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
2001-08-27
2003-06-03
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, C428S500000, C428S515000
Reexamination Certificate
active
06573332
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a propylene-based copolymer, a producing process thereof and film comprising the copolymer. More particularly, the present invention relates to a propylene-based copolymer having a practical transparency and excellent low-temperature heat sealability and rigidity, to a producing process thereof and to film comprising the copolymer.
2. Description of Related Arts
Polypropylene resins are excellent in transparency, heat-resistance, food hygiene and the like, and therefore, widely utilized in fields such as film, sheet and the like. Recently, with increase in bag production speed in packaging fields of foods and the like, materials having a low temperature heat sealability are desired.
As a polypropylene having a low temperature heat sealability, for example, JP-2882237B discloses a copolymer excellent in low temperature heat sealability obtained by copolymerizing propylene and an &agr;-olefin other than propylene, or propylene, ethylene and an &agr;-olefin other than propylene with a Ziegler-Natta catalyst, wherein the propylene content, ethylene content, &agr;-olefin content and the content of 20° C. xylene soluble part are restricted to specified ranges. However, the random copolymer having a good low temperature heat sealability, namely being low in heat sealing temperature, is insufficient in rigidity, and therefore, further improvements have been required.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a propylene-based copolymer having a practical transparency, and excellent low temperature heat sealability and rigidity.
Another object of the present invention is to provide a process for producing the propylene-based copolymer.
Still another object of the present invention is to provide film comprising the copolymer.
Other objects and advantages of the present invention will be apparent from the following description.
Namely, the present invention relates to a propylene-based copolymer obtained by copolymerizing propylene with ethylene and/or an &agr;-olefins having 4 or more carbon atoms in the presence of a polymerization catalyst in a first step to produce a copolymer having a content of the &agr;-olefins of 1 mol % or more and less than 15 mol % and an ethylene content of 5 mol % or less in amount of 1 to 30% by weight as a copolymer component (A), and subsequently copolymerizing propylene with ethylene and/or an &agr;-olefins having 4 or more carbon atoms in a second step or later steps to produce a copolymer having a content of the &agr;-olefins of 15 to 30 mol % and an ethylene content of 5 mol % or less in amount of 70 to 99% by weight as a copolymer component (B), to a process for producing the copolymer, and to film comprising the same.
The present invention will be illustrated in detail below.
DETAILED DESCRIPTION OF THE INVENTION
The propylene-based copolymer of the present invention is a copolymer obtained by copolymerizing propylene with an &agr;-olefin having 4 or more carbon atoms and/or ethylene in a first step to produce a component(A), and subsequently copolymerizing propylene with an &agr;-olefin having 4 or more carbon atoms and/or ethylene in a second step or later steps to produce a component (B). The component (A) is preferably a copolymer component obtained by copolymerizing propylene with an &agr;-olefin having 4 or more carbon atoms, and the component (B) is preferably a copolymer component obtained by copolymerizing propylene with an &agr;-olefin having 4 or more carbon atoms.
The content of the component (A) is from 1 to 30% by weight, preferably from 5 to 30% by weight, more preferably from 5 to 20% by weight. The content of the component (B) is from 70 to 99% by weight, preferably from 70 to 95% by weight, more preferably from 80 to 95% by weight. The sum of the components (A) and (B) is 100% by weight.
When the content of the component (A) is less than 1% by weight, properties of polymer powder formed in copolymerization may be deteriorated to decrease productivity, and when the content of the component (a) is over 30% by weight, the low temperature heat sealability of a film made of the copolymer may be insufficient.
The content of the &agr;-olefin having 4 or more carbon atoms contained in the component (A) is 1 mol % or more and less than 15 mol %, preferably 5 mol % or more and less than 15 mol %, more preferably from 5 to 10 mol %. When the content of the &agr;-olefins having 4 or more carbon atoms contained in the component (A) is less than 1 mol %, processability may be insufficient, and when 15 mol % or more, it may be difficult in some cases to stably produce the component (A).
The content of the &agr;-olefin having 4 or more carbon atoms contained in the component (B) is from 15 to 30 mol %, preferably from 15 to 25 mol %. When the content of the &agr;-olefin having 4 or more carbon atoms contained in the component (B) is less than 15 mol %, the low temperature heat sealability of film may be insufficient, and when over 30 mol %, the rigidity of film may decrease.
The ethylene content in the component (A) is 5 mol % or less, preferably 3 mol % or less. The ethylene content in the component (B) is also 5 mol % or less, preferably 3 mol % or less. When the content of ethylene in the component (A) or (B) is over 5 mol %, film may be whitened with the lapse of time and the rigidity thereof may decrease.
Herein, the sum of propylene and an &agr;-olefin having 4 or more carbon atoms and ethylene is 100 mol %.
Examples of the &agr;-olefin having 4 or more carbon atoms include, for example, 1-butene, 2-methyl-1-propene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, ethyl-1-pentene, trimethyl-1-buene, methylethyl-1-butene, 1-octene, methyl-1-pentene, ethyl-1-hexene, dimethyl-1-hexene, propyl-1-heptene, methylethyl-1-heptene, trimethyl-1-pentene, propyl-1-pentene, diethyl-1-butene, 1-nonene, 1-decene, 1-undecene, 1-dodecene and the like are exemplified, and preferable are 1-butene, 1-pentene, 1-hexene and 1-octene, further preferable are 1-butene and 1-hexene from the standpoints of copolymerization property and economy and the like.
As the component (A) or (B), for example, a propylene-1-butene copolymer component, propylene-1-hexene copolymer component, propylene-ethylene-1-butene copolymer component, propylene-ethylene-1-hexene copolymer component and the like are listed, and preferable are a propylene-1-butene copolymer component and propylene-1-hexene copolymer component. The components (A) and (B) may be the same or different in combination of the monomers to be copolymerized.
As the propylene-based copolymer of the present invention, for example, a (propylene-1-butene)-(propylene-1-butene) copolymer, (propylene-1-butene)-(propylene -ethylene-1-butene) copolymer, (propylene-ethylene-1-butene)-(propylene-1-butene) copolymer, (propylene-ethylene-1-butene)-(propylene-ethylene-1-butene) copolymer, (propylene-1-hexene)-(propylene-1-hexene) copolymer and the like are listed, and a (propylene-1-butene)-(propylene-1-butene) copolymer and (propylene-1-hexene)-(propylene-1-hexene) copolymer, and further preferable is a (propylene-1-butene)-(propylene-1-butene) copolymer.
The melt flow rate (hereinafter, sometimes abbreviated as “MFR”) measured at 230° C. under a load of 21.18N according to JIS K7210 of the propylene-based copolymer of the present invention is not particularly limited, but preferably from 0.1 to 50 g/10 minutes, more preferably from 1 to 20 g/10 minutes, from the standpoint of flowability or film formability.
The MFR of the propylene-based copolymer may be changed by a known method during melt-kneading. For example, a method of adding an organic peroxide to the propylene-based copolymer and the like so far as the object and effect of the present invention are not damaged, are listed.
Production of the propylene-based copolymer of the p
Kishiro Shigeki
Kume Takanori
Wakamatsu Kazuki
Nutter Nathan M.
Sumitomo Chemical Company Limited
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