Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-03-07
2004-06-22
Huff, Mark F. (Department: 1752)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S405000, C524S416000, C524S417000, C524S280000, C524S399000, C525S056000, C525S057000, C525S060000, C526S160000, C526S943000, C428S036600, C428S035400, C428S515000, C428S516000, C428S518000, C428S520000, C428S523000
Reexamination Certificate
active
06753370
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin composition having superior melt molding properties, gas barrier properties, flexural fatigue resistance, and impact resistance. The present invention also relates to a multilayered structure, particularly one which has good appearance, good delamination resistance, good transparency, good impact resistance, and good gas barrier properties.
2. Description of the Background
Ethylene-vinyl alcohol copolymer (occasionally referred to as EVOH hereinafter) finds general use because of its good melt molding properties and gas barrier properties. In particular, it is useful in the form of multilayered plastic packaging material after lamination with a thermoplastic resin, (especially a polyolefin resin), which possesses superior moisture resistance and mechanical properties. This packaging material finds applications in the manufacture of bags, bottles, cups, pouches, and the like in a variety of areas, including foods, cosmetics, medicines, chemicals, and toiletries, on account of its good oxygen barrier properties.
Production of multilayered plastic containers inevitably gives rise to regrinds (scraps), such as edges trimmed from extruded sheets and films, flashes pinched from blow-molded bottles, and scraps punched from molded cups. Recycling of these regrinds is necessary for cost and material savings. To this end, a method for utilizing regrinds has been proposed by incorporating such into layers of a thermoplastic resin such as a polyolefin as a major constituent (Examined Published Japanese Patent Application No. 59-29409) and a method for utilizing regrinds by interposing a layer of regrinds between a layer of thermoplastic such as a polyolefin and a layer of EVOH (Unexamined Published Japanese Patent Application No. 59-101338).
The recycling of regrinds in the above-mentioned manner presents several difficulties. That is, when a thermoplastic resin, especially a polyolefin resin, and EVOH are extruded together with regrinds, EVOH tends to deteriorate, giving rise to black scorches which adhere to the insides extruders and to gel-like substances (gum) which adhere to the die lips of extruders. Moreover, deterioration of EVOH is accompanied by heterogeneous phase separation, which gives rise to foreign matter and anomalous flow. This results in containers having a poor appearance, having an odor of decomposed resin, and having poor mechanical properties such as impact resistance These difficulties prevent normal extrusion operation or restrict operation times. In addition, the presence of regrinds causes a wavy pattern on the surface of molded articles or causes interlayer or intralayer delamination when a blend of polyolefin and EVOH is coextruded with EVOH or polyolefin.
One way to address this problem is to incorporate the blend of EVOH and polyolefin resin into a polar group-modified polyolefin (typified by carboxylic acid-modified polyolefin), as disclosed in Unexamined Published Japanese Patent Application Nos. 49-57086, 3-72539, 5-98084, 61-111346, and 8-27332.
On the other hand, EVOH has the disadvantage of having poor flexibility, flexural fatigue resistance, and impact resistance. Therefore, it is not necessarily suitable for flexible bags and pouches, which need good flexural fatigue resistance, and bottles and cups, which need good impact resistance.
One way to improve the impact resistance and flexural resistance of EVOH is to incorporate a soft polyolefin into EVOH. An example of a soft polyolefin is a low-density polyethylene having a density of 0.086-0.91 g/cm
3
, which is produced by using a Ziegler catalyst. (See Unexamined Published Japanese Patent Application No. 62-153333.) Nevertheless, the object of improving impact resistance and flexural resistance has not been achieved satisfactorily
A recent polyolefin, which is attracting attention, is produced with a single-site catalyst having uniform polymerization active sites. In comparison to conventional polyolefins, it has a narrower molecular weight distribution and composition distribution. Consequently, it has superior transparency, strength, adhesiveness, heat-sealability, impact resistance, leaching resistance, and blocking resistance. It is under extensive study for development.
The ethylene-&agr;-olefin copolymer produced by using a single-site catalyst finds many uses in the form of laminate with EVOH. Applications of the laminate include packaging laminate film (Unexamined Published Japanese Patent Application No. 7-232418), coextrusion film (Unexamined Published Japanese Patent Application No. 7-314624), multilayered film for balloon forming (Unexamined Published Japanese Patent Application No. 7-284570), heat-shrinkable film (Unexamined Published Japanese Patent Application No. 7-309962), and retort packaging material (Unexamined Published Japanese Patent Application No. 7-266520). These patent publications, however, do not mention anything about compositions of EVOH and ethylene-&agr;-olefin copolymer and the recycling of regrinds.
A laminate is disclosed in Unexamined Published Japanese Patent Application No. 7-102133, which is made of a layer of EVOH and a layer of a resin composition comprising an ethylene-&agr;-olefin copolymer produced with a single-site catalyst and a carboxylic acid-modified polyolefin. This resin composition is designed so as to provide good adhesiveness for a variety of resins such as nylon, EVOH, polyester, and ethylene-vinyl acetate copolymer. This patent application does not mention anything about composition comprising an ethylene-&agr;-olefin copolymer, a carboxylic acid-modified polyolefin, and EVOH, nor does it mention anything about laminate having a layer of regrinds.
A laminate is disclosed in Unexamined Published Japanese Patent Application No. 7-329262 which is made up of a layer of a composition comprising recovered polyethylene, produced with a conventional catalyst, and a carboxylic acid-modified polyolefin, a layer of ethylene-&agr;-olefin copolymer produced with a single-site catalyst, and a layer of EVOH. The laminate is characterized by good adhesion between the first two layers. This patent application, however, does not mention anything about incorporating the ethylene-&agr;-olefin copolymer produced with a single-site catalyst with EVOH and further with a carboxylic acid modified polyolefin.
A laminate is disclosed in Unexamined Published Japanese Patent Application No. 6-166157 which is made up of a layer of syndiotactic polypropylene produced with a single-site catalyst, a layer of EVOH, a layer of a carboxylic acid-modified polyolefin, and a layer of regrinds. This patent publication, however, does not mention anything about the composition used for the layer of regrinds. In addition, the laminate does not have a layer of an ethylene-&agr;-olefin copolymer produced by using a single-site catalyst. A need continues to exist for a laminate of improved properties, which is prepared from regrinds.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a resin formulation which contains regrinds, which possesses improved impact resistance, flexural fatigue resistance, delamination resistance and gas barrier properties.
Briefly, this object and other objects of the present invention as hereinafter will become more readily apparent can be attained by a resin composition which comprises a copolymer (A) comprising ethylene as a major component produced with a single-site catalyst, and an ethylene-vinyl alcohol copolymer (B) having an ethylene content of 20-60 mol. % and a degree of hydrolysis of 95% or above, said resin composition satisfying the following equation (1):
1/99≦(weight of (
A
)}/{weight of (
B
)}≦99/1 (1)
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An ethylene-&agr;-olefin copolymer produced with a single-site catalyst displays marked characteristics when used as a laminate with EVOH, as mentioned above. Production of laminates accompanies regrinds, and an effective use of regrinds is
Nakatsukasa Shigeki
Ohgi Hiroyuki
Yoshimi Kazuyori
Gilliam Barbara
Huff Mark F.
Kuraray Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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