Stock material or miscellaneous articles – Composite – Of polycarbonate
Reexamination Certificate
2002-07-19
2004-08-31
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polycarbonate
C428S035400, C428S036600, C428S475800, C428S476300, C428S483000, C428S520000, C428S522000, C524S321000, C525S061000, C525S330300, C525S386000
Reexamination Certificate
active
06783857
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a gas barrier resin composition, a gas barrier coating agent, and a gas barrier molded material.
BACKGROUND ART
A thermoplastic resin film comprising polyamide, polyester or the like has excellent strength, transparency, moldability and gas barrier property, and so it is broadly used as a wrapping material. However, where the thermoplastic resin film is used for retort food or the like, which needs long-term keeping quality, further higher gas barrier property is required.
Thus, to improve gas barrier property, a laminated film obtained by placing a layer comprising polyvinylidene chloride (PVDC) on the surface of such a thermoplastic resin, is broadly used to, for example, wrap food. However, since PVDC generates an organic substance such as acidic gas when it is incinerated, with a recent increasing interest in the natural environment, there is a strong desire for substitution by other materials.
An example of materials used instead of PVDC is polyvinyl alcohol. A film comprising polyvinyl alcohol does not generate poisonous gas when it is subjected to an incineration treatment and is friendly to the natural environment. However, although the film comprising polyvinyl alcohol is excellent in gas barrier property in a low humidity atmosphere, as the humidity increases, the gas barrier property tends to be sharply reduced. Accordingly, in many cases, such a film is not suitable for wrapping food containing water or the like.
As a material for solving such a problem, there is known a film comprising a copolymer of vinyl alcohol and ethylene (EVOH), or a film obtained by applying EVOH as a coating material onto a thermoplastic resin film. However, it cannot be said yet that the film comprising a copolymer of vinyl alcohol and ethylene has sufficient gas barrier property in a high humidity atmosphere. When EVOH is used as a coating material, EVOH is dissolved in a solvent before use. Since EVOH is hard to dissolve in water, a mixed solvent obtained by mixing water and an organic solvent is used as a solvent. To maintain the gas barrier property in a high humidity atmosphere at a practical level, it is necessary to keep the amount of ethylene contained in EVOH large to a certain extent. When EVOH has such a composition, it becomes hard to dissolve in water. Accordingly, there emerges a need to increase the ratio of an organic solvent in a solvent or to use an organic solvent singly. Nevertheless, in terms of the environmental issue, the use of an organic solvent is not desired, and further, the use of the organic solvent is not preferable because this comes at a high cost due to the necessity of a process of recovering the organic solvent.
Moreover, in Japanese Patent Laid-Open No. 10-237180, is proposed a method of applying a solution comprising a partially neutralized product of polyacrylic acid or polymethacrylic acid and polyvinyl alcohol onto a thermoplastic resin film followed by heat processing in order to impart gas barrier property to the thermoplastic resin film. By this method, however, there is a need for heating at a high temperature for a long time to enhance gas barrier property, and so this method has a problem regarding low productivity. Furthermore, since the thermoplastic resin film is colored by heating at a high temperature for a long time and thereby the appearance is impaired, when the film is used to wrap food or the like, improvement is needed.
Still further, there have previously been known various techniques, in which a film comprising polyvinyl alcohol is allowed to have water resistant property by a crosslinking reaction by addition of a crosslinking agent to polyvinyl alcohol. For example, it is broadly known that a film comprising a polymer containing a maleic acid unit is allowed to have water resistant property by a crosslinking reaction between the above described polymer and a hydroxyl group such as polyvinyl alcohol or polysaccharide. As examples of applying this technique, Japanese Patent Laid-Open No. 8-66991 discloses that a film comprising a 25 to 50% partially neutralized product of an isobutylene/maleic acid anhydride copolymer and polyvinyl alcohol, has excellent water resistant property, and Japanese Patent Laid-Open No. 49-1649 discloses a method of allowing a film to have water resistant property by mixing an alkylvinyl ether-maleic acid copolymer into polyvinyl alcohol.
However, water resistant property imparted to a film by allowing the film to have water resistant property (that is, water insolubility) is a property which differs from gas barrier property. Generally, water resistant property is obtained by crosslinking polymer molecules. In contrast, since gas barrier property is a property of preventing invasion or diffusion of relatively small molecules such as oxygen, the gas barrier property is not always obtained by simply crosslinking polymers. For example, a three-dimensional crosslinked polymer such as epoxy resin or phenol resin has water resistant property, but does not have gas barrier property.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a molded material having high gas barrier property, which overcomes the above described problems, has excellent transparency, does not generate poisonous gas when it is subjected to an incineration treatment, is preferable in terms of both environmental protection and productivity because it does not use an organic solvent, and is capable of being used in a high humidity atmosphere. In addition, it is another object of the present invention to provide a gas barrier resin composition and a gas barrier coating agent, which can easily realize this molded material.
Through intensive studies directed toward the above objects, the present inventors have found that the above objects can be achieved by forming a molded material with a specific resin composition, or producing a molded material by applying a coating agent containing the specific composition onto the surface of a substrate, thereby completing the present invention.
That is to say, the gist of the present invention is as follows.
The gas barrier resin composition of the present invention is a composition comprising 83 to 15% by mass of a compound (A) having two or more hydroxyl groups in a molecule thereof and 17 to 85% by mass of a compound (B) in which at least one carboxyl group is bound to each of three or more consecutive carbon atoms in a molecule thereof, wherein the compound (B) is any one of a compound in which no anhydrous structure is made among the carboxyl groups and a compound in which at least one anhydrous structure is made among the carboxyl groups, and thereby the obtained gas barrier resin composition has good moldability and excellent gas barrier property.
The gas barrier coating agent of the present invention is an agent comprising 83 to 15% by mass of a compound (A) having two or more hydroxyl groups in a molecule thereof, 17 to 85% by mass of a compound (B) in which at least one carboxyl group is bound to each of three or more consecutive carbon atoms in a molecule thereof, and a solvent, wherein the compound (B) is any one of a compound in which no anhydrous structure is made among the carboxyl groups and a compound in which at least one anhydrous structure is made among the carboxyl groups, and thereby the obtained gas barrier coating agent has good applicability and excellent gas barrier property.
A gas barrier molded material of the present invention comprises the gas barrier resin composition of the present invention, and by an ester linkage between the compound (A) and the compound (B) comprised in the resin composition, the obtained molded material has excellent gas barrier property.
Moreover, another gas barrier molded material of the present invention has excellent gas barrier property by that a coating layer is formed by applying the gas barrier coating agent of the present invention on at least a single side of a substrate.
The gas barrier film of the present invention has excellent gas barrier property by that a coati
Anada Arihiro
Okamoto Shoji
Onishi Hayami
Shiba Kenjin
Fildes & Outland, P.C.
Nakarani D. S.
Unitika Ltd.
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