Food or edible material: processes – compositions – and products – Processes – Packaging or treatment of packaged product
Reexamination Certificate
1995-02-08
2003-02-04
Pyon, Harold (Department: 1772)
Food or edible material: processes, compositions, and products
Processes
Packaging or treatment of packaged product
C428S034800, C138S118100, C452S021000, C053S258000, C162S175000
Reexamination Certificate
active
06514553
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of manufacturing a fibrous cellulose casing and a casing manufactured by this method.
2. Description of Prior Art
Artificial cellulose casings, fibrous cellulose casings and fiber reinforced casings are manufactured from a long fiber paper base impregnated with cellulose which has been regenerated from viscose. Prior to viscose impregnation the paper is wet strengthened by the paper manufacturer, also using cellulose regenerated from viscose or alternatively using other wet strengthening materials such as polyamide epihalohydrin resins, polyvinyl alcohol, hydroxyethyl cellulose and various synthetically produced lattices either singly or in combination one with another. The chief reason for conferring this wet strength is to enable the paper to retain its integrity and withstand the subsequent heavy impregnation with the strongly alkaline viscose, which is applied by the casing manufacturer, and the subsequent strongly acidic cellulose coagulation and regeneration stage by which the casing is made.
Whereas the paper manufacturer may apply only one to six percent regenerated cellulose from viscose and/or other wet-strengthening resins calculated on the basis of total fiber weight to provide the necessary wet strength, the casing manufacturer usually applies a quantity of viscose of two to three times the total weight of the paper to construct the casing. For example, in the case of paper which weighs 21 g/m
2
, the casing manufacturer would add an additional 42 to 63 g/
2
regenerated cellulose from viscose in making the casing, amounting to a total cellulose weight 63 to 84 g/m
2
. Fiber-reinforced cellulose of this example would be commercially prepared or plasticized with a quantity of 20 to 25 percent glycerol and moisturized with 5 to 10 percent water, to prevent it drying out and becoming brittle prior to use, achieving an overall basis weight given of between 78,8 and 119 g/m
2
.
The process for making the paper and the process for making casing are very different. For example, imparting wet-strength to the paper is relatively easy and inexpensive for the paper manufacturer, and may be carried on in-line, whereas wet strengthening is totally impracticable and prohibitively expensive for the casing manufacturer who requires the paper fully wet-strengthened from the outset of the casing manufacturing process.
The fiber of the paper substrate used to make fibrous casing is usually a carefully selected choice of abaca fibers, also known as manila hemp fibers, grown in either the Philippines or Ecuador, which are subjected to a chemical pulping treatment to remove non-cellulosic material and to soften the fibers for paper-making. A portion of this fiber may be provided by alternative plant fiber such as sisal, jute, or wood pulp, etc., but not without affecting the casing strength characteristics, usually in a negative way. Papers so prepared, of basis weight between 17 and 28 g/m
2
, are well known in the art for manufacturing fibrous cellulose casings, in the range of size typically from 32 to 163 mm in diameter, or even larger, and usually the basis weight of the paper is increased, for example, from 17 to 19 g/m
2
, from 19 to 21 g/m
2
, from 21 to 23 g/m
2
, and so on in stages, as diameter increases and the need for greater strength increases. This is because the weight of the sausage product increases exponentially as a function of a squaring of the radius of the sausage.
The casing manufacturer's process usually involves unwinding the paper, supplied in rolls by the paper manufacturer, from an unwind stand, by drawing and forming the paper into the shape of a tube with overlapping margins. The paper is drawn continuously about its longitudinal axis by bending actions with the assistance of metal guides, while sticking the margins together using viscose immediately prior to the impregnation with bulk viscose which makes up the reinforced cellulose wall of the casing.
The composition of the aqueous viscose solution varies but may comprise, for example, 7 to 8 percent (wt-%) cellulose, 30-33 percent (wt-%) sodium cellulose xanthate of xanthate sulphur, 4-5 percent (wt-%) sodium hydroxide and water, with a ball-fall viscosity of 50 to 70 seconds (130 mg steel ball of 3,175 mm diameter over a distance of 20 cm). A Hottenroth ripening (salt) index of 4 to 5 at a temperature of 25 to 30 degrees Celsius may be regarded typical.
Once impregnated, the viscose is coagulated and regenerated into cellulose by passing the impregnated tube through a sulfuric acid and salt bath, usually containing ammonium and sodium sulphate mixtures, followed by various acid and water wash baths to complete the regeneration and remove all remaining sulphur from the viscose. Acid strength may vary from 40 to 60 g/l and a salt strength between 180 and 260 g/l with respect to sodium sulphate and between 10 and 50 g/l with respect to ammonium sulphate may be regarded typical. Before drying this fiber-reinforced tube it is usually passed through a bath containing a dilute aqueous glycerol solution, of 10-20 percent strength, to act as a plasticizer for the cellulose. Drying is preferably conducted with the casing in an inflated condition. Tension throughout the casing machine is maintained such that the diameter of the casing at the outset, that is the diameter provided by the original width of paper in the roll, less that used for overlapping, is reproduced as far as possible in the finished casing tube.
Viscose impregnation may be effected by pouring the viscose onto the outer surface of the paper substrate, well ahead of the acid bath, in order to ensure that the paper is thoroughly impregnated prior to regeneration of the cellulose with acid. Alternatively, the paper-impregnation may be accomplished with a specially constructed viscose die, wherein the viscose is presented under pressure, through the lips of the die, directly onto the outer surface of the paper or substrate. The paper is temporarily supported during transit across the ??? lips by a metal ring or cylinder, the gap between ring and die being such as to allow the paper to pass unimpeded, but not of such a width as to fully dissipate the pressure of the viscose before impregnating the paper. Impregnation is completed by passing paper between the die and the supporting ring for some distance within fixed gap dimensions, and thereafter passing the paper for some distance unsupported through air before entering the acid coagulation and regeneration bath.
Such impregnations may result in a product in which the two surfaces of the paper are unequally viscosed, only one side being fully impregnated owing to the resistance to penetration of papers of 17 g/m
2
and greater; greater paper weight usually equating to greater resistance.
In still another variant, viscose may be supplied to both sides of the paper simultaneously in order to effect a so-called double-viscose coating. This ensures that the paper is properly covered by viscose prior to coagulation and regeneration of cellulose.
Cellulosic tubings produced in these various ways are tough and strong and have low stretch characteristics. For these reasons they may be used as containers or casings for sausages, meats, or other articles of food, particularly in applications where size, in terms of diameter control, is a critical parameter, and where a highly mechanized sausage stuffing plant places high demands for consistency of performance, and where strength with toughness is at a premium.
While exact size is achieved from a fibrous casing exhibiting low stretch, this also means that for differences in sausage diameter of only a few millimeters, another size of viscose die has to be used. This entails additional costs for the separate inventorying on the part of the paper supplier, the casing manufacturer and the sausage maker and for additional dies.
In parallel with the development of ever more demanding packaging equipment in technologically advanced countries, which as desc
Höglund Boris
Kalm Vidar
King Edmund
Hon Sow-Fun
Oy Visco AB
Pyon Harold
Rothwell Figg Ernst & Manbeck
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