Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1982-03-11
1984-01-31
Ziegler, J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
428 35, 428523, C08L 2308
Patent
active
044290799
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
This invention relates to an ethylene/alpha-olefin copolymer composition comprising a blend of ethylene/alpha-olefin copolymers which has excellent heat sealing properties and flexural resistance and improved properties suitable, for example, for packaging films.
BACKGROUND TECHNOLOGY
Techniques of setting off the defects of different kinds of films by laminating them into a composite have been known heretofore in the field of packaging bags. Particularly, in the field of packaging foodstuffs, laminated packaging bags composed of a resin layer having excellent transparency, mechanical properties, rigidity, heat resistance and gas-barrier property, such as polypropylene, a polyester, nylon, cellophane or an ethylene/vinyl alcohol copolymer, and a resin layer having good transparency and heat sealability, such as polyethylene, polypropylene or an ethylene/vinyl acetate copolymer have come into widespread use.
In order to produce such laminated packaging bags, there is usually employed a method which comprising heat-sealing the top and bottom end portions or all end portions of a film, and in the resulting bag, the innermost layer is a resin layer having good heat sealability. Accordingly, films use as the innermost layer of the packaging bags are required not only to have good heat sealing characteristics but also to be free from extraction or degradation of the resin components which may be caused by an article packaged therein. In recent years, there have been a variety of articles to be packed and a variety of modes of using the packaging materials and some problems have arisen with regard to films which have heretofore been used to form the heat sealed layer. These problems include, for example, the high and narrow heat-sealing temperature range of polypropylene films, the poor heat resistance, strength and oil resistance and acetic acid odor of ethylene/vinyl acetate copolymer films, the poor heat sealing strength and hot tack property of films of high-pressure low-density polyethylene, and the poor flexural resistance of each of such films which is likely to lead to the formation of pinholes in bags during handling in transportation, etc. and to cause leakage of the contents.
The present invention has successfully given a solution to the above new problems, and as will be described below in detail, provides an ethylene/alpha-olefin copolymer composition having excellent low-temperature heat sealability, heat seal strength, flexural resistance, transparency and impact strength and being suitable for packaging films.
DISCLOSURE OF THE INVENTION
The present inventors have made investigations about the solving of the above new problems, and found that a blend of at least two ethylene-rich ethylene/alpha-olefin random copolymers (A) and (B) having specified properties gives a solution to the above problems and exhibits excellent properties.
The investigations of the present inventors have led to the discovery that a blended composition of 95 to 40% of (A) a random copolymer of ethylene and an alpha-olefin having 5 to 10 carbon atoms which has a melt index of 0.1 to 20 g/10 min., a density of 0.910 to 0.940 g/cm.sup.3, a crystallinity by X-rays of 40 to 70%, a melting point of 115.degree. to 130.degree. C. and an ethylene content of 94 to 99.5 mole% and 5 to 60% by weight of (B) a random copolymer of ethylene and an alpha-olefin having 3 to 10 carbon atoms which has a melt index of 0.1 to 50 g/10 min., a density of 0.870 to 0.900 g/cm.sup.3, a crystallinity by X-rays of 5 to 40%, a melting point of 40.degree. to 100.degree. C. and an ethylene content of 85 to 95 mole% has excellent low-temperature heat sealability, heat seal strength and flexural resistance and other excellent properties, especially transparency and impact strength.
In the present invention, examples of the alpha-olefin having 5 to 10 carbon atoms to be copolymerized with ethylene in the copolymer (A) include 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and 1-decene, and mixtures of at least two of these alpha
REFERENCES:
patent: 4188350 (1980-02-01), Vicik et al.
Naganuma Seikoh
Shibata Yuzo
Mitsui Petrochemical Industries Ltd.
Ziegler J.
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