Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-02-15
2002-04-02
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...
C526S348000, C526S348100, C526S351000, C526S184000, C526S943000
Reexamination Certificate
active
06365689
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to new propylene/ethylene random copolymers with very high randomness. More particularly, the invention relates to propylene/ethylene random copolymers which are suitable as materials for the production of molded articles excellent in stiffness, heat resistance, transparency, etc.
BACKGROUND ART
Olefin polymers represented by polypropylene and polyethylene have been extensively used as a base resin in the field of various moldings, because of their good mechanical properties, good chemical resistance and very useful balance with economy. These olefin copolymers have been produced by polymerizing olefins using Ziegler-Natta catalyst system comprising a transition metal catalyst component having titanium trichloride, titanium tetrachloride or the mixture thereof supported on a support such as magnesium chloride, in combination with an organoaluminum compound.
In recent years, various processes of polymerizing olefins have been proposed using a metallocene catalyst system comprising an organic transition metal compound having specified organic radical different from an inorganic transition metal compound, what is called a metallocene compound in combination with an aluminoxane. The olefin copolymers produced using the metallocene catalyst system are generally those having narrow molecular weight distribution. In particular, where two or more olefins are copolymerized, comonomers are dispersed homogenously and copolymerized, thus producing more homogenous copolymers with high randomness as compared with those using Ziegler-Natta catalyst system. Further, choice of metallocene species can produce an isotactic polypropylene having high stereoregularity.
These propylene/ethylene random copolymers are compounded with various additives to form pellets and provided for the manufacture of various molded articles such as films, injection moldings, blow moldings, sheets, fibers, etc. For these molding materials, basic properties of propylene/ethylene copolymers are specified and the additives are selected in accordance with the intended object.
EP 0629631, JPA 7-149833 and JPA 8-73532 disclose the application to films of isotactic polypropylenes produced using a metallocene catalyst system. JPA 7-149833 and JPA 8-73532 disclose that propylene/ethylene random copolymers produced by copolymerizing propylene and ethylene using a metallocene catalyst system comprising a particular chiral metallocene compound are characterized by
13
C-NMR spectroscopy and that propylene/ethylene random copolymers having the following characteristics exhibit a heat-sealing property which is one of performances required for film.
JPA-7-149833
JPA-8-73532
Ethylene unit content (mol %)
5-50
0.5-5
Triadocticity of propylene unit (%)
≧90
≧95
2,1- and 1,3-propylene units (%)
0.05-0.5
0.05-0.5
Intrinsic viscosity (dl/g)
0.1-12
0.1-12
Melt flow rate (g/10 min)
≦20
≦20
However, these publications give no reference to the randomness of the ethylene unit present in the polymer chain.
As one embodiment of polypropylene films, there are biaxially oriented multi-layer films produced generally by laminating a basic layer comprising a crystalline polypropylene film and a heat-seal layer being heat sealable at lower temperature, followed by biaxial orientation. JPA 8-238729 discloses a composite film using as a heat seal layer a propylene/1-butene random copolymer produced with a metallocene catalyst system. This copolymer has 1.0 to 1.5 of parameter B value indicating the randomness in chain distribution of comonomers in the polymer chain. Parameter B value indicating the randomness is represented by the following equation.
B=P
12
/(2
P
1
·P
2
)
wherein P
1
and P
2
represent a first monomer content fraction and a second monomer content fraction, respectively, and P
12
represents the proportion of (first monomer)—(second monomer) chain in the whole two molecule chains.
JPA 9-110934 (Japanese Patent Appln. 7-272428) filed by the present applicant discloses propylene/ethylene random copolymers produced by copolymerizing propylene and ethylene using an olefin polymerization catalyst comprising a single mixture system of a specific chiral metallocene compound and aluminoxane, and injection moldings and films comprising these copolymers as a base resin.
JPA-5-9225, JPA-5-9226 and JPA-5-32723 disclose polypropylene resins produced with the intention of improving the mechanical properties such as stiffness and heat resistance of moldings. These polypropylene resins contain propylene polymers having the temperature (T max) of above 117.0° C. or 118.0° C., which indicates a position of the main elution peak by a temperature fractionation method, and also contain a nucleating agent as a desired component.
JPA 7-10932 also discloses a polypropylene resin composition for injection molding which comprises a propylene polymer as a base resin into which a nucleating agent is incorporated. In this propylene polymer, the weight percent of the amount of the propylene polymer dissolved in o-dichlorobenzene between 120° C. and 135° C., based on the total weight of the propylene polymer is more than the value calculated from the equation: (40-15 logMFR)×100 wherein MFR represents a melt flow rate of propylene polymer.
WO 94/28219 discloses a composition for the formation of fibers wherein a low-melting homopolypropylene produced using a metallocene catalyst system is kneaded with a radical generating agent to lower a molecular weight of propylene.
As discussed above, different characteristics are required for propylene polymers, depending on the object of molding. Producing separately propylene polymers satisfying such respective characteristics complicates process step and process control, thus increasing the cost of production.
OBJECT OF THE INVENTION
An object of the invention is to provide a propylene/ethylene random copolymer which is suitable as a base resin for molding materials applicable to a wide variety of molding fields.
Another object of the invention is to provide a molding material comprising a propylene/ethylene random copolymer as a main component, which is usable in a wide variety of molding fields.
A further object of the invention is to provide a biaxially oriented multi-layer polypropylene film with high transparency, which comprises a polypropylene film having excellent heat resistance and stiffness and very high transparency, and a heat-seal layer having excellent heat-sealing and anti-blocking properties.
DISCLOSURE OF THE INVENTION
A propylene/ethylene random copolymer of the present invention is characterized in that:
an ethylene content (Ew) is 0.1-10 wt %,
a relationship between an isolated ethylene content (E
1
) and the ethylene content (Ew) is represented by the following equation:
E
1
>0.85−0.01
Ew
2,1- and 1,3-propylene units present in a polymer chain are 0-1 mol %,
a weight average molecular weight (Mw) is in the range of 40,000-1,000,000, and
a ratio (Mw/Mn) of the weight average molecular weight (Mw) to a number average molecular weight (Mn) is in the range of 1.5-3.8.
The propylene/ethylene random copolymer can be produced by copolymerizing propylene and ethylene in the presence of a supported metallocene catalyst comprising a transition metal compound and aluminoxane or the reaction product thereof supported on a fine particle support and an organoaluminum compound.
The above-mentioned transition metal compound is represented by the following formula
wherein M represents a transition metal selected from the group consisting of titanium, zirconium and hafnium; X and Y may be the same or different and each represents a hydrogen, a halogen or a hydrocarbyl radical; (C
5
H
4−m
R
1
m
) and (C
5
H
4−n
R
2
n
) represent a substituted cyclopentadienyl group in which m and n are an integer of 1-3; R
1
and R
2
may be the same or different and each represents a hydrocarbyl radical of 1 to 20 carbons or a silicone-containing hydrocarbyl radical, with the position of R
1
and R
2
on the cyclop
Adachi Minoru
Fujita Hiroyuki
Hirose Taketo
Kugimiya Youichi
Morimoto Yoshitaka
Chisso Corporation
Choi Ling-Siu
Wu David W.
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