Note: Descriptions are shown in the official language in which they were submitted.
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PACKAGING CASING BASED ON CELLULOSE HAVING
IMPROVED PROCESSING CHARACTERISTICS
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~ Backaround of the Invention
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The present invention relates to a packaging
casing, built up from a base tube of fiber-reinforced
cellulose, the fiber reinforcement being coated at
least on one surface with a layer of regenerated
cellulose. The inyention also relates to a process
~;for production of the packaging casing, in which a
~!10 fibrous base tube is provided with a cellulose layer
at least on its outside, by means of the viscose
process.
Tubular synthetic sausage casings of this
general type have long been known. It has also
~5~i15 previously been disclosed that the adhesion of dyes,
fungicidal salts and synthetic resin layers to the
outer cellulose layer of fiber-reinforced tubular
casings can be improved by an external coating layer
~,or adhesion-promoting interlayer of cationic resins
(U.S. Patents No. 3,695,904; No. 4,666,750 and No.
4,283,426).
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It is also known that sausage emulsions are
filled into these cellulose casings when they are n
the moistened state. The water thus serves as a
plasticizer for the cellulose and gives the casing
the necessary pliability and extensibility. When
i~ these soft, flexible casings, in the form of sections
; tied off at one end, are pushed onto the stuffing
horn of the filling machine, however, there are
problems in gripping and retaining the casings
-~ 10 manually.
~ ~,
Summary of the Invention
It is therefore an object of the present
invention to provide improved packaging casings with
- respect to their processing characteristics.
It is a particular object to provide a sausage
casing that, on the one hand, can easily be pushed
~; onto a stuffing horn in the wet state, but on the
other hand, retains unimpaired its optical
appearance, particularly its surface gloss.
It is also an object of the invention to
provide an improved process for producing the
sj packaging casings according to the invention.
In accomplishing the foregoing objects, there
has been provided in accordance with one aspect of
the present invention a tubular packaging casing,
`^~ comprising a base tube of fiber-reinforced cellulose,
the fiber reinforcement being completely coated with
a cellulose layer at least on the outside: and an
outer surface layer on the outer cellulose layer of
the base tube, the outer surface layer comprising a
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~` water-insoluble cationic resin and particles or
,; fibers of cellulose or a synthetic resin.
"''~J In accordance with another aspect of the
`; invention, there has been provided a process for the
production of the packaging casing as defined above,
comprising the steps of impregnating a tubular
.`,,5 fibrous substance and coating same at least on its
`~ outside with viscose; precipitating the viscose to
produce a resulting tube of fiber-reinforced
cellulose hydrate gel; coating the tube of cellulose
hydrate gel on its outside with an aqueous dispersion
of the still water-soluble cationic resin; and drying
the tube at an elevated temperature sufficient to
crosslink the cationic resin and convert it to its
water-insoluble form. In the process, the aqueous
dispersion contains from about 0.5% to 10% by weight
of particles or fibers of cellulose or a synthetic
resin.
Other objects, features and advantages of the
. .,
.20 present invention will become apparent from the
following detailed description of preferred
embodiments. It should be understood, however, that
;~the detailed description and the specific examples,
while indicating preferred embodiments of the
~,~25 invention, are given by way of illustration only,
since various changes and modifications within the
~,spirit and scope of the invention will become
;~sapparent to those skilled in the art from this
jdetailed description.
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30Detailed Description of Preferred Embodiments
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-` The achievement of this improvement is
attained by the combination of a heat-cured resin
with synthetic resin or cellulose fibers, in
particular with synthetic resin or cellulose
5 particles as the two principal components of the
surface layer. The outer surface of the packaging
.~ casing shows a distinct roughness. As a result, the
.
- casing possesses improved processing characteristics,
and in particular can readily be fitted onto the
s lO stuffing horn of filling machines in the moist state.
Virtually no change is detectable in the surface
gloss or the transparency of the casing. The tubes
:~ can also be wound up in the flattened state without
~,i damage to the relatively soft and scratch-sensitive
cellulose surface. The particles or fibers are
permanently bonded with the surface of the casing.
The resin layer encloses the particles or fibers
completely, or at least to the extent that they
adhere firmly.
The particles or fibers embedded in the outer
resin layer consist of cellulose or synthetic resin,
the selection of the synthetic resin being governed
by the following criteria. During the final drying
process, when the resin of the outer layer makes the
transition into its water-insoluble form, the
material used for the particles or fibers must not
run to form a film or dissolve in the resin, but must
retain its particulate structure as far as possible.
In addition, the synthetic resin and cellulose
particles should if possible possess a specific
weight which approximately corresponds to the density
of the coating dispersion containing the cationic
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~ resin, so that they remain suspended in this
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dlspers~on and possess no tendency to float or sedlment.
Partlcularly suitable synthetlc resln particles are
~ those based on homopolymers or copolymers contalnlng vlnyl
.; chlorlde unlts, and ln particular those of polyvlnyl chlorlde
, .
havlng a partlcle slze greater than about 0.1 ~m. These rela-
~`~ tlvely coarse partlcles are formed as a byproduct in the centrl-
-;~ fuglng of PVC dlsperslons whlch have to be freed of partlcles of a
~ slze greater than 0.1 ym for paper coatlng. Thls provldes a
"~ .
partlcularly economlcal startlng substance for the productlon of
the casing accordlng to the lnventlon.
In the case of partlcles havlng a slze of less than
about 0.2 ym, the effect almed at ls relatlvely slight, whereas ln
~ the case of partlcles greater than about 5 ym the danger exlsts
.~ that they wlll not be sufflclently retained by the resln layer.
In general, partlcles havlng a diameter ln the range from about
` 0.2 to 2 ym are partlcularly advantageous. When flbers are used,
;~; preference ls given to flbers havlng a relatlvely short length,
that ls to say less than about 10 ~m, ln partlcular less than
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~ about 5 ym. Fibers havlng an average length of from about 0.1 to
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.l 20 1 ym are generally used.
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~ The catlonlc resln ls, for example, a product of a con-
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~;' densatlon reactlon of proteln of anlmal or vegetable orlgln, such
as gelatln, soybean proteln, groundnut proteln or wheat proteln,
ln partlcular caseln, or a phenol, wlth an aldehyde, such as
malonaldehyde or glutaraldehyde, ln partlcular formaldehyde or
~`;, glyoxal, the proportlon of aldehyde belng from about 5 to 15, ln
partlcular from about 6% to 10% by
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weight, or a product o~ a condensation reaction of urea with
formaldehyde (United States Patent No. 2,616,874) or of melamine
.~ and formaldehyde (United States Patent No. 2,796,362 and No.
~x 2,345,543). Preferred products are those obtained by a condensa-
~ tion reaction of a bifunctional halohydrin such as epichloro-
`A~` hydrin with a polyamine, polyamide or polyaminepolyamide (United
~. States Patents No. 2,573,956, No. 2,926,154 or No. 3,378,379).
~,
Suitable polyamines for the reaction with epichlorohydrin are
simple alkylenediamines or polyalkylenepolyamines, such as for
~: 10 example, diethylenetriamine, triethylenetetramine, tetraethylene-
pentamine and the corresponding polypropylene- and polybutylene-
polyamines.
The polyamide-polyamines are preferably products of
a condensation reaction of a saturated, aliphatic, dibasic acid
having 3 to 8 carbon atoms in the molecule with one of the above-
mentioned polyamines which possesses at least one secondary and
two primary amino groups.
In other preferred embodiments: the weight ratio of
cationic resin to particles or fibers is in the range from about
1:5 to 5:1, preferably 1:3 to 2:1; said casing possesses, at a
water content of from about 5% to 15% by weight and a glycerol
content of from about 18% to 22% by weight based on the total
weight of the casing in each case, a weight per unit area of from
about 70 to 130 g/m2, preferably 80 to 120 g/m2; and in the
process, the aqueous dispersion contains from about 2~ to 4% by
weight of P~C particles and from about 1~ to 5~ by weight of a
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~ crosslinkable cationic resin comprising a crosslinkable epichloro-
:~. hydrin/polyamine-polyamide resin.
The coating on the outside of the tube comprises a
total of from about 40 to 200 mg, preferably from about 60 to
~ 150 mg, of water-insoluble cationic resin, based on a square
~ meter of base surface. These values were determined as follows:
200 mg of surface material are scraped off from
s 500 cm2 of the outer surface, and the nitrogen content of the
. scraped-off material is determin~d, for example, by combustion
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'-~ 10 analysis. For compariSQn, the outside of the tube composed of
the same base material, though without coating, is tested for its
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~r;: nitrogen content. For this purpose, 200 mg of~i surface material are scraped off in an analogous
i~; manner from 500 cm2 of inner surface in each case,
s and the nitrogen content is determined in the same
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way. Obtaining the difference between the nitrogen
values for the coated and the uncoated tube gives the
.. nitrogen value for the outer coating, and from this
the content of cationic resin on the outside of the
tube can be obtained.
The outer coating -- due to the use of aqueous
resin dispersion in the production process --
contains small amounts of chemical emulsifier, so
that the intended properties of the coating or of the
tube casing with coating on the outside are not
influenced.
The sausage casing is used primarily in the
production of sausages of the raw sausage type, such
~ as salami or hard sausage. In this case, it
-~~ possesses an inner coating, which is conventional for
this sausage, to improve the adhesion between sausage
meat and cellulose casing or to improve the peel-
ability of the casing from the sausage meat.
The sausage casing has a conventional water
content of, for example, from about 5% to 15% by
weight or possesses a very high water content of
about 25% by weight or more, so that it need not be
moistened before filling.
,~ The production of fiber-reinforced tubulàr
casings based on cellulose hydrate is known. They
are conventionally produced by coagulation of the
alkaline viscose solution, applied to the outside of
a tubular fiber reinforcement, with acidic
precipitation liquid and regeneration of the
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cellulose, and contain plasticizers, such as
j glycerol.
;~ The fiber reinforcement usually has a weight
~ per unit area of about 17 to 28 g/m2 and is
i; 5 preferably a paper inlay or a fiber nonwoven of hemp
fibers. It is preferably impregnated and coated with
viscose only on the outside. If an additional
viscose coating takes place on the inside of the
~- fiber tube, the proportion of the viscose on the
~ lO inside relative to the total viscose applied is a
;~ maximum of about 30% by weight. The regenerated
cellulose is distributed in a corresponding manner in
`~ the cross-section of the casing, that is to say that
~-;; about 70% to 100% of the cellulose is on the outside.
Processes for the external coating of
cellulose hydrate tubes have likewise been described,
for example, in European Patent No. 37,025 and in the
" references cited therein.
The invention is explained in detail by means
of the examples which follow. The starting material
~, in each case is a fiber-reinforced tube having an
outer layer of cellulose hydrate gel, which has been
~ produced by treating the outside of the fiber tube
..~
~j with viscose, conventional coagulation and
regeneration of the outer viscose layer with acidic
precipitation and regeneration li~uid, and washing
with water. The tube of fiber-reinforced cellulose
hydrate gel obtained is coated on its outside with
the dispersion according to the invention and is
dried in the inflated state in a drying tunnel at
120C to 150C, the cationic resin being cured and,
in its water-insoluble form, fixed together with the
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~,r particles to the cellulose surface. The tube is then
'~ adjusted to the desired moisture content.
The finished tube is further processed as a
-~ section tied off at one end. The tie comprises a
string or cord, with or without an additional metal
: ., clip.
. . ~
~ Example 1
~; .
; The aqueous coating dispersion has the~ following composition:
-~ 10 - 2% by weight of a heat-curable, still
water-soluble polymer of ethylene
diamine, diethylene triamine, adipic acid
and epichlorohydrin (RESAMIN HW 601 from
~` Cassella) as cationic resin,
;~ 15 - 6% by weight of a 50% strength by weight
;v~ PVC dispersion, equivalent to 3% by
i weight PVC solids content, having a
,~ particle size of 0.1 to 1.6 ~m (HOSTALIT
E 1069/072~from Hoechst),
- 10% by weight of glycerol.
The finished tube possesses on its outer
`~ surface a layer of 80 mg of cationic resin and 120 mg
of PVC particles per square meter of surface.
Sections tied off at one end are produced from
the externally coated tube (caliber 65 mm). After
moistening, they can readily be pulled onto the
stuffing horn of a sausage filling machine, and are
much improved in their processing characteristics.
The hard sausage produced exhibits the desired high
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surface layer.
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Example 2
The aqueous coating dispersion has the
following composition:
- 2% by weight of the cationic resin of
~ Example 1,
5~ - 4% by weight of the 50% strength by
"f' weight PVC dispersion of Example 1,
,f.............. 10 - 10% by weight of glycerol.
The finished tube (caliber 85 mm) possesses on
.its outside a layer of 65 mg of cationic resin and 65
mg of PVC particles per square meter of surface.
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The pieces of tube, tied off into sections and
;~15 moistened, can readily be pulled onto the stuffing
~horn of the filllng machine in the production of
f~isausages of the salami type. As a result of the
increased surface roughness, they possess improved
performance characteristics. The finished sausages
exhibit the desired surface gloss and good trans-
,~
parency which are known for sausage casings made from
this material.
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