U.S. patent application number 13/069465 was filed with the patent office on 2011-09-22 for biodegradable nano-polymer compositions and biodegradable articles made thereof.
This patent application is currently assigned to Cereplast, Inc.. Invention is credited to Frederic Scheer.
Application Number | 20110229669 13/069465 |
Document ID | / |
Family ID | 38190793 |
Filed Date | 2011-09-22 |
United States Patent
Application |
20110229669 |
Kind Code |
A1 |
Scheer; Frederic |
September 22, 2011 |
BIODEGRADABLE NANO-POLYMER COMPOSITIONS AND BIODEGRADABLE ARTICLES
MADE THEREOF
Abstract
The invention relates to biodegradable nano-polymer
compositions, or nanocomposites, comprising poly(lactic acid) and
co-polyester polymer with adipic acid compounded with nanoparticles
of a mineral material having a degree of purity of at least 99.9%,
preferably 99.99%, selected from the group of silica and magnesium
silicate. In addition, the present invention refers to a process
for manufacturing the said compositions as well as biodegradable
articles made on the basis of such compositions, such as molded,
formed and extruded articles.
Inventors: |
Scheer; Frederic;
(Hawthorne, CA) |
Assignee: |
Cereplast, Inc.
El Segundo
CA
|
Family ID: |
38190793 |
Appl. No.: |
13/069465 |
Filed: |
March 23, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11365579 |
Feb 28, 2006 |
7927532 |
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13069465 |
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Current U.S.
Class: |
428/36.4 ;
220/573.1; 220/574; 264/319; 264/328.1; 294/218; 30/322; 30/324;
30/345; 428/338; 524/451; 524/493; 524/539; 977/779 |
Current CPC
Class: |
C08K 3/346 20130101;
C08L 67/04 20130101; C08L 67/04 20130101; Y10T 428/1372 20150115;
C08K 3/34 20130101; C08L 67/00 20130101; C08K 3/36 20130101; C08L
2666/18 20130101; Y10T 428/268 20150115 |
Class at
Publication: |
428/36.4 ;
524/539; 524/451; 524/493; 428/338; 30/322; 30/324; 30/345;
220/573.1; 220/574; 294/218; 264/328.1; 264/319; 977/779 |
International
Class: |
B32B 27/18 20060101
B32B027/18; C08L 67/04 20060101 C08L067/04; C08K 3/34 20060101
C08K003/34; C08K 3/36 20060101 C08K003/36; C08L 67/02 20060101
C08L067/02; B32B 1/02 20060101 B32B001/02; A47G 21/02 20060101
A47G021/02; A47G 21/04 20060101 A47G021/04; B26B 3/00 20060101
B26B003/00; A47J 36/00 20060101 A47J036/00; A47G 19/02 20060101
A47G019/02; A47G 21/10 20060101 A47G021/10; A47G 19/22 20060101
A47G019/22; A47G 21/00 20060101 A47G021/00; B29C 47/00 20060101
B29C047/00; B29C 45/00 20060101 B29C045/00 |
Claims
1. A biodegradable composition, comprising: between 40 and 97% by
weight of poly(lactic acid) polymer (PLA); between 0.5 and 35% by
weight of a co-polyester polymer with adipic acid; and more than 0%
and up to 6% by weight of nanoparticles of an extremely pure
mineral material selected from the group consisting of silica and
magnesium silicate, each on the basis of the total weight of the
biodegradable polymer composition.
2. The biodegradable polymer composition according to claim 1,
wherein the nanoparticles of mineral material have a size comprised
between about 20 and 500 nanometers.
3. The biodegradable polymer composition according to claim 1,
wherein the nanoparticles of mineral material have a degree of
purity of at least 99.9%.
4. The biodegradable polymer composition according to claim 1,
comprising between 1 and 32% of particles of mineral filler
comprising magnesium silicate or talc having a particle size
comprised between about 0.2 and 4.0 microns.
5. The biodegradable polymer composition according to claim 1, to
which composition during its preparation more than 0% and less than
5% of an organic peroxide, on the basis of the total weight of the
final biodegradable composition, has been added.
6. The biodegradable polymer composition according to claim 3,
wherein said organic peroxide is selected from the group consisting
of diacetyl peroxide, cumyl-hydro-peroxide, and dibenzoyl peroxide,
dialkyl peroxide, 2,5-methyl-2,5-di(terbutylperoxy)-hexane and
mixtures thereof.
7. A molded, extruded or thermoformed article comprising a
biodegradable composition, said biodegradable composition
comprising: between 40 and 97% by weight of poly(lactic acid)
polymer; between 0.5 and 35% by weight of co-polyester polymer with
adipic acid; and more than 0% and up to 6% by weight of
nanoparticles of an extremely pure mineral material selected from
the group consisting of silica and magnesium silicate, each on the
basis of the total weight of the biodegradable polymer
composition.
8. The article according to claim 7, wherein the nanoparticles of
mineral material have a size comprised between about 20 and about
500 nanometers.
9. The article according to claim 7, wherein the nanoparticles of
mineral material have a degree of purity of at least 99.9%.
10. The article according to claim 7, said article being selected
from the group consisting of utensils, food service-ware, forks,
spoons, knives, chopsticks, containers, cups, plates and pots.
11. The article according to claim 7, which further comprises
particles of mineral filler comprising magnesium silicate or talc
having the particle size comprised between about 0.2 and about 4.0
microns.
12. The article according to claim 7, to which composition during
its preparation more than 0% and less than 5%, of organic peroxide,
on the basis of the total weight of the biodegradable composition,
has been added.
13. A method of producing an article comprising a biodegradable
composition, said process comprising the steps of: (i) providing a
biodegradable composition, said composition comprising between 40
and 97% by weight of poly(lactic acid) polymer, and between 0.5 and
35% by weight of co-polyester polymer with adipic acid, each on the
basis of the total weight of the biodegradable composition, and
more than 0% and up to 6% by weight of nanoparticles of an
extremely pure mineral material selected from the group consisting
of silica and magnesium silicate; (ii) mixing the constituents of
(i) so as to prevent the creation of aggregates; (iii) heating the
mixture to a temperature of from 95 to 135.degree. C.; and (iv)
forming the resultant mixture to obtain a desired shape.
14. The method according to claim 13, wherein the mineral
nanoparticles are directly introduced into the barrel of the
mixer/extruder.
15. The method according to claim 14, wherein the mineral
nanoparticles are introduced into the barrel of the mixer/extruder
through a side feeder.
16. The method according to claim 13, wherein the nanoparticles of
mineral material have a size comprised between about 20 and about
500 nanometers.
17. The method according to claim 13, wherein the nanoparticles of
mineral material have a degree of purity of at least 99.9%.
18. The method according to claim 13, which comprises adding to the
biodegradable composition provided according to step i) between 1%
and 32% of particles of mineral filler comprising magnesium
silicate or talc having a particle size comprised between about 0.2
and about 4.0 microns.
19. The method according to claim 13, which comprises adding to the
biodegradable composition provided according to step i) more than
0% and less than 5% of organic peroxide.
20. The method according to claim 13, wherein the step of forming
includes subjecting said biodegradable composition to a process
selected from the group consisting of injection molding, profile
extrusion, and thermoform extrusion.
21. The biodegradable polymer composition according to claim 3,
wherein the degree of purity is 99.99%.
22. The article according to claim 9, wherein the degree of purity
is 99.99%.
23. The method according to claim 17, wherein the degree of purity
is 99.99%.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/365,579, filed Feb. 28, 2006, which is
incorporated herein by reference in its entirety.
FIELD
[0002] The present invention relates to biodegradable polymer
nanocomposites comprising poly(lactic acid) compounded with
nanoparticles of an extremely pure mineral, silica based material.
The invention further refers to a process for manufacturing said
nanocomposites or, in other words biodegradable nano-polymer
compositions, and to biodegradable articles made on the basis of
said compositions as well.
BACKGROUND
[0003] 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.
[0004] 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.
[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.
[0006] 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 bioabsorbable
materials. A few biodegradable resins have been used in
applications such as described above but cost has made them
un-affordable by the consumers.
[0007] An object of the present invention is thus to provide a
biodegradable articles or items comprising a polymer composition,
which composition 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. 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.
[0008] Another object of the invention is to provide biodegradable
compositions which exhibit increased mechanical and/or thermal
performance as compared to the current ones, e.g. thermal stability
or thermal resistance, improved processability or flexibility.
[0009] Nanocomposites are rapidly expanding new plastic technology,
offering promise for enabling novel polymer material. It appears
that the "nano effect" allows certain polymers or polymer
compositions such as biobased or biodegradable polymer compositions
to bridge the gap with the use of conventional petroleum based
plastics, allowing such novel material to achieve physical
properties that open the uses of these novel materials in
significantly broader technical or commercial applications.
[0010] The incorporation into such plastics of nano-sized fillers,
whether they are minerals or organic fibers, creates foundation of
polymer nanocomposites. The benefits of nanocomposites extend well
beyond one or two improvements but translate into several
improvements of physical and thermal properties of polymers at such
degree that the starting core polymer matrix composition is
modified into new shapes or structures, which allow eventually the
creation of completely novel material or features.
[0011] The physical and thermal properties of the new polymer
nanocomposites are so altered as compared to standard polymer
material that the inventor retains that there is creation of a
brand new material to be called "biodegradable nano-polymer
composition".
[0012] These and other objects which will become apparent from the
subsequent detailed description of the present invention, which
provides among others a composition comprising between about 40 and
97% by weight of poly(lactic acid) polymer, between about 0.5 and
35% by weight of co-polyester polymer with adipic acid, and up to
about 6% of nanoparticles of an extremely pure mineral material, in
particular a mineral material having a degree of purity of at least
99.9%, selected from the group of silica and magnesium silicate,
each on the basis of the total weight of the biodegradable polymer
composition.
SUMMARY
[0013] A composition 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 biooxidation 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) and co-polyester polymer with adipic
acid 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 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 according to the present invention
may be produced completely or partially from renewable sources,
when desired. In addition, a composition according to the present
invention may be adapted to various processing methods known in the
art.
[0016] Biodegradable polymers such as polylactides (PLAs) have been
produced for many years. PLA resemble clear polystyrene and have
good gloss and clarity for aesthetic appeal, along with physical
properties well suited for use as fibers, films, and thermoformed
packaging. PLA is also biocompatible and have been used extensively
in medical and surgical applications, i.e. sutures and drug
delivery devices. Unfortunately, PLA present major weaknesses such
as brittleness as well as low thermal resistance, 136.degree. F.
(58.degree. Celsius) and moisture-related degradation, limiting a
lot of commercial applications.
[0017] Unexpectedly, the compositions according to the present
invention provide physical properties which are not inherent to
poly(lactic acid) and provide significant improvements with respect
to the processability, production costs or heat resistance along
with improved flexibility and ductility without decreasing their
biodegradability.
[0018] It is assumed that the combination of a blending step
performed at ambient temperature followed by extrusion at
relatively high temperature and pressure through e.g. a twin screw
extruder allow the creation of a brand new shape, structure or
morphology of the polymer. Extrusion of the blended polymer mass
compounded with the selected mineral nanoparticles at a high
temperature induces shear forces which promote an exfoliation and
dispersion of the components: as a result of it, the new polymer
composition is constructed by evenly dispersing the selected
mineral material into nanoparticles that form platelets.
[0019] The dispersion of the platelets is critical to make the
compositions improved and the inventor has especially worked on
avoiding the creation of aggregate of platelets, which would
prevent the improvement in the properties herein described.
[0020] Such a performance has been achieved according to the
present invention by making use for mixing the mineral
nanoparticles of a custom designed side feeder, e.g. a tower to
enter the barrel of the extruder; while doing so the inventor avoid
direct injection of the nanoparticles to the molten polymer
material and so allows the necessary good and smooth distribution
of the said platelets during mixing and extrusion. As a result of
it, these platelets are evenly distributed throughout the polymer
matrix to create multiple parallel layers typical of the new
polymer morphology mentioned here above.
[0021] It has been further noted that not only the size, namely the
average size of the nanoparticles is important, but that the degree
of purity of the selected mineral material is crucial to achieve
the desired new features: a degree of purity of at least 99.9%,
preferably of at least 99.99% is necessary for that.
[0022] The new shape, structure or morphology which characterizes
the nano-polymer composition of the invention is tremendously and
surprisingly improving the physical properties of the composition,
namely its thermal properties and thermal stability: e.g., such
compositions exhibit a significant improvement in terms of thermal
resistance, of the magnitude of 35 to 45.degree. F. (about 1.7 to
7.2.degree. C.) depending on specific formulations.
[0023] Additional features and advantages are described herein, and
will be apparent from, the following Detailed Description.
DETAILED DESCRIPTION
[0024] The present invention relates to a biodegradable plastic.
The term "biodegradable plastic" pertains to a degradable plastic
in which the degradation results from the action of naturally
occurring microorganisms such as bacteria, fungi, and algae. A
degradable plastic is a plastic 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
would biodegrade within less than 180 days. Articles made from PE
would not degrade under normal composting conditions and PLA-based
article would degrade in compost environment in weeks (about 6 to 8
weeks).
[0025] 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)
[0026] A biodegradable composition according to the present
invention comprises between about 40% by weight to 97% by weight of
poly(lactic acid) polymer, between about 0.5% by weight to 35% by
weight of co-polyester polymer with adipic acid, and up to about 6%
of nanoparticles of an extremely pure mineral material selected
from the group of silica and magnesium silicate, each on the basis
of the total weight of the biodegradable composition.
[0027] A composition according to the present invention may be
obtained by mixing or blending the respective constituents in the
desired amounts. This may be performed according to any method
known in by the skilled artisan. For example, poly(lactic acid)
polymer and co-polyester polymer with adipic acid may be mixed in
pure form, for example blended by means of mill roll blending, and
heated to a temperature chosen according to the general knowledge
in the art such that at least one of the above-mentioned components
is partially or essentially completely molten.
[0028] Poly(lactic acid) may be represented by the following
structure:
##STR00001##
[0029] 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).
[0030] The preparation of polyesters and copolyesters is well known
in the art, such as disclosed in U.S. Pat. No. 2,012,267. Such
reactions are typically operated at temperatures from 150.degree.
C. to 300.degree. C. in the presence of polycondensation catalysts
such as titanium isopropoxide, manganese diacetate, antimony oxide,
dibutyl tin diacetate, zinc chloride, or combinations thereof. The
catalysts are typically employed in amounts between 10 to 1000
parts per million (ppm), based on total weight of the reactants
(cf. U.S. Pat. No. 6,020,393).
[0031] In addition to the Poly(lactic acid) and the copolyester of
adipic acid, the composition is compounded with nanoparticles of a
mineral material selected from the group of silica and magnesium
silicate. Nanoparticles according to the invention define particles
having a size definitely lower than the common size of current
ground mineral equivalents which are usually of the order of
several microns; according to the present invention the
nanoparticles have a size comprised between about 20 and a maximum
of 500 nanometers; good performance can be achieved with a mineral
material the nanoparticles of which have an average particle size
of the order of 200 to 400, e.g. of about 250 nanometers.
[0032] Although size particle is a critical parameter to achieve
the desired performance, the extremely high degree of purity of the
mineral selected therefore is crucial. Best results are achieved by
using nanoparticles of at least 99.9%, preferably 99.99% pure
silica or magnesium silicate. Special qualities of finely ground
silica as provided by the specialized trade have been proved
suitable within the frame of the present invention.
[0033] The biodegradable polymer can further comprise between 1 and
32% by weight of mineral particles, each on the basis of the total
weight of the biodegradable composition, said mineral particles
comprising at least one of magnesium and silicate. Examples for
such minerals are e.g. montmorillonite or talc. The mineral act as
filler adds strength and imparts stiffness. Usually, the mineral
particles have a size of 0.2 to 4.0 microns, more frequently a size
of 1 to 2 microns.
[0034] Moreover, during the preparation of a biodegradable polymer
according to the present invention organic peroxide may be added to
the reaction mixture in an amount of less than 5% by weight, on the
basis of the total weight of the biodegradable final polymer
composition.
[0035] Examples for organic peroxides which may be used for
preparing a composition according to the present invention are e.g.
diacetyl peroxide, cumyl-hydroperoxide, and dibenzoyl peroxide.
Other organic peroxides known to a skilled person may be used as
well. The organic peroxides serve as radical starter molecules
initiating a polymerization and help to provide connections, in
particular covalent bonds, between the components present in a
composition according to the present invention.
[0036] Depending on the specific applications desired, a
biodegradable polymer composition of the present invention may also
comprise additional additives or components well known in the art,
namely biodegradable components or additives such as e.g. natural
coloring agents, additional polymeric compounds like starch,
processed starch, cellulose, cellulose fibers, proteins, protein
fibers, etc.
[0037] A 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.
[0038] The figures here below are provided for exemplification only
and they can be modified by the skilled artisan to the necessary
extent, depending on the special features which are looked for.
[0039] A molded article according to the present invention
comprises a biodegradable composition, which biodegradable
composition comprises between 40 and 97%, e.g. about 91% by weight
of poly(lactic acid) polymer, and between 0.5 and 35%, e.g. 5% by
weight of co-polyester polymer with adipic acid, and about 4% of at
least 99.9%, preferably 99.99% pure finely ground silica, each on
the basis of the total weight of the biodegradable composition.
[0040] According to another embodiment of the invention the molded
article comprises a biodegradable composition, which biodegradable
composition comprises e.g. about 75% by weight of poly(lactic acid)
polymer, e.g. 5% by weight of co-polyester polymer with adipic
acid, e.g. about 15% of mineral particles of magnesium silicate or
talc, and about 5% of at least 99.9%, preferably 99.99% pure finely
ground silica, each on the basis of the total weight of the
biodegradable composition. Examples for various molded article are
utensils, forks, spoons, knives, chopsticks, containers and
cups.
[0041] An extruded article according to the present invention
comprises a biodegradable composition, which biodegradable
composition comprises between 40 and 97% by weight of poly(lactic
acid) polymer, and between 0.5 and 35% by weight of co-polyester
polymer with adipic acid, each on the basis of the total weight of
the biodegradable composition. In particular, a biodegradable
composition for an extruded article according to the present
invention can comprise between 50 and 85%, e.g. 75% by weight of
poly(lactic acid) polymer, between 2 and 20%, e.g. 15% by weight of
co-polyester polymer with adipic acid and about 5% of at least
99.9%, preferably 99.99% pure finely ground silica, each on the
basis of the total weight of the biodegradable composition.
Extruded articles may be for example films, trash bags, grocery
bags, container sealing films, pipes, drinking straws, spun-bonded
non-woven materials, and sheets.
[0042] A formulation for a profile extrusion process on the basis
of a composition according to the present invention can comprise
e.g. 75% by weight of poly(lactic acid) polymer, about 15% by
weight of co-polyester polymer with adipic acid, and about 5% of at
least 99.9%, preferably 99.99% pure finely ground silica, each on
the basis of the total weight of the biodegradable composition.
Articles according to the present invention made from a profile
extrusion formulation are for example drinking straws and
pipes.
[0043] A formulation for a thermoform extrusion process on the
basis of a composition according to the present invention can
comprise between 75% and 85% by weight of poly(lactic acid)
polymer, between 5% and 15% by weight of co-polyester polymer with
adipic acid, between 5% and 15% by weight of mineral particles
comprising at least one element selected from the group consisting
of magnesium and silicate, preferably about 75% by weight of
poly(lactic acid) polymer, about 15% by weight of co-polyester
polymer with adipic acid, about 9% by weight of magnesium silicate
or talc, and about 5% of at least 99.9%, preferably 99.99% pure
finely ground silica.
[0044] Articles according to the present invention made from a
thermoform extrusion method are e.g. sheets for producing cups,
plates and other objects, which could be outside of the food
service industry.
[0045] As outlined in detail before, the composition for the
preparation of such molded articles can comprise in addition to the
above-mentioned components organic peroxide(s), mono ester(s),
and/or natural plasticizer(s).
[0046] Injection molding, profile extrusion and thermoform
extrusion are processes known to a skilled person and are described
for example in Modern Plastics Encyclopedia, Published by
McGraw-Hill, Inc. --mid-October 1991 edition.
[0047] 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
[0048] Injection Molding Formulations
[0049] Several injection molding formulations have been using the
following ingredients in proportions varying within the ranges
provided here below:
[0050] from 75% to 91% by weight poly(lactic acid) polymer
[0051] from 2% to 5% by weight (co-polyester polymer with adipic
acid)
[0052] from 0.2% to 4% by weight of finely ground 99.99% pure
silica**.
[0053] (** average size particle of about 250 nanometers)
[0054] It is crucial that introducing the mineral nanoparticles be
performed without creating aggregates, using for instance a
side-feeder that would not inject the nanoparticles directly into
the barrel of the extruder but through a tower letting the
nanoparticles fall and mix smoothly with the molten material.
[0055] The above-mentioned compounds are mixed by means of
extrusion compounding at a temperature not to exceed 160.degree. C.
over a period ranging from 25 sec to 2 min. Then, the resulting
mixture is filled in an 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 cup.
Example 2
[0056] Injection Molding Formulation (Specific)
[0057] An injection molding formulation is prepared which
comprises:
[0058] 74.5% by weight poly (lactic acid) polymer
[0059] 5% by weight (co-polyester polymer with adipic acid)
[0060] 15% by weight of magnesium silicate (talc)
[0061] 5% by weight of finely ground 99.99% pure silica**, and
[0062] 0.5% by weight of 2,5-Dimethyl-2,5-di(t-butyl peroxy)
hexane.
[0063] (** average size particle of about 250 nanometers)
[0064] The injection molding formulation is prepared as detailed in
Example 1 and injection molded products may be obtained according
to the steps lined out in said Example 1.
[0065] The above formulations are provided for exemplification only
and they can be modified by the skilled artisan to the necessary
extent, depending on the special features which are looked for.
Example 3
[0066] Profile Extrusion Formulation
[0067] Several profile extrusion formulations have been using the
following ingredients in proportions varying within the ranges
provided here below:
[0068] from 65% to 75% by weight poly lactic acid polymer
[0069] from 15% to 20% by weight of co-polyester polymer with
adipic acid, and
[0070] from 1% to 5% by weight finely ground 9.99% pure
silica**.
[0071] (**average size particle of about 250 nanometers)
[0072] The above-mentioned compounds are mixed by twin screw
compounding. The resulting mixture is filled in a profile extrusion
device at a temperature not to exceed 160.degree. C. and a tube is
obtained which may be used as a drinking straw.
[0073] The above formulations are provided for exemplification only
and they can be modified by the skilled artisan to the necessary
extent, depending on the special features which are looked for.
Example 4
[0074] Thermoform Extrusion Formulation
[0075] Several thermo form extrusion formulations have been using
the following ingredients in proportions varying within the ranges
provided here below:
[0076] from 55% to 75% by weight poly lactic acid polymer
[0077] from 5% to 15% by weight of co-polyester polymer with adipic
acid
[0078] from 4% to 9% by weight of magnesium silicate (talc)
[0079] from 1% to 5% by weight finely ground 99.99% pure silica**,
and
[0080] from 0.2% to 1% by weight of 2,5-Dimethyl-2,5-di(t-butyl
peroxy) hexane.
[0081] (**average size particle of about 250 nanometers)
[0082] The above-mentioned compounds are mixed by twin screw
compounding. The resulting mixture is filled in a thermoform
extrusion device at a temperature not to exceed 160.degree. C. and
a sheet having a thickness between 0.1 mm to 45 mm is obtained
which may be used for forming cups, plates or bottles.
[0083] The above formulations are provided for exemplification only
and they can be modified by the skilled artisan to the necessary
extent, depending on the special features which are looked for.
[0084] Numerous modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
[0085] 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.
* * * * *