WO2016174116A1

WO2016174116A1 - Polyester composition and method for producing the same

Info

Publication number: WO2016174116A1
Application number: PCT/EP2016/059450
Authority: WO
Inventors: Paolo STUFANO; Vito Emanuele CAROFIGLIO; Domenico CENTRONE
Original assignee: Eggplant S.R.L.
Priority date: 2015-04-27
Filing date: 2016-04-27
Publication date: 2016-11-03

Abstract

The present invention provides a polyester composition in the form of soft paste, cream or gel. The composition includes a polyester and at least one dispersing agent other than water which is miscible with or soluble in water. The composition preferably comprises a covalent conjugate of the polyester with the dispersing agent. The composition is biodegradable and preferably totally bio-derived, and thus environmentally friendly. In a preferred embodiment the composition is prepared by a method comprising contacting said polyester with the dispersing agent at a temperature lower than the melting point of the polyester, thereby covalently conjugating the dispersing agent to the polyester.

Description

POLYESTER COMPOSITION AND METHOD FOR PRODUCING THE SAME

Technical field

The invention relates to a polyester composition in the form of a soft paste, cream or gel. The composition includes at least one dispersing agent which is miscible with or soluble in water, which is contacted with the polyester. Such a composition is useful when contacted with water containing systems or aqueous environments, thus including applications in agriculture, food industry, cosmetics and cosmeceuticals, packaging and coatings, bio-medical products and pharmaceuticals, personal care products and detergents, inks and varnishes, and electronics.

Background of the invention

Conventional fossil carbon derived plastics represent an important concern for the environment, being at once a problem due to limited fossil resources and as a source of pollution, increasing interest in using bio-derived and bio-degradable polymers to produce sustainable eco-friendly materials as an alternative to conventional plastics. Natural bio-polyesters, which are derived and/or bio-degradable, represent a promising solution. They include polyhydroxyalkanoates (PHA), polyglycolide (PGA), polylactide (PLA), polylactideglycolide (PLGA), polycaprolactone (PCL), polydioxanone (PDO), bio- based aliphatic co-polymers, such as polyethyleneadipate (PEA) and polybutylenesuccinate (PBS), polyethylenefuranoate (PEF), bio-based terephthalate co-polymers, such as polyethyleneterephtalate (PET), polytrimethyleneterephtalate (PTT), and polybutyleneterephtalate (PBT).

Among all the known bio-polyesters, PHAs have been widely investigated and studied as they can be produced by a variety of microorganisms and from a large number of natural sources including organic waste. Different bacterial strains, upon feeding by appropriate carbon sources and mineral additives, accumulate PHAs as intracellular polymers, which can be extracted by cell lysis. As they are naturally produced, PHAs are completely biodegradable in soft and sea water and soils. Moreover PHAs are thermoplastic polyesters and thus they can potentially substitute for conventional fossil derived polymers as polyethylene (PE), polypropylene (PP) and PET. Different homo- and co- polymers from the family of PHAs are known, the most representative being the homo-polymer poly(3 -hydro xybutyrate) (PHB) and the co-polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Depending on the length of the alkyl side chain PHAs can be grouped in short- (scl), medium- (mlc) and long-chain-length (lcl). (see, e.g., M. Koller et al. Food Technol. Biotechnol. 2010, 48:255-269; C. Du et al. Curr. Chem. Biol. 2012, 6: 14-25).

PHAs have been successfully investigated for a number of applications. Nonetheless, as with the majority of polyesters, they are highly insoluble in water, which precludes their use in different fields, as the polyester particles sink or float in aqueous environments and water solutions causing an undesired phase separation. An effective homogeneous dispersion of bio-polyesters in water obtained through simple processes, without altering the environmental friendliness of the whole system in terms of bio-derivation and bio-degradation of the single components, represents a need in the art. The most common approach to obtaining a good polyester dispersion in water is the addition polymeric or monomeric suspending agents and/or surfactants.

Polymer dispersions can be prepared starting from appropriate monomers which are polymerized in a non-solvent matrix, preferably in the presence of suspending aids. For example US 3925295 teaches the general preparation of polymer dispersions by in situ condensation of reactive monomers into a dispersing matrix, in which at least one of the monomers used is insoluble, in the presence of an emulsifying agent. A different method is described in US 6146665, which reports the enzymatic polymerization of hydroxyalkanoate in water to form an oil-in water emulsion with entrapped lipophilic drugs, for the preparation of drug delivery systems.

Alternatively polymers themselves can be dispersed in the presence of appropriate suspending agents. EP 0866829 describes the use of a co-polymeric dispersant to stabilize the PHAs dispersion in water. The dispersant offers a steric stabilization of PHAs chains thanks to a double domain in its chemical structure made of hydrophilic and PHA-compatible units. US 7754229 discloses the preparation of gels and creams based on bio-polyesters in water by using amphiphilic binders mainly derived from polyalkyleneoxides to stabilize bio-polyester chains. WO 2014/023319 reports the use of colloidal stabilizers, i.e. natural polymers mainly based on starch and cellulose, to directly disperse PHA powders in water at room temperature. US 2013/0225761 teaches melt emulsification for producing polymer latex in water: melt polymers, such as PHAs, are mixed with water solution containing a number of additives, colloid stabilizers and surfactants, to finally afford a stable PHA-in- water emulsion; high temperatures, equal to or higher than the PHA melting temperature, are required to carry on the melt emulsification process. High temperatures are generally useful for pretreating the polymer by melting and consequently making it more prone to dispersion into appropriate matrices, in order to limit the use of suspending aids. US 8101675 reports the formation of comminutable polyester powders useful for producing latex and water dispersions, by physical and chemical pretreatments such as irradiation and reactive melt-blending.

Soft dispersed polyester compositions have very interesting properties due to their tunable chemical, physical and mechanical properties (polarity, crosslinking degree, melting temperature, density, viscosity etc.) and are suitable to be used as thickeners, as active bio-materials or as highly stable carriers for chemical agents such as drugs or other bio-active substances. Polyester soft pastes, creams, gels and latexes find application in numerous fields including agriculture, food industry, oil industry, cosmetics and cosmeceuticals, packaging and coatings, bio-medical devices and

pharmaceuticals, personal care and detergents, inks, varnishes, and electronics. In all of these systems the primary desired properties of the polyester dispersion are bio-derivation and bio-degradability, especially in bio-medical and pharmaceutical applications where the absolute absence of toxic compounds is mandatory, or in applications that involve the direct dispersion of the material in the environment, such as for agriculture, detergents or the oil industry, from the beginning to the end, i.e. disposal, of the product life cycle. Some approaches to obtain bio-polyester dispersed systems for specific applications include physical or chemical pretreatment of the polyester, as disclosed for example in US 6555123, which describes the preparation of PHA microdispersions and liquid compositions for soft tissue repair. Low-molecular weight PHAs with low melting temperatures are produced by reaction with diols in organic solvents catalyzed by strong acid at elevated temperatures. Similar treatment of PLA is reported in US 7442322 for preparing environmentally benign anti-icing or deicing fluids. EP 1042388 describes the use of acidic or basic additives as hydrolysis promoters, pore- forming agents or hydrophobic additives in the preparation of PHA compositions with controlled degradation rates for use in medical implants. EP 1661574 reports the use of scl- and mcl-PHAs by oral administration for animal feeding and prevention and treatment of intestinal cancer. Oral administration of soft PHA compositions is also reported in WO 99/39588, which discloses environmentally friendly chewing gum bases including PHA with a number of natural additives, and in US 5229158, which describes PHA compositions useful as fat substitutes which are obtained by chemical pretreatment of PHA with micro-emulsion formation. The possibility of using such compositions as flavor and color carriers is also reported in this patent. US 5616315 describes a polyester based paste for delivering antimicrobial agents to the mouth. The preparation of a biodegradable binder resin and its use in toner for electrophotography is reported in EP 1255166. The preparation of water-based, biodegradable, flexographic inks for printers is described in EP 1470199. Another class of applications of bio- polyester aqueous dispersions is represented by personal care products and cleaning agents, where biodegradable polyester particles are the optimum substitute for polyester and polypropylene analogues. US 8470759 teaches the use of abrasive polyhydroxyalkanoate micro-particles in liquid compositions, both for personal care products and cleaning agents for a number of surfaces and objects; suitable different additives can be added as suspending aids to avoid sinking of the microparticles in water. US 2014/0026916 describes the use of PHA microbeads with sizes lower than 400 μηι in personal care formulations, for example exfoliants, cosmetics and tooth paste, as a suitable method for reducing marine pollution. As a matter of fact, the end of life cycle of such a product is usually its disposal in wastewater that ends up in marine environments, causing significant environmental pollution when it contains conventional plastic components such as PE, PP or polystyrene (PS). The bio-degradability and bio-compatibility of a polyester paste are also of fundamental importance in applications which involve contact with food, as with packaging and food-coating. This is the case for the PHA compositions described in US 7094840 which are useful as hot melt adhesives for producing food-stuff protective coatings; these compositions are prepared with PHA oligomers and additives such as waxes and tackifiers in the form of an aqueous latex for film formation by simple food coating followed by water evaporation or spray drying techniques.

It is evident that there is general interest in the production of bio-polyester soft pastes and aqueous dispersions as demonstrated by the aforementioned patents and patent applications. A simple bio-derived and biodegradable composition and method for producing the same is still absent in the art and is therefore highly desirable. Also it would be highly desirable to provide a new versatile composition and a method for preparing the same which is of general applicability and not dependent on the specific final use. Moreover, the environmental friendliness, the bio-derivation and the biodegradability of the composition are considered priorities, not only for the ingredients of the composition but also for all of the steps of its preparation. Although different solutions have been proposed in the art, they all involve the use of additives, utilize polymers which are often not both bio- derived and bio-degradable, and/or involve the use of toxic and dangerous organic solvents.

Furthermore a number of approaches to forming bio-polyester water dispersions involve the use of low-molecular-weight (LMW) polymers and oligomers. These methods also employ chemical reactions conducted under harsh conditions of temperature and pressure, or in the presence of organic chlorinated solvents, and preferably in the presence of a catalyst, as discussed hereinafter. There is a need for a new composition and method for preparing the same which solves these problems and all of the limitations discussed in the above -referenced documents. Summary of the invention

The present invention relates to compositions and methods for preparing thereof that meet the needs of the art. It is therefore an object of the present invention to provide a polyester composition which can be effectively contacted with water solutions and aqueous environments to afford a stable polyester dispersion.

The compositions of the invention are preferably in the form of a soft paste, cream or gel, depending on the specific embodiments, useful as it is or when contacted with water. It is also an object of the present invention to provide a polyester soft paste which has a tunable viscosity depending on the percentage by weight of the polyester used in the total composition, on the amount of water optionally added, and on the presence of other natural additives, such as thickeners and/or crosslinking agents.

It is another object of the present invention to provide a simple, environmentally friendly, method for producing such a composition, comprising the step of contacting a polyester with a dispersing agent which is preferably bio-degradable and/or bio-derived, and which contains hydrophilic domains in its chemical structure and is miscible with or soluble in water. In a highly preferred embodiment the polyester in the composition is a low-molecular- weight polymer or oligomer, i.e. a polyester having a number average molecular weight lower than 100 kDa and preferably lower than about 50 kDa. The invention further provides a method for producing a composition, such as a polyester dispersion, comprising the step of reacting a polyester with the dispersing agent and thus conjugating the dispersing agent and the polyester. In one preferred embodiment of the present invention the polyester is a high-molecular-weight (HMW) polyesters, i.e., a polyester having a number average molecular weight greater than 100 kDa, and reaction between the polyester and the dispersing agent affords LMW-polyester chains chemically bonded, e.g., covalently bonded, to at least one molecule of the dispersing agent. In one highly preferred embodiment the conjugation reaction occurs at a temperature below the Tm, preferably at least 15°C below the Tm, where the Tm is the melting temperature of the starting HMW-polyester. In certain embodiments the reaction forms LMW- polyester chains which react directly with the dispersing agent. Alternatively, the LMW-polyester chains are formed by in situ polymerization of selected monomers and then react with the selected dispersing agent at a temperature appropriate for the polymerization reaction.

In one embodiment, the invention provides a composition, such as a polyester dispersion, for example, in the form of a cream, paste or gel, which is produced by the method of the invention. In preferred embodiments, the compositions of the invention are substantially free of polyester degradation products, including thermal degradation products, acid degradation products and base degradation products.

In one embodiment, the invention provides a composition comprising: a modified polyester having a number average molecular weight less than about 100 kDa, wherein at least a portion of the polyester chains are conjugated to at least one molecule of a hydrophilic dispersing agent, where said polymer is dispersed in the dispersing medium. In certain embodiments, the dispersing medium is water or an aqueous solution, such as an aqueous buffer. In another embodiment, the dispersing medium is excess dispersing agent, i.e., dispersing agent which is not conjugated to the polymer, under conditions in which the dispersing agent is a liquid. In another embodiment, the dispersing medium is a mixture of water and excess dispersing agent or a solution of excess dispersing agent in water. The composition can have a range of viscosities, depending in part on the nature of the dispersion medium and the relative amounts of polyester and the dispersion medium. In general, increasing the amount of polyester relative to the dispersion medium increases the viscosity of the composition. The composition is preferably in the form of a viscous dispersion. For example, the composition can take the form of a paste, a cream or a gel.

In preferred embodiments, the composition is bio-derived, at least in part, and bio-degradable, and is produced using only bio-degradable and/or bio-derived ingredients. Although the compositions of the invention can in certain embodiments be produced with the use of organic solvents, additives or catalysts, a highly preferred embodiment of the production method of the invention involves the use of only bio-derived and/or bio-degradable chemicals. Preferred embodiments of the compositions of the invention comprise LMW-polyesters which increase the bio-degradability of the composition because LMW-polyesters are more prone to bio -degradation than corresponding HMW-polyesters.

In one embodiment, the composition of the invention has an overall amphiphilic nature, due to highly hydrophobic polyester and highly hydrophilic dispersing agent components. The LMW- polyesters conjugated to the dispersing agent also have an intrinsic amphiphilic nature due to the polymer hydrophobic domain and the hydrophilic domain of the dispersing agent.

The compositions and methods of the invention provide a number of advantages. For example, using a bio-polyester as a thickener in pastes like gel or creams in place of natural occurring bio- polymers such as polysaccharides and proteins is highly advantageous since bio-polyesters are much more stable and less susceptible to degradation in standard conditions in air. Thermoplastic polyesters are also highly stable and can be processed at relatively high temperature. Finally, biopolyesters can be produced readily in large amounts using a variety of feedstocks. Detailed description of the invention

The present invention relates to a polyester composition which can be effectively contacted with water solutions and aqueous environments affording a stable bio-polyester dispersion. A number of substances may be used to prepare such a composition without departing from the scope of the present invention.

Polyesters

The compositions of the present invention comprise at least one polyester which in a preferred embodiment is present in an amount ranging from 0.1 to 80% by weight of the composition. In a more preferred embodiment, the polyester is present in an amount which is below about 50%, preferably from 1 to about 45%, more preferably from about 5 to about 35% by weight. The amount of the polyester in the composition is the primary factor determining the viscosity of the composition.

The term "polyester" as used herein refers to a chemical entity having repeating units, i.e. monomers, chemically bounded together through an ester bond. The polyester can be a homo-polymer, with identical repeating monomers or a co-polymer, with at least two different repeating monomers. Preferably, the polyester is a bio-polyester. A "bio-polyester" as this term is used herein, is a polyester which is bio-derived and/or bio-degradable, and is preferably both bio-derived and bio-degradable. For use in specific areas, especially in biomedical or pharmacological applications, the bio-polyester is preferably bio-compatible. The term "bio-derived", as used herein, refers to a chemical substance or material which is produced starting from natural and renewable resources as opposed to fossil carbon based substances and materials; when referred to polymers, the term "bio-derived" is thus used for a carbon-based polymeric material which can be extracted or produced by synthetic, i.e. not involving living microorganisms, such as polymerization of bio-derived monomers, and natural, i.e., involving plants and microorganisms, such as bacterial digestion, processes from natural sources. Examples of bio-polyesters include polyhydroxyalkanoates (PHA), polyglycolide (PGA), polylactide (PLA), polylactide-co-glycolide (PLGA), polycaprolactone (PCL), polydioxanone (PDO), bio-derived aliphatic co-polymers, such as polyethyleneadipate (PEA) and polybutylenesuccinate (PBS), polyethylenefuranoate (PEF), bio-derived terephthalate co-polymers, such as polyethyleneterephtalate (PET), polytrimethyleneterephtalate (PTT), and polybutyleneterephtalate (PBT).

Polyhydroxyalkanoates include a number of poly-hydroxyacids in the form of homo-polymers and co-polymers. Exemplary PHAs include poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxypropionate, or poly(3-hydroxybutyrate-4-hydroxyvalerate) and other homo -polymers and co-polymers of 3-hydroxyacids, 4-hydroxyacids, and 5-hydroxyacids.

Suitable polyesters for use in the compositions of the present invention include, but are not limited to, polyhydroxyalkanoates (PHA), polyglycolide (PGA), polylactide (PLA),

polylactideglycolide (PLGA), polycaprolactone (PCL), polydioxanone (PDO), bio-derived aliphatic copolymers, such as polyethyleneadipate (PEA) and polybutylenesuccinate (PBS), polyethyleneiuranoate (PEF), bio-derived terephthalate co-polymers, such as polyethyleneterephtalate (PET),

polytrimethyleneterephtalate (PTT), and polybutyleneterephtalate (PBT), homo -polymers, co-polymers and blends thereof.

In a preferred embodiment, the polyester used in the composition of the present invention is a PHA selected from homo-polymers of 3-hydroxyacids, 4-hydroxyacids, 5-hydroxyacids, co-polymers and/or blends thereof. In another preferred embodiment the polyester is a co-polymer of two or more monomers independently selected from 3-hydroxyacids, 4-hydroxyacids, 5-hydroxyacids, glycolic acid, lactic acid, capro lactone and suitable bio-derived monomers to form an ester bond, including bio- derived poly-carboxylic acids, containing in their molecular structure at least two carboxylic functional groups, and bio-derived poly- functional monomers, containing in their molecular structure at least two functional groups able to form an ester bond if reacted with carboxylic functional groups, as for instance diols and polyols. In another preferred embodiment the bio-polyester used in the composition of the present invention is selected from poly(3-hydroxybutyrate), poly(3-hydroxyvalerate), poly(3- hydroxybutyrate-co-3-hydroxyvalerate) and blends thereof.

Dispersing agent

In a preferred embodiment of the present invention at least one dispersing agent is used to homogeneously disperse the aforesaid bio-polyester, in a percentage ranging from 20 to 99.9% by weight of the total mass of the final composition. In a more preferred embodiment such percentage is above 50%, preferably from about 55% to about 99%, more preferably between about 65% and about 95%. In a highly preferred embodiment the dispersing agent is bio-derived and/or bio-degradable, and is preferably both bio-degradable and bio-derived. Such dispersing agent is selected from compounds which are miscible with or soluble in water. In a preferred embodiment the molecular structure of the dispersing agent contains at least one functional group, i.e. molecular moiety, which is able to establish chemical interactions with water molecules. Examples of such interactions are hydrogen bonding, dipole-dipole interactions, induced dipole interactions, and Van der Waals interactions. Such functional groups include, but are not limited to, hydroxyl, carboxy, ketone, amino and guanidinium groups. In one embodiment of the present invention the dispersing agent reacts with the bio-polyester when contacted with it, as better discussed hereinafter for the preparation methods. Thus in a preferred embodiment, in addition to moieties which allow to establish chemical interactions with water, the molecular structure of the dispersing agent contains at least one functional group which can react itself or upon preliminary activation or in combination with other reactants and/or catalyst, with an ester bond of a polyester structure, consequently causing the break of the polyester chain in the positions in which the reaction with the dispersing agent takes place. Such functional groups include, but are not limited to, -OR, -OM, - C(0)OR, -NRR', -SR, -SM, -X, -SiRR'R", -SiRR'X, -SiRX₂, -SiX₃, - LiAlHR₂, -MgX (R = H, aliphatic radical, or aromatic radical; R' = H, aliphatic radical, aromatic radical, or R; R" = H, aliphatic radical, aromatic radical, R, or R'; M = monovalent cation of an atom other than carbon and hydrogen, for example an alkali metal, or ammonium; X = halogen). Exemplary classes of dispersing agents containing different functional groups that can establish chemical interactions with water molecules and react with ester bond include diols, polyols, aminoalcohols, dithiols, polythiols, aminothiols, diamines and polyamines. In a more preferred embodiment of the present invention the molecular structure of the dispersing agent contains at least one hydroxyl group able to establish chemical interactions with water molecules, and more preferably at least one additional hydroxyl group to be reacted with an ester bond of a polyester breaking the polyester chain in the position in which the reaction occurs. Bio-derived and/or bio-degradable aliphatic diols and polyols and their derivatives, such as their alkoxy derivatives, their salts, their ethers, their esters or their polymers, are an exemplary class of dispersing agents that may be used in the present invention. Examples of such aliphatic diols and polyols include, but are not limited to, 1 ,2-ethanediol (ethylene glycol), 1 ,2 -propanediol (propylene glycol), 1 ,3 -propanediol, 1,2-, 2,3- 1,3- and 1 ,4-butanediol, neopentyl glycol, 1,1-, 2,2-, 3,3-, 1 ,2-, 1,3-, 1 ,4-, 1 ,5- 2,3-, 2,4- 2,5-, 3,4-, 1 ,6-hexanediol, 1,1-, 1 ,2-, 1,3-, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, di- and tetra-ethylene glycol, glycerol, erythritol, pentaerythritol, sorbitol, mannitol, maltitol, isomalt, xylitol, sugars, and cyclitols. In a more preferred embodiment of the present invention the dispersing agent suitable to be used in the composition is from the class of aliphatic diols and polyols that are liquid, viscous liquid, or semi-solid at room temperature and in any case at temperatures lower than 50°C. Although diols and polyols in solid physical status may be effectively used in the composition of the present invention, polyols that are liquid, viscous liquid, or semi-solid at a temperature close to the melting temperature of the bio- polyester used in the composition, are preferred.

Preparation

The composition of the present invention may be prepared by different methods. Although organic solvents including chlorinated solvents, inorganic and acid/base catalyst, harsh reaction conditions of temperature and pressure are well within the scope of this invention, i.e. the preparation of the aforesaid composition, in highly preferred embodiments of the present invention all the reactants used in the preparation of the aforesaid composition are bio-derived and the reaction occurs under milder conditions of pressure and temperature than those reported in the art. In a preferred embodiment the polyester is contacted with the dispersing agent at a temperature lower than the polyester melting temperature. In another preferred embodiment the reaction occurs at ambient pressure in the presence of air or alternatively in an inert gas atmosphere (e.g. helium, nitrogen, argon) to prevent the presence of moisture, oxygen and other undesired air components. In another preferred embodiment the preparation method allows for production of low molecular weight (LMW) polymers and oligomers of the polyester used in the composition. LMW polyesters may be produced by a top-down approach, i.e. breaking higher molecular weight (HMW) polymer chain into smaller chains, or by a bottom-up approach, i.e. the controlled polymerization of monomers. In certain embodiments, LMW polyesters are directly contacted with the dispersing agent, without a reaction step involving the chain breaking of HMW polymers or the controlled in situ polymerization of monomers. In a preferred embodiment the LMW polyester reacts with the dispersing agent when contacted with it at a temperature lower than the polyester melting temperature. In the resulting polyester/dispersing agent conjugate, dispersing agent molecules are covalently attached to terminal positions of the polyester chains, and, if the polyester has appropriate pendant functional groups able to react with dispersing agent, also in the positions of the chain bearing such functional groups. Depending on the temperature and the reaction time LMW polyesters can be further broken in even smaller chains. In a highly preferred embodiment the polyesters in the final composition are in the form of LMW polymers or oligomers, i.e. with a number average molecular weight lower than 100 kDa and preferably lower than 50 kDa.

In a preferred embodiment of the present invention LMW polyesters are produced in situ during the preparation of the polyester composition by contacting HMW polyesters with at least one dispersing agent able to react with said HMW polyesters at a temperature lower than the melting temperature of the HMW bio-polyester, due to scission of the HMW polyester chains due to the reaction of the dispersing agent molecules with the ester bonds of the polymer. All of the polyesters and dispersing agents listed previously may be used accordingly to the preparation method described here in any possible combination. In a preferred embodiment, the aforesaid polyesters are contacted with a dispersing agent containing at least one hydroxyl group which thus induces an alcoholysis reaction of the polyester employed. In another preferred embodiment the polyester is a PHA.

Alcoholysis of polyhydroxyalkanoates has been widely investigated as a method to produce LMW PHA. One of the first reports is from Akita et al. (Macromolecules , 1976, 9, 774-780), which described the alcoholysis reaction of poly(3-hydroxybutyrate) (PHB) with methanol in

dichloromethane using p-toluensulfonic acid as catalyst. When diols or polyols are used in place of methanol, HO-terminated PHB can be obtained, which can be further reacted to form acrylate copolymers, as reported by Oh et al. in Macromol. Symp. 2007, 249-250, 76-80; in this work PHB was reacted with 1 ,4-butanediol in chloroform again in presence of p-toluensulfonic acid. Alcoholysis with 1 ,4-butanediol has been also used by Wang et al. (Polymer Preprints, 2009, 50, 69-70) to make polymers useful for meltblown nonwoven applications using titanium propoxide catalyst in a twin screw extruder. It must be underlined that thermal degradation of PHB at high temperatures (170-

200°C) and acid or basic hydrolysis in absence of alcohols, producing different chemical terminations of fragmented PHA chains has been reported (Yu et al. Polymer, 2000, 41, 1087-1098; Nguyen et al. Biomacromolecules, 2002, 3, 219-224). More recently the production of LMW polyhydroxyalkanoates has been reported by Liu et al. (J. Polym. Res. 2012, 19, 9756-9765) by reacting PHBV with ethylene glycol at 140°C in diglyme (diglycol-methyl-ether) with continuous addition of dibutyltin dilaurate for 6-1 Oh. Similarly Spitalsky et al. previously described the reaction with ethylene glycol or glycerol in chloroform at reflux, optionally in presence of p-toluenesulfonic, acid for a controlled degradation of PHB in Polym. Degrad. Stabil. 2006, 91, 856-861. LMW PHB has been produced by reaction of PHB with polyethylene glycol (PEG400) at 165°C for 6h (Hong et al. J. Therm. Anal. Calorim. 2013, 1 11 , 1243-1250). The alcoholysis reaction has been reported to occur for PHB when melted (T > 170°C) in extruder or similar melt processing instrument in presence of polyol plasticizers (Ianigova et al. Polym. Degrad. Stabil. 2002, 77, 35^1 ; Fernandes et al. Macromol. Symp. 2004, 218, 157-164).

The industrial interest in producing LMW bio-polyesters and optionally HO-terminated bio- polyesters by alcoholysis is demonstrated by the related patent and patent applications. WO 03/051813 and US 6933404 describes various methods for making intermediates from PHA, including esters: high temperatures (> Tm of PHA), high pressures, tin -based catalyst and optionally halogenated solvents are used to form esters through reaction of PHA with alcohols. In US 5107016 the preparation of hydro xybutyric acid esters through PHB alcoho lysis, in the presence of alcohols in halogenated solvents and strong acid catalyst is described; a complex work-up procedure of the reaction mixture (neutralization, isolation, and purification of the esters) is necessary. US 5550173 describes the use of oligomers as fillers/plasticizers to increase the biodegradability of polyesters; one method involves the alcoholysis of polyesters carried out in presence of a polyfunctional alcohol and tin-based (dibutyltin laurate) catalyst: long time reflux (50h) is required when water is the dispersing agent, or, alternatively, halogenated solvents are used to facilitate the reaction. US 6555123 reports the preparation LMW PHA by reaction with 1,3-butanediol in refluxing dioxane catalyzed by strong acid. Another class of patents describe the reactive blending of melt PHA in presence of alcohols, diols and polyols. This is the case of US 2013/0090449 which discloses a method for producing bio-based hydroxyl-terminated polyesters by reacting polyesters with diols or polyols at reaction temperatures very close to the Tm of the polyester, when organic solvents are not used, typically in presence of tin-based catalyst. An alternative for the production of such HO-terminated PHA produced directly by micro-organisms in presence of diols or polyols is reported in US 6204341. In both of the latter cases hydroxyl-terminated polyesters are reported to be useful for block-copolymer synthesis (e.g. if reacted with di-isocyanates). Reactive blending is also used in US 8710172 for melt blowing of aliphatic-aromatic co-polyesters for biodegradable nonwoven webs. Very high temperatures and pressures have been reported to favor the solubility of PLA and PGA in some alcohols as described for a recovery procedure of such polyesters in US 5264614. LMW PHA are also produced in the form of hard solid matter by thermal degradation of HMW PHA at temperatures higher than the Tm of the starting HMW PHA for a specific time, with the help of high viscosity diluters, such as polyols, for a better heat-transfer and stirring while melting the polymer (US 7361725).

In accordance with the references discussed above, two main strategies for the preparation of LMW bio-polyesters by alcoholysis have been identified prior to the present invention: melting the bio- polyester in the presence of an alcohol, i.e. carrying out the alcoholysis reaction at temperature very close to or higher than the melting temperature of the polyester, or using a specific metal (tin, titanium)-based or strong acid catalyst, often dissolving the reactants in halogenated organic solvents, to carry on the reaction at lower temperatures.

Applicants have surprisingly found that the method of preparing the polyester composition of the present invention involving an alcoholysis reaction is particularly advantageous with respect to the various procedures known in the state of the art. In a preferred embodiment of the present invention, the method of preparing the polyester composition of the invention provides the advantages of working at temperatures below the melting temperature (Tm) of the starting polyester and of having a melt form of the polyester used in the composition that provides ease of stirring and heat transfer to produce a homogeneous soft paste. In fact, when the polyester is reacted with the dispersing agent bearing at least one group able to react with the ester bond, preferably a hydro xyl group, partial fragmentation of the polyester occurs.

Therefore, in the reaction with the dispersing agent, the polyester chains start to break down and this chain scission results in lower molecular weight polyester chains having a lower Tm. It is known that LMW bio-polyesters, and particularly LMW PHA (see e.g. Ianigova et al. Polym. Degrad. Stabil. 2002, 77, 35-41 ; Spitalsky et al. Polym. Degrad. Stabil. 2006, 91, 856-861), have a Tm significantly lower than corresponding HMW polymers, for example, up to 30-50°C lower in some cases.

Applicants have found that, according to the latter observation, by carrying out the reaction at temperatures lower than the Tm of the starting polyester and sufficient for the ester bond breaking, i.e. polymer chain scission, to occur and using a dispersing agent which is liquid at the reaction temperature, a soft homogeneous paste or cream is obtained, formed by the dispersing agent and the melted lower molecular weight bio-polyester produced during the reaction. When this condition is reached, with a highly homogeneous system, the stirring and the heat transfer are improved compared the beginning of the reaction when the bio-polyester is still solid, i.e. a highly heterogeneous system, and thus the reaction process itself is more effective. It is worth noting that upon cooling such a soft paste to room temperature, the reaction product remained in the form of a homogeneous cream as observed by naked eye and even by electron microscopy (SEM) analyses which were unable to detect solid particles. No particles greater than ΙΟμηι in their longer dimension were detected in any experiment, and particles lower than ΙΟμηι were highly isolated if present. Although it is well within the scope of this invention that solvents, such as organic solvents, and/or catalysts may be used to improve the reaction or decrease the time required, in a preferred embodiment they are avoided. In a highly preferred embodiment the cream produced by the aforesaid preparation method is ready-to-use and does not require any isolation or purification step or any work-up procedure. Without departing from the scope of the present invention, optional additives, some of which are hereinafter described, may be added before, after or in any moment during the process, depending on the nature and the function of the optional additive itself. In a preferred embodiment of the present invention the reaction is carried out at a temperature not higher than 15°C below the Tm of the starting polyester, preferably at a temperature at least 30°C lower than the Tm. When the dispersing agent used in the reactive process contains more than one hydroxyl group in its chemical structure, LMW HO-terminated bio- polyester chains can be produced. It is also worth noting that no purely thermal degradation or hydrolysis products as for instance terminal C=C bonds (see e.g. Yu et al. Polymer, 2000, 41, 1087- 1098; Nguyen et al. Biomacromolecules, 2002, 3, 219-224) were detected by ^!H NMR analyses in the experiments, indicating that the conditions used in the reaction, including the mild temperature, allow only the alcoholysis reaction to take place.

The preparation method for the polyester composition of the invention can be described as a melt reactive blending, which is performed without initially melting the polyester, as is usually done in melt reactive blending processes as for instance in reactive extrusion, and thus allows the

advantageous use of much lower temperatures than Tm, thereby also avoiding the thermal degradation of the polyester which can occur at temperatures close to its Tm.

Optional additives

In some embodiments of the present invention optional additives can be used in the

composition in addition to the bio-polyester and the dispersing agent. These additives can modify the properties of the composition, for example, the chemical structure and/or physical properties, primarily mechanical properties, such as viscosity. In addition to structural and mechanical functions, such additives may also confer other properties to the composition as for instance electrical, thermal, biological, optical or magnetic properties, depending on the intrinsic properties of the specific additive. In a preferred embodiment of the present invention, optional additives with structural and mechanical functions are bio-derived and/or bio-degradable, preferably both bio-degradable and bio-derived. In a preferred embodiment the percentage of each optional additive in the composition does not exceed the percentage by weight of the bio-polyester, i.e. each optional additive is used in a weight ratio of 1 or less, preferably of 0.5 or less, where the weight ratio is calculated as the weight of the optional additive divided by the weight of the bio-polyester used in the composition.

In a preferred embodiment such optional additives with structural and mechanical functions have a molecular structure with molecular moieties and functional groups able to establish chemical interactions with the polyester and/or the dispersing agent, preferably with both the polyester and the dispersing agent. Exemplary classes of such functional groups include but are not limited to carboxylic groups as carboxylates, esters, amides, thioesters, acyl halides, carbonates, carbamates, diamines, amino-alcohols. A non-limiting example of chemical interaction between an additive bearing a carboxylate or other carboxylic groups and the LMW HO-terminated bio-polyester and the dispersing agent from the class of polyols, is the formation of an ester bond from the reaction between the hydro xyl groups of the bio-polyester and the dispersing agent and the carboxylic groups of the additive, with the formation of three-dimensional network, affording a chemical gel. In another preferred embodiment of the present invention optional additives, especially natural ones can induce a variation of structural and mechanical properties by physical entrapment of a polymeric chain, for example, the polyester chain, by forming a viscous dispersion or a three-dimensional network with the dispersing agent, affording a physical gel. In another preferred embodiment additives providing both chemical and physical interactions are used. Non-limiting example of such additives are polyglucosides containing carboxyl functional groups, such as carboxyalkylcellulose derivatives, alginate, hyaluronic acid and its derivatives. Many optional additives, and especially natural ones, are suitable to modulate the structural and mechanical properties of the composition thanks to the just described properties. Such additives include natural polymers, surfactants, resins, and different emulsifying, gelling, thickeners, and cross- linking agents. Examples of optional additives include without limiting the invention to

polysaccharides, polycarboxylates, polyacrylates, gums, animal proteins as whey proteins or vegetable proteins such as soy proteins, starches, polyglucosides, for instance carboxymethylcellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxymethyl cellulose, starch, pregelatinized starch (e.g. high amylose; hydrolyzed), maltodextrins, starch chemically-modifed derivatives, succinoglycan, xylose, arabinose, ribose, xylitol, erythritol, glucose, methylglucoside, mannose, galactose, fructose, sorbitol, maltose, lactylated glycerides, propylene glycol esters, polyglycerol esters, sorbitan esters, diacetylated tartaric acid esters of mono- and diglycerides, citric acid esters of monoglycerides, stearoyl 2-lactylates, polysorbates, succinylated monoglycerides, acetylated monoglycerides, ethoxylated monoglycerides, lecithin, sucrose monoester, lactose, sucrose, raffinose, maltotriose, alginate, hyaluronic acid, schizophyllan, chitosan, chitin, glucomannan, cross- linked dextran, curdlan, xanthan gum, gellan gum, guar gum, locust bean gum, tragacanth gum, succinoglucan gum, or derivatives and/or mixtures thereof.

Although both cationic and anionic surfactants may be suitable optional additives, non-ionic and anionic, especially naturally occurring, surfactants such as polyalkoxy ethers and alkyl and carboxy polysaccharides are preferred.

According to some preferred embodiments of the preparation method, one or more additives are mixed in the composition after contacting the dispersing agent with the bio-polyester. In a preferred embodiment, one or more additives are directly mixed with the composition, and the system is optionally heated at the desired temperature, in any case below the Tm of the polyester in the composition. In another preferred embodiment water-soluble optional additives such as polyglucosides are added to the composition in an aqueous solution with a concentration preferably below 25% by weight, and the water is then evaporated by keeping the composition under stirring at temperatures higher than 80°C. These procedures are only exemplary of the addition of optional additives to the composition of the present invention.

Applications and uses of the composition

The composition of the present invention may have different applications thanks to its unique properties evident from the detailed description above.

A first exemplary application of the composition is in the preparation of water latexes and stable aqueous dispersions of the polyester contained in the composition that is highly desirable for a number of industrial applications as previously stated. The present composition can be easily mixed with water to afford a homogeneous dispersion of the polyester in water. The nature of the polyester in the composition in some preferred embodiment, i.e. HO-terminated LMW bio-polyester, is particularly appropriate to favor the stable dispersion of the bio-polyester in water thanks to the reduced length of the molecular hydrophobic chains and to the increased hydrophilic character due to the dispersing agent used in the composition. In a preferred embodiment water can be added in ratios up to 10:1 with respect to the weight of the composition, preferably while continuously mixing the dispersion during the addition of water. In a more preferred embodiment water is added in weight ratio lower than 10: 1, preferably lower than 5: 1 relative to the weight of the composition.

The compositions of the invention have a variety of uses. In certain embodiments, the compositions are useful as host materials, for example, as support, storage, carrier/de livery, and/or release systems for substances such as chemicals and nano- and micro-structured materials (e.g. nano- /micro-capsules, inorganic, organic or hybrid inorganic/organic nano-materials, and nano-sized carbon materials). The guest substance, for example, a compound or material, can be either hydrophilic or hydrophobic in view of the amphiphilic nature of the host polyester composition. The host-guest interaction may be purely chemical, purely physical or a combination of the two. The viscosity of the host polyester composition of the present invention can be modulated to be suitable for forming stable dispersions with the entrapped guest in the form of a gas, liquid, solid or semi-solid. The dispersion of the guest substance may usefully confer properties to the combined host-guest combination that are intrinsic to the guest substance, including but not limited to, physical, chemical, and/or biological properties such as, for example, enhanced thermal or electrical conductivity, color, odor and flavor, pH, anti-bacterial properties and pharmacological activity. As an example, polyphenols, a class of natural substances with antioxidant activity, in concentrated water solutions can be easily mixed with the composition of the present invention to obtain a paste or a viscous solution with antioxidant activity, for use, for example, in agriculture, the food industry or generally as a drug delivery system. To better explain the utility of the present composition other non-limiting examples of applications of the compositions of the invention include: agriculture (e.g. adhesive, chemical release etc.), food industry (e.g. human or animal food additives, fat-substitute, thickener, tooth-paste, gum-like paste etc.), cosmetics and cosmeceuticals (anti-aging, anti-bacterial, UV-protection creams, personal care items etc.), packaging and coatings (adhesive layer for films, smart-packaging, anti-oxidant, stabilizer, chemical release etc.), bio-medical and pharmaceuticals (drug delivery, cell/gene delivery, dental paste, soft filler, tissue repair, wound dressing and healing etc.), personal care and detergents

(environmentally cleaning agent, thickener, sanitizer etc.), oil industry (biodegradable well filler, drilling aid etc.), as technical fluids (thermo-vectors, anti-frost, anti- or de-icing fluids, etc.) inks and varnish (biodegradable inks, varnishes etc.), electronics (conductive gels, electrolyte for energy storage/production devices etc.).

In one embodiment, the present invention provides a composition containing an HO-terminated LMW polyester. These are desirable polymers for use for example as plasticizers or additives for higher molecular weight polymers, with the aim of increasing their biodegradability, or as building blocks for synthesis of grafted or block-copolymers. An example of the latter process is the reaction of LMW HO-terminated PHA with di-isocyanates. LMW polyesters are also interesting polymers for their different thermo-mechanical properties with respect to the correspondent HMW ones. The polyester contained in the composition can be recovered with a variety of methods, including, for example, centrifugation, membrane filtration, and solvent extraction. Although organic solvents, especially halogenated ones, are suitable for recovering the polyester from the composition, the use of water and procedures not involving toxic solvents are preferred. In a preferred embodiment a useful method for the polyester recovery from the composition of the present invention consists of decreasing the viscosity of said composition by adding a suitable amount of water and then recovering the polyester by one of the techniques listed above. In the case of PHA, suitable solvents for solvent extraction procedures include halogenated solvents, such as chloroform or dichloromethane.

All of these applications are only exemplary and explanatory of the technical and industrial interest of the object of the present invention. One skilled in the art will understand that various changes in the form and the use of the composition may be made herein without departing from the scope of the present invention.

Examples

Example 1 Preparation of a PHB dispersion in glycerol

lg of Poly-(3-hydroxybutyrate) (PHB, Tm = 175°C) and glycerol (4g) were mixed at room temperature for a few minutes. Then the mixture was heated at 130°C with vigorous stirring. After 2-3 minutes the white powder began to melt and a homogeneous cream formed, which was kept under heating for the desired time (typically up to 2 hours). The reaction product required no work-up procedures. All the operations were carried out in air. The obtained product was characterized by DSC and rheological measurements as described in detail in the following examples. 'H-NMR analyses showed signals analogous to the starting PHB as expected indicating that the 3-hydroxybutyrate monomers were not affected by the thermal reaction. No signals of alkenyl protons were detected, confirming that no hydrolysis or thermal degradation pathways occurred. Signals attributable to glyceryl chain terminations were detected. DSC analyses showed a peak at 133.8°C, which was attributed to the Tm of LMW-PHB with glyceryl termination produced by the reaction of the original HMW-PHB (Tm = 175°C) with glycerol at 130°C. Example 2 Preparation of PHB and PHBV dispersions in ethylene glycol and propylene glycol

An analogous procedure used in example 1 was repeated varying the mass percentage of PHB, by using poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV, Tm = 165 °C) in place of PHB, by using ethylene and propylene glycols as dispersing agents in place of glycerol. Many combinations were attempted obtaining in any case a homogeneous viscous cream. Instrumental analyses showed results analogous to that obtained in the experiment 1 for PHB. The conditions of temperature and reaction time for experiments and compositions performed on a number of five replications are summarized in Table 1. Bio-polymer (A) Dispersant (B) A content (wt%) Reaction time (h) Temperature (°C)

PHB Glycerol 10 1 130

15 1 130

20 2 130

25 2 130

Ethylene Glycol 20 2 130

Propylene Glycol 20 2 130

PHBV Glycerol 10 1 120

20 2 120

25 2 120

Ethylene Glycol 20 2 120

Propylene Glycol 20 2 120

Example 3 Preparation of PHB dispersions in glycerol with additives

Analogously to the procedure reported in the example 1, PHB (Tm =175°C, 1.5 g) and glycerol (6 g) were mixed at room temperature for few minutes. Then the mixture was heated at 130°C while vigorously stirring. After 2-3 minutes the white powder started melting and a homogeneous cream formed, which was kept under heating for 1 hour. An additive (sodium alginate or chitosan) was added in the form of powder or as an aqueous solution (5% w/w). The additive to PHB mass ratio was typically 1 :2. When the additive was added as an aqueous solution the resulting mixture was kept at 130°C for the time necessary to let the water evaporate, typically 1 hour. At the end of this time a viscous cream was obtained. A control experiment was performed by mixing glycerol, PHB and the desired additive at room temperature for 2 hours, obtaining a white suspension. Rheological measurements were performed to compare the cream obtained from the previous reaction with the control one, i.e. a suspension. All the samples showed a non-Newtonian behavior. The creams heated at 130°C showed a much higher, 1 -2 orders of magnitude, apparent viscosity (n_a [Pas]) than the suspensions prepared at room temperature (data recorded at a shear rate (γ) of Is^"1 at 25°C).

Characterization (rheology, DSC, ^!H NMR)

Rheological tests were carried out using a strain-controlled rheometer Rheometric ARES. The tests were carried out with cone and plate flow geometry (radius of the plate, 12.5 mm) in steady rate sweep mode. Each sample was tested twice at 25°C. Different scanning calorimetry (DSC) was performed on DSC1 Stare System (Mettler Toledo) and was employed to assess the melting temperature (Tm) of the LMW-PHA after the cream preparation. The sample was left in steady condition at -20°C for 5 min and then heated from -20°C to 300°C at a constant rate of 10°C min ¹. Measurements were carried out under 50 mL min^"1 of N₂ flow on 5-15 mg samples. Nuclear Magnetic Resonance (^!H NMR) spectra were recorded in deuterated chloroform CDC at 25°C, by using a 600 MHz Bruker Avance II Ultrashield Plus spectrometer.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

claim:

A composition comprising a dispersion of a dispersed polyester in a dispersing agent, produced by a method comprising the step of heating a mixture of a starting polyester and a dispersing agent to a temperature below the melting point of the starting polyester for a time sufficient to form a dispersion of a dispersed polyester in the dispersing agent, wherein at least a portion of the polymer chains of the dispersed polyester are conjugated with at least one molecule of the dispersing agent.

The composition of claim 1 , wherein the starting polyester is a bio-polyester.

The composition of claim 1 , wherein the starting polyester is a homopolymer or a copolymer.

The composition of claim 1 , wherein the starting polyester is selected from the group consisting of polyhydroxyalkanoates (PHA), polyglycolide (PGA), polylactide (PLA), polylactide-co- glycolide (PLGA), polycaprolactone (PCL), polydioxanone (PDO), bio-derived aliphatic copolymers, such as polyethyleneadipate (PEA) and polybutylenesuccinate (PBS),

polyethylenefuranoate (PEF), bio-derived terephthalate co-polymers, such as

polyethyleneterephtalate (PET), polytrimethyleneterephtalate (PTT), and

polybutyleneterephtalate (PBT).

The composition of claim 4, wherein the starting polyester is selected from the group consisting of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxyvalerate), poly(3- hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3- hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co- 3-hydroxypropionate, poly(3-hydroxybutyrate-4-hydroxyvalerate) and combinations thereof.

The composition of claim 5, wherein the starting polyester is selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3- hydroxy valerate) .

7. The composition of any one of claims 1 to 6, wherein the dispersing agent is miscible with or soluble in water and comprises a functional group capable of reacting with an ester bond of the polyester. 8. The composition of claim 7, wherein the dispersing agent is a diol, a polyol, an aminoalcohol, a dithiol, a polythiol, an aminothiol, a diamine or a polyamine.

9. The composition of claim 8, wherein the dispersing agent is an aliphatic diol or an aliphatic polyol.

10. The composition of claim 9, wherein the dispersing agent is selected from the group consisting of ethylene glycol; propylene glycol; 1 ,3-propanediol; 1 ,2-, 2,3- 1 ,3- and 1 ,4-butanediol;

neopentyl glycol; 1,1-, 2,2-, 3,3-, 1 ,2-, 1 ,3-, 1 ,4-, 1 ,5- 2,3-, 2,4- 2,5-, 3,4-, 1 ,6-hexanediol; 1 ,1-, 1,2-, 1,3-, 1 ,4-cyclohexanediol; 1 ,4-cyclohexanedimethanol; di- and tetra-ethylene glycol; glycerol; erythritol; pentaerythritol; sorbitol; mannitol; maltitol; isomalt; xylitol; sugars; and cyclitols.

1 1. The composition of any of claims 1 to 9, wherein the dispersing agent is a liquid or a semi solid at a temperature below about 50 C.

12. The composition of claim 11 , wherein the dispersing agent is a liquid at a temperature below about 50 C.

13. The composition of claim 11 , wherein the dispersing agent is a viscous liquid at a temperature below about 50 C.

14. The composition of any one of claims 1-9, wherein the dispersing agent is a liquid or a

semisolid at a temperature in the range of 20-30 C. 15. The composition of claim 14, wherein the dispersing agent is a liquid at a temperature in the range of 20-30 C.

16. The composition of any one of claims 1 to 6, wherein the dispersing agent is ethylene glycol, propylene glycol, glycerol or a combination thereof.

17. The composition of any one of claims 1-16, wherein the starting polyester is a high molecular weight polyester and and the dispersed polyester is a low molecular weight polyester.

18. The composition of claim 17, wherein the dispersed polyester has a number average molelcular weight of about 100 kDa or less. 19. The composition of claim 18, wherein the dispersed polyester has a number average molecular weight of about 50 kDa or less.

20. The composition of claim any one of claims 1 to 19, where the composition is substantially free of polyester degradation products.

21. A method for producing a dispersion of a dispersed polyester in a dispersing agent, comprising the step of heating a mixture of a starting polyester and a dispersing agent to a temperature below the melting point of the starting polyester for a time sufficient to form a dispersion of a dispersed polyester in the dispersing agent, wherein at least a portion of the polymer chains of the dispersed polyester are conjugated with at least one molecule of the dispersing agent.

22. The method of claim 21 , wherein the starting polyester is a bio-polyester.

23. The method of claim 21 , wherein the starting polyester is a homopolymer or a copolymer.

24. The method of claim 21 , wherein the starting polyester is selected from the group consisting of polyhydroxyalkanoates (PHA), polyglycolide (PGA), polylactide (PLA), polylactide-co- glycolide (PLGA), polycapro lactone (PCL), polydioxanone (PDO), bio-derived aliphatic copolymers, such as polyethyleneadipate (PEA) and polybutylenesuccinate (PBS),

polyethylenefuranoate (PEF), bio-derived terephthalate co-polymers, such as

polyethyleneterephtalate (PET), polytrimethyleneterephtalate (PTT), and

polybutyleneterephtalate (PBT). The method of claim 22, wherein the starting polyester is selected from the group consisting of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3 -hydro xyvalerate), poly(3- hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3- hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydro xyvalerate), poly(3-hydroxybutyrate-co 3-hydroxypropionate, and poly(3-hydroxybutyrate-4-hydroxyvalerate).

The method of claim 25, wherein the starting polyester is selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3- hydro xyvalerate) .

The method of any one of claims 21 to 26, wherein the dispersing agent is miscible with or soluble in water and comprises a functional group capable of reacting with an ester bond of the polyester.

The method of claim 27, wherein the dispersing agent is a diol, a polyol, an aminoalcohol, a dithiol, a polythiol, an aminothiol, a diamine or a polyamine.

The method of claim 28, wherein the dispersing agent is an aliphatic diol or an aliphatic polyol.

The method of claim 29, wherein the dispersing agent is selected from the group consisting of ethylene glycol; propylene glycol; 1,3 -propanediol; 1 ,2-, 2,3- 1 ,3- and 1 ,4-butanediol;

31. The method of any of claims 21 to 29, wherein the dispersing agent is a liquid or a semi solid at a temperature below about 50 C.

32. The method of claim 31 , wherein the dispersing agent is a liquid at a temperature below about 50 C.

33. The method of claim 32, wherein the dispersing agent is a viscous liquid at a temperature below about 50 C.

34. The method of any one of claims 21 -29, wherein the dispersing agent is a liquid or a semisolid at a temperature in the range of 20-30 C. 35. The method of claim 34, wherein the dispersing agent is a liquid at a temperature in the range of 20-30 C.

36. The method of any one of claims 21 to 26, wherein the dispersing agent is ethylene glycol, propylene glycol, glycerol or a combination thereof.

37. The method of any one of claims 21 -36, wherein the starting polyester is a high molecular

weight polyester and the dispersed polyester is a low molecular weight polyester.

38. The method of claim 37, wherein the dispersed polyester has a number average molecular

weight of about 100 kDa or less.

39. The method of claim 38, wherein the dispersed polyester has a number average molecular

weight of about 50 kDa or less. 40. A composition comprising a dispersion of a polyester in a dispersing agent, produced by a

method comprising the step of heating a mixture of a low molecular weight polyester and a dispersing agent to a temperature at or above the melting point of the polyester for a time sufficient to conjugate at least a portion of the polyester polymer chains with the dispersing agent and forming a dispersion of the polyester in the dispersing agent.

41. The composition of claim 40, wherein the polyester is a bio-polyester. The composition of claim 40, wherein the polyester is a homopolymer or a copolymer.

The composition of claim 40, wherein the polyester is selected from the group consisting of polyhydroxyalkanoates (PHA), polyglycolide (PGA), polylactide (PLA), polylactide-co- glycolide (PLGA), polycaprolactone (PCL), polydioxanone (PDO), bio-derived aliphatic copolymers, such as polyethyleneadipate (PEA) and polybutylenesuccinate (PBS),

polyethylenefuranoate (PEF), bio-derived terephthalate co-polymers, such as

polyethyleneterephtalate (PET), polytrimethyleneterephtalate (PTT), and

polybutyleneterephtalate (PBT).

The composition of claim 43, wherein the polyester is selected from the group consisting of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3 -hydro xyvalerate), poly(3- hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polyhy(3-droxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3- hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydro xyvalerate), poly(3-hydroxybutyrate-co- 3-hydroxypropionate, and poly(3-hydroxybutyrate-4-hydroxyvalerate).

The composition of claim 44, wherein the polyester is selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3- hydro xyvalerate) .

The composition of any one of claims 40 to 45, wherein the dispersing agent is miscible with or soluble in water and comprises a functional group capable of reacting with an ester bond of the polyester.

The composition of claim 46, wherein the dispersing agent is a diol, a polyol, an aminoalcohol, a dithiol, a polythiol, an aminothiol, a diamine or a polyamine.

The composition of claim 47, wherein the dispersing agent is an aliphatic diol or an aliphatic polyol.

49. The composition of claim 48, wherein the dispersing agent is selected from the group consisting of ethylene glycol; propylene glycol; 1 ,3-propanediol; 1 ,2-, 2,3- 1 ,3- and 1 ,4-butanediol;

50. The composition of any of claims 40 to 48, wherein the dispersing agent is a liquid or a semi solid at a temperature below about 50 C.

51. The composition of claim 50, wherein the dispersing agent is a liquid at a temperature below about 50 C.

52. The composition of claim 51 , wherein the dispersing agent is a viscous liquid at a temperature below about 50 C.

53. The composition of any one of claims 40 to 48, wherein the dispersing agent is a liquid or a semisolid at a temperature in the range of 20-30 C. 54. The composition of claim 53, wherein the dispersing agent is a liquid at a temperature in the range of 20-30 C.

55. The composition of any one of claims 40 to 45, wherein the dispersing agent is ethylene glycol, propylene glycol, glycerol or a combination thereof.

56. The composition of any one of claims 40 to 55, wherein the polyester has a number average molelcular weight of about 100 kDa or less.

57. The composition of claim 56, wherein the polyester has a number average molecular weight of about 50 kDa or less.

58. The composition of any one of claims 40 to 57, wherein the composition is substantially free of polyester degradation products.

59. A method for producing a dispersion of a polyester in a dispersing agent, comprising the step of heating a mixture of a low molecular weight polyester and a dispersing agent to a temperature at or above the melting point of the polyester for a time sufficient to conjugate at least a portion of the polyester chains with at least one molecule of the dispersing agent and form a dispersion of the polyester in the dispersing agent.

The method of claim 59, wherein the polyester is a bio-polyester.

The method of claim 59, wherein the polyester is a homopolymer or a copolymer.

The method of claim 59, wherein the polyester is selected from the group consisting of polyhydroxyalkanoates (PHA), polyglycolide (PGA), polylactide (PLA), polylactide-co- glycolide (PLGA), polycapro lactone (PCL), polydioxanone (PDO), bio-derived aliphatic copolymers, such as polyethyleneadipate (PEA) and polybutylenesuccinate (PBS),

polyethylenefuranoate (PEF), bio-derived terephthalate co-polymers, such as

polyethyleneterephtalate (PET), polytrimethyleneterephtalate (PTT), and

polybutyleneterephtalate (PBT).

The method of claim 62, wherein the polyester is selected from the group consisting of poly(3- hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxyvalerate), poly(3-hydroxybutyrate- co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3- hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3 -hydro xybutyrate-co-3 -hydroxyoctanoate), poly(3 -hydro xybutyrate-co -3 - hydroxypropionate, and poly(3-hydroxybutyrate-4-hydroxyvalerate).

The method of claim 63, wherein the polyester is selected from the group consisting of poly(3- hydroxybutyrate), poly(3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate).

65. The method of any one of claims 59 to 64, wherein the dispersing agent is miscible with or soluble in water and comprises a functional group capable of reacting with an ester bond of the polyester. 66. The method of claim 65, wherein the dispersing agent is a diol, a polyol, an aminoalcohol, a dithiol, a polythiol, an aminothiol, a diamine or a polyamine.

67. The method of claim 66, wherein the dispersing agent is an aliphatic diol or an aliphatic polyol. 68. The method of claim 67, wherein the dispersing agent is selected from the group consisting of ethylene glycol; propylene glycol; 1,3 -propanediol; 1 ,2-, 2,3- 1 ,3- and 1 ,4-butanediol;

69. The method of any of claims 59 to 67, wherein the dispersing agent is a liquid or a semi solid at a temperature below about 50 C. 70. The method of claim 69, wherein the dispersing agent is a liquid at a temperature below about 50 C.

71. The method of claim 70, wherein the dispersing agent is a viscous liquid at a temperature below about 50 C.

72. The method of any one of claims 59-66, wherein the dispersing agent is a liquid or a semisolid at a temperature in the range of 20-30 C.

73. The method of claim 72, wherein the dispersing agent is a liquid at a temperature in the range of

74. The method of any one of claims 59 to 64, wherein the dispersing agent is ethylene glycol, propylene glycol, glycerol or a combination thereof.

75. The method of any one of claims 59 to 74, wherein the polyester has a number average

molelcular weight of about 100 kDa or less.

76. The method of claim 75, wherein the modified polyester has a number average molecular

weight of about 50 kDa or less. 77. A composition comprising a dispersion of a polyester in a dispersing agent, wherein at least a portion of the polymer chains of the polyester are conjugated to at least one molecule of the dispersing agent.

78. The composition of claim 77, wherein the polyester is a bio-polyester.

79. The composition of claim 77, wherein the polyester is a homopolymer or a copolymer.

80. The composition of claim 77, wherein the polyester is selected from the group consisting of polyhydroxyalkanoates (PHA), polyglycolide (PGA), polylactide (PLA), polylactide-co- glycolide (PLGA), polycapro lactone (PCL), polydioxanone (PDO), bio-derived aliphatic copolymers, such as polyethyleneadipate (PEA) and polybutylenesuccinate (PBS),

polyethylenefuranoate (PEF), bio-derived terephthalate co-polymers, such as

polyethyleneterephtalate (PET), polytrimethyleneterephtalate (PTT), and

polybutyleneterephtalate (PBT).

81. The composition of claim 80, wherein the polyester is selected from the group consisting of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3 -hydro xyvalerate), poly(3- hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polyhy(3-droxybutyrate-co-3- hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3 -hydro xybutyrate- co-3-hydroxypropionate, and poly(3-hydroxybutyrate-4-hydroxyvalerate).

82. The composition of claim 81 , wherein the polyester is selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3- hydroxy valerate) . 83. The composition of any one of claims 77 to 82, wherein the dispersing agent is miscible with or soluble in water and comprises a functional group capable of reacting with an ester bond of the polyester.

84. The composition of claim 83, wherein the dispersing agent is a diol, a polyol, an aminoalcohol, a dithiol, a polythiol, an aminothiol, a diamine or a polyamine.

85. The composition of claim 84, wherein the dispersing agent is an aliphatic diol or an aliphatic polyol. 86. The composition of claim 85, wherein the dispersing agent is selected from the group consisting of ethylene glycol; propylene glycol; 1 ,3-propanediol; 1 ,2-, 2,3- 1 ,3- and 1 ,4-butanediol;

87. The composition of any of claims 77 to 85, wherein the dispersing agent is a liquid or a semi solid at a temperature below about 50 C. 88. The composition of claim 87, wherein the dispersing agent is a liquid at a temperature below about 50 C.

89. The composition of claim 88, wherein the dispersing agent is a viscous liquid at a temperature below about 50 C.

90. The composition of any one of claims 77 to 85, wherein the dispersing agent is a liquid or a semisolid at a temperature in the range of 20-30 C. The composition of claim 90, wherein the dispersing agent is a liquid at a temperature in the range of 20-30 C.

The composition of any one of claims 77 to 82, wherein the dispersing agent is ethylene glycol, propylene glycol, glycerol or a combination thereof.

The composition of any one of claims 77 to 92, wherein the polyester has a number average molelcular weight of about 100 kDa or less.

The composition of claim 93, wherein the polyester has a number average molecular weight of about 50 kDa or less.

The composition of any one of claims 77 to 94, wherein the composition is substantially free of polyester degradation products.