Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
2000-10-11
2003-08-12
Tarazano, D. Lawrence (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S520000, C428S522000, C428S461000, C427S388400
Reexamination Certificate
active
06605344
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a gas-barrier film which is produced through application of a metallic compound to the surface of a polymer layer formed from a specific polymer, and more particularly to a gas-barrier film which is produced through application of a metallic compound to a polymer layer formed from a mixture of a poly(meth)acrylic acid polymer and a polyalcohol such as sugar. The present invention provides a gas-barrier film which exhibits excellent oxygen-gas-barrier properties, particularly in an atmosphere of high humidity, and which is suitably used in sterilization treatment such as retorting or boiling.
BACKGROUND ART
Conventionally, in order to enhance gas-barrier properties of plastic films, several processes have been proposed. For example, Japanese Patent Application Laid-Open (kokai) No. 9-157406 discloses a process in which an inorganic layer compound serving as a filler is incorporated into a plastic film, and Japanese Patent Application LaidOpen (kokai) No. 4-366142 discloses a process in which an inorganic compound is deposited on the surface of a plastic film. In the former process, in order to enhance gas-barrier properties of a plastic film, a large amount of inorganic layer compound must be incorporated into the film, and thus properties of a matrix resin, such as transparency and mechanical strength, are impaired. In the latter process, deposition is carried out at high temperature to form a thin film, and a plastic layer may soften due to heat load, and thus a heat-resistant plastic such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or polyimide must be exclusively employed. Also, the latter process is disadvantageous in that when a resin of low Young's modulus is employed, gas-barrier properties of a produced film may deteriorate, since the tensile strength of the resin decreases during deposition and the deposited film is prone to crack.
The latter process is also disadvantageous in that operation is cumbersome and an expensive apparatus is required, since deposition must be carried out in a vacuum apparatus. Japanese Patent Application Laid-Open (kokai) No. 8-142256 discloses a moisture-resistant composite deposition film comprising at least one laminated structure containing a polymer film substrate (A), a deposition film (B) formed of inorganic material which is laminated on at least one surface of the substrate (A), a water-resistant film (C) formed of a sugar and a polycarboxylic acid or a partially neutralized polycarboxylic acid, the film (C) being laminated on the film (B); and a polymer composition layer (D) containing a drying agent, such that the layer (D) is provided on at least one side of the laminated structure. However, the composition film may involve drawbacks similar to those as described above, since a deposition film is employed in the composite film. Therefore, there has been demand for a process for producing a gas-barrier film more simply and conveniently.
In view of the foregoing, an object of the present invention is to provide a gas-barrier film which can be produced through a simple, convenient process and which exhibits excellent gas-barrier properties.
DISCLOSURE OF THE INVENTION
The present inventors have found that the aforementioned problems can be solved by a gas-barrier film which is produced through application of a layer containing a metallic compound (hereinafter the layer may be referred to as a “metallic-compound-containing layer”) to the surface of a polymer layer formed from a mixture of a polyalcohol and at least one poly(meth)acrylic acid polymer selected from the group consisting of poly(meth)acrylic acids and partially neutralized poly(meth)acrylic acids. The present invention has been accomplished on the basis of this finding. Japanese Patent Application Laid-Open (kokai) No. 8-224825 discloses a gas-barrier laminate which is produced from a plastic film and a metallic compound. Japanese Patent Application LaidOpen (kokai) No. 58-128852 discloses a laminate exhibiting excellent adhesion, which is produced from a plastic film and a carboxyl-group-containing polyolefin film with the intervention of a metallic compound. In the aforementioned laminates, metallic compound layers of continuous phase are formed through deposition or sputtering.
Accordingly, in a first aspect of the present invention, there is provided a gas-barrier film which is produced through applying a layer containing a metallic compound to the surface of a polymer layer formed from a mixture of a polyalcohol and at least one poly(meth)acrylic acid polymer selected from the group consisting of poly(meth)acrylic acids and partially neutralized poly(meth)acrylic acids. There is also provided a gas-barrier film wherein the surface of the polymer layer to which the metallic-compound-containing layer is not applied is fixed onto a surface of a substrate. There is also provided a gas-barrier film wherein at least the polymer layer is subjected to heat treatment. There is also provided a gas-barrier film wherein the metallic compound is at least one species selected from the group consisting of magnesium oxide, calcium oxide, zinc oxide, magnesium hydroxide, calcium hydroxide, and zinc hydroxide. There is also provided a gas-barrier film wherein the metallic-compound-containing layer is produced from a mixture of the metallic compound and a resin. There is also provided a gas-barrier film for use in sterilization treatment.
In a second aspect of the present invention, there is provided a laminated gas-barrier film comprising a gas-barrier film as recited in the first aspect, wherein a plastic film is laminated on either surface of the gas-barrier film.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will next be described in detail.
In the present invention, a metallic-compound-containing layer which is applied to the surface of a polymer layer may be a layer containing a metallic compound alone, or a layer containing a resin in which a metallic compound is mixed or dispersed (hereinafter the layer will be referred to as “layer of a mixture of metallic compound and resin”). As used herein, the phrase “a metallic-compound-containing layer is applied to the surface of a polymer layer” refers to “a metallic compound or a suspension of a mixture of metallic compound and resin is applied or sprayed to the surface of a polymer layer,” “the metallic compound or the suspension is applied to the surface of a polymer layer through dipping,” or “powder of the metallic compound is applied to the surface of a polymer layer through powdering or spraying.” The phrase does not refer to application of a metallic-compound-containing layer through deposition or sputtering.
The metallic-compound-containing layer of the gas-barrier film of the present invention differs in terms of surface roughness from a metallic compound layer of continuous phase which is produced through deposition or sputtering. The metallic-compound-containing layer may have a non-continuous phase or a continuous phase. In the present invention, a metallic-compound-containing layer can be introduced through a convenient process as described below, such as powdering of a metallic compound, or application or spraying of a suspension of the metallic compound. As described above, a metallic-compound-containing layer which contains a heat-resistant resin of high Young's modulus as a plastic film and which is produced through deposition or sputtering, which processes require complicated operation and expensive apparatus, has a mean surface roughness (Ra) of 0.0002-0.002 &mgr;m as measured by use of an atomic force microscope (AFM), or an Ra of 0.0001-0.002 &mgr;m as calculated through the below-described method making use of a micrograph of transmission electron microscope (TEM). In contrast, in the present invention, a layer containing a metallic compound alone or a layer of a mixture of metallic compound and resin has an Ra of 0.003-0.03 &mgr;m as measured by AFM, preferably 0.003-0.02 &mgr;m, and an Ra of 0.
Hasegawa Tomohisa
Ohba Hiroyuki
Saika Toru
Sato Tomoaki
Tanaka Hideaki
Kureha Chemical Industry Co. Ltd.
Tarazano D. Lawrence
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