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
2000-04-05
2002-03-05
Hoke, Veronica P. (Department: 1714)
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
active
06353048
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a resin composition comprising a saponified ethylene-vinyl acetate copolymer (hereinafter referred to briefly as EVOH) and a specified metal soap. The invention further relates to a resin composition comprising, in addition to said copolymer and metal soap, a thermoplastic resin and/or an inorganic filler.
This invention further relates to a laminate comprising such a resin composition.
BACKGROUND OF THE INVENTION
EVOH in general is excellent in clarity, gas-barrier properties, aroma retention, solvent resistance, oil resistance, etc. and, by taking advantage of these characteristics, has been utilized in various forms such as film, sheet, bottle, etc. in the packaging of foods, pharmaceutical products, industrial chemicals, agrochemicals and other articles of commerce.
The film, sheet, bottle, cup, tube, pipe, etc. of EVOH are generally manufactured by the melt-molding technique and the processability (moldability) of the material resin composition is of great importance.
Thus, prevention of streaking in long-run molding, prevention of resin stagnation in the extruder, and purgeability are crucial factors in the quality of finished products.
Addressing itself to improving said processability, JP Kokai S64-64843 discloses a laminate manufactured by using an EVOH having a specified viscosity characteristic, particularly an EVOH treated with a specified metal salt and a specified acid in combination.
JP Kokai H2-99546 describes a resin composition comprising EVOH and a fluorine-containing compound and JP H9-234833 teaches formulating a crosslinking agent in EVOH. The present applicant also proposed to incorporate a hydrotalcite compound in EVOH in JP Kokai H1-308440.
The technology disclosed in JP Kokai S64-64843 referred to above contributes somewhat to improved processability but fails to insure sufficient thermal stability so that the problems of malodor and discoloration under the heat of melt-molding are sometimes encountered. The technology disclosed in JP H2-99546 also contributes to improved processability but the effect is not sufficient and the product appearance is sometimes sacrificed. The technology disclosed in JP H9-234833 is not sufficiently effective in improving processability and, moreover, has been found to be poor in purgeability. The technology disclosed in JP H1-308440 is also found to be insufficient in the prevention of stagnation at the die lip. Thus, the prior art in general has room for improvement.
In applications such as the packaging film, sheet, bottle etc. in the fields of foods, pharmaceutical products, industrial chemicals, and agrochemicals, EVOH is frequently used as blended with thermoplastic or other resins. Thus, in the multi-layer coextrusion of EVOH and thermoplastic resin, a resin blend in lieu of the respective resins is used or a layer of such blend is often interposed between the EVOH and the thermoplastic resin layer. The former technology is intended to attain a synergistic effect in terms of the gas barrier properties of EVOH and the mechanical strength of thermoplastic resin as well as an improvement in drawing characteristic, while the latter technology is intended to improve the interlayer bond strength between the EVOH and thermoplastic resin layers.
However, such polymer blends as mentioned above are not always good in compatibility and tend to undergo phase separation or overreaction in molding to adversely affect the appearance of products.
Therefore, it was proposed to improve said compatibility by formulating an oxide or fatty acid salt of a metal selected from the metals belonging to Groups 1, 2 and 3 of Periodic Table of the Elements in a blend of EVOH and thermoplastic resin [JP Kokai H3-149239, JP Kokai H6-212038].
The above technology is somewhat effective but still unsatisfactory in the compatibility in long-run processing so that a further improvement is required.
Meanwhile, EVOH products are liable to be affected by heat and water, for example in retort sterilization, and be markedly reduced in post-treatment gas barrier properties. To overcome this drawback, JP Kokai H5-193076 proposes a multi-layer container comprising a resin composition layer comprising EVOH and a specified inorganic filler.
Formulating an inorganic powder, such as an inorganic filler powder, in EVOH results in some improvement in said gas barrier properties but in long-run melt-molding, the inorganic particles aggregate to cause poor dispersion, or because of the strong tendency of the resin composition toward thickening with time, the resin is liable to pool in the die region. Therefore, a further improvement is required.
OBJECT OF THE INVENTION
The object of this invention is to reconcile the thermal stability and processability of EVOH, improve the compatibility of EVOH and thermoplastic resin in a polymer blend, and improve the dispersibility of an inorganic filler and anti-stagnation property of a blend comprising EVOH and said inorganic filler in long-run molding.
SUMMARY OF THE INVENTION
The resin composition of this invention is characterized by its comprising a saponified ethylene-vinyl acetate copolymer (A) with an ethylene content of 20~60 mole % and a saponification degree of not less than 90 mole % and a metal soap (B) of the following general formula (1) as obtainable by reacting one or more species of aliphatic monocarboxylic acid containing 12~30 carbon atoms with an oxide or hydroxide of a metal belonging to Group 2 of Periodic Table of the Elements by a dry direct reaction method.
&agr;MO.M(OOCR)
2
(1)
wherein a represents a numerical value of 0.1~1.0; M represents a bivalent metal belonging to Group 2 of Periodic Table of the Elements; R represents a saturated or unsaturated alkyl group containing 11~29 carbon atoms.
Optionally, the above composition may comprise a thermoplastic resin (C) in addition to said saponified ethylene-vinyl acetate copolymer (A) and metal soap (B).
Furthermore, the composition may comprise an inorganic filler in addition to said saponified ethylene-vinyl acetate copolymer (A) and metal soap
DETAILED DESCRIPTION OF THE INVENTION
EVOH (A) for use in this invention has an ethylene content of 20~60 mole % (preferably 25~55 mole %) and a saponification degree of not less than 90 mole % (preferably not less than 95 mole %). If the ethylene content is less than 20 mole %, high-humidity gas barrier properties and melt moldability will be inadequate. Conversely, if the ethylene content exceeds 60 mole %, no sufficient gas barrier properties will be obtained. Further, if the degree of saponification is less than 90 mole %, gas barrier properties, thermal stability and moisture resistance will be sacrificed.
Within the range not detracting from the effect of the invention, it is possible to use two or more kinds of EVOH varying in chemical structure and/or molecular weight or even add an acid component (acetic acid, phosphoric acid, boric acid, etc.).
The melt index (MI) (210° C., load 2160 g) of said EVOH (A) is not particularly restricted but is preferably 1~100 g/10 minutes (preferably 3~50 g/10 minutes). If said melt index is smaller than said range, high torques will develop within the extruder to make extrusion difficult. On the other hand, if said melt index is larger than said range, the mechanical strength of products will be undesirably low.
The EVOH (A) mentioned above can be obtained by saponifying an ethylene-vinyl acetate copolymer and this ethylene-vinyl acetate copolymer can be prepared by a known polymerization reaction such as solution polymerization, suspension polymerization, emulsion polymerization or the like. The saponification of such an ethylene-vinyl acetate copolymer can also be carried out by a known procedure.
In the practice of the invention, said EVOH (A) may further contain a copolymerizable ethylenically unsaturated monomer component within the range not interfering with the effect of the invention and as such monomer or monomers, there can be mentioned olefins, e.g. propylene, 1-butene, isobutene; unsatu
Onishi Hideshi
Sogawa Masashi
Armstrong, Wester & Hattori, LLP
Hoke Veronica P.
Nippon Gohsei Kagaku Kogyo Kabushiki Kaisha
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