Resin compositions and use of the same

Details Resin compositions and use of the same Resin compositions and use of the same

2002-04-29

2004-03-30

Wilson, Donald R. (Department: 1713)

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

active

06713562

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a polyethylene resin composition excellent in moldability and capable of providing moldings having excellent pliability.
The present invention relates to a soft resin composition containing a polyethylene resin, which is capable of providing moldings excellent, particularly, in pliability and heat resistance and has an excellent moldability.
The present invention also relates to an ethylene/&agr;-olefin copolymer composition suitable for use mainly in packaging films. More particularly, the present invention relates to an ethylene/&agr;-olefin copolymer composition which is, as compared with the conventional ethylene copolymer compositions, excellent in film-moldability and capable of high-speed molding, and also capable of providing a film excellent in machanical strength properties, low temperature heat-sealing properties and heat-sealing stability, and further in slip characteristics and anti-blocking properties thereby being excellent in suitability for high-speed filling upon packaging by automaticcally filling, and to a film from the same.
BACKGROUND OF THE INVENTION
Polyethylene resins include various kinds of resins, such as high-pressure low-density polyethylene resins, high-density polyethylene resins and linear low-density polyethylene resins including ethylene/&agr;-olefin copolymers.
Of these, the low-density polyethylene resins are excellent in the balance between pliability and heat resistance and, therefore, are widely used for gaskets of injection molding machines, and for various packing, tube and sheet materials.
The conventional low-density polyethylene resins are excellent in heat resistance but do not have sufficient pliability. Therefore, improvement in the properties has been desired.
For example, a method of blending various elastomers (e.g., ethylene/propylene copolymer rubber and ethylene/1-butene copolymer rubber) with the low-density polyethylene resin to give pliability to the resins has been proposed.
However, such a method has a drawback in that, when the conventional ethylene elastomer is blended with the low-density polyethylene resins, the pliability of the resins is improved but the heat resistance thereof becomes remarkably worse.
Accordingly, now desired is development of the polyethylene resin composition capable of providing moldings being well-balanced in pliability and heat resistance, and exhibiting an improved flowability in various molding processes.
Among the polyethylene resins as mentioned above, for example, the high-pressure low-density polyethylene resins, the high-density polyethylene resins and the linear low-density polyethylene resins including ethylene/&agr;-olefin copolymers have been molded into films and widely used in various fields, such as in packaging of products from the past.
Specifically, the films of the linear low-density polyethylene resins including ethylene/&agr;-olefin copolymers are used for sealants of various packaging materials, because the linear low-density polyethylene resins as film materials can be made at low energy consumption (i.e., small production cost) of production, as compared with the conventional high-pressure low-density polyethylenes, and are excellent in heat-sealability through contaminants, hot tack and mechanical properties, such as tear strength and impact strength.
Though the suitability for high-speed filling upon packaging by automatic filling machines is required for the purpose of packaging, the film made singly from the linear low-density ethylene/&agr;-olefin copolymer does not always sufficiently satisfy the required handling characteristics and suitability for high-speed filling.
Accordingly, now desired is development of the resins capable of providing films having more excellent low temperature heat-sealing properties, sealing stability, slip characteristics and antiblocking properties.
The linear low-density ethylene/&agr;-olefin copolymer is low in melt tension for its molecular weight, as compared with the high-pressure polyethylene. Therefore, it has a drawback in that, when they are molded into films at high speed in inflation molding, rocking or breakage of bubbles is liable to occur. The linear low-density ethylene/&agr;-olefin copolymer has a further drawback in that, since the number of branchings in its molecular chain is small, the flowability thereof in high-shear region becomes worse.
Accordingly, in order to solve the above problems, many kinds of compositions or films have been proposed. For example, there have been proposed a composition made by blending a low-crystalline ethylene copolymer having a density of not more than 0.905 g/cm
3
with the ethylene/&agr;-olefin copolymer (Japanese Patent L-O-P No. 34145/1982) and a composition made by blending an ethylene/vinyl acetate copolymer with the ethylene/&agr;-olefin copolymer (Japanese Patent L-O-P No. 109543/1984).
However, films of these compositions could not solve the above problems and, therefore, there is room for improvement in melt tension, flowability in high shearing region, low temperature heat-sealing properties, mechanical properties including tear strength, transparency, and antiblocking properties.
OBJECT OF THE INVENTION
The present invention has been made in order to solve the above problems associated with the prior art.
An object of the invention is to provide a resin composition excellent in moldability and capable of providing moldings having excellent pliability.
Another object of the invention is to provide particularly a soft resin composition containing a polyethylene resin, which is capable of providing moldings excellent in pliability and heat resistance and has an excellent moldability.
Still another object of the present invention is to provide an ethylene/&agr;-olefin copolymer, resin composition and a film therefrom, which composition is excellent in heat stability and stability for high-speed molding, and can provide films excellent in low temperature heat-sealing properties and sealing stability, and, further, in slip characteristics and anti-blocking properties thereby being excellent in handling properties and suitability for high-speed filling upon packaging by automatically filling.
SUMMARY OF THE INVENTION
The resin composition of the present invention is a composition comprising:
a polyethylene resin (A) at an amount of 100 parts by weight; and
a long-chain branched ethylene/&agr;-olefin random copolymer (B) comprising ethylene and an &agr;-olefin having 3 to 20 carbon atoms at an amount of 0.5 to 5000 parts by weight (that is, the composition contains 2 to 20000 parts by weight of the polyethylene resin (A) based on 100 parts by weight of the copolymer (B)),
wherein the polyethylene resin (A) has:
(a) a melt flow rate (MFR) (ASTM D 1238, 190° C., a load of 2.16 kg) of 0.01 to 150 g/10 min and;
(b) a density of 0.901 to 0.970 g/cm
3
, and
wherein the ethylene/&agr;-olefin random copolymer (B) has:
(a) a density of not more than 0.900 g/cm
3
;
(b) an intrinsic viscosity (&eegr;), as measured in decalin at 135° C., of 0.3 to 3.0 dl/g;
(c) a glass transition temperature (Tg) of not more than −50° C.;
(d) a crystallinity, as measured by X-ray diffractometry, of less than 40%;
(e) a molecular weight distribution (Mw/Mn), as measured by GPC, of not more than 3.0;
(f) a B value, as determined by the
13
C-NMR spectrum and the following equation, of 1.0 to 1.4; and
(g) a ratio g&eegr;* of the intrinsic viscosity (&eegr;) determined in the property (b) to the intrinsic viscosity (&eegr;)
blank
of a linear ethylene-propylene copolymer having the same weight-average molecular weight (measured by a light scattering method) as the copolymer rubber (B) and having an ethylene content of 70% by mol, (&eegr;)/(&eegr;)
blank
, of 0.2 to 0.95,
 B value=(P
OE
)/(2·(P
E
)·(P
O
)
wherein (P
E
) and (P
O
) are respectively a molar fraction of the units derived from ethylene and a molar fraction of the units derived from the &agr;-olefin in the copolymer rubber (B), and (P
OE
) is a proportion of the number of the

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