Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2000-05-01
2001-09-11
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S515000, C428S516000
Reexamination Certificate
active
06287705
ABSTRACT:
TECHNICAL FIELD
The present invention relates to propylene-based random copolymers and propylene-based resin compositions, to their films, and to multi-layered, propylene-based resin laminates. Precisely, the invention relates to propylene-based random copolymers and propylene-based resin compositions with improved moldability, and to their films and multi-layered, propylene-based resin laminates with improved physical properties for films including heat-sealability, etc.
BACKGROUND ART
As being highly tough, transparent and moisture-proof, films of crystalline propylene-based polymers are widely used for wrapping and packaging films. For their use, wrapping and packaging films are often formed into bags. In an ordinary process that comprises forming a film into bags, filling the bags with objects, and sealing the open end of the thus-filled bags, two film edges are heat-sealed by pressing them against a hot rod. In the recent process of forming film bags or wrapping or packaging objects with films, used are large-scale high-speed wrapping machines for improving the productivity. For these, it is much desired to develop materials with good heat-sealability. Wrapping and packaging films must be smoothly worked into secondary products, and are therefore desired to have good slip characteristics and anti-blocking characteristics as their indispensable properties.
However, films of propylene homopolymers are defective in that, when heat-sealed, they require high temperatures and take a lot of time. To solve this problem, a technique of copolymerizing propylene with ethylene, 1-butene and any other &agr;-olefins is widely employed.
However, in the prior art technique of producing propylene-based polymers in the presence of a Ziegler-Natta catalyst, a large amount of comonomers including ethylene, 1-butene and other &agr;-olefins must be copolymerized with propylene in order that the resulting copolymers could have satisfactory heat-sealability. These comonomers often remain in the copolymers, essentially forming a low-molecular-weight fraction therein, and the fraction has a low degree of crystallinity and makes the copolymers sticky (the fraction is hereinafter referred to as a sticky fraction). As a result, films of the copolymers lose the advantage of toughness that is intrinsic to polypropylene films, and, in addition, their surfaces are often blocked to detract from the secondary workability of the films. What is more, the comonomers remaining in the copolymers will often bleed out to whiten the surfaces of the copolymer films. For these reasons, the copolymers are not on the practicable level.
To solve the problem with the prior art technique, tried is dissolving the sticky fraction in an inert solvent for removing it. However, it is extremely difficult to effectively wash out the sticky fraction while the low-temperature-melting fraction that contributes to the heat-sealability of the copolymer films is prevented from being washed away along with the sticky fraction. Therefore, the method of dissolving the sticky fraction could not produce satisfactory results in industrial applications.
On the other hand, various studies are being made these days for using metallocene catalysts in production of propylene-based polymers. Polymers produced in the presence of metallocene catalysts are characterized in that they have extremely narrowed molecular weight distribution and compositional distribution. However, for ensuring molding stability of polymers and for making polymer moldings have various physical properties that will be contradictory to each other, it is said that polymers having broad molecular weight distribution and compositional distribution are rather better. Taking it into consideration, various compositions of propylene-based polymers produced in the presence of metallocene catalysts have been proposed. Until now, however, no one has succeeded in realizing a satisfactory industrial-scale method of freely producing resin polymers that have desired properties and are suitable to intended applications and molding methods.
DISCLOSURE OF THE INVENTION
Given the situation as above, we, the present inventors have made the invention, of which the object is to provide improved propylene-based random copolymers and propylene-based resin compositions, their films, and multi-layered, propylene-based resin laminates. The copolymers and resin compositions of the invention can be formed into films that exhibit excellent heat-sealability not interfering with the favorable characteristics (including good toughness, transparency, moisture-proofness, etc.) intrinsic to ordinary polypropylene films. The films of the invention have good slip characteristics and anti-blocking characteristics that are needed in high-speed working lines for forming them into bags, and even in such high-speed working lines, the quality of the films is lowered little.
Specifically, the invention includes the following first to fourth aspects.
First Aspect of the Invention
1. A propylene-based, propylene-ethylene random copolymer satisfying the following <1> to <3>:
<1> Its ethylene unit content, &agr; (% by weight), as measured through
13
C-NMR, falls between 0.2 and 10% by weight;
<2> The amount of its fraction, Wp (% by weight), eluted within the temperature range between (Tp−5)° C. and (Tp+5)° C. in temperature-programmed fractionation chromatography is at least 20% by weight, with Tp (° C.) being the peak temperature for essential elution;
<3> The amount of its fraction, W0 (% by weight), eluted within the temperature range not higher than 0° C. in temperature-programmed fractionation chromatography, and a satisfy the relationship therebetween given by the following formula (I-1):
W0≦(3+2&agr;)/4 (I-1).
2. The propylene-based random copolymer of above 1, of which the melting point, Tm (° C.), as measured through differential scanning calorimetry (DSC), and &agr; satisfy the relationship therebetween given by the following formula (I-2):
Tm≦160−5&agr; (I-2).
3. The propylene-based random copolymer of above 1 or 2, of which the amount of the fraction, WH (% by weight), eluted within the temperature range not lower than (Tp+5)° C. in temperature-programmed fractionation chromatography, with Tp (° C.) being the peak temperature for essential elution, and &agr; satisfy the relationship therebetween given by the following formula (I-3):
0.1≦WH≦3&agr; (I-3).
4. The propylene-based random copolymer of any of above 1 to 3, of which the amount of the fraction, E (% by weight), extracted with boiling diethyl ether is at most 2.5% by weight, and E and &agr; satisfy the relationship therebetween given by the following formula (I-4):
E≦(2&agr;+15)/10 (I-4).
5. The propylene-based random copolymer of any of above 1 to 4, of which the melt index, MI (g/10 min), falls between 0.1 and 200 g/10 min.
6. The propylene-based random copolymer of any of above 1 to 5, of which the stereospecificity index, P (mol %), as measured through
13
C-NMR, is at least 98 mol %.
7. The propylene-based random copolymer of any of above 1 to 6, of which a falls between 3 and 7% by weight.
8. A film of the propylene-based random copolymer of any of above 1 to 7.
Second Aspect of the Invention
1. A propylene-based random copolymer composition comprising (i) a propylene-ethylene random copolymer and (ii) a nucleating agent, of which the peak top temperature, Tc (° C.), on the highest temperature side in its crystallization curve plotted in differential scanning calorimetry (DSC), and the peak top temperature, Tm (° C.), on the lowermost temperature side in its melting curve plotted in DSC satisfy the following formula (II-1):
Tc≧0.75×Tm−5 (II-1),
and the amount of the fraction, W0 (% by weight), eluted within the temperature range not higher than 0° C. in temperature-programmed fractionation chromatography is at most 6% by weight.
2. A propylene-based random copolymer composition comprising (i) a pro
Minami Yutaka
Seta Yasushi
Idemitsu Petrochemical Co. Ltd.
Jackson Monique
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Thibodeau Paul
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