Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-03-20
2004-11-09
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S240000
Reexamination Certificate
active
06815503
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel polypropylene resin composition, a gas permeable film comprising the same and provided with satisfactory optical characteristics (transparency, gloss and see throughness) as well as an excellent gas permeability (water vapor, oxygen and ethylene gas) without damaging a rigidity and a method for maintaining a freshness of vegetables and fruits over a long period of time using the above gas permeable film for a wrapping film.
2. Description of the Related Art
A polypropylene film has a rigidity and excellent optical characteristics (transparency, gloss and the like) which are required to packaging materials and therefore has widely been used. However, when a polypropylene film is used as a wrapping material for vegetables and fruits, it does not have a satisfactory gas permeability against water vapor, oxygen and ethylene gas, and therefore it has been used making holes for permeating gas. In this case, ethylene gas generated from vegetables and fruits which are wrapped matters can sufficiently be discharged, and oxygen necessary for breathing of vegetables and fruits can sufficiently be taken in. However, water vapor can not be prevented from vaporizing from vegetables and fruits, so that there has been the problem that vegetables and fruits are liable to be dried and freshness thereof is lost.
Known is a film which shows a gas permeability without carrying out such drilling work and can maintain a freshness of vegetables and fruits (International Publication WO99/51665), but there has been the problem that the film does not have satisfactory transparency, gloss and see throughness (hereinafter referred to as ┌optical characteristics┘) which are required in an actual distribution route.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a resin composition capable of preparing a gas permeable film which is endowed with satisfactory optical characteristics as well as an excellent gas permeability (water vapor, oxygen and ethylene gas) without damaging a rigidity and a method for maintaining a freshness of vegetables and fruits over a long period of time by using the above gas permeable film for a wrapping film.
Intensive researches repeated by the present inventors in order to achieve the object described above have resulted in finding that a film produced from a polypropylene resin composition comprising a propylene polymer (A) and an ethylene/propylene/butene random copolymer (B) containing the specific amounts of butene and ethylene has an excellent gas permeability (water vapor, oxygen and ethylene gas) without damaging a rigidity and is endowed with satisfactory optical characteristics in combination therewith. Thus, they have come to complete the present invention.
That is, the polypropylene resin composition according to the present invention is characterized by comprising a propylene polymer as a component (A) and an ethylene/propylene/butene random copolymer as a component (B). More specifically, it is characterized by comprising 40 to 95% by weight of a propylene polymer as the component (A) and 5 to 60% by weight of an ethylene/propylene/butene random copolymer having a butene content of 3 to 40% by weight and an ethylene content of 10 to 30% by weight as the component (B).
Further, the polypropylene resin composition according to the present invention is characterized by that a ratio &eegr;
B
/&eegr;
A
of an intrinsic viscosity &eegr;
B
of the component (B) described above to an intrinsic viscosity &eegr;
A
of the component (A) described above falls in a range of 0.5 to 1.3. Also, the polypropylene resin composition according to the present invention is characterized by that the component (B) described above has an intrinsic viscosity &eegr;
B
falling in a range of 0.5 to 3.0 dl/g.
Further, the gas permeable film according to the present invention is characterized by that it is a single layer or multilayer film comprising at least one layer of a film of the polypropylene resin composition described above according to the present invention and having a thickness of 10 to 100 &mgr;m and that it has the following characteristics:
(1) a permeability T
H2O
of water vapor is 9 to 50 g/m
2
·24 h (based on JIS Z 0208),
(2) a permeability T
O2
of oxygen is 600 to 12500 nmol/m
2
·s·100 kPa (based on JIS K 7126-A) and
(3) a permeability T
ethylene
of ethylene gas is 600 to 22500 nmol/m
2
·s·100 kPa (based on JIS K 7126-A).
Further, the gas permeable film according to the present invention is characterized by that the film described above is oriented at least in a monoaxial direction and includes a film oriented at an orienting magnification of 3 to 60 times at least in a monoaxial direction.
The vegetable and fruit freshness long term-maintaining method according to the present invention is characterized by using the gas permeable film according to the present invention as a film for wrapping vegetables and fruits.
BRIEF DESCRIPTIONS OF THE DRAWINGS
Shown is a flow sheet of a continuous polymerization apparatus used in the examples and the comparative examples.
REFERENCES:
patent: 4820775 (1989-04-01), Shiga et al.
patent: 5990242 (1999-11-01), Naga et al.
patent: 6191219 (2001-02-01), Tanaka et al.
patent: 6242535 (2001-06-01), Kagami et al.
patent: 6355736 (2002-03-01), Nakashima et al.
patent: 0863183 (1996-11-01), None
patent: 0987290 (1999-04-01), None
patent: 01-225648 (1989-08-01), None
patent: 04-202409 (1992-07-01), None
patent: 2001-123038 (2001-08-01), None
Akitaya Shinichi
Nakashima Takanori
Nakata Shinji
Shiraishi Yasuhiro
Chisso Corporation
J.C. Patents
Nutter Nathan M.
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