Package making – Methods – Forming or partial forming a receptacle and subsequent filling
Reexamination Certificate
2001-05-09
2003-04-08
Rada, Rinaldi I (Department: 3721)
Package making
Methods
Forming or partial forming a receptacle and subsequent filling
C428S483000, C428S036700
Reexamination Certificate
active
06543208
ABSTRACT:
1. Field of the Invention
The present invention relates to a bag for packaging snacks such as potato chips, especially those that require oxygen and/or water vapor barriers. The present invention also relates to a method of packaging food products, as well as a method of using a laminated film for packaging food products in a bag.
2. Description of Related Art
There are various types of structures of packaging materials in conventional bags for packaging snacks (hereinafter referred to as snack bags). Mainly, there are following two types:
(a)
A five-layered structure having, from an inner side, polypropylene resin layer/vapor-deposited metal aluminum layer/biaxially stretched polyethylene terephthalate layer/polyethylene resin layer/biaxially stretched polypropylene resin layer; and
(b)
A four-layered structure having, from an inner side, polypropylene resin layer/vapor-deposited metal aluminum layer/polyethylene resin layer/biaxially stretched polypropylene resin layer.
The innermost polypropylene resin (PP) layer functions as a sealant. Polypropylene, especially non-stretched polypropylene resin (CPP) is selected as the innermost layer because the innermost layer has to be able to heat-seal at a low temperature, and also because the innermost layer has to have hot tack properties right after the sealing, and oil repellency properties. The hot tack property is necessary because small pressure is applied to the bag while the bag is being packaged with air or nitrogen being inserted into the bag. The bag is expanded in order to prevent breakage of the snacks, which are contents of the bag. The thickness of this innermost polypropylene resin layer is often set as 20-50 &mgr;m.
The vapor-deposited metal aluminum layer functions to shut out external light and prevent permeation of oxygen and water vapor. Its thickness is 300-1500 Å. Normally, the metal aluminum layer is vapor-deposited on the biaxially stretched PET film or polypropylene resin.
The biaxially stretched polyethyleneterephthalate (PET) is a material on which metal aluminum can be vapor-deposited most stably. PET having a thickness of 12 &mgr;m is frequently utilized.
The polyethylene resin (PE) layer functions as an adhesive by attaching the biaxially stretched PET film and the outermost biaxially stretched polypropylene (OPP) film, or by attaching the innermost non-stretched polypropylene resin layer and the biaxially stretched PET film. Its thickness is about 15 &mgr;m. Ethylene(meta)acrylic acid copolymer is sometimes utilized as a polyethylene resin layer. Additionally, urethane-type adhesive or adhesives that include monomer but do not include organic solvent may be used instead of a polyethylene resin layer.
The outermost biaxially stretched polypropylene layer such as biaxially stretched polypropylene film directly contacts the heated heat seal member (seal bar), and thereby transmits the heat to the innermost polypropylene resin layer. Its thickness is 15-25 &mgr;m.
The packaging material having the above-described 4-5 layered structures has the total thickness of 40-117 &mgr;m.
As a manufacturing method of the packaging material having the above-described structure, a manufacturing method such as OPP film/PE extrusion laminate/PET film/vapor-deposited metal aluminum layer/PP extrusion laminate is often utilized from a cost point of view.
However, in such packaging material structure, since different resins including polypropylene resin, PET resin, and polyethylene resin are combined, material recycling is extremely difficult. Additionally, since polypropylene resin is the innermost layer, the flavor of the snack tends to be adsorbed. Accordingly, the taste of the snack is weakened. Furthermore, since the total thickness is about 60-120 &mgr;m, it is difficult to transmit the heat. Furthermore, a pinhole is often created at a fin-sealed portion in the pillow packaging. (See
FIGS. 4 and 5
.)
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide a bag for packaging food products whose materials can be easily recycled while avoiding the above-described problems.
A bag for packaging food products in accordance with the present invention is formed of a laminated film having a structure of polyester-type sealant layer with a low melting point/barrier layer having barrier properties against oxygen and water vapor/polyester-type heat-resistant layer with a high melting point. The bag is formed by heat sealing such that the polyester-type low melting point sealant layer forms an inner side.
Here, the polyester-type low melting point sealant layer is disposed as the innermost layer of the bag. Preferably, this sealant layer should have a low melting point (the melting point being below 160° C.), to be used by the high-speed properties of the packaging machine. It is possible to obtain various polyester-type resins having various melting points because various polymers in polyester-type resins can be obtained by combining different monomers, in other words, diols and dicarboxylic acids.
Among monomers of polyester-type resins having low melting point, terephthalic acid is well suited among the dicarboxylic acids from the cost point of view. Among diols, 1,3 butanediol (a polyester resin having a melting point of about 80° C. and can be obtained by condensing with terephthalic acid) or 1,2-propylene glycol (a polyester resin having a melting point of about 122° C. can be obtained by condensing with terephthalic acid) is preferable. Furthermore, amorphous copolymer PET with amorphous cyclohexane dimethanol (for instance, PETG, a product of U.S. Eastman Chemical Company) is also preferable because low-temperature heat sealing can be conducted. Furthermore, polybutylene succinate, polyethylene succinate, and polybutylene succinate adipate copolymer (these are publicly sold as biodegradable resin BIONOLLE) that are obtained by using succinic acid and/or adipic acid such as dicarboxylic acid, 1,4-butanediol or ethylene glycol such as diol can also be used as polyester for a low melting point sealant layer. These resins can be heat-sealed at a low temperature. Additionally, since these resins are polyester resins, the resins do not absorb the flavor of the contents, such as snacks, of the bag. The thickness is preferably 15-50 &mgr;m.
Preferably, the innermost polyester-type low melting point sealant layer should be a non-oriented resin layer that has been formed without being stretched. Generally, stretching of the plastic is performed at a temperature that is 10-20° C. below the melting point with heat-setting while the plastic is stretched along two axes that extend in longitudinal and latitudinal directions. The stretched film trebles its rigidity, transparency, and capacity as an O
2
barrier. These properties are maintained up to the heat setting temperature. However, once the temperature rises beyond this heat-setting temperature, a disorder occurs in the molecular orientation. Accordingly, the effects of the biaxial stretching are lost, and the film shrinks. In that case, the heat-sealed portion becomes wrinkled at the time of heat sealing, or heat sealing cannot be conducted in a satisfactory manner. Therefore, the innermost polyester-type low melting point sealant layer should preferably be an effectively non-oriented resin layer which is formed without being stretched.
It is also preferable to form the polyester-type low melting point sealant layer as a laminate having a low melting point polyester resin and a high melting point polyester resin. In this case, the thickness of the low melting point polyester resin should be 5-25 &mgr;m, the thickness of the high melting point polyester resin should be 10-45 &mgr;m, and the thickness of the polyester-type low melting point sealant layer should be 15-50 &mgr;m. The polyester of the high melting point polyester resin of the polyester-type low melting point sealant layer may be the same as or different from the polyester of the low melting point polyester resin of the polyester-type low melting point sealant layer. The polyester of the
Iwasaki Yoshio
Kobayashi Yukio
Mori Hirotsugu
Ishida Co. Ltd.
Rada Rinaldi I
Shinjyu Global IP Counselors, LLP
Weeks Gloria R
LandOfFree
Food-packaging bag, method of food packaging, and use of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Food-packaging bag, method of food packaging, and use of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Food-packaging bag, method of food packaging, and use of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3030598