CA2141562C

CA2141562C - Biodegradable polymeric composition

Info

Publication number: CA2141562C
Application number: CA002141562A
Authority: CA
Inventors: Catia Bastioli; Vittorio Bellotti; Roberto Lombi; Matteo Nicolini
Original assignee: Novamont SpA
Current assignee: Novamont SpA
Priority date: 1992-08-03
Filing date: 1993-06-14
Publication date: 2004-03-30
Anticipated expiration: 2013-06-14
Also published as: DE69321730D1; ITTO920672A0; AU4418693A; ATE172483T1; HK1013302A1; KR100272484B1; IT1256914B; EP0652910A1; WO1994003543A1; DK0652910T3; US5874486A; ITTO920672A1; DE69321730T2; EP0652910B1; JP3549203B2; ES2124313T3; TW492995B; JPH07509514A; AU675954B2; KR950702600A

Abstract

A polymeric composition comprises a matrix including a starch component and at least one synthetic thermoplastics polymeric component in which a filler is dispersed, characterised in that the matrix includes a fluidising agent selected from the group consisting of C12-C22 fatty acids, C12-C22 fatty alcohols, esters and amides of the said fatty acids, polyolefin waxes and polyglycol ethers of alditols or polyglycerols esterified with the said fatty acids and their mixtures and the said filler comprises natural fillers of an organic nature dispersed in the matrix in quantities of from 5 % to 70 % by weight with reference to the total weight of the composition.

Description

BIODEGRADABLE POLYMERIC COMPOSITION
The present invention relates to a biodegradable polymeric composition of the type including starch and synthetic thermoplastics polymers, suitable for the production of biodegradable articles having satisfactory physical and mechanical properties, by means of conventional techniques applied to thermoplastics materials of synthetic origin.
Thermoplastics compositions of the type specified above are known and available commercially and are described, for example, in patent applications EP-A-0 032 802, EP-A-0 327 505, WO 90/10671, EP-A-0 400 532, EP-A=0 404 723, EP-A-0 404 727, EP-A-0 404 728, WO 91/02024, W0 91/02025 and US 5,095,054.
Typically these compositions can be obtained by the mixing of a starch component with a synthetic thermoplastics polymeric component in conditions typical of the "extrusion-cooking" process, is in the presence of a limited quantity of water (typically 5-40% by weight with reference to the starch-water system) or of a plastisizer at a high enough temperature and pressure to destroy the crystalline structure of the starch and to obtain a molten thermoplastics mass.
The object of the present invention is to provide PCT/EP93/015:~~

compositions of the type specified above which have improved mechanical properties, particularly a higher rigidity, even in the presence of high humidity, and properties of processability comparable with those of conventional plastics, while retaining or surpassing the rate of biodegradability of the known compositions.
This object is achieved by virtue of a polymeric composition comprising a matrix including a starch component and at least one synthetic thermoplastics polymeric component in which a filler is dispersed, characterised in that the matrix includes a fluidising agent selected from the group consisting of:
~ fatty acids, C12-C~ fatty alcohols, _esters and amides of the said fatty acids, polyolefin waxes and polyglycol ethers of alditols or polyglycerols esterified with the said fatty acids and their mixtures and the said filler comprises natural fillers of an organic nature dispersed in the matrix in quantities of from 5% to 70%
by weight with reference to the total weight of the composition.
The materials constituting the fillers are preferably selected from wood flour, walnut shells, cellulose, cotton, jute, raffia, rice chaff, animal bristles, chitin and granular starch and their mixtures; of these the preferred are the fibrous materials. The dimensions of the fillers may vary within wide limits according to the mechanical properties which it is intended to bestow.
Typically the average dimensions are between 0.5 and 500 microns, preferably between 1.5 and 300 microns; the shape ratio L/D is generally between 1 and 100 and preferably between 2 and 50.
The preferred filler concentrations are in the range 20%-50% by weight with reference to the weight of the composition. In combination with the natural organic fillers listed above, the compositions may include inorganic fillers such as talc, mica, titanium dioxide, aluminium oxide in concentrations preferably no higher than 5% by weight. The fillers may be surface treated to improve their affinity with the matrix material, for example, by means of linking agents such as titanates or zirconates or by silanisation.
The preferred matrix materials include the starch component and the synthetic thermoplastics component typically in a ratio of from 1:9 to 9.8:0.2, preferably from 1:4 to 4:1 and more preferably from 1.5:1 to 1:1.5.
The starch used is generally a natural starch extracted from various plants such as maize, potato, tapioca and cereals; it is intended that the term starch should be understood to include starches with a high amylopectin content (waxy starches) and chemically and physically modified starches, such as for example starches whose 214~~62~
acid values have been reduced to between 3 and 6, 'starches in which the type and concentration of caticns associated with the phosphate groups have been modified, ethoxylated starches, starch acetates, cationic starches, r exidated starches and cross-linked starches.
As the pclymeric component, tr.e of p ymers described in the pa ten t 1 l ter a tur a mentioned in the intr oduc tion to the P
resent specification may be used.
The synthetic poly,-aeric component is preferably selected from the following polymers and copolymers and their l mixtures:
l (A) Polyvinyl alcohol, polyvinyl acetate and copolymers of an olefin selected from ethylene, propylene, isobutene and styrene with one or more monomers selected from acrylic acid, methacrylic acid, C~-C1 k al ~y'_aciylate, C,-C, al~yl:~ethacrylate, vinyl alcohol, vinyl acetate and malefic acid, such as ethylene-acryl,;c acid, ethylene-vinyl alcohol, ethylene-vinyl acetate, ethylene-malefic anhydride copolymers and their mixtures; the particularly preferred compounds are ethylene-vinyl alcohol copolymers with an ethylene content of from 10-44%
by weight produced by the hydrolysis of the corresponding poly-ethylene-vinyl acetate with a degree of hydrolysis of between 50 and I00;
(B) Thermoplastics polyesters such as, in particular, pI~IIEN~E~ ;~'v._~i 2141:52 hemopolymers and copolv:«ers of hydrox~raliphatic I
acids having from 2 to 24 carbon atoms, preferably 2 to 8 carbon atoms, the corresponding lactones or lactides and polyesters derived from bifunctional carboxylic acids with aliphatic diols.
(C) Graft copolymers of polysaccharides and their der'_vatives, such as starches, cellulose, modified cel l a Lose , rubber s, algina tes , pec tins, dextr t r~5 and pul~~ular.s wit:z nonomers such as styrene, methylmethacrylate, nethylacrylate, butylacry~ate, bu tadiene, isoprene, acry lonitr i1 e; gr aft copolymers ef polysacchar ides are descr ibed in the Encyclopedia of Polymer Science and Engineering, John wiley &
Sons, Volume 3, 1986. In particular, in group B the preferred polymers and mixtures of polymers selected are:
I
B1) poly-epsilon-caprolactone, copolymers of epsilon-caprolactone with isocyanates such as, in particular, 4,4'-diphenylmethane diisocyanate, toluylene diisocyanate, isophorone diisocyanate or hexamethylene diisocyanate;
B2) polymers of lactic acid or polylactides, of glycolic acid or polyglycolides, copolymers of lactic acid and glycolic acid;
B3) polyhydroxybutyr~ate, polyhydroxybutyr~ate/valerate;
B4) polymers derived from dicarboxylic acids with aliphatic diols such as, in particular, polyethylene and polybutylene adipate or sebacate;

WO 94/03543 _ ~ ~ ~ ~ ~ PCT/EP93/015~~' B5) block or graft copolymers formed between homopolymers and copolymers of hydroxyacids, in particular poly-epsilon-caprolactone, and one or more of the following components:
i) cellulose or modified cellulose, for example, carboxymethylcellulose and cellulose acetate;
ii) amylose, amylopectin, natural or modified starches;
iii) polymers resulting from the reaction of a compound selected from aliphatic diols (such as ethylene glycol, propylene glycol; butylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, neopentyl glycol, 1,4-butanediol, cyclohexanediol), prepolymers or polymers of polyesters having terminal diol groups with monomers selected from:
- bifunctional aromatic or aliphatic isocyanates, - bifunctional aromatic or aliphatic epoxides, - dicarboxylic aliphatic acids (such as malonic, succinic, malefic, fumaric, itaconic, glutaric, adipic, pimelic, suberic, azeleic and sebacic acids), - dicarboxylic cycloaliphatic acids (such as cyclohexanedicarboxylic acid, 2,2,2-dicyclooctanedicarboxylic acid) or - aromatic acids or anhydrides (such as phthalic acid) , iv) polyurethanes, polyamides-urethanes from diisocyanates and aminoalcohols, polyamides, polyesters-amides from dicarboxylic acids and aminoalcohols, polyester-urea from aminoacids and diesters of glycols, _214~~s~

v) polyhydroxy polymers (such as polyvinyl alcohol, ethylene-vinyl alcohol copolymers, totally or partially hydrolysed), vi) polyvinyl pyrrolidone, polyvinyl pyrrolidone-vinyl-acetate copolymers and polyethyloxazoline, 86) polyesters obtained from monomers of hydroxyacids upgraded with chain lengtheners such as isocyanates, epoxides, phenylesters and aliphatic carbonates;
B7) polyesters obtained from monomers of hydroxyacids partly cross-linked with polyfunctional acids such as trimellitic acid, pyromellitic acid, polyisocyanates and polyepoxides.
More particularly, the polymers B5-B7 are useful to provi3e compatibility in combination with the polymers B1-B4, optionally in combination with polymers of the group A.
The matrix materials used within the scope of the invention preferably have a melt flow rate greater than 2g/10 minutes, more preferably greater than 5g/10 minutes and still more preferably, greater than 10 g/10 minutes (determined in a capillary tube having a diameter of 2.lmm and a length of 8mm at 170°C with a load of5 kg) and preferably have a water content of from 2-10% by weight (as extruded and without conditioning).
Preferably the synthetic component of the matrix material includes a mixture of one or more polymers from the group A) with one or more polymers from the groups B) and/or C) listed above in a weight ratio to each other preferably of from I :6 to 6:1 and more preferably from 1:4 to 4:1.
A further component preferably used in the matrix material of the invention is a plasticizer in a total quantity of between 1 and 50% with reference to the sum of the starch component and the synthetic polymer component and preferably between 5 and 25% by weight. In the term plasticizer it is intended to include aliphatic polyols and their acetate, ethoxylate and propoxylate derivatives, in particular, glycerine, ethylene or propylene glycol, ethylene or propylene diglycol, ethylene or propylene triglycol, polyethylene glycol, polypropylene glycol, 1, 2-propanediol, 1,3-propanediol, 1, 2-, 1,3-, 1,4-butanediol, 1,5-pentanediol, 1,6-, 1,5-hexanediol, 1, 2,6-, 1,3,5-hexanediol neopentyl glycol, trimethylol propane, pentanediol, 1,6-, 1,5-hexanediol, 1,2,6-, 1,3,5-hexanetriol, neopentyl glycol, trimethylol propane, pentaerithritol, sorbitol and their acetate, exthoxylate and propoxylate derivatives, in particular sorbitol ethoxylate, glycerol ethoxylate, pentaerithritol ethoxylate, sorbitol acetate, pentaerithritol acetate and polyvinyl alcohol; a mixture of different plasticizers may be used.
Plasticizers suitable for use are described in International patent application PCT/EP92/14782.

9.
The fluidising agents previously mentioned are I particularly useful for the production of compositions with a high filler content.
These agents include fatty acids such as oleic, palmitic, stearic, linoleic, linolenic, recinoleic, erucic acids, the cerrespcnding fatty alcohols or esters or amides of the fatty acids listed above, in particular, :ono-,di-, or tri-glycerides of the said fatty acids.
i Particu'_arly advantageous as fluidisers for the matrix material are polyglycol ethers of alditols or polyglycerois esterified with fatty acids, where the polyglycol is preferably ethylene glycol or propylene glycol, the alditel is preferably selected from sorbitol, i ' xylitol, mannitol, the polyglycerol preferably has from 3 to 10 repeat units and the fatty acid is preferably a , , C,2-C." acid, preferably saturated; preferred compounds include in particular:
- sorbitol ethoxylate mono- di- or tri-octadecanoate (CAS
n. 68025-57-0) in particular poly(oxy-1,2- ethanediol), alpha-hydro-omega-hydroxy-ether with D-glucitol (3:1), tris-(Z)-octadecanoate; and - sorbitol propoxylate mono- di- or tri-octadecanoate where the ethoxylation or propoxylation of the free hydroxyl crroups may be complete or partial.
~F~U~~ ~l"G,~~

WO 94/03543 ~ PCT/EP93/01530 The f luidiser is typically used in concentrations of from 0.1 to 10% by weight with reference to the weight of the matrix component.
The compositions according to the invention are preferably prepared by means of the prior preparation of the matrix material including the fluidising agent or mixture of fluidising agents listed above. The preparation of the matrix material is effected by conventional processes described in the patent literature mentioned in the introduction to the present specification, that is in conditions typical of the "extrusion-cooking" process. This process comprises the mixing of the components, preferably in a heated extruder or in any device which ensures a temperature and shearing stress sufficient to render the starch material and the polymeric component compatible from a rheological point of view; in the presence of water (up to 40% with reference to the starch/water system) and/or a plastisizer at a temperature of from 80 to 210°C. The preferred method for the preparation of the matrix material comprises:
- a first stage in which the components are conveyed and/or mixed in an extruder for periods of time of the order of 2 to 50 seconds in which the starch component and the synthetic polymeric component are fled by means of the plastisizer available and/or any water present at a temperature of between 80 and 180°C;

- a mixing stage in which the mixture is subjected to shearing stresses which correspond to similar values of viscosity of the polymeric and starch components, - optionally, a degassing phase in which the mixture is degassed under free conditions or under controlled conditions of pressure or under vacuum to obtain a melt preferably at a temperature of from 130 to 180°C with a water content preferably less than 6% such as not to create bubbles at atmospheric pressure, for example, at the outlet from the extruder, whenever it is not wished to produce expanded products.
The melt may then be extruded directly in stranded, spaghetti-like form and in a subsequent stage the strands are mixed with the desired filler content, possibly with the addition of further fluidisers and/or plasticizers in a heated extruder to obtain an extrusion in the form of pellets suitable for conversion by conventional working processes for plastics materials.
Alternatively, the components of the matrix material and the fillers may be mixed directly in a single stage. The matrix material may also include small quantities of hydrophobic polymers in its formulation, such as polyethylene, polypropylene, polystyrene, even though, in order to maintain good characteristics of biodegradability, these polymers are preferably used in quantities no greater than 5% by weight of the total -;
y 2:141~s~
weight of the composition.
The matrix mater ial may further include additives such as i cress-linking agents such as aldehydes, ketones, and glyoxals, process adjuvants, antioxidants, release agents, opacifiers or stabilisers.
Exa~rple 1 CCor.~~rative., A two-scre~:/single-scr?w APV/V30 extruder was supplied with the following co:~pos=tion expressed in parts by weight:
Globe Cerestar (~egist_r.ed Trade :dark) starch with an intrinsic water content of 12% by weight 40.5 EVCH (*) 30.4 (**) 4.3 Erucamide 0.25 Plasticizer '' ~" ~' ) 21 . 5 Fluidizer (****) 3.1 (*) poly-ethylene-vinyl alcohol, 44% molar ethylene ,. .
content hycrolysys ~ieglee: 99.5 of the acetate groups (**) poly-ethylene-acrylic acid, 20% by weight ethylene (***) mixture of plasticizers: sorbitol acetate 65.5%, water 14%, glycerine 20.5% by weight, containing 0.5~ of free acetic acid (****) sorbitol ethoxylate trioctadecanoate.
The two-screw section of the extruder was operated with a heat profile of between 60 and 170°C.
L.r, ~~h,L ; ~;~

Screw rotation:250 rpm; screw diameter 30mm; L/D = 10.
The two-screw section was provided with an intermediate portion with a pressure of 0.9 bar.
The single-screw section was operated with a heat profile of between 150 and 140°C; screw rotation 80 rpm; screw diameter 38 mm, L/D = 16.
The extruded strands with a water content of about 5.2%
by weight, were granulated and then fed to a Sandretto inj ection moulding press from which dumb-bell shaped test pieces (ASTM 638) were obtained which were subjected to tests to determine their mechanical properties:
- Modulus of elasticity 197 MPa - Breaking load: 14.4 MPa - Elongation , 656%
- MFR: 15 g/10 minutes Example 2 The matrix material of Example 1 was used for the production of compositions including fillers according to the invention with the following formulation, expressed in parts by weight:
Matrix material: Example 1 53 Filler: wood flour (*) 40 Polyethylene wax 7 (*) maximum particle size: 200 microns PCT/EP93/015~:.
21~~562 The composition listed above was supplied to a two-screw/single-screw MPC/V30 extruder operated with the following conditions:
Two-screw extruder: L/D = 10: D = lOmm; screw rotation;
250 rpm, with a heat profile between 160 and 170°C.
Single screw: D 38mm; L/D - 16; screw rotation 50 rpm with a heat profile between 170 and 160°C.
The extruded strands were supplied to an injection press provided with a mould for forming dumb-bell shaped test pieces (ASTM 638) and the test pieces were obtained under the following conditions:
Heat profile: 155/160/165/165°C
Mould temperature: 18°C
Injection pressure: 1600 bar Injection speed: 114cm3/s _ The mechanical properties of the test pieces obtained are given in Table 1.
Example 3 The procedure of Example 1 was repeated with the use of a filler constituted by wood fibres with a maximum fibre length of about 3.5mm.
The results of mechanical tests are given in Table 1.
Example 4 The procedure of Example 2 was repeated with the .... ~ 14 ~ ~ 6 ~ PCT/EP93/01530 variation that a profiled section in the form of a platelet having a thickness of 5.7 mm was extruded directly from the two-screw/single-screw extruder and subjected to the determination of its mechanical properties according to ASTM 638.
The values of the mechanical properties are given in Table 1.

Example 2 3 4 Breaking Load (MPa) 31.6 32.6 15 Elongation ;%) 1.4 1 1 Modulus of Elasticity (MPa) 4797 5455 2846 Breaking Energy (kj/m2) 13.43 9.5 3 Examples 5-6 The procedure of Example 2 was repeated with the use of the following formulations expressed in parts by weight:
E8. 6 E8. 7 Matrix material: Ex. 1 70 60 Filler: Wood Flour (*) 25 40 Polyethylene wax 5 --The test pieces obtained from the injection moulding process were subjected to determinations of their extensibility and in all cases the results were less than 50%.

i ~ i Examples 7-11 The matrix material of Example 1 was used for the preparation of formulations further including a polymer of poly-epsilon-caprolactone, in the formulations given ' in the table below and under described the conditions in Example 2.

Example 7 8 9 10 11 Matrix: Ex. 1 70 70 70 65 55 Wood Flour 20 -- -- 25 25 Cellulose() -- 20 -- -- --Raft is (*) -- -- 20 -- --P 787 -- -_ 10 _- --glycerine -- -- -- l0 10 P 300, P 767, P 787: poly-epsilon-caprolactone Union Carbide (~): Cellulose Solka*Floc BW300 FCC
:, (*): Raffia Satralit*FNT / 134-4SG
In all cases, the dumb-bell shaped test pieces obtained in accordance with Example 2 were seen to have a modulus of elasticity greater than 1000 MPa with a water content in the samples of between 4 acrd 5~ .
The compositions according to the invention could be worked by conventional working processes for plastics * trade mark WO 94/03543 _ 214 ~ ~ 6 ~ p~/Ep93/01530 materials in particular by extrusion and injection moulding to produce shaped articles such as profiled sections and containers and expanded articles. These articles fall within the scope of the invention.

Claims

WE CLAIM:

1. A polymeric composition obtainable by melt-dispersing a natural filler of organic nature in a matrix extruded from a composition comprising a starch component, a synthetic thermoplastics polymeric component and a fluidising agent selected from the group consisting of C12-C22 fatty acids, C12-C22 fatty alcohols, esters and amides of the said fatty acids, polyolefin waxes and polyglycol ethers of alditols or polyglycerols esterified with the said fatty acids and their mixtures and the said filler being dispersed in the matrix in quantities of from 5% to 70% by weight with reference to the total weight of the composition and the content of water of the matrix being less thin 6% by weight.

2. A polymeric composition according to claim 1, characterised in that the fillers are selected from the group consisting of wood flour, walnut shell flour, cellulose, cotton, jute, raffia, rice chaff, animal bristles, chitin and granular starch and their mixtures.

3. A polymeric composition according to claim 2, characterised in that the fillers have an average size of between 0.5 and 500 microns.

4. A polymeric composition according to claim 1 in which the fillers are surface treated with linking agents selected from silane, titanates, and zirconates.

5. A polymeric composition according to any one of claims 1 to 4 in which the matrix material is obtained by extrusion-cooking of the starch component together with the synthetic thermoplastics polymeric component in the presence of a plastisizer and/or water.

6. A polymeric composition according to any one of claims 1 to 5, in which the synthetic component comprises:
a polymer selected from the group consisting of polyvinyl alcohol; polyvinyl acetate; copolymers of an olefin selected from ethylene, propylene, isobutene and styrene with one or more monomers selected from the group consisting of acrylic acid, methacrylic acid, alkylacrylate, alkylmethacrylate, maleic acid, vinyl alcohol and vinyl acetate; homopolymers and copolymers of hydroxyaliphatic acids having from 2 to 24 carbon atoms, the corresponding lactones or lactides; polyester polymers of bifunctional carboxylic acids with aliphatic diols; graft copolymers of polysaccharides and their mixtures.

7. A polymeric composition according to claim 6; in which the synthetic polymeric component of the matrix material includes a polymer selected from the group consisting of polyvinyl alcohol, poly-ethylene-acrylic acid, poly-ethylene-vinyl-alcohol, polyvinyl acetate, poly-ethylene-vinyl acetate, poly-ethylene-maleic anhydride and mixtures thereof.

8. A polymeric composition according to any one of claims 1 to 6, in which the synthetic thermoplastic polymeric component includes one or more polymers selected from:

B1) poly-epsilon-caprolactone, copolymers of epsilon-caprolactone with isocyanates;
B2) polymers of lactic acid or polylactides, or glycolic acid or polyglycolides, copolymers of lactic acid and glycolic acid;
B3) polyhydroxybutyrate, polyhydroxybutyrate/valerate;
B4) polymers derived from dicarboyxlic acids with aliphatic diols B5) block or graft copolymers formed between homopolymers and copolymers of hydroxyacid, and one or more of the following components:
i) cellulose or modified cellulose, ii) amylose, amylopectin, natural or modified starches;
iii) polymers resulting from the reaction of a compound selected from diols prepolymers or polymers of polyesters having terminal diol groups with monomers selected from:

- bifunctional aromatic or aliphatic isocyantes, - bifunctional aromatic or aliphatic epoxides, - dicarboxylic aliphatic acids - dicarboxylic cycloaliphatic acids or - aromatic acids or anhydrides iv) polyurethanes, polyamides-urethanes from diisocyanates and aminoalcohols, polyamides, polyesters-amides from dicarboxylic acids and aminoalcohols, polyester-urea from aminoacids and diesters of glycols, v) polyhydroxylated polymers vi) polyvinyl pyrrolidone, polyvinyl pyrrolidone-vinyl-acetate copolymers and polyethyloxazoline, B6) polyesters obtained from monomers of hydroxyacids with chain lengtheners B7) polyesters obtained from monomers of hydroxyacids partly cross-linked with polyfunctional acids.

9. A polymeric composition according to claim 6, in which the synthetic polymeric component of the matrix material includes at least one polymer selected from the group consisting of:

A) polyvinyl alcohol, poly-ethylene-vinyl alcohol, poly-ethylene-acrylic acid, poly-ethylene-vinyl acetate, polyvinyl acetate and at least one polymer selected from the group consisting of:
B) poly-epsilon-caprolactone,copolymers of epsilon-caprolactone,polylactic acid, polyglycolic acid, copolymers of epsilon-caprolactone with isocyanates, polyhydroxybutyrate, polyhydroxybutyrate/valerate, the ratio by weight between the polymer of group (A) and the polymer (B) being between 1:4 and 4:1.

10. A polymeric composition according to any one of claims 1 to 6, including a plasticiser selected from the group consisting of:

glycerine, ethylene glycol, propylene glycol, ethylene diglycol, propylene diglycol, ethylene triglycol, propylene triglycol, polyethylene glycol, polypropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-, 1,3-, 1,4-butanediol, 1,5-pentanediol, 1,6-, 1,5-hexanediol, 1, 2, 6-, 1, 3, 5-hexanetriol, neopentyl glycol, trimethylol propane, pentaerithritol, sorbitol and their acetate, ethoxylate and propoxylate derivatives.

11. A polymeric composition according to claim 10, in which the plasticiser is selected from the group consisting of:

sorbitol ethoxylate, glycerol ethoxylate, pentaerithritol ethoxylate, sorbitol acetate, pentaerithritol acetate.

12. A polymeric composition according to claim 10, in which the plasticiser is present in quantities of from 1% to 50% by weight with reference to the weight of the matrix material.

13. A polymeric composition according to claim 12 in which the plasticiser is present in quantities of from 5% to 25% by weight with reference to the weight of the matrix material.

14. A polymeric composition according to any one of claims 1 to 13, in which the polymeric component and the starch component are present in the matrix material in a weight ratio of from 1:4 to 4:1.

15. A polymeric composition according to any one preceding claims 1 to 14, in which the matrix material includes a polyglycol ether of an alditol or polyglycerol esterified with a C12-C22 fatty acid as the fluidising agent.

16. A polymeric composition according to claim 15, in which the alditol of the fluidising agent is selected from the group consisting of sorbitol, xylitol and mannitol.

17. A polymeric composition according to claim 15, in which the polyglycol of the fluidising agent is selected from the group consisting of polyethylene glycol and polypropylene glycol.

18. A polymeric composition according to any one of claims 1 to 17, in which the fluidising agent is present in quantities of from 0.1 to 10% by weight with reference to the weight of the matrix material.

19. Shaped articles made from a composition according to any one of claims 1 to 18.