Stock material or miscellaneous articles – Structurally defined web or sheet – Physical dimension specified
Reexamination Certificate
2002-04-10
2004-07-20
Woodward, Ana (Department: 1711)
Stock material or miscellaneous articles
Structurally defined web or sheet
Physical dimension specified
C264S209500, C264S632000
Reexamination Certificate
active
06764753
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a smokable synthetic film, preferably in the form of a tubular casing. This film can be used for encasing foodstuffs, in particular sausages, meat, cheese.
2. Background Discussion and Related Art
Generally, foodstuff casings are made either of natural material such as cellulose or animal guts, or of synthetic material. Usually, the foodstuff is packed into the casing. When smoked products are desired, the encased foodstuff is further subjected to a smoking process. The product is suspended into a chamber wherein hot smoke is processed. This process has the disadvantage that it can only be used with natural casings such as guts, or with cellulose or collagen casings which all show a natural permeability to gas, and therefore to smoke.
A critical point in the preparation and storage of smoked products is that the casings must show different permeabilities depending on the step of the process. A high permeability is needed at high temperatures (typically between 50 and 100° C.) and high humidity, during the smoking process. Once the product is smoked and cooled, it is preferable that the casing acts as a barrier against humidity: so the permeability should preferably be low at temperatures less than 50° C., particularly less than 30° C.
Other important features of casings are their abilities to both stretch and shrink. When subjected to heat treatment, the volume of the filling of the casing increases. Because of its stretchability, the casing extends. But after cooling, the volume of filling decreases and the casing must be able to shrink in a way that the final product is free of wrinkles. It is also important that no jelly forms out of the casing when cooling down.
Natural guts and cellulose present many disadvantages : they are expensive, their great permeability to steam causes great weight losses, the stability of the product is limited with regard to drying, superficial fat oxidation and graying caused by microbial spoiling often appear on casings.
CA 1 235 018 discloses synthetic smokable films comprising polyamides. But these films do not have a satisfactory water vapor permeability.
It still remains problematic to realize synthetic smokable films, easy to use, for foodstuff casings, showing a high permeability at high temperatures and a low permeability around room temperature.
Now, it has been surprisingly found that the combination of two specific types of polymers in an oriented film lead to a film showing excellent properties as regards water vapor permeability at high temperatures, excellent properties as regards barrier properties at room temperature and excellent properties as regards mechanical resistance (such as toughness, dimensional stability).
A first aspect of the invention is an oriented film comprising i) an aliphatic polyamide and ii) a block copolyetherester elastomer.
A second aspect of the invention is a tubular casing comprising the above film.
Another aspect of the invention is a process of manufacturing an oriented film comprising the steps of:
1) providing a composition comprising i) an aliphatic polyamide and ii) a block copolyetherester elastomer,
2) extruding an extrudate of composition of step 1),
3) quenching and orienting the extrudate of step 2) in at least one direction.
Another aspect of the invention is a process of manufacturing a tubular film comprising the steps of:
1) providing a composition comprising i) an aliphatic polyamide and ii) a block copolyetherester elastomer,
2) processing the composition of step 1) through double bubble extrusion to obtain an oriented blown film.
The film of the invention shows excellent water vapor permeability at high temperatures, say for temperatures ranging from 50° C. to 100° C., and barrier properties at lower temperatures, particularly room temperature, say for temperatures between 20° C. and 25° C. Thanks to the film of the invention, it is now possible to smoke products very efficiently: the high water vapor permeability of the film at high temperatures allows the smoke to go through the film and come in contact with the product during the smoking process. On another hand, because of the barrier properties of the film at room temperature, no humidity is lost when the product is cooled. Thanks to the shrinkability of the film of the invention, no wrinkle appear on the casing after cooling down the product.
The films of the invention can find use in casings for smoked foodstuffs. This includes sausage casings, but also meat and/or cheese casings. The films of the invention can also find use in the roofing field as well as for clothing.
The first essential component of the film of the invention is an aliphatic polyamide. By “aliphatic polyamide” is meant herein aliphatic polyamides, aliphatic copolyamides, blends and mixtures thereof. Preferred aliphatic polyamides for use in the invention are polyamide 6, polyamide 6.66, blends and mixtures thereof. Polyamides 6.66 are commercially available under the tradenames “Ultramid C4”, “Ultramid C35” from BASF, Germany, or under the tradename “Ube5033FXD27” from Ube Industries Ltd. Polyamide 6 is commercially available under the tradename Nylon 4.12 from E.I. du Pont de Nemours and Company, Delaware.
In a preferred embodiment of the invention, the aliphatic polyamide has a viscosity ranging from about 140 to about 270 cubic centimeters per gram (cm
3
/g) measured according to ISO307 at 0.5% in 96% H
2
SO
4
.
The aliphatic polyamide is usually present in the film of the invention in an amount from about 50 weight % to about 99.9 weight %, preferably from about 70 weight % to about 99.9 weight %, relative to the weight of the film.
The film may further comprise other polyamides such as those described in U.S. Pat. Nos. 5,408,000; 4,174,358; 3,393,210; 2,512,606; 2,312,966 and 2,241,322, which are incorporated herein by reference. The film may also comprise partially aromatic polyamides. A suitable partially aromatic polyamide is the amorphous copolyamide 6-I/6-T of the following formula:
Some suitable partially aromatic copolyamides for use in the present invention are the amorphous nylon resins 6-I/6-T commercially available under the tradename Selar® PA from E.I. du Pont de Nemours and Company or commercially available under the tradename Grivory® G 21 from EMS-Chemie AG.
The second essential component of the invention is a block copolyetherester elastomer.
The copolyetherester(s) are generally hydrophilic, as described in more detail below.
The viscosity of the copolyetheresters is preferably less than about 3000 pascal seconds (Pa.s) and preferably at least 20 Pa.s, measured according to the standard ISO11443. Preferably, the viscosity is in the range from about 20 to about 2000 Pa.s, more preferably from about 40 to about 1000 Pa.s, and more preferably from about 50 to about 700 Pa.s, measured according to the standard ISO11443. The viscosity in Pa.s is measured according to the standard ISO 11443 as a function of shear rate in sec
−1
and temperature. The temperatures used in the measurement of viscosity are from a minimum of just above the melting (or softening) point of the polymer up to a maximum of just above the temperatures used in the processing methods (for example, coextrusion, injection molding and lamination, blown film extrusion) of thermoplastic materials. The temperatures used in the processing of thermoplastics are generally from about 20 to about 50° C., and particularly from about 40 to about 50° C., above the melting point of the thermoplastic. The shear rates used in the measurement of viscosity were from about 10 to about 10000 sec
−1
, which encompass those typically encountered in the processing methods of thermoplastic materials.
Preferably, the melting point of the copolyetheresters is greater than 120° C., usually from about 120° C. to above about 220° C. The melting points are determined by differential scanning calorimetry (DSC) in accordance with the standard ISO 3146.
In one embodiment of the invention, the copolyetheresters are sel
Albertone Yannick
Laue Dagmar
Schenck Heiko E.
E. I. du Pont de Nemours and Company
Woodward Ana
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