NZ614394B2 - Biodegradable polymer blend - Google Patents
Biodegradable polymer blend Download PDFInfo
- Publication number
- NZ614394B2 NZ614394B2 NZ614394A NZ61439412A NZ614394B2 NZ 614394 B2 NZ614394 B2 NZ 614394B2 NZ 614394 A NZ614394 A NZ 614394A NZ 61439412 A NZ61439412 A NZ 61439412A NZ 614394 B2 NZ614394 B2 NZ 614394B2
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- NZ
- New Zealand
- Prior art keywords
- polyester
- blend
- weight
- molecular weight
- flow rate
- Prior art date
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- 239000000203 mixture Substances 0.000 title claims abstract description 111
- 229920002988 biodegradable polymer Polymers 0.000 title claims abstract description 13
- 239000004621 biodegradable polymer Substances 0.000 title claims abstract description 13
- 229920000747 poly(lactic acid) polymer Polymers 0.000 claims abstract description 93
- 239000004626 polylactic acid Substances 0.000 claims abstract description 93
- 229920000728 polyester Polymers 0.000 claims abstract description 87
- 229920001610 polycaprolactone Polymers 0.000 claims abstract description 67
- 239000004632 polycaprolactone Substances 0.000 claims abstract description 42
- -1 polybutylene succinate Polymers 0.000 claims abstract description 36
- 239000004629 polybutylene adipate terephthalate Substances 0.000 claims abstract description 26
- 229920002961 Polybutylene succinate Polymers 0.000 claims abstract description 23
- 239000004631 polybutylene succinate Substances 0.000 claims abstract description 23
- 239000000155 melt Substances 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 20
- 238000000465 moulding Methods 0.000 claims abstract description 16
- 239000004630 polybutylene succinate adipate Substances 0.000 claims abstract description 16
- 239000005014 poly(hydroxyalkanoate) Substances 0.000 claims abstract description 8
- 229920000642 polymer Polymers 0.000 claims description 16
- 238000006065 biodegradation reaction Methods 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 12
- 229920002959 polymer blend Polymers 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 238000001746 injection moulding Methods 0.000 claims description 6
- 238000004806 packaging method and process Methods 0.000 claims description 5
- 229920001577 copolymer Polymers 0.000 claims description 4
- 238000001125 extrusion Methods 0.000 claims description 4
- 235000013361 beverage Nutrition 0.000 claims description 3
- 238000000071 blow moulding Methods 0.000 claims description 3
- 238000003490 calendering Methods 0.000 claims description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 238000000748 compression moulding Methods 0.000 claims description 3
- 238000007493 shaping process Methods 0.000 claims description 3
- 238000007666 vacuum forming Methods 0.000 claims description 3
- 239000007921 spray Substances 0.000 claims description 2
- 238000010102 injection blow moulding Methods 0.000 claims 1
- 239000000654 additive Substances 0.000 abstract description 20
- 239000000126 substance Substances 0.000 abstract description 9
- 229920000229 biodegradable polyester Polymers 0.000 abstract description 6
- 239000004622 biodegradable polyester Substances 0.000 abstract description 6
- 230000002708 enhancing Effects 0.000 abstract description 6
- 239000002667 nucleating agent Substances 0.000 abstract description 3
- 239000000463 material Substances 0.000 description 18
- 230000000694 effects Effects 0.000 description 16
- 229920001169 thermoplastic Polymers 0.000 description 16
- 239000004416 thermosoftening plastic Substances 0.000 description 16
- 239000002131 composite material Substances 0.000 description 15
- 238000002425 crystallisation Methods 0.000 description 14
- 230000005712 crystallization Effects 0.000 description 12
- 239000011521 glass Substances 0.000 description 11
- 230000000996 additive Effects 0.000 description 8
- 230000001965 increased Effects 0.000 description 6
- 238000011068 load Methods 0.000 description 6
- 238000003860 storage Methods 0.000 description 6
- 238000007792 addition Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 235000020127 ayran Nutrition 0.000 description 4
- 238000002347 injection Methods 0.000 description 4
- 239000007924 injection Substances 0.000 description 4
- 239000002105 nanoparticle Substances 0.000 description 4
- 238000005191 phase separation Methods 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicium dioxide Chemical class O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 3
- 230000004059 degradation Effects 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 description 3
- 239000011707 mineral Substances 0.000 description 3
- 230000002787 reinforcement Effects 0.000 description 3
- JVTAAEKCZFNVCJ-REOHCLBHSA-N L-lactic acid Chemical compound C[C@H](O)C(O)=O JVTAAEKCZFNVCJ-REOHCLBHSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 229920001519 homopolymer Polymers 0.000 description 2
- 238000010103 injection stretch blow moulding Methods 0.000 description 2
- 238000009114 investigational therapy Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000006011 modification reaction Methods 0.000 description 2
- 239000002114 nanocomposite Substances 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000003287 optical Effects 0.000 description 2
- 229920001432 poly(L-lactide) Polymers 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- 229920001142 polymer nanocomposite Polymers 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000003303 reheating Methods 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 239000005060 rubber Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 238000002076 thermal analysis method Methods 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 229960003563 Calcium Carbonate Drugs 0.000 description 1
- 101700000128 HACL1 Proteins 0.000 description 1
- 102100001922 HACL1 Human genes 0.000 description 1
- 101710036925 Os01g0505400 Proteins 0.000 description 1
- 229920001748 Polybutylene Polymers 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 210000003135 Vibrissae Anatomy 0.000 description 1
- 238000002679 ablation Methods 0.000 description 1
- 230000003679 aging effect Effects 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminum Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000003247 decreasing Effects 0.000 description 1
- 230000000994 depressed Effects 0.000 description 1
- 230000001627 detrimental Effects 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- KARVSHNNUWMXFO-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane;hydrate Chemical class O.O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O KARVSHNNUWMXFO-UHFFFAOYSA-N 0.000 description 1
- 229920005839 ecoflex® Polymers 0.000 description 1
- 238000001493 electron microscopy Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000010096 film blowing Methods 0.000 description 1
- 238000005206 flow analysis Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 230000003301 hydrolyzing Effects 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 239000004790 ingeo Substances 0.000 description 1
- 230000004301 light adaptation Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- CWEFIMQKSZFZNY-UHFFFAOYSA-N pentyl 2-[4-[[4-[4-[[4-[[4-(pentoxycarbonylamino)phenyl]methyl]phenyl]carbamoyloxy]butoxycarbonylamino]phenyl]methyl]phenyl]acetate Chemical compound C1=CC(CC(=O)OCCCCC)=CC=C1CC(C=C1)=CC=C1NC(=O)OCCCCOC(=O)NC(C=C1)=CC=C1CC1=CC=C(NC(=O)OCCCCC)C=C1 CWEFIMQKSZFZNY-UHFFFAOYSA-N 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 229920000844 poly(butylene succinate-co-adipate) Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 230000002829 reduced Effects 0.000 description 1
- 230000003014 reinforcing Effects 0.000 description 1
- 230000000717 retained Effects 0.000 description 1
- 238000000518 rheometry Methods 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 125000000383 tetramethylene group Chemical group [H]C([H])([*:1])C([H])([H])C([H])([H])C([H])([H])[*:2] 0.000 description 1
- 229920001187 thermosetting polymer Polymers 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
- NQPDZGIKBAWPEJ-UHFFFAOYSA-M valerate Chemical compound CCCCC([O-])=O NQPDZGIKBAWPEJ-UHFFFAOYSA-M 0.000 description 1
- 229940070710 valerate Drugs 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D1/00—Containers having bodies formed in one piece, e.g. by casting metallic material, by moulding plastics, by blowing vitreous material, by throwing ceramic material, by moulding pulped fibrous material, by deep-drawing operations performed on sheet material
- B65D1/02—Bottles or similar containers with necks or like restricted apertures, designed for pouring contents
- B65D1/0207—Bottles or similar containers with necks or like restricted apertures, designed for pouring contents characterised by material, e.g. composition, physical features
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
- B65D65/38—Packaging materials of special type or form
- B65D65/46—Applications of disintegrable, dissolvable or edible materials
- B65D65/466—Bio- or photodegradable packaging materials
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2205/00—Polymer mixtures characterised by other features
- C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
- C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
- C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
Abstract
Disclosed herein is a biodegradable polymer blend comprising: (i) not less than 70% by weight of poly lactic acid; (ii) between 0.5% to 15% by weight of a first polyester having an average molecular weight of not more than 40,000 and a melt flow rate of greater than 7g/10 mins with 2.16kg at 80°C wherein the first polyester comprises polycaprolactone (PCL) or a linear polyhydroxy alkanoate (PHA); and (iii) between 0.5% to 15% by weight of a second polyester having an average molecular weight greater than that of the first polyester and a melt flow rate less than the first polyester wherein the second polyester comprises: polybutylene succinate (PBS), polycaprolactone (PCL), polybutylene succinate adipate (PBSA), polybutylene adipate (PBA), or polybutylene adipate terephthalate (PBAT). This fully degradable and a compostable polyester based blend is free from non- degradable organic or inorganic additives such as nucleating agents and the like. The thermal properties of the present blend are configured for optimised flow rate during process moulding via a 'flow rate enhancing component' being a relative low molecular weight biodegradable polyester. The blend also provides a resultant moulded article having the appropriate mechanical, physical and chemical properties including greatly improved toughness over existing PLA based blends. This is achieved by incorporating a 'toughening component' within the blend being a relatively high molecular weight component relative to the flow rate enhancing component. erein the first polyester comprises polycaprolactone (PCL) or a linear polyhydroxy alkanoate (PHA); and (iii) between 0.5% to 15% by weight of a second polyester having an average molecular weight greater than that of the first polyester and a melt flow rate less than the first polyester wherein the second polyester comprises: polybutylene succinate (PBS), polycaprolactone (PCL), polybutylene succinate adipate (PBSA), polybutylene adipate (PBA), or polybutylene adipate terephthalate (PBAT). This fully degradable and a compostable polyester based blend is free from non- degradable organic or inorganic additives such as nucleating agents and the like. The thermal properties of the present blend are configured for optimised flow rate during process moulding via a 'flow rate enhancing component' being a relative low molecular weight biodegradable polyester. The blend also provides a resultant moulded article having the appropriate mechanical, physical and chemical properties including greatly improved toughness over existing PLA based blends. This is achieved by incorporating a 'toughening component' within the blend being a relatively high molecular weight component relative to the flow rate enhancing component.
Description
BIODEGRADABLE POLYMER BLEND
The present invention relates to a biodegradable polymer blend and in particular a
polyester based blend comprising polylactic acid (PLA).
Polylactic acid (PLA) is a synthetic thermoplastic polyester, now readily available in large
volumes, used primarily for packaging applications. It has desirable environmental
credentials, as it is readily produced from sustainable (plant) feedstock, with lower carbon
footprint and non-renewable energy usage than any mineral thermoplastic, including 100%
recycled PET. In principle PLA can be recycled either by thermoplastic methods or by
hydrolytic cracking back down to monomer, although at present this is still only in
commercial development. Furthermore, the original commercial strength of PLA remains
in its moderately rapid biodegradation, by a two stage process consisting of hydrolysis to
low molecular weight oligomers, followed by complete digestion by microorganisms.
At room temperature PLA has high modulus and high strength, but very poor toughness.
This is due largely to its glass transition point which lies between 50°C and 60°C. In
certain applications this presents further problems due to deformation and loss in strength
under storage conditions in warmer climates. Solutions to these problems do exist by
control of polymer chemistry, producing copolymers and branched chains. With a remit of
producing a tougher, yet commercially viable thermoplastic which would still be
biodegradable in a similar manner, various approaches have been examined based on
thermoplastic compounding or blending.
Many researchers have examined the potential for nanoparticulate reinforcement of PLA,
with various objectives and degrees of success. Of relevance is work on nanoscale
biologically derived reinforcements, for example cellulose nano-whiskers [Bondeson D.,
Oksman K.,: “Polylactic acid/cellulose whisker nanocomposites modified by polyvinyl
alcohol”. Composites: Part A, 38, 2486–2492 (2007)]. A majority of work on PLA
nanocomposites has focused on improving strength and modulus. However, for many
thermoplastic applications this is largely irrelevant. Previous workers have also noted that
limited dispersion of inorganic nanoparticles has been shown to give considerable
improvement in toughness [Jiang L., Zhang J., Wolcott M.P., “Comparison of
polylactide/nano-sized calcium carbonate and polylactide/montmorillonite composites:
Reinforcing effects and toughening mechanisms”. Polymer, 48, 7632-7644 (2007)]. While
not strictly biodegradable, many inorganic nanoparticles are produced directly from
mineral sources and may be deemed inert when the surrounding polymer has broken down.
However, inorganic nanoparticles are generally recognised as requiring an organic surface
modification to render them compatible with thermoplastics. Current commercially
available materials are supplied with a thick layer of organic modifier which is not
biodegradable, and may partially dissolve in the matrix polymer causing concerns for food
contact materials. Finally, commercial supplies of nanoparticulates are so expensive that
they prohibit the use of any prospective composite for bulk applications such as packaging.
A more promising avenue of investigation lies in blending other thermoplastics with PLA.
Specific additives for PLA are already available, based on non-biodegradable, mineral
based thermoplastics. Researchers examining routes to produce a more compliant
polymeric material have examined the effects of fairly large volume fractions of other
biodegradable polyesters [ Todo M., Park S.-D., Takayama T., Arakawa K., “Fracture
micromechanisms of bioabsorbable PLLA/PCL polymer blends”. Engineering Fracture
Mechanics 74, 1872–1883 (2007); Wang R., Wang S.,, Zhang Y., “Morphology,
Mechanical Properties, and Thermal Stability of Poly(L-lactic acid)/Poly(butylene
succinate-co-adipate)/Silicon Dioxide Composites”. Journal of Applied Polymer Science,
113, 3630-3637 (2009); Jiang L., Zhang J., Wolcott M.P., “Study of Biodegradable
Polylactide/Poly(butylene adipate-co-terephthalate) Blends”. Biomacromolecules, 7, 199-
207 (2006)]. All have observed phase separation in the blended material and other workers
[Wang R., Wang S., Zhang Y., Wan C., Ma P., “Toughening Modification of PLLA/PBS
Blends via in situ Compatibilization”] have demonstrated that compatibilisers can
successfully be used to control the domain size of the minor phase, if necessary, to
improve performance. Considering an analogy to structural thermosetting resins, which
also generally operate in their glassy state, a small addition of a more compliant polymer
can greatly improve toughness. Many commercial epoxy resins incorporate a rubber or
thermoplastic which produces phase separated globules in the cured material. Certain
literature [Smith R., “Biodegradable Polymers for Industrial Applications” (2000) CRC
Press ISBN 03466-7] claims that most of the biodegradable polyesters are in fact
completely miscible with PLA and though this seems improbable, it does not dispute the
potential improvements in toughness.
Additionally, the patent literature includes a number of disclosures that describe
multicomponent PLA based degradable resins and examples include US 5,883,199; US
2005/0043462; US 2005/0288399; US 2008/0041810 and US 2010/0086718.
However, there remains a need for a PLA based biodegradable blend suitable for
manufacturing degradable articles such as bottles and the like having improved
mechanical, physical, chemical and thermal properties so as to be energy efficient during
processing of the blend to the finished article and to provide a finished article of the
required durability including in particular toughness. Of course, durability or toughness
does need to be optimised against those properties responsible for timely degradation of
the blend given the overriding objective to provide a fully biodegradable and in particular
compostable article.
Accordingly, the inventors provide a fully degradable and a compostable polyester based
blend that is free from non-degradable organic or inorganic additives such as nucleating
agents and the like. Accordingly, the present blend does not require secondary processing
that would otherwise be required. The present blend and the associated methods of
manufacture and moulding are therefore very energy efficient and environmentally
friendly.
The thermal properties of the present blend are configured for optimised flow rate
during process moulding to firstly extend the range of type and sizes of articles that may
be moulded and secondly to improve processing efficiency with regard to time and
energy consumption. Accordingly, the present blend comprises a ‘flow rate enhancing
component’ being a relative low molecular weight biodegradable polyester. The present
blend is also configured to provide a resultant moulded article having the appropriate
mechanical, physical and chemical properties including greatly improved toughness
over existing PLA based blends. This is achieved by incorporating a ‘toughening
component’ within the blend being a relatively high molecular weight component
relative to the flow rate enhancing component.
By selectively configuring the relative concentrations of the components and the type of
components, the inventors provide a formulation having certain optimised properties.
These include in particular: i) a required melt flow rate and macroscopic viscosity
during processing; ii) a resulting moulded article with a required toughness and a
tailored degradation rate so as to provide a desired shelf-life whilst being fully
degradable and in particular compostable, following use.
According to a first aspect of the present invention there is provided a biodegradable
polymer blend comprising: not less than 70% by weight of polylactic acid; between
0.5% to 15% by weight of a first polyester having an average molecular weight of not
more than 40,000 and a melt flow rate of greater than 7g/10mins with 2.16kg at 80°C;
wherein the first polyester comprises polycaprolactone (PCL) or a linear
polyhydroxyalkanoate (PHA); between 0.5% to 15% by weight of a second polyester
having an average molecular weight greater than that of the first polyester and melt
flow rate less than that of the first polyester; wherein the second polyester comprises
any one of: polybutylene succinate (PBS); polycaprolactone (PCL); polybutylene
succinate adipate (PBSA); polybutylene adipate (PBA); or polybutylene adipate
terephthalate (PBAT).
Preferably the ternary blend comprises not less than 85% PLA, or more preferably not
less than 90% by weight PLA. Preferably the blend comprises between 3% to 7% by
weight of the first polyester and between 3% to 7% by weight of the second polyester.
More preferably the blend comprises approximately 5% by weight of the first polyester
and approximately 5% by weight of the second polyester.
Preferably, the first polyester has an average molecular weight of not more than
25,000 or more preferably 15,000. Alternatively the first polyester may have an
average molecular weight of not more than 35,000. Preferably, the second polyester
has an average molecular weight of not less than 40,000 and more preferably
50,000.
Preferably, the first and second polyesters are substantially linear polyesters with no
or minimal branching of the main polymer backbone, and more preferably no side-
groups thereon.
Preferably, the PLA comprises L-polylactic acid, D-polylactic acid or a copolymer
of L and D-polylactic acid.
Preferably, the blend comprises a melt temperature in the range 180°C to 220°C.
Optionally, the first polyester may comprise a viscosity of less than 10 Pa.s at 100°C.
Additionally, the melt flow rate of the second polyester may be approximately
3g/10mins at 160°C; 2.7g-4.9g/10mins at 190°C or 15g/10mins at approximately 200°C.
Optionally, first polyester may comprise a thermoplastic polyester having a melting
point less than 100 °C and preferably less than 60 °C. Optionally, the first polyester may
comprise a viscosity less than 40 Pa.s at 100°C Pa.s at a shear rate of 1s and
temperature of 180 °C. More preferably, the first polyester may comprise a viscosity
less than 5 Pa.s at a shear rate of 1s and temperature of 180 °C.
Optionally, second polyester may comprise a thermoplastic polyester having a melting
point less than 160 °C. Optionally, the second polyester may comprise a viscosity
greater than 60 Pa.s at a shear rate of 1s and temperature of 180 °C. More preferably
the second polyester may comprise a viscosity greater than 1000 Pa.s at a shear rate of
1s and temperature of 180 °C.
Optionally, the PLA may comprise a melt point being substantially equal to, greater than,
or less than approximately 158 °C. Optionally, the PLA may comprise a viscosity being
substantially equal to, greater than, or less than 1500 Pa.s at a shear rate of 1s and
temperature of 180 °C.
According to a second aspect of the present invention there is provided a biodegradable
polymer blend comprising: not less than 70% by weight of polylactic acid; between 0.5%
to 15% by weight of a first polyester having a melt flow rate of greater than 7g/10mins
with 2.16kg at 80°C, wherein the first polyester comprises polycaprolactone (PCL) or a
linear polyhydroxy alkanoate (PHA); between 0.5% to 15 % by weight of a second
polyester having an average molecular weight greater than the average molecular weight of
the first polyester and melt flow rate less than that of the first polyester; wherein the second
polyester comprises any one of: polybutylene succinate (PBS); polycaprolactone (PCL);
polybutylene succinate adipate (PBSA); polybutylene adipate (PBA); or polybutylene
adipate terephthalate (PBAT).
Preferably, the majority of the blend comprises PLA and the two minor components
comprise PCL of relative low molecular weight and PBS as a relative high molecular
weight component relative to the PCL. This blend preferably comprises approximately
90% by weight PLA; 5% by weight PCL (at an average molecular weight of 10,000)
and 5% by weight PBS (at an average molecular weight of 50,000). Importantly, the
inventors have observed a surprising synergy by the addition of the two minor
components at their relative concentrations and molecular weights such that an
enhanced melt flow rate of the blend is achieved that is greater than the melt flow rates
of the three blend components when independent. From experimental investigation, this
synergy is thought to arise due to difference in the respective melt flow rates (and the
molecular weights) of the first polyester and the combination of PLA with the second
polyester.
Preferably, the blend comprises trace levels of additional components and is
substantially devoid of non-polyester compounds. Accordingly, any remaining weight
% comprises any one or a combination of the three blend components. Preferably, the
blend consists of substantially 90% by weight PLA; substantially 5% by weight PCL
and substantially 5% by weight PBS.
According to a third aspect of the present invention there is provided an article and in
particular a bottle, water bottle, water cooler bottle or container for foodstuffs or beverages
comprising a polymer blend as described herein. According to a fourth aspect of the
present invention there is provided a cap, lid or spray head for a bottle or container
comprising a polymer blend as described herein. The present blend is suitable for the
moulding of a plurality of different articles of varying wall thickness via a plurality of
different moulding processes with only minor or modest changes to the relative
concentrations of the three components and their respective molecular weights. According
to a fifth aspect of the present invention there is provided a film; a substantially flexible or
rigid planar film; a film sleeve; a document wallet; a packaging film; and/or a sheet
comprising the blend as described herein.
According to a sixth aspect of the present invention there is provided a method of
manufacturing a biodegradable polymer blend comprising: providing not less than 70%
(especially not less than 75%) by weight of polylactic acid; blending between 0.5% to 15%
by weight of a first polyester having an average molecular weight of not more than 40,000
and a melt flow rate of greater than 7g/10mins with 2.16kg at 80°C with the polylactic
acid, wherein the first polyester comprises polycaprolactone (PCL) or a linear polyhydroxy
alkanoate (PHA); blending between 0.5% to 15% by weight of a second polyester having
an average molecular weight greater than that of the first polyester and melt flow rate less
than that of the first polyester with the polylactic acid and the first polyester; wherein the
second polyester comprises any one of: polybutylene succinate (PBS); polycaprolactone
(PCL); polybutylene succinate adipate (PBSA); polybutylene adipate (PBA); or
polybutylene adipate terephthalate (PBAT).
Preferably, the method of manufacturing the biodegradable article comprises shaping
the blend into the article by any one of the following moulding processes: injection
moulding; compression moulding; blow moulding; thermal forming; vacuum forming;
extrusion moulding and in particular twin screw extrusion; calendaring; a polymer draw
processes. In a further aspect of the present invention there is provided a method of
manufacturing a biodegradable article from a polymer blend as described herein
comprising shaping the blend into the article by any one of the following moulding
processes:
injection moulding; compression moulding; blow moulding; thermal forming; vacuum
forming; extrusion moulding; calendaring; a polymer draw process.
Optionally, the process further comprises adding less than 1% by weight of carbon or
other particulates such as for example titania or silica with strong infrared absorbency
prior to the moulding process, in order to facilitate later reheating processes.
Preferably, the PLA, the first and/or second polyesters are homopolymers. Preferably,
the PLA, the first and second polyesters are blendable to provide a homogeneous
blended phase. Preferably, the PLA is substantially a linear polymer and in particular a
linear homopolymer.
Preferably, the present blend and any resulting article manufactured from the blend does
not include or is substantially devoid of a compatibilizing agent or surfactant, a
reinforcement compound and/or a plasticiser.
Optionally, the present blend and any resulting article manufactured from the blend may
comprise a relatively small amount of an additive to affect the physical, mechanical,
chemical, electrical and in particular, optical properties. Preferable, the blend comprises an
additive, a pigment, a dye included at not greater than 10%, 5% or 2% by weight and
optionally less than 1% by weight.
According to the experimental results described herein, improved properties (both in terms
of processing and in the final moulded products) are achieved by blending PLA with other
biodegradable polyester thermoplastics.
Specific embodiments of the present invention will now be described with reference to
examples and the accompanying drawings in which:
figure 1 illustrates mechanical test results for various binary blends based on 95%
by weight PLA with the 5% by weight polyester additive;
figure 2 is a photograph illustrating melt flow behaviour of specimens of the
binary blends of figure 1;
figure 3 is a summary of the mechanical and thermal test results for the different
binary blends of figure 1;
figure 4 illustrates scanning electron micrographs of the binary blends of figure 1;
figure 5 is a graph of the storage modulus and tan 8 for the different binary blends
of figure 1;
figure 6 is a graph of the loss modulus for the different binary blends of figure 1;
figure 7 is a graph of the storage modulus verses temperature for pure PLA at
three different frequencies;
figure 8 is a graph of crystallisation tests of various ternary blends according to
specific examples of the present invention;
figure 9 illustrates failure strain and melt flow results for ternary blends of figure
figure 10 is a 3D representation of the melt flow results for the ternary blends of
figure 9.
Blending of PLA with other commercially available biodegradable polymers was
investigated via two and three component blend formulations.
Raw Materials and Compositions
Blends were based on Natureworks Ingeo 7000D grade polylactic acid (PLA).
For the minor phase, four types of commercial biodegradable polymer were selected, of
which two were available in significantly different grades:
Polyhydroxybutyrate-co-valerate (PHBV) was obtained from Sigma Aldrich Ltd,
composition typically 8% valerate (this material is available in bulk quantities from
Biomer).
Polycaprolactone (PCL) was obtained from Perstorp Caprolactones, in two grades: Capa
6100, mean molecular weight 10000 (designated l-PCL); Capa 6800, mean molecular
weight 80000 (designated h-PCL).
Polybutylene succinate (PBS) was obtained from Zhejiang Hangzhou Xinfu
Pharmaceutical Co. Ltd in two grades: Biocosafe 1903, pure PBS for injection moulding
(designated h-PBS) with average molecular weight 50,000 and; Biocosafe 2003, modified
PBS for film blowing (designated l-PBS).
Polybutylene adipate-co-terephthalate (PBAT) was obtained from BASF; tradename
Ecoflex grade FBX7011.
All measurements reported and discussed herein were made on material dried in a manner
which should result in less than 200ppm moisture content.
Binary Blends
To investigate the physical and mechanical properties of adding various additional
polyester components to PLA the following binary blends were investigated:
1. PLA at 90% by weight and PHBV at 5% by weight;
2. PLA at 90% by weight and h-PCL at 5% by weight;
3. PLA at 90% by weight and l-PCL at 5% by weight;
4. PLA at 90% by weight and h-PBS at 5% by weight;
5. PLA at 90% by weight and l-PBS at 5% by weight;
6. PLA at 90% by weight and PBAT at 5% by weight.
Test data was for blends of PLA with each of the six additives. Pure PLA reference
material (designated PLA0) was also investigated under the same compounding process to
ensure a calibrated comparison with pure material subject to the same thermal and shear
history.
Compounding and Moulding
Raw materials were dried in a vacuum oven at 50°C for a minimum of 5 days prior to
compounding. Batches of 150g were weighed into sealable bags and tumble mixed prior to
compounding.
Blending was conducted using a Prism twin screw extruder with counter rotating 250mm
screws, 16mm in diameter, with a diameter ratio of 15. Screw speed was set at 100rpm. For
all blends the following temperature profile was utilised: feed section 160°C, mixing
section 190°C, metering section at 185°C. The compounded polymers were drawn off as
thick filament, cooled in a water bath, and chopped to produce a fine moulding chip, which
was collected then immediately dried in a vacuum oven.
For mechanical and dynamic tests, standard dumb-bell specimens were injection moulded
with a gauge length of 25mm; cross section 2mm x 4mm. A Haake Minijet II injection
moulder was used, with a barrel temperature of 215°C, nozzle pressure of 600bar, and
mould temperature of 40°C. A typical charge of 6.2g provided sufficient material to mould
3 specimens and took 5 minutes to melt.
Moulded specimens were aged prior to test for 5 days in ambient conditions of 45 ± 5
%RH at 22 ± 2°C.
Mechanical and Dynamic Testing
Tensile tests were conducted at a crosshead speed of 50mm/minute, on a minimum of 5
specimens per composition.
Dynamic mechanical thermal analysis (DMTA) was performed between room temperature
and 150°C using a Perkin Elmer DMA8000, running a temperature ramp rate of
2°C/minute. Dual cantilever specimen geometry was used with free length of 5mm, using
the gauge section of injection moulded specimens as detailed above. Glass transition was
determined as the onset of the drop in storage modulus. This gives a worst case value of
the temperature at which significant deformation may start to occur under load, for most
applications.
To examine the effect of the second phase on post-crystallisation of PLA, the DMTA test
was repeated on specimens which were heat treated to induce maximum crystallisation.
Specimens were placed in an air circulating oven at 100°C for one hour, then removed and
allowed to cool to room temperature before cropping and loading into the instrument.
Melt Flow Assessment
Melt flow rheometry was conducted using an adaptation of the Haake Minijet II, using its
standard die: diameter 4mm, length 18mm. Applied force was measured for constant piston
speed of 400mm/minute at 190°C. Taking the steady state load from this test, the Hagen-
Poisselle equation for fluid flow through a pipe was used to estimate the steady state flow
at a fixed load of 21.6N in the shorter, narrower die (diameter 2.095mm, length 8mm) as
specified by BS EN ISO 1133. This is only an approximate conversion since end effects
cannot be easily accounted for, nor can the compressibility and potential turbulence of the
melt. However this approach did provide usefully comparable figures, which were
approximately commensurate with the manufacturer's specification for pure PLA.
Electron Microscopy of Phase Structure
Specimens were prepared by cryofracture after cooling in liquid nitrogen, again using the
gauge section of injection moulded dumb-bells. The specimens were mounted on an
aluminium stub using epoxy resin and sputter coated with gold. While the coating was
detrimental to the size of features which can be observed, this was necessary to prevent the
build up of surface charge, as well as ablation or volatilisation from the surface. An Inspect
field emission gun secondary electron microscope (FEGSEM) was used to examine the
samples, providing typical resolution of 10nm.
Tensile Test Results
Results of tensile tests are illustrated in figure 1 and tabulated in table 1, with observations
on transparency of blended material.
Table 1: Tensile test results for 5% phase separated composites with PLA matrix
Sample Peak Stress Drawing Stress Strain at Modulus Clarity
(MPa) (MPa) Break (GPa)
70.2 ± 1.0 n/a 12 ± 1 0.926 ± 0.026 Transparent
PLA0
PHBV 72.0 ± 0.3 n/a 11 ± 1 1.013 ± 0.048 Transparent
h-PBS 68.1 ± 0.4 31.6 ± 0.7 110 ± 100 0.810 ± 0.031 Transparent
l-PBS 67.3 ± 0.0 29.4 ± 0.6 142 ± 44 0.711 ± 0.024 Translucent
h-PCL 67.9 ± 1.1 31.1 ± 1.0 75 ± 50 0.920 ± 0.040 Transparent
l-PCL 62.7 ± 1.3 24.4 ± 0.9 19 ± 8 0.862 ± 0.025 Translucent
PBAT 69.1 ± 0.7 31.2 ± 0.4 116 ± 63 0.723 ± 0.035 Opaque
Dynamic Mechanical Thermal Analysis
DMTA tests did not reveal any significant change in the modulus of the phase separated
composites compared with the pure PLA reference material. As will be noted in table 2
below, the glass transition shows only slight variation between compositions in the as-
moulded condition. The effects of post-crystallisation are more significant in the composite
specimens; the retention of modulus above transition is much higher. As might be
expected, post crystallisation reduced the drop in modulus over the glass transition from in
excess of two orders of magnitude, to little over one order of magnitude.
Table 2: Glass transition and modulus above transition as determined by DMTA
Sample Tg Tg Modulus at 85°C Modulus at 85°C
as moulded post-crystallised as moulded post-crystallised
(°C ± 0.2) (°C ± 0.2) (MPa ± 0.1) (MPa ± 0.1)
PLA0 46.9 49.1 6.8 38.5
PHBV 45.7 50.4 6.8 34.0
h-PBS 45.7 50.3 6.8 40.3
l-PBS 46.9 50.8 6.8 40.3
h-PCL 47.0 50.7 6.8 42.5
l-PCL 46.4 50.8 6.8 38.3
PBAT 47.5 50.9 6.8 60.2
Melt Flow Rate
The effects of a second phase on melt flow are illustrated in figure 2 and tabulated in table
3. The introduction of a second phase effectively acted in the same manner as a particulate
loading, increasing the overall viscosity of the system (therefore lowering the melt flow
rate). One exception was found in the low molecular weight PCL, which significantly
increased MFR; this implies decreased bulk viscosity. A summary of the mechanical and
thermal test results are illustrated in figure 3.
Table 3: Melt flow characteristics (converted to estimated MFR)
Sample Calculated MFR (2.16kg)
PLA0 4.18 ± 0.10
PHBV 4.20 ± 0.05
h-PBS 3.89 ± 0.18
l-PBS 3.63 ± 0.04
h-PCL 3.89 ± 0.18
l-PCL 4.85 ± 0.14
PBAT 3.18 ± 0.30
Phase Structure
Micrographs of the cryofractured surfaces showing phase separated blends are shown in
Figure 4. The blends in the left hand column show a low density of widely separated minor
phase particles; this fits well with their good optical transparency recorded earlier. By
comparison, the three blends which form the right hand column have a high density of
small globules of the minor phase. In the case of l-PBS and PBAT these are at the limit of
features which can be resolved under the gold coating and are apparent largely as a more
textured surface at the magnification presented.
Table 4 shows typical globule sizes of the second phase determined from micrographs and
the volume fraction. In all cases the volume fraction is significantly less than 5%. Given
that the density of all six additives is within 8% of PLA, a large proportion of the minor
phase is clearly dissolved in the PLA.
Table 4: Phase separation and transparency of 2-phase blends at 5% additive
Composition Typical globule Volume fraction Transparency
size separated (10 = equals pure PLA
1 = completely opaque)
PHBV 5% 630 nm 0.10 % 10
HPBS 5% 350 nm 0.01 % 9
LPBS 5% 310 nm 2.55 % 2
HPCL 5% 590 nm 0.03 % 9
LPCL 5% 240 nm 0.44 % 5
PBAT 5% 280 nm 2.37 % 1
Binary Blend Effects
All the binary polymer blends examined were found to form polymer-polymer composites
with a low volume fraction of the minor phase. In all cases the composites exhibited
improved elongation at break which may be attributed to combined effects of plasticisation
and rubber toughening due to the minor phase globules whose glass transition points are
significantly below room temperature. It is probable that a degree of control may be
exerted over the dissolved proportion of the minor phase, by varying the processing
temperature and dwell time.
With the exception of PHBV as a minor phase, the modulus and strength of the composites
is lower than that of pure PLA. Since PLA has very high modulus and strength compared
with other commodity thermoplastics, at room temperature, this is of little concern for
many applications.
It is particularly interesting to contrast the behaviour of the low molecular weight PCL.
Here the increase in elongation at break is relatively trivial, but the MFR has been
significantly increased. The micrograph of cryofractured surface shows that the minor
phase globules are smaller than the cavities in which they sit, indicating considerable
mismatch in thermal expansion. This would suggest the l-PCL additive has a much lower
melt density. It is proposed that since it is less readily miscible than other additives, the
very low density and viscosity of the l-PCL allows a lubricant effect which dominates the
increase in bulk viscosity which might be expected with the addition of any dispersed
phase in the melt.
The polyesters blended with PLA are all readily biodegradable thermoplastics and once
blended with PLA form phase separated composites. Limited solubility of the minor phase
results in a dispersion of minor phase globules. The bulk material is toughened in the solid
state and the effect of post crystallisation on glass transition and modulus in the high
elastic regime is enhanced when compared with pure PLA.
Tensile tests (illustrated in figures 1, 3, 5 to 9) were conducted at a moderately high
extension rate of 50mm/minute. The mechanical results show the effect of the additives on
stiffness and strength of the composite and are indicative of changes in the behaviour of
the material.
A melt flow rate test was also conducted to check for any severely adverse effects on the
processability of the material during moulding and the results are illustrated in figures 1 to
3, 9 and 10. Figure 4 clearly shows different levels of phase separation for the different
additives. Under higher magnification it is possible to resolve a high density of much
smaller second phase globules in LPBS and PBAT compositions.
Image analysis gives greater insight into the meaning of these morphologies. Table 4
shows that the highly transparent blends have very little phase separation. Logically this
makes good sense, since the globules are present in only very low density, with sizes
around the wavelength of visible light. The opacity of the remaining blends seems slightly
surprising, since the globules are noticeably smaller than visible wavelengths, and still in
relatively low density. The implication of this is that the polymer has higher crystallinity
throughout.
DMA was used to examine the effects of the additive on glass transitional behaviour of the
composite. A standard testing regime was employed with specimens prepared by injection
moulding and aged for one week in ambient conditions, then tested in dual cantilever
loading at 3 frequencies.
This confirmed that the polymer-polymer composites produced by blending had
commensurate thermal performance with the pure PLA. Key features to note from figures
and 6 include:
The storage moduli confirm that the onset of transition is largely unaffected, but
PHBV has depressed it by 2 °C, while PBAT has raised it by 5 °C.
The peaks in tan δ traces indicate that the primary transition point has been raised
by up to 5°C by the additives.
The loss modulus shows a split peak, even in pure PLA implying that two
conformations are present. These peaks are generally broadened in the composites,
suggesting that the minor component (the dissolved polyester additive) is
plasticising the major component PLA.
The higher temperature peak in loss modulus becomes more dominant with most
additives and is shifted up in temperature. For PBAT this is particularly strong, the
second, lower peak having almost disappeared.
DMA results indicated improved thermal performance in the 2-phase polymer-polymer
nanocomposites over pure PLA. The traces in figure 5 would generally be considered the
usual way of examining the data, but in seeking to verify offset points for glass transition
behaviour, it became apparent that crystallisation started to occur shortly above the glass
transition. Literature confirms that this would be expected in PLA, but has not been
observed in this manner before.
Viewing a trace for pure PLA in logarithmic scale, it was noted that the storage modulus
increases again just after transition, as seen in figure 7. It is to be noted that this is data for
3 frequencies, indicating that the glass transition is time dependent, but the subsequent
stiffening is not. Accordingly this provides confirmation that the phase change observation
is crystallisation. It is unusual that the physical manifestation of this phenomenon is
observable in the stiffness from about 90 °C, yet tan δ (of figure 5) shows nothing until a
sharper peak around 110 °C. The tan δ trace of figure 5 is in closer agreement with DSC (a
standard method of determining crystallisation point).
Referring to figure 8, and examining the data of all the test blend specimens in this manner,
it appeared that certain blends stiffened more rapidly than others. A series of isothermal
tests were conducted to examine the difference in crystallisation rate. The different binary
blend specimens were then re-tested in the usual manner, revealing that crystallisation
significantly improves the stiffness and thermal stability. Crystal melt point was observed
around 140 °C, suggesting that a deliberately crystallised material might well retain
adequate handling strength even in contact with boiling water.
Relative to unblended PLA, the crystallisation rate at 85 °C is increased by a factor of
eight, and the hot stiffness magnified by an order of magnitude. There are two main
implications of this:
care must be taken to achieve adequately rapid cooling and reheating of the
performs;
the blends exhibit good potential for use as thermoplastics for re-useable consumer
products such as bottles and in particular water cooler bottles amounts other
products.
Ternary Blends
Given the surprising effect of l-PLC in improving melt flow rate, ternary phase blends
were investigated by adding an additional third component h-PBS, which gave the best
improvement in toughness while retaining transparency. It was proposed that this could
give better processability and toughness, as well as strong patentability, in one family of
blends.
Since the very low molecular weight PCL may be inconvenient for compounding at a
commercial scale, a slightly higher molecular weight product was also tested, which can be
supplied as moulding chip. The affect of addition of this third phase component was
evaluated by the same tensile and melt flow analysis described with reference to the binary
blends. Although transparency is adversely affected with total additions much above 5%, it
is believed that this would be tolerable up to 10% or even higher total additive level.
Using the same chemicals and testing analysis employed for the two component systems,
the three phase blends investigated were:
1. PLA at 94% by weight with h-PBS at 5% by weight and l-PCL at 1% by weight;
2. PLA at 93% by weight with h-PBS at 5% by weight and l-PCL at 2% by weight;
3. PLA at 90% by weight with h-PBS at 5% by weight and l-PCL at 5% by weight;
4. PLA at 85% by weight with h-PBS at 5% by weight and l-PCL at 10% by weight;
. PLA at 89% by weight with h-PBS at 10% by weight and l-PCL at 1% by weight;
6. PLA at 88% by weight with h-PBS at 10% by weight and l-PCL at 2% by weight.
7. PLA at 85% by weight with h-PBS at 10% by weight and l-PCL at 5% by weight;
8. PLA at 80% by weight with h-PBS at 10% by weight and l-PCL at 10% by
weight;
Ternary Blends Effects
From figure 9, it can be seen that higher l-PCL addition adversely affects toughening, and
that the higher molecular weight l-PCL is less effective at improving melt flow. However,
from figure 9 and particularly figure 10, it is to be noted that some synergy is achieved in
melt flow with 5% h-PBS and above 5% l-PCL (through to 10% l-PCL as confirmed by the
results but possibly even higher by extrapolation). At and around these component
concentrations the improvement in melt flow is much greater. This surprising and
advantageous effect may be due to the h-PBS being more readily soluble and increasing
the proportion of l-PCL which remains phase separated.
Preliminary results from first attempts at preform production have confirmed that it is
necessary to pre-blend the additives with the PLA. In particular, good blending is
important to the processability of the material in injection stretch blow moulding (ISBM)
processes. The crystallisation behaviour of the polymer-polymer nanocomposites
developed will also be beneficial in other applications. Additionally, the freshly moulded
material has a higher heat deformation resistance than pure PLA and preliminary tests
indicate that if it were to be deliberately crystallised, an acceptable strength level could be
retained up to 140 °C. In summary, toughening can be achieved either in a phase separated
polymer-polymer composite or by the plasticising effect of a dissolved second phase, but
normal compounding operations result in a hybrid of these two effects.
According to further testing, the moulded preforms are configurable to exhibit a strictly
finite and desired shelf-life when produced for example by bottle blowing processes.
Additionally, ageing effects in contact with chemicals do not appear to affect the physical,
mechanical and chemical properties so as to change the toughness, predetermined shelf-life
or degradation rate of the moulded articles. Accordingly the present blend is suitable for
use in the manufacture of degradable, and in particular compostable, bottles and containers
for chemicals and packaging and containers in direct contact with foodstuffs and
beverages. Heat resistant products (for example re-useable plastic plates, cups and cutlery)
are also achievable using the present blends due, inter alia, to the increased rate of
crystallisation and the resulting hot stiffness of the blend relative to unblended PLA.
Claims (22)
1. A biodegradable polymer blend comprising: not less than 70% by weight of polylactic acid; between 0.5% to 15% by weight of a first polyester having an average 5 molecular weight of not more than 40,000 and a melt flow rate of greater than 7g/10 mins with 2.16kg at 80°C; wherein the first polyester comprises polycaprolactone (PCL) or a linear polyhydroxyalkanoate (PHA); between 0.5% to 15% by weight of a second polyester having an average 10 molecular weight greater than that of the first polyester and a melt flow rate less than that of the first polyester; wherein the second polyester comprises any one of: • polybutylene succinate (PBS); • polycaprolactone (PCL); 15 • polybutylene succinate adipate (PBSA); • polybutylene adipate (PBA); or • polybutylene adipate terephthalate (PBAT).
2. The blend as claimed in claim 1 comprising not less than 85% by weight 20 of polylactic acid.
3. The blend as claimed in claim 1 comprising not less than 90% by weight of the polylactic acid. 25
4. The blend as claimed in any one of the preceding claims comprising between 3% to 7% by weight of the first polyester.
5. The blend as claimed in any one of the preceding claims comprising between 3% to 7% by weight of the second polyester.
6. The blend as claimed in any one of the preceding claims wherein the first polyester has an average molecular weight of not more than 15,000.
7. The blend as claimed in any one of the preceding claims wherein the first polyester has an average molecular weight of not more than 35,000.
8. The blend as claimed in any one of the preceding claims wherein the second polyester has an average molecular weight of not less than 50,000.
9. The blend as claimed in any one of the preceding claims wherein polylactic acid 10 comprises L-polylactic acid, D-polylactic acid or a copolymer of L and D-polylactic acid.
10. The blend as claimed in any one of the preceding claims comprising a melt temperature in the range 180°C to 220°C. 15
11. A biodegradable polymer blend comprising: not less than 70% by weight of polylactic acid; between 0.5% to 15% by weight of a first polyester having a melt flow rate of greater than 7g/10 mins with 2.16kg at 80 C, wherein the first polyester comprises polycaprolactone (PCL) or a linear 20 polyhydroxy alkanoate (PHA); between 0.5% to 15 % by weight of a second polyester having an average molecular weight greater than the average molecular weight of the first polyester and a melt flow rate less than that of the first polyester, wherein the second polyester comprises any one of: 25 polybutylene succinate (PBS); polycaprolactone (PCL); polybutylene succinate adipate (PBSA); polybutylene adipate (PBA); or polybutylene adipate terephthalate (PBAT).
12. An article comprising a polymer blend as claimed in any one of the preceding claims.
13. A bottle comprising the polymer blend as claimed in any one of claims 1 to 11.
14. A container for foodstuffs or beverages comprising a polymer blend as claimed in any one of claims 1 to 11.
15. A cap, lid or spray head for a bottle or container comprising a polymer blend as claimed in any one of claims 1 to 11.
16. A sheet like article comprising any one or a combination of the following set of: 10 a film; a substantially flexible or rigid planar film; a film sleeve; a document wallet; a packaging film; 15 a sheet; comprising a polymer blend as claimed in any one of claims 1 to 11.
17. A method of manufacturing a biodegradable polymer blend comprising: providing not less than 70% by weight of polylactic acid; 20 blending between 0.5% to 15% by weight of a first polyester having an average molecular weight of not more than 40,000 and a melt flow rate of greater than 7g/10 mins with 2.16kg at 80 C with the polylactic acid, wherein the first polyester comprises polycaprolactone (PCL) or a linear polyhydroxy alkanoate (PHA); blending between 0.5% to 15% by weight of a second polyester having an average 25 molecular weight greater than that of the first polyester and a melt flow rate less than that of the first polyester with the polylactic acid and the first polyester; wherein the second polyester comprises any one of: polybutylene succinate (PBS); polycaprolactone (PCL); polybutylene succinate adipate (PBSA); polybutylene adipate (PBA); or polybutylene adipate terephthalate (PBAT).
18. The method of claim 17, wherein the method comprises providing not less than 75% by weight of polylactic acid.
19. A method of manufacturing a biodegradable article from the polymer blend according to any one of claims 1 to 11 comprising shaping the blend into the article by any one of the following moulding processes: 5 injection moulding; compression moulding; blow moulding; thermal forming; vacuum forming; 10 extrusion moulding; calendaring; a polymer draw process.
20. The method as claimed in claim 19 wherein the moulding process comprises 15 injection moulding or blow moulding and the process further comprises adding less than 1% by weight of carbon or other particulates with strong infrared absorbency prior to the moulding process.
21. The blend as claimed in claim 1 or 11, substantially hereinbefore described with 20 reference to any one of the examples.
22. The method as claimed in claim 17, substantially hereinbefore described with reference to any one of the examples.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB201104018A GB2488811B (en) | 2011-03-09 | 2011-03-09 | Biodegradable polymer blend |
GB1104018.5 | 2011-03-09 | ||
PCT/GB2012/050525 WO2012120309A2 (en) | 2011-03-09 | 2012-03-09 | Biodegradable polymer blend |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ614394A NZ614394A (en) | 2014-10-31 |
NZ614394B2 true NZ614394B2 (en) | 2015-02-03 |
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