Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2001-11-09
2003-05-20
Tarazano, D. Lawrence (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036700, C428S475800, C428S476100, C428S476300, C428S520000, C428S522000, C524S404000, C524S405000, C525S060000
Reexamination Certificate
active
06565938
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a resin composition comprising a saponified ethylene-vinyl acetate copolymer (hereinafter referred to briefly as EVOH) and a laminate comprising the same. More particularly, the invention relates to a resin composition capable of providing shaped articles outstanding in such characteristics as gas barrier properties, low-temperature heat drawability, long-run melt moldability, and appearance and to a laminate comprising said resin composition, such as a multi-lamellar vessel.
BACKGROUND ART
EVOH generally is good in clarity, gas barrier properties, aroma retentivity, solvent resistance and oil resistance, among other properties, and, exploiting these features, have heretofore been used in various packaging applications, namely as packaging materials for foods, pharmaceuticals, industrial chemicals and agrochemicals.
The sheet (inclusive of film) of EVOH is frequently stretched under heating for improving its mechanical strength and other properties and the heat-drawability of an exclusive EVOH sheet or a multi-layer sheet comprising an EVOH layer is an important requirement.
Particularly in recent years, a multi-lamellar vessel comprising a laminate comprised of a polystyrene resin layer and an EVOH layer, which is excellent in rigidity, clarity and surface gloss, is attracting attention. Thus, a multi-lamellar vessel having a laminar structure having a polystyrene resin layer on either side, i.e. the inside and outside of the vessel, namely “the polystyrene resin layer/adhesive resin layer/EVOH layer/adhesive resin layer/polystyrene layer” and a multi-lamellar vessel comprising a polyethylene layer, which has good heat sealability by itself, as the innermost layer constituting the inside wall of the vessel and a polystyrene resin layer as the outermost layer constituting the outside wall of the vessel, namely the “polyethylene resin layer/adhesive resin layer/EVOH layer/adhesive resin layer/polystyrene resin layer” are demanded by the market as very useful packaging materials.
Furthermore, laminates not using polystyrene resin, such as one having the “polyethylene resin layer/adhesive resin layer/EVOH layer/adhesive resin layer/polyethylene resin layer structure” and one having the “polyethylene resin layer/adhesive resin layer/EVOH layer/adhesive resin layer/polypropylene resin layer structure” are also demanded by the ecology-conscious market.
However, EVOH is inferior to thermoplastic resins such as polystyrene and polyolefin in heat-drawability or heat-moldability. To overcome this drawback, the following corrective methods, among others, have so far been proposed.
(1) The method which comprises adding a plasticizer to EVOH (JP Kokai S53-88067; JP Kokai H59-20345).
(2) The method which comprises blending a polyamide resin with EVOH (JP Kokai S52-141785; JP Kokai S58-36412).
(3) The method which comprises using a resin composition comprising two or more different grades of EVOH (JP Kokai S61-4752, S60-173038, S63-196645, S63-230757, S63-264656, H2-261847).
(4) The method which comprises blending a copolymer polyamide resin having a defined melting point with EVOH (JP Kokai S62-225543, S62-225544, S63-114645).
However, detained investigations by the present inventors revealed that the EVOH compositions described in the above literature have the following disadvantages.
The compositions disclosed in the above first group (1) of literature are drastically handicapped in gas barrier properties.
The compositions disclosed in the second group (2) of literature tend to be low in long-run melt-moldability.
The compositions disclosed in the above third and fourth groups (3) and (4) of literature have been somewhat improved in heat-drawability but are not satisfactory enough for use in applications where laminates with a polystyrene resin are heat-drawn in a high draw ratio at a low temperature, and have room for further improvement.
In addition, there is room for improvement in the appearance of a multi-lamellar vessel and in deep-drawability.
Under the circumstances, the present invention has for its object to provide an EVOH resin composition capable of providing shaped articles outstanding in gas barrier properties, low-temperature heat-drawability, long-run melt-moldability and appearance, among other characteristics, and a multi-lamellar vessel or other laminate comprising said resin composition.
DISCLOSURE OF INVENTION
The resin composition of the invention comprises a saponified ethylene-vinyl acetate copolymer (A), a polyamide resin having a melting point of not higher than 160° C. (B), and a boron compound (C).
The laminate of the invention is a multi-lamellar shaped article comprising a resin composition layer (X) composed of a saponified ethylene-vinyl acetate copolymer (A), a polyamide resin (B) having a melting point not exceeding 160° C., and a boron compound (C) and, as disposed on at least one side of said layer (X), a thermoplastic resin layer (Y). A representative example of said laminate is a heat-drawn multi-lammelar vessel as draw-molded in a draw ratio of 4~20.
The invention is now described in detail.
<EVOH (A)>
The EVOH (A) for use in the invention is not particularly restricted but is preferably one having an ethylene content of 10~70 mole % (especially 20~60 mole %, particularly 25~50 mole %) and a saponification degree of not less than 90 mole % (especially not less than 95 mole %, particularly not less than 99 mole %) If the ethylene content is less than 10 mole %, the high-temperature gas barrier properties, melt-moldability and appearance will become inadequate. On the other hand, if it exceeds 70 mole %, no sufficient gas barrier properties will be obtained. If the degree of saponification is less than 90 mole %, the gas barrier properties, thermal stability and moisture resistance will be inadequate.
The melt flow rate (MFR) (as measured at 210° C. under a load of 2160 g) of EVOH (A) is not particularly restricted but is preferably in the range of 0.5~100 g/10 min (especially 1~50 g/10 min, particularly 3~35 g/10 min). If the melt flow rate is below the above-mentioned range, the extruder interior will develop a high-torque condition at molding to make extrusion difficult. On the other hand, if the MFR is in excess of the above-mentioned range, the thickness accuracy of the shaped article tends to be decreased.
EVOH (A) can be obtained by saponifying an ethylene-vinyl acetate copolymer (EVA) produced by the known polymerization technology such as solution polymerization, suspension polymerization or emulsion polymerization. The saponification of the ethylene-vinyl acetate copolymer (EVA) can also be carried out by the known technology.
The EVOH (A) mentioned above may have been “copolymerization-modified” with a copolymerizable ethylenically unsaturated monomer up to the extent not interfering with the effect of the invention. The monomer which can be used in this manner includes
olefins such as propylene, 1-butene, isobutene, etc.;
unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, phthalic acid (anhydride), maleic acid (anhydride), itaconic acid (anhydride), etc. and their salts or mono- or dialkyl (C
1-18
) esters;
acrylamides such as acrylamide, N-(C
1-18
)alkylacrylamides, N,N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid and its salts, and acrylamidopropyldimethylamine and its acid salts or quaternary salts;
methacrylamides such as methacrylamide, N-(C
1-18
)alkylmethacrylamides, N,N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid and its salts, methacrylamidopropyldimethylamine and its acid salts or quaternary salts;
N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, etc.;
vinyl cyanides such as acrylonitrile, methacrylonitrile, etc.;
vinyl ethers such as (C
1-18
) alkyl vinyl ethers, hydroxyalkyl vinyl ethers, alkoxyalkyl vinyl ethers, etc.;
vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl bromide, etc.;
vinylsilanes such as trimethoxyvinylsilane etc.;
allyl acetate,
Ninomiya Kenji
Toyosumi Masahiko
Armstrong Westerman & Hattori, LLP
Nippon Gohsei Kagaku Kogyo Kabushiki Kaisha
Tarazano D. Lawrence
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