Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2001-02-12
2003-01-28
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S213000, C428S515000, C428S523000, C525S088000, C525S089000, C525S240000
Reexamination Certificate
active
06511755
ABSTRACT:
TECHNICAL FIELD
This invention relates to a polypropylene film, multi-layered polypropylene film, a self-tacky film, a multi-layered self-tacky film and multi-layered polypropylene film for a high-temperature sterilization packing. More particularly, this invention relates to a film having excellent transparency, impact resistance at low temperature and heat sealing property and also having excellent property of little whitening property upon bending and property of preventing the deterioration of transparency after heating; to a multi-layered film having excellent transparency, impact resistance at low temperature and heat sealing property and also having excellent property of little whitening property upon bending and property of preventing the deterioration of transparency after heating; to a self-tacky film having excellent transparency, impact resistance at low temperature and heat sealing property; a self-tacky multi-layered film having excellent transparency, impact resistance at low temperature and heat sealing property; and a multi-layered polypropylene film having little deterioration of transparency after a high-temperature sterilizing treatment, having excellent heat resistance, impact resistance at low temperature and tight sealing of the content and being suitable for a high-temperature sterilizing treatment packing for food.
BACKGROUND OF THE INVENTION
Polypropylene has mechanical, optical and thermal characteristics and is excellent in a packing aptitude and, therefore, it has been widely utilized in the use for packing of food and in the use for daily necessities.
With regard to a polypropylene material for polypropylene film, a propylene homopolymer, a copolymer or a terpolymer of propylene with &agr;-olefin and a composition comprising a propylene homopolymer and a copolymer of propylene with ethylene (the so-called block copolymer) are used and each of them is used for a packing use meeting with each characteristic.
However, the conventional known polypropylene film is insufficient in terms of a balance of transparency, impact resistance at low temperature, heat sealing property, self-tackiness, little whitening property upon bending and effect of preventing the lowering of transparency after heating. Thus, there are problems that, in the film of a propylene homopolymer, impact resistance at low temperature, heat sealing property and self tackiness are poor and, in addition, little whitening property upon bending is insufficient; in the film using a copolymer or a terpolymer of propylene with &agr;-olefin, transparency and heat sealing property are excellent but impact resistance at low temperature, self-tackiness, little wh itening property upon bending and an effect of preventing the lowering of transparency after heating are poor; and, in the film using a polypropylene composition comprising crystalline polypropylene which does not satisfy the specific limiting viscosity ratio, weight ratio, etc. and a copolymer of propylene with &agr;-olefin, impact resistance at low temperature is excellent but transparency, heat sealing property, self-tackiness and little whitening property upon bending are poor and, in addition, f ish eye is apt to be generated.
In such a film using the conveational polypropylene, it is difficult to satisfy all of the requirements for transparency, impact resistance at low temperature, heat sealing property, self-tackiness, little whitening property upon bending and an effect of preventing the lowering of transparency after heating treatment.
In addition, as a result of development of distribution mechanism and improvement in freeze transportation technique, there has been a quick increase in food product where cooked food or processed food is packed, sterilized with steam at high temperature and distributed at ambient temperature or in a warmed or frozen state. As to a film used for sterilization by steam (hereinafter, referred to as “film for retort pouch”), the film which is made of polyolefin has been used and, with an object of prevention of generation of deformation (wrinkles, shrinking, etc.) and fusion of the film at the steam sterilization temperature (120° C. or higher but lower than 140° C.) or prevention of breakage of the film for retort pouch during the distribution at low temperature, a film using a crystalline propylene-ethylene block copolymer having excellent heat resistance and impact resistance at low temperature is used as polyolefin. However, the film using a crystalline propylene-ethylene block copolymerhas a poor transparency and there is a disadvantage that the content therein cannot be seen. When transparency is needed for the packing material with an object of seeing the content, a polyolefin film in which a crystalline propylene random copolymer is compounded with a non-crystalline ethylene-propylene copolymer is used. However, in a film where a crystalline propylene random copolymer is compounded with a non-crystalline ethylene-propylene copolymer, there are disadvantages that the transparency lowers after steam sterilization and that fusion occurs during the steam sterilization at high temperature. Recently, film for retort pouch having a transparency by the use of a linear low-density polyethylene is developed but, even in the said film, there is a problem that the film is deformed or fused upon steam sterilization. Under such circumstances, with an object of making the lowering of transparency after a high-temperature sterilization treatment little and of improving the heat resistance and the impact resistance at low temperature, there is a proposal for a compounded film where (i) the first layer comprising polypropylene or an ethylene-propylene random copolymer, (ii) the second layer comprising an ethylene-propylene block copolymer or a blend of an ethylene-propylene block copolymer with a polyolefin polymer well compatible with rubber components in the said block copolymer and (iii) the third layer comprising polypropylene or an ethylene-propylene random copolymer are layered (Japanese Patent Laid-Open No. 3950/1987).
In the meanwhile, the present applicant already filed a Japanese Patent Application No. 181,141/1996 (International Laid-Open WO 97/19135) for a multi-layered film comprising a layer using a propylene block copolymer where a limiting viscosity is within a specific range and a layer using polypropylene having well-balanced heat resistance, impact resistance at low temperature, tear strength, transparency, appearance and heat sealing property.
The present invention is to provide a film having excellent transparency, impact resistance at low temperature, heat sealingproperty and self-tackiness and also having little whitening property upon bending and an effect of preventing the lowering of transparency after heating treatment and also to provide a multi-layered film having excellent transparency, impact resistance at low temperature, heat sealing property and self-tackiness and also having little whitening property upon bending and an effect of preventing the lowering of transparency after heating treatment. Further, from the above-mentioned characteristics, the present invention is to provide a polypropylene film and multi-layered film which can be appropriately used in various uses such as a film for retort pouch to be sterilized by heating, a film for medical use, a film for layered bag package and a film for the manufacture of boxes.
DISCLOSURE OF THE INVENTION
The present inventors have carried out an intensive investigation for preparing a film which satisfies all of transparency, impact resistance at low temperature, heat sealing property, self-tackiness, little whitening property upon bending and an effect of preventing the lowering of transparency after heating treatment. As a result, it has been found that a polypropylene composition comprising crystalline polypropylene and a copolymer of propylene with &agr;-olefin in which a limiting viscosity of the copolymer, a limiting viscosity ratio of both crystalline polypropylene and copolymer components and a product of the limiting
Akitaya Sinichi
Hattori Takayuki
Hirose Taketo
Kugimiya Youichi
Mochizuki Yasuhiro
Chisso Corporation
Fay Sharpe Fagan Minnich & McKee LLP
Nakarani D. S.
LandOfFree
Polypropylene film and multilayered polypropylene film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polypropylene film and multilayered polypropylene film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polypropylene film and multilayered polypropylene film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3066341