Note: Descriptions are shown in the official language in which they were submitted.
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Biaxially stretched, bio~f,~l d~ble and ~ ompostible film having improved
properties
The invention relates to a biaxially stretched, biodegradable and compostible film.
It is known that certain polymeric mate rials may be subject to biological
degradation. Materials to be mentioned 1 ere are mainly those obtained from
naturally occurring polymers, directly o- after modification, for example
polyhydroxy alkanoates such as polyhydrox~ butyrate, plastic celluloses, cellulose
10 esters, plastic starches, chitosan and pullulan Purposeful variation of the polymer
composition or of the stucts, such as is desira ble from the point of view of polymer
application, is only possible with difficulty and often in very limited manner by
reason of the natural synthesis process.
15 Many synthetic polymers, on the other hand, ;~re not attacked by micro-org~ni~m~ or
are only attacked extremely slowly. Mai nly synthetic polymers that contain
heteroatoms in the principal chain are regar,led as potentially biodegradable. An
important class within these materials is rep~esented by the polyesters. Although
synthetic raw materials that contain only aliphatic monomers exhibit relatively good
20 biodegradability, by reason of their material )roperties they can be used only to an
extremely limited extent; cf. Witt et al in Macrom. Chem. Phys. 195 (1994) pp 793 -
802. In comparison, aromatic polyesters, whilst having good material properties,show clearly impaired biodegradability.
25 In recent years various biodegradable polym~rs have become known (see DE 44 32
161). These have the property that they can be readily worked thermoplastically
and, on the other hand, are biodegradable - ie, their entire polymer chain is
dissociated by micro-org:~ni~m~ (bacteria and moulds) with the aid of enzymes and
is totally degraded into carbon dioxide, wate- and biomass. An al~propliate test in
30 the natural environment subject to the actior of micro-org~ni~m~ such as prevails,
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inter alia, in a compost is given, inter alia, in DIN 54 900. By reason of theirthermoplastic behaviour these biodegradable materials can be processed into semi-
finished products such as cast or blown films Nevertheless, the use of these semi-
finished products is greatly restricted. ~ )n the one hand, these films are
5 distinguished by poor mechanical properties and, on the other hand, the physical
sealing properties with respect to water ~apour and gases are very poor in
comparison with films consisting of typical ~ ut non-biodegradable plastics such as
polyethylene, polypropylene or polyamide.
10 The present invention provides a process for producing a biodegradable and
compostible film having improved mechani~al and optical properties as well as
superior barrier properties. This objective is achieved by a biodegradable and
compostible polymer or a mixture of several F olymers which are each biodegradable
and compostible being subjected to biaxial crientation. The terms "biodegradable15 and compostible polymers or films" in th~ sense of the invention are to be
understood to mean materials that, correspor ding to the test according to DIN 54
900 from the draft dated 1996, are tested as ha ving "biodegradability".
For the inventor it was surprising that these biodegradable polymers, in addition to
20 their thermoplastic processing, can also be biaxially oriented and that, as a result of
this orientation process, the physical properti~ s of the film can be clearly improved.
These include a clear increase in strength, an improvement in the optical properties
and also an increased barrier effect of the film
25 The invention provides a film that exhibits a biaxial orientation and consists of one
or more polymers, all of which are biodegrada ble and compostible, and also possibly
contains additional additives for improving ~rocessability. The biaxial orientation
takes place in the case of amorphous thermop astics in temperature ranges above the
glass transition temperature and, in the case ~f partially crystalline thermoplastics,
30 below the crystallite melting-temperature.
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The invention provides furthermore the use of certain biodegradable and
compostible polymers or a mixture of these pc lymers for producing the film.
Suitable as polymers are:
Aliphatic and partially aromatic polyesters for med from
A) linear bifunctional alcohols, for example ethylene glycol, hexanediol or,
preferably, butanediol, and/or, optionall y, cycloaliphatic bifunctional alcohols,
for example cyclohexanedimethanol, and, optionally in addition, small
quantities of alcohols of higher function 11ity, for example 1,2,3-propanetriol or
neopentyl glycol, and also from linear b if unctional acids, for example succinic
acid or adipic acid, andlor, optionally, cycloaliphatic bifunctional acids, for
example cyclohexanedicarboxylic a cid, and/or, optionally, aromatic
bifunctional acids, for example terephthalic acid or isophthalic acid or
naphthalenedicarboxylic acid, and, optionally in addition, small quantities of
acids of higher functionality, for examp e trimellitic acid, or
B) from acid-functionalised and alcoho ~-functionalised structural units, for
example hydroxybutyric acid or hydrox ~valeric acid or derivatives thereof, for
example ~-caprolactone,
or from a mixture or a copolymer of A and B
whereby the aromatic acids make up a propol tion of no more than 50 wt-%, relative
to all acids.
The acids may also be employed in the f)rm of derivatives, for example acid
chlorides or esters.
Aliphatic polyester urethanes formed from
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C) an ester portion formed from linear biful ctional alcohols, for example ethylene
glycol, butanediol, hexanediol, prefel ably butanediol, and/or, optionally,
cycloaliphatic bifunctional alcohols, for example cyclohexanedimethanol, and,
optionally in addition, small quantities ~ ~f alcohols of higher functionality, for
example 1,2,3-propanetriol or neope ltyl glycol, and also from linear
bifunctional acids, for example succinic acid or adipic acid, and/or, optionally,
cycloaliphatic and/or aromatic ~ if unctional acids, for example
cyclohexanedicarboxylic acid and te ephthalic acid, and, optionally in
addition, small quantities of acids c f higher functionality, for example
trimellitic acid, or
D) from an ester portion formed from acid-functionalised and alcohol-
functionalised structural units, for example hydroxybutyric acid and
hydroxyvaleric acid or derivatives there( f, for example ~:-caprolactone,
or from a mixture or a copolymer of C) and D' and
E) from the reaction product of C) and/or ] )) with aliphatic and/or cycloaliphatic
bifunctional isocyanates and, optional]y in addition, isocyanates of higher
functionality, for example tetrametl.ylene diisocyanate, hexamethylene
diisocyanate, isophorone diisocyanate, ~.nd, optionally in addition, with linearand/or cycloaliphatic bifunctional a: cohols and/or alcohols of higher
functionality, for example ethylene glyeol, butanediol, hexanediol, neopentyl
glycol, cyclohexanedimethanol,
whereby the ester portion C) and/or D) amou ItS to at least 75 wt-%, relative to the
sum of C), D) and E).
30 Aliphatic-aromatic polyester carbonates forme d from
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F) an ester portion formed from linear bifu utional alcohols, for example ethylene
glycol, butanediol, hexanediol, preferably butanediol, and/or cycloaliphatic
bifunctional alcohols, for example cyc]ohexanedimethanol, and, optionally in
addition, small quantities of alcohols of higher functionality, for example
S 1,2,3-propanetriol or neopentyl glycol, Ind also from linear bifunctional acids,
for example succinic acid or adipic 2cid, and/or, optionally, cycloaliphatic
bifunctional acids, for example cycloh~ xanedicarboxylic acid, and, optionally
in addition, small quantities of acids of higher functionality, for example
trimellitic acid, or
G) from an ester portion formed fro n acid-functionalised and alcohol-
functionalised structural units, for example hydroxybutyric acid or
hydroxyvaleric acid or derivatives there )f, for example ~-caprolactone,
or from a mixture or a copolymer of F) and G I and
H) from a carbonate portion which is produced from aromatic bifunctional
phenols, preferably bisphenol A, and ca bonate donors, for example phosgene,
whereby the ester portion F) andlor G) amo~ nts to at least 70 wt-%, relative to the
sum of F), G) and H).
Aliphatic polyester amides formed from
25 I) an ester portion formed from linear andl or cycloaliphatic bifunctional alcohols,
for example ethylene glycol, hexanedi~l or butanediol, preferably butanediol
or cyclohexanedimethanol, and, optiolally in addition, small quantities of
alcohols of higher functionality, for e~ample 1,2,3-propanetriol or neopentyl
glycol, and also from linear and/or cycloaliphatic bifunctional acids, for
example succinic acid, adipic acid, cy,,lohe~ne-licarboxylic acid, preferably
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adipic acid and, optionally in additiol, small quantities of acids of higher
functionality, for example trimellitic ac d, or
K) from an ester portion formed frc m acid-functionalised and alcohol-
functionalised structural units, for example hydroxybutyric acid or
hydroxyvaleric acid or derivatives ther~ of, for example ~-caprolactone,
or from a mixture or a copolymer of I) and K and
10 L) from an amide portion fornaed from lilear and/or cycloaliphatic bifunctional
amines and, optionally in addition, ~mall quantities of amines of higher
functionality, for example tetramethyl~ne diamine, hexamethylene diamine,
isophorone diamine, and also from linear and/or cycloaliphatic bifunctional
acids and, optionally in addition, ~ mall quantities of acids of higher
functionality, for example succinic acid or adipic acid, or
M) from an amide portion formed fr ~m acid-functionalised and amine-
functionalised structural units, prefer lbly cl)-laurolactam and, particulaLrly
preferred, ~-caprolactam,
or from a mixture of L) and M) as amide porti on,
whereby the ester portion I) and/or K) amoults to at least 30 wt-%, relative to the
sum of I), K), L) and M).
The biodegradable and compostible raw mate ials according to the invention may be
furnished with processing aids and additives ~ uch as, for example, nucleation agents
(for example, 1 ,5-naphthalenedisodium sulfon ate), stabilisers or lubricants.
30 The invention provides furthermore the us of a certain material class of the
biodegradable and compostible polymers for producing the film, it being a question,
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with this material class, of polyester amide. I 1 this connection the film according to
the invention may be produced from a polyes er amide or from a mixture of various
polyester amides.
5 The invention provides furthermore a process ~or producing the film according to the
invention. This process is characterised in that the biodegradable and compostible
material or materials is/are firstly broken dov n by the action of heat and shear, this
melt is discharged in a tool, is cooled do~m until it solidifies, is subsequently
regulated in the case of partially crystalline materials to tempcldluies below the
10 crystallite melting-temperature and in th~ case of amorphous materials to
tempeldlules above the glass transition temperature and is subsequently biaxially
stretched once or several times. After the stre tching stage or stages, in each instance
a fixation of the film may optionally be effecl ed. After the stretching processes and
the possibly prevailing fixing stages, the filnr that has consequently been produced
15 may possibly be subjected to in-line surface Frctlcallllent. The plcllc~ ent may be
carried out with a corona, a flame, a plasma or with an oxidative substance or
mixture of substances in such a way as to result in an increase in the surface tension
on the film.
20 The invention provides furthermore a process for stretching the film. The biaxial
stretching may be effected in a simultaneou i stretching process or in a two-stage
sequential process, whereby stretching may be effected both firstly longitudinally
and then transversely and firstly transversely and then longih1-lin~11y, or in a three-
stage sequential process, whereby stretcl ing may be effected both firstly
25 longihl~lin~lly~ then transversely and finally ~ongi~l~1in~11y, and firstly transversely
then longihl~lin~lly and finally transversely, or in a four-stage sequential process,
whereby stretching may be effected both fi stly longihlt1in~11y, then transversely,
then longitudinally and finally transver ely and firstly transversely, then
longitudinally, then transversely and fina~ ly longitl1~in~11y. Each individual
30 stretching may possibly be immediately follr)wed by a fixation of the film. The
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individual stretching, both in the longitud nal direction and in the transverse
direction, may be effected in one stage or in s~ veral stages.
In a preferred form of the film according to the invention the biaxial stretching is
5 characterised in that it is a question of a s~quential process beginning with the
longitudinal stretching.
In a still more preferred form of the film ~ccording to the invention the biaxial
stretching is characterised in that the overall stretching ratio in the longitudinal
direction amounts to 1: 1.5 to 1 : 10 and the c verall stretching ratio in the transverse
direction amounts to 1: 2 to 1: 20.
In a still more preferred form of the film ~ccording to the invention the biaxial
stretching is characterised in that the overall stretching ratio in the longitudinal
direction amounts to 1: 2.8 to 1: 8 and the overall stretching ratio in the transverse
direction amounts to 1: 3.8 to 1: 15.
In a still more preferred form of the film acc )rding to the invention the latter has a
thickness that is less than 500 llm.
In a still more preferred form of the film acc )rding to the invention the latter has a
thickness that is less than 80 ~lm.
The invention provides fi~rthermore the apFlication of the film according to the25 invention. The use of this film as a solo filln in pretreated or non-p,t;lleated form
and also in printed or non-printed form for pa~ kaging in the food and non-food fields
or as a solo film in pretreated or non-pretre~ ted form for greenhouse coverings or
mulch films in the fields of horticulture or ~griculture or, finished so as to form
sacks, for the storage and transport of materi lls, for example biowaste, or as a solo
30 film in pretreated or non-pretreated form for protective and separating functions in
cormection with cosmetics and sanitar,v articll s, for example for nappies or sanitary
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towels, or as a solo film in pretreated or non pretreated form for surface protection
or surface fini~hing in the field of cardboard l~min~tion, paper l~min~tion and
window-envelope l~min~tion or as a finis~ed film which can be employed in
e~led or non-pl~lle~led form and also in printed or non-printed form and also,
5 provided with adhesive, as a label or an adh~ sive tape comes into consideration by
way of application. With a view to impro~ing the pleS~ adhesion or bonding
properties, the surface of the film can be pretreated during production andlor
subsequently during further processing with a corona, a flame, a plasma or with
another oxidative substance or mixture of sub itances in such a way as to result in an
10 increase in the surface tension.
The invention provides furthermore the apFlication of the film according to the
invention in a composite film. In this conne,tion it may likewise be a question, in
the case of the other films of the composite, c f biodegradable and compostible films
l S or also of non-degradable film. Likewise, th~ adhesives employed may pertain both
to the biodegradable and compostible raw m iterials and to normal non-degradablesystems.
In a particularly preferred form of the app ication of this film according to the
20 invention only substances that are biodegrad~ ble and compostible are employed for
the purpose of producing a composite film, so that the overall composite is likewise
biodegradable and compostible.
The invention provides furthermore the ap~lication of the film according to the
25 invention as primary material for the produc ion of a bag that releases its contents
after decomposition as a result of the biologi ,al degradation process. The bag may
be produced by adhesion bonding and also b~ sealing of the film and may either be
closed or may possess an opening with an app ropriate seal or connection.
30 The invention provides furthermore the a~plication of the film or composites
according to the invention as primary materi; ~1 for the production of a p~c1~ging or
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separating or surface-protecting film having ~ ery high water-vapour permeability, in
that said film is pierced by a cold or temperature-regulated needle roller. The end
use of this film is the packaging of goods that emit moisture, for example bread or
various kinds of vegetable, or as a separating and protecting film in the sanitary
5 field.
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Example 1
A biodegradable polyester amide having a melt viscosity of 250 Pas at 190~C
(measured in accordance with DIN 54 811 - B) and also a melting-point of 125~C,
measured according to ISO 3146 / C2, w~s biaxially stretched subject to the
following process parameters. The m~ximun extrusion-temperature amounted to
205~C. Correspondingly, the constant-tem~erature zones of the extruder were
regulated to a maximum of 182~C and also t~e tool was regulated to a m~imllm of
205~C. The melt was cooled as a flat fi]m on a cooling roller mill at roller
temperatures of 20~C. A solid, thick film was formed which was heated up to
stretching-temperature in the next process step by constant-te~ )el~ e rollers
having temperatures of 65~C. The actual ~tretching rollers were operated at a
temperature of 70~C. In this process, first~y the flat film was stretched in thelongitudinal direction in two stages, once by a ratio of 1: 1.5 and then by a ratio of 1
: 2.5. Consequently, an overall stretching rati o in the longitudinal direction resulted
of 1: 3.75. The reheating rollers, over which the film then ran, had a temperature of
85~C. The preheating zones of the transvers~-stretching furnace were regulated to
100~C. The temperature in the actual transv/:rse-stretching part amounted to 95~C.
Here the film was stretched in the trans~ erse direction by a ratio of 1 : 5.
Consequently, an arithmetical area-stretching ratio resulted of 1: 18.75. After the
transverse stretching, the film was fixed at a temperature of 105~C. The speed of
production at the outlet of the transverse stret~ hing amounted to 32.0 m/min. A film
having a thickness of 46 ~m was able to be pr )duced.
Example 2
The same biodegradable polyester amide fr~ m Example 1 was worked under the
process conditions of Example 1 that have b~ en described so as to form a biaxially
oriented film. As a result of lowering the e~trusion speed, a film was produced in
this case having a thickness of 24 llm.
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Comparative Example 1
The same biodegradable polyester amide from Examples 1 and 2 was worked on a
film-blowing appalalus. The melting-temF erature measured at the nozzle exit
S amounted to 152~C. In this connection the c~ linder temperature of the extruder was
regulated to max. 145~C and the nozzle was r~ gulated to 145~C. The diameter of the
nozzle employed amounted to 400 mm. The horizontal width of the film that was
produced amounted to 9S0 mm. The film w lS produced at a drawing-off speed of
6.3 m/min. The thickness of the blown film a nounted to 30 llm.
The following physical properties and comFostibility in respect of the specimensproduced were measured as follows:
Mechanical properties:
lS The mechanical variables constituted by tear resistance and elongation at tear were
determined in respect of the specimens, both n the longitudinal direction and in the
transverse direction, in accordance with DIN 53 455. The modulus of elasticity in
the longitudinal and transverse directions was determined in accordance with DIN53 457. The thickness of the individual spe~imens was determined in accordance
with DIN 53 370. With a view to ascertainilg the piercing force and the piercingdistance, the specimens were analysed by the ~iaxial piercing test in accordance with
DIN 53 373.
Permeation
The oxygen permeability of the specimens w Is determined in accordance with DIN
53 380 at 23~C test-temperature and at 0 % relative humidity. The water-vapour
permeability was carried out in accordance with DIN 53 122 at a test-temperature of
23~C and at 85 % relative humidity.
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Optics
By way of optical properties, the surface lustI~ in accordance with DIN 67 530 at a
test-angle of 20~ and the haze in accordance w ith ASTM D 1003 were determined in
respect of the films. The lustre on both sides of the film was measured. An
S averaging of the values alscertained in this process was then carried out, and this
average was presented as the result.
Compostibility
The compostibility was carried out in accordance with the test specification of DIN
draft standard DIN 54 900 Part 3 dated 199 ). On the basis of the results of theinvestigation, the film specimens are g~ aded in the corresponding cla~ss,
corresponding to the DIN standards.
The results of the investigations in respect of he specimens from Examples 1 and 2
15 and also from Comparative Example 1 are list~ d in Table 1.
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Table 1
Example 1 Example2 Comparative
Example 1
Mechanical properties
Thickness [~lm] 46 24 30
Modulus of elasticity, 226 252 296
longitudinal [MPa]
Modulus of elasticity, 292 306 392
transverse [MPa]
Tear resistance, longitudinal 90 91 61
[MPa]
Tear resistance, transverse [MPa] 109 111 50
Elongation at tear, longitudinal 224 186 388
[%]
Elongation at tear, transverse [%] 111 75 639
Piercing force rN] 227 151 47
Piercing distance [rnm] 18 16 38
Permeation
Oxygen 23~C/0 % rel. hum. 384 690 1270
[cm31mld/bar]
Water vapour 23~C/85 % rel. 200 300 360
hurn. [g/m /d]
Optics
Lustre [GE] 110 120 3.1
Haze [%] 14 3.3 38.9
Compostibility
Biodegradability yes yes yes
