Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1999-06-23
2001-05-01
Wilson, Donald R. (Department: 1713)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S910000, C525S227000
Reexamination Certificate
active
06224970
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polyolefin resin composition suitable for producing effectively an oriented polyolefin resin film which is excellent in transparency, slipperiness and antiblocking property, and an oriented polyolefin resin film using the same.
2. Prior Arts
Oriented polyolefin resin films, especially oriented polypropylene films, have found application in food packing, fiber packing and other wide purposes because of their excellent transparency and mechanical properties. These excellent oriented polypropylene films have, however, not been free from fault; when the films are overlapped, they adhere to with each other causing the so-called blocking phenomenon and therefore cause a problem in that the packing-work efficiency is significantly lowered.
Conventionally, methods have been proposed in which a fine powdery inorganic substance as an antiblocking agent (hereinafter referred to as “ABA”) is added to a polypropylene, the mixture is kneaded and molded into a sheet followed by orientation in order to improve slipperiness and the antiblocking property of the oriented polypropylene resin film. Those methods include a method which adds zeolite, magnesium silicate or the like (for example, JP-B-53-16134 and JP-B-48-14423), and a method which adds fine powdery silica (for example, JP-B-63-58170 and JP-A-4-288353). Since, however, the fine powdery inorganic substances are easily agglomerated and the affinity between the polypropylene resin and the inorganic substance is insufficient, there is a problem in that voids are produced during orientation around the inorganic substance acting as a nucleus, resulting in inferior transparency represented by LSI (light scattering transmission intensity).
In order to improve the drawbacks of these films containing the fine powdery inorganic substance ABA, methods have been proposed in which oriented films are obtained after dispersing a fine powdery high molecular substance ABA in the polypropylene resin (for example, JP-A-57-64522, JP-A-5-214120, JP-A-6-107868, JP-A-7-178805, JP-A-7-196819 and the like). In these methods, however, LSI may become inferior because of voids produced during orientation and an insufficient affinity between the polypropylene resin and the high molecular substance ABA, or the transparency of the film represented by haze may become inferior because of a large difference in refraction index between the polypropylene resin and the high molecular substance ABA. Further, there is a problem in that antiblocking property of the oriented film is not sufficient because of an insufficient degree of crosslinking.
Under these circumstances, the present inventors have conducted extensive studies for improving slipperiness and the antiblocking property without accompanying significant damage regarding transparency. As the result, they have discovered that a polyolefin resin composition which meets the above requirement and an oriented film therefrom can be obtained by using as an ABA a crosslinked polymer bead having a specific structure and thus completed the present invention.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a polyolefin resin composition which produces on oriented polyolefin resin film excellent in transparency, slipperiness and the antiblocking property, and the oriented film produced therefrom.
According to the present invention, there is provided a polyolefin resin composition comprising:
(a) 100 parts by weight of a polyolefin resin; and
(b) 0.05 to 1 part by weight of beads of a crosslinked polymer comprising (1) 5 to 99% by weight of a radically polymerizable monomer unit represented by the general formula (A):
wherein R
1
is hydrogen or a hydrocarbon group having 1 to 5 carbon atoms and R
2
is a hydrocarbon group having 5 to 30 carbon atoms, (2) 0 to 94% by weight of a radically polymerizable monomer unit other than the monomer unit of the general formula (A), and (3) 1 to 20% by weight of a crosslinking monomer unit, said crosslinked polymer beads having a critical surface tension of 40 dyne/cm or less, the percentages being measured relative to the total weight of components (1), (2) and (3).
Further, the present invention provides an oriented polyolefin resin film obtained by orienting a sheet of said composition at least in a uniaxial direction.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
The polyolefin resin used in the present invention includes a crystalline homopolymer of, for example, propylene, ethylene, butene-1, hexene-1, 4-methylpentene-1 and the like, a crystalline copolymer of two or more kinds of these olefins or mixture of two or more kinds of these polymers, among which a crystalline polypropylene resin is preferred. The crystalline polypropylene resin used in the present invention is a known polymer mainly comprising propylene. Examples of such resin include a crystalline propylene homopolymer, a crystalline copolymer of propylene with one or more &agr;-olefins, such as propylene-ethylene copolymer, propylene-butene-1 copolymer and propylene-ethylene-butene-1 terpolymer, and a mixture two or more thereof. Further, it is possible to optionally add to the polypropylene resin described above a polyolefin polymer such as a polyethylene resin, a polybutene-1 resin, a polystyrene resin, an ethylene-propylene copolymer rubber, an ethylene-propylene-diene terpolymer rubber or the like.
The crosslinked polymer beads used in the present invention are beads of a crosslinked polymer comprising (1) 5 to 99% by weight of a radically polymerizable monomer unit (hereinafter, abbreviated as “Unit (1)”).
In the general formula (A), R
1
is hydrogen or a hydrocarbon group having 1 to 5 carbon atoms (e.g. an alkyl group), preferably hydrogen or a hydrocarbon group having 1 to 3 carbon atoms and more preferably hydrogen or methyl.
Also, R
2
is a hydrocarbon group having 5 to 30 carbon atoms, preferably a hydrocarbon group having 5 to 20 carbon atoms and more preferably a hydrocarbon group having 5 to 10 carbon atoms. The hydrocarbon group represented by R
2
includes generally an alkyl group, a cycloalkyl group, an arlyl group, an aralkyl group and the like. When R
2
is a hydrocarbon group having up to 4 carbon atoms or hydrogen, the transparency of the film obtained is inferior.
Specific examples of the monomer represented by the general formula (A) which gives the Unit(1) constituting the crosslinked polymer beads used in the present invention include pentyl acrylate, isopentyl acrylate, neopentyl acrylate, 2-methylbutyl acrylate, 3-methylbutyl acrylate, hexyl acrylate, 2-methylpentyl acrylate, 2-ethylbutyl acrylate, 1,3-dimethylbutyl acrylate, heptyl acrylate, octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, isodecyl acrylate, undecyl acrylate, dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, 2-methyl-7-ethyl-4-undecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, heptadecyl acrylate, octadecyl acrylate, nonadecyl acrylate, eicosyl acrylate, behenyl acrylate, phenyl acrylate, benzyl acrylate, tolyl acrylate, 2-tert-butylphenyl acrylate, 4-tert-butylphenyl acrylate, phenethyl acrylate, 2-naphthyl acrylate, 4-biphenyl acrylate, isobornyl acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 4-methylcyclohexyl acrylate, cyclododecyl acrylate, pentyl methacrylate, isopentyl methacrylate, neopentyl methacrylate, 2-methylbutyl methacrylate, 3-methylbutyl methacrylate, hexyl methacrylate, 2-methylpentyl methacrylate, 2-ethylbutyl methacrylate, 1,3-dimethylbutyl methacrylate, heptyl methacrylate, octyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, 2-methyl-7-ethyl-4-undecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate, eicosyl methacryla
Hiroyuki Tanimura
Kazuhiro Yamazaki
Taiji Yamada
Takeshi Ebara
Tuyoshi Hashimoto
Birch & Stewart Kolasch & Birch, LLP
Sumitomo Chemical Company Limited
Wilson Donald R.
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