Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1993-02-26
1994-07-26
Teskin, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525 88, 525 95, 525240, 525247, 525319, 525324, 526124, 526125, 526351, 526905, C08F21006
Patent
active
053327896
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a polypropylene based resin having extremely high stiffness, good heat resistance and high impact strength and a resin composition comprising the resin.
Further, the present invention relates to a polypropylene resin having high stiffness and good heat resistance as well as having good dimensional stability resulting in prevention of warping or deformation of the resulting product.
Further, the present invention relates to a polypropylene resin which exhibits high stiffness and high impact strength and thus is useful in a wide variety of fields such as automotive, electrical appliances or the like.
Furthermore, the present invention provides a less expensive polypropylene resin having high stiffness and high impact strength and high melt tension, and a resin composition comprising the resin.
RELATED ART
In general, polymers prepared from homopolymerization or copolymerization of propylene in a first stage and random copolymerization of propylene and the other alpha-olefin in a second stage, are called propylene block copolymers. These block copolymers are drastically improved in low temperature impact strength without substantially sacrificing good properties of polypropylene, i.e., high stiffness and good heat resistance.
Heretofore, propylene block copolymers are produced by a method which comprises subjecting propylene to homopolymerization or copolymerization in the presence of a high stereoregular catalyst in the former polymerization step in a homopolymerization vessel, and then subjecting propylene and the other alpha-olefin to random copolymerization in the presence of the homopolymer or copolymer obtained as above in the latter polymerization step in a random copolymerization vessel.
As mentioned above, in the presence of a highly stereoregular catalyst, propylene/olefin copolymerization is carried out one after another to improve impact strength. However, as the copolymerized portions increase, the stiffness decreases. Good balance of stiffness and impact strength has not been sufficiently achieved.
In the meanwhile, techniques to improve impact strength of a propylene block copolymer is known (Japanese Patent Application Publication Nos. 23565/1991 and 26203/1991). Either of these techniques improves stereoregularity of the propylene homopolymers. However, the improvement is still within the prior art level, and improvement in stiffness and heat resistance is not sufficient.
Further, according to the technique disclosed in Japanese Patent Application Laid-Open No. 187043/1984, the resultant polymers have extremely poor impact strength when compared with a polymer having the same amount of copolymerized portion since formulation control of the copolymerized portion is not sufficient. Thus, it cannot be said that balance of stiffness and impact strength is sufficient.
The present invention was made in view of the above situations, and has its object of providing a polypropylene based resin having extremely high stiffness, good heat resistance and high impact strength.
Further, in the field of injection-molding using a polypropylene resin, in order to improve stiffness and heat resistance of the resin itself, it is generally conducted to broaden molecular weight distribution by way of a multi-stage polymerization or the other methods, and then keeping molecular orientation in the molding stage. However, in this method, after molding the product suffers large shrinkage and anisotropy. Particularly, in the case of producing precise parts and large products, a problem readily occurs due to warping or deformation of the products, or poor engagement of the molded products. It is desired to overcome these problems.
On the other hand, to improve the above-mentioned molding shrinkage, it is adapted to narrows molecular weight distribution of a polypropylene resin by way of decomposition using peroxide. However, this method has a problem in that decrease in mechanical and physical properties such as stiffness and heat resistance is substantial to e
REFERENCES:
patent: 4981938 (1991-01-01), Hanari et al.
patent: 5077341 (1991-12-01), Saito et al.
patent: 5141994 (1992-08-01), Kakugo et al.
Housaki Tatsuya
Kusuyama Hideo
Miyazaki Sueto
Nakagawa Masaru
Tanaka Akira
Idemitsu Petrochemical Co. Ltd.
Teskin Fred
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