JPS6151548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermoplastic pouch-like structure made from a thermoplastic film laminate consisting of two film layers molded from different thermoplastic resins.

Traditionally, polyethylene bags have been used for food storage, and in particular for frozen food storage. Such food containers are particularly advantageous for storing food products in their packaging that may be reheated later. Therefore, such food storage bags are manufactured in large quantities from polyethylene of low density, i.e. 0.91-0.93 g/cc. However, for reheating, the food must be removed from such low density polyethylene bags. This is because it tends to partially melt at temperatures below 100°C (212°C) and adhere to the surface of the cooking container.

In order to eliminate the above-mentioned disadvantages of low density polyethylene bags, attempts have been made to use polyester bags, such as polyethylene terephthalate, in bags used at high temperatures as "boiling" bags. However, such polyester films are not only difficult to seal, but more importantly, they are too expensive to be used as disposable bags.

The present invention can be used to keep food contained not only during storage, but most importantly, during heating for consumption. To provide affordable thermoplastic bags. The bag-like structure according to the invention has a two-layer laminate structure, the inner layer of the bag, ie the surface layer in contact with the food product, being composed of polyethylene, preferably a high-density ethylene copolymer. Meanwhile, the outer layer of bag laminate material,
That is, the surface of the bag that comes into direct contact with the cooking container consists of a relatively thin layer of polypropylene film.
Due to the presence of this outer polypropylene film layer, the inner, more thermally weak polyethylene layer does not come into contact with the surface of the cooking container, so that the bag itself can withstand higher temperatures. Since the polypropylene layer has a melting point or sticking point of 150° C. or higher, it is stable and does not adhere to the side walls of the container even while the food is being reheated. Obviously, the bag containing the food product is to be submerged in a fluid, such as water, during the reheating process. Accordingly, the present invention provides a bag made of laminate material for optimal storage and containment of food, and the food inside the bag can be reheated without being removed from the bag. The bag of the present invention is constructed from a two-layer laminate consisting of an inner film layer of high density ethylene/alpha-olefin copolymer and an outer layer of polypropylene film. This high density ethylene copolymer is preferably used in small amounts, e.g.
% or less of ethylene copolymerized with another type of alpha-olefin having 3 to 10 carbon atoms, such as octene-1.

EXAMPLES Tubular thermoplastic laminates were manufactured by a conventional blown tube film coextrusion process. The tubular inner layer consisted of a 1.0 mil thick layer of high density polyethylene copolymer and the outer layer consisted of a 0.2 mil thick polypropylene layer. This continuous laminate tube was then formed into a bag-like structure using methods well known in the art. The high density polyethylene copolymer described above was a copolymer of ethylene and about 3% by weight octene-1. This resin is called Alathon 7810 by the manufacturer and has the following typical physical properties for a 1.25 mil film extruded at a 4.3/1 expansion ratio.

Density 0.945g/cc Melt Index 0.25g/10min Tensile Yield (MD) 3000psi (TD) 3100psi Elongation (MD) 660% (2 inches/min) 730% Secant Modulus (MD) 80M psi (TD) 82M psi Elmendorf Tear (MD) 45 gm/mil (TD) 247 gm/mil Spencer Impact 2.8 in. lb/mil Dart Drop (26 in.) 115 gm/mil Tear (MD) 3.2 Kg force ASTM D-2582 ( TD) 3.7Kg Force The propylene outer layer was constructed from a resin called Tenite 612F by the manufacturer and having the following typical physical properties:

Density 0.902 g/cc Flow properties 4.5 g/10 minutes Tensile yield 5000 psi Vigor Softening point 145°C A two-layer laminate film made by integrally bonding a high-density ethylene-octene-1 copolymer layer and a polypropylene layer has the following physical properties. It had certain characteristics.

Film Thickness 1.20 Mil Expansion Ratio 2.5/1 Tensile Yield (MD) 3200psi (TD) 3400psi Elongation (MD) 525% (TD) 850% Elmendorf Tear (MD) 24gm/mil (TD) 477gm/mil Modulus (MD) 80M psi (TD) 105M psi In the present invention, the thickness of the inner high density polyethylene copolymer layer can vary from about 0.5 mil to about 3.0 mil, preferably the thickness is 1.0 mil. The outer polypropylene layer, on the other hand, can vary from about 0.1 mil to about 3.0 mil, and preferably has a thickness of about 0.2 mil.

Claims (1)

[Claims] 1. The outer layer is a continuous layer of polypropylene, and the inner layer is a continuous layer of a high density ethylene-octene-1 copolymer containing less than about 10% by weight of octene-1 and having a density of 0.945 grams/ ^cc3 . A two-layer co-extruded thermoplastic laminate bag made from a thermoplastic laminate consisting of. 2. The thermoplastic laminate bag of claim 1, wherein the polypropylene layer has a thickness of 0.1 to 0.2 mil and the copolymer layer has a thickness of 0.5 to 3 mil.