Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02292983 1999-12-21
WW 5528-'1.L~
-1-
Mo5396
WW-5528
READY-TO-FILL PLASTIC SAUSAGE SKIN
This invention relates to a gathered, multilayer, biaxially oriented,
shrinkable, polyamide-based tubular film conditioned in ready-to-fill form
for wrapping fillings which are packaged in liquid or pasty state, preferably
for sausage meat.
Developments relating to synthetic sausage casings are
characterised by the desire to provide products which meet the changing
demands of the meat processing industry with regard to economic and
environmental factors.
Multilayer, biaxially oriented plastic casings based on polyamide
(PA) in conjunction with other plastics have for many years in many
respects proved successful for the production of boiled and boiling
sausages.
The person skilled in the art takes biaxial orientation to mean the
transverse and longitudinal stretching of the thermoplastic extrudate at
temperatures between the glass transition temperature and melting
temperature of the polymeric materials. Biaxial orientation is
conventionally performed by means of a bubble filled with a gas or fluid
pressure cushion enclosed between two gas- or fluid-tight roller pairs
running at different peripheral speeds. During orientation, the molecules of
the tubular film, which is in the solid state, become aligned in such a
manner that the modulus of elasticity and strength in both the transverse
and longitudinal direction are considerably increased. Orientation is
generally followed by a further heat treatment.
DE 4,339,337 describes a five-layer, biaxially oriented tubular film
for packaging and wrapping foodstuffs. This casing is characterised in that
it is made from an internal and external layer of the same polyamide
CA 02292983 1999-12-21
WW 5528-Foreign
-2-
material and a central polyolefin layer together with two coupling layers
consisting of the same material.
EP 530 538 describes a five-layer, coextruded, biaxially oriented
tubular film having at least 3 polyamide layers, wherein polymer layers
having barrier properties for water and oxygen are arranged between the
inner and outer polyamide layers.
Highly efficient processing of, for example, the above-stated tubular
films is of particular interest to the meat processing industry. The tubular
films are accordingly subjected to a gathering process in which they are
folded together on a gathering mandrel to form a gathered "caterpillar", so
dramatically reducing the length of the gathered tube. Gathering of a
tubular material is known, for example, from DE 89 44 623 C2.
The flexibility of the polyamide-based tubular films in the dry state is
insufficient for them to be filled without creases and to be applied so as to
retain sufficient shrinkage properties after the boiling or cooking operation,
such that a smooth, crease-free sausage is obtained. For this reason, the
tubular polyamide film is dipped in or rinsed with cold and also hot water
shortly before filling with meat. This procedure is described inter alia in DE
3,426,723.
EP 0 248 860 describes that the gathered tubular films exhibit
variable water absorption on rinsing with water, for example due to
differing application rates of gathering lubricant, so giving rise to
differing
levels of elasticity of the tubular film within the "caterpillar", which is
also
accompanied by variations in diameter on filling. For this reason, the
tubular film is premoistened before gathering by rolling the tubular film with
an internal bubble of water. This has the disadvantage of non-uniform
moistening over the length of the roll, as the quantity of water decreases
with the length of the roll.
CA 02292983 1999-12-21
'23189-8501
- 3 -
EP 0 640 289 describes a gathered footstuff casing
conditioned in ready-to-fill form which, on gathering, is
sprayed with a mixture (emulsion) of water and gathering
lubricant, wherein production and ensuring uniformity of
spraying properties are particularly problematic.
EP 0 815 732 describes a ready-to-fill sausage skin
which, before gathering, is sprayed with a spraying solution
which, together with an emulsifier, comprises a substance to
establish the pH value, for example potassium sorbate, a
bactericide and a lubricant. The complicated production
process for the emulsion may be considered a disadvantage.
The object thus arose of providing a ready-to-fill,
gathered tubular film having a large compression ratio, which
film is simply conditioned in such a manner that it need not
be additionally rinsed by the user and retains elevated
consistency in diameter during the filling process and
reliable machinability.
This object was achieved by the provision of a
tubular film which is biaxially oriented, has at least three
layers, is shrinkable and has polyamide-based layers on both
sides (inside and outside) and a water barrier layer in the
middle, may optionally preferably have between the inner layer
and/or outer layer and central layer one or also more further
layers) and is conditioned in ready-to-fill form by means of
prior spray mositening and gathering.
Accordingly, in one aspect the present invention
provides a gathered, biaxially oriented, shrinkable tubular
film laminate conditioned in ready-to-fill form, comprising
an outside film, an inside film and at least one water barrier
layer interposed therebetween, wherein said outside film and
said inside film are polyamide-based characterized in that
said outside film contains a spraying medium in an amount
corresponding to the saturation limit thereof.
In another aspect the invention provides a process
for making a gathered film laminate comprising (i) preparing
a biaxially oriented, shrinkable tubular film laminate, and
(ii) spraying on said laminate a spraying medium, and (iii)
CA 02292983 1999-12-21
23189-8501
- 3a -
gathering said tubular film laminate, and (iv) storing said
gathered tubular film laminate under conditions sufficient to
promote the soaking of said spraying medium into the outer
layer.
Owing to specific spray moistening conditions and a
simply prepared spraying agent, the tubular films according
to the invention have surprisingly been found to provide
excellent processing characteristics on gathering and filling
in the case of the preferred use as a synthetic sausage skin.
Spray moistening is performed according to the
invention by applying the spraying medium used for moistening,
preferabl water, which may optionally additionally contain a
conventional fungicide (for
CA 02292983 1999-12-21
WW 5528-Forei
-4-
example quaternary ammonium chloride compounds as are offered for
sale by Bode Chemie under the commercial name
Sokrena) andlor conventional preservatives (for example sodium
salts, manufacturer: Merck), preferably at a droplet size of 0.01 to 0.5 mm,
preferably of 0.05 to 0.1 mm, on the outside, preferably on both sides of
the collapsed tubular film as it passes through a conventional commercial
winding machine (for example supplied by Kuko or Eichel). The quantity of
the spraying medium applied in this operation is established, preferably by
the arrangement of the spraying apparatus and the speed of the rolling
operation, such that the quantity of spraying agent applied at most
corresponds to the saturation limit of the outer polyamide layer. In another,
specific embodiment of the invention, in addition to the application of the
spraying agent, gathering lubricants, for example triglyceride mixtures,
may simultaneously be transferred onto the tubular film in the same
operation using a further apparatus.
The rolled tubular film is subsequently preferably stored in the rolled
state in a manner that permits no exchange of moisture with the
surroundings, for example in a polyethylene pouch having a wall thickness
of approx. 100 pm, until the spraying medium has soaked in to such an
extent that no liquid droplets are any longer visible on the surface. The
storage time required for this purpose is generally at least 24 hours.
The tubular film moistened according to the invention may be
gathered with a much higher compression ratio than unmoistened tubular
film. The compression ratio, i.e. the ratio of the gathering length of the
ungathered tubular film to the length of the gathered "caterpillar" may be
increased from <50 to greater than 100. Moreover, both in the unfilled and
filled state, virtually no gathering creases are any longer visible or
detectable as surface markings, wherein the improvement is achieved
both with axial gathering and helical gathering. The consistency in
CA 02292983 1999-12-21
WW 5528-Foreign
-5-
diameter of the filled sausage is distinctly increased and filling may be
performed on automatic filling machinery in a substantially more trouble-
free manner.
The polyamide based layers of the tubular films according to the
invention preferably contain as the substantial constituent a linear aliphatic
polyamide (PA) selected from among PA 6, PA 66, PA 11, PA 12, andlor
linear, aliphatic copolyamide, selected from among PA 6,66, PA 4,6, PA
6,6, PA 6,8, PA 6,9, PA 6,10, PA 6,11, PA 6,12 or a blend of the above-
stated polyamides andlor copolyamides, and may additionally contain
conventional auxiliary substances in conventional quantities. Proportions
of aromatic polyamide or partially aromatic polyamide may be incorporated
into the polyamide, copolyamide or blends, for example in order to improve
the processing or the barrier properties of the casing. Tubular films, in
particular synthetic sausage skins, which are suitable for the production of
the gathered tubular films conditioned in ready-to-film form according to
the invention are commercially available under the name Walsroder~ K
flex or Walsroder~ K plus (Wolff Walsrode AG).
The water barrier layer in the middle and optionally further water
barrier layers preferably substantially consist of one or more polyolefins
having water vapour barrier properties, such as in particular polyethylene
or polypropylene or polybutene or the copolymers thereof, which may
additionally have modified terminal groups in order to improve composite
adhesion, or also contain so-called ionomer polymers, such as in particular
Zn ionomers prepared from ethylenelacrylic acid copolymers and may
additionally contain conventional auxiliary substances in conventional
quantities.
In order to reduce greying effects and in order to improve the shelf
life of the finished sausages, the tubular films may, apart from the water
barrier layer, additionally contain at least one further layer having oxygen
CA 02292983 1999-12-21
WW 5528-Foreign
-6-
barrier properties. These oxygen barrier layers preferably substantially
consist of saponified ethylene vinyl acetate or blends thereof with other
polymers.
Examples & Comparative Examples
The tests listed below were performed with the following Examples:
Compression ratio Unit (m/m)
As mentioned above, the compression ratio is the ratio of the length
of the gathered sausage skin before gathering to the length of the
gathered "caterpillar" at a given gathering tube diameter. For example,
with a 60 mm diameter sausage skin, 40 mm gathering mandrel, length of
gathered sausage skin = 30 m and length of gathered "caterpillar" = 0.42
m, the compression ratio is 3010.42 mlm = 71 mlm.
Flexural rigidity
Flexural rigidity is taken to mean the force with which the gathered
"caterpillar" resists being changed from its straight shape into a bent or
other shape deviating from the straight shape. This test may
advantageously only be used with helical gathering. A quality rating on a
scale of 1 to 5 is awarded, with 1 meaning a large force and 5 meaning
very little force.
Evaluation of gathering creases (roughness of finished sausage)
The extreme mechanical loads to which the sausage skin is
exposed during the gathering process result in the formation of gathering
creases, which may sometimes still be seen on the finished sausage.
Evaluation was performed on a scale from 1 = no visible gathering crease
marks to 5 = severe gathering crease marks.
Consistency of diameter
The geometric uniformity of the sausage products, which may inter
alia be determined by a uniform diameter of the products, is of great
importance to industrial users. Evaluation was performed using a scale
CA 02292983 1999-12-21
WW 5528-Foreign
from 1 = t 0.1 mm tolerance in diameter to 5 = t 0.5 mm tolerance in
diameter, wherein the diameter was measured in the middle of the
sausages, which were approx. 25 cm in length.
Filling behaviour
Filling behaviour is taken to mean the reliability with which the
sausage skin may be filled without bursting or other defects. Evaluation
was performed using a rating scale from 1 = no defects within 100
"caterpillars" to 5 = at least 5 defects within 100 "caterpillars".
EXAMPI FS
The following Examples and Comparative Examples are intended to
illustrate the invention.
The various polymers used in the casings produced according to
the invention and in the Comparative Examples are abbreviated as
follows:
PA Polyamide 6 e.g. Durethan B 40 F (Bayer
AG)
PO-HV Propylene-based copolymere.g. Bynel E 379 (DuPont)
coupling agent
XX Ethylene/vinyl alcohol e.g. EVAL LC F 101 BZ (Kuraray)
copolymer
aPA Partially aromatic copolyamidee.g. Selar PA 3426 (DuPont)
MB Polyamide 6-based e.g. coloured masterbatch
PA
masterbatch gold
Example 1 (B1):
The commercial product Walsroder~ K plus SK, nominal diameter
60 mm (manufacturer: Wolff Walsrode AG, Walsrode) is spray moistened
according to the invention with a total weight gain of 8% and, after a
waiting period of 24 hours, 50 m are gathered with a gathering lubricant on
an axial gathering machine with a gathering tube diameter of 40 mm to a
"caterpillar" length of 420 mm. This sausage skin was filled without further
rinsing.
CA 02292983 1999-12-21
WW 5528-Forei
_g_
Comparative Example 1.1. (VB1.1):
25 m of the sausage skin used in Example 1 are gathered without
moistening with a gathering lubricant on an axial gathering machine with a
gathering tube diameter of 40 mm to a "caterpillar" length of 420 mm.
The sausage skin was rinsed in accordance with the manufacturer's
instructions (for example 30 minutes in hand hot water) and filled.
Example 2 (B2):
The commercial product Walsroder~ K flex red, nominal diameter
60 mm (manufacturer: Wolff Walsrode AG, Walsrode) is spray moistened
according to the invention with a total weight gain of 6% and, after a
waiting period of 24 hours, 60 m are gathered with a gathering lubricant on
a helical gathering machine with a gathering tube diameter of 40 mm to a
"caterpillar" length of 420 mm. This sausage skin was filled without further
rinsing.
Comparative Example 2 (VB2):
25 m of the sausage skin used in Example 2 are gathered without
moistening with a gathering lubricant on a helical gathering machine with a
gathering tube diameter of 40 mm to a "caterpillar" length of 420 mm.
The sausage skin was rinsed in accordance with the manufacturer's
instructions (for example 30 minutes in hand hot water) and filled.
Comparative Example 3 (VB3.1):
A three-layer plastic sausage skin was produced by the tubular film
orientation process. The sausage skin had a nominal diameter of 60 mm
and a total thickness of 45 pm.
The layer structure is: (inside) PA I copolyamide I PA (outside)
Thickness profile: (pm) (inside) 10 I 10 I 25 (outside)
CA 02292983 1999-12-21
WW 5528-Foreign
-9-
This sausage skin is spray moistened as described as above with a
total weight gain of 6% and, after a waiting period of 24 hours, 60 m are
gathered with a gathering lubricant on an axial gathering machine with a
gathering tube diameter of 40 mm to a "caterpillar" length of 420 mm. This
sausage skin was filled without further rinsing.
Comparative Example 3 (VB3.2):
As in VB3.1, but 30 m are gathered in an unmoistened state to a
"caterpillar" length of 420 mm and rinsed for 30 minutes before filling.
Example 4 (B4):
A five-layer plastic sausage skin was produced by the tubular film
orientation process. The sausage skin had a nominal diameter of 60 mm
and a total thickness of 55 Vim.
The layer structure is: (inside) PA I PA+MB+aPA I PO-HV I
PA+MB+aPA / PA (outside)
Thickness profile: (pm) (inside) 5 I 20 I 5 I20I 5 (outside)
This sausage skin is spray moistened according to the invention
with a total weight gain of 6% and, after a waiting period of 24 hours, 60 m
are gathered with a gathering lubricant on an axial gathering machine with
a gathering tube diameter of 40 mm to a "caterpillar" length of 420 mm.
This sausage skin was filled without further rinsing.
Example 5:
A five-layer plastic sausage skin was produced by the tubular film
orientation process. The sausage skin had a nominal diameter of 60 mm
and a total thickness of 41 p.m.
The layer structure is: (inside) PA I PO-HV I XX I PA+aPA I
PA+MB (outside)
Thickness profile: (gym) (inside) 8 I 4 I 3 I 20 I 6 (outside)
CA 02292983 1999-12-21
WW 5528-Foreign
- 10-
This sausage skin is spray moistened according to the invention
with a total weight gain of 6% and, after a waiting period of 24 hours, 50 m
are gathered with a gathering lubricant on an axial gathering machine with
a gathering tube diameter of 40 mm to a "caterpillar" length of 420 mm.
This sausage skin was filled without further rinsing.
The following Table shows the test results:
Sample B1 VB1.1 B2 VB2 VB3.1 VB3.2 B4 B5
Nominal diameter 60 60 60 60 60 60 60 60
Compression (m/m) 119 60 143 60 143 71 143 119
ratio on gathering
Flexural rigidityRating- 1 5
of
gathered
"caterpillar"
Evaluation Rating1 4 1 3 4 3 1 1
of
gathering creases
(roughness)
in
filled state
Filled diametermm 62 62 62 62 62 62 62 62
Consistency Rating1 4 1 3 3 3 1 1
of
sausage diameter
Filling behaviourRating1 4 1 4 4 1 2 1
on filling
machine
Although the invention has been described in detail in the foregoing
for the purpose of illustration, it is to be understood that such detail is
solely
for that purpose and that variations can be made therein by those skilled in
the art without departing from the spirit and scope of the invention except as
it may be limited by the claims.
