Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-08-29
2003-12-23
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S234000, C526S236000, C526S348200, C526S348500, C526S348600
Reexamination Certificate
active
06667375
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ethylene-&agr;-olefin copolymer obtained by a gas phase polymerization method in the presence a catalyst, a polyethylene composition comprising said copolymer, and a film made of said copolymer or composition. More particularly, the present invention relates to an ethylene-&agr;-olefin copolymer which contains a small amount of a cold xylene-soluble portion (CXS component) and does not easily cause problems such as blocking and the like when made into a film or sheet, a polyethylene composition which is excellent in appearances such as gloss, transparency and the like when made into a film and is excellent in handling properties such as blocking-resistance, slipping property and the like, and a film composed of said copolymer or said composition.
BACKGROUND OF THE INVENTION
Properties required for films used as wrapping materials include excellent film-forming processability in processing a film, excellent appearances such as the gloss, transparency and the like concerning clear visibility of contents, easy handling in bag manufacturing, and excellent blocking-resistance, slipping property and the like of a film concerning easiness in opening a bag in filling, particularly, in automatic filling, and the like.
As the ethylene-based resin used for such films, ethylene-&agr;-olefin copolymers are listed.
An ethylene-&agr;-olefin copolymer obtained according to a high-pressure ion polymerization method in the presence of a catalyst had problems such as fuming in molding working, inclusion of a volatile component which is a cause for generation of a gas, and the like, due to problematical process (Japanese Patent Application Laid-Open (JP-A) No. 52-125590).
On the other hand, a copolymer produced by a gas phase polymerization method has a merit that the content of a volatile component causing gas generation and fuming in molding working is low, as the polymerization can be performed substantially in the absence of a solvent.
The ethylene-&agr;-olefin copolymer obtained by a gas phase polymerization method also had problems that the copolymer contains a large amount of a cold xylene-soluble portion (CXS component) causing blocking and the like (JP-A No. 54-154488), or the copolymer has a little hexane extracted portion, however, the content of a cold xylene-soluble portion (CXS component) becomes high (JP-A No. 5-155938).
JP-A No. 56-152853 discloses a resin composition comprising an ethylene-&agr;-olefin copolymer obtained by a gas phase polymerization method in the presence a catalyst and a low density polyethylene produced by a high pressure radical polymerization method, and a film thereof. However, a film obtained from said composition has not been satisfactory in transparency and gloss, though the impact strength thereof has been improved. Further, JP-A No. 56-152853 does not disclose the addition of an anti-blocking agent and slipping agent, therefore anti-blocking property and slipping property have not been satisfactory.
Therefore, there has been desired for an ethylene-&agr;-olefin copolymer or resin composition which has lower content of a volatile component, causes no problems such as gas generation, fuming and the like in molding working, has a small amount of a cold xylene-soluble portion (CXS component), does not easily cause problems such as blocking and the like when made into a film or sheet, and has good balance between appearances of a film such as gloss, transparency and the like and handling properties thereof such as anti-blocking property, slipping property and the like.
OBJECT OF THE INVENTION
The present inventors have intensively studied a copolymer and a composition containing the composition which have no problems as described above, and resultantly found that a specific ethylene-&agr;-olefin copolymer obtained by a gas phase polymerization method has a small amount of a cold xylene-soluble portion (CXS component) and does not easily cause problems such as blocking and the like when made into a film or sheet. Further, the present inventors have found that a resin composition comprising said and a specific low density polyethylene obtained by a high pressure radical polymerization method, when made into a film, has a small content of a volatile component, provides no problems such as fuming, gas generation and the like in molding, has excellent appearances such as gloss, transparency and the like, and has excellent handling properties such as anti-blocking property, slipping property and the like, and have completed the present invention.
SUMMARY OF THE INVENTION
Namely, the present invention relates to a polyethylene composition comprising 60 to 95 wt % of an ethylene-&agr;-olefin copolymer component (A) obtained by a gas phase polymerization method in the presence of a catalyst and 5 to 40 wt % of a low density polyethylene component (B) obtained by a high pressure radical polymerization method (wherein, the total amount of component (A) and component (B) is 100 wt %), wherein said ethylene-&agr;-olefin copolymer component (A) satisfies the following conditions (A-1) to (A-4):
(A-1) Melt flow rate (MFR): 0.3 to 5.0 g/10 minutes
(A-2) Melt flow rate ratio (MFRR): 20 or more
(A-3) Density (d): 0.910 to 0.930 g/cm
3
(A-4) Cold xylene-soluble portion (CXS) (wt %) is in the range defined by the formula (1):
1.5×10
−4
×d
−125
×MFR
0.5
+0.3
≧CXS
formula (1).
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be illustrated in detail below.
The gas phase polymerization method of the present invention is not particularly restricted providing it is a method in which no solvent substantially exist, and polymerization is performed under solid phase or gas phase to produce a polymer. Known reactors such as a vertical reactor, horizontal reactor and the like can be used. Reactors may or may not have a stirrer. Further, a plurality of reactors may also be used. The production method may be continuous or batch-wise. The polymerization pressure is preferably from atmospheric pressure to 40 kg/m
2
, and the polymerization temperature is preferably from 55 to 95° C.
The catalyst used in the present invention is a solid catalyst for olefin polymerization which can copolymerize ethylene with an &agr;-olefin. As the catalyst, there are listed, for example, catalyst systems described in Japanese Patent Application Nos. 10-59846, 10-59848, 11-65433 and the like.
The solid catalyst component (I) for olefin polymerization used in the present invention is a solid catalyst component for olefin polymerization obtained by contacting a halide of a XIII or XIV group element and an electron donor with a solid catalyst component precursor containing a magnesium atom, titanium atom and a hydrocarbyloxy group.
The halogen contained in the solid catalyst component (I) is a halogen atom in the XVII group of the periodic table, for example, chlorine atom, bromine atom, iodine atom or the like, and preferably chlorine atom.
The electron donor contained in the solid catalyst component (I) is an organic compound containing at least one atom selected from the group consisting of an oxygen atom, sulfur atom, nitrogen atom and phosphorus atom, and for example, amines, sulfoxides, ethers, esters or the like are listed, and ethers and esters are preferable.
As the ethers, dialkyl ethers are listed, and specifically, diethyl ether, dibutyl ether, tetrahydrofuran and the like are listed. Dibutyl ether and tetrahydrofuran are preferable.
Examples of the esters include saturated aliphatic carboxylates, unsaturated aliphatic carboxylates, alicyclic carboxylates, aromatic carboxylates and the like. Specifically, there are listed ethyl acetate, ethyl acrylate, ethyl methacrylate, butyl benzoate, dibutyl succinate, dibutyl malonate, dibutyl maleate, dibutyl itaconate, di-n-butyl phthalate, diisobutyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate and the like, and di-2-ethylhexyl phthalate and di-n-octyl phthalate are preferable.
The solid catalyst component (I) can be obt
Ima Seiichiro
Mitsuno Tadahiro
Shiraishi Hiroyuki
Cheung William
Sumitomo Chemical Company Limited
Wu David W.
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