Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1998-05-06
2000-02-08
Nutter, Nathan M.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 31, 524 32, 524 35, 524 47, 524 51, 525 5424, 525 5426, 525 55, 525 56, 525 57, 525 58, 525 59, B32B 2736, B65D 8124, C08G 8102, C08J 518
Patent
active
060229136
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a container for retort packaging composed of a specified film and a retort method using the same; and a resin composition and a film comprising the same having a gas barrier property, and a method for producing the same. In more detail, the present invention relates to a container for retort packaging being excellent in hot-water resistance and gas barrier property against oxygen and the like comprising a reaction product of poly(meth)acrylic acid and a polyalcoholic polymer and a retort method using the same, as well as to a resin composition comprising poly(meth)acrylic acid, polyalcoholic polymers and metals and a film being excellent in hot-water resistance, gas barrier property against oxygen and the like, especially in oxygen gas barrier property in a high humidity atmosphere, and a method for producing the same.
The film according to the present invention is not only excellent in hot-water resistance and oxygen gas barrier property but also is able to maintain a good oxygen gas barrier property even after a hot water treatment such as boiling and retort treatment. Therefor, it is suitable as a packaging material for articles, infusion solutions, foodstuffs and beverages that are susceptible to deterioration with oxygen. The film is especially suitable for use in containers for retort packaging since the oxygen gas barrier property is securely maintained even after the film is exposed to hot water or steam for retort treatment.
BACKGROUND ART
PVA and poly(meth)acrylic acid and partially hydrolyzed products thereof are water soluble polymers, being widely used for water adsorbents, thickeners, flocculants, dispersants and treatment agents for paper and textiles. Poly(meth) acrylic acid or its partially neutralized product can be formed into a film by casting from its solution and the film obtained has an excellent gas barrier property under dry conditions. However, since this film is strongly hydrophilic, the gas barrier property is remarkably lost under high humidity circumstances besides being readily dissolved in water. Accordingly, this film is not suitable for packaging of foodstuffs containing a large amount of moisture.
While films made of starch and its derivatives have a good oil resistance and oxygen gas barrier property, on the other hand, they have a drawback that their mechanical strength is weak and water resistance is poor. Starch is one of the natural polysaccharides available in plants, its constituents being composed of linear amylose in which glucose units are linked by .alpha. (1-4) bonds and high molecular weight amylopectin in which multiple short amylose chains are branched with each other via .alpha. (1-6) bonds. Starch and its derivatives include, in addition to crude starch, processed starch, e.g., physically modified starch, such as purified starch, chemically modified starch prepared by hydrolysis of starch with an acid or enzyme, or by heating to enhance solubility in cold water, graft-modified starch obtained by graft polymerization with monomers such as acrylamide, acrylic acid, vinyl acetate or acrylonitrile. These modified starch derivatives are hydrophilic polymers, similarly to poly(meth)acrylic acid and, therefore, are used in a wide range of industrial fields, including not only in food industries but also for water adsorbents, thickeners, flocculants, dispersants and processing agents for paper and textiles by taking advantage of their hydrophilic property. The substance having good water solubility of these starch derivatives can be readily formed into a film by casting from an aqueous solution. However, films made of starch derivatives are not suitable for use in packaging of food stuffs because the films are so strongly hydrophilic that their oxygen gas barrier property is remarkably lost under high humidity conditions.
When PVA films are used for the purpose where a practical oxygen gas barrier property is required, it was attempted to diminish the effect of humidity as much as possible by forming the film i
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Hasegawa Tomohisa
Ohba Hiroyuki
Sato Tomoaki
Tanaka Hideaki
Kureha Chemical Industry Co. Ltd.
Nutter Nathan M.
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