Note: Descriptions are shown in the official language in which they were submitted.
~ W094/280~ 216 3 ~ 4 ~ PCT/GB94/01182
IPROCESSING OF POLYESTERS
THIS INVENTION relates to a polyester composition and
in particular to such a composition containing biodegradable polyester
and capable of producing shaped articles resistant to embrittlement.
It has been disclosed by de Koning et al in Polymer 1992, 33,
(15),3295-3297 that whereas one such polyester poly[(R)-3-
hydroxybutyrate] (PHB) when freshly moulded shows ductile behaviour,
subsequent ageing seriously embrittles it and hampers its applicability.
Within several weeks of storage at room temperature, the tensile
modulus doubles, and the elongation at break drops below 10%. A
typical feature of the ageing process is that it can be partly reversed by
the employment of heat or mechanical strain. Using mild 'deageing'
treatments, the improvement in toughness is only small and temporary.
Such deageing appears to cause stability of physical properties of
PHB homopolymer and of copolymers (PHBHA) having also
hydroxyalkanoate (HA) other than hydroxybutyrate (HB) residue units.
The effect on the copolymer, although important, is not as great as with
PHB.
It has now been found that "deageing" treatment of
hydroxyalkanoate copolymers is significantly more effective if a
plasticiser is present and that "deaged" plasticised PHA homopolymer
and copolymers have improved properties.
According to the present invention there is provided a polyester
composition comprising at least one polyhydroxyalkanoate (PHA) and at
least one plasticiser thereof, in which ageing has occurred, characterised
in that (i) the polyester is restored to its original non-aged properties by a
heat treatment, and (ii) subsequent ageing of the polyester is retarded as
indicated by substantial improvement of at least one measurement
indicative of ageing compared to non heat treated polyester of the same
age. Alternately the retardation of subsequent ageing may be indicated
by substantial improvement of at least one measurement indicative of
ageing compared to heat treated polyester of the same age without
P!asticiser.
According to a further aspect of the invention there is provided a
2 ~
WO 94/28048 ~ . PCT/GB94/01182
shaped article at ieast partly made from a polyester composition
comprising at least one polyhydroxyalkanoate (PHA) and at least one
plasticiser thereof, in which ageing has occurred, characterised in that (i)
the shaped article is restored to its original non-aged properties by
heating, and (ii) subsequent ageing of the polyester is retarded as
indicated by substantial improvement of at least one measurement
indicative of ageing compared to non heat treated polyester of the same
age. Alternately the retardation of subsequent ageing may be indicated
by substantial improvement of at least one measurement indicative of
ageing compared to heat treated polyester of the same age without
plasticiser.
"At least partly made" means having structural components made
of PHA to such an extent that ageing of the PHA component ages the
whole article. Thus for example, PHA may be homogeneously mixed
with other biodegradable polymers such as polylactides or
polycaprolactone. In such mixtures the minimum amount of PHBV is at
least B0% W/w. Also articles having PHA components linked to other
components such as razors and toothbrushes, and articles made of a
matrix of some other biodegradable (e.g. starch) or non-biodegradable
polymer (e.g. polypropylene) with PHA inclusions, are within the
invention. In such mixtures the minimum amount of PHA is at least 30%
W/w. Articles made of PHA alone, nucleated or otherwise, benefit most
from the invention.
"Substantial improvement" means that the measurement indicative
of ageing, for example, elongation to break, is improved by 50% or more,
preferably 100% or more, compared to the heat treated aged polyester
without plasticiser at the same age as the heat treated aged polyester
with plasticiser, or alternately it can be compared to the non-heat treated
polyester of the same age. The "same age" means the same period of
ageing after the heat treatment i.e. one month after initial preparation of
the polyester for the non heat treated polyester is the equivalent age to
one month after heat treatment for the heat treated polyester.
By "restored to the original non-aged properties" is meant that the
heat treatment restores at least 50% of the ductility of the polyester as
~ WO 94128048 2 16 3 ~ ~ 3 PCT/GB94/0ll82
measured by conventional methods e.g. elongation to break, impact
testing (IZOD). Preferably the heat treatment restores at least 75% of
the ductility, especially at least 80%.
Aged polyester or shaped article in the present context means that
it has the mechanical properties equivalent to the polyester or article
having been stored for 24 hours or more at 20C. Non-aged polyester or
shaped article in the present context means that it has the mechanical
properties equivalent to the polyester or shaped article having been
freshly processed, i.e. mechanical properties equivalent to storage for up
to 24 hours at 20C, preferably storage for up to and including 1 hour at
20C of having been processed.
According to a preferred aspect of the present invention there is
provided a polyester composition comprising polyhydroxybutyrate (PHB)
or copolymer of hydroxybutyrate units and hydroxyvalerate (PHBV) units
and at least one plasticiser thereof, in which ageing has occurred,
characterised in that (i) the polyester is restored to its original non-aged
properties by a heat treatment, and (ii) subsequent ageing of the
polyester is re~arded as indicated by substantial improvement of at least
one measurement indicative of ageing compared to non heat treated
polyester of the same age. Alternately the retardation of subsequent
ageing may be indicated by substantial improvement of at least one
measurement indicative of ageing compared to heat treated polyester of
the same age without plasticiser.
The PHA is especially capable of a relatively high level of
crystallinity, for example over 30%, especially 50-90%, in the absence of
plasticiser. Suitably it is or includes at least one microbiologically
produced polyester having units of formula l:
~ ~ Cm Hn ~ CO -
where m is in the range 1-13 and n is 2m or (if m is at least 2) 2m-2.
Typically Cm Hn contains 2-5 carbon atoms in the polymer chain and the
remainder (if any) in a side chain. In very suitable polyesters n is 2m and
especially there are units with m = 3 and m --4 copolymerised together
and with respectively a Cl and C2 side chain on the carbon next to
oxygen in the chain. The polymer may be homopolymer, especially PHB,
2 1 ~
WO 94/28048 PCT/GB94/01182
or a copolymer PHBV containing preferably 4-20 mol% of m=4 units.
Thus, particular polyesters contain a preponderance of m = 3 units,
especially with 70 - 98 mol % of such units, the balance (if any) being
units in which m = 4. The molecular weight of the PHA is preferably
over 50000, especially over 100000, up to eg 2 x 106.
The PHA is conveniently a blend of two or more copolymers
differing in the value of m. A particular example contains
(a) PHA consisting essentially of Formula I units in which 2-5 mol %
of units have m = 4, the rest m = 3; and
(b) PHA consisting essentially of Formula I units in which 5-30 mol%
of units have m = 4, the rest m = 3.
In each such PHA there are side chains as above mentioned. The
proportions in such a blend are preferably such as give an average m = 4
content in the range 4 - 20 mol %.
In each such PHA having units with m = 3 and m = 4 there may
be very small, typically fractional, percentages of units having higher
values of m.
PHA comprising hydroxybutyrate units and hydroxyvalerate units
includes PHBV copolymers containing up to 1 mol percent of other
oxyalkanoate units whether introduced deliberately or not.
The PHA is preferably a fermentation product, especially of a
microbiological process in which a microorganism lays down PHA during
normal growth or is caused to do so by cultivation in the absence of one
or more nutrients necessary for cell multiplication. The microorganism
may be wild or mutated or may have had the necessary genetic material
introduced into it. Alternatively the necessary genetic material may be
harboured by a eukariote, to effect the microbiological process.
Examples of suitable microbiological processes are the following:
for Formula I material with m = 3 or m = partly 3, partly 4:
EP-A-69497 (Alcali~enes eutroPhus)
for Formula I material with m = 3: US 4101533 (A. eutrophus H-16), EP-
A-144017 (A. Iatus);
for Formula I material with m = 7-13: EP-A-0392687 (various
Pseudomonas) .
~WO 94/28048 ~ 'I 3 PCT/GB94101182
The PHA can be extracted from the fermentation product cells by
means of an organic solvent, or the cellular protein material may be
decomposed leaving microscopic granules of polymer. For specialised
end uses the cellular protein may be partly or wholly allowed to remain
with the PHA, but preferably subjected to cell breakage.
The polyhydroxyalkanoate is preferably polyhydroxy-butyrate
(PHB) or polyhydroxybutyrate-co-valerate (PHBV), which may be 3-
hydroxy or 4-hydroxy or a mixture of both. Especially preferred are the
(R)-3-hydroxy forms of PHB and PHBV.
Typically the composition contains microbiologically produced PHA
to the extent of over 50% w/w, especially over 80% w/w.
Alternately, the PHB or PHBV can be a product of synthetic
chemistry (Bloembergen and Holden, Macromolecules 1989, 22, p1656-
1663. Bloembergen, Holden, Bluhm, Hamer and Marchessault,
Macromolecules 1989, 22, p1663-1669).
The polyester composition can contain the usual additional
polymer processing additives such as particulate or fibrous or platy filler
or reinforcer, fibres, nucleating agents (for example boron nitride, talc or
ammonium chloride), and pigments. The nucleant is preferably present in
0 1 to 1 Ophr, especially 1 to 5phr. The composition can be in the form
of mouldings, extrudates, coatings, films or fibres, including multilayer
coatings, films or fibres.
The plasticiser is any material capable of plasticising polyester, i.e.
capable of improving the ductility of the polyester and especially any
material capable of plasticising PHB or PHBV. There may be one or more
plasticisers present. The ratio of such plasticiser to PHA is in the range
up to and including 40 phr w/w which includes most of the likely uses,
particularly 1 to 40 phr w/w, and for making effectively rigid but not
brittle articles the range 5-20 phr especially 6-12 phr w/w is generally
suitable.
Examples of suitable plasticisers are:
(a) high-boiling esters of polybasic acids, such as phthalates,
isophthalates, citrates, fumarates, g!utamates, phosphates or
phosphites. The esterified radicals may be for example Cl - C,2
~634~3
WO 94128048 PCT/GB94/01182 ~
alkyl, aryl, aralkyl or aralkyl. Particular examples are dioctyl-,
dibaptyl- and dirindecyl- phthalates and dialkylalkylene oxide t
glutamate (Plasthall 7050);
(b) high-boiling esters and part- of polyhydric alcohols, especially
glycols, polyglycols and glycerol. The acid-derived radical of the
ester typically contains 2-10 carbon atoms. Examples are
triacetin, diacetin and glycerol dibenzoate;
(c) aromatic sulphonamides such as paratoluenesulphonamide
Particular examples of such plasticisers are esters of polyhydric
alcohols, for example glyceryl esters of C1 - C4 carboxylic acids.
Generally it is preferred that the plasticiser should be biodegradable.
A particularly preferred plasticiser is a doubly esterified
hydroxycarboxylic acid having at least 3 ester groups in its molecule.
"Doubly esterified" means that at least some of the hydroxy
groups of the hydroxycarboxylic acid are esterified with a carboxylic acid
and at least some of the carboxy groups thereof are esterified with an
alcohol or phenol. Preferably at least the hydroxycarboxylic acid from
which the ester is derived is aliphatic or cycloaliphatic. Its backbone
structure (that is, apart from carboxy groups) preferably contains 2-6
carbon atoms. It contains preferably 2-4 carboxy groups and 1-3
hydroxy groups; and preferably the number of carboxy groups exceeds
the number of hydroxy groups.
The groups with which the carboxy groups are esterified contain
preferably 1-7, especially 2-5 carbon atoms. In the ester molecule they
can be the same or different. Preferably they are aliphatic. For thermal
stability but biodegradability such aliphatic groups preferably have
straight chains. If desired, a small portion of these groups are divalent,
so as to give an oligomer suitably containing up to 3 repeating units.
The groups with which the hydroxy groups are esterified
preferably contain 2-7, especially up to 4, carbon atoms, including the
carbon atom of the carboxy of such groups. In the ester molecule such
groups can be the same or different. Preferably they are aliphatic and,
for thermal stability and biodegradability, have straight chains. If desired,
a small proportion of these groups are divalent, so as to give an oligomer
~ WO g4/28048 21~ 3 ~ 13 PCT/~B94/01182
suitably containing up to 3 repeating units.
Other polyhydroxyalkanoates may act as plasticisers in this
system, for example polycapralactone.
This list is not exhaustive and any plasticiser of polyester which is
not listed above or which becomes available after the date of this
application would be suitable for use in this invention.
The invention also provides a process for improving mechanical
properties of an aged polyester comprising at least one
polyhydroxyalkanoate and at least one plasticiser thereof, which
comprises heating at a temperature whereby (i) the polyester is restored
to its original non-aged properties, and (ii) subsequent ageing of the
polyester is retarded as indicated by substantial improvement of at least
one measurement indicative of ageing compared to non heat treated
polyester of the same age. Alternately the retardation of subsequent
ageing may be indicated by substantial improvement of at least one
rneasurement indicative of ageing compared to heat treated polyester of
the same age without plasticiser.
The properties of the polyester or article of the present invention
can be assessed using the following measurements: stress-strain curve
including calculations of elongation to break, Youngs modulus, and
tensile strength; impact testing, for example IZOD; and dynamic
mechanical thermal analysis (DMTA). These are all standard methods for
testing mechanical properties.
Any one or more of the above-mentioned characterising properties
can be used to monitor the progress of the heat treatment. In practice it
is often sufficient to test the article by taking a sample from a batch,
cooling it to room temperature and subjecting it to manual flexing. In
established manufacturing it is often possible to fix the heating
temperature and then adopt a time that is fully adequate and affords a
small margin to cover accidental variations.
A further advantage of the present invention is that after
treatment the rate of ageing appears to get slower over a period of a few
weeks indicating that substantial stability of measurements indicative of
aseing occurs faster in the heat treated polyester than the non heat
~ ~3~3
WO 94/28048 PCT/GB94/01182
treated polyester. As a consequence, substantial stability occurs at a
level significantly above that for the non heat treated polyester,
preferably 50%, especially 100% above that for the non heat treated
polyester, i.e. the mechanical properties stabilise at a level substantially
improved compared to the non heat treated polyester.
The invention also extends to shaped articles of the polyester
subjected to the above process.
The heating temperature is preferably in the range from 80C to
1 50 C, especia I Iy in the range f rom 1 00 C to 1 40 C .
The heating time is typically at least 0.5 min after the article has
reached the intended temperature. Since times up to a few hours appear
to have no detrimental effect, the time can be chosen to suit the
characteristics of the processing plant and economic requirements.
Heating can be effected in air or oxygen-depleted or inert gas or in
vacuo, or in water or a fluid which does not interfere with the integrity of
the polyester, or in a mould.
Heat transfer can be by conduction, radiation, convection or
resistive heating. Heat transfer methods may include ovens, water baths
and hot rollers. A preferred form of heat transfer is by infra red radiation,
for example, black body and quartz tubes. The shaped article is generally
subjected to infra red radiation for 30 seconds to 15 minutes, preferably
30 seconds to 10 minutes.
The shaped articles may be run through the oven or other heating
method on a continuous belt at a speed which is optimal to enable the
shaped article to reach the correct temperature. A preferred method is to
have a multi-zone system, preferably a 2 zone heat system in which the
first zone gives a rapid rate of heating (i.e. the actual temperature in the
zone may higher than that to be achieved by the shaped article) to bring
it to the actual temperature required and then in the second zone the
shaped article is maintained at the actual temperature to be achieved for
the desired time period.
The composition can contain the usual polymer processing
additives such as fillers, fibres, nucleants and pigments. It can be in the
form of mouldings, extrudates, coatings, films or fibres, including
~ WO 94/28048 ~ 1 ~ 3 4 ~ ~ PCT/GB94/01182
multilayer coatings, films or fibres.
The invention provides methods of making the composition by
mixing its components. If desired, this may be effected in a solvent,
such as a halogenated hydrocarbon or alkylene carbonate. Such a
method is convenient for coating or for centrifugal spinning of fibres.
More conveniently the plasticiser is mixed with powdered dry polymer
and the mixture is treated in conditions of shear, such as in a plastic mill
or extruder. The product is then granulated and used as feed for a
shaping operation such as extrusion, injection moulding, injection blow-
moulding or compression moulding.
The composition is especially useful for making the following
shaped articles: films, especially for packaging, fibres, non-woven fabrics,
e~truded nets, personal hygiene products, bottles and drinking vessels,
agricultural and horticultural films and vessels, ostomy bags, coated
products Isuch as paper, paperboard, non-woven fabrics), agricultural and
horticultural films and vessels, slow-release devices. Alternatively, the
polymer composition with suitable additives can be used as an adhesive.
The invention is now further described, but is not limited by, the
following examples. In the following examples the tests were conducted
with PHBV of the (R)-3-hydroxy form.
Formulation and Test Procedures
Compositions were prepared by mixing copolymer (500 9) with 1
phr boron nitride acid (if required) plasticiser, and extruding the mixture in
a IBetol 2520 extruder in these conditions:
Zone 1 130C
Zone 2 140C
Zone 3 150C
Die 150 C
Screw Speed 100 rpm
The extrudate, a single 4mm lace, was crystallised at 50-60C in
a water bath, dried in a current of air and cut into granules.
The granules were then injection moulded (Boy 15S) into tensile
bars, dumbbell-shaped according to IS0 R 537/2, their prismatic part
measuring 40 x 5 x 2 mm. The bars were numbered as they came out of
~ . . . - , ~
S~l 3~j0 21~3~3
1 0
the mould, then allowed to cool at ambient temperature.
Injection moulding conditions were:-
Barrel Zone 1130 C
Barrei Zone 2130 C
Nozzle 130C
Mould heater temperature 74-77 C
Mould temperature 60 C
Pressure hold on time 12 sec
Cooling time 30 sec
Injection pressure 45 bar
Screw speed 250 rpm
Tensile testing was carried out using an Instron 1122 fitted with a
l\lene data analysis system. The jaw separation used was 50 mm and
crosshead speed was 10 mm/min~1.
Example 1
The following formulations were compared:
A Copolymer 90B/10V, 1 phr BN, no plasticiser
(aged for 1 week before heating, at 120C for 1 h);
B Copolymer 90B/10V, 1 phr BN, 20 phr dioctylphthalate (Jayflex
DIOP) (RTM)
(aged for 3 weeks, heated at 110C for 1 h)
C PHB homopolymer, 1 phr BN, 20phr Reoplas 39
(aged 1 week, heated at 140C for 30 mins)
Results are shown in Tables 1 A and 1 B. Table 1 A compares the treated
polymers with a control sample which was measured for elongation to .
break prior to administering the heat treatment to the samples.
Table 1A
Control: Period after Heating
Before
Heating 0.5h 7 days 28 days
% Extension A 8.85 256 29.35 23.3
to break B 23.2 453 358.5 321
.
W0 94/28048 2 1 ~ 3 ~ PCT/GB94/01182
The results show that the plasticised polymer is 3 times as ductile as the
non plasticised polymer prior to heat treatment. After heat treatment this
is initially reduced to 2 times as ductile, but after 7 days and a month
after heat treatment the ductility of the plasticised polymer is well over
10 times that of the non plasticised polymer. The rate of ageing of the
non plasticised material after the heat treatment is much greater in the
first week after treatment than for the plasticised material leading to a
much longer life. Thus the heat treatment has synergised the effect of
the plasticiser.
Table 1 B
sample days
0 1 7 10 28 84 199
control 55.2 20.5 10.5 - 7.4 6.3 5.9
treated 60.7 43.7 - 42.9 - 35.6 26.4
The extension to break of the plasticised homopolymer is higher
than that of A or B before the heat treatment. It is not greatly increased
by the heat treatment but after only 1 day ageing it can be seen that the
extension to break is over 100% better than the untreated control. This
trend is maintained over a period of over 6 months as indicated by the
600% and 500% improvements in extension to break compared to the
untreated control for the 84 day and 199 day periods respectively.
Example 2
Compositions each consisting of copolymer 90B 10V, 1 phr of
boron nitride and 20 phr of plasticisers were mixed, moulded and tested
as described. The bars were aged at room temperature for 56 days,
deaged at 110C for 1 h and tested.
The plasticisers were
D diundecyl phthalate (Jayflex DIUP) (RTM)
E di-isoheptyl phthalate (Jayflex 77) (RTM)
F acetyl tributyl cltrate ~Es~aflex- ATBC) (RTM)
Results are shown in Table 2.
SBI 37~0 2163~43
12
Table 2
Control Period after Heating
before
heating 0 1 day 1 wk 1 mth
% B 8.58 256 - 29.4 23.3
Extension D 12.9 286 157 108 56
to break E 16.3 463 452 381 267
F 12.1 412 - 213 134
Conclusion
It is evident that using plasticisers D, E and F the decrease in
extension is relativeiy slower in the period of one week from the heat
treatment compared to the non plasticised polymer. Thus, at one month
after treatment the elongation to break values are significantly higher for
the plasticised polymer than those for the non plasticised polymer.
Example 3
Corr.positions each consisting of copolymer having 8% HV units,
1 5 1 phr of boron nitride and 10 phr of plasticisers were mixed, moulded as
380ml (12 fl oz) bottles. The bottles were aged at room temperature for
at least one week, and then heated treated at approximately 130C
(surface temperature of the bottles) for the period given in Table 3 and
then aged for 21 days. The bottles (10 replicates) were filled with water
and dropped from a height of 60 inches onto a 1.3cm (% inch) steel plate
angled at 5. Untreated bottles were dropped in the same test as a
cornparison. The results are given in Table 2
The plasticisers were
F acetyl tributyl citrate (Estaflex' ATBC) (RTM)
G triacetin (glycerol triacetate)
~he results are shown in Table 3.
WO 94/28048 ~ ~ 6 ~ 4 4 ~ PCT/GB94101182
13
1 able 3
IR TIME (SECONDS)OVEN TEMP C%BOTTLE
SURVIVAL
F 0 - 10
F 180 250 100
F 300 245 100
F 75 300 100
F 90 300 100
G 0 - 12
G 180 180 100
G 90 300 100
Conclusion
All the heat treatments caused highly significant improvement in
the impact properties of the bottles compared to the untreated bottles.
E)~ample 4
The elongation to break (%E) was measured on bottles prepared as
described in Example 3. The heat treated bottles were given 4 minutes in
an infra red oven with a heater temperature of 250C. This gave a bottle
surface temperature of approximately 125C-130C. The bottles were
aged for several months prior to deaging and testing. Two bottle
formulations were tested:
H 5phr Estaflex and 5phr epoxidised soya bean oil (Paraplex G62);
10phr polycaprolactone (Tone 787', Union Carbide), 5phr
Estaflex and 3phr talc.
The results are given in Table 4.
~ ~ ~ 3 ~
WO 94/28048 PCT/GB94/01182
14
Table 4
untreated treated
H 9.9 18.3
7.9 22.3
Conclusion
The heat treatment restored the bottles to a significantly increased
level of ductility compared to the untreated bottles.
Example 5
Dart drop impact performance testing was carried out on bottle
walls. The bottles were prepared as described in Example 3, a piece of
the bottle wall is cut out and flattened and subjected to the dart drop test
which involves dropping an instrumented dart on to the bottle wall held
horizontally and measuring the energy absorbed in the impact. The drop
conditions were 12% relative humidity, 23.4C temperature, weight
3.4kg (7.51bs), height of drop 107cm (42 inches), the ring was 3.8cm
(1.5 inches). The measurement is energy/thickness given in Jm~'.
Bottles were also subjected to the bottle drop test as previously
described in Example 4. The bottles were aged for 3 weeks prior to heat
treatment and then aged for 4 weeks and 8 week at 40C after heat
treatment and were tested 2-3 hours after the heat treatment. The infra
red heat treatment gave 3 to 6 minutes in the IR oven providing a
temperature at the bottle surface of 130 to 135C.
Two formulations as follows were tested:
J 6.5phr Estaflex, 1 phr boron nitride, 0.5phr titanium dioxide and
0.15 silicon dioxide
K 8.5phr Estaflex, 1 phr boron nitride, 0.5phr titanium dioxide, 2phr
talc and 10phr polycaprolactone.
The results are given in Table 5 and Table 6.0
t~ W0 94/28048 21~ 3 ~ ~ ~ PCT/GB94/01182
Table 5: Dart drop impact pe.ro,.,.ance (Jm ')
Not treatedIR (3mn) IR (4mn) IR (6mn)
J
0 days 229.7 NT 615.8 NT
1 day 177.7 NT NT NT
4 weeks NT 274 341.3 392.7
8 weeks NT NT 348.9 NT
K
0 days 208.4 NT654.2 NT
1day 212.8 NT NT NT
4 weeks NT 438404.3 665.7
8 weeks NT NT445.4 NT
Table 6: Percentage of bottles surviving impact from 48 or 60 inches
Not treated IR treated
48 60 48 60
1 day 60 NT 100 87
4 weeks 60 NT 85 85
8 weeks 40 NT 100 NT
K
1 day 100 100 100 100
4 weeks 100 60 100 100
8 weeks 40 NT 100 NT
Conclusion
The results given in Table 5 indicate that the infra red heat treatment
gave a very large increase in the energy to break of the bottles after the
heat treatment even after a period of 8 weeks. These observations are
backed up by visual inspection of the broken samples which showed that
2~ ~34~
WO 94/28048 . PCT/GB94/01182 ~t
1 6
the bottles which had not been subjected to heat treatment gave a brittle
fracture whereas the bottles which were given the heat treatment gave a
ductile fracture. With a brittle fracture there is a punctured hole with
radiating cracks or a flap with radiating cracks. This indicates that the
polymer has become brittle. The ductile fracture indicates that the
polymer is still ductile. These results and observations are further backed
up by the results given in Table 6 which indicate that the infra red heat
treatment gives a large increase in the impact resistance of the bottles
even after the bottles have been aged for 2 months.
Example 6
A further bottle impact test was conducted using bottles prepared
from the following compositions:
L 8 % HV, 1 Ophr Estaflex
M 12% HV, 1 Ophr Estaflex
N 8% HV, 10phr Tone' 700
0 8% HV, 10phr Tone 100
The bottles were aged for at least one weak prior to heat
treatment. The bottle size was 300ml and the bottles were heat treated
in an air oven pre-heated to 130C. The temperature dropped to 108C
whilst treating the bottles and the oven took 20 minutes to re-equilibrate
at 130C. The bottles were held at 120 to 130C for 20 minutes (or 30
minutes at 120C). The bottles were drop tested from 122cm (48
inches) and 152cm (60 inches) at 1 week and 1 month after heat
treatment. The percentage of bottles surviving the drop test results are
given in Table 7.
Table 7
TreatmentAge at drop 122 cm 152 cm
L none 1 month 78
L 130C 1 week - 100
L 130 C 1 month - 100
M none 1 month - 40
~WO 94128048 2 ~ ~ 3 ~ ~ 3 PCT/GB94/01182
M 130C 1 week - 100
M 1 30C 1 month - 100
N none 1 month 70
N 1 20C 1 week - 100
N 1 20 C 1 month - 1 00
0 none 1 month 70
0 125C 1 week - 100
0 125C 1 month - 100
Cey: - means not tested
1 0 Conclusion
In all cases the heat treated bottles at one month post heat
treatment were significantly more impact resistant than the non-heat
treated bottles at one month post moulding.
93SKM10S MS - 26 May 1994
