Patent Application
20240117112
The present invention relates to a process for the preparation of a biodegradable polyester particularly suitable for use for foaming and to the product thereof.
Extrusion and injection moulding are industrial processes widely used in the foam industry. In particular, extrusion refers to the pumping of a melt at high temperature and high viscosity through a nozzle where it takes on the desired shape and size, while injection moulding refers to the injection of a molten polymer into a mould. Foamed articles obtained by these industrial processes are particularly suitable for the protective packaging sector for electronics and in the sporting goods sector.
In order to obtain foamed articles with properties suitable for use in the above sectors, materials such as ethylene vinyl acetate (EVA) and expanded polyethylene (XPE) have traditionally been used. However, use of these materials has limitations in terms of environmental impact as they are not biodegradable or recyclable, while the use of biodegradable materials (such as PLA or unbranched PBTA) with properties suitable for use in the above sectors has limitations in terms of the complexity of the foaming process, which requires cross-linking using chemical additives.
The development of new materials that not only provide similar performance to conventional materials in foaming processes, but which do not require cross-linking with chemical additives and are also biodegradable, is therefore of particular interest.
Thus a first object of the present invention is a process for obtaining a biodegradable branched polyester for foaming. The process according to the present invention comprises (i) an esterification/transesterification step in the presence of a diol and dicarboxylic components of the polyester, and at least one polyfunctional compound containing at least four acid (COOH) or at least four hydroxyl (OH) functional groups, present in a concentration of 0.2-0.7% mol with respect to the total moles of the dicarboxylic component, wherein at least two of said hydroxyl functional groups are primary and at least further two of said hydroxyl functional groups are primary or secondary, providing that, if present, the secondary hydroxyl group is not vicinal to another secondary hydroxyl group, and an esterification/transesterification catalyst; and (ii) a polycondensation step in the presence of a polycondensation catalyst. In esterification/transesterification step (i) the dicarboxylic acids, their esters or their salts, the aliphatic diols, the polyfunctional compound and any other co-monomers constituting the polyester may be fed separately, thus mixing in the reactor. Alternatively, in esterification/transesterification step (i) the dicarboxylic acids, their esters or salts, the aliphatic diols, the polyfunctional compound and any other co-monomers constituting the polyester may be pre-mixed, preferably at a temperature below 70° C., before being sent to the reactor. It is also possible for some of the components to be pre-mixed, and subsequently change their composition, for example during the esterification/transesterification reaction.
In the case of polyesters in which the dicarboxylic component comprises repeating units derived from several dicarboxylic acids, whether aliphatic or aromatic, it is also possible to pre-mix some of these with aliphatic diols, preferably at a temperature below 70° C., by adding the remaining portion of the dicarboxylic acids, diols and any other co-monomers to the esterification/transesterification reactor in step (i).
Esterification/transesterification step (i) is preferably fed with a molar ratio between the aliphatic diols and the dicarboxylic acids, their esters and their salts, that preferably lies between 1 and 2.5, preferably between 1.05 and 1.9.
Esterification/transesterification step (i) in the process according to the present invention is advantageously performed at a temperature of 200-250° C., preferably 220-240° C., and a pressure of 0.7-1.5 bar, in the presence of an esterification/transesterification catalyst. The catalyst in esterification/transesterification step (i), which can advantageously also be used as a component of the catalyst of polycondensation step (ii), may in turn be fed directly to the esterification/transesterification reactor or may also first be dissolved in an aliquot of one or more of the dicarboxylic acids, their esters or salts, and/or aliphatic diols, so as to facilitate dispersion in the reaction mixture and make it more uniform.
The catalyst in the esterification/transesterification step(s) is chosen from among organometallic tin compounds, for example stannoic acid derivatives, titanium compounds, for example titanates such as tetrabutyl ortho-titanate or tetra(isopropyl) ortho-titanate, or diisopropyl triethanolamine titanate, zirconium compounds, for example zirconates such as tetrabutyl ortho zirconate or tetra(isopropyl) ortho zirconate, compounds of Antimony or Aluminium, for example Al-triisopropyl, Magnesium compounds, and Zinc compounds and mixtures thereof.
In a preferred embodiment, the titanium-based catalyst for esterification/transesterification step (i) is a titanate advantageously chosen from compounds having the general formula Ti(OR)4 in which R is a ligand group comprising one or more Carbon, Oxygen, Phosphorus and/or Hydrogen atoms.
Several R ligand groups may be present on the same titanium atom, but are preferably identical in order to facilitate preparation of the titanate.
In addition, 2 or more R ligands may be derived from a single compound and may be chemically bound together in addition to being bound to the titanium (so-called multidentate ligands such as triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, ethane diamine).
R is advantageously selected from H, triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, 3-oxobutanoic acid, ethane diamine and linear or branched C1-C12 alkyl residues such as ethyl, propyl, n-butyl, pentyl, isopropyl, isobutyl, isopentyl, hexyl, ethylhexyl. In a preferred embodiment, R is selected from C1-C12 alkyl residues, preferably C1-C8, more preferably n-butyl.
The preparation of the titanates is known from the literature. These are typically prepared by reacting titanium tetrachloride and the precursor alcohol of formula ROH in the presence of a base such as ammonia, or by the transesterification of other titanates.
Commercial examples of titanates that may be used in the process according to the present invention include Tyzor® TPT (tetra isopropyl titanate), Tyzor® TnBT (tetra n-butyl titanate) and Tyzor® TE (diisopropyl triethanolamino titanate).
If the Zirconium-based esterification/transesterification catalyst is used in conjunction with the Titanium-based catalyst, this will be a zirconate advantageously chosen from compounds having the general formula Zr(OR)4 in which R is a ligand group comprising one or more atoms of Carbon, Oxygen, Phosphorus and/or Hydrogen.
As in the case of titanates, several different, but preferably identical, R ligand groups may be present on the same zirconium atom to facilitate preparation of the zirconate.
In addition, 2 or more R ligands may be derived from a single compound or may be chemically bound together in addition to being bound to the Zirconium (so-called multidentate ligands such as triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, ethane diamine). R is advantageously chosen from H, triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, 3-oxobutanoic acid, ethane diamine and linear or branched C1-C12 alkyl residues such as ethyl, propyl, n-butyl, pentyl, isopropyl, isobutyl, isopentyl, hexyl or ethylhexyl. In a preferred embodiment R is chosen from C1-C12, preferably C1-C8, alkyl residues, more preferably n-butyl.
The preparation of zirconates is known in the literature, and is similar to that described above for titanates.
Commercial examples of zirconates which may be used in the process according to the present invention include Tyzor® NBZ (tetra n-butyl zirconate), Tyzor NPZ (tetra n-propyl zirconate), IG-NBZ (tetra n-butyl zirconate), Tytan TNBZ (tetra n-butyl zirconate), Tytan TNPZ (tetra n-propyl zirconate).
With respect to the organometallic catalysts of the above-mentioned type in esterification/transesterification step (i), during the esterification/transesterification step in the process according to the present invention they are present in concentrations preferably between 12 and 120 ppm of metal with respect to the amount of polyester that can theoretically be obtained by converting all the dicarboxylic acid fed to the reactor.
In a preferred embodiment, the catalyst for esterification/transesterification step (i) is a titanate, more preferably diisopropyl, triethanolamine titanate, preferably used in a concentration of 12-120 ppm of metal relative to an amount of polyester that can theoretically be obtained by converting all the dicarboxylic acid fed to the reactor.
Preferably, the reaction time for the esterification/transesterification step(s) in the process according to the present invention is between 4 and 8 hours.
At the end of esterification/transesterification step (i), an oligomer product having an Mn below 5000, an inherent viscosity of 0.05-0.15 dl/g, and an acidity of less than 150 meq/kg, preferably less than 100 meq/kg, is obtained.
The Mn value is measured using chloroform as eluent at 0.5 ml/min on suitable columns (e.g., PL-gel columns (300×7.5 mm, 5 μm—mixed bed C and E) and a PLgel Guard precolumn (50×7.5 mm 5 μm) connected in series and a refractive index detector. The determination is made using universal calibration with PS standard.
The inherent viscosity is measured in chloroform at 25° C. with a concentration of 2 g/l according to ISO 1628-2015.
Acidity is measured by potentiometric titration. An exactly weighed quantity of sample is dissolved in 60 ml chloroform, 25 ml of 2-propanol is added to the clear solution and, immediately before titration, 1 ml water is added. The titration is carried out with a 0.025N KOH solution in ethanol using an electrode for non-aqueous solutions (e.g., Solvotrode Metrohm). The solvent mixture is titrated in the same way as for the blank determination. The acidity value, expressed in meq/kg of polymer, is derived from the following equation
CEG=(Veq−V0)×titre/Psample
In a preferred embodiment of the process according to the present invention, the catalyst is fed to polycondensation step (ii) together with the oligomer product obtained at the end of esterification/transesterification step (i).
Polycondensation step (ii) in the process according to the present invention is advantageously performed at a temperature of 200-270° C., preferably 230-260° C., and a pressure of less than 10 mbar, preferably less than 3 mbar, and greater than 0.5 mbar, in the presence of a polycondensation catalyst.
Polycondensation step (ii) in the process according to the present invention is performed in the presence of a catalyst based on a metal preferably selected from titanium, zirconium or mixtures thereof, with a total amount of metal of 80-500 ppm compared to the amount of polyester that could theoretically be obtained by converting all the dicarboxylic acid fed to the reactor. If present, the total amount of Zirconium should be such that the Ti/(Ti+Zr) ratio is kept within the range 0.01-0.70.
In a preferred embodiment, the titanium-based catalyst for polycondensation step (ii) is a titanate advantageously chosen from compounds having the general formula Ti(OR)4 in which R is a ligand group comprising one or more Carbon, Oxygen, Phosphorus and/or Hydrogen atoms.
Several R ligand groups may be present on the same titanium atom, but are preferably identical in order to facilitate preparation of the titanate.
In addition, 2 or more R ligands may be derived from a single compound and may be chemically bound together in addition to being bound to the titanium (so-called multidentate ligands such as triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, ethane diamine).
R is advantageously selected from H, triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, 3-oxobutanoic acid, ethane diamine and linear or branched C1-C12 alkyl residues such as ethyl, propyl, n-butyl, pentyl, isopropyl, isobutyl, isopentyl, hexyl, ethylhexyl. In a preferred embodiment, R is selected from C1-C12 alkyl residues, preferably C1-C8, more preferably n-butyl.
The preparation of the titanates is known from the literature. These are typically prepared by reacting titanium tetrachloride and the precursor alcohol of formula ROH in the presence of a base such as ammonia, or by the transesterification of other titanates.
Commercial examples of titanates that may be used in the process according to the present invention include Tyzor® TPT (tetra isopropyl titanate), Tyzor® TnBT (tetra n-butyl titanate) and Tyzor® TE (diisopropyl triethanolamino titanate).
If the Zirconium-based polycondensation catalyst is used in conjunction with the Titanium-based catalyst, this will be a zirconate advantageously chosen from compounds having the general formula Zr(OR)4 in which R is a ligand group comprising one or more atoms of Carbon, Oxygen, Phosphorus and/or Hydrogen.
As in the case of titanates, several different, but preferably identical, R ligand groups may be present on the same zirconium atom to facilitate preparation of the zirconate.
In addition, 2 or more R ligands may be derived from a single compound or may be chemically bound together in addition to being bound to the Zirconium (so-called multidentate ligands such as triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, ethane diamine). R is advantageously chosen from H, triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, 3-oxobutanoic acid, ethane diamine and linear or branched C1-C12 alkyl residues such as ethyl, propyl, n-butyl, pentyl, isopropyl, isobutyl, isopentyl, hexyl or ethylhexyl. In a preferred embodiment R is chosen from C1-C12, preferably C1-C8, alkyl residues, more preferably n-butyl.
The preparation of zirconates is known in the literature, and is similar to that described above for titanates.
Commercial examples of zirconates which may be used in the process according to the present invention include Tyzor® NBZ (tetra n-butyl zirconate), Tyzor NPZ (tetra n-propyl zirconate), IG-NBZ (tetra n-butyl zirconate), Tytan TNBZ (tetra n-butyl zirconate), Tytan TNPZ (tetra n-propyl zirconate).
When a catalyst containing Titanium and/or Zirconium compounds is used in esterification/transesterification step (i), in a preferred embodiment of the process according to the present invention this catalyst is not separated from the product of step (i) and is fed together with it to polycondensation step (ii) and advantageously used as a polycondensation catalyst or as a component thereof, with possible adjustment of the molar ratio between Titanium and Zirconium through the addition of suitable amounts of Titanium and Zirconium compounds to said polycondensation step (ii).
It is possible that the catalyst for polycondensation step (ii) is the same as that for esterification/transesterification step (i).
More preferably, the catalyst used in esterification/transesterification step (i) and polycondensation step (ii) is a Titanium compound.
Polycondensation step (ii) is advantageously carried out by feeding the product of step (i) to the polycondensation reactor and reacting it in the presence of the catalyst at a temperature of 220-260° C. and a pressure of between 0.5 mbar and 350 mbar.
Preferably, the reaction time for the polycondensation step in the process according to the present invention is between 4 and 8 hours.
Polycondensation step (ii) in the process according to the present invention may be carried out in the presence of a phosphorus-containing compound belonging to the phosphate family or organic phosphites.
At the end of polycondensation step (ii), a polyester according to the present invention is obtained having Mn between 20000 and 70000, preferably between 30000 and 50000, an inherent viscosity between 0.3 and 1.1 dl/g, preferably between 0.6 and 1.0 dl/g, and an acidity of less than 100 meq/kg, preferably less than 60 meq/kg.
This process does not require an additional reactive extrusion stage to bring about branching. In a preferred embodiment, the process according to the present invention consists of (i) an esterification/transesterification step in the presence of a diol and dicarboxylic components of the polyester, and at least one polyfunctional compound containing at least four acid (COOH) or at least four hydroxyl (OH) functional groups, present in a concentration of 0.2-0.7% mol with respect to the total moles of the dicarboxylic component, wherein at least two of said hydroxyl functional groups are primary and at least two of said hydroxyl functional groups are primary or secondary as long as they are not vicinal or geminal, and an esterification/transesterification catalyst; and (ii) a polycondensation step in the presence of a polycondensation catalyst.
In another preferred embodiment, the process according to the present invention consists of (i) an esterification step in the presence of a diol and dicarboxylic components of the polyester, and at least one polyfunctional compound containing at least four acid (COOH) or at least four hydroxyl (OH) functional groups, present in a concentration of 0.2-0.7% mol with respect to the total moles of the dicarboxylic component, wherein at least two of said hydroxyl functional groups are primary and at least two of said hydroxyl functional groups are primary or secondary as long as they are not vicinal or geminal, and an esterification catalyst; and (ii) a polycondensation step in the presence of a polycondensation catalyst.
Biodegradable branched polyesters obtained by means of the process according to the present invention constitute a second object of the present invention, such polyesters being characterised by branching obtained by means of at least one polyfunctional compound containing at least four acid (COOH) or at least four hydroxyl (OH) functional groups, present in a concentration of 0.2-0.7% mol with respect to the total moles of the dicarboxylic component, wherein at least two of said hydroxyl functional groups are primary and at least further two of said hydroxyl functional groups are primary or secondary, providing that, if present, the secondary hydroxyl group is not vicinal to another secondary hydroxyl group, and characterised by a viscoelastic ratio (RVE) of less than 40000. The polyester object of the present invention is characterised by a lower RVE in comparison with polyesters subjected to the reactive extrusion step, and is advantageously processable at lower temperatures, favouring energy savings and limiting the risks of thermal degradation of the material.
Surprisingly, the polyester obtained by the process according to the present invention exhibits improved rheological properties in terms of melt thermal stability, high Breaking Stretching Ratio and polydispersity index.
From a rheological point of view, a polymer with long chain branches is characterised by high melt strength values and low shear viscosity values, the elongational properties being much more amplified by the long branches than by the molecular weight. In order to assess the quality of the melt and its possible processing behaviour in industrial coating processes it is therefore necessary to consider both properties by means of the viscoelastic ratio, RVE. This is calculated from the quotient of shear viscosity and melt strength. Shear viscosity is determined at 180° C. and flow gradient γ=103.7s−1 with a 1 mm diameter capillary and L/D=30 according to ASTM D3835-90 “Standard Test Method for Determining Properties of Polymer Materials by means of a Capillary Rheometer”, while melt strength is measured according to ISO 16790:2005 at 180° C. and γ=103.7s−1 using a capillary of diameter 1 mm and L/D=30 at a constant acceleration of 6 mm/sec2 and a stretching length of 110 mm.
Branching of the polyester according to the present invention is obtained using monomers comprising at least one polyfunctional compound containing at least four acid (COOH) or at least four hydroxyl (OH) functional groups, wherein at least two of said hydroxyl functional groups are primary and at least further two of said hydroxyl functional groups are primary or secondary, providing that, if present, the secondary hydroxyl group is not vicinal to another secondary hydroxyl group.
In another embodiment, the biodegradable branched polyester according to the present invention is characterised by branching obtained by a preparation process employing at least one polyfunctional compound containing at least four acid (COOH) or at least four hydroxyl (OH) functional groups, wherein at least two of said hydroxyl functional groups are primary and at least further two of said hydroxyl functional groups are primary or secondary, providing that, if present, the secondary hydroxyl group is not vicinal to another secondary hydroxyl group. By a primary hydroxyl functional group is meant a functional group in which the carbon atom bonded to the hydroxyl group is bonded to only one carbon atom. By a secondary hydroxyl functional group is meant a functional group in which the carbon atom bonded to the hydroxyl group is bound to two carbon atoms. By a vicinal hydroxyl functional group is meant two hydroxyl groups bonded to two adjacent carbon atoms.
Polyester branching according to the present invention is brought about using monomers comprising at least one polyfunctional compound containing at least four acid (COOH) or at least four hydroxyl (OH) functional groups present in a concentration of 0.2-0.7% mol, preferably 0.3-0.65% mol with respect to the total moles of the dicarboxylic component, wherein at least two of said hydroxyl functional groups are primary and at least further two of said hydroxyl functional groups are primary or secondary, providing that, if present, the secondary hydroxyl group is not vicinal to another secondary hydroxyl group.
In another embodiment the biodegradable branched polyester according to the present invention is characterised by branching obtained by a preparation process employing a mixture of polyfunctional compounds comprising at least 50% mol with respect to the total number of polyfunctional compounds of at least one polyfunctional compound containing at least four four acid (COOH) or at least four hydroxyl (OH) functional groups, wherein at least two of said hydroxyl functional groups are primary and at least further two of said hydroxyl functional groups are primary or secondary, providing that, if present, the secondary hydroxyl group is not vicinal to another secondary hydroxyl group.
Said polyfunctional compound is chosen from the group of polyfunctional molecules such as polyacids, polyols and mixtures thereof.
Examples of these polyacids are: pyromellitic acid, pyromellitic anhydride, ethylenediamine tetraacetic acid, furan-2,3,4,5-tetracarboxylic acid, naphthalene-1,4,5,8-tetracarboxylic acid, naphthalene-1,4,5,8-tetracarboxylic anhydride.
Examples of said polyols are: pentaerythritol, dipentaerythritol, ditrimethylolpropane, digylcerol, triglycerol, tetraglycerol and mixtures thereof.
Preferably the polyfunctional compound is pentaerythritol.
Surprisingly, the use of polyester according to the present invention in foaming processes makes it possible to obtain improved properties in terms of thermal stability of the melt, Breaking Stretching Ratio and polydispersity index. Preferably, the thermal stability (K) of the polyester according to the present invention is less than 1.4×10−4 and preferably greater than −0.2×10−4, more preferably less than 1.2×10−4 and greater than 0 determined at 180° C. and flow gradient γ=103.7s−1 with a capillary having a diameter of 1 mm and L/D=30 according to ASTM D3835-90 “Standard Test Method for Determining Properties of Polymer Materials by means of a Capillary Rheometer”. Preferably the Breaking Stretching Ratio (BSR) of the polyester according to the present invention is less than 120, preferably less than 110, and preferably more than 50, more preferably more than 70 measured according to ISO 16790:2005 at 180° C. and γ=103.7s−1 using a capillary having a diameter of 1 mm and L/D=30 at a constant acceleration of 6 mm/sec2 and a stretching length of 110 mm.
Preferably the polydispersity index (D) of the polyester according to the present invention is 3.5-4.5 measured using chloroform as eluent at 0.5 ml/min on columns suitable for the purpose (e.g., PL-gel columns (300×7.5 mm, 5 μm—mixed bed C and E) and a PLgel Guard precolumn (50×7.5 mm 5 μm) connected in series and a refractive index detector. The determination is made using a universal calibration with PS standard. The determination of the Mn and Mw indexes needed for the polydispersity index calculation is made by integrating the chromatogram by establishing a mass equal to 1500 as the lower limit. The polydispersity index (D) can be obtained as the ratio Mw/Mn, where Mw is the weight-average molar mass and Mn is the number-average molar mass.
A further object of the present invention is the use of polyester having improved rheological properties obtained according to the process according to the present invention for foaming processes. The use of polyester according to the present invention in foaming processes makes it possible to ensure good processing conditions, including in terms of the thermal resistance of the melt, a thermal profile that is slightly higher than the melting temperature of the polymer without the need to activate chemical cross-linking reactions (e.g. by means of peroxides), low neck-in, limited variation in the cross-sectional area of the melt film (so-called draw-resonance), as well as acceptable extruder motor consumption.
The polyester according to the present invention is characterised by a shear viscosity of less than 500 Pa·s, preferably 400 Pa·s, more preferably less than 350 Pa·s, and preferably greater than 100 Pa·s, determined at 180° C. and with a flow gradient γ=103.7s−1 with a capillary having a diameter of 1 mm and L/D=30 according to ASTM D3835-90 “Standard test method for determining the properties of polymer materials by means of a capillary rheometer”, and by a melt strength greater than 0.007 N, preferably greater than 0.008 N, and preferably less than 0.09 N, more preferably less than 0.02 N, measured according to ISO 16790:2005 at 180° C. and γ=103.7s−1 using a capillary of diameter 1 mm and L/D=30 at a constant acceleration of 6 mm/sec2 and a stretching length of 110 mm. The polyester according to the present invention is characterised by a ratio of viscosity to melt strength, viscoelastic ratio (RVE) of less than 40000, preferably less than 30000, more preferably less than 27000, even more preferably less than 25000 and preferably greater than 10000. Such RVE values make the polyester according to the present invention particularly suitable for use in common foaming equipment by injection moulding and/or extrusion.
In a preferred embodiment, the biodegradable branched polyester for foaming according to the present invention is characterised by a shear viscosity from 500 Pa·s to 100 Pa·s, preferably from 400 Pa·s to 120, more preferably from 350 Pa·s to 150, a melt strength from 0.09 N to 0.007 N, preferably from 0.02 N to 0.008 N, a viscoelastic ratio RVE from 40000 to 10000, preferably from 30000 to 12000, more preferably from 27000 to 13000, even more preferably from 25000 to 15000.
The rheological properties of the polyester according to the present invention are such that good foaming capability is ensured using known technologies for biodegradable plastics, such as extrusion or injection moulding.
Among numerous advantages, the biodegradable branched polyester according to the present invention exhibits an improvement in colour compared to branched polyesters using polyfunctional compounds other than those described above. The effects on colour are advantageously determined according to the L*a*b* colour space using a Konica Minolta CR410 colorimeter. The measurement is made on a circular area with a diameter of 50 mm, standard observer at 2° and illuminant C. The polyester according to the present invention is characterised by a value of L* greater than 70, more preferably greater than 75, even more preferably greater than 80; by a value of a* less than 20, preferably less than 10, even more preferably less than 5 and a value of b* less than 30, preferably less than 20, even more preferably less than 15.
The biodegradable branched polyester according to the present invention is advantageously chosen from aliphatic and aliphatic-aromatic biodegradable polyesters. In a preferred embodiment the polyester according to the present invention is an aliphatic-aromatic polyester. As far as the aliphatic-aromatic polyesters are concerned, they have an aromatic part consisting mainly of polyfunctional aromatic acids, an aliphatic part consisting of aliphatic diacids and aliphatic diols and their mixtures. As far as the aliphatic-aromatic polyesters are concerned, the dicarboxylic component according to the present invention mainly comprises polyfunctional aromatic acids and aliphatic diacids, and the diol component mainly comprises aliphatic diols.
The aliphatic polyesters are obtained from aliphatic diacids and aliphatic diols and mixtures thereof. As far as the aliphatic polyesters are concerned, the dicarboxylic component according to the present invention mainly comprises aliphatic diacids, and the diol component mainly comprises aliphatic diols.
By polyfunctional aromatic acids are meant dicarboxylic aromatic compounds of the phthalic acid type, preferably terephthalic acid or isophthalic acid, more preferably terephthalic acid, and heterocyclic dicarboxylic aromatic compounds, preferably 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 2,3-furandicarboxylic acid, 3,4-furandicarboxylic acid, their esters, salts and mixtures.
By aliphatic diacids are meant aliphatic dicarboxylic acids with numbers of carbon atoms from C2 to C24, preferably C4-C13, more preferably C4-C11, their C1-C24, more preferably C1-C4, alkyl esters, their salts and mixtures thereof. Preferably, the aliphatic dicarboxylic acids are selected from: succinic acid, 2-methylsuccinic acid, 2-ethylsuccinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecendioic acid, brassylic acid and their C1-C24 alkyl esters. Preferably said aliphatic dicarboxylic acids are selected from the group consisting of succinic acid, adipic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecendioic acid, brassylic acid and mixtures thereof.
The dicarboxylic component of the aliphatic or aliphatic-aromatic polyesters according to the present invention may comprise up to 5% unsaturated aliphatic dicarboxylic acids, preferably selected from itaconic acid, fumaric acid, 4-methylene-pimelic acid, 3,4-bis (methylene) nonanedioic acid, 5-methylene-nonanedioic acid, their C1-C24, preferably C1-C4, alkyl esters, their salts and mixtures thereof. In a preferred embodiment of the present invention, the unsaturated aliphatic dicarboxylic acids comprise mixtures comprising at least 50% in moles, preferably more than 60% in moles, more preferably more than 65% in moles of itaconic acid and/or its C1-C24, preferably C1-C4 esters. More preferably, the unsaturated aliphatic dicarboxylic acids comprise itaconic acid.
In the aliphatic or aliphatic-aromatic polyesters according to the present invention diols are understood to mean compounds bearing two hydroxyl groups, preferably selected from 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,4-cyclohexanedimethanol, neopentylglycol, 2-methyl-1,3propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, cyclohexanediol, 1,4-bis(hydroxymethyl)cyclohexane, dialkylene glycols and polyalkylene glycols of molecular weight 100-4000 such as polyethylene glycol, polypropylene glycol and mixtures thereof. Preferably, the diol component comprises at least 50% in moles of one or more diols chosen from 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol. In a preferred embodiment of the present invention, the saturated aliphatic diol is 1,4-butanediol.
Advantageously, the diol may be obtained from a renewable source, from first or second generation sugars.
The diol component of the aliphatic or aliphatic-aromatic polyesters according to the present invention may comprise up to 5% of unsaturated aliphatic diols, preferably selected from cis 2-butene-1,4-diol, trans 2-butene-1,4-diol, 2-butyne-1,4-diol, cis 2-pentene-1,5-diol, trans 2-pentene-1,5-diol, 2-pentyne-1,5-diol, cis 2-hexene-1,6-diol, trans 2-hexene-1,6-diol, 2-hexyne-1,6-diol, cis 3-hexyne-1,6-diol, trans 3-hexene-1,6-diol, 3-hexyne-1,6-diol. The aliphatic or aliphatic-aromatic polyesters according to the present invention may further advantageously comprise repeating units derived from at least one hydroxy acid in an amount of 0-49% preferably 0-30% in moles relative to the total moles of the dicarboxylic component. Examples of convenient hydroxy acids are glycolic acid, glycolide, hydroxybutyric acid, hydroxycaproic acid, hydroxyvaleric acid, 7-hydroxyheptanoic acid, 8-hydroxyproic acid, 9-hydroxynonanoic acid, lactic acid or lactide. The hydroxy acids may be inserted into the chain as such or as prepolymers/oligomers, or they may also be reacted with diacid diols in advance.
The aliphatic-aromatic polyesters according to the present invention are characterised by an aromatic acid content with respect to the total dicarboxylic component of between 30 and 70% in moles, preferably between 40 and 60% in moles.
In a preferred embodiment, the aliphatic-aromatic polyesters are preferably selected from the group consisting of: poly(1,4-butylene adipate-co-1,4-butylene terephthalate), poly(1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene terephthalate), poly(1,4-butylene brassylate-co-1,4-butylene terephthalate), poly(1,4-butylene succinate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene azelate-co-1,4-butylene terephthalate), poly(1,4-butylene succinate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene succinate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene adipate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene brassylate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene adipate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene adipate-co-1,4-butylene brassylate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene brassylate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene adipate-co-1,4-butylene sebacate-co-1,4-butylene brassylate-co-1,4-butylene terephthalate). In a particularly preferred embodiment, the aliphatic-aromatic polyester is poly(1,4-butylene adipate-co-1,4-butylene terephthalate) or poly(1,4-butylene adipate-co-1,4-butylene azelate-co-1,4-butylene terephthalate).
Mixtures of the various polyesters according to the invention also form part of the invention. The biodegradable branched polyester according to the present invention is substantially gel-free.
The biodegradable branched polyesters according to the invention are biodegradable according to EN13432.
The polyester according to the present invention may further optionally comprise 0-5% by weight, more preferably 0.05-4% by weight, even more preferably 0.05-3% by weight of the total mixture, of at least one crosslinking agent and/or chain extender.
Said crosslinking agent and/or chain extender improves stability to hydrolysis and is selected from di- and/or poly-functional compounds bearing isocyanate, peroxide, carbodiimide, isocyanurate, oxazoline, epoxy, anhydride, divinyl ether groups and mixtures thereof. Preferably, the crosslinking agent and/or chain extender comprises at least one di- and/or polyfunctional compound bearing epoxy or carbodiimide groups.
Preferably, the crosslinking agent and/or chain extender comprises at least one di- and/or polyfunctional compound bearing isocyanate groups. More preferably, the crosslinking agent and/or chain extender comprises at least 25% by weight of one or more di- and/or polyfunctional compounds bearing isocyanate groups. Particularly preferred are mixtures of di- and/or polyfunctional compounds bearing isocyanate groups with di- and/or polyfunctional compounds bearing epoxy groups, even more preferably comprising at least 75% by weight of di- and/or polyfunctional compounds bearing isocyanate groups.
The di- and polyfunctional compounds bearing isocyanate groups are preferably selected from p-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4-diphenylmethane diisocyanate, 1,3-phenylene-4-chloro diisocyanate, 1,5-naphthalene diisocyanate, 4,4-diphenylene diisocyanate, 3,3′-dimethyl-4,4-diphenylmethane diisocyanate, 3-methyl-4,4′-diphenylmethane diisocyanate, diphenyl ester diisocyanate, 2,4-cyclohexane diisocyanate, 2,3-cyclohexane diisocyanate, 1-methyl-2,4-cyclohexyl diisocyanate, 1-methyl-2,6-cyclohexyl diisocyanate, bis(isocyanate cyclohexyl) methane, 2,4,6-toluene triisocyanate, 2,4,4-diphenylether triisocyanate, polymethylene-polyphenyl-polyisocyanates, methylene diphenyl diisocyanate, triphenylmethane triisocyanate, 3,3′-ditolylene-4,4-diisocyanate, 4,4′-methylenebis(2-methyl-phenyl isocyanate), hexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,2-cyclohexylene diisocyanate and mixtures thereof. In a preferred embodiment, the compound bearing isocyanate groups is 4,4-diphenylmethane diisocyanate.
As for the di- and poly-functional compounds bearing peroxide groups, these are preferably selected from benzoyl peroxide, lauroyl peroxide, isononanoyl peroxide, di-(t-butylperoxyisopropyl)benzene, t-butyl peroxide, dicumyl peroxide, alpha,alpha′-di(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butyl cumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hex-3-yne, di(4-t-butylcyclohexyl)peroxy dicarbonate dicetyl peroxycarbonate, dimyristyl peroxycarbonate, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, di(2-ethylhexyl) peroxycarbonate and mixtures thereof. The di- and poly-functional compounds bearing carbodiimide groups which are preferably used in the mixture according to the present invention are chosen from poly(cyclooctylene carbodiimide), poly(1,4-dimethylcyclohexylene carbodiimide), poly(cyclohexylene carbodiimide), poly(ethylene carbodiimide), poly(butylene carbodiimide), poly(isobutylene carbodiimide), poly(nonylene carbodiimide), poly(dodecylene carbodiimide), poly(neopentylene carbodiimide), poly(1,4-dimethylene phenylene carbodiimide), poly(2,2′,6,6′-tetraisopropyldiphenylene carbodiimide) (Stabaxol® D), poly(2,4,6-triisopropyl-1,3-phenylene carbodiimide) (Stabaxol® P-100), poly(2,6-diisopropyl-1,3-phenylene carbodiimide) (Stabaxol® P), poly(tolyl carbodiimide), poly(4,4′-diphenylmethane carbodiimide), poly(3,3′-dimethyl-4,4′biphenylene carbodiimide), poly(p-phenylene carbodiimide), poly(m-phenylene carbodiimide), poly(3,3′-dimethyl-4,4′-diphenylmethane carbodiimide), poly(naphthylene carbodiimide), poly(isophorone carbodiimide), poly(cumene carbodiimide), p-phenylene bis(ethylcarbodiimide), 1,6-hexamethylene bis(ethylcarbodiimide), 1,8-octamethylene bis(ethylcarbodiimide), 1,10-decamethylene bis(ethylcarbodiimide), 1,12-dodecamethylene bis(ethylcarbodiimide) and mixtures thereof.
Examples of di- and polyfunctional compounds bearing epoxide groups which may advantageously be used in the mixture according to the present invention are all polyepoxides from epoxidised oils and/or styrene-glycidyl ether-methyl methacrylate, glycidyl ether-methyl methacrylate, within a molecular weight range from 1000 to 10000 and with a number of epoxides per molecule in the range from 1 to 30 and preferably 5 to 25, and epoxides selected from the group comprising: diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, 1,2-epoxybutane, polyglycerol polyglycidyl ether, isoprene diepoxide, and cycloaliphatic diepoxides, 1,4-cyclohexanedimethanol diglycidyl ether, glycidyl 2-methylphenyl ether, glycerol propoxylatotriglycidyl ether, 1,4-butanediol diglycidyl ether, sorbitol polyglycidyl ether, glycerol diglycidyl ether, tetraglycidyl ether of meta-xylenediamine and diglycidyl ether of bisphenol A and mixtures thereof.
In a particularly preferred embodiment of the invention, the crosslinking agent and/or chain extender comprises compounds bearing isocyanate groups, preferably 4,4-diphenylmethane diisocyanate, and/or bearing carbodiimide groups, and/or bearing epoxy groups, preferably of the styrene-glycidyl ether-methylmethacrylate type. In a particularly preferred embodiment of the invention, the crosslinking agent and/or chain extender comprises compounds bearing epoxy groups of the styrene-glycidyl ether-methylmethacrylate type.
Along with di- and polyfunctional compounds bearing isocyanate, peroxy, carbodiimide, isocyanurate, oxazoline, epoxy, anhydride, divinyl ether groups, catalysts may also be used to increase the reactivity of the reactive groups. In the case of polyepoxides, fatty acid salts are preferably used, even more preferably calcium and zinc stearates.
The biodegradable branched polyester according to the invention may be mixed with other polymers of synthetic or natural origin, whether biodegradable or not. Compositions comprising polyester according to the present invention are also an object of the present invention.
As regards the biodegradable and non-biodegradable polymers of synthetic or natural origin, these are advantageously selected from the group consisting of polyhydroxyalkanoates, vinyl polymers, polyesters from diol diacid, polyamides, polyurethanes, polyethers, polyureas, polycarbonates and mixtures thereof. In a particularly preferred embodiment, said polymers may be mixed with the biodegradable polyester according to the invention in amounts of up to 80% by weight.
As for polyhydroxyalkanoates, these may be present in amounts between 30 and 80% w/w, preferably between 40 and 75% w/w, even more preferably between 45 and 70% w/w, relative to the total composition.
Said polyhydroxyalkanoates are preferably selected from the group consisting of the polyesters of lactic acid, poly-ε-caprolactone, polyhydroxybutyrate, polyhydroxybutyrate-valerate, polyhydroxybutyrate-propanoate, polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decanoate, polyhydroxybutyrate-dodec anoate, polyhydroxybutyrate-hexadec anoate, polyhydroxybutyrate-octadecanoate, poly 3-hydroxybutyrate-4-hydroxybutyrate. Preferably, the polyhydroxyalkanoate according to the composition comprises at least 80% w/w of one or more polyesters of lactic acid.
In a preferred embodiment, the lactic acid polyesters are selected from the group consisting of poly L-lactic acid, poly D-lactic acid, poly D-L lactic acid stereo complex, copolymers comprising more than 50% in moles of said lactic acid polyesters or mixtures thereof.
Particularly preferred are lactic acid polyesters containing at least 95% by weight of repeating units derived from L-lactic or D-lactic acid or combinations thereof, of molecular weight Mw greater than 50000 and with shear viscosity of between 50 and 700 Pa·s, preferably between 80 and 500 Pa·s (measured according to ASTM D3835 standard at T=190° C., shear rate=1000s−1, D=1 mm, L/D=10).
In a particularly preferred embodiment of the present invention, the lactic acid polyester comprises at least 95% w/w of units derived from L-lactic acid, ≤5% w/w of repetitive units derived from D-lactic acid, has a Melting Temperature in the range 135-175° C., a Glass Transition Temperature (Tg) in the range 55-65° C. and an MFR (measured according to standard ASTM-D1238 at 190° C. and 2.16 kg) in the range 1-50 g/10 min.
Commercial examples of lactic acid polyesters with these properties include Ingeo™ Biopolymer brand products 4043D, 3251D, 6202D, Luminy® brand product L105.
Preferred vinyl polymers include polyethylene, polypropylene, their copolymers, polyvinyl alcohol, polyvinyl acetate, polyethylene vinyl acetate and polyethylene vinyl alcohol, polystyrene, chlorinated vinyl polymers, polyacrylates.
Chlorinated vinyl polymers include, in addition to polyvinyl chloride, polyvinylidene chloride, polyethylene chloride, poly(vinyl chloride-vinyl acetate), poly(vinyl chloride-ethylene), poly(vinyl chloride-propylene), poly(vinyl chloride-styrene), poly(vinyl chloride-isobutylene) as well as copolymers in which polyvinyl chloride accounts for more than 50% in moles. Said copolymers may be random, block or alternating.
With regard to the polyamides in the composition according to the present invention, these are preferably selected from the group consisting of polyamide 6 and 6,6, polyamide 9 and 9,9, polyamide 10 and 10,10, polyamide 11 and 11,11, polyamide 12 and 12,12 and combinations thereof of the 6/9, 6/10, 6/11, 6/12 types, their blends and both random and block copolymers. Preferably, the polycarbonates in the composition according to the present invention are selected from the group consisting of polyalkylene carbonates, more preferably polyethylene carbonates, polypropylene carbonates, polybutylene carbonates, mixtures thereof and both random and block copolymers.
Among the polyethers, those preferred are selected from the group consisting of polyethylene glycols, polypropylene glycols, polybutylene glycols, their copolymers and their mixtures, having molecular weights from 5000 to 100000.
As for the diacid diol polyesters, these preferably comprise:
Preferably, aromatic dicarboxylic acids a1, saturated aliphatic dicarboxylic acids a2, unsaturated aliphatic dicarboxylic acids a3, saturated aliphatic diols b1 and unsaturated aliphatic diols b2 for said polyesters are selected from those described above for the polyester according to the present invention.
As for polymers of natural origin, these are advantageously selected from starch, chitin, chitosan, alginates, proteins such as gluten, zein, casein, collagen, gelatine, natural gums, cellulose (also in nanofibrils) and pectin.
The term starch is understood here to mean all types of starch, namely: flour, native starch, hydrolysed starch, de-structured starch, gelatinised starch, plasticised starch, thermoplastic starch, biofillers comprising complexed starch or mixtures thereof. Particularly suitable according to the invention are starches such as potato, maize, tapioca and pea starch. Particularly advantageous are starches which can be easily deconstructed and which have high initial molecular weights, such as potato or maize starch. Starch can be present both as such and in a chemically modified form, e.g., as starch esters with a degree of substitution between 0.2 and 2.5, as hydroxypropylated starch, as modified starch with fat chains.
By destructured starch, reference is made herein to the teachings contained in Patents EP-0 118 240 and EP-0 327 505, the starch being understood to be processed in such a way that it does not substantially exhibit so-called “Maltese crosses” under the optical microscope in polarised light and so-called “ghosts” under the optical microscope in phase contrast. Advantageously destructuring of the starch is carried out by an extrusion process at temperatures between 110-250° C., preferably 130-180° C., pressures between 0.1-7 MPa, preferably 0.3-6 MPa, preferably providing, a specific energy greater than 0.1 kWh/kg during said extrusion.
Destructuring of the starch preferably takes place in the presence of 1-40% by weight, with respect to the weight of the starch, of one or more plasticisers chosen from water and polyols having from 2 to 22 carbon atoms. The water may also be the water naturally present in the starch. Among the polyols, preference is given to polyols having 1 to 20 hydroxyl groups containing 2 to 6 carbon atoms, their ethers, thioethers and organic and inorganic esters.
Examples of such polyols are glycerol, digylcerol, polyglycerol, pentaerythritol, ethoxylated polyglycerol, ethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentylglycol, sorbitol, sorbitol monoacetate, sorbitol diacetate, sorbitol monoethoxylate, sorbitol diethoxylate, and mixtures thereof.
In a preferred embodiment, the starch is destructured in the presence of glycerol or a mixture of plasticisers comprising glycerol, more preferably comprising between 2% and 90% by weight of glycerol. Preferably, the destructured and cross-linked starch according to the present invention comprises between 1-40% w/w of plasticisers relative to the weight of the starch. When present, the starch in the composition according to the present invention is preferably in the form of particles having a circular, elliptical or otherwise ellipse-like cross-section having an arithmetic mean diameter of less than 1 μm, measured taking into account the major axis of the particle, and more preferably less than 0.5 μm mean diameter.
The biodegradable branched polyester according to the invention may also optionally be mixed with one or more additives selected from the group consisting of plasticisers, UV stabilisers, lubricants, nucleating agents, surfactants, antistatic agents, pigments, compatibilising agents, lignin, silymarin organic acids, antioxidants, anti-mould agents, waxes, process aids and polymeric components preferably selected from the group consisting of vinyl polymers and diol diacid polyesters other than or the same as the aliphatic and/or aliphatic-aromatic polyesters described above.
Each additive is present in quantities preferably less than 10% by weight, more preferably less than 5% by weight, and even more preferably less than 1% by weight of the total weight of the mixture.
With respect to the plasticisers, in addition to the plasticisers preferably used for the preparation of destructured starch described above, these are selected from the group consisting of trimellitates, such as trimellitic acid esters with C4-C20 mono-alcohols preferably selected from the group consisting of n-octanol and n-decanol, and aliphatic esters having the following structure:
R1-O—C(O)-R4-C(O)—[—O-R2-O—C(O)-R5-C(O)—]m-O-R3
in which:
Preferably, in said esters at least one of the R1 and/or R3 groups comprises, preferably in an amount ≥10% in moles, more preferably ≥20%, even more preferably ≥25% in moles with respect to the total amount of R1 and/or R3 groups, polyol residues esterified with at least one C1-C24 monocarboxylic acid selected from the group consisting of stearic acid, palmitic acid, 9-ketostearic acid, 10-ketostearic acid and mixtures thereof. Examples of such aliphatic esters are described in Italian patent application MI2014A000030 and international patent applications WO 2015/104375 and WO 2015/104377.
The lubricants are preferably chosen from esters and metal salts of fatty acids such as, for example, zinc stearate, calcium stearate, aluminium stearate and acetyl stearate. Preferably, the composition according to the present invention comprises up to 1% by weight of lubricants, more preferably up to 0.5% by weight, relative to the total weight of the composition.
Examples of nucleating agents include saccharin sodium salt, calcium silicate, sodium benzoate, calcium titanate, boron nitride, isotactic polypropylene, low molecular weight PLA. Pigments may also be added, if necessary, e.g., titanium dioxide, clays, copper phthalocyanine, titanium dioxide, silicates, iron oxides and hydroxides, carbon black, and magnesium oxide. With regard to process aids such as slipping and/or releasing agents, these include, for example, biodegradable fatty acid amides such as oleamide, erucamide, ethylene-bis-stearylamide, fatty acid esters such as glycerol oleates or glycerol stearates, saponified fatty acids such as stearates, inorganic agents such as silicas or talc. The process aids are present in an amount preferably less than 10% by weight, more preferably less than 5% by weight, even more preferably less than 2% by weight of the total weight of the mixture.
It is also an object of the present invention to use polyester according to the present invention for producing foamed articles, preferably foamed articles obtained by extrusion or injection moulding. It is an object of the present invention to use foamed articles, comprising polyester according to the present invention, obtained by physical foaming, without cross-linking by chemical additives. It is also an object of the present invention to provide foamed articles comprising polyester according to the invention obtained by physical foaming, without cross-linking by chemical additives. Said articles include protective packaging for the electronics sector such as separators or films, sports articles such as technical equipment and footwear, articles for the footwear sector. Preferably the foamed articles according to the present invention are used in the footwear sector.
It is an object of the present invention to provide fibres, films or sheets comprising polyester according to the present invention, consisting of one or more layers. Advantageously, the polyester according to the present invention can be used as a tie layer between the different layers.
The invention will now be illustrated with a few examples of embodiments, which are intended to illustrate but not limit the scope of protection of the present patent application.
Branched polyesters:
The data in Table 1 show that optimum RVE values are obtained only in the presence of a biodegradable branched polyester characterised by branching obtained through a preparation process employing a polyfunctional compound containing at least four acid (COOH) or at least four hydroxyl (OH) functional groups, present in a concentration of 0.2-0.7% mol with respect to the final polyester, wherein at least two of said hydroxyl functional groups are primary and at least further two of said hydroxyl functional groups are primary or secondary, providing that, if present, the secondary hydroxyl group is not vicinal to another secondary hydroxyl group.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021000002135 | Feb 2021 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/052345 | 2/1/2022 | WO |
