Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-01-11
2003-03-11
Lu, Caixia (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S124300, C526S348000, C526S351000, C502S109000, C502S132000
Reexamination Certificate
active
06531551
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polypropylene composition that provides excellent productivity for polypropylene film and from which a film having high transparency and high rigidity can be obtained, and a method for producing the same, and to processes for preparing a catalyst and a preactivated catalyst for polypropylene production used in the method. More particularly, the present invention relates to a polypropylene composition from which a non-oriented polypropylene film excellent in transparency and rigidity and having high productivity, in which little neck-in is caused and on which a sweeper roll mark is not easily formed in producing a thick polypropylene film having a thickness of 30 &mgr;m or more, can be produced, and to a method for producing the same, and to processes for preparing a catalyst and a preactivated catalyst for polypropylene production used in the method.
BACKGROUND OF THE INVENTION
Since crystalline polypropylene is excellent in mechanical properties, chemical resistance and the like, and is very useful with respect to cost effectiveness, it has been widely utilized in every molding field. In particular, it is excellent in optical properties, mechanical properties, packaging suitability and the like, and it has been widely used as packaging materials for food, fiber wrapping and the like.
However, when producing a polypropylene film at a high speed using a conventional polypropylene resin, there may be problems. First, neck-in, in which the width of the resin film molded with a T die narrows so much that the width of the film having uniform thickness is reduced, can occur. This is economically inefficient. Second, a spiral mark may be transferred onto the film due to the use of a sweeper roll to prevent a slipping agent such as fatty amide, which is generally added to a polypropylene resin, from being deposited on a chilled roll surface. As a result, optical properties of the film are lowered and the productivity is greatly reduced. Particularly in production of a thick non-oriented film, a sweeper roll mark may be transferred onto the film and causes irregular transparency in the optical property, so that the productivity of a film having high transparency is limited.
A method of copolymerizing &agr;-olefins such as propylene, ethylene and butene-1 is generally carried out in order to improve transparency in a non-oriented polypropylene film. However, when producing a non-oriented film by melt extrusion with a T die using the random copolymer obtained, because the random copolymer is low in crystallization temperature and in crystallization rate, it is not solidified by the time it is contacted with a sweeper roll. As a result, a spiral mark is easily transferred onto the film due to the sweeper roll, so that a film having a desirable high and uniform transparency is difficult to obtain, especially in producing a thick film. In addition, because the non-oriented film obtained is low in rigidity, elongation or dimensional change may occur when conducting printing on the film at a high speed and the product value is reduced.
Methods of adding metallic salts such as aluminum carboxylate (Japanese Published Unexamined Patent Application (Tokukai) No. HEI 3-220208), or adding nucleating agents such as a sorbitol type derivative, organic phosphate and the like (Japanese Published Unexamined Patent Applications (Tokukai) No. SHO 51-22740 and No. SHO 58-225143, and the like) to a polypropylene resin are used in order to improve transparency and rigidity of the polypropylene resin. However, there are problems in any of these methods as follows: insufficient dispersion of a nucleating agent may cause a reduction in product quality, and in some cases an odor remains in the modified propylene obtained and the odor is transferred to packaging materials for food and reduces the food product value.
In order to solve this problem, use of nucleating agents made of polymer with a high melting point have been proposed (Japanese Published Unexamined Patent Applications (Tokukai) No. SHO 60-139710, No. SHO 62-1738 and No. HEI 1-156305, and the like). However, there were problems in these methods such as the high cost of the nucleating agents of polymer with high melting point used, or that sufficient properties were not always observed depending upon the use. Thus, improvements in these methods have been required.
Furthermore, a method comprising preliminarily polymerizing &agr;-olefin having 2 or more carbon atoms in the presence of a catalyst comprising a titanium complex and an organic metal compound, and then polymerizing &agr;-olefin having 3 or more carbon atoms (Japanese Published Examined Patent Application (Tokko) No. HEI 5-58003), a method of using a preactivated catalyst for &agr;-olefin polymerization formed by allowing a catalyst comprising a titanium trichloride composition and an organic aluminum compound to react simultaneously with &agr;-olefin and an electron donor (Japanese Published Unexamined Patent Application (Tokukai) No. SHO 61-64704), a method which comprises polymerizing olefin after preliminary polymerization of 0.01 to 1 g of olefin per a solid catalyst composition (Japanese Published Unexamined Patent Application (Tokukai) No. SHO 57-151602), and the like have been proposed to improve the transparency and rigidity of polypropylene resins. However, the preliminarily polymerized poly-&agr;-olefin did not have a proper intrinsic viscosity [&eegr;] in any of these methods. Therefore, if a polypropylene film is produced by using a polypropylene resin obtained by such methods, the transparency and rigidity of the polypropylene film may be greatly reduced.
In the various compositions and the methods for producing the same which have been proposed as mentioned above, transparency and rigidity of polyolefin are improved to a certain degree. However, problems with regard to odor due to nucleating agents, crystallization rate, thermal stability and the like still remain to be solved. Particularly in production of thick films, detailed studies have not been carried out so as to provide all of high transparency, high rigidity and high productivity.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a polypropylene composition from which a polypropylene film excellent in transparency and rigidity and having high productivity can be obtained, a method for producing the same, and processes for preparing a catalyst and a preactivated catalyst for polypropylene production used in the method.
As a result of researches so as to accomplish the above-mentioned object, the inventors have completed this invention.
A polypropylene composition of the present invention comprises:
(a) 0.001 to 10 weight parts of polyethylene having an intrinsic viscosity [&eegr;E] of at least 0.01 dl/g but less than 15 dl/g measured in tetralin at 135° C.; and
(b) 100 weight parts of polyolefin comprising at least polypropylene; wherein
(c) said polyethylene exists as dispersed fine particles in said polyolefin comprising at least polypropylene.
In the polypropylene composition of the present invention, it is preferable that the polyethylene exists as dispersed fine particles having a number average particle diameter of 1 to 5,000 nm.
In the polypropylene composition of the present invention, it is further preferable that the number average particle diameter of the polyethylene is 10 to 500 nm.
In the polypropylene composition of the present invention, it is preferable that the intrinsic viscosity [&eegr;E] of the polypropylene composition measured in tetralin at 135° C. is 0.2 to 15 dl/g.
In the polypropylene composition of the present invention, it is preferable that the polyolefin comprising polypropylene is either a propylene homopolymer or an ethylene-propylene copolymer containing 0.05 to 3 weight % of ethylene.
In the polypropylene composition of the present invention, it is preferable that the density of the polyethylene (a) is 0.93 to 0.960 g/cm
3
.
In the polypropylene composition of the present inv
Hirose Taketo
Kimura Masami
Morimoto Yoshitaka
Ohno Katsuhiko
Saito Jun
Chisso Corporation
Lu Caixia
Merchant & Gould P.C.
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