Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSITION CONTAINING A POI,YMER OF UNSATUR~TED
HYDROCARBON AND A STARCH DERIVATIVE
Background of the Invention
Field of the Invention
The invention herein is a composition
containing a polymer of an unsaturated hydrocarbon and
a starch derivative such that the composition has
improved biodegradability.
In the past there have been research attempts
to develop biodegxadable material. The reason for this
research activity is that polymers of unsaturated
hydrocarbons, such as polyethylene, polypropylene and
polystyrene, poses little biodegradable properties.
The use of biodegradable material is advantageous since
the majority of the product will degrade so that there
will be less ~aste in processing and/or environmental
pollution.
One such development in the field is the
incorporation of an artificial resin of gelatinized or
ungelatinized starch or derivatives thereof. The
starch or starch derivative functions as a filler
therein. According to US Patent No. 4,016,117, blown
films of polyethylene with a predried starch and small
amounts of ethyl oleate and oleic acid were
manufactured in this manner. However, more than 15
percent of these films became paper-like.
In another US Patent No. 4,021,388,
pretreated starch is used, and one can obtain with 8
percent pretreated starch a film with better properties
than those obtained in the '117 Patent. The '338
Patent states that one may use a maximum of 50 percent
starch derivative. Additionally, according to US
Patent No. 4,125,495, a pretreated starch is used as a
filler in polyvinyl chloride composition that contains
up to 50 percent of plasticizers and a typical
stabilizing agent. The content of the pretreated starch
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here is 51 weight percent. According to this patent,
the critical limit would here amount to 60 weight
percent, at which the material becomes porous, because
the amount of polymer is not su~Eficient to fill the
interstices between the starch grains. A11 of these
patents thus mentioned are in the name of Coloroll
Limited, and this company, on the basis of these,
patents now produces a polyethy:Lene bag which contains
7 to 10 percent starch.
Another proposal for the use of starch as a
filler occurred in _d Enq. Chem. Prod._Res. Dev., 16
(4), 305-3-08 (1977) and in Ind. Enq. Chem.~ Prod. Res.
Dev., 19 (4), 592-595 (1980). According to the first
mentioned article, a flexible film is prepared from a
composition of a water-dispersible copolymer of
ethylene and acrylic acid (EAA) and a starchy material.
The starchy product is unmodified starch, but one may
also use amylase or amylospectine component or also
modified starch products, such as partially
depolymerized starches and starch derivatives.
The proposal in Ind. Enq. Chem.. Prod. ResO
Dev. also discloses the preferred use of starch
materials that have been gelatinized. The starch
grains should be sufficiently swollen and broken in
order to form a smooth, viscous, aqueous dispersion.
Preferably, essential amino acids (EAA) are used as a
wat~r-dispersible copolymer obtained from a mixture of
20 weight percent acrylic acid and 80 weight percent
ethylene. In the second article mentioned above, in
Ind. Enq. Chem. Prod. Res. Dev., further experiments
were completed with an extrusion-blowing technique,
wherein the EAA could also be partially replaced with
low pressure polyethylene. With air-dried corn-starch
(11 percent m~isture), it was reported that clear,
flexible and uniform films in the case of mixtures
contained 40 percent of starch and no more than about
. 12. ~0 ~12: 42 PM >kFITCH, EVE~ T. hL. PrJ~
2 ~ 2 1~
40 perc~l3nt o~ thcl low ~r~u~R poly~hylene~ In ~hl~
techni~aus app~n~ly ~he oarboxy groupl3 o~ the ESAA
promote th~ ~ter~ p~r~ability o~ the ~o~npo~ltlon and
pos;~lbly al~o ~ondlng ~w~an the carboxy gr~u~ o:E the
5 EA~ zlnd th~ nydroxy group~ Q~ ~ho ~tarc;h occure, but no
commer~$~1 usel Df thi~ re~ars~h hi~s b~com~ known~
Anot:~r t~hnlque 1~ th-3 u~ o~ g~t
polyme~ o~ starc~ ln ~r~ lal ~4sin~. ~h~ prinalple
oï thi~ hcd i~ ~h~t a ~re~ radical i~ ~o~med on the
10 bac:~cbo~0 o~ the ~t~rch, wh~r~:eter thllt; le. re~cte~ with
~ polyr~riza~lR ~finyli~ or aaryllc: ~nom~r~ Initi~tion
c~n take pl~3 ch~ ally~ or l:~y rældi~tion. Severe~l
monomsr~ hav~ b~en tri~dl u~1~g thl~ method, ~e~ YÇ1
~9~ Suppl. n~ 5-6~g ~1977)
15 and E?Q~ cl~, 17 ~5) 311~ 316 (1~77) .
Accordia~ to t~iR t~chniqu~, ~ynthetio
pol~mer~ c~an be ~b~a~necl having a varying gla~s
tran~iition tempera~ure [~g). The obtained ~raft
~opolymer~: wer~ extru~ed without thQ addition o~
20 thsrmoplastic:~ ho~cspolymer, and in thi~ way, contihuous,
poly~ac~:haride-~ille~ pla~tics were obt;~ined which were
deg~adable. ~ith poly~tryen~ and methylmet~c:rylate,
hard and ~rittle p~oduct~ were obtain~d, and w~th
methy- and bu~ylacrylat~, t~e pro~uot~ were more
flexibl~ ~n~ leather-like~ In the ~e~hyl acryla~e
~eri~s, it appeare~ that bettet r~sults wer~ obtained
wlth yelatini~ed s~arch th~ wi h ~arch in the form of
grni~s. Addlt$onally, ~cording to Starke, 21, 47
~1~6~ the ac~ta~e, propion~te and ~tyra~e esters of
graft oopol~mer~ oP st~rah with ~hyl acryla~e and
~t~r~h wlth butyl acrylate are also thermopla~tic
ma~erlal~ whi~h c~n ~a~ily be ~haped.
In u~ing the gr~ing technique, i~ is not
possi~le to obtain flexible f~lm material~ ~uch a~
35 th~se mad~ fr~m polyethyl~ne, polypropylene and pol~
~lnyl chlorlde. Howerer, one does obtain a moldable
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plastic, but only when exclusively untreated or
gelatinized starch are used.
Another technique is proposed, which
encompasses incorporating a polysaccharide, i.e.
pullulan and resin. Pullulan is a high molecular
weight polymer-containing unit of maltriose, a glucose-
trimer where the glucose molecules have been bonded to
each other in a repeating way through a ~-1,6 bond.
Pullulan is a white powder which is easily soluble in
water and can be recovered as a sticky substance ~rom a
culture broth of a strain of the incomplete
microorganism Pullaria.
Pullulan not only is water-soluble, but it is
also not toxic and is edible. Furthermore, even during
burning, Pullulan does not emit noxious gas, and is
spontaneously decomposed by micro-organisms, even if it
is dumped as waste in the unmodified state.
Furthermore, a thin pullulan film is impermeable to
oxygen and consequently can protect pharmaceuticals or
food products against oxidation. Compositions of
pullulan and thermoplastic r~sins have been disclosed
in U.S. Patents 3,976,605, 3,992,496 and 4,045,388.
The decomposition temperature of the pullulan
resin is the temperature at which th~ resin during
gradual heating starts to give off heat as a result of
oxidative decomposition and starts to show a clear
weight loss. This temperature is 250C to ~60C.
It appears that, by etherification or
esterification of pullulan, products may be obtained
having decomposition temperatures varying from 170C to
300C. Thus, pullenan per se is a promising material,
but the high production costs thereof ~orm an obstacle
for its practical use, particularly for using it in
cheap packaging materials. Etheri~ication or
esterification may further improve the properties of
the pullulan, but thereby the material becomes still
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more expensive.
Therefore, until now it had been highly
desirable to find a simple and economical method of
producing biodegradable products.
Summary of the Invention
The invention herein is a composition
comprising a polymer of an unsaturated hydrocarbon, a
starch derivative and a compatibilizing agent, where
the starch derivative is a C14 alXyl or hydroxyalkyl
starch ether having a degree of substitution of at
least 0.25 and the compatibilizing agent is selected
from the group consisting of a vinyl copolymer, an
acryl copolymer, and one or more esters of C14 alcohols
and C620 organic acids-
The composition preferably contains a
plasticizer when the compatible-making agent is a vinyl
copolymer, an acryl copolymer or mixtures thereof. The
plasticizer is of the carboxylic acid type and it is
preferably oleic acid.
When the compatible-making agent is a vlnyl
or acryl copolymer, it is either a copolymer of
ethylene and vinyl acetate or a copolymer of ethylene
and acrylic acid. When the compatible-making agent is
one or more esters of C14 alcohols and ~6-20 organic
acids, such as carboxylic acids, the esters are methyl
or ethyl esters.
This composition can be used in a variety of
applications. Typically, the composition can be used
to make articles that were, prior to the invention
herein, made with polyethylene, polypropylene and poly
vinyl chloride.
Detailed Description
It has now been found that, with a simple and
cheaply prepared starch derivative, it is possible to
obtain a composition which is degradable to a
considerable degree and which, in view of its price and
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properties, is also suitable as a packaging film.
The invention herein is a composition
comprising a polymer of an unsaturated hydrocarbon, a
starch derivative and a compatibilizing agent, where
the starch derivative is a C14 alkyl or hydroxyalkyl
starch ether having a degree of substitution of at
least 0.25 and the compatibilizing agent is selected
from the group consisting of a vinyl copolymer, an
acryl copolymer, and one or more esters of C14 alcohols
and C620 organic acids.
The starch is esterified to decrystallize the
starch grains and to disrupt the hydrogen bonds between
the starch molecules, whereby the rigid structure
vanishes. By ~Ising elevated temperatures and friction
forces, the esterified starch qrains can be easily
disintegrated. The disintegrated material, when
combined with the plasticizers, already has the per se
possibility to form plastic films. Furthermore, in
combination with the polymer of unsaturated
hydrocarbon, the starch ether does not function as the
primary filler, but forms a copolymer with the
hydrocarbon.
The unsaturated hydrocarbons used herein are
polyolefins, such as polyethylene, both high pressure
and low pressure polyethylene, and polypropylene, as
well as polystryene and copolymers of these unsaturated
hydrocarbons.
As stated previously, the degree of
substitution for the starch, for the present purposes,
should be at least 0.25. Preferably, the degree of
substitution for the starch is higher- suitably at
about 0.4 to about 1. On the other hand, a starch that
has a substitution that is too high is disadvantageous
for the degradability, and for this reason, the degree
of substitution for the starch is preferably not higher
than 2.
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Hydroxypropyl ethers are prefsrably used and
can be obtained by condensation of staxch with
propylene oxide. These product:s are already known and
available. The hydroxypropyl ether is prepared in
accordance with the general principles of condensation
of compounds having an active hydrogen~ ie. a hydroxy
group with alkylene oxides. Basic or acid catalysis
can be used, but basic is preferred for starch
derivatives. More specifically, the basic cakalyst one
can use simply and cheaply is sodium hydroxide. Of
course, substitution at several of the hydroxyl groups
on the starch can occur and also the introduction of
the hydroxypropyl group may further react with the
molecules of the propylene oxide. It is well known
that, in such condensation reactions with basic,
catalyst usually a static distribution is established.
The hydroxypropylation of starch has been described in
more detail in "Modified Starches: Properties and
Uses", Editor O.B. Wurzburg, M.S., CRC Press, Inc.,
chapter 6, by J.V. Tuschoff., which is incorporated
herein by reference.
The compatible making agent can be selected
from the group consisting of a vinyl copolymer, an
acryl copolymer, and one or more esters of C14 alcohols
and C620 organic acids. The vinyl and acryl copolymers
are units of an olefin that may contain hydrophilic
groups. More specifically, the vinyl and acryl
copolymers are copolymers of ethylene and vinyl
acetate, EVA polymers, and copolymers of ethylene and
acrylic acid and EAA polymers.
The esters of Cl4 alcohols and C620 organic
acids are preferred, because the esters can be used in
smaller amounts than the vinyl and acryl copolymers.
Furthermore, if the asters are used as the compatible-
making agent, plasticizers or lubricating agents arenot necessary for superior results. It is speculated
2 ~
that when the composition is subjected to a shaping
process where heat is liberated, the ~ster undergoes a
reaction, possibly saponification, whereby the
resulting free acid functions as a lubricator. This is
just a theoretical explanation, and the invention is
independent of such an explanation.
In this respect, the methyl and ethyl esters
are preferred, because the alcohols liberated therefrom
by heating or saponification are more volatile than the
propanols and butanols. The acid moiety of the ester
can be derived from each of the C620 carboxylic acids,
i.e., oleic acid, caproic acid, behenic acid and
mixtures thereof. The acid moiety can also be derived
from carboxylic acids having an intermediate number of
carbon atoms, and furthermore, both naturally occurring
acids having even number of carbon atoms and the
synthetic acids having odd number of carbon atoms, as
well as mixtures of such acids, can be used.
Additionally, these acids may be saturated or
unsaturated. Esters of oleic acid are preferred,
particularly methyl and ethyl oleat~.
In the composition described above, the
amount of components may vary. The composition
contains about 20 to about 80 weight percent polymer of
unsaturated hydrocarbon, about 30 to about 70 weight
percent starch derivative, and about ll to about 19
weight percent compatible-making agent, if the agent is
a vinyl or acryl copolymer and can also further contain
a plasticizer if so desired in an amount greater than
zero to about 8 weight percent. If the composition
contains as the compatible-making agent esters of C14
alcohols and C620 organic acids, then the composition
contains about 20 to about 79 weight percent polymer of
unsaturated hydrocarbon, about 20 to about 70 weight
percent of starch derivative and about 1 to about lO
weight percent of the ester. The higher the ester
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value within the prescribed ranye, the higher the
starch value to obtain the mors preferred results. By
increasing the amount of starch derivative and ester
used in the composition, the tensile strength of the
resulting product decreases somewhat. However, because
of the concern and d~sire to have biodegradable
products, for instance in packaging materials, for
which flexibility is also more important then tensile
strength, this decraase in tensile strength is
completely acceptable~
It is also ~dvantageous for the composition
to also contain a plasticizer of the carboxylic acid
type for the hydrocarbon polymer if the compatible-
making agent is a vinyl or acryl copolymer. Examples
of such plasticizers include stearic acid, oleic acid
and di-oleic acid. If a plasticizer is used, it is
used in an amount generally no greater than 8 weight
percent of the total composition. Furthermore, the
amount of plasticizer is preferably related to the
amount of compatible-making agent, with the ratio
between the plasticizer and the compatible-making agent
being about 2:1 to about 4:1, and ratios in-between
these ranges. The plasticizer functions to make the
starch derivative more hydrophilic and helps protect
the composition against discolorization.
~ he composition can be made by simply
admixing all the components at a temperature above the
melting point of the hydrocarbon polymer employed and
subjPcting the admixture to a shaping treatment, i.e.,
extrusion or pressing.
The following Examples are for illustrative
purposes only and are not meant to limit the scope of
the invention herein.
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09. 12. 90 ~2: 42 PM ~kFITCH, EVEN, ET. AL. PO~
2 ~ ~ ~J ~
An ~lmixtur~ w~ m~de og 30 p~l~tB by weight
o~ hlgh prelc~ure polye~hyl~ne, 5~ p~rt~ ~y ~lght o~
5 cond~n~atlon p~odu~t ~ g~ h ~nd propyl~n~ oxidl3
having a dlagr~ oi~ ti~lltiG31 0~ O. 5, 15 E)ZlrtlEI by
wi~i~h~ o~ ~YA. aop~ r ~na 5 pArts by wal~ht o~
o~lc aoi~ . The a~ xtur~3 wa~ he~at~d ~t 1~ ln an
extru~r ~d 0xtrud~ to ~o~ a ~r~ula~ n~ ~he
lO gr~n1~1ate wa~ ~ur~hor p~roae~ed. ~:o tr~n~luc~nt ~ilm~
'rhe~e fllm~ d ~ n~ rangth to ~ d ~15
paa)ca~in~ ~lm~, ~nd du~ to éhe pre~enco o~ the ~arc;h
derlvative, th~ w~re ~oio~eg~adable ~n ~ mu~h b~ter
de~re~ th~ h~a u~ual polyethyler~ ~llma~
15 ~m~le ~
Admlxture~ w~ pr~par~d ~ ~n ~x~mpl~ I wl~h
low pre~su~ poly~t;hylone ~DP~), and l~neAr low
pressur~ pc~ly~hyle~ (L~DPE~ 3ç~p~tlv~1y, ~nd wi~h
the u ~ of EAA a~ oompa~ e-m~klhg c:opolymer, and the
~o obtairled admixturR~ w~re pre~d to sh~t~, and ~om~
ph~sical proper~ were m~ured. The compo~i'cion~ of
the mixt.ure~ and the~e reE~ults are as ~ollows
A B ~ l
~ I
I.~P:~ 30 __ __
3 0 LLDPE -- 3 o 5 0
E~A 15 15 15
S~ari~ a~ld S 5 5
3S Hydroxypropyl ~tarch 50 5~ 30
Elongati,on ~t l:~re~k 9s 0 57 ~300
Tensils ~treng~h N/mm2 14 . 4lS 17 ~ ~
Dens~y kg~m3 954
_~_
2J ~3 ~J ~j fi~
~Qa
~ o~po~ on ~:: o~ E3c~ple II W~~ proc~e~ d t~
form a ~llm WhiC:h hACl t.h~ ~ollowing p~operti~s:
E~n~ lo~ A~; b2~3a)~ 35~
T~n~ ns~th, 2~ 18 . 9
~lou~ Tran;~pilr~n~e,
v~ browr
~en~al a~pear~n-;:e +~
Compo~itiono we~o ~pr~p~Fed on th~ o~
linear low pr~s~iu~* poly~thylon~ ~T.,L~P~ ompos~tlc:r~
1 cont~in~ ~6 w~gh~ p~rcon~ o~ LLE~P}~, 30 w~lght
p~arc~nt o~E hydroxypr~pyl ~tarc:h on ~ w~ight p~rcent o~
ethyl oleate . Compo~ n ~ c:ont~ ~ n~ ~3 w~ight
15 p~ ent o~ PI3:, 40 we~gh~ per~ n~ o~ hydroxyp~opyl
æ~roh ~nd 7 w~i~ht p~rcent o~ l3thyl olez~ For
~somp~ra~ e E~urpo~e~ 10~ per~ent S.~PE
~ompo itlon wa te~d. F~lms w~r~ ext;rud~d ~roln nll
th~æ~a ~h~ee c:ompo~t~on~ an~ the ~;~n. 11~ ~r~ng~h ~T~3)
2 o and elongation at break ~13B) in th~ machin~ direc:ti~n
~MD) and in the tran~Y~rse ~lrec~ion ~TD) w~r~ m~a~ur~d
thereof, The result~; are a~; ~ollow~:
~k~
_-- _ I
est ~ ;~
I ...... r
~ ~ ~ ~ I
~ompo~ition 1 1~ 14 ~80 710
C~ompo~i~ion ~ 10 9 6~0 7g3
100~ ~I.13PE 38 ~6 ~80 ~33
_ . _
~m~}
A c:ompo ition o~ 4~6 L~DPE, 15~ EAA. 5%
~:te~ric ac:id an~ 40~ hyt~roxy butyl starch wa~ proce~s~d
to fo~m a film wh~c:h h~d the :~ollow~n~ properties.
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12 -
Elongation at break % 330
Tensile strength, N/mmZ 23
Colour Transparent,
~ery light brown
General appearance ++
Example 6
A composition of 50% polystyrene, 15% SMA
(styrene maleic anhydride) 5% stearic acid and 30%
hydroxy propyl starch was processed to form a 1.2 mm
thick sheet which had the following properties:
Elongation at break % 2
Tensile strength, N/mm2 21
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