Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
2000-06-22
2003-07-15
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S500000, C428S518000, C428S913000
Reexamination Certificate
active
06592975
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a laminated packaging material, and more particularly to a laminated packaging material which comprises at least three layers of polymer materials comprising a surface layer, one or more intermediate layers adjacent thereto, and another surface layer and which has excellent transparency, gloss, slidability, and extrudability; and to a process for producing the packaging material. The laminated packaging material of the present invention is suitable for use as a packaging film for foods.
BACKGROUND ART
When a film or sheet is to be set in a packaging machine, slidability of the film or sheet is considered an important property. Conventionally, there is a method for improving operation efficiency or machine adaptability of a production apparatus of film or sheet, a bag-producing machine, or a packaging machine; i.e., a method for improving slidability between films or between sheets and slidability between a film or sheet and the apparatus or the machine, in which starch powder or a similar substance is sprinkled on the surface of the film or sheet. There is another method for improving such slidability, in which an organic lubricant such as fatty acid amide or an inorganic lubricant such as silica is incorporated into a surface layer of such a film or sheet, and this method is used widely.
These methods involve problems in terms of performance of the film produced and the film production process. Specifically, when a film is wound up in a roll after a large amount of powder is sprinkled onto the film, the powder may form irregularities on the surface layer of the film, resulting in deteriorated transparency and poor gloss of the film. In addition, in a film roll, there arises a difference in transparency and gloss between the core portion and the outermost portion. Therefore, there has been keen demand among persons skilled in the art for a method in which a small amount of powder is sprinkled onto a film.
When an organic or inorganic lubricant is incorporated into a surface layer of a film or sheet, the organic or inorganic lubricant adheres to a die lip portion during the production process which takes a long time. As a result, the adhering lubricant may scratch the surface layer of the film or sheet, causing poor transparency and gloss of the film or sheet. In order to prevent such a problem, the die lip portion must be cleaned at predetermined points in time; i.e., film or sheet production must be stopped temporarily, which reduces extrudability. Incidentally, when an inorganic lubricant such as organic glass or feldspar is incorporated into a surface layer of a film, the irregularities attributed to the inorganic lubricant may form on the surface of the film, and thus the film tends to have poor transparency and gloss.
DISCLOSURE OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a laminated packaging material which exhibits excellent transparency, gloss, productivity, and extrudability, a surface layer thereof having excellent slidability, and a process for producing the packaging material.
In order to solve the aforementioned conventional technical problems, the present inventors have performed extensive studies and have found that, in the case of production of a laminated packaging material, when the amount of a lubricant contained in a surface layer of the material is smaller than that contained in an intermediate layer adjacent to the surface layer, adhesion of the lubricant to a die lip is reduced during extrusion of the material, and that when the lubricant bleeds out from the intermediate layer into the surface layer with passage of time, slidability is imparted to the surface layer, and thus the amount of starch powder which is sprinkled onto the surface layer can be reduced. As a result, the present inventors have confirmed that slidability of the surface layer and extrudability of the packaging material can be improved while transparency, gloss, and productivity of the material are maintained. The present invention has been accomplished on the basis of these findings.
According to a first aspect of the present invention, there is provided a laminated packaging material which comprises at least three layers of polymer materials comprising a surface layer, one or more intermediate layers adjacent thereto, and another surface layer, characterized in that the intermediate layer adjacent to each surface layer without an adhesive layer therebetween contains a lubricant, at least one of the intermediate layers has gas-barrier properties, and the total amount of a lubricant contained in both surface layers is smaller than that contained in the intermediate layer(s) adjacent thereto without adhesive layer(s) therebetween.
According to a second aspect of the present invention, there is provided a laminated packaging material which comprises at least three layers of polymer materials comprising a surface layer, one or more intermediate layers adjacent thereto, and another surface layer, characterized in that the intermediate layer adjacent to each surface layer without an adhesive layer therebetween contains a lubricant and at least one of the surface layers is formed of polyethylene which is produced by use of a metallocene catalyst (hereinafter the polyethylene may be referred to as “metallocene catalyst polyethylene”). According to a third aspect of the present invention, there is provided a process for producing a laminated packaging material which comprises at least four layers of polymer materials comprising a surface layer, one or more intermediate layers adjacent thereto, an intermediate layer having gas-barrier properties, and another surface layer, characterized in that a lubricant is incorporated into the intermediate layer adjacent to each surface layer without adhesive layer(s) therebetween and no lubricant is incorporated into either of the surface layers, or the total amount of a lubricant contained in the two surface layers is determined such that the total amount is smaller than that contained in the intermediate layers adjacent to the respective surface layers.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention provides a laminated packaging material which comprises at least three layers comprising a surface layer, one or more intermediate layers containing a lubricant adjacent to the surface layer, and another surface layer.
As used herein, the term “a laminated packaging material” refers to a laminated packaging material which predominantly comprises polymer materials, particularly a multi-layer film or sheet formed of thermoplastic resin, the packaging material being employed singly, both surface layers being employed by affixing together for use, the packaging material being employed by affixing to other films, sheets or paper materials, the packaging material being formed into bags or pouches, or the packaging material being formed into a container such as a tray so as to enhance the gas-barrier or water vapor barrier properties of the container.
As used herein, the term “surface layer” refers to each of the outermost layers which are surface layers of the laminated packaging material of the present invention. The two surface layers may be formed of the same resin or different resins. When both surface layers are affixed together to form a bag, one of the surface layers serves as a sealing layer. When the laminated packaging material of the present invention is shaped into an envelope form, one surface layer overlaps the other surface layer and are sealed for use.
As used herein, the term “intermediate layer which is adjacent to a surface layer and contains a lubricant” refers to an intermediate layer adjacent to a surface layer without an adhesive layer. The laminated packaging material may comprise a plurality of intermediate layers.
When the laminated packaging material comprises a plurality of intermediate layers, at least one intermediate layer adjacent to a surface layer contains a lubricant. An intermediate layer may be employed for obtaining
Itoh Tadayoshi
Tobita Hisanori
Ueyama Takahisa
Dinsmore & Shohl LLP
Kelly Cynthia H.
Kureha Chemical Industry Co. Ltd.
Shewareged B.
LandOfFree
Laminated packaging material and process for producing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Laminated packaging material and process for producing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laminated packaging material and process for producing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3014663