Copolymers having epoxy groups and their use as chain extenders Description The present invention relates to novel copolymers having epoxy groups. These polymers are particularly useful as chain extenders for hydroxyl- and/or carboxyl-terminated polymers, in particular as chain extenders for biodegradable hydroxyl- and/or carboxyl- terminated polymers. Background of the Invention:

Many condensation or step-growth polymers, including polyesters, polyamides, polyes- teramides, polycarbonates, polyurethanes and polyesterurethanes are widely used to make plastic products. The mechanical and physical properties of these polymers are highly dependent on their molecular weights. In a life cycle, these materials may experience a synthesis process, followed by an extrusion step, and a final processing step where the polymers are subjected to a thermoplastic shapeforming step in the molten state. Typically, all of these steps occur under high temperature conditions. In addition, in recent years, increased attention has been focused on improved methods of reclaim- ing and recycling the plastics made from these polymers, with an eye toward resource conservation and environmental protection. The processing steps involved in recycling these polymers also involve high temperatures. In a life cycle, some degree of polymer molecular weight degradation occurs. This molecular weight degradation may occur via high temperature hydrolysis, alcoholysis or other depolymerization mechanisms well know for these condensation or step-growth polymers. It is known that molecular weight degradation negatively affects the mechanical, thermal and rheological properties of materials, thus preventing them from being used in demanding applications or from being recycled in large proportions for their original applications. Today, there exists a considerable number of processes in the art employed to minimize loss in molecular weight and to maintain or even increase the molecular weight of the polycondensates for processing or recycling. As an instrumental part of any of these processes, chemical reactants known in the art as "chain extenders" are employed. Chain extenders are, for the most part, multi-functional molecules that are in- eluded as additives in the reactor or extruder during any or all of the described processing steps with the purpose of "re-coupling" the polymer chains that have depoly- merized to some degree. Normally the chain extender has two or more chemical groups that are reactive with the chemical groups formed during the molecular weight degradation process. By reacting the chain extender molecule with two or more poly- mer fragments it is possible to re-couple them (by bridging them), thus decreasing or even reverting the molecular weight degradation process. In the art there are numerous chain extender types and compositions, polycondensate formulations, and processing conditions described to this end.

Biodegradable polymers such as biodegradable polyesters, polyester amides, polyester urethanes, polycarbonates and polysaccharides are of particular interest for ecological reasons as they degrade when discarded into the environment. Unfortunately, the thermal or mechanical properties of biodegradable polymers as well as their processa- bility is sometimes somewhat limited. Although a large number of biodegradable polymers have been developed in the last years, they rarely have well-balanced mechanical properties. For example, some biodegradable polymers are quite rigid and brittle, which makes them poor candidates when flexible sheets or films are desired. Other biodegradable polymers such as polycaprolactone and certain aliphatic or semiaro- matic polyesters are very flexible but due to their low melting points they tend to be self-adhesive when processed or exposed to heat. Chain extension is often a prerequisite for obtaining high strength/high modulus biodegradable polymers having at the same time good processability. Di- or poly-functional epoxides, epoxy resins or other chemicals having two or more epoxy radicals, are an example of chain extending modifiers that have been used to increase the molecular weight of polymers having terminal hydroxyl or carboxyl groups. These di- or poly-functional epoxides are generally made using conventional methods by reacting an epichlorohydrin with a molecule having two or more terminal active hy- drogen groups. Examples of such chain extenders include bisphenol type or novolak type epoxy compounds, polyglycidyl esters formed by reacting carboxylic acids with epichlorohydrin, and glycidyl ethers prepared from aliphatic alcohols and epichlorohydrin. Additionally, various acrylic copolymers have been used as polymer additives to improve the melt strength and melt viscosity of polyesters and polycarbonates. These additives generally include copolymers derived from various epoxy containing compounds and olefins, such as ethylene. However, these chain extenders have met with limited success in solving the problem of molecular weight degradation in reprocessed polymers. The shortcomings of these copolymer chain extenders can be attributed, at least in part, to the fact that they are produced by conventional polymerization tech- niques which produce copolymers of very high molecular weight, which when coupled with a polycondensate can dramatically increase the molecular weight leading to localized gelation and other defects with physical characteristics which limit their capacity to act as chain extenders. US 2004/0138381 describes copolymers of (a) epoxy functionalized (meth)acrylic monomers and (b) at least one comonomer selected from styrenic monomers and (meth)acrylic monomers, the copolymers having an epoxy equivalent weight of 180 to 2800, which are useful as chain extenders to improve the properties of virgin, recycled and reprocessed condensation polymers. Heat stability of these polymers is not always satisfying.

US 2012/0083572 describes a process for preparing copolymers of styrenic monomers and (meth)acrylate monomers, which results in copolymers having improved thermal stability. These polymers have been improved with regard to heat stability, but for some application they still could be ameliorated.

Agrawal, Polymer Chem., 1 (2010) 953-964 describe homo- and copolymers having polylactone type repeating units of the formula I, which are obtained by radical ring- opening polymerization of cyclic ketene acetals, e.g. compounds of the formula M-l , such as 2-methylene-1 ,3-dioxane, 2-methylene-1 ,3-dioxepane, 4,7-dimethyl-2- methylene-1 ,3-dioxepane or 5,6-benzo-2-methylene-1 ,3-dioxepane:

(I) (M-l)

In formulae I and M-l, the variable A is a bivalent radical of the formula (CH2) _m with m being an integer from 2 to 6, wherein 1 or 2 hydrogen atoms of (CH2) _m may be replaced by 1 or 2 radicals selected form Ci-Cio-alkyl and phenyl, where one CH2 group of A, which is not adjacent to the oxygen atom, may be replaced by oxygen and where a moiety CH2CH2 may be replaced by CH=CH, 2,2-dimethyl-1 ,3-dioxolan-4,5-diyl or 1 ,2- phenylene, which is unsubstituted or may carry 1 or 2 radicals selected from halogen and Ci-C3-alkyl. Due to the presence of repeating units of formula I, these homo- and copolymers are susceptible to biodegradation.

Summary of the Invention:

The inventors of the present invention surprisingly found that the copolymers having repeating units of formula I and repeating units of monoethylenically unsaturated glyc- idyl monomers are particularly beneficial as chain extenders for hydroxyl- and/or car- boxyl-terminated polymers in that they provide polymer compositions having on the one hand good heat stability and good thermoplastic processability and on the other hand do not impart biodegradability when used as chain extenders for biodegradable polymers.

Therefore, the present invention relates to copolymers having

(a) repeating units of the formula I

where A is a radical of the formula (CH2) _m with m being an integer from 2 to 6, wherein 1 or 2 hydrogen atoms of (CH2) _m may be replaced by 1 or 2 radicals se- lected from Ci-Cio-alkyl and phenyl, where one CH2 group of A, which is not adjacent to the oxygen atom, may be replaced by oxygen and where a moiety CH2CH2 may be replaced by CH=CH, 1 ,3-dioxolan-4,5-diyl, 2,2-dimethyl-1 ,3- dioxolan-4,5-diyl or 1 ,2-phenylene, which is unsubstituted or may carry 1 or 2 radicals selected from halogen and Ci-C3-alkyl; and repeating units of the form

wherein R is hydrogen or methyl, X is CH ₂ or C=0 and Y is O or NH; wherein the total amount of repeating units of formula I and of formula II make up at least 50 mol-%, in particular at least 80 mol-% of the total number of repeating units in the copolymer.

The present invention also relates to a process for preparing these copolymers, which comprises radically copolymerizing a monomer mixture comprising at least one monomer of the formula M-l and at least one copolymer of the formula M-ll

where A, R, X and Y in formulae M-l and M-ll are as defined for formulae I and II, respectively, where the total amount of monomers M-l and M-ll is at least 50 mol-%, in particular at least 80 mol-%, based on the total amount of monomers in the monomer mixture.

The present invention also relates to the use of the copolymers of the present invention having repeating units of the formulae I and II as a chain extender for hydroxyl- terminated and/or carboxyl-terminated polymers, in particular as a chain extender for biodegradable hydroxyl-terminated and/or carboxyl-terminated polymers.

Furthermore, the present invention relates to

a method for producing a chain-extended polymer composition, which comprises reacting a copolymer of the present invention as defined herein with one or more hydroxyl- and/or carboxyl-terminated polymers as defined herein, in particular with one ore more biodegradable hydroxyl- and/or carboxyl-terminated polymers, to the polymer compositions, which are obtainable by this process,

to plastic articles made from such a polymer composition and

to methods for preparing such plastic articles, which comprises thermoplastic shaping of such a polymer composition.

Detailed Description of the Invention:

In terms of the present invention the term "alkyl" refers to saturated, linear or branched aliphatic hydrocarbon radicals having preferably 1 to 10 carbon atoms, in particular 1 , 2 or 3 carbon atoms such as methyl, ethyl, n-propyl, 2-propyl, n-butyl, 2-butyl, isobutyl, 2- methyl-2-propyl (= tert-butyl), n-pentyl, 2-pentyl, isopentyl, n-hexyl, 1-methylpentyl, 2- methylpentyl, n-heptyl, 1 -methylhexyl, 2-methylhexyl, n-octyl, 1-methylheptyl, 2- ethylhexyl, n-decyl and 2-propylheptyl.

The beneficial properties of the copolymers of the invention are achieved by the combination of the repeating units of formulae I and II. While the repeating units of formula II provide sufficient reactivity of the copolymers towards the carboxyl groups or hydrox- yl groups of the polymers which shall be subjected to chain extension, the repeating units of formula I provide the biodegradability of the copolymers and thus the biodegra- dability of the chain extended polymers. Furthermore, the copolymers of the present invention have an excellent thermal stability.

In this regard, copolymers are preferred, where the variable A of the repeating units of formula I is selected from the group consisting of (CH2) _m with m being 3, 4 or 5, where 1 or 2 hydrogen atoms may be replaced by methyl groups, CH2-CH=CH-CH2,

CH ₂ -(1 ,2-phenylene)-CH ₂ and CH2-CH2-O-CH2-CH2. In particular, A in formula I is (CH ₂ )4 or CH ₂ -(1 ,2-phenylene)-CH ₂ , especially (CH ₂ )4.

According to the present invention, copolymers are preferred, where the variable X of the repeating units of formula II is CO. According to the present invention, copolymers are preferred, where the variable Y of the repeating units of formula II is O. In particular, X is CO and Y is O.

According to the present invention, copolymers are preferred, where the variable Y of the repeating units of formula II is CH3. In particular, X is CO and R is CH3. Especially, X is CO, Y is O and R is CH ₃ .

According to the present invention, copolymers are preferred, where the molar ratio of the repeating units of formula I to the repeating units of formula II is from 5:1 to 1 :5, in particular from 1 :2 to 2:1.

In addition to the aforementioned repeating units of the formulae I and II, the polymer may also have repeating units derived from other monoethylenically unsaturated monomers C, which are different from the monomers M-ll forming repeating units of formula II. The amount of repeating units of other monomers C will generally not exceed 50 mol-%, based on the total number of repeating units. In a particular embodiment, the amount of repeating units derived from monomers C will be less than 20 mol-%, in particular less than 10 mol-%, more particularly less than 5 mol-% and especially less then 1 mol-%, based on the average total number of repeating units in the polymer. In another particular embodiment, the amount of repeating units derived from monomers C will be in the range from 1 to 50 mol-%, in particular 5 to 50 mol-%, more particularly 10 to 40 mol-% and especially less then 20 to 40 mol-%, based on the average total number of repeating units in the polymer.

Suitable monomers C are in particular selected from the following groups C.1 to C.5: C.1 esters of monoethylenically unsaturated C3-C6 monocarboxylic acids with C1-C20 alkanols, Cs-Ce cycloalkanols, phenyl-Ci-C4 alkanols or phenoxy-Ci-C4 alkanols, more particularly the aforementioned esters of acrylic acid and also the aforementioned esters of methacrylic acid;

C.2 diesters of monoethylenically unsaturated C4-C6 dicarboxylic acids with C1-C20 alkanols, Cs-Ce cycloalkanols, phenyl-Ci-C4 alkanols or phenoxy-Ci-C4 alkanols, more particularly the aforementioned esters of maleic acid;

C.3 monovinylaromatic hydrocarbons;

C.4 vinyl, allyl, and methallyl esters of saturated aliphatic C2-C18 monocarboxylic

acids; and

C.5 a-olefins having 2 to 20 C atoms, and also conjugated diolefins such as

butadiene and isoprene. Examples of monomers C.1 are, in particular, the esters of acrylic acid such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, 3- propylheptyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, benzyl acrylate, 2-phenylethyl acrylate, 1-phenylethyl acrylate, 2-phenoxyethyl acrylate, and also the esters of methacrylic acid such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, 2- butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, lauryl methacrylate, stearyl

methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-phenylethyl

methacrylate, 1-phenylethyl methacrylate, and 2-phenoxyethyl methacrylate.

Examples of monomers C.2 are, in particular, the diesters of maleic acid and the diesters of fumaric acid, more particularly di-Ci-C2o alkyl maleinates and di-Ci-C2o alkyl fumarates such as dimethyl maleinate, diethyl maleinate, di-n-butyl maleinate, dimethyl fumarate, diethyl fumarate, and di-n-butyl fumarate.

Examples of monomers C.3 are styrene, vinyltoluenes, tert-butylstyrene, a- methylstyrene, and the like, more particularly styrene.

Examples of monomers C.4 are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl hexanoate, vinyl-2-ethylhexanoate, vinyl laurate, and vinyl stearate, and also the corresponding allyl and methallyl esters. Examples of monomers C.5 are ethylene, propylene, 1-butene, isobutene, 1 -pentene, 1-hexene, diisobutene, and the like.

Among the monomers C, the monomers C.1 and C.3, in particular the esters of acrylic acid or of methacrylic acid, with C1-C20 alkanols, Cs-Cs-cycloalkanols, phenyl-Ci-C4 alkanols or phenoxy-Ci-C4 alkanols and styrene, are preferred.

Among the monomers C, the esters of acrylic acid with C2-C10 alkanols (= C2-Cio alkyl acrylates), the esters of methacrylic acid with C1-C10 alkanols (= Ci-Cio alkyl methacrylates), and styrene, are very particularly preferred.

For the purpose of the present invention, copolymers are preferred, which have a number average weight M _n in the range from 1000 to 50000, in particular in the range from 1500 to 40000 and especially in the range from 2000 to 30000. In particular the weight average weight M _w of the copolymers of the present invention is in the range from 1100 to 150000, in particular in the range from 1700 to 100000 and especially in the range from 2500 to 60000. The polydispersity index, i.e. the ratio Mw/Mn, is in the range from 1.1 to 10, in particular from 1.2 to 6. For the purpose of the present invention, copolymers are preferred, which have an epoxy equivalent weight (EEW) of from about 180 to about 2800, in particular from about 190 to 1400, especially from 200 to 1000. The EEW is understood as the amount of polymer in gram per one mol of epoxy groups in the polymer. Generally, the average amount of epoxy groups per polymer chain is at least 2 and may be generally as high as about 200 and is in particular from 4 to 150 and in particular 8 to 100, based on the number average molecular weight M _n .

The copolymers of the present invention can be prepared by radically copolymerizing a monomer mixture comprising at least one monomer of the formula M-l and at least one copolymer of the formula M-ll and optionally one or more monomers C.

Radical copolymerisation of monomers M-l, M-ll and optionally monomers C can be performed by analogy to well-established methods of radical copolymerisation of eth- ylenically unsaturated monomers, e.g. by using a polymerisation initiator, or by applying actinic radiation or by photo initiation.

As regards the monomers of the formula M-l, the preferred meanings of A given for formula I also apply to formula M-l . Examples of suitable monomers of the formula M-l include, but are not limited to, 2-methylene-1 ,3-dioxolane, 4-phenyl-2-methylene-1 ,3- dioxolane, 4-hexyl-2-methylene-1 ,3-dioxolane, 4-decyl-2-methylene-1 ,3-dioxolane, 2- methylene-1 ,3-dioxane, 2-methylene-1 ,3-dioxepane, 4,7-dimethyl-2-methylene-1 ,3- dioxepane, 2-methylene-1 ,3-dioxe-5-pene, 2-methylene-1 ,3,6-trioxocane, 4-methylene- 3,5,8,10-tetraoxabicyclo[5.3.0]decane, 9,9-dimethyl-4-methylene-3,5,8,10- tetraoxabicyclo[5.3.0]decane and 5, 6-benzo-2-methylene-1 ,3-dioxepane. Amongst those, preference is given to 2-methylene-1 ,3-dioxolane, 2-methylene-1 ,3-dioxane, 2- methylene-1 ,3-dioxepane, 4,7-dimethyl-2-methylene-1 ,3-dioxepane, 2-methylene- 1 ,3,6-trioxocane and 5, 6-benzo-2-methylene-1 ,3-dioxepane. Particular preference is given to 2-methylene-1 ,3-dioxepane and 5,6-benzo-2-methylene-1 ,3-dioxepane. Especially, monomer M-l is 2-methylene-1 ,3-dioxepane.

As regards the monomers of the formula M-l I, the preferred meanings of R, X and Y given for formula II also apply to formula M-l I. Examples of suitable monomers of the formula M-l I include, but are not limited to, allylglycidyl ether, glycidyl acrylate and glyc- idyl methacrylate. Especially, monomer M-l I is glycidyl methacrylate.

The copolymerization of monomers M-l and M-l I, and optionally monomers C, is preferably performed in the presence of a free radical polymerization initiator, in particular a thermally activatable free-radical polymerization initiator or a redox initiator system. In particular, the polymerization initiator compound is a thermally activatable free-radical polymerization initiator, i.e. a compound, which forms a carbon radical or an oxygen radical upon heating, especially an organic compound, which forms a carbon radical or an oxygen radical upon heating.

Suitable thermally activatable free-radical initiators are primarily those of the peroxy type and of the azo type. Thermally activatable free-radical initiators of the peroxy type include, inter alia, hydrogen peroxide, peracetic acid, t-butyl hydroperoxide, di-t-butyl peroxide, dibenzoyl peroxide, benzoyl hydroperoxide, 2,4-dichlorobenzoyl peroxide, 2,5-dimethyl-2,5-bis(hydroperoxy)hexane, perbenzoic acid, t-butyl peroxypivalate, t-butyl peracetate, dilauroyl peroxide, dicapryloyl peroxide, distearoyl peroxide, dibenzoyl peroxide, diisopropyl peroxydicarbonate, didecyl peroxydicarbonate, dieicosyl per- oxydicarbonate, di-t-butyl perbenzoate, ammonium persulfate, potassium persulfate, sodium persulfate and sodium perphosphate. Thermally activatable free-radical initia- tors of the azo type include, inter alia, azobisisobutyronitrile, 2,2'-azobis-2,4- dimethylvaleronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis[2-methyl-N-(2- hydroxyethyl)propionamide], 1 ,1'-azobis(1-cyclohexancarbonitrile), 2,2'-azobis(2,4- dimethylvaleronitrile), 2,2'-azobis(N,N'-dimethylenisobutyroamidine),

2,2'-azobis(N,N'-dimethylenisobutyroamidine), 2,2'-azobis(2-methylpropionamidine), N-(3-hydroxy-1 ,1-bis-hydroxymethylpropyl)-2-[1 -(3-hydroxy-1 ,1-bis-hydroxymethyl- propylcarbamoyl)-1 -methyl-ethylazo]-2-methyl-propionamide and

N-(1 -ethyl-3-hydroxypropyl)-2-[1 -(1 -ethyl-3-hydroxypropylcarbamoyl)-1 -methyl- ethylazo]-2-methyl-propionamide. Preferred are those of the azo type, in particular 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)- propionamide], 1 ,1 '-azobis(1 -cyclohexancarbonitrile) and 2,2'-azobis(2,4- dimethylvaleronitrile).

The amount of polymerization initiator is preferably about 0.1 to 20% by weight and in particular 0.5 to 10% by weight, based on the total weight of the monomers to be polymerized.

The copolymerization of monomers M-l and M-ll, and optionally monomers C, may be performed in an organic solvent or in bulk. If a solvent is used, the concentration of the monomers in the solvent will generally be in the range from 10 to 70 % by weight. If a solvent is used, the copolymerisation is preferably carried out as a solution or precipitation polymerisation.

Suitable organic solvents for carrying out the copolymerisation include, but are not lim- ited to, aromatic hydrocarbon solvents and solvent mixtures such as benzene, toluene, xylenes, ethyl benzene, aromatic-100, aromatic-150, aromatic-200, ketones such as acetone, methylamylketone, methylethylketone or methyl-iso-butylketone, lactams such as N-methyl pyrrolidone (NMP), esters such as ethyl-3-ethoxypropionate, propyl- eneglycol monomethyl ether acetate, alkanols, cycloalkanols and ether alkanols such as cyclohexanol, dipropyleneglycol (mono)methyl ether, n-butanol, n-hexanol, carbitol, hexyl carbitol, iso-octanol, iso-propanol, methyl cyclohexane methanol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, or iso- paraffins. In some embodiments, the solvent is an aprotic solvent, in particular an aromatic hydrocarbon such as xylene, toluene, ethyl benzene, aromatic-100, aromatic-150 or aromatic-200, acetone, a ketone such as methylethylketone (MEK), methylamylketone (MAK), methyl-iso-butylketone (MIBK), or a lactam such as N-methylpyrrolidone.

The copolymerization is preferably carried out at a temperature of from 30°C to 300°C, in particular at a temperature in the range from 50°C to 200°C, in particular in the range from 80 to 180°C.

The copolymerization may be performed under atmospheric pressure or under reduced or elevated pressure. A preferred pressure range is 1 to 10 bar, more preferably 1 to 5 bar. In a preferred embodiment, the copolymerization is performed under inert at- mosphere, i.e. under an atmosphere of at least one inert gas such as, for example, nitrogen or argon, which contains less than 0.5 vol.-%, in particular less than

0.1 vol.-%, of oxygen. The polymerization can be performed as a batch process, as a semi-batch or feed process with an initial charge or as a continuous process. Suitable techniques are known and described e.g. in US 2004/0138381 or US 2012/008083572.

The copolymers of the present invention are useful as a chain extender for hydroxyl- terminated and/or carboxyl-terminated polymers and mixtures of hydroxyl-terminated and/or carboxyl-terminated polymers. Use as a chain extender means that the hydrox- yl- and/or carboxyl-terminated polymers undergo a reaction with the copolymers of the present invention, thereby increasing the molecular weight of the resulting polymer composition. The increase in molecular weight results from a coupling reaction of the epoxy groups of the copolymer with the carboxyl or hydroxyl groups of the hydroxyl- terminated and/or carboxyl-terminated polymer or polymer mixture.

The copolymers of the present invention have demonstrated enhanced ability to restore or even improve the properties of reprocessed or recycled hydroxyl- and/or carboxyl- terminated polymers or of lower grade virgin condensation polymers. The improvements provided by the copolymers can be seen directly in the physical properties of the chain extended hydroxyl- and/or carboxyl-terminated polymers compared to the same properties in the unmodified low grade virgin polymers or reprocessed or recycled hydroxyl- and/or carboxyl-terminated polymers. The efficacy of chain extension and mo- lecular weight increase can be assessed in a number of different ways. Some common methods for the assessment of chain extension are change in melt viscosity, which may be measured by capillary rheometry, melt flow index (MFI), cone-and-plate or parallel plate rheometry. Other common methods are based on changes in solution viscosity, which may be measured for example by Ostwall-Fenske or Ubbelohde capillary viscometers as changes in relative, inherent, or intrinsic viscosity (I.V.). Viscosities can be measured according to ASTM D-2857. The increase in the viscosity of the hydroxyl and/or carboxyl polymers following chain extension may also be measured by melt viscosity as measured by capillary rheometry. The increase in the molecular weight of the hydroxyl- and/or carboxyl-terminated polymers following chain extension is also demonstrated by the decrease in the melt flow index (MFI) of the hydroxyl- and/or carboxyl-terminated polymer after chain extension has occurred.

Due to their ability to provide recycled or processed materials with properties equivalent to those of the un-recycled or un-processed materials, the copolymers of the pre- sent invention have the advantage that more of the recycled or reprocessed material can be incorporated into the final product. The copolymers have the further advantage that the mechanical, thermal and impact properties of chain extended hydroxyl- and/or carboxyl-terminated polymers are not negatively impacted and in many instances are enhanced with respect to those of the un-recycled or un-processed hydroxyl- and/or carboxyl-terminated polymers.

Suitable hydroxyl- and/or carboxyl-terminated polymers include, but are not limited to, polyesters (PEs), polyamides (PAs), polyester amides, polycarbonates (PCs), polyure- thanes (PUs), polyesterurethanes, polyacetals, polysulfones, polyphenylene ethers

(PPEs), polyether sulfones, polyimides, polyether imides, polyether ketones, polyether- ether ketones, polyarylether ketones, polyarylates, polyphenylene sulfides and polysaccharides. The number-average molecular weight MN of the hydroxyl- and/or carboxyl-terminated polymers reacted with the copolymers of the invention is typically in the range from 5000 to 1 000 000 daltons, in particular in the range from 8000 to 800 000 daltons, and specifically in the range from 10 000 to 500 000 daltons. The weight-average molecular weight Mw of the polymer is generally in the range from 20 000 to 5 000 000 daltons, frequently in the range from 30 000 daltons to 4 000 000 daltons, and in particular in the range from 40 000 to 2 500 000 daltons. The polydispersity index MW/MN is generally at least 2, and is frequently in the range from 3 to 20, in particular in the range from 5 to 15. Molecular weight and polydispersity index can by way of example be determined via gel permeation chromatography (GPC) to DIN 55672-1. The intrinsic viscosi- ty of the hydroxyl- and/or carboxyl-terminated polymers, which is an indirect measure of molecular weight, is typically in the range from 50 to 500 ml/g, frequently in the range from 80 to 300 ml/g, and in particular in the range from 100 to 250 ml/g (determined according to EN ISO 1628-1 at 25°C on 0.5% strength by weight solution of the polymer in o-dichlorobenzene/phenol (1 :1 w/w)).

In particular, the hydroxyl- and/or carboxyl-terminated polymers are selected from the group consisting of polysaccharides, polyesters, polyester amides, polyesterurethanes and polycarbonates, especially from the group of biodegradable polyesters, biodegradable polyester amide, biodegradable polycarbonates and polysaccharides such as starch, cellulose or cellulose derivatives.

In terms of the present invention, biodegradability means that the polymers decompose in an appropriate and demonstrable period of time when exposed to the effects of the environment. The degradation mechanism can be hydrolytic and/or oxidative, and is based mainly on exposure to microorganisms, such as bacteria, yeasts, fungi, and algae. An example of a method for determining biodegradability mixes the polymer with compost and stores it for a particular time. According to ASTM D5338, ASTM D6400, EN 13432, and DIN V 54900, CCVfree air, b way of example, is passed through rip- ened compost during the composting process, and this compost is subjected to a defined temperature program. Biodegradability is defined here by way of the ratio of the net amount of CO2 liberated from the specimen (after deducting the amount of CO2 liberated by the compost without the specimen) to the maximum possible amount of CO2 liberated by the specimen (calculated from the carbon content of the specimen). Even after a few days of composting, biodegradable polymers generally show marked signs of degradation, for example fungal growth, cracking, and perforation.

In another method of determining biodegradability, the polymer is incubated with a certain amount of a suitable enzyme at a certain temperature for a defined period, and then the concentration of the organic degradation products dissolved in the incubation medium is determined. By way of example, by analogy with Y. Tokiwa et al., American Chemical Society Symposium 1990, Chapter 12, "Biodegradation of Synthetic Polymers Containing Ester Bonds", the polymer can be incubated for a number of hours at from 30 to 37°C with a predetermined amount of a lipase, for example from hizopus arrhizus, Rhizopus delemar, Achromobacter sp., or Candida cylindracea, and the DOC value (dissolved organic carbon) can then be measured on the reaction mixture freed from insoluble constituents. For the purposes of the present invention, biodegradable polymers are those which after enzymatic treatment with a lipase from Rhizopus arrhizus for 16 h at 35°C give a DOC value which is at least 10 times higher than that for the same polymer which has not been treated with the enzyme.

Particularly suitable biodegradable polymers, which are carboxyl- and/or hydroxyl- terminated, include polylactic acid, polypropylene carbonate, polycaprolactone, polyhy- droxyalkanoates, aliphatic copolyesters, semi-aromatic copolyesters and polysaccha- rides such as starch, cellulose and cellulose derivatives.

In a particular embodiment of the invention, the hydroxyl- and or carboxyl-terminated polymer is selected from the group of the aliphatic polyesters, aliphatic copolyesters, aliphatic-aromatic copolyesters (semi-aromatic copolyesters), and mixtures of these.

An aliphatic polyester is a polyester composed exclusively of aliphatic monomers. An aliphatic copolyester is a polyester composed exclusively of at least two, in particular at least three, aliphatic monomers, where the acid component and/or the alcohol component preferably comprises at least two monomers that differ from one another. An ali- phatic-aromatic copolyester is a polyester which is composed of aliphatic monomers but also of aromatic monomers, and it is preferable here that the acid component comprises at least one aliphatic acid and at least one aromatic acid. The aliphatic polyesters and copolyesters suitable for chain extension are in particular polylactides, polycaprolactone, block copolymers made of polylactide with P0IV-C2-C4- alkylene glycol, block copolymers made of polycaprolactone with poly-C2-C4-alkylene glycol, and also the copolyesters defined below which are composed of at least one aliphatic or cycloaliphatic dicarboxylic acid or an ester-forming derivative thereof, and of at least one aliphatic or cycloaliphatic diol component, and also optionally of further components.

The term "polylactides" denotes polycondensates of lactic acid. Suitable polylactides are described in WO 97/41836, WO 96/18591 , WO 94/05484, US 5,310,865,

US 5,428,126, US 5,440,008, US 5,142,023, US 5,247,058, US 5,247,059,

US 5,484,881 , WO 98/09613, US 4,045,418, US 4,057,537, and also in Adv. Mater.

2000, 12, 1841-1846. These products are polymers based on lactide acid lactone (A), which is converted via ring-opening polymerization to polylactic acid polymers (B):

The degree of polymerization n in formula (B) is in the range from 1000 to 4000, preferably from 1500 to 3500, and particularly preferably from 1500 to 2000 (number average). The average molar masses (number average) of these products are, in accord- ance with the degree of polymerization, in the range from 71 000 to 284 000 g/mol. Suitable polylactides are obtainable by way of example from NatureWorks LLC (e.g. PLA 4043D, PLA 8052D, PLA 4060D, PLA 3052D) or from Mitsui Chemicals (Lactea). Other suitable materials are diblock and triblock copolymers of polylactides with poly- C2-C4-alkylene glycol, in particular with poly(ethylene glycol). These block copolymers are marketed by way of example by Aldrich (e.g. product number 659649). These are polymers that have polylactide blocks and poly-C2-C4-alkylene oxide blocks. These block copolymers are obtainable by way of example via condensation of lactic acid or via ring-opening polymerization as lactide (A) in the presence of poly-C2-C4-alkylene glycols. Other aliphatic esters suitable for chain extension by the copolymers of the invention are polycaprolactones. The person skilled in the art understands these to be polymers described by the formula D indicated below, where n is the number of repeat units in the polymer, i.e. the degree of polymerization.

The degree of polymerization n in formula (D) is in the range from 100 to 1000, preferably from 500 to 1000 (number average). The number-average molar masses of these products are, in accordance with the degree of polymerization, in the range from

10 000 g/mol to 100 000 g/mol. Particularly preferred polymers of the formula (D) have average molar masses (number average) of 50 000 g/mol (CAPA 6500), 80 000 g/mol (CAPA 6800), and 100 000 g/mol (CAPA FB 100). Polycaprolactones are generally produced via ring-opening polymerization of ε-caprolactone (compound C) in the pres- ence of a catalyst. Polycaprolactones are obtainable commercially from Solvay as CAPA polymers, e.g. CAPA 6100, 6250, 6500 or CAPA FB 100. Other suitable polymers are diblock and triblock copolymers of polycaprolactone with poly-C2-C4-alkylene glycols, in particular with polyethylene glycols (= polyethylene oxides), i.e. polymers which have at least one polycaprolactone block of the formula D and at least one polyalkylene glycol block. These polymers can by way of example be produced via polymerization of caprolactone in the presence of polyalkylene glycols, for example by analogy with the processes described in Macromolecules 2003, 36, pp 8825-8829.

Particular polymers that are suitable in the invention are copolyesters, where these are composed of at least one aliphatic or cycloaliphatic dicarboxylic acid or of an ester- forming derivative thereof, and of at least one aliphatic or cycloaliphatic diol component, and also optionally of further components.

In particular, the polymer suitable in the invention is an aliphatic or aliphatic-aromatic copolyester which is in essence composed of: a) at least one dicarboxylic acid component A, which is composed of

a1 ) at least one aliphatic or cycloaliphatic dicarboxylic acid or ester-forming derivative thereof, or a mixture thereof, and

a2) optionally one or more aromatic dicarboxylic acids or ester-forming derivative thereof, or a mixture thereof; b) at least one diol component B, selected from aliphatic and cycloaliphatic diols and mixtures thereof;

c) optionally one or more further bifunctional compounds C which react with carbox- ylic acid groups or with hydroxy groups to form bonds; and

d) optionally one or more compounds D which have at least 3 functionalities which react with carboxylic acid groups or with hydroxy groups to form bonds; where either the compounds a1 ), a2), B), C), and D) have no sulfonic acid group, or the compounds of groups a1 ), a2), B), C), and D) comprise, based on the total amount of compounds of component A, up to 3 mol-% of a compound which has one or more sulfonic acid groups, e.g. from 0.1 to 3 mol-% or from 0.1 to 2 mol-% or from 0.2 to 1 .5 mol-%,

where the molar ratio of component A to component B is in the range from 0.4:1 to 1 :1 , in particular in the range from 0.6:1 to 0.99:1 , and components A and B make up at least 80% by weight, in particular at least 90% by weight, and specifically at least 96% by weight, of all of the ester-forming constituents of the polyester and, respectively, of the total weight of the polyester.

Here and hereinafter, the % by weight data referring to the ester-forming constituents are based on the constituents of components A, B, C, and D in the form condensed into the molecule, and are thus based on the total mass of the polyester, and not on the amounts used to produce the polyester, unless otherwise stated.

The acid component A in said copolyesters preferably comprises

a1 ) from 30 to 100 mol-%, in particular from 35 to 90 mol-%, or from 40 to 90 mol-%, of at least one aliphatic or at least one cycloaliphatic dicarboxylic acid, or ester- forming derivative thereof, or a mixture thereof,

a2) from 0 to 70 mol-%, in particular from 10 to 65 mol-%, or from 10 to 60 mol-%, of at least one aromatic dicarboxylic acid, or ester-forming derivative thereof, or a mixture thereof,

where the total of the molar percentages of components a1 ) and a2) is 100%.

Aliphatic dicarboxylic acids a1 ) generally have from 2 to 10 carbon atoms, preferably from 4 to 8 carbon atoms, and in particular 6 carbon atoms. They can be either linear or branched acids. The cycloaliphatic dicarboxylic acids that can be used for the purposes of the present invention are generally those having from 7 to 10 carbon atoms and in particular those having 8 carbon atoms. However, it is also possible in principle to use dicarboxylic acids having a greater number of carbon atoms, for example up to 30 carbon atoms. Examples that may be mentioned are: malonic acid, succinic acid, glutaric acid, 2-methylglutaric acid, 3-methylglutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, fumaric acid, 2,2-dimethylglutaric acid, suberic acid, 1 ,3- cyclopentanedicarboxylic acid, 1 ,4-cyclohexanedicarboxylic acid, 1 ,3- cyclohexanedicarboxylic acid, diglycolic acid, itaconic acid, maleic acid, and 2,5- norbornanedicarboxylic acid. Ester-forming derivatives of the abovementioned aliphatic or cycloaliphatic dicarboxylic acids which can equally be used and which may be mentioned are in particular the di-Ci-C6-alkyl esters, e.g. dimethyl, diethyl, di-n-propyl, diisopropyl, di-n-butyl, diisobutyl, di-t-butyl, di-n-pentyl, diisopentyl, or di-n-hexyl ester. It is equally possible to use anhydrides of the dicarboxylic acids. Preferred dicarboxylic acids are succinic acid, adipic acid, sebacic acid, azelaic acid, and brassylic acid, and also the respective ester-forming derivatives thereof, or a mixture thereof. Particular preference is given to adipic acid, sebacic acid, or succinic acid, and also to the respective ester-forming derivatives thereof, or a mixture thereof. Aromatic dicarboxylic acids a2) that may be mentioned are generally those having from 8 to 12 carbon atoms and preferably those having 8 carbon atoms. Examples that may be mentioned are terephthalic acid, isophthalic acid, 2,6-naphthoic acid, and 1 ,5- naphthoic acid, and also ester-forming derivatives thereof. Particular mention may be made here of the di-Ci-C6-alkyl esters, e.g. dimethyl, diethyl, diethyl, di-n-propyl, diiso- propyl, di-n-butyl, diisobutyl, di-t-butyl, di-n-pentyl, diisopentyl, or di-n-hexyl ester. The anhydrides of the dicarboxylic acids a2) are equally suitable ester-forming derivatives. However, it is also in principle possible to use aromatic dicarboxylic acids a2) having a greater number of carbon atoms, for example up to 20 carbon atoms. The aromatic dicarboxylic acids or ester-forming derivatives thereof, a2), can be used individually or in the form of mixture made of two or more thereof. It is particularly preferable to use terephthalic acid or ester-forming derivatives thereof, e.g. dimethyl terephthalate.

Among the aromatic dicarboxylic acids and ester-forming derivatives thereof are especially preferred those which have no sulfonic acid groups. Here and hereinafter these are also termed aromatic dicarboxylic acids a2.1 ). Among the aromatic sulfonic acids are also sulfonated aromatic dicarboxylic acids and ester-forming derivatives thereof preferred (aromatic dicarboxylic acids a.2.2)). These typically derive from the above- mentioned aromatic dicarboxylic acids and bear 1 or 2 sulfonic acid groups. An example that may be mentioned is sulfoisophthalic acid or a salt thereof, e.g. the sodium salt (Nasip). The content of the sulfonated carboxylic acid generally makes up no more than 3 mol-%, based on component A, and by way of example is in the range from 0.1 to 3 mol-%, or from 0.1 to 2 mol-%, or from 0.2 to 1.5 mol-%, based on the total amount of compounds of component A. In one embodiment of the invention, the amount of sul- fonated carboxylic acids, based on component A, is less than 1 mol-%, in particular less than 0.5 mol-%.

The diols B are generally selected from branched or linear alkanediols having from 2 to 12 carbon atoms, preferably from 4 to 8 carbon atoms, or in particular 6 carbon atoms, or from cycloalkanediols having from 5 to 10 carbon atoms.

Examples of suitable alkanediols are ethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,2-butanediol, 1 ,4-butanediol, 1 ,5-pentanediol, 2,4-dimethyl-2-ethylhexane-1 ,3-diol, 2,2-dimethyl-1 ,3-propanediol, 2-ethyl-2-butyl-1 ,3-propanediol, 2-ethyl-2-isobutyl-1 ,3- propanediol, 2,2,4-trimethyl-1 ,6-hexanediol, in particular ethylene glycol, 1 ,3- propanediol, 1 ,4-butanediol or 2,2-dimethyl-1 ,3-propanediol (neopentyl glycol); cyclo- pentanediol, 1 ,4-cyclohexanediol, 1 ,2-cyclohexanedimethanol, 1 ,3- cyclohexanedimethanol, 1 ,4-cyclohexanedimethanol, or 2,2,4,4-tetramethyl-1 ,3- cyclobutanediol. It is also possible to use mixtures of various alkanediols. Diol component B in said copolyesters is preferably selected from C2-C12 alkanediols and mixtures thereof. Preference is given to 1 ,3-propanediol and in particular to 1 ,4-butanediol.

Depending on whether an excess of OH end groups is desired, an excess of compo- nent B can be used. In one preferred embodiment, the molar ratio of components used A:B can be in the range from 0.4:1 to 1.1 :1 , preferably in the range from 0.6:1 to 1.05:1 , and in particular in the range from 0.7:1 to 1.02:1. The molar ratio of component A incorporated into the polymer to component B incorporated into the polymer is preferably in the range from 0.8:1 to 1.01 :1 , with preference from 0.9:1 to 1 :1 , and in particular in the range from 0.99:1 to 1 :1.

The polyesters can comprise, condensed into the molecule, not only components A and B but also further bifunctional components C. Said bifunctional compounds have two functional groups which react with carboxylic acid groups or preferably hydroxy groups, to form bonds. Examples of functional groups which react with OH groups are in particular isocyanate groups, epoxy groups, oxazoline groups, carboxy groups in free or esterified form, and amide groups. Particular functional groups which react with carboxy groups are hydroxy groups and primary amino groups. These materials are particularly those known as bifunctional chain extenders, in particular the compounds of groups c3) to c7). Among components C are: c1 ) dihydroxy compounds of the formula I HO-[(A)-0] _m -H (I) in which A is a C2-C4-alkylene unit, such as 1 ,2-ethanediyl, 1 ,2-propanediyl, 1 ,3-propanediyl, or 1 ,4-butanediyl, and m is an integer from 2 to 250; hydroxycarboxylic acids of the formula lla or lib

(lla) (lib) in which p is an integer from 1 to 1500 and r is an integer from 1 to 4, and G is a radical selected from the group consisting of phenylene, -(CH2) _q -, where q is an integer from 1 to 5, -C(R)H-, and -C(R)HCH2, where R is methyl or ethyl; c3) amino-C2-Ci2 alkanols, amino-Cs-C-io cycloalkanols, or a mixture thereof; diamino-d-Cs alkanes;

2,2'-bisoxazolines of the general formula III

(III) where Ri is a single bond, a (CH2)z-alkylene group, where z = 2, 3, or 4, or a phenylene group; c6) aminocarboxylic acids which by way of example are selected from naturally occurring amino acids, polyamides with a molar mass of at most 18 000 g/mol, obtainable via polycondensation of a dicarboxylic acid having from 4 to 6 carbon atoms and of a diamine having from 4 to 10 carbon atoms, compounds of the formulae IVa and IVb

(IVa) (IVb) in which s is an integer from 1 to 1500 and t is an integer from 1 to 4, and T is a radical selected from the group consisting of phenylene, -(Chb , where u is an integer from 1 to 12, -C(R ² )H-, and -C(R ² )HCH ₂ , where R ² is methyl or ethyl, and polyoxazolines having the repeat unit V

(V) in which R ³ is hydrogen, Ci-C6-alkyl, Cs-Ce-cycloalkyl, unsubstituted phenyl or phenyl substituted up to three times with Ci-C4-alkyl groups, or is tetrahydrofuryl; and c7) diisocyanates.

Examples of component c1 ) are diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, and polytetrahydrofuran (polyTHF), particularly preferably diethylene glycol, triethylene glycol, and polyethylene glycol, and it is also possible here to use mixtures thereof, or compounds which have different alkylene units A (see c1 ), formula I), e.g. polyethylene glycol which comprises propylene units (A = 1 ,2- or 1 ,3-propanediyl). The latter are obtainable by way of example via polymerization of first ethylene oxide and then propylene oxide, by methods known per se. Particular preference is given to copolymers based on polyalkylene glycols having various variables A, where units formed from ethylene oxide (A = 1 ,2-ethanediyl) predominate. The molar mass (number average M _n ) of the polyethylene glycol is generally selected to be in the range from 250 to 8000 g/mol, preferably from 600 to 3000 g/mol.

In one of the embodiments it is possible, by way of example, to use, for the production of the copolyesters, from 80 to 99.8 mol-%, preferably from 90 to 99.5 mol-%, of the diols B, and from 0.2 to 20 mol-%, preferably from 0.5 to 10 mol-%, of the dihydroxy compounds c1 ), based on the molar amount of B and c1 ). Examples of preferred components c2) are glycolic acid, D-, L-, or D,L-lactic acid, 6-hydroxyhexanoic acid, cyclic derivatives thereof, e.g. glycolide (1 ,4-dioxane-2,5- dione), D- or L-dilactide (3,6-dimethyl-1 ,4-dioxane-2,5-dione), p-hydroxybenzoic acid, and also oligomers thereof, and polymers, such as 3-polyhydroxybutyric acid, polyhy- droxyvaleric acid, polylactide (obtainable by way of example in the form of EcoPLA® (Cargill)), or else a mixture of 3-polyhydroxybutyric acid and polyhydroxyvaleric acid (the latter being obtainable as Biopol® from Zeneca). The low-molecular-weight and cyclic derivatives thereof are particularly preferred for producing copolyesters. Exam- pies of amounts that can be used of the hydroxycarboxylic acids or their oligomers and/or polymers are from 0.01 to 20% by weight, preferably from 0.1 to 10% by weight, based on the amount of A and B.

Preferred components c3) are amino-C2-C6 alkanols, such as 2-aminoethanol, 3-aminopropanol, 4-aminobutanol, 5-aminopentanol, 6-aminohexanol, and also amino- C5-C6 cycloalkanols, such as aminocyclopentanol and aminocyclohexanol, or a mixture thereof.

Preferred components c4) are diamino-C4-C6 alkanes, such as 1 ,4-diaminobutane, 1 ,5-diaminopentane, and 1 ,6-diaminohexane.

In one preferred embodiment, the amounts used for producing the copolyesters are from 0.5 to 20 mol-%, preferably from 0.5 to 10 mol-%, of c3), based on the molar amount of B, and from 0 to 15 mol-%, preferably from 0 to 10 mol-%, of c4), based on the molar amount of B.

Preferred bisoxazolines III of component c5) are those in which ¹ is a single bond, a (CH2)z-alkylene group, where z = 2, 3, or 4, e.g. methylene, ethane-1 ,2-diyl, propane- 1 ,3-diyl, propane-1 ,2-diyl, or a phenylene group. Particularly preferred bisoxazolines that may be mentioned are 2,2'-bis(2-oxazoline), bis(2-oxazolinyl)methane, 1 ,2-bis(2- oxazolinyl)ethane, 1 ,3-bis(2-oxazolinyl)propane, or 1 ,4-bis(2-oxazolinyl)butane, 1 ,4- bis(2-oxazolinyl)benzene, 1 ,2-bis(2-oxazolinyl)benzene, or 1 ,3-bis(2-oxazolinyl)- benzene. Bisoxazolines of the general formula III are generally obtainable via the process of Angew. Chem. Int. Edit., Vol. 1 1 (1972), pp. 287-288.

Examples of amounts that can be used for producing the polyesters are from 80 to 98 mol-% of B, up to 20 mol-% of c3), e.g. from 0.5 to 20 mol-% of c3), up to 20 mol-% of c4), e.g. from 0.5 to 20 mol-%, and up to 20 mol-% of c5), e.g. from 0.5 to 20 mol-%, based in each case on the total of the molar amounts of components B, c3), c4), and c5). In another preferred embodiment, it is possible to use from 0.1 to 5% by weight of c5), preferably from 0.2 to 4% by weight, based on the total weight of A and B.

Component c6) used can comprise naturally occurring aminocarboxylic acids. Among these are valine, leucine, isoleucine, threonine, methionine, phenylalanine, tryptophan, lysine, alanine, arginine, aspartamic acid, cysteine, glutamic acid, glycine, histidine, proline, serine, tryosine, asparagine, and glutamine.

Preferred aminocarboxylic acids of the general formulae IVa and IVb are those in which s is an integer from 1 to 1000 and t is an integer from 1 to 4, preferably 1 or 2, and T is selected from the group of phenylene and -(CH ₂ ) _U -, where u is 1 , 5, or 12. c6) can moreover be a polyoxazoline of the general formula V. However, component c6) can also be a mixture of various aminocarboxylic acids and/or polyoxazolines.

Amounts of c6) that can be used in one preferred embodiment are from 0.01 to 20% by weight, preferably from 0.1 to 10% by weight, based on the total amount of components A and B. Component c7) used can comprise aromatic or aliphatic diisocyanates. However, it is also possible to use isocyanates of higher functionality. Examples of aromatic diisocyanates are tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, diphenylmethane-2,2'- diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, naphthylene-1 ,5-diisocyanate, and xylylene diisocyanate. Examples of aliphatic diiso- cyanates are especially linear or branched alkylene diisocyanates or cycloalkylene diisocyanates having from 2 to 20 carbon atoms, preferably having from 3 to 12 carbon atoms, e.g. hexamethylene-1 ,6-diisocyanate, isophorone diisocyanate, or methylene- bis(4-isocyanatocyclohexane). Other components c7) that can be used are tri(4-iso- cyanatophenyl)methane, and also the cyanurates, uretdiones, and biurets of the abovementioned diisocyanates.

Amounts generally used of component c7), if desired, are from 0.01 to 5 mol-%, preferably from 0.05 to 4 mol-%, particularly preferably from 0.1 to 4 mol-%, based on the total of the molar amounts of A and B.

Among other components which can optionally be used for producing the polyesters are compounds D which comprise at least three groups/functionalities which react with carboxylic acid groups or with hydroxy groups, to form bonds. Particular examples of functional groups which react with OH groups are isocyanate groups, epoxy groups, oxazoline groups, carboxy groups in free or esterified form, and amide groups. Particular functional groups which react with carboxy groups are hydroxy groups and primary amino groups. Compounds of this type are also termed crosslinking agents. By using the compound D, it is possible to construct biodegradable copolyesters which are pseudoplastic. The rheology of the melts improves; the biodegradable copolyesters are easier to process, for example easier to draw by melt-solidification processes to give foils. The compounds D have a shear-thinning effect, i.e. viscosity decreases under load. The compounds D preferably comprise from 3 to 10, e.g. 3, 4, 5, or 6, functional groups capable of forming ester bonds. Particularly preferred compounds D have from three to six functional groups of this type in the molecule, in particular from three to six hydroxy groups and/or carboxy groups. Examples that may be mentioned are: polycar- boxylic acids and hydroxycarboxylic acids, e.g. tartaric acid, citric acid, malic acid; tri- mesic acid; trimellitic acid, trimellitic anhydride; pyromellitic acid, pyromellitic dianhy- dride, and hydroxyisophthalic acid, and also polyols, such as trimethylolpropane and trimethylolethane; pentaerythritol, polyethertriols, and glycerol. Preferred compounds D are polyols, preferably trimethylolpropane, pentaerythritol, and in particular glycerol. The amounts used of the compounds D, insofar as these are desired, are generally from 0.0005 to 1 mol/kg, preferably from 0.001 to 0.5 mol/kg, and in particular from 0.005 to 0.3 mol/kg, based on total amount of components A, B, C, and D, or on the total weight of the polyester. The amounts used of the compounds D, insofar as these are desired, are preferably from 0.01 to 5% by weight, in particular from 0.05 to 3% by weight, and in particular from 0.1 to 2% by weight, and specifically from 0.2 to 2% by weight, based on the total amount of components A, B, C, and D, or on the total weight of the polyester.

In another particular embodiment, the hydroxyl- and/or carboxyl-terminated polymer which is chain extended is a polysaccharides, in particular a starch or a cellulose or a modified cellulose or a blend thereof with another hydroxyl- and/or carboxyl-terminated polymer, in particular a blend of a polysaccharide with an aliphatic or semiaromatic polyester or with a polycarbonate. Suitable starch may be native starch including cereal starch, potato starch, tapioca starch or rice starch, or degraded starch. Suitable cellulose may be native cellulose, mechanically processed cellulose such as micro- or nanocellulose or chemically modified cellulose such as methylcellulose, hydroxyethyl- cellulose, hydroxyethylmethylcellulose or carboxymethylcellulose.

In the method for producing a chain-extended polymer composition according to the present invention, the copolymer of the present invention is reacted with one or more of the above defined hydroxyl- and/or carboxyl-terminated polymers or with a blend thereof. Because the chain extenders provide low EEWs they are effective even in very small quantities. In some embodiments of the invention, the copolymer is present in an amount of about 10% (w/w) or less, about 5% (w/w) or less, based on the total weight of the mixture. This includes embodiments where the chain extender is present in an amount of from about 0.01 to about 15% (w/w), in particular in an amount of from 0.1 to 10 % by weight, especially in an amount of from 0.2 to 5 % by weight, based on the total weight of the hydroxyl- and/or carboxyl-terminated polymer. Chain extension of the hydroxyl- and/or carboxyl-terminated polymers may be accomplished through any conventional mean, many of which are known in the art. For example, chain extension of the hydroxyl- and/or carboxyl-terminated polymers may be accomplished through dry tumbling together or cofeeding the copolymer with a desired hydroxyl- and/or carboxyl-terminated polymer. The chain extender may then be melt- or solution-blended with the hydroxyl- and/or carboxyl-terminated polymer by methods well known in the art, such as by reactive extrusion. In addition, other suitable formulation ingredients such as pigments, fillers, reinforcants, or additives such as stabilizers, antioxidants, lubricants, and/or any other additives known in the art needed for specific applications may be added to the formula in typical amounts.

Examples of suitable reactors for reactive extrusion include single and twin screw extruders systems, of different screw designs, configurations, L/D and compression ratios, operating at suitable RPMs to provide the prescribed average residence times at known feed rates. Other suitable reactors include Banbury mixers, Farrell continuous mixers, Buss co-kneaders, and roll mills. These systems may operate at temperatures above the glass transition temperature T _g of the copolymer and above the glass transition temperature T _g or of the melting temperature T _m of the hydroxyl- and/or carboxyl- terminated polymer in what is known in the art as reactive extrusion. The average residence time in the reactor may vary, but the chain extenders of the present invention need only short residence times compared to other presently available chain extenders. Typically, the residence times will range from about 0.5 to about 15 minutes. This includes embodiments where the residence time is from about 1 minute to about 10 minutes and further includes embodiments where the residence time is from about 2 minutes to about 7 minutes.

The chain extending operations can be followed by plastic forming operations, i.e. a thermoplastic shaping to produce a plastic article. Suitable methods for thermoplastic shaping include blow molding, injection molding, extrusion, extrusion foaming, com- pression molding, rotational molding, calendaring, and fiber spinning. Extrusion can also take place within primary processing equipment without pre-compounding.

Plastic articles which can be prepared by using the chain extended polymer composi- tions of the invention include e.g. food containers, non-food containers, films, coatings, tapes, moldings, fibers, extrusion profiles, and strapping.

The chain extending operations may also be followed by a polymer recovery and a pelletization stage to obtain pellets or granules of the chain extended polycondensates suitable for further processing.

The copolymers of the present invention provide a number of processing advantages compared to other chain extenders. For example, pre-drying of the hydroxyl- and/or carboxyl-terminated polymer is not required prior to chain extension. This is of particu- lar commercial advantage as pre-drying adds cost and complexity to the process of recycling by requiring another process step as well as more time. In addition, unlike many of the chain extenders currently available, the copolymers of the present invention do not require the addition of a catalyst or high vacuum operation in order to drive the reaction to the desired extent. This significantly reduces processing costs. Thus, in preferred embodiments at least a portion of the copolymer, in particular at least 50 % especially at least 80 % or all of the copolymer, is reacted with at least a portion of the hydroxyl- and/or carboxyl-terminated polymer, in particular at least 50 % especially at least 80 % or all of the hydroxyl- and/or carboxyl-terminated polymer, in the absence of a catalyst. The thus produced chain-extended polymers are substantially free of gel particles. In a special embodiment of the invention, the chain-extended polymer composition is produced without pre-drying the hydroxyl- and/or carboxyl-terminated polymer, and the reaction of the copolymer and the hydroxyl- and/or carboxyl-terminated polymer is carried out in a single stage of conventional equipment in the absence of additional catalyst and/or without vacuum operation. Furthermore, in some of these embodiments, the chain-extended polymer compositions obtained have molecular weights that are similar to or higher than those obtained through solid state polymerization, and have properties that are similar or even better than those obtained through solid state polymerization, thus allowing for the replacement of expensive and cumbersome solid state polymerization processes by simpler reactive extrusion processes.

Applications of this invention include, but are not limited to, recycling of scrap plastics, such as polyesters, polyesteramides, polyesterurethanes, polycarbonates, polyamides, polysaccharides and blends and alloys of scrap plastics by either a reactive extrusion or a solid state polymerization process of this invention, and post-processing of the recycled material through extrusion/blow molding into various articles including, but not limited to, food or non-food contact containers and transparent colored applications, films, coatings, tapes, moldings, fibers, strapping and other consumer products. In general the epoxy-functional copolymers of this invention show storage stability, safety of handling, no need for catalysts for effective chain extension, high thermal stability, low volatility and biodegradability. The copolymers may take the form of solids, or low viscosity liquids, or easy to handle wax forms. The invention is described in greater detail in the following, non-limiting examples.

The following abbreviations are used:

MDO: 2-methylene-1 ,3-dioxepan

GMA: glycidylmethacrylate

AIBN: azobisisobutyronitrile

DTBP: di-tert-butylperoxide

THF: tetrahydrofuran

GC: gas chromatography

FID: Flame lonisation Detector

PMMA: Polymethylmethacrylate

Analytics:

The composition of the copolymer was determined by ¹ H-NM : A solution of the copol- ymer in C2D2CI4 was analysed by means of an NMR spectrometer Bruker Avance 500 Prodigy. Specifically, the molar ratio of MDO and GMA was calculated from the values of the integrated signals attributed to the GMA units observed at approx. 3.2 and the value of the integrated signals attributed to the MDO units observed at approx. 4.0 ppm.

Thermogravimetric analysis was performed on a Mettler thermal analyzer having 851 TG module by recording TG traces in nitrogen atmosphere (flow rate = 50 ml min ^-1 ) using powdered samples. A sample size of 10 ± 1 mg was used in each experiment and heated from 40 to 800°C at a heating rate of 10 K min- ¹ .

GC is performed by using a HP 5890 Series GC equipped with a FID Detector and a DB-1 30 m x 0.25 mm x 0.25 pm column. The GC conditions were as follows: Detector 250°C, Injector 250°C. Start 40°C for 5 minutes, 10°C/min until 240°C, then 5 minutes at 240°C. The sample was prepared in THF (0.05%). The molecular weight and molecular weight distributions of the polymer was determined by gel permeation chromatography (GPC) using Knauer system equipped with 2 columns PSS-SDV (linear, 10 ml, 60 x 0:8), a differential refractive index detector and a UV photometer at 25°C, using THF as the eluent at a flow rate of 0.5 ml/min. PMMA standards were used for conventional calibration.

I Preparation of polymers Example 1 :

3.625 g of MDO, 4.554 g of GMA, 20 ml of xylene and 408 mg (512 μΙ) of DTBP were placed into a 100 ml glass autoclave. The mixture was flushed with argon for one hour to remove oxygen. The glass autoclave was sealed and then placed in a preheated oil bath at 200°C for 15 min. The reaction was stopped by cooling to room temperature. Solvent was removed under reduced pressure at 150°C and then dried at 50°C for 16 h. Thereby 5.28 g of the polymer were obtained. The molar ratio of MDO:GMA was 0.5:1 as determined by ¹ H-NMR. Example 2:

8 g of MDO, 3.43 g of GMA, 32 ml of xylene and 570 mg of DTBP were placed into a 50 ml glass autoclave. The mixture was polymerized and worked up as described for example 1. Thereby 4.8 g of the polymer were obtained. The molar ratio of MDO:GMA was 0.8:1 as determined by ¹ H-NMR.

Example 3:

9.13 g of MDO, 1.42 g of GMA, 25 ml of xylene and 665 μΙ of DTBP were placed into a 100 ml glass autoclave. The mixture was polymerized and worked up as described for example 1. Thereby 3.12 g of the polymer were obtained. The molar ratio of MDO:GMA was 1.7:1 as determined by ¹ H-NMR.

Example 4:

3.1 15 g of MDO, 0.97 g of GMA and 151 mg of DTBP were placed into a 50 ml glass autoclave. The mixture was polymerized for 17 min at 150°C and worked up as described for example 1 . Thereby 1.1 g of the polymer were obtained. The molar ratio of MDO:GMA was 0.7:1 as determined by ¹ H-NMR. Example 5:

1.68 g of MDO, 1.31 g of GMA and 1 10 mg of DTBP were placed into a 50 ml glass autoclave. The mixture was polymerized for 12 min at 170°C and worked up as described for example 1 . Thereby 1.3 g of the polymer were obtained. The molar ratio of MDO:GMA was 0.7:1 as determined by ¹ H-NM .

Example 6:

3.77 g of MDO, 1.56 g of GMA, 25 ml of xylene and 295 mg of DTBP were placed into a 100 ml glass autoclave. The mixture was polymerized and worked up as described for example 1 . Thereby 1.8 g of the polymer were obtained. The molar ratio of MDO:GMA was 0.7:1 as determined by ¹ H-NMR.

Example 7:

3.12 g of MDO, 1.0 g of GMA, 1 ml of xylene and 264 μΙ of DTBP were placed into a 50 ml glass Schlenk tube. The mixture was polymerized at 170°C for 30 min. The reaction was stopped by placing the Schlenk tube in liquid nitrogen. The reaction mixture was given into 300 ml of hexane and the precipitated polymer was isolated. The molar ratio of MDO:GMA in the polymer was 1.6:1 as determined by ¹ H-NMR.

The molar ratios of MDO:GMA in the monomer mixture and in the obtained polymer as well the number average molecular weight M _n and the yields are summarized in table 1 (n.d. = not determined):

Table 1 :

Example MDO:GMA in monoM„ Yield [%] MDO:GMA in polymer mer mixture [mokmol] [mokmol]

1 1 :1 7760 62 0.5 1

2 3:1 5160 43 0.8 1

3 8:1 3270 30 1 .7 1

4 4:1 1 1 1000 26 0.7 1

5 1.6:1 35000 42 0.7 1

6 3:1 6000 32 0.7 1

7 4:1 n.d. n.d. 1 .6 1 General Polymerization Procedure:

A mixture of xylenes and tetradecane is placed in a suitable reaction vessel. The mixture in flushed with nitrogen for 20 min. MDO is added to the vessel by means of a sy- ringe. The mixture is heated to 90°C. AIBN is dissolved in xylene and added to the reaction vessel. Further AIBN is dissolved in GMA and the solution is added to the reaction vessel within 2.5 h at 90°C. After the addition is complete the temperature of 90°C is maintained for further 3 h. The conversion is controlled by GC. When 100% conversion of the monomers is achieved, the polymerisation is stopped by cooling. The sol- vent is distilled off to yield the polymer.

II Assessment of thermal stability

1. Pyrolysis

A 0.3 mg sample of the copolymer of example 1 or a commercial reference copolymer CP (copolymer of styrene and glycidylmethacrylate, prepared according to US 2004/01383831 ) was placed into a tube. The tube was flushed with nitrogen, sealed and then heated for 5 minutes to 200°C or 300°C, respectively. Then the release of GMA was determined by GC. The release of GMA at 300°C of the commercial copolymer was set as 100%. The relative release of GMA is summarized in table 2.

Table 2:

2. Thermogravimetric analysis

Samples of the copolymer and the reference copolymer CP were heated from 40 to 800°C with a heating rate of 10 K/min. The temperature where the weight of the samp was 95%) (T 95%>) was determined. The results are summarized in the following table.

Polymer T 95% [°C]

CP 270

Example 1 340

Example 2 320

Example 4 320

Example 5 335 Example 6 305

III Assessment of degradability

Degradability by alkaline hydrolysis was assessed as follows. 1 g of the polymer of example 7 or the commercial copolymer CP was dissolved in a mixture of 50 ml of 5% (w/w) methanolic solution of KOH and 50 ml of THF. The solution was stirred at 22°C for 24 h. Then, the mixture was acidified to acidic pH by addition of concentrated hydrochloric acid. The mixture was extracted with trichloromethane and the organic phase was washed with water. The organic phase was evaporated under reduced pressure and the remaining solid was dried in vacuo at 22°C. The solids were analysed by GPC using THF as an eluent and polystyrene as a standard.

While the commercial copolymer CP showed virtually no degradation the copolymer of example 7 was completely hydrolyzed.

IV Use as chain extender

A mixture of commercial polylactic acid (PLA 4043D, Nature Works) and a copolyester of adipic acid, terephthalic acid and 1 ,4-butanediol (exoflex F Blend C1200, M _w 1 15000 g/mol) was dried at 40°C and 20 mbar for 15 h. The dried mixture was mixed with 0.6 % or 1.2% by weight of the respective copolymer in a DSM 15cc mini-extruder at 240°C (residence time 3 minutes, 80 rpm). During that time the torque was monitored. The results are given in table 3. Table 3:

Type of CP Amount of Torque [Nm]

CP%

t = 0 min t = 1 min t = 2 min t = 3 min

- 0 5000 4500 4100 3800

Commercial 1.2 5800 6800 7300 7500 Copolymer

Example 1 0.6 5400 5900 6200 6600

Example 1 1.2 5400 6800 8400 9300

Example 3 1.2 5000 5300 5800 6100