WO2015092073A1 - Polyester - Google Patents

Abstract

The present invention relates to a process for producing a polyester, which method comprises: (i) providing a dicarboxylic acid comprising an amount of an organic acid not more than 50ppm, wherein the pKa value of the organic acid at 25°C is not more than 3.7, and a diol; and (ii) reacting the said dicarboxylic acid and diol in the presence of from 0ppm to 2000ppm of the organic acid relative to the polyester. The invention also relates to use of an organic acid having a pKa value at 25°C of not more than 3.7 in a process for producing a polyester by reacting the organic acid with a dicarboxylic acid comprising not more than 50ppm of the organic acid and a diol, wherein the organic acid is present in an amount of not more than 2000 ppm relative to the polyester.

Description

POLYESTER

Field of the invention

The present invention relates to a method for the preparation of a polyester and to the polyester obtainable by such a process. The invention also relates to the use of organic acids in such a process

Background to the invention

Conventional polyesters produced by the polymerization of dicarboxylic acids and diols are widely used in industry. Depending upon the end use, these polyesters typically require a particular combination of characteristics.

Accordingly, new processes for the production of new polyesters may be required to generate polyesters with new characteristics or combinations of characteristics. In addition, new raw materials and new processes may lead to new process advantages in terms of better suitability of raw materials for use in a polyester production process.

Summary of the invention

The present invention is based on a new process for the preparation of a polyester made from a dicarboxylic acid (diacid) and a diol, one or both may be in part or completely bio-based, i.e. biomass-resource-derived.

In this process, long chain branching in polymers may be controlled, in particular to reduce long chain branching and/or to restore long chain brandhing to any desired level by adding multi-functional monomers. The invention offers a broader range of branching degree than previously could be obtained:

the lower limit of branching may be set by the purity of the raw materials used; the upper limit may be set by adding more branching agent, and may be capped by the dose where excessive branching turns into crosslinking (ie gelling).

Thus, when using biobased succinic acid, it is possible to make polyester with a very low degree of branching. This may be useful in processes where a very low viscosity is desired, such as in melt blown fibers.

In this process, the amount of organic acids, more specifically multifunctional monomers, (ie. monomers with functionality > 2) such as malic acid, is controlled so that there is an appropriate amount of such organic acid present in the condensation reaction. We show that accurately controlling the amounts of organic acids, such as multifunctional acids, can be advantageous in the preparation of a polyester.

Typically, monomers contain some degree of impurities, which, depending on type and amount of impurities, may affect the polymerization characteristics of such a monomer and/or the application potential of the resulting polyester.

The presence of such impurities can manifest itself in different ways, for example by color formation, interference with catalyst activity or by influencing the polymerization process directly. Examples of the latter case may be a) mono-functional monomers, which can lead to slower polymerisation speed, incomplete polymerization and low molecular weight materials, or b) multifunctional monomers, which may lead to branching, and eventually to crosslinking, which in turn affects many physical properties of a polymer like viscosity, melt strength, tensile strength, crystallinity, etc

It was found that certain monomers, such as succinic acid derived from a biomass resource, may contain very low amounts of certain impurities, such as for example malic acid. Malic acid is a three-functional molecule (two carboxylic acid groups and one hydroxy group) and can thus lead to branching in typical polycondensation reactions.

Monomers with a low malic acid content may have the following advantages: in pure form, they allow for the synthesis of highly linear polymers, which are advantageous in some applications;

by manually adding malic acid (or other multi-functional monomers) to either the pure monomer, or to the polycondensation reaction mixture, it allows for tuning the degree of branching in the resulting polymer from very low (lower than is typical) to very high, in order to reach a specific property profile suitable for a specific application. Accordingly, polyesters can be specifically for any one of a wide range of applications.

A second part of the invention is the realisation that, in order to reach high / improved/commercially attractive polymerisation speeds, it may be necessary to manually add malic acid (or other multifunctional monomers). This will increase the polymerisation speed, and thereby lower the risk of colour formation or polymer degradation.

Accordingly, the invention provides a process for producing a polyester, which method comprises:

(i) providing a dicarboxylic acid comprising an amount of an organic acid not more than 50ppm, wherein the pKa value of the organic acid at 25° is not more than 3.7, and a diol; and

(ii) reacting the said dicarboxylic acid and diol in the presence of from Oppm to 2000ppm of the organic acid relative to the polyester (i.e. total amount of dicarboxylic acid and diol).

The invention also provides use of an organic acid having a pKa value at 25°C of not more than 3.7 in a process for producing a polyester by reacting the organic acid with a dicarboxylic acid comprising not more than 50ppm of the organic acid and a diol, wherein the organic acid is present in an amount of not more than 2000 ppm relative to the polyester (i.e. total amount of dicarboxylic acid and diol).

When carrying out polymerization in the presence of too much branching agent (i.e. more than 2000ppm of the organic acid), there is a risk of excessive crosslinking/gelling, potentially leading to defects in the polyester and products derived from such polyesters.

The invention further provides a polyester, comprising as a main repeating unit thereof a dicarboxylic acid unit and a diol unit, obtainable by a process or use of the invention. The polyester typically has an improved balance between degree of branching on one hand, and polymerisation speed on the other hand.

Further, the invention relates to a moulded product obtainable by moulding a polyester obtainable by a process or use of the invention and a pellet obtained from or comprising a polyester obtainable by a process or use of the invention. Brief description of the drawings

Figure 1 shows the molecular mass distribution curve (bell shaped curves) and the diagonal lines represent the Mark Houwink curves for different PBS types.

Figure 2 shows some key parameters of the polymerization process. Temperature is plotted on the primary Y-axis, while stirrer torque is plotted on the secondary Y-axis, both as function of polymerisation time (on X-axis). One curve represents a fossil-based PBS, whereas the other curve represent a bio-based PBS

Detailed description of the invention

Throughout the present specification and the accompanying claims, the words "comprise", "include" and "having" and variations such as "comprises", "comprising", "includes" and "including" are to be interpreted inclusively. That is, these words are intended to convey the possible inclusion of other elements or integers not specifically recited, where the context allows.

The articles "a" and "an" are used herein to refer to one or to more than one (i.e. to one or at least one) of the grammatical object of the article. By way of example, "an element" may mean one element or more than one element.

The present invention relates to a method for the preparation of a polyester having a diol unit and a dicarboxylic acid unit as main constituent units and to the polyester obtainable or obtained using such a process.

Monomers (succinic acid) available today are mainly derived from fossil resources, and typically contain fairly high levels of malic acid (ie > l OOOppm).

Such monomers can be used to make polymers, but will inherently result in branched polymers and thus to polymers with limited application potential.

We found that monomers (such as succinic acid) obtained from biomass by a fermentation process contain very low levels of impurities, specifically malic acid.

The application and use of polymers depends on their chemistry and composition. Monomers with certain levels of impurities effect and limit the properties of the resulting polymers. However, in some cases polymer properties are actively tuned by adding certain (low) amounts of additives or monomers. Having a high level of those impurities prevents or limits the possibility to add additives or monomers. As such, it is difficult to tune the properties of these polymers. Thus, the invention provides a method and use in which the amount of an organic acid, such as malic acid, may be tuned depending the desired properties of the resulting polyester. The invention may concern a method and use for the preparation of a polyester which is not a co-polyester.

In polyethylenes and polypropylenes, it is known that the degree of branching in a polymer may affect its theological properties. That is to say, the polymer processing behaviour and many end-use properties are influenced not only by molecular weight and molecular weight distribution, but also by long chain branching. The chain structural parameters have interactive effects on polymer properties. Numerous investigations have been carried out in the past few decades for the effects of long chain branching on rheological properties. This is especially due to the great variety in long-chain branching. For example, the position, number and length of the branches can lead to many different topologies. Long-chain branched polymers offer significantly different physical properties than linear polymers and polymer networks. For example, a low concentration of long chain branching in the polymer backbone influences melt rheology, mechanical behaviour, and solution properties, while large degrees of branching readily affects crystallinity.

More recently, polyesters such as poly(butylene adipate) (PBA) and poly(butylene succinate) (PBS), which decompose rapidly under natural environmental conditions, are replacing some commodity polymers due to environmental concerns.

Processing these polymers is sometimes difficult due to low melt strength and melt viscosity. Thus, researchers have focused on modifying the degree of long chain branching in polyesters for enhanced melt strength and melt viscosity and depending on the polyester properties for new high performance applications. The current invention is thus based on processes for the preparation of polymers in which the amount of , for example, long chain branching may be controlled so that the resulting polymer may be matched to its intended end use. Thus, the invention relates to the use of raw material and the subsequent polyester with, typically, not more than 50ppm organic acid relative to the dicarboxylic acid. The invention also concerns use of added organic acid in a polyester polymerization reaction, typically up to 2000ppm on the basis of the total amount of dicarboxylic acid and diol. A polyester low in organic acid, such as malic acid may show:

faster crystallisation;

a lower viscosity at low shear rates (beneficial for certain processing methods like thin-wall injection muolding).

A polyester high in organic acid may show:

easier to reach higher molecular weights;

a higher viscosity at low shear rates;

a higher melt strength (beneficial for certain processing methods like extrusion, film blowing);

a higher polymerisation speed, leading to increased output, less risk of polymer degradation during processing, and less risk of colour formation.

A polyester too rich (ie > 2000ppm relative to the total amount of dicarboxylic acid and diol) in malic acid bears the risk of crosslinking / gelling and should preferably be avoided.

Accordingly, the invention relates to a process for producing a polyester, which method comprises;

(i) providing a dicarboxylic acid comprising an amount of an organic acid not more than 50ppm, wherein the pKa value of the organic acid at 25°C is not more than 3.7, and a diol; and

(ii) reacting the said dicarboxylic acid and diol in the presence of from Oppm to 2000ppm of the organic acid relative to the total amount of dicarboxylic acid and diol.

In the method of the invention, a dicarboxylic acid unit and a diol unit are used. Either one of the dicarboxylic acid and/or diol, or a portion of either thereof, may be derived from a biomass resource or resources.

Critically, the process of the invention is carried out in the presence of low amounts of an organic acid, typically a multifunctional organic acid, such as malic acid. Thus, the dicarboxylic acid monomer used in the polymerization process typically comprises not more than 50ppm of the organic acid, not more than 40ppm of the organic acid, not more than 40 ppm, not more than 30ppm or not more than 20ppm of the organic acid. That is to say, the dicarboxylic acid monomer is typically isolated in such a way that it comprises not more than 50ppm of the organic acid. Accordingly, low amounts of the organic acid, such as malic acid, may be present in the dicarboxylic acid monomer (i.e. as an impurity). Additional organic acid, typically the same organic acid present in low amounts in the dicarboxylic acid monomer may be added to the dicarboxylic acid and/or diol. That is to say, organic acid may be added to the dicarboxylic acid and/or to the diol prior to reacting the dicarboxylic acid with the diol. That is to say, the method of the reaction may be carried out in the presence of an amount of added organic acid, such as malic acid. This is organic acid that is present in addition to that present, for example as an impurity, in the dicarboxylic acid monomer.

The dicarboxylic acid, diol and, optionally, added malic acid may be combined simultaneously, separately or sequentially.

Thus, the polymerization reaction may be carried out in the presence of not more than 2000ppm of additionally added organic acid (relative to the total amount of dicarboxylic acid and diol). That is to say from 0 to 2000ppm relative to the total amount of dicarboxylic acid and diol may be added to the dicarboxylic acid and/or diol.

In a process of the invention, the dicarboxylic acid unit constituting the main repeating unit of the polyester may be a succinic acid unit. At least a part of such succinic acid used as raw material may be biomass-resource-derived.

In a process of the invention, the organic acid has two or more, typically three or more active hydrogen groups per molecule.

In the invention, the organic acid may be one other than a mono-acid and/or other than a di-acid. The organic acid may be one other than citric acid.

The organic acid may be malic acid or tartaric acid. The organic acid could be fumaric acid or orotic acid.

The invention also relates to use of an organic acid having a pKa value at 25°C of not more than 3.7 in a process for producing a polyester by reacting the organic acid with a dicarboxylic acid comprising not more than 50ppm of the organic acid and a diol, wherein the organic acid is present in an amount of not more than 2000 ppm relative to the total amount of dicarboxylic acid and diol.

In the use of the invention, the organic acid is used in an amount to achieve a desired level of branching in the polyester and/or a desired viscocity of the polyester.

In the use of the invention, a dicarboxylic acid unit and a diol unit are used. Either one of the dicarboxylic acid and/or diol, or a portion of either thereof, may be derived from a biomass resource or resources. Critically, the use of the invention is carried out in the presence of low amounts of an organic acid, such as malic acid. The organic acid is added to the dicarboxylic acid and/or to the diol prior to reacting the dicarboxylic acid with the diol.

In the invention, the pKa value at 25°C of not more than 3.7 may be the lowest pKa value (where the acid has more than one pKa value).

The low amounts of malate may be present in the dicarboxylic acid monomer (i.e. as an impurity) and/or may be added to the dicarboxylic acid and diol. That is to say, the organic acid may be added to the dicarboxylic acid and/or to the diol prior to reacting the dicarboxylic acid with the diol.

Typically, the total amount of organic acid added to the polymerization reaction (in a process or use of the invention) will be not more than 2000ppm, not more than 1500, not more than 1000, not more than 900ppm, not more than 800ppm, not more than 700ppm, not more than 600ppm, not more than 500ppm, not more than 400ppm, not more than 300ppm, not more than 200ppm, not more than 100ppm, not more than 50ppm or not more than 20ppm relative to the total amount of dicarboxylic acid and diol.

Here, the total amount of organic acid refers to the amount added in addition to that present in the dicarboxylic acid (or diol) if any is added.

Typically, the total amount of organic acid present in the polymerization reaction (in a process or use of the invention) will be not more than 2000ppm, not more than 1500, not more than 1000, not more than 900ppm, not more than 800ppm, not more than 700ppm, not more than 600ppm, not more than 500ppm, not more than 400ppm, not more than 300ppm, not more than 200ppm, not more than 100ppm, not more than 50ppm or not more than 20ppm relative to the total amount of dicarboxylic acid and diol.

Here, the total amount of organic acid refers to the amount present in the dicarboxylic acid and diol combined with the amount of added organic acid (if any is added).

In the process or use of the invention, the dicarboxylic acid unit constituting the main repeating unit of the polyester may be a succinic acid unit. At least a part of such succinic acid used as raw material may be biomass-resource-derived.

In a process or use of the invention, the organic acid has two or more, typically three or more active hydrogen groups per molecule. In the invention, the organic acid may be one other than a mono-acid and/or other than a di-acid. The organic acid may be one other than citric acid.

The organic acid may be malic acid or tartaric acid. The organic acid could be fumaric acid or orotic acid.

Examples of the organic acid having a pKa value at 25°C of not more than 3.7 include organic acids described in CRC Handbook of Chemistry and Physics, 7th Edition, p.8-43 to p.8-56, CRC Press (1995).

Of these, a lower limit value of the pKa value is preferably 2.0 or more, more preferably 2.5 or more, and especially preferably 3.1 or more; and an upper limit value thereof is preferably not more than 3.5. Incidentally, among the organic acids, there are compounds displaying two or more pKa values. In the present invention, the pKa value of a compound as referred to in that case means the lowest value.

Though the organic acid having a pKa value at 25°C of not more than 3.7 is not particularly limited, organic acids having three or more active hydrogen groups per molecule are preferable; malic or tartaric acid, and a mixture thereof are more preferable; and a mixture thereof are the most preferable; and especially preferable.

In particular, in the case of using succinic acid as a raw material, there may be the case where malic acid is contained in the raw material succinic acid depending upon the production method of succinic acid. In such case, the production of a polyester polyol can also be carried out by as a combination with a diol component choosing -containing succinic acid and using it as it is or using it by adding according to the need.

In the organic acid having three or more active hydrogen groups per molecule, its pKa value tends to decrease due to the effect of OH group at a position of carbonyl group as compared with that of an organic acid having not more than 2 active hydrogen groups per molecule.

As to the content of the organic acid having a pKa value at 25°C of not more than 3.7, in general, a lower limit value thereof is more than 0 ppm, preferably 0.001 ppm or more, more preferably 0.01 ppm or more, still more preferably 0.05 ppm or more, especially preferably 0.07 ppm or more, and most preferably 0.1 ppm or more relative to the dicarboxylic acid. An upper limit thereof is in general not more than 1 ,000 ppm, for example not more than 800 ppm, such as not more than 600 ppm. In the present description, an analysis (detection) method of the organic acid having a pKa value at 25°C of not more than 3.7 is classified into two cases, and the analysis is carried out in accordance with these cases.

In the present description, an analysis (detection) method of the organic acid having a pKa value at 25°C of not more than 3.7 may be as follows. The analysis may be carried out by means of UPLC-MS/MS method with a total runtime of 7 min, using a Waters UPLC system with triple quadrupole mass detection (Waters TQD). The column used is a Waters Acquity UPLC HSS T3 column (150x2.1 mm, 1 .8 μηι); the column temperature is kept at 40°C; as the mobile phase, either 0.1 % formic acid in water or in acetonitrile is used is used as an eluent and allowed to pass at a flow rate of 0.4 mL/min. Successively, the fractionated components are introduced into an MS detector. The fractionated component having been introduced into the MS detector is detected by ESI (negative ionisation), MRM mode (dwell 0.0s, 0-2min). The LOQ is set at 0.05 mg/L while the LOD is set at 0.01 mg/L based on the S/N ratio of 10 and 3, respectively.

In this process one of more additions of one or more substances may be made, either in the polymerization step, to one or both of the dicarboxylic acid and diol, or during preparation of one or both of the dicarboxylic acid (in particular if one of those is bio-based).

These additions lead to improved qualities, either in terms of an improved quality of the dicarboxylic acid and/or diol or in terms of the resulting polyester.

In the production of a dicarboxylic acid from a biomass-resource-derived, a microorganism capable of producing a dicarboxylic acid may be used to generate that dicarboxylic acid, typically be fermentation. The dicarboxylic acid may then be recovered from the fermentation broth, for example in a crystalline form.

Examples of the dicarboxylic acid constituting the dicarboxylic acid unit include aliphatic dicarboxylic acids or a mixtures thereof, aromatic dicarboxylic acids or a mixture thereof, and a mixture of aromatic dicarboxylic acid and aliphatic dicarboxylic acid.

Of these, dicarboxylic acids having, as a primary component thereof, an aliphatic dicarboxylic acid may be preferred. The term "main component" as used herein means that the component is contained in an amount of typically 50 mole% or greater, preferably 60 mole% or greater, more preferably 70 mole% or greater, especially preferably 90 mole% or greater based on the whole dicarboxylic acid unit.

Examples of the aromatic dicarboxylic acids include terephthalic acid and isophthalic acid. Examples of the derivatives of the aromatic dicarboxylic acid include lower alkyl esters of an aromatic dicarboxylic acid, more specifically, methyl ester, ethyl ester, propyl ester and butyl ester of an aromatic dicarboxylic acid. Of these, terephthalic acid is preferred as the aromatic dicarboxylic acid and dimethyl terephthalate is preferred as the derivative of an aromatic dicarboxylic acid. Even when an aromatic dicarboxylic acid as disclosed herein is used, a desired aromatic polyester, for example, a polyester of dimethyl terephthalate and 1 ,4-butanediol is available by using an arbitrary aromatic dicarboxylic acid.

As the aliphatic dicarboxylic acid, aliphatic dicarboxylic acids or derivatives thereof are used. Specific examples of the aliphatic dicarboxylic acid include linear or alicyclic dicarboxylic acids having typically 2 or greater but not greater than 40 carbon atoms such as oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid and cyclohexanedicarboxylic acid. As the derivative of the aliphatic dicarboxylic acid, lower alkyl esters of the aliphatic dicarboxylic acid such as methyl ester, ethyl ester, propyl ester and butyl ester of the aliphatic dicarboxylic acid and cyclic acid anhydrides of the aliphatic dicarboxylic acid such as succinic anhydride are usable. Of these, adipic acid, succinic acid, and dimer acid and mixtures thereof are preferred as the aliphatic dicarboxylic acid from the viewpoint of the physical properties of the polymer thus available, with the aliphatic dicarboxylic acids having succinic acid as a main component being especially preferred. As the derivative of the aliphatic dicarboxylic acid, methyl adipate and methyl succinate, and mixture thereof are more preferred.

These dicarboxylic acids may be used either singly or as a mixture of two or more thereof.

The term "diol unit" as used herein means a unit derived from aromatic diols and/or aliphatic diols. Known diol compounds are usable as them, but aliphatic diols are preferred.

Although no particular limitation is imposed on the aliphatic diol insofar as it is an aliphatic or alicyclic compound having two OH groups, examples of it include aliphatic diols having carbon atoms, as the lower limit thereof, of 2 or greater and, as the upper limit, of typically 10 or less, preferably 6 or less. Of these, diols having an even number of carbon atoms and mixtures thereof are preferred because polymers having a higher melting point are available from them.

Specific examples of the aliphatic diol include ethylene glycol, 1 ,3-propylene glycol, neopentyl glycol, 1 ,6-hexamethylene glycol, decamethylene glycol, 1 ,4- butanediol and 1 ,4-cyclohexanedimethanol. These may be used either singly or as a mixture of two or more of them.

Of these, ethylene glycol, 1 ,4-butanediol, 1 ,3-propylene glycol, and 1 ,4- cyclohexanedimethanol are preferred, of which ethylene glycol and 1 ,4-butanediol, and mixtures thereof are preferred. Furthermore, aliphatic diols having 1 ,4-butanediol as a main component thereof are more preferred, with 1 ,4-butanediol being especially preferred. The term "main component" as used herein means that it is contained in an amount of typically 50 mole% or greater, preferably 60 mole% or greater, more preferably 70 mole% or greater, especially preferably 90 mole% or greater based on all the diol units.

Although no particular limitation is imposed on the aromatic diol insofar as it is an aromatic compound having two OH groups, examples of it include aromatic diols having 6 or greater carbon atoms as a lower limit and 15 or less carbon atoms as an upper limit. Specific examples of it include hydroquinone, 1 ,5-dihydroxynaphthalene, 4,4'-dihydroxydiphenyl, bis(p-hydroxyphenyl)methane and bis (p-hydroxy-phenyl) -2,2- propane. The content of the aromatic diol in the total amount of all the diols is typically 30 mole% or less, preferably 20 mole% or less, more preferably 10 mole% or less.

Furthermore, a both-hydroxy-terminated polyether (polyether having a hydroxyl at both terminals) may be used in combination with the above-described aliphatic diol. With regard to the number of carbon atoms of the both-hydroxy-terminated polyether, the lower limit is typically 4 or greater, preferably 10 or greater, while the upper limit is typically 1000 or less, preferably 200 or less, more preferably 100 or less. Specific examples of the both-hydroxy-terminated polyether include diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly-1 ,3-propanediol and poly-1 ,6-hexamethylene glycol. Moreover, copolymer polyether between polyethylene glycol and polypropylene glycol, and the like can be also used. The using amount of the both-hydroxy-terminated polyether is typically 90 wt.% or less, preferably 50 wt.% or less, more preferably 30 wt.% or less in terms of a calculated content in the polyester.

In the invention, the dicarboxylic acid and/or diol may be derived wholly or in part from a biomass resource, i.e. it may be biobased.

The term "biomass resource" as used herein indicates a resource in which the energy of sunlight has been stored in the form of starches or celluloses by the photosynthesis of plants, animal bodies which have grown by eating plant bodies, and to products available by processing plant or animal bodies.

Of these, plant resources are more preferred as biomass resources. Examples include wood, paddy straws, rice husks, rice bran, long-stored rice, corn, sugarcanes, cassava, sago palms, bean curd refuses, corn cobs, tapioca wastes, bagasse, plant oil wastes, potatoes, buckwheats, soybeans, oils or fats, used paper, residues after paper manufacture, residues of marine products, livestock excrement, sewage sludge and leftover food. Of these, wood, paddy straws, rice husks, rice bran, lang-stored rice, corn, sugarcanes, cassava, sago palms, bean curd refuses, corn cobs, tapioca wastes, bagasse, plant oil wastes, potatoes, buckwheats, soybeans, oils or fats, used gaper, and residues after paper manufacture are preferred, with wood, paddy straws, rice husks, long-stored rice, corn, sugarcanes, cassava, sago palms, potatoes, oils or fats, used paper, and residues after paper manufacture being more preferred. Corn, sugarcanes, cassava and sago palms are most preferred. These biomass resources typically contain a nitrogen element, and many alkali metals and alkaline earth metals such as Na, K, Mg and Ca.

These biomass resources are transformed into carbon sources after, not particularly limited to, known pretreatment and glycosylation steps such as chemical treatment with acids or alkalis, biological treatment with microorganisms and physical treatment. This step typically includes, but not particularly limited to, a miniaturization step by pretreatment to make biomass resources into chips, or shave or grind them. It includes if necessary a pulverization step in a grinder or mill. The biomass resources thus miniaturized are converted into carbon sources after the pretreatment and glycosylation-steps. Specific examples of the pretreatment and glycosylation methods include chemical methods such as treatment with a strong acid such as sulfuric acid, nitric acid, hydrochloric acid or phosphoric acid, alkali treatment, ammonia freeze explosion treatment, solvent extraction, supercritical fluid treatment and treatment with an oxidizing agent; physical methods such as fine grinding, steam explosion treatment, treatment with microwaves and exposure to electron beam; and biological treatment such as hydrolysis with microorganisms or enzymatic treatment.

As the carbon sources derived from the above-described biomass resources, typically used are fermentable carbohydrates such as hexoses such as glucose, mannose, galactose, fructose, sorbose and tagatose; pentoses such as arabinose, xylose, ribose, xylulose and ribulose; disaccharides and polysaccharides such as pentosan, saccharose, starch and cellulose; oils or fats such as butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, monocutinic acid, arachic acid, eicosenoic acid, arachidonic acid, behenic acid, erucic acid, docosapentaenoic acid, docosahexaenoic acid, lignoceric acid, and ceracoreic acid; and polyalcohols such as glycerin, mannitol, xylitol and ribitol. Of these, glucose, fructose and xylose are preferred, with glucose being especially preferred. As carbon sources derived from plant resources in a broad sense, celluloses, a main component of paper, are preferred.

A dicarboxylic acid is synthesized using the above-described carbon sources in accordance with the fermentation process utilizing microbial conversion, a chemical conversion process including a reaction step such as hydrolysis, dehydration, hydration or oxidation, or a combination of the fermentation process and chemical conversion process. Of these, the fermentation process utilizing microbial conversion is preferred. No particular limitation is imposed on the microorganism used for microbial conversion insofar as it has a producing capacity of a dicarboxylic acid.

For example, a process for recovering of succinic acid from a biomass-derived- resource may comprise fermenting a microbial cell in a fermentation broth to produce succinic acid. Fermenting a microbial cell usually comprises growth phase during which a microbial cell is grown to a desired cell density, and a production phase during which succinic acid is produced. The fermentation conditions during a growth phase and a (succinic) production phase may be similar or different, for instance with respect to the composition of a fermentation medium, pH or temperature.

A fermentation broth may be any suitable broth allowing growth of a microbial cell and/or production of succinic acid. The fermentation broth may comprise any suitable carbon source such as glucose, fructose, galactose, xylose, arabinose, sucrose, lactose, raffinose and glycerol. Fermenting a microbial cell may be carried out under aerobic conditions, anaerobic conditions, micro-aerophilic or oxygen limited conditions, or a combination of these fermentation conditions, for instance as disclosed in WO2009/083756. An anaerobic fermentation process is herein defined as a fermentation process run in the absence of oxygen or in which substantially no oxygen is consumed, preferably less than 5, 2.5 or 1 mmol/L/h, and wherein organic molecules serve as both electron donor and electron acceptors.

Fermenting of a microbial cell may be carried out at any suitable pH between 1 and 9, depending on the microbial cell. In the event a microbial cell is a bacterial cell, the pH in the fermentation broth preferably is between 5 and 8, preferably between 5.5 and 7.5. Usually the pH of a bacterial fermentation broth is maintained at these values by adding neutralizing agents such potassium- or sodium hydroxide, or ammonium. In the event the microbial cell is a fungal cell the pH in the fermentation broth may range between 1 and 7, preferably between 2 and 6, preferably between 2.5 and 5. The pH value during a growth phase of a fungal cell may be higher than during a (succinic acid) production phase. During fermentative production of succinic acid by a fungal cell the pH value may decrease to a pH of between 1 and 4, for instance between 2 and 3, for instance between 2.5 and 3.5. The pH during a growth phase and/or a production phase during fungal fermentation may be maintained at a desired pH value by adding a neutralizing agent.

A suitable temperature at which the fermenting of a microbial cell may be carried out may be between 5 and 60 degrees Celsius, preferably between 10 and 50 degrees Celsius, more preferably between 15 and 40 degrees Celsius, more preferably between 20°C and 30 degrees Celsius, depending on the microbial cell. The skilled man in the art knows the optimal temperatures for fermenting a microbial cell.

In one embodiment, the microbial cell is a bacterium from the genus Mannheimia, Anaerobiospirillum, Bacillus, or Escherichia, or a fungal cell from the genus Schizosaccharomyces, Saccharomyces, Aspergillus, Penicillium, Pichia, Kluyveromyces, Yarrowia, Candida, Hansenula, Humicola, Torulaspora, Trichosporon, Brettanomyces, Rhizopus, Zygosaccharomyces, Pachysolen, Issatchenkia or Yamadazyma. A bacterial cell may belong to a species Mannheimia succiniciproducens, Anaerobiospirillum succiniciproducens Bacillus amylophylus, B. ruminucola or E. coli, for instance an E. coli. A fungal cell may belong to a species Saccharomyces cervisiae, Saccharomyces uvarum, Saccharomyces bayanus, Schizosaccharomyces pombe, Aspergillus niger, Penicillium chrysogenum, P. symplissicum, Pichia stipidis, Kluyveromyces marxianus, K. lactis, K. thermotolerans, Yarrowia lipolytica, Candida sonorensis, C. glabrata, Hansenula polymorpha, Torulaspora delbrueckii, Brettanomyces bruxellensis, Rhizopus orizae, Issatchenkia orientalis or Zygosaccharomyces bailii. A fungal is for instance a yeast, for instance a Saccharomyces cerevisiae.

The microbial cell may be any suitable wild-type organism, or a genetically modified microorganism. Suitable genetically modified E. coli cells are disclosed in Sanchez et al., Metabolic Engineering, 7 (2005) 229-239, WO2006/031424, and US 7,223,567. Suitable fungal cells are disclosed in WO2009/065780 and WO2009/065778.

In the present invention, these diols may be derived from biomass resources. More specifically, the diol compound may be prepared directly from carbon sources such as glucose by the fermentation process or it may be prepared by the conversion of a dicarboxylic acid, dicarboxylic anhydride or cyclic ether, which has been obtained by the fermentation process, by a chemical reaction.

For example, 1 , 4-butanediol may be prepared by a chemical reaction of succinic acid, succinic anhydride, succinate ester, maleic acid, maleic anhydride, maleate ester, tetrahydrofuran or -butyrolactone, or it may be prepared from 1 ,3- butadiene obtained by the fermentation process. Of these, a method of obtaining 1 ,4- butanediol by the hydrogenation of succinic acid in the presence of a reduction catalyst is efficient and is therefore preferred.

A process of preparing a diol compound from biomass resources by using known organic chemical catalytic reactions in combination is also used preferably. For example, when pentose is used as a biomass resource, a diol such as butane diol can easily be prepared by using known dehydration reaction and catalytic reaction in combination. The diol derived from biomass resources sometimes contains a nitrogen atom as an impurity originating from the biomass resources themselves, fermentation treatment or purification treatment including a neutralization step with an acid. In this case, specifically, it contains a nitrogen atom derived from amino acids, proteins, ammonia, urea, and fermentation microorganisms. In the present invention, any polyesters produced by a reaction of components composed mainly of various compounds belonging to the above-described respective ranges of the dicarboxylic acid unit and diol unit are embraced in the polyester obtainable by a process of the present invention. Following polyesters can be exemplified specifically as typical examples. Examples of the polyester produced using succinic acid include polyester composed of succinic acid and ethylene glycol, polyester composed of succinic acid and 1 ,3-propylene glycol, polyester composed of succinic acid and neopentyl glycol, polyester composed of succinic acid and 1 ,6- hexamethylene glycol, polyester composed of succinic acid and 1 ,4-butanediol, and polyester composed of succinic acid and 1 ,4-cyclohexanedimethanol.

Examples of the polyester produced using oxalic acid include polyester composed of oxalic acid and ethylene glycol, polyester composed of oxalic acid and 1 ,3-propylene glycol, polyester composed of oxalic acid and neopentyl glycol, polyester composed of oxalic acid and 1 , 6-hexamethylene glycol, polyester composed of oxalic acid and 1 ,4-butanediol, and polyester composed of oxalic acid and 1 ,4- cyclohexanedimethanol.

Examples of the polyester produced using adipic acid include polyester composed of adipic acid and ethylene glycol, polyester composed of adipic acid and 1 ,3-propylene glycol, polyester composed of adipic acid and neopentyl glycol, polyester composed of adipic acid and 1 , 6-hexamethylene glycol, polyester composed of adipic acid and 1 ,4-butanediol, and polyester composed of adipic acid and 1 ,4- cyclohexanedimethanol.

Polyesters obtained using the above-described dicarboxylic acid in combination are also preferred. Examples include polyester composed of succinic acid, adipic acid and ethylene glycol, polyester composed of succinic acid, adipic acid and 1 ,4- butanediol, polyester composed of terephthalic acid, adipic acid and 1 ,4-butanediol and polyester composed of terephthalic acid, succinic acid and 1 ,4-butanediol.

Polyesters obtained using the above-described process may be used to provide a copolymer polyester composed of, in addition to the diol component and dicarboxylic acid component, a copolymerizable component as a third component. As specific examples of the copolymerizable component, at least one polyfunctional compound selected from the group consisting of bifunctional oxycarboxylic acids and tri- or higher functional polyhydric alcohols, tri- or higher functional polycarboxylic acids and/or anhydrides thereof, and tri- or higher functional oxycarboxylic acids for forming a crosslinked structure. Of these copolymerizable components, bifunctional and/or tri- or higher functional oxycarboxylic acids are especially preferred because they facilitate preparation of a copolyester having a high degree of polymerization.

Specific examples of the bifunctional oxycarboxylic acid include lactic acid, glycolic acid, hydroxybutyric acid, hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydraxyisocaproic acid, and caprolactone. They may be derivatives of an oxycarboxylic acid such as esters or lactones of the oxycarboxylic acid and polymers of the oxycarboxylic acid. Moreover, these oxycarboxylic acids may be used either singly or as mixtures of two or more thereof. In the case where they have optical isomers, the optical isomers may be any of D-form, L- form, or racemic-form and they may be in the form of a solid, liquid, or aqueous solution. Of these, easily available lactic acid or glycolic acid is especially preferred. Lactic acid or glycolic acid in the form of a 30 to 95% aqueous solution is preferred because it is easily available. When a bifunctional oxycarboxylic acid is used as a copolymerizable component in order to produce a polyester having a high degree of polymerization, a desired copolyester can be obtained by the addition of any bifunctional oxycarboxylic acid during polymerization. The lower limit of the using amount at which it exhibits its effect is typically 0.02 mole% or greater, preferably 0.5 mole% or greater, more preferably 1 .0 mole% or greater based on the raw material monomer. The upper limit of the using amount is, on the other hand, typically 30 mole% or less, preferably 20 mole% or less, more preferably 10 mole% or less.

Specific modes of the polyester include, when lactic acid is used as the bifunctional oxycarboxylic acid, a succinic acid-1 ,4-butanediol-lactic acid copolyester and a succinic acid-adipic acid-1 , 4-butanediol-lactic acid copolyester; and when glycolic acid is used, a succinic acid-1 ,4-butanediol-glycolic acid copolyester.

Specific examples of the tri- or higher functional polyhydric alcohol include glycerin, trimethylolpropane and pentaerythritol. They may be used either singly or as a mixture of two or more thereof.

When pentaerythritol is used as the tri- or higher functional polyhydric alcohol as the copolymerizable component, a succinic acid-1 ,4-butanediol-pentaerythritol copolyester or a succinic acid-adipic acid-1 ,4-butanediol-pentaerythritol copolyester can be obtained. A desired copolyester can be produced by changing the tri- or higher functional polyhydric alcohol as needed. High molecular weight polyesters obtained by chain extension (coupling) of these copolyesters may also be prepared.

For the production of a polyester according to the process of the present invention, a chain extender such as carbonate compound or diisocyanate compound can be used. The using amount of it is, in terms of a carbonate bond or urethane bond content, typically 10 mole% or less, preferably 5 mole% or less, more preferably 3 mole% or less based on all the monomer units constituting the polyester. When the polyester achieved using the process of the present invention is used as a biodegradable resin, a diisocyanate or carbonate bond present therein may inhibit the biodegradability so that it is used in the following amount based on all the monomer units constituting the polyester. The carbonate bond content is less than 1 mole%, preferably 0.5 mole% or less, more preferably 0.1 mole% or less, while the urethane bond content is less than 0.06 mole%, preferably 0.01 mole% or less, more preferably 0.001 mole% or less. The carbonate bond or urethane bond content can be determined by NMR measurement such as ¹³C NMR.

Specific examples of the carbonate compound include diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, ethylene carbonate, diamyl carbonate, and dicyclohexyl carbonate. In addition, carbonate compounds derived from hydroxy compounds, which may be the same or different, such as phenols and alcohols are also usable.

Specific examples of the diisocyanate compound include known diisocyanates such as 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6- tolylene diisocyanate, diphenylmethane diisocyanate, 1 ,5-naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

Production of a high molecular weight polyester using the above-described chain extender (coupling agent) can be performed in a manner known per se in the art. After completion of the polycondensation, the chain extender is added under a homogeneous molten state to a reaction system in a solventless manner and is reacted with a polyester obtained by the polycondensation.

More specifically, a polyester resin having an increased molecular weight is available by reacting, with the above-described chain extender, a polyester which has been obtained by the catalytic reaction of the diol and the dicarboxylic acid (or anhydride thereof), has substantially a hydroxyl group as the terminal group, and has a weight average molecular weight (Mw) of 20,000 or greater, preferably 40,000 or greater. Owing to the use of a small amount of the coupling agent, the prepolymer having a weight-average molecular weight of 20, 000 or greater is free from the influence of a remaining catalyst even under severe molten condition. As a result, a high molecular weight polyester can be produced without generating a gel during the reaction.

Accordingly, when the above-described diisocyanate, for example, is used as a chain extender for the purpose of increasing the molecular weight further, a polyester having a linear structure in which prepolymers each made of a diol and a dicarboxylic acid and having a weight average molecular weight of 20, 000 or greater, preferably 40, 000 or greater have been chained via a urethane bond derived from the diisocyanate is produced.

The pressure upon chain extension is typically 0.01 MPa or greater but not greater than 1 MPa, preferably 0.05 MPa or greater but not greater than 0.5 MPa, more preferably 0.07 MPa or greater but not greater than 0.3 MPa, with the normal pressure being most preferred.

With respect to the reaction temperature upon chain extension, the lower limit is typically 100°C or greater, preferably 150°C or greater, more preferably 190°C or greater, most preferably 200°C or greater, while the upper limit is typically 250°C or less, preferably 240°C or less, more preferably 230°C or less. Too low reaction temperatures raise a viscosity and disturb homogeneous reaction. They sometimes tend to need a high stirring power. Too high reaction temperatures tend to cause gelation or decomposition of the polyester simultaneously.

With respect to the chain extension time, the lower limit is typically 0.1 minute or greater, preferably 1 minute or greater, more preferably 5 minutes or greater, while the upper limit is typically 5 hours or less, preferably 1 hour or less, more preferably 30 minutes or less, most preferably 15 minutes or less. Too short extension time tends to disturb the appearance of addition effect. Too long extension time, on the other hand, tends to cause gelation or decomposition of the polyester simultaneously.

Thus, the term "polyester" as used herein is a generic name that collectively embraces polyesters, copolyesters, high molecular weight polyesters having chain- extended (coupled), and modified polyesters. A polyester herein may be one other than a co-polyester

Typically, a polyester produced according to a method of use of the invention will have a molecular weight of at least 15,000g/mol, at least 20,000g/mol, at least 25,000g/mol, at least 30,000g/mol or higher.

Size Exclusion Chromatography (SEC) may be used to measure molecular mass of the polymers such a PBS.

SEC chromatograms for molecular mass determination of polymers such as PBS may be recorded with a Hewlett Packard 1090M2 liquid chromatograph, provided with a UV-DAD detector system and TriSEC 3.0 software. The refractive index may be measured with a HP 1047 differential refractometer at 35°C and the differential viscosity with a Viscotek H502B. The Viscotek data manager may be DM400. The signal of the light scattering may be collected at an angle of 90°. A column set 3 PPS PFG linear XL, 7 m; 8^*300 mm may be used with 1 ,1 ,1 ,3,3,3-hexafluoro-2- isopropanol/0.1 m% potassium trifluoro acetate eluent at 35 °C at a flow rate of 0.4 ml/min.

A polyester composed mainly of a diol unit and a dicarboxylic acid unit can be produced in a manner known per se in the art in the production of polyesters. The polymerization reaction for producing polyesters can be carried out under conventionally employed appropriate conditions and no particular limitation is imposed on them. Described specifically, it can be produced by the ordinarily employed melt polymerization in which an esterification reaction and/or ester exchange reaction of the above-described dicarboxylic acid component and diol component, and the oxycarboxylic acid unit or tri- or higher functional component if it is introduced, is carried out, followed by a polycondensation reaction under reduced pressure; or by the known thermal dehydration condensation method in an organic solvent. From the standpoints of economy and simplicity of the production steps, melt polymerization in a solventless manner is preferred.

The term "production reaction" as used herein defines a reaction from the starting of temperature elevation after raw materials are charged in an esterification tank to returning of the pressure of the reaction tank from reduced pressure to normal pressure or greater after preparation of a polymer having a desired viscosity under reduced pressure in a polycondensation reactor. When a polyester is produced, the diol is used in a substantially equimolar amount to the dicarboxylic acid or derivative thereof, however, it is usually employed in 0.1 to 20 moles% excess in consideration of the distillation during the esterification reaction and/or ester exchange reaction and/or polycondensation reaction. When an aromatic polyester is produced, on the other hand, the number of terminal carboxyl groups tend to increase so that the diol is used in 10 to 60 mole% excess of the dicarboxylic acid or derivative thereof.

The polycondensation reaction is preferably performed in the presence of a polymerization catalyst. The polymerization catalyst may be added in any stage without particular limitation insofar as it is prior to the polycondensation reaction. It may be added at the time of charging raw materials or at the time of starting pressure reduction at the polycondensation stage.

As the polymerization catalyst, compounds containing a metal element in Group I to Group XIV of the periodic table except hydrogen and carbon are usable. Specific examples include organic-group-containing compounds such as carboxylates, alkoxy salts, organic sulfonates and -diketonate salts each containing at least one metal selected from the group consisting of titanium, zirconium, tin, antimony, cerium, germanium, zinc, cobalt, manganese, iron, aluminum, magnesium, calcium, strontium, sodium and potassium, and inorganic compounds such as oxides or halides of the above-described metals, and mixtures thereof. These catalyst components may be contained in the raw materials of a polyester derived from biomass resources because of the above-described reason. In this case, the raw materials may be used as are as metal-containing raw materials without purifying them particularly. Polyesters having a higher degree of polymerization are sometimes prepared easily by using raw materials having a lower content of metal elements in Group I such as sodium or potassium. In such a case, raw materials purified until they become substantially free from metal elements in Group I are preferred.

Of these, metal compounds containing titanium, zirconium, germanium, zinc, aluminum, magnesium, or calcium, or a mixture thereof are preferred, of which titanium compounds, zirconium compounds and germanium compounds are especially preferred.

The catalyst is preferably a compound in the liquid form or compound soluble in an ester oligomer or polyester, because the catalyst in the molten or dissolved form at the time of polymerization increases the polymerization rate.

When the above-described metal compound is used as the polymerization catalyst, the lower limit of the using amount of it is, in terms of a metal amount based on the resulting polyester, typically 5 ppm or greater, preferably 10 ppm or greater and the upper limit is typically 30000 ppm or less, preferably 1000 ppm or less, more preferably 250 ppm or less, especially preferably 130 ppm or less. Too large amounts of the catalyst are not only economically disadvantageous but also deteriorate the thermal stability of the polymer. Too small amounts, on the other hand, lower the polymerization activity and tend to induce decomposition of the polymer during the preparation thereof. The concentration of the terminal carboxyl group of the resulting polyester decreases with a reduction in the using amount of the catalyst so that a method of reducing the using amount of the catalyst is preferred.

With regard to the temperature of the esterification reaction/or ester exchange reaction of the dicarboxylic acid component and diol component, the lower limit is typically 150°C or greater, preferably 180°C or greater and the upper limit is typically 260 °C or less, preferably 250°C or less. The reaction atmosphere is typically an inert gas atmosphere such as nitrogen or argon. The reaction pressure is typically from normal pressure to 10 kPa, with normal pressure being preferred. With regard to the reaction time, the lower limit is typically 1 hour or greater, while the upper limit is typically 10 hours or less, preferably 4 hours or less.

The polycondensation reaction after the esterification reaction and/or ester exchange reaction of the dicarboxylic acid component and the diol component is performed under vacuum while controlling the lower limit of the pressure to typically 0.01 X 10³ Pa or greater, preferably 0.05 X 10³ Pa or greater and the upper limit to typically 1 .4 X 10³ Pa or less, preferably 0.4 X 10³ Pa or less. With regard to the reaction temperature during the polycondensation reaction, the lower limit is typically 150°C or greater, preferably 180°C or greater and the upper limit is typically 260°C or less, preferably 250°C or less. The lower limit of the reaction time is typically 2 hours or greater, while the upper limit is typically 15 hours or less, preferably 10 hours or less.

During the production process of the polyester or after production of the polyester, various additives, for example, a plasticizer, ultraviolet stabilizer, coloration preventive, matting agent, deodorant, flame retardant, weathering stabilizer, antistatic, yarn friction reducing agent, release agent, antioxidant, ion exchange agent, and inorganic fine particles and organic compounds as coloring pigments may be added as needed within a range not impairing the properties of the polyester. Examples of the coloring pigment include inorganic pigments such as carbon black, titanium oxide, zinc oxide and iron oxide and organic pigments such as cyanine, styrene, phthalocyanine, anthraquinone, perynone, isoindolinone, quinophthalone, quinocridone and thioindigo. A quality additive such as calcium carbonate or silica can also be added.

In the invention, the temperature of the polyester when it is taken out from a polymerization reactor after completion of the polymerization reaction may be controlled. This makes it possible to take out a high viscosity polyester while suppressing thermal decomposition of it.

After completion, of the polymerization reaction, the polyester taken out from the polymerization reactor in the form of strands is cooled with water, air or the like. Then, it is pelletized by a known fixed or rotary cutter or pelletizer. The pellets thus obtained may be stored.

The shape of the pellets is typically spherical or cylindrical with a circular or elliptical cross-section.

The diameter of the polyester pellets is adjusted by controlling the diameter of a discharging outlet of the polymerization reactor, discharging rate of strands, taking-up rate, cutting speed or the like. Described specifically, it is adjusted, for example, by controlling the pressure in the reactor at the time of discharging the polymer therefrom or a cutting speed of a rotary strand cutter.

With respect to the diameter of the polyester pellets thus obtained, the lower limit (minimum diameter) is typically 0.1 mm or greater, preferably 0.2 mm or greater, more preferably 0.5 mm or greater, most preferably 1 mm or greater, while the upper limit (maximum diameter) is 20 mm or less, preferably 10 mm or less, more preferably 7 mm or less, most preferably 4 mm or less. Too small diameters tend to cause marked deterioration of the pellets due to hydrolysis during the storage of the pellets. Too large diameters, on the other hand, tend to cause unevenness in the product because of inferiority in the feed stability of the pellets at the time of molding.

The term "diameter of the polyester pellets" as used herein means the diameter or length of the cross-section of the polyester pellets. The term "the cross-section of the polyester pellets" means the cross-section of the polyester pellets having the maximum cross-sectional area.

A polyester composition is available by blending (kneading) the aliphatic polyester obtained in the above-described process with a conventionally known resin.

As such a resin, various conventionally-known general-purpose resins such as thermoplastic resins, biodegradable resins and natural resins are usable. Biodegradable polymers and general-purpose thermoplastic resins are preferred. They may be used either singly or as a mixture of two or more thereof. These various resins may be derived from biomass resources.

An aliphatic polyester produced according to the method of the present invention is blended (kneaded) with a known resin to yield a polyester composition having desired and wide range of properties.

The polyester composition is also available by incorporating various conventionally-known fillers therein. As a functional additive, chemical fertilizer, soil improver, plant activator or the like can also be added. The fillers can be classified roughly into inorganic fillers and organic fillers. They may be used either singly or as a mixture of two or more of them.

The polyester or composition thereof can be molded by various molding methods employed for general-purpose plastics. Examples include compression molding (compression molding, lamination molding, stampable molding), injection molding, extrusion or co-extrusion (film extrusion using inflation or T-die method, lamination, sheet extrusion, pipe extrusion, wire/cable extrusion, profile extrusion), hollow molding (blow molding of every kind), calendering, foam molding (melt foam molding, solid-phase foam molding), solid forming (uniaxial stretching, biaxial stretching, rolling, formation of oriented nonwoven cloth, thermoforming [vacuum forming, compression air forming, plastic forming), powder molding (rotation molding), and nonwoven fabric forming (dry method, adhesion method, entanglement method, spunbond method, and the like).

The polyester or composition thereof may be subjected to secondary processing suited for various purposes in order to impart it with surface functions such as chemical function, electrical function, magnetic function, mechanical function, friction/abrasion/lubrication function, optical function, thermal function or biocompatibility. Examples of the secondary processing include embossing, painting, adhesion, printing, metalizing (plating or the like), mechanical processing, and surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, coating or the like).

By the above-described molding methods, various molded products such as monolayer film, multilayer film, stretched film, shrink film, laminate film, monolayer sheet, multilayer sheet, stretched sheet, pipe, wire/cable, monofilament, multifilament, various nonwoven fabrics, flat yarn, staple, crimped fibers, stretched tape or band, striated tape, split yarn, composite fibers, blow bottle and foam. The molded products thus obtained are expected to be used for shopping bags, garbage bags, various films such as agricultural films, various containers such as cosmetic containers, detergent containers, food container, and containers for bleaching agent, fishing lines, fish nets, ropes, binding materials, surgical yarns, sanitary cover stock materials, cooling boxes, buffer materials, medical materials, electric appliance materials, chassis for household electric appliances and automobile materials.

A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.

The disclosure of each reference set forth herein is incorporated herein by reference in its entirety.

The present invention is further illustrated by the following Examples:

EXAMPLES

Example 1 :Production of polybutylene succiniate

Polybutylene succinate (PBS) polycondensations were carried out with biobased succinic acid, biobased succinic acid spiked with 1800 ppm of malic acid, and also fossil-based succinic acid. See Table 1 for an overview of succinic acid types used. All other materials were similar for all three succinic acid types and the diol was fossil- based 1 ,4 BDO.

The polymerisation process was conducted as follows:

A 2L volume, double walled oil heated stainless steel autoclave equipped with electric motor driven stirrer with torque measurement, thermocouple and vacuum system was charged with 1 ,4-butanediol and succinic acid. For the succinic acid to be spiked with malic acid, the required quantity of malic acid was added The reactor was purged during 5 minutes with nitrogen, thereafter the reactor was evacuated, and again purged with nitrogen. This cycle was repeated three times. The catalyst, titanium (IV) n- butoxide was added with syringe. A very small blanketing flow of nitrogen was maintained. The reactor was heated at atmospheric pressure under nitrogen and esterification started under stirring at 100 RPM, the product temperature was gradually increased to 210°C when no more water distilled. Vacuum was drawn, reaching 200 Pa after 25 minutes. At start of the transesterification stage, stirring was at 100 RPM after 65 min. this was gradually reduced to 25 RPM. The product temperature was allowed to rise from 210°C to end temperature of 230°C in approximately 160 min., while vacuum was gradually decreased from atmospheric pressure to 60 Pa. Stirring was kept constant at 25 RPM, allowing torque measurement for viscosity steering. When a torque of approximately 20 Nm was reached, the reactor was nitrogen pressurised to 2 bar and the polymer melt extruded at the bottom of the reactor. After solidifying the melt strand in a water bath and cutting to pellets, the polymer pellets were dried under vacuum at 50°C overnight.

Table 1 : Succinic acid types were used

Using the above mentioned raw materials, and fossil based 1 ,4-BDO, polymers have been made of similar molecular mass and molecular mass distribution as set out in Table 2.

Table 2: Polyesters prepared

Figure 1 shows the molecular mass distribution curve (bell shaped curves) and the diagonal lines represent the Mark Houwink curves of the polyesters generated in Table 2.

These Mark Houwink curves, ie the plot of log [η] vs. log M_w, usually gives a straight line with slope (a) and intercept log (K). The slope (a) can vary from 0 (compact sphere) over 0.65-0.85 (random coil) to 1 .8 (very stiff chain) revealing information about the polymer conformation in solution.

Although SA and BDO (both 2-functional monomers) will result in a predominantly linear polymer, the presence of multi-functional monomers will lead to a degree of branching, which will lead to a decrease in the Mark-Houwink plot, which is ususally especially noticeable in the higher molecular weight range. This decrease is due to the fact that branching reduces the hydrodynamic radius of a polymer and therefore also the intrinsic viscosity, without a decrease in the molecular weight.

As the curve in Figure 1 clearly shows, the curves for fossil-based PBS and biobased-PBS spiked with malic acid (both are synthesised in the presence of high levels of malic acid) strongly decreases at higher molecular weights, as opposed to the curve for non-spiked bio-based PBS, whih cshows a much more linear behaviour.

As clearly indicated above, the presence of multifunctional monomers leads to branching which in turn causes an effect on physical properties.

Additionally the degree of branching also affects the polymerisation process, as illustrated by the Figure 2. This graph shows a) temperature (primary Y-axis), b) pressure in reactor, and c) the torque (secondary Y-axis), all versus polymerisation time (X-axis); one curve represents a fossil-based PBS, whereas the other curve represent a bio-based PBS.

In order to ensure proper mixing during the polymerisation process, the rotational speed of the stirrer is stepwise reduced from 100rpm to 50rpm and 25rpm, at the time that a torque of 16Nm is reached. Once operating at 25rpm, the torque is allowed to increase until the desired end point of approximately 20Nm is reached.

The time it takes to reach a similar torque under equal conditions, is significantly longer for a PBS polymerisation based on biobased succinic acid; the torque at the end of the polymerisation is the same.

Table 3: The following table lists the time (in minutes) it takes to achieve a certain torque level, while stirring at 100. 50 and 20rpm respectively. Also the time required to reach the process end point is listed.

Time to reach torque of 16Nm @ 16Nm @ 16Nm @ End torque

100rpm 50rpm 25rpm of ~20Nm

Fossil-PBS 147 181 212 228

Bio-PBS 170 238 284 307

Claims

1 . A process for producing a polyester, which method comprises:

(i) providing a dicarboxylic acid comprising an amount of an organic acid not more than 50ppm, wherein the pKa value of the organic acid at 25°C is not more than 3.7, and a diol; and

(ii) reacting the said dicarboxylic acid and diol in the presence of from Oppm to 2000ppm of the organic acid relative to the polyester.

2. A process according to claim 1 , wherein the organic acid is added to the dicarboxylic acid and/or to the diol prior to reacting the dicarboxylic acid with the diol.

3. A process according to claim 1 or 2, wherein at least one component of the dicarboxylic acid and/or the diol is derived from a biomass resource.

4. A process according to any one the preceding claims, wherein the dicarboxylic acid unit constituting the main repeating unit of the polyester is a succinic acid unit.

5. A process according to claim 4, wherein at least a part of the succinic acid used as raw material is biomass-resource-derived.

6. A process according to any one of the preceding claims, wherein the organic acid has two or more active hydrogen groups per molecule.

7. A process according to claim 6, wherein the organic acid is malic acid, tartaric acid or citric acid.

8. Use of an organic acid having a pKa value at 25°C of not more than 3.7 in a process for producing a polyester by reacting the organic acid with a dicarboxylic acid comprising not more than 50ppm of the organic acid and a diol, wherein the organic acid is present in an amount of not more than 2000 ppm relative to the polyester.

9. Use according to claim 8, wherein the organic acid is used in an amount to achieve a desired level of branching in the polyester and/or a desired viscocity of the polyester.

10. Use according to claim 9, wherein the organic acid is added to the dicarboxylic acid and/or to the diol prior to reacting the dicarboxylic acid with the diol.

1 1 . Use according to any one of claims 8 to 10, wherein at least one component of the dicarboxylic acid and/or the diol is derived from a biomass resource.

12. Use according to any one of claims 8 to 1 1 , wherein the dicarboxylic acid unit constituting the main repeating unit of the polyester is a succinic acid unit.

13. Use according to claim 12, wherein at least a part of the succinic acid used as raw material is biomass-resource-derived.

14. Use according to any one of claims 8 to 13, wherein the organic acid has two or more active hydrogen groups per molecule.

15. Use according to claim 14, wherein the organic acid is malic acid, tartaric acid or citric acid.

16. A polyester obtainable by a process according to any one of claim 1 to 7 or use according to any one of claims 8 to 15.

17. A polyester according to claim 16 which is at least 15,000g/mol.

18. A moulded product obtained by moulding a polyester according to claim 16 or 17.

19. A pellet obtained from or comprising a polyester according to claim 18.