Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2002-01-17
2004-09-28
Harlan, Robert D. (Department: 1713)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S374000, C428S369000, C525S240000, C524S451000, C524S515000
Reexamination Certificate
active
06797378
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polypropylene resin composition containing an organic fiber filler and an article obtained from the same, more specifically to an organic fiber filler-containing polypropylene resin composition providing an article which is excellent in a moldability and a strength and an article obtained from the same.
RELATED ART
A large number of trials to blend a polypropylene resin with an organic fiber filler for the purposes of improving a rigidity, a molding contraction property, a heat resistance and a coating property of the above resin has so far been made.
However, polypropylene resins have a low melt viscosity, so that it has been difficult to obtain desired shapes even with the resins blended with organic fiber fillers by a profile extrusion molding method, an extrusion sheet molding method and a calender molding method. To be specific, under the situation that a tensile stress is applied in a melting state in blending a polypropylene resin with an organic fiber filler and extruding the molten resin in the form of a strand to pelletize it or in passing an organic fiber filler-blended polypropylene resin through a sizer such as a sizing plate when profile-extruding the resin or in extruding the resin in the form of a sheet to mold it by means of a roller, the phenomenon that the above organic fiber filler-blended polypropylene resin is torn off takes place.
In order to elevate a melt viscosity of a polypropylene resin, proposed are methods in which polypropylene is reduced into a high polymer and in which added is a processability-improving agent such as an elastomer and polyethylene, but the tearing-off phenomenon described above has not yet come to be solved.
A molded foam article obtained by foam-molding an organic fiber filler-blended polypropylene resin is very fragile and has the defect that it is liable to be cracked when it is subjected to after-working such as nailing. A reason therefor is estimated to be that because of a low melt viscosity of the polypropylene resin, a shape and a size of the foamed cell become unequal when foam-molded, which results in a reduction in a strength of the molded foam article. Because of these reasons, an organic fiber filler-containing polypropylene resin has not yet come to be sufficiently put to practical use.
DISCLOSURE OF THE INVENTION
The present invention has been made in light of the existing situation described above related to an organic fiber filler-containing polypropylene resin composition, and an object of the present invention is to solve the existing problems described above. That is, an object of the present invention is to provide an organic fiber filler-containing polypropylene resin composition providing a molded article which is excellent in a moldability and a strength and a molded article obtained from the same.
Intensive investigations repeated by the present inventors in order to solve the problems described above related to an organic fiber filler-containing polypropylene resin composition have resulted in finding that the foregoing problems related to an organic fiber filler-containing polypropylene resin composition can be solved by using a polypropylene resin having a specific relation between a melt tension and a intrinsic viscosity as the polypropylene resin in the organic fiber filler-containing polypropylene resin composition, and they have come to complete the present invention based on this knowledge.
That is, the present invention is composed of the following.
(1) An organic fiber filler-containing polypropylene resin composition comprising a polypropylene resin satisfying the following equation and an organic fiber filler in a proportion of 1 to 250 parts by weight of the filler per 100 parts by weight of the resin composition:
log
MT
>4.24×log [&eegr;]−1.2 (1)
wherein MT represents a melt tension (unit: cN) of the polypropylene resin at 230° C., and [&eegr;] represents a intrinsic viscosity (unit: dl/g) of the polypropylene resin measured in tetralin at 135° C.
(2) The organic fiber filler-containing polypropylene resin composition as described in the above item (1), wherein the polypropylene resin is an olefin polymer composition (A) described below or a mixture comprising the above olefin polymer composition (A) and a polypropylene base resin (B) described below, and a mixing proportion of the above polypropylene base resin (B) is 90% by weight or less based on the mixture: the olefin polymer composition (A): an olefin polymer composition comprising (a) and (b) described below:
(a) 0.01 to 5.0 parts by weight of polyethylene which is an ethylene homopolymer or an ethylene-olefin copolymer having an ethylene polymer unit of 50% by weight or more and which has a intrinsic viscosity [&eegr;E] falling in a range of 15 to 100 dl/g measured in tetralin at 135° C., and
(b) 100 parts by weight of polypropylene which comprises a propylene homopolymer or a propylene-olefin copolymer having a propylene polymer unit of 50% by weight or more and which has a intrinsic viscosity [&eegr;P] of 0.2 to 10 dl/g measured in tetralin at 135° C.; and
the polypropylene base resin (B): a propylene homopolymer or a propylene/&agr;-olefin copolymer comprising propylene as a principal component.
(3) The organic fiber filler-containing polypropylene resin composition as described in the above item (1) or (2), further comprising a foaming agent.
(4) A molded article obtained by extrusion-molding the organic fiber filler-containing polypropylene resin composition as described in any of the above items (1) to (3).
EMBODIMENT OF THE INVENTION
The polypropylene resin used in the present invention is a polypropylene resin having the following characteristic:
log
MT
>4.24×log [&eegr;]−1.2 (1)
wherein MT represents a melt tension (unit: cN) of the polypropylene resin at 230° C., and [&eegr;] represents a intrinsic viscosity (unit: dl/g) of the polypropylene resin measured in tetralin at 135° C.
If the melt tension and the intrinsic viscosity fall in the ranges of values satisfying the equation (1) described above, capable of being avoided is the phenomenon that the molten resin is torn off in extruding the organic fiber filler-containing polypropylene resin composition.
The melt tension is a tension (unit: cN) observed when a strand obtained by extruding the resin molten by heating at 230° C. from an orifice having a diameter of 2.095 mm and a length of 40 mm at a speed of 20 mm/minute is received at a speed of 3.14 m/minute by means of a melt tension tester model 2 (manufactured by Toyo Seiki Mfg. Co., Ltd.). The intrinsic viscosity ([&eegr;]) is a value (unit: dl/g) measured on a temperature condition of 135° C. by means of an automatic viscosity-measuring instrument (AVS model 2 manufactured by Mitsui Toatsu Chemical Co., Ltd.) using tetralin as a solvent.
The polypropylene resin used in the present invention is preferably the olefin polymer composition (A) having the following characteristic:
the olefin polymer composition (A): an olefin polymer composition comprising (a) and (b) described below:
(a) 0.01 to 5.0 parts by weight of polyethylene which is an ethylene homopolymer or an ethylene-olefin copolymer having an ethylene polymer unit of 50% by weight or more and which has a intrinsic viscosity [&eegr;E] falling in a range of 15 to 100 dl/g measured in tetralin at 135° C., and
(b) 100 parts by weight of polypropylene which comprises a propylene homopolymer or a propylene-olefin copolymer having a propylene polymer unit of 50% by weight or more and which has a intrinsic viscosity [&eegr;P] of 0.2 to 10 dl/g measured in tetralin at 135° C.
A method for obtaining such olefin polymer composition (A) shall not specifically be restricted, and it can be prepared, for example, by a method disclosed in International Publication No. WO97/14725, that is, a two-stage polymerization method in which a prescribed amount of high molecular weight p
Chisso Corporation
Harlan Robert D.
J. C. Patents
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