Note: Descriptions are shown in the official language in which they were submitted.
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BIODEGRADABLE POLYESTER FILM
Description
The present invention relates to a biodegradable polyester film comprising:
i) from 75 to 100% by weight, based on the total weight of components i to
ii, of a
biodegradable polyester based on aliphatic and/or aromatic dicarboxylic acids
and
on an aliphatic dihydroxy compound;
ii) from 0 to 25% by weight, based on the total weight of components i to
ii, of polylactic
acid;
iii) from 10 to 25% by weight, based on the total weight of components i to
v, of calcium
carbonate;
iv) from 3 to 15% by weight, based on the total weight of components i to
v, of talc;
v) from 0 to 1% by weight, based on the total weight of components i to v,
of a
copolymer which contains epoxy groups and is based on styrene, acrylic ester,
and/or methacrylic ester;
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vi) from 0 to 2% by weight, based on the total weight of components i
to v, of 2-(4,6-
bisbipheny1-4-y1-1,3,5-triazin-2-y1)-5-(2-ethyl-(n)-hexyloxy)phenol.
The invention further relates to the use of said polyester films and to a
masterbatch
comprising:
i) from 75 to 95% by weight, based on the total weight of the
components, of a
biodegradable polyester selected from the group consisting of: polyesters
based on
aliphatic and/or on aromatic dicarboxylic acids and on aliphatic dihydroxy
compound,
and polymer lactic acid;
vi) from 5 to 25% by weight, based on the total weight of the
components of 2-(4,6-
bisbipheny1-4-y1-1,3,5-triazin-2-y1)-5-(2-ethyl-(n)-hexyloxy)phenol,
and also to a process for producing a preferably transparent mulch film with
defined
"breakdown time" with use of the abovementioned masterbatch.
The UV absorber (vi) used in the masterbatch is based on an extremely stable
chromophore which belongs to the triazines class and which has exceptional
absorption
capability. This UV absorber is superior to all other currently used UV
absorbers in the
wavelength range from 290 to 350 nanometers because it has a very high degree
of
t 1-
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absorption and also a very broad absorption curve. The UV absorber also has
excellent
light resistance and low volatility, and there is therefore hardly any
alteration in absorption
capability over the course of time.
W02002/016468 discloses filled biodegradable polyester films. Said
specification does not
indicate any combination of the fillers calcium carbonate (component iii) and
talc
(component iv). The polyester films disclosed in W02002/016468 are not always
fully
satisfactory in respect of their processing properties (low film bubble
stability) and tear-
propagation resistance.
It was therefore an objective of the present invention to develop polyester
films with
improved tear-propagation resistance which can be reliably processed to give
blown films.
Biodegradable polyester films can by way of example be used as mulch films. A
decisive
requirement here alongside the requirement for high tear-propagation
resistance is
resistance to insolation, in particular for transparent mulch films. Although
black-colored
(carbon-black-colored) mulch films absorb UV, thermal radiation is also
absorbed, and
therefore less heat is transmitted through to the soil and the yield/earlier-
harvesting effect
that can be achieved, at least for particular crops such as melons and maize,
is reduced.
WO 2009/071475 discloses mulch films based on, for example, polyethylene and
comprising hydroxyphenyltriazines as stabilizer. WO 2009/071475 likewise
mentions
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polyester films based on PMMA. WO 2009/071475 does not explicitly describe
biodegradable polyester films. The service time of biodegradable transparent
mulch films
based on a biodegradable polyester composed of aliphatic and/or aromatic
dicarboxylic
acids and of aliphatic dihydroxy compound is often in practice excessively
short: only 2
weeks, depending on wall thickness. Light stabilizers such as UV absorbers and
HALS
stabilizers, or a combination of both, are usually recommended for providing
UV
stabilization to mulch films. UV absorbers filter the ultraviolet content out
from the light,
and the energy of the absorbed light is thus converted into heat. The use of
HALS
stabilizers suppresses the reaction of photooxidatively generated cleavage
products in the
polymer. The combination of the abovementioned active ingredients achieves a
synergistic
effect for inhibition of the two different degradation mechanisms. Studies on
Ecoflex
semiaromatic polyester (BASF SE) have revealed that even when
hydroxyphenyltriazine-
based UV absorbers, e.g. Tinuvin 1577, are combined with a HALS stabilizer,
e.g.
Tinuvin 111, or UV absorber based on benzophenones, e.g. Uvinul 3008,
although they
provide a certain stabilizing effect, this is by no means fully satisfactory
for transparent
mulch films, in particular with low wall thickness.
Thin embodiments of said mulch films (below 30 microns) moreover do not have
fully
satisfactory tear-propagation resistance.
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It was therefore an object of the present invention to provide biodegradable,
preferably
transparent mulch films with longer service times in the field and with higher
tear-
propagation resistance.
The biodegradable polyester film comprising:
i) from 75 to 100% by weight, preferably from 80 to 95% by weight,
particularly
preferably from 85 to 95% by weight, based on the total weight of components i
to ii,
of a biodegradable polyester based on aliphatic and/or aromatic dicarboxylic
acids
and on an aliphatic dihydroxy compound;
ii) from 0 to 25% by weight, preferably from 5 to 20% by weight,
particularly preferably
from 5 to 15% by weight, based on the total weight of components i to ii, of
polylactic
acid;
iii) from 10 to 25% by weight, preferably from 10 to 20% by weight,
particularly
preferably from 12 to 17% by weight, based on the total weight of components i
to v,
of calcium carbonate;
iv) from 3 to 15% by weight, preferably from 5 to 10% by weight,
particularly preferably
from 5 to 8% by weight, based on the total weight of components i to v, of
talc;
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v) from 0 to 1% by weight, preferably from 0.01 to 0,8% by weight,
particularly
preferably from 0.05 to 0.5% by weight, based on the total weight of
components i
to v, of a copolymer which contains epoxy groups and is based on styrene,
acrylic
ester, and/or methacrylic ester;
vi) from 0 to 2% by weight, preferably from 0.1 to 1.5% by weight,
particularly
preferably from 0.5 to 1.2%, based on the total weight of components i to v,
of 2-
(4,6-bisbipheny1-4-y1-1,3,5-triazin-2-y1)-5-(2-ethyl-(n)-hexyloxy)phenol has
accordingly been developed.
Component vi is useful only for films which have long-term exposure to
insolation, for
example mulch films.
Comparison of results from Tables 4 and 5 shows that films with from 5 to 20%
by
weight polylactic acid content, particularly preferably from 5 to 15% by
weight, based on
the total weight of components i to ii, have particularly high tear-
propagation resistance.
Preference is further given to mulch films with components i to vi, which
exhibit
improvement not only in respect of their tear-propagation resistance but also
in respect
of their service time in the field.
The invention is described in more detail below.
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Materials that can in principle be used as component i for producing the
biodegradable
polyester mixtures of the invention are any of the polyesters known as
semiaromatic
polyesters, based on aliphatic and aromatic dicarboxylic acids and on
aliphatic dihydroxy
compound, and any of the aliphatic polyesters made of aliphatic dicarboxylic
acids and
of aliphatic diols. A feature common to said polyesters is that they are
biodegradable to
DIN EN 13432. Mixtures of a plurality of these polyesters are of course also
suitable as
component i.
In the invention, the expression "semiaromatic polyesters" (component i) is
also intended
to mean polyester derivatives, such as polyetheresters, polyesteramides, or
polyetheresteramides, and polyester urethanes. Among the suitable semiaromatic
polyesters are linear non-chain-extended polyesters (WO 92/09654). Preference
is given
to chain-extended and/or branched semiaromatic polyesters. The latter are
known from
the specifications mentioned in the introduction, WO 96/15173 to 15176, 21689
to
21692, 25446, 25448, or WO 98/12242. It is also possible to use mixtures of
various
semiaromatic polyesters. Relatively recent developments of interest are based
on
renewable raw materials (see WO-A 2006/097353, WO-A 2006/097354, also WO-
A 2010/034710). The expression "semiaromatic polyesters" in particular means
products
such as Ecoflexe (BASF SE) and Eastar Bio, and OrigoBi (Novamont).
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Among the particularly preferred semiaromatic polyesters are polyesters which
comprise,
as essential components,
A) an acid component made of:
al) from 30 to 99 moN/0 of at least one aliphatic dicarboxylic acid or
ester-forming
derivatives thereof, or a mixture thereof,
a2) from 1 to 70 mol /0 of at least one aromatic dicarboxylic acid or ester-
forming
derivative thereof, or a mixture thereof, and
B) from 98 to 102 mol%, based on acid component A, of a diol component B
selected
from at least one C2-C12-alkanediol or a mixture thereof
and
C) from 0.01 to 3% by weight, based on components A and B, of a component C
selected from
cl) a compound having at least three groups capable of ester formation or
of amide
formation,
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c2) a di- or polyisocyanate,
c3) a di- or polyepoxide,
or a mixture made of cl) to c3).
Compounds which can be used as aliphatic acids or as the corresponding
derivatives al
are generally those having from 2 to 18 carbon atoms, preferably from 4 to 10
carbon
atoms. They can be either linear or branched compounds. In principle, however,
it is also
possible to use dicarboxylic acids having a larger number of carbon atoms, for
example
having up to 30 carbon atoms.
Examples that may be mentioned are: oxalic acid, malonic acid, succinic acid,
glutaric
acid, 2-methylglutaric acid, 3-methylglutaric acid, a-ketoglutaric acid,
adipic acid, pimelic
acid, azelaic acid, sebacic acid, brassylic acid, fumaric acid, 2,2-
dimethylglutaric acid,
suberic acid, diglycolic acid, oxaloacetic acid, glutamic acid, aspartic acid,
itaconic acid,
and maleic acid. It is possible here to use the dicarboxylic acids or ester-
forming
derivatives thereof, individually or in the form of a mixture made of two or
more thereof.
It is preferable to use succinic acid, adipic acid, azelaic acid, sebacic
acid, brassylic acid,
or respective ester-forming derivatives thereof, or a mixture thereof. It is
particularly
preferable to use succinic acid, adipic acid, or sebacic acid, or respective
ester-forming
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derivatives thereof, or a mixture thereof. Succinic acid, azelaic acid,
sebacic acid, and
brassylic acid have the additional advantage that they are obtainable from
renewable raw
materials.
Particular preference is given to the following aliphatic-aromatic polyesters:
polybutylene
adipate terephthalate (PBAT), polybutylene sebacate terephthalate (PBSeT), and
polybutylene succinate terephthalate (PBST).
The aromatic dicarboxylic acids or ester-forming derivatives thereof a2 can be
used
individually or in the form of a mixture made of two or more thereof. It is
particularly
preferable to use terephthalic acid or ester-forming derivatives thereof, e.g.
dimethyl
terephthalate.
The diols B are generally selected from branched or linear alkanediols having
from 2 to 12
carbon atoms, preferably from 4 to 6 carbon atoms, or from cycloalkanediols
having from 5
to 10 carbon atoms.
Examples of suitable alkanediols are ethylene glycol, 1,2-propanediol, 1,3-
propanediol,
1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,4-dimethy1-2-ethylhexane-
1,3-diol, 2,2-
dimethy1-1,3-propanediol, 2-ethy1-2-buty1-1,3-propanediol, 2-ethy1-2-isobuty1-
1,3-
propanediol, 2,2,4-trimethy1-1,6-hexanediol, and in particular ethylene
glycol, 1,3-
propanediol, 1,4-butanediol, and 2,2-dimethy1-1,3-propanediol (neopentyl
glycol);
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cyclopentanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-
cyclohexanedimethanol, 1,4-cyclohexanedimethanol, and 2,2,4,4-tetramethy1-1,3-
cyclobutanediol. Particular preference is given to 1,4-butanediol,
particularly in
combination with adipic acid as component al), and 1,3-propanediol,
particularly in
combination with sebacic acid as component al). 1,3-Propanediol also has the
advantage that it is obtainable in the form of renewable raw material. It is
also possible
to use a mixture of various alkanediols.
The preferred semiaromatic polyesters are characterized by a molar mass (Me)
in the
range from 1000 to 100 000 g/mol, in particular in the range from 9000 to 75
000 g/mol,
preferably in the range from 10 000 to 50 000 g/mol, and by a melting point in
the range
from 60 to 170 C, preferably in the range from 80 to 150 C.
The expression "aliphatic polyesters" (component i) means polyesters made of
aliphatic
diols and of aliphatic dicarboxylic acids, e.g. polybutylene succinate (PBS),
polybutylene
adipate (PBA), polybutylene succinate adipate (PBSA), polybutylene succinate
sebacate
(PBSSe), and polybutylene sebacate (PBSe), or corresponding polyester amides
or
polyester urethanes. The aliphatic polyesters are marketed by way of example
by Showa
Highpolymers as BionolleTM and by Mitsubishi as GSP1a. WO-A 2010/034711
describes
more recent developments.
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The polyesters in component i can also comprise mixtures made of aliphatic-
aromatic
polyesters and of purely aliphatic polyesters, examples being mixtures made of
PBAT and
PBS.
Component ii in particular comprises polylactic acid (PLA).
It is preferable to use polylactic acid with the following property profile:
melt volume rate (MVR for 190 C and 2.16 kg to ISO 1133) of from 0.5¨
preferably from
2 ¨ to 30 m1/10 minutes, in particular 9 m1/10 minutes
melting point below 240 C;
glass transition temperature (Tg) above 55 C
water content smaller than 1000 ppm
residual monomer content (Lactid) smaller than 0.3%
molecular weight above 80 000 daltons.
Examples of preferred polylactic acids are NatureWorks0 6201D, 6202 D, 6251 D,
3051
D, and in particular 4020 D or 4043D (polylactic acid from NatureWorks).
The amount used of component ii is from 0 to 25% by weight, based on
components i and
ii, preferably from 5 to 20% by weight and with particular preference from 5
to 15% by
weight.
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It is preferable to use, as component iii, from 10 to 25% by weight,
particularly from 12 to
18% by weight, based on the total weight of components i to v, of calcium
carbonate. The
calcium carbonate from Omya has proven to be suitable inter alia. The average
particle
size of the calcium carbonate is generally from 0.5 to 10 micrometers,
preferably from Ito
micrometers, particularly preferably from 1 to 2.5 micrometers.
From 3 to 15% by weight, preferably from 5 to 10% by weight, particularly
preferably from
5 to 8% by weight, based on the total weight of components i to v, of talc is
used as
component iv. The talc from Mondo Minerals has proven to be suitable inter
alia. The
average particle size of the talc is generally from 0.5 to 10 micrometers,
preferably from 1
to 8 micrometers, particularly preferably from 1 to 3 micrometers.
Interestingly, it has been found that the addition of calcium carbonate iii
(chalk) can
achieve a further improvement in the biodegradability of the products. Talc iv
in turn
provides an effective method of increasing the modulus of elasticity.
The entirety of the fillers iii) and iv), based on the total weight of
components i to v, is
generally from 13 to 40% by weight, preferably from 15 to 30% by weight, and
with
particular preference from 18 to 25% by weight.
It may also be possible to add to the polymer mixtures, in particular to the
polylactic-acid-
containing mixtures, from 0 to 1% by weight, preferably from 0.01 to 0.8% by
weight,
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particularly preferably from 0.05 to 0.5% by weight, based on the total weight
of
components i to v, of a copolymer which contains epoxy groups and which is
based on
styrene, acrylate, and/or methacrylate (component v). The units bearing epoxy
groups are
preferably glycidyl (meth)acrylate. Copolymers that have proven advantageous
are those
having glycidyl methacrylate content greater than 20% by weight, particularly
preferably
greater than 30% by weight, and with particular preference greater than 50% by
weight,
based on the copolymer. The epoxy equivalent weight (EEW) in said polymers is
preferably from 150 to 3000 g/equivalent, and with particular preference from
200 to
500 g/equivalent. The average molecular weight (weight-average) Mw of the
polymers is
preferably from 2000 to 25 000, in particular from 3000 to 8000. The average
molecular
weight (number-average) Mr, of the polymers is preferably from 400 to 6000, in
particular
from 1000 to 4000. Polydispersity (Q) is generally from 1.5 to 5. Copolymers
of the
abovementioned type containing epoxy groups are marketed by way of example by
BASF
Resins B.V. with trademark Joncry10 ADR. Joncry10 ADR 4368 is particularly
suitable.
Component v is in particular used in PLA-containing polyester mixtures.
From 0 to 2% by weight, preferably from 0.1 to 1.5% by weight, particularly
preferably from
0.5 to 1.2% by weight, based on the total weight of components i to vi, of
244,6-
bisbipheny1-4-y1-1,3,5-triazin-2-y1)-5-(2-ethyl-(n)-hexyloxy)phenol is used as
component vi.
WO 2009/071475 discloses production and properties of the UV absorber vi.
Explicit
reference may be made to WO 2009/071475 in this connection.
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The polyester film of the invention can moreover comprise other additives
known to the
person skilled in the art, for example the additives conventional in plastics
technology, e.g.
stabilizers; nucleating agents; lubricants and release agents, such as
stearates (in
particular calcium stearate); plasticizers, such as citrates (in particular
tributyl acetyl-
citrate), glycerol esters, such as triacetylglycerol, or ethylene glycol
derivatives,
surfactants, such as polysorbates, palmitates, or laurates; waxes, e.g.
erucamide,
stearamide, or behenamide, beeswax, or beeswax esters; antistatic agent, UV
absorbers;
UV stabilizers; antifogging agents, or dyes. The concentrations used of the
additives are
from 0 to 5% by weight, in particular from 0.1 to 2% by weight, based on the
polyesters of
the invention. The polyesters of the invention can comprise from 0.1 to 10% by
weight of
plasticizers.
For the purposes of the present invention, a substance or substance mixture
complies with
the "biodegradable" feature if the percentage degree of biodegradation of said
substance
or the substance mixture to DIN EN 13432 is at least 90%.
Biodegradation generally leads to decomposition of the polyesters or polyester
mixtures in
an appropriate and demonstrable period of time. The degradation can take place
by an
enzymatic, hydrolytic, or oxidative route, and/or via exposure to
electromagnetic radiation,
such as UV radiation, and can mostly be brought about predominantly via
exposure to
microorganisms, such as bacteria, yeasts, fungi, and algae. Biodegradability
can be
quantified by way of example by mixing polyester with compost and storing it
for a
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particular period. By way of example, in DIN EN 13432 (with reference to ISO
14855),
CO2-free air is passed through ripened compost during the composting process,
and the
compost is subjected to a defined temperature profile. Biodegradability here
is defined as
a percentage degree of biodegradation, by taking the ratio of the net amount
of CO2
released from the specimen (after subtraction of the amount of CO2 released by
the
compost without specimen) to the maximum amount of CO2 that can be released
from the
specimen (calculated from the carbon content of the specimen). Biodegradable
polyesters
or biodegradable polyester mixtures generally exhibit clear signs of
degradation after just a
few days of composting, examples being fungal growth, cracking, and
perforation.
Other methods of determining biodegradability are described by way of example
in ASTM
D5338 and ASTM D6400-4.
The biodegradable films mentioned in the introduction are suitable for
producing nets and
fabric, blown films, and chill-roll films, with or without any orientation, in
a further
processing step, and with or without metallization, or SiOx coating.
In particular, the polyester films mentioned in the introduction comprising
components i) to
v) or, respectively, i) to vi) are suitable for blown films and stretch films.
Possible
applications here are basal-fold bags, lateral-seam bags, carrier bags with
hole grip, shrink
labels, or vest-style carrier bags, inliners, heavy-duty bags, freezer bags,
composting
bags, agricultural films (mulch films), film bags for food packaging, peelable
closure film -
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transparent or opaque ¨ weldable closure film - transparent or opaque, sausage
casing,
salad film, freshness-retention film (stretch film) for fruit and vegetables,
meat, and fish,
stretch film for pallet-wrapping, net film, packaging films for snacks,
chocolate bars, and
muesli bars, peelable lid films for dairy packaging (yoghurt, cream, etc.),
fruit, and
vegetables, semirigid packaging for smoked sausage and for cheese.
When the polyester films comprising components i to vi) have been extruded to
give
single- or multilayer blown, cast, or pressed films they exhibit markedly
higher tear
resistance (to EN ISO 6383-2:2004) in comparison with mixtures without
components ii to
v). Tear-propagation resistance is a very important product property
especially in the
sector of thin (blown) films for, for example, biodegradable-waste bags, or
thin-walled
carrier bags (e.g. vest-style carrier bags, fruit bags). It is also
particularly important in
mulch films in the agricultural sector.
Polyester films provided with light stabilizer vi) are in particular used for
outdoor
applications, for example in the construction sector and in particular for
agricultural
products. The expression "agricultural products" means mulch films, protective
covering
films, silo films, film strips, fabrics, nonwovens, clips, textiles, threads,
fishing nets and
wrapping, e.g. heavy-duty bags for, for example, peat, fertilizer, cement,
plant-protection
agents, or seed, or for flower pots.
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Agricultural products generally have exposure to wind and weathering, and in
particular to
insolation. They require stabilization in order to provide a defined service
time in the field.
Component vi) has proven to be particularly efficient here. A masterbatch
comprising:
i) from 75 to 95% by weight, based on the total weight of the
components i to v, of a
biodegradable polyester based on aliphatic and/or on aromatic dicarboxylic
acids
and on aliphatic dihydroxy compound;
vi) from 5 to 25% by weight, based on the total weight of the
components i to v, of 2-
(4,6-bisbipheny1-4-y1-1,3,5-triazin-2-y1)-5-(2-ethyl-(n)-hexyloxy)phenol;
has proven to be particularly helpful in producing mulch films which are
preferably
transparent or translucent.
In particular, a process has been found for producing transparent mulch films
comprising:
i) from 75 to 100% by weight, based on the total weight of components i to
ii, of a
biodegradable polyester based on aliphatic and/or aromatic dicarboxylic acids
and
on an aliphatic dihydroxy compound;
ii) from 0 to 25% by weight, based on the total weight of components i to
ii, of polylactic
acid;
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iii) from 10 to 25% by weight, based on the total weight of components i to
v, of calcium
carbonate;
iv) from 3 to 15% by weight, based on the total weight of components i to
v, of talc;
v) from 0 to 1% by weight, based on the total weight of components i to v,
of a
copolymer which contains epoxy groups and is based on styrene, acrylic ester,
and/or methacrylic ester;
vi) from 0.1 to 1.5% by weight, based on the total weight of components i
to v, of 244,6-
bisbipheny1-4-y1-1,3,5-triazin-2-y1)-5-(2-ethyl-(n)-hexyloxy)phenol.
With the aid of the masterbatch it is possible to adjust to a defined service
time, depending
on the layer thickness of the mulch film and on the climatic zone in which the
mulch film is
to be used. The weathering test to DIN EN ISO 4892-2 can serve as a measure
here. The
film is exposed to a xenon arc lamp for a period of 250 h. This corresponds to
3 months of
outdoor weathering in the southern European climatic zone.
Performance testing:
4-
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The molecular weights Mn and Mw of the semiaromatic polyesters were determined
to
DIN 55672-1 with eluate hexafluoroisopropanol (HFIP) + 0.05% by weight of
potassium
trifluoroacetate; narrowly distributed polymethyl methacrylate standards were
used for
calibration. Intrinsic viscosities were determined to DIN 53728, Part 3,
January 3, 1985,
Capillary viscosimetry. An M-I1 Ubbelohde viscometer was used. The solvent
used was the
following mixture: phenol/o-dichlorobenzene in a ratio of 50/50 by weight.
Modulus of elasticity and tensile strain at break were determined by means of
a tensile test
on pressed films of thickness about 420 pm to ISO 527-3: 2003.
Tear propagation resistance was determined by an Elmendorf test to EN ISO 6383-
2:
2004 on test specimens with constant radius (tear length 43 mm), using
equipment from
ProTear.
A puncture resistance test on pressed films of thickness 420 pm was used to
measure
maximum force and fracture energy of the polyesters:
The test machine used is a Zwick 1120 equipped with a spherical punch of
diameter
2.5 mm. The specimen, a circular piece of the film to be tested, was clamped
perpendicularly with respect to the test punch, and the punch was moved at a
constant
test velocity of 50 mm/min through the plane clamped by the clamping device.
Force and
elongation were recorded during the test and were used to determine
penetration energy.
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The degradation rates of the biodegradable polyester mixtures and of the
mixtures
produced for comparison were determined as follows:
The biodegradable polyester mixtures and the mixtures produced for comparison
were
pressed at 190 C in each case to produce films of thickness 30 pm. Each of
said films was
cut into square pieces with edge lengths of 2 x 5 cm. The weight of each of
these pieces of
film was determined and defined as "100% by weight". The pieces of film were
heated to
58 C in an oven for a period of four weeks in a plastics jar filled with a
moistened compost.
At weekly intervals, the residual weight of each piece of film was measured
and converted
to % by weight (based on the weight defined as "100% by weight" determined at
the start
of the experiment).
Masterbatch production (light stabilizer)
I. Materials used:
Al) Polybutylene adipate terephthalate
To produce the polyester Al, 87.3 kg of dimethyl terephthalate, 80.3 kg of
adipic acid,
117 kg of 1,4-butanediol, and 0.2 kg of glycerol were mixed together with
0.028 kg of
tetrabutyl orthotitanate (TBOT), where the molar ratio of alcohol components
to acid
components was 1.30. The reaction mixture was heated to a temperature of 180 C
and
reacted for 6 h at said temperature. The temperature was then increased to 240
C, and
22
the excess dihydroxy compound was removed by distillation in vacuo over a
period of
3 h. 0.9 kg of hexamethylene diisocyanate were then slowly metered into the
mixture
within a period of 1 h at 240 C.
The melting point of the resultant polyester Al (component i-1) was 119 C and
its molar
mass (Mr) was 23 000 g/mol.
B1-613) Light stabilizers, UV absorbers (UVA), and UV stabilizers (HALS)
of Table 1:
Table 1:
No. Name Type Chemical name
Light stabilizer of the invention
CGX UVA 006
(W02009/071475, 2-(4,6-bisbipheny1-4-y1-1,3,5-triazin-
2-y1)-
B1 Example A) UVA 5-(2-ethylhexyloxy)phenol
Comparative systems
TINUV1N0 P 2-(2H-benzotriazol-2-y1)-p-cresol
B2 CAS No.: 2440-22-4 UVA
TINUVIN 234 2-(2H-benzotriazol-2-y1)-4,6-bis(1-
B3 CAS No.: 70321-86-7 UVA methyl-1-phenylethyl)phenol
T1NUVIN 312 ¨1C1-(2-ethoxypheny1)-N'-(2-
ethylpheny1)-
64 CAS No.: 23949-66-8 UVA oxamide
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TINUVINO 326 2-(3-tert-buty1-2-hydroxy-5-
B5 CAS No.: 3896-11-5 UVA methylphenyI)-5-chloro-2H-
benzotriazole
TINUVINO 360 2,2'-methylenebis(6-(2H-benzotriazol-2-
B6 CAS No.: 103597-45-1 UVA yI)-4-(1,1,3,3-
tetramethylbutyl)phenol)
TINUVIN 1577 2-(4,6-dipheny1-1,3,5-triazin-2-y1)-5-
B7 CAS No.: 147315-50-2 UVA [(hexyl)oxy]phenol
CH1MASSORBTm 81
B8 CAS No.: 1843-05-6 UVA benzophenone
2-cyano-3,3-dipheny1-2-propenoic acid,
2,2-bis[[(2-cyano-1-oxo-3,3-dipheny1-2-
Uvinul 3030 propenyl)oxy]methyl]-1,3-propanediy1
B9 CAS No.: 178671-58-4 UVA ester
CHIMASSORBTm 944
B10 CAS No.: 71878-19-8 HALS
HALS
B11 T1NUVIN NOR 371 HALS triazine derivative
TINUVINO 111
CAS No.: 106990-43-6
B12 and 65447-77-0 HALS
TINUVINO 622
B13 CAS No.. 65447-77-0 HALS
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1-
= CA 02834651 2013-10-29
24
II. Compounding of masterbatches MB1 and C-MB2 to C-MB13:
9000 g of Al and respectively 1000 g of Bl-B13 were compounded at a melt
temperature
of about 220-260 C in a Werner & Pfleiderer MC-26 extruder. Al was metered by
the cold-
feed method into zone 0 and Bl-B13 was metered by the side-feed method into
zone 4,
and the entrained air was removed via vacuum devolatilization in reverse
direction in zone
3.
The resultant masterbatches were termed MB1 and C-MB2 to C-MB13.
Ill. Film production:
Blown-film system 1
The blown-film system was operated with an extruder of length 30D, using a 75
mm screw
equipped with a cooled, grooved feed zone and with a barrier screw having
Maddock
shear mixing elements and crosshole mixing elements. The zone temperatures
were
selected in such a way as to give a melt temperature of from 170 to 190 C. The
die
temperatures were in the range 165-170 C. Die diameter was 225 mm, gap width
was
1.5 mm, throughput was 140 kg/h, melt temperature was 188 C, and melt pressure
prior to
the sieve was 185 bar. The blow-up ratio of 4.0: 1 gave a film bubble with
laid-flat width
1400 mm. Other components of the system were as follows:
gravimetric feed unit for 4 components (batch mixer)
capacitive thickness measurement
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- thickness control by way of segment cooling ring
- double-lip cooling ring
internal and external cooling by cooled air
- 2 winding units.
Blown-film system 2
The blown-film system was operated with an extruder of length 25D, using a 45
mm screw
equipped with a grooved feed zone and a three-zone screw with shearing and
mixing
section. The feed zone was cooled with cold water at maximum throughput. The
zone
temperatures were selected in such a way as to give a melt temperature of from
170 to
190 C. The die temperatures were in the range of 165-185 C. Die diameter was
75 mm,
gap width was 0.8 mm. The blow-up ratio of 3.5:1 gave a film bubble with laid-
flat width
412 mm.
IV. Effect of light stabilizers
Materials used
1-i) Semiaromatic polyester Al
2-i) Masterbatch A: 10% strength by weight masterbatch of erucamide in
polyester Al
2-ii) Masterbatch B: 60% strength by weight masterbatch of calcium carbonate
in
polyester Al
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26
2-iii) Masterbatch C: 25% strength by weight masterbatch of pigment black in
polyester
Al
3-i) MB1 and C-MB2 to C-MB13: 10% strength by weight masterbatch of light
stabilizer
in polyester Al
The materials were then processed in film system 2 as blend of components 1-i,
2-i, 2-ii,
and 3-i (by the cold-feed system in the extruder) to give films of thickness
12 pm. The
respective light-stabilizer masterbatches MB1 and C-MB2 to C-MB13 were metered
at a
concentration of 10% into the mixture, and this corresponded to a
concentration of
000 ppm of active ingredient in the film. HALS stabilizers or combinations
made of
HALS and UVA with addition of component 2-iii) were also used for some
selected black-
colored films. The film samples were then subjected to artificial weathering
(xenon arc
lamp) to DIN EN ISO 4892-2, method A for a period of 250 h (corresponding to 3
months
of outdoor weathering in the south-European climatic zone), and after
weathering were
tensile-tested to ISO 527-3. The results were compared with those from an
unweathered
reference film. The assessment of mechanical properties for films after
weathering was as
follows: films exhibiting more than 50% decrease in tensile strain at break
after the
weathering period were generally of no further use at least after the
simulated period:
AL [%] = L1/L2
LL: residual tensile strain at break
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L1: tensile strain at break to ISO 527-3 of reference film, in this case
unweathered film
(334 'Yu )
L2: tensile strain at break to ISO 527-3 of weathered film
The results for tensile strain at break determined in the tensile tests on the
12 pm films
from experiments Nos. 1-14 were compared with the tensile strain at break of
an
unweathered film based on the following components: 97% 1-i + 1% 2-i + 2% 2-ii
(transparent film). Table 2 collates the formulations and results:
Table 2
No. Blend UVA/HALS type AL [%]
Experiment using masterbatch of the invention
Biphenylhydroxy-
1 87% 1-i + 1% 2-i + 2% 2-ii + 10% MB1
phenyltriazine 97%
(HPT)
Experiments using comparative masterbatches
2 87% 1-i + 1% 2-i + 2% -2-ii + 10% C-MB2
Benzotriazole 40%
3 87% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB3
Benzotriazole 43%
4 87% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB4 Oxanilide
50%
-1-
87% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB5 ; Benzotriazole 60%
6 87% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB6 Benzotriazole
55
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Hydroxyphenyl-
7 87% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB7 51
triazine (HPT)
8 87% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB8 Benzophenone 70%
9 87% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB9 1 Cyanoacrylate
55%
87% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB10 HALS 20%
11 87% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB11 HALS not
measurable
12 , 87% 1-i + 1% 2i + 2% 2-ii + 10% C-MB12 HALS not measurable
13 87% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB13 HALS not
measurable
Hydroxyphenyl-
81% 1-i + 1% 2-i + 2% 2-ii + 10% C-MB7 + triazine (HPT)/
14 40%
6% C-MB13 HALS
combination
-------------------------------------------------------------------------------
------------------------------------------------------------------------------
The results clearly show that UV absorbers based on benzotriazole have some
degree of
light-stabilizing effect on the films produced, but this is not adequate in
particular for very
thin transparent mulch films which moreover undergo extension and also
thinning during
laying. HALS stabilizers do not provide any stabilization with respect to UV
radiation even
when combined with UV absorbers.
The stabilizing effect of benzophenone UV absorbers on semiaromatic polyesters
Al is
confirmed, as described above in the introduction. Even after 250 h of
artificial weathering,
the tensile strain at break achieved is still 70% of that of the reference
film (unweathered);
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however, the tension-tensile strain curve exhibits a pronounced yield point
(ductile
behavior). The value reached by the tear resistance is also only 10 MPa, which
is largely
below the tear resistance of the reference film: about 34 MPa.
Excellent UV stabilization can be achieved by using the masterbatch of the
invention,
comprising the light stabilizer 2-(4,6-bisbipheny1-4-y1-1,3,5-triazin-2-y1)-5-
(2-ethyl-(n)-
hexyloxy)phenol (MB1). Even after 250 h of artificial weathering, tensile
strain at break
corresponds approximately to the value measured for the reference film. The
tension-
tensile strain curve also exhibits no yield point. The triazine-based
chromophore therefore
provides very reliable stabilization of very thin films based on semiaromatic
polyesters Al.
The intensity of UV absorption depends on the concentration of active
ingredient and on
the wall thickness of the film. It is likely that adequate UV stability can be
provided to even
thinner films < 12 pm. In the case of thicker films it is moreover possible to
reduce the
concentration of active ingredient, when comparison is made with the
benzophenone. The
light stabilizer exhibits, as mentioned above, inherent lightfastness, and
little susceptibility
to migration when comparison is made with benzophenones. Both properties
contribute to
reliable stabilization of the films.
The very good and reproducible results that can be achieved with the MB1 of
the invention
can firstly provide a process in which the service time of mulch films in the
field can be
specifically tailored, depending on layer thickness and on average level of
insolation. It
thus becomes possible to use biodegradable, transparent or translucent films
for crops
i=
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which have relatively long vegetation periods and which therefore were not
accessible or
not economically accessible.
In the case of black-colored films, the light stabilizer masterbatch MB1 of
the invention
exhibited very good light stabilizer effect even at relatively low
concentration. HALS
compounds such as Chimasorb 944 (B8) exhibited ideal UV stabilization ¨ alone
or in
combination with the light stabilizer of the invention.
Examples providing evidence of the effect of the light stabilizer:
Materials used:
i-1) semiaromatic polyester Al
ii-1) polylactic acid (PLA) 4043D from Natureworks LLC
iii-1) calcium carbonate with topcut (d 98%) 5 pm from OMYA
iv-1) talc with topcut (d 98%) 8 pm from Mondo Minerals
v-1) Masterbatch A: 20% strength by weight masterbatch of Joncryl ADR 4368 in
polyester Al (see EP-A 1838784 for production process)
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vi-1) Masterbatch MB1: 10% strength by weight masterbatch of light stabilizer
B1 in
polyester Al, where light stabilizer B1 corresponds to Example A of
WO 2009/071475
vi-V2) Masterbatch C-MB8: 10% strength by weight masterbatch of light
stabilizer B8 in
polyester Al.
670 kg of i-1, 75 kg of ii-1, 180 kg of iii-1, 70 kg of iv-1, and 5 kg of v-1
were compounded
at a melt temperature of about 220-260 C in a Werner & Pfleiderer MC-26
extruder. 1-1,
ii-1 and v-1 were metered by the cold-feed method into zone 0 and iii-1 and iv-
1 were
metered by the side-feed method into zone 4, and the entrained air was removed
via
vacuum devolatilization in reverse direction in zone 3.
The compounded material was then processed on film system 2 with addition of
component vi-1 and, respectively, vi-C2 to give blown films of thickness 12,
20, 50, and
100 micrometers. The film samples were then subjected by analogy with the
masterbatch
films described above to artificial weathering (xenon arc lamp) to DIN EN ISO
4892-2,
Method A for a period of 250 h (corresponding to 3 months of outdoor
weathering in the
southern European climatic zone), and, after weathering, tensile-tested to ISO
527-3.
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Table 3
No. Blend Film thickness AL [h)]
1 100% compounded material 12 pm 4%
2 100% compounded material 20 pm 2%
4
3 100% compounded material 50 pm 2%
4 100% compounded material 100 pm 2%
97% compounded material + 3%
12 pm 4%
vi-C2
97% compounded material + 3%
6 20 pm 4%
vi-C2
, 97% compounded material + 3%
7 ; 50 pm 7%
vi-C2
97% compounded material + 3%
8 ; 100 pm 56%
vi-C2
; 95% compounded material + 5%
9 12 pm 10%
' vi-C2
90% compounded material + 10%
12 pm 15%
vi-C2
4- ____________________________ t-
97% compounded material + 3%
11 12 pm 10%
vi-1
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97% compounded material + 3%
12 20 pm 12%
vi-1
97% compounded material + 3%
13 50 pm 57%
vi-1
97% compounded material + 3%
14 100 pm 92%
vi-1
95% compounded material + 5%
15 12 pm 20%
vi-1
90% compounded material + 10%
16 12 pm 55%
' vi-1
Again, the results in Table 3 clearly show the favorable effect of the
masterbatch of the
invention based on the light stabilizer 2-(4,6-bisbipheny1-4-y1-1,3,5-triazin-
2-y1)-5-(2-ethyl-
(n)-hexyloxy)phenol (Table 1: No. B1; Table 3: vi-1). Again, in the compounded
materials
of the invention based on components i-1, ii-1, iii-1 and iv-1, the films
stabilized with
masterbatch MB-1 of the invention (vi-1) performed markedly better than the
films
stabilized with the comparative system C-MB8 (vi-C2). The intensity of UV
absorption
depends on the concentration of active ingredient and on the wall thickness of
the film.
Transparent films of thickness starting from 50 micrometers can be stabilized
by a
concentration of as little as about 3000 ppm of light stabilizer vi-1. Very
thin transparent
films based on the compounded material require a concentration of about 10 000
ppm of
light stabilizer vi-1 in the abovementioned experiment.
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34
Examples providing evidence of the improved tear resistance of the films of
the invention:
Inventive example 1:
720 kg of i-1 (polyester Al), 80 kg of ii-1 (PLA), 140 kg of iii-1 (calcium
carbonate), and
60 kg of iv-1 (talc) were compounded at a melt temperature of about 220-260 C
in a
Leistritz extruder with L/D ratio of 46. The fillers iii-1 and iv-1 were fed
in zones 3 and 6,
and the remainder was fed by the cold-feed method in zone 0. Entrained air and
low-
molecular-weight components were removed via vacuum devolatilization in
reverse
direction in zone 10. The compounded material was then processed in film
system 1 with
addition of 7% by weight of vi-1 (masterbatch MB1) (by the cold-feed method at
the
compounding extruder) to give a film of thickness 12 micrometers and width
1400 mm, the
speed of the system being 56 m/min. The film could be processed without
difficulty, and
the stability of the film bubble was assessed as good.
Inventive example 2:
715 kg of i-1 (polyester Al), 80 kg of ii-1 (PLA), 140 kg of iii-1 (calcium
carbonate), 60 kg
of iv-1 (talc), and also 5 kg of v-1 (Joncryl masterbatch) were compounded at
a melt
temperature of about 220-260 C in a Leistritz extruder with L/D ratio of 46.
The fillers iii-1
and iv-1 were fed in zones 3 and 6, and the remainder was fed by the cold-feed
method in
= CA 02834651 2013-10-29
zone 0. Entrained air and low-molecular-weight components were removed via
vacuum
devolatilization in reverse direction in zone 10. The compounded material was
then
processed in film system 1 with addition of 7% by weight of vi-1 (masterbatch
MB1) (by the
cold-feed method at the compounding extruder) to give a film of thickness 12
micrometers
and width 1400 mm, the speed of the system being 56 m/min. The film could be
processed
without difficulty, and the stability of the film bubble was assessed as very
good.
Comparative example 1:
720 kg of i-1 (polyester Al), 80 kg of ii-1 (PLA), 200 kg of iii-1 (calcium
carbonate) were
compounded at a melt temperature of about 220-260 C in a Leistritz extruder
with L/D
ratio of 46. The filler iii-1 was fed in zone 3, and the remainder was fed by
the cold-feed
method in zone 0. Entrained air and low-molecular-weight components were
removed via
vacuum devolatilization in reverse direction in zone 10. The compounded
material was
then processed in film system 1 with addition of 7% by weight of vi-1
(masterbatch MB1)
(by the cold-feed method at the compounding extruder) to give a film of
thickness
12 micrometers and width 1400 mm, the speed of the system being 56 m/min. The
film
was initially very unstable and could not be processed at this thickness until
some
stabilization measures had been adopted (e.g. lowering the calibration
basket). The
stability of the film bubble can therefore be evaluated as no more than
adequate.
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The results of the tear-propagation experiments of Inventive examples 1 and 2,
and also of
Comparative example 1, have been collated in Table 4. It is clearly seen that
Inventive
example 1 (combination of fillers iii-1 and iv-1) and the particularly
preferred embodiment
in Inventive example 2 (combination of iii-1 and iv-1, and also addition of v-
1) exhibit
significantly better tear-propagation resistances than Comparative example 1
(addition
exclusively of iii-1), not only in machine direction (MD) but also especially
in cross direction
(CD).
Table 4:
Test Film Inv. ex. 1 Inv. ex. 2 Comp. ex. 1
thickness
Elmendorf test*, 12 pm 936 mN 1309 mN 874 mN
machine direction (MD)
Elmendorf test*, cross 12 pm 878 mN 1010 mN 445 mN
direction (CD)
Elmendorf test*, 23 pm 1782 mN 1657 mN
machine direction (MD)
Elmendorf test*, cross 23 pm 1949 mN 810 mN
direction (CD)
* Standard: EN ISO 6383-2:2004
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Inventive example 3:
9720 g of i-1 (polyester Al), 2160 g of ii-1 (PLA), 2250 g of iii-1 (calcium
carbonate), 750 g
of iv-1 (talc), and 120 g of v-1 (Joncryl masterbatch) were compounded at melt
temperature about 220-260 C in a Werner & Pfleiderer MC-26 extruder.
Components i-1,
ii-1, and v-1 were fed by the cold-feed method in zone 0, the fillers iii-1
and iv-1 were
metered into the mixture by the side-feed method in zone 4, and entrained air
was
removed via vacuum devolatilization in reverse direction in zone 3.
The compounded material was then processed in film system 2 to give a blown
film of
thickness 30 micrometers.
Comparative example 2:
9690 g of i-1 (polyester Al), 2160 g of ii-1 (PLA), 3000 g of iii-1 (calcium
carbonate), and
150 g of v-1 (Joncryl masterbatch) were compounded at melt temperature about
220-260 C in a Werner & Pfleiderer MC-26 extruder. Components i-1, ii-1, and v-
1 were
fed by the cold-feed method in zone 0, the filler iii-1 was metered into the
mixture by the
side-feed method in zone 4, and entrained air was removed via vacuum
devolatilization in
reverse direction in zone 3.
CA 02834651 2013-10-29
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The compounded material was then processed in film system 2 to give a blown
film of
thickness 30 micrometers.
Comparative example 3:
24.3 kg of i-1 (polyester Al), 5.4 kg of ii-1 (PLA), and 0.3 kg of v-1
(Joncryl masterbatch)
were compounded at melt temperature about 220-260 C in a Werner & Pfleiderer
MC-26
extruder. All of the starting materials were metered into the mixture by the
cold-feed
method.
The compounded material was then processed in film system 2 to give a blown
film of
thickness 30 micrometers.
Table 5 collates the testing of tear-propagation resistances of Inventive
example 3 and of
Comparative examples 2 and 3. It is clearly seen that Inventive example 3 has
significantly
better tear-propagation resistance in machine direction (MD) than Comparative
examples
2 and 3, more than compensating for the somewhat smaller value in cross
direction.
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39
Table 5:
Test Film Inv. ex. 3 Comp. ex. 2 Comp. ex. 3
thickness
Elmendorf test*, 30 pm 1628 mN 1100 mN 735 mN
machine
direction (MD)
Elmendorf test*, 30 pm 635 mN 717 mN 604 mN
cross direction
(CD)
*Standard: EN ISO 6383-2:2004
Comparison of the results from Tables 4 and 5 also shows that, for similar
filler
concentrations, the films specified in Table 5 (with relatively high content
of component ii-1
(PLA) in the polymer matrix) have markedly poorer tear-propagation resistances
than the
films from Table 4. Tear-propagation resistance does not have linear
correlation with film
thickness and normally increases more than proportionally in thicker films,
and the
difference is therefore actually more pronounced than might be implied by
comparison of
the pure numerical values. The relatively small proportion of ii-1 in
Inventive examples 1
and 2 is therefore particularly preferred for achieving films with high tear-
propagation
resistances.
