Note: Descriptions are shown in the official language in which they were submitted.
105~0~38
This invention relates to thermoplastics
compositions.
The use of disposable plastics wrappings,
containers and the like and their subsequent discarding,
either intentionally or accidentally, has led to the
problem of plastics litter. This invention relates to a
plastics composition the use of which can alleviate the
problem.
According to the invention a thermoplastics
composition contains as prodegradant a free carboxylic
acid and a metal salt of a carboxylic acid said metal having
an atomic number of 22 to 29, each being present in such a
concentration that; ~-
(a) The total amount of metal salt ~ free
carboxylic acid is between 0.001~ and
40% by weight based on the total composition;
(b) the amount of free carboxylic acid is
from 10% up to 95~ by weight, preferably
from 50% up to 90% by weight, of the
total amount of metal salt plus free
carboxylic acid.
The metals with atomic numbers 22 to 29 are Ti,
V, Cr, Mn, Fe, Co, Ni and Cu; of these the preferred metals
are iron and manganese.
The thermoplastics compositions described above
include both end-use compositions and masterbatch
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compositions, i.e. compositions which contain high concentr-
ations of additives and the utility of which is that they
can be added to the pure polymer to give an end-use composition.
In the case of end-use compositions concentration (a) above
is usually between 0.01% and 2%, preferably between 0.1% and
1%. The composition may contain a single polymer or it may
contain a blend of several polymers.
The free carboxylic acid is preferably, but not
necessarily, the same as that of the metal carboxylate.
However both are preferably selected from the group of
those with the formula R.COOH where R is a hydrocarbon
group with up to 30 carbon atoms. Particularly suitable
acids are those in which R iS a straight chain hydrocarbon
group with 8 up to 21 carbon atoms and having less than
3 double bonds.
The prodegradant according to the invention is
particularly suitable for increasing the rate of degradation
of olefine polymers, olefine copolymers with other monomers
copolymerisable with olefine monomers and blends of the
olefine polymers and/or copolymers.
The preferred olefine polymers are: ;
(1) Homopolymers of ethylene, propylene, butene-1,
4-methyl pentene-l and styrene.
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(2) Copolymers of these with one another and
other ~-olefines. ~ :
The preferred olefine copolymers are those which
contain at least 50~ by weight of ethylene, propylene,
butene-l, 4-methyl pentene-l and/or styrene together with
at least one of the following comonomers:
vinyl chloride
vinyl acetate -
methyl acrylate
methyl methacrylate ~ :
acrylic acid
methacrylic acid
hydroxyethyl methacrylate
The preferred olefine copolymers include the ionomers ~ ~
produced by neutralising or partially neutralising the : --
carboxylic groups of those copolymers which contain ~; ~
carboxylic groups. .- .`
Copolymers which contain at least 50% by weight :~
of ethylene are particularly suitable. .
In addition to the polymer and the prodegradant
a composition according to the invention may also include .~-
other additives~which are conventionally incorporated in ~ :
thermoplastics polymer compositions, for example in the : -~
case of polyolefines they may incorporate anti-blocking
: agents, slip agents, anti:static agents, stabilisers to -
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stabilise the composition during processiny as well as
stabilisers to stabilise the composition during use
(i.e. after processing has finished).
The invention includes wrapping material, string
and containers (including lids for containers) made of the
plastics composition described above. The following are
examples of containers; bags, sacks, boxes, cartons, bottles,
sachets, cups and cartridge cases.
The invention also includes an item of merchandise
packed in a material made of a plastics composition as
described above.
Several compositions according to the invention
will now be described by way of example. In all the
examples powdered ferric stearate and a powdered carboxylic -
acid or a liquid carboxylic acid dissolved in an alcohol
(and in some cases an antioxidant) were milled with po~yeth-
ylene. Milling was continued for lO minutes after mixing
had been achieved so as to form a crepe. The crepe was
compression moulded between polyethylene terephthalate foils
at a suitable temperature to give a coherent film 125 ~m thick.
Samples 1 cm x 3 cm were cut from the foil and tested in the
FS/BL Test.
FS/B~ Test
The samples were exposed to W irradiati~n using
a combination of equal numbers of 20 watt fluorescent
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~unlamp~ and 20 watt black lamps. '~he samples
circulated around the lamps at a distance of 10 cm
from the lamps. (~he circulation help~ to obtain
uniform irradiation). The samples were inspected
daily and tested for flex-crack failure. The time
to failure indicates the effect of the prodegradant,
a shorter time indicating a more effective prodegradant.
Table 1 gives embrittlement times in the FS/~
~est (in days) on high density polyethylene samples
which contained the stated quantities of ferric ~tearate
(metal saltj and free stearic acid. ~able 1 also
includes results on samples which also contained 0.02~/o
w/w of BHT. (BHT is a conventional "name" for a common
antioxidant the full chemical name of which is
2,6-ditertiarybutyl-4-methyl phenol).
~ABLE 1
Metal Salt Free Acid ~otal Pro- Free Acid Life in days
~ w/w % w/w degradant as % of at BHT conc.
~ w/w total Pro-
degradant NONE %.ow2fw
. ,,
0.008 0.002 0.01 20 23 ~
0.008 0.102 0.11 93 12 11 ;:
0.08 0.02 0.1 20 14 13 ~' ~
0.0~ 0.12 0.2 60 ~ 15
0.08 0.22 0.3 73 2 6
0.08 0. 52 0 . 6 86 . 5 2 _
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(The blank, i.e. high density polyethylene with no
additives, was 23 days.)
~able 2 gives similar re~ults on low density
polyethylene whioh contained the stated quantities of
ferric ~tearate (metal salt) and free stearic acid.
TAB~E 2
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Metal Salt ~ree Acid Total Pro- ~ree Acid ~ife
% w/w % w/w degradant as % of in
% w/w total Pro- days
degradant
.
Nil Nil Nil _ 5o
0.008 0.002 0.01 20 35
0 . 08 0 . 02 0 . 1 20 20
0.20 Nil 0.2 0 24
0.10 0.10 0. 2 50 19
0.08 0.12 0.2 60 17
~il 0. 20 0. 2 100 35
0.08 0.22 0.3 73-4 15
0. 08 0~ 6 86. 5 18
The four results at 0.2% total prodegradant show
that both the acid and the salt have prodegradant activity
but the two together give an enhanced effect.
- 10 Table 3 shows the effect of adding a variety of
other acids to the seme base mixture. In all caæes
the mixture contains:
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0~08% w/w of ferric stearate
o.o~h w/w of stearic acid
0.1% w/w of the other acid (as stated)
(i.e. O.Z~ w/w total prodegradant and 60% free acid
based on the total prodegradant.)
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=
~ame of Acid No. of C-atoms qype Life in days
_ :.
Benzoic 7 aromatic 19 ;~
Pelargonic 9 saturated 14
~auric 12 saturated 13
Stearic 18 saturated 18
Oleic 18 1 double bond 15
~inoleic 18 2 double bonds ~18 -
Behenic 22 saturated ~ 18
able 3 suggests that in the case of acids R.COOH
where R is hydrocarbon, the nature of R does not have a
.
large influence on the rate of degradation.
A result was obtained for the degradation of high
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density polyethylene u8ing manganese stearate as
prodegradant. With 0.6% wjw of manganese stearate and
1% w/w of stearic acid (i.e. 1.6% total prodegradant
~: 6~h of which is acid) the life in the ~S/BL test was 2 days;
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-~ithout the acid the life was 9 days. The manganese stearate
gave less colour than the iron.
The prodegradant effect of the synergistic combination
of 0.0~ ferric stearate and 0.02% stearic acid is exemplified
by the results shown in Table 4 for a series of thermoplastics
when exposed to FS~B~ radiation.
TABLE 4
_ Life in Days
Polymer Prodegradant Control
composition
.
7 1~2% vinyl Acetate/
Ethylene a) 34 75 -~
Polypropylene homopolymer b) 46 10
"Surlyn" Trade Mark A 1555 c) 13 71
a) MFI 2.0; density 0.926 g/cc.
The film was compression moulded to 125~ m.
b) The polypropylene was stabilised by 0.1% of calcium
stearate and 0.1% of 2:6 di-tertbutyl-4-methyl phenol
and blown at 220~C. to 20 ~m. ~-~
c) A partially neutralised copolymer of ethylene and
methacrylic acid compression moulded to 125 ~m thick
film.
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