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
2001-07-12
2003-09-23
Tarazano, D. Lawrence (Department: 1773)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C428S515000, C428S523000, C428S484100, C524S543000
Reexamination Certificate
active
06624253
ABSTRACT:
The present invention relates to a propylene type resin composition having high transparency and low blocking tendency, a film made thereof, and a laminated resin film.
As compared with a conventional propylene type resin obtained by a Ziegler catalyst containing Ti, Mg, Cl, etc., as the main components, a propylene type resin produced by means of a metallocene catalyst has a large melting point drop relative to the comonomer content, and a film obtained by T-die molding has low blocking tendency and is excellent in a low temperature heat sealing property. Therefore, its development for application to a sealant film is very much expected.
However, as a result of a study conducted by the present inventors, it has been found that the propylene type resin obtained by a metallocene catalyst provides excellent transparency when molded into a film by means of a T-die if the molding is carried out by taking a sufficient time for cooling the film, for example, by lowering the taking up speed, but the transparency decreases if the cooling tends to be insufficient, for example, by increasing the molding speed.
The cause may be such that the polypropylene type resin obtained by a metallocene catalyst usually has a narrow molecular weight distribution, and aligned crystals tend to be small during molding of the film, whereby crystallization tends to delay, and depending upon the cooling conditions, spherulites in the film are likely to grow large, whereby irregularities are likely to form on the film surface to reduce the transparency of the film.
In order to sufficiently cool the film, it is desired to lower the molding speed. However, in a commercial production line, the productivity is important, and it is not desirable to lower the molding speed. Otherwise, it is conceivable to lower the cooling temperature. However, in order to lower the cooling temperature, a cooling apparatus of a large size will be required, which will create a problem of an increase in the production cost, Accordingly, it is necessary to develop a resin whereby the product quality can be secured without depending on the molding conditions.
For this purpose, it is conceivable to add a nucleating agent to let crystal nuclei form. However, when a nucleating agent is added, it becomes important to effectively disperse the nucleating agent in the resin, and there will be a problem that due to inadequate dispersion, deterioration of the quality of the film is likely to result. Further, there is a problem that by the addition of a nucleating agent, no adequate effect for improving the transparency can be attained.
Accordingly, it is desired to develop a propylene type resin whereby a resin film excellent in transparency can be obtained even when the production speed is high.
Further, a resin film is used widely in an application as a packaging material whereby not only a low temperature impact resistance but also a low temperature heat sealing property is required. Especially, in recent years, the packaging process tends to have a high speed, whereby it is important that heat sealing can be carried out at a low temperature, and it has been common to employ a technique of incorporating an elastomer. However, if an elastomer is incorporated, crystallization will further be lowered, whereby there is a problem that the transparency of the film decreases.
Under these circumstances, it is also desired to develop a propylene type resin whereby a resin film is obtainable which is excellent in transparency even when the production speed is high and which is excellent not only in a low temperature impact resistance but also in a low temperature heat sealing property.
Accordingly, it is an object of the present invention to provide a propylene type resin composition whereby the cooling condition dependency of the film transparency can be reduced, and a film having a good surface smoothness and being excellent in transparency, can be obtained and which is excellent in moldability in T-die molding, a propylene type resin film made thereof, and a laminated resin film.
Another object of the present invention is to provide a propylene type resin composition whereby a film having excellent low temperature impact resistance and low temperature beat sealing properties in addition to the above-mentioned excellent characteristics, can be obtained, a propylene type resin film made thereof, and a laminated resin film.
As a result of an extensive study, the present inventors have found that a film excellent in transparency can be obtained by adding a small amount of a polyethylene wax having certain specific properties to a certain specific propylene/&agr;-olefin random copolymer polymerized by a metallocene catalyst. The present invention has been accomplished on the basis of this discovery.
Specifically, the present invention provides a propylene type resin composition comprising from 95.0 to 99.999 parts by weight of component (A) which is a propylene/&agr;-olefin random copolymer polymerized by a metallocene catalyst, and from 0.001 to 5.0 parts by weight of component (C) which is a polyethylene wax, wherein components (A) and (C) satisfy the following conditions:
Component (A): Propylene/&agr;-olefin random copolymer
1) Melt index at 230° C.: 2 to 30 g/10 min
2) Main melting pea% temperature (Tm) obtained by DSC: 110 to 145° C.
Component (C): Polyethylene wax
1) Density: 0.94 to 0.98 g/cm
3
2) Melt viscosity at 140° C.: At least 10 cps.
The present invention also provides a propylene type resin composition comprising from 50 to 98 parts by weight of component (A) which is a propylene/&agr;-olefin random copolymer polymerized by a metallocene catalyst, from 2 to 50 parts by weight of component (B) which is a propylene type elastomer or an ethylene type elastomer, and from 0.001 to 5.0 parts by weight of component (C) which is a polyethylene wax, wherein components (A), (B) and (C) satisfy the following conditions:
Component (A): Propylene/&agr;-olefin random copolymer
1) Melt index at 230° C: 2 to 30 g/10 min
2) Main melting peak temperature (Tm) obtained by DSC: 110 to 145° C.
Component (B): Elastomer
(B-1) Propylene type elastomer
Propylene/&agr;-olefin copolymer satisfying the following 1) and 2):
1) Content of units derived from propylene: 5 to 95 mol %
2) Content of units derived from a C
4-20
&agr;-olefin: 5 to 95 mol %
(B-2) Ethylene type elastomer
Ethylene-&agr;-olefin copolymer satisfying the following 3) and 4)
3) Content of units derived from ethylene: 5 to 95 mol %
4) Content of units derived from an &agr;-olefin: 5 to 95 mol %
Component (C): Polyethylene wax
1) Density: 0.94 to 0.98 g/cm
3
2) Melt viscosity at 140° C: At least 10 cps.
Further, the present invention provides such a propylene type resin composition, wherein the metallocene catalyst for component (A) is a compound of the following formula (1) or its partially hydrogenated product:
wherein Q is a linking group which links the two conjugated five-membered cyclic ligands, M is a metal atom selected from the group consisting of titanium, zirconium and hafnium, each of X and Y is a hydrogen atom, a halogen atom, a hydrocarbon groups an alkoxy group, an amino group, a nitrogen-containing hydrocarbon group, a phosphorus-containing hydrocarbon group or a silicon-containing hydrocarbon group, each of R
1
and R
3
is a hydrogen atom, a C
1-20
hydrocarbon group, a halogen atom, a C
1-20
halogenated hydrocarbon group, a silicon-containing hydrocarbon group, a nitrogen-containing hydrocarbon group, an oxygen-containing hydrocarbon group, a boron-containing hydrocarbon group or a phosphorus-containing hydrocarbon group, and each R
2
is a hydrogen atom, a C
1-20
hydrocarbon group, a halogen atom, a C
1-20
halogenated hydrocarbon group, a silicon-containing hydrocarbon group, a nitrogen-containing hydrocarbon group, an oxygen-containing hydrocarbon group, a boron-containing hydrocarbon group or a phosphorus-containing hydrocarbon group.
Still further, the present invention provides a propylene type resin film molded from such a propylene type resin composition by mean
Nakamura Yasunori
Sezume Tadashi
Tayano Takao
Japan Polychem Corporation
Tarazano D. Lawrence
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