Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2000-02-17
2001-07-10
Woodward, Ana (Department: 1711)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S515000, C428S520000
Reexamination Certificate
active
06258464
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a resin composition which has good compatibility of individual components contained therein and is substantially free of any flow anomaly, and also to a multilayered structure which exhibits a good appearance and has good impact resistance, delamination resistance, and gas barrier properties.
2. Description of the Prior Art
Multilayered plastic packaging materials are known wherein a layer of a thermoplastic resin, particularly a polyolefin resin (hereinafter referred to simply as PO), having good moistureproofing and mechanical characteristics and a layer of a saponified product of an ethylene-vinyl ester copolymer (hereinafter referred to simply as EVOH) having good oxygen barrier properties are laminated through an adhesive resin. Such packaging materials have wide utility in various fields such as of foods, cosmetics, medicines and chemicals, toiletries and the like as containers having good oxygen barrier properties in the form of bottles, cups, pouches and the like.
When the multilayered plastic containers are fabricated, it is inevitable that burrs be undesirably produced owing to the pinch-off for blow molding and regrinds (scraps) such as of waste plastics after punching be left for cup molding. Accordingly, the re-use of these inevitable scraps has been accepted as being necessary from the standpoint of costs and resource saving. In order to effectively re-use the regrinds, there have been proposed several methods including a method wherein the regrinds are mixed in the thermoplastic resin layer primarily made of a polyolefin (Japanese Patent Publication No. Sho 59-29409), and a method wherein a regrind layer is provided between the thermoplastic layer such as of a polyolefin and the EVOH layer (Japanese Patent Laid-open No. Sho 59-101338). However, where regrind resins containing thermoplastic resins, especially polyolefin resins, and the EVOH are subjected to co-melt extrusion molding, the EVOH tends to deteriorate. During the course of the blend melt extrusion, black deposits (“charred resin”) may be formed in the inside of the extruder, or gel-like matters (“lip stain”) may be deposited such as on the dielip during the extrusion. This eventually leads to the troubles such as the formation of foreign matters resulting from non-uniform phase separation, flow anomalies, a lowering in appearance of the resultant molded container, the generation of offensive odor from the decomposed resins, lowerings of mechanical characteristics such as impact resistance, and the like. Thus, the extrusion molding of such a composition as mentioned above has been substantially impossible to perform, or can, if ever, be carried out only for a short time in most cases. On the other hand, where the blend of a polyolefin and EVOH and EVOH are subjected to co-extrusion molding, wavy patterns are formed on the surfaces of molded articles, along with delamination (intralayer and interlaminar separations) occurring in the articles.
Japanese Patent Laid-open No. Sho 49-57086 (corresponding to U.S. Pat. No. 3,931,449) has proposed the blends of thermoplastic resins having carbonyl groups at the main chain or side chains thereof (e.g., ionomers, maleic anhydride-grafted polypropylene, ethylene-maleic anhydride copolymer and the like) with low density polyethylene and EVOH in order to improve working properties thereof. Japanese Patent Laid-open No. Hei 3-72539 (corresponding to European Patent 401,666) has proposed the blends of an EVOH having a high content of ethylene and polyolefins modified through grafting of unsaturated carboxylic acids thereto, with polyolefins and EVOH so as to improve the appearance of molded articles obtained therefrom. Further, Japanese Patent Laid-open No. Hei 5-98084 has proposed the blends of unsaturated carboxylic acid-modified polyolefins with polyolefins and EVOH in order to improve a resistance to environmental stress-cracking.
However, as will become apparent from Comparative Examples 5 to 7 and 12 to 14, the compositions comprising ionomers, maleic anhydride-grafted polypropylene and ethylene-maleic anhydride copolymer, respectively, are not satisfactory with respect to the impact resistance and the intralayer separation strength.
Moreover, it is stated in Japanese Patent Laid-open No. Sho 61-111346 (U.S. Pat. No. 4,619,969) that the impact resistance is improved by blending copolymers of ethylene, unsaturated dicarboxylic acid anhydrides and unsaturated esters having from 4 to 12 carbon atoms.
In Japanese Patent Laid-open No. Hei 2-16163, it is set out that blending of inorganic fillers and copolymers of ethylene, acrylic esters and maleic acid derivatives with thermoplastic resins such as EVOH can suppress whitening on mechanical rubbing. However, the above-mentioned U.S. Pat. No. 4,619,969 and the Japanese Patent Laid-open No. Hei 2-16163 do not set forth the use of the ethylene-maleic anhydride-acrylic ester copolymer as a compatible agent for EVOH and polyolefins.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a resin composition which can overcome flow anomalies such as charring, lip stain and the like and wherein scrap resin compositions such as regrinds are effectively re-used.
It is another object of the invention to provide molded articles, particularly multilayered structures, using at least such a resin composition as mentioned above which are substantially free of any wavy pattern and have a good appearance along with good impact resistance, interlaminar separation resistance and gas barrier properties.
The above objects can be achieved, according to one embodiment of the invention, by a resin composition which comprises:
(A) a polyolefin (abbreviated as PO (A));
(B) a saponified product of an ethylene-vinyl ester copolymer having an ethylene content of from 10 to 70 mole %, and a saponification degree of the vinyl ester component of not less than 80%, and a melting point of from 125° C. to 220° C. (abbreviated as EVOH (B)); and
(C) an olefin-unsaturated dicarboxylic anhydride-unsaturated carboxylic ester or vinyl ester copolymer (abbreviated as modified PO (C))
wherein the following formulas (I) and (II) are satisfied
1/99≦weight of (
B
)/weight of (
A
)≦40/60 (I)
0.1/99.9
≦X
≦20/80 (II)
wherein X=weight of (C)/total weight of (A) and (B).
According to another embodiment of the invention, there is also provided a multilayered structure which comprises at least two layers including a layer made of the composition defined above and a layer made of a saponified product of an ethylene-vinyl ester copolymer (abbreviated as EVOH (B)) having an ethylene content of 10 to 70 mole % and a saponification degree of the vinyl ester component of not less than 90%.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the practice of the invention, the polyolefins (A) (PO (A)) used in the resin composition include, for example, olefin homopolymers or copolymers of olefins and monomers copolymerizable with the olefins such as polyethylene resins, polypropylene resins, polystyrene resins, ionomers, ethylene-vinyl acetate copolymers, ethylene-(meth)acrylate copolymers, ethylene-propylene copolymers, ethylene-butylene copolymers and the like. Of these, polyethylene resins such as low density polyethylene, medium density polyethylene, high density polyethylene and linear low density polyethylene, polypropylene resins, ethylene-propylene copolymers and ethylene-butylene copolymers are preferred. The polyolefins, especially polyethylene resins, should preferably have a melt index (MI, determined at 190° C. under a load of 2160 g) of from 0.01 to 100 g/10 minutes, more preferably from 0.01 to 50 g/10 minutes, more preferably from 0.01 to 30 g/10 minutes, and most preferably from 0.01 to 10 g/10 minutes.
The EVOH (B) means a saponified product of an ethylene-vinyl ester copolymer. The ethylene content in the product should be in the range of from 10 to 70 mole %, preferably from 20 to 65 mole %, and most preferab
Ikeda Kaoru
Nakano Hiromichi
Negi Taichi
Cummings & Lockwood
Kuraray Co. Ltd.
Woodward Ana
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