported or stored. The films of the type are required to have such characteristics that after they have been applied temporarily to the above-mentioned manufactured article and have fulfilled the above-mentioned purposes, they are capable of being stripped therefrom readily and integrally.
Heretofore, there have been used resin compositions for strippable protective films, said resin compositions containing their principal components, for examples, ethylene/vinyl acetate copolymers (hereinafter abbreviated to EVA) or ethylene/.alpha.-olefin copolymers having a low crystallinity. While these resin compositions have favorable initial adhesive properties, they involve such drawbacks that because of their poor heat resistance, films prepared therefrom increase in adhesive force during a long-term storage thereof, particularly when they are held under the circumstances of high temperature, and sharply deteriorate in strippability.
Japanese Patent Publn. No. 45974/1983 proposes strippable protective films of polyolefin obtained by improving heat resistance of EVA films.
Although the heat resistance of the proposed films has been improved, however, there were such problems that the films increase in adhesive force due to change on standing when they are stored for a long period of time, or when they are stripped from articles to which they are applied, bleeding matters remain on the surface of the articles.
The present invention is intended to solve such problems associated with the prior art as mentioned above, and accordingly an object of the invention is to provide strippable protective films which are excellent in flexibility, scratch resistance and heat resistance and, at the same time, which have appropriate initial adhesive force to articles to which they are applied and strippability therefrom and, moreover, which are less in change on standing even when they are stored for an extended period of time and are free from bleeding on the article surface when they are stripped therefrom, and compositions therefor.
DISCLOSURE OF THE INVENTION
The compositions for strippable protective films according to the present invention contain index (ASTM D 1238-65T, 230.degree. C.) of 0.1-100 g/10 min, propylene content of 60-85 mol % and a heat of fusion, as measured by thermal analysis with a differential scanning calorimeter, of 20-80 joule/g, index (ASTM D 1238-65T, 190.degree. C.) of 0.1-100 g/10 min, ethylene content of 75-95 mol %, crystallinity index of 0-30%, and .alpha.-olefin having 3-10 carbon atoms, and 100% by weight.
The above-mentioned tackifier (C) used in the invention includes usually one or two or more resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic/aromatic copolymer hydrocarbon resins, alicyclic hydrocarbon resins, synthetic terpene hydrocarbon resins, terpene hydrocarbon resins, coumarone-indene hydrocarbon resins, low molecular weight styrene resins and rosin hydrocarbon resins.
The strippable protective films according to the invention are a single-layer or multi-layer films, with the proviso that at least one of the outermost surface layers is composed of the composition according to the invention as illustrated above.
PREFERRED EMBODIMENT OF THE INVENTION
The strippable protect
REFERENCES:
patent: 3630980 (1971-12-01), Russell
patent: 3635861 (1972-01-01), Russell
patent: 4284541 (1981-08-01), Takeda et al.
patent: 4734328 (1988-03-01), Kohyama et al.
patent: 4769284 (1988-09-01), Kakugo et al.
World Patents Index Latest, week 8104, No. 81-04951D, Derwent Publ. Ltd. London, GB & JP-A-55 149364 (Nitto Electric) 21 Nov. 1980 Abstract.
Sugi Masahiro
Tanaka Mutsuhiro
Guarriello John J.
Michl Paul R.
Mitsui Petrochemical Industries Ltd.
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