Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2000-07-07
2004-07-06
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036600, C428S327000, C428S407000
Reexamination Certificate
active
06759107
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermoplastic resin composition having oxygen absorbency. The present invention further relates to a resin composition having good gas barrier properties against oxygen, carbon dioxide gas or the like, good moisture-resistance, good aroma retentivity, and good flavor barrier properties, in addition to good oxygen absorbency. The present invention further relates to a multilayered structure using such a composition that has a good appearance, in particular good transparency, in uses such as packaging containers for drinks, foods, medicines, cosmetics and the like.
2. Description of the Related Art
Gas barrier resins such as an ethylene-vinyl alcohol copolymer (hereinafter may be referred to as EVOH) generally can be melt-molded, and thus are used in a wide range as a material having excellent oxygen or carbon dioxide gas barrier properties to be formed into packaging films, sheets, bottles and containers. Multilayered gas-barrier resin packaging materials obtained by laminating the above-mentioned gas barrier resin and a thermoplastic resin having excellent moisture resistance, mechanical properties and the like, especially polyolefin resin, are broadly used as containers that have excellent oxygen barrier properties in the form of bags, bottles, cups and pouches, for example, in a variety of fields such as foods, cosmetics, medicines, chemicals and toiletries.
The above packaging materials using gas barrier resins have good barrier properties against oxygen and carbon dioxide gas. However, the permeability thereof against gases such as oxygen gas is not exactly zero, unlike metals, used for cans and the like, and glass, used for bottles and the like, but still permits transmission of an amount of gas that is not negligible. As for packaging materials, especially for foods, the degradation of foods due to oxidation when they are preserved for an extended period of time is of great concern.
As mentioned above, in order to protect packaged contents such as foods, in particular, contents that are susceptible to oxidation or the like, a means for blocking oxygen and carbon dioxide gas such as the multilayered gas barrier resin materials can be used. Moreover, it is desired to absorb the oxygen that entered the container together with the contents during the packaging and filling of the contents in order to prevent the contents from being degraded. For this purpose, it is proposed to enclose an oxygen absorbent or to provide the oxygen absorption function to a resin of a packaging material by mixing an oxygen absorbent in the resin.
As the method of providing the oxygen absorption function to the EVOH that is a packaging material, the following methods are proposed: (1) An oxidation catalyst such as a transition metal is added to the EVOH to facilitate the oxidation of the EVOH so that oxygen can react with the EVOH as it is transmitted in a film composed of the EVOH, thereby giving the oxygen absorption function to the EVOH (Japanese Laid-Open Patent Publication No. 4-211444); (2) A mixture substantially composed of polyolefin and an oxidation catalyst is dispersed in the EVOH so that oxygen can react with the polyolefin in the EVOH as it is transmitted in a film of EVOH containing the mixture, thereby obtaining a resin composition having the oxygen absorption function (Japanese Laid-Open Patent Publication No. 05-156095); and (3) EVOH, polyolefin, and an oxidation catalyst are blended so that oxygen can react with the polyolefin and the EVOH as the oxygen is transmitted in a film of the mixture of the EVOH and polyolefin, thereby obtaining a resin composition having the oxygen absorption function (Japanese Laid-Open Patent Publication No. 05-170980).
However, method (1) fails to provide sufficiently improved oxygen barrier properties. Moreover, the transparency is not adequate due to the addition of the large amount of oxidation catalyst. Methods (2) and (3) also have a drawback in that the transparency is reduced due to the addition of polyolefin to the EVOH.
SUMMARY OF THE INVENTION
A first thermoplastic resin composition of the present invention comprises a thermoplastic resin (A), a multilayered polymer particle (B) and a transition metal salt (C), wherein the multilayered polymer particle (B) has at least one oxygen absorption layer, the oxygen absorption layer comprises a diene polymer (B1) containing a conjugated diene monomer as a polymerization component, and the transition metal salt (C) is contained in an amount of 1 to 5000 ppm in terms of a metal element thereof.
A second thermoplastic resin composition of the present invention comprises a thermoplastic resin (A) and a multilayered polymer particle (B), wherein the multilayered polymer particle (B) has at least one oxygen absorption layer, the oxygen absorption layer comprises a diene polymer (B1) containing a conjugated diene monomer as a polymerization component, and the oxygen absorption rate of the composition is 0.01 ml/m
2
·day or more.
In a preferred embodiment, the resin composition comprises the thermoplastic resin (A) in an amount of 10 to 99.9 wt %, and the multilayered polymer particle (B) in an amount of 0.1 to 90 wt %.
In a preferred embodiment, the thermoplastic resin (A) is at least one selected from the group consisting of a polyvinyl alcohol resin (A1), a polyamide resin (A2), and a polyester resin (A3).
In a preferred embodiment, the diene polymer (B1) is at least one selected from the group consisting of a polymer having only a conjugated diene monomer as a polymerization component, and a polymer having a conjugated diene monomer and another copolymerizable vinyl monomer as polymerization components.
In a preferred embodiment, the transition metal salt (C) is at least one selected from the group consisting of iron salts, nickel salts, copper salts, manganese salts, and cobalt salts.
In a preferred embodiment, the thermoplastic resin (A) is a polyvinyl alcohol resin (A1), and the polyvinyl alcohol resin (A1) is an ethylene-vinyl alcohol copolymer having an ethylene content of 3 to 60 mol % and a degree of saponification of 90% or more.
In a preferred embodiment, a polymer constituting the multilayered polymer particle (B) contains carbon-carbon double bonds in an amount of 0.0001 eq/g or more based on the weight of the particle (B).
In a preferred embodiment, the difference in the refractive index between the thermoplastic resin (A) and the multilayered polymer particle (B) is 0.01 or less.
In a preferred embodiment, a plurality of the multilayered polymer particles (B) are dispersed in a matrix of the thermoplastic resin (A).
A third thermoplastic resin composition of the present invention comprises a multilayered polymer particle (B) and a transition metal salt (C); wherein the multilayered polymer particle (B) has at least two thermoplastic resin layers, one of which is an oxygen absorption layer made of a resin or a resin mixture containing a diene polymer (B1) having a conjugated diene monomer as a polymerization component; wherein the diene polymer (B1) contains the conjugated diene monomer as a polymerization component in an amount of 10 mol % or more, based on the total amount of the resin constituting the oxygen absorption layer; wherein the other layer does not substantially contain the diene polymer (B1), and the layer is the outermost layer of the multilayered polymer particle (B); and the transition metal salt (C) is contained in an amount of 1 to 5000 ppm in terms of a metal element thereof.
The present invention also includes a multilayered structure comprising any one of the above-mentioned thermoplastic resin compositions.
The present invention further includes a multilayered container comprising any one of the above-mentioned thermoplastic resin compositions.
The present invention further includes a multilayered film comprising any one of the above-mentioned thermoplastic resin compositions and having a total thickness of 300 &mgr;m or less.
The present invention further includes a multilayere
Mukoo Yoshiki
Nakaya Masakazu
Sato Toshiaki
Shimo Hiroyuki
Tai Shinji
Kuraray Co. Ltd.
Nolan Sandra M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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