U.S. patent application number 11/293517 was filed with the patent office on 2007-06-07 for bio based biodegradable polymer compositions and use of same.
Invention is credited to Frederic Scheer.
Application Number | 20070129467 11/293517 |
Document ID | / |
Family ID | 37031766 |
Filed Date | 2007-06-07 |
United States Patent
Application |
20070129467 |
Kind Code |
A1 |
Scheer; Frederic |
June 7, 2007 |
Bio based biodegradable polymer compositions and use of same
Abstract
A biodegradable polymer composition useful for manufacturing
biodegradable items or articles with improved mechanical properties
comprising poly(lactic acid) polymer (PLA), starch and protein
material, obtainable by providing poly(lactic acid) polymer (PLA),
starch and protein material in such ratios that PLA/starch blend
represents at least 95% weight of the above three components and
that starch represents at least 23% weight of PLA; mixing the above
three components at room temperature in a controlled moisture
atmosphere to afford a homogeneous mixture; subjecting the above
homogeneous mixture to extrusion compounding under controlled heat,
speed and pressure conditions; and drying down to a maximum of
approximately 1% weight of moisture and subsequently conditioning
the extruded polymeric composition.
Inventors: |
Scheer; Frederic;
(Hawthorne, CA) |
Correspondence
Address: |
BELL, BOYD & LLOYD, LLP
P.O. Box 1135
CHICAGO
IL
60690
US
|
Family ID: |
37031766 |
Appl. No.: |
11/293517 |
Filed: |
December 2, 2005 |
Current U.S.
Class: |
524/47 |
Current CPC
Class: |
C08L 67/04 20130101;
C08L 89/00 20130101; C08L 3/02 20130101; C08L 3/02 20130101; C08L
2666/02 20130101; C08L 67/04 20130101; C08L 2666/26 20130101 |
Class at
Publication: |
524/047 |
International
Class: |
D21H 19/54 20060101
D21H019/54 |
Claims
1. A biodegradable polymer composition useful for manufacturing
biodegradable items or articles with improved mechanical properties
comprising poly(lactic acid) polymer (PLA), starch and protein
material, obtainable by i) providing poly(lactic acid) polymer
(PLA), starch and protein material in such ratios that PLA/starch
blend represents at least 95% weight of the above three components
and that starch represents at least 23% weight of PLA; ii) mixing
the above three components at room temperature in a controlled
moisture atmosphere to afford a homogeneous mixture; iii)
subjecting the above homogeneous mixture to extrusion compounding
under controlled heat, speed and pressure conditions; and iv)
drying down to a maximum of approximately 1% weight of moisture and
subsequently conditioning the extruded polymeric composition.
2. The biodegradable polymeric composition according to claim 1
wherein the protein material is gluten and wherein it represents
from 1 to 5% weight of the PLA/starch blend.
3. The biodegradable polymeric composition according to claim 1
wherein starch is either native or thermoplastic starch and wherein
it represents from 15 to 55% weight of the PLA/starch blend.
4. The biodegradable polymeric composition according to claim 3
wherein starch represents from 25 to 45% weight of the PLA/starch
blend.
5. The biodegradable polymer composition according to claim 1
wherein PLA, starch and the protein material are further mixed with
additional components selected from the group consisting of a
polymerization initiator and an inert material.
6. The biodegradable polymer composition according to claim 1
wherein the components provided in step i) are dried down to a
maximum of approximately 1% weight of moisture prior mixing.
7. The biodegradable polymer composition according to claim 1
wherein the components subjected to blending and subsequent
extrusion compounding are dried down to a maximum of approximately
1 weight % of moisture prior to conditioning.
8. The biodegradable polymer composition according to claim 1
wherein extrusion compounding is multiple screw extrusion performed
at a temperature of about 95.degree. C. to about 190.degree. C. for
a period of about 1 to about 10 minutes.
9. A process for manufacturing substantially or totally bio based
biodegradable items or articles with improved mechanical properties
which comprises subjecting a biodegradable polymer composition
useful for manufacturing biodegradable items or articles with
improved mechanical properties comprising poly(lactic acid) polymer
(PLA), starch and protein material, obtainable by i) providing
poly(lactic acid) polymer (PLA), starch and protein material in
such ratios that PLA/starch blend represents at least 95% weight of
the above three components and that starch represents at least 23%
weight of PLA; ii) mixing the above three components at room
temperature in a controlled moisture atmosphere to afford a
homogeneous mixture; iii) subjecting the above homogeneous mixture
to extrusion compounding under controlled heat, speed and pressure
conditions; and iv) drying down to a maximum of approximately 1%
weight of moisture and subsequently conditioning the extruded
polymeric composition to an operation selected from the group of
forming, molding, injection, molding, extrusion coating and
thermoform extrusion.
10. A substantially or totally bio based biodegradable item or
article with improved mechanical properties obtainable by means of
the process according to claim 9.
11. An item or an article according to claim 10 which is designed
to be totally degraded in a natural environment, preferably in a
time period that is significantly shorter than that required for
the degradation of conventional polymer or plastic materials.
12. An item or an article according to claim 10 which is designed
to be in contact with food material or food products.
13. An item or an article according to claim 10 which is selected
from the group consisting of utensils, food service-ware, forks,
spoon, knives, chopsticks, containers, bottles, foam material
products, plates and pots or films, trash bags, grocery bags,
container sealing films, pipes, drinking straws, spun-bonded
non-woven material and sheets.
14. A process for preparing a biodegradable polymer composition
useful for manufacturing bio based biodegradable items or articles,
which comprises i) providing poly(lactic acid) polymer (PLA),
starch and protein material in such ratios that PLA/starch blend
represents at least 95% weight of the above three components and
that starch represents at least 23% weight of PLA; ii) mixing the
above three components at room temperature in a controlled moisture
atmosphere to afford a homogeneous mixture; iii) subjecting the
above homogeneous mixture to extrusion compounding under controlled
heat, speed and pressure conditions; and iv) drying down to a
maximum of approximately 1% weight of moisture and subsequently
conditioning the extruded polymeric composition.
15. A process for improving processability of biodegradable
polymers based on poly(lactic acid) polymer (PLA), starch and
protein material, which comprises i) providing poly(lactic acid)
polymer (PLA), starch and protein material in such ratios that
PLA/starch blend represents at least 95% weight of the above three
components and that starch represents at least 23% weight of PLA;
ii) mixing the above three components at room temperature in a
controlled moisture atmosphere to afford a homogeneous mixture;
iii) subjecting the above homogeneous mixture to extrusion
compounding under controlled heat, speed and pressure conditions;
and iv) drying down to a maximum of approximately 1% weight of
moisture and subsequently conditioning the extruded polymeric
composition.
Description
FIELD
[0001] The present invention relates to bio based, biodegradable
polymer compositions comprising poly(lactic acid) and further
components of natural origin which exhibit improved mechanical
properties as compared to currently available similar material. In
addition, the present invention also relates to products, items or
articles made on the basis of said compositions.
BACKGROUND
[0002] Packaging material and disposable beakers, cups and cutlery
are used nowadays widely and allow that food material may be sold
and/or consumed under hygienic conditions. Such disposable
materials and objects are highly estimated by the consumers and the
retailers, since they may be simply disposed after use and do not
have to be washed and cleaned like conventional dishes, glasses or
cutlery.
[0003] Yet, the widespread and even growing use of such materials
result in a mounting amount of litter produced each day. Currently,
the plastic waste is either provided to garbage incinerators or
accumulates in refuse dumps, with both of the above-mentioned
solutions for waste disposal being associated with problems for the
environment.
[0004] For preparing the above mentioned items several
biodegradable polymers are already known in the state of the art
and comprise materials on the basis of e.g. poly(glycolic acid),
poly(epsilon-caprolactone), poly(lactic acid), and polydioxanone.
The production of these polymers is, however, rather cumbersome and
expensive, so that the use thereof is presently mainly restricted
to high value medical applications requiring bio absorbable
materials. A few biodegradable resins have been used in
applications such as described above but cost has made them
unaffordable by the consumers.
[0005] Thus, there is a need in the art to obviate the above
problem and to provide materials, which combine the advantages of
currently used plastics material and do not add to environmental
pollution and, also, which remain cost and price competitive.
[0006] It has been indeed observed that even if relevant costs
could be sometimes reduced significantly, e.g. so that articles
manufactured on the basis of such biodegradable resins are no
longer more expensive than the current equivalent plastic articles,
this did not provide real incentive to consumers for replacing the
traditional plastic articles or goods by the new biodegradable
articles or goods which have been proposed.
[0007] U.S. Pat. No. 6,235,815 provides biodegradable polymer
compositions made of mixtures of native and thermoplastic starch in
relatively high proportions (ca 50% weight), poly(lactic acid) and
plasticizer like polyester amide type plasticizers. It has been
observed, however, that the necessity to use plasticizers does not
provide the expected reductions manufacture costs.
[0008] US 2004/0034128 discloses biodegradable polylactide resin
compositions comprising at least one protein like e.g. silk
protein, gelatin, keratin, elastin, gluten or zein so that a
polylactide, in other terms a poly(lactic acid) composition having
excellent biodegradability can be obtained while maintaining good
physical properties and strengths.
[0009] This document further teaches, however, that when a
naturally occurring polymer such as starch is blended into the
polylactide the good mechanical strength or physical properties
thereof are lost and merely provides examples of blends wherein
poly(lactic acid) is by far the major component, i.e. represents 95
weight % or more of the composition.
[0010] Surprisingly, duly selected blends of poly(lactic acid),
starch and proteins, namely blends comprising up to ca 50 weight %
of starch, when processed according to the present invention lead
to biodegradable polymer material having all the desired and
necessary physical or mechanical features, which does not comprise
any added plasticizer and which proves cost and price
competitive.
[0011] Consequently, an object of the present invention is to
provide a cost and price attractive composition or article, which
composition or article is degraded in a natural environment in a
time period which is significantly shorter as compared to the time
period required for the degradation of conventional plastic
materials, such as e.g. polyethylene or polypropylene. In a
controlled environment such as a composting site the composition
will allow biodegradation in period of time not to exceed 180 days,
one of the time requirements set by the US specification set by
ASTM (ASTM 6400 D99). Moreover, such a composition should also
enable production of bags, bottles or cutlery, exhibiting desired
properties for the respective purpose.
[0012] These and other objects which will become apparent from the
subsequent detailed description of the present invention, which
provides a composition comprising poly(lactic acid), starch and
protein material like e.g. gluten and which is obtainable by the
process according to claim 1 and following.
SUMMARY
[0013] A composition or an article of the present invention is
biodegradable when exposed to specific environmental conditions,
such as composting, which will result in a loss of some properties
that may be measured by standard methods appropriate to the plastic
and in the application in a period of time that determines its
classification. For instance composting is a managed process that
controls the biological decomposition and transformation of
biodegradable materials into humus-like substance called compost:
the aerobic mesophilic and thermophilic degradation of organic
matter to make compost; the transformation of biologically
decomposable material through a controlled process of bio oxidation
that proceed through mesophilic and thermophilic phases and results
in the production of carbon dioxide, water, minerals, and
stabilized organic matter (compost or humus) (ASTM Terminology)
Consequently all main components, poly(lactic acid), starch and
proteins will be degraded to small organic fragments which will
create stabilized organic matter and will not introduce any hazard
or heavy metals into soil.
[0014] As a result, objects made from the composition of the
present invention will not contribute to a further increase of
refuse dumps; on the contrary they will allow creation of organic
fertilizers such as compost, while such objects simultaneously
provide all advantages of disposable objects highly estimated by
the consumers and producer. Objects made of a composition according
to the present invention may be disposed after use, are essentially
of lightweight, and have not to be transported to a location where
they have to be cleaned. In particular, objects made from a
composition according to the present invention provide the
advantage that objects thrown away in parks or at the beach will
degrade and will vanish after some time. However this invention
should not be publicize as a license to litter the environment.
[0015] Moreover, a composition or an article according to the
present invention can be produced completely from renewable
sources. In addition, a composition according to the present
invention may be adapted to various processing methods known in the
art.
[0016] Also, the compositions according to the present invention
provide improved mechanical properties not inherent to poly(lactic
acid) and provide improvements with respect to the processability,
production costs and heat or mechanical resistance along with
improved flexibility and ductility.
DETAILED DESCRIPTION
[0017] The present invention relates to a biodegradable polymer
compositions or articles. The term "biodegradable polymer" pertains
to a degradable polymer material in which the degradation results
from the action of naturally occurring microorganisms such as
bacteria, fungi, and algae. A degradable polymer material is a
material designed to undergo a significant change in its chemical
structure under specific environmental conditions, resulting in a
loss of some properties that may be measured by standard tests
methods appropriate to the plastic and the application in a period
of time that determines its classification. Depending on the
additional components present in the composition and the dimensions
of the object made from said biodegradable material, the time
period required for degradation will vary and may also be
controlled when desired. Generally, the time span for
biodegradation will be significantly shorter than the time span
required for a degradation of objects made from conventional
plastic materials having the same dimensions, such as e.g.
polyethylene, which have been designed to last for as long as
possible. For example, cellulose and Kraft paper is to biodegrade
within 83 days in a compost environment. Our formulation is to
biodegrade in a shorter period of time and will pass the tests
required by ASTM 6400 D99, which demand that compostable plastic or
polymer material would biodegrade within less than 180 days.
Articles made from e.g. PE would not degrade under normal
composting conditions and PLA-based article would degrade in
compost environment in weeks (about 6 to 8 weeks).
[0018] Biodegradable polymers are comprised of components which are
reduced in film or fiber strength by microbial catalyzed
degradation. The biodegradable polymers are reduced to monomers or
short chains, which are then assimilated by the microbes. In an
aerobic environment, these monomers or short chains are ultimately
oxidized to CO.sub.2, H.sub.2O, and new cell biomass. In an
anaerobic environment the monomers or short chains are ultimately
oxidized to CO.sub.2, H.sub.2O, acetate, methane, and cell biomass.
Successful biodegradation requires direct physical contact between
the biodegradable polymers and the active microbial population or
the enzymes produced by the active microbial population. Moreover,
certain minimal physical and chemical requirements such as suitable
pH, temperature, oxygen concentration, proper nutrients, and
moisture level must be met (cf. U.S. Pat. No. 6,020,393).
[0019] The present invention also relates to a substantially or
totally bio based biodegradable article or composition. The term
"bio based" means that the major weight portion if not the whole of
such an article or composition consists of naturally occurring
components like starch, e.g. corn or wheat starch, i.e. a material
simply extracted from their natural source without any subsequent
chemical treatment; or components such poly(lactic acid) or esters
thereof which results from e.g. enzymatic treatment of naturally
occurring material like starch and subsequent polymerization and/or
subsequent ester formation if any.
[0020] The biodegradable polymer composition according to the
present invention can be obtained by means of a process which
comprises
[0021] i) providing poly(lactic acid) polymer (PLA), starch and
protein material in such ratios that PLA/starch blend represents
min. 95% weight of the above three components and that starch
represents min. 23% weight of PLA;
[0022] ii) mixing the above three components at room temperature in
a controlled moisture atmosphere, to afford a homogeneous
mixture;
[0023] iii) subjecting the above homogeneous mixture to extrusion
compounding under controlled heat, speed and pressure
conditions;
[0024] iv) drying down the extruded polymer composition to a max.
of ca 1% weight of moisture and subsequently conditioning it.
[0025] The invention further provides a process for improving
processability of biodegradable polymers based on poly(lactic acid)
polymer (PLA), starch and protein material, which comprises
subjecting said components to a process defined here above.
[0026] The invention also provides a process for manufacturing
substantially or totally bio based biodegradable items or articles
with improved mechanical properties which comprises subjecting the
polymeric composition prepared according to the process defined
here above to an operation selected from the group of forming,
molding, injection, molding, extrusion, extrusion coating and
thermoform extrusion.
[0027] Surprisingly, these polymer compositions show significantly
improved process ability and/or physical and/or mechanical
properties when compared to prior known compositions made of same
or similar components but processed in a quite different way and
also present in quite different respective ratios (see e.g. U.S.
Pat. No. 6,235,815 and US 2004/0034128).
[0028] Preferably, the composition here above is made of mixtures
wherein the protein material is gluten, still more preferably corn
gluten or wheat gluten and represents from min. 1 to max. 5 weight
% of the PLA/starch blend.
[0029] Proportions of starch in the PLA/starch blend, e.g. wheat
starch or corn starch represent preferably from min 15 to 55 weight
% of the said blend and still more preferably from min. 25 to max.
45 weight % of the said blend. Starch can be either native or
thermoplastic starch.
[0030] Poly(lactic acid) may be represented by the following
structure: ##STR1##
[0031] wherein n for example can be an integer between 10 and 250.
Poly(lactic acid) can be prepared according to any method known in
the state of the art. For example, poly(lactic acid) can be
prepared from lactic acid and/or from one or more of D-lactide
(i.e. a dilactone, or a cyclic dimer of D-lactic acid), L-lactide
(i.e. a dilactone, or a cyclic dimer of L-lactic acid), meso
D,L-lactide (i.e. a cyclic dimer of D-, and L-lactic acid), and
racemic D,L-lactide (racemic D,L-lactide comprises a 1/1 mixture of
D-, and L-lactide). The preparation of polyesters and copolyesters
of lactic acid is well known in the art, such as disclosed in U.S.
Pat. No. 2,012,267.
[0032] The present biodegradable polymer composition may be used
for various applications and should not be restricted to those the
exemplarily disclosed herein. For example, also applications in the
medical field, such as e.g. for sutures, and drug release matrices,
or in the agricultural industry are conceivable.
[0033] According to the invention the selected components can be
first subjected to drying operations provided they do not have the
required moisture yet, i.e. a max. of about 1 weight % of moisture.
Moisture control is in fact critical for achieving the necessary
conditions, namely to improve or increase the processability of the
biopolymer material used for blending
[0034] Mixing the above components is performed at room temperature
by means of standard techniques like e.g. twin screw extrusion or
ball milling until achieving a fully homogenized mass. During that
operation the mixture can be further blended with additional
polymer material like e.g. biodegradable polyester and/ or
components like polymerization initiators and, optionally, inert
mineral filler like a silicate or talc. Such a mixing operation is
furthermore performed in a well controlled moisture atmosphere,
preferably in a way that allows keeping moisture at a max. of ca 1%
weight or even lower if ever necessary.
[0035] The homogenized blend is then further mixed by means of
extrusion compounding like e.g. multiple screw extrusion, which is
usually run at a temperature varying from about 95.degree. C. to
about 190.degree. C. depending on the zones of the mixing, for a
period extending from about 2 minutes to about 5 minutes in most
cases. The extruded mass is subsequently cooled using e.g. water
bath or ice cold air current and eventually dried to the required
humidity content.
[0036] The extruded polymer composition can be transformed into
pellets or balls or flakes or filaments depending on the necessity
of its subsequent transformation into finished goods or articles;
packaging and storage are done in such a way that the required
humidity level is preserved.
[0037] The extruded polymer composition can also be directly used
for the subsequent transformation without any preliminary packaging
or storage.
[0038] A polymer composition of the present invention may be used
for the production of various articles, such as e.g. molded
articles and/or extruded articles. The term "molded article" (or
"extruded article") as used in the present invention comprises
articles made according to a molding process (or an extrusion
process). A "molded article" (or "extruded article") can also be
part of another object, such as e.g. an insert in a container or a
knife blade or fork insert in a corresponding handle.
[0039] A molded article according to the present invention
comprises a biodegradable composition, which biodegradable
composition comprises between about 15 and about 55% by weight of
starch and 45 and about 75% by weight of poly(lactic acid) polymer.
As outlined in detail before, the composition for the preparation
of such molded articles can comprise in addition to the
above-mentioned components mineral particles comprising at least
one of magnesium and silicium.
[0040] Examples for various molded article are utensils, forks,
spoons, knives, chopsticks, containers, cups, foam material
products, and pots.
[0041] Articles according to the present invention made from a
thermoform extrusion method are e.g. sheets for producing cups,
plates and bottles and other objects, which could be outside of the
food service industry.
[0042] Injection molding, blown film extrusion, profile extrusion
and thermoform extrusion are processes known to a skilled person
and are described for example in Modem Plastics Encyclopedia,
Published by McGraw-Hill, Inc. -mid-October 1991 edition.
[0043] The present invention will be described now in detail on the
basis of the following non-limiting examples given by way of an
example only.
EXAMPLE 1
[0044] Various formulations have been prepared within the frame of
the present invention using the components mentioned here below;
respective amounts (weight percent) of each of the selected
component are adjusted to the eventual use of the resulting polymer
composition and to the physical and/or mechanical properties which
are required. TABLE-US-00001 Ingredients Composition A Composition
B Composition C Starch 15-25% 15-25% 14-45% PLA 65-75% 65-75%
55-75% Gluten 1-5% 1-5% 1-5% Polyester 1-5% 1-5% 1-5% Silicate 1-5%
0 0 Ingredients Composition D Composition E Composition F Starch
15-25% 15-25% 20-55% PLA 55-65% 65-75% 45-55% Gluten 1-5% 1-5% 1-5%
Silicate 1-5% 0 0
[0045] "PLA" is a polymer created from Lactic Acid a three carbon
organic acid: one terminal carbon atom is part of an acid or
carboxyl group; the other terminal carbon atom is part of a methyl
or hydrocarbon group; and a central carbon atom having an alcohol
carbon group. Lactic acid exists in two optically active isometric
forms. Poly-Lactic Acid is commercially available from different
sources. The principal source being NatureWorks, LLC, a wholly own
subsidiary of Cargill, Inc., a U.S. company.
[0046] "Gluten" is corn gluten or wheat gluten. Both can be used in
the formulations. Corn gluten is preferred because of its stability
and consistency. Both products are available commercially from
companies such as e.g. Sigma Aldrich, Penford Co., Archer Daniel
Midlands (USA).
[0047] "Polyester" is a Co-Polyester commercially available like
e.g. Bio-Eastar from Eastman Chemical (USA) or Ecoflex from BASF
(Germany).
EXAMPLE 2
[0048] Injection Molding Formulation
[0049] An injection molding formulation is prepared which comprises
the following components: TABLE-US-00002 Ingredients Composition D
Composition E Composition F Starch 15-25% 15-25% 20-55% PLA 55-65%
65-75% 45-55% Gluten 1-5% 1-5% 1-5% Silicate 1-5% 0 0
[0050] The selected components (humidity max. 1 weight %) are first
blended in a rotating screw mixer at room temperature to afford a
homogeneous powdered mass. That mass is then subjected to further
mixing, heating and pressurizing in a twin screw extruder under the
following conditions:
[0051] temperature: from min. 95.degree. C. to max. 190.degree.
C.
[0052] speed: from 125 to 300 rpm
[0053] humidity: maximum 1% weight
[0054] The extruded plasticized polymer mass is cooled by means of
a water bath, then converted into pellets using a strand pelletizer
or an under water pelletizer and eventually dried under vacuum
until reaching again a humidity of max. 1 weight % and then packed
and stored until further processing. Drying of the pellets is done
using a draying conveyor combining air blowing, vacuum and
extraction; such a drying step is performed within milliseconds, in
any case within a max. of 3 seconds after pellets move out of the
water bath.
[0055] Pellets as collected here above are then filled in a
conventional injection molding device at a temperature of about
160.degree. C. and is injected into a mold at a temperature of
about 20.degree. C. in order to obtain an injection molded utensils
or other shapes.
[0056] Further examples for various molded article are utensils,
forks, spoons, knives, chopsticks, containers, cups and pots.
EXAMPLE 3
[0057] Thermoform Extrusion Formulation
[0058] A thermoform extrusion formulation is prepared which
comprises: TABLE-US-00003 Ingredients Composition A Composition B
Composition C Starch 15-25% 15-25% 14-45% PLA 65-75% 65-75% 55-75%
Gluten 1-5% 1-5% 1-5% Polyester 1-5% 1-5% 1-5% Silicate 1-5% 0 0
Ingredients Composition D Composition E Composition F Starch 15-25%
15-25% 20-55% PLA 55-65% 65-75% 45-55% Gluten 1-5% 1-5% 1-5%
Silicate 1-5% 0 0
[0059] The above-mentioned compounds are mixed and subjected to
twin screw extrusion as defined in Example 2. The resulting polymer
material is filled in a thermoform extrusion device at a
temperature of 160.degree. C. and a sheet having a thickness
between 0.1 mm to 45mm is obtained which may be used for forming
cups, plates or bottles.
[0060] It should be understood that various changes and
modifications to the presently preferred embodiments described
herein will be apparent to those skilled in the art. Such changes
and modifications can be made without departing from the spirit and
scope of the present subject matter and without diminishing its
intended advantages. It is therefore intended that such changes and
modifications be covered by the appended claims.
* * * * *