Ethylene polymer and processes for obtaining it

Details Ethylene polymer and processes for obtaining it Ethylene polymer and processes for obtaining it

1996-04-18

2001-03-13

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...

C526S065000, C526S114000, C526S348200, C526S348400, C526S348500, C526S348600, C526S352000, C525S053000, C525S240000

Reexamination Certificate

active

06201078

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to ethylene polymers having an advantageous combination of characteristics which makes them particularly suitable for use by extrusion and by extrusion blow-moulding in order to manufacture articles (for example tubes) which have excellent mechanical properties and, in particular, high resistance to crazing under stress. The invention also relates to various processes for obtaining these ethylene polymers.
TECHNOLOGY REVIEW
It is generally known that resins having a high elongational viscosity (which is reflected by a high die swell ratio) lend themselves particularly well to use by extrusion and by extrusion blow-moulding. For example, Belgium patent BE 84,0378 (Solvay & Co.) describes polyethylenes obtained by polymerization in a single reactor in the presence of a catalytic solid which is prepared by reacting an oxygen-containing organomagnesium compound with an oxygen-containing organotitanium compound and an oxygen-containing organozirconium compound, and by subsequently treating the reaction product thus obtained with an aluminium halide. The known polyethylenes have a high die swell ratio. However, their mechanical properties are such that the resistance to crazing under stress of tubes extruded from these polyethylenes is low.
Moreover, polyethylenes of improved mechanical properties, and in particular of high resistance to crazing under stress, are known. For example, patent application EP 603935 (Solvay) discloses ethylene polymers obtained by polymerization in at least two reactors in series, in the presence of a titanium catalyst. The ethylene polymers thus obtained have good mechanical properties (high resistance to crazing under stress). However, the ethylene polymers have a low die swell ratio.
The present invention is directed towards overcoming the abovementioned drawbacks by providing a novel ethylene polymer having both a high die swell ratio and a high resistance to crazing under stress, which is particularly suitable for use by extrusion and by extrusion blow-moulding.
SUMMARY OF THE INVENTION
Consequently, the invention relates to an ethylene polymer having a die swell ratio (R
B
) of at least 1.4, a resistance to crazing under stress (ESCR) of at least 55 h and a melt index (MI
5
) of at least 0.2 g/10 min.
One of the essential characteristics of the ethylene polymer according to the invention thus lies in the combination of a high die swell ratio with a high resistance to crazing under stress.


REFERENCES:
patent: 3759918 (1973-09-01), Yamaguchi et al.
patent: 4109071 (1978-08-01), Berger et al.
patent: 4230831 (1980-10-01), Sakurai et al.
patent: 4336352 (1982-06-01), Sakurai et al.
patent: 4511704 (1985-04-01), Tanaka et al.
patent: 4547551 (1985-10-01), Bailey et al.
patent: 4859749 (1989-08-01), Franke
patent: 4975485 (1990-12-01), Sato et al.
patent: 5149738 (1992-09-01), Lee et al.
patent: 5260384 (1993-11-01), Morimoto et al.
patent: 840378 (1976-04-01), None
patent: 0100843 (1984-02-01), None
patent: 0134427 (1985-03-01), None
patent: 0 129 312 B1 (1988-03-01), None
patent: 0273284 (1988-07-01), None
patent: 273284 (1988-07-01), None
patent: 0 302 242 B1 (1991-07-01), None
patent: 0 273 284 B1 (1991-10-01), None
patent: 0572003 (1993-12-01), None
patent: 0603935 (1994-06-01), None
patent: 603935 (1994-06-01), None
patent: 0 602 508 A2 (1994-06-01), None
patent: 94/26790 (1994-11-01), None
patent: 94/26791 (1994-11-01), None
M.P. McDaniel et al., “A Comparison of Cr/S1O2and Cr/AIPO4Polymerization Catalysts”, Journal of Catalysis 101, pp. 446-457 (1986).
X. Lu et al., “Notchology—The Effect of the Notching Method on the Slow Crack Growth Failure in a Tough Polyethylene”, Journal of Materials Science 26, pp. 881-888 (1991).
“Unipol Process Polyethylene Products” Union Carbide, 1993).
“High-Density Polyethylene Resin”, DMDA-6143 Natural 7, Blow Molding Resins, Unipol Polymers.
“High-Density Polyethylene Resin”, DMDC-6143 Natural 7, Molding Resins, Unipol Polymers.
“High-Density Polyethylene Resin” DMDA-6150 Natural 7, Blow Molding Resins, Unipol Polymers.
“High-Density Polyethylene Resin”, Unival DMDA-6200 Natural 7, Blow Molding Resins, Unival.
Product Sheet SUNTEC, Asahi Chemical.

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