NZ239123A - Biodegradeable polymer blend comprising a copolymer containing 3-hydroxy - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £391 £3 231123 Priority Dste{3): 71'.*?S5...........

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COMPLETE SPECIFICATION ■POLYMER BLENDS" We, IMPERIAL CHEMICAL INDUSTRIES PLC, a British Company, of Imperial Chemical House, Mill bank, London SW1P 3JF, England; and ICI AMERICAS INC., a Corporation organised under the laws of the State of Delaware, United States of America, of Concord Pike and New Murphy Road, Wilmington, Delaware 19897, United States of America, hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- (followed by page la) 1Q Polymer Blends This invention relates to biodegenerable polymer blends comprising 3-hydroxybutyrate copolymer.

There is an increasing need for plastics materials which 5 degenerate after use to environmentally acceptable waste products when in contact with microbiologically active systems such as soil, compost, activated sludge and sediment. •' Conventional plastics materials containing synthetic polymers such as low density polyethylene (LDPE) and ethylene 10 vinyl acetate (EVA) generally do not degenerate, i.e. disintegrate or degrade, through microbiological action in time periods of less than five years.

An LDPE-containing biodegenerable composite comprising LDPE and starch has been proposed. When in the form of a film, it is 15 believed that the composite is degenerable by microbiological action within five years. Unfortunately, high levels of starch have been shown to be required before a suitable biodegenerable composite is obtained. The presence of high levels of starch have an unacceptable detrimental effect on the physical and 20 processing characteristics of the composite. An ethylene-acrylic acid copolymer has been used to improve the physical properties of LDPE-starch composite, but only at low starch levels, at which levels the composite is not suitably biodegenerable.

We have found that a biodegenerable plastics composition 25 having satisfactory physical properties comprises a microbiologically produced copolymer comprising 3-hydroxybutyrate and at least one of polyethylene, polypropylene, polystyrene, and an ethylene copolymer.

Accordingly to the invention a biodegenerable plastics 30 composition comprises at least one synthetic polymer selected from the class consisting of polyethylene, polypropylene, polystyrene and ethylene copolymer blended with 10 to 90% w/w on said composition of a biodegradable material, at least 20 % w/w of which is a microbiologically produced copolymer "PHBV" ^ containing 3-hydroxybutyrate and 3-hyflroxyvalerate. 7 £ ^^5 v 23dEC19932j tih 2 3^ ISO 2 Preferably the biodegradable material represents between 20 and 50 % w/w of the composition and at least half thereof is said microbiologically produced copolymer. Compositions showing particularly good biodegenerable characteristics contain at least 20% w/w of said microbiologically produced copolymer.

The ethylene copolymer may be one or more copolymers of ethylene with one or more carboxylic derivatives of ethylene, especially acrylic acid, methacrylic acid, maleic anhydride, ethyl acrylate and vinyl-acetate (EVA). A particularly preferred ethylene copolymer is EVA, especially containing 5 to 30 w/w % of vinyl acetate on the total of ethylene and vinyl acetate as illustrated in Examples 3 and 4 below. The EVA preferably has a melt index (ASTMD 1238) in the range 1.0 to 5.0, especially 1.5 to 3.5, g/10 min. It is advantageous for some uses to provide the EVA as a mixture with wax grade EVA in proportions in the range 90:10 to 40:60.

The composition , especially if containing high levels (at least 20% w/w) of microbiologically produced copolymer may also contain one or more biodegradable or environmentally acceptable improvers to optimise characteristics in respect of particular uses. Such improvers include plasticisers, processability improving agents and toughening agents. Examples of such plasticisers are glycerol triesters such as triacetin, glycerol tributyrate and glycerol tricaproate, in particular triacetin. An example of a biodegradable toughening agent is a crystalline polyester such as polycaprolactone.

The composition may also contain at least one biodegradable filler such as starch or cellulose, and/or environmentally acceptable filler such as calcium carbonate or talc.

The presence of at least one improver and/or filler is particularly preferred where the total biodegradable material represents at least 40 % w/w of the composition; and then it is particularly preferred that the microbiologically produced copolymer represent 35 to 65 % w/w of said biodegradable material.

I 3 The physical properties of the composition may be altered by varying the relative proportions of the constituents. Thus, the Young's Modulus of such plastics compositions may vary between 70 and 225 (MPa), the Flexural Modulus may vary between 200 and 500 (Mpa), and the Extension at Break may vary between 50 and 500%. Particularly useful plastics compositions exhibit physical properties within at least two of the above ranges.

Particularly useful compositions comprising a binary blend of said biodegradable material with EVA contain between 5 and 50%, particularly between 10 and 40%, w/w of EVA.

A particularly useful composition comprises a ternary blend of (1) said biodegradable material, (2) at least one polymer selected from polyethylene, polypropylene and polystyrene, and (3) ethylene copolymer as hereinbefore defined. A particularly preferred such composition comprises said biodegradable material, polyethylene and EVA. The preferred such composition contains between 5 and 30 % w/w polyethylene (especially low density polyethylene) LDPE, and between 5 and 20 % w/w of EVA.

The microbiologically produced copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate herein termed PHBV, may include minor proportions of other oxy-alkanoate residues. The PHBV copolymers show better compatibility with LDPE and EVA as compared with PHB homopolymer. Especially preferred are PHBV copolymers containing at least 2 especially at least 4, mol % of 3-hydroxyvalerate, and more particularly those copolymers containing 3 and 25, especially between 5 and 15, mol %.

The molecular weight of the PHBV in the composition is preferably at least 300000, especially at least 500000 and up to the limit of convenient processability, for example 1.5 million. Such molecular weights are characteristic of the polymer as now available commercially.

The composition may additionally contain one or more components such as fibrous fillers (which may be biodegenerable), pigments, anti-oxidants (other than those inhibiting iodegeneration), antistatic agents, stabilisers, foaming agents, 9 c o 7 1 slip agents, antiblocking agents and others commonly used in plastics processing. To facilitate processing and development of crystallinity of the PHBV, the composition may contain a nucleating agent as described below.

In all, the choice of constituents and their proportions is preferably such that articles made from the composition are denser than fresh water. For the purpose of this invention, the density of fresh water is defined as 1 gem 3 at 3.98°C or 0.99823 gem"3 at 20°C which is the definition of pure water free from air given in The Handbook of Chemistry and Physics, Ed. Weast, 70th ' Edition, 1989-1990, CRC Press. This density is preferred to allow the compositions to sink in fresh water.

The invention provides also methods of making the composition by mixing the constituents in conditions in which at 10 least one of its polymeric constituents is at least partly in liquid form. Examples of such methods are solution blending, slurry blending and melt blending. Preferably the constituents of the mixture are mechanically worked together, for example by screw-extrusion, roller-milling or kneading. The product of 15 such mechanical working is typically formed into granules suitable for processing to shaped articles. The molecular weight of the microbiologically produced copolymer as introduced is preferably at least 500000, especially at least 800000, to allow for a decrease during melt processing. The mixture may contain 20 processing aids such as one or more nucleating agents; and processing conditions are chosen preferably so as to maximise the development of crystallinity, to exploit this known property of the PHBV copolymer. Examples of nucleating agents are boron nitride, calcium carbonate and metal soaps such as zinc stearate. 25 In a further aspect the invention provides a process of making a shaped article by confining the composition to shaping surfaces. Methods of confining include casting from melt into a surface or in a mould, injection moulding , blow moulding and extrusion. A particularly useful method comprises extrusion of 30 melt through a flat or circular die to give a flat or tubular film. The film may be subjected to stretching in the extrusion direction or transversely thereto or both, possibly with application of heat; for tubular film such stretchings may be effected at least partly by pneumatic pressure. As a sub-genus 2,3^ la_3 of extrusion through a circular due to give tubular film, the method may employ a die with a rotating dentate core and/or stator, so that a tubular net results. The tube or net may be slit to produce sheet. Processing is e.g. at 100-200°C.

In a yet further aspect the invention provides shaped articles made of the composition and compound structures comprising one or more such articles. Such shaped articles include substantially rigid articles such as vessels, pipes and pipe fittings, and flexible articles e.g. films, sacks, fibres and tubes of thickness typically in the range 0.001 to 1mm especially up to 0.1mm; and also nets of thread thickness typically in the range 0.01 to 1mm. Compound structures include especially combinations of such film, sack or tube or net with wood pulp, cellulose fibres or fibres of microbiologically produced copolymer such as PHB, PHBV and, indeed, compositions according to the invention. Particular structures include disposable diapers, tampons and wound dressings.

The invention may be further illustrated by reference to the following examples, in which percentage compositions are by weight unless otherwise stated and MI denotes the melt index in g/10 min according to ASTMD 1238.

EXAMPLE 1 A series of compositions was prepared comprising at least two of the following ingredients: PHBV of 15 or 22 mol % 3-hydroxyvalerate.

EVA of VA content 19% w/w, MI 23 g/10 min ("MICROTHENE" MV 769-00 ex Quantum Chemicals).

EVA wax AC400 ex Allied Chemicals (viscosity 610 cps at 140°C).

LDPE of MI 6g/10 min ("MICROTHENE" MN72200 ex Quantum Chemicals).

The compositions were injection moulded into ASTM D356 impact and D638 tensile bars. Physical properties were determined approximately 1.5 months after moulding.

Flexural Modulus (3 point bend) represents the average value obtained from 4 replicates as determined on an Instron 1122, using a span length of 67 mm, and a crosshead speed of 5mm.min \ Tensile properties represent the average obtained from 5 replicates as determined on an Instron 1122, using a gauge length -i tpjof 10 mm and a crosshead speed of 10 mm.min 2.3°l 1*2-3 6 Izod impact strength (1 mm notch radius) represents the average obtained from 5 replicates as determined using a Zwick pendulum impact testing machine.

Weight loss is as determined on samples left in contact with microbiologically active soil for 79 days; under such conditions 20 a sample of homopolymer of 3-hydroxybutyrate showed an 18% loss in weight. 23°\ 12-3 TABLE 1 7 i LDPE EVA PHBV HV FLEX.

YOUNGS STRESS EXTEN.

IMPACT WEIGHT a O, "o % o, *o (2) MOD.

MOD. @ e (J.m"1) LOSS % (1) BREAK BREAK % (3) (MPa) (MPa) % 100 0 0 0 265 84 19.5 133 * - 0 100 0 0 0 245 82 21.8 164 * - - 100 0 0 0 285 77 18.2 148 * - - 60 40 22 588 203 .4 22 43 - - 50 50 22 668 230 .9 19 38 - - 60 40 499 195 9.4 63 .9 70 441 169 9.4 78 9.13 -2 80 420 152 .1 51 105 .68 3.5 70 213 58 2.4 564 208 - - 40 377 121 3.5 125 141 - - 40 330 102 0.3 283 188 - - 50 363 119 7.4 61 94 - - 40 40 22 403 122 1.9 97 85 - - 40 22 306 121 6.6 61 64 - - 50 333 121 7.4 70 112 - - 60 395 149 .1 60 86 - - 40 233 62 .3 91 240 1.7 0 40 278 93 .0 72 60 .2 0 40 263 93 .9 49 64 - - 40 40 347 128 7.1 56 55 .96 40 40 326 122 8.0 49 51 - - 50 40 421 159 9.6 39 47 8.46 4.5 80 22 162 47 9.8 -- 174 - - 40/20 40 22 403 122 1.9 97 85 - - 60 10/10 337 104 9.1 130 266 - 60 10/10 22 304 102 .2 85 245 - - 20/20 40 22 258 91 7.2 36 38 - - 30/10 40 22 348 112 7.3 38 50 - (1) double entry indicates the percentages of EVA and EVA .-/LI EN/- /'<t * V z — n \ "2 AUGi99i v 23 °\ (2-3 8 (2) HV indicates the mol % of 3-hydroxyvalerate in the PHBV copolymer.

* Sample failed to break. (3) Indicates change in force at break.

It is evident that significant biodegeneration takes place, despite the presence of LDPE and/or EVA. However, it was observed also that exposure to soil caused only slight loss in mechanical strength.

EXAMPLE 2 The following polymer ingredients were used: PHBV containing 14 mol % of HV units, with 10 phr of triacetin plasticiser; EVA of MI 3.0 ml/10 min, 18% w/w VA. (CIL 1820) LDPE CIL type 209 Various compositions % w/w were blown into films,by the conventional bubble method. Mechanical properties were measured and the biodegenerability of the films was assessed after 56 days' contact with a microbiologically active soil.

TABLE 2 % 50 100 YIELD BREAK ELONG DENSITY WEIGHT EVA PHBV STGTH STGTH ACTION KG M~3 LOSS % % MPa MPa % % 50 50 MD 9.5 .4 479 TD 10.9 19.8 487 Over 1.0 41.7 75 MD 7.8 22.1 560 TD 6.4 14.2 476 995-1000 .1 - • 50 - - - - 41.1 80 - - - - 81.4+ - - 9.0 14.0 650 919 0.0 - _ _ 100.0 LOSS % 23.1 - 7.8 40.5 100 -26 100 * MD + machine direction; TD - transverse direction correction of copying error in priority application It is evident that significant biodegradation, lending to 35 loss in weight and strength, can be obtained if the content of PHBV is high enough. Thus material at under 50% PHBV could be ^^used in making diapers, tampons and dressings to be disposed of s landfill. 2-3A i 23 EXftMPLE 3 Using a PHBV sample containing 15.6 mol % HV and 1 phr boron nitride as nucleating agent, further compositions were formed into films and the biodegenerability assessed in a similar manner 5 to Example 2, except that the time period was 79 days.

TABLE 3 EVA VA EVA PHBV YIELD BREAK YOUNG'S WEIGH!! ft, 'o IN MI % STGTH STGTH MODULUS LOSS EVA MPa MPa MPa % M0L% 70 1.8 MD 7.4 7.9 290 .5 TD 4.3 .2 140 80 1.8 MD .8 6.5 201 2.67 TD 4.5 4.9 79 70 12 2.5 MD 9.55 11.7 327 11.6 TD .8 6.0 177 80 12 2.5 MD 7.5 .6 222 2.22 TD 4.4 .5 112 It is evident that significant weight loss occurs at the higher PHBV and EVA contents. 2 S°\ (a_3 EXAMPLE 4 Farther compositions were injection moulded into impact and tensile test bars. The following physical properties were determined.

TABLE 4 EVA VA PHBV HV FLEX.

YOUNGS IMPACT % IN % IN MOD.

MOD.

EVA PHBV (MPa) (MPa) (J.nT1) (4) 100 4 2375 1170 92 8.5 90 4 1090 39 12.0 90 4 1050 36 .0 90 4 1120 48 28.0 90 4 1080 57 8.5 70 4 778 41 12.0 70 4 734 44 .0 70 4 711 52 28.0 70 4 642 67 50 8.5 50 4 524 58 50 12.0 50 4 487 60 50 .0 50 4 480 89 50 28.0 50 4 619 396 193 100 .6 1207 642 197 8.5 90 .6 533 65 12.0 90 .6 558 69 .0 90 .6 554 84 28.0 90 .6 509 132 8.5 70 .6 404 52 12.0 70 .6 414 56 .0 70 .6 397 76 28.0 70 .6 362 107 50 8.5 50 .6 300 77 50 12.0 50 .6 271 93 50 .0 50 .6 247 139 50 28.0 50 .6 302 202 292 (4) VA % w/w 8. MI g/10 min 2. 12. 0 2, .0 20 .5 1 .0 28. .8 3. 0 0 .ft* H "C EAf CT 23°l 123 11 EXAMPLE 5 Further compositions were formed into impact and tensile test bars and the physical properties determined as in Example 4. TABLE 5 EVA PHBV HV FLEX.

YOUNGS NOTCHED WEIGHT (5) % IN MOD.

MOD.

IMPACT LOSS % PHBV (MPa) (MPa) (J.m"1) % 100 .6 1082 642 250 24.01 90 .6 867 465 151 - 80 .6 619 374 101 - 70 .6 462 117 23.6 40 60 .6 457 273 304 22.35 50 50 .6 323 51 461 17.75 60 40 .6 232 132 367 .36 70 .6 156 80 287 4.38 80 .6 97 50 210 1.5 100 0 - 47 17 - - (5) EVA containing 28% w/w of VA and having NI 3.0 g/10 min was 20 used in all compositions in this example.

EXAMPLE 6 Further compositions, using PHBV comprising 15 mol % of HV and including some which contained other biodegradable materials apart from PHBV, were formed into tensile test bars and the 25 physical properties determined as in Examples 4 and 5. Some of these compositions, as 0.5 mm compression moulded film, were tested for biodegradation for 30 days at 25°C in microbially active soil. zf? *~1 >% //% os fiy nJ J? IV 23°t )2.3> Results were as follows.

TABLE 6 LDPE EVA PHBV ST. TRI. Ca BIO POLY FLEX. YOUNGS STRS EXTN WGT % (6) o. *o (1) (2) (3) (4) (5) MOD.

MOD.

@ BK LOSS % % % % % % (MPa) (MPa) MPa % % - 10a 50 - 90 56 344 204 7 27 45.1 90 44 379 193 - - - - 10a 50 90 56 609 248 11 78.9 - 20a 40 80 50 345 134 - - - 60 50 291 132 - - - - 40a - - 60 50 580 352 - - - 60 50 904 527 - - - - 40a 60 50 458 211 - - - - 50a 7.5 7.5 50 50 331 137 - - - 50 40 216 86 - - - 50 60 645 332 6 31.2 50 60 375 219 - - - - 40 75 329 191 3 28 .6 - 40 75 486 274 - - - - lOx 60 83. 3 605 345 14 16 43.3 - lOy 66 85 461 355 13 50 63.8 (1) ST. = starch (2) TRI. = triacetin (3) Ca. — calcium carbonate (4) BIO = Biodegradable content of composition (5) POLY = Percentage of biodegradable content which is PHBV. (6) VA = 12% w/w in samples marked a; 8% in others. MI 2g/10mins for all EVAs. (x) Contained also 30% ) polycaprolactone "TONE" 700 30 (y) Contained also 24% ) ex Union Carbide All these samples were denser than fresh water.

The samples for which weight loss data are quoted had the following properties after the exposure to soil.

CT1 2 4(76/9 «l\ o 9 /W

Claims (15)

1. 23=1 U3. 33 TABLE 7 I 1 | % WGT LOSS | 1 COMMENTS | 5 1 ] 78.9 | Broke into small pieces. Very fragile 1 1 45.1 | Large amount of degradation - some fragmentation! | 31.2 | Large amount of degradation - but still complete| | 10.6 | Some degradation, but still complete | 1 43.3 1 Degradation occurred at one end of strip | 10 1 63.8 j Significant degradation, broke into several ) 1 1 1 pieces | PA/EJN/JNA/MP 91TJL006 KHC/MS/15 July 1991 ! V '^AUqj 991i WHAT0WE CLAIM IS: u 2 3 9 1 2 1 A biodegenerable plastics composition comprising at least one synthetic polymer selected from the class consisting of polyethylene, polypropylene, polystyrene and an ethylene copolymer blended with 10 to 90% w/w of said composition of a biodegradable material, at least 20% w/w of which is tfc* microbiologically produced copolymer containing 3-hydroxybutyrate and 3-hydroxyvalerate.
2. 2 A composition according to Claim 1 in which the ethylene copolymer contains 5 to 30 w/w % of vinyl acetate on the total of ethylene and vinyl acetate.
3. 3 A composition according to Claim 1 or Claim 2 containing also one or more biodegradable or environmentally acceptable improvers.
4. 4 A composition according to any one of Claims 1 to 3 which comprises a ternary blend of (1) said biodegradable material; (2) at least one synthetic polymer selected from polyethylene, polypropylene and polystyrene; and (3) said ethylene copolymer.
5. 5 A composition according to any one of the preceding Claims in which the microbiologically produced copolymer contains between 3 and 20 mol % of 3-hydroxyvalerate.
6. 6 A composition according to any one of the preceding claims having a density greater than that of fresh water (1 gem 3 at 3.98°C or 0.99823 gem"3 at 20°C) such that said composition sinks in water.
7. 7 A method of making a composition according to any one of the preceding claims by mixing the constituents in conditions in which at least one of its polymeric constituents is in liquid form.
8. 8 A process of making a shaped article by confining to shaping surfaces a composition according to any one of Claims 1 to 6 or as made by a method according to Claim 7.
9. 9 A shaped article made of a composition according to any one of Claims 1 to 6 or as made by a method according to Claim 7.
10. 10 A compound structure comprising combinations of one or more t \r ' 23 9 12 3 15
11. 11. A biodegenerable plastics composition as defined in claim 1 substantially as herein described with reference to any example thereof.
12. 12. A method as defined in claim 7 substantially as herein described with reference to any example thereof.
13. 13. A process of making a shaped article as defined in claim 8 substantially as herein described with reference to any example thereof.
14. 14. A shaped article as defined in claim 9 substantially as herein described with reference to any example thereof.
15. 15. A compound structure as defined in claim 10 substantially as herein described with reference to any example thereof. (\tob - By JihtfTheir authorised Agent A. J. PARK & SOW