U.S. patent application number 09/335238 was filed with the patent office on 2002-01-17 for complexed starch-containing compositions having high mechanical properties.
Invention is credited to BASTIOLI, CATIA, BELLOTTI, VITTORIO, DEL TREDICI, GIANFRANCO, GUANELLA, ITALO, LOMBI, ROBERTO.
Application Number | 20020006989 09/335238 |
Document ID | / |
Family ID | 11416852 |
Filed Date | 2002-01-17 |
United States Patent
Application |
20020006989 |
Kind Code |
A1 |
BASTIOLI, CATIA ; et
al. |
January 17, 2002 |
COMPLEXED STARCH-CONTAINING COMPOSITIONS HAVING HIGH MECHANICAL
PROPERTIES
Abstract
Heterophasic compositions comprising starch and a thermoplastic
polymer that is incompatible with the starch, in which the starch
constitutes the discontinuous phase and the thermoplastic polymer
the continuous matrix, having an impact strength greater than 30
KJ/m2 (measured on blown film of 30 microns thick at 10.degree. C.
and RH less than 5%), and further characterised by the presence in
the X-ray diffraction spectrum of a peak at an angle 2-theta from
13 to 14.degree. the ratio of the intensity of which to that of the
peak of the amorphous starch which occurs at 20.5.degree., is less
than 2 and greater than 0.02.
Inventors: |
BASTIOLI, CATIA; (NOVARA,
IT) ; BELLOTTI, VITTORIO; (NOVARA, IT) ; DEL
TREDICI, GIANFRANCO; (VARESE, IT) ; GUANELLA,
ITALO; (NOVARA, IT) ; LOMBI, ROBERTO; (NOVARA,
IT) |
Correspondence
Address: |
BRYAN CAVE LLP
245 PARK AVENUE
NEW YORK
NY
10167
|
Family ID: |
11416852 |
Appl. No.: |
09/335238 |
Filed: |
June 17, 1999 |
Current U.S.
Class: |
524/47 ; 524/50;
524/52; 524/734 |
Current CPC
Class: |
C08J 2367/02 20130101;
C08L 77/12 20130101; C08L 67/02 20130101; C08J 2367/04 20130101;
C08J 5/18 20130101; C08L 3/02 20130101; C08L 67/04 20130101; C08L
3/02 20130101; C08L 2666/02 20130101; C08L 67/02 20130101; C08L
2666/26 20130101; C08L 67/04 20130101; C08L 2666/26 20130101; C08L
77/12 20130101; C08L 2666/26 20130101 |
Class at
Publication: |
524/47 ; 524/50;
524/52; 524/734 |
International
Class: |
C08L 003/00; C08L
089/00; C08K 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 17, 1998 |
IT |
T098A000524 |
Claims
What is claimed is:
1. Heterophasic compositions comprising starch, a thermoplastic
polymer which is incompatible with starch and a plasticizer, in
which the starch constitutes the dispersed phase and the
thermoplastic polymer the continuous phase, said compositions
having impact strength greater than 30 KJ/m2 (measured on blown
film having a thickness of 30 microns at 10.degree. C. and RH less
than 5%).
2. Heterophasic compositions according to claim 1 comprising
starch, a thermoplastic polymer which is incompatible with starch
and a plasticizer, in which the starch constitutes the dispersed
phase and the thermoplastic polymer the continuous phase, having
impact strength greater than 30 KJ/m2 (measured on blown film
having a thickness of 30 microns at 10.degree. C. and RH less than
5%), and further characterised in that the X-ray diffraction
spectrum of the compositions present a peak at an angle 2 theta in
the range of 13-14.degree. the ratio of the intensity of which in
relation to that of the peak of the amorphous starch which appears
at about an angle 2 theta of 20.5.degree. is less than 2 and
greater than 0.02.
3. Heterophasic compositions comprising starch, and a thermoplastic
polymer which is incompatible with starch, in which the starch
constitutes the dispersed phase and the thermoplastic polymer the
continuous phase having impact strength greater than 30 KJ/m2
(measured on blown film having a thickness of 30 microns at
10.degree. C. and RH less than 5%) obtainable by extrusion of a
melt comprising starch, the thermoplastic incompatible polymer, a
plasticizer liquid at room temperature used in amount from 2 to 8%
on the weight of the starch and the thermoplastic polymer and water
in amount less than 5% measured at the exit of the extruder before
conditioning said melt being extruded by applying an extrusion
energy of 0.2 to 0.5 Kw.h/Kg.
4. Compositions according to claim 3, in which the quantity of
plasticiser or mixture of plasticisers is between 3 and 7% by
weight of the total of the starch and the thermoplastic polymer and
the specific extrusion energy is from 0.2 to 0.5 Kw.h/Kg.
5. Compositions according to any of claims 1 to 4 in which the
starch-incompatible thermoplastic polymer is chosen from the group
comprising the aliphatic polyesters obtainable from aliphatic
hydroxyacids having 2 or more carbon atoms, or from the
corresponding lactones or lactides, or from aliphatic bicarboxylic
acids having 2 or more carbon atoms, and from diols having 2 or
more carbon atoms, from aliphatic-aromatic copolyesters,
polyester-amides, polyester-ether-amides, polyester-urethanes,
polyester-urea and mixtures therof.
6. Compositions according to claim 5, in which the polyester is
poly-epsylon-caprolactone, polyethylene or polybutylene-succinate,
polyalkyleneadipate, diphenol diglycidylether polyadipate,
polyalkyleneadipate-succinate,
polyalkyleneadipate-epsylon-caprolactone,
poly-epsylon-caprolactone/epsylon-caprolactame,
polybutyleneadipate-co-te- rephthalate, polyalkylenesebaca-te,
polyalkylenezelate.
7. Compositions according to any of claims from 2 to 6, in which
the plasticiser is a polyhydric alcohol having from 2 to 22 carbon
atoms.
8. Compositions according to claim 7, in which the plasticiser is
chosen from the group comprising glycerine, polyglycerol, glycerol
ethoxylate, sorbitol acetate, sorbitol diacetate, sorbitol mono-
and diethoxylate and mixtures thereof.
9. Compositions according to claim 8 wherein the plasticizer is
glycerine.
10. Compositions according to any of claims 1 to 9, including an
interfacing agent chosen from the following classes of compounds:
a) esters of polyhydric alcohols with mono- or polycarboxylic acid
with a dissociation constant pK less than 4.5 (compared to the pK
of the first carboxylic group in the case of polycarboxylic acids),
and a hydrophilic/lipophilic index (HLB) greater than 8; b) esters
of polyhydric alcohols with mono- or polycarboxylic acid having
fewer than 12 carbon atoms, pK values of less than 4.5 and an HLB
index of from 5.5 to 8; c) esters of polyhydric alcohols with
C12-C22 fatty acids having an HLB index less than 5.5; d)
non-ionic, water soluble surfactants; and e) reaction products of
aliphatic or aromatic diisocyanates with polymers containing
terminal groups reactive with the diisocyanates.
11. Compositions according to any of claims from 1 to 10,
presenting a band at 947 cm-1 in the second derivative FTIR
spectrum thereof.
12. Manufactured products obtainable from the compositions of any
of claims from 1 to 11.
13. Films, sheets, bags, laminates, moulded articles, profiles,
expanded sheets, thermoformed articles, expanded materials
obtainable from the compositions of any of claims from 1 to 12.
14. Shopping bags obtainable from the compositions of any of claims
from 1 to 11.
15. Mulch films obtainable from the compositions of any of claims
from 1 to 11.
16. Wrapping films obtainable from the compositions of any of
claims from 1 to 11.
17. A method for preparing the compositions of any of claims from 1
to 11, in which a melt comprising the starch, the
starch-incompatible thermoplastic polymer, the plasticizer and
water with a final content adjusted to less than 5% by weight, is
extruded in an extruder provided with screws having a reverse
profile for more than 30% of the length of the screw.
Description
[0001] The present invention relates to heterophasic polymeric
compositions having a high resistance to ageing, even under
conditions of low temperature and humidity, comprising
thermoplastic starch and a thermoplastic polymer incompatible with
starch, in which the starch constitutes the dispersed phase and the
polymer the continuous phase.
[0002] The invention relates particularly to manufactured products
which maintain high impact strength and tear strength in low
humidity conditions.
[0003] It is known that products (in particular films) manufactured
from compositions containing thermoplastic starch and a
thermoplastic polymer incompatible with starch, in which the starch
constitutes the dispersed phase, show a significant deterioration
in their mechanical properties, in particular, their impact
strength and tear strength, due to the fact that the starch gives
up or absorbs water until it reaches equilibrium with the ambient
humidity at its interface.
[0004] In relatively low humidity conditions, the material tends to
become brittle, as the dispersed phase becomes insufficiently
plasticised due to the loss of water which takes the glass
transition temperature above ambient temperature.
[0005] This phenomenon can damage the interface with the matrix
when the interface is not sufficiently bonded.
[0006] Under these conditions, when the starch particles
constituting the dispersed phase are subjected to stress, they are
unable to deform and absorb the stress, but instead remain rigid,
thus initiating a tear.
[0007] Italian patent application No. T096A000890 filed by the
Applicant describes compositions comprising thermoplastic starch
and a thermoplastic polymer incompatible with the starch, having
improved characteristics of resistance to ageing under conditions
of relatively low humidity, obtained by introducing an agent having
an interfacing action during the mixing of the components. This
compatibility-inducing action improves the adhesion between the
matrix and the dispersed particles.
[0008] Reducing the interface tension also enables the dimensions
of the particles to be reduced to submicronic values, whereby the
materials have the characteristics of a polymeric alloy.
Compositions comprising starch , a thermoplastic polymer and a
plasticiser are widely described in patent literature.
[0009] However, the concentrations of these plasticisers at which
the mechanical properties of the compositions are greatest are
never taught, nor suggested, in the prior art.
[0010] EP-A-0 327 505 describes compositions in which the
plasticiser is used in a quantity of from 0.5 to 15%, preferably
between 0.5 and 5% by weight, together with such quantities of
water that the sum of the plasticiser and the water does not exceed
25% by weight of the compositions (the quantitative minimum of
water in these compositions is 10% by weight).
[0011] WO92/19680 describes compositions comprising starch, a
polyester of a hydroxyacid or the corresponding lactone such as,
for example, polycaprolactone, and a plasticiser usable in a
quantity of from 1 to 50% by weight, preferably 1-40%, and more
preferably 5-25% by weight of the composition.
[0012] The compositions preferably have a final water content of
between 1.5 and 5% by weight (measured on leaving the extrusion
press, before conditioning).
[0013] In the aforementioned document, there is no use of nor any
indication of the existence of a possible critical range of the
concentration of the plasticiser corresponding to that for
obtaining very high mechanical properties, nor is there any
indication of which plasticisers are suitable for this purpose.
[0014] The quantity of plasticiser used in the examples is always
greater than 10% by weight of the composition.
[0015] U.S. Pat. No. 5,334,634 describes compositions comprising
starch, an ethylene-vinyl alcohol copolymer and a plasticiser
usable in a quantity of from 0.5 to 100% by weight of the
starch
[0016] In this case also, the quantity of plasticiser effectively
used is always greater than 10% by weight of the composition.
[0017] It is known that starch, in particular, its amylose
fraction, forms "V"-type complexes with synthetic polymers such as
polyethylene vinyl alcohol or polyethylene-acid acrylate (C.
Bastioli and others in "Biodegradable Plastics and Polymers", pages
200-213; 1994, Elsevier Science). In such multiphase systems in
which the synthetic polymer comprises the continuous phase and the
starch the dispersed phase, the complex acts as a
compatibility-inducer or phasing agent.
[0018] Similar complexes can form between starch and aliphatic
polyesters or aliphatic/aromatic copolyesters. However, if, in the
preparation of the compositions comprising starch and the
aforementioned polyesters, relatively high quantities of the starch
plasticisers are used to ensure the plasticity of the material
under the conditions of use of the manufactured product and low
specific energy for destructurization and complexation is used, the
quality of the interface is insufficient to ensure the toughness of
the material at low temperatures and humidity in the presence of
the plasticiser itself.
[0019] Furthermore, if plasticisers which are solid at room
temperature are used in relatively high concentrations, at which
the complex between starch and incompatible polymer can form in a
quantity sufficient to ensure an effective compatibility-inducing
action, these plasticisers cause, in conditions changing from high
to low relative humidity, brittleness in the material.
[0020] It has unexpectedly been found that it is possible to
prepare heterophasic compositions comprising starch and a
thermoplastic polymer incompatible with starch, in which the starch
constitutes the dispersed phase and the thermoplastic polymer the
continuous matrix, which compositions have characteristics of high
impact strength even when passing from conditions of high to low
relative humidity if they are prepared using a quantity of
plasticiser that is liquid at room temperature comprised within a
critical range wherein the concentration of the complex between
starch and the incompatible polymer reaches a maximum, and a
specific energy of destructurization of starch higher than a
certain value.
[0021] The critical quantity of plasticiser, which is preferably
glycerin, is generally from 2 to 8% and preferably from 3 to 7% by
weight of the starch and the thermoplastic polymer. Quantities
outside this range are, however, possible, depending on the type of
plasticiser and its efficacy.
[0022] The specific energy for the destructurization of the starch
and its complexation are comprised from 0,1 to 0.5 Kw.h/Kg,
preferably from 0,15 to 0,4 Kw.h/Kg and most preferably from 0,2 to
0,35 Kw.h/Kg.
[0023] For specific energy for the destructurization and
complexation of the starch it is to meant the energy supplied by an
extruder the screw or screws of which are capable of developing a
specific energy of at least 0,1 Kw.h/Kg at the extrusion
temperature of 120-210.degree. C.
[0024] The specific energy is determined according to the formula:
A.times.B.times.C/D.times.E.times.F wherein
[0025] A=engine power
[0026] B=RPM
[0027] C=energy absorption
[0028] D=RPM max
[0029] E=energy absorption max
[0030] F=flow rate
[0031] Until now, critical values as indicated above had never been
used nor suggested in prior art compositions.
[0032] It has been discovered, and this constitutes a
characterising aspect of the invention, that the complex of starch
and incompatible polymer reaches maximum concentration values
within the aforesaid critical range.
[0033] The presence of the complexes of starch and incompatible
polymer can be demonstrated by the presence in the second
derivative FTIR spectra of a band at a wavelength of 947 cm-1
(specific to the complex) and in the X-ray diffraction spectra of a
peak in the range of 13-14.degree. on the 2 theta scale (with Cu
K.sub.alfa radiation of 1.5418 A.degree.). In both cases, the
position of the band or the peak of the complex remains unchanged,
even on changing the nature of the complexed polymer. FIGS. 1 and 2
show the X-ray and second derivative FTIR spectra, and are typical
of the formulations based on starch and aliphatic polyesters (PCL
in particular).
[0034] It has been found that in the X-ray spectra of the
compositions of the invention, the Hc/Ha ratio between the height
of the peak (Hc) in the range of 13-14.degree. of the complex and
the height of the peak (Ha) of the amorphous starch which appears
at about 20.5.degree. (the profile of the peak in the amorphous
phase having been reconstructed) is less than 2 and greater than
0.02. In the spectrum of FIG. 1, the heights Ha and Ha, are
indicated for the peaks of the complex and the amorphous starch
respectively.
[0035] In case of crystalline polymers with a crystallinity content
higher than 30% the lower limit of the ratio Hc/Ha is 0.2; in case
of amorphous polymers or polymers with a cristallinity content less
than 30% the lower limit of the ratio Hc/Ha is lower than 0.2.
[0036] The heterophasic compositions of the invention therefore
comprise starch, a thermoplastic polymer incompatible with the
starch, a starch plasticiser or a mixture of starch plasticisers,
in which the starch constitutes the discontinuous phase and the
thermoplastic polymer the continuous phase, and are characterised
in that they form films having characteristics of high impact
strength higher than 30 Kj/m.sup.2, preferably higher than 45
Kj/m.sup.2 and most preferably higher than 60 Kj/m.sup.2 (measured
on blown film 30 micron thick at 10.degree. C. and less than 5%
relative humidity) and have an X-ray spectrum having a peak at
angle 2 theta in the range from 13 to 14.degree. with an intensity
related to that of the peak of the amorphous starch which appears
at an angle 2 theta of 20.5.degree. less than 2 and greater than
0.02.
[0037] The compositions are obtainable by extrusion of a melt
comprising starch, the thermoplastic polymer, the plasticiser in a
quantity within the critical range, and water in a quantity less
than 5% by weight (measured on leaving the extrusion press, before
conditioning) and supplying a specific energy of at least 0,1
Kw.h/Kg and lower than 0,5 Kw.h/Kg.
[0038] The preparation of the compositions by extrusion is carried
out according to known temperature conditions, operating, for
example, at temperatures of between 120 and 210.degree. C.,
preferably from 130 to 190.degree. C. Suitable usable extruders are
those provided with screws having a "reverse" profile for more than
30% of the length of the screw (a reverse profile causes the
material to advance with a piston effect).
[0039] The water content in the extrusion stage can be high in the
phase of destructurization of starch and can be regulated at the
end of the estrusion at the desired values of less than 5% by
weight by degassing or by using a starting starch with a low water
content (the water content is measured at the exit of the extruder,
prior conditioning).
[0040] If the compositions or the manufactured products obtainable
therefrom are washed with water, the plasticiser contained therein
is extracted but the compositions and the manufactured product
maintain mechanical properties, in particular impact strength,
comparable to the properties of the film before washing. These
compositions and manufactured products also form part of the
invention.
[0041] The starch-incompatible thermoplastic polymers are
preferably chosen from the aliphatic (co)polyesters obtained from
hydroxyacids having 2 or more carbon atoms, and from the
corresponding lactones or lactides, or from aliphatic bicarboxylic
acids having 2-22 carbon atoms, and from diols having 2-22 carbon
atoms, polyester-amides, polyester-urea and aliphatic-aromatic
copolyesters and mixtures thereof.
[0042] These thermoplastic polymers, or mixtures thereof, have a
melting point lower than 130.degree. C. and preferably lower than
110.degree. C.
[0043] Representative examples of the polymers mentioned above
are:
[0044] poly-epsylon-caprolactone, polyethylene- and
polybutylene-succinate, polyhydroxybutyrate-hydroxyvalerate,
polylactic acid, polyalkyleneadipate,
polyalkyleneadipate-succinate, polyalkyleneadipate-caprolactame,
polyalkyleneadipate-epsylon-caprolacton- e, polyadipate of diphenol
diglycidylether, poly-epsylon-caprolactone/epsy- lon-caprolactame,
polybutylene adipate-co-terephthalate, polyalkylenesebacate,
polyalkylene-azelate and copolymers thereof or mixtures
thereof.
[0045] These polymers can also be "chain-extended" with
diisocyanates, polyepoxides and similar multifunctional
compositions.
[0046] Poly-epsylon-caprolactone and the aliphatic-aromatic
copolyesters are preferred. Other polymers which can be used are
the esters and ethers of cellulose and of starch.
[0047] The starch-incompatible polymer is present in a quantity
sufficient to form the continuous phase of the heterophasic
composition. In general, this quantity is between approximately 30
and 90% by weight of the starch.
[0048] The polymers can be used in mixtures having smaller
proportions of polymers of the ethylene/vinyl alcohol,
ethylene/acrylic acid type and polyvinylalchol.
[0049] The usable starch is native starch such as, for example,
corn, potato, rice, tapioca starch, or is a physically or
chemically modified starch such as, for example, ethoxylated
starch, starch acetate and hydroxypropylated starch, cross-linked
starch or oxidated starch, dextrinized starch, dextrins and
mixtures thereof.
[0050] The starch plasticisers which can be used are polyhydric
alcohols having from 2 to 22 carbon atoms, in particular,
polyhydric alcohols having from 1 to 20 hydroxylated units
containing from 2 to 6 carbon atoms, the ethers, thioethers and the
organic and inorganic esters of these polyhydric alcohols.
[0051] Examples of plasticisers that can be used are: glycerine,
ethoxylated polyglycerol, ethylene glycol, polyethylene glycol,
1,2-propandiol, 1,3-propandiol, 1,4-butandiol, neopentylglycol,
sorbitol monoacetate, sorbitol diacetate, sorbitol monoethoxylate,
sorbitol diethoxylate and mixtures thereof.
[0052] The compositions can also include interfacial agents of the
kind described in Italian patent application T096A000890, chosen
from:
[0053] a) esters of polyhydric alcohols with mono- or
polycarboxylic acid having a dissociation constant pK less than 4.5
(with reference to the pK of the first carboxylic group in the case
of the polycarboxylic acids), and a hydrophilic/lipophilic index
(HLB) greater than 8;
[0054] b) esters of polyhydric alcohols with mono- or
polycarboxylic acid having fewer than 12 carbon atoms, pK values
greater than 4.5, and HLB indexes of from 5.5 to 8;
[0055] c) esters of polyhydric alcohols with C12-C22 fatty acids,
having an HLB index of less than 5.5;
[0056] d) non-ionic, water soluble surfactants, and
[0057] e) products of the reaction between aliphatic or aromatic
diisocyanates and polymers containing terminal groups that react
with the diisocyanates.
[0058] The compositions of the invention can also contain additives
such as urea in a quantity of up to 20% by weight, compounds of
boron, particularly boric acid, proteins such as casein, gluten and
abietinic acid or rosinic acid, natural rubbers, flame retardant
agents, antioxidants, fungicides, herbicides, fertilisers,
opacifiers, compositions having a repellent effect on rodents,
waxes, antislipping agents (such as erucamide, calcium stearate,
zinc stearate).
[0059] They can also contain organic and inorganic fillers from 0.5
to 70% by weight and natural fibers. The compositions of the
invention find particular application in the preparation of films,
sheets, in thermoforming and, in general, in all applications in
which good mechanical properties of the manufactured product are
required, together with high resistance to ageing, even under
conditions of low temperature and humidity.
[0060] Examples of products which can be manufactured using the
compositions of the invention include, in addition to those
mentioned above, bags, laminates, moulded and blown articles,
expanded sheets, expanded materials, biofillers for tires,
backsheets for diapers, wrapping films, mulching films, multilayer
films, sacks for mowing grass, shoppers, nonwoven fabric, toys, pet
toys, dog collars, products with controlled release for use in the
agricultural field, threads.
[0061] The following examples are given to illustrate and not to
limit the scope of the invention.
EXAMPLE 1
[0062]
1 A mixture formed from (parts by weight): Globe 03401-Cerestar
natural starch* 27 Tone-787 PCL 65 glycerine 4.5 water 3.5 100.0
*water content 12% wt
[0063] was supplied to a two screw OMC extruder of 60 mm diameter,
L/D=36, RPM=180.
[0064] The temperature profile was as follows:
60/145/175/180.times.4/155.- times.2.degree. C.
[0065] It was operated with free degassing.
[0066] The specific energy supplied was 0,4 Kw.h/Kg.
[0067] The extruded material was pelletised. The water content was
1.3% by weight.
[0068] The pellets were used to manufacture films using Ghioldi
apparatus provided with Maillefer-type screws of 60 mm diameter and
L/D=30. The thermal profile was as follows:
90/120/140/150.times.3/147.times.2.degree- . C.
[0069] The film head had a diameter of 180 mm.
[0070] The film produced, approximately 30.mu. thick, was tested as
such for its mechanical properties. A sample of the same film was
on the other hand immersed in water for 24 hours to remove the
starch plasticisers; after this, the samples taken from the washed
film were left to condition for 72 hours in an environment with a
temperature and humidity equal to those used for detecting the
mechanical properties.
EXAMPLE 2
[0071]
2 A mixture of (parts by weight): Globe 03401 corn starch 33.4
Tone-787 PCL 54.3 glycerine 5.8 water 6.5 100.0
[0072] was supplied to a two screw APV-2030 extruder; L/D=35+5XLT;
RPM=170; thermal profile: 60/100/170.times.14.degree. C.
[0073] The extruder was operated with free degassing.
[0074] The specific energy supplied was 0,17 Kw.h/Kg.
[0075] The extruded material was pelletised. The water content was
1.5% in weight.
[0076] The pellets were used to produce a sheet via cast-extrusion,
using a modified AEMME extruder provided with 1:3 constant taper
screws; diameter 30 mm; L/D=25; RPM=35. The extruder had a flat
head 150 mm wide with a lip aperture of 0.8 mm. The sheet obtained
was 0.6 mm thick.
[0077] A quantity of pellets was separately made into a film as
described in example 1 to obtain samples to test for their
mechanical properties (samples of the film as produced and washed
in water).
EXAMPLE 3
[0078] The test of example 2 was repeated using a composition
(parts by weight) of 33.4 parts starch of the type used in example
2, 54.3 parts of Tone-787 PCL, 4.8 parts of glycerine and 7.5 parts
of water. The film thus obtained was tested for its mechanical
properties (film as produced and washed in water).
Comparison Example 1
[0079]
3 A mixture formed from (parts by weight): Globe 03401 corn starch
33.4 Tone-787 PCL 54.3 glycerine 9.7 water 5.5 100.0
[0080] was mixed in an extruder and made into a film as in example
1.
[0081] The specific energy supplied was 0,22 Kw.h/Kg.
[0082] The film obtained was tested for its mechanical properties
(film as produced and washed in water as in example 1).
Comparison Example 2
[0083] A composition comprising 65 parts potato starch at 6%
humidity and 35 parts of a mixture of glycerine: sorbitol 1:1 by
weight (sorbitol is solid at ambient temperature) was supplied to
the two screw APV-2030 extruder, as used in example 1, operating
with the following thermal profile: 60/100/190.times.14.degree. C.
Compounding was done with active degassing to obtain an extrudate
having a water content of less than 0.5%.
[0084] Then, 35 parts of dried pellets and 65 parts of Tone-787 PCL
were mixed in an APV-2030 extruder; the extruded material was made
into pellets and finally made into a film of approximately 30.mu.
thickness, exactly as in example 1.
EXAMPLE 4
[0085] The test of example 3 was repeated with the only difference
being that 3.8 parts glycerine and 8.5 parts water were used.
[0086] The film thus obtained was tested for its mechanical
properties (film as produced and washed in water as in example
1).
EXAMPLE 5
[0087]
4 A mixture formed from (parts by weight): Globe 03401-Cerestar
natural starch 26.4 Ecoflex .RTM. 63.8 glycerine 5.5 water 4.3
Erucamide 0.3 100.0
[0088] was supplied to a two screw OMC extruder of 60 mm diameter,
L/D=36, RPM=180.
[0089] Ecoflex is a registered trade mark of BASF and refers to a
polybutylene adipate-co-terephthalate copolymer.
[0090] The temperature profile was as follows:
60/140/175/180.times.4.degr- ee. C.
[0091] It was operated with free degassing.
[0092] The specific energy supplied was 0,36 Kw.h/Kg.
[0093] The extruded material was pelletised. The water content was
1.7% by weight.
[0094] The pellets were used to manufacture films using Ghioldi
apparatus provided with Maillefer-type screws of 60 mm diameter and
L/D=30. The thermal profile was as follows:
120/135/145.times.5/140.degree. C.
[0095] The film head had a diameter of 100 mm.
[0096] The film produced, approximately 30.mu. thick, was tested as
such for its mechanical properties. A sample of the same film was
on the other hand immersed in water for 24 hours to remove the
starch plasticisers; after this, the samples taken from the washed
film were left to condition for 72 hours in an environment with a
temperature and humidity equal to those used for detecting the
mechanical properties.
5TABLE 1 PROPERTIES OF BLOWN FILM AT 23.degree. C. & 50% RH
(ASTM Standard d 882) Modulus Breaking Breaking of Breaking Load
elongation elasticity energy Examples Mpa % Mpa KJ/m2 Hc/Ha 1 as
produced 37.1 880 503 8600 0.44 1 washed 31.6 747 501 7750 1 cf. as
28.3 810 310 5640 0.07 produced 1 cf. Washed 20.0 120 603 327 2 as
produced 31.2 880 520 8230 0.33 2 washed 25.8 637 631 6630 3 as
produced 29.2 756 541 6194 0.29 3 washed 21.1 539 598 4930 4 as
produced 24.5 662 632 5980 0.27 4 washed 20.2 521 606 4760 5 as
produced 23.1 489 136 4155 0.07
[0097] Table 2 shows the chacteristics of roughness of the sheets
of examples 2-4, and comparison examples 1-2. A high level of
roughness, although spoiling the aesthetic appearance, is critical
for the printability of the sheet with printing inks.
6TABLE 2 SURFACE ROUGHNESS EXAMPLE ROUGHNESS (micron) 2 0.20 3 0.20
4 0.24 cf. 1 0.14 cf. 2 1.17
[0098] Tables 3 and 4 show test data for tear and impact
traction.
7TABLE 3 TEAR TESTS AT 23.degree. C. & 50% RH(*) Start tearing
Propagation Examples N/mm N/mm 1 as produced 116.5 116.5 2 as
produced 85.6 85.7 1 cf. as produced 64 63.8 (*) ASTM standard
d-1938
[0099]
8TABLE 4 IMPACT-TRACTION TESTS AT 10.degree. C. AND RH < 5% (**)
ON FILM OF 30 micron Energy Load Example KJ/m2 Mpa 1 110 30 2 73 24
1 cf. 6 12 2 cf. 22 23 5 145 18 (**) The tests were carried out
using instrumentation comprising a conventional "piezoelectric"
cell for detecting the energy, which cell is located on a terminal
on which the end of a test specimen is fixed, 30-40 micron thick,
30 mm wide and 35 mm long.
[0100] The tests were carried out using instrumentation comprising
a conventional "piezoelectric load cell" for detecting the energy,
which cell is located on a terminal on which the end of a test
specimen is fixed, 30-40 micron thick, 30 mm wide and 35 mm
long.
[0101] A double incision was made symmetrically half way along the
sample such that each incision extended over a quarter of the width
of the sample. A rod was connected to the other end of the sample,
which rod acts as a guide for an axially-pierced cylinder, 500 g in
weight. The rod terminates in a plate onto which the weight is
released from a height of 5 cm at a velocity of 1 m/sec.
[0102] The apparatus was arranged within a climatic cell operating
at 10.degree. C. and RH<5%.
[0103] The samples were conditioned at the same temperature for 48
hours before the test.
9TABLE 5 PROPERTIES OF SHEET FORMED VIA CAST-EXTRUSION Load
Elongation Modulus Examples Mpa % Mpa 2 as produced 37.3 892 271 2
washed 30.1 630 464 3 as produced 35.0 846 379 3 washed 26.2 595
550 4 as produced 32.5 745 351 4 washed 21.0 531 495
[0104] FIGS. 1 and 2 show respectively the second derivative FTIR
and X-ray spectra of the composition of example 1.
* * * * *