Stock material or miscellaneous articles – Composite – Of polyamide
Reexamination Certificate
1999-03-05
2001-09-25
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyamide
C428S474700, C428S474400, C428S474900, C428S475500, C428S475800, C428S476300, C428S910000
Reexamination Certificate
active
06294263
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polyamide laminated film.
PRIOR ART
A film formed of a polyamide containing xylylenediamine as a constituent has characteristics that it is excellent in a gas barrier property and a heat resistance and further high in film strengths such as a break strength, a Young's modulus and the like in comparison with films formed of other plastics.
However, this polyamide film involves a problem that when it is used as a packaging material, pinholes tend to occur owing to a fatigue failure by bending in steps of vacuum packaging, transportation of commercial products packed with the packaging material, and the like. When pinholes occur in packaging materials of commercial products, the contents are contaminated, rotted, mildewed and further wetted, which leads to the decrease in the value of commercial products.
Meanwhile, an unstretched film or a stretched film formed of an aliphatic polyamide typified by nylon 6 or nylon 66 has been widely used as various packaging materials. This film is excellent in film strengths such as a flexural fatigue resistance, an impact strength and the like, but has a defect that a gas barrier property is poor.
Accordingly, in order to impart a gas barrier property to a film formed of an aliphatic polyamide, a polymer latex of vinylidene chloride has been coated on the surface of the film.
Nevertheless, this coated film has a defect that it becomes cloudy by itself through a treatment with hot water. It is further indicated that there is a possibility that an ingredient toxic to the human being, such as dioxin or the like is generated when a spent film is subjected to thermal disposal. This is a serious problem in the environmental pollution.
In order to solve the problems, a method in which a film is formed from a mixture of a polyamide polymer containing xylylenediamine as a constituent with an aliphatic polyamide (JP-B-51-29192), a method in which respective polyamides are melt-extruded with separate extruders, and laminated (JP-A-8-281889) and the like have been proposed.
However, even the films obtained by these methods do not reach satisfactory levels in which a gas barrier property is good and film properties required as a packaging film, such as a flexural fatigue resistance, a transparency and the like are provided.
DISCLOSURE OF THE INVENTION
A main object of the present invention is to solve the problems associated with the conventional polyamide laminated film, and to provide a polyamide laminated film suited for use in packaging, which is excellent in an oxygen gas barrier property, a flexural fatigue resistance, a transparency and the like, which can prevent deterioration or discoloration of contents when used as various packaging materials, and which can further protect contents from shock or the like during transportation.
The present inventors have assiduously conducted investigations to achieve the above-mentioned object, and have consequently found that a laminated film obtained by laminating a resin layer formed of a mixed polymer containing an aliphatic polyamide and an elastomer at a specific ratio on at least one surface of a resin layer formed of a specific m-xylylene group-containing polyamide polymer is good in a gas barrier property and also in a flexural fatigue resistance and a transparency.
Further, when the m-xylylene group-containing polyamide polymer is used as a mixture with a compatible polymer that meets specific requirements, a flexural fatigue resistance is further improved. These findings have led to the completion of the present invention.
That is, the present invention is to provide the following polyamide laminated film.
1. A polyamide laminated film comprising a resin layer A and a resin layer B formed on at least one surface of the resin layer A,
the resin layer A being composed mainly of a m-xylylene group-containing polyamide polymer (a-1) which is one prepared from monomer components containing a xylylenediamine compound as a main diamine component and an &agr;,&ohgr;-aliphatic dicarboxylic acid having from 6 to 12 carbon atoms as a main dicarboxylic acid component, the xylylenediamine compound being m-xylylenediamine alone or a mixture of m-xylylenediamine and p-xylylenediamine, and
the resin layer B being mainly composed of a mixed polymer (b-3) which is a mixture of from 99 to 80% by weight of an aliphatic polyamide (b-1) and from 1 to 20% by weight of an elastomer (b-2).
2. A polyamide laminated film comprising a resin layer A and a resin layer B formed on at least one surface of the resin layer A,
the resin layer A being composed mainly of a mixed polymer (a-3) which comprises 50% by weight or more of a m-xylylene group-containing polyamide polymer (a-1) and 50% by weight or less of a polymer (a-2), the polyamide polymer (a-1) being one prepared from monomer components containing a xylylenediamine compound as a main diamine component and an &agr;,&ohgr;-aliphatic dicarboxylic acid having from 6 to 12 carbon atoms as a main dicarboxylic acid component, the xylylenediamine compound being m-xylylenediamine alone or a mixture of m-xylylenediamine and p-xylylenediamine, the polymer (a-2) having a melting point of 160° C. or more, a difference in melting point between the polymer (a-2) and the polyamide polymer (a-1) being 50° C. or less, the polymer (a-2) having a glass transition point of 60° C. or less, the polymer (a-2) having a compatibility with the polyamide polymer (a-1), and
the resin layer B being mainly composed of a mixed polymer (b-3) which is a mixture of from 99 to 80% by weight of an aliphatic polyamide (b-1) and from 1 to 20% by weight of an elastomer (b-2).
3. The polyamide laminated film according to item 1, wherein the elastomer (b-2) is a polyamide-containing block copolymer comprising polyamide sections as hard segment and polyoxyalkylene glycol sections as soft segment,
the polyamide sections being prepared from monomer components containing any of (1) a lactam, (2) an &ohgr;-amino-aliphatic carboxylic acid, (3) an aliphatic diamine and an aliphatic dicarboxylic acid and (4) an aliphatic diamine and an aromatic dicarboxylic acid.
4. The laminated polyamide film according to item 2, wherein the elastomer (b-2) is a polyamide-containing block copolymer comprising polyamide sections as hard segment and polyoxyalkylene glycol sections as soft segment,
the polyamide sections being prepared from monomer components containing any of (1) a lactam, (2) an &ohgr;-amino-aliphatic carboxylic acid, (3) an aliphatic diamine and an aliphatic dicarboxylic acid and (4) an aliphatic diamine and an aromatic dicarboxylic acid.
5. A food packaging material formed from the polyamide laminated film according to any one of items 1 to 4.
The polyamide laminated film of the present invention is described in detail below.
The polyamide laminated film of the present invention is formed by laminating a resin layer B on one surface or both surface of a resin layer A. The resin layer A is composed mainly of a m-xylylene group-containing polyamide polymer (a-1) which is one prepared from monomer components containing a xylylenediamine compound as a main diamine component and an &agr;,&ohgr;-aliphatic dicarboxylic acid having from 6 to 12 carbon atoms as a main dicarboxylic acid component. The resin layer B is composed mainly of a mixed polymer (b-3) which is a mixture of from 99 to 80% by weight of an aliphatic polyamide (b-1) and from 1 to 20% by weight of an elastomer (b-2).
As the xylylenediamine compound which is the diamine component of the m-xylylene group-containing polyamide polymer (a-1) constituting the resin layer A, it is required that m-xylylenediamine is used alone or m-xylylenediamine and p-xylylenediamine are used as a mixture.
When the mixture of m-xylylenediamine and p-xylylenediamine are used, it is preferable that m-xylylenediamine is used at a ratio of 70% or more based on the total xylylenediamine.
Examples of the &agr;,&ohgr;-aliphatic dicarboxylic acid having from 6 to 12 carbon atoms which is used as the dicarboxylic acid component
Imai Kazumoto
Matsuda Akira
Oko Tsutomu
Okudaira Haruo
Okumura Sinitiro
Kiliman Leszek
Leydig , Voit & Mayer, Ltd.
Toyo Boseki Kabushiki Kaisha
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