Ethylene-based polymer

Details Ethylene-based polymer Ethylene-based polymer

1999-10-25

2001-09-11

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...

C526S126000, C526S160000, C526S161000, C526S308000, C526S916000, C526S943000, C502S117000, C502S152000, C502S153000, C556S011000, C556S012000, C556S150000, C556S150000

Reexamination Certificate

active

06288193

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ethylene-based polymer comprising ethylene and a vinyl compound having a substituent having specific steric parameter, an ethylene-based polymer having excellent mechanical strength property, and an ethylene-based polymer having excellent processing property and mechanical strength property, a method for producing the ethylene-based polymer, and a use thereof.
2. Description of the Related Art
Ethylene-based polymers are widely used in various fields as general resins, and required to have mechanical properties such as rigidity, impact strength and the like, for example, and excellent appearance such as transparency and the like, in addition to molding processability. Regarding a conventional linear low density polyethylene prepared by using butene-1 or hexene-1 as a copolymerization component for ethylene, increase in molecular weight and decrease in density for improving mechanical properties are proposed, however, these means are not admitted as appropriate methods since deterioration in processability due to increase in extrusion tolque in processing and decrease in heat-resistance are occurred, and there is limitation to improvement in mechanical properties.
As an ethylene-based copolymer having specific viscoelastic property, an ethylene-based copolymer prepared by using styrene or 4-vinylcyclohexene as a copolymerization component for ethylene is disclosed (Japanese Patent Application Laid-Open (JP-A) No. 7-70223). However, an ethylene-styrene copolymer is not preferable since it causes decrease in impact strength and deterioration in transparency due to inclusion of a polystyrene by-produced in production. Further, an ethylene-vinyl cyclohexene copolymer exhibits poor heat stability since it contains a double bond in a significant amount derived from 4-vinylcyclohexene, and includes problems such as occurring of fish eye due to gelling in molding process and the like.
On the other hand, an ethylene-based copolymer using vinylcyclohexane as a copolymerization component for ethylene is reported (Polymer Science (1991), vol. 33(11), p. 2318). However, it is not admitted to have excellent mechanical strength and transparency since it has wide composition distribution due to production in the presence of a Ziegler Natta catalyst system. There is also a report of production in the presence of a metallocene catalyst system (Polymer (1993), vol. 34(9), 1941/Polymer Science USSR (1990), vol. 32(9), 1868), however, it has extremely low molecular weight and therefore the mechanical strength can not be admitted as in satisfactory level.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an ethylene-based polymer excellent in transparency, mechanical properties and viscoelasticity, and ethylene-based polymer having excellent mechanical strength property and an ethylene-based polymer having excellent processing property and mechanical strength property, a method for producing said polymer, and a film, sheet and molded article excellent in transparency, mechanical properties and viscoelasticity.
The present inventors have intensively studied regarding an ethylene-based polymer excellent in transparency and mechanical strength or viscoelasticity, and as a result, have found that an ethylene-based polymer prepared by using a vinyl compound having a substituent having specific steric parameter as a copolymerization component, and an ethylene-based polymer having specific melt viscosity and fusion heat quantity and having excellent balance between melt tension and impact strength achieves the object of the present invention, and have completed the present invention.
Namely, the present invention relates to an ethylene-based polymer comprising ethylene and at least one addition polymerizable monomer containing a vinyl compound (A) described below, wherein the ethylene-based polymer has a melting temperature (Tm) of 119° C. or lower and, the melt index MI (g/10 minutes) of the ethylene-based polymer and the molar content m (mol %) of the vinyl compound (A) satisfy the following formula (1):
Vinyl compound (A): a vinyl compound represented by the structural formula CH
2
═CH—R containing a saturated hydrocarbon group R wherein the substituent R has a steric parameter Es of not less than −2.77 and not more than −1.64 and the substituent R has a steric parameter B1 of not less than 1.53 and not more than 2.90:
0.01≦MI≦18+m
1.4
  (1).
Further, the present invention provides an ethylene-based polymer wherein the polymer has a melt viscosity &eegr;*
190
at a temperature of 190° C. and at a shearing speed of 100 rad/sec in the range from 3.0×10
2
to 6.0×10
3
Pa·s, the polymer has a fusion heat quantity &Dgr;H in the range from 70 to 145 J/g, and the tensile impact strength TI (kJ/m
2
) and the melt tension MT (cN) at a temperature of 150° C. satisfy the following formulae (2) and (3):
 TI≧−31×&Dgr;H+1.57×10
4
×log &eegr;*
190
−980  (2),
MT<6.2×10
−3
×log &eegr;*
190
−4.3  (3).
Furthermore, the present invention provides an ethylene-based polymer wherein the polymer has a melt viscosity &eegr;*
190
at a temperature of 190° C. and at a shearing speed of 100 rad/sec in the range from 3.0×10
2
to 6.0×10
3
Pa·s, the polymer has a fusion heat quantity &Dgr;H in the range from 70 to 145 kJ/kg, and the tensile impact strength TI (kJ/m
2
) and the melt tension MT (cN) at a temperature of 150° C. satisfy the following formulae (4) and (5):
TI≧−15×&Dgr;H+0.76×10
4
×log &eegr;*
190
−470  (4),
MT≧6.2×10
−3
×log &eegr;*
190
−4.3  (5).
The present invention will be described in detail below.
DETAILED DESCRIPTION OF THE PRACTICAL EMBODIMENTS
The ethylene-based polymer of the present invention usually means a copolymer of ethylene with an addition polymerizable monomer, and also includes an ethylene homopolymer.
The ethylene-based polymer of the present invention is an ethylene-based copolymer comprising ethylene and at least one addition polymerizable monomer containing the above-described vinyl compound (A).
The ethylene-based polymer of the present invention is preferably an ethylene-vinyl compound binary copolymer comprising ethylene and the vinyl compound (A); or an ethylene-vinyl compound-addition polymerizable monomer ternary copolymer comprising ethylene, the vinyl compound (A) and an addition polymerizable monomer other than the vinyl compound (A).
The vinyl compound (A) used as a copolymerization component in the ethylene-based polymer of the present invention is a vinyl compound which is represented by CH
2
═CH—R having a saturated hydrocarbon group R which has steric parameters Es and B1 in specific ranges.
The steric parameters Es and B1 herein referred to are parameters showing steric bulkiness of a substituent, and values described in a literature (C. Hansch and A. Leo: “Exploring QSAR Fundamentals and Applications in Chemistry and Biology” Chapter 3 (ACS Professional Reference Book, Washington, D.C. (1995)) are used. When the thickness value and the width value of a substituent are known, an average thereof is used.
The steric parameter Es is not less than −2.77 and not more than −1.64, preferably not less than −2.37 and not more than −1.71, more preferably not less than −2.22 and not more than −1.75, and the steric parameter B1 of the substituent R is not less than 1.53 and not more than 2.90, preferably not less than 1.70 and not more than 2.50.
In the case of a vinyl compound (A) having a saturated hydrocarbon group R having a steric parameter Es of less than −2.77, it does not form a copolymer with ethylene or formation thereof is substantially extremely difficult, and when the steric parameter Es is more than −1. 64, improvement in impact strength of a copolymer is scarcely recognized. In th

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