Note: Descriptions are shown in the official language in which they were submitted.
~01~ 3~
The present invention relates to high density
polyethylene films for wrapping butter and margarine and
more particularlly to such high den~ity polyethylene films
containing finely divided a'uminum pigment.
At present butter and margarine are usually
wrapped in parchment or aluminum ~oil. Recently, paper-
like thermoplastic films have become available as wrapping
material for butter and margarine. Canadian application
Serial No. 186,508 which was filed November 22, 1973 on
an invention by V.G. Zboril descrlbes such a paper-like
thermoplastic film.
Aluminum foil is a good wrapping material for
butter and margarine. However, aluminum foil tend~ to be
expensive. Parchment and the known thermoplastic ~ilms
such as the paper-like thermoplastic films discussed above
are more economical than aluminum foil, but have the
disadvantage that when butter or margarine is wrapped therein
and stored in a brightly illuminated display case~the
flavour of the butter or margarine tends to deteriorateO Attempts
to overcome ~his disadvantage of such paper-like therm~-
plastic film by the addition of the pigment TiO2 were ~`~
unsuccessful as is discussed hereinafter.
It is an ob~ect of the present invention to providea wrapping material for butter or margarine which is more
ec~nomical than aluminum foil and which is more ef~ective
than parchment ~nd the known thermoplastic films in
protecting butter or margarine from deterioration of its
flavour upon stoIage in a brlghtly illuminated display case.
With this ob~ect in view,the present invention
provides wrapping material for butter or margarine comprislng
a high density polyethylene film made from polyethylene
having a density in the range of from 0.945 to 0.970 g/cm3
3~3~
and containing finely divided aluminum pigment, the aluminum
pigment being pre~ent in an amount o~ at least 0.1 g/m2 O~
the film and the film havlng a thLckness in the range o~ from
15 to 200~um.
In one embodiment of the present invention, the
aluminum pigment is present in an amount in the range of from
0.5 to 3.0 g/m2 of the film and the film has a thickness in
the range of from 20 to 60 ,urn.
In another embodiment of the present invention, the
film also contains mica particles, the mica particles being
present in an amount in the range of ~rom 1.5 to 4.5 g/m2 of
film, the largest dimension of the mica particles being less
than 150,um.
The film comprising the wrapping material of the
present invention may be prepared by a blown film or other process~
from any film-~orming polyethylene having a density in the
range of from 0.945 to 0.970 g/cm3 and containing alumlnum
pigment as described above. Preferably, however, the
polymer of the blown film is a polyethylene having a densitg
in the range of from 0.945 to 0.970 g/cm3, a melt flow index
(Ml:) in the range of from 0.1 to 2.0 especially in the range
of from 0,4 to 1.5 decigrams per minute and a stress exponent
(S.E.) in the range of from 1.6 to 2Ø
The melt flow index (M::) o~ the polyethylene is
measured according to the procedures o~ A.S.T.M. D-1238.
Stress exponent (S~Eo ) is discussed in Canadian
Patent 664,699 which issued 11th June, 1963 to C.E. Ashby,
S.P. Foster and E.T. Pieski and in Canadian Patent 771,260
which issued 7th Noveniber 1967 to D.J. Ryan and B.J. Starkey.
3 The stress exponent is determined by measuring the throughput
of a melt indexer at two stresses (2160 and 6480g loading)
-- 2 --
.. . .
:~ ~)43~3~L
using the procedures of the ASTM melt index test method
; D-1238. The stress exponent i9 calculated using the ~ormula:
Stress exponent (S,E.) = 1 (wt extruded witth 6480 g wt
0.477
The stress exponent of a polymer is a measure of melt
viscosity and is not a direct measure of molecular weight
distribution. Stress exponent may be a ~unction of polymer
molecular weight and it is preferred that the stress exponent
values of different polymers be measured at similar levels
of molecular weight or melt index whenever possible.
The film should have a thickness in the range of `
from 15 to 200Jum, preferably in the range of from 20 to 60
~m.
The minimum amount of finely divided aluminum pigment
which should be present in the film comprising the wrapping
material of the present invent~on depends on the particle
shape and the particle size distribution of the particular
pigment being used. ~owever, the alumin~m pigment should be
present in an amount of at least 0.1 g/m2 of film, The
maximum amount of aluminum pigment which may be present in
the film is governed by economic considerations and by the
processability of the film in the film making process.
Preferably the aluminum pigment is present in an amount in the
range of from 0.5 to 3.0 especially in the range of from o,8
to 1.5 g/m2 of film.
Optionally, inorganic lamellar filler partlcles such
as mica particles may also be present in the film comprising
the wrapping material of the present invention in order to
improve the processability of the film on the packaging
3o machinery therefor and to make the film more paper-like in
appearance, texture and the like~ The mica particles should
~ 0~3~3~
be present in an amount in the range of from 1.5 to 4.5
preferably in the range o~ from 2.0 to 3.5 g/m2 and should
have a largest dimension (diameter) o~ less than 150~um.
Preferably the mica particles should have a weight median
size of about 12 ~m with less than 0.2% by welght of the
particles being larger than 44~um i.e., being retained on
a 325 mesh (U.S. Sieve Series) screenO
As illustrated herelnafter~ the rate of
- deterioration, as evidenced by peroxide build-up and taste
deterioration, of butter and margarlne wrapped in the
wrapping material of the present invention is much lower than
the rate of deterioration of butter and margarine wrapped in
(1) parchment, (2) unfilled and unpigmented high density
- polyethylene, (3) TiO2 pigmented hlgh density polyethylene
fllm, (4) mica fllled high density polyethylene film or (5)
mica filled and TiO2 plgmented hlgh density polyethylene fllm,
when each of the above packages ls stored in a brightly
llluminated display case.
The wrapplng material of the present inventlon
ls illustrated by the ~ollowing E~amples.
Three lots of fresh butter and three lots of
freshly produced margarine were obtained and packaged in
indlvidual small packages (21 + 0.2 g/package) made from
twelve different wrapping materials; three packages of butter
and three packages of margarine being made up from each
wrapping material for each lot for a total of 216 packages.
Ten of the wrapping materials were high density polyethylene
(HDPE) film materials of which eight were modified by the
addition of a mica filler and/or a pigment. The other two
wrapping materials were conventional butter parchment paper
and aluminum foil wrap. The details of the high density
polyethylene (HDPE) film materials are given below in Table
I.
T.~
. . .
Pigment
HDPEl- Film Mica Fil er2~ TiO2 Aluminum
Film Thickness g/m~ by g/m % by g m Y
No. ~ m o~ film weight of welght of weigh
film film
. ._ . . .~ . ..
1 22.6 _ _ _ _ _ _ -
2 25.9 _ _ _ _ _ _
3 27.1 _ _ 1029 5 - _
4 32 2 _ _ 1.53 5 _ _
27 9 2.64 10 _ _ _ _
6 2206 2.13 10 _ _ _ _
7 23.9 2.25 10 1.13 5 - - `
8 29.2 2.76 10 1,38 5 _ _
9 2506 2,42 10 _ _ o.g7 4
10 - 31.2 2.96 ld - - 1.18 4
. . . . ~_ . _ _ . . ~ .
(1) made from a ethylene homopolymer having a density of
o.~60 g/cm3, a MI of 0.75 decigrams/minute and a SoE~ 0~
1.8, ln a blown film process with a blow-up ratio of 4.4;
(2) wet ground mica having a weight median size of about 12 ~m
with less than 0.2~ by weig~t of the particles being larger
than 44 ~m i,e, being retained on a 325 mesh (U,S, Sieve
Serie~) screen, was compounded ~rom a dry blend with the
above ethylene homopolymer to a concentrate containing
40~ by weight mica. This concentrate was dry blended with
- more of the ethylene homopolymer to the concentration
indicated;
(3) TiO2 pigment available from the AMPACET* CORPORATION under
the designation "whit,e concentrate No. 11,200" was made up --
as a concentrate containing 70~ by weight TiO2 and then `
; dry blended with re of the ethylene homopolymer to the
concentration indicated; and
(4) CANBRO* 952 aluminum pigment was compounded from a dry
blend with the above ethylene homopolymer to a concentrate
containing 25% by weight aluminumO This concentrate was
dry blended with more of the ethylene homopolymer to the
concentration indicatedO
Table 1 indicates that only the small packages wrapped
in HDPE film Nos. 9 and 10 were wrapped in wrapping material
4 according to the present invention as these were the only two
of the ten HDPE film materials whlch contained aluminum pigment.
The packages of butter and margarine were exposed
for a period of 12, 24 or 4~ hours to the light from two 40 watt
cold-white fluorescent tubes mounted above an open refrigerated
denotes trade mark
- 5
.. . - , ~ ,
-
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display cabinet in whlch the temperature varied between 7 and
10C, The packages were placed 32.4 cm from the lights on a
shelf mid way between the ends o~ the cabinet where the llght
intenslty, as measured with a GE~ERAL ELECTRIC* light meter,
Model 213, varied bet~een 275 and 300 foot candles~i.e.
between 2960 and 3230 lux or lumens/m2.) To minimize the
effect o~ the position of the sample packages on the shelf,
the positions of the sample packages during exposure were
randomly selected for each trial.
After each exposure time, the entire contents of
each sample package was transferred to a test tube and melted
at approx. 60C. The samples were then thoroughly mixed and
after fat-serum separation, 5 g aliquots were removed for
duplicate Peroxide Value determinations made by the method
given in the 11th edition of the "O~ficial Methods of
Analysis of the Association of O~f~cial Analytical Chemists"
1970 pp. 445.
The peroxide values for the various package
samples of butter and margarine are given below in Table 2
and Table 3, respectively.
Sensory analysis of the above butter and margarine
samples was conducted by a panel of three experienced ~udges
using the 9 point hedonic scale for scoring level of oxidlzed
flavour as described by Larmond, Elizabeth in "Methods for
Sensory Evaluation of Food", Canada Department of Agriculture,
Publication 1284, 1970. In thls flavour scale, a numerlcal
value of 1 represents no detectable oxidized flavour and a
numerical value of g represents an extremely oxidized sample.
To overcome the problem of los~ of taste sensitivity due to
3o excessive coating of oral flavour buds with high fat product,
3% emulsions of the package samples in high quality skim milk
were prepared and served to the ~udges ln the form of re-
constituted milk.
* denotes trade mark
-- 6 --
~43~
A summary of the test panel results for the
various package samples for butte:r and margarine are given
below in Table 4 and Table 5, respectively~
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- 11
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Table 2 and 3 indicate that the lncrease in the
peroxide values of butter or margarine wrapped ~n wrapping
materials according to the present invention i,e. wrapped in
HDPE films 9 or 10, on exposure to a light intensity o~ 275
to 300 foot candles (i.e. 2,690 to 3,230 lux or 1umens/m2)for
periods of 12, 24 and 48 hours, was only 10 to 25% as great
as the increase in the peroxide values of butter or margarine
wrapped in parchment or any of the EDPE ~ilms 1 to 8 (HDPE
films without aluminum pigment) on exposure to the same
lighting conditions. Tables 4 and 5 indicate that under the
same conditions the increase in the oxidized flavour values
of the butter or margarine correlates with the increase in
the peroxide values indicated in Tables 2 and 3. Thus
the data in Tables 4 and 5 show the superiority of the
wrapping materials of the present invention over parchment
and the other HDPE film in protecting butter or margarine
from light induced oxidized flavour.
- 12 -
