Note: Descriptions are shown in the official language in which they were submitted.
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Br/by/S-P
Compostable supportin~ web
The invention relates to biodegradable, particularly compostable films which aremanufactured by extrusion from the melt.
The invention relates to multi-layer, at least two-layer films with an asymmetrical
layer structure and a low tendency to curl, which may be prepared by coextrusionand are obtained in the ple~aldlion process directly as matt films without further
treatment stages. The films are composed of compostable polymers or copolymers
10 and contain, in one of the outer layers, relatively large amounts of mineral filler. Due
to the unexpectedly similar volume contraction of the filled and unfilled layers of the
at least two-layer film during the preparation process, the films according to the
invention have an extremely low tendency to curl. In addition, they may contain
proportions of processing auxiliaries, coloured pigments and stabilisers. As a result
15 of their silk-matt surface characteristics, said films are suitable for the low-gloss
covering of surfaces. They may be used, for example as supporting films for
adhesive plasters, sticking plasters or plaster strips.
The films according to the invention are suitable for a multiplicity of applications,
20 the use as supporting films for adhesive plasters being emphasised here in particular.
Adhesive plasters are generally composed of a supporting material, coated with apressure-sensitive adhesive, a wound cover which has a smaller surface area than the
supporting material, and a release material which protects pressure-sensitive
adhesive and wound cover during storage. Films for such applications have to meet a
25 multiplicity of requirements, aesthetic as well as technical requirements having to be
satisfied in particular.
Films for medical plasters have to be dimensionally stable and able to withstand a
chemical or physical pretreatment in order to be printed and/or coated.
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The aesthetic requirements include primarily a silk-matt surface which guarantees a
skin-like appearance. Matt surfaces are generally assessed by gloss, and minim~lgloss values are desired. Generally speaking, gloss values of <10 have proved
acceptable for plasters, measured in accordance with DIN 67 530, at an angle of 20~.
S The tactile properties of plaster films must also be attractive, said properties
including in particular a soft feel.
In the use of a cut-to-size plaster piece, the load due to tensile forces remains small
in practice since the pressure-sensitive adhesive has particularly low adhesion to a
10 conventionally used release material such as, for example, silicone-coated paper or
rigid films. Cut-to-size plaster pieces differ in this context from rolls of plaster
where relatively high pull forces may occur since a release layer is dispensed with in
this case and the adhesive layer is situated on the outside of the plaster.
15 Similarly, films for rolls of plaster are not very soft materials. When a longitudinal
load is applied of the kind that occurs e.g. during removal as an adhesive tape from
the roll, low longitudinal expansion is desirable and generally obtained.
To this extent, not only are the high ultimate tensile stress values or elongation at
20 break values important for characterising a suitable film material for use assupporting film for cut-to-size plaster pieces, but also the initial elongation values in
the event of a tensile stress are important criteria of assessment.
In the past, matt-calendered polyvinyl chloride (PVC) films were used in many cases
25 as supporting films. The public discussion about the effects on health of the vinyl
chloride monomer and the so-called external plasticisers, criticism focusing on the
phthalate plasticisers in particular, intensified the pressure to replace plasticised
PVC.
30 The requirements in respect of films for medical plasters are set out, for exarnple, in
the German utility model applications GM 90 12 161.9 and GM 93 06 768.2 (both
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Beiersdorf). The classification of plasters is regulated by the relevant
ph~rm~copoeias, this being for example the DAB 10 (1991) in Germany.
It is known that certain polymer materials are subject to biological degradation.
5 These mainly include materials which are obtained from naturally occurring
polymers directly or after modification, for example, polyhydroxyalkanoates such as
polyhydroxybutyrate, plastic celluloses, cellulose esters, plastic starches, chitin and
pullulan. A controlled variation of the polymer composition or of the structures, of
the kind that is desirable from the point of view of the polymer application, is10 difficult to achieve in view of the natural synthesis process and often achieved only
to a very limited degree.
Many of the synthetic polymers, on the other hand, are attacked only extremely
slowly by microorg~ni~m~, if at all. Mainly synthetic polymers containing
15 heteroatoms in the main chain are regarded as potentially biodegradable. An
important class within these materials are the polyesters. Synthetic raw materials
containing only aliphatic monomers have relatively good biodegradability but
because of their material properties can be used only to an extremely limited degree;
cf. Witt et al. in Macrom. Chem. Phys., 195 ( 1994) p. 793 - 802. Aromatic
20 polyesters, on the other hand, exhibit markedly worse biodegradability whilst having
good material properties.
Various biodegradable polymers have become known recently (see DE 44 32 161).
These have the property of being highly melt processable and on the other hand
25 biodegradable, i.e. their whole polymer chain is cleaved by microorg~ni~m~ (bacteria
and fungi) by way of enzymes and degraded completely to carbon dioxide, water
and biomass. A corresponding test in the natural environment with the action of
microorg~ni.~m~, of the kind predomin~ting i.a. in a compost, is given i.a. in DIN 54
900.
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The object of the present invention is to provide melt processable and fully
biodegradable plastic films with fillers such that no synthetic materials remain in the
compost and which have a good range of mechanical properties, particularly strength
and impact resistance.
The object was to provide a matt film obtainable from the film preparation process
without further mechanical treatment stages. In order to guarantee simple further
processing to supporting films for cut-to-size plaster pieces, the film was to have a
low tendency to curl. From an ecological standpoint, the film according to the
10 invention was to be free from halogen compounds and aromatic plasticisers with a
comparatively low molecular weight. It was to have at least one adhesive-tolerant
side so that it can be coated without difficulty with a pressure-sensitive adhesive on
common transfer l~min~ting machines. In addition, the film was to be elastic so that
it can adjust in a flexible manner to skin movements in the wound area. Very largely
15 isotropic properties in the film plane are an advantage for the use of the film on the
widest possible scale.
The object is achieved by incorporating mineral fillers in at least one layer of a
multi-layer film to be prepared from thermoplastic, biodegradable moulding
20 compositions.
The present invention thus provides rigid and yet biodegradable plastic films,
characterised in that mineral fillers, particularly of natural origin, which areincorporated in the melt in fully biodegradable polymers, are used as base material
25 of at least one outer layer of the film. Accordingly, the present invention is to be
regarded as providing a biodegradable and compostable film with improved
mechanical and optical properties. The terms "biodegradable and compostable
polymers or films" within the meaning of this invention mean materials whose
biodegradability is tested according to the test of DIN 54 900 from the 1996 draft.
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The film according to the invention is obtained preferably by processing from the
melt, the various layers exhibiting only minor differences in their volume
contraction on cooling so that a structure with a low tendency to curl is obtained.
The film according to the invention may contain the additives customary in plastics
5 processing.
The invention also provides a film which has biaxial orientation and is composed of
one or more polymers which are all biodegradable and compostable, and possibly
contains additional additives for improving processability. Biaxial orientation is
10 carried out in the case of amorphous thermoplastics in temperature ranges above the
glass transition temperature and in the case of partially crystalline thermoplastics
below the crystalline melting point.
The invention also provides the use of the matt compostable films as supporting web
15 of adhesive tapes which are coated on one side with the pressure-sensitive adhesives
known according to the prior art. In particular, this relates to adhesive tapes which
are further processed to adhesive plasters or active ingredient plasters.
The layer structure according to the invention is formed from at least one layer (I) of
20 a compostable polymer and/or a compostable copolymer and/or mixtures thereof,this taking place optionally with the addition of suitable colorants and stabilisation
additives in effective amounts, and at least a second matt layer (2).
Layer (2) is characterised in that said layer has compostable polymers as matrix, i.e.
25 in a majority proportion, and is flatted by the addition of a filler. The matrix material
used in preference for layer (2) is the same polymer as for layer (1). Further layers
(3) may optionally be arranged between layers (1) and (2), said further layers being
formed in turn preferably from a compostable matrix resin.
30 Suitable polymers are:
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aliphatic and partly aromatic polyesters of
A) linear bifunctional alcohols, for example, ethylene glycol, hexane diol or
preferably butane diol, and/or optionally cycloaliphatic bifunctional alcohols,
for example, cyclohexane dimethanol and, in addition, optionally small
amounts of higher-functionality alcohols, for example, 1,2,3-propane triol or
neopentyl glycol, and of linear bifunctional acids, for example, succinic acid
or adipic acid, and/or optionally cycloaliphatic bifunctional acids, for
example, cyclohexane dicarboxylic acid, and/or optionally aromatic
bifunctional acids, for example, terephthalic acid or isophthalic acid or
naphthalene dicarboxylic acid and, in addition, optionally small amounts of
higher-functionality acids, for example trimellitic acid, or
B) acid- and alcohol-functionalised building blocks, for example,
hydroxybutyric acid or hydroxyvaleric acid or derivatives thereof, for
example, ~-caprolactone,
or a mixture or a copolymer of A) and B)
wherein the aromatic acids account for a proportion of not more than 50 wt.%, based
on all the acids.
The acids may also be used in the form of derivatives, for example, acid chlorides or
esters.
Aliphatic polyester urethanes of
C) an ester proportion of linear bifunctional alcohols, for example, ethylene
glycol, butane diol, hexane diol, preferably butane diol, and/or optionally
cycloaliphatic bifunctional alcohols, for example, cyclohexane dimethanol
and, in addition, optionally small amounts of higher-functionality alcohols,
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for example, 1,2,3-propane triol or neopentyl glycol, and of linear
bifunctional acids, for example, succinic acid or adipic acid, and/or
optionally cycloaliphatic and/or aromatic bifunctional acids, for example,
cyclohexane dicarboxylic acid and terephthalic acid and, in addition,
optionally small amounts of higher-functionality acids, for example
trimellitic acid, or
D) an ester proportion of acid- and alcohol-functionalised building blocks, for
example, hydroxybutyric acid and hydroxyvaleric acid or derivatives thereof,
for example, ~-caprolactone,
or a mixture or a copolymer of C) and D), and
E) the reaction product of C) and/or D) with aliphatic and/or cycloaliphatic
bifunctional isocyanates and, in addition, optionally higher-functionality
isocyanates, for example, tetramethylene diisocyanate, hexamethylene
diisocyanate, isophorone diisocyanate and optionally, in addition, with linear
and/or cycloaliphatic bifunctional and/or higher-functionality alcohols, for
example, ethylene glycol, butane diol, hexane diol, neopentyl glycol,
cyclohexane dimethanol,
wherein the ester proportion C) and/or D) is at least 75 wt.%, based on the sum of
C), D) and E).
25 Aliphatic-aromatic polyester carbonates of
F) an ester proportion of linear bifunctional alcohols, for example, ethylene
glycol, butane diol, hexane diol, preferably butane diol, and/or cycloaliphatic
bifunctional alcohols, for example, cyclohexane dimethanol and, in addition,
optionally small amounts of higher-functionality alcohols, for example,
1,2,3-propane triol or neopentyl glycol, and of linear bifunctional acids, for
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example, succinic acid or adipic acid, and/or optionally cycloaliphatic
bifunctional acids, for example, cyclohexane dicarboxylic acid and, in
addition, optionally small amounts of higher-functionality acids, for example
trimellitic acid, or
s
G) an ester proportion of acid- and alcohol-functionalised building blocks, for
example, hydroxybutyric acid or hydroxyvaleric acid or derivatives thereof,
for example, ~-caprolactone,
or a mixture or a copolymer of F) and G) and
H) a carbonate proportion which is prepared from aromatic bifunctional phenols,
preferably bisphenol A and carbonate donors, for example, phosgene,
wherein the ester proportion F) and/or G) is at least 70 wt.% based on the sum of F),
G) and H).
Aliphatic polyester amides of
20 I) an ester proportion of linear and/or cycloaliphatic bifunctional alcohols, for
example, ethylene glycol, hexane diol or butane diol, preferably butane diol,
or cyclohexane dimethanol and, in addition, optionally small amounts of
higher-functionality alcohols, for example, 1,2,3-propane triol or neopentyl
glycol, and of linear and/or cycloaliphatic bifunctional acids, for example,
succinic acid, adipic acid, cyclohexane dicarboxylic acid, preferably adipic
acid and, in addition, optionally small amounts of higher-functionality acids,
for example trimellitic acid, or
K) an ester proportion of acid- and alcohol-functionalised building blocks, for
example, hydroxybutyric acid or hydroxyvaleric acid or derivatives thereof,
for example, ~-caprolactone,
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or a mixture or a copolymer of I) and K) and
L) an amide proportion of linear and/or cycloaliphatic bifunctional and, in
S addition, optionally small amounts of higher-functionality amines, forexample tetramethylene (1i~mine, hexamethylene diamine, isophorone
diamine, and of linear and/or cycloaliphatic bifunctional acids and, in
addition, optionally small amounts of higher-functionality acids, for
example, succinic acid or adipic acid, or
M) an amide proportion of acid- and amine-functionalised building blocks,
preferably c3-laurinlactam and in particular preference ~-caprolactam,
or a mixture of L) and M) as amide proportion,
wherein the ester proportion I) and/or K) is at least 30 wt.% based on the sum of I),
K), L) and M).
The biodegradable and compostable raw materials according to the invention may be
20 furnished with processing auxiliaries and additives such as, for example, nucleating
agents (for example, 1,5-naphthalene disodium sulfonate), stabilisers or lubricants.
The biodegradable copolyesters, polyester urethanes, polyester carbonates and
polyester amides have a molecular weight of at least 10,000 g/mole and have a
25 random distribution of the starting materials (monomers) in the polymer.
The biodegradable polymers mentioned are preferably polyester urethanes and
polyester carbonates and particularly preferably polyester amides.
30 The invention also provides the use of a certain class of materials of biodegradable
and compostable polymers for the plepaldlion of the film, said class of materials
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being polyester amide. The film according to the invention may be prepared from a
polyester amide or a mixture of various polyester amides.
Suitable flatting agents for layer (1) of the film according to the invention are
5 minerals which are used in the form of powder, as is customary for incorporation in
non-biodegradable thermoplastics.
The mineral fillers include, for example and in preference gypsum, wollastonite and
in particular preference chalk and kaolin. Natural and synthetic silicas are likewise to
10 be regarded as suitable. Layer silicates are particularly suitable.
The thermoplastic moulding compositions according to the invention for layer (1)contain 1 wt.% to 80 wt.%, preferably 10 wt.% to 60 wt.%, particularly preferably
20 wt.% to 40 wt.% of minerals, preferably of natural origin.
The layer silicate proportion of the matt layer of the film according to the invention
should be, in a particularly preferred embodiment, advantageously at least 10 wt.%,
so that a marked flatting is obtained and on the other hand it should not exceed 25
wt.%. Surprisingly, no appreciable impairment of the mechanical strength occurs in
20 this case.
The invention also provides a process for the preparation of the reinforced
thermoplastic moulding compositions according to the invention, characterised inthat the fillers are intim~tely mixed with the biodegradable polymer, e.g. in a
25 kneader or preferably an extruder.
It is generally advantageous, mainly from an economic angle, if the matt layer
accounts for a small proportion of the total layer thickness of the film flatted on one
side. Consequently, thickness combinations in which the proportion of the layer
30 flatted with layer silicate is 15 - 40% of the total layer thickness are of particular
interest.
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The addition of the flatting layer silicate is carried out preferably in the form of an
additive masterbatch which, in a particularly preferred embodiment, has a weightproportion of layer silicate between 30 and 80 wt.%. A smaller proportion has
5 economic disadvantages whilst a higher proportion of layer silicate in the
masterbatch brings about a poor distribution which becomes appale~ll, for example,
in undesirable silicate agglomerates. This causes a more uneven rollghn~cs and
hence less pleasant tactile properties.
10 Compostable polymers or compostable copolymers with colllpalalively high meltflow indices between 8 and 24 g/10 min, measured in accordance with DIN 53 735
at 190~C and under a test load of 2.16 kg, have proved to be suitable for the
preparation of such additive masterbatches. In order to be able to improve the
masterbatch homogeneity, further plasticising auxiliaries such as, e.g., waxes, may
15 optionally be contained. To prevent thermal damage of the polymer component of
the masterbatch, the latter are usually furnished with stabilisers.
In a preferred embodiment, individual or all layers of the multi-layer-film according
to the invention may be modified by the further addition of processing aids, fillers,
20 colorants and stabilisers. Colorants permit the production of plasters for special
fields of application.
In one of these selected embodiments, at least one of the layers contains coloured
pigments. Beige-coloured film is popular if wound and wound cover are not to be
25 openly visible. Bright colourings and printing applications are used in many cases in
children's plasters. Further additives such as silicates and waxes modify the
application properties, particularly the surface slip behaviour. Stabilisers make it
possible to keep the films according to the invention over a lengthy period and to
prevent damage during processing. The common additives for plastics are described
30 by Gachter and Muller in: Handbuch der Kunststoff Additive, Hanser Verlag,
Munich 1983.
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The invention also provides processes for the plepalalion of the film according to the
mventlon.
5 Said processes are characterised in that the biodegradable and compostable
material(s) are initially broken down by the effect of heat and shear, the melt streams
are placed one over the other in a die and discharged and cooled until solidification.
This may be carried out by conventional processes of flat or blown film extrusion.
10 Said processes are described, for example, by Michaeli in: Extrusionswerkzeuge fur
Kunststoffe und Kautschuk, Carl Hanser Verlag, Munich 1991. Further information
is given in Handbuch der Kunststoff Extrusionstechnik, published by Hensen,
Knappe and Potente, Carl Hanser Verlag, Munich 1989.
15 The winding of the film, and also a further treatment by heating and/or orientation
and/or a surface treatment on one or both sides may take place immediately
afterwards.
With regard to their later use, the films according to the invention may be modified
20 in terms of their surface properties by a surface treatment process. Corona, plasma or
fluorine and flame treatments are particularly suitable for this purpose. Such
processes were described in detail, for example, by Dorn and Wahono in
Maschinenmarkt 96 (1990) 34-39 or Milker and Moller in Kunststoffe 82 (1992)
978-981. A preferred process is the corona treatment.
In the corona treatment, the procedure is advantageously such that the film is passed
between two conducting elements acting as electrodes, whereby such a high current -
usually alternating current of about 10 kV with a frequency of 10 kHz - is applied
between the electrodes that corona discharges can take place. As a result of these
30 discharges, the air along the film surface is ionised so that reactions take place on the
film surface during which polar groups are produced in comparison with the
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polymer matrix. The treatment intensities required for the pretreatment of the films
according to the invention lie within the usual bounds, treatment intensities that
yield surface tensions from 38 to 50 mN/m being preferred.
5 The films according to the invention may be pretreated on one or both sides. The
purpose of such treatments is to improve the surfaces in terms of their properties of
adhesion to the printing and/or coating materials. In the case of plasters,
conventional printing applications are, for example, brightly coloured ~nim~l~ or
articles which are printed preferably on the matter side of children's plasters. The
10 coating with pressure-sensitive adhesives is generally a conventional process with
plasters, and takes place preferably on the smoother side of the film.
In the case of orientation, heating in the case of partially crystalline materials takes
place to temperatures below the crystalline melting point and in the case of
15 amorphous materials to above the glass transition temperature, followed by one or
more biaxial orientation operations. After the orientation stage(s), a fixing of the
film may optionally be carried out in each case. After the orientation processes and
the possibly predominant fixing stages, the film thus manufactured may optionally
be surface-treated in line. The treatment may be carried out with a corona, flame,
20 plasma or an oxidative substance or mixture of substances such that an increase in
the surface tension on the film is obtained.
The invention also provides a process for orienting the film. Biaxial orientation may
be carried out in a simultaneous stretching process or in a two-stage sequential25 process wherein both longitudinal followed by transverse stretching and transverse
followed by longitudinal stretching may take place, or in a three-stage sequential
process wherein both longitudinal followed by transverse and finally longitudinal
stretching and transverse followed by longitudinal and finally transverse stretching
may take place, or in a four-stage sequential process wherein both longitudinal
30 followed by transverse followed by longitudinal and finally transverse stretching and
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transverse followed by longitudinal followed by transverse and finally longitudinal
stretching may take place.
Each individual orientation may optionally be followed by a fixing of the film. The
individual orientation in a longitudinal and transverse direction may take place in
one or more stages in this case.
In a preferred form of the film according to the invention, biaxial orientation is
characterised in that it is a sequential process that starts with longitudinal stretching.
In an even more preferred form of the film according to the invention, biaxial
orientation is characterised in that the total stretch ratio in the longitudinal direction
is 1: 1.5 to 1: 10 and the total stretch ratio in the transverse direction is 1: 2 to 1:
20.
In an even more preferred form of the film according to the invention, biaxial
orientation is characterised in that the total stretch ratio in the longitudinal direction
is 1: 2.8 to 1: 8 and the total stretch ratio in the transverse direction is 1: 3.8 to 1:
15.
In an even more preferred form of the film according to the invention, said film has a
thickness of < 500 llm.
A particular embodiment of the films according to the invention is characterised in
that the film has a total thickness between at least 30 ~Lm and at most 200 ~m. Films
with a thickness of at least 50 ~lm and at most 100 ~m are particularly suitable.
The invention also provides the use of the film according to the invention. A suitable
application is the use of said film as a solo film in pretreated or non-pretreated and in
printed or unprinted form for coating with pressure-sensitive adhesives. The film
coated in this way is suitable, for example, as a label or adhesive strip. A further
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fini~hing stage is the provision of wound coverings or active substance release
functions which are customary with plasters.
In order to improve printing adhesion or anchoring of the adhesive, the film surface
5 may be pretreated during preparation and/or afterwards during further processing
with a corona, flame, plasma or another oxidative substance or mixture of substances
such that an increase in the surface tension is obtained.
In a particularly preferred use of said film according to the invention, only
10 substances which are biodegradable and compostable are used to prepare a plaster
structure, so that the entire composite is likewise biodegradable and compostable.
The invention also provides the use of the film according to the invention as starting
material for the ~repaldlion of an adhesive tape or plaster with very high water15 vapour permeability, said film being pierced with a cold or heated spiked roller. The
intended use of said film is wound covering and protective film in the hygiene
sector.
The invention is explained in even more detail below on the basis of examples and
20 comparative examples, and a comparison of the examples with one another and with
the comparative examples is made on the basis of the summary of relevant properties
shown in Table 1.
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Example 1
Within the context of the first example a two-layer film was produced by
coextrusion on a blown film unit. The extruders used for melting were operated with
temperature programmes of 130 - 145~C, the temperature of the blown film die
being 145~C.
The formed film had a layer thickness sequence of 20 ~m, 60 ~lm. In view of the
inaccuracy of a thickness determined by mechanical sc~nning due to the roughening
effect of the addition of layer silicate according to the invention, the stated
thicknesses are nominal layer thicknesses which were determined by calculation on
the assumption of a smooth surface of what was actually the rough, matt side. On the
basis of the densities of the raw materials and the averaged densities of the raw
material mixtures, these nominal layer thicknesses and the total nominal layer
thickness can be calculated by adding the values obtained for the respective layers.
The non-matt 60 llm thick layer which formed the outer layer (1) of the film bubble
during film production was produced from a compostable polyester amide. The
polyester amide used was composed of the building blocks butane diol, adipic acid
and caprolactam. It had a melt viscosity of 250 Pas at 190~C (measured in
accordance with DIN 54811-B) and a melting point of 125~C, measured in
accordance with ISO 3146/C2. The density of the polyester amide was 1.07 g/cm3,
measured in accordance with ISO 1183.
The outer layer formed from the polyester amide resin with the addition of lubricants
underwent a corona treatment after film production, and a surface tension of 35
mN/m was obtained.
The 20 ~m thick inner layer (2) of the film was produced from a mixture composedof 70 wt.% of the polyester amide resin used for the 60 ~m thick layer and 30 wt.%
of a layer silicate masterbatch. Said masterbatch had a talc proportion of 50 wt.%.
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The size of the talc particles was less than 22 ~lm. The melt temperature measured
after the die exit was 152~C.
Example 2
A two-layer film structure with a total thickness of 51 ~Lm of biodegradable polyester
amide with a melt viscosity of 250 Pas at 190~C (measured in accordance with DIN54 811 - B) and a melting point of 125 ~C measured in accordance with ISO
3146/C2 was biaxially oriented under the following process parameters. The
maximum extrusion temperature was 205~C.
Accordingly, the extruder heating zones were heated to a maximum of 182~C and
the die to a maximum of 205~C. The melt was cooled as a two-layer flat film on
chill rolls at roll temperatures of 20~C. A rigid thick film was obtained which was
heated to orientation temperature in the next process stage by means of heating rolls
with temperatures of 65~C. The smooth layer (1) was composed of polyester amide
with the addition of lubricants. It had a thickness of 39 ~m.
The matt layer (1) with a thickness of 12 llm was prepared from a mixture composed
of 80 wt.% of the polyester amide resin used for the 39 llm thick layer and 20 wt.%
of a silica masterbatch. The masterbatch had a silica proportion of 40 wt.%. The size
of the silica particles was < 15 llm.
The actual stretching rolls were operated at a temperature of 70~C. Initially, the flat
film was stretched longitudinally in two stages firstly by the ratio 1: 1.5 and then by
the ratio 1: 2.5. A total stretch ratio of 1: 3.75 was thus obtained in the longitudinal
direction. The post-heating rolls over which the film then passed had a temperature
of 85~C. The pre-heating zones of the transverse stretching oven were heated to
100~C. The temperature in the actual transverse stretching part was 95~C. Here the
film was stretched in the transverse direction by the ratio of 1: 5 . By calculation, a
surface stretch ratio of 1: 18.75 was thus obtained. After transverse stretching, the
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film was fixed at a temperature of 105~C. The production speed at the outlet of
transverse stretching was 32.0 m/min.
Comparative example A
A single-layer film with a thickness of 100 ~lm was formed with a blown film die as
in Example 1. The polyester amide resin used was furnished with lubricants.
Comparative example B
A single-layer flat film of polyester amide was oriented as in Example 2. The
polyester amide resin was furnished with lubricants. The film thickness was 46 llm.
The following physical properties and compostability were measured as follows onthe samples produced.
Mechanical properties:
The mechanical variables ultimate tensile strength and elongation at break were
determined on the samples both in the longitudinal and in the transverse direction
according to DIN 53 455. The E-modulus in the longitudinal and transverse
direction was determined according to DIN 53 457. The thickness of the individual
samples was determined according to D~N 53 370.
Optical properties:
The optical properties determined on the films were the surface gloss according to
DIN 67 530 at a test angle of 20~. The gloss measurement was carried out separately
on both sides of the film.
Compostability:
The compostability was carried out in accordance with the test specification of the
D~N draft standard DIN 54 900 part 3 of 1996. On the basis of the test results, the
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classification of the film samples in the apl)ropliate class is carried out according to
the DIN recommendations.
The results of the tests on the samples from Example 1 and 2 and comparative
5 examples I and 2 are given in Table 1.
Table 1
Example Example Comparative Comparative
2 example 1 example2
Mechanical
properties
Thickness [~m] 80 51 100 46
E-modulus long. [MPa] 280 255 270 226
E-modulus transv. [MPa] 323 305 350 292
Ultimate tensile 54 92 SS 90
strength long. [MPa]
Ultimate tensile 42 111 40 109
strength transv. [MPa]
Elongation at break 390 186 412 224
long. [%]
Elongation at break 630 98 654 111
transv. [%]
Optical properties
Gloss [GU], matter side 0.8 S 3.1 105
Gloss [GU], smoother side 3.0 78 3.2 116
Compostability yes yes yes yes
Biodegradability
All the films according to the invention given in the examples have reduced gloss
10 compared with the films examined within the context of the comparative examples.
CA 02262000 1999-01-22
