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
2003-09-24
2004-11-02
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S088000, C525S247000, C525S268000
Reexamination Certificate
active
06812292
ABSTRACT:
TECHNICAL FIELD
The present invention I relates to a novel polypropylene block copolymer, which has a high molecular weight and comprises polypropylene-b-poly(ethylene-co-propylene) including a polypropylene segment and a poly(ethylene-co-propylene) segment, with the two types of segments being chemically linked.
The present invention II relates to a blushing-resistant transparent polypropylene resin for molding, comprising a novel polypropylene block copolymer, polypropylene-b-poly(ethylene-co-propylene), including a polypropylene segment and a poly(ethylene-co-propylene) segment, with the two types of segments being chemically linked, and to molded articles obtained therefrom. The molded articles exhibit excellent transparency and blushing resistance, as well as well-balanced tensile strength, tensile elongation, impact resistance at low temperature, and heat resistance.
The present invention III relates to an elastomer for molding, comprising a novel polypropylene block copolymer, polypropylene-b-poly(ethylene-co-propylene), including a polypropylene segment and a poly(ethylene-co-propylene) segment, with the two types of segments being chemically linked. Molded articles obtained therefrom exhibit excellent transparency, blushing resistance, and flexibility and have excellent impact resistance, mechanical strength, and appearance.
BACKGROUND ART
Today, polypropylene resins, which are comparatively inexpensive and exhibit excellent thermal and mechanical strength, are used in a variety of fields. Propylene homopolymers generally have high rigidity, but have poor transparency, impact resistance, and particularly, poor impact resistance at low temperatures.
Propylene-&agr;-olefin random copolymers, which are produced by copolymerizing propylene and a small amount of a olefin so as to enhance transparency of propylene homopolymers, are widely employed in a variety of industrial fields, beginning with in domestic electric appliances and articles for daily use. These conventionally employed propylene random copolymers have excellent transparency. However, these copolymers have poor impact resistance as compared with propylene homopolymers and have considerably low heat resistance, imposing a limitation on the temperature at which they are used. Thus, the field of use of these copolymers is limited.
In order to enhance impact resistance of propylene homopolymers at low temperatures, propylene block copolymers, which are produced by forming a propylene homopolymer component and, subsequently forming an ethylene-propylene random copolymer, are widely employed in a variety industrial fields, beginning with in automobiles and domestic electric appliances and articles for daily use.
These conventionally employed propylene block copolymers have excellent impact resistance, but have considerably poor transparency as compared with propylene homopolymers. Thus, the block copolymers undergo severe blushing under impact.
In order to overcome undesirable impact-induced-blushing of these propylene block copolymers, there have been proposed a method involving increasing the ethylene content of a copolymer and a method involving addition of polyethylene to a propylene block copolymer. These two methods are excellent in view of mitigation of impact-induced-blushing; however, the transparency of molded articles decreases.
In addition, Japanese Patent Application Laid-Open (kokai) No. 5-331327 discloses a polymer composition in which only the ratio of intrinsic viscosity of the propylene homopolymer component to that of the ethylene-propylene random copolymer component is specified in a propylene block copolymer and, Japanese Patent Application Laid-Open (kokai) No. 6-145268 discloses a polymer composition in which the ratio of intrinsic viscosity of the propylene homopolymer component to that of the ethylene-propylene random copolymer component and the ethylene content of the ethylene-propylene random copolymer component are both specified.
However, when injection-molded articles of the aforementioned polymer composition were tested for properties including impact resistance, blushing, and haze (which is an index of transparency), it was found that these properties were improved as compared with conventional propylene block copolymer, but that the degree of improvement was still unsatisfactory.
As described in Japanese Patent Application Laid-Open (kokai) Nos. 56-72042 and 57-63350 discloses a polyolefin resin compositions formed by blending an ethylene-propylene copolymer containing a small amount of ethylene with an ethylene-propylene block copolymer. However, the resin composition has drawbacks; e.g., an economical disadvantage due to the requirement for a blending step and a decrease in performance of final products due to poor dispersion of components.
Japanese Patent Application Laid-Open (kokai) Nos. 8-92338 and 9-87343 disclose a polypropylene-b-poly(ethylene-co-propylene) comprising a polypropylene segment and a poly(ethylene-co-propylene) segment, with the two types of segments being chemically linked, and a method of producing the same. Specifically, disclosed therein are block copolymers having a number-average molecular weight (Mn) of 11,000-20,000; a molecular weight distribution index (weight-average molecular weight (Mw)
umber-average molecular weight (Mn)) of 3.3-3.8; and an ethylene content of 26 mol %.
However, such polymers having a low weight-average molecular weight are not suitable for producing general-purpose molded articles.
Japanese Patent Application Laid-Open (kokai) No. 9-241334 discloses a block copolymer having an intrinsic viscosity [&eegr;] of 0.8, a block copolymer segment content of 34 wt. %, and an ethylene content of the block copolymer segment of 40 wt. %.
However, the polymer disclosed therein also has a weight-average molecular weight of as low as approximately 80,000, and thus, it is not suitable for producing general-purpose molded articles.
In addition, there have conventionally been known polyolefin thermoplastic elastomers produced by incorporating, into a polypropylene polymer, an amorphous ethylene-&agr;-olefin random copolymer or by incorporating, into a polypropylene polymer, a hydrogenated product of a styrene-butadiene block copolymer. These elastomers are disclosed in, for example, Japanese Patent Application Laid-Open (kokai) Nos. 50-14742, 52-65551, 58-206644, and 58-215446.
However, the elastomer compositions produced by incorporating, into a polypropylene copolymer, a hydrogenated product of a styrene-butadiene block copolymer and hydrocarbon oil for improving flowability provide molded articles having a disadvantageously decreased mechanical strength (tensile strength and bending strength). Although the elastomer compositions produced by incorporating, into a polypropylene polymer, an amorphous ethylene-&agr;-olefin random copolymer have good rubber elasticity, the compositions disadvantageously exhibit poor mold-releasability during molding thereof and, if the amorphous ethylene-&agr;-olefin random copolymer content is high, even no mold-releasability at all.
Japanese Patent Application Laid-Open (kokai) No. 61-14248 discloses an elastomer composition produced by incorporating, into a propylene-ethylene block copolymer, a hydrogenated product of a styrene-butadiene-styrene block copolymer and, optionally, an amorphous ethylene-propylene rubber.
However, the above elastomer composition still have a problem in that it provides molded articles with a defective appearance due to, e.g., flow marking on the surfaces of produced articles.
The elastomer composition produced by adding optional amorphous ethylene-propylene rubber to a mixture of a propylene homopolymer and the aforementioned hydrogenated product of a styrene-butadiene block copolymer cannot attain favorable rubber elasticity and has an insufficient impact resistance at low temperatures. Although a similar elastomer composition employing a propylene-ethylene random copolymer instead of the aforementioned propylene homopolymer provides molded articles having excellent mech
Matsukawa Tetsuya
Satake Hideshi
Takahashi Masato
Terano Minoru
Chisso Petrochemical Corporation
Teskin Fred
Wenderoth , Lind & Ponack, L.L.P.
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